texts: Single phase double pole cap. start motor siezes up

texts:
Power off- motor freewheels
Power on- motor runs for a few minutes then siezes up.
Power off immediately-  Motor freewheels.

Is the capacitor shorting out internally from heat?  How can I check for this, continuity from terminal to case AFTER discharging, maybe?


texts:
I would like to use a pull-down resistor on the input of a NOT logic gate. I am using a 5V microcontroller, and I want to ensure that the input of the gate will never be floating (eg. microcontroller damage).

General information:
The logic gate I am using is a HD74LS04 inverter whose datasheet can be found here. I am testing the output by placing my positive multi-meter lead on R4 and the negative lead on GND. With the digital pin floating, the output of 1Y is 4.33V. This is the expected behavior.

The logic gate requires a minimum of 2.0V for Vih. If I understand this circuit correctly, I expect the voltage at pin 1A to be 3.76V since R2 and R3 will form a voltage divider. This value seems plenty to signify a 'high' in the logic gate.

R2 exists to protect the digital pin. Ideally, I would have liked R2 to be 1KΩ. Increasing the value of R2 means I have to increase the value of R3 to maintain the same voltage divider. During testing I found that if R3 was any value over 3.3KΩ, the pin 1A would not get pulled down all the way if I left the digital pin floating.

Tests:
If I disconnect everything except GND and Vcc and place the positive lead of my multi-meter on pin 1A (now floating) and the negative lead to GND, I read 1.49V. Placing a pull-down resistor (R3) on pin 1A to GND with a value of 100Ω changes the reading to 0.02V. Increasing the resistor's value to 330Ω increases the reading to 0.07V. At the value I need, 3.3KΩ, the reading increases to 0.60V. Finally, changing the resistor's value to 1MΩ increases the reading to 1.47V and actually changes the output of pin 1Y to low.

The test that uses the 3.3KΩ resistor is concerning. The reading I took (0.60V) seems to be approaching the Vil maximum of the logic gate which is 0.80V.

Questions:
This must be a trivial question, but why does an R3 value of 3.3KΩ not pull pin 1A all the way to GND? Is there a formula for determining the correct pull-down resistor value? Other answers I found on here simply state 10KΩ as a 'good' value for a pull-up resistor. I'm not sure where that value comes from or if it is applicable to a pull-down resistor.

simulate this circuit – Schematic created using CircuitLab

Edit:
Although Ignacio's answer technically answers the question, I thought I would share some information I found for others who may come across this question.

User 'Papabravo' on the All About Circuits form states that the calculation for a pull down resistor can be calculated by taking the Vil (0.8V) and dividing it by the "standard TTL load" of 1.6mA. As Ignacio pointed out, my specific logic gate can source up to 0.4mA, so the calculation would be 0.8/0.0004A which equals 2KΩ. For safety, I performed the calculation at 0.5V in order to give myself some headroom.

Other Resources:
Sparkfun's logic gate tutorial


texts: A question about very simple light Dimmer circuit?

texts:
I've learned that a Triac works as a switch for controlling AC current. Why not connecting the load (L1) and Triac in series? at the position of red arrow? My reason is that a small amount of current will always flows at the direction of green arrow. So, the load will always consume power and I don't think it is a good thing. Am I right?

Also, I don't understand the importance of DIAC. Would you give me a quick tip (information) about it?


texts: Low-pass cutoff frequency definition (-3dB vs. filter design)

texts:
For low-pass filters, we usually define the cutoff frequency as the frequency at which the gain drops by -3dB.

Another definition, however, comes up in filter design as one of the parameters that specify the filter (along with maximum passband attenuation, minimum stopband attenuation and the stopband frequency, see figure below.)

I fail to see how are these related as these two do not seem to be linked.


texts: Designing op amp circuit that has the following signal at the output

texts:
I tried combining several inverters, one summation op amp and one op amp for integration. However, LT-spice produced rubbish at the output, and was really having a tough time doing ac analysis on this big circuit.
The circuit I am talking about is this one:

Few of my colleagues briefly mentioned that this can be done using only two op-amps, but I cant't seem to find that solution. All suggestions will be appreciated. And I am sorry for posting the circuit drawn on paper, but it was easier for me that way to sketch the (presumed) output signals of each stage.


texts: Zener diode with breakdown voltage of 12V. How to plot a graph of V vs I indicating all important points?

texts:
I am bit confused with the question here, because as per my understanding if the breakdown voltage is 12V, then if they are connected in opposite directions there will be no current flow through the circuit.

Then how could I plot a graph of voltage vs current?


texts: Two TVs use the same antenna, but one affects the other

texts:
I’m having a problem with my TVs. I will call them TV1 and TV2. TV1 is Asanzo brand, and TV2 is LG 4K, which is much more expensive.

After replacing the antenna wall socket of TV2 (The TV is near to me in the video), the silly thing happens. Every time I turn off the TV1, TV2 has very weak or no signal. To watch in TV2, I have to turn on TV1 (even when the two TV have different channels) . But when I turn off TV2, TV1 still works normally.

(update: disconnect TV1 from power supply and antenna wire, TV2 still won't work.)

Video: https://www.youtube.com/watch?v=COGERGH66oU

The two TVs have integrated DVB decoder,  use the same antenna with USB power for each one. The antenna has amplifier circuit.

I’m not sure if it’s caused by the new wall socket, because I had replaced it very carefully. Hope to hear your explanation about this and of course the solution. I don’t want to have both TVs on all the time just to watch one. Thank you!


texts:
i have a question..

I have a 4 layer PCB where top layer is a track layer, 1st middle layer is a GND plane, 2rd middle layer is a Vcc plane and bottom layer is a trace layer.

The layer stak table is the following (total thickness 0.81544 mm):

I use "Saturn Design PCB Toolkit", where the situation is described as follow:

for the top layer line, how thickness H must be used for the calculation of the impedance? Is correct 0.076mm? Is the correct tool for the scoope?

Thx,
Loris


texts: Why do lithium batteries vary so much in price?

texts: Ok my actual problem has to do with 2 specific products that are confusing me. So for my camper I’m looking into a 12v 100ah lithium ion LiFeP04 battery and they’re about 850-950 USD link Why does this 100ah cost 950 yet this solar battery pack with 24000mAh costs 40 link. That would mean 4 of these tiny battery packs (24ah) hold the same ah as the battle born beast that’s 950 usd. What am I missing here? If anyone could answer this stupid question I have I would immensely appreciate it!


texts: Limited Wien-Bridge Oscillator Amplitude

texts:
I've already seen a similar question but the circuit was a little bit different.
My question is simple: how do I calculate the maximum amplitude of the oscillation at Vo, as a function of the resistors present here?

Thank you all!


texts: Relationship between sampling rate and number of levels/bits in PCM

texts:
It is said in the books that increasing the levels of quantisation codes in Pulse Code Modulation, or in other words increase the number of bits, could give a better signal.

I understand that having a higher number of bits can represent a value closer to the voltage of the original signal sent out. However, I don't understand how by just increasing the levels could give a better signal if the sampling rate remains constant.

I have a feeling that the sampling rate would affect more on the quality of the signal than increasing the number of levels or bits. Higher sampling rate takes more samples from the original signal to form another signal closer to it.

It's like so what if I had 64 bits if my sampling rate isn't high enough. Then increasing the number of bits will not affect anything to the sampled signal, will it?
Is there a relationship between the sampling rate and the number of levels/bits during PCM quantisation that at one point, increasing either one of them(sampling rate or levels) will not do any difference until the other is being increased?


texts:
Just a simple question, how many poles has this circuit and where are they located?. This circuit is  used to represent the process of charging capacitor 2 from a charged capacitor 1.

I have this 2 simple equations:

1) (V1-V2)/R=V1/sC1

2) (V1-V2)/R=V2/sC2

And then i don't know what to do cause you can simplify the "s" variable by trying to find the Gain as A=sC2/sC1


texts: What technology do IR temperature guns use?

texts: I've seen contactless thermometer guns for sale for ~£40-50, which can read temperatures up to 1000°C. However, the only electronics components I can find which can measure these temperatures without contact seem to be very specialist and very expensive (>£100). The only hobby electronics level IR sensors I can find seem to be rated to either 260°C or 380°C. So what technology are the commercial 1000°C guns using inside?


texts: What are the standard connectors used on 12V hobby batteries?

texts:
I'm looking for a right-angle PCB board mate for the standard 12V hobby battery connectors.

Where can I find these connectors?


texts: Uniden BC780XLT Radio scanner, unknown modification

texts:
I recently purchased an old Uniden BC780XLT scanner. It has been modified replacing two smd resistor with THT resistors with different values. I am curious about this modification: what does it do?

I found the schematic for this radio:  Schematics

In particular, I think the modification involves this part of the circuit with the OPAMP chip IC11 (JRC 3403A)

Datasheet

The two resistor new values are 27kohm and 1.2Mohm, the old ones are 22k and 120k.
From the block diagram of the radio (one of the first pages of the schematics), the IC11 (the circuit in question), is a buffer stage after the FM demodulator.

Help me solve the mystery. The radio works, but I'm still curious!


texts:
I'm attempting to build a noise sensor that detects loud environmental noise. The idea is that the sensor would be able to detect loud music or a loud television within 30 feet, in order to record a noise disturbance.

I've tried a couple of electret mics. The Grove Loudness sensor's signal has too much variance and "bounces" around a lot:
http://www.seeedstudio.com/wiki/Grove_-_Loudness_Sensor

The DFRobot noise sensor's signal is more stable, but it does not detect sound as well as the Grove sensor:
http://www.dfrobot.com/index.php?route=product/product&product_id=83#.U6fDE5RdVYU

Both mics are far too sensitive to vibration, and will output higher signals when a door closes, platform shakes etc than when loud music is playing. And neither mic will have a range of 30 ft.

Does anyone know of better types of mics to try? Or should I consider building my own mic?  Any advice on building my own mic?


texts: Should the error term of PID be normalized?

texts:
By "normalized", I mean +/-1 ~= the maximum error the system can reasonably be expected to experience, or divided by the setpoint.

Background: I am working on a PID controller for an SSR heater which is very responsive (5°C/s up, 0.5-1°C/s cooldown). The setpoint is in the range 100-400°C. In code, this is implemented as:

$$u(t) = K_pe(t) + K_i\sum_{t}e(t) dt + K_d[e(t)-e(t_{-1})]dt^{-1} + K_k$$

(Summation is just an accumulator and Kk is a small steady-state correction)

This form is pretty common in a lot of the open-source PID code out there. However, it occurred to me that if I were to switch to °F, suddenly my K terms would be off by 1.8. This does not feel very mathematically "pure" to me. Furthermore, I found when trying to Ziegler-Nichols tune it, my critical oscillation is ~24s, but when I put this as Ki, I got wild fluctuations. After some digging, I found the equation listed as

$$u(t) = K_c\left( e(t) + \frac{1}{T_i}\sum_{t}e(t) dt + {T_d}\Delta e(t)dt^{-1} + K_k \right)$$

And I had a lightbulb moment. Is this the more "pure" form to use? This makes more sense when dealing with transfer function analysis and the like.


texts: How to calculate current consumption of this sensor?

texts:
I am calculating the current consumption of an IR ranging detection sensor. Below is the related part I captured from the sensor's specification. The working mechanism of the sensor is that it will send out an IR beam, and then measure the elapse time when it receive back the beam.

From the table below, I think it means the sensor will take 33ms to take one measurement. So what does the "Active Ranging average consumption" actually means? How to calculate the current consumption if I take measurement every 0.5s, 1s and 2s?


texts: Output power vs idle power of an audio amplifier

texts:
Let's say I have a AB class power amplifier that is able to give an average output power of 30W on a 6 ohm loudspeaker. Now in general, how much power should the amplifier dissipate when there is no signal applied?

I am asking this because I have an amplifier that dissipates about Vdc*Idc =30W when it is idle. The maximum amplitude (when clipping starts) of the output signal is 20V on a load of 6 ohm and with Ltspice I found that the maximum output power v(t)*i(t) is about 66W and the average power is about 30W. To me it seems like the amplifier dissipates too much when idle, doesn't it?


texts: Why do they keep series resistor with each open drain output during Wired OR logic?

texts:
In a design schematic I have seen series resistors being used in WIRED OR logic.
All 4 input signals are open-drain signals and hence being represented as switches. Can anyone explain why we need R1-R4? Is it for any fault tolerance?

simulate this circuit – Schematic created using CircuitLab


texts: How do I know that enamelled wire is actually conducting the current?

texts:
I am trying to make an electromagnet so I bought magnet wire to wrap around an iron core. I am pretty sure that there is a current running through the copper wire because I attached an alligator clip to one end of the wire and in the process and created a gap and saw sparks. I also tried burning with a lighter the insulator and scraping that part off. I attached the ends of my multimeter to check current and it is showing a very small voltage, like ~100 mV, though my power supply is 9V. I checked to see if my electromagnet is magnetic and just weak and it is not working. I tried using a potentiometer to put current instead of voltage and I got nothing. I am really confused and could use some help.
Thanks in advance!


texts:
Okay so I'm running into trouble with my small setup, and I'm not sure how to go from here.

I've drawn up a very (terrible) schematic of what I currently have wired up:

So currently, I have 12v being supplied to the step down regulator, which pumps out 5v to my Raspberry Pi (green one). This works great!

Now, I'm wanting to use the EN pin, which is, the ENABLE pin. If this pin is grounded, it seems to disable the regulator (not really, but lower the voltage almost completly)

Now, I've wired up the yellow Raspberry Pi this way, and it seems to disable to regulator. If I remove the blue wire, the regulator goes back on, and the green Raspberry Pi gets power again.

I can't seem to control this GND pin, atleast, not with software. I'm wanting to find another solution to this. I'm thinking a transistor, but I'm not entirely sure how that would work out.

Can anyone help me out?

Also, please tell me if I'm doing something wrong. Are these pins being used this way safe? Is it not going to ruin my Raspberry Pi or regulator?

Thanks!


texts:
I have a switch for a water heater. The electric kind that heats instantly overhead as you take a shower. I am an electric engineering student and I am very curious. This switch has six terminals yet it controls one heater. Anyone who has an idea how this is so and how the wiring diagram would look. The switch  has a red light that is on when it is heating. But two of the terminals are separate from the rest and on both sides they end up where the screws to the patrice box are. Hence I they must be for earthing. Can anyone help please?

Photo of the item in question:


texts: I am using atmega16, and i need to use ADC feature in my project. As i know that there is a formula to set flag register ADPS2, ADPS1, and ADPS0. Which is used for determine the division factor between the XTAL frequency and the input clock to the ADC. But i don't know, which one the best division factor i need. How to determine? Should i use division factor 2, 4, 8 or?


texts: L293D and PWM on enable pin: TTL voltage drops to 4 Volts

texts:
I'm building a simple motor shield for Arduino based on the L293D bridge driver. I'm doing some tests on a breadboard everything is fine as long as I drive the motor at full throttle with DC inputs (enable HIGH, inputs HIGH and LOW to spin CW/CCW).

I can regulate the speed applying a TTL PWM signal on the enable pin with a function generator. It works fine but using the oscilloscope I can see the TTL signal drop from 5 to 3,5/4 Volts as soon as I connect it to the L293D enable pin, even with no motor attached. Why is that happening? Is that supposed to be? I thought an enable pin should draw no current and cause no voltage drop.

I tried replacing the IC and the function generator but I still get that behavior. I get no voltage drop using a regular PS and 5V DC.

What's wrong?


texts: Using 2 I2C RGB Color Sensors in Arduino

texts:
I want to use two I2C RGB color sensors (TCS3414-A) in Arduino, but I cannot figure how I change his adresses and I'm asking this because I want them both in use.

They come with 0x39 as default addresses, but as I want to change one to 0x40 and I don't know how to change it, I come here to ask you how I can solve that.

Regards,
Fábio.


texts: Phase lag in output 3 phase 2-level inverter ouput

texts:
I am trying to simulate a 3-phase, 2-level inverter connected to the AC grid in MATLAB, using sinusoidal PWM pulses generated by taking reference from grid voltage.
source voltage(phase rms)=220v;
from the images ,you can see that the reference voltage has a phase angle 0, but the inverter phase voltage has a phase angle of -0.9 degrees(similarly for phase b -1.5 degrees,for phase c -0.3 degrees ). What is the reason of his phase angle and how can I remove this phase difference.
[The abc/dq and dq/abc are for other purpose ,here I just placed them to just check whether the blocks are working or no and the phase lag is not because of these blocks they are working fine.]
#block diagram#
#control block#
#reference voltage from grid

inverter phase voltage


texts: Measuring a potentiometer with noisy power

texts:
I need to measure a potentiometer where the voltage supplied is very noisy and cannot be filtered.

I run into this a lot in my work, but currently I'm trying to measure a steering angle potentiometer on an autonomous ATV using an external Arduino. The problem is that an inaccessible onboard computer is providing the power to the potentiometer, and sensing it for it's own calculations, meaning I cannot supply my own voltage to power the pot. Because of the strong EMI from the engine, the computer/pot ground varies +-1v from the ground rail powering the Arduino(or whatever other sensor I might add). So I need a high impedance way to sense the voltage ratio across the potentiometer without disturbing it. The nominal voltage difference between the ends of the pot is 5V and the wiper swings from 1 to 4V relative to pot ground.

I feel like the obvious solution is to get some kind of differential amplifier/measurement boards with synchronized sampling and do the division in software, but is there a better/more elegant/cheaper way? If not, can anyone recommend differential measurement boards for the Arduino?

I would prefer not to make a custom board, but if I can do it in perfboard, that wouldn't be too bad.

This is like a noisy version of Measuring external voltage on Arduino


texts: How to calculate required voltage + amperage for a linear servo array?

texts:
I would like to control a set of 10 Linear actuators for a robotics project.

The actuators require:

3.7VDC operating voltage
150mA unloaded travelling current draw
450mA stalled current draw

The Arduino UNO requires 5VDC to operate. Say I power the linear actuators externally, what kind of calculations do I make to figure out how much power I need to get them to work for at least two hours?
So worst case scenario is that the 10 actuators are constantly drawing 450mA, so I need a power source that can provide 10 X 450mA = 4500mA.
So this means I need to purchase something like this battery which provides 12v at 4500mA assuming I also connect a voltage regulator to drop to 3.7V?
Update #1
It was suggested (thank you Douglas B. Staple) that I use a Lithium IOn battery because they are a standard at 3.7V this way I would not need to use a regulator.
However, how can I account for the duration of servo usage based on mAh? I previously calculated that since I have 10 servos I would need 4500mAh battery. But how long will that last?
Update #2
Just so that I understand this correctly: Say I want to extend the number of actuators to 32. This means 32 x 150 mA = 4,800 mAh. This means I would need 5 x "18650 cells" to run all 32 actuators continuously for 2 hours?


texts: How to convert 10K Pot raw output ADC data to voltage and resistance from arduino uno?

texts:
I have a simple and basic question. I am using Arduino uno to read the output from a 10K potentiometer. I understand that Uno uses a 10 bit ADC, therefore it can display outputs from 0 as 0V to 1024 as 5V.

Question: I am getting these values from the pot and displayed on the serial monitor of arduino IDE, while I vary the resistance of the 10K Pot. How am I supposed to calculate or know the output voltage and resistance corresponding to the values from 0 to 1024?

Another question is, when I vary the POT's knob to a maximum point i.e. 5V, the output displayed is 1007 or 1008. Isn't it supposed to output 1024 for 5V?


texts:
Let's say I want to put transistor in a circuit; a transistor that amplifies the current. So after amplification components are able to "take" more current for themselves if needed. But the question is: if I amplify the current from 1 Amp to 5 Amps, does the transformer, which I used to power the circuit has to be capable of working at 5 Amps too? Have to all components be able to work at 5 Amps? Or is this required only for components after the amplification part of circuit?

I know this question is not clear but this thing bothers me all the time when learning about transistors. Please reply.


texts: Can a positive-control thyratron be used as a logic inverter/NOT gate?

texts: FTR: I am not actually planning on building a vacuum tube computer. But I am interested as to whether one could build an inverter circuit using a thyratron and string an odd number of them together to form a ring oscillator.


texts: Are there any non-ideal side-effects of putting capacitors in parallel to increase capacitance?

texts:
I want a 500uF capacitor. Theoretically, I should be able to place 5 100uF capacitors in parallel to achieve 500uF of capacitance.

However, are there any side effects of practically implementing this? Are there non-ideal effects that I should account for?

Note: I'm looking for a 500uF surface mount ceramic capacitor. I've been able to find these, however, the tolerances are only +/- 20%. Furthermore, I've only found one manufacturer of these and I would prefer not be too dependent on a single manufacturer.


texts: Fundamental reason why RAM is faster then second storage device

texts: Let's consider dynamic RAM - 1 cell = capacitor+ transistor and second storage device, - for example ordinary mmc NAND flash. DRAM, so called volatile memory, need to be refreshed to keep capacitors charged. That is why DRAM couldn't work without power supply. I don't know how NAND flash exactly works, but it seems that it uses floating gate transistors and some quantum tunnelling magic to hold a charge even if the power supply is disabled. So the question is what is fundamental most significant reason why NAND (NOR) flash couldn't be so fast as DRAM? Thanks.


texts:
I ran into a problem lately, with using triac and because I don't have any engineering school just yet, I could make a mistake... and bad circuits with mains electricity? meh bad idea...

so, I have seen few circuits on Internet like this -

I would use some kind of optocoupler triac driver... MOC30XX family - but what exact type? Since I want to use it on 240AC I guess the resistors need to be selected precisely... but how?

and about "if it is an inductive load" it is... but I have no idea how to measure "how much inductive it is"

I thank you for any answer or if you just redirect me somewhere I can find answer.


texts:
I am toying with designing a simple 8-bit CPU out of basic logic components. I have a fairly good idea of how my ALU and registers will interact, but the one thing I feel can use some improvement is how to toggle when a line is allowed to connect to the main data bus.

My initial thought was to use and gates to drive the bus. The output from the various lines in the ALU could all go into a set of quad-AND chips that output onto the bus. Only one set of AND gates at a time would have all of its B inputs pulled high to let it out onto the bus.

A couple of things I am unsure about: It seems wasteful to use eight full AND gates per line, when I only need one control line going in. Is there a better chip more suited to this purpose? I'm sure I could also do it with eight transistors, but I would like to stick with fairly common (and cheap) ICs.

A solution like this only lets data flow one way from the bus. Is this a problem? I think not, since I have other control lines stopping registers from loading the bus data until I want them to.

Is there a standard chip to use for a bus gate like this?


texts: Incorrect signal from signal generator H11887 DDS

texts:
I'm a newbie in engineering. I bought this generator on ali and built it.

Problem in signal from DDS out: it has incorrect form. I don't have +/- power supply so tested only on +5V.

Reasons could be:

I made a mistake: put wrong resistor or something else.
There is bad component: capacitor or resistor.
+/-12V could affect signal form
Wrong firmware on chip

How can I find problem?

I can provide more pictures - low reputation here.

Thanks!


texts: Derivation of discrete-time steady-state and transient response

texts:
My discrete-time signals textbook (Oppenheim) jumps through the derivation of steady-state and transient LTI system response to a complex exponential input-
$$y[n]=y_{SS}[n]+y_t[n]$$
It says, given input \$x[n]=e^{j\omega n}u[n]\$ and impulse response \$h[n]\$, the system response can be found using convolution as:
$$
y[n] = \left\{\begin{aligned}
&0 &&: n < 0\\
&e^{j\omega n}\sum_{k=0}^{n}h[k]e^{-j\omega k} &&: n\ge 0
\end{aligned}
\right.$$

But where did the \$n\$ as the upper sum limit come from? When I try to do this myself, I end up with:
$$
y[n]=x[n]\ast h[n]=\sum_{k=-\infty}^{\infty}h[k]x[n-k]\\
=\sum_{k=-\infty}^{\infty}h[k]e^{j\omega(n-k)}u[n-k]\\
=\sum_{k=0}^{\infty}h[k]e^{j\omega n}e^{-j\omega k}\\
=e^{j\omega n}\sum_{k=0}^{\infty}h[k]e^{-j\omega k}
$$

Where did I go wrong?


texts: Are there any application where flex pcb's (rigid/flex) are really being used and required? or is this a more luxury product which is not entirely mature yet to the level where it can be implemented in every day products.


texts:
I am working on how 8051 performs serial communication. I couldn't figure out how both transmission and receive operations are performed by same register, SBUF.

To make it more clear, I will give an example. Assume that I'm receiving information through Rx pin continuously. What if I want to transmit information? How can I interrupt receiving while transmitting data because I don't want the data that I put in SBUF register to be replaced by the incoming data.

There were two bits in SCON, namely receive interrupt(RI) and transmit interrupt(TI), but they were used to check whether the data is received or transmitted succesfully, not to decide whether the chip is gonna transmit or receive.

What I'm asking is, shouldn't there be a bit in SCON like transmit enable or receive enable which allows one operation and inhibits the other when asserted. There is actually one receive enable(REN) in SCON but in all examples it was asserted both when transmitting and receiving so I thought this bit was for something else.

What is it I'm missing?


texts: Can I connect a heating element to a solar panel to heat a hot tub

texts:
I’ve just moved into a house that has a hot tub (lucky me!). It uses a lot of power to keep it warm so I’d like to try heating it from the sun. Although a solar water might be more normal, I’d like to try heating it with a solar PV system. I live in Berkeley, CA and the google calculator thing tells me I’ll get 1756 hours of usable Sun. I can get used panels locally for $0.60/W. So my idea is to connect a panel directly to hot water heating element and put that in my hot tub. At this stage I’m looking for some validation on the overall idea, my particular calculations and any safety tips.

Vmp|Imp|Pmax|Voc|Isc|Ideal resistance

Solar panel 1|35.68|8.15|290.792|44.9|8.94|4.37791411|

Using the Vmp and Imp I calculated the “ideal resistance”. I think it’s vital that the resistance of the heating element matches this pretty closely. I found a 600W 48V element which should have a resistance of 3.84 ohms which is pretty close (and I think gives me an efficiency of 87% based on (8.15 * 3.84 * 3.84) to get the power and dividing that by Pmax).
I can do slightly better by getting a pair of cheaper and smaller mains heating elements 120V 1650W which have a resistance of 8.72 ohms or 4.36 for two in parallel. Which is now very close to my ideal!

Question1: For this ideal resistance calculation, I’m assuming the panel will be operating at Pmax, but presumably the panel never will be (unless it’s directly facing the sun on a clear day). Should I be calculating a different ideal resistance based on more realistic typical conditions?

Question2: What fuses and isolation switches should I have? I plan to have an isolation switch between the panel and the heating element (is something like this good enough). Do I need any fuses too? I can’t really get my head round how a fuse could help. I’m basically trying to short the panel out in the most efficient way possible, so a fuse will always be sized for more current than the panel could ever provide!

Question3: Any tips on cabling that’s OK if it comes into contact with the hot tub water (which contains some chlorine).

Thanks in advance for any tips, advice or warnings!
Tom


texts: Is the system linear, time-invariant and causal? Does the decomposition property hold? Sallen Key bandpass filter

texts:
I have this ordinary Sallen Key bandpass filter: -

simulate this circuit – Schematic created using CircuitLab
I'm being asked, if the system is linear and/or time-invariant and/or causal. Furthermore, if the decomposition property holds for this system.
My answers

The system is linear, because the superposition principle holds.

The system is time-invariant, because a time-shifted input yields a correspondingly time-shifted output.

The system is causal, because the output depends only on present and past inputs.

The decomposition property is based on the principle of superposition. Since superposition holds, the system has the decomposition property.

As you can see, my answers doesn't have much argumentation, and I'm not 100% sure if what I've written is correct. Is there a reliable way to check if these properties, for example through simulation?


texts: After power supply is turned off, voltage still exists and is slowly dropping over a minute + long period

texts:
I just bought this power supply for a project:

https://uk.farnell.com/mean-well/gst120a20-p1m/adaptor-ac-dc-20v-6a/dp/2815845

It is supposed to power two somewhat larger stepper motors (and an Arduino), so I needed something with a beefier amp rating.

After attaching it to a panel mount DC connector, I just went in with a multimeter to test the voltage and PINs, which gives me a 20V reading as expected.

However, after I remove the power supply from the wall, I still see 20V initially, and then I see the voltage dropping quite slowly, over a fairly long period; I'd say around half a volt per second, or even slower.

I'm a beginner, and don't know what to make of this?
Is this a normal phenomenon and does it have a name?
Is my power supply broken or low-quality (it didn't come cheap!) Did I measure it wrong?
Might this not be an issue with devices that expect a certain minimum voltage?


texts:
I'm trying to control my 3v motor from my 5v arduino.

For this i use :

5 volt power source from pc for the arduino
L9110 H-bridge module
2 AA Battery as power source for the L9110 H-bridge

Here is the setup :

however if I touch the h-bridge pin with the 5v source from the arduino (red cable on the image), nothing happens....

Any idea ? if I power the motor directly from the battery, the motor works

Maybe the problem is that I have 2 different power source


texts:
Hello fellow engineers,

I need some design design help with a Z80 based computer I am building.  It will feature a binary Front Panel.

The following functions may be performed via the front panel.  These are the usual things one would find on a vintage mini-computer.

Bootstrapping
Memory examination and loading.
CPU status display
CPU cycle identification LEDs
Mode identification (Instruction Fetch, ISR, I/O, DMA, etc.)
Processor control
Interrupt control
Memory protect
Reset
DMA assert
Clock speed selection
Run / Stop
Front Panel Design Choice

A front panel can be built in several ways.  A lot still needs to be decided here.  There are basically two design options named A and B.

Option A:  The Front Panel is tied directly to the address, data, and control buses which it monitors.  Additional hardware is employed to read and write to memory and load (and track) the program counter.  The original Altair 8800 actually jammed a Jump instructions onto the bus when the Run switch was depressed.
Option B:  The Front Panel is essentially an elaborate LED display and binary input peripheral that is controlled by software (a driver).  This could add CPU register display.

Considerations are noted below.

Certainty:  In Option A, the actual state of the buses will always be faithfully displayed. In Option B, the state of the buses may not always be reliably depicted because an intermediating software layer is required which is less reliable than hardware.  Also, the software will need to distinguish between the reported state of the processor, and the actual real-time state of the processor when displaying the front panel status.
Readability:  If, in Option A, the Front Panel LEDs follow the buses at all times, indeterminate displays can be expected representing the bus between valid data times.  This could prove misleading.  At a minimum, latches will be needed to capture the bus states at the proper time.  This will take a bit of hardware.  Option B poses no such problems - or rather, this is done in software.
Confusion:  The display is to run during user applications.  In Option B, the display software will need to run with the application.  This complicates things.  How frequently can the front panel get updated?  Should it be updated after every instruction?
Authenticity:  Option A is tied to the hardware and is representative of the actual front panels used on vintage mini and mainframe computers.  Option B has a more modern and emulation feel to it.
Utility:  Can the front panel be designed in a way, with either Option A or Option B, to support breakpoints and debugging?

Here a few thoughts on Option B.

A. Using Option B, the front panel could be updated on every instruction using instruction fetch bus signals, interrupt(s) and a few gates.  But application performance will nose dive.

B. Alternatively, a front panel driver could take periodic snapshots of the processor state at a specified rate and posts the findings to the front panel.

C. If Option B is used, the Front Panel could be ignored during application execution and made available to the application for blinky lights and switch inputs which is appealing and has much merit.  Option A does not provide for application use of the Front Panel.

D. Utility, as defined above, and availability to the application are most important design considerations.   Certainty, as defined above, is the next important design consideration.

Option A, I fear, will significantly add to the chip count.

Does anybody have any thoughts on this? Has anyone solved this issue before me?


texts: How do I wire a Rasberry Pi 3B+ to a WS2812b RGB strip?

texts:
I am working on a project where I need to use a WS2812b RGB strip. I am really worried because I have already burnt 2 Raspberry Pis with my wiring. I just want to show my schematics, and be assured as to whether they are correct or not.

I am using a Sparkfun Level Shifter to convert the Raspberry Pi's 3.3V data signal into 5V (used for the WS2812b strip). I am very new to working with hardware (I am more used to software), so please go easy on me.

Here are the schematics, one in visual form, one in a more blueprint-ish form. PLEASE NOTE that the power supply (which is 12V) is not in the schematics. This is because I have already taken care of it (it works and all the lights turn white when it is plugged in).


texts: How should I use this laser diode from eBay?

texts:
I am new to lasers. I have some 5mW pointers, but thats it. I want to have something more powerful, and I happened to find this 50mW laser diode with driver:

http://pages.ebay.com/link/?nav=item.view&id=311028329241&alt=web

From the meager description it seems to me all I have to do is putting a 3V supply voltage on the two wires. I, however, could not find anything related to their usage, and due to my lack of experience I am pretty unsure.
Am I right? Is there any other thing I should do to make them work as long and as bright as possible?

(I am not really sure if this is on-topic here, and sorry if it isn't. I just couldn't find a better place to ask this.)


texts:
This question is in relation to an answer I made to my question here. Wherein I need to enable the TS12A12511 depending on the input voltage. my input voltage can range from 3V to 9V.

The problem is that the TS12A12511 has different logic voltages for depending on VCC where in HIGH is 2.4V (when input V is 5V) and 5V (when input V is 12V). It does not say what is the voltage for input voltages that is in between. Since the input voltage is not fixed, to play it safe I must generate 0V and 5V to the IN pin of the IC.

How do I generate logic voltages (0V and 5V) for a set range of voltages. I would like for this magic circuit or IC to output 0V if the input voltage is less than 5V and to output 5V (or higher as long as it's less than the input voltage) if the input voltage is higher than 6V. Using minimal components and no components that need to be manipulated by the user.

I have tried to come up with some ideas to solve this but I have failed to come up with one that works, I have tried:

Using a voltage divider configured in the image above, but the scaling is not linearly.
Using a 5V regulator but it turns out voltage regulator starts producing voltages even if the input voltages does not reach 5V yet.
Using a 5V regulator with Power/Good and Under voltage Lock out protection. Power good generates a signal way before 5V input.


texts: What is the very basic electronic component to generate pulse wave (high or low) we commonly see in digital?

texts:
Very common we hear ON/OFF, HIGH/LOW, 1/0, or something similar in digital system. It is called binary. I would like to know what is the very basic component to generate such that binary system? I have searched to know about it, but I could not find. I know about transistor used to make logic gate or even processor. But that component still need to be triggered or fed with binary, to ON or to OFF the input (either base or gate). I doubt the component to generate such LOW/HIGH or ON/OFF is clock as it is work constant. If it is the thing, then how it change to one state to another state?

So my question, what is the very basic component to generate that binary system? There is one similar post here, but is is about logic gate. What I am asking is component, a level of transistor or Christal clock, not logic gate.


texts: ADE7953 smart energy metering - how to connect it

texts: I am currently looking for a IC that would allow me to aggregate energy metering data in my house. I came upon ADE7953 chip from Analog Devices but there is no info how to connect it with power source like power socket. I would be really gratefull if you could help me with that and show me the way. Any schematics, current, voltage sensors needed will be priceless.


texts:
Hello, I am attempting to determine the small signal output resistance \$R_o = v_x / i_x\$ of the Darlington pair common emitter's small signal model.
I have written the equation KCL at node c,
\$ i_x = g_{m_1}v_1 + (v_x - v_2)/r_{o_1} + g_{m_2}v_2 + v_x/r_{o2}\$
and KCL at node a,
\$ v_1r_{\pi_1} + (v_x - v_2)/r_{o_1} + g_{m_1}v_1 = v_2r_{\pi_2}\$
How many more equations do I need to find a solution? How to I apply node voltage analysis to this circuit? Thank you much!


texts: Ultra low ripple constant-current LED driver design

texts:
I designed a LED driver(SMPS configuration) with ILD6150XUMA1 and below is the circuit. I used it with AC/DC adapter. The thing is, th optical system is ultra sensitive and ripple from the LED supresses the actual signal(Between 1K - 20KHz). It is the schematic and the board below:

I need to draw 1 A current per LED strings so ripples quite high in the system. The question is how can I eliminate those ripples. I calculated my limit as 5mV Vpp ripple for 1 A current draw and 5V supply. I know this is so hard to do, but I need any suggestions now. Configurations, topologies, some special cares anything. Only thing I have to do is to draw 1 A current from the LEDs and ripples should be very very less.


texts:
I work on DE1-Soc. I am using a linux BSP (linux console) that i found in terasic's website linux image.

I have some questions about the AXI bridge. In fact i would like to send some data from the hps to the fpga through the AXI bridge ( HPS-to-FPGA AXI ) and then use those data by the FPGA. I created a Quartus project based on the DE1-SOC-GHRD. The DE1-SOC-GHRD includes the file soc_system.qsys which includes hps_0 (HPS component). I would like to use the EPCQ to store the fpga configuration (.sof) And sD card for linux and my app.

Can someone give me some advices about how to use the AXI bridge? work to do for the FPGA and work to do for processor?

I am new in Soc, and i found it hard to understand how it works. I read cyclone V handbook but i feel that i missed something and i don't know what.

update:

I used Qsys to generate my hps component ans my system. I created 2 slave component(read and write) ( avalon memory mapped slave) and i can  through the lightweight HPS-to-FPGA bridge map the address of the first slave (write) and write data. Also with the second one i can read data from it by the hps. The problem is that the lightweight HPS-to-FPGA bridge has a capacity of 32 bits. So i would like to use the HPS-to-FPGA bridge which has a capacity of 128 bits. I did the same thing that i did for the lightweight. but it doesn't work. I don't know why??

What is the difference between those two bridges? is there something to add (configuration)? I didn't find the base address of the HPS-to-FPGA bridge? where can i find it?

for example: what I did for the lightweight bridge

first:

define HW_REGS_BASE ( ALT_STM_OFST )

define HW_REGS_SPAN ( 0x04000000 )

define HW_REGS_MASK ( HW_REGS_SPAN - 1 )

define WRITE 0x0

define READ 0x10

// lightweight base address

define ALT_LWFPGASLVS_OFST        0xff200000

virtual_base = mmap( NULL, HW_REGS_SPAN, ( PROT_READ | PROT_WRITE ), MAP_SHARED, fd, HW_REGS_BASE );

then:

// address for write

h2f_write=virtual_base + ( ( unsigned long  )( ALT_LWFPGASLVS_OFST + WRITE ) & ( unsigned long)( HW_REGS_MASK ) );

//address for read

h2f_read=virtual_base + ( ( unsigned long  )( ALT_LWFPGASLVS_OFST + READ ) & ( unsigned long)( HW_REGS_MASK ) );


texts:
I want to build a data acquisition device to collect electromagnetic interference signatures of household appliances on the home electrical network (power line). In fact I hope to harvest datasets similar to the ones presented in this competition.

I want to build a power line interface like this one described in
the paper titled "An In Depth Study into Using EMI Signatures for Appliance Identification".

Now I seemed to have stumbled right at the start: I live in Belgium and unlike other parts of the world we have no Neutral in the mains network (single phase): we have two phases and we have 220V between the two. How should I modify this wiring diagram so that there is a high pass filter on both of the phases and make sure I don't fry the spectrum analyzer?


texts: How to convert Proteus PCB design (ARES .LYT) to Altium Designer (.PCB)?

texts:
I am familiar with Proteus software and have designed my PCB with its ARES package. Now I want to order it and found a company that offers good price but they only accept PCB layouts in .PCB format. They said I have to design it with Protel ( I think they meant Altium Designer ?) but I am not familiar with it and don't want to buy a new software package and also it may be so time consuming to start designing from the beginning. Is there any way to convert the file made by ARES (.LYT) to .PCB ?

I am so sorry if I mentioned the formats incorrectly because I don't know much about softwares other than Proteus !


texts: Is it safe to exceed an LED max current when ON time is less than 100%?

texts:
For an LED that is rated at 20mA, is it safe to PWM it at 40mA half the time? Will that make it nearly as bright as if continuously supplied with 20mA?

Addendum:

Thanks Olin and tcrosley for your answers. I didn't want to distract from the question by adding the details of what I am doing, but here it is:

I am working with an LED strip from http://www.environmentallights.com/LED-Strip-Light-Double-Density-4-Wire-Red-Green-Blue-by-the-5-meter-reel_P3846.aspx. They do not have a datasheet per se. I think the LEDs are connected as shown in this image http://www.ladyada.net/wiki/_media/products/ledstrip/astripsch.png.

Based on what I read about LEDs in general, 20mA per color seemed safe. I tested it - using 12V, potentiometer and 3 inches long strip, that is 3 leds in series each color -  for short periods, few minutes, and 20mA per color seems to have worked fine, good enough brightness and no overheating or color intensity variation.

I will be working with up to 2 feet length strips, that is 160mA per color and 480mA to get White. I may have up to 10 strands to control. That will add up to about 5Amps. I will be using the Propeller microcontroller from Parallax to flash the strips in various patterns and colors. Will use mosfets to drive the LEDs.

I was thinking of supplying about 200mA instead of the 160mA needed per color, but then I will PWM the leds such that only one color is on at a time; at a frequency of 1KHz. So to get white, each color will be on for one third the time, that is 0.3 msec. At any moment only one color is on, only 200mA is drawn. I imagine the leds will be less bright, hopefully not by much.

So, for 10 strands, I will deal with only 2A instead of 5A.

Please let me know if what I am thinking is off.

Thanks.


texts: How to estimate inductive coupling between distant air coils

texts:
I have two air coils. They both have diameter d. There is a distance D between their centres.

D is much greater than d (more than 10x greater)

Both coils are at different angles, a and b, relative to the line between their centers. There is an alternating current in one coil.

Is there some simple function which estimates the current induced in the second coil?  I would be happy if the form of the function was:

k * f(D, a, b)   (where k had to be measured)

For example: k * cos(a) * cos(b) * D^-2


texts: datasheet register address is not in HEX?

texts:
I am reading the this datasheet for the CAP1188 touch sensor and can't figure out what these "register addresses" in the far left column mean. I am used to seeing HEX addresses in datasheets such as 0x00, 0x72 etc., but this datasheet is adding an h to the end of.... I don't even know I just don't get it.

For example, I am porting this library which has all these addresses in HEX form, but how did they get say 0x29 from 03h?


texts:
I am trying to use the Arduino IDE to program an ESP8266 (ESP-12F). I am able to upload a simple program that blinks the built-in led. As soon as I put a reference to Serial.begin() anywhere in the code, my program no longer works. Even code that executes before the call to Serial.begin() fails to run.

I am using the following code:

const int ledPin = 2;

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  digitalWrite(ledPin, LOW);
  delay(1000);
  digitalWrite(ledPin, HIGH);
  delay(2000);

  // If this line is present, the led never turns on, not even the first time.
  // Removing it makes the led blink, as expected.
  Serial.begin(115200);
}

I am connecting the ESP as follows. It is probably not very relevant since I am able to upload and run code successfully as long as it does not attempt to use the serial port. I have also tried replacing the connection to RTS and DTR with push buttons to GND, and the result is the same.

What am I doing wrong ? How do I use the serial port on the ESP8266 ?

PS: I know that Serial.begin() should not go inside the loop(). I've only moved it there so that it happens after turning the led on.

Update

I tried to flash the latest firmware using the official tool, but this process always fails with an "Invalid head of packet" error. It seems to occur when writing the last packet, because if I flash a large file, it gives the error only at 99%.

After these attempts, I have been unable to make any program work. Even the simple led blinker without any Serial reference seems to do nothing, although the serial monitor shows the ESP boot messages.


texts: What is this resistor for in this circuit?

texts:
I am studying electronics and I am currently reading/working my way through "Make: Electronics" by Charles Platt. Here is one of the circuit diagrams that he gives for making a basic burglar alarm:

My question is, what is the purpose of the 1K resistor after the switch. I understand the point of all the other components, but why does that resistor have to be there? I have re-read this part of the book a few times but it doesn't seem to mention why that resistor is there or what it does. Can it be omitted?


texts: Two line 220V to 12V AC and 5V DC power supply for valve amplifier and MP3 radio

texts:
I need 12V AC out for a valve preamplifier and a 5V DC out for a MP3 radio.

valve preamp: Fever 6J1 tube preamp amplifier

mp3 radio: DC 5V Micro USB Power Supply TF Radio MP3 Decoder Board 5V Audio Module for Car Remote Music Speaker

My first Idea was to build a very simple supply with a classic transformer as you can see in the picture.

I make some calculations and to be sure to have enough power I should use a 12V 20W transformer (12V 0.8A valve amp and 5V 1.5A MP3 radio).

A classic metal core transformer is heavy and too big for my project, so I was thinking to use a LED driver 0-50W 11.5V AC output for example ETZ50 0-50 W ZAMEL. (sorry stack don't let me to put the link)

I have some doubts about this solution.

will work only few minutes?
is good for power applications?
the output is a square or sine wave?
the design of the circuit can smooth enough the output signal to avoid MP3 damage?
if the LED driver is not a good solution how is possible to power the device using a switching transformer? (classic transformers are outdated)


texts:
Currently, all 'wireless' EEG systems acquire signals from electrodes which are wired to an amplifier, a filter, a digitizer and then finally a wireless module.

I want to design a system that's completely wireless, maybe using wireless sensor networks. Is it possible to transmit data wirelessly (RF or bluetooth), from the electrode itself, to a station where the amplification/filtering would be done?

I do realize the raw EEG signal from a single electrode would have a LOT of noise.


texts: What is the symbol for a Fan on a circuit? Is it just Motor?

texts:
I've been looking around for the schematic symbol to use in a circuit drawing for a FAN. I'm not sure it exists. Do we use a Motor symbol when wanting to show a FAN? And just specify the motor ratings? IE 12V DC?

I've looked @ all the websites listed on Wikipedia (http://en.wikipedia.org/wiki/Electronic_symbols) as references for symbols and many Google searches.

After all, a FAN is just an electro-magnetic motor, isn't it? Does electronics specify at all between motors? (Not by 2 / 3 phase or various speed). But by different type?

I've also found symbols used in other engineering fields that specify a fan in their schematics. Can this be used?

So, essentially the question is, What symbol to use to specify a FAN in an electronic circuit?

Thanks all,


texts: Why can we use less voltage drop to transmit the power if the higher voltage is used?

texts:
In power distribution systems, a given amount of power can be transmitted with less voltage drop if a higher voltage is used. However,i  don't  understand the reason about this

In my thinking,if i use 110V(high voltage),the power can be transmitted with 10V (less voltage drop);However,if i use 11V(high voltage),the power can be transmitted with 10V (less voltage drop) too

It seems we can use  less voltage drop to transmit the power if the "less" voltage is used too.Can anyone tell me about the mistake i do or explain the true meaning about "a given amount of power can be transmitted with less voltage drop if a higher voltage is used"


texts: Finding Rout of differential pair with active current mirror (from Razavi's "Design of Analog CMOS Integrated Circuits 1st Edition")

texts:
According to Razavi, \$R_{out}\$ is approximately \$r_{o2}||r_{o4}\$:

I get the same answer (assuming \$2r_{02} >> \frac{1}{g_{m3}}||r_{o3}\$):

But how did he get equation 5.27? In particular, how is \$I_{xy} = I_{d4}\$. I.e. how did he get the \$2I_{xy}\$ term (where \$I_{xy}\$ is the current through \$R_{xy}\$)? I understand that M4 will copy M3's current, but won't the copying be unequal when considering channel length modulation and if \$V_{ds3} \neq V_{ds4}\$?


texts: Good easy soldering projects like Bristlebots?

texts: What are some good projects to give to beginners? I want something that involves some soldering, and ideally has some room for creativity. For example, with Bristlebots, everyone can get their own toothbrush, attach the motor in different orientations, etc, and they will all be a little different. Something where I just solder a bunch of components to a PCB and then everyone's result is exactly the same, feels a little too boring & restrictive to me. I'm looking for things maybe a little more complex than bristlebot, but not so advanced that it requires a microcontroller. Maybe something involving a 555 timer?


texts: Which low voltage single supply opamp for ultrasound mic?

texts:
I have a problem choosing right opamp to amplify signal from 10KHz-65KHz mic SPM0204UD5. According to microphone's datasheet, it has max output impedance of 300Ω, and supply voltage from 1.5 to 3.6 V.

Datasheet also has recommended interface circuit as follows:

More precisely, my question is: should I use voltage divider to get 3.6v max on the mic? Can opamp be connected with single-supply or do I need two (and thus 2 voltage dividers to put the mic "around" the Vref, or just up the ground)?
Of course, I'd preferred single supply.

Are there single-supply opamps for 3.6v? (I have not found), which are capable
to amplify up to 65kHz signals?

I guess, there is some implicit knowledge required to interface the mic.

The output will be some circuit, which will convert part of the bandwidth to audible domain or maybe just measuring the volume. Actually, at first I just want to check if the device work in the audible range, covered by the mic (10KHz-20kHz).

UPDATE: I get it to work with Vcc=3.3v, C1=10uF, R1=1k, R2=100k, Vref obtained by voltage divider with 100k and 100k resistors to Vcc and ground, Load 820 ohm to the ground. U1 - LM4562 device. Pls note, that pin numbers on schematic are different ones than LM4562 uses.


texts: LTspice- Comparing Load current of capacitance multiplier and RC filter circuit

texts:
I have simulated two circuits, one is an RC filter and other is a Capacitance multiplier.
My aim of experiment is to validate a decrease in Iout (load current) of CM circuit as compared to load current in RC filter circuit.
Theoretically,
Iout (CM circuit) < Iout (RC filter)
Vp-p (CM circuit) < Vp-p (RC filter)
My results:
1.RC filter
Vout (dc) = 0.0458716 ( .op 300ms)
Iout (dc) = 0.00458716
Vout (ac) = 43.7 ~ 48 mV  (.tran 300ms)
Iout (ac) = 4.80 ~ 4.37 mA
Vp-p (ripple) = 0.00437018  (.meas)
2.CM circuit
Vout (dc) = 0.323751
Iout (dc) = 0.0323751
Vout (ac) = 322 ~ 327 mV
Iout (ac) = 32.65 ~ 32.15 ma
Vp-p (ripple) = 0.00521016 (.meas)
From the above results its quite clear that implementing CM circuit causes Iout to increase which particularly against the aim of the CM circuit. As the CM circuit works by decreasing the load current which according to load POV can be visualised as increase in capacitance.
We can also see the peak to peak ripple voltage in both the circuits, Vp-p for CM circuit should be less than Vp-p ripple of an RC filter, but again the simulations results are quite opposite.
Whats wrong here??
Link to LTspice files -https://filebin.net/d1d2wnjhi6wskl3n


texts:
I am trying to use a piezo as a speaker.

(I know that a piezo has a bad frequency-response. However, In my application it is better to use one instead of a speaker, since normal speakers don't like to be covered in gel.)

Since a piezo is so much softer than a normal speaker, I want to amplify the signal. After looking for some tutorials on the internet, I found that i should be possible to use an Op-Amp connected in the Non-inverting Amplifier way. I bought a LM324 Op-Amp to use in this circuit.
The 2.5mm jack is the plug that is used in most computer headphones.

Here is my curcuit, as connected on my protoboard:

This does not seem to do any amplification of the signal. So I must have connected something wrong, or maybe my understanding of the different parts involved is incorrect. I hope someone can point the problem out.


texts: Phase or polarity for North America residential 240V

texts: I understand that for North American residential, the three wires coming into the panel box are +120V,-120V, and Neutral.  Is there such a thing as phase or polarity between these three wires? How is hot-to-hot 240 different than hot-to-neutral 120 in this respect?


texts: Using single-loop analysis in multi-loop structure

texts:
Here is regarding Kenneth Kundert's explaination of the loop based stability analysis

Two factors affect the applicability of this circuit: the local
return loop inside the transistor and the reverse-loop transmission
around the return loop. There are four cases:

If both the local loop and reverse transmission can be ignored, both our loop-based and device-based algorithms produce accurate and
consistent stability information for the network.
If the reverse transmission can be ignored, only the device-based algorithm produces accurate stability information for the network. If
the network is a multiloop network, the loop-based algorithm can no
longer be applied since no wire can be found to break both global and
local loops.
If the local return loop can be ignored, only the loop-based algorithm produces accurate stability information for the network. The
loop-based algorithm produces accurate stability information for a
multiloop network as long as a critical wire can be found to break all
loops. Nulling the normal transmissioncontrolled source does not
render the whole network to be passive, thus the device-based
algorithm cannot be applied
If none of these two factors can be ignored, this corresponds to general multiloop networks. Neither our loop-based nor our
device-based algorithms can be applied

"....a critical wire can be found to break all loops..."
What does he mean by that?
Are there any multi-loop examples that "a critical wire cannot be found to break all loops" and multi-loop examples that "wires can be found to break all loops"?


texts: Definition and calculation of distortion in grounded emitter amplifier

texts:
My question is related to How can I set the quiescent current for a grounded-emitter amplifier and AoE3: Grounded Emitter Amplifier Distortion originated in TAOE3 on the nonlinearity of grounded emitter amplifier. Specifically on how distortion is defined and calculated.

In 2.3.4.A on page 94-95 where it states:

  ... It's easy to estimate the distortion ... with a grounded emitter, the incremental (small signal) gain is \$G_V = -R_C/r_e = -I_CR_C/V_T = -V_{drop}/V_T\$, where \$V_{drop}\$ is the instantaneous voltage drop across the collector resistor ...

  ... the nonlinearity (fractional change of gain with swing) equals the ratio of instantaneous swing to average quiescent drop across the collector resistor: \$\Delta G/G = \Delta V_{out}/\Delta V_{drop}\$, where \$V_{drop}\$ is the average, or quiescent, voltage drop across the collector resistor \$R_C\$

  ... the overall waveform 'distortion' (usually stated as the amplitude of the residual waveform after subtraction of the strictly linear component) will be smaller by roughly a factor of 3. Note that the distortion depends on only the ratio of swing to quiescent drop, and not directly on the operating current...

  ... As an example, in a grounded emitter amplifier powered from +10V,
  biased to half the supply (i.e. \$V_{drop} = 5V\$) \$\star\$, we measured a
  distortion of 0.7% at 0.1V output sine-wave amplitude and 6.6% at 1V
  amplitude; these values are in good agreement with the predicted
  values ...

The explanation is somewhat confusing - my take is that the book defines 'distortion' by the ratio, i.e. \$\Delta G/G \ \ or \ \  \Delta V_{out}/\Delta V_{drop}\$, essentially a slope value from a region of the output waveform. How can the magnitude of a ratio represent distortion or nonlinearity. Shouldn't distortion measures how non-linear a graph is?

I don't understand how 0.7% (@0.1V output) or 6.6% (@1V output) came about. If output wave amplitude peak at 0.1V, the voltage drop of \$I_CR_C\$ has to be 5-0.1 = 4.9V. Then the distortion or ratio of \$\Delta V_{drop}\$ / \$V_{drop}\$ = 0.1 / 4.9 = 2%, instead of 0.7% stated in the book. I am either misunderstanding the description or misinterpreting it.

\$\star\$: "biased to half the supply" ... when the term biased appear in BJT throughout TAOE it implies biasing the base, but here specifically it is trying to say curbing the \$V_{CC}\$ supply from +10V to +5V on the collector side, perhaps with a voltage divider on the collector side before connecting to \$R_C\$. Please correct me if I'm wrong.


texts:
simulate this circuit – Schematic created using CircuitLab

Can somebody please explain me how a transistor mirror circuit works and how can it be used as over current detector?

I badly need a crystal clear explanation for the above circuit. Anybody can please help with this.


texts:
I am trying to get this well known circuit
[

work inserted in a series of 69 LEDs to protect them according to this specification.
Transistor is 2N2222, hfe=18 according to multimeter.
The free-running current is 19mA and I use Rcl=100R to limit Iout to 25mA.
Calculating R1 is uneasy, so I made the following tests.

R1=470Ω   V1=0.1  I1=0.2mA  Vi=1.9  VB=1.8  VE=1.09 ICL=10,9 mA
VBE=1.8-1.09=0.71V  VCE=0.81
R1=2.2kΩ  V1=0.5  I1=0.2mA  Vi=3.0  VB=2.5  VE=1.8  ICL=18.0 mA
VBE=2.5-1.8=0.7V  VCE=1.2
R1=10kΩ   V1=1.85 I1=0.18mA Vi=4.38 VB=2.53 VE=1.85 ICL=18.5 mA
VBE=2.53-1.85=0.7V  VCE=2.53

My main concern is that 7.4 and 9.1 say:

  more than 1mA (Imin(max)) must be supplied in to the cathode pin. Under this condition, feedback can be applied from the Cathode and Ref pins to create a replica of the internal reference voltage.

OK, OK, but how do I supply the 1 mA that seems to be required for correct operation? I see no minimum Vi spec and the TL431 seems to increase its resistance as I lower R1.

Another concern is that rather much less that 19mA flows in RCL.
What does a constant VBE=0.7V mean? Perfectly conducting?
And, BTW, how does the TL431 in the off (<2.5V) state know what VB=VK=to output?

Update: thanks for your answers and you want more detail.
I have bought 5730 LEDs corn cob lamps.
They are cleverly very simple:
Basically: mains, dephasing cap, MB6S rectifier, smoothing cap, LED chain. Cap's cos φ aka power factor determines the voltage at the LED chain. Some lamp models use pairs of parallel LEDs like 2×36. My 95 and 36 LED models are OK. But the 69 (or 2×36) LED ones constantly failed in some homes of this country.
I replaced burned LEDs with a 220kΩ resistor but more LEDs burned. I suspected over-voltage peaks and that current limiting is something to try. So, I wired data sheet's fig 38 in a delicious layout on a 2×5 holes veroboard. Component wires folded and 3 solder points, no need for soldering pads.
I can tuck it inside a E25 lamp socket well immobile at the end of a hard wire. But the value of R1 is not clear and I found no simple howto on the Web.

Just random remarks here and there plus 7.1-7.4's "no Vi minimum".
So, the best was to try R1 values and that took me here, thanks for your answers. So, Fig 38 "limiter" should be called instead "Vi≥5 current limiter" which is not my case. Your advice: use fig 39 with a separate 5V Vi. Unfortunately, the lamp PCB provides no 5V (and forces LEDs on - ground side).

So, I want a low Ik at 1 mA. I finally figured that I can add some 100 Ω resistor between collector and + source. Then, relative to negative ground, Vi will be higher. What do you think of that? I will try when I'll have time and probably come back here.


texts:
This might be a simple one to answer.

I am using a controller IC (MCP73871) whose load output is connected to an LDO (lm1117Mp3.3). Now according to the datasheet of the MCP73871, I should be adding a capacitor of 4.7uF at the output, while according to lm1117Mp3.3, I need a 10uF capacitor at its input. So is it ok to use both capacitors or just use the one with higher capacity, or it doesn't really matter. Many thanks in advance.


texts: Can a 1S BMS be used for a parallel arrangement of 4 Li-ion batteries?

texts:
Currently I am on a Mini UPS for a modem router project. So my router needs a 12V and 0.6A current. I have four 3.7V, 2800mAh Li-ion batteries.
So I need to keep the voltage at 3.7V but I need to increase the total battery pack capacity for long periods of use.
So I connected all the batteries in parallel to achieve this.
2800 × 4 = 11200mAh and 3.7V
Finally, I used a DC step-up converter to transform 3.7V to 12V.
My question is: Can I use a 1S 3.7V charging BMS to charge all batteries that are connected in parallel? Could it cause any damage to the batteries?
Or is a 1S BMS only for a single cell?


texts:
I've read that that the output voltage available at the Vout pin is approximately equal to the Vcc applied to pin 8 minus 1.7V. This is for an input voltage of +15V.
I wanted to know if there is an equation for Vout in terms of input based on  threshold/trigger?


texts: Safety of Aluminium for enclosure earthing

texts:
To earth an Aluminium enclosure, is it safe to use a welded Aluminium stud and then use a nut and washer to attach a hook-ended earthing wire to the stud?

Aluminium oxidises to develop a thin insulating layer of Aluminium Oxide. Could this increase the resistance of the earth path and render this solution unsafe?

Also, galvanic corrosion between steel and Aluminium seems to be an additional potential problem at the interface between Aluminium and Steel. Does this limits the types of materials usable for the nut, washer and hook?


texts: What is the limit I have to take so that the capacitance formula for concentric cylinders shows the capacitance of infinite plates per surface area?

texts:
I'm trying to figure out how to solve this problem. The formula for the capacitance of two concentric cylinders is given as \$C=2\pi\varepsilon L/ln(b/a)\$, where b is the outer radius, a is the inner radius and L is the length.
So I guess the goal is to prove that by taking a limit, it converges to \$C=\varepsilon \frac{A}{d}\$, where d is the distance between them, or b-a, and A is the area of the plates.
What I've thought is taking the limit of a and b as they approach infinity, i.e. the cylinders expand to infinite perimeters, but I couldn't find anything.
Thanks in advance.


texts: How are components with contacts under the ICs soldered onto boards?

texts:
Consider an IC that looks like this, or similar:

Note how the leads that are soldered to the board are on the underside of the IC.

I am barely an electronics novice.  My work with electronics is basically making simple repairs to old gaming hardware, so my expertise is very limited.

I've tried to google this but I must be mis-naming these components when I try to search for how this is done but how are components like these soldered onto boards in production units?  I could easily see either these pins being coated in a bit of solder, or maybe a thin layer of solder is already on the PCB when the chip is placed on it.  Regardless, how is each pin heated up to the proper temp so that the solder will melt and the chip will stick to the board?

I've tried to figure this out on my own, but so far this just seems like "black magic".

As a minor follow-up, if you are developing electronic hardware that needs a component like this, how do you use a chip like this in prototyping and testing?  Is there a manual way to solder chips like this?  Regardless of how it's done, it seems to me it'd at least have to be a mechanical process because you'd need a certain degree of precision.


texts: How does the transistor topology look like for a gate of this logic inverter?

texts:
How does a single inverter gate of this hex inverter, look like in transistor level?

I don't mean the actual photo, but how does the transistor topology look like?

Does the BJT inverter (see below), with two resistors, represent the exact topology of the gate of a hex inverter IC?:


texts: I'm looking for an easy solution to identify data formats, protocols. I have an outdoor temperature - humidity sensor which is connected to my HVAC system. I want to decode the data coming back from the sensor into another processor. I do not know the format - protocol and can not get any documentation from Honeywell. Short of buying a protocol analyzer are there any software solutions out there?  is an example of 40 deg. F with 53% humidity.


texts: Soldered wire or test connector for VNA measurement?

texts:
I am designing a PCB for a IoT device, which will have an antenna inside a space-constrained plastic enclosure with metal screws. I know that I will have to tune the frequency response of the antenna with a matching network. I am planning to tune my matching network empirically, measuring S11 with a VNA. Of course I will do this with the device in its final environment inside the case, including the battery, etc. The antenna signal is in LTE band 12, center frequency 700MHz, maximum gain 1.3dBi. The antenna is stationary, and only transmits.

For my VNA measurement, a SMA connector and coaxial cable will connect Port 1 of the VNA to the input of my matching network. I don't the best way to terminate the end of the coax connecting to my PCB. My two ideas are bare soldered wire, or a test connector on my PCB.

My favourite approach is the bare wire, because it is cheaper and I think it is less intrusive. With the bare wire, I plan to solder the signal wire connected to Port 1 directly to the same pad as the signal entering the matching network, and the ground wire to my ground plane. This should have less coupling to the antenna than a metal U.FL or SMA connector soldered to my board. The problem with this is I don't know how to calibrate this type of termination. I could originally have a SMA termination to connect to the calibrator, then calibrate, then cut it off, then solder, but I'm not sure if that would invalidate the calibration.

simulate this circuit – Schematic created using CircuitLab

Alternatively, I could have an extra RF input port on my PCB feeding the matching network. Then I could just connect a calibrated coax cable to it and test. I don't like this for two reasons. First, it adds a metal object near the antenna, which I want to minimize since they cause losses. Second, if I have to include this extra connector in every copy of the device, that's an added cost, and it's a stub in the network. If I calibrate with it and don't include in production, then my matching network will be less valid, and I'll still have a stub where I would have soldered it.

simulate this circuit

All of this is based on three assumptions: that stubs and metal components near the antenna affect performance, and calibration is critical. If stubs and metal didn't matter, then I would simply populate the connector during testing, and remove it when testing was done. On the other hand, if VNA calibration isn't critical, then I'll just use the soldered wire technique.

Overall, my question is: what is the best way for me to measure S11 of my antenna?


texts: Eagle SPICE MOSFET Simulation Has the Wrong Operating Point

texts:
Having a lot of trouble getting an N-Channel MOSFET to work correctly in any spice program.  Trying something really simple to get started and I can't seem to get the MOSFET to "turn-on".  Am I missing something basic with how to simulation this type of circuit?  To be honest, I'm a little embarrassed I can't get this to work.
* SpiceNetList
*
* Exported from Inverter.sch at 9/27/2020 7:28 PM
*
* EAGLE Version 9.6.2 Copyright (c) 1988-2020 Autodesk, Inc.
*
.TEMP=25.0

* --------- .OPTIONS ---------
.OPTIONS ABSTOL=1e-12 GMIN=1e-12 PIVREL=1e-3 ITL1=100 ITL2=50 PIVTOL=1e-13 RELTOL=1e-3 VNTOL=1e-6 CHGTOL=1e-15 ITL4=10 METHOD=TRAP SRCSTEPS=0 TRTOL=7 NODE

* --------- .PARAMS ---------

* --------- devices ---------
R_R1 N_2 N_3 100
V_V1 N_1 0 10
M_M1 N_2 N_4 0 0 NFET
R_R3 0 N_4 80k
V_V2 N_3 0 100V
R_R2 N_4 N_1 80k

* --------- models ---------

* (model found in library)

**********************
* Autodesk EAGLE - Spice Model File
* Date: 9/17/17
* basic nfet intrinsic model
**********************
.MODEL NFET NMOS (LEVEL=3)

* --------- simulation ---------
.control
set filetype=ascii
OP
write Inverter.sch.sim
.endc

.END


texts: Converting gates in XOR circuit to NAND gates

texts:
I have this XOR circuit:

I tried to write it using only NAND gates and this was the furthest I got:

According to my book, it should look like this:

I did this:
$$(x.y')+(x' . y) = ( (x. y')+(x' . y))'' = ((x. y')'.(x' . y)')'$$
Which is the second circuit.
I know NOT gates can be done with NAND gates but you'd have to use 2 in this case and the book only uses one. How do I do that?


texts: Trouble converting 12VDC incandescent to LED: lack of resistance

texts:
I'm converting two, independent, incandescent bulbs (OEM 212-2) fixtures to use LEDs for automotive map reading.  Each incandescent bulb (12-volt/system) measures 1.5 ohms with a meter; however, there is no resistance across the LED [replacement] bulbs.  The LEDs will not light up with their respective switches (however they do come on properly when a door is opened).

When I press the switch to "on" with no bulb installed, I see 4.55-volts DC at the socket connectors.  This is not enough voltage to light the LED bulb.  However, when I reinstall the incandescent bulb and switch it "on", it lights and I see 12.2-volts across the lighted bulb.  It appears the circuit (computer?) tests for resistance initially with 4.55-volts, then ups the voltage to 12.2-volts if the resistance is proper (perhaps a method to detect if bulb is good/proper?).

Does anyone have any suggestions regarding how to make this LED work?  I'm hesitant to install any resistor, but the reality is that's exectly what's there now albeit in a "controlled-burn" setting.  My concern is simply installing a parallel resistor would generate similar heat and merely burn it.

Thanks for the opportunity to ask this question and for any help/suggestions. -Brian


texts: Thickness of low frequency Mu shield calculation

texts:
I am dealing with a low frequency varying magnetic field, say 10 - 100Hz with a magnitude of 0.8T. It seems shielding at this frequency gets tricky. Even though Mu is capable of doing it, there should be a thickness derivative formula with which I am struck.

How can I calculate the thickness to attenuate by a factor of 4? Is it possible? Also, inputs on eddy currents which will be generated in that shielding is appreciated.


texts:
I am building a MCP2200 breakout circuit getting reference from the guide by Microchip itself MCP2200 Breakout Board and I tried with two MCP2200 ICs but it doesn't get detected by the PC. I salvaged a 12MHz Oscillator from an old Arduino Mega board using CH340G IC which didn't work for some reason.

I checked out this post MCP2200 doesn't work everytime and tried to increase the capacitor values across the oscillator pins but still no luck. So my assumption is the oscillator is not working.

Could it really be? As a crystal oscillator is a simple circuit as follows;

I tried measuring the voltage values across osc pins and they were 0.17 V. Could overheating with hot air damage the crystal?


texts: single-cycle design using and shared memory for both data and instruction

texts:
This is not really a question on electronics , it's more a question on logical design.
I hope this is the right place to ask.

How come it is not possible two use a single-cycle design
and have a single memory for both data and instructions ?

I mean , why it is not possible to access that single memory with the address we find in the pc and then access it again using the address we find in the instruction ?

Thanks


texts: What is significance of these variables in given block diagram of system

texts:
This figure is from book by Norman S. Nise and can anyone explain me following variables and their effect on the system
1.'r' , as far as I know it is reference and here author considered its value zero but
who provide this reference ?(designer or its disturbance)
what is its purpose (or what impact it has on this system)in context to this figure?
What will be its effect on this system if let's say its value doesn't equal to zero?
2.'U', is it input given from outside to the system ?But in figure it didn't look like it is given  from outside so from where this variable comes from and what it is?


texts: Who was the first person to appreciate the value and usefulness of normalizing electric potential energy to each charge carrier (i.e. electric potential)?


texts: Why would this Class D Audio Amplifier have low current draw?

texts:
Disclaimer: Saying I have very little knowledge of electrical engineering theory is an understatement. I very much appreciate your help and patience. I'm not finding any questions similar to mine, but this could very well be due to me being completely off base in my understanding of the problem.
Since I have so little knowledge on the principles at work in this problem, I will try to detail everything I'm doing. That way there is no assumptions made in terms of what I know and don't know.
The general scenario:
When I connect a multimeter to the output of a ac to dc power adapter and then to the input of an amplifier board it is reading very low amperage, even when the volume is set to maximum on the computer which is creating the input. Below is a very rudimentary, and probably comical, drawing of the setup.

Specific components used
Amplifier Board:
The class d amplifier board that I'm using is the wondom 2x25watt audio amplifier board using the TDA7492. the Sku is AA-AB32165 and can be found here http://store.sure-electronics.com/product/AA-AB32165. The specifications on store page require a 14V-19V power supply.

Power Supply:
I am using an old Toshiba laptop power ac/dc adapter which states its input as 100-240V~1.2A 50-60Hz and its output at 19V 2.37A.

Speakers:
I am using two 16 ohm, 25watt speakers.

Input generation (not sure what the term for this is)
I'm using a RCA to 3.5mm Aux cable from my computer to the board.

My question:
The multimeter on the DC amps setting is reading only 0.05A. It is my understanding that Power = voltage x current. If this applies here that means the board is only being supplied 0.95watts. Wouldn't that mean this board is not capable of supplying a total of 25 watts to each speaker if not even that much power is inputted into the board. If these assumptions on my part are right and I'm measuring the amperage correctly, why is the amperage so low and how can I increase the current draw?


texts: How to adjust output temperature of a PTC ceramic heating element?

texts:
I'm planning to buy a PTC ceramic heating element like the one shown  here.
I wanted to know how to adjust the output temperature of such an element within the given output temperature range?
I'm fine with regulating the input voltage or current if that can change the output temperature.


texts: Lack of documentation on batteries? Trying to understand why LR1130 and LR1131 aren't equivalents

texts:
Recently I purchased some AG10 button cells for a device I have. The device specifically calls for LR1131 batteries, but someone online told me that AG10 was equivalent (and they are in a way: same voltage and same size.

The batteries I got in the mail say LR1130 on them, which I trust is equivalent to AG10 (see previous charts). Basically the device doesn't have enough power. It works for a few minutes and then shuts off, and other odd behavior happens when it's not working like it should. On my quest for answers I've understood now that there's quite a bit more than just voltage, but every single search I try fails to give me good information on why these batteries differ in a way that would keep my device from working (it works with the proper LR1131 batteries, I just have no more left).

I've noticed that the batteries appear to differ in their charge, which would suggest that maybe that's why I'm having problems. I have no battery tester to see if I was actually sold good batteries.

At this point I know quite well that I just bought the wrong batteries, and will soon buy the correct set. But how can I trust it? How can I be sure that they'll work when other items say that they're LR1130 and LR1131?

Edit: Actually called for LR1131 not L1131, even though this likely doesn't change anything.


texts: How good are Time-Of-Fligt (light) sensors for measuring small objects?

texts:
I found this sensor VCNL4040 and it has the emitter angle and the sensor angle.

Question:
How good is a Time-Of-Flight (light) sensor to measure small objects that are 100mm away and about 20x20mm in square? The material is metallic, gray with a small film of transparent yellow oil onto. So it quite shiny.
The accuracy must be in ±1 mm.
If you have a better one, please tell me.


texts: Linearizing multi-star network for home automation

texts:
I'm designing a communication network for private home automation. My design goals are:

Local wrt network changes. That is, changing one part of the network should not require modification of the network as a whole.
Easy to use. Adding or removing devices should be simple.
Allow complex topologies, ideally multi-star.
Being able to use existing infrastructure (CAT 5 cables).
Inexpensive.

Originally I considered 1-Wire, but further investigation lead me to the conclusion that it doesn't cope well with EMI noise and that the available hardware is becoming obsolete.
Learning about CAN, I then considered ISO 11898-3 physical layer, which does allow multi-star topology. However, it seems that it's not being widely used nor supported, and I only found a very few ICs that support it. And most importantly, it's lacking the locality property: The terminator resistance should be split equally between all terminal nodes, which means either updating the whole network after adding a new node, or accepting improper termination.

Eventually I came to the idea to make the CAN bus internally linear, and achieve arbitrary topology by connecting each node to it by two pairs of wires. One pair connects to the "left" part of the bus (pins 3 and 4  below) and the other pair to the "right" part (pins 5 and 6). Both ends of the bus will be terminated in the master node. Essentially this is traversing the network tree:

Parts of the bus could be connected as follows (Vcc is power distributed from the master node to all the others):

I see these advantages:

The bus will be linear, adhering to the standard and making its behavior predictable.
Can use standard ISO 11898-2 components.
Satisfies my design criteria above.

And potential disadvantages:

Uses 2 pairs of wires instead of 1, making the bus twice as long, However, the actual length of cabling will be the same, since I'd use CAT 5 cables anyway.
Somewhat less resilient - a broken connection cuts off the rest of the bus, not just a sub-tree.
All sockets need to be plugged in, otherwise the bus gets broken. So if a node is removed, either its closest split needs to be removed as well, or it needs to be replaced by a stub that connects 3⬌5 and 4⬌6.

Is this a viable, or commonly used approach? Are there any potential pitfalls?


texts: designing a circuit that accepts n 1-bit inputs and adds them

texts:
In my Digital System design course, there is a recurring question in exams that I can't manage to know how to tackle.

You are given the design of a half-adder that accepts two 1-bit inputs and adds them.

You are also given the design of full-adder.

You are asked to cascade several of these adders to design a circuit that accepts n 1-bit inputs (for example 9 1-bit inputs) and adds them.

Any way I could figure out how to think about this type of problem?


texts:
I know that similar questions have been asked before. I just want to get a better understanding of some details. Please bear with me.

I learnt that I could use an analog CMOS switch or some other dedicated bus switches such as a multiplexer to 'switch off' a segment of a bus. Now I wonder: when a switch is in the 'off' state, will the switch itself contribute to the bus capacitance? If it does, how significant is the influence? is there any way to switch off a part of the bus and completely remove its influence(including the switch) on bus capacitance ?

My application requires a large amount (could be over 400) of I2C devices connected to the bus. However, only 2 or 3 need to be online at any moment. I think the 400pF (or 3000pF when using a buffer?) capacitance limit is the main concern here. I believe a cascade structure of bus switches could solve the problem, but I need the system to be modular which means that each device are equipped with a switch and no cascade structure.

Pardon me if I'm not making this clear. This is my first time asking questions here. Thanks!


texts: What is the difference between context switching and interrupt handling?

texts:
I'm an embedded developer. I haven't worked with RTOS/linux. I was going through RTOS concepts when I stumbled upon 'context switching'. I understand that when context switch occurs, all the registers along with PC(Program Counter) gets saved in stack before another thread is loaded to the processor. Isn't a similar thing happening when an interrupt occurs(in a controller which doesn't use any kind of  OS)?

How different are those two terms?


texts: Can arcing in IEC 60320 C13/C14 connectors damage a device?

texts:
I have a 'guitar effects power supply' built to supply 9v/12v/18v power to  guitar effects pedals. It is powered using a IEC 60320 C13/C14 power receptacle and cable.
After using this device for the majority of the day, I finally turned off the unit by removing the C13/C14 power cable from the device. When the cable was still half-way in (as I removed it in a 'skewed' fashion) I heard arcing, saw sparks, heard a pop and smelled some 'magic smoke' escape. From this point on my device was dead! (Luckily, it's fairly new and it's got warranty!)
The device manual says nothing about hazards of plugging/unplugging at the C13/C14 connectors. I've seen other C13/C14 devices like a guitar amplifier (and I believe some PC power supplies) have manuals that warn to "always plug and unplug the device at the wall".

Questions:

May plugging/unplugging powered C13/C14 cables into unpowered devices cause arcing that can damage devices?
May this cause over-voltage conditions in badly designed power supplies? (as in: damage to the devices the powersupply was feeding)
Was this user error? Should I always plug/unplug devices from the wall?
Does IEC 60320 even say anything at all about arcing situations or usage scenarios like this?

I think I may have once heard an old adage of "always connect data cables to devices first, then connect power". I've got suspicions it might be true after all...


texts: Why PU currents are equal to PU powers with DCPF assumptions?

texts: Can someone explain to me why PU currents are equal to PU powers with DC Power Flow (DCPF) assumptions? I tried to find something on google but I didn't find anything. :(


texts:
I am using LCD with below power interface.

But as per below note in LCD datasheet, VCC and VGL need to apply first and then VGH. My query is why such power sequencing is needed ?

If I use below circuit for power, is it enough for power requirement of TFT?

LCD Connection:


texts: Does an electric motor benefit by being given a rest?

texts:
Will the following two scenarios give different results on the wear/safety of a consumer-grade electric motor:

A: Run motor for 12 hours/day for 20 days
B: Run motor for 24 hours/day for 10 days

(In each case the motor runs for 240 hours)


texts: How is "conversion loss" defined for an IQ mixer?

texts:
Suppose I use an IQ mixer to downconvert an RF (i.e. 8 GHz) signal to IF (i.e. 50 MHz).
For example, the RF signal might be \$V_\text{RF}(t) = A \cos((\Omega + \omega) t + \phi)\$ and the LO signal could be at frequency \$\Omega \$, resulting in IF signals

\begin{align}
V_I(t) &= I \cos(\omega t + \phi) \\
V_Q(t) &= Q \sin(\omega t + \phi)
\end{align}

where we've assumed that there are antialiasing filters on the I and Q ports rejecting the signals at \$2\Omega + \omega\$.

How is the mixer's "conversion loss" defined in terms of the RF amplitude \$A\$ and the IF amplitudes \$I\$ and \$Q\$?
In other words, if I know my RF and I know the mixer's rated "conversion loss", what what is the equation giving the IF power in terms of the RF power?


texts:
I'm currently working on a small hobby robot, where I want to use a FEZ Panda II along with a RX433 to remote control it. My power source is a Turnigy 3000mAh 3S 20C Lipo which gives me 11.1V to work with, which is too much for the FEZ, but perfect for the motors. I could easily use a resistor to get the right voltage for the FEZ, but I'd like a more generic solution, so I don't have to worry about varying current consumption from different sensors and what not. Using an LM317, I can regulate the voltage to my needs. My question is this:

When I turn on/control the motors, will this affect the input of the power regulator and in turn affect the output, and if it does, how do I stabilize it? I could test it, but I don't want to risk frying my FEZ just yet.

Also, I see people talking about an LDO regulator for the Arduino, is this more appropriate than a simple LM317 regulator?

 - Motor Specs
Voltage             =  12 V
No-Load Current     = 3.5 mA
Normal Load Current = 120 mA
Stall Current       = 360 mA

 - FEZ Panda II Specs
Voltage             = Through USB port or an external DC 6-9V power supply (connecting both is safe).
Active Current      = 103 mA.
Idle Current        = 65 mA.
Hibernate Current   = 3.75mA.


texts: What heat sink should I use for this 50W resistor?

texts:
I want to run 80 Watts of power through 2 50W 1Ohm resistors:

http://www.upe-inc.com/upe-ate-resistors/wirewound-aluminum-housed-axial-resistor/

It's the RB50 series.

When trying to calculate what kind of heat sink I need it seems my values don't make sense.

I'm going to calculate with half power through 1 first:

So let's assume 30 degrees ambient, 40 watts of power. The resistor is rated at 1.9K/W, I'll be using thermal paste rated at 0.11K/W, and then I need a heat sink which is the unknown in the equation. The effective operating temperature range goes up to 250C, but I'd rather stay lower.

40*(1.9+0.11+X)+30 < 250
76+4.4+40X+30 < 250
110.4+40X < 250
40X < 139.6
X < 3.49

But if I want to take some margin into account

X < (maxTemp - 110.4) / 40

So for 150C maxTemp it would mean X < 0.99, which seems impossible for a small size heat sink? Considering the physical dimensions of the resistor, how can this be used if it needs a huge heat sink for it to function?

Does this mean that if the resistor receives 40 Watts of power, it would by itself emit 76C above ambient? So why all of a sudden I get 200+ degrees in my calculation by adding a heat sink and thermal paste? It seems I am missing something fundamental in my understanding of things.

Also I found a document (but it's in French) about this resistor in which they stated that the resistor needs derating unless it is attached to "a standard heat sink". No explanation about what a "standard" heat sink might be. For those who happen to understand French it's here:

https://produktinfo.conrad.com/datenblaetter/400000-424999/421545-an-01-fr-ATE_RB_50.pdf

If the values are correct, is there a way of calculating how warm the ambient temperature around the heat sink will become? Or is it trial and error? I will be making my own ventilated enclosure but I don't want the plastic to melt so it would be good to know how hot it will become on the inside.

Could someone explain me where I am wrong? I'd rather not burn up stuff by figuring this out through trial and error.


texts: What happens when data is written to LATCH?

texts:
This is what I found in PIC16F1947 data sheet:

  Reading the PORTB register reads the status of the pins,
  whereas writing to it will write to
  the PORT latch. All write operations
  are read-modify-write operations.
  Therefore, a write to a port implies
  that the port pins are read, this
  value is modified and then written to
  the PORT data latch (LATB).

I'm a firmware developer and my background is Computer Science. I still struggle to understand electronics and logic in hardware level. I only have the basic knowledge.

So, I want to understand what happens when data is written to latch in hardware level.

Thank you.


texts:
I'm building a sensitive analog circuit powered by a wall wart. I'm using a DCV01 family DC/DC converter with dual outputs (+/- 6.5V) followed by linear regulators. The SYNC pin of the DCV01 converter unintentionally generates a signal that transmits wirelessly...the package's pin acts as antenna I suppose. Bringing a wire near it allows me to see the SYNC pin timing on an oscilloscope. While I have filtered the output of the DCV01 as suggested (I think), some of this periodic ripple (looks like a wavepacket every 1/400MHz) remains. The amplitude is millivolts--way over my noise budget. My circuits operate on microvolts.

I'm attaching an image of the circuit design. It's pretty trivial. How can I get rid of this signal? Is there a standard filtering approach that I should have impelmented?


texts:
I've got a small 12v 4A water pump that I want to power from a standard 12v car battery. Which calculations do I need to use to figure out the right gauge of wire and fuses?

How would I calculate whether the pump will burn out if I was to connect it directly to the battery? Do I need a transformer or regulator to keep the current and voltage at 12v and 4A?


texts: Is it normal for a SMPS mains smoothing cap to still hold a charge after many many hours

texts:
I have a PSU with 2 200V 330μF main smoothing caps.
I noticed that > 6 hours after having shut down the PSU there was still 0.6v that could be measured on one of the main filter caps.
Would that be considered normal , or should I expect this to have been gone to 0v (or a couple of microvolts)
I do have to say that the PSU is currently not working (not outputting any DC voltages) and that it was turned on for about 1 minute to do some diagnostics.


texts:
For a quite while, I've been using an avr ATmega324PA controller and Atmel studio to write the programs. we wrote a TCP bootloader. It works fine without any interrupt. Later we did add an external inetrrupt to that program and now controller always restarts when jumping to the ISR. Here is the code

void main()
{
  init_interrupt();
  init_uart();
  while(1);
}

void init_interrupt()
{
  /* PortA3 as input for external interrupt*/
 DDRB|=(0<<2);
  /*Pulll up disable*/
 PORTB &=~ (1<<PORTB2);
  /*Interrupt_vector change enable*/
 MCUCR|=(1<<IVCE);
  /*Interrupt vector change to boot section*/
 MCUCR|=(1<<IVSEL);
  /*Interrupt_vector change enable*/
 MCUCR&=~(1<<IVSEL);
 _delay_ms(5000);
  /* Enable external interrupt-2*/
 EIMSK |= (1<<INT2);
  /* Enable rising edge of the input signal as interrupt*/
 EICRA |= (1<<ISC21)|(1<<ISC20);
  /* Enable global interrupt*/
 sei();
}

ISR(INT2_vect)
{
    uart_send("Print on interrupt");
}

Here i am trying to change the interrupt vector to boot section.

NOTE: BOOTRST fuse is already set

EDITED:
After changing the MCUCR value as shown below, i sent it through UART instead of '01', the output is displayed as "A0 2E 57 C9 D1 95 91 FF"

    MCUCR|=(1<<IVCE);

Must be a problem with the MCUCR register