texts:
Can vector control in induction motors be considered as power factor correction ?
From my researchs, it seemed to me angle between rotor and stator flux is 90 degree when load is purely resistive (power factor is unity).The goal of vector control is to make this angle 90 and get the maximum torque. Is that right ?

Thanks in advance.


texts: What is the internal resistance of a LiPo battery determined by?

texts: Given DKNguyen's answer to my last question, I wanted to know what determines the internal resistance of a LiPo battery. Does it have something to do with its inside chemistry? Is it just roughly calculated by the manufacturer via testing?


texts:
In the circuit shown here the conventional current direction is from V2 to V1 and is equal to 3 Amp. I understand the theory.
But, if I make this circuit with two batteries, according to the schematic the current(positive charge) leaves a positive side of one battery and  goes through the positive side of the second battery.

So my question is, if I actually make this circuit with two batteries, does it mean that a battery (V1 here) accepts current to its positive side and send current from its negative side? How is that possible? How would the current circulates?

simulate this circuit – Schematic created using CircuitLab


texts: I am looking for some advice on motor/motor controller?

texts:
I am planning to create a rig to check my wheel speed probes. I am going to mount a gear and rotate it with an appropriate motor/motor controller.

Unfortunately I don't have much experience selecting motors. I have a 35V DC/25V AC power pack but don't know whether to select an AC/DC motor with a controller or use a potentiometer.

If I can vary the speed that would be great. Any advice on models of motor would be great.


texts: What is a good electronics kit for the everyday inventor

texts:
I am looking for a good electronics kit with lots of capacitors, trimmers, resistors, pots, diodes, transisters, leds and laser diodes, timers(like the 555), inductors ICs and common microchips, LOTS of sensors(temperature, gasses, radiation, light, sound, motion, etc etc etc) and sensor like pieces (like selenium chips), and a bunch of other things, a really good kit for all around for the chaotic inventor in me, What would you recommend? The more complete the kit, the better

Thank you for your time

PS it has been such a long time since ive used the names of these so if I have mixed some up or using the wrong name, please understand I am looking for everythign to make devices from smoke detectors, in communication devices over laser, wireless and such.

Thank you all again for your patience and taking the time to help, I understand how time consuming some of these posts can be and I hope I am not causing too much trouble


texts: Does this optocoupler circuit work practically?

texts:
I've been trying to make a circuit that:

Outputs 12V when the power is off
Outputs 0V when the power is on.

Input is 230V 50Hz AC.
I have a question about the voltage across the output capacitor. When the mains is on, it seems the average voltage across the capacitor is 0V. Am I correct or missing anything? I'd highly appreciate your input before going to mess with the high voltages...

simulate this circuit – Schematic created using CircuitLab


texts:
Analysis
I'm trying to find the resonant frequency for this circuit

simulate this circuit – Schematic created using CircuitLab
Writing up the node voltage equation for \$V_o \$
$$\frac{V_o-V_{in}}{Z_L}+\frac{V_o}{Z_C} + \frac{V_o}{R}=0 $$
And using that \$\frac{V_o-V_{in}}{Z_L}= \frac{1}{L} \cdot \displaystyle\int (V_o-V_{in} )\: dt \$ and \$\frac{V_o}{Z_C}=C \cdot \frac{dV_o}{dt} \$ brings us
$$C \cdot \frac{dV_o}{dt} + \frac{1}{L} \cdot \displaystyle\int (V_o-V_{in} )\: dt + \frac{V_o}{R}=0$$
Dividing through with \$C \$, differentiating every term and moving \$V_{in} \$ to the right hand side gives me
$$\frac{d^2V_o}{dt}+ \frac{1}{RC} \frac{dV_o}{dt} + \frac{1}{LC}V_o = \frac{1}{LC} V_{in}$$
Calculations
According to "Eletrical Engineering principles and applications by Hambley", the square root of the term before \$V_o \$ is called the undamped resonant frequency \$\omega_0 \$.
In this case the resonant frequency is
$$\omega_0 = \frac{1}{\sqrt{LC}} = \frac{1}{\sqrt{62 \text{uH} \cdot 63 \text{nF}}} = 0.5059 \: \text{MHz}$$
Also according to Hambley, at the resonance frequency the equivalent circuit impedance is purely resistive, so \$\Im{(Z_{eq})} = 0 \$.
The equivalent impedance of this circuit is
$$Z_{eq} = Z_L + \frac{R \cdot Z_C}{R + Z_C} = sL + \frac{R}{sC(R+ \frac{1}{sC})}$$
Plugging \$s= j\omega_0 \$ and plugging in component value into the above equation gives me
$$Z_{eq} = 15.14 + j11.57 \Omega$$
Question
Which clearly shows that the impedance isn't purely resistive. So my question is, why not? Is my equivalent impedance wrong, or perhaps my resonance frequency?
Edit
Source about resonant frequency

Figure 6.23


texts: How can I make a capacitive touch panel that can sense position?

texts:
I'm trying to make a fairly large touch panel (no display). Or if that's any easier: a set of touch ribbons.

The Wikipedia page on capacitive sensing and other online resources seem to pretty much boil down to "measure the capacitance created by your finger at the corners of a conductor".

There are also a bunch of breakouts and tutorials on Adafruit, Sparkfun, and similar websites. But they are all binary buttons, they don't sense location. These companies also sell LCD panels with touch screens, but nothing without the display.

The Teensy has touch pins that can be trivially read with touchRead, with similar on/off examples. But owning a Teensy, it seemed easy enough to experiment with sensing position.

I connected about a meter of wire between two Teensy touch pins, and tried to subtract the values I got. That's what the simplified model would led you to believe: take a conductor, measure capacitance at the ends and compare. However, this result was pretty useless, and no clear difference could be found.

So then I thought, alright, maybe it needs to have more resistance? Supposedly there is some R and C involved, and the R of a copper wire might just be too small. Next experiment was to connect a 10k resistor between the pins. Touching either end of the resistor was kind of discernable, but still not super reliable. I got some nichrome wire to play with, but I'm not hopeful.

So this begs the question: how does position sensing with capacitive really work. What kind of material is needed? How is capacitance actually sensed?


texts: How to connect a net to a power plane in Altium?

texts: How do I connect a net to a power plane in Altium? I'm using Altium 15 for 4 Layer PCB project. I've created a rule assigning a net to a power plane but it doesn't work as the pads that should be routed through the power plane they still showing that the connection is missing. In the Altium tech docs I understood that they should be connected already but they are not.


texts: High voltage square wave drives induction motor

texts:
This is the problem, i'm designing a water pump's universal drive (3 HP Max) controlled by Arduino, so my first vision is to convert 220VAC/50Hz to DC, Then reduce the voltage by DC-DC chopper circuit, and finally use DC-AC inverter to control the frequency, and the switching is controlled by Arduino, but the problem is the output of inverter will be square wave (Not sin), which contains a lot of Harmonics.

So the question is this, how much the harmonics will affect the system??

And is it possible to design a low-pass filter(100Hz Cut-off frequency for example)for this high voltage system to reduce the harmonics?


texts: I am a beginner at PCB designing. I believe a good way to learn to design PCBs is to design them myself and then check how I did. I wanted to know of any resourses where people post their PCB designs and respective circuit diagrams online? So that I can refer to these designs?


texts: Powering a usb hub using a different source

texts:
I dont really know much about electronics and I tried to seach online if this specific thing im thinking of doing has ever been posted and i cant find anything exactly the same.

So what im trying to do is make a makeshift powered usb hub. Ive seen several online but they are made differently. Basically, i wish to just connect the data + and - from the computer to the hub, disconnect vcc and gnd from the computer by cutting the ends of those wires coming from the pc, and finally connect a 5v 2a power supply from a tablet charger to the hub vcc and gnd.

Is this viable? I just thought this could be cool because since only the charger's power is connected to the hub, i wont need a diode since there is no possibility that voltage will be sent to the computer as that line is cut. Will this allow the pc to send data to the hub?

I hope this is not a dumb question. Thanks in advance!


texts: Nth order Butterworth filter transfer function for a given roll-off frequency

texts:
I want to plot a fourth order low pass Butterworth for any given cut off freq. But I'm lacking the correct transfer function. I saw some polynomial transfer functions in s domain. But their cutoff is 1rad/s. Here is a table I found for wc=1rad/s:

Is there a quick way to modify for example the 4th order filter transfer function above for a different wc other than 1rad/s? Is there a quick way to obtain or is there a lookup table designated for filter transfer functions?


texts: why power supplies won't work with laptops?

texts:
laptops need a supply and it is a DC voltage isn't it? so why my lab power supply can't turn my laptop on. it is tune on the desired voltage and polarity, when i press the on button, the laptop starts, leds on, tries to boot and suddenly dead with a beep!!

the power supply can provide 3A and it shows on its front Ammeter that the laptop is consuming 1.5A.

what technologies makes my laptop adapter different?


texts:
Recently, I built a fuzz effect for my guitar, and it all works great except for one thing: no sound is coming through the amp until I press the footswitch; then, the fuzz effect comes through. Normally, the guitar should play as normal through the amp, and by pressing the footswitch it should simply add the effect. The image I found to create the pedal was this visualization:

As you can see, the build involves two potentiometers, one for volume and one for gain. What I DIDN'T notice before building it was that the 100k was a logarithmic pot and the 5k was a linear. Both of the pots I used in the circuit were linear. Could this have something to do with the main issue? Trying to figure this out before I go and buy the log 100k pot. If it's not the issue, any ideas what could be causing this?


texts: Simulating a non-linear system in Simulink

texts:
I have a set of non-linear equations, which I would like to model in Simulink in order to compare to their linear counterpart.

Here is the block diagram of my setup. The state-space block represents the linear model, while the Matlab function contains the non-linear equations.

Linearised Response:

Non Linear Response:

I am trying to simulate the following non linear equations:

  The function \$\dot{\vec x} = f(\vec x, u)\$ is outputting
  derivative of \$\vec x\$, not \$\vec x\$ itself.  The function block that  finds \$\dot{\vec x}\$ from \$\vec x\$ and \$u\$, then
  feeds it to an integrator and feeds the \$\vec x\$ back to the block,
  and extracts \$y\$ from it.

with these parameters:

g = 9.81;
m = 0.05;
R = 1;
L = 0.01;
C = 0.0001;
x1 = 0.012; %initial condition 1: displacement
x2 = 0;     %initial condition 2: velocity
x3 = 0.84;  %initial condition 3: acceleration

This is how I coding the Matlab function to represent my non-linear system:

    function [xdot,y] = fcn(x,u)

    % define your constants
    g = 9.81;
    m = 0.05;
    R = 1;
    L = 0.01;
    C = 0.0001;
%   x1 = 0.012; %initial condition 1: displacement
%   x2 = 0;     %initial condition 2: velocity
%   x3 = 0.84;  %initial condition 3: acceleration

    % nonlinear set of equations
    xdot = [x(2); g-((C/m)*(x(3)/x(1))^2); -((R/L) +(((2*C)/L)*(((x(2)*x(3))/((x(1))^2)))))] + [0;0;1/L]*u;

    y = x';

My question is: Where do the initial conditions come into play with the non-linear mode? To calculate Matrix A in the state space block for the linear systems the initial conditions are used.

How should they be included in the non linear model coded above? Since as they are defined, they will never be utilized within the code.


texts: LED tachometer with PIC MCU (requires more current)

texts:
I've been working on an LED tachometer that will be installed on an open wheel race car. After putting the order through for the PCB I re-calculated the current draw and turns out the PIC's (16F877A) IO pin will not source enough current to drive 15 individual LEDs. So I have been searching for ways to drive multiple LEDs with more current. Each LED will draw approximately 35-40mA and 16F877A's source/sinking current is 25mA.

Most of my findings seem to point to transistors, using MCU's output as a control. After drawing a sketch on a notepad I noticed I'd need 1x transistor for each LED -- I think this will make the PCB/design quite big considering this LED array will be installed on the steering wheel.

So is there a way to drive multiple LEDs without having a transistor for each of the LED?


texts: How would I design a cable line that doesn't leak heat to the ground surface?

texts:
A loaded underground power cable dissipates some power as heat which heats the surroundings. The following scenario is possible in regions where large amounts of snow accumulate on the ground during winter.

At some point (late autumn or early winter) temperature gets below water freezing point. Snow starts accumulating. Then in spring temperature rises and snow starts melting. Loose heat from a cable line can be enough to accelerate melting of snow right above the cable line. The same scenario can happen if there's sudden warm weather in winter - recently accumulated snow starts melting.

This may cause the following curious observation: you're in some field or forest, everything is covered in snow, expect a narrow trace running across that area where snow has melted to the ground. The power cable is immediately traceable.

I've also heard that sometimes cables are not plotted on publicly available location plans and this is done to keep the cables secret (some government organizations might do that, I have no evidence of that, let's just assume this happens). Clearly leaking heat which melts snow and makes the cable traceable in warm weather makes it hard to keep the cable location secret. Spotting and plotting such cable requires no special equipment and no special skills - just take a GPS tracker in your pocket and walk the trace and if anyone questions you - then say you're going for a walk.

How can a cable line be designed such that it doesn't leak heat enough to make it traceable in the scenario above? An underground cable is covered with at least half meter of ground and even that is not enough. Obviously adding more thermal insulation would reduce the effect but not eliminate it completely.

How could one design a cable line that doesn't leak heat to ground surface?


texts:
I ordered a few ULN2002As.

I have it wired as follows:

Pin 1 -> GPIO of Arduino Pro Mini 3.3V

Pin 16 -> 300Ω resistor in series with an LED

Pin 8 -> GND

Pin 9 (COM) -> 5V (which is also RAW for the Arduino).

Pins 1-4 were wired similarly with LEDs but I've removed 2-4 because it wasn't working and testing with 1 was simpler.

When I apply 3.3V from the GPIO to Pin 1, nothing happens. When I disconnect GPIO and just apply 3.3V with a jumper, nothing happens. If I apply 5V, nothing happens. The output just swings around 300mV.

Am I totally misunderstanding how this chip works? I thought applying at least Von (2V according to the datasheet) at Pin 1 should make Pin 16 turn on.


texts:
I'm designing active electrodes for surface EMG, active electrodes being electrodes directly connected to a pre-amp and filtering stage on the measurement site.
Im working with the AD8221 IN-AMP to pick up the differential signal and I am trying to eliminate the need for a reference electrode by driving the reference pin of the IN-AMP via a voltage divider and buffer to bring the AD8221 to midsupply level.
However with my simulations I have failed to receive the desired midsupply voltage level at the reference pin and infact only get a few hundred millivolts. Can someone please explain to me the theory of operation with the reference pin? and whether this method will effectively eliminate the need for the reference electrode?

Circuit specs;
+/- 5V power supply for the entire circuit.
Gain = 100. (Rg = 499 Ohms)

I have read through the other threads related to my topic, but none have encountered the problem I have. I am running a simulation on MultiSim v.13

Update:  the current schematic


texts: Molex to SATA power adapter from a Cooler Master modular PSU?

texts:
I know this might sound weird at first, but hear me out. I have an old 400W PSU, which I plan on using in my headless server. It won't be anything crazy. One problem: It comes with only two SATA power cables, meaning I can only power two drives (one SSD and one HDD at the moment).

I want to make something like this:

Since I need to power a total of 5 drives. Luckily I have a modular Cooler Master PSU, which comes with some extra cables I don't need. One of those is this:

It has one modular connector at the end and four SATA power plugs, which is exactly what I need. I know the modular connector isn't molex, because it has 5 pins instead of molex' 4 pins. The modular connector looks like this:

Does anyone know if I can wire this up to a molex plug, so I can use the four SATA power plugs? I have a spare female molex laying around I can chop up. I'm not sure how the modular plug is wired and if all 5 are needed (there could be 2 GND for example).

EDIT:

If we assume the upper ones are correct, would this technically be doable just doing this:

I don't need 3.3v as far as I've read.


texts: Calculating maximum permissible track amperage for intrinsic safe PCB

texts:
I'm reading IEC 60079-11 standard (Equipment protection by intrinsic safety "i") which discusses how to design intrinsic safe circuit boards. In section 5.6.4 it talks about permissible termperature of copper tracks/boards and gives an example. Hence I'm not expert on PCB design, I cannot figure it out how the current calculated. Here is the example provided in the text and the reference table. Can somebody please explain how the values calculated in the example?

Example provided in the text:


texts:
Background Information

I am designing a small PCB for 4*  I2C devices, the baud rate of the I2C is not a major issue so 100kHz was the target.  The I2C devices are a RTC, LM75, 24AA04 and a MSP23017 to drive an LCD, the board is made using a LPKF milling machine.  Before fully populating the board I thought I would test one of the devices and the LM75 seemed like the easiest option.
Quick edit:  VCC is 5V and the Pull-Ups are both 10K

Have included some images to give you an idea of the layout:

1st image shows the PCB top view (Address jumpers to the top right, all grounded for testing)

2nd image shows the I2C traces, the grid dimension shown is 1.27mm (J11 to the left is connected to the OS pin, but left floating at the moment)

The Issue

I am testing this with an Arduino Uno (5V VDD) with some very simple code that polls the LM75 every second.  Establish a valid reading is intermittant but once established it works fine for about 2 minutes and then hangs, both I2C lines go high.  To establish a link again I have found sending an alternative slave address a few times and reverting back to the correct address usually works, then the same thing will happen.

Again I have some more images as capture the handshaking on my oscilloscope:

3rd image shows the setup (not the best I know, ignore the resistors by the jumpers originally fitted 1k's here and the inserted shorting links as per the 1st image))

4th image shows the first oscilloscope trace with valid data and some visible cross talk (circled in red), is this level of cross talk worth worrying about?
Good post I was reading on this subject At what point does crosstalk on I2C become a problem?

5th image is just a smaller time base so the waveform can be seen in more detail

Would be really interested in any advice possible, I probably need to re-work the board but any suggestions on testing would be great.  I have read a few post and was under the impression I2C on these lengths and low speeds should be ok, but quite sure I have made a rookie mistake!

Thanks in-advance,
Ant

----UPDATE----

I found the issue eventually a week or so ago but not had time to post an update until now.  I was convinced it was my PCB but it turns out that I was only requesting 1 byte from the LM75A, when I needed to request 2.

All the pointers on the hardware where incredibly useful, these allowed me to improve the design and I eventually settled on 2k2 pull-ups, which improved the I2C waveform (image below).

I accepted the only answer and also some of the comments as all proved useful.


texts: Need help in wiring two Peltier Plates together

texts:
I have two of the BXQINLENX 55x55MM 7V 1.25A TEG1-241-1.4-1.2 Thermoelectric Power Generation Peltier Modules.

I am trying to make something like an Ecofan by sandwiching them between one aluminum plate and a heat sink. I need urgent help as the deadline of my project is approaching fast. Should I connect them in series or parallel? I mean should I lay them side by side and connect each of their red wire to a red wire or connect their red and black together? I eventually want to power a fan and hopefully a USB device with them by using a step up module. This is the one I have.

I am not noticing much of a change in output with two Peltier and similar results are with just one Peltier tile only. I know I am doing something wrong.

Also, can I use this product to join the aluminum parts or will that affect the functionality of the project?

I have two of the following heat sinks, should I use both to create a greater temperature difference?

First heat sink.
This second heat sink that I have is without a fan but I have attached a fan to it.

Sorry if this questions are very basic but I don’t have an engineering background. Any help is highly appreciated.


texts: Designing a CANbus+DC power network of sensors

texts:
I'm designing a network of sensors to be placed in an outdoor environment, see the attached diagram. The network will consist of 30 data acquisition boards (very low power consumption), divided in 10 zones ("Silo bags" in the image). Each zone will be separated by 5m and the Main node (in charge of the communication with a remote server, power distribution and configuration) installed in the middle, so the horizontal wires will have a maximum length of 25m. Each zone have a length of up to 75m (vertical wires) with 3 data acquisition boards in each zone.

I was planning on using UTP CAT5 or CAT6 cables, with 2 conductors for data (CAN bus) and the other 6 for power distribution (3 for GND and 3 for Vcc). The idea is to design the nodes with 2 RJ45 connectors and connect each data acquisition board in a chain. I would also need to design a board with 3 RJ45 connectors as a T-connector for the UTP cables (UTP splitter in the image).

What do you think about this scheme?
I know that CANbus is very immune against noise and the length are not near the limits, but can it bring me trouble having so many connectors?
What about the DC power distribution? considering that the whole system will be powered by a battery placed near the main board (I will make intense use of the low-power modes of the MCUs). What about the power losses?.


texts:
If a single wire is moving at \$v\$, inside a magnetic field \$B\$, with length \$L\$ then induced EMF is:$$\epsilon\ = -vBL$$

That is for a vertical wire that's motion is perpendicular to a magnetic field, the direction of induced \$I\$ is quite simple to find.

What about this diagram:

I know there is induced EMF, however, the wire is tilted. Is $$\epsilon\ = -vBL$$ still valid or must I add a trig-function due to the change in orientation?

There is no current flow because this is an open circuit, however, if connected to a circuit from the upper and lower ends, what would \$\epsilon\$ = ?


texts: What is the purpose of CRC_IDR in STM32 processors?

texts: The STM32's CRC calculation unit has a register named CRC_IDR. This 32 bit register allows the user to store 8bits of data. There seems to be no link between this register and rest of the CRC operation. Does this register have a purpose? Is there some aspect of computing 32 bit CRC that makes this 8bit register useful?


texts:
I'm working on an experiment to find Planck's constant with a phototube. I built the following circuit and pointed an LED light to the phototube in a dark room, but I had a few problems:

When there is no capacitor, the reading of the voltmeter was very unstable (mainly from 1V to 3V). If I'm correct, the charge should accumulate until the blocking voltage for the phototube is reached.

Reducing the capacitance (to 1uF and 0.1uF) again gave unstable values. Also, with small capacitance, the voltmeter reading increased significantly when I lowered the light intensity.

When there is no light incident, the voltage still read around 500mV without the capacitor.

What is the flaw in this circuit, and what are the causes for the above issues? The op amp I used for the voltage follower is LMC6081 and operates with single supply. I'm completely a beginner in electric circuits so I hope if you could explain me from the basics.


texts: non-inverting op-amp with reference voltage on negative feedback?

texts:
Hi,

I am having a lot of trouble understanding this configuration. When i first saw it, it thought that the 2.5V reference voltage would force 1.25V on the negative terminal but after opening it up again i saw that R97 and R98 are not going to ground, therefore that assumption is not true.

Can anybody explain to me how this particular configuration would work?


texts: What were the transfer curves of major recording technology from Wax cylinders to HiFi electronics?

texts:
I am interested in the evolution of the quality / fidelity of audio recording.
Specifically in the actual frequency response curves and dynamics behavior of those technologies, not just rough ideas.
While I can find rough functional discriptions of things like

edison wax cylinders
early phonographs
78 era records

I have not found detailed information about the transfer behavior.
I have seen rough mentionings of typical bandwith of analog open reel magnetic tape recorders of the 1970's, and I guess there was probably far greater variety in quality between differently priced products when the level of technology got to "HiFi" vs. the early days of recording, so that presenting "one typical response curve" may be more difficult (or is there a good average, or worst/best corridor kinda graph?).

What I'd ideally like to see is a list of the major recording technology steps from ~1900 to, I would guess, 1970s, when quality started to get really good for high end magnetic recording devices - accompanied with typical response curves and maybe hints about special quirks / limitations, if applicable.

So that you can (primarily) visually see in what way and by how much things evolved, from tech step to tech step, if that makes sense.

This is really the level that I'm interested in with this subject. I'm interested in the "deltas".
But I can see how maybe some might see this as "too broad" a question.
If that is true, then I guess one could make a question for a "complete" list of all major recording tech evolutionary steps - and from that, branch out with further individual questions, one per recording technology, to ask for the specifics of each?

(I realize that the earliest forms with only mechanical sound reproduction are maybe out of place on EE - but, I figure from the technical knowledge held by the crowd, this is very much the most likely place, no? And it "seemlessly" grows into electrical tech... it seems historically connected)


texts:
By default net names and pin numbers are displayed inside pads in the pcb editor. Is it possible to have pin names visible instead of just their number?

Thanks


texts: Confusing PNP transistor configuration on PCB, trying to understand how it is wired

texts:
I was hoping someone could help me decipher this Q4 PNP transistor. It is labeled Y2 on top of it but it didn't come out in the image. Looking around on google I see that it is a PNP transistor and looks like it is probably very similar to this one here.
All of the components I am worried about are pictured on the top of the PCB.
There are some strange things going on there that I am uncertain about inbetween the transistor's base and emitter, and the R7 10k (103) resistor that I am hoping a more experienced eye will be able to figure out.
Does my interpretation look sane?

Attempt and circuit schematic here:


texts: explain 12 pulse rectifier output and filter circuit?

texts:
Parameter

3 phase 115/200 volts AC Input
200-amp output
Input Frequency is 400
DC output is 28 volts
Output ripple is 1.5-volt maximum

Question : on transformer secondary side it is star and delta connection with rectifiers (check the link: 12 pulse rectifier). In this transformer, secondary first is 12.5 volt and second secondary voltage is 21.6 volts approx. which is line to line is 21.6 and phase to phase is 12.5 in star connection.for all transformers it is like this.

Now my question is I want to know the output voltage of the rectifier circuit. can someone explain to me how to calculate output voltage?

2nd question: the filter circuit which you can see in image is what type of circuit? you can see the value of capacitors like c5 is 4uf, c4 800uf, c6 40uf, c7 0.22uf, L is 8uH, and resistance is 60 ohm. how this capacitor value calculated??

Please explain if you know anything about the circuit. b1 is fan.


texts: How do I connect up a replacement run capacitor

texts:
I have bought a replacement Run Capacitor for a forced action mixer (special cement mixer), as the run cap on the mixer blew. The mixer has a single phase motor, and although we are in the UK, it runs from a 110V power supply (standard on UK construction sites).

Possible reason it blew is that we used a power supply that didn't provide enough continuous power. Manufacturer recommends 5KVA continuous but we used 3KVA. Or we left the mixer on too long. Either way we have purchased a new 10KVA power converter and the electrician connected up to a 32A type C RCBO.

The motor is labelled with run cap and start cap values (130uF and 1200uF respectively) and I have researched a replacement capacitor and purchased this: https://www.mouser.co.uk/ProductDetail/80-C9TS6MD6137AARX. Unfortunately the manufacturer was unable to send a like-for-like replacement as the mixer is an old model.

I researched the subject and bought a polypropylene / film capacitor of 137uF, slightly more than the old one.

However my new replacement capacitor has three terminal blocks on the top, not two, and came with a tag on the connectors. I have looked at the data sheet but still don't know how to hook this up, or what the tag does. Behind the label of the tag appears to be PCB traces. The tab may be there to keep it discharged?

I am aware of the dangers of handling capacitors and how to discharge them.

1/ Have I bought the right capacitor? It is much larger in physical size than the original.

2/ Should this tab be removed? What is it for?

3/ Please see photo, showing three connections on the new cap. Which terminals do I hook up to the brown and blue wires (i.e. + and -) on the capacitor connection box on the back of the motor?


texts:
I got this automatic antenna for a project, but the torque is a little too high. It runs on 12V. I've figured the way it works is, it knows to stop when the load increases to a certain point (i.e. something stops it from moving any more). It uses some digital circuitry to determine this.

Would it be possible to decrease the torque of the motor while retaining the properties of stopping when enough load is supplied? Would reducing the voltage be effective here?


texts: Composite video signal detection problem?

texts:
I have an android headunit and I installed a reversing camera to it.

The problem is that the headunit does not seem to detect the camera signal if the environment is too bright. It just shows black screen until I block the camera lens momentarily with my finger and release.

I think, it did not have this problem when I tried the camera with my monitor (which also has composite input). Also the picture quality was much better. But it is also possible that it was not bright enough inside. I have to re-check that.

I do not have access to oscilloscope but I checked the output voltage of the camera when NOT connected to headunit and it was about 1.5v DC. Another camera was showing about 0.7v DC. Not sure why there is so big difference between cameras. Any ideas?

I do not know how the headunit checks the existance of composite signal  or why the quality is worse when camera is used with the headunit. But I would like to fix this problem. Any pointers would be appreciated.

Perhaps I need to attenuate the signal?

Thanks!


texts: how hard can it be to soldier and assemble Sanguinololu 1.3a without prior experience

texts:
I'm interested in building a 3d printer myself. I need to get Sanguinololu 1.3a board.

I saw two options on ebay, assembled and unassembled.

Cost difference is quite large where assembled (DIY £35, built £58).

I'm wondering exactly what challenges am I facing with this project? I have no prior experience in soldering, but I believe in curiosity and that fact that nothing is impossible.

Would experience be worth it? Will I get some interesting skills that will go into my future electrical engineering career? (joking).

Both kits available on eBay here (check dropdowns).


texts: Is This Dual Inductor Mode or Series Mode?

texts:
I'm speccing out another DRQ series inductor for modifying the DC1787A boost regulator demo board.

I'm unsure whether the placement in the demo board schematic is in "dual inductor mode" or "series mode".

In general, what is the purpose of the "dual inductor mode"? Is it just a convenient package for two separate inductors?

Demo board schematic


texts: Programming languages for electronics engineers

texts:
I am an Electronics and Communications Engineering student, before I got to college, I have been interested in programming and computer applications. I had focused on designing Windows applications and learning its techniques, but now, I feel that this is useless in my field... I don't have to learn everything about computer science and developing software! (Am I right about this?)

I know VB .Net, C# and C++. I have plenty of time in my holiday so I want to delve deeper programmatically in "electronics field". So what would you recommend to learn or to focus on?

I want those languages used in programming Microcontrollers and other integrated circuits. Is C++ enough or I should master C as well? Tell me your thoughts please.


texts: Battery reads 5V but can't power a 5V sensor?

texts:
I have a circuit set up similar to that shown bellow which allows readings to be taken from an infrared sensor (MLX90614) using an Adafruit Feather HUZZAH ESP8266.

This works fine when the battery is connected to the USB port on my computer, but not to a 5V power bank (PURIDEA 10). I get readings of 1037.55 Celsius, which is a common error. I have confirmed that the voltage of the power bank is 5V with a multimeter. The sensor needs a minimum of 4.5V.

This image says there is discharging protection of the power bank. could this cause the voltage to decrease to lower than 4.5V?

I'm really unsure of why the power bank cannot supply the voltage. Thanks


texts:
i want to change the position of the transistor pins (2N3904 & 2N3906, Q3,Q4,Q5 and Q7), on the first image is what i got so far (inside green oval area), the footprints are TO92.

i want to change the position of the transistor pins, something like its shown on the last image, so how i can do that ?

If i change the footprint i think i have to start over (design all the tracks, placing all components, etc, it takes again a lot of time and pacience) so if i can avoid that, that would be great.

i want to change all TO92 footprints to TO92VAR.


texts:
I am trying to understand the sentence "to give the crystal maximum control of the loop gain...". Assuming by maximum control it is saying to maximize the feedback factor, which in series resonance case should be:
$$\beta=\frac{R_{load}}{R_{load} + R_{source} + R_s},R_s=ISR$$

But if we want to maximize beta, we should increase the load resistance. For example, say ISR (Internal Series Resistance) is 10 ohms, if we assume load and series resistance to be 100 ohms each, then beta is 100/(100 + 100 + 10) = 0.476

But if we take load and source resistance to be 10 ohms each, then beta is
10 / (10 + 10 + 10) = 0.333

Clearly increasing the load resistance is going to increase my loop gain, but the statement is claiming the opposite. So what this sentence meant when it said to give the crystal maximum control of the loop gain I have to reduce the values of my source and load resistances.


texts: Why did aliasing occur at a frequency before the Nyquist cutoff?

texts:
I sampled frequencies of 400, 500, and 600 Hz at a sampling frequency of 1 kHz. My oscilloscope showed aliasing at 400 Hz, nothing at 500Hz, and then a lot of aliasing at  I saw some aliasing

aliasing should not occur when the sampling frequency is more than two times the max frequency of the signal. so why was aliasing occurring at 400 Hz?


texts:
Because my system needs higher power for the ultrasonic transducer, I need to drive the transducer with higher voltage.

I came up with following ideas driving transducer with 10V peak to peak voltage.

a) High = 10V, Low = 0 V

b) High = 5V, Low = 0V

Method a) works with negative connection tied to ground, and positive connection oscillating between 0V and 10V.

Method b) works without negative connection tied to ground. Rather, both negative and positive connection is driven with 5V high and 0V low oscillation, but with 180 degree phase shifted resulting in POS-NEG oscillating between (-5V ~ +5V).

Below is graph showing V(pos) - V(neg)

Is there difference between the two methods in terms of driving power and longevity of the transducer? Or Does it depend on transducers?


texts: 5-V CPLD family in-circuit programmability

texts:
I have a need for a relatively small amount of 5V-logic (active at power-up) that would perfectly fit a package like that of the ATF750CL CPLD from Atmel/Microchip, the DigiKey page for these devices lists them as "In-System programmable" yet, try as I might, I don't seem to find any information on designing the JTAG programming interface for them (I looked through all of the documentation I have been able to find).

A missing feature is something that clearly does not make the datasheet. The smaller ATF16V8B would also work, save for that in-circuit programmability issue.
Is this just a mistake on Digikey's part? (I already reported it to them). Am I really stuck with much larger devices like the ATF15xxx or their equivalents from other vendors? (I do need 5V-functionality).


texts: Which connector would I use for a non standard low voltage wall connection? How can I label it?

texts:
(Please see this question for background info)

In my pantry, I'm going to be connecting a door jamb switch across a low voltage application. I'd like to (instead of fishing the bare wire through a hole the wall) use a wall-plate with two connectors. I see that banana plugs can support 30v at 15a (way more than I would need), and come in a keystone jack. I am wondering though if using connectors typically for audio would present a hazard and if there is a better option that would be available in a keystone jack or standard wallplate.


texts: Does an official I2S specification exist?

texts:
So, is there an official, preferably up-to-date, specification of the I2S bus, and if yes, where can one obtain it?

I've spent some time searching through NXP's website and couldn't find anything.

Note: I did check Wikipedia, but the link to the NXP's website there leads to I2C specification, instead of I2S. I did go through the 7-page document from 1996, but I'm hoping for something more in-depth, if available.


texts: About spring loaded solderless connector for JTAG pads

texts: The 14-pin JTAG header on a PCB, JTAG pads without holes, no other holes on PCB around JTAG connection area. Does it exist a special solderless JTAG connector for connecting JTAG cable to such JTAG header, by connecting spring loaded Pogo Pins to the top of the JTAG pads and fixing them in this position for reliable contact? The main problem is to fix Pogo pins vertically on JTAG pads on PCBs.


texts: Microvolt to milivolt/volt amplifier with common components

texts:
Suppose one has access to common components and gear only : basic milivolt multimeter, badly regulated supply, linear regulators, 1% resistors, common BJT/FET, voltage references like LM431 or zener diodes, and not-too-bad op-amps with external null offset trimming like LM725, LM301, or even the old 741.

Is it possible to build a reasonably simple general-purpose pre-amplifier, in order to measure µ-volt — or tens of µ-volt — DC or near-DC signals, with such components ? What precision can be reasonably attained ?

Is a simple non-inverting configuration in two stages (e.g. 50x + 50x) good enough, or does one should use a more (or less) sophisticated design ? Can/should discrete components be used for the input stage ?

What precautions should be taken in practice, in addition to proper shielding ?

Are there references on the subject ?


texts:
The question is as follows:

  An interfering signal from a transmitter is found to have a frequency of 57 MHz (TV Channel 2 is 54 - 60 MHz). This signal could be the:

And the options are as follows:

A) crystal oscillator operating on its fundamental
B) second harmonic of a 10 metre transmission
C) seventh harmonic of an 80 metre transmission
D) third harmonic of a 15 metre transmission

Now in my mind options B and D are the same frequency as the second harmonic of a 10 meter transmission is 30 MHz*2=60 MHz and the third harmonic of a 15 meter transmission should be 20 MHz*3=60 MHz. I don’t see how one answer could be more correct than the other.


texts: Design essentials when working with 12bit ADCs

texts:
I'm currently designing a board that is attaching a 12bit ADC (MCP3208) to a Raspberry Pi (besides a few other low speed I/O related stuff). It will mostly be attached to analog sensors (temp sensors, IR distance sensors and similar things, while not always needing 12bit resolution, there are cases where it would really be nice to have that extra chunk of information).

I don't have much experience with analog circuitry and don't have a good understanding of the underlying math and physics involved.

I'm reading into several design guides regarding ADCs and often read about things like anti aliasing filters, ADC drivers for high impedance signals, analog ground planes, laying out traces in certain patterns to reduce noise, keeping high speed digital electronics separated as much as possible from the ADC to reduce switching noise, precision voltage references and much more stuff that I don't fully understand yet.

So what I started wondering was if it even makes any sense for me to use a 12bit ADC, if I don't have the expertise to implement it correctly because I may loose 2 LSBs anyways because of sub-optimal circuit design and should rather just go with a 10bit ADC. Or is optimal circuit design not as crucial in the 12 bit realm as I come to believe it is.

What are things that should always be implemented to reduce noise (f.e. the obvious bypass cap)? What are the biggest causes of noise in an mixed signal application like mine (having a GHz processor talking to the ADC)?
What are the things that are actually only needed in higher accuracy applications (14-16bit+)?

I would really like to know what are sensible and essential things that I should look out for.


texts: I'm playing around with some simple RF beacons, many of these use a multi stage LC ladder to filter the outgoing signal after passing through a class C amp. Can anyone point me to a good reference/book discussing how these filters are designed? (including different topologies) I know that tables are often used when calculating these filters. A brief explanation of how these tables are generated would help as well.


texts: What is the rule to put grounding in the circuit schematic, and what is that grounding for?

texts:
Already so many discussions about grounding. But the more I read, the more I got confuse as there are many disputes. The above are cases where grounding are quite confusing. Grounding or earthing, I consider are same. There stacked lines, three parallel diagonal lines, and a triangle pointing down I consider are same function even they are referring to specific purpose. In this case the picture 1 also is not valid using them. But for now, we may forget it.

The first schematic is showing a simple circuit with grounding. The second picture also a simple circuit schematic without grounding. As you can see, both are designed by two professors from two high class universities.

The third and the fourth picture are schematic of a boost converter I designed in an online electronic software design here, which the source voltage is 5V DC output of USB or 5V DC Power Bank, and expected the output voltage will be around 12V DC. The third picture shows one warning 1 bad connection, but it works. The fourth circuit shows no warning (except telling that no resistor to the grounding line) but the circuit doesn't work. It only loop between the capacitor and the 1k ohm resistor. If I add resistor between the circuit and the grounding sign, then circuit works exactly as what is in the picture three, without grounding, and also show the same error, 1 bad connection.

Then my question, what is the canonical (valid) rule to put grounding in schematic? And what is that grounding for? As I knew, sometimes grounding place in a schematic is due to the complexity of the schematic which is not easy to connect them to a common line which will finally connect to the neutral (0V) of the source.


texts: Communication between device for 5 meters and low speeds

texts:
I need to make a communication between only two devices with a distance of 5 meters, which are connected by a cable of 4x2.5mm² (see in the image), being 1 wire for GND and wire for 12v, that would pass nominal current lower than 10A, and the other two wires will be for communication.
I thought to use rs485, would it be possible to use 4 way cable without being twisted for a 5 meter distance and slow speed rate (1 byte every 50ms at most)? Would you have any other suggestions?
Thanks in advance.


texts: Input protection with MAX366 exhibits very slow falling edge. Why?

texts:
I'm using the following circuitry to protect my microcontroller input pin from the dangers of the bad and ugly outside world (a trigger signal coming from an unknown source).

The signal comes in from the right, goes through some preliminary filtering/clamping, and then enters the MAX366CSA (a signal-line protector IC, see datasheet). The output pin of the MAX366 goes straight to the microcontroller pin (Atmega2560).

For the measurement I'm using a 10x/500MHz/8pF, properly compensated scope probe. The blue curve is measured at the MAX366 output pin, The yellow curve shows the 4.5V square wave that's being fed into the TRIG IN connector.

As you can see, the rising edge is fine, but the falling edge shows a strange double-decay characteristic. After a fast drop to about 1.6V, a very slow decay with a time constant of around 500µs follows. From the MAX366 datasheet I couldn't find an obvious reason for that behaviour, i.e. their application examples never show any special requirement for the output, like a pull-down to discharge the output or something. The signal at the MAX366 input is fine and has a fall time comparable to the rise time.

Can anyone shed light onto this behaviour? Is there a design flaw on my side, or something obvious I've overlooked in the datasheet?

To improve the falling edge, would you suggest a ~20k pulldown to do the job?


texts: Can varnish affect the performance of the air gap in an SMPS transformer?

texts:
In the past I have built several switched-mode supplies using off-the-shelf transformers just using the datasheet properties without having to worry too much about their construction, however I am working on a flyback design at the moment for which no readily available product will do, so I decided to wind my own.

I have some ungapped ferrite cores which I need to shave down to create the gap I require, I am quite comfortable calculating how big this has to be, however one little detail caught my eye - I am wondering whether the introduction of varnish will affect the behaviour of the air gap (assuming that varnish can get into the gap if I dip the whole thing in it). I have not seen any mentions of this anywhere, I am wondering whether it's because it does not matter or because I'm looking in the wrong places. I am not an expert in magnetics so I don't want to rely on my vague intuition, however I have the following equation for the flux \$\phi\$ in a gapped transformer core:

$$\phi=\frac{ANi}{l_c/\mu_c+l_g/\mu_g}$$

Here \$N\$ is the number of turns, \$i\$ is the current through each turn, \$l_c\$ and \$l_g\$ are the effective path lengths in the core material and gap respectively, \$\mu_c\$ and \$\mu_g\$ are the permeabilities of the core material and gap respectively (the latter being practically \$\mu_0\$ if it's air), and the effective cross sectional area \$A\$ is assumed constant for both the core material and the gap (neglecting fringing). Of course all of this assumes the core is not saturated.

I figured I can rearrange the equation to see the effect of the gap more directly:

$$\phi=\frac{ANi\mu_c/l_c}{1+l_g/l_c\cdot\mu_c/\mu_g}$$

The ratio of the gap length to the effective length in the core \$l_g/l_c\$ is somewhere in the order of \$10^{-2}\$, and (assuming the gap permeability is in the order of \$\mu_0\$) the ratio \$\mu_c/\mu_g\$ will be somewhere in the order of \$10^{3}\$. Hence, the combined term \$l_g/l_c\cdot\mu_c/\mu_g>>1\$, so - just for the purposes of a crude simplification - the equation can be approximated as:

$$\phi\approx\frac{ANi\mu_g}{l_g}$$

This shows that for the given approximate range of gap sizes and magentic properties, the magnetic circuit behaves (almost) as if it consisted only of the air gap, but more relevant to the current topic, that the flux is close to being proportional to \$\mu_g\$. I suppose this makes sense as in this scenario the core acts basically as a magnetic short circuit - but, the question this raises is that if the gap is calculated assuming that it contains air with a permeability very close to \$\mu_0\$, what happens when I dip the transformer in insulating varnish? If the varnish gets into the gap, does it change the effective permeability in the gap? Magnetic permeability does not seem to be a commonly listed property in insulating varnish spec sheets, and I don't know enough about magnetics to comfortably assume that the permeability of varnish would be close to \$\mu_0\$. Is this a valid assumption, or is there anything missing here? If it is valid, is there perhaps anything funny that happens at higher frequencies that would affect these effective material properties?

Many thanks!


texts: Is there an analog circuit or filter that can produce constant phase shift over a specific bandwidth?

texts:
I need to match the phase of two signals coming from a pair of transducers over the 10Hz to 4 KHz range, the difference between the two transducers is really close, however one of the transducer lags 7° in phase over the entire band with respect to the other transducer. I need something like an all-pass filter, but instead of it having linear phase shift which varies linearly over frequency, I need a constant phase shift, in my case I need it to be a constant 7° phase shift over the desired bandwidth, I know of no analog network that can perform this.

Any ideas?


texts: Microamp-milliamp Measuring Circuit: will my circuit work? Feedback/Advice

texts:
I'm developing a device which must be able to measure milliamps and microamps on one of its lines (down to 1 microamp, but also clearly seeing if it's less than 1uA). It's going to be DC of different voltages (0-3.3V), but always fixed when measuring current.
So the total scale is 1uA - 10ma. It doesn't have to be a megaprecision device, there are no fixed specs regarding accuracy (actually, I set them). Besides, I might have a calibration setting in the software, I can build a calibration circuit no problem.
I'm still on the brainstorming stage, some parts of the future device have already their final form, or at least I have a clear idea of how it should work, but most are still not finalized. So everything can be changed. Especially if you propose some good ideas, I'm open to ideas.
I haven't decided what my core MCU is going to be, to be honest, there are options. The project doesn't require much magic, so probably naked Atmega328p programmed in Arduino IDE. No need to make it more complicated than it is. But yeah, there are options, it could also be PIC. And it's not what the question is about.
I decided to use 10 Ohm shunt resistor with two current sense amplifiers attached to it, INA186. The current sense amplifiers have 0.5 NANOamp bias current (DATASHEET), which, I think, is totally tolerable.
So the questions are:
1. Can I get away with the circuit in the picture? How reliable would that circuit be? What problems could I expect with it? What are other options to measure 1uA - 10mA?
2. I feel like staying with jelly bean 10-bit ADC MCUs that I have around me, but if some 12-bit or 14-bit MCU (in my case, PIC) would offer significant advantage in circuit design and/or reliability at little or no extra cost, I would consider that. I have enough free pins on MCU for multiple ADC inputs.
3. Any, as Dave from EEVBlog says, traps for young players?


texts: Is it a disadvantage for a generator to supply both resistive and reactive current to its load?

texts:
Suppose

The power network 1 has a resistive load and therefore the current supplied by the generator 1 to the load is purely resistive.

The power network 2 has a resistive + inductive load and therefore the current supplied by the generator 2 is resistive and reactive.

My question is what does it mean for the generator 2 to supply both resistive and reactive current to its load? Is it a disadvantage for that generator to do so? Are there more losses?


texts:
I need the IR repeater to pass IR (TV and so on) remote signal to remote devices in some box (pass the IR signal from outside the box). So, I bought a cheap IR repeater on single 2TY transistor, 4838 IR receiver and IR LED. It works just fine doing exactly what I want:

I tried to reproduce the schematic in my project, and I've got this (without power led):

And I assembled it on the breadboard and it does not work. When I use simple ordinary visible light D2 LED, I see it blinking when I use any remote on the sensor. But when I replace it with the IR LED, even from working device I bought or 50mA L-53F3C for example, it does not work with TV etc.

And I don't understand the capacitor C5 capacitance, it actually looks like this:

And closer picture:

So I wonder, is it capacitor at all? Tried with different capacitors and with no capacitor at all - no success. But I guess it does not matter. Please help, what's wrong and what could be the reason that it does not work?


texts: How to relate voltage Output to temperature with a Wheastone bridge

texts:
I have a circuit like the one below :

with R1=10kOhms, R2 = R4 = 20kOhms and R3 is my thermistor (=10kOhms at 25°C).

I want to read the voltage V-Out on an arduino so that I can measure a temperature.

My question is, how can I link my changes in voltage to the temperature ?

Everything is a bit blurred in my head with the Steinhart–Hart....


texts: How VGA monitor detects video resolution?

texts: How VGA monitor detects video resolution. I'm asking this because with different VSYNC, HSYNC intervals it's possible to have different dot clock.


texts: Why don't ICs include bypass capacitors?

texts:
I'm a newbie to electronics, so apart from the obvious physical size issues there may be a clear reason as to why this is a dumb question, but if the general rule of thumb is to use a bypass capacitor for all ICs on a board, why not just build capacitors right into the components? Is there a reason this never became a standard feature?

Sure, there's a size issue on smaller ICs (especially SMD chips and the like), but in a lot of applications vertical height doesn't seem to be an issue and it would simplify circuitry and BOMs etc.


texts: Arduino Nano: This schematic would work?

texts:
If I used this 9v battery, and a 6v battery pack(AA battery), would this combination work.
I want to it run disconnected from the PC.

Sorry my bad english.


texts: Where does the output current of an op amp come from?

texts:
I am trying to build a circuit that will amplify a 3.3V signal to 5V, but I also need to have an output current of 100mA. The source of \$V_i\$ (an FPGA) only has an output current of around 15mA. Where does the output current come from in a non-inverting setup; the voltage supply or \$V_i\$?

If the current comes from \$V_i\$ (and therefore wouldn't be able to supply the necessary current to \$V_o\$), then would it just be better to have a setup using transistors to increase the current and voltage?


texts: Noise resilient, hot-pluggable communication bus over long cables?

texts:
I'm working on a setup, where we need communication between a master device and several slave microcontrollers distributed out in different boxes connected by "long" cat5e cables (3-10 meters)
The microcontroller boxes (MC-boxes) should be hot-pluggable, such that the master device can communicate with whatever is connected at any time. The MC-boxes need not to communicate with each other.

We have achieved this in the comfortable and controllable surroundings of our office in an I2C-based setup, utilizing the TI's P82B715 I2C extenders. However, we've observed that this solution is not reliable in noisy environments where the I2C-bus locks up within hours or days requiring a hard reset.

Thus, I have started looking into differential signaling protocols due to their inherent noise resilience. CAN-bus seems especially interesting due to it's error handling capabilities. And, as far as I have read, it should be possible to make devices on a CAN-bus hot-pluggable (several comments in this post also states so). However, in our application, the bus cannot be laid out beforehand, but should be extended as MC-boxes are dynamically added.
The CAN spec states that the bus should be terminated by two 120Ω resistors, which makes the dynamic expansion troublesome. So, how can I achieve something like that, I have tried to depict below?

simulate this circuit – Schematic created using CircuitLab
(PS: The boxes don't have to be daisy-chained like shown above)

Thus, my questions are:

How can I achieve an extendable CAN-bus, that retains the constant impedance on the signal lines as required by the spec, when new 'boxes' are added or removed?
Can I achieve the above with a completely different protocol?

I hope you are able to help!

Edit - Clarifications:
 - The master unit will be connected to the internet, so I have some security concerns with using IP-based protocols such as TCP and UDP.
 - The boxes should be water-proof, so all electronics must be kept inside the boxes.


texts: I am curious as to how the ultrasonic sensor calculates relative velocity and distance to an object. What methods does it use? Triangulation or trilateration? Doppler effect? How can I model this sensor in Simulink? I know I may need a time delay for the time for the machine to process but how is that determined?


texts: What am I misunderstanding in electrical circuits regarding voltage/current/resistance

texts:
I thought I understand electricity but some thing don't add up so I'm hoping someone can tell me what I am doing wrong. So, to me, voltage represents a potential ability/energy of a charge to do some work/to transfer energy. Resistor uses some of that energy to heat itself or do something else (doesn't matter what really), in order to drop the voltage of the charge. By dropping voltage, it also reduces the current (because the charge is now 'less needy' to get to the other terminal). With this understanding of electricity, I tried to understand the following circuit:

simulate this circuit – Schematic created using CircuitLab

The Voltage source is 3V. The current is easily calculated as 1A.

So the story goes: Source is giving 1 amper of current an 'ability' of 3 volts. The first resistor causes a 2V voltage drop. Now that amper has only 1 volt of 'ability' left.  The current reaches the branch. It divides equally, 0.5A goes to each branch. But the resistance of the resistors in parallel branches is 2 ohms, and I only have 1V left per ampere! Not only that, but my current that passes through the resistor is not even 1A anymore, now it's only 0.5A, which means it has only 0.5V of 'ability' left! So what's going on here?

A side question that arises: By Kirchhoffs laws, the sum of voltage drops has to equal the voltage of the source. So in the end, the voltage of a charge is 0 (after it passes thorough the last resistor). Why does it even move then, if it's 'willingness' to get to the other terminal is now 0?


texts:
I connected CS4270 to my ST32F446 nucleo board. Currently only I2C pins are connected, GND, AGND, all 3 power lines and address select pins.
AD0,AD1 and AD2 are connected to GND. (the thing I don't understand is that datasheet says that 5 from 7 bits are foxed, so 3 address select pins don't make much sense to me.)
Taking that to consideration I expect the device to be available under address 0x24, but I get NACT.
I also tried I2C scanner without any success neither. I can't get any any communication to work with this IC.


texts: Arduino w/ PWM expander and DC motor issue

texts:
I am new to the forum. so.. Hi everyone
I am trying to control several DC 3-5v motor/pump with Arduino, using PCA9685 PWM expander.
I have connected one such motor, with a rectifying diode (IN4007), to 5V using a BC547 transistor, 2.2K resistor, the PCA9685 module, Arduino Due and 3.3V and 5V sources (with common ground). as in the diagram below.
The program on it runs a sweep on 0-100% and back on port 0.
Now..
IF I do NOT connect the motor, but instead put some random resistor load, everything works fine. I can measure across the load resistor a voltage going up from 0 to 5 and back down. All works 100% fine.
HOWEVER..
IF instead, I connected the motor where it should be, the program goes crazy as soon as the load across the motor gets to about 2-3 volts (or about 1.5V on the port 0 PWM).
The PWM stops updating and the serial console debugging clearly shows that something drags down the Arduino (the console stats updating slowly instead of the regular speed), due to I2C communication issues apparently (which hints that the PWM expander module went crazy). The Arduino can't seem to communicate with it anymore.
Disconnecting the motor at this stage doesn't help. Even then, the PWM doesn't update. The voltage on the 0 port remains stuck at the same level.. same for the motor. Things just get stuck.
Resetting the Arduino doesn't help.
If I disconnect the PWM module, the console logging goes back to regular speed (again, hinting that the PWM module went "crazy" and it is what is causing the console log drag).
Also, plugging the PWM module back in, doesn't solve the issue right away all the time, even at the beginning. It sometimes needs to "rest" for a bit. Then, once plugged in again it resumes working again like before.. meaning, only for the first second or so, until it goes crazy again.
I have no idea what is going on.
At first, I thought it has to do with a voltage created by the engine.. so I've added the rectifying diode. But that didn't help. Same issue.
I've also added a diode on the base, thinking maybe for some reason there is a current trying to flow back into the PWM module through the (orange) PWM port. But that also didn't help.
Why would the PWM module go crazy like that?
What causes it?
How do I fix it?


texts: What are the minimum and maximum number of cycles consumed when executing an interrupt on an STM32F0 MCU?

texts:
Assuming I set an external GPIO interrupt to highest priority, how many cycles does an STM32F0 MCU take to:

start executing the interrupt handler code
return from the interrupt

I expect that the answers will be ranges, but I might be wrong.

Will these two figures, plus the time my interrupt handler code takes to execute, equal the number of cycles "stolen" from the main loop?


texts: How can I make my RFID reader restrict itself to the tag in the closest proximity and read only this tag?

texts: I'm looking for a way to detect the user closest to a certain object that has the RFID reader attached to it. Therefore I need my RFID reader to restrict itself to the user closest to it and not read any other tag. I'm open to using other technologies too.


texts: Multiple wireless chargers in parallel or in series and what voltage/current

texts:
I am using an Adafruit Inductive Charging Set to charge a device with a 400mAh LiPo battery I have hooked up to a TP4056 LiPo charger.

I can charge one device at a time from a variable power supply unit set to 9V, however I am unsure how to hook up multiple inductive chargers to it (I need 10). Should I hook these up in parallel or in series, and at what power outputs?

Also if I have all the circuits hooked up but only have one device charging out of the 10, would this effect it?


texts:
Has anyone tried to use a programmable cutting machine like a Silhouette CAMEO to cut a stencil for a circuit and then used conductive paint to transfer it to a board?
Could that work? What kind of paint would that require? How expensive would it be?
I there maybe paint that contains solder particles or something, so that I could properly solder other things to it?

I'm not interested in etching PCBs or any alternatives, I just want to know if that could work and what it's limitations would be.


texts:
I like to design a single master, several slave (up to 100) application and looking for a reliable (up to 30meter) multi drop bus. One or two lane is preferred, I will use daisy chain topology therefore USB is not suitable and also it is an overkill.

My data rate is low and intermittent, once every 3-5 sec and probably <10KB. The slaves are not synchronized.

I thought about using RS232 and implement an algo where slave transmits if there is no traffic. (Similar to Ethernet). I prefer something a bit more robust.

Also, current thinking is to wake all slaves when master transmit where all slaves receive the message, they all parse it but the one we targeted takes action. Not very efficient but it would work.


texts: lm13700 as Diode laser voltage to current converter

texts: I generated two Signals,   one using dac7611 (ramped signal with fre = 0.04hz ) and the other one, using AD9833 DDS (sin wave with fre = 32 KHz) then  generated signals  added using ad620an. Is this possible to convert Voltage to current using Lm13700 to power up two Diode laser without losing the precision of 0.01 Hz of frequency of DDS ? if Not what is the better option?


texts:
I am connecting a 10k potentiometer to an ADC chip (LTC1273BCN) that has a 12-bit parallel output, like in the diagram at the end of the post. The 12-bits will be connected to an FPGA input bus after I can get it to work correctly. The ADC chip circuit is powered off a stable 5V from a lab benchtop power supply.
I have tied the CS and RD inputs low as I thought this will continuously run the conversion but maybe this is my problem, I am unsure.
When I measure the voltage of the 12 output pins, only pin 14 (D2) seems to be high, the rest are 0V. The Ain voltage is perfect between 0 and 4.99V from the potentiometer, and I have tied the HBEN input to 5V as I want to use all 12-bits in one conversion.
Any advice as to how to use this chip correctly? Will I have to pulse the CS and RD inputs low to get the chip to behave as I would like? I don't really want to use signals from the FPGA to control the analog to digital conversion.
EDIT
Below is my reasoning behind the pin connections:
Pin 1 : 0V to 5V from potentiometer, to be converted to 0 to 4095 by ADC chip.
Pin 2 : I haven't used this pin but have attached capacitors to pin 3 according to datasheet.
Pin 3 : Tied to analog ground which is the same ground as chip supply.
Pins 4 to 11 : D11 to D4 output bits are left unconnected.
Pin 12 : Tied to ground of power supply.
Pins 13 to 16 : D3 to D0 output bits are left unconnected.
Pins 17 and 18 : Left unconnected as in datasheet.
Pin 19 : Tied to 5V to use the full 12 bits in one conversion instead of splitting into 2 conversions in one byte.
Pin 20 : Tied to ground for continuous conversion ( if this is possible).
Pin 21 : Tied to ground to allow for continuous conversion ( if this is possible).
Pin 22 : Left unconnected as I am not using it.
Pin 23 : NC
Pin 24 : +5V from power supply to power up ADC chip.
Thanks everyone.


texts:
Do ESD discharges pass through capacitors?

My circuit is shown below. Basically i'm concerned that if there is a DC component to ESD that ESD Sensitive IC 2 may not be protected by the ESD diode. The diode can't be placed earlier because there is DC power on the antenna line which would short through the ESD diode.

simulate this circuit – Schematic created using CircuitLab


texts: Can I use a soft switching IGBT (FGA 25n120: given in specification) for my variable frequency drive power circuit (frequency around 10-20kHz)?

texts: I am building a variable frequency drive from scratch. The design worked well with switching MOSFET. Now I need to increase the power output and DC bus voltage so that I would like to implement FGA25N120 into my circuit. But the datasheet says it is a soft switching IGBT designed for resonant circuits. Should I use it with my hard switching circuit? Which are the best switching IGBT models I can choose  for 1KW motor driver?


texts: Help me choose the communication protocols that I need

texts:
I am developing an industrial sensor using a sensor IC and an ARM MCU which communicate via I2C. The data size is 3 bytes. Because the environment in which the sensor is located is harsh ( high temperature and high humidity ) the sensor has a watertight enclosure, and I can't afford to have more than 1 cable coming out of it.

I want to offer the possibility of connecting the sensor to a PLC, PC and to a custom LCD display at the same time. It doesn't need to be real time.
I am considering building a communication module that has an integrated LCD screen and who can pass the data to a PLC and a PC. For the PC communication, I will use USB, but for the PLC, I'm not very sure. What is a common serial protocol that most PLCs have which doesn't an expansion module for the PLC? Thank you.


texts: what sensors to use in touch sensitive furniture

texts: I'm trying to make a wooden table with a touch-sensitive top, made up of a mosaic of small wooden pieces resembling scrabble playing pieces separated by thin glass separations. each wooden piece would be connected to its own sensor(s) and also to LED lights that would glow through the glass around the wooden piece touched. What would be the appropriate sensor to use? I want the table to be as rigid as possible, and i don't want that clicking feel when you press any wooden block...


texts: I2C level shifting to multiple voltages inside a BMS

texts:
We're building a BMS that has a micro on each cell in the pack.
I know this isn't standard and the issues that come with it, however the pack isn't a standard layout, and the benefits out weigh the issues (if I can figure out solutions ;) )

The main issue I'm stuck on is connecting micros at different voltage levels to the same I2C bus (actually SMBus) at a reasonable cost (aiming 50c, any lower is a bonus)

Ideas looked at:

Opto/Capacitive isolation

Opto/capacitive isolation for each channel, while this is by far simplest I believe this is too expensive $2 per channel. (Happy to be corrected)

(very useful resource for those interested  AN10364: Opto-electrical isolation of the I²C bus www.nxp.com/documents/application_note/AN10364.pdf)

Level Shifters

simulate this circuit – Schematic created using CircuitLab

The obvious first place to look is at gnd:3.3V -> gnd:5V level shifters that are used in i2c networks, there are two ways I can see these be used, but with their own issues.

Daisy Chain

simulate this circuit

If you level shift between each cell, you get low voltage shifts (making it lower cost) and infinitely scale able (in theory) in terms of cells in series.

However, you don't have common grounds, So while it works in one direction (3.3v signal pulls the 5v signal low) it doesn't in the other (5v can't pull the 3.3v signal low)

Branches

simulate this circuit

With this design, it effectively a direct replacement for the opto/cap isolation. It goes from what ever the voltage is at the cell down to 3.3V on the i2c bus.
This should fit closer to the traditional level shifter, but when the signal drops to digital O on the high side, it should only drop to the cell voltage,

As opposed to all the way to ground.

Intrigued to know if

a) I've totally missed an easier way of doing this,

b) If anyone has any helpful pointers to anyone who's done this before,

c) I'm a bubbling buffoon and it'll never work.


texts: How to make a variable frequency circuit

texts: Anybody can explain how do I make my circuit for variable frequency output with variable resistor not trimmer/variable capacitor my circuit shown in fig


texts: Using a Normally Closed PCB mounted Solid State Relay

texts:
Summary:
Continuing my search for a solution to my problem, I have landed on normally closed solid state relays (NC 1 FORM B SSR). Could you tell me if I'm doing this right?

What I need:
What I need, is a switch, that is closed when the power to my MCU is off, and that is open when the power to my MCU is on. I have a 12V PWM coming in and when power is on, I substitute it with my own 12V PWM. (Basically a normally closed switch, which opens completely when power is on.)

In the schematic below, I have tried to illustrate my situation.

Why I need it:
Since PNP Transistors (due to high Emitter-Base Voltage), P-MOSFETs (due to at times negative Source-Drain Voltage) and JFETs (due to maximally 12V available as control signal) don't work, I have landed on SSRs.

I have no experience with PCB mounted SSRs, so I need your help.
I found this relay which seems to suit my application: G3VM-353G
Do you think this will work as intended?

Schematic 1: My "challenge"/problem

simulate this circuit – Schematic created using CircuitLab

Schematic 2: Will this work?

simulate this circuit

Thank you!

Edit specifiying the signal:
As per request: The PWM signal to be passed through or interrupted is a 1kHZ, normally 0-12V, 0-100% duty cycle signal. To pass through states, the amplitude is sometimes modulated, changing it to 0-9V, 0-6V or 0-3V. Current is minimal (except for measuring, no current is drawn from the signal).
Voltage drop tolerance is ±3%, duty cycle tolerance is ±0.1%.


texts: What is the typical load resistance for a thermostatic circuit?

texts:
I’m looking at retro-fitting a dehumidifier with a condensate removal pump to eliminate the need to empty the bin (daily during the summer); specifically this pump.  This pump has a safety switch designed to be connected to a class II low voltage circuit in series with a thermostat circuit.  However, the dehumidifier doesn’t have a low voltage thermostat and the humidistat runs on line voltage:

Based on this, I’m thinking of replacing the bucket shut-off switch with a relay control that is connected to the safety switch and a step-down transformer.  However, I’m concerned that without the expected thermostat (and the resistance that would be associated with it) the current in the circuit would be higher than the relay could tolerate.  What size resistor should I be using to replace the non-existant thermostat?


texts:
I have been experimenting on transistors recently with this simulation , it works as expected and all make sense except the V1 value.

In the schematics below I used a voltage devider between R1 and R2 and therefore I was expecting V1 to be half of the source voltage minus VBE, which should be 9/2 - 0.7 = 3.8V

However when the potentiometer is at 0 V1 is 2.77V

But when it's at 170Kohm V1 changes to 4.22V

Why does V1 change like that instead of being constant 3.8V?


texts: An effective way to knock down GSM on demand

texts:
I am building a test rig for a device that has a GSM module to communicate and I want to test how the FW behaves when there is a comms loss and recovery. The GSM module of the device has an antenna connector where I can potentially tap into.
Just disconnecting the antenna doesn't work, because PCB traces some times are enough!
My thought was to have like a T connector and inject noise when I want to simulate loss of signal and then stop injecting to simulate a recovery.
What would be the easiest and most effective way to do this?
Note some devices use GPRS, others 2G, 3G or even 4G.
Edit just a note here, covering the device in some kind of Faraday cage is not possible. I am looking for an automated way of doing this.


texts: What kind of circuit do I need with a 6N138 optocoupler to get proportional output?

texts: I have 0-5V input that I need to isolate and still output ~ 0-5V to an isolated circuit. I purchased some 6N138 optocouplers to do this but I'm not getting a voltage output with a 5V input. There are some transistors built into the optocoupler that are complicating things. How do I create a circuit with the transistors to get an output of approximately the same magnitude to the input?


texts:
What does "FB" mean? I can only guess it's some kind of protective device because of F, like with FU for fuse.

Is there any comprehensive online guide for such kind of symbols?


texts: Is the current rating of the buck converter must match the dc load current?

texts: I am designing solar system for 1.2kw, 12vdc load and I want to insert a 48vdc to 12vdc converter between charge controller and load.what are the main things that I have to look at when I select this converter beside looking their voltage rating?


texts: Programmable system on chip (SOC) pluggable on a host via PCIe

texts:
Does anyone know a COM which is put on a PCIe card, which has some flash memory, some RAM, JTAG support (or some kind of debugging support), some input ports like USB, perhaps support some output like via VGA or LVDS, just like this board: http://www.knjn.com/FPGA-PCIe.html but not for FPGA development, but for microprocessors, preferably x86.

Something similar has been done in the past, but the link is dead, and it should have enough documentation and be hacker-friendly (and cheap, not more than 100-150 USD).

I will be writing the driver for the host system (linux), for inter-system communication, but the PCIe board itself should be pretty stand-alone (beside the operating system for the "guest OS" on the PCIe card which I will also have to write).

Addendum

(upon more research)

Sun used to have SunPCI, but those cards are hard to get. Besides, I want something more modern.

Thanks


texts:
I saw a post on YouTube where somebody was able to make ice with a 90 watt solar panel, two 12 volt batteries, an ice maker (800 watt spikes) and 1000 watt DC-AC inverter.

https://www.youtube.com/watch?v=T9CcPZMK-bc

In another post, somebody else uses a 12 volt fan and cooler of ice to make a 12 volt air conditioner that cools a small space nicely for about 4 hours until the ice melts.

https://www.youtube.com/watch?v=-NcUDMpk6ms

Two separate systems, both DIY experiments riddled with apparent inefficiencies I'm sure.

Made me wonder if it might be possible under the footprint of a 90 watt solar panel to silently cool a 10x10 room for 8 hours overnight?   Is Ice the most efficient to store cold air? Possible to create cold air more efficiently from stored power?  If ice is still the best way, the system would need to reuse the same water and I wonder if a 90 watt solar panel could both charge batteries for the fan and somehow freeze a single block of ice for the system.


texts: What is a good lab surface to hot-air rework on?

texts:
I have been scouring the internet for information regarding what would be a good surface to do hot air rework on.

Right now, my lab, if you want to call it that, is a wooden bench with cardboard surface...not the greatest.  I recently got a hot air rework station to do some awesome SMD work but considering it gets so hot, I'm worried that my workstation will spontaneously combust.  At previous employments and labs, there were ESD mats that we'd used.  Considering those are pretty expensive, what would be a suitable affordable solution?


texts: capture cis transient convergence problem

texts:
I have this schematics and I want op amp to saturate but I am not able to finish simulation due to convergence error. I have tried add 1 ohm resistance,1p capacitance to circuit, reduce ABSTOL to 10uA, reduce RELTOL to 0.1 ohm, reduce minimal step to 100ps and change iteration metod in setting but without success. Any suggestions?
Reducing minimum delta to make the circuit converge.

ERROR(ORPSIM-15138): Convergence problem in Transient Analysis at Time =  2.710E-06.
         Time step =  186.3E-21, minimum allowable step size =  1.000E-18

  These voltages failed to converge:

    V(X_U1.44)                =    540.58V  \   -236.81V

  These supply currents failed to converge:

    I(E_MULT1)                =    13.99uA  \    13.37uA
    I(X_U1.EOS)               =   253.09nA  \   250.76nA
    I(X_U1.EO4)               =  -153.14pA  \  -278.53pA

  These devices failed to converge:
    Q_Q1      X_U1.Q4

ERROR(ORPSIM-15659): Discontinuing simulation due to convergence problem


texts: Low voltage form a NAND logic gate then the state is high

texts:
I've been trying to learn how to use logic gates. I wanted to use logic gate to bump digital signal from 3.3V MCU to a 5V. I took a T74LS38D1 and mocked the solution using two switches connected to 3.3v and GND instead an actual MCU. I also connected a multimeter to check the voltage between GND and the output of the gate.

I was surprised to see that the voltage for both input set to low was something around 1.2 to 1.4V. It was supposed to be a high state so I expected close to 5V.

When I set both inputs to GND the voltage on gate output was around 0.15V which is what I expected.

Why is the voltage of high gate output so low? Am I missing something obvious?

simulate this circuit – Schematic created using CircuitLab

I also used a different NAND gate chip, SN74LS38N and same thing happened. So this hints that my understanding is wrong.
I have grounded any unused input pins on NAND logic gate chip.


texts: Eagle tstop and tcream layer values unable to change

texts: In my eagle design )I added a package from eagle lib. to my own library. I need to change the default values of tstop and tcream for this package. I was able to change the left-side tstop and tcream values and adjust accordingly. But as I tried to apply the same on the other 3 sides i am not able to do. I tried turning off the default tstop and tcream layer even that is not working. It is resetting again to 'on'.


texts:
I have found a circuit that does AM modulation with a JFET transistor(2N5485.) I modified it slightly and ended up with the circuit below.  A sample output is also given.
I used Microcap 12 for the simulation.
For my message signal I used an AC amplitude of 0.5V and I also gave it a DC bias of -1.7 V to the gate of the JFET.  The frequency of the AC is 500Hz.  For the carrier I used a 40kHz AC signal of 0.5V amplitude.
I noticed that if I play a little with the DC bias (close to the threshold voltage of -1.71V) it changes the output  noticeably and hence the amplitude modulation.
I also noticed that the message signal in red is not exactly the envelope of the blue (modulated output.)
Is there anything I can change to have better modulation?
I am new in this field of electronics so I am sorry for anything I might have misunderstood about the whole process.
AM output(blue) and message signal(red)


texts: How to correctly use a address in assembler?

texts:
Im trying to use several registers on the M4/tm4c1294 in a way to avoid write every time the same register number.

The question is how to make the number of the register and if the reference is correct.

Let say Im working with the RCGCGPIO, so from the data sheet, the RCGCGPIO has the base address

0x400F.E000

and the offset

0x608

so the address to work for would be

0x400FE608

The general view of the assembler code is

RCGCGPIO_ADDRES EQU 0x400FE608 /*Making the mask at start
AREA....CODE
MORE CODE
LDR  R1,=RCGCGPIO_ADDRES
ORR  R0.....

The reference and the adress is valid?


texts:
I have a differential manchester data stream (channel1) in the form of packets. I'm showing a capture of one packet. All packets begin with a stream of 1's. This is key, as per Maxim application note 3671: "

  This circuit functions well when the received data stream has enough
  extra bits at the beginning of a packet or frame (in the form of a
  preamble or synch pattern) that it can afford to lose while the R1-C4
  circuit charges up to the correct slicing threshold.

It is then suggested a fundamental data slicer can decode manchester encoded signals.

I need to convert this to to something an arduino, etc.  can work with.

So I built the data slicer and tried various R and C value. I get a waveform as shown in channel 0. I need to obviously change my circuit, but will the fundamental circuit even get the job done?

Other Information:

This is a follow up to this question. This user stated in a comment:

  It is trivial to make a Manchester decoder from simple logic and 3/4 1shot.

I think he is referring to a "one-shot multivibrator op-amp circuit", with specific voltage cut-offs?

UPDATE
This FCC filing shows the schematic for reading and writing the DeLaval Alcom bus. I have reproduced my version below minus the protection portion.


texts: Multiple serial ports to an old 8051 I have numerous of

texts:
Ok, I own quite a few of the AT89S52 IC and the AT89C4051. Both have only UART, but my project requires two because the same device will control a radio module that requires a UART for interfacing and it will also communicate with the PC through serial port. As a last resort, I would use the parallel port to communicate with PC but the parallel port cable will be too bulky and my project needs to be several meters away from the PC.

I have researched and found IC's with dual UARTs but that may be a waste of time since I have to order them from ebay (china) and wait 6+ weeks for them on top of learning new 8051 commands to interface with them. I'd rather get things done easier and quicker than 5 weeks.

The only other idea I thought of is to use some sort of multiplexer/demultiplexer IC connected to the UART port so it doubles into 2 ports (I hope).

I plan to make all UART action will be half-duplex and time-sliced. By that I mean in one time frame, the micro sends data through UART to radio module, then in another time frame, the micro receives data from radio module, then in another time frame, the micro sends data to the PC then in the final time frame, the micro receives data from the PC.

Is this as simple as the following?:

connecting the micro transmit (data out) pin to an input of a multiplexer and each output to each device's UART transmit pin (where data is happily accepted)
connecting the micro receive (data in) pin to the output of a demultiplexer and each input to each device's UART receive pin and
connecting the address line of the demultiplexer/multiplexer to a gpio pin to allow me to select a UART.

or do I need to add resistors as well? and if I use cmos parts like 4051, would that affect performance if I decided to make all UART devices run at 115200bps?


texts: 300 amp 12vdc power supply on a standard(American) wall outlet

texts:
I am building a project that will draw around 300 amps at 12vdc, for about 40-60 minutes then it will rest for a few minutes.  For this projects application it will be very impractical to build a dedicated circuit.  How can I power this on a standard(American) wall outlet?

I was thinking of using multiple optima yellow top deep cycle batteries hooked up in parallel and having a heavy duty battery charger that will constantly be charging the batteries at around 100-200 amps that way during the rest period the batteries will completely recoup and during the use the constant charging will allow the batteries to last for at least an hour.  Will this work?

If I have to build a dedicated circuit, do I have to step up the voltage to 240Vac?  If it is necessary to use a dedicated circuit, can you guys please recommend a 120V (or 240V) to 12v high current converter.


texts: Wiring Nest Thermostat E Heatlink in place of original Thermostat

texts:
I have a Nest Thermostat E, which requires me to replace my thermostat with the Nest Heatlink.

Google provides step by step instructions on how to do this using a series of questions and answers. However, I'm struggling with a lack of knowledge.

  Does your diagram have any of these labels for the common wire?

  COM
  Common
  HCOM
  No exact match

-> No exact match

  Does your diagram have any of these labels for the normally open wire?

  NO
  NA
  CALL
  H ON
  Demand
  Call of heat
  N/O
  On
  No exact match

-> No exact match

  The common wire is always connected to one end of your switch...

I identified the brown wire (1) as the Common wire.

  When your heating is off, the "normally open" wire is the one that
  isn't connected to your switch

By my admittedly very limited understanding of this description, this could either be the Grey wire (2) or the Black wire (3)?

The instructions then go on to say wire the Common, and Normally open wires into the Heatlink E, and disconnect all of the others and cap them off.

So at this point i'm left with some questions I'm hoping someone here could please answer for me:

Exactly which wire I should use as the 'normally open' wire?
I recognise the Yellow/Green as earth/ground. Should this really be
capped off and not connected?
I like to learn rather than just do, so an explanation on why it may
be laid out like it is (Wire's 2 and 3 leading to the same switch).

Here are pictures of the current wiring and the diagram.

Thanks


texts: Input voltage for feedback pin on LM2596 Voltage regulator

texts:
I am using LM2596 for a dc supply where I could alter the output voltage. Datasheet here.

I have setup according to page 9 "Adjustable Output Voltage Versions". Everything worked fine. The output voltage alters as I changes the value of R2 (potentiometer used for R2, R1 remains 1K).

Now, I was thinking that the feedback pin is just taking a the voltage potential between R1 and R2. Thus instead of using R1 and R2, I supply a voltage (0-2V) from the bench power supply directly to the feedback pin. But as I vary the bench power supply, the output voltage does not vary. The power supply and the chip is common grounded.

Why is that? When using R1 and R2, the voltage on the feedback pin is around 1.3V. Removing R1 and R2, and supply feedback pin with a 1.3V does not yield the same output voltage. Or must there be a certain current flow?

The final destination would be to digitally control the chip (e.g. using a digital potentiometer or DAC).


texts:
I am working with a digital sensor (magnetometer) that can operate at multiple frequencies.  The application note (http://www.st.com/resource/en/application_note/dm00136626.pdf) gives RMS noise values at each of these frequencies:

I would like to get a sense of the actual power spectral density curve (i.e. mGauss/sqrt(Hz)) so I can better understand what my SNR will be if I apply a bandpass filter on a narrow range of frequenies.  Is it valid to 'back-calculate' a rough curve from these values by determining the average noise spectral density of each frequency region as follows?

$$(3.5-0)/sqrt(77.5-0) \approx .398$$

$$(4.0-3.5)/sqrt(150-77.5) \approx .059$$

$$(4.6-4.0)/sqrt(280-150) \approx .053$$

$$(5.3-4.6)/sqrt(500-280) \approx .047$$

(Note: I assume that the internal circuitry of the sensor is applying the appropriate low-pass filter in accordance with the Nyquist theorem; e.g. 1000Hz signal has 500Hz LPF applied.)

Edit: Just to clarify from Dave's answer below, I believe the RMS can be calculated as:

$$noise^2_{RMS} = \int_{f_{min}}^{f_{max}} PSD(f)df$$

Where \$PSD(f)\$ (given in units \$mGauss^2/Hz\$) is the square of the plot above.  However, it is possible that the underlying PSD changes for each sampling mode, while the plot assumes there is a fixed underlying PSD for all sampling modes.


texts: USB header pinout, connecting a poorly marked cable

texts:
I have a "USB Cable" (http://www.evga.com/support/manuals/files/120-PG-1500.pdf pg 5 is all the info I can find on it) that connects my PSU to my computer for communication. My problem is the USB header on my MOBO and the "USB cable" do not matchup pinouts in a logical manner.

The standardized USB header pinout is such (?)

I can see around the heat shrink on the USB cable and can see a Red, White, Green, Black cables. There is no blocked pin that might represent the "key" position, and those are the only four wires.

I take it I need to align it so the Red wire sits on one of the +5v pins, but which one?


texts: Difference between a frequency synthesizer and a frequency mixer

texts:
I have tried looking a couple different places but cannot find a concise explanation on the difference between a frequency synthesizer and a frequency mixer. My goal is to take a signal at 915 MHz and upconvert it to a 2.4 GHz signal. I am not trying to amplify so that I can stay down on noise. Would somebody be so kind as to help me out?
Thanks in advance.


texts: Is there an accepted measure of noise in a data set? I am taking a series of reading from an ADC, which follow a trend (they are not random data points). However, they generally lie above and below the averaged value (running average, FIR low pass effectively). How do I get a measure of how much noise there is over a given interval?


texts:
I am planning to buy a photomultiplier tube for my lab experiment but I am not sure how to use it exactly. For eg. I was looking at the hamamatsu HC-120-05. http://mi-lasers.com/wp-content/uploads/HAMAMATSU-HC120_series.pdf

It is written in the datasheet that the operating voltage is -1100V. Is that the supply voltage?
How do you see the output from a coaxial cable.using oscilloscope?
Do I have to use another amplification circuit to see very low light output?

Another one i checked was senstech P30A-03 http://www.sens-tech.com/assets/media/files/Data%20Sheets/P30A_iss2.pdf
This one says power input is +/-5V and HV control sensitivity is -1000V. WHat's that?

Anyone who has ever use any photomultiplier please help. Its very expensive, I don't want to buy it without understanding how to use it.

Thanks so much.


texts:
In the following circuit the explanation of D1 says:

“D1 connected across the input to output terminals is for protection and prevents the regulator from being reverse biased when the input supply voltage is switched OFF while the output supply remains ON or active for a short period of time due to a large inductive load such as a solenoid or motor.”

Questions that come up:

Is the “feedback” diode acting as a “fly back” diode if there’s an inductive load on the output? If so does this voltage just dissipate across the diode? Wouldn’t it also go back into the input supply and cause damage?
Is D2 acting as protection to the rest of the circuit in the case of reverse voltage coming in at the output? If so it’s relying on whatever is connected at the output to have a built in fuse of some sort to cut constant power?


texts:
I am a programmer but new to electronics and trying to combine voltage two DC voltages. This works when I use two separate batteries i.e. I can use two 9v batteries and connect them in series to get total of 18V power supply.

However when I try to do the same using the two 5V output from the power supply as in Solderless Breadboard with Power and I/O Breakout Board. It just stops working. What I did is connect positive from the 1st 5V output to negative of 2nd 5V output, and as soon as I do that the power supply stops working (may be it shorts). Can anyone tell what I am doing wrong? and if it is not possible then why?


texts: What is the current through a parallel LC tank circuit in its resonant frequency?

texts:
I read that in a quartz crystal:

For a series-resonant crystal, the crystal current is the RMS voltage across the crystal divided by the crystal internal series resistance. Meanwhile, for a parallel-resonant oscillator, the crystal current equals the RMS voltage across the load capacitor divided by the load capacitor's reactance at the oscillator frequency.

The model given on the site is:

The bold context confuses me. It's like saying that the impedance of the whole LC tank circuit at parallel resonance is equal to the reactance of the load capacitance Why is that?
What I only know is that impedance is max at parallel resonance but I don't know why the max impedance in this configuration is equal to the load cap
source:https://www.maximintegrated.com/en/design/technical-documents/tutorials/7/726.html