texts: Why the Locking Buttons? (Project for blind user)

texts:
I was trying to build this: http://www.shaungehring.com/2013/01/03/raspberry-pi-project-1-pandora-streamer/ for a blind user. The large buttons are a key aspect for this target user. But, I've noticed it has locking buttons listed in the supply instead of the momentary switches I would've expected. Would someone be so kind as to tell me why? Unless the design keeps them from locking.

Also, if anyone knows any similar tutorials for making it a C.D. music player, please let me know.

I love learning to program new things, but I'm in a little hurry on this one, so I'm more than willing to follow instructions.

Note: I initially asked this question here: https://raspberrypi.stackexchange.com/questions/5571/why-the-locking-buttons-project-for-blind-user, but figured this site was more appropriate.


texts:
When describing telecommunication systems, it is often important to note whether it is a simplex, half-duplex, or a full duplex communication.

In trying to explain this variable or attribute, I couldn't find an appropriate word to describe these types of communications.

Is there a common term that engineers use to describe the 'simplexity' or 'duplexity' of a communication scheme?

I'm thinking along the lines of transmission direction or transmission type, but both of these descriptions suffer from being potentially incorrect or too vague.  It seems there isn't yet a practical, nor concise, way of explaining this communication attribute.


texts: Soldering iron struggling to solder to ground plane

texts:
I've got a 48W Soldering iron which I'm using on PCB's, which I'm designing with Eagle and getting made up for me. I'm a hobbyist, so needless to say, I may well have the wrong tool for the job here.

My designs use surface mount components and my soldering iron is really struggling to melt the solder when I'm trying to solder to a surface mount pad which is connected to the ground plane.

Is 48W a bit on the small side? Should I replace the iron with a more powerful one or is that not the problem? I'd be very grateful for any help.


texts: Will LEDs in opposing directions be damaged?

texts:
I was trying to build a simple RC circuit that causes an LED to fade in and out.  However, I have electrolytic capacitors, which means that they have polarity.

If I connect a circuit as follows , is the circuit capable of damaging an LED due to back voltage?  (The capacitor is supposed to have polarity, but I didn't know how to put the symbol in CircuitLab.)

I think not, because the other LED has very little resistance when the voltage is at any substantial level.

simulate this circuit – Schematic created using CircuitLab

When making the circuit in CircuitLab, I left the component values (e.g. 100 ohms or 1V) as default, as I'm mainly interested in the generic circuit, not a specific one.


texts:
I've seen in many reference designs capacitors that were referred to as "placeholder" capacitors. what are these capacitors exactly needed for?
for example, in DDR4 SODIMM Design:


texts: Unable to generate AM wave using opamp log antiog multiplier

texts:
I was trying to make a op amp based AM modulator. I used a log anti-log multiplier to generate the below waveform.

This is the output I am getting as from this circuit

What I intended to generate


texts:
Below is a small portion of a schematic which I have seen

It mentions that the transmission line will have a differential impedance of 100ohms between them.
In case of Single ended it would be 50 ohms between the signal and the ground.
Can someone help me to understand how does a single ended 50 ohm impedance would look like 100ohm differential impedance with a diagram?


texts: "Inverse problem" for resistor network: finding applied voltages to produce desired currents

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I am working with a large network of resistors. Here I will illustrate my question with a scaled-down version (5 resistors).

The current flow through the each of the 5 resistors is fully determined by the potentials at each of 6 nodes, or 5 nodes if I ground one.

simulate this circuit – Schematic created using CircuitLab

I would like to specify a set of currents \$[i_1,  i_2, i_3, i_4, i_5]\$ and calculate the required voltages \$[v_1, v_2, v_3, v_4, v_5]\$ which generate these currents. Since I have five independent node voltages, I can find a combination of voltages that generates any desired combination of five currents - I am comfortable with this part.

I am interested in the case where I want to generate a set of currents \$[i_1 ... i_5]\$, but I can only set some of the node voltages, say \$v_1, v_4,\$ and \$v_5\$. The other voltages (i.e., \$v_2\$ and \$v_3\$) are determined by the applied voltages and the arrangement of resistors.

Since I now only have three independent voltage sources, I can't generate any arbitrary combination of five currents - only a subset will be possible.

I have three questions:
(1) How can I determine whether my desired combination of currents is possible?
(2) If this combination of currents is possible, how do I calculate the combination of voltages I need to apply to \$v_1, v_4, v_5\$?
(3) If the combination of currents is not possible, what is the closest I can get, perhaps in a least-squares sense (or some other relevant measure)?


texts: driving high-side N-channel MOSFETs in H-Bridge

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What is the most efficient / best way to make an H-bridge? I want low power loss but also fast switching time since I will using PWM. I have considered using 2 P-channel and 2 N-channel MOSFETs to make this. But, I realized that P-channel devices have a much higher channel resistance causing more power loss.

So, I was considering using 4 N-channel MOSFETs but the problem lies with the gate voltage. My power source will be approximately 15V and I am going to be using a arduino/atmega for PWM signal (5V). So, I am wondering what is the best way to amplify this gate voltage so that the high side N-channel MOSFETs turn on while also giving me a rapid switch time. Or, am I digging a hole for myself and should just stick with a P-channel?


texts: How did I manage to not be hurt after accidentally making an electric contact between mains wires?

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Warning: mains is dangerous, often fatal and should not be messed with.

I accidentally touched both live and neutral of a 230 AC mains via dupont wires after a shower (still wet feet). However I merely felt a muscle-interrupting itch rather than any deadly consequence. This shall need luck and I strongly discourage anyone to try this.  However, what is the underlying cause that saved me from a deadly shock?


texts:
In the attached figure, input impedances of the right hand, right leg and left hand are respectively \$20k,50k\$ and \$10k\$ Ohms. The input impedance of the opamp is also assumed to be \$1M\, \Omega\$. Power line induces a displacement current of \$100\$ nA into the body.
Problem: What is the ratio of common-mode voltage on the body when the right legged is ungrounded with respect to when it is gorunded?

Attempt to solve:
In the first case when the right leg is ungrounded, the current has to go through the left hand, the opamp and the right hand. However the common-mode voltage is assumed to be equal throughout the entire body (?), so the left and right hands form a closed loop:
$$ V_L - V_R = 10^{-7}\times (10^6 + 3\times 10^4) = 0.1 + 0.003  \approx0.1V. $$
In the second case when the leg is grounded, all the resistors short-circuit and the current goes directly into the right leg:
$$V_{leg} = 10^{-7}\times 5\times 10^4 = 0.005V.$$
The ratio thus is \$0.1/0.005=20\$. However my solution manual says \$10\$ is the correct answer. I'd be grateful if you could help me figure out why.
This is also my first question on EE site, so forgive me if I'm a noob!


texts: I have a 15V power supply powering 2 Dc/dc converters that are the same.  The converters are connected so that the outputs are 10V and -10V (the - terminal of the 10V converter is tied to the + terminal of the -10V converter .  the 10V converter has a 10ohm load.  the -10V converter also have a 10ohm load.  What's the output current for the the 15V supply? My guess would be 2 amps (1 amp from each converter). Or is it dependent on a spec of the dc/dc converter?


texts: How much AH should my battery has for my sound system (3 Amplifiers)?

texts:
I would like to know if I can mount my sound system in my car.

My current battery is 45AH, and the problem is that I can't go higher than a battery with 50AH, because there isn't space for it on the battery spot near engine.

My question, will I be able to use my sound system upgrading to a 50AH battery or it won't even be possible?

I am not planning to play music with the car turned-off by the way, so the car alternator will help right?

I don't know the capacity of my alternator, but the car is a Chevrolet Aveo Bi-Fuel 2011 (T250 Model).

My sound system specifications are the following:

Amplifier 1: Gravity PS1000 - RMS power: 2 x 125 Watt 4 ohm - Max. power: 2 x 500 Watt 4 ohm powering this Subwoofer: Climax Hazard 5000 - 500W RMS - 1000W Max Power

Amplifier 2 (next buy): L2.210 - Class A/B 2 Channel Amplifier 70W RMS x2 @4 ohm

Amplifier 3 (next buy): EV200.2 - Class A/B 200 W MAX Power, 38 W X 2 RMS @ 4 ohm

My calculation result in a total RMS of 466W (2x125 + 2x70 + 2x38)

And according to this rule Total RMS Wattage times 2 (Inverse of Amp Efficiency) divided by 13.8 Volts equals Current Draw in Amperes (explanation below) I will drain from my battery 68 A  [ my calculation was ( (250+140+76) * 2 ) / 13,8 ]

So concluding my question, what will happen if I use a battery of 50AH in my car? supporting all this system draining 68 A?

Thank you so much for your help!


texts:
As far as I understand, an ideal transformer wouldn't show any net flux inside its core, as any such net flux would induce electric fields and in turn currents in the windings such that it will disappear. So an ideal transformer would show no (net) flux at all, correct? So it would kind of act like a control loop trying to keep the flux at 0.
A real transformer requires energy in order to magnetize its core. This energy is provided to the transformer in the form of the magnetizing current \$ I_\mu \$ and a corresponding magnetizing flux \$ \phi_m \$.
It was introduced to me as $$ \phi_m = \phi_1 - \phi_2 $$
with \$\phi_1 \$ being the flux put into the system by the primary winding, and \$\phi_2 \$ being the induced flux coming back from the secondary winding. So what's left after taking this difference is the magnetization flux.
We were shown this visualization in class:

It suggests this flux flows in the whole ferrite core. My internal model was that the energy provided by the additional current \$ I_\mu \$ would be "absorbed" by the core in order to magnetize itself and the flux wouldn't make it to the secondary winding. If it does flow throughout the whole core, and also through the secondary winding, wouldn't it play into the "control loop" described above and vanish as soon as it arises?
What am I missing? Thank you for your time in advance!


texts:
Let's say I have a current regulator, or a LED driver, set at 4V that can sink 20mA. If I connect a white LED rated 20mA at 4V to it, then everything is fine.

But what happens if I replace, in the same setup, the LED with a red one which works at 2V and also 20mA? Will it work? Will the regulator limit the current to 20mA and adjust the voltage accordingly? Or will the red LED blow up due to over-voltage?


texts: Performance of solar panel vs. DC power supply

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I am building a solar swamp cooler for burning man (hot dry desert environment).

Purchased a 15w solar panel that outputs 0.9a at 20V in full sun (verified as true with my voltmeter). The solar panel apparently provides 0.8a at 17V under load.

I applied the output to power a 12V fan rated at 0.4a, and it seemed to work fine, although a little slow.

THEN, I applied my PC power supply output to the fan, and it hummed along superfast, providing an awesome air current.

What's the story here? If the fan draws 0.4a, what is the solar panel lacking?!

Thanks for any insights!


texts: 8PST switches, do they exist? (not 8SPST DIP Switch)

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I'm looking for a switch that can connect/disconnect 8 signals at a time with one button/lever/slide whatever. Power requirements are very low. I do not want to use analog switches due to interference with my measurements, which are in the nanoamp range.

I would prefer something that is through-hole or surface mount instead of solder lugs. Does such a switch exist?


texts: How do I keep a square wave output voltage high for a TTL application?

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I am passing an AC signal (24 Vrms at 1K Hz) down a line through a diode of unknown bias.

Due to uncontrollable variables in the environment, there are 4 possible outcomes:

Positively Rectified -> XMM1 = 5V, XMM2 = 0V
Negatively Rectified -> XMM1 = 0V, XMM2 = 5V
Open (No signal)     -> XMM1 = 0V, XMM2 = 0V
Unaffected Signal    -> XMM1 ~=2.5V, XMM2 ~= 2.5V

Outcomes 1, 2 and 3 are easy to work with, but outcome 4 is a problem. For outcome 4 I would prefer to have an output of XMM1 = 5V, XMM2 = 5V; however, 0V on both would be acceptable too.

I've been thinking about and experimenting with different component configurations, but I haven't found anything particularly effective. If there is a better way of going about this whole thing then please let me know of an alternative approach. This is a part of a cable tester that I'm building to detect the order of 6 conductors that need to be connected in a specific order.


texts: Driving high impedance load with Crystek Sine Wave Oscillator- CCSS-945X-25-100.000

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I am planning to use Crystek CCSS-945X-25-100.000 sine wave oscillator to drive the reference CLKin pins of TI PLL IC LMK04832 .

Now in datasheet of oscillator, output power mentioned is 5dBm into 50 Ohms.

But lets say if load is not 50 Ohms but a high impedance load, then what will be the output power of oscillator?

Is sine wave oscillator like this, only required a 50 Ohms load for stable oscillations and if load other than 50 Ohms is connected to output of oscillator it will not oscillate at all?

EDIT:

Actually this sine wave oscillator will be on a separate PCB which we are calling as "CLOCK DISTRIBUTION BOARD".

Sine wave clock from "CLOCK DISTRIBUTION BOARD" will be connected to main board which has LMK04832 PLL through a SMA cable.

I have checked the CMOS version of the oscillator : CVHD-950.

In datasheet of CMOS oscillator ,they mentioned the load as 15pF.

Now I need to know how much load in capacitance, this sine wave oscillator version can drive because this SMA cable will be having some capacitance and also LMK04832 refclock inputs will be having some capacitance.

Is there any way to know the value of load capacitance, this sine wave oscillator can drive ,from the available oscillator specification in datasheet like 5dBm into 50 Ohms?


texts: How far can a terminating resistor be from the literal end of a CAN bus?

texts:
I'm wondering if anyone knows if there is an upper limit for the distance a terminating resistor can be from the literal end of the CAN bus or where the last node is.

We have an HMI that is connected to the CAN bus and it is located beside a panel. We are wondering if it is acceptable to have the terminating resistor within the panel itself (via a terminal block) and a harness would run from there to the HMI. The cable distance would be about 10' (including strip length and distance between the panel and HMI).

We are hoping this will be acceptable purely for aesthetics, because this will eliminate the amount of loose wires hanging near the HMI.

I've gone through the TI physical layer instructions and did not find any such constraint.

I'm guessing the distance would only be an issue if the line impedance increases dramatically due to the length of cable but I'd like to know for sure.

Thanks.


texts: What IC can I use as controlled inverter

texts:
Pretty much I want to find an IC with the following structure:

Inputs: I, a0...a7
Outputs: b0...b7

Where b0=a0 xor I, b1=a1 xor I, etc.


texts: How do I design a 2A or more power supply for my consumer USB devices?

texts:
I understand that many of my consumer devices charged by USB ports can charge at higher rates than 0.5A.  However, in testing, I've found they don't consume more than this.
Test Setup

I have a power supply that outputs between 0 and 30 volts, and 0 to 20 amps.
I set the voltage to 5 volts, then connected up a female USB to the wires correctly.
When I plug in a Samsung Galaxy S4 Mini, it pulls around 0.44 amps. It is the same with a Samsung Galaxy Tab Pro.
However, when I connect an iPad Air with an official lightning cable, it only pulls around 0.11 amps.
Also, I tried connecting a ZGPAX S28 smartwatch and it was still about 0.44-0.45 amps.

The power supply is more than capable of outputting the maximum 2.1 amps, so why doesn't it to at least the tablets?
What do I need to do in my test setup to convince the devices to consume their maximum charging current?


texts: MOSFETs acting strange on different power supply

texts:
I have created a circuit for controlling my 12V RGB LED strip using 3.3V microcontroler (ESP8266). I have used IRLZ44N N-MOSFETs to regulate the colors. The circuit worked great, when the microcontroller was powered by external power supply, but when I added a voltage regulator (LF33CD to drop 12V to 3V) and disconnected the 3.3V source, the MOSFETs started to act strange. The LEDs stays on, and also, the ESP8266 won't connect to WiFi.

//EDIT: I have updated the schematics, I have made the schematic wrong

Schematic with the external PS (this one works)

Schematic with 3.3V regulator

I am new to electronics, I was mostly making software before, so please excuse me if I made some stupid mistake.


texts: Microwave Stub Design(Choice between Series & Shunt and Open & Short)

texts:
George Vendelin,in his book(MICROWAVE CIRCUIT DESIGN USING LINEAR AND NONLINEAR TECHNIQUES 2nd Edition Page no. 249 & 250) tells that shunt stub is the only viable option for stub design.The question is why.
I guessed it is because we get the ground plane readily available while implementing shunt  design using microstrip lines.

Now the choice narrows down to whether it should be open or short configuration.

On discussion, my friend pointed out that there's no standard for what will be defined as short because any 'short' termination will not exactly be short (for eg,by drilling a hole in PCB & soldering will be of a finite length & a finite impedance)

So we concluded that Open Shunt is the most viable choice for shunt design.

Are the views & reasoning expressed here correct?


texts: Why do I need to put a low pass filter in front of an analog to digital converter (ADC?)

texts:
Is the low pass filter in front of the ADC just to filter higher frequencies or does it serve another purpose?
I am talking about the ADS8320 ADC.


texts: I'd like to use a relay to switch on and off a standard 12 V DC motor, which is 6 W according to its specification. A 2 A relay looks good on paper, but will it be able to deal with the surge of current when it switches on?


texts: Does anyone have problems with micro USB connectors on PCB?

texts:
In a PCB I've been developing, I included a micro USB connector. The problem is that when I plug in and out cables on it, seems to get weaker and weaker and needs to be resoldered, even the pins on the center seem to give some problems.

Is there something I can do on this board that can improve it or another type of connector? Anyone had problems with it?


texts: I am working on a circuit where i have to measure currents from -500uA to 5mA. For this i am using 100ohm resistor for converting current to voltage and then this voltage is sent to OP07 and output of this is given to HP7840 isollator whose gain is 8. circuit is working correctly for higher currents but i want to measure .05uA. But since output of this circuit is fluctuating when i am taking readings in 5 decimal points, due to this my readings are not coming accurate. I have no idea why their is fluctuations upto 0-100uV  which is not desired. OP07 thermal noise is 0.2uV/`C and HP-7840 have only 0.1% nonlinearity.


texts: Why is there no current in this part of the circuit?

texts:
Can someone give an explanation to why there no current in i0 (or why does i0 equal 0)? It was a step I had to know before using Kirchoff's laws.

Also, is there a voltage across the nodes that i0 goes between?


texts: Loop v.s. nodal analysis of periodic circuit network

texts:
I vaguely know there are basically the loop/mesh analysis and the nodal analysis corresponding to Kirchhoff’s voltage law and Kirchhoff’s current law, respectively. And one can do Fourier transform of a periodic circuit network and then solve a system of linear equations. However, in the following example, it seems that the two analyses look quite different.

In the periodic network shown, the building blocks are three different capacitors C0, C1, C2 on the hexagonal edges. For simplicity, I only show a few of them. In nodal analysis, the independent nodes are just the red and blue ones, hence two unknown voltages. On the other hand, in loop/mesh analysis, it appears to me that only one unknown, the loop charge/current, would be enough. This means that, after Fourier transform, the numbers of linear equations are different, 2 and 1, respectively.

This looks rather mysterious to me. I am not very sure of the loop analysis. Please correct me if anything wrong.


texts: Why after changing ideal OPAMP to a real one, there appeared bounding in negative part of the sine wave(Proteus)?

texts:
I am trying to get sine wave from square wave (555 timer) by applying low pass filter. For ideal OP-AMP it works fine, but when I changed it to 741 for example, there appeared some bounding of low part. Could you please suggest why it is?

741:

The circuit:


texts:
I was looking for a PMIC with battery charger and built-in power path when I came across one of TI's new chip. BQ25601 http://www.ti.com/product/BQ25601. while I was trying its performance and doing some tests I noticed that it cannot withstand load steps when it's working without battery and enabled charger. as long as the charger is enabled and there is no battery connected, the chip works in suspend mode and cannot respond to transient currents. although it can provide the magnitude of the current,  significant deeps appear in the output at the beginning of the load step. However, the chip works perfectly with battery irrespective of how much discharge is.

Because I don't know when he is about to connect I'm after something that can work perfectly even with no battery.


texts: Using BRAM instead of SRAM in Virtex-5 FPGA

texts: I am working on a project where we are capturing signals from an ADC using a Virtex-5 FPGA and the samples are being stored on a 128K x 256 SRAM from where the data samples are acquired by a PC. I believe the Virtex-5 provides an option for a BRAM and while I understand that the depth is nowhere close to what the SRAM provides, I'd like to make use of the BRAM option in the Virtex-5 as a buffer to hold the samples temporarily until they are acquired by the PC. How difficult would this be to implement ?


texts: How Precise can I get with Accelerometer and Gyroscope

texts:
I want to build a little project to track an objects position in space. For this I intend to use an accelerometer and a gyroscope.

The problem is I want this tracking to be very precise, and I haven't been able to figure out how precise you can actually get (for a fair amount of money). Are we talking 1 centimeter, or centimeters / 1000 ?

The specific combination I'm looking to buy is from SparkFun: IMU Fusion Board - ADXL345 & IMU3000 But I'm more interested in a general answer, as I could go with other combinations. Maybe just a general guideline of how to determine it from the specs.


texts:
I found the following schematic for a rudimentary mini UPS:

(Original source website)

and in the description on the original website (link above) it says:

  D2 → Prevents backfeeding of 5v wall transformer when power unplugged and battery supplying circuit.

  D1 → Acts as a Switch. When plugged in, VA ≈ 5.17v, VB=3.7v. D1 is reverse biased and battery will not energize circuit (But will Charge). When unplugged, power will flow through D1. VA ≈ 3.4v which is high enough for power boost. VC always ≈ 5.2v.

I am wondering if this would work as an UPS. The charging circuit is a 5.2v to 3.7v buck converter and the powerboost is a 3.7v to 5.2v boost converter.The push button is unnecessary.

Another thing I don't understand is the term "reversed biased diode", is that just a normal diode like 1N4007, or is another type of special diode?

Any advice would be useful, thanks.


texts: acceptable bounds for replacement DC adapter

texts:
Possible Duplicate:
  Chosing power supply, how to get the voltage and current ratings?

I've got a broken gadget that is discontinued.  The only thing broken is the power supply (verified by my multimeter).  I'm confident enough to open up a replacement power supply and solder in the wire I'll salvage from the broken one.  What I don't know is what Volt and Amp bounds are acceptable for the replacement.

The broken adapter states it outputs 8V DC 2.6A
The gadget it plugs in to states it expects a 8V input
The battery it goes to charge is 6V

I can't find a power supply that outputs exactly 8V DC 2.6A
 Is it safe to change this to 9V DC 1A?
 Or perhaps to 9V DC 2A?


texts:
I am using the CC1110 RF IC and I am having trouble when matching the differential RF output impedance with the antenna. The datasheet states that the differential impedance seen from the RF output towards the antenna must be: $$(86.5+\mathrm j43)\Omega$$ when operating at 868 MHz.
The application circuit proposes a balun and matching network for a 50 Ω load but mine isn't. I want to know if I'm doing my calculations correctly:

simulate this circuit – Schematic created using CircuitLab
I am simulating the above schematic (don't take into account component values shown as they are not the used ones) with a AC current source (I1) with 1 amp AC magnitude and measuring voltage across its terminals and calculating the impedance as
$$|Z|=\frac{V_{RF_P}-V_{RF_N}}{I_1}$$
$$\angle Z=\angle(V_{RF_P}-V_{RF_N})-\angle I_1$$
$$Z=|Z|\exp(\mathrm j \angle Z)$$
Are my calculations correct? Is this impedance found (Z) the one that has to be matched to the value specified above?

Edit
After @Bimpelrekkie I performed the simulation using the values stated in the datasheet (page 38-40) and obtained this output:

The amplitude and phase difference are:
$$\frac{V_{RF_P}-V_{RF_N}}{I_1}=126.52\ \Omega$$
$$\angle(V_{RF_P}-V_{RF_N})-\angle I_1=1.21\ \mathrm{rad}$$
Which gives an impedance of:
$$Z=(46.6+\mathrm j118.7)\Omega$$
Which is far from the (86.5+j43)Ω stated in the datasheet?
Are my simulations wrong? Is the application circuit wrong?


texts: Solution for level-translation (3.3V Arduino Due  5V shield)

texts:
The new Arduino Due board has its microcontroller running at 3.3V, but unfortunately most standard Arduino add-on shields (boards) run at 5V, thus their I/O signals are at different logic levels.

The number of signals is approximately 20, and includes:

standard digital lines (some with hardware interrupt capability)
analog I/O
Serial UART lines
as well as SPI and I2C signals

Now, I would like to add an in-between shield (board) so as to facilitate compatibility between the 3.3V Arduino Due board and all the signals of any given 5V shield. This in-between board would need to allow interfacing between the 3.3V signals and the 5V signals (i.e., both ways).

What is the best way to create bidirectional level-translation for a case like the above? Here, by "best", I just mean straightforward, inexpensive, and would work without problems across the various shields and signal types.

Based on my research of this kind of level shifting so far, the options available seem to be:

A set of diodes that create a voltage drop (but this would be uni-directional)
A set of resistive dividers (again uni-directional)
A specialized level shifting chip?...


texts: How to trigger siren (buzzer) with ESP8266

texts:
According to the attached images, I am creating a small circuit where I need to trigger a siren (12vdc 200ma) through a pin signal of the ESP8266 microcontroller (NodeMCU).

The signal output of the pin of the ESP8266 is 3.3v 5ma. However, to trigger the siren I need the values already mentioned.

In this circuit, I have a voltage amplifier (like this: https://www.ebay.com/itm/DC-3-3V-3-7V-5V-6V-to-12V-Step-up-Power-Supply-Boost-Voltage-Regulator-Converter/201919379310?hash=item2f0355376e:g:IsoAAOSwcB5ZEIrx) where, coming in with 3.3v or 5v, we have 12v output. Great! Question of tension is resolved.

However, the current remains the same, not stabilizing the circuit (so the siren is "gaga"! Rsrs).

Can anyone help me how I would go up the chain?

PS: I have transistors (TIP31C, BC548, BC547, BC458, BC457), diodes (1N4148), relays (5v-12v, max 30a), capacitors (various capacitances) and leds (red, green, yellow, white and blue).

Thank you in advance, thank you for your promptness and promptness.


texts: Radio controlled car / Arduino control algorithm ideas

texts:
I have a brushless radio controlled car that is far, far too powerful, such that at about 60% throttle the front wheels will come off the ground, the car flips and stuff breaks.

To remedy this, I have bought a Wii motion plus 3-axis gyro, and successfully interfaced it with an Arduino. I have a method of reading in the throttle using an interrupt, and the Arduino is quite happy to output the throttle too.

I am now stuck with the bit in the middle; how would be best to retard the throttle as the front begins to lift?


texts: Newbie: ATmega32u2 USB-powered application - which variant?

texts:
In manual for ATmega32u2, there are two slightly different diagrams for powering the µC via USB. One of them is described as: "with 3.3V I/O", other: "with 5V I/O" (see images below).

For 3.3V, VCC and AVCC are connected (together with UCAP) to decoupling capacitor, while for 5V, they're connected (together with UVCC) to USB's VBUS power line.

Why? How can I decide which configuration to use?


texts: How do I calculate the root mean square voltage of a square wave (with drawing)?

texts:
I need to find the root mean square voltage based on this drawing, knowing that the period (T) is equal to 6 seconds, and the voltage (V) is equal to 14 Volt.
I know that the rms can be calculated using this formula. How do I apply this into my exercise?

knowing that T = 6s, V = 14V find rms voltage.


texts:
This is the question:

And this is my solution:

(a)

(b)

When vI > 2.7, D1 is on and D2 is off.
The circuit will look like:

vo = vR2 + V1 + VDo.
VR2 = vI (R2/(R1+R2)) + 2.7 (R1/(R1+R2))
=> vo = vI (R2/(R1+R2)) + 2.7 (R1/(R1+R2)) + 2 + 0.7.

When vI < -4.7, D1 is off and D2 is on.
The circuit will look like:

Vo = - 4.7 V

When - 4.7 < vI < 2.7, both diodes are off.
vo = vI

So,
vo =

vI (R2/(R1+R2)) + 2.7 (R1/(R1+R2)) + 2 + 0.7 ,  when vI > 2.7 V
- 4.7 V  ,  when vI < - 4.7 V
vI  ,  when - 4.7 < vI < 2.7

Is this solution right or there are some mistakes?

Is there a better way to express vo when vI > 2.7 V ?


texts: Connecting LED to iPhone's dock connector

texts: Is it possible to connect a single LED to iPhone dock connector?


texts: I have seen many UPS circuits in which MOSFET transistors have been blown up in their inverter part. According to following circuit what are the  various failures that can cause this to happen?


texts:
Hello community

My first post here. I am fairly new to electronics and I’m building my own pyrography power supply. I have done a couple things to accomplish this but have not yet been successful. I found a tutorial online on how to make one using an Arduino and an ATtiny85 chip.

Here is my question: In the schematic, I can see that I need 2 resistors, but I don’t know what wattage to allow for R1 and what value to use for R2. I know that R2 is connected to an LED, but I don’t know the voltage that comes out of the ATtiny85 to calculate using the formula. Can anyone help me please?

Edit:

Thank you guys for all the help. It clears a lot of my doubts. I’m not sure if I’m allowed to post external links, but here is the project I’m doing:

https://gerritsendesign.wordpress.com/2016/11/03/pyrography-power-supply/

I already made a bench power supply and have a LTC3780 to have variable voltage and current. I thought this was going to be enough, as I am using the 12 V rail which carries 14 A, and I made a pen with nichrome wire. But it doesn’t work. It heats up, but it burns the fuse in my LTC3780. So, I decided to do the project in the previous link, to try my luck.

Thank you very much.


texts: How to solder wires on Li-ion cell phone batteries?

texts:
I am making a obstacle avoiding robot and wanted to power it with mobile phone batteries.
But wondering how to solder wires on battery correctly for no inconvenience.

p.s. I am a new arduino enthusiast.


texts: In which region should a MOSFET be operated as a switch?

texts:
I have a question about MOSFET switching operation.

According to an article:

  In order to operate a MOSFET as a switch, it must be operated in cut-off and linear (or triode) region.

According to another article:

  MOSFET in saturation region is preferred to make it work as a switch.

I am very much confused about the operating region of MOSFET to be used as a switch.

Should I operate the MOSFET to "Turn ON" in a (linear/ohmic/triode) or saturation region?


texts: Totem Pole / Push Pull Circuit is not working properly

texts:
I have a simple switching circuit around 500Hz with 120V supply using Push Pull mosfet with high resistive load showed below

but the output was not as expected, like this

the blue line is the voltage across R1

i have searched for totem pole circuit and the result exactly same like my circuit, but i do not know why my circuit didn't work, any ideas?

big thanks


texts: How to decide a Filter circuit and Cut-off frequency to my application?

texts:
I have to design a Gas sensor(SEN-09405) interfacing circuit with STM32F030CCT6 Controller ADC Pin through a filter circuit(To improve the Analog signal). Based on which parameter, I can decide Filter type and cut-off frequency?
How to decide the same to any other sensors like (Temperature, Light, pressure.etc).


texts: Why the pins of a port in some microcontrollers are not in order?

texts:
In some ICs the pin numbers are not in proper order. For example, in msp430x12x2 series (following pic).

In the pic, why don't P2.0 be available at pin 20 (or adjacent to P1.0 ??)

Why is that few pins of both ports P2 and P3 are on either sides of the IC?


texts: How are system level test requiring use of common lab bench equipment usually implemented?

texts:
Assume that a system level test setup needs to be created for a design. This shall require use of power supply with multiple outputs, signal sources that can output sinusoidal or arbitrary signals and  measurement equipment that can measure frequency, spectrum or magnitude of signals at different points in the device under test.
Such a setup could be controlled from the PC if all the equipment has ports that can be used to communicate with the PC e.g serial ports.
Q1. Is this how system level test setup is created? Are there software or hardware tools out there that can be used to simplify design and implementation of hardware tests?
A software program would be one that easily integrates with power supply, signal source and measurement equipment by containing drivers to communicate with each of them so that the user does not need to bother with low level details. A hardware solution would be some device that simplify creation of such tests.
By system I mean my PCB with FPGA, ADC, DAC, Flash, RAM, Serial Port e.t.c. The purpose is to test all the functions of the FPGA board.
Only for prototype.


texts: How to prevent connector from corrosion?

texts:
I have problem with my water level sensor of washing machine. Its connector corroded at its center terminal.

Is it true that the corrosion will only occur on the terminal that have negative polarity?
How to prevent this corrosion?
Can you explain more about this?


texts: SIMCom module (SIM7605CE/SIM7600CE) not responding to AT commands from ESP32

texts:
I connected an ESP32 module to a SIMCom module with the name SIM7605CE (shown below).

The connection was quite straightforward. I connected the ESP32 to my PC and the SimModule to a DC generator (since it takes a lot of power). The connections are as follows.
IO14 -- Tx
IO13 -- Rx
The connections are shown in the diagram below.

I used a simple code to try and send AT commands to it and get a response. Even though I get responses if I directly connect the SIM module to the PC and use PUTTY, I get no response at all if I use the ESP32 module. The code used is given below.
#include <SoftwareSerial.h>

SoftwareSerial mySerial(14, 13);

void setup()
{
  Serial.begin(115200);
  mySerial.begin(9600);

  Serial.println("Initializing...");
  delay(1000);

  mySerial.println("AT"); //Once the handshake test is successful, it will back to OK
  updateSerial();
  mySerial.println("AT+CSQ"); //Signal quality test, value range is 0-31 , 31 is the best
  updateSerial();
  mySerial.println("AT+CCID"); //Read SIM information to confirm whether the SIM is plugged
  updateSerial();
  mySerial.println("AT+CREG?"); //Check whether it has registered in the network
  updateSerial();
}

void loop()
{
  updateSerial();
}

void updateSerial()
{
  delay(500);
  while (Serial.available())
  {
    mySerial.write(Serial.read());//Forward what Serial received to Software Serial Port
  }
  while(mySerial.available())
  {
    Serial.write(mySerial.read());//Forward what Software Serial received to Serial Port
  }
}

The only response I get from the serial monitor is 'Initializing...'
What could be causing this issue?


texts:
I am new to electronics and am trying to figure something out:

I have a source putting out 12.6V and an unknown current.
I know that I can calculate current by finding the voltage drop over a resistor.

simulate this circuit – Schematic created using CircuitLab

V = IR, so a drop of 1.77V = I * 10kΩ; I = 0.000177A

However, this is a VERY low number, and also I know that I can attach a 12V fan to this circuit which draws 70mA (0.007A), so the circuit must have at least that much current.

Is there some basic law of electronics which I am not understanding, or are my calculations incorrect?


texts: Confusion over a simple 4060 LED blinker

texts:
I'm trying to build a simple LED blinker using a 4060BP binary counter, as per the following:
(source: bhs4.com)
and
(Originals here and here).  When I have built either circuit, the LED (I'm just using one for now) is permanently on. Looking at the circuits this seems logical, since because the negative terminal of the power source is connected to ground, there is a closed circuit between the positive terminal, the LED and the negative terminal. In fact, the LED stays on even if I remove the power from the 4060 IC! Should these circuits as per the two diagrams work as LED blinkers, or am I missing something? Thanks!


texts: Phase difference of voltages at one side of a transformer

texts:
Consider the circuit in picture

simulate this circuit – Schematic created using CircuitLab

Suppose that I measure VA and VB with respect to GND using an oscilloscope.

Will VA and VB be in phase or out of phase with respect to each other?

Edit : I tried to make measurement on a real circuit with the values of parameters as in picture (V1 is 220V). I measured VA and VB with an oscilloscope and I got

VA=6 V

VB=17.5 V

I used the MATH function on oscilloscope to get the difference VA-VB

VA-VB= 20 V

I did not measure directly the phase shift between VA and VB signals, but, from the amplitude I can deduce that pase shift d was such that

sqrt(VA^2+VB^2-2*VAVBcos(d))=20

Solving I find d around 106°.

Is this normal? I expected a 180° shift while I get a value which is much lower


texts: how to calculate rms value for current square wave

texts:
How do I  calculate the RMS value for the current waveform during a transient event like the picture below?

Assuming:
Ix=6A

Iy=38A

duty cycle= 38%

frequency= unknown

My goal is to know what is the behavior of the voltage regulator of a CPU(AMD/Intel)  under transient load. Hope someone can help me. Thanks!


texts: Using Audio Jack Switches as Paralell/Series toggle? (guitar amp and cabinets)

texts:
I have a guitar amp that has one output that can handle either an 8 or 16 Ohm load.

I have a cabinet with two 8 ohm speakers (each with a separate input). I could wire the speakers in series, and get 16 Ohms.

The way I want to do this is by adding a second output jack to my amplifier chassis and use a DPDT switch to toggle between parallel and series wiring. Easy enough (see schematic).

My question is: is it really necessary to add a separate switch? Could I not install two female stereo jacks in my amp and use the ring connection as a switch?

Then if both (mono) speaker jacks are inserted, I get a series connection, but if only one is connected it, it just passes the signal through without any splitting?

I tried to draw this up but couldn't figure how to achieve this using audio switches in place of the DPDT? Perhaps it can't be done?

Can anybody help?


texts: Why too many capacitors in parallel for Vdd supply net? Can't we just add all to replace with one big capacitor?

texts:
Here is a schematic of a Basys-2 board's power regulator IC and filters. It is just an example but this is fairly similar to many designs I've seen.

Why are there so many capacitors added in parallel rather than just one big capacitor? Can someone give me pros and cons of adding many many capacitors in parallel rather than one big capacitor for each supply net?


texts:
I have a possible project coming up that looks like it needs a small amount of digital logic (to generate some synchronous timing/control signals). Speed is not that high, in the low megahertz.

My background is a wide mix of analogue/low speed control/embedded microcontrollers and also application software - over quite a few decades. I did some digital design back in college (a lot of wire wrap 74LS doing really primitive digital audio) but that is long ago. If I took that approach to this project, it would probably be 9 or 10 chips - but I know how long that can take to put together, just wiring, testing, bug fixing.

I have a couple of Numato dev boards with Spartan 6 FPGA's on them, I'm sure that they could handle this, but the tool suite is a bit daunting right now. (Also I don't have the right programmer, the USB app they give is not that great.) I don't mind spending some time on getting up to speed, but it can't be too much. I probably don't have time to pick up an HDL for this one.

There is a lot of attraction to using a CPLD/FPGA - simulating and checking the design on-screen, being able to make bug fixes and changes - but I need a tool chain that I can get into reasonably quickly, and I need to get the thing doing something that starts to look like progress pretty fast.

Any advice? Recommendations? I might spend a little time with the Xilinx and see how it goes in the next days.


texts: Wiring a eTopxizu 12v 30a Dc Switching Power Supply to USA 240 volt plug?

texts: I have a eTopxizu 12v 30a DC Universal Regulated Switching Power Supply. The power inputs are marked Ground-Neutral-Load. It has a switch on the side that adjusts it from 110 volts to 220. When I adjust it to 220 volts does this change the inputs to the USA standard for 220 volt where it is Ground-Hot1-Hot2 OR does it still require a neutral with a 220 load on the single L input? The reason is I would like to use this power supply to convert a USA 220 three prong output to 12 volts.


texts:
I'm trying to create a rule to ignore a collision between some pads on the top layer, and a track on another layer. So far my rule is this:

But it still says a have a collision.

These are the pads that I want to ignore:


texts:
Hi I am trying to use 2 nested for loops in vhdl but I get this error.

[Synth 8-561] range expression could not be resolved to a constant [318]

I do not understand why this code is not working since cursor_pos_x or cursor_pos_y are not constants.

this is the for loops I have

   for i in (cursor_pos_x) to (cursor_pos_x + length - 1) loop --318
   for j in (cursor_pos_y) to (cursor_pos_y + length - 1) loop

cursor_pos_x and cursor_pos_y are signals and have integer type.
and length is

signal length : integer range 0 to 250:= 250
signal cursor_pos_x : integer range 0 to 250 := 0;

How can I fix this?

I am using vivado2017.2


texts: HVAC fan relay intermittently sticks closed; opens when touched

texts:
I have constructed a simple OR gate using two HVAC fan relays to control a 120VAC/1.5A booster fan for my home HVAC system. I have a zoned system, with multiple thermostats, but only one zone/thermostat controls the booster fan. The thermostat switches 24VAC on one wire when calling for heat, and 24VAC on another wire when calling for cool. The voltage is supplied by the control board of the furnace. When there is no temp call, there is no voltage across either wire to common (ground). The relays are sized correctly; they are typical mechanical HVAC relays, SPST-NO - commonly used in the HVAC industry.

I want the fan to turn on whether calling for heat or cool, hence the OR gate. It seems a simple enough task and circuit. However, I've noticed some strange behavior. Intermittently, when the thermostat ceases to call for heat or cool, the fan does not turn off. So the 120V side of the relay stays closed, even when there is no voltage across the coil. The weird thing is, to get it to open again (and the fan to turn off), all I have to do is touch the metal junction box containing the relays. Note that I did not say 'hit' the relays. I don't have to touch the relays at all. I don't think it is a typical fused contact situation. The relays are new and all I have to do is make contact with the metal box in which the relays are mounted. Everything is well grounded.

My first thought was for a flyback diode (as you would have for any inductive load) but of course this is 24 volts AC, not DC, so a diode wouldn't make any sense. I don't think this is an arcing issue, so the typical MOV solution doesn't seem like the solution, but I may be wrong.

I am not completely certain if the low voltage or high voltage side is 'sticking', but I suspect it is the high voltage side (not sure why I suspect this, though). I know the thermostat is cutting the voltage to the coil. The part that stymies me is that it is intermittent.

Has anyone seen this type of behavior with an AC relay?
Can anyone offer any troubleshooting advice?
Do I need to add something to the circuit?
Are there any suggestions to make this circuit reliably turn the fan on and off depending on the heat and cool inputs?

Here is a quick and dirty schematic, showing only the relevant parts.


texts: Is voltage measurement of a battery done in series?

texts:
This might be a stupid question but I can't find an explanation.

Voltage measurement is done in parallel. But when we measure the voltage of a stand alone voltage source, say a battery, it looks like we are doing it in series and yet we get the correct reading.

simulate this circuit – Schematic created using CircuitLab

So we connect the voltmeter like above to measure the voltage of an isolated voltage source. Although it is connected in series, we get the correct reading.

Am I missing something here?


texts:
In a German tutorial video about EAGLE, starting at 1:15 the author adds a trim potentiometer for regulating the contrast of an A162 display. Between the slider and ground he adds a 100 nF capacitor.

What is the capacitor for?

Screen shot showing the circuit with capacitor C4:

Note that the author stresses that the video is about the basic features of EAGLE, not about circuit design and not even about good layout of a circuit. He says that he didn't build the circuit, and it may not work. The tutorial is very good —  I learned using EAGLE from scratch.


texts: DHCP with ENC28J60 on PowerLine Adaptors

texts:
I have a board based on an Atmega328 and an ENC28J60 which uses uIP.

When the board is connected to the network via a switch it can acquire an address via DHCP faultlessly. The DISCOVER, OFFER, REQUEST and ACKs come through fine.

When it is then connected to the network via Powerline/Homeplug adaptors, it fails to aquire an address via DHCP. Using Wireshark I can see that the DISCOVER is sent out and an OFFER is made after that nothing happens and the process repeats itself. From some debugging I can tell that the ENC28J60 does not seem to receive the OFFER and hence keeps sending out DISCOVER messages. I've also run a Wireshark downstream of the Powerline adaptors and the OFFER is getting through past the adaptors.

I have tried setting up an alternative DHCP server on the network and the same problem remains. Also, I have connected a laptop to the Powerline adaptors and it can aquire an address via DHCP (this has also been confirmed from a Wireshark capture).

I have played with the QoS settings on the Powerline adaptors without any success and am now not entirely sure how to proceed?


texts:
What is the bode plot of an inverting op amp if you replace the resistors with caps? What if you now add a capacitive load to the output?
Update:
I ran a quick simulation and the bode plot looks as follows. It looks as though there are two poles but I am still confused about how to analytically derive the transfer function and analytically calculate the poles. Would it just be -C1/Cf where the frequency terms (jw) cancel out?
Update 2:
It seems some clarification is needed on this question. A non-inverting op amp is shown below. In this common configuration, I want to analyze the circuit if you were to replace the resistors with capacitors. I ran a quick simulation as seen in my first update. I now understand that the gain of the circuit is -C1/Cf. However I am confused as to how to hand calculate poles for the bode plot of this circuit. Any help is much appreciated.


texts:
I am developing a board that has a couple of small SMD chips. I have successfully made a couple of working boards.

Unfortunately I found out that one of the chips in my original design is going to be phased out soon (LSM330DLC), so I'm replacing it with manufacturer's suggested part (LSM6DS3).

I ordered a test batch with this new chip and it has a couple of problems.

On all 4 of the boards that I ordered the LSM6DS3 chip is somewhat more shiny than other chips (see attached image)
2 of my 4 boards have electrical short somewhere that I am not able to pinpoint visually. I tried removing the LSM6DS3 from one of the shorted boards and suddenly there is no more short. It is worth noting, that in the process of removing the chip I also accidentally removed some of the solder pads.
The weirdest thing is the data that I receive from the motion chip (LSM6DS3). I couldn't get anything from the shorted boards. Board number 3. outputs constant max value on all accelerometer axes. Board number 4 outputs good data only on accel Y and Z axes - the X axis always shows a value near 0 no matter how i turn the sensor chip.
I tried soldering leads to the hand removed part from one of the shorted boards and wired it by jumpers back to the board that I removed it from and suddenly it also started outputting good data on all 3 axes and the short was still gone.

I have tried using leaded evaluation board to develop my code and it works fine with it (I got the good data reference from it). I also triple checked my design and everything seems to be OK. I still kept the old chip (LSM330DLC) on the I2C line and on all of the 4 boards it works flawlessly.

I am now suspecting manufacturer's fault. Either they managed to burn the chips during the reflowing or they somehow used some quick test-run lower quality setting on PCB production. I'm just guessing.

So my question is: Are there any telltale signs, that a chip might be burnt or damaged during reflow? Would the shininess of chips be any good way to tell whether the chip is burnt?
Any other possible problem causes?


texts: ATmega (Arduino) programming in 3V system

texts:
I want to use a ATmega (168 or 328) with a 3V button cell. Which isn't the problem but at the moment I think about how to make it pogrammable in the target board. The board will have some peripheral devices like leds which can't operatet at a higher voltage.

So can a normal ISP programmer or even a USB to TTL adapter be used to programm this 3V system?


texts:
I have the following problem.

MY ATTEMPT
I found the formula for the total harmonic distortion to be this:
\$THD = \frac{\sqrt{V_2^2+V_3^2+V_4^2+V_5^2+...}}{V_1} \$, where the subscript denotes the harmonic.
Looking at the spectrum above, it seems like I'm supposed to make the following conclusions: V1 = 18.9241, V2 = -67.363, V3 = -8.5635, V4 = -61.8046, V5 = -13.3634.
Inserting these values in the formula gives me a result of \$THD = 4.90 \$ which doesn't seem reasonable at all, I must be doing something wrong. I'm also unsure of where I'm supposed to use the information about the forward voltage of the diode.
I hope someone can help me or clarify things for me.


texts: COMP2 to trigger One-Pulse mode on STM32L1

texts:
I am trying to use the output of COMP2 to trigger the One-Pulse mode of a timer (in my example TIM4, but it's quite flexible if it needs to change to another timer) on the STM32L1 series.

In the reference manual, the explanation for the One-Pulse mode uses TI2FP2 as the timer trigger, which is linked to the Input Capture on channel 2 of the timer, however the output of the comparator can only be redirected to Input Capture on channel 4 (except for TIM10 but it doesn't have a second channel to output the PWM on...), or to OCREF Clear.

I have tried redirecting the COMP2 output to:

“OCxREF Clear” of TIM4,
the Input Capture 4 of TIM4,
the Input Capture 4 of TIM3 and using ITR2 as the TIM4 trigger (ITR2 is TIM3 when used on TIM4)

but none of those options worked.

Should any of these configurations have worked and I just didn’t set them up properly?

Am I supposed to do it differently?

Is there no way to connect the two directly and I should for example start the One-Pulse mode from the COMP2 interrupt?


texts: What is the point of the zero ohm resistor between LED_VCC and VCC_3V3?

texts: I am designing a IR sensor transimpedance amplifier circuit based off of the Texas Instruments Particle Sensor (TIDA-00378). Between the separate power buses (LED,TIA,VCC) there is a connection with a zero ohm resistor. Am I supposed to put a ferrite bead there to reduce some sort of noise? Or is it just to act as a jumper if I want to use separate power supplies? Thanks!


texts: How to keep a wall power supply from dyeing?

texts:
I recently had a 12v 1200mA wall power supply that I was playing with. I was making a aluminum can cutter using gator clamps and .7 pencil lead (graphite) it was ok for about 10 minutes but then I shorted out my power supply. Can someone tell me how I can stop it from frying my power supply???or do I have to makes bench power supply out of it?
      My idea : connect a appropriate resistor and a diode to my power supply. Or maybe and a fuse or ground


texts: Noise figure of an attenuator is equal to the loss

texts:
Does anyone know a mathematical proof of this concept? Are there limitations of some kind or is this a general statement for all passive elements?

Thanks in advance.


texts: Using 3.5 mm cable to connect load cells?

texts:
I have some 300 lbs. 4-wire load cells that I need to connect to a PCB. Their nominal resistance is 350 Ω, and they will be excited at 3.3 V. The goal is to read the force on a PSoC microcontroller. As the ADC only measures up to 1.024 V and the load cells output a differential voltage of 20 mV/V, I am using an instrumentation amplifier to amplify the output to 1.024 V.

My question is can I use a TRRS (4-lead) jack with a 3.5 mm audio cable to carry this signal? Will the excitation and ground wires carry too much current for the audio cable?


texts:
I have a boolean expression and I need to get to the canonical forms of it (sum of minterms and product of maxterms).

In order to get an expression for the first canonical form, I need to multiply every term by (x + ~x), where x is the missing variable. Is there a similar algorithm to get to the second canonical form?


texts: Why is this current source with both sides grounded still supplying current

texts:
Now if we write a node equation at \$C\$ we get

  \$I_C = g_m − sC_μ V_π \$

But my question is, is it correct, how do we define the current through the branch with \$g_mV_π \$ since both of its terminals are connected to ground now, which means that there is no potential difference between both terminals ?

My initial thought was that since there is a constant current source then the current would be held constant by it. But then that would mean there is a potential difference between those ends. Now that means potential difference across \$C_μ\$ is not \$V_π \$ since one end is connected to the current source which if working would create potential difference (since current is held constant).

But here the equation suggests that the current source is working and as well as the capacitor \$C_μ\$ is grounded too.

Where are my wrong ? Please point it out. Thank you.


texts: Am I in danger using this lithium polymer 3S 11.1V battery?

texts:
I have an odd problem (to me, at least), and I really need some advice before tossing $40 to the recycler, as well as for my own personal safety and knowledge.
I'm building a robot, and in fact have built a couple using this battery - all well and good. But somehow I managed to drain it to around +/-8V, and my charger laughed at me when I tried charging it.
After a bit of forum reading, I don't have a NiCad charger, or trickle charger, so I opted to take another piece of advice I read - just let it sit overnight.  So I did.  This morning, it tested at 10.1V - I was quite surprised already!
Thinking it might be my lucky day, I hooked it up to the charger, and after 10 mins, checked it for warmth (nothing) and tested it at 10.4V so it seemed to be charging.
After awhile, and periodically checking it for heat (never any: not on wires, connectors, battery, nor charger), I thought I would test it again, and UH OH - 12.2 volts!  With all the horror stories I've heard, and only being a 2-year hobbyist, I dropped it on my desk and carefully finger-probed it for heat / soft spots.  Nothing.
Is this battery a dangerous bomb?  It seems the over-drain killed the over-charge protection. I dunno, I just think maybe I'm better off tossing it, but ya, 40 bucks is 40 bucks.
Any thoughts, suggestions, or comments would be greatly appreciated.


texts: How to get the phase response of an arbitrary LTI system?

texts:
If I have a frequency response (of a discrete-time system) composed of several complex exponentials such as $$H(e^{j\omega}) = A_0 + A_1 e^{-j\omega  } + A_2 e^{-j\omega t 2} + A_3 e^{-j\omega 3} + ...$$
How can I determine its phase response? I can't add them up as phasors because they're different frequencies. Here is an example in my textbook:
$$H(e^{j\omega}) = 1 + 2e^{-j\omega} + e^{-j \omega 2} = (2 + 2\cos{\omega})e^{-j\omega} \implies \angle H(e^{j\omega}) = -\omega$$
Here, they manipulate the response to make the phase response look obvious but I would like to know if there is a more algorithmic way to get the phase response by looking at the superposition of the exponentials or something like that? I don't find the "tricks" they use to be very intuitive in getting the phase response.


texts: Remove high-speed noise from power supply

texts:
Could anyone help me a bit sort this out?

I have implemented the following schematic on a PCB for the decoupling of a supply rail of an Ethernet Switch.

More specifically it is the IO supply of the SSMII interface. This implementation is also what the manufacturer proposes. The 3.3V comes from a step-down DC-DC converter.

I have noticed that the power supply after the L (so IC side) is not very clean. When measured with the oscilloscope on pin 1 of L462, I had the following waveform

The frequency measured by the oscilloscope is not always the same. It varies a bit between 25MHz and 60MHz. Although this was true before making the following changes (the measurement was taken with These)

Substitute one 10nF and one 100nF with two 330pF capacitors
Add an additional 4.7uF capacitor (all ceramic) at the L462.1 pin.

On the other side, the L462.2 side, all Looks quieter.

What can I additionally do in order to have a cleaner power supply? Use an additional capacitor? Replace with another value? Normally at these frequencies the 100nF and 10nF are indeed effective, no?

Here also the layout. The supply rail after the bead (the relative big component upper left) is coloured with yellow. They are all connected through a small plane on an inner layer. It is probably not ideal that many capacitors share the same via, but at this area there are not any more GND balls. Also probably the light green capacitors should be turned horizontally and be connected to the two GND vias on the right side of the image.

So, I took some new measurements by using the technique of soldering a Coax cable directly on a capacitor and the results can be seen in the waveforms below.

First at L462.1:

and second at the L462.2 pin:

I mean, apart from the frequency (here I detected more clearly the 31.25MHz, which is the half of the 62.5MHz with which the data signals of this Interface work), it is still clear that the disturbances are there and that they are filtered away from the main board's supply with the ferrite bead.

Then, lastly, I substituted the ferrite bead with a 0-Ohm resistor:

I think it is clear that the disturbances come from the IC and that without the filtering the situation would be worse.

So the question remains, how to make the power supply quieter?


texts:
hei Guys, im not sure about but i think is the input Vin<0 the Output Voltage will remain 0,7 and when the input higher than Vin>3 the output Voltage will stay -3 ....
and in case we remove the resistance R2 and the vin <0 than the Vout=0,7 and the if Vin>0  than it will stay  -3V ? thank you for ur help ...


texts: I want to measure the current that can be supplied from a lead acid battery I have. (To know it's remaining current supplying capacity). To measure current I need to connect a load and an ammeter (multimeter, with knob to direct current) in series with the battery. Can I use another multimeter (I have two of them) with a larger internal resistance (knob towards dc voltage), as the series load, if I don't have any spare loads with me?


texts: Task switching on Cortext-M3 crashes after IRQ

texts:
I've used an exokernel model for my ARM OS. When a task wants to read from a UART it calls a library function, which, if there's no data, makes a SVC call to block the task (which causes the kernel to put the task in the wait queue for that IRQ and enables the IRQ). When the interrupt happens, all the tasks waiting on it are moved to the runnable queue and the interrupt is disabled again.

This model was working fine when I had a fixed array of tasks, but now I've moved to linked lists to allow for more types of wait queue (e.g. IPC messages). Something in the change is causing a crash. Here's the debug output:

Creating task 0 (idle task)
task0 stack top is 2007cd20
Starting SysTick @ 100Hz
Becoming task 0
Switching to task gsm@2007c008 with SP 2007c3e8
GSM task starting
Switching to task rfid@2007c430 with SP 2007c810
Monitoring RFID reader
Blocking task rfid on IRQ 7
Switching to task gps@2007c858 with SP 2007cc38
Switching to task task0@2007cc80 with SP 2007ccd8
Switching to task gsm@2007c008 with SP 2007c390
Blocking task gsm on IRQ 8
Switching to task gps@2007c858 with SP 2007cc38
Switching to task task0@2007cc80 with SP 2007ccd8
Switching to task gps@2007c858 with SP 2007cc38
Starting GPS tracking
Blocking task gps on IRQ 6
Switching to task task0@2007cc80 with SP 2007ccd8
[... repeats...]
Switching to task task0@2007cc80 with SP 2007ccd8
Unblocking tasks waiting on IRQ 8
Switching to task gsm@2007c008 with SP 2007c3a0
Switching to task task0@2007cc80 with SP 2007ccd8
Switching to task gsm@2007c008 with SP 2007c3a0
Fault: �� �
   r0 = 2007c3a0
   r1 = 10007fb8
   r2 = 2007ccd8
   r3 = 10007fb8
  r12 = 00000008
   lr = fffffffd
   pc = 0070c858
  psr = 00000003
 BFAR = e000ed38
 CFSR = 00040000
 DFSR = 00000000
 AFSR = 00000000
SHCSR = 00070008

So everything is fine until the interrupt. The actual output varies depending on which UART has data first, but the pattern is the same: when an interrupt happens, a fault occurs when the unblocked task is switched to the second time.

Here's the relevant bits of code. An assembly shim:

zeptos_pendsv_isr:
    push {lr}
    mrs r0, psp
    stmfd r0!, {r4-r11}
    bl zeptos_schedule
    ldmfd r0!, {r4-r11}
    msr psp, r0
    pop {pc}

And the C functions:

static void pendsv(void) {
    SCB->ICSR |= 1 << 28;
}

void *zeptos_schedule(void *sp) {
    if (current_task) {
        current_task->sp = sp;
        DL_APPEND(runnable_tasks, current_task);
    }
    current_task = runnable_tasks;
    DL_DELETE(runnable_tasks, current_task);
    zeptos_printf("Switching to task %s@%p with SP %p\n", current_task->name, current_task, current_task->sp);
    return current_task->sp;
}

static void block(void *sp, uint8_t irq) {
    zeptos_printf("Blocking task %s on IRQ %i\n", current_task->name, irq);
    current_task->sp = sp;
    DL_APPEND(irq_blocked_tasks[irq], current_task);
    current_task = 0;
    NVIC_EnableIRQ(irq);
    pendsv();
}

void __attribute__((interrupt)) zeptos_isr(void) {
    int irq = (SCB->ICSR & 0xff) - 16;
    zeptos_printf("Unblocking tasks waiting on IRQ %i\n", irq);
    NVIC_DisableIRQ(irq);
    // NVIC_ClearPendingIRQ(irq);
    DL_CONCAT(runnable_tasks, irq_blocked_tasks[irq]);
    irq_blocked_tasks[irq] = 0;
    pendsv();
}

void __attribute__((interrupt)) zeptos_svc_isr(void) {
    __disable_irq();
    uint32_t *sp = (uint32_t *) __get_PSP();
    uint32_t pc = sp[6];
    uint8_t svc_type = *((uint8_t *) pc - 2);
    switch (svc_type) {
        case 0:
            sleep(sp[0]);
            break;

        case 1:
            block(sp, sp[0]);
            break;

        default:
            zeptos_puts("Bad SVC type\n");
    }
    __enable_irq();
}

void Zeptos_BlockOnIrq(uint8_t irq) {
    asm("svc 1");
}

SVC, SysTick and PendSV are priority 29, 30 and 31 respectively.

Any suggestions? Where should I be looking?


texts: Trying to understand the difference between a regular clocked flip flop and a falling edge triggered one

texts:
I tried simulating both:

Falling edge triggered one

Regular clocked JK flip flop

I think there is something wrong with them because when both inputs are high they look like they are having a seizure rather than toggling.

I thought I understood it, I've tinkered with it, I've looked at the scopes but at this point I am a bit lost.


texts:
I have some extra 1n4007 diodes, and was wondering whether, instead of using a power supply to drop the voltage, could I could power LEDs by just making a full wave rectifier, Using a capacitor to smooth out the power and powering n LEDs in series?

Here is the spec sheet: http://www.jameco.com/Jameco/Products/ProdDS/2095171.pdf

These LEDs are rated to go as high as 2.6V (red) or down to 1.9V.  Could I create a series of 120/2.1 = 58 of them? With voltage going up as high as 128V, that's still 2.2V, well within spec.

This would mean that each LED would be less bright than maximum but would run cooler. Would that result in less efficiency? From the spec sheet, it looks like within a fairly large range, light output is pretty linear.

The current for this would be somewhere in the 20-30mA range.
Aside from the potential for failure of one LED in series to kill the light, is this a reasonable hack? It seems to me that it's at least very efficient.  The only losses I can see in this circuit would be in the diodes.  I should see perhaps a 1V drop in the 1n4007?

Is there anything more efficient I can do?


texts: Stepper Motors (NEMA-17) Won't Run When Wheels Are Attached

texts:
My team and I are creating a robot using 4 stepper motors with mecanum wheels and an Arduino Uno. The code appears to be correct, and the motors seem to run just fine on their own, but once we screw on the mecanum wheels they can no longer turn. If we unscrew the mecanum wheels until they are not at all gripping the motor shaft, they wheels will turn with the motors but then we have the issue of the wheels falling off. We are running out of time to complete this robot, and we are struggling with mobility right now due to the inconsistency of the motors with the wheels. Any ideas as to why they won't turn properly?

Can post code if needed.
Motors do turn by hand.


texts: How to connect wires between power supply and switch?

texts:
I'm trying to connect non-fused and European AC power socket/toggle switch to power supply. Probably very "newbie" question but as a starter I didn't want to try-fail with this thing for safety reasons and decided to ask.

I found several wiring diagrams for different types of sockets but couldn't find exact same one with my parts.

Here is my parts on image, how can I connect these properly and safely?


texts: Circuit analysis by local application of Kirchhoff's current law and Ohm's law

texts:
First of all I want to say that this is a new field for me, so please excuse any inaccuracy in the used terminology and the lack of understanding of some concepts.

I am trying to understand whether it is possible to perform a circuit analysis (find voltage and current around complex circuit) by applying the following constraints:

Apply Kirchhoff's current law  for every junction
Ohm's law for all electrical components
For each energy source one terminal has a predefined V, while for the other the V is 0

I have found a description of the method for Nodal Voltage Analysis which seems not to need to enumerate all closed circuits and apply Kirchhoffs's voltage law.

In the end, I want to be able to perform such circuit analysis by applying the above defined "local rules" which do not rely on knowing of the whole network. So it is an algorithm which relies on the assumption that "the whole = the sum of the parts". What do you think, is such an approach possible?


texts:
Can someone tell me on what how to detect a short circuit and LED open circuit for the below circuit?
Is it possible to detect which LED?
Could someone provide a circuit which would help to detect an LED short circuit or LED open circuit if all the below LEDs are connected in series as a single string?
I just require a circuit which will detect LED Failure (LED open or LED Short) when the LEDs are working during its normal operation.


texts: short circuit on the output of a linear voltage regulator

texts:
I am using the L78L33 on my board in TO-92 package; the weather outside is cold (it is used inside vehicles) and I have had it fail in one of six boards. It has worked for some hours then died out, and the vehicle is a new passenger car with its 12V socket doing fine with other equipment (i.e. not causing them any damage). It looks as in the pictures, with non apparent damage to it besides that small cutter-made-like mark. No other parts got damaged.

I have just noticed how the datasheet said

  If adequate heat-sink is provided, they can deliver up to 100 mA
  output current.

I am drawing about 40-50 mA max and there is no heat sink installed. Can this be why the part has failed, even in cold weather ? I am thinking more of some bad soldering, but I don't know really...

Hmm, there is one other thing. There is one switch button connected to an INPUT pin of the MCU, and I am always sloppy with the solder joints around that pin. meaning that I do short the designated INPUT pin with one or two surrounding unused pins which are left to be just as the MCU configures them on start-up, so I would think OUTPUT. Could this be causing issues ?


texts:
I've seen a partially diffusing flexible optic fiber used in several places, but I can't figure out what exactly to google to find the stuff. Does it have a name?

I'd like to stick leds to each end of a ~50cm piece of it, and have it light up all the way.


texts: Any good solutions for dealing with resistors for color-deficient tinkerers?

texts:
Possible Duplicate:
  Resistor suggestions for colorblind person

My color deficiency is bad enough that a year of fiddling with resistors in high school was enough to frustrate me right out of considering EE as a career.  I'm spending a fair chunk of time on the arduino now, but it is still a frustration: identifying resistors.

Most of the seasoned EEs I know could scan through a pile of resistors and spot the one that they're after, looking for the pattern of colors that they knew would be on the parts.  For me, this is quite simply impossible.  If you think it's no big deal, try finding your resistors in a pile with only the light of a deep blue LED to work from.

So, before I go out and buy 500 of every resistor and just dispose of them every time I pull them off a breadboard, does anyone have any suggestions?  I'd love to find a supplier of axial resistors who actually prints resistance values instead of color bands.  Failing in that, I'd even resort to stickers.  I'm not about to pull out my phone to try to ID resistors.  That would take more time than futzing with the multimeter, and I want a better solution than that.

Thanks.


texts: Photodiode Circuit for measuring light intensity

texts:
I was wondering how to effectively read a photodiode datasheet. Leds have max current ratings and voltage drops clearly listed but the photodiode one confuses me.

Im trying to calculate a resistance value to add in series with it but am unsure.

I see light current, dark current, and some have forward voltage and some have just reverse on the datasheets, so I am really confused.

I just want my photodiode to be most sensitive to changes in light.

Using this PD

http://www.marktechopto.com/pdf/products/datasheet/MTD5052N.pdf

I wanted to drive it with 5V supply.

UPDATE:

I just tested it with the photodiode in series with a resistor to give its light current rating. I measure the voltage across the photodiode and it changes with more light, but I thought the voltage is supposed to stay constant im confused. Is there a problem with my current setup?


texts: Making a parallel connection = increasing the total current?

texts:
Considering the scheme below

simulate this circuit – Schematic created using CircuitLab

Am, I understand correct, in real life, if I will step-by-step add the parallel resistors, the total curent will grow, and even there only 1V, the value of curent can be over 10 50 100 or more A? And hence, even an 1V voltage source can melt a wire, or create strong magnetic field?


texts: Error in my efficiency calculation for FWB rectifier?

texts:
Question reads:

  A full-wave bridge rectifier with an RL load is connected to a 120V source. If the load resistance is 10.8 \$\Omega\$ and L is very large, find:

  (a) Average load voltage

  (b) Average load current

  (c) Max load current

  (d) RMS value of load current

  (e) Average current in each diode

  (f) RMS current in each diode

  (g) Power supplied to the load

  (h) Ripple factors of the load voltage and current

  (i) Rectifier efficiency

So,

(a) $$V_{o(avg)}=\frac{2V_m}{\pi} =\frac{2\sqrt{2}V_s}{\pi} =108.04 \text{ V} $$

(b) $$\frac{V_{o(avg)}}{R}=\frac{2V_m}{\pi R}=10 \text{ A} $$

(c) $$\text{Should just be when $V_{m}$ is peak and $R$ is minimum, hence, }10 \text{ A} $$

(d) $$\text{Very large $L$ as given in the question}$$
$$\text{therefore the RMS current can be assumed to be equal to $I_{o(avg)}$, hence, }10 \text{ A} $$

(e) $$I_{D(avg)}=\frac{I_{o(avg)}}{2}=5 \text{ A} $$

(f) $$I_{D(RMS)}=\frac{I_{o(avg)}}{\sqrt{2}}=3.54 \text{ A} $$

(g) $$P_o=I_{o(avg)} \cdot V_{o(avg)}=1080.4 \text{ W} $$

(h) $$RF_V=\sqrt{\frac{V^2_{RMS}}{V^2_{o(avg)}}-1} = 0.619$$

$$RF_I=\sqrt{\frac{I^2_{RMS}}{I^2_{o(avg)}}-1} = 0 $$

(i)  $$\text{Efficiency}=\frac{V_{o(avg)}\cdot I_{o(avg)}}{V_{RMS}\cdot I_{RMS}} = \frac{108.048\cdot 10}{\frac{120\sqrt{2}}{2}\cdot 10} = 1.273$$

Assuming, \$V_{RMS} = \frac{V_s \sqrt{2}}{2}\$

Obviously the efficiency shouldn't be greater than one... What have I done wrong?

Following Felthry's comment, I notice the above formula for \$V_{RMS}\$ only stands for half-wave rectification, hence, \$V_{RMS} = 120 \text{ V}\$ and the efficiency ~90%.


texts: How multiple data transmission (in the form electrical signals) work?

texts: I am studying data communication and networking. While reading about data transfer using electrical signals, I came across 'frequency division multiplexing'. I understood how data is transferred in the form of electrical signals i.e. by way of modulating frequency, amplitude etc. Understanding a one way transmission is easy but I am having difficulty grasping the concept of two-way simultaneous transmission as well as multiple transmissions on high speed lines :( I am wondering how multiple electrical signals are transferred without disturbing each other. Don't they interfere into each others frequency ?


texts: Noise on Bluetooth Low Energy module power supply

texts:
I have a bluetooth low energy module (BLE112), which I'm trying to use on my PCB. When I supply JUST the module with a coin cell battery, it works great and I can see it advertising on my wireless packet sniffer. But when I switch to powering it with the 3.3V rail on my PCB, it won't do any wireless communication anymore, though I can still communicate with it over the USART. I am pretty confident that the problem is related to noise on the supply line, as it will still fail when the only wires going to the module are 3.3V and ground. The documentation for the module says that the RF ground is connected internally to the regular ground; is that part of the problem? The documentation also says a ferrite bead is recommended to be used to filter out excessive noise in the power supply lines, but how do I choose one and where does it go?

What can I do to get rid of the noise?


texts: Power consumption of APA102c LED 10mm grid

texts:
I have two of these 16x16 grids (https://www.pololu.com/product/2533) with leds programmed to have white color (255, 255, 255) and brightness level = 16. I have a power supply with maximum of 16A current.

This entire setup has a power consumption of 12.8A at 5V. This is a lot of power being consumed and I might have to switch the power supply in case I need to connect 6 more panels to the current setup.

Any idea how I can reduce the power consumption while having brightness level = 16 and white color for all leds? I would highly appreciate.

Thanks


texts: Which one is the correct symbol of enhancement type MOSFET?

texts:
I studied MOSFET from ' Electric Devices and Circuit Theories by Robert L. Boylestad ' The symbols of depletion type and enhancement type MOSFET are given below from the book.

But recently, in the book of Sedra/Smith named Microelectronic Circuits, I have found that the symbol of enhancement type is similar to the symbol of depletion type of Boylestad's book.

I've seen in the datasheet of many MOSFET that the enhancement type symbol is like the Boylestad's book.

Which one is correct?


texts:
I need to measure 3-phases. Usually I would use CTs on the differential port on a LTC1966, then connect Vout+ to an ADC port on a uC.

I do that on a 1-phase application. The problem is now, that we have only one available ADC port in our existing application and it cannot be changed. However, we could use I2C (RX/TX) communication.

As example, I could use three LTC1966 and some uC with more ADC and send data through RX/TX or maybe even a standalone ADC. But if possible I would like a SoC.

We cannot touch existing installed cables therefore the usage of CTs. I also know of the problem not actually being able to measure the real voltage level on each phase, but as said, cannot go into existing installation.


texts: What is the advantage of RLC low pass filter over two RC conneced in series?

texts:
I guess two RC in series should be a second order low pass filter. Because the transfer function will have s^2. And an RLC low pass filter is a second order filter for sure.

So what is the difference between to RC in series and one RLC filter.


texts:
I've been working on providing power for high current applications for my project. I'm working on a project with high current (or at least compared to what I'm used to...)

What a lot of people point to online is tables that you can look up the resistance for AWG per foot, and then you can calculate the current drop of your wire. However, with that current drop, how much of  a voltage drop will make my wire "too hot" and risk a fire? Am I looking at this the wrong way? How do I calculate the temperature of the wire and decide when it'll be too hot, and I should use a thicker wire?


texts: Calculating input impedance of 3 port network

texts:
I am trying to derive a expression for calculating the input impedance of a 3 port network to use as direct calculating code and avoid SPICE/simulator solving of the same.

I am able to solve the input impedance of a 2 port system  with a load, \$Z_{load}\$, connected to port 2. The impedance looking into port 1 would be (by solving basic 2 port theory):

$$
Z_{in} = Z_{11} - \frac{Z_{21}Z_{12}}{Z_{22}+Z_{load}}
$$

If I have a 3 port network with 2 ports connected to different loads, \$Z_{load1}\$ and \$Z_{load2}\$, how can I generate an expression for \$Z_{in}\$ looking in from port 1 starting from only the Z-matrix, \$Z_{load1}\$ and \$Z_{load2}\$?


texts:
I need to a single mode 1550 optical circulator at my lab. I have a varied supply of components, but no circulator. Any idea how I can make one myself? Perhaps using coupler and isolator?

Thanks.

-D


texts: MOSFET selection for reverse polarity detection

texts:
I'm building a reverse polarity protection circuit using an N-channel MOSFET (see figure below)

For the battery I'll be using an 18650 cell which will range from 4.2 - 3.3V. The max discharge of my circuit will be about 10A. I'm currently looking at this MOSFET. The specs all seem to fall within my parameters but I have a feeling that there's no way a MOSFET this small could provide that much power; am I just over thinking this?


texts: Safety Equipment and Precautions for DC Circuit Experimentation and Development

texts:
What safety equipment and precautions should I use when learning about, experimenting with, and analyzing DC circuits? I have a power supply capable of 32V@5A and 16V@10A (which supports selectable constant current or constant voltage). I'll be working with multimeters and oscilloscopes for analysis while creating circuits.

I don't want to kill myself, burn off a finger, or burn down my house. Not destroying my equipment would be nice too, but that is secondary to not destroying myself. Primarily, what safety equipment should be used? For example, gloves, eye protection, insulated and/or grounding mats, etc.


texts:
I was put in charge of redesigning a motor control circuit which accepts 24-40V DC on its input.

As a side note: As far as i know, the existing circuit has been working fine for several years. The redesign aims to make the production cheaper and replace all obsolete THT parts with SMD and optimizing some other stuff.

The current circuit is protected by a 3A fuse and a varistor of type S10K30. Looking at the datasheet (see below), the "30" obviously refers to the \$ V_{RMS} \$ rating.

What bothers me is, that \$ V_{dc} \$ is 38V. I would've chosen the next lager type with a continuous DC voltage rating of at least >40V (more like 44V for +/-10% supply tolerance).

I am trying to understand if this varistor type was a poor choice by the engineer, or if I am missing something (I never had to choose a varistor before).

The data-sheet further specifies \$ V_v=47V \$, but I am not sure how to interpret this parameter.

What does the (1 mA) exactly mean? Does the varistor sink about 1 mA @ 47V? Is this the reason why the original developer was fine with this particular type, because he did not care if the varistor permanently consumes

$$ P = 47V * 1mA = 0,047W $$

Is this bad practice or somehow justified?
How to properly choose the correct varistor for this application?


texts:
I could not find I2C app note or pinout details in datasheet.
Based on my understanding i have drawn the I2C connection from FT4232H.
Is it my understanding is correct ?


texts: How to use 1PPS to Synchronize ESP32 Clocks and Peripherals

texts:
I've read a few posts (example) about what the 1PPS signal is and how it can be used at a high-level, but I'm still not sure how to actually implement it on a PCB schematic to sync up with my microcontroller (ESP32). Do I just connect the 1PPS to a GPIO on the ESP32 and configure the rest in software? What would that look like?

For reference, here's my schematic showing just the MCU, external flash, and my crystal (configured based on the ESP32 Hardware Design Guidelines). You'll notice there's four different clock frequencies. How can I calibrate all of them based on the 1PPS? What are the hardware steps and subsequent firmware steps?


texts:
Here is my program:

int32_t socket;
uint8_t *sendbuf;

void SetSCK(){

            socket = netUDP_GetSocket(udp_cb_func);
            if (socket >= 0)
            {
                    netUDP_Open(socket,0);
                    netUDP_SetOption (socket, netUDP_OptionTTL, 20);
            }
}

void Time3(void){
TIM_TimeBaseInitTypeDef TimeStruct;
NVIC_InitTypeDef nvicStructure;

NVIC_PriorityGroupConfig(NVIC_PriorityGroup_3);
nvicStructure.NVIC_IRQChannel = TIM3_IRQn;
nvicStructure.NVIC_IRQChannelPreemptionPriority =1;
nvicStructure.NVIC_IRQChannelSubPriority = 0;
nvicStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&nvicStructure);

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);
TimeStruct.TIM_Prescaler=35;
TimeStruct.TIM_Period=200;  ///200=100us
TimeStruct.TIM_ClockDivision=TIM_CKD_DIV1;
TimeStruct.TIM_CounterMode= TIM_CounterMode_Up ;
TIM_TimeBaseInit(TIM3, &TimeStruct);
TIM_Cmd(TIM3, ENABLE);
TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE);
}

/*###########################################
##############Main Function##################
###########################################*/

int main (void){
    CLOCK();
    GPIO_SetBits(GPIOA,GPIO_Pin_5);
    LongDelay();
    netInitialize();
    LongDelay();
    Time3();
    GPIO_ResetBits(GPIOA,GPIO_Pin_5);

    do {
    osDelay(500U);
    netIF_GetOption(NET_IF_CLASS_ETH | 0, netIF_OptionIP4_Address, (uint8_t *)&addr, sizeof (addr));
    } while (addr == 0U);

    SetSCK();

    while (1)

    {

        if(Alarm==1)
        {
            Alarm=0;
            Ethers();
        }

    }
}

void Ethers(void)
{
            NET_ADDR addrUDP={ NET_ADDR_IP4, 5022, 192, 168,1,10};
            if(socket>=0){
            CheckAlarm=0;
            Data();
            sendbuf =  netUDP_GetBuffer (Ether.Size);
            memcpy (sendbuf, MSG, Ether.Size);
            State=netUDP_Send (socket,&addrUDP,sendbuf,Ether.Size);
}

void TIM3_IRQHandler(){

    Alarm=1;
    TIM_ClearITPendingBit(TIM3, TIM_IT_Update);
}

This program has two main problems:

1) It sends 16bytes each 100 microS, during its transmission it doesn't respond to ping command while it sends data correctly.

2)Sometimes, it stops working for checking its IP has been set correctly

    do {
    osDelay(500U);
    netIF_GetOption(NET_IF_CLASS_ETH | 0, netIF_OptionIP4_Address, (uint8_t *)&addr, sizeof (addr));
    } while (addr == 0U);

I will be grateful if you could help me.


texts: LED strip negative wire connected from the end

texts:
Recently I ordered some christmas led ligths from China, and I wanted to mess with it a bit (dimming, cutting it to parts), and i noticed that it is wired differently than I expected.

It seems that the negative wire is carried all the way to the last LED and only then it is connected to each one of them one by one, while the positive, is connected from the source side.

Is there any advantage, on the electrical side, to do this instead of just going straight like this:

Or maybe the only benefit is in toughness.


texts:
Basically I want to create a BPM calculator on an ATMega1284.

So I have a mic hooked to the ADC already (with potentiometer). I can probably calculate the BPM by getting samples for a while and getting the avg Sound level. From there I can check for peaks by comparing to the avg sound level. If its 6db (twice the volume) its usually a peak/beat in music. But then we have 8th notes and other things messing up the BPM as they're faster. And also the music overall could get louder in chorus...

I just need a cheap way to get close enough and make it feel like I have the BPM down. Maybe just calculate the BPM for the first 4-8 secs then move on...

The calculator microcontroller can then transfer the BPM via UART to another microcontroller and from then on I can just transfer the volume intensity. The project is basically a light show.

Some thing's I need. I'm not sure how to see the time elapsed between calculations. In C++ in the computer I would just check the clock on the computer. How on AVR?


texts:
I have a Kvaser mPCIE card on my embedded Linux machine. Most standard Unix distributions come with a socketCAN driver module which takes care of any CAN devices present in the system, hence I can easily communicate with the CAN bus using socketCAN only.

On Kvaser's website they have their own drivers available which are based on socketCAN, but are distinctively different. Once I install them, I am unable to use socketCAN any more as it gets blacklisted from auto-loading.

What are the advantages of using Kvaser's own drivers (if any) and should I be using them?


texts: I have achieved FAN Dimming using Phase chopping method, here I get smooth dimming on Incandescent Bulbs and I am also able to dim FAN using the same. But during FAN dimming it makes a lot of humming noise due to added harmonics. Can anyone explain this humming in detail and tell how to reduce this noise?


texts:
I asked to design a sequence detector to detect 0110 and when this sequence happend turn it's output to 1 for 2 clock cycles.

Here is what I designed:

But the problem is it turns the output to 1, one clock cycle late IE if it encountered 0110 it doesn't turn output to 1 but instead it turns output to 1 on next positive edge of clk as you can see in below timing diagram.

I tried so much to solve it but I can't :(
Can someone help me please

Edit: I have to add I know the problem is: y2 D flip flop is synchronised with Q1 D flip flop but what to do instead?

Edit 2:

New state diagram

Edit 3:

New state diagram


texts: Trying to optimize simple PLL phase discriminator - Isn't there an off-the-shelf equivalent?

texts:
What I'm after is the "number 3" phase discriminator from the venerable 4046 PLL. That is, an edge-detected SR latch, effectively. A rising edge on input 1 makes the output go high. A rising edge on input 2 makes the output return low.

That's it. No fancy shenanigans. Here's one:

simulate this circuit – Schematic created using CircuitLab

Trouble is, that's a bunch of discrete logic. The 4046 is one TSSOP-16 package, but you throw away most of the functionality.

Frankly, I just can't believe that this exact thing isn't available as a SOT23-5 out there somewhere. But all of the SR latch / flip-flops I find on DigiKey are neither edge triggered, nor are they positive (rising edge) logic.


texts:
I work for a small office that is relocating. Recently all new computers have been purchased for staff. In preparation for the move, I noticed that virtually all the surge protectors in the office seem probably older than 10 years. Is there a surge protector replacement guideline? Should we buy all brand new surge protectors/UPS?

The lights on all of the current surge protectors indicate that working. Earlier this summer there was an explosion at substation a few blocks away, so there could have been a power surge at the office. However it did not seem to impact the computers or surge protectors.

Thanks for any advice!


texts: What happens to a  charged capacitor when it is short circuited ? Will it going to damage ? Or will it going to be safe ?


texts:
To clarify the question: As far as I understand, a ADC (Analogue to Digital Convertor) will sample and therefore quantize an analogue signal. Does a ADC therefore output a Pulse Amplitude Modulation (PAM) signal? And if not, why not?

If you look at Pulse Amplitude Modulation, on Wikipedia, you see that PAM "..is a form of signal modulation where the message is encoded in the amplitude of a series of signal pulses". Therefore, the mere sampling of an analogue signal results in PAM. The article goes on to say "Demodulation is performed by detecting the amplitude level of the carrier at every single period." However, when an analogue signal is sampled, the information is encoded. No actual need for modulating a carrier. It seems.

P.S. The question may appear rather odd, but I'm coming from the world of AM and SSB amateur radio, where modulation conjures a certain image of what modulation amounts to.


texts: Why is my N-channel MOSFET getting very hot and the power it provides to device increases with temperature?

texts:
I have a fairly simple situation:
N-Channel MOSFET with base connected to Raspberry Pi's 3.3V source connected to ground and Drain connected this way: +12V ----> Vacuum Cleaner (60W) -----> Drain. Guy in the electronics shop told me, this transistor's (1D33AA BUZ11) gonna carry big current no problem, but as I stated in the question it is getting very hot, and the vacuum cleaner reaches its full power slowly (but the hotter the transistor the more power provided)


texts: How do I re-wire my Airstream Fusebox so as to follow best practices?

texts:
I was not sure if this was better suited for Automotive Stack Exchange, but here goes. I'm tying to redo the fuse panel in my Airstream and I have some questions about the best way to wire it. The current panel is wired like this.

The system has two batteries that are connected in parallel, and fused across each battery. Currently there is no off switch other than to disconnect the battery. I'm looking to replace with modern components like this fuse block but also potentially ad a duel battery switch like this one. My question is this, what is my optimal setup, if the batteries are matching batteries, do I need to fuse them both, and do i need to do that on both the negative and the positive side like the current configuration?

The three configurations I envisioned are below, not sure what is overkill. Also, thought on using ANL, vs Maxi, VS AGO fuses for the bigger fuses ? the ANL fuses take up allot of space and as you can see from the photo space is limited.


texts: Voltage requirements for charging Nokia phone

texts:
I have an old Nokia phone which charges fine from the adaptor, but refuses to charge using a USB charging cable.

Note that this isn't a normal USB cable, as you can see from the picture, it's got a USB A connector at one end, and a Nokia DC jack at the other.

What's strange is that even if connect this cable to a beefy 5v power supply, the phone still refuses to charge. I know that power is getting through because I can measure the voltage at the phone end of the cable, and the phone seems to notice when I connect the cable, but still won't charge.

Do Nokia phones have some nasty trick they use to prevent unlicensed chargers working with them?


texts: Problem interfacing Platform Cable USB DLC9G

texts:
I just started working with FPGAs/CPLDs. Coding and simulation went well and now I wish to program a device. So, I bought the DLC9G programmer plugged it into the USB port. I di not install any drivers, since the cable drivers were installed during the ISE WebPACK installation process. The message popped up:

So, I clicked on it for detailed information:

I went to the Device Manager and right-clicked one the Unknown device to update the driver. I manually pointed out the path suggested by @Tut in his comment, but it said that the driver was up-to-date (hopefully that was said about the driver for the cable).

I decided to take a different route and followed the ug344 guide for device configuration. For my Win7 x64 and ISE 14.7 WEBAPCK I downloaded a ug344_windows.zip dirver stated on p.15, Step 5.2 of the guide. After extracting the files and running the install_xusb.bat as administrator, I got the following message from the console window "cannot run x86 build of this utility on x64 platform":

Any one has an idea if this is a defective device, or it's because of the driver issues? what's the problem with the driver installation? Should this device be at least recognized as programming cable/xilinx product if no driver is present?


texts: So I have battery cells with a rated capacity of 3.5Ah and a nominal voltage of 3.5v Now, say I have a system that requires 12A for a period of 10 seconds. For this battery it is advised not to discharge beyond 2C or the efficiency hit becomes unreasonable. From my understanding, I can increase the amount of batteries in parallel to increase the capacity, but cannot increase the available current. Correct? Will this cell be unable to meet the 12A requirement? I think I'm missing a concept here. At 1C this battery can discharge 3.5A for 1hour. So then can it discharge 14A for 15 minutes then? If that's the case, then can I not use a much lower c rate to achieve this requirement? at C/10 I discharge .35A for one hour. Or it could be more if I decrease the time, possibly getting me my 12A for 10 seconds. What is the limit on this?