texts: How much does the physical size and shape of a RF antenna affect its range/penetration?

texts:
I'm curious about the physical propterties of the tiny antennas inside many embedded devices (so ~2.4ghz if frequency matters).

Made this graphic to reduce typage:

Red Circle = target
Grey bar = concrete obstruction
Black bar = just dividers for the different senarios
1: regular antenna
2: 2x as long antenna
3: 3x as long, curved antenna

What would the difference be in these cases?
Does any of these changes impact the overall signal strength?
If so, roughly by how many times relative to the first one?


texts:
We have a battery & UPS setup on communication systems for an isolated site (wind farm). Last night was the first time the system was put to the test when our grid connection was lost at 11.30 pm, at 8.00 am we had no internet connection, we cannot say precisely at what time the UPS was drained.

The grid was reconnected at 11.30 am and we arrived onsite at midday, all electronics were functioning correctly and the battery had a voltage of 13.1 V. The inverter is a EATON ELISPE ECO 500 but we swapped out the internal battery for a BSB Solar 12-200.

With a charge of 5A the battery should last at least 20 hours. But in this case it didn't even make 9 hours. It is worth noting that onsite it would have been about -5°C during the night time. I am trying to figure out why are battery is draining so fast, has anyone got any pointers ?


texts: How to use the Shutdown pin of a switching regulator?

texts:
What are the systematic/standard methods for incorporating the SHDN (shutdown) pin of a buck/boost IC?
Take MAX756 for example (datasheet).
Here are its I_q profile:

Suppose I'm using an Arduino nano (ATmega328) as the MCU and nRF24l01+ as the transmitter. I'm reading some sensor values via ADC and transferring the data over the RF link. So the system has a sampling frequency (suppose 100Hz).
If I want to save battery, the system should sleep most of the time and wake up and transfer the data 100 times a second. All Vccs should come from the boost converter. Now:

1- I should make MCU and nRF sleep but how about the step-up IC? Should it also be shutdown and waked up 100 times a second? I guess I should take the IC's  start-up delay into account? Here is its profile:

Regarding this profile, I guess the IC wakes up in ~2ms... So the maximum sampling rate would be at best 500Hz?

2- What voltage would be on the OUT pin of MAX756 if it is shutdown? The same as Vin? or is it floating?

3- Is SHDN the same as Enable in different ICs?

4- If there is no way that the main MCU could control the SHDN pin, can I use like a 555 timer solution to control SHDN instead of an auxiliary tiny PIC MCU just for controlling the step-up IC? Because using a separate MCU just to control when an IC should shutdown seems to me rather an overdesign solution...Although if it is used in industry I have no problems then

Thank you very much


texts:
Some of our boards have a damaged SCR.  I just witnessed one in person today.
The SCR actually exploded upon power-on.  A part of its packaging material just flew off along with an exploding sound. The resulting dead body of the SCR is shown here:

I have a few questions about the circuit:

Q1 (S6020L) is the SCR in question.  It is rated 600V, 20A.  AC input is 220V.  What I did is:

Remove AC/Power off.
Discharge C5
Power on.  At the very same moment, Q1 exploded in pieces.

If the SCR is turned on when the rectified AC signal is right near its peak and the voltage at C5 is close to zero, I would imagine there is a huge inrush current to charge up the big capacitor.

The questions I am having are:

How do I calculate the magnitude and duration of this inrush current.
Does this inrush current exceed the specification of this particular SCR?

The rectifying bridge, GBJ2006, is not damaged in this case.

We have produced and sold a few hundred boards. There have been some occurrences of this problem. I am wondering if we should somehow change the design (I am not a hardware guy).

The SCR in question is not really from Littelfuse, but it matches S6020L in specification, as I heard from our hardware designer.  I have no idea what manufacturer it is from and trying to determine if it is a design issue or a part quality problem.

The MCU (not in the schematics attached) sees the SYNC signal and triggers the SCR at appropriate times to ramp up the voltage at C5.  This way the inrush current would be reduced considerably.
The problem is that before my software takes charge, there may a glitch that triggers MOC3052M upon power-on.  This is a one time thing and after that the software takes full control.  I am having the doubt about the quality of the SCR part because this inrush current is not repetitive.  The moment I witnessed the SCR explosion is without any load and right at the switch-on of the power switch.  I know the obvious solution is to get rid of the glitch; however, I just want to know if this part is faulty.

HV_Bus (C5) is connected to a 1.25-HP motor, whose other terminal is connected to a MOSFET.  MCU will turn on and off the MOSFET with a PWM signal and C5 gets discharged with this load.  When the PWM signal is active, MCU triggers the SCR with a 2kHz frequency and keeps C5 charged.

AC mains hazards:


texts: Power a laptop from 12V Battery using DC-DC Step Up Circuit

texts:
I have following items

1) DC - DC Step Up Boost (150W)

http://www.ebay.in/itm/131625051992

2) 12V 12Ah Battery (Sealed Lead Acid Battery)

3) LCD Lead-acid Battery Capacity Tester

I charge my battery using Solar Panel. Since, lot of power is wasted while running on inverter.
So, i decided to use directly using DC to DC Step Up circuit.

My Questions:

1) It is safe to power a laptop from 12v battery using DC - DC Step Up Circuit ?

2) Any protection circuit is required (current limiting)?

3) I need to take care any other additional things ?

4) Can i also go higher capacity battery (12v 100AH) with same circuit ?


texts: #pragma statements in PIC18F4550 C programming

texts:
I am new to Microcontroller programming and I thought maybe I should try blinking around 24 LEDs as a self project using PIC18F4550.
I searched for a simple 1 LED blinking source code on net and what I am unable to understand are the following lines which are at the top of the code:-

#pragma config PLLDIV = 5 , CPUDIV = OSC1_PLL2 , USBDIV = 2    // You can write this way
// OR
#pragma config FOSC = INTOSCIO_EC
#pragma config FCMEN = OFF                                 // OR this way
#pragma config BORV = 3
#pragma config WDT = OFF
#pragma config CPB = OFF
#pragma config CPD = OFF

After this the author has used simple LAT statements which I am able to understand.

Can someone please explain the above codes and what each of them are doing or can point to some tutorial which explains (briefly) the use of following codes?

Note:- Just out of curiosity, these #pragma codes were used for 1 LED blinking, do I need to change them when using more than 1 LED?

Thank you.


texts: How does bipolar line coding such as AMI work with medium like fiber optics

texts:
We know that in bipolar encoding (sometimes called multilevel binary), there are three voltage levels: positive, negative, and zero. The voltage level for one data element is at zero, while the voltage level for the other element alternates between positive and negative as picture below shows:

but I always think for medium like optical fiber only support two signals, just like the classic approach high voltage means 1 and low voltage means 0.
so for AMI, optical fiber has to use 3 different light signals to represent +, - and zero. And considering we have other mutilevel schemes like 2B1Q as the picture below shows:

now it seems like optical fiber has to use 4 different light signals to support it.
so my questions are:
Q1. how many different light signals can be produced to support bipolar encoding?is it a limited number?
Q2. we know that fiber optics has a lot of tiny optical fibers as the picture below shows:

so does each tiny fiber represent one light signal?
Q3. Does optical fiber transmit data by parallel transmission or serial transmission.

since fiber optics uses a lot of tiny fibers, so I guess it is parallel transmission?


texts: How to operate a 12V/5V NE555 timer relay from 12V DC supply and capacitor

texts:
Problem:
I need to switch ON a NE555 timer relay from 12V DC supply when the DC supply is switched ON. Also, when I switch OFF the 12V DC supply, the relay should switch ON again as it is a timer relay.
What I am doing currently:
I am connecting 12V DC to an NPN transistor. The 12V supply gives power to the collector and the emitter emits 12V and gives it to a 4700uF/25V capacitor and also to the timer relay and the relay switches ON and OFF (because it is a timer relay.) Now when I switch off the power supply the capacitor discharges immediately and as I guess it is not allowing the timer relay to de-energize there by not switching on the relay. I have tried adding resistor and it still doesn't work. But when I try to discharge the capacitor directly to the relay, the relay operates.
My use case:
I need to switch ON and OFF a CPU(NUC) from the ignition of a car battery. That is, when I switch ON 12V I need an ON pulse and when I turn OFF the 12V supply I need an another pulse. Just a pulse is enough (like pressing the  switch to ON or OFF the CPU.)
Maybe if even my capacitor starts discharging after a 2 second delay when I switch off the 12V DC in the circuit I have provided, would be great.
Is there any device to delay capacitor discharge start timing or any modification needed in this circuit?


texts: Best practice for layout of balanced audio grounds

texts:
I'm designing a simple board with a differential ADC. The inputs are from TRS jacks that will (usually) carry balanced audio signals.

The datasheet, and general best practice, advises keeping analog and digital grounds separate. This makes sense to keep the digital ground currents away from the analog circuitry where they would contribute to noise.

I wonder then, where should I attach the screen from the TRS jacks? If these are balanced audio, the screen should contain only noise (RF and potentially ground loop hum) so it might make sense to dump it with the digital ground. On the other hand, it's not unusual for an unbalanced phono plug to get shoved in the jack, and now the screen is also the reference point for the signal so should be kept quiet.

What's best practice in this situation? And does the answer change if I'm certain if the equipment will only ever be used for balanced connections versus trying to design for either balanced or unbalanced cases?


texts: VHDL - Can't see why these two architectures produce a different RTL

texts:
I have the following examples:

architecture two of andex is
begin
process(abus)
variable y: bit :='1';
begin
    for i in 7 downto 0 loop
        y:=abus(i) and y;
    end loop;
    x<=y;
end process;
end;
architecture three of andex is
begin
process(abus)
variable y: bit;
begin
    y:='1';
    for i in 7 downto 0 loop
        y:=abus(i) and y;
    end loop;
    x<=y;
end process;
end;

The only difference between the two architectures is the location of the variable initialization.

The first architecture produces this RTL:

Why is there a feedback path ? y is known for the first loop iteration and every iteration there after.

I had expected it to produce an 8 bit AND gate like the 2nd architecture does.


texts: Why do buck (step-down) switching regulators require an inductor and diode?

texts:
So, I understand, at least at a basic level, the method of operation of switching converters, both buck and boost. What puzzles me, though, is why buck converters in particular aren't simpler.

Why not build a buck converter as a switch that charges a capacitor, with the switch controlled by a comparator comparing the output voltage to a reference? Wouldn't that be a lot simpler, allow you to use a more easily and cheaply available capacitor in place of the inductor, and skip the diode entirely?


texts: Why are these USB data lines conned to pull-up resistors?

texts:
I recently got a car lighter to USB adapter which I planned to use to charge my mobile phone. Unfortunately, the phone won't charge (and I know that the phone is capable of charging over USB port), so I opened it to see what could be the reason. The charger itself is pretty simple. It has a rectifier, MC34063A regulator and needed components, an LED and resistor and USB port.

Of particular interest to me was the USB port itself. If I remember correctly, for USB chargers, there should be a 220Ω resistor between data lines to signal to the device that the host is a charger.

In my case there was this circuit:

I used black rectangles to mark junctions.

So if I'm reading this correctly, the D- and D+ lines are connected via pull-up resistors to Vcc.

I'm thinking of removing these resistors and putting a 220Ω resistor between the data lines.

My questions are:

Is there any obvious reason why should the data lines be connected to Vcc through this complicated system of resistors?
Is there any reason why I shouldn't remove those resistors and just put a 220Ω resistor between the data lines?


texts:
I have a problem with a circuit I designed and which I am trouble shooting at the moment. I am trying to generate 50 Volt pulses from a microcontroller to an NMOS with a Load attached with help of a Bootstrap circuit. These pulses are in this case 1 ms the off time is 19 ms (50Hz). I simulated this in LTSpice and it seemed to work fine. instead of transistor Q1 and resistor R1 I use in real life an opto-coupler with a 330 ohm resistor to the micro controller output. After building the circuit on PCB I did not have success. It could be some Soldering issues or circuit issues I am not sure what is going on.
I did try to troubleshoot and what is odd to me is that at "node1" I measure the correct 50 V peaks on my scope. However at node 2 the Voltage stays zero. Which means the Vgs of the MOSFET stays zero as well and thus the Vds stays 50V so no switch on.
Any ideas what could be the problem?

Edit:  Brian Drummond pointed out to have Node2 on the bootstrap Voltage. So I updated the schematic to:


texts:
I want to create an electronics project that will involve cameras.
Though i want to create my own system, i want to create my own PCB and not be dependant upon existing solutions like development boards or raspberry pi.

I have come along sensors from omnivions.

These are MIPI CSI camera sensors. This is a datasheet of one of these sensors:

sensor datasheet

What application processor can i use to interface with them?
In page 15 you can see a list of all the pins.
Can this work only with CSI chipsets like DaVinci? Or i can interface it with an arduino DUE or other solutions?

The application i want to experiment on is the standard video record and store to SD card. If there is an OS (Linux or other RTOS) in the application processor even better.


texts: I am trying to figure out difference between these two header types. One appears larger than the other with names differing by 'RA' at the end.


texts:
I am basically a rank "newbie" and the only electrical project I have ever undertaken was to take a "light fan" and rip it apart and glue magnets in it and with a pair of vise grips spin it around and generate about 16 volts on a multi meter...serious..

I am interested in building a basic joule thief to power small LED lights off of low power sources like solar garden lights, and I am also investigating alterative low power sources that produce very small amounts of electricity, but would need to "boost the "juice" LOL.. Anyways from what I have seen these folks are building the "core" of a joule thief and they say you have to use a "ferrite core"..

Pardon my ignorance, I do not know a lot of "electronic jargon" so not sure what a "ferrite core" is.. It sounds like and looks a "ring magnet", like what one would find in a music speaker or microwave oven.. IS this what folks are using for the basic "ferrite core", and would a round magnet work for a joule thief??

I asked "google" and never got a proper satisfactory answer. thanks for help!


texts: Changing between usb power and battery power using P-Channel MOSFETs and a CMOS Invertor

texts:
I am trying to switch between USB power and a single cell lipo using two mosfets. Would the circuit below be ideal or is there a more efficient/reliable way to do this?

When the USB is connected the mosfet for the battery should turn off and when the battery is connected and the USB is not the mosfet for the battery should turn on.


texts:
I have a USB powered system. The system on occasion for a short period of time, needs more than 500mA. I have additional caps that can provide this current.

The problem is, despite these caps have enough power in them, during the excess current phase, I see the USB rail goes down 0.2V. This is probably ok for my application but I like to be cautious since I am worried some hosts out there doesn't like this behaviour and may disconnect me from the host.

I am looking for a simple solution where during the transient USB current is limited to 500mA. I have seen some ICs that can do this but I prefer a discrete solution.


texts: Different parallel windings in a transformer

texts:
Normally to reduce Rdc value in a transformer/inductor you put several windings with the same Number N of turns in parallel.
But what would happen if these had different number of windings?
Could I get winding numbers that are not round?
where is my mistake?


texts: Mountin electrical components and tubes inside an aluminum travel case

texts:
I've got a project involving al electric valve, water counter and some electronic parts (Arduino and similar). Of course, the electric valve and the water counter are connected with water pipes.

Is there a solution if I need to attach all these things inside an aluminum travel case? I've seen, for pipes, there are things called pipes' collar or something but, I still have to understand how to attach everything to the case.


texts: LM317T Simulation in Eagle giving an Error, unkown subckt

texts:
I am a beginner in Eagle and I am trying to do a simulation of the circuit attached to this post. I keep getting the same error and I have tried other solutions posted but the error remains. Anyone who can help me with this?
This is the error:
Error: unknown subckt: x_vr1 +24v n_6 n_11 lm317t
Note: No ".plot", ".print", or ".fourier" lines; no simulations run
I have some of the other chips working and I have followed the same approach but no success on this one.
Thank you,


texts: Why are Halbach Arrays useful in PM motors?

texts: I understand how Halbach arrays strengthen the magnetic field on one side of the array. I also know that, in a permanent magnet (PM) motor, there is already a limit on the air gap flux you can design for, as beyond a point, there is magnetic saturation in various parts of the stator steel. If you can achieve this flux using a regular array of strong magnets with high remanence, what is the point of the Halbach array? Are they only used for cheaper magnets to get to that near-saturation level of flux? Or is there something I am missing?


texts: How to properly connect and drive varicap diodes?

texts:
can someone explain me how to connect and use varicap diodes?

Please consider that I am a novice, so would be ok to use a clear and an exhaustive language/terms. Thank you.

I often see these schematics:

The first thing is: from what I heard, a resistor between the V tuning and the varicap is needed to remove the DC signal, or is also possible to insert an inductor or a capacitor; which component is better to choose and of what value? And if I avoid to insert the resistor/inductor/capacitor in what "risks" I can fall?

The schematic also shows that is possible to connect these varicap in a back-to-back configuration (anode to anode): in this way the total capacitance is the half of one diode. But I have a doubt: in this schematic (bottom left image) the varicaps are DC shorted by the inductor, right? Why aren't DC isolated from the circuit? So, is better to prefer the schematic in the top right image? Seems that here, the capacitors are used to isolate the varicaps. But from what I can see, in a lot of schematics, varicaps aren't isolated from the circuit. Is not very clear to me.

Anyway, in the following image:

I can also see that is possible to connect them with the cathode in common: which configuration is better?

Can someone explain me which connection is preferable and why (anode to anode, cathode to cathode or just with a capacitor in series - and how to choose the series capacitor to avoid to reduce the capacitance range of the varicap), how to properly isolate them from the DC signal and from the circuit? Would be also nice to see some practical/didactic schematic (with component value) to exactly show and understand howa circuit can operate.

Many thanks.


texts:
I'm confused, and I hope you can help me figuring out, what I misunderstood. I am not an electronics engineer, so bear with me :)

I have a chip, from the engine control unit of a Toyota Yaris Verso from year 2000, with the following print:

ATMEL010
25020NB
9D3203C

I have not been able to find a datasheet. And that really surprises me. I did find one for At25020B, but not for one with the NB suffix. Why would Atmel make a chip and not publish the datasheet?

First of all, from what I can find, the Atmel AT25 series are all EEPROM (source). So this chip should be an EEPROM. Am I right?

I looked up, what the suffices mean and found the following (source: Explanation of Atmel’s Part Number Code). B means some kind of military compliance. The N says something about the package:

N = Leadless Chip Carrier, One Time Programmable

I think the N in some cases mean "Leadless Chip Carrier" and in some cases "One Time Programmable", since they are not related. Do you agree?

Looking at the picture, it obviously has 8 leads, so it is not leadless, and thus N must mean one-time-programmable. Do you agree?

As far as I understand the EEPROM technology it is by definition erasable/rewritable.

Is this really a one-time-programmable (and therefore not erasable/rewritable) EEPROM? Or what have I misunderstood? :)

The background for even asking is because I have not had luck with communicating with the chip. A friend, who is an experienced tingler tried to with Bus Pirate and command line tool flashrom, without luck.


texts: Capacitor Sizing for A Full Wave Bridge Rectifier?

texts:
Building my understanding of the issue from (First PSU - need help with capacitor size) (especially the comments/ripple wiki/several capacitor sizing webpages) the calculation for rectifying a full wave bridge rectifier at 50A 16V should be:

$$\frac{50A}{2 * 60Hz * 2V (Ripple)} = .208333$$
Converting from F to uF, I get $$.208333*10^6=208,333uF$$

So I should get a filter capacitor close to 0.21000uF at greater than 30V (Peak/rounded/safety margin)? This is my first time doing such calculations, are there any glaring errors? I know that the person several people struggled with some of the complexity, and I'm not sure if my interpretation of some of the variables (particularly dV) is correct.


texts: How to generate a bipolar waveform using MOSFET?

texts:
I'm trying to generate bipolar waveform using MOSFET (IRF9630 & IRF630):

Basically the bipolar waveform looks like below:

The load is a wounded coil (260 Ohm).

For the experiment I need this three conditions:

both coil ends at GND
one end at +12V and other GND
one end at -12V and other GND.

The frequency is provided by a MCU signal.

How can I proceed?

[update 1]
@FakeMoustache: Square Wave i have generated with MOSFET and MCU -

For the case MCU output is High we will get +12V_Regulated on one pin and -12V_Regulated on other and when on MCU output is Low we will get -12V_Regulated on one pin and +12V_Regulated on another.

Here for the illustration i have shown When MCU is High, but you can get the idea.

[update 2] @FakeMoustache: Updated the schematic.


texts:
I need to source +15V or -15V resp. on several pins (20+) using a few TTL level pins (SPI, I2C, serial) from my microcontroller. Only one of the pins will source +15V at a time, the rest are -15V.

I can only find shift registers that can sink high current, for example the TPIC6B595, not source it. The only components I've found are analog arrays with serial interfaces, but that's overkill and becomes very expensive.

Maybe I don't understand the spec of the TPIC6B595 correct, but I think I want the same component but I want them to sink current (from a Vdd pin) instead of draining to GND as the DRAIN pins do now.

I'm looking for a component that can be connected like U1 below and the Pin1-Pin8 can be toggled to either +15V or -15V. The actual serial interface is not important, just any serial interface. Maybe two components are needed, one for +15V and one for -15V.


texts: Do simple LED strip dimmers consume power while turned off?

texts:
I am referring to this kind of LED strip dimmers:

I want to know if it consumes power while the LED strip is off, and if so, how much.


texts: Peak value of sine wave for capacitively coupled inverting amplifier

texts:
I was working on question 2.23(a) and there is asked what input voltage is needed in order to ensure that the output does not clip. The clipping limits are +10 to -10 V.

I solved that, and, basically, what I did was that first I nulled the input voltage and found the output voltage due to the offset voltage source connected to the positive terminal of the opamp and then I nulled the offset source and found the contribution of the input voltage to the output voltage (superposition) and then I added the two (output voltage contributions) and put them equal to 10, which is the saturation voltage for the opamp.

However, my answer to question 2.23 is not correct. So I wanted to ask: if I am not doing it correctly, how do I do it then?
Here is the circuit I used:

simulate this circuit – Schematic created using CircuitLab


texts: Is there a preferable way to amplify the signal from an electret microphone?

texts:
I need to amplify the microphone output to some level about 3-4 Vpp without a DC offset. The output voltage will only be sensed (it will pass through a peak detector). So I assume I don't need any current supplying ability.

I first thought of using a common emitter with around 400 gain, but there is also an option of using a non-inverting or inverting (I don't care phase shift) opAmp circuit with the required gain.

I wonder are there benefits of using one over the another, in which aspects do they differ?

Or, are both these two options a bad idea?


texts: Is there a way to batch copy port names over to net names

texts:
version Altium Designer 15.1
Scenario

I have a several pins wired to ports.
I want to remove the ports and add net names to the corresponding wire
I want the wire net names to be the same as the port name for now.  I will add to the net name later.

Question
How do I go about doing this in the most efficient way possible?  Right now I'm creating each net name, assigning them to a wire and copy/pasting the corresponding port name over to the net name.


texts:
I have a NOS universal ac/dc motor and don't know how to wire it. The motor has 4 unmarked leads. Two black, one red and one white. The motor label is marked VOLTS 115, CYCLES 60, AMPS. 1.0, SER. 12V39607, 900 rpm, thermally protected. Can someone provide the proper the wiring info?
Thanks,
Henry Rancourt


texts:
I was just going through a text book on digital communication where something related to ac coupling was mentioned.It was mentioned that if a long stream of one(1) is encountered at the receiving end then an erroneous bit is supposed to occur (sorry for not being able to quote the text).So for that purpose they are somewhat DC balanced in order to avoid DC WANDER.

I tried to look for it but did not get a proper, thirst quenching response.
Is it possible to get a conceptual explanation for what they mean by DC wander?


texts: LED Light changes color on being turned on/off simultaneously

texts:
What type of circuitry/driver is present in the lights that change color on being turned on/off ?

I have a LED tube light which cycles through 3 modes (i.e. color 1, color 2, both color). Its circuit utilities only one chip (i.e. 9934A 7101H8, SO-8 package, there is Si written on it) for the above effect.

I was unable to get the datasheet of the IC.

The IC seems to be connected in the following way:

simulate this circuit – Schematic created using CircuitLab


texts: How BCD Ader shows the correct BCD number?

texts: let's say 9(1001)bcd are given both as Addened and Augend, so Binary sum is 10010, so correction is needed and 6(0110) is added to Binary sum the result is 18(0001 1000) requires 8 bits but output of second four bit binary adder is only four bits i.e S8S4S2S1.  How this could happen? Or what I'm lacking in my concept? Best wishes!


texts:
How to understand this oscillating circuit made of two transistors and R C?
This is an oscillating circuit which is made of two transistors and some R C.
As below schematic shows,  during the power on the capacitors, C1 and C2 are charged through R1 and R2.
After about 0.5s the C1 is fully charged to 24*(1/(1+0.2))V = 20V and after about 10s the C2 is charged to about 20V+0.34V=20.34V.
The voltage difference between E and B of Q1 makes the Q1 PNP transistor to work, the current flow through the R5 resistor then makes the Q2 NPN turn on. after then the current flow to the LED D2, then the D2 turns on and emit light.
But quickly as soon as almost 3-5ms the energy in C1 and C2 capacitors will be exhausted which then makes the process go back to the very beginning.
Then the capacitors C1 and C2 are recharged.
The above process is the basic description of the circuit. I simulate the circuit by using the Tina V9 software and the result is as the pic. shows.
My questions are:

How to calculate the suitable value of the R and C which can make
the oscillating time equal to 5s?
How does the circuit work which very precisely makes the circuit to
oscillating?
What are the roles of the two transistors and how they work?

simulate this circuit – Schematic created using CircuitLab


texts:
I need to develop for my business an weight emitter. Basically all I need is that a weight sensor that will continually emit weight from a connected bin, which will be captured by bluetooth from a phone APP.
I was able to do this using online tutorials with a combination of Arduino Uno+Weight Sensor+ Amplifier+ Blue Tooth IC. However I was wondering since all I need in essence is a emitter beacon, Is there a way I can simplify the components. For example can I remove the Uno, and just have the bluetooth emit from the sensor.
I will need to scale this up to 1000+ bins, hence any suggestions will be highly welcome.


texts: How to avoid mutual inductance at UHF frequencies?

texts:
I know that keeping inductors at right angles helps to avoid mutual inductance. But I can't find any information minimal spacing between inductors such that they have no mutual inductance. In my particular case, the frequency is 319MHz, and the 0603 inductors vary from 20uH 20nH to maybe 150uH 150nH (thanks to Andy for pointing pointing out wrong units!). I have to think that 1/2" spacing is more than enough but want to be sure.

I guess I could set up a test with a spectrum analyzer and tracking generator to find out for myself.


texts: How to test a Peltier module TEC1-12705 to determine if it works as intended?

texts:
Background:
The module comes from a 70W mini-cooler which doesn't really cool anymore. I took it apart and got the module out, I could read the model TEC1-12705 from the module itself. The specifications can be found here.
The performance specifications are:

Tests I've done:

Tested voltage at the power supply and it outputs DC 12V to the module connectors.
Disconnected the module and measured resistance across it at a room temperature of 24º Celsius, which resulted in an average resistance of 120 Ohms .
Connected the module to 11.30V DC from a power supply with a max output of 5A.

Using Ohms law the current flowing is 0.094 amps, and the power supplied to the device 1.06 watts.
Using and ammeter connected in series with the module and the same power supply I get a reading of 0.02 amp, which starts decreasing as soon as I close the circuit.

After the last test now the resistance is 150 Ohms average.

My conclusion:
The module is toast now. I don't know how these things fail, but:

I never could get a reading of 2.4 Ohms resistance from the module.
The increasing resistance indicates to me that the module does not handle the power supply well and  must be burning the cells inside.

Question:

Would you consider buying a new module, or does it sound to you I am doing something wrong when taking measurements?


texts: Is it possible to damage a VFD by raising the anode voltage?

texts: Is it possible to cause damage to a vacuum fluorescent display by raising the anode/grid voltage above the recommended level (not the filament voltage)?


texts:
coplanar waveguide vs microstrip for gnss and cellular?
I read on internet microstrip is better for signals <30Ghz but some gps manufacturer (Delorme) said that coplanar is most efficient so it's kinda confusing me. any advices?


texts: Will 2 600mAh batteries give me the same usage level as one 1200mAh?

texts:
I am considering obtaining a pair (2) 3.2V AA Lithium Phosphate batteries rated at 600mAh for a project that needs to operate at 3.7v/1.8ohm at peak times and next to nothing the rest. Obviously the mAh significantly impacts on the usage time but would running two 600mAh batteries give me a similar usage time as a single 1200mAh might?

In other words does twice as many cells give me twice the mAh?


texts: Mosfet controlling one power source with another

texts:
Can I have an N-Mosfet controlled by one power source to control a separate power source.  I want to have power from a USB port to control wether power is going to a fan and water cooling pump, and to leave the power on for some time after the computer is turned off.  It simulates ok, but simulations are not always real life.

Any other notes are appreciated.

Below is an image of the circuit.  The lower left corner from the ADC on is only for testing.  A simulatable version is at Falstad, but I had to remove the timer.


texts:
In my project I already have all the circuits for a PWM driving some high power MOSFET. Now the hardware guys are coming with this AC heater, and I've been breaking my head around Triacs and phase controllers but that will be an extra design time that we don't have available.

I wonder if I get the AC through a bridge rectifier (240V, 60Hz) and then through my PWMed MOSFET controlled at 1Khz.
I know the final wave won't be pretty to look at in an oscilloscope, but it's just a heater (a resistance), it shouldn't matter if the current is really going or not to both sides.

Does anyone see any problems in doing this setup?

Edit:
The PWMs already working in the project through high power MOSFETsare isolate through OpAmps that keeps the proper gate charge levels on the MOSFETs. Those already work nicely controlling a compressor and a pump. The difference from those and the one I'm asking about is only a proper stable DC or a mirrored sine AC between drain and source.

Below is the circuity that is already working for the pump and compressor and the main idea I was trying to re-use it a bit for the heaters. I mean, just because the heater manufacturer said the heater is 240Vac it doesn't meant I can put 240Vdc (full rectified but no capacitor) on it.


texts: LDO datasheet dont provide open loop gain plot

texts:
To make LDO stable compensation. How to obtain open loop gain phase plot to compensate LDO, since it is not available in the datasheet.

Since its very much required for LDO load transient, load regulation etc. This information is essential I belive.

From datasheet (not given in block diagram). How to understand its internally compensated or externally compensated.

Datasheet: ZXCL280
MAX1726


texts: Total current in two circuits - two methods

texts:
I have two norton's theorem questions and I am confused about the two solutions.
In the first one below, the current can be found by simply subtracting one current from another. (I believe this is correct)
\$I_N\$ = current through \$R_L\$ in the first circuit
\$R_L = 21 \Omega\$

But in the second circuit, you have to use the current divider rule.

Am I missing something completely obvious? why is the first one so simple?


texts:
I have learnt about Seebeck effect and peltier effect in college physics, but it was more of  theory than hands on numbers and practicals.

Now is there a commercial or DIY module that can produce some current from a black body heated from sunlight.

Are there any graphs, and numbers you can provide. Any research papers. I am not looking for ways to convert heat to current using rotary generators. Rather I need a direct conversion, like a solar panel converts light to current. Is there a material that can convert heat from a surface to potential difference and current.

I need enough power to make a mobile phone charger out of its output.

The gradient I might have is around 70 to 80°C at the hot junction and 20 to 25 °C at the cold junction. My plan is to have a hot junction with a large surface area, with less volume (like a large sheet). And a dense cold junction with far less surface area. Has anyone tried this as a home project, Any personal experience in trying out this principle would be much helpful.


texts: Why does curling a wire decrease its amperage/wattage?

texts:
I picked up an extension cord today, and I noticed that it had a different value for its wattage and its ampage, based on whether the cord is wound around its base or not.

(I apologize that the picture is blurry. In the left box it says, ”Max current wound - 4 Amps (960 Watts),” and in the right box it says, “WARNING - Max current unwound - 13 Amps (3120 Watts).”)

Why does this make a difference? Assuming that the wire is properly insulated, shouldn’t it transfer the electricity just as efficiently wound as unwound?
Is there a formula that I can use to calculate a cord’s wattage/amperage when only part of it is wound, or when all of it is wound, given its wattage/amperage when straight, how much of it is wound, and how tightly it’s wound, and maybe some other variable I can’t think of?

Obviously my question assumes that it has nothing to do with a liability concern or the like.


texts: Group velocity dispersion for coupled waveguide system

texts: I am an EE undergrad currently studying group velocity dispersion (GVD) for coupled waveguides, and am quite confused on the following question: how do you characterize group velocity dispersion for a coupled waveguide system, like a conventional symmetric directional coupler? I can certainly get the dispersion relation (\$\beta-\omega\$ relation) for the individual waveguides, be them planar, rectangular and so on as they are almost always treated in an integrated optics or photonics textbook, but how do you characterize GVD for the coupled system (come up with a "coupled propagation constant"?), and is there a general treatment for it? Any help or even suggestion on references is appreciated!


texts: Bandwidth calculation of second order Sallen-Key low pass filter

texts:
I am trying to figure out how to derive this second-order op-amp circuit.
I understand that I should be trying to find Vo/Vi, but I’m endup calculating a function that leaves me with a bandwidth much higher than the listed specification.

*I do realize that I can divide through with a factor of R2, but that still would not change the bandwidth.
I created a bode plot that gave me a natural frequency of 662Hz, which using \$B=\frac{w_n}{2\zeta}\$ leaves me with a bandwidth of 172Hz, while the active filter on the circuit board is listed at 100Hz.
Bode plot created through matlab "bode" function:

is there somewhere where I am going wrong with the derivation, or is the method of how I approach calculating bandwidth wrong?


texts: What are the additional transistors used for in this hex inverter?

texts:
I'm learning about electronics and was studying the SN7404 hex inverter schematic when I saw this:

I naively expected just a single transistor (the one in the bottom right) and the input at the base of that transistor to give the inverted input at Output Y.

Yet there are 3 other transistors, a bunch of resistors and a couple of diodes in addition.

Can someone here help to explain what the purposes of these are and the reason for the resistor values?

Source datasheet here: http://www.ti.com/lit/ds/symlink/sn54ls04-sp.pdf


texts: Limitations of When to Use Mesh Current Method

texts:
For this circuit, is it possible to solve for i solely with the mesh current method? I know that this would be even easier to do with application of the fundamental laws or the node voltage method; I just want to better understand the limitations of the mesh current method, and when it's best to use it.
By the way, if you wanted to know, this is where I got the question from: https://web.cecs.pdx.edu/~tymerski/ece241/Examples_Node_Mesh.pdf
It's the second question, and they answer it using application of the fundamental laws on the 13th page.


texts:
I have several large LG multi-cell batteries. Images & description can be seen here:

I'm wondering if I can use a 14S BMS for each of these batteries in order to keep every cell balanced and in check and run them in the series.
For example, I want to use 3 of these batteries which has fourteen cells each (total of 42 cells) , so I'd purchase 3x 14s BMS.
Pictures attached show the packs opened containing the 14 cells in two separate packs of 7.
I was wondering if the stock MBMS that you can find a picture below of could be of any use, I doubt it however.
Any advice would be very helpful, thanks in advance!


texts:
I am struggling with an STM32l053C8T6 microcontroller and testing touch/proximity in regard of size and shape of the electrodes.

I am using a Discovery 32L053C8 board. It has implemented support of capacitive sensing built in MCU. It also has example electrodes, which are working fine. Sensing is based on charge transfer principle.

Now, I am trying to do exact same configuration as in the example but with my own electrode. I assigned sampling capacitor to the one which is built in for the example and chose the channel from the same analog group of IOs (as described in documentation.)  I have added my own electrode. Pin configuration is PB2 electrode (Group 3 IO4) and PB1 sampling (Group 3 IO3, built in on the board). I have added piece of copper foil with a 1 kΩ resistor for ESD protection to pin 2.

Now I get Max count error (maximum transfer charge cycles) and I have no idea why. Can you help me?


texts: I'm using a STM32F4 with lwIP to host a website, and I also have an SD card which I save csv type files to using FatFS. Just wondering how I would allow users to download files directly from the SD card to their computer from my website? I have ~ 0 experience with websites prior to this project so forgive my ignorance. Thanks!


texts: Can I add a Sense connection to this power supply?

texts:
I have a synthesizer (Yamaha CS-50) and the power supply is broken. I don't know why but it always blows the fuse. I tried everything, changing components, testing the transformer, etc. The fault is in the +15/-15V circuit, it doesn't give me the correct voltages, but the others are perfect.

I decided to build a new modern power supply, this one adapted to +15/-15V

My question is about the Sense circuit of the original power supply. Can I add a sense circuit to the new power supply, will something like this work? Do I need a resistor in between?

Sorry if the question is a stupid question, I am a rookie.

I have a progress, I did find the fault on the original power supply, was a rectifier diode, leakage diode, I did replace and now don't blow the fuse.
Now the problem is that I receive a high voltage in the outputs on the +15/-15 circuit
I receive the following:
+15V output= +27V
+15V S output= 0V
-15V output= -27V
-15V S output= +27V
If you see in the original p.s, in the union of zd1 and 820 resistor I have +15V, and in the union of zd2 and the other resistor I have -15V, so the problem is onwards I suppose.
I did replace the 4558 and all electrolitic capacitors.
the other outputs 6.8V and 8.5V are perfect, what do you think where is the possible failure?
I don't understand why I have this values, perhaps the zener diodes or transistors associated?
Of course the connector of the synth is not connected, I not want to destroy the boards until the values are correct.
Thanks in advance.


texts: Can I use SQFP package instead LQFP for PCB design in Proteus 8?

texts:
I have to design sound card with CM108AH and its package is LQFP with 48 pins.
I use Proteus 8 for designing but there is no LQFP package for PCB.
Can I use SQFP 48 pins instead ?


texts: In powering household devices, is the voltage preset and the amperage varies as needed?

texts:
When powering household devices, does a power adapter have a preset (or in some cases user-defined) voltage, while the device (while turned on) "selects"/draws whatever amount of amperage it needs at any given time?

Part of why I ask is while searching for replacement power adapters for speakers, one device says it needs 6V DC input and also says max power input is 4W. The adapters I find online have labels with a max amperage listed but a set voltage or selectable voltage. This makes me think amperage can vary based on device use, but voltage is set by the adapter; the voltage needs to be correct but the ultimate power draw can be limited (to under 4W, or with 6V that'd be ~500mA) as needed by the device. Is it the case that an adapter sets voltage but amperage can vary based on device needs/"request" of electricity?


texts: How to use FETs to switch supplies in circuit

texts:
I'm working on a project  that can be powered either by USB or an battery power supply. They can both be plugged in at the same time.I'd like the battery to provide 5V if its plugged in, but fall back to the USB if possible.
The one solution into my mind is using diodes.But i can't stand the voltage drop.As diodes will definately  drop some voltage.
other solution i have heard about is by using FETs.But i do not know very much about FETs use.
Will some body will guide me how to use FETs to switch between supplies in this scenario with explanation.


texts: Implementing IMU, help with neccessary components?

texts:
I am looking at making a schematic for the ISM330DHCX alongside a ATmega328P processor for Arduino. I have the Adafruit version of it (LSM6DSOX is same footprint).
Schematic:

PCB:

I just wanted to see if half of the components on them are neccessary. My intention is to only do I2C communication, with no need for interrupt pins, Chip Select etc.; only Voltage, SCL, SDA, ground.
The ISM330DHCX datasheet has the connections guide below,
from what I can tell all I should need is:

AP2112K-3.3: Voltage Regulator for 5V to 3.3V
2*10kOhm Resistors: for Pull-up in I2C
2*100nF Capacitors: for Power Supply decoupling
EDIT: Logic shifter for SDA and SCL

Is there anything else I am missing?
Also I read up on VDD and VDD_IO, I am assuming for my application both are connected to 3.3V with no problem.
I appreciate any help, thanks!


texts: How to increase the lifespan of an Arduino.

texts:
I have made a device with arduino MEGA with 50+ one wire  sensors, 4-6 shift registers, SIM800l module, ethernet module, wifi module, RTC, SD card module, OLED, buttons, thermal printer, LM2596 buck converter etc.. All modules are soldered on my new board powered with external power supply through LM2596. My board with modules fits to arduino like a shield with male header pins.

I want to make this device to work for years continuously  (if possible) how can I increase the lifespan?

  Arduino Mega

  Description:

  The Mega 2560 is an update for the Arduino Mega, which it replaces.
  The board is a microcontroller board based on the ATmega2560-16AU . It
  has 54 digital input/output pins (of which 14 can be used as PWM
  outputs), 16 analog inputs, 4 UARTs (hardware serial ports), a 16 MHz
  crystal oscillator, a USB connection, a power jack, an ICSP header,
  and a reset button. It contains everything needed to support the
  microcontroller;  simply connect it to a computer with a USB cable or
  power it with a AC-to-DC adapter or battery to get started. The Mega
  is compatible with most shields designed for the Arduino Duemilanove
  or Diecimila.

  Product Summary:

  CH340G replace the Atmega 8U2/16U2 CH340G Driver Download link, please
  copy the link and paste in browser: http://www.5v.ru/ch340g.htm
  Microcontroller:ATmega2560 Clock Speed:16 MHz EEPROM:4 KB SRAM:8 KB
  Flash Memory:256 KB of which 8 KB used by bootloader Operating
  Voltage:5V Input Voltage (recommended):7-12V Analog Input Pins:16
  Digital I/O Pins:54 (of which 14 provide PWM output) DC Current for
  3.3V Pin:50 mA DC Current per I/O Pin:40 mA

  Package Included: 1 x ATmega2560-16AU CH340G Board


texts: Floating neutral in TN-S or TN-C-S earthing system

texts:
Since neutral is bonded to ground at building distribution point in a TN-S or TN-C-S earthing system, could floating neutral happen under the following conditions:

Loss of N and/or PE at transformer
Loss of N and/or PE at building distribution point
Loss of N and/or PE at transformer and building distribution point

I'm trying to understand how to prevent floating neutral in a 3-phase power supply and thus avoid damage to low voltage equipments connected to a single phase.


texts:
I am a medical physicist, and I program software for MRI scanners as well as develop electronic devices that interact with them. Because of the way MRI works, it is necessary to use very large power amplifiers (~300 kVA) to drive large currents through low resistance coils of wire, producing a precisely controlled magnetic field that varies linearly in space (and is in addition to that produced by the main, static magnetic field). These devices are called "gradient sets", and there are three of them, each with an associated power amplifier. The load is almost entirely reactive.

I recently had cause to look at the wiring of one of these amplifiers into the wall. Its isolator is a large three phase supply mechanical switch, a photo of part of which is below. There are two electrical symbols on the box for a switch -- one with a square on it and a 160 A rating, and one without.

What do these symbols mean? Not being an electrical engineer, I've never seen them before, and some quick googling hasn't shown anything up. Is one stating that there is a 160 A RMS fuse present (at three phase 415 V), but that the instantaneous current might be up to 315 A?


texts: Micron NOR unused pins have pull-ups. Any danger just leaving them there?

texts:
I have a board designed for a dual-die Micron MT25QL512 QSPI NOR flash.  These parts are in short supply, but the board fabricator had some single-die MT25QL128, and used them instead. The single-die chip has the same footprint as the dual-die chip, but the pins for the second die are marked 'RFU' in the datasheet, with the note:

"Reserved by Micron for future device functionality and enhancement. Recommend that these be left floating. May be connected internally, but external connections will not affect operation."

Is there any risk in just leaving the weak pull-ups on the unused pins? (On the MCU I'll mux the pins to GPIO input).

UPDATE:  It seems to be okay just to leave the pull-ups on the unused pins.  I've been running for 3 weeks like that, without noticing anything strange.


texts: Transmission Parameters for a 2nd order butterworth bandpass filter

texts:
I am trying to find the transmission parameters (ABCD parameters) for the above circuit.
$$a_{11}= \frac{V_1}{V_2} |I_2=0$$
$$a_{12}= -\frac{V_1}{I_2} |V_2=0$$
$$a_{21}= \frac{I_1}{V_2} |I_2=0$$
$$a_{22}= -\frac{I_1}{I_2} |V_2=0$$
I have performed an analysis for when $$V_2 = 0$$ and concluded that $$V_1 = (sL_1 + \frac{1}{sC_1})I_1$$ $$I_1 = -I_2$$ so therefore $$a_{12} = sL_1 + \frac{1}{sC_1}$$  $$a_{22} = 1$$
However, these results seem incorrect, so how should I find the transmission parameters for a circuit like this? Especially for the section with $$I_2 = 0$$ which seems much more complex.


texts: Why is it dangerous for human being to touch one of contacts in AC wall outlet?

texts:
Let say we have some DC voltage source which produce some voltage which I will label as V. Let also say that we have some real bulb which is supposed to work when voltage V is applied across its terminals. That bulb has some internal resistance R_internal. I will model real bulb as ideal bulb in series with its internal resistance R_internal. We know that for current to flow we need closed path between source and load so if we connect our voltage source and our bulb like on picture below, we will see light from bulb because current will flow:

I draw two equivalent schematics for this situation.

Let us now see another situation.
We know that in AC wall outlet there are two "holes". Mathematical expression for voltage waveform between these two "holes" is shown on picture below:

If we represent voltage between these two "holes" as voltage generator like on picture below and if we connect to it some real bulb which is supposed to work with this AC voltage we will see light from bulb because we have completed circuit and alternating current can flow:

Why is it dangerous for human being to touch one of contacts in "holes" in AC wall outlet? I mean, according to previously discussed situations, there should be no closed path for current to flow If I stand on earth and touch one of contacts in AC wall outlet. I should touch both contacts in wall outlet for current to flow through me and that will be very dangerous.
Thanks in advance.


texts: Where is Interrupt Vector Table stored in ATmega32A?

texts:
Given that Atmega32A has three types of memory :
1) SRAM.
2) Flash (Program memory).
3)EEPROM.
In which section the Interrupt Vector Table is stored ?


texts:
I have been trying to flash firmware onto the PC Engines APU2 platform. I'm using an SPI interface. RPi3's SPI is hooked up to the three-state quad buffer SN74LV125AD. For now, it is just a proof of concept. But when I do flashing, I get an error like that

pi@raspberrypi:~/Desktop $ flashrom -w apu2_v4.8.0.3.rom -p linux_spi:dev=/dev/spidev0.0,spispeed=8000
flashrom v0.9.9-r1954 on Linux 4.14.50-v7+ (armv7l)
flashrom is free software, get the source code at https://flashrom.org

Calibrating delay loop... OK.
Found Generic flash chip "unknown SPI chip (RDID)" (0 kB, SPI) on linux_spi.
===
This flash part has status NOT WORKING for operations: PROBE READ ERASE WRITE
The test status of this chip may have been updated in the latest development
version of flashrom. If you are running the latest development version,
please email a report to flashrom@flashrom.org if any of the above operations
work correctly for you with this flash chip. Please include the flashrom log
file for all operations you tested (see the man page for details), and mention
which mainboard or programmer you tested in the subject line.
Thanks for your help!
Read is not working on this chip. Aborting.

I was trying to increase or decrease speed, but it doesn't solve the problem. Generally, the Raspberry Pi can't find the APU2 when using the buffer. For now, I use the buffer in THT package and all is hooked up on a breadboard. Thus, I use 2 IDC cables.

Where I'm making a mistake. Can length of the wires be a cause of why flashing doesn't work?


texts:
I'm in the edX class and failed on all my three attempts on one of the questions. Clearly my reasoning is wrong, but I can't figure out where exactly. I would really appreciate if somebody could help me answer it.

Here is the figure for the question:

Here are the questions:

What is the contamination delay?
What is the propagation delay?

Horizontal resolution is 20ps.

As I said before, I've failed on all 3 attempts. But I sill would like to know how to solve this. Any help is appreciated.


texts: Is a 40109 fit for 3V3  5V level shifting?

texts:
I have checked couple of datasheets for 40109 and although they specify "Supply Voltage Range" as min: 3V, max: 18V, none of the other tables specify values for < 5V.

Can I safely order these chips for use in a (Bluetooth master) 3V3 <=> 5V (ATtiny) level shifter application? And how can I conclude that from the datasheets?


texts: Delay between electric current and light intensity of LED

texts:
I'm currently writing a physics report of an experiment, which is about optical fiber.

One of experiments was about compare input & output signal of optical fiber, and the result was this:

As you can see, there's difference (6ms) between input and output signal, and one question on the experiment instruction was to explain this delay.

I found that two things can affect this delay - optical fiber itself and delay happened at light source: LED. However, I can't sure about both things..

Is the delay between electric current and light intensity of LED significant?


texts: Two black boxes display the same impedance at all frequencies. Which has the single resistor?

texts:
Two black boxes display the same impedance at all frequencies.  The first contains a single 1 Ohm resistor.  Each end is connected to a wire, so that two wires protrude from the box.  The second box looks identical from the outside, but inside there are 4 components.  A 1 F capacitor is in parallel with a 1 Ohm resistor, and a 1 H inductor is in parallel with the other 1 Ohm resistor.  The RC combo is in series with the RL combo, as shown in the figure

The boxes are painted black, unbreakable, impervious to x-rays, and magnetically shielded.
    Demonstrate that the impedance of each box is 1 Ohm at all frequencies.
    What measurement would allow one to determine which box contains the single resistor?


texts:
I'm designing a schematic for a system that will utilize plug-in daughter boards.  I'd like to provide the daughter boards with high quality 12V, 5V, 3.3V, and 1.2V, with up to 5A, available via pins on the daughter board connector.

The main board will utilize a 12V power supply.

I'm trying to find a good approach to using one or more voltage regulator chips to accomplish this.

I've noticed the LMZ22005 which appears to fit the bill, but I would need to use several in order to offer the desired voltages.

I'd like to request suggestions for how to best accomplish this.  The device will be for RF use, so EMI is highly undesirable. Recommendations for other chips or general caveats will be much appreciated.

I would prefer to use SMT parts and cost is not the major consideration.


texts:
In the below circuit of Timer Relay, how I can calculate the time for C1 to be fully charged?
please don't use regulator, transistor or any other device I just want to use Resistance and want to calculate how much resistance required to charge the C1 for how much time?
If ohms law(E=IR) is suitable than what is the relation of (I) with C1?


texts: Can't program ATmega with ICSP on custom pcb

texts:
I'm fairly new to PCB design, and I've been trying to program the microcontrollers on the board I designed with no luck. The board uses an ATmega32u4 and an ATmega328P. I've been trying to program them with a cheap $10 ICSP programmer from Amazon, with no luck. avrdude tells me that "initialization failed" and if I try to force it, I get this:

I tested the pins and confirmed that the ICSP header is properly connected to the microcontrollers. I've been racking my brain trying to figure out what went wrong and the only thing I can think of is maybe it's a bad programmer?
Here's the schematic:

I appreciate any feedback you might have.


texts: I have a sonar sensor which has 4 pins and may be due to a bug in my code, they are freezing in a few seconds after functioning. I found out if I reconnect the Vcc pin, they start working and yeah they freeze again. So I'm thinking rather than unplugging and plugging in the Vcc pin, to use an inverter (NOT gate) to activate it when I need the sonar to work and disable it whenever I don't need it. With an inverter we are setting ground voltage as we are disabling and I wonder if it would harm the sensor circuit by any mean.


texts: How does a consumer microphone achieve a sensitivity of -20 dB?

texts: How does a consumer microphone achieve a sensitivity of -20 dB (Edutige EIM-001), when one of the best industrial electret microphones I could find (Primo EM158) has a sensitivity of only -32dB (1 kHz at 1 Pa)? Is there some internal amplification going on? Didn't I search hard enough?


texts: How can a light dimmer in series modulate a load?

texts:
Not after a full breakdown of how this specific light dimmer works, but rather how a device in series can control a load.

A light dimmer has the following wiring diagram. As you can see, the light dimmer is in series with the load.

From my research, most household dimmers modify the AC waveform to reduce the RMS voltage, hence lower the light, rather than using a rheostat.

Most of the information suggests the switching is done by a TRIAC, but in here there seems to be a power MOSFET (IRF840A) with a heatsink. There seems to be a 555 timer and a 324 op amp, which I'm guessing does the modulating.

Of course a definite answer of how this device works cannot be observed without reverse engineering it, however in general I don't understand how a device in series can operate when it's purpose is to control the load. The circuitry needs current to operate, but it's purpose is to (partially) kill the power to the load, and thereby killing it's own power (since the device is in series).

This is my interpretation of how a device could modulate it, but it doesn't make much sense to me.

simulate this circuit – Schematic created using CircuitLab


texts: What should I look out for when driving high power relays with MOSFETs?

texts:
Initially I was designing a relay controller for lower powered relay, but since I could not find the optocoupler that is rated for my application, I turned to MOSFETs. and it so happens that the logic level MOSFETs I find are way overkill for my application.

Since the FETs I am using can do more than my original target, I decided to upgrade my circuit so that I may use it again in the future more versatility.

So here is what I have so far, I decided to use 2 out 4 channels of my controller using NMOS and the other 2 using PMOS. I did this because I thought in the future if I ever need it to power something else that needs to be referenced to the same ground. Although this might not happen but why not when you can.

The FETs I am planning to use are the:

NMOS - CSD88539ND
PMOS - FDS8935

Here is basically how each channel would look like in the schematic:

I have decided that the absolute limit that my controller should carry is 50V 1A DC. I don't know if relays like that even exist, but nonetheless that is my target. What other things I should look out for when powering this big of a load relay? Is there a chance that that power might surge back to GPIO pins?


texts:
For a portable application, I would be using a single 3.7V 2600mAh li-ion cell. The circuit requires 2.5V to 5V to function with the current requirement being 100mA.

So obviously a voltage regulator is required.

I would want to know for how long, using an appropriate regulator, could the cell power the circuitry continuously. Is it almost 20 hours? I guess the health of the cell also needs to be considered, so it should not be discharged below 3.3V, right? If we consider this, then what will be the run time?

Thanks.


texts: How to read the Bluetooth Tracker to fetch the data about its coordinates?

texts:
I am working on App Concept which is similar to any Bluetooth device which works as Tracking. I need to use the Bluetooth and collect its location coordinates on every 5 mins.

How to read the Bluetooth Tracker to fetch the data about its coordinates ?

Where can i find the online materials to study and implement this concept?

It will be very helpful to have the details related to open source.


texts:
In a circuit like this, can the crystal oscillator be replaced with a DDS such as a AD9850? If so can it just be dropped in or would other components have to be changed?

Second question, how sensitive are simple transceivers like this to slight changes in capacitance, for example, a 110pf capacitor instead of the 120pf one below the crystal?

Final question, if I want to change the DDS frequency(to 14Mhz for example) do all the capacitors, etc need to be changed?

Thanks so much for your time.


texts: What will this OP_AMP output if it's VCC is off?

texts:
I have a board with this voltage divider and follower, for all my ADC channels I can use, as shown in the pic attached.

Ignore top LHS / ANA_IN1.   With J14 on, VCC_OPAMP on,  all works as expected - the other 3 channels I'm using.

But I would like to understand what should be the output of the OP_AMP when they all off - i.e. J14 is off, and VCC_OPAMP is off .. ?  If I remove the jumper, all my 3 ADC readings / 3 channels read about 500mV, even when nothing is applied to the pins, nothing attached.

I've looked at the datasheet of the OPA4342EA/250 link to product, and ,I whole honestly don't understand what it will output when the component is off. :/

Also, will the voltage divider work if OP-AMP is off ..?


texts:
I design a pcb with STM's STM32F4 microcontroller and i'm going to use the SWD interface for programming.
My Question is: Could those pins to shared (after programming) with other signals on pcb? Signals such as led on/off trace, chip's reset trace, etc.


texts: Which AGM battery terminals should be used when wiring 3 or more batteries in parallel?

texts:
With a 12V AGM battery bank of 3 or more batteries wired in parallel, is charge able to be drawn by attaching to any random positive and negative terminal across the battery bank?

Is it optimal to draw charge by attaching to the positive and negative terminals that are furthest apart?

If so, what is the advantage?


texts:
We have a quad copter which had an arm partially detach mid-flight, which in turn destabilized the vehicle, plummeting it into the ocean. After two hours of searching we were finally able to recover the copter which had already suffered severe terminal corrosion. We immediately disconnected the batteries upon pulling it out of the water (a 12v and a 18.5v LiPo,).

My questions:

What are your recommendations for de-salenating the electronic components?
Are my batteries salvageable? The 18v (Li Po) is puffed up pretty bad, but the 12v (Li Po) appears just fine.
Are there any other words of wisdom for this situation?

Currently, the quad copter is sitting in the bath tub filled with water (batteries removed,) as I don't want to expose it to air until we know how to deal with this situation.


texts:
I am new to the forum, so please forgive me if I am asking a stupid question or posting the wrong thing at the wrong place.

I recently bought a Led ceiling light online that comes with a remote control which allowed me to change the light temperature and brightness. However, I have noticed that if I used the remote to turn off the light, the light still glow (dim, but enough to notice and bother me at night…) If I use the wall switch, this will not happen (but doing so kind of defeated the feature of the dimmable light remote control). Based on what I searched so far, I figured that this is probably a mismatch of the controller and the LED strip. My ceiling light is supposed to be a 24W light, but on the controller, it said (36-48w)x2. So I am guessing that they have gave me the light with the incorrect controller installed…. The thing is, If I return the item, the postage would probably cost me at least half the price of the light, so it is really not worth returning…. So I am looking at ways to fix this rather than returning it. I have tried to switch the L and N wire  that goes into the controller (just in case the switch was on the wrong side), but it made no difference ☹ After reading online, I noticed that I might be able to put a resistor into the circuit to fix this, but I am not too sure where I should install it, and what would be a safe value of resistor to try out for. It would be great if anyone could shed some light on my problem.

I have attached a picture of my ceiling light, and a close up picture of the controller (the writing is in Chinese though). Each of the led strip are 2835 2b4C x2.

Many thanks in advance.


texts: I am currently studying data communications, and I read somewhere that data is represented as an electromagnetic signal such as voltage, microwave and radio wave. Now I know electromagnetic radiation is a range of different wavelengths with different properties which radio waves and microwaves are part of, but I did not think electrical voltages was an EM wave, so I don't understand this sentence.


texts: How Would One Analyze a Circuit with Two Voltage Sources?

texts:
I'm studying Circuit Analysis and a sample problem is as follows:

I'm not really sure how to approach the problem. My intuition leads me to believe that the two voltage sources are acting against one another versus stacking their effect. When I search this problem online, I come across examples of superposition, which breaks the circuit apart, analyzes the individual parts, then brings the parts together in an additive or subtractive manner. Thus far in my studies I haven't learned superposition, thus I feel that I shouldn't need it to find the required values.

I'm not looking for a walkthrough for this problem, just somewhere to start. I've thus far learned KVL, KCL, and Ohm's Law. Apparently KVL should be sufficient for solving this problem, I'm just not seeing it.

What method would I use to find the current? I believe that if I know the current I can solve the remainder of the problem.


texts: Where can I Find the Memory map and register table for the S70FL01GS

texts:
I am currently working with this device:

https://www.mouser.com/datasheet/2/100/001-98295_S70FL01GS_1_Gbit_128_Mbyte_3.0V_SPI_Flas-1102682.pdf

The datasheet provides some high-level details about this flash memory device, but it doesn't show me the memory map, the register table, or how exactly I can store/load values in this flash mem. I was wondering if there was a separate document for the more detailed stuff.


texts: Can the STK500 program the XMEGA as it arrives from Atmel?


texts: Interrupt handler starts behaving unexpectedly when scheduler runs

texts:
I have an IRQ handler that gets fired upon receiving a character over serial, and everything is fine until I run a FreeRTOS scheduler inside main, and now what I see is IRQ handler still getting invoked but it isn't behaving as expected: the following API isn't disabling the event register as it would if the scheduler wasn't running, resulting in the IRQ handler getting invoked again and again
pInstance->setEvent(NRF_UART_EVENT_RXDRDY, 0);

// logger.cpp
TaskHandle_t Logger::loggerThread;
TaskHandle_t Logger::taskMsgBuffer;
StreamBufferHandle_t Logger::streamBuffer;

typedef enum
{
    totalStreamBufferBytes = 100,
    triggerLevel = 5
} streamBufferParams;

Logger::Logger()
{
   Logger::streamBuffer = xStreamBufferCreate(totalStreamBufferBytes, triggerLevel);

    // create a task
    if (pdPASS != xTaskCreate(Logger::Process, "PROCESS_LOG", 256, this, 5, &Logger::loggerThread))
    {
        // error handle
    }
}

// uart.cpp
static Uart* pInstance;

extern "C" {
    void UARTE0_UART0_IRQHandler(void)
    {
       // ...
       if (rxIrqEnabled && dataRxd)
       {
           pInstance->setEvent(NRF_UART_EVENT_RXDRDY, 0); // disable event -- DOESN'T SEEM TO WORK AS EXPECTED WHEN SCHEDULER RUNS!
       }

    }
}

Uart::Uart()
{
   pInstance = this;
   // ...
}

// main.c
int main(void)
{
   Logger logger;
   Uart uart;
   clockInit();
   vTaskStartScheduler();
}

Edit:
MCU = nRF52 which uses cortex M4
To clarify the situation further, the NRF_UART_EVENT_RXDRDY doesn't get RESET at all when the scheduler runs whereas when no scheduler is involved, IRQ works as expected i.e NRF_UART_EVENT_RXDRDY does get reset


texts:
I am making a project that requires two different voltage levels, 5V and 12V (although this can be lowered to 7V minimum). I have two voltage regulators as described by the schematics below:

I want to have one power source that can supply enough current and last a decent amount of time to power both regulator circuits. I was thinking single A batteries in series but I'm not sure how many would be sufficient because the input for each says 3-40V, so technically I can get away with just two batteries in series or maybe two sets of two in series and those sets in parallel to get longer battery length. Or is a rechargeable battery better? The problem I'm having is I am not aware of a way to figure out what works and why because of my elementary electronics knowledge.

Thanks in advance


texts: What does a battery's C rating mean and how does it relate to its maximum discharge current?

texts:
In another question, I was trying to figure out what kind of battery I could use to provide enough current to power my circuit.  Someone pointed out that batteries often have a maximum discharge rate.  In looking at data sheets, I found that these rates are often noted in units of "C."

At first I assumed it was related to coulombs and 1C was 1 amp for 1 second, but that doesn't appear to be the case (except, I guess, coincidentally for a 60,000 mAh battery maybe?).

Instead it appears that 1C is the nominal rating of the battery?  So, a battery rated at 3500 mAh was tested and from fully charged it will discharge 3.5 amps continuously for 1 hour before it is fully discharged?

So, if I have a circuit that requires .5 amps and a 840 mAh battery, I only need a 1C maximum discharge rating to be able to power my circuit?  Will it power my circuit for roughly 1.68 hours (potentially more because of the reduced stress)?

If, on the other hand, I switch to a battery that's rated at 2700 mAh, then my current draw is closer to .2C or .54A/hour?  Would that power my .5A circuit for roughly 5 and a half hours?

Finally, why do we rate batteries this way?  And why isn't the maximum discharge current rated in amps instead of ratios of discharge rates?


texts: Low voltage control for actuation analysis. How to do it?

texts:
I would like to create a circuit, where I can modify the output voltage between -5V to +5V such I can customize values between this interval, like -3.2 V to +1.4V or -1.0V to +1.0V etc. Is it possible with an 555 timer IC?
My project would be to create an automated circuit for actuation analysis, i.e. switching from +1.5V to -1.5V with a time period of 5 seconds for several tenths of cycles. I saw Arduino can be easily programmed, but as I know Arduino modules cannot produce negative voltages, maybe with an L298N DC Motor interface, but I do not know how to start this.
So after all I need to generate a bidirectional square wave with adjustable frequency.
Could you give me some advice about this?
Thanks for your help.


texts: Is the Q2 in this diagram based on J2 and K2?

texts:
Down here is a basic diagram Im practicing on. Im not sure if I get the answers correctly. But should I find Q2 based on J2 and K2?
X = J1 = K1
Q1 = J2* = K2
Q2
Z = Q1* + Q2*


texts:
I have simulated the following circuit on MultiSim, and it seems to work well doing its job.
The first element is a full wave bridge rectifier. At its output is connected the input of the zero-cross circuit and also to another diode which is connected to a bulk capacitance. I plan to run a flyback power supply from the capacitor's voltage (10uF).
My doubt is about the circuit in practice.
Will there be current leak from the capacitor the the bridge output sufficient to make the zero-cross circuit have an unexpected different behavior? Is there any problem on connecting a flyback PSU and the that zero-cross circuit on the same bridge-rectifier? Will the power supply / capacitor of 10uF interfere on the working of my zero-cross?

edit: zero cross circuit


texts:
First, I'm not interested in numbers or the general math behind this. I know how to split voltage into some particular value(s). But what is actually going on?

I get Kirchoff's Voltage Law, or at least in terms of numbers. But how do the "electrons" know, where to drop which amount of energy?

Let's say I've got two 1000 ohm resistors in series and 6V DC source.

Well the voltage just between the resistors will be 3V, the electrons lost half of their energy.

If there were 3 of those resistors, it would be 2V.

This "voltage drop" is determined by "what is about to come" after the resistor.

How is that possible?

The resistors are always the same but they still "eat" different amount of volts based on the entire circuit, not just on themselves.

How do the "electrons" know how to distribute their energy?


texts:
Let's consider an impedance Z inside a certain circuit. Let's suppose that we are working with a generic non periodic signal (so it is possible to analyze the circuit with the Fourier Transform).

How can we calculate the complex electric power absorbed by Z? If the signal is purely sinusoidal, we work with phasors and we write:

P = V × I*,

Where V is the voltage across Z and I is the current flowing on it.

But what if we are not in AC, but with generic signals?


texts:
I'm trying to make a decent audio amplifier using two lm386 wired in parallel. I used Jericho Uno's schematic (below) as a guide (link to video).

My circuit looks pretty similar, but I wanted to increase the volume, so I put a 100 ohm resistor between pins 1 & 8 on both amplifiers. As you can probably guess the resulting sound at max volume was very bad. I'm trying to find the maximum clear sound lm386 is capable of without an oscilloscope, and so far it has been trial and error. It would really help  if someone could explain the finer details of the diagram below- specifically those responsible for reducing distortion- so I can figure out how to improve my circuit.

Also, is it accurate to say lm386 in parallel produce "Double the power and performance"? Does that mean I can keep adding lm386 in parallel to boost sound as long as I have sufficient power?

Some key differences in my circuit:

32 ohm/2 watt speaker and 15 Watt 8 ohm speaker (used both not sure which is more appropriate)
2700 microfarad dc filter (instead of 470 microfarad in the schematic)
100 ohm resistors connecting pins 1 & 8

Everything else is pretty much the same. Would really appreciate your thoughts ! building this has been fun so far


texts: Smallest stepper motor (that one could buy)

texts:
I'm looking into embedding a stepper motor into a wearable device like a wrist watch. I've found these on digikey:

http://www.nmbtc.com/pdf/motors/standard-pg/PG15S-D20-HHB9.pdf

The resolution is great and it's aligned with what I need, but I'm afraid it will draw too much power (100mA @ 15V), and I would appreciate something even smaller. There's no torque requirement. It will just turn a handle.

Do you know a source where to buy even smaller (in power and size) stepper motor?


texts:
Can somebody indentifier this part?
It is mark as CASW


texts: SlewRate and Output Swing for a differential OpAmp

texts:
I want to calculate SR and output swing for a fully differential OpAmp, using simulation.

I came across this solution for a single-ended OpAmp:
A. SR calculation:

B. swing - make 'Vin' in the above a sine-wave source, and increase Vin amplitude to the point where the output is not distorted, than extract the swing.

So first - is this method acceptable [A,B or both]?
if so - how can I match this for a fully diff OpAmp? I can't understand how to set both inputs/outputs. Let's please use this notation:

The OpAmp topology that I'm using is:

if the above method is wrong - what would you recommend?

Thank you very much,
Daniel


texts: Arduino UK Mains Light Switch 230v to 5v

texts:
My aim is to create a wall light switch similar to the LightwaveRF ones with a momentary switch rather than a rocker style switch. To handle the momentary switch I will create a custom chip based on the Arduino with a small AVR and a solid state relay switch and will also be controlled by radio frequency.

So my question is how can I safely power the custom chip behind the switch with 5v stepping down the 230v used for UK mains? Obviously I am aware of similar methods of reducing power such as the ones used in iPhone chargers for example using resistors and capacitors but I need this to be as small as possible and be safe in the event of a power surge. I am more than happy to purchase all of the parts separately and create the circuit myself but I could do with some guidance. I am guessing the LightwaveRF switches must use a similar method what I am proposing.


texts: I found what looks like a crystal oscillator with an xdl stamp I haven't seen before

texts:
I found an old transmitter with a crystal oscillator on it, when I looked at this I saw that it had "xdl 17.734475m" stamped onto it, I've only ever seen oscillators with just their frequency written on them.

I tried searching the internet but it just came up with Chinese websites, so I was wondering what the "xdl" meant (brand name?) and what the "m" after the number means.

Any thoughts?

P.s. I'm fairly new to this so I'm not sure my terms are completely correct.


texts:
I will like to know if a baud-rate of 9600 is so fast for an 8051 MCU using an 11.0952Mhz crystal. Why? I have observed some inconsistency in the behavior of my MCU, in that when I send a set of characters looking for a particular character to perform certain operations, I discover that my MCU does not perform the required operation. Meaning that there was a misplacement along the line during receiving.
Then I did some serial routine. I sent a "ABC" from terminal to the MCU, which should transmit back to the terminal an increment of each character sent, hence it should give "BCD". But this is what i got consistently - "BD" missing "C". Meaning that the MCU missed "B". I also send other set of characters and discovered that some characters get missed by the MCU. What could be the cause of this. Could it be the Baud-rate or in my code. How can I possibly rectify this.

Here is the code.

void initUART()
{
  SCON = 0x50;
  TMOD = 0x20;
  TH1 = TL1 =-3;
  TR1 = 1;
}

void sendCHAR()
{
  SBUF = uartBUFF[s];
  while(!TI);
  TI=0;
}

void serial_isr(void) interrupt 4
{
  if (RI)
  {
    RI = 0;
    tmpBUFF = SBUF;
    charFLAG=1;
  }
}

main()
{
  IE= 0x91;
  initUART();
  while (1)
  {
    if(charFLAG)
    {
      SBUF = (tmpBUFF+1);
      while(!TI);
      TI=0;
      charFLAG = 0;
    }
  }
}

Thanks!


texts: Should every logic IC be power decoupled?

texts:
I've read before that "every IC" should be decoupled.  I've never before bothered on gates, buffers, etc.  No datasheet that I've read for those chips has ever suggested to do so, until I came across a TI buffer chip that suggested putting a cap across power and ground.  That got me wondering if that's just common best practice anyway?

Should I be putting a cap between every VCC/GND I come across, no matter what?  Or it just isn't that important?

Specifically I wonder then why, for example, a buffer 14-pin almost always has the VCC and GND chips on completely opposite corners.  If it was the design intent to decouple it, shouldn't they be adjacent?

My experience tells me it can't possibly be that important, since I've never done it and I have devices operating reliably for years in the field... but always looking to improve.


texts: I am tinkering with a ZYPDS power delivery board to develop, in combination with a XL4015 step-down module (https://www.ebay.com/itm/5Pcs-5A-XL4015-DC-Step-Down-Power-Supply-Lithium-Charging-Module-Buck-Converter/114213959434), a mobile charger for my DJI Mavic Air batteries. I set the ZYPDS to 15 V and for a while, I did measure 15 V when plugging it into my Xiaomi Power Bank 3 Pro which supports 45 W PD. Then, I attached the XL4015 and the voltage dropped to 5 V (not only at the XL4015 in/output but also at the ZYPDS output), even when I remove the XL4015. Did I fry the PD part (either on power-bank side or on the board) somehow so it's down to the regular 5 V supply? Or is it hard to break and if I did, it would stop working entirely? I guess there's a safety mechanism integrated into the power bank which prevents overloads > 45 W, right? Unfortunately, I don't have another PD power bank available to check if it's the power bank or the ZYPDS. I hope you guys can help me figure out the issue.


texts:
Can someone explain to me what slipping a pole pitch means in regards to generators?

The following paragraph is from some class notes I was revising:

'A generator could lose synchronism with the power system because of a severe system fault disturbance, or operation at a high load with a leading power factor. This shock may cause the rotor to oscillate with consequent variations of current, voltage and power factor. If the angular displacement of the rotor exceeds the stable limit, the rotor will slip a pole pitch.'


texts: detect if open wire has been cut after test point

texts:
So I'm trying to design a circuit for a situation with the following scenario:

SW1 is representing a cut wire after the access box. I can't tap into anywhere except the access box shown in the picture and I can T in (preferred) or cut into the supply and/or ground lines. I have found one way where I can use a current sensor but that would only solve half the problem. If SW2 is open(chip is good)/closed(chip is bad) and would give false positives if SW1 is open(wire cut). So the problem is needing to accurately detect if it's 27.119V open, open with fault, shorted with fault, shorted.

I've been looking all over and found some similar situations but all had more access than I have. I have found a circuit for doing a time domain reflectometer as a last resort but hoping it can be simpler than that. Thank you for any help.

--EDIT--

To reiterate: for the circuit I need to make it can only affect what's in the square "access box". It's for a senior design project for school and the rest of the circuit shown is a closed system and the red SW1 is a hypothetical we need to be able to test for (wire gets cut/contact in a connector comes loose/etc).

If it helps with the design: from the access box to the chip sensor it's roughly 10' of wire.

--EDIT--

After doing a little more research and with regard to the comments this is a little better representation and now simulatable (I didn't know about the schematic button in the text editor previously... The previous one I made was requiring me to pay for a subscription to share because I made it on their site first so I just screenshot it instead)

simulate this circuit – Schematic created using CircuitLab


texts: How to properly convert a balanced (line level) audio signal to unbalanced?

texts:
I want to connect a balanced line output of a pro grade mixer to a consumer grade power amp that only accepts unbalanced RCA aux in connectors. The mixer has balanced TRS (tip-ring-sleeve) 1/4 inch output sockets, one for each channel.

If I connect a mono/unbalanced TS (tip-sleeve) 1/4 inch to RCA jack converter to the balanced mixer output, the negative/cold signal will be shorted to the sleeve (ground). I know that the simplest way to convert balanced to unbalanced is to short the negative/cold signal of a balanced to ground, BUT... I'm not sure if it's going to work fine with line level signal, especially for long term use.

Such shorting, if done on a higher impedance mic level signal won't likely affect anything. I've seen people do that on line level signal, but I'm not sure if they're aware about any long term effects that might exist.

That leads to another question: What would happen if I do that at a line level balanced signal? Does the short between the negative signal to the ground will result in any sort of equipment failures or damages in the long run? (Forget about any short term effects such as noise issues).


texts: 4 bit binary full adders, bcd and seven segment displays

texts:
I'm having fun with some 74LS283[1] 4 bit binary adders but I am having trouble working out how I should convert the output to a decimal which could be used to drive two 7 segement displays which are powered by 74LS47s.

The adder outputs correctly 0001 + 0010 = 0011 but I'm not sure of the best way to approach converting this to BCD to drive my displays. Could someone tell me the best approach for this?

Thanks,

Andrew

[1] http://www.ti.com/lit/ds/symlink/sn74ls283.pdf

[2] http://www.ti.com/lit/ds/symlink/sn74ls47.pdf


texts: Why don't large Decoupling/Bypass Caps use current limiting resistors?

texts:
I use large bypass/decoupling caps(10-470uf) across power lines and ICs and I never place a current limiting resistor in series with them. I was wondering if over time, that would damage the device because of the huge current demands from charging (especially if the power is being turned on and off several times an hour)?

Also, are bleed resistors recommended in designs where several large (10-470uf) caps are used and where power is being turned on and off several times an hour?


texts: Cheapest dummy load? 450w, 15V, 30A, only for a few seconds

texts:
What is the cheapest and simplest way to dummy load 450w, 15V, 30A, only for a few seconds?

I would like to measure the max output capability of an MPPT charger controller, basically as a "all losses included" way of measuring actual solar panel maximum power capability.

The theoretical maximum output is 440w. In reality, the solar panels probably won't output more than 350-400w on the sunniest day.

The controller has a load-side shunt, allowing me to measure current easily.

I'm planning to use a MOSFET to short-circuit the load-side through a dummy load. The resistance needs to be very low to allow 30A to flow at 14.4V. I've considered using a ceramic heater, but they are typically dimensioned to have a resistance that restricts current to their dissipation-capability under continuous load, to prevent overheating.
I could buy a heater dimensioned at 500w, but it would probably take up a lot of space.
Since it only needs to operate for a few seconds, the concern is different.


texts: Why is Ic constant in the plot of Vce vs Ic in a common emitter NPN transistor (in active region)?

texts:
In this plot, when \$V_{ce}\$ increases in the active region, shouldn't \$I_c\$ also increase as more electrons are getting diffused into the collector?

Then, why is it that for a large range of \$V_{ce}\$ , \$I_c\$ doesn't seem to change at all?


texts:
I have a speed control circuit for a 230V AC motor. It has a BTA16 TRIAC for phase control and it is driven by an optocoupler MOC3021. The trigger signal is coming from a PIC16F676 microcontroller. The trigger signal is given according to an input event to the microcontroller.

The problem is the TRIAC is getting switched on automatically sometimes when I turn on mains. I found that is because somehow the TRIAC driver gets the drive voltage from the microcontroller. But it is not happening always and I cannot change anything in hardware. I also tried in software not to trigger the TRIAC for 2 seconds from power on but still the problem persists. Is there anything that I should try to get around this problem?


texts: combine 2 x 5A circuits from a single phase 240V mainline

texts:
I have had no formal electrical engineering education, my comments maybe incorrect, if so please advice.

I live in a Condominium the main single phase drop is routed via a Main Breaker called Safe-T-Cut that provides a selection between Direct, 25A, 15A, 5A (currently its set to 5A) this is connected to a breaker box with a Main breaker is 10A and individual circuits are at 5A

With some parttime hobby my electrical requirement has gone pass the individual circuit limit of 5A, biggest challenge is that the 7 circuits in the house are divide as such

all electrical outlets
Aircondition 1
Aircon 2
Aircon 3
Cooker
Lights
Hot water

(all electrical outlets in 3 rooms are all in one circuit, this is a design which I am foreign to)

I am looking at alternatives, the easiest would be to take another outlet from one of the under utilized of the remaining 6.

I was also wondering If I am doing so would it be beneficial / possible to take both 5A circuits (there will not be other appliances on it)

is there some device that can be used for such composition? where input would be 5A capable line and output is a near 10A (I would limit it to around 8.5A so that I am not reaching the main breaker limit, and adjust safety-cut to 15A)

is it a stabilizer what I would be needing?

UPDATE: each unit in the condominium has a direct connect to the main supply from the provider with a main switch at 30A, condomeniums are individually owned and maintained. Internal wiring at the unit is for the owner of each unit.

I am more interested in a academic aspect of my question as an understanding of it. i read in a 3 phase system where each phase is 60 degrees apart the combination of the phases appears to be somewhat trivial from a high level design and understanding.

so in my case since two circuits of 5A each is coming from the same phase maybe i would require a phase shifter first? (haven't googled that yet, just thought of it as i was writing this sentence)


texts: Why do I2C lines use open drain driver instead of tri-state drivers?

texts:
My understanding is that I2C lines use pull-up resistors to passively pull up the bus to logic high because the drivers used on the bus are active drivers, namely open collector/open-drain. Since open collector/open-drain drivers can drive the line low but not high, the issue of bus contention is mitigated.

My question is however, why does the I2C protocol use these drivers as opposed to tri-state drivers? If you have multiple tri-state output drivers connected to the same bus, as long as the enable signals for the tri-states are mutually exclusive, shouldn't we be able to take care of bus contention and also achieve faster rise times in comparison to open-collector/open-drain topologies?


texts: Some parameters on the datasheet are a little bit confusing. What does the datasheet mean?


texts:
I've read some very good threads here on power and heat dissipation in VRs and believe I understand (most of) it.  I have a 5V circuit operating a 12V relay (nominal operating current of 53mA), an ATtiny85, a couple BJTs, and a few passive components. I measure 54mA across the circuit.  I didn't give much thought to VR-generated heat but did the math nonetheless.

TO-92  The input voltage is 12.8V so the power consumed is 7.8V * 0.054A = 421mW. With a TO-92 case and Rja(ambient) of 157.4C/W, I get a 66C temp rise and when coupled with an ambient temp of 25C results in 91C if I understand correctly.  Although it's not approaching the max junction temp of 125C, it's quite hot.  Other LDO VRs (e.g., 7805) generated even more heat.  I could reduce the heat with a series resistor but that can create other problems according to other threads I've read.

TO-220  The TO-220 has a Rja of 23.3 yielding a total temp (including ambient air) of 35C.  I have it mounted horizontally using the PCB as a heat sink.  More PCB space required but much lower temp.

Have I calculated the temperatures correctly?  The relay is not energized 100% of the time (closer to 75% worst case) but the circuit is in a small enclosed ABS box.  Is it fair to say that a TO-92 would be a poor choice for this circuit?  Anything I haven't considered?

Relay datasheet

TO-92 datasheet

TO-220 datasheet


texts: Arduino: why does Serial.println(int, HEX) display 4 bytes?

texts:
An int is 2 bytes but Serial.print with HEX or BIN formatting outputs 4 bytes:

  int x = 0x9876;
  Serial.println(x, HEX);
  // output is FFFF9876

Why?

(and what is a good way to print out only 2 bytes)


texts:
I built metal detector called MiniPulse Plus (it is a kit. comes with calibration instructions but says nothing about the coil, except that it should be between 300-500uH). A circuit sends a pulse into the coil (58uS width, at 1KHz), it waits for coil's magnetic field to decay, then it uses the same coil to listen for signals coming back from the ground (generated by possible buried metal items). A 470ohm resistor mounted on the coil help its magnetic field to fade quicker. The resistance of the coil in my case is 3 ohm, 24 turns, gauge 0.45, diameter 23cm, enamel Cu wire.

I want to know what are the most important parameters for the coil.

For example, the size of the coil (diameter). Will a 20cm coil be better than a 10cm coil (while both have 400uH).
Since the coil operates at only 1KHz, does the wire gauge matter?
Should I use wire with thick insulation? (some recommend speaker wire because the distance between the cooper wire will be big, decreasing this way coil's capacity)


texts: Attaching a decoupling capacitor to PCB. What should go where?

texts:
I'm nearly finished with the recreation of a PCB that'll be used in creating a modchip for my PlayStation 1 that is gathering dust. I'm basing it off a modchip I bought last year but accidentally threw out while cleaning and contacting the seller to purchase a new one now is difficult.

Right now I have the capacitor connecting to the pads that are connected to where pin1(VDD) and pin8(VSS) of a PIC12F508-I/SN will be mounted. I have absolutely no idea if this is correct and if it is not where should I be connecting it to?


texts: controlling singing-dancing santa with Arduino

texts:
We have a 3 AA batteries-powered Santa figure (which sings and dances :P ) we want to control from an Arduino Uno board.

Being quite noob to electronics and Arduino, we have been able so far to light up a set of Xmas AC-connected lights using Arduino and a relay.

The complimentary Santa figure is giving more problems:
We have connected the Arduino board's GND pin to the negative pole of the batteries' case and a digital output pin (pin 10) to the switch of the figure (which is always switched on, to let current turn the figure on).

But the most we could get was a bit of led blinking in the figure, as if the current was not being constantly held.

So is there any standard layout to connect the figure to the Arduino board or do we have to connect the pins in a different way?


texts: What is the difference between the rated and withstand Voltage?

texts:
In case of a common mode choke,

I have seen in two different component manufacturers these two terms:

rated voltage
withstand voltage

Are they the same? How are they related?