texts: Three 1 phases vs one 3 phase power cost

texts:
Case1:

If I have three single phase connections with each having its own single phase energy meters And I connect 1kw load on each of these phase continuosly 24/7 for a month.

Case2:

Now next month instead of three single phase connections I opt for a single three phase connection with a 3 phase energy meter and I connect the same single phase loads (1kw) on each of the 3 phases 24/7 for a month.

At the end of the month will by electricity bill in Case 2 be lower than that of Case 1 and why?

P.S. This is not a homework question, I'm trying to understand 3 phase power vs 1 phase power.

Edit:

So single phase loads don't seem to have an advantage in a 3 phase power supply system.

Now how about a single phase 2kW motor running 24/7 on a single phase supply for a month and then the next month i use a  2kw 3phase motor and run it 24/7 on a three phase supply. In this case surely the 3phase system will have an advantage of lower consumption (lower electricity bill). Isn't it?


texts: Design considerations for a high voltage boost converter?

texts:
I'm trying to figure out the best method to get around 200V @ 15mA from a LiPo battery, and had a few questions.

Should I be converting down to some voltage (eg. my microcontroller supply rail) with a buck converter and then boosting up?
Should I go with a boost converter or a flyback converter?
What good off the shelf ICs exist for this type of design?
What kind of losses would I expect in conversion?

My application is a wearable device, and these are the design concerns I'm juggling:

Minimize power dissipation from losses (do I need heatsinking? assuming 75% efficiency, I'd have to drop 750mW somewhere)
Needs to be small form factor (how much will this decrease efficiency?)
How should I implement short circuit protection/current limiting?

Sorry if I missed anything and thanks for the help.


texts:
I am trying to send data (not Ethernet data, but sFPDP data) from a PCIe device to a Infiniband device. I know Infiniband sends its data serially vs parallel for PCIe.
If I want to send data from my PCIe device to my Infiniband devices, would it be as simple as just getting a mellanox switch and just routing all the PCIe ports to the one Infiniband port? I know they both use QSFP cages. Seems like I would just need to make sure the QSFP cables are HDR or FDR compliant?


texts:
this is my first attempt ever at building an H bridge for brushed DC motors. The board is controlled externally with an Arduino that sends the EN and PWM signals. I also need to measure the motor current to do torque/current control.
For current sensing I decided to adopt low-side sensing with shunt resistor (10mOhm) and op-amp in non-inverting configuration to amplify the voltage drop.
The bridge-part of the board works quite as expected, I'm able to move a dc motor in both directions with varying duty cycle, but I have 2 problems:

Not crucial, but I noticed that the Green LED (I put it in order to signal that the board is powered) turns on even when the VBATT is disconnected if I apply the EN signal from the Arduino, and I really can't understand why.

Current sensing is not working. When I just power the circuit with a DC power supply I have 0.08A drawn by the op-amp. If I remove the IC, the current goes to 0. If I apply PWM, at 0.27A drawn from the supply (of which 0.19A = 0.27A-0.08A are due to the motor) I have:

1.9mV across the shunt resistor (which is reasonable, at 0.19A * 10mOhm)
1.9mV on the opamp non inverting input (of course)
0.42V on the opamp inverting input (?). This value is more or less fixed varying duty cycle.
10.63V on opamp out (?). This value is more or less fixed varying duty cycle.

Moreover, the op-amp gets rather hot in few seconds.
I already double checked the pcb for shorts or wrong connections.
To measure I'm using a multimeter since at the moment I don't have an oscilloscope at hand, planning on buying one.
So the questions are:

Why is the green LED turning ON when it is not supposed to
Why is the op-amp amplifier not working as expected
If possible, some recommendations on better ways/components for current sensing.

PS. At the moment I considered only through hole components for ease of soldering, but for future versions I will probably consider also SMD components.


texts: Solving an ideal opamp-circuit leads to a contradiction

texts:
Well, I am trying to analyze the following circuit:

simulate this circuit – Schematic created using CircuitLab

When I use and apply KCL, I can write the following set of equations:

$$
\begin{cases}
\text{I}_1+\text{I}_4=\text{I}_2+\text{I}_3\\
\\
\text{I}_1=\text{I}_2\\
\\
\text{I}_3+\text{I}_5=0\\
\\
\text{I}_6=\text{I}_4+\text{I}_5
\end{cases}\tag1
$$

When I use and apply Ohm's law, I can write the following set of equations:

$$
\begin{cases}
\text{I}_1=\frac{\text{V}_\text{x}-\text{V}_1}{\text{R}_1}\\
\\
\text{I}_2=\frac{\text{V}_1}{\text{R}_2}\\
\\
\text{I}_3=\frac{\text{V}_1-\text{V}_2}{\text{R}_3}\\
\\
\text{I}_4=\frac{\text{V}_3-\text{V}_1}{\text{R}_4}\\
\\
\text{I}_5=\frac{\text{V}_3-\text{V}_2}{\text{R}_5}
\end{cases}\tag2
$$

Substitute \$(2)\$ into \$(1)\$, in order to get:

$$
\begin{cases}
\frac{\text{V}_\text{x}-\text{V}_1}{\text{R}_1}+\frac{\text{V}_3-\text{V}_1}{\text{R}_4}=\frac{\text{V}_1}{\text{R}_2}+\frac{\text{V}_1-\text{V}_2}{\text{R}_3}\\
\\
\frac{\text{V}_\text{x}-\text{V}_1}{\text{R}_1}=\frac{\text{V}_1}{\text{R}_2}\\
\\
\frac{\text{V}_1-\text{V}_2}{\text{R}_3}+\frac{\text{V}_3-\text{V}_2}{\text{R}_5}=0\\
\\
\text{I}_6=\frac{\text{V}_3-\text{V}_1}{\text{R}_4}+\frac{\text{V}_3-\text{V}_2}{\text{R}_5}
\end{cases}\tag3
$$

Now, I have an ideal opamp, so I know that \$\text{V}_+=\text{V}_-=\text{V}_2=0\$. So I can rewrite equation \$(3)\$ as follows:

$$
\begin{cases}
\frac{\text{V}_\text{x}-\text{V}_1}{\text{R}_1}+\frac{\text{V}_3-\text{V}_1}{\text{R}_4}=\frac{\text{V}_1}{\text{R}_2}+\frac{\text{V}_1}{\text{R}_3}\\
\\
\frac{\text{V}_\text{x}-\text{V}_1}{\text{R}_1}=\frac{\text{V}_1}{\text{R}_2}\\
\\
\frac{\text{V}_1}{\text{R}_3}+\frac{\text{V}_3}{\text{R}_5}=0\\
\\
\text{I}_6=\frac{\text{V}_3-\text{V}_1}{\text{R}_4}+\frac{\text{V}_3}{\text{R}_5}
\end{cases}\tag4
$$

  But this system contains a contradiction so it is impossible to solve. Where is my mistake?


texts: How does the QTR-8RC capacitor charging works?

texts:
I would like to understand how does work the polulu Reflectance Sensor internally. I can make it work but I would like to know what is happening electrically.

http://www.pololu.com/catalog/product/961

This is the schema (focus on the bottom left part, the squared area).

http://a.pololu-files.com/picture/0J629.650.png?7975fd7128a0eb0861e253d9c7f439c0

An these are the steps to read a value:

Turn on IR LEDs (optional)
Set the I/O line to an output and drive it high
Allow at least 10 us for the 10 nF capacitor to charge
Make the I/O line an input (high impedance)
Measure the time for the capacitor to discharge by waiting for the
I/O line to go low
Turn off IR LEDs (optional)

I guess initially the 10 nF capacitor is charged. Why does it say in step 3 to charge it again. Do you charge "the other side" of the capacitor?.


texts: Compensate centrifugal force in accelerometer measurements

texts:
I'm working on a project that includes counting the revolutions of a cylinder connected to an engine. This engine runs at a minimum of 5 revolution per second and a maximum of 9 revolution per second.

A device is fixed and mounted on this cylinder.
The device integrates a lis2dh12 accelerometer which is mounted so that the z axis intersects the rotational axis. This video will give you a clearer idea of the situation (the device is the one in red):

Video here

For the calculation of the revolutions, my algorithm takes the data of the accelerometer (set to 100hz) of the weight force and calculates the angle of inclination (pitch) as follows: atan2(y,z)

Then, I convert it to degrees and use 4 flags to understand when the device goes from 0-90, then 90-180, then 180-270 and finally 270-360, so the revolution counter is increased.

This worked for the rotations done with the device in hand, but then I bought a motor to perform the tests and the approach no longer worked: not having taken into account the centrifugal force (which exceeds that weight) the calculation of the pitch no longer works.

This is the engine used for the tests:

Motor picture with dimensions

The engine is blocked by a wooden system that attenuates vibrations as much as possible. With a potentiometer, I adjust the speed of rotation of the motor between 3 rpm and up.

NOTE: In this case the mass of the device is very significant because it is large compared to the complete system, while in the final case (situation of the video) the device has a very small mass compared to the complete system. I do not know if mounting the device on the real roller the calculation of the pitch would be done correctly and at the moment I can not perform the test, but hypothetically I believe that the problem will occur in that case, as the centrifugal force is proportional to the radius (in rotary motion).

Am I saying right?

My question then: is it possible to compensate the centrifugal forces, calculating their intensity for each sample of the accelerometer (every 10 ms) and subtracting this force to z, in order to reuse the old approach of pitch calculation?

The data acquired by the accelerometer while the small engine was running at (about) 5 revolutions per second shows that the value of z had assumed a maximum of -0.828 g and a minimum of -2.484 g.

Increasing the speed, however, also exceeds -5 g.

Unfortunately, the device is not equipped with a gyroscope and no hardware can be added to it, so I would like to find a way to calculate the number of revolution made using only data from the accelerometer.

Thanks in advance


texts:
I am wondering if there is a more practical way to provide optical isolation for a BNC trigger. I am currently using the following: https://www.eagleharbortech.com/product-categories/fiber-optic-isolation/

These are several hundred dollars each and I am thinking a cheaper option or other work-around should be available.


texts: Is a darlington constructed with 2 BJTs fully equivalent to an integrated one? The reason I'm asking is that there are obvious differences, like the collectors which are separated, and also the emitter of one BJT and the base of the other.


texts: Connecting different DC grounds to a single motor driver IC

texts: I'm building a simple robot and have a L293D motor controller (details here and diagram below on the left).  It takes two positive input voltages - one for powering the IC and one for driving the motors (in my case it will be +5V and +9V).  However, it has four grounds and doesn't give any indication how those should be matched up with each power source.  Does it not matter what's connected to what with regards to the grounds? I'm concerned that if I wire the ground for 5V to the wrong pin, that there will be a mismatch and mess something up.  Sorry if this is a noob question - I don't have EE background.


texts: SAMD controlling BLDC resets during high current spike; EMI problem?

texts:
I have been making a brushless DC motor controller that is controlled through an ATSAMD21E16L and a MIC4609 mosfet driver. At low average currents of 2A or so, I drive the motor just fine, but when I give the motor a high current spike, like when trying to start it quickly to a high power, or increase the drive current from an already high current, the microcontroller will reset.

I currently have a setup where I drive the motor with 17V and a start-up duty cycle of about 33%, which causes the reset to happen reliably and instantly. I have used this reliability to probe all the pins connected to the microcontroller for anything suspicious, but everything appears normal. The reset pin has a small transient from 3.3V to 3.2V. The coil sense pins see the transients reaching no more than 1.5V. The current sense pin reaches no more than about 2V. The single-wire-debug clock and io pins also change only marginally. The PWM and enable values going to the mosfet driver also have small transients.

Basically, I can't find anything on my scope that goes at all out of spec, and yet the microcontroller resets reliably like this. I also have a separate board built up the same way with the same problem.

Since there is a fair amount of protection between the high current and voltage stuff driving the motor and the microntroller, I am starting to wonder if it is possible that EMI is somehow reaching inside the microcontroller to reset it? I really have no clue what is going on.

I tried adding a 100nF cap from RESET to GND, too, but this made no difference.

Any ideas about what may be going on or how to fix it is much appreciated!

EDIT: There is a 330uF electrolytic on +V_MOTOR (using the GND pad shown on the front render below). The motor power and ground connections are directly on the pads shown in this front render view. My hope is that the short low-impedance connections (aided by some extra copper wire on those strips) means the large motor currents have a short enough path to not effect the rest of the circuit too much.

I also don't have any interrupts enabled.

The logic power is a completely different power source than the motor voltage. The motor voltage now is from a bench power supply and the logic supply is from an Arduino.

Shorting RESET to +3.3V also did not help.

Conclusion: Changing the 4.7 ohm high side gate resistors to 100 ohm causes the resets to happen only half the time under my testing setup. So while I don't know exactly how the EMI is affecting the microcontroller, I do know that reducing the startup transients is helping.


texts: Spikes, surges and noise sources in LTSpice

texts:
I am attempting to simulate a DC-DC power supply in LTSpice (using LT3748, 48V in, 5V 3A out).

There is concern about the amount of noise that will be on the 48V input rail, and so we want to simulate with a noisy input (exact figures on the noise levels are also part of my research, but that will be a different question).

To simulate the noise on the power rail I started with something similar to the answer given to this question:
How do you simulate voltage noise with LTSpice?
Using two voltage sources to give the power, separated from each other with resistors:

This then gives a noisy output based on what SIG and NOISE are set to. My question is; if I know what I want to have on the power rail, how do I set the voltages of NOISE to give me the spike etc that I want? The current draw will clearly play a part, but that is part of what I'm trying to measure. Is there a way to work out what my voltage spikes on V2 should be to get a 200V surge spike on the IN rail based on the value of R9 and R8?

I should add that the NOISE simulation in LTSpice is not really what I am after, I am looking more at surges and spike than noise. There is also an issue with the model of LT3748 (and error about it being time dependant is raised), and so the voltages on OUT are not correctly modelled.

(While this is an isolated supply, I haven't isolated the grounds on either side just to make it that bit quicker to draw).

EDIT: I realise that when I've been saying "noise", that has been wrong. I should have used "surges" and "transients", as they are a better description of what I'm interested in. So the question would be better phrased "how do I put a surge onto my input rail?". With that as the question, PlasmaHH probably has a good answer; putting two supplies in series with one another so that my stable 48V has the pulses put on top of it.


texts: Why are watts used as a measurement for some appliances?

texts:
Why do some appliances tout watts and some others advertise volts. I know watts is a measurement of volts*current but looking at just watts alone, what does that tell us about the appliance? Can't volts be low and current be high to get the same amount of power in watts?

Why is the watts measurement necessary is what I'm really trying to ask. Why not just provide volts and current?

Here's a drill advertising volts.

Here's a juicer advertising watts.


texts: Multiple MOSFET based AC switching circuits on the same supply

texts:
I am trying to build a MOSFET based AC switching circuit, with multiple switching circuits running on the same DC power supply. Each switching circuit is basically an expanded solid state relay.

The MOSFETs are switching 240V 50Hz AC (UK Mains) at ~300mA (though the design should take up to 4A in theory).

Each switching circuit on it's own works exactly as intended but when placed together on the same +5/GND bus each circuit interacts with & partially activates the others.

My current theory is that some transient voltage is making it back through the circuit somewhere to the gates of MOSFETs that are meant to be off.

The best I can describe the symptom is that when switching circuit A is 'on' and switching circuit 'B' is off, the load connected to the switched live on circuit 'B' buzzes at 50Hz, I assume getting a half wave of AC power. One of the MOSFETs in circuit B also gets extremely hot implying flow either backwards through the diode or through the gate.

I've included the circuit diagram I'm working with, the opto isolators are controlled by an IC but I've simplified that side of the circuit to a connector as I've powered the optos with other means and still had the same problem.

Is there an obvious solution I'm missing? I feel like I'm doing something stupid. Any ideas how I could better isolate the gates from each other?

Some clarification of the circuit if you need:

AC Live is attached to pin 1 of both P1 and P2
Each switched live is attached to pin 2 of P1 and P2 seperately
The dashed line is simply to clarify where the low voltage control circuit is isolated from the high voltage switching circuits.
U1 is a 5V DC-DC isolator (ROE-0505S)
The diodes D1 and D2 are my attempt to stop 240V mains making it from one circuit to another through the shared ground connection, removing them or replacing them with a large resistor makes no difference to the symptoms.


texts:
I am using Olson square 1 W LEDs, and I am wondering do I need to dissipate heat through thermal pads and how should I connect the thermal pads(their size and are they connected to ground?)
Here is the datasheet recommended footprint:
.


texts:
So, I was annoyed that my Yagi antenna was enclosed in a plastic-tube, which lets it roll around and fall off the table occasionally, but without its enclosure the elements hooked in anywhere. So I wondered, since the material (I assume it's PVC) is radio-transparent anyways: Couldn't the antenna be enclosed in other shapes as well - as long as they are radio-transparent?

Note: The antenna I'm talking about is just a simple 19 Element (17 Directors) Yagi antenna for 2.442 GHz home Wi-Fi.

Basically my questions are:

Is it ok to completely enclose the elements themselves - or do they have to have air (or any free space) around them?
Is the boom required to be at the center?
Does the boom actually have any effect when it's radio-transparent and non-conductive anyways?
Would it affect the Antennas performance, if there were two (non conductive) booms, holding the elements with their edges?

I just wondered about this, because I remembered my physics teacher telling us (decades ago), when frequencies are involved, things vibrate/oscillate. A tight enclosure might hinder this eventually.

I have drawn (sorry for my rather poor paint-skills) two designs, which I would like to try out.

This first design would enclose all elements in pockets, to prevent them from moving and possibly even corrosion if it's airtight.

This ladder-type design was just an idea to save some PLA material first, with just the benefits of saving space and preventing the elements from hooking in anywhere.

I know one could probably simply slide the original Yagi inside some sort of flat plastic sleeve - keeping its boom, and keeping the elements "free". But such projects simply trigger me ^^ - and the antenna that I bought is manufactured rather... "creative"... so I'd like to rebuild this whole thing anyways.


texts:
I was just trying to make a passive cavity resonator based listening device just the same way as Leon Theremin did (the great seal bug). I know that I am to use metallized mylar film as the diaphargm, and I am aware that the cavity dimensions are frequency based.

So what I do not know is how to calculate the cavity dimensions at 400MHz and what is to be the size of the Tuning post stationed in the center of the cavity, and the monopole antenna would be transmitting the harmonics.

The cavity resonator is energized remotely by an RF transmitter @ 400MHz, 17dB.


texts:
I have created a very simple circuit using arduino, in which I have 4 switches used to control the lamp ON/OFF as shown in the below schematic.

simulate this circuit – Schematic created using CircuitLab

Here is the program written in Arduino IDE:

int switch1 = 8;
int switch2 = 9;
int switch3 = 10;
int switch4 = 11;
int outputPin = 12;

void setup()
{
    pinMode(switch1, INPUT);
    pinMode(switch2, INPUT);
    pinMode(switch3, INPUT);
    pinMode(switch4, INPUT);
    pinMode(outputPin, OUTPUT);
}

void loop()
{
    if(digitalRead(switch2) || digitalRead(switch4))
    {
        digitalWrite(outputPin, HIGH);
    }

    if(digitalRead(switch1) && digitalRead(switch2))
    {
        digitalWrite(outputPin, LOW);
    }
}

Basically, my original project has a Motor instead of Lamp, & the four switches shown above are the two pairs of switches in each tank. i.e. I have two tanks and two switches in each tank. 1 switch at the bottom of the tank to measure the water level. If tank is empty then this switch will be open. Another switch at the top of the tank, which will verify that if the tank is full or not and accordingly it will turn on/off the valve which is not shown in the below diagrams, as I think it's not necessary now.

The above circuit works perfectly, but now I want to complete the same circuit using logic gates, instead of arduino. I have tried the circuit shown in below schematic, but I was not successful as I am new to electronics & Logic gates.

simulate this circuit

I want to use logic gates instead of Arduino to bring down the cost.

Thanks for any help.


texts: Cheap way to communicate between microcontrollers with rf

texts:
Firstly I apologise if this has been answered, I searched and found nothing specific to my question.

Background:

I'm getting married! I would like to create some light boxes for the table names using fibre optics in the shape of constellations (simple enough), I would like to control the LEDs remotely via RF, react to the beat of the music or something similar (not decided yet).

What is the simplest but budget friendly way to make 4-5 Adafruit trinkets (or similar) keep in sync or if I get enough coding time, control independently via a master device (Rpi, Arduino or PC etc)?

I have a handful of the Ebay modules that are about £1 each, terrible things it would seem.  My budget is about £15-£20 per box including any micro controller and other components.  I checked out my usual haunts of Arduino and Raspberry Pi suppliers as well as a good google but found I was flooded by hundreds of products all differing slightly.


texts: Does a reverse-biased P-N junction create quantum noise?

texts: It is my understanding that a highly doped, thin depletion region, reverse-biased P-N junction  at low voltage can cause quantum mechanical tunneling. This (or sometimes avalanche breakdown) is used in some hardware random number generators. However, is the noise created in the junction truly quantum mechanically random, or is it chaotic but deterministic?


texts:
I'm looking through the following app note http://www.ti.com/lit/ug/slau520/slau520.pdf

If we look at page 19 of that pdf, there's the following histogram.

I'm trying to work backwards to see what voltage they received for the various bins, but I'm not sure if my values are correct.

According to their design,
Vref = 1.64
Rzero = 120
PGA = 128

The resolution or 1LSB would be \${Vref \over PGA} \over 2^{23} - 1 \$ or ~ 1.52nV

1.52nV * any of the bins = ~ 12mV.

Which to me, seems way to high for this type of circuit. That would translate into 7 ohms off, which is huge in this case. The ideal value we should be seeing is somewhere in the vicinity of 0 because of the Rzero set to 120ohm, it would pretty much cancel the 120 ohm resistor they are using for an RTD.

The only thing I can think of that would make this data make sense, is, if they offset the data by 2^23 -1 to ensure that all bins are positive. I couldn't find anything in any of the pages that would say that this is what they did.

Is my thinking correct that they shifted everything so rather than having a range of +/- 8M, its now just 0 to 16M ?


texts: How can I modify single-cycle MIPS processor to implement jal command?

texts:
Hello Stack exchange community
I was wondering which modification should I have to make in order to enable single-cycle MIPS processor to run a jal(jump and link) command?
My most pressing confusion relating to this command is that I can't figure out a way to derive the address of the next instruction and how to connect it to PC counter.
I would really appreciate if anyone can provide me with some insights concerning this issue.


texts:
I own a car audio amplifier which uses a DC to DC converter having a MOSFET of the type of FP50N06. However, after prolonged use, the three of the positive rail switching MOSFET cooked and smoked.

I was trying to replace that MOSFET, however, the FP50N06 is not available in my location so I had decided to replace it by readily available IRFZ44N MOSFET.

Here is the question: Can I replace it without major consequences? Thank you for your answer.

Based on your suggestions, here are the datasheets for the two MOSFET's:

FP50N06
IRFZ44N

Don't care about their difference in power. :)


texts:
I am replacing some igbt transistors on a circuit board from my Samsung TV.  While de-soldering one of the 4 components one of the traces from the gate lead fell off.
I am looking for the best practice to solder the gate of the transistor into the broken trace.
Option 1 would be to sand or use a solvent to remove the remaining insulation from the trace.  This would expose enough area for me to solder the transistor gate.
Option 2 would be to use a small wire and solder onto one side of the surface mount resistor to connect the gate.
The black areas around the board are from some insulation that was glued to the board (not heat and burn marks).
I am open to suggestions.

Update:

Update:  It took 2 weeks to have the IGBT transistors shipped from China.  I used a piece of 26 AWG wire to replace the lost trace.


texts: Calculating resistance for metal layer from LEF File

texts:
I have a .LEF File which has various metals description and their parasitics information. I am trying to calculate R. It is specified as  RPERSQ = 0.278.
In the File description it is written as Units of Resistance is Ohms and also resistancePrecision       = 1000000.
I think that RPERSQ = 0.278 is not ohms and it has something to calculate with the resistancePrecision.
Can anyone please help me on this.

Thanks,
Ramu


texts:
I've managed to blow a capacitor while doing maintenance on my 1967 electric organ. It's a 80uf 25V. I've done some searching and found that I can replace it with one that has a higher voltage rating but the same farad value. Is there anything else that I need to know before I buy a replacement? I've read some things about ripple current and resistance? The numbers on the capacitor are:
B41283-s5806-z2
80uf 25V
A 0-507-24
W9


texts: How can I power the blue LEDs separetely on this aquarium light?

texts:
I have a Beamswork LED aquarium light like this. It has a 3 way switch:

All LEDs off
Blue LEDs on only
White AND blue LEDs on

It has a single mains power plug.

What I want to do is make it have two mains wall plugs. I want one to power the blue LEDs all the time, always on.

I want the 2nd plug to power the white LEDs only, and this will be plugged into a plug timer like this, so the white LEDs will independently go on and off by time, while the blues stay on (because that will be plugged in separately - I hope).

I opened the cover and found this:

The 2 black wires connected to the brown PCB is where the mains adapter plugs into. Then there are 3 blue-covered connectors which are connected to the 3 way switch. I don't know which ones control which colour as I didn't test it plugged in, but I think the white one is white LED, the middle one is power, the one I'm holding had a blue wire so probably blue LED. Is there a way to connect a 2nd mains plug to that blue LED connector (if it is that) so it powers separately? Drilling through the plastic to get a wire in is fine, but I don't know how what electric connectors or connections I need.

I don't know much about electrics, first-time project! Thanks.

EDIT: This is is the spec of the adapter:

And here I have done a few tests:

Wire 1 controls the "blue ONLY" LEDs from the switch
Wire 2 comes from the mains adapter
Wire 3 controls the "white AND blue" LEDs from the switch
Wire 4 goes to a metal thing on the LED board saying "Ground"

If I disconnect wire 1 and put the switch into the "blue only" position, the blue LEDs don't come on. But if I put the switch into the "all on" position, the white AND blue LEDs do come on.

If I disconnect wire 3 and put the switch into the "blue only" position, the blue LEDs do come on. But if I put the switch into the "all on" position, the white AND blue LEDs don't come on.

I'm thinking of getting a second power adapter and a male connector to fit directly to wire 1 (so disconnecting wire 1 from the original switch above), so I can keep the blue LEDs always on. But I'm worried, since wire 3 turns on both the blue and white LEDs (even if wire 1 is disconnected), will this make the blue LEDs get double power and cause a problem?

My goal in the end is to have the blue LEDs always on (because they will be powered separately from a new mains adapter) 24 hours a day. And the white LEDS (which also turn on the blue LEDs too) to be plugged into a plug timer and turn off at certain times of the day. Any suggestions?


texts: Need an extra pin to control my driver board

texts: I've been searching for a way to add an extra pin to a driver board. The MCU board that i'm using only has 8 pins on the left side and i'm already using all of them. 2 are for powering the driver and the other 6 are analog inputs. I need only one more control which has to be a digital output. Is there a way to put some kind of multiplexer on the driver and use the MCU pins that i'm using as analog but as digital outputs to control the mux outputs? I know it is kinda strange what i'm asking, but i have to have a solution for the lack of MCU pins.


texts:
I simulated this circuit in TINA-TI. However I could not understand the output waveform for the negative half of the cycle.

Waveform:
Green- Voltage across C2 (10 u cap)
Brown- Voltage across C1 (1 u cap)
Yello- the input square wave

For the first half at t=0, both the capacitors will charge instantaneously. Of course the capacitor with higher capacitance will charge to a lower voltage as compared to the smaller capacitor.

For t>0, C1 starts to discharge through the resistor R1 which means C2 must start charging so as to maintain an over all voltage of 1V at the input terminal.

However, in the negative half of the cycle the voltage for C2 remains positive and for C1 it drops to less than -1 volts. Why is the voltage of C2 not negative (similar to C1)? Why isn't voltage across C1 more than -1 volt and across C2 <0 such that VC1 + VC2 = -1 volt?


texts: Connecting arduino pro mini (3.3v) to wall wart via dc jack

texts:
So I've built this circuit on my breadboard with an arduino uno and largely have it working.
http://makezine.com/projects/make-34/the-dryer-messenger/

Now I'm trying to miniaturize it by using a pro mini; however, I keep blowing them up. I've confirmed that the soldering is fine and there are no shorts on the board since I've powered it up fine with a FTDI friend.

I have 9.2 DCV coming from the wall wart, when I connect the positive to the raw pin and the negative to the ground pin then I get a red flashing light on the arduino, and the wall wart also flashes red.  If I leave it on for about 10 seconds, then it blows up and I see sparks.

A picture of the setup:

The arduino pro mini : http://www.sparkfun.com/tutorials/244

The arduino pro mini schematic : http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Dev/Arduino/Boards/Arduino-Pro-Mini-v13.pdf

The dc plug:
http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Prototyping/18742.pdf

The voltage regulator stage of the arduino pro mini board

Any idea as to what I'm doing wrong?


texts: Serial Programming and I2C port "conflict"

texts:
I'm designing a board in which an Attiny85 is connected to an accelerometer (MPU-6050) via I2C.

The I2C pins are in the ISP bus (SDA/MOSI, SCL/SCK). I wonder what happens to the accelerometer during programming of the MCU?

Are there any best practices I should follow? I considered just adding some solder jumpers, but I wonder if any precaution is even necessary.

Edit:

After finding out this is problematic, I'll try a solution based on Bruce Abbotts answer in another question.


texts:
I want to remove the electronics of a YETOR Remote Control (purchased on Amazon) and remove the two momentary thumb switches that lie underneath the ON/OFF keypad and wire in a Solid State Rely (SSR) to replace each thumb switch.
I was thinking of using an optical SSR switch of some kind.
This will allow me to control the remote control's ON/OFF via an electronic circuit where a momentary voltage of around 6 volts will activate the SSR thus acting like someone pressing a thumb switch. This design will automate a motor being turned on when a mechanical lever position closes a mechanical microswitch for about 250 milliseconds; thus allowing the 6-volt circuit to be energized for that time.
Is my reasoning sound and practical? If so, any recommendations as to which SSR to use?


texts: Very long distance Ethernet connection for internet and other data (2000 feet)

texts:
I am building a house. It's located about 2000 feet away from the nearest internet cable.  I had to run our electrical service underground the whole way, and have already installed a conduit for internet/phone cables from end to end with pull points every 1000 feet.
My question is: what's a cost-effective way to establish a reliable, high-speed Ethernet connection at this distance?  It will be used to provide internet service as well as video/audio feeds and control signals.  I think 100 Mbps each direction would be satisfactory as a target maximum speed for the connection.
We will have electrical power available at both ends of the connection.
I have looked into Ethernet extenders, but the maximum speed seems to drop drastically as the distance increases.
I would love to use fiber, but I can't find an inexpensive termination method.
I don't think wireless is practical because we don't have line-of-sight between the endpoints due to a large area of trees.
A satellite or 4G connection is not suitable due to price, speed, and reliability, plus the need for audio/video/control signals across the distance.
UPDATE 2016:
I installed RG6 gel-filled direct-bury coax cable (in PVC conduit for added protection) and used Ethernet-to-coax extenders (TrendNet TPA-311) and am VERY pleased with the results.  At a cost of $50 or less per device, it's very reasonable cost. Also, RG6 coax, if you shop around, is very cheap.
I am able to achieve 60Mbit internet speed (which is my ISP's maximum offering in my area) and these devices are very stable - no crashes or need to reboot them.  I even installed a T to split the line halfway in order to connect another building to the network.
One very important note: Be sure to install high quality grounded surge protection at EACH termination point.  I used these.  I tried the system without surge protection, and within a week my TPA-311 devices were destroyed.  I disassembled them to diagnose the problem and found several components vaporized due to a high energy event.  Lesson learned.  Since installing surge protection, we've had several large lightning storms and we're still working rock solid.
Other installation notes:

Get a cheap coax crimper and bulk coax terminators.  They are very easy to install. No need for any expensive tools.

For long pulls, a cable lubricant is absolutely essential.  Our first pull of about 800 feet was without lubricant, and I began to doubt we would ever make it.  Subsequent pulls (even longer distances) with lubricant were easy.

Update after 1.5 years - still working perfectly!  Have not needed to replace any components (except a battery in my UPS).  Very pleased with this solution!
Update after 5 years - still working perfectly!


texts: Is a minimum of 1000µF capacitance needed between an lm386's output and a speaker and if so why?

texts:
In this video explaining how to make an audio amplifier, the narrator warns

  Don’t be misled by crappy schematics…with low values like 100 µF.  You want to use at least 1000 µF [between the LM386's output and the speaker] to guarantee good bass with a wide variety of speakers.

However, in the circuit that I made following this video's instructions, replacing a 1000 µF cap with one of lower value resulted in no difference in sound quality which was audible to me.

Is the assertion that a capacitor of 1000 µF or higher is necessary true?  If so, and if the reason is that given in the video of allowing for "good" bass, how does such a capacitance allow for that?  If this is not the reason (or the only reason), what is another?

(I did not test with a wide variety of speakers; are there certain speakers for which the difference between capacitances is more pronounced?)


texts:
Why don't they use different colors of covers for LEDs, like they do with light bulbs instead of making them form differnt semiconductors to have different colors?

In other words, why they don't make all LEDs from one semiconductor and then use LED cases with different colors?


texts: ESC disconnecting battery while BLDC is rotating protection

texts:
I was experimenting with LittleBee-S 30A ESC and the BLDC did not want to stop so I disconnected the battery while BLDC was rotating and after that the ESC voltage regulator got destroyed. The battery is 5S LiPo battery and the BLDC can handle max 20V so I think the problem is that the motor generated over 20V when I disconnected the battery.
Is there a way to protect the ESC from disconnection of battery while BLDC is rotating? Will a 20V zener diode over the voltage regulator suffice?
Another option is to swap the voltage regulator with a one that can handle more than 20V.
I think the voltage regulator is SPX1521

ABSOLUTE MAXIMUM RATINGS
Input Supply Voltage................................................... -20V to
+20V


texts: Board requirements for a chip PCB antenna?

texts:
TL;DR: What are the requirements of chip antennas like this one (without LNA) or this one (with LNA)? I see PCB size specs in the PDF, but I am not sure I understand how the rest has to look.Does this assume that there is a solid uninterrupted ground plane e.g.?

Long version:
To start with, I am a physicist, not an electrical engineer, and I admit that this project is a bit over my head, but that is research ...
Rough assessment of myself: I know what a trace impedance is and I can use an online calculator to calculate one.

I am trying to built a tracker device with GPS (differential, with postprocessing of RAW output), barometric pressure sensors and an IMU, based on a Teensy 3.6. The hardware and software is running, in principle, but I am struggeling with a good GPS antenna solution. It should be as light as possible and have as little footprint as possible. Optimally, The Teensy would dictate the dimensions and everything else would be on the back of the PCB holding the Teensy (grinded down to castellated holes).

I found this product (without LNA) and this one (with LNA), which seems to suit my needs just fine, but I do not fully understand the requirements on the PCB apart from it's physical dimensions. The Antenova Quick Guide seems to imply that the former can be used without a keepout area on the back site (in contrast to the Antenova Sinica) but I don't understand if there has to be a solid groundplane all over the board or something like that (and if that could be just one layer of a 4-layer board, and if yes, which one).

Any help?


texts: Is zero loss turn-off possible for thyristors?

texts:
Consider this very basic circuit:

simulate this circuit – Schematic created using CircuitLab

Don't mind the values - they don't matter, as this question is conceptual.

Imagine that Vcomm is completely controllable, and ideal for the example's sake.

To begin, imagine that SCR1 is conducting. Current is being pushed through SCR1, through Vcap, and back to ground.  During this time, all 4 MOSFETs are off, and Vcomm = 1.1*Vcap.

Then, we want to commutate current away from SCR1 and into the full-bridge.  To do this (assuming current flows in the direction of the arrow), Vcomm will generate a voltage that is about 10% less than Vcap, meanwhile MOSFETs 2 and 3 will be turned on.  This will cause the current to be commutated away from SCR1 and through the full-bridge/inductor.  This will occur at a rate that is inversely proportional to the inductance, and proportional to (Vcomm-Vcap).

The losses through thyristors seem to be a function of di/dt, as well as the quasi-stationary voltage after the current has changed polarity.  My question is this: if, at the instance when the current through the thyristor changes polarity, Vcomm is increased to ~Vcap, so that the voltage across SCR1 is basically zero, will the losses at turn-off also be basically zero?

This way, it seems that the di/dt can be designed to be the thyristors maximum value, without negatively impacting the turn-off losses.

Opinions? I know this is a weird question. Thanks for your time.


texts: Rectifier diode failure not showing on multimeter diode test

texts:
A rectifier diode RM3 failure is not showing on diode test. I get the usual around 600mV and blocking (OL) in the other direction on the multimeter diode test. Also I tried connecting to a 15V supply to see if it is still blocking - no current flows. So according to the meter the diode is good. The output of the rectifier should be around 15V normally.
I desoldered this diode and replaced it with a new one and the circuit rectifies just fine.
So I was wondering what kind diode failure is possible that does not show on the static diode test yet shows under circuit conditions?
Any explaination would be good even an article or book on faults like this.


texts:
I'm making a simple battery-powered project that measures water flow with a liquid flow meter and transmits the value with an nRF24L01+.  The microcontroller I've chosen is a TI MSP430FR2110 (family datasheet), which includes an asynchronous timer (Timer_B) and a low-power sleep mode (LPM4) that disables the CPU and all clocks.

The liquid flow meter comprises a simple magnet and hall effect sensor to output 450 pulses per liter.  From what I've gathered from the family datasheet (Figure 13-1, pg. 385), I'll connect the pulse signal (reduced to DVCC, max) to the TB0CLK pin for counting operation, clear the TBSSEL bits, and set the ID and IDEX dividers to 1.

Here's my high-level plan of operation:

Put MSP430 to sleep while flow meter pulses are incrementing TB0
Wake up microcontroller after, say, 8s (1L/min --> 60 pulses/8s)
Read TB0 value into variable, clear TB0
Send variable with nRF24L01+
Repeat

Question: Is this a reasonable approach?  I've tested most parts in isolation, but would like to make sure I'm not missing big gotchas before I order parts.

TI provides a water meter reference design with more bells and whistles than I care for, but the basic operation seems the same (section 3.2.2, pg. 9).

  The measurement principle uses MSP430 Timer0_A3 as the pulse counter. Timer0_A3 operates without any CPU intervention, allowing the CPU to remain in low-power mode. The CPU then wakes up and read the TA0R register once per second. The TA0R value will be the instantaneous flow.

(Since my application is more for abnormal operation detection (e.g. unexpected flow or lack thereof) I can get away with a longer sleep period to reduce battery consumption.)


texts: How does a three-phase transformer work with phases sharing a common core?

texts:
Google search reveals a lot of pictures of three-phase transformers. Looks like a common setup is to have three pairs of winding and a shared core. The core typically consists of three "bars" in parallel and each pair of windings is wrapped onto its own "bar" and the "bars" are connected on both ends so the core is closed and effectively it is one single core of complex shape and each pair of windings occupies its dedicated place on the core.

-----------  << the two horizontal bars are free
|    |    |
|    |    |  << windings are wrapped onto this vertical bars
|    |    |  << each pair occupies a separate bar
|    |    |
|    |    |
-----------

Now as I see it each phase will induce its own magnetic flux and since each phase is offset by 120 degrees its flux will also be offset and those three fluxes should mix and more or less annihilate each other (full annihilation should happen when all phases are loaded equally) and so the transformer should not output any power on the secondary windings. However three-phase transformers work just fine.

How does a three-phase transformer work with magnetic flux of each phase passing through the common core?


texts: How can I reduce this circuit to a source in series with a single impedance?

texts:
How can I Thevenize the following circuit looking into the out terminal:

I want to deduce this circuit to a source and a single series impedance.

Here what I tried:

\$\frac{R1\cdot R2}{R1+R2}\$ is in series with C1

This becomes \$\sqrt{\frac{R1\cdot R2}{R1+R2}^2 + \frac{1}{\omega C1}^2 }\$

And now \$\sqrt{\frac{R1\cdot R2}{R1+R2}^2 + \frac{1}{\omega C1}^2 }\$ is in parallel with R5

I cannot proceed more. How could this be achieved if mine is wrong as an alternative way?

is the following correct?:
\$\frac{R1\cdot R2}{R1+R2}\$ is in series with C1

\$Z_{thevenin} = \frac
{\sqrt{\frac{R1\cdot R2}{R1+R2}^2 + \frac{1}{\omega C1}^2 } \cdot R5}
{\sqrt{\frac{R1\cdot R2}{R1+R2}^2 + \frac{1}{\omega C1}^2 } + R5}\$

And the Thevenin voltage needed to be found as well.

Vth = V1 * ((|R5+(1/jwc)| // R2)/ (R1 + (|R5+(1/jwc)| // R2))) * R5/|R5+(1/jwc)|


texts:
Would it be possible to send a 5  V "true" signal from the Tx of a UART dongle?  As if it were a digital output?

Here is the UART adapter I purchased.


texts:
I am trying to develop a design for a power supply. At the output of my design is a diode rectifier with a capacitive filter output. I've been told that I should expect to see an ESR of zero or something along those lines in my frequency response, but I'm not quite sure what that typically looks like or what that would look like in my frequency response.

Does the filter create a zero and how can I calculate the location of the zero?  How would I know there is no additional poles added to my response as well? Is there some way I can simulate this to see what it looks like?

I can provide you a general schematic of the rectifier and output capacitor filter (this is the same as my design):


texts: Question on adafruit feather M0 LoRa SPI and LoRa radio

texts:
I am getting readings from CS5463 power monitoring chip using SPI on the feather. I want to transmit these readings onto the LoRa gateway I have setup. I have no problems only transmitting the values.
However when I am trying to transmit and get the power readings simultaneously, I am facing problems.
It seems that LoRa radio also uses the CLK, MOSI and MISO pins which are being used for SPI transactions as well. Could anyone help me with this? I want to read power and transmit simultaneously.


texts: How to calculate duty cycle of a servo motor?

texts:
I have this servo motor and in its specifications only speed and torque is given:
Torque At 4.8V  3.5 kg-cm / 49 oz-in
Torque At 6.0V  4.4 kg-cm / 61 oz-in
Speed At 4.8V   0.25 sec / 60°
Speed At 6.0V   0.22 sec / 60°

How to determine frequency and duty cycle of this motor? I am connecting this motor to 5V pin of a microcontroller.


texts:
So I found an old washing machine and salvaged the motor. However I can't find any information about how to wire it because it has 9 wires coming out.
So 2 of them are speed control = 7 to go.
2 are brushes and that leaves 5 for windings which seems like a lot.

This picture shows the inside where there are to connections in the top and one at the bottom. Also the two whites are connected and I don't know what they are supposed to do.

This picture shows the outside wires. I will explain what I have done as it has actually run already. I will number them 1-9 starting from the top.

2&3 are brushes.
7&8 are speed control
5&6 were connected before I touched it

I did the following:

Connected 1&2
Set power on 3&4
Leaving 9 which goes inside, unused in the setup.

The motor ran but it leaves me wondering what the two whites connected inside does as well as wire nr 9 which I didn't use.

Can anyone help?

Update:

Here is some information about it if it could help. I've searched a lot for a datasheet on it I've been unable to find anything so far.

Thx for the answers so far.


texts: Can transformerless power supplies be UL/CSA certified and is there any specific standard they must meet?

texts:
I am trying to bias a linear optocoupler on the AC mains side of a circuit, in order to transfer analog information to the secondary side of the circuit. I have designed the following capacitive power supply to provide the 6mA required and it works.

However, the reviewer at the certification lab is indicating that the voltage specifications for the capacitors after the bridge rectifier must be rated for line voltage (~400V). I am skeptical of this, because this would make the capacitors massive to meet the capacitance needs and transformerless power supplies are typically smaller units limited by the size of the X capacitor used to provide the reactance. It also doesn't make sense, because the zener would burn out long before the capacitors could fail.

Even this application note suggests that the capacitors only need to be 2x the zener voltage:

Microchip Application Note AN954 - Transformerless Power Supplies: Resistive and Capacitive

Does anyone know the specification that would govern this or have appropriate experience in getting a power supply like this certified, to let me know what to look for? Can these power supplies be certified or are they an internet relic?

Thanks.


texts: Why LED reversed bias voltage cannot be measured?

texts: As I have just found out, typical LED does not behave similarly to standard diode when measuring reversed bias voltage. On typical diode, you can measure reverse bias voltage about .3 to .6V, but not on LED. I have read you can measure it using constant current source, but why? What is the physical principle behind this?


texts:
I have so far used opamps for near-DC work (connecting transducers to AD and the like) and have not studied electronics in school. Now i made voltage follower based on classic LF412.

When i passed 125KHz square wave to opamp noninverting input through 10k resistor then nice suqare wave was seen on output (like expected).

When i increased resistance on input only about four times - to 36k then the square wave got clearly rounded corners like is seen when higher frequency components of square wave are attenuated. When i used 681k reisistor there was nothing like square wave any more.

What is going on? Is this effect of input capacitance or anything else? What to do if one needs high input impedance on relatively high frequency?


texts: Using SMD capacitor as a decoupling capacitor

texts:
I'm trying to figure out if one SMD capacitor is the same as a through hole decoupling capacitor. With the through hole capacitor the  positive current is on one side of the capacitor and the negative current is on the other. And each pin distributes the current to the rest of the circut. It looks as if the capacitor is crossing the connections but everything works as it should. I want to apply the same set up in SMD format.

But I am unsure if I would use one Capacitor with both currents going through it on oposite sides or should I have two SMD capacitors one for positive current and the other for negative?


texts: How does the contact pad used with Duracell myGrid mat work?

texts:
Duracell myGrid puzzles me. It's a charging system consisting of a base pad where devices with special contact pads (called Power Sleeve or Power Clip) are placed for charging.

The base pad surface is covered in parallel metal stripes connected to the power source such that even pads are positive terminals and odd pads are negative terminals. The device to charge is equipped with a matching pad that has four small edge contacts projecting downwards and aligned in star pattern such that however the device is positioned on the pad there exist at least two contacts that connect to different stripes on the base pad. This is guaranteed by following the right proportions between the stripes widths and the distances between the contacts on the device pad. So however the device is positioned on the pad it gets connected to both a positive and a negative base terminal and receives power for charging.

The latter is what puzzles me. How is such contact pad (the one of the device) designed that it allows up to three contacts to be connected to the same terminal and no matter which fourth contact is connected to the opposite terminal the device is being powered correctly regardless of how the device is positioned on the base pad?


texts:
I was going through an article related to SPI. There was a configuration named 'Daisy Chaining', in case of multiple slaves. So far, what I have understood about SPI (based on Wikipedia) is:

SPI can transfer and receive some data simultaneously.

My questions are:

In case of multiple slaves, does it mean, that it transfers data to many slaves, or it transfers data to one of the slaves, amidst a connection to many slave devices?
According to Application note 3947, Daisy-Chaining SPI Devices, figure 4, it is given that, the master keeps its SS low, until all the data it needs to send to the three slave devices is sent and then it makes the pin high. If so, what data & from which slave device, does the master receive at the end? (As, I've learnt that, the master always receive something in return.)
As stated in Architecture and programming of 8051 MCU's, in enhanced mode the load enable (LDEN) & WCOL is checked for moving the next byte into the buffer. Why do we need to check them both? Isn't the WCOL sufficient for that?
It's states: "Master configures the clock - frequency less than or equal to the maximum frequency the slave device supports. Such frequencies are commonly in the range of 1–100 MHz." How does the master find the clock frequency of the slave?
Does the SPSR, SPCR and SPDR registers remain in both master and slave?
It is given that, the SPIF flag is set after the completion of transmission. If the SPIE is also enabled, then an interrupt is produced. Does the flags get set in both master and slave? Is the interrupt produced in both master and slave? It's stated in AVR151: Setup And Use of The SPI about interrupts in both master and slave. But, I couldn't understand it clearly.
What is the application-oriented difference between the normal mode and enhanced mode? Both seem to wait for data to send/receive. What's the main difference?


texts: Does a spinning plasma vortex work with ac?

texts:
I am making some plasma arcs with this flyback transformer and I power it by passing the exposed wires of my charger to a halogen ballast. I've seen people online make spinning plasma vortexes
I was wondering if that would be possible with my setup since I heard it only works with dc.


texts: finding out the bandwidth of m(t)*m(t) if the bandwidth of m(t) is a known quantity

texts: m(t)*m(t) in time domain is equivalent to the convolution of m(w) and m(w) in frequency domain.Thus if the bandwidth of m(t) is a known quantity then how is the bandwidth of m(t)*m(t) is determined?


texts: USB connections, which is the most common and reliable?

texts:
I've found a lot of different ways to connect USB power and D+ D- in EVBoards and other kind of boards.

I've summarized this ways in this schematic:

(Right click and open image to zoom)

As you can see I will not use ID pin, board will be powered from usb just for trasfer data with D+ and D-.

I'm looking for a general and good way to wire USB so I want to ask, is this a correct connection? What I can remove and what I should add?


texts:
My stepper rating is 0.33A per phase, 23.9Ω phase resistance and 29.8mH inductance/phase.

What voltage should I use to drive this motor so that it provides holding torque around 13.7Ncm (rated on motor)?


texts: ETSI EN 300 220-1 General performance criteria

texts:
In Chapter "general performance criteria" the standard states that these criteria, for receiver performance tests, are equivlent:

after demodulation, a data signal with a bit error ratio of 1% without correction
after demodulation, a message acceptance ratio of 80%

My questions are:
What is a message and is it equivalent to a packet?
If not, how does it relate to a packet?

I am asking this because there is a formula which converts BER to PER and I would like to know if I can use it but just exchange message with packet.


texts: Best and safest supply for 12 standard servos or more?

texts:
I am building an hexapod 2DOF robot,  and I had planned a Power supply (5V/5A) for all devices, like this :

Would that work and be safe?

I have another plan , to seperate the power between servos and others .

5 x 1.2 AA battery = 6 V for Servos
6 x 1.2 AA battery = 7.2 V for others

But, the battery pack for servos actually goes over voltage the ,it can be over 6 V whereas the maximum voltage for servo is 6 V.

is there a better option?


texts:
Devices:

RapberryPi 3 Model B+
GrovePi+
Grove LCD RGB

As a learning exercise, I'd like to write a driver for the LCD listed above.

I'm using the HD44780 instruction set as reference, and can understand the 8-bit commands needed to control the display, eg 0x01 to clear the display. Furthermore, I can relate all the commands listed in this driver source back to the instruction set.

My confusion is around the leading byte the library sends:

0x80 for "commands"
0x40 for "data"

Experimentally, I can see that 0x80 is required before any of the instruction commands, and 0x40 for text to be displayed.

My question is: where are these two values (0x80 & 0x40) defined in the spec? Without existing driver sources, how would one know to use those seemingly magic bytes?


texts: Circuit for free energy from radio waves

texts: Has anybody tried this circuit? this circuit supposedly takes radio waves and turns them into a voltage. My questions are what are the peak voltages? and what current could i possibly hope to get if i run a 5v circuit with say a voltage regulator or a buck-boost converter


texts: I've got an unusual use case (optical communications) that would benefit from access to the wifi baseband signal before it is upconverted/modulated at 2.5Ghz. However most modern wifi chips combine baseband encoding and transmission encoding/transceiver functions on a single chip. Are there chips, or chipsets, that split these functions and would allow for custom final encoding - in my case OOK laser diode modulation at << GHz frequencies?


texts: voltage regulator connected between positive and negative voltages

texts:
I'm kind of new to the world of electronics, so bear with me.
I need to regulate +24 volts down to about +21 volts (for supplying a really pretentious heating resistor). I already have the circuit for the v-reg using +24v. The problem I'm having is that I don't have +24 volts, but I do have +12 and -12 volts. Could I connect the input of the v-reg to +12v and use the -12v as the circuit's GND?
The voltages come from a PC PSU.

This is basically what I need:

EDIT: I calculated the output as +9V. Combined with -12V the load should get 21V, right?
But now I'm not sure about what I use for the ULN2003's ground? Should I use the actual GND or should I leave it to -12V.
Thanks.


texts: Circuit diagram of an oscilloscope with 50 ohm load impedance

texts: I was told some oscilloscopes have 50 ohm impedance settings for radio frequency measurements for impedance matching (as opposed to one 1M ohm  resistor and a 10pF capacitor in parallel for load impedance, which is good for low frequency measurements).  I was able to find a circuit schematic of an oscilloscope. for the usual 1M ohm and 10pF capacitor in parallel. But i haven't been able to find a circuit diagram for the 50 ohm impedance oscilloscope. Id lile to know what the oscilloscope circuit looks like for the rf 50ohm impedance settings


texts:
Not an electrical expert so please bear with me.
I bought a no-name brand LED lamp that I would like to use with my 9V DC adapter as power source. The lamp uses 3 AA batteries in series. Batteries supplied with the lamp are HDX brand and I found their specification via the seller's site. The only technical data I have for the lamp is that it's 500 lumens.
I opened the case and saw that the circuit leads from batteries/power supply to a PCB, and then from PCB via separate LED+ and LED- contacts to the light itself. There is also a push button on the PCB to turn the lamp on or off. So what I want to do is to take out only the LED light, without the PCB and use it with my 9V power supply.
From my understanding, if I want to change the power supply from 3.5V (AA batteries in series) to 9V (power brick), I need to add a resistor. To determine the resistor's capacity I need to know what the current through the LED is. I was able to measure only the voltage, as the whole circuit is already soldered. I'm reading 3.5V on the battery bank/PCB and 3.0V on the LED. From this I understand that I have a 0.5V voltage drop on the LED. Is this correct?
Next, I have two ways of approaching it:

Max. current through the battery bank should be 1000mA, as per the spec document. In this case, R = (9 - 0.5) / 1 = 8.5 Ohm. This looks oddly low to me and this is another thing I'm not certain of.
If I assume that 500 lumens is approx. 5W, and following rule of thumb from this thread that 5W will give me approx. 1500mA, I arrive at a similar value of 5.7 Ohm. Again, I'm really not sure if this makes sense.

How would you approach this problem? At the moment, I only plan to turn the light on occasionally, but I'd like to think about adding a heat sink and have it run continuously in the future.


texts: What specs does the "gros condo" (big capacitor) needs to have?

texts:
I have a pair of Dynaudio Air 20 at home. Unfortunately, the cable that used to control the speakers via RS232 died. I opened the cable, and saw that it was a customized RS-232 to TTL adapter, but ending in a RJ45 (Dynaudio's TC-LINK proprietary communication).
I made a schematic out of what I can find on the Internet, plus the pictures of the internals of the cable, but I need to find the value of what is the "big capacitor" ("gros condo", C8) on the right hand side.

You can refer to this picture for reference :

(never mind, everything is broken on this PCB, I made too much experiments on it)

Also, if you see something that is not right for you (like something where it shouldn't be), feel free to add a comment ! I need to make a functional and safe board !

Thanks you very much !


texts: Is it possible to use Bluetooth serial and BLE client simultaneously in ESP32?

texts:
Is it possible to use classic Bluetooth and BLE at same time in esp32 with Arduino ?

IDE - Arduino ide


texts: BJT Saturation with small load/ H-bridge

texts:
I am trying to analyze the operation of a BJT H-bridge configuration. I have searched through these forums and Google and can't seem to find an answer to my question.

It is my understanding that it would be desirable to have the "ON" transistors in the saturated state, to provide maximum supply voltage to the motor. This is also a general practice whenever using BJTs as switches. They should operate at cutoff and saturation.

I tried to simulate a simpler circuit, ignoring the two "OFF" transistors and only looked at the two "ON" transistors. Suppose I wanted to have my bridge supply 1 amp of current with a 5 volt supply (arbitrarily chosen). I used a 5 ohm resistor as the load to simulate the motor. If both transistors saturate (Vce <= 0.2 V), then the load should receive about 4.6 V. In simulation the load receives only about 1 or 2 volts.

If I lower the base resistances to increase base currents, it improves to about a maximum on 2.8 V across the load. If I increase the load resistance to about 50 ohms, then I can get about 4.7 V across the load, but obviously the current is not what I want.

I've read for saturation that Vbc should be forward biased, or Vb > Vc. This explains why increasing the load resistance causes the bridge to go into saturation, since the voltage drop across the resistor gets large enough for Vc to become less than Vb. Though, with such a small load resistor it takes a lot of current to make an appreciable voltage drop. If beta is a worst case of 50, then an Ib of 20 mA should be enough to provide 1 A at the collector. However, even when I make the base resistance ridiculously low (10 ohms), I still do not get anywhere near supply voltage across the load.

Does this mean that it is not possible to saturate the transistors with such a small load resistor?


texts: STM32CubeMX/STM32L0 UART Transmit unknown symbols

texts:
I am trying to connect UART communication with STM32L053C8-Discovery. But the problem is on terminal I get unknown symbols.

My Setup on CubeMX

/* USER CODE BEGIN Includes */
uint8_t tx_buff[]={1};
uint8_t rx_buff[10];

  while (1)
  {
    HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
    HAL_UART_Transmit_DMA(&huart1,tx_buff,sizeof(tx_buff));// Sending in DMA mode
    HAL_Delay(1000);
}

To RX,TX pins I connected FT232RL FTDI module.

With Arduino it works but with STM32 in terminal I get only symbols. Maybe someone could explain me how to correctly set the format?

Also there is a full code of main.c:
https://pastebin.com/kST92XWZ


texts: Operating frequency of microcontroller PIC18f4550

texts:
I am new to PIC Programming, and thought of blinking LEDs as my first project. Now I copied a code from net which blinks two LEDs and its working, the LEDs are blinking.

My settings:-

I haven't connected any external oscillator to the PIC18f4550 and I am simulating the project using Proteus 8.1, In the Edit Components of PIC, Processor Clock Frequency is at 4MHz. But when I stop the simulation, I get the following message,"clocking 4Mhz specified in the component is ignored for oscillator mode INT-RC , NO CLKO". And note, I haven't used OSCCON register in my code.

My code:-

#include<PIC18f4550.h>

#pragma config PLLDIV = 5 , CPUDIV = OSC1_PLL2 , USBDIV = 2
#pragma config FOSC = INTOSCIO_EC
#pragma config FCMEN = OFF
#pragma config BORV = 3
#pragma config WDT = OFF
#pragma config CPB = OFF
#pragma config CPD = OFF
void main(void)
{
//blinking code here
//OSCCON register is not set.
}

My question:-

I am curious, if there is no external oscillator, internal oscillator register is not set and the Proteus is ignoring the schematic 4Mhz as clock frequency, then at what frequency is the microcontroller operating?


texts: BDCM for small DIY overhead stirrer, how to choose based on Kv?

texts:
I want to make a DIY overhead stirrer, to stir a glass of 5 Litres of pure water to bewtween 100-2000 rpm using a common impeller. I want to use a brushless DC motor (BLDC) to drive the impeller. After some calculations, and some research from commercial stirrers which also use BLDCs, I found that I need one with an output power of about 15 watts (which will be connected to an appropriate power supply, itself connected to the wall outlet of the house: 220 V, 50 Hz). The torque could be around 20 N.cm if I'm not mistaken.
After browsing, most BLDC offers seem to be for the RC hobby, and the motors are rated by a "Kv" unit (rpm/volt). I tried searching for a way to convert Kv to Watts, but couldn't find one. I simply want to buy one of these BLDCs that will be appropiate for my apparatus, but I can't seem to get that from the Kv value.
Can someone suggest me a way to decide which Kv rate of BLDC is appropiate for my apparatus?


texts: Step down transformer when wattage is close

texts:
Please tell me if my cooking appliance (programmable pressure cooker/slow cooker) is safe to use with my step-down transformer.  I live the UK and received a Japanese cooking appliance.
I have a step down transformer (UK 240 V to 100 V for Japanese appliances).
The step-down transformer is marked: Output 100 V. TOTAL 660 VA. MAX: 6.6 A. I understand VA is wattage and you get it by multiplying V times A.
The appliance is marked: 100 V. 700 W. [Japanese] 3.15 A. I'm reliably told the Japanese part translates as "current fuse".
The applicable wattage 700 W is higher than the transformer 660 W but not by much. The current 3.15 A is less than half 6.6 A.
I don't understand why the wattage of the applicance 700 W is greater than 100 V times 3.15 A.


texts: Using a PNP over an NPN to activate a solenoid

texts:
I am working on a circuit that controls a solenoid through the use of an Arduino. One question I had was if there was any advantage to using a PNP transistor over an NPN transistor? From class, I know that PNP's are usually better for pulling devices high and NPNs are better for pulling devices low, although I am unsure why this is the case.
For reference, I want to use an Arduino to control the transistor that activates the solenoid. So when the Arduino outputs a HIGH signal, the solenoid should activate, and at LOW signal, it shouldn't do anything. After searching around online, it seems that a general schematic for that would look like this (asides from the BJT):

It seems like an NPN would be the best choice for this scenario, but I don't really understand how connecting the solenoid to ground would activate it? It seems to logically make more sense to have the solenoid connected to ground all the time, then when it's time to activate the solenoid, simply pull up the solenoid using a PNP. However due to the inverse behavior of a PNP to an NPN, it would take a little more work then just having the Arduino output a HIGH signal.


texts: When a capacitor is charged in a first order RC circuit, it charges exponentially. I understand this behavior via equations. But can anyone explain the physical reason?


texts:
This battery is rated at 12V, and it says it provides 7Ah of power.

Does that mean that it can provide 12V at the terminals for 1 hour if 7 amps are being drawn from it?

Also, what does it mean when someone say some appliance is X watts. Like a 60 watt bulb or a 200 watt ice crusher? Doesn't the amount of watts depend on the voltage applied and the appliance's internal resistance?


texts: Arduino fio avrdude: stk500_getsync(): not in sync: resp=0x00

texts:
I have tried EVERYTHING to make this work, including replacing the board.

I have an arduino fio

I am attempting to upload a sketch to it (just a blink to validate it works)
with an FTDI to USB cable

I am using Arduino 1.5 BETA and I also tried Arduino 1.0.5
Neither of which worked and resulted in the same error.

I attempted to use a different comp with a fresh install that resulted in the same error.

I updated my FTDI driver to 2.0.8.30 still the same error

I dismantled the FTDI wire and re-soldered it to new wires to verify it wasn't a bad connection.

I attempted setting the baud rate in device manager to 9600,57600, and 115200

I tried pressing the reset button as I uploaded the sketch

I tried changing COMS

I tried plugging an Arduino Uno in, validating that it works no problem. Then I plugged the fio back in. Got the same error again same error.

This is the second board I have gotten that does this. It's not the board. What the hell is wrong with this software. I shouldn't have to work this hard to upload a freaking sketch.

IDE output

avrdude: Version 5.11, compiled on Sep  2 2011 at 19:38:36
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2009 Joerg Wunsch

         System wide configuration file is "C:\Program Files (x86)\Arduino/hardware/tools/avr/etc/avrdude.conf"

         Using Port                    : COM4
         Using Programmer              : arduino
         Overriding Baud Rate          : 57600
avrdude: Send: 0 [30]   [20]
avrdude: Send: 0 [30]   [20]
avrdude: Send: 0 [30]   [20]
avrdude: Recv:
avrdude: stk500_getsync(): not in sync: resp=0x00

avrdude done.  Thank you.

And yes, I have tried restarting both the IDE and the computer(s).


texts: Multiple LED over Serial communication with Arduino

texts:
Several LEDs are being driven by Arduino. The LEDs to be lit up are sent to Arduino over serial port. When Arduino receives 12H\n over serial, it will execute digitalWrite(12, HIGH). Then the buffer is flushed. And before executing the write, all other output pins are set to LOW.

Question: \n is currently used to indicate the end of a LED pin number for a single pin. How would you label the end of a sequence of LEDs that should be lit up at a time? Eg: 7H 13H 11H\t? Or 7H,13H,11H\n? Is there a best practice?

How will you parse it with Arduino?


texts: How to Connect this Crocodile Clips to my Multimeter?

texts:
I got crocodile clips with my multimeter, but no cable with them. The tips of the probes I have, do not fit into the plug on the crocodile clips.

How do I connect them to my multimeter? What kind of cable do I need?

I assume this is some kind of standard connector, I searched around but did not find anything useful. Seems I just lack the exact name of this kind of connector.

Update: The multimeter is a Testo 760-3 with the default probes. They have a small ~2mm conic tip.

Here a picture of the probe tip:


texts: Would you approve use of these PCBs??? Delamination issue

texts:
Our vendor pulled some PCBA out of storage, been sitting for about a year.
They found about 5% delaminated.   They claim it was 'because of the storage duration', but I'm not buying that.  I think these boards were defective from day one.

Yes, I know a hatched pattern for the pours is better - These aren't my design.
Anybody think this is a "storage" issue?   They're (supposed to be) FR4, so presumably they are fiberglass resin, and shouldn't be hygroscopic.  Vendor is in south-east China (Shen Zhen) where the humidity and temperatures are "jungle like" most of the year.  I'm sure there was no climate control during storage, I wouldn't be surprised if they were subjected to months of 130F+ temperatures.   Maybe storage EXPOSED the issue, but I don't like the theory it CAUSED the issue.
In field, these boards will get quite hot during normal operation.  There's a number of high-power MOSFETs on the other side, and the board regularly will see 15A, sometimes much higher during surges (about 35A max or so)
Further, the vendor is suggesting subjecting the entire inventory to a heat-test, basically a shorter version of a reflow oven cycle, to ferret out the bad ones.  They're suggesting use some kind of profilometer to detect the 'bubbles'.
This is a 4-layer PCB.  We almost "never" use multilayer boards, and I doubt our vendor sees them often either (maybe "never").
This is also a 'safety critical' component.
Any and all comments & suggestions welcome!!!


texts: Determining number of poles on permanent magnet alternator

texts:
I was able to buy a cheap used permanent magnet alternator, however the seller was not able to tell me much about the specifications. I could determine that it has a built in voltage regulator, however I would have to disassemble it more to check how many poles it has and was wondering if there was a way to determine it from the outside.
By manually turning it slowly it takes 16 "steps" (stable positions) to rotate it one full turn. This seems to point towards 16 poles, since there seem to be 16 magnets. However when looking at some images and reading some documentation about other alternators I am now suddenly no longer sure if it is maybe 8 poles?


texts:
I've a digital counter (Kubler Codix 908) with integrated 30Hz interference input filter integrated, but sometimes (when the contact that will increment the counter is closed) it counts two pieces... the mechanical counter work perfectly but the digital one is affected by signal interference. Is it possible to use a RC snubber (in parallel with the contatc) to solve the problem? Wich values of R and C I should use?
Thanx in advance, Andrea from Italy.


texts: q point keeps shifting when there is input signal

texts:
Why is that, even at transistor idle conditions, where my q point is exactly midway in the transistor loadline, when i start to inject ac signal at the input, the q point starts to shift somewhere else, therefore causing clipping. So this means that the act of inputting an ac signal sometimes causes the q point to shift naturally? Are there any counter measures against this? (Like compensating by means of finding a new q point wherein at idle conditions, it is exactly not at the middle anymore)

I have a 12 Vcc supply, emitter voltage is at .97 Volts, and so the collector voltage should be at

(12-.97)(1/2) = 5.5 V

which is in accordance here in my simulation

Here is the schematic


texts: Transistor current amplifier for 20W speaker

texts:
I have a 5 Vpp max audio signal in my circuit which I obtain from earlier stages of processing. I would like to deliver the signal to a 20W 4 ohms speaker. But since an OPAMP circuit generates the signal, it won't be able to supply enough current. How can I use transistors to amplify the current delivered? I don't think I need a common emitter voltage amplifier since the voltage is already large. What amplifier topology should I use? What kind of transistors do I need for the purpose?

I'm trying to refrain from using specific ICs and use transistors instead, and I don't need a very complicated adjustable amplifier, my only goal is be able to listen to the contents of the signal. The 20 W speaker is necessary for my application, a weaker speaker will not do. I already have a 12 V and 30 V power supply used in the previous stages.


texts: Can this schematic protect my load cell/strain gauges from lightning?

texts:
Today I was soldering gas discharge tubes (GDTs) to one of my PCBs used in a column load cell.
I found the placement of the GDTs very odd as the main aim of GDT is to protect load cell or strain gauges from lightning.
Below is the schematic showing the placement of the GDTs.
Please guide me whether the placement of GDTs protects the load cells or strain gauges from lightning.


texts: Cell phone battery with solar shield, arduino

texts:
I was looking for your opinion on this product: http://www.seeedstudio.com/wiki/Solar_Charger_Shield_v2.0b

Do you think I could use a cell phone battery (3.7v 1000mA) with this? I have a standard Li-Ion battery with these specs that seems to work fine with this product, but I'm not sure if there is anything special about a cell phone battery that would cause it to explode or act differently if hooked up to this solar shield.

I was looking at a cell phone battery like this one: http://www.amazon.com/LG-1100mAh-Standard-Battery-manufactured/dp/B000IBRSIS

I was thinking I would just epoxy (not solder) on some leads to a JST connector.

Can I just leave the third terminal empty? I think it is usually to sense heat or charge or something, right?

Thanks!


texts: Metal Effect on Trace Impedance and Ground

texts:
I am working on a project that will have some impedance controlled traces running next to a large metal plate grounded at 1 point. I wanted to confirm that:

1) The metal plate will still impact the impedance of the traces even though it is grounded at only 1 point.

2) In fact, even if the metal was floating it would still impact the impedance of the traces...however it would be capacitivley coupled to system ground and so modeling it could not be done with a simple impedance calculator that assumes GND planes.

3) If the flex is placed on top of a large metal plate that is grounded at only 1 point, the metal plate will still provide some shielding.

Thanks


texts:
I'm trying to create a project but I'm stuck somewhere. I decided to put a small portion into a simulator and it seems like the MOSFET is able to turn on and electrons can flow from the second diode. How is that possible in real life? Or maybe does it only work on a simulator?
The circuit:

Thanks a lot!


texts: Full bridge HVDC to modfied square sine - random half side MOSFET burn

texts:
I am trying to make a step-down 350V to 220V voltage converter. I decided to go with rather simple circuit of full bridge MOSFET inverter since my loads are only resistive or switched.

I had built it and tested today, however, without any success. It runs well with intended loads then, randomly, it blows the fuse. Further investigation shows that two fets (upper & lower) on one side dead shorted. I install another pair, after some time (mostly from minutes to no more than one hour) it burn. Then again, but opposite side. In all cases, both high and low fets burn. When I lucky to run it for a long time without blows, I remove power then check fets temperature and they are OK.

My fets are IRFP460.

I use two IR2110 unified into full bridge, the load is purely resistive (a set of series lamps plus one single bulb) and draws 450mA @ 220VAC. This load is not the intended load, I plan to power more resistive loads with this circuit. IR2110 are driven by TL494 as signal generator which has a onboard trimmer to adjust duty cycle. .

This picture is reference only showing how my bridge is being built

TL494 and IR2110 are powered by small onboard flyback converter which is NOT isolated from network common. Whole circuit gets power directly, no diode bridges. The power is 350VDC line which is another SMPS driven by lead acid battery pack.

For two years I use exactly same circuit, but low voltage version: fets are IRF1404 (40V), and it gets power from separate 12V 1A low voltage flyback. Confirmed operation up to 30V on input. I probably miss something obvious, but can't figure out exactly what. Snubbers?

If needed, I can post my development PCB picture.

UPDATE:

This is my old scope showing signal between TL494 and IR2110 (IR2110's input). Those IR2110 are working and there are no shorts on board after them.

I can vary duty cycle from 0 to 97%.

This is exactly signal waveform I want to see at device output.


texts: Class D amplifier - equation for peak current?

texts:
I'm trying to spec a power supply for a class D amplifier IC. I have figured out the maximum RMS current draw by taking the RMS power rating of the amp, increasing that to compensate for efficiency losses, then applying: $$P = I^2R$$
Where \$R\$ is the speaker impedance.

However my power supply needs to be spec'd for the peak current, not the RMS current, right? So, assuming the above approach is correct, how do I get the peak current draw of a class D amp?


texts: Convert Power to a Peak Voltage, when to multiply by sqrt(2) - Not so simple?

texts:
I have a dBW value and dBW I understand to normally be given as representing a RMS Power (however this is not specificically ever stated and I am told its just assumed?)

from dBW to Watts = \$10^{\frac{dBW}{10}}\$. This then gives RMS power in Watts

At what point do I convert this from a RMS to a peak value?

Multiply RMS Power in Watts by \$\sqrt{2}\$ before using \$V = \sqrt{P\cdot 50}\$
Or multiply the result from \$V = \sqrt{P\cdot 50}\$ by \$\sqrt{2}\$

Because they give two different values...


texts:
I need to design a stencil for reballing.
0.76 is the diameter of the ball.

What should be the size of each hole in the stencil?

I was thinking about 0.8mm. Is that correct?


texts:
I had to design a circuit to work as an inverting amplifier.

The circuit is as shown below, and in order to obtain Gain 5, input resistance of 30kΩ, R6 has to be a potentiometer of 100kΩ and the op-amp is the uA741C, the resistors used are:

R1=30kΩ

R2=150kΩ

R3=10Ω

R4=100Ω

R5=1000Ω

R6above=1236Ω

R6below=98763Ω

Now I´m asked to find and justify what the input voltage range will be, and the maximum frequency the amplifier can work at.

Any ideas on how I should proceed or what the answer is?

I thought that this parameters would depend only on the op-amp used, and therefore the maximum voltage range and frequency of the circuit should be the same of those of the op-amp.


texts:
I have been wondering about this for a while:

Since the phosphor will remain excited for a certain period of time, I could imagine a single electron gun could target the red, green and blue phosphors sequentially instead having 3 parallel beams.
This would also solve all the convergence problems.

As the industry went with 3 beams and the tubes are designed by people a lot more knowledgeable than me, they obviously have a good reason to use 3 beams and I would like to know where the flaw is in my thinking.


texts:
I try to make a custom board for the STM32F303K8T6 and I am not sure if I do it right. Actually the design is oriented on the STM32F3Discovery. I will not run time critical applications so that I don't need an external oscillator. To flash and debug, I want to use the SWD, but there I am not sure, if I really need the V3.3 pin? Is this PIN not to power the board with the SWD? So when I activate the voltage regulator when I flash, this should be redundant, right?

Schematic:


texts: Does a boost converter lower the source current of a solar panel?

texts:
I am trying to build a solar powered phone charger using small size solar panels. I have two solar panel connected in series, each of them are 4 V and 50 mAmps. When I connect the solar panels to the input of the following boost converter, it shows its charging but the battery level actually goes down, instead of going up.

http://www.amazon.com/Module-Battery-Converter-Charge-Samsung/dp/B00C93Z8JY/ref=sr_1_9?ie=UTF8&qid=1451591616&sr=8-9&keywords=dc+dc+step+up+converter
I am not sure if using a boost converter a good idea since in cloudy days the voltage goes down to approximately 4-5 V. The current for the solar panels are 50 mAmps. So is the boost converter actually lowering the current?
Thank you

Sorry I meant connecting the solar panels in parallel giving an output of 4V and 100 mA


texts: Why is this line connected to the microcontroller input in this schematic?

texts:
I found this wheelchair board and am trying to dissect some parts. I don't have many fancy tools so am just using continuity test to trace what goes where and this piece belongs to relay control circuit.

where uC is microcontroller input/output. What is the purpose of D1 and D4?

Before: What is the purpose of this specific piece (highlighted in red). Why is the relay pin 85 connected to the microcontroller. I know the diodes are for protection but what else?

here is the actual image from the board:

Edit: I renamed the diodes and also refactored the circuit a bit.


texts: I am trying to design a desktop audio amplifier, and I'd like to better understand the effects of phase shift on my output. I'm trying to design this amplifier to be of the highest quality I can, and as I understand, phase shift cannot be completely eliminated. Is there an approximate level of phase shift that is considered "acceptable" by some standard? For example, a common filter I see recommended for flat phase response is the biquad filter, but even that one has a phase shift that goes like arctan(f), so that a corner frequency even at 100kHz produces significant phase shift in the audible region. What are some good topologies/techniques to reduce phase shift for an audio amplifier?


texts: What is the percentage modulation of phase modulation PM?

texts:
What is the percentage modulation of a phase modulation (PM)?
Can you further explain and give detail? I am currently stuck in finding the information about this


texts:
I'm trying to use the random command in PBASIC and I'm not sure how it works. I'm using a PICAXE-08 Proto Board Kit, and the chip specifically is a PICAXE-08M2.

Here is the code I'm using:

symbol randnum = w0
RANDOM randnum
randnum = randnum // 2

FOR action = 1 TO 5
    IF randnum > 0 THEN
        LOW led_red
        PAUSE 500
        HIGH led_red
        PAUSE 500
    ELSE
        SOUND buzzer,(100, 100)
        PAUSE 500
    ENDIF
NEXT action

(Perhaps due to assembly mistakes, the LED's HIGH corresponds to LOW and vice-versa).

First of all, I expected to put the RANDOM randnum command within the for loop, but if I do this, the loop count becomes incorrect. Instead of 5 actions, I get only 2.

The second problem is that I'm expecting randnum to be either 0 or 1, so that 50% of the time the LED is lit and 50% of the time the buzzer sounds. However, the LED is lighting 100% of the time, even across multiple trials. Obviously, randnum is never 0. However, according to documentation, RANDOM should give the variable a value between 0 and 65535, inclusive.

What is the issue here?


texts: How to calculate current in a symmetric circuit diagram

texts: I am relatively new to circuit diagram and I am trying to find out how I can calculate Io shown in the above diagram. From my understanding, this looks like a symmetric circuit diagram, however I can't wrap my head around it on how to calculate the current on that point.


texts:
Yesterday in lab, we were asked why all of our green LED had large forward voltage than expected. We expected for the forward voltage to be at around 2.1V as according to hf=Egap=eV. Yet, we experienced forward voltages of 2.6-2.7 for our LEDs in the lab. Professor said that there is a reason, but I cannot seem to figure it out. Can I get help?

Could it be that the Green LED had some different composition as expected, allowing it to emit green light while having high forward voltage?

I searched through the internet, and a lot of sources say that Green LED forward voltage is 2.1V whereas other sources say that Green LED forward voltage is like 3.0V. Why the discrepancy?


texts: Altium - Strange issue with Library part

texts: I see a strange issue while placing the above library part on the PCB file. After placement,the silkscreen and mechanical layer gets an offset .Any suggestion what could be the issue?


texts:
I am working on a project on the Raspberry Pi, it is a bit experimental as I am learning the electronics side as I go along... please edit out any problems with terminology.

My aim is to replace a switch with a transistor on an existing circuit, so I can use the 3V3 output from a GPIO pin on the RPi to control the open/close of a switch on an existing circuit.

I used a multimeter to test the voltage through the switch (from one + to -) which is 3V. I created a circuit on a breadboard which uses a BC547B transistor to replace the switch, connecting the + and - to the Emitter and Collector, with Base acting as the switch (3V3 output through a resistor). When I connect the Emitter and Collector to the transistor the reading is only 1V8.

The circuit seems to work, but with intermittent results. Is this due to the loss of voltage when using the transistor? Will I need to design around this or can I just use a different transistor? I just used one I had from another project without really knowing if it would work at all.

Edit;

I changed the circuit so that the voltage through the transistor came from the 5V pin on the RPi, and it worked perfectly. However, this is a power pin and not controllable via software, so it is not a solution, just evidence that the transistor is the problem. I think its time to start reading again.


texts:
I am using msp430g2553 microcontroller and a 4x4 HC543 keypad. I am using Energia IDE.
I have connected the keypad from pin 2 through 9.
My code is as follows:

#include <Keypad.h>

const byte ROWS = 4; //four rows
const byte COLS = 4; //four columns
char keys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};
byte rowPins[ROWS] = {2, 3, 4, 5}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {6, 7, 8, 9}; //connect to the column pinouts of the keypad

Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

void setup(){
  Serial.begin(9600);
}

void loop(){
  char key = keypad.getKey();

  if (key){
    Serial.println(key);
  }
}

However I am unable to get an output at the Serial Monitor. I am especially confused if I am using the right pin configuration.

I have downloaded the Keypad.h library from Arduino website and imported it in Energia. Can this be a problem? Since all the functions (like makeKeymap and getKey) related to Keypad.h are properly colored.


texts: Why use two 0.1 µF capacitors in parallel?

texts:
Below is the schematic of the Pololu A4988 driver board:

There are three capacitors on the motor power input. I can understand why engineers decided to use separate 4.7 µF with larger size (1206, 0.1 µF are either 0805 or 0402): because physically small capacitors have lower ESR, and they effectively filter out higher frequencies (correct me if I'm wrong). But what is the reason to use two 0.1 µF capacitors in parallel? Can they be replaced by a single 0.22 µF in order to save PCB space and cost?

Image of the board; it can be clearly seen that all capacitors are ceramic:


texts: LVDS: length matching within a pair and between pairs

texts:
I'm interested in the LVDS communication between a Zynq (Xilinx, xc7z020-1C) and a camera (ON semiconductor Python 1300 NOIP1SE1300A−QDI).

I have read some articles about USB2.0 where the maximum skew for the differential pair is given; it can then be derived the maximum length difference between two traces of a pair.

However, I looked for similar specifications in the Zynq documentation without success, so I went more into the current design on the demo board. 6 LVDS pairs goes from the camera to the Zynq (4 data, 1 clock, 1 sync). Internal terminations from the Zynq are used for differential pairs. The Avnet IP to connect the Python 1300 to the Zynq uses 3 primitives for the data channels:

IBUFDS
IDELAYE2
ISERDESE2

I found some info about the setup and hold time for the ISERDESE2 primitive:

My guess is that the length difference tolerance within a pair can be derived from the setup and hold time of the ISERDESE2 primitive, and the IDELAYE2 is there to compensate for the length difference between pairs.  However, I do not understand how I can derive a timing budget based on these information.

Could anyone give me some hints to better understand how to calculate the length matching tolerances in this scenario? Rule of thumbs are also welcome.

Thank you


texts:
I have harvested a small transformer from a tablet's charger,but I couldn't really find the exact model.

After searching the net,it was clear that the transformer belongs to the EF20 series,but when entering the exact inscription,I got useless results in Japanese.

I find it hard to distinguish the part number from the series code when judging the marking  on the back of a component in general,if I never heard about that component name before and if there is a mix of letters and numbers which represent different things.

A datasheet I found:EF20 datasheet

Transformer inscription:EF20-0502-SDC JT
Charger model:BSC12-050200-E

I want to download its datsheet.Please help me find it.


texts: I'm needing to create a booster and the easiest schematic I've found is this: http://electronics-diy.com/500mW_FM_VHF_Transmitter_Amplifier_Booster.php however, they do not document what part they use for the amp. Does anyone know what amp they may use? Or a similarly easy way to create booster inexpensively?


texts: I am wondering are there any standards for the order of signals on I2C header? We get many I2C devices on the market, but the order of pins on the headers is inconsistent and hence we may not be able to insert any I2C device to our board. For example, some devices have VCC GND SCL SDA, some of them have GND VCC SDA SCL and like this there are many combinations. I understand that I2C is typically used  within the board itself and hence order may not be defined. But the order of pins would matter for external devices that may be soldered directly to the header.


texts: AC voltage measurement using microcontroller

texts:
I am using this below circuit to measure AC voltage using a pic microcontroller
PIC32MX330F064H.

Here in this circuit resisitor R1 and R2 form a voltage divider to attenuate the AC Line voltage. Resisitor R3 and R4 acts a level shitfer so that the AC signal zero level is shifted to mid voltage level of the DC 3.3V. This prevents negative voltage developing at analog pin of the microcontroller. Resisitor R5 acts a current limiting resistor.

Now my question is wheter this circuit will load the analog pin of the microcontroller? If it loads than how to prevent it. Secondly do i have to add some components like diode for safety of the microcontroller.

What will the voltage developed at analog pin if Neutral is not connected or gets disconnected during measurement?
It is possible to detect Open Neutral using the same circuit?


texts: Using multiple sensors on the same i2C circuit

texts:
It’s possible to control multiple pH probes with one single i2C ph circuit (like this https://www.atlas-scientific.com/product_pages/circuits/ezo_ph.html) ?

Rather than buying I2C circuit for each probe, I would like to know if it’s possible to use the same I2C pH circuit for several probes (figure). In this case, I’m aware that I need to temporally separate the samples.
Is it possible to use octocouplers to switch on/off each probe?