texts: ATmega328p TQFP and unconnected pins, what is it the best practice?

texts:
I'm designing a board based on ATmega328p in TQFP package.
I'm not using all the ports, so, for example, ports from PC0->PC5, ADC6 and ADC7 won't be connected to anything.

Can I left them unconnected or is it better to connect them to ground (or VCC)?
I do not have to read from these ports, so even if there will be some noise, it will be not a problem for me.

What is the best practice in this case?

Thank you!


texts: Does replacing an audio device's AC adapter with a 9v battery require filtering?

texts: I have two devices that use 'wall wart' adapters - an audio mixer and an audio headphone amplifier. Each is 120vac input and 9vdc output. I'm a technician so understand how to check for proper voltage, current and polarity for each device. But is there a way that I can determine if my devices require some degree of filtering or steady delivery that a 9v or 12v battery as a substitute wouldn't be able to provide? For ex. - for a laptop computer to perform well, it may need a very stable power supply free of spikes or other small aberrations.


texts:
I would like to know how to shift a signal in Simulink. The case is I am using PWM generator(DC-DC) and the input D is from a lookup table,a sine wave. From the PWM generator block i am taking the pulses i want(a sine PWM). However, because of having two mosfets i need second pulses signal which should be shifted like when the first pulse in the first signal finish, the first pulse of the second signal will start. I think the real issue here is this: the Duty cycle is changing for each pulse so each pulse should be shifted with different time.

The shifting i want is described in the image. The the magnitudes of D's are forming a sine wave. For example if i have 5 pulses(so D1,D2,D3,D4,D5), the variation of D's will be like D1=0.1, D2=0.2, D3=0.3, D4=0.2 and D5=0.1 ( the numbers are just for example) So the i need to have shift every pulses according to their own width(Duty cycle)


texts: How this remote control generates radio signal?

texts:
I have this RF remote control that I'm trying to understand (here is spec: http://www.telran.co.il/images/980305%20QK-M04%20TECH%20SPECS.pdf ).

I recognize crystal oscillator that is responsible for getting required frequency of the signal, I understand how this hcs301 chip provides KeeLoq encryption, I recognize a battery as a power source ;) . But what here is actually generating the radio signal? I cannot find anything resembling an antenna here, and this remote has quite a long range (about 100m).

Could someone find an antenna here and explain what component(s) is responsible for generating an actual radio signal in this device?


texts: What is the current classification of linear motors used for positioning and scanning applications?

texts:
I am doing some research on positioning and scanning systems but I am encountering some problems trying to categorize linear motors. I can't understand what type of linear motors based on induction are available. I tried to categorize into the following table where each cell corresponds to the possibility to choose between one of the element.
TYPE            SUB-TYPE       BEARINGS
induction       stepper motor  air bearings
                servo motor    guide bearings

piezoelectric   stepper motor
                squiggle motor

For instance, I can have an induction stepper motor with air bearing, or an induction servo motor with air bearings and so on with the other combinations.
I don't understand if the induction linear motor can be subdivided in stepper and servo motor as I did. And this hold true also for thrust-tube motors, that however, I think are not used in positioning and scanning applications. Is there a more extensive and precise categorization of the linear motors available for positioning and scanning applications?


texts: MOSFET's drain and source short out in high side driver circuit

texts:
The circuit above is used to drive a 48 Volt 1000 Watt motor "MY1020"
using high side driver configuration. 48 Volts are achieved using 4 sealed lead acid batteries in series and the 12V battery is from one of the 4 batteries.

The data sheets for the used components are:

Power MOSFET: IRF3205

http://www.irf.com/product-info/datasheets/data/irf3205.pdf

High and Low Side Driver: IR2110

http://www.infineon.com/dgdl/ir2110.pdf?fileId=5546d462533600a4015355c80333167e

Pin 10 (HIN) in the IR2110  is connected to Arduino's PWM pin 9. Pin 9 produces a PWM signal with frequency set to: 22 kHz
and a code is written to test the circuit. The code begins with duty cycle=30%, equivalent to 4 Volts which is the threshold of the MOSFET, and gradually increases the duty cycle=90%, equivalent to 10.8 Volts.

The code:

/* The code changes the PWM frequency of the Arduino
* and increases the gate voltage of the transistor
* from 4 Volts(30% Duty cycle) to 10.8 volts (90% Duty cycle)
* with a step of 0.5 Volts every 2 seconds. The process is repeated.
*/

#include <PWM.h>

int32_t freq= 22000; //PWM frequency = 22KHz
int x=85; // Initial Duty Cycle=30% at x=85

void setup() {
InitTimersSafe();
SetPinFrequencySafe(9, freq);

}

void loop() {
while(x<230)  // Duty cycle =90% at x=230
{
analogWrite(9,x); // pin 9 is connected to pin : HIN
delay(2000); // delay for 2 seconds
x+=10; // step by 0.5 Volts

}
x=85; // x is reset to 85 to repeat the process again

}

I tried the circuit with this code and here is the problem. The motor begins at a low speed as expected and its speed increases gradually. The motor should witness 14 increments in speed, since (230-85)/10 =14.5 =~ 14 steps. In about the 4th step, the speed increased immediately to its maximum like if one shorted the motor to a battery. I ran a continuity test on the IRF3205 using the multi-meter and found that the Drain and Source terminals shorted out.

I tested the same circuit earlier on a small 12v motor and it ran perfectly fine on different duty cycle ranges and PWM frequencies.

What could possibly be the problem? The MOSFET's Vds rating is 55 Volts and the batteries are 48 Volts. Can this be too much for the MOSFET assuming low quality components are sold where I live? Is there a problem in the driver? Are the increments in gate voltage per Arduino's execution time dV/dT too high?

For the sake of a real life picture; here is the test bench:


texts: How can I adapt a 8-WFDFN Exposed Pad to a breadboard?

texts:
I got a few of these:http://www.digikey.com/product-detail/en/DRV8837DSGR/296-34806-2-ND/3471184 without looking close enough at the package type. Is there an adapter for this so I can fit it on to a breadboard?

(would something like this help? http://www.ebay.com/itm/36pcs-IC-SOP8-SSOP8-TSSOP8-SOIC8-to-DIP-0-65-1-27mm-Adapter-PCB-Board-Converter-/271296415484?pt=LH_DefaultDomain_0&hash=item3f2a86c6fc)


texts: power a 5V source from an android headphone

texts:
I need an android headphone to turn off and on a 5V source
The android heafphone supplies an AC voltage (maybe 0.6V) at a frequency of my choice.
I want this to open/close the 5V supply (from another battery) such that when I play a note down the headphone, the 5V device is powered.

Alternatively, what is the simplest circuit that will allow my headphone to power an LED and have that LED always on?  I can then use the light from the led into my optoelectronic switch to control the 5V


texts: Hold Time Violations with Shift Registers/Ring Counters

texts:
I have read (and been told) numerous times that for a shift register, the clock should run reversely to the data (e.g. http://www.edaboard.com/thread103493.html).

Main Question: Is this definitely also true for Ring Counters (or LSFRs)?

I am building a block like this, where the output is again connected to the input ("ring counter"):

Each square consists of a D flip flop and a 2-1 MUX which initializes the register from D when LOAD is high. This is just a tiny example, in reality it will be between 20 and 30 registers.

Now I am facing unexpected problems which I think are due to hold time violations. I nailed down one problem when initializing the register with "11000...1". In the first cycle, all data is consistent. However, in the second cycle, the content is "01100....0" instead of "111000...0".
The clock of the last register is the fastest, so it switches from 1 to zero first (which is the output and also input to the first register). However, the clock of the first register is much delayed and hence stores the new value 0 rather than the old one, 1.

So I doubt that this rule applies to ring counters/LFSR. If this is the case, what is the correct way to implement a ring counter to minimize hold time violation issues?


texts:
I am working on an Arduino project where am controlling a motor through one of the Arduino I/O pins. The motor has nothing special just a regular 3-5V motor.
In my circuit am using a diode and a N-Channel MOSFET that has low Rds, The diode is 1N4001 and MOSFET is RFP30N06LE.
Everything works! so far so good.

Now am making a PCB of my circuit and i don't want to use these THT components i would like to use SMT components/alternatives.
To replace the 1N4001 diode i found S1-A and to replace the MOSFET i found
PMV15UNEAR.

My question is simply, are the replacement components similar enough to control my 3-5V motor like how i had it working on the breadboard setup? if not do you know of any better choices.

Thanks


texts:
I've got a strange setup:

Background:
I'm building a wireless binary transmitter with a couple of low powered CB radios. I've re-soldered the activator button and microphone on one; that sends two different tones (1500hz for 1, 1000hz for 0); this end of the setup runs beautifully with my Arduino.

My issue is with the receiving end: I've tried reading directly from the speaker pins using analogRead, but can't see any difference in the values from before the sounds are received, to after.

My question: how can I patch my way into the speaker on the second CB to Arduino so that I can read the tone/pitch value?

Sort of what I have:

simulate this circuit – Schematic created using CircuitLab


texts: Charging and discharging of a capacitor experiment

texts:
I set up an RC circuit and connected it with a signal generator. In the lab instructions, I was told to apply a "square wave signal" in order to see the transient response of the circuit in the oscilloscope screen.

My question:

Could someone please tell me why a square wave is necessary in this case? What would be the problem with a sinusoidal signal?


texts: Whether phase congruency and phase coherence terms are same or different?

texts:
I am studying the importance of phase in signal.Can anybody explain what is phase congruency ?

Also,I am confused between terms i.e. phase congruency and phase coherence. Whether phase congruency and phase coherence are one and the same or different


texts:
When an electromagnetic wave enter the waveguide, what is the change in the phase and group velocity that happen in waveguide?

Does wavelength or frequency of wave change when it enter the wave guide?


texts: Cheap switch-mode regulator "comparable" to LM317

texts:
I've always appreciated the LM317 linear power supply regulator for being a sturdy workhorse. In particular, it's easy to build a simple regulator circuit which "just works" using an handful of external parts: a couple of resistors and caps, maybe a couple of cheap diodes for protection, and you are done with it. I've used it also as a basic building block for lab experiments with my students at school (I'm an high school teacher). It is really difficult to kill one of those IC, even in the hands of the most careless student.

Since I'd like to enhance my lab experiments with some switched mode power supply circuits, I wondered whether there exists a switching regulator IC "comparable" with the LM317 among the metric ton of regulators out there. In particular, my question is whether there is a regulator which has, more or less, the following characteristics:

cheap (like the LM317 - ideally less than about 1 EUR retail);
through-hole package: it must be suitable for breadboarding;
sturdy: it should survive being handled carelessly by students without particular anti-ESD contermeasures during circuit construction and should resist a fair amount of abuse when operated (so it should have short-circuit protections, overtemp protection, etc.);
buck, boost and, hopefully, buck/boost mode capable (actually I don't care about the internal topology, as long as the IC can be used both to increase and decrease the input voltage);
reasonably wide input voltage range (~1V-20V); it would be nice if it could be used in boost mode using a single AA cell as input;
easily adjustable output voltage;
1-2A max continuous load current, so that it could be also used for lower currents (say up to 200-300mA) without heat sinking;
reasonable efficiency (>60%) even when used in non optimized designs;
few external additional components needed; in particular it should already contain the switching transistor and, if possible, any switching diode (ideally it should contain any component which can reasonably be integrated, leaving only inductors, big caps and settings resistors outside);
non-critical typical application circuits: it should be easy to select external parts and achieve stability;
external parts should not be critical, especially the inductor (or transformer): I'd like to be able to wind it up myself around a, say, 3C90 large (~30mm) ferrite toroid with (not too many turns of) enameled wire without much hassle (a beginner student should be able to do it without too much trouble);
datasheet with clear instructions/formulas on how to select external parts values to achieve desired specs;

Any hint, suggestion and pointer is appreciated!

EDIT

It turns out the suggestion from Dwayne Reid about the LM2576 family of ICs was spot-on. I happened to come across an inexpensive batch of LM2595 (from ONsemi) and tried it. Almost painless! I bread-boarded  a prototype not even selecting a proper inductor: I just wound a dozen of turns on a ferrite toroid I had lying around until I got about the inductance required by the application examples. And I threw in the first electrolytic caps I had at hand (just a bit oversized, to keep ESR down). It worked without problems. Just a bit of oscillations in some load conditions. Once put on a veroboard with proper star-ground and no
wires flapping around in the breeze even the oscillations went away.

I meddled with that IC again and also designed a tracking preregulator for an LM317 regulator. Nothing fancy, but just to test the part (and my skills). No problem whatsoever!

Most of my requirements were met. The only downside is it cannot act as a boost converter.


texts:
In the common-source on the left, one can solve for the transfer function and see that there's a right-half plane zero at \$s_z = +g_m/C_{gd}\$. For the source-follower on the right, similarly you can solve for the transfer function and see that this time there's a left-half plane zero at \$ s_z = -g_m/C_{gs} \$.
A couple things I'm wondering about:

How could one look at these circuits and reason about whether or not there's a zero (without explicitly solving for the transfer function)?
How could one reason about whether a zero is in the right-half plane or left-half plane (again intuitively)?
At a high level, why do RHP and LHP zeros have opposite phase behavior?


texts: Using/Charging a backup battery in a 12VDC circuit

texts:
EDIT: I've revised the circuit in response to comments from Andy aka.  I have also updated my questions to make it more clear what I am asking.  I'm leaving the top paragraphs for completeness' sake.

I am trying to design a circuit using an Arduino (U2) that will detect the incoming voltage from my car (V1) in addition to detecting the voltage on a backup battery (V2) in the circuit.  I wrote all of the Arduino code for this before even realizing that the schematic design for this circuit was beyond my beginner's knowledge.  I've taken a crack at producing the schematic of my system, below.

The Arduino code triggers a relay that energizes my load (a raspberry pi computer with some other accessories) when the car is providing voltage (my cigarette lighter is keyed with the accessory switch) and when the system loses power, it will run from battery for 30 minutes before gracefully shutting down the raspberry pi.  It's just about done except for the circuit in this post.  While the system is operating, I am hoping that the input current from the car electrical system will top-off the battery (it is a 12V SLA deep-cycle.)

When I run the simulator on this circuit, the voltage out at VBat is not 12 or 13.8V as I was anticipating, so I'm hoping that someone else can shed some light.  I'm also curious about how I can prevent the voltage from the backup battery in this circuit from seeping back into the car electric system (I'm assuming I need a diode, however I was unable to make a diode behave as I would expect in the below circuit)

What is the proper way to hook up a backup battery in this scenario so that the battery not only is appropriately isolated from sending back-voltage to the car, but also receives charging voltage from the car?

simulate this circuit – Schematic created using CircuitLab

After Andy Aka's circuit revision, I have a now properly-operating circuit according to circuitlab.  The only problem I need to solve for is how to properly charge the 12V battery from the 13.8V line.  Andy aka's answer below makes reference to a Schottky diode but I'm not sure how I would wire that up to provide charging voltage to the battery.

simulate this circuit


texts: I can't find a PFET protected against ESD

texts:
I like to use OmniFETs for MOSFETs because they have internal protection against ESD so I am unlikely to damage them while handling and then when they don't work I don't have to wonder if it was damaged or I have a circuit mistake.  These are n-channel FETs, but now I need a p-channel FET.  I tried to find one Mouser and Digikey, but was unsuccessful.  Is there such a thing?

It would basically be a MOSFET and a diode in one package.  Other things like over-current and over-temperature protection would also be nice, but are less important.


texts: Multiple Step-Down Voltage Rails from a single DC Power Supply

texts:
I have one working PCB which has three different Voltage Rails: 3.3V, 4V and 1.8V. They are generated using three separate step-down buck converters. The input voltage to all the converters is a single DC Power Supply (12V).

Buck Converter Generating 4V powers 4G LTE Module (Load 2.5A)
Buck Converter generating 1.8V powers LoRa IC SX1301 (Load 1A)
Buck Converter generating 3.3V powers iMX6ULL System-on-module (Load: 3A)

These three different buck converters are occupying alot of PCB space and increasing the BOM. I am thinking to implement single IC solution for my system. A quick google search landed me on two solutions.

A Triple Step-Down Converter from TI (TPS6526x)
Using a single Buck Converter to generate multiple voltages. (The link is over here).

What should I consider? Is there any different solution other than listed above?

EDIT:
The LoRaWAN IC is SX1301 and it requires 1.8V power supply.


texts: What cause Diode bridge to short circuit?

texts:
My circuit got

220V to 36V Transformer (Approximately 50VA)
KBPC2510 bridge rectifier (1kV, 25A)
relay to coltrol motor of/off
36V DC motor (100W, 4A), just drive rotary knife to cut fabric.

At first place, primary side of transformer got short circuit winding and triped fuse. after replace transformer and fuse I found that diode bridge broken as well by 2 diode act like short circuit (negative pole to both AC pole)
My question is.

Is that normal failure mode of bridge rectifier? How it happen?
Is my circuit lead to failure and how to prevent.

-- Edit --
Added schematic.
Note: For record I draw this schematic as it's wire in actual mechine, not my design. and I still wonder why it's look  so minimal.

simulate this circuit – Schematic created using CircuitLab
Edit 2
Additional information

Transformer has no datasheet or VA rate. I measure E core and got 3"x1.5"x2.5" . As I found similare size transformer It say 50VA.
DC Motor nameplate say ZD Motor(Z3D100-36A2), 100W 36V 4.0A But it's used to cut fabric with rotary knife, shouldn't draw much current.


texts: Feedback Control: Unexpected result for block diagram simplifications using matlab

texts:
I made some simple calculations regarding block diagram algebra. The problem is that I don't get the same result using matlab.

Here is the system with it's corresponding blocks:

$$H_1 = z+2$$ $$H_2 = \frac{1}{z^2+2z+1}$$ $$H_3 = \frac{z}{z+2}$$

This simplifies to the following according to the block diagram rules:

$$H = \frac{H_1*H_2}{1-H_1*H_2*H_3}$$

After some simple math I get:

$$H = \frac{\frac{z+2}{z^2+2z+1}}{1 - \frac{z+2}{z^2+2z+1}*\frac{z}{z+2}} = \frac{\frac{z+2}{z^2+2z+1}}{\frac{z^2+2z+1-z}{z^2+2z+1}} = \frac{z+2}{z^2+z+1}$$

Now if I try to get the same result using matlab it results in a system of order 5 and a system of order 3 after reducing it using matlab's minreal command:

% initialization
z = tf('z',0.1);
H1 = z+2;
H2 = 1/(z^2+2*z+1);
H3 = z/(z+2);

H_ = (H1*H2)/(1-H1*H2*H3)
H_ =

      z^4 + 6 z^3 + 13 z^2 + 12 z + 4
  ---------------------------------------
  z^5 + 5 z^4 + 10 z^3 + 11 z^2 + 7 z + 2

Sample time: 0.1 seconds
Discrete-time transfer function.

H_ = minreal(H_)
H_ =

      z^2 + 4 z + 4
  ---------------------
  z^3 + 3 z^2 + 3 z + 2

Sample time: 0.1 seconds
Discrete-time transfer function.

Only using Matlab's built in feedback command yields the correct result after evaluating minreal:

% calculate system transfer function using matlab's feedback command
H = feedback(H1*H2,-H3)
H =

      z^2 + 4 z + 4
  ---------------------
  z^3 + 3 z^2 + 3 z + 2

Sample time: 0.1 seconds
Discrete-time transfer function.

%
H = minreal(H)
H =

     z + 2
  -----------
  z^2 + z + 1

Sample time: 0.1 seconds
Discrete-time transfer function.

Could you please guide me what I am doing wrong using the straight forward calculations for H_. Why do I get a system of order 3 after using minreal and not the same result as done by hand (or using feedback command)?

num = minreal(simplify(H1*H2))
den = minreal(simplify(1-H1*H2*H3))
H_nd = simplify(minreal(minreal(num/den)))

num =

      z + 2
  -------------
  z^2 + 2 z + 1

Sample time: 0.1 seconds
Discrete-time transfer function.

den =

   z^2 + z + 1
  -------------
  z^2 + 2 z + 1

Sample time: 0.1 seconds
Discrete-time transfer function.

H_nd =

      z^3 + 4 z^2 + 5 z + 2
  -----------------------------
  z^4 + 3 z^3 + 4 z^2 + 3 z + 1

Sample time: 0.1 seconds
Discrete-time transfer function.


texts: EAGLE: how to find where the pin is connected - navigating fairly large schematics

texts:
I have a fairly large schematic loaded in EAGLE (netlist file is ~2500 lines long) and I want to find out where exactly some pin is connected, given chip name and pin name.

What I'm trying to do:

I can easily locate chip in question on the zoomed out view, it's not too many of them and they're clearly labelled
I can more or less quickly locate desired pin by browsing through all the pins of the chip (it's "less quickly" if the chip in question is a CPU with ~600 pins)
I can trace where the wire goes then by eye, but there are two major obstacles: buses and named nets. Both basically mean that this point connects to the net that can be scattered all around the drawing.

What I already tried:

"Info" command makes it possible to highlight only one particular instance of the net/bus connected, not highlighting all the rest.
"Show" command technically does exactly what I want - it highlights all the connected pieces in all instances of the net, but this highlighting stuff is fairly hard to notice (contrast between "highlighted" and "normal" is not so great) and basically it only works on high zoom levels (where there's at most 8-10 inches fit on the screen). Hunting for that "highlighted" pixels on bird's eye view is very tedious task.
find.ulp can highlight and zoom onto particular element by name, and that works for nets too. But, alas, I can't seem to understand how it works:

Just asking for net/bus by name (with count=0 by default) yields random piece of that net
Asking for net/bus by name + count=1000 yields another pretty much random piece of that net, and reports how much of them are available (for example, "9")
Then asking for net/bus name + count=(1..9) tends to yield various pieces of the net, but sometimes they clearly repeat and the result seems to be pretty much random. How can I make sure that I've browsed through all 9 instances of a given net?

Any tips on how seasoned pros get through this basic navigation stuff? I might guess there's a way to add more contrast to highlighting to make it more obvious, or there's some proper way to use find.ulp to iterate over every one of the pieces of the net/bus?


texts: How to find and overcome run-time RAM corruption in a Microcontrollers?

texts:
How can I find and overcome any RAM corruption in a Microcontroller (ARM Cortex M0) during run-time?
For example what if two or three locations are corrupted, say 0x2E 0x2F,0x30.
How can I still let the system run by overcoming or ignoring this corruption.


texts:
I am attempting to use this relay, the CC12, to turn the 120VAC power to a motor/motor controller on and off using a 24VDC signal (These voltages are specified in the datasheet.), and I've gotten rather lost as to which connectors to plug into what.

I know that the A1 and A2 input and output are the main power terminals, but other than that, I'm stuck. How would I achieve the result I have described?

I am providing a picture of the contactor here to give more context:

(The A1 and A2 inputs and outputs are on the sides, not shown in the picture.)

EDIT: I realized that a diagram I had included as part of my question didn't actually apply to the screw-terminal version of the contactor (which I have).


texts: Where/what functions as a clock on a (say intel i3-7) microprocessor?

texts:
In my Microcontrollers class today, our professor talked about how for the microcontrollers we use in lab, the clock is actually a "crystal" (either his command of English or of chemistry prevented him from talking more about it). He discussed how watches use a "crystal" to keep time (I know the crystal to be quartz).

This led to a discussion in lab about what material the Intel line of microprocessors use. A few of the questions that came up were, is the clock built into the motherboard like our microcontroller, or is it built into the microprocessor? What material is it made of? I've been looking at the the technical specifications, but I haven't found anything about this yet.


texts: Can i use an AC 15A 250V / 30A 125V rocker in place of a 15A 125V / 10A 250V one?

texts:
Amazon sent me the wrong replacement switch so i am wondering if i can use it?

Original switch is AC 15A 125V / 10A 250V

new one is AC 15A 250V / 30A 125V

can i use it without damaging the appliance?


texts: Why must the voltage drop over resistors in parallel be the same?

texts:
I am wondering why it is the case the when resistors are connected in parallel the voltage drop over them must be the same?
The reason I have seen arguing for this is that the electrons before the resistors appears in the same place, and the electrons after the resistors appears at the same place. And that means that the electrons that goes through resistor \$R_1\$ and those going through resistor \$R_2\$ are at the state before and after.
But why does this argument hold? Voltage is energy per charge, why couldn't it be the case that even though the electrons are at the same place before and after going through the resistors, the work done on the electrons going through \$R_1\$ is higher than the work done to the electrons going through resistor \$R_2\$?


texts: Are there still programmable clock synthesizers with single ended TTL output leves (in 2019)?

texts:
I'm looking for a clock synthesizer IC that can drive my vintage 5V NMOS CPU in the range of 5 - 50MHz. The granularity would preferably be in the range of 100kHz or less. All I can find when searching the net are contemporary devices that have their lowest frequencies too high, and their output levels too low.

Any suggestions to current or legacy chips that could meet my demands are most welcome. I could even accept a complete circuit built from a small number components (due to restricted PCB estate), as an answer.


texts: DDR4 pull-up resistors and decoupling clock lines

texts:
I am trying to understand the layout of a DDR4 chip connected to a FPGA. The schematic follows:

I tried to look for datasheets from the memory manufacturer explaining how to properly pull-up or pull-down pins that might be in high-impedance state FPGA side to no avail. There seems to be no material for any  decoupling on clock lines either.

I have the following questions:

How are the pull-up and pull-down resistor values calculated? The majority of them are at 39.2 Ohms. Is the value low as such to not interfere with the signal integrity (parasitic capacitance charging/discharging) under high switch frequencies?
Why is there a capacitor in series with the pull-up resistors for the clock pins (CK_t and CK_p)?


texts: How do I drive a TRIAC from a microcontroller (for low voltages)?

texts:
As a followup to this question, I would like to figure out how exactly one might go about driving a TRIAC from a microcontroller (for low-voltage applications, such as 24VAC). Imagine a scenario where I've got a low-voltage AC source running a simple switch-mode power supply that supplies my microcontroller. Is it as simple as hooking a GPIO pin to the TRIAC gate and driving the GPIO high (3.3V in this particular case)? Assume I'm using a simple, cheap, and common (apparently) MAC97 TRIAC. Do I need a resistor on the GPIO pin? Does the TRIAC gate conduct current, or is it like a MOSFET gate? If it conducts current, where does it conduct to (the only other two connections are to the AC line)?

Note that I'm not working with mains voltage here; this is for driving low-voltage AC solenoids. I understand that when working with mains voltage that extreme caution is advised and experimentation can be deadly.


texts:
Latetly we recognized a parasitic signal in our voltage measurements. It is a perfect sine wave with a period of a few hours (f = uHz).
What could be the origin of such a signals?

Ok, a few more details:

We do Hall-Effect measurements in a cryostat. The temperature is held constant at a few hundred mili Kelvin. We use a standart six terminal measurement to obtain the hall resistance and the magnetoresistance. We use standart lock-in amplifiers at a detection frequency of ca 22 Hz to measure the voltage along and transverse the current path through the sample.


texts: Voltage regulator's input capacitor "Required if regulator is locate an appreciable distance from power supply filter."

texts: The datasheet of a 78XX voltage regulator states that the input capacitor is "Required if regulator is locate [sic!] an appreciable distance from power supply filter". What constitutes an "appreciable distance"? I'm adding a heat sink, which forces me to place the filter (or input) cap a bit off of the regulator. Maybe 10 mm or even further, depending on how I lay it out. Do I need to worry about that?


texts:
I have always used VHDL and now need to use Verilog, so I'm learning Verilog.  .   .

How can I define and use user-defined data type in Verilog for state machines.

for eg : In VHDL I would write something like below

VHDL example :

       type Command_Byte_state_type is (C0,C1,C2,C3,C4,C5);
       signal Command_Byte_state : Command_Byte_state_type;

Verilog equivalent :

       parameter State0=0, State1=1, State2=2, State3=3, State4=4 ;

My question is , do you have to assign a 0 /1/2/3/4  value to the defined parameter ?

How can i DEFINE OWN DATA type in Verilog and use it like in VHDL ?
Naming convention becomes so much easier when doing this in VHDL. Also, I can easily change the state mc implementation to one hot / gray or any other, by just selecting an option in synthesis.


texts:
I was looking at the product description of a 300W Peltier AC (Link) and encountered a curve like this

While I'm aware that there will be a dT between the Peltier hot and cold sides, I am not able to understand what's going on in the curve. Also, how can dT be an operational parameter considering it's dependent on the cooling setup on the hot side.


texts: P channel MOSFET unexpected current leakage

texts:
I am using a P-channel MOSFET to drive a load. My load is an bluetooth module consuming 6 uA (according to datasheet) in sleep mode. I am controlling the gate with the main MCU which is stm32l4.

The problem is as follows:

While drinvg bluetooth module with the MOSFET, I observe the current of 70 uA (ampermeter between VCC and MOSFET source)
When I remove the MOSFET and capacitor from the circuit and short circuit the drain and source of the mosfet pads, I measured 6 uA (ampermeter between VCC and MOSFET source pad).
According to the mosfets document, gate source leakage current is only 100 nA. My GPIO configuration is push pull output. After the mosfet Cgs capacitance has charged there should be no current flow.

What can be the reason of current increase?

simulate this circuit – Schematic created using CircuitLab


texts: Zener diode selection in a led boost ic circuit

texts:
I'm wondering how to select a correct zener diode value for this led driver I am using RT4533AGJ6 (link to datasheet). My understanding of boost converters is limited, although I understand that there is an internal switch that charges up the inductor and when switched off, the inductor discharges onto the load...through the zener diode, which is to my point. The datasheet does not give any values for breakdown voltage, let alone why its required.. i did some further searching on other led driver datasheets and ran into an additional issue, the reaction/reset speed of the zener diode, which is of course dependent on the switching speed.

To make matters worse, I had contacted a customer service representative from a electronics warehouse, he said that it didn't matter what value diode I choose....which just seems silly and must be wrong in some way.


texts: Question about hooking up two generators in parallel

texts:
So I read this question: Hooking two (gasoline) generators together to make 220VAC

And it’s close to what I’m wanting to do but not quite. We had a power outage due to weather. I purchased a generator that is 30 amps but 120 V. Initially I was going to wire this to allow power to come to both phases of my panel but I decided against it. I just opted for bare minimum until the power came back on. I want to purchase a second generator and come up with a better solution in the future just in case.

The generator manufacturer makes a parallel kit but it appears to only double the output wattage not the volts which is understandable. I get that running 220 V can cause phase issues. That’s not what I want to do. I don’t care about running any 220 V devices during an outage. My hot water heater is the only 220 V device I missed and I’m swapping it out with a gas one.

Can I possibly buy two of these generators, the parallel kit, and somehow make a plug/setup that will allow me to have the combined 60 amp capacity, still 120 V but on both legs of the power?

I realize that a standby generator and transfer switch is the way to go but I don’t want to spend that much money.


texts: For my application I have to read 12V pulses from a optical encoder into a GPIO pin of a Raspberry Pi. What could be the best solution to convert 12v HTL signals to 3.3V for RPi GPIO input? Is a level shifter, resistor+clamping diode or an opto isolator good for this application?


texts: Are parts parameter supposed to agree with each other in datasheets

texts:
Say, given a power BJT that has a \$V_{CE_{SAT}}\$ = 2V and rated at \$I_{C_{MAX}}\$ = 6A, but \$P_{MAX}\$ = 8W.

Clearly, even only considering the \$P_{C}\$, it cannot continuously provide that current near saturation (assuming we put a collector resistor, worse even if we don't).

Then again, most of the times a heatsink tab is provided in the package, extending the power dissipation; maybe that's a way for them to justify the 6A.

Or maybe this justification isn't industry practice? Is it alright if certain parameters don't agree?


texts: Hi I am basically using cortex m3 series of processors for our application. I am looking for some GUI library that can be used for HMI. Is there any GUI libraries available? I recently heard about Qt. Is it a library written in C? Can I be able to port it to keil or IAR or Eclipse or any IDE? Or can you guys provide some other GUI library suggestions? Thanks!


texts: How does high feedback resistor (gain) affect offset voltage or noise?

texts: I wanted to get some insight on how high feedback resistor or high gain can affect offset voltage/ noise of an op-amp. I'm using 100M ohm as my feedback resistor for LMC6001, will it increase offset voltage/noise? If so then how is it related? Kindly share your thoughts.


texts: Gate and routing delays as a function of voltage and temperature

texts:
As I understand from watching overclocking videos, the maximum operating frequency of a digital ASIC is a function of voltage and temperature. Specifically, it seems that the maximum operating frequency increases with higher voltages and lower temperatures.

My guess is that gate delay and routing delay both vary with operating voltage and temperature. Is that correct? Given a process node (e.g. TSMC's 16nm FinFET+) where can I find documentation (e.g. datasheets) explaining how gate and routing delays vary with voltage and temperature?


texts: Transistor 2N2222A wont accept base input from arduino

texts:
I'm New in electronics. I read "Robot Building for Beginners" book and I'm trying to make a line follower circuit. Instead of LM393 and 2N2907A I'm using arduino nano and 2N2222A. Here's my code:

const int leftPin = 9;
const int rightPin = 2;

int leftSensor;
int rightSensor;

bool switchLine = HIGH;

void setup() {
  pinMode(11, INPUT_PULLUP);

  pinMode(rightPin,OUTPUT);
  pinMode(leftPin,OUTPUT);
  digitalWrite(rightPin,LOW);
  digitalWrite(leftPin,LOW);
}

void loop() {
  switchLine = digitalRead(11);

  leftSensor = analogRead(6);
  rightSensor = analogRead(5);

  if(leftSensor > rightSensor)
  {
    if(switchLine)
    {
      digitalWrite(rightPin,LOW);
      digitalWrite(leftPin,HIGH);
    }
    else
    {
      digitalWrite(rightPin,HIGH);
      digitalWrite(leftPin,LOW);
    };
  }

  if(leftSensor < rightSensor)
  {
    if(switchLine)
    {
      digitalWrite(rightPin,HIGH);
      digitalWrite(leftPin,LOW);
    }
    else
    {
      digitalWrite(rightPin,LOW);
      digitalWrite(leftPin,HIGH);
    };
  }
  delay(20);
}

And here's my circuit (I did not draw other parts of the circuit because they work fine):

simulate this circuit – Schematic created using CircuitLab

If I connect one LED without transistor to arduino output it works, if I connect base of transistor to positive terminal three LEDs light up, but when I connect base to arduino it does not work. Multimeter shows there is 5V on base of the transistor but no current.


texts: I'm looking for a high side current monitor which can measure 0-3A on a 12V rail with either a built in sense resistor or with a hall effect current sensor. I'm also space constrained, to SOT-23 or so in size. Does anyone have any suggestions?


texts:
I am building GPS datalogger. It will consist of Arduino Pro Mini 3.3V, GPS module - GY-GPS6MV2 (GPS Ublox NEO-6M) (bypassing 3.3V  regulator) or Skylab SKM53 (MT3329). Data will be written to SPI Flash W25Q64FVSIG and later read via USB with FT232RL FTDI 3.3V.

I am looking for a power supply solution having following criteria:

powering with multiple standard rechargable NiMH 1.2V AA batteries
effective power supply capable of higher current (my guess is 150mA but I am not 100% sure about this)
automatic circuit cutoff on voltage drop below minimum recommended for the circuit and also for NiMH batteries to not to overdischarge and damage them
notification of low battery power (eg. by bliking LED) before cutoff

So far I was trying to use DC-DC step-up voltage convertor with together 4 batteries - two pairs of serially connected baterries finally connected in parallel so they can provide doulbe current, but the circuit seems to require more current. Maybe I should probably consider rather some more powerful DC-DC step-down voltage convertor.

I've asked about automatic circuit cutoff and notification of low battery power already but I would appreciate to have a complete solution combined with all four requirements.

I will appreciate a solution to this complex yet common problem.


texts: Neon bulb lamp replacement for surge suppression

texts:
I'm restoring an HP 141T and it has a broken neon lamp which is used I believe as surge protection in the following configuration:

On the right is the CRT. I believe the only purpose for such lamps is so discharge a build up of charge between cathode and grid which may damage the cathode being that very close to the grid protecting also the bleeding resistor R86 which may blow up in case of too much charge build up.
The lamps used are NE-96 or 4AB which are of course not very readily available. The bulb has the following specifications:

I deduce that this is designed so that a build up of (worst case) 450V is discharged through the bulbs instead of through R86.
What would be a suitable modern day replacement for the series of the three bulbs in this application?


texts: Understanding the Maximum Speed that can be Transmitted over a Cable

texts:
I am trying to source a FFC/FPC cable for USB3.0 (+5gbps). This brought me to the question of signal transmission.  I'm somewhat of a beginner in this topic. I know that you should match impedance on your PCB with your connector/cable to minimize reflections.

I was wondering how to tell how fast of a signal you can transmit over a wire. Specifically what kind of cable parameters affect transmission speed?
Any help is appreciated.


texts:
I can't believe how much trouble I've had figuring out how to do such a simple thing.

I have a variable frequency, variably duty cycle 555 configuration in astable mode.  I'm using a set of pots to get a wide range of control.  It works beautifully.  The output is great, but I have a problem.

I am driving a couple mosfets directly from the output.  But I want to have a third mosfet that turns on and off opposite to the timing of the first two.  So if I'm running 25% duty cycle, the first two are ON for 25% of the cycle while the third one is OFF during that portion and then reverse this for the OFF period of the cycle.

I've seen some diagrams that talk about using one extra mosfet or one extra transistor along with a resistor to invert a signal, but they don't create hard/fast rise and fall times.  The resistor causes slow rise times.   I want a nearly perfect inversion of the square signal.  Right at the moment that the first two mosfets flip off, the third mosfet needs to flip full on.  It's critical that I get this to be as accurate as is feasible without getting into overly complex circuitry.  Anything more than two or three 555s and/or  two or three extra transistors (possibly needed to invert the signal) is more than I'm bargaining for.

Can anyone offer a simple solution to this?

I have both CMOS and non-CMOS 555's on-hand.  I have a reasonable collection of other components as well.  I can order what is needed.

PFET is not an option. I'm working with extremely high demands and my selection of NFETs is already highly limited.  I wish it was as simple as a PFET.

I'm not posting this as an answer yet, because I'm waiting to hear a response from the other answerer. But apaprently you can run a 555 as a 200mA signal inverter.  This is really simple for a person who already has 555s on hand, and the best part is that the 200mA current is WAY higher than a typical logic unit inverter (often topping out at least than 10 or 20mA).  Here's a page with a circuit at the bottom explaining Inverter mode: http://electronicsclub.info/555timer.htm


texts:
I have a doubt regarding the thermal resistance of the MOSFETs. Most MOSFETs data sheet have a parameter called thermal resistance (Rj).

For, eg , assume that Rj = 10C/W for a certain MOSFET . the RDS = 0.1, and the current through the MOSFET = 2amps.

So, the power dissipated = iiRds.
So power = 0.4W.
Now, applying the thermal resistance formula, we get the temperature = power*Rj.
Temp = 4degrees celcius !!!!!!

How can that be ?
Or the other explanation is that the Rj is measured at 25degrees celcius. So, we start calculation from there. Is my understanding right ?


texts:
This is a relatively simple, dumb transistor question, but for some reason I can't seem to figure out how I would go about this. I've been Googling transistor flip flops, but haven't quite gotten it the way I want it yet and would like to see what you all think.

I'm trying to save pins on an MCU and I need to alternate between two LEDs to indicate the status of the program. So I thought about doing it like this:

Each LED is hooked up to a transistor.
When the pin of the MCU outputs high, one of the LEDs will turn on, the other remain off.
When that pin of the MCU outputs low, the original LED will turn off, then the other LED turns on.

Essentially it's a flip flop circuit. I'm looking for it to be as simple as possible with the smallest component count\cost.

Thoughts? Thanks in advance!


texts: Differences in SPI SCK for half and full duplex mode

texts:
I am using SPI to communicate with the radio module; I want to use full duplex but I noticed a few things:

when I set the BIDIMODE to 1 (1-line bidirectional), I see a clock running at 6KHz. I am using a prescalar of 2 and my system clock is 16MHz, so shouldn't it be generating 8MHz clock?

when I use BIDIMODE to 0 (2-line unidirectional == full duplex),  I don't even see a single clock pulse. Interestingly, I receive 28 in the rx buffer but I don't see anything like that in the LA output. Why am I seeing this difference by changing the mode? Changing the mode afaik shouldn't change the clock's behavior, but rather in full duplex, you're receiving and sending simultaneously.

MCU: STM32F401RE nucleo
Following is my full duplex config for SPI:
SPI_InitTypeDef spi_config = {
        Mode: SPI_MODE_MASTER,
        Direction: SPI_DIRECTION_2LINES,
        DataSize: SPI_DATASIZE_8BIT,
        CLKPolarity: SPI_POLARITY_LOW,
        CLKPhase: SPI_PHASE_1EDGE,
        NSS: SPI_NSS_SOFT,
        BaudRatePrescaler: SPI_BAUDRATEPRESCALER_2,
        FirstBit: SPI_FIRSTBIT_MSB,
        TIMode: SPI_TIMODE_DISABLE,
        CRCCalculation: SPI_CRCCALCULATION_DISABLE,
        CRCPolynomial: 7
};
SPI_Init(&spi_config, SPI2);


texts: Dynamic voltage balancing in series-connected varistors

texts: I have several varistors (of type MOV-14DxxxK) in series connection. Voltage balancing is very good when applying DC voltage. Does anybody know if there would occur problems concerning dynamic voltage balancing in case of large step-wise voltage changes (e.g. when applying rectangular voltage)?


texts: Difference between two integrator circuits

texts: What is the difference between the two integrator circuits? They are used in an amplifier with feedback. There's heaps of information online about the one on the right but not so much about the one on the left.


texts: What is the easiest way to lower the DC output (reduce voltage)?

texts: I have 13.5 VDC output, and i want to power up a small radio that takes 4.5 VDC. I thought about adding 5/6 used 1.5V batteries in series, so it would be about 4.5 VDC for radio and about 8 VDC for batteries. Would that "battery voltage reducer" work? If not, how can i reduce voltage without using any complicated electronical stuff? (I am not an electrician)


texts:
Background:
I am not a professional teacher, but I have been helping out some kids (including my own) with math and science.  I thought it might be fun for the kids to decide on a project of their choosing, and work on it together to make math and science a little more "Real World".
They chose to build an e-cycle (we compromised on a trike for safety reasons).  I don't have much budget-wise for the project, so I challenged them to also turn this into an ecology project, and use used/recycled items.  For the motor, one of the kids got a mechanic to donate a couple of slightly-used, but matching starter motors from a heavy-duty truck.  Since starter motors are short duty-cycle motors, I figured the pulsed controller would be a good way to go, but also want to alternate between the two motors to allow more cool-down, and keep them from burning out too quickly.

Question:
I have found designs for PWM controllers, but am lost at alternating the signal between the two motors.  At present, my only solution is a mechanical one, where a disk would be connected to the drive wheel, with contacts routing power to one motor around one half, and the other motor around the other.  This is far from an ideal solution, but is so far the only one we have come up with.

Is there a circuit that can be used in conjunction with the PWM controller to alternate which motor is getting the pulses?  Or are we best off keeping with the mechanical solution?


texts:
I need to calculate \$V_B-V_A\$ but I am having difficulties deciphering how this electric field intensity is formulated which resulted in me getting stuck.
$$\mathbf{E}=\hat{a}_x4x+\hat{a}_y3y$$
What do does \$\hat{a}_x\$ and \$\hat{a}_y\$
exactly mean in this context?
I know for a fact that they are unit vectors but what is \$\hat{a}_x\$ and \$\hat{a}_y\$ exactly is I don't know, it could be related to cylindrical coordinates...


texts:
Regarding the number of bits that is sent using UART and configuring the UART handle is unclear as well as setting the parity bit, is it odd or even.

"uint8_t data[] = " I want to send this sentence "

EDIT:

The above consists of 30 bytes.

If I configure the UART to have a wordlength of 8 bits in a stm32f4

WordLength = UART_WORDLENGTH_8B;
BaudRate = 9600;
StopBits = 1;

how will it send the 30 bits if I configured the UART in 8 bits/1 byte?

Will it send it one by one so 30 times:

(space)
I
want
...
sentence
(space)

Also, the parity bit, if the data is 011001 then parity is odd but how to translate data[] into 0's and 1's?


texts: Customized PICKit can't write data in PIC12F629

texts:
I have a PICkit 2 Microcontroller Programmer, but it is not exactly the one that microchip is selling as PICkit2, I bought it because there is nothing else in my area, anyway, it has USB that connects to computer and send/receive power and data, it is something like this link and software which I use is this link - microchip.com.ru/images/PICkit2_3.JPG - , and the software detect hardware and show exactly my chip ID.

I have tried to program PIC12F629 with the programmer, but it can't write anything and it gives me this error:

"Programming failed at Program Memory address 0x[first address which is not zero]".look like this link - i62.tinypic.com/2jbl55z.jpg - .

I googled it a lot and I have checked with another PIC12F626 and different kinds of Operating system but the same Error appeared. I also tried use MPLAB IDE software but when I try to write the program to micro-controller, it gave me this error :

"The programmer could not be started: Failed to program the target device".

and

"
....

Verifying Program Memory (0x0 - 0x5)

PK2Error0027:  Failed verify (Address = 0x0 - Expected Value 0x1683 - Value Read 0x0)

PK2Error0027:  Failed verify (Address = 0x0 - Expected Value 0x1683 - Value Read 0x0)".

I also tried to set MCLRE flag off and on software still but no luck.

I should mention my program compile without any error and the IC is supported by my pickit2 board and the company support lines is too busy and the company is too far from me.

Beside of hardware malfunction, any idea why it doesn't work?


texts: Why can only analog signals pass through air (wireless channel)?

texts:
I read the following in a book:

  "When the transmitted signal is passed through the air using electromagnetic waves, it must take the form of a continuous (analog) waveform."

Why is this so? Why can't the signal take the form of a digital waveform?


texts: How can i design butterworth low and high pass filter?

texts: I want to design 1002MHZ low pass and 950MHZ high pass filter. It is a tv/sat combiner. I calculated the parameters for a butterworth filter like below, but it didn't work. How can I fix this design?


texts: How to bring a digital input pin to high state?

texts:
This sounds really very easy, but I'm afraid to try it because I don't want to fry my microcontroller.

I'll use an Arduino for an example, but it should be the same for all microcontrollers.

Anyway, say you have a switch and you want for when you press the switch to bring a digital pin to high(1) and when it's not pressed, to low(0). Would this require resistors? Or would you just straight wire from 3.3v into the input pin?

Or to further simplify what I'm asking. If for some reason you wanted a certain digital input pin to always be high, would you just stick a wire from 3.3v into the digital pin? Or would you need a resistor somewhere in there?


texts: High Vds across MOSFET in saturation mode in Flyback converter during simulation

texts:
While simulating a flyback converter, I find that even in saturation mode the MOSFET, in spite of having Rds(on) around 0.74 ohms and the Ids = 5.75mA, is dropping almost the entire drain supply input voltage. The snubber circuit and the sense resister also consumes very less power.

Looks like a newbie query but I am not able to answer, is this high Vds in saturation mode expected, if yes, why? Is it because the power is a pulsating one ?  Can a floating gate destroy a MOSFET? Practically I found Vds = 1.4V, does that mean the MOSFET is bad ?

DC Analysis

Transient Analysis


texts: I have got a clipper circuit as shown in the pic .I am confused why there are two differnt waveforms in two halves (separated by the red vertical line). And what is the actual waveform we obtain considering every components to be idle.


texts: What will happen if we excite a Synchronous Machine with AC?

texts: Normally we excite Synchronous Machines with DC. But what would happen if we provide AC in place of DC in field winding of Synchronous Machine? Will Synchronous Motor start in with AC excitation?


texts: Is there a way I can convert from USB to LVDS UART (~1Mbps)?

texts:
I'm working on a spacecraft that requires very low noise levels so it was requested that we pursue LVDS UART. So it's using something similar to RS-422 because it's differential, but instead of a signal that is 0-5V, it is a current loop that produces a differential signal that's about 300 mV.
My issue is that for testing purposes we need to be able to talk to that interface from a computer using USB. Normally we would use USB to TTL UART but that won't work for this situation. It would be nice if there was a USB to LVDS UART such that it presented a standard serial interface to the computer but used LVDS to connect to our board for testing.  An FPGA on the board is handling the UART. The connection needs ~1 Mbps.
So far I've been looking for something like a USB-FTDI TTL cable but that would work with LVDS UART. So far I haven't found anything. Maybe someone with more knowledge than  I can help me find a solution.
Edit I don't need product recommendations. When I mentioned looking for products I was merely trying to explain what I had been exploring in trying to find a solution. The core of my question is whether or not doing this was possible and if it was, what kind of solutions should I explore.


texts: Why does my varistor cause my fuse to blew up?

texts:
I have made the following circuit (copied from a very similar picture on internet):

At one side of AC/DC I put a normal fuse.

The MOV is a 14D391K 14K391 390V varistor diameter 14mm AC 250V DC 320V (similar to this datasheet.

However, as soon as I put 220 AC on the circuit, the fuse blew. I would expect that it would blow when it gets a power spike of over 390 V (AC).

I don't know if the varistor still works, but I removed it and the circuit works as it should be.

What did I do wrong?

Update

I see that the voltage rating is 390 VDC, and the clamping rating is 650 V

Does this mean that this varistor is not meant to be for AC ?
How can the clamping rating be higher than the voltage rating?
In case this varistor is to be used for AC, why does my fuse blows up when using this varistor?


texts: Is using the CH340G on a commercial product a horrible idea?

texts:
I'm developing a niche product that will be produced at a fairly low volume (low hundreds). I'm using an Atmega uC, and one of the requirements is the ability to be field-flashable by the user. My plan is to use the Arduino bootloader with a USB-to-UART IC (lazy, I know, but at this volume it is probably the best option).

There are many choices. My prototype board right now is using the FTDI FT232RL, but that is too expensive for production, as the price point for the whole board is around $20.

ICs I've considered include:

CH340G

Cheapest option, but what's the status of signed drivers for OSX? I can't determine whether this will be completely plug and play. Does anyone know what the status of this is?

CP2102

Robust, no worries about signed drivers etc. But it is more expensive.

MCP2200

Also robust, no worries about signed drivers. How do I choose this versus the CP2102? They are nearly the same price.

Are there any other "gotchas" with the above choices other than signed drivers? I don't want to force the user to install unsigned drivers/add a potentially painful process to the re-flashing procedure, but I also don't really want to add $2 to the BOM cost just for user-flashability.

Any general guidance/advice would be useful. Thanks.


texts:
Hello, I am currently studying for a digital circuit design course and had a question regarding circuit design here. The sample we were given was unfortunately incomplete and I am not told why this person was wrong here. I know the width sizing (assuming length is constant) of PMOS transistors in CMOS design is ~2.5x the width of NMOS in order to ensure similar current flow and more importantly propagation time, but I am a little confused on how those rules apply to series PMOS/NMOS and parallel PMOS/NMOS.

Am I right to assume that the width of Mpa should be such that the same current flows through that branch as in the parallel branch with Mpc, and thus would need to have double the width of Mpc, 20 microns? And that the width of Mpc is 10 microns because the two 5 micron width PMOS transistors Mpd and Mpe below add up to a 10 micron width transistor in the amount of current that passes through them?

Thank you for any help.


texts: Is it bad to short a DC motor for a long time?

texts:
I am using one of those small yellow "robot" DC motor like this one, on a circuit where the motor will turn on a couple of times under certain circumstances.

I am thinking of designing a normally-closed circuit where both poles of the motor are shorted at all times to keep it stopped.

When a sensor goes off, one of the poles will be grounded and the motor will spin until the sensor goes on again, shorting the motor and braking it.

My question is: is it bad to keep the poles shorted for a very long period? Both in terms of damaging the motor and power consumption.

The "very long period" would be 24/7, with the motor turning on for ~5 seconds every 6 hours.

EDIT: Here's the schematic, haven't tested it yet but this is more or less what I'm planning to do.

simulate this circuit – Schematic created using CircuitLab


texts: What have I done wrong with my Sine Oscillator circuit schematic in LTspice

texts:
How do I improve my circuit schematic so that I obtain the desired result in LTSpice?
I have recreated a circuit of a Sine oscillator from a textbook. However, when I simulate it, the result is different to what is expected.
I have compared the 2 schematics and they are similar in every sense. The only difference is that the Textbook specifies a Philips NPN transistor and my library only contains a NXP equivalent.
Any insight that anyone can provide will be very much appreciated.


texts: Implementing powerline communication on a high voltage DC line with an AC power-line adapter

texts:
I am currently working on a tethered UAV project (please refer this). I am thinking of tethering the power as well as data through the two power cables that will go up to the UAV. I plan to use 300V dc (rectified,filtered,regulated AC mains) for transmission along the tethering cable and thus, want to implement a powerline communication over this voltage.

However, I already have an AC powerline adapter (this) and was wondering if I could use this existing adapter on a 300V dc line.

If yes,  what exactly would I have to do to achieve this? Also, I am unsure about the exact data rate desired but I want to stream an HD video to my ground station.

Please find the system description (block diagram) below.

simulate this circuit – Schematic created using CircuitLab

Any guidance is appreciated. Thanks in advance.

Update : 20th March,2020

I have ripped open my receiver; sharing the images below :

This board has the AC stepdown and filtering alongwith Atheros controller ICs.

This has the ethernet ports and (probably) a buck converter for powering the electronics.

They were connected with board-to-board connectors like this (I forgot to take a photo before I separated them) -


texts: Is it possible to driver two parallel MOSFET by using single optocupler (TLP250)?

texts: I am Using TLP250 to drive IRFP260N MOSFET . If i use separate driver to drive MOSFET i need two power supply . so i am looking for single drive solution for multiple mosfet .


texts:
I have implemented a long time delay using a small microcontroller (MSP430) however I need to test and verify that it does as I expect.

My algorithm is as follows:

main()
{
    //Init Timer
    //Init Output
    //Sleep
}

ISR_Timer()
{
    //increment minutes
    //if output off and enough time elapsed
        //Turn output on
        //Reset elapsed time
    //else if output on and enough time elapsed
        //Turn output off
        //Reset elapsed time

}

Due to the delays being 21 hours and 3 hours, how can I go about testing this as it doesn't happen instantly. I have swapped the hours to minutes, although I will need a way to test that the output is off for 21 hours and on for 3 hours, and that nothing happens inside of the microcontroller, such as the watchdog timer reseting the CPU. The code is simple enough that going through it it can be seen that nothing is actually wrong with the implementation but it still needs to be tested in some way.


texts: I am searching for 2 Pin Wire terminal connector in orcad. Can anyone suggest me where i can find Wire Terminal Connectors? Under which category in orcad library can i find 2 Pin wire terminal connector. Thanks in advance.


texts: How could I design a circuit for a solar panel so that it only produces output from a red laser?

texts: I'm designing a little laser tag system with some arduino's as a little project for Christmas break and I'm having trouble figuring out how to make my solar panel receive information from my laser only, and not from ambient light sources. Right now, I have been able to code the arduino to modulate the laser and carry a message. I can decipher this message with the solar panel and another arduino in complete darkness obviously, but I'm having trouble as to how to make my circuit sensitive to my laser in daylight. I've heard about band pass filters, but I'm not sure I really understand how I am suppose to implement them. I'm sorry if I sound like a total nube!


texts: How to find the voltage drop in this circuit?

texts:
For the following circuit, what equations do I have to use to get \$v_0\$? I have tried using Kirchhoff's voltage law, but I am only able to get 3 equations whereas I have 4 unknowns.

I am only looking for guidance.


texts: Measuring the impedance of dry EEG electrodes?

texts:
Does anyone have recommendations or good resources on measuring the impedance of active dry EEG electrodes? I'm working on a project to create my own electrodes, and I'm pretty new to the electronics world. I'd like tips on both the hardware to use and a test setup.

Specific points/questions:

I don't think I can just clip the electrode into a multimeter, I think I need to measure it with an appropriate electrolyte and skin material model to mock the skin-electrode chemical. Right?
I think I have to use at least two similar electrodes for this. If I generate a signal and run it through the skin model, there will de facto be an electrode interface between the signal generator and the skin model, right? I think it would be better to use two similar electrodes so the half-cell potentials cancel out.
This paper discusses a "head phantom", and there are some details for creating a simple phantom with gelatin/agar/agarose in this paper. Would that be a suitable skin model? Suggestions for alternatives?
This paper value (pg 12) discusses a procedure for measuring impedance that uses lots of similar electrodes to drive the skin surface potential to a known value. Is there a simpler way to do this?
I don't need super precise values for the impedance. A ballpark value with an error of +/- 10% would be nice. I want to measure both resistive and capacitive components of the impedance over a spectrum of EEG-relevant frequencies (1 Hz to ~1k). Any recommendations for a measurement circuit and relatively cheap hardware to do this? LCR meter, arbitrary wave generator, oscope?

Many thanks! I know I put a lot here, feel free to answer in whole or in part.


texts: What kind of component was used in this demodulation circuit?

texts:
I was trying to gather components as well as some desoldering experience from an old television tuner when I found those little fellows:

They were sitting next to an IC with the Code TDA 6160-2X. According to it's datasheet it's a

  Multistandard sound IF-device consisting of a mixer as a frequency converter, a voltage-controlled
  oscillator (VCO) that can be continuously tuned in 10-kHz increments with crystal accuracy by
  means of a PLL, and three following parallel FM-limiter amplifiers with coincidence demodulators.

In the same datasheet one can find the following block diagram which shows  that the caps were part of the demodulation circuit.

Now I can measure a short circuit between the two legs which were connected to the IC. The two sitting in the middle are a bit wider and connected with the case so those would be the mounting pins but the remaining three aren't connected internally to anything I can measure. I couldn't measure any capacitance between them and anything else either but then again I have only the component tester of my old scope available right now.

What kind of component is this and what's the purpose of the three pins previously connected to ground?

Edit: I found a little plastic screw for adjusting the component under the little plastic sticker.


texts: Voltage drop across opposite diodes in series

texts:
I know that a silicon diode with forward bias drops 0.7V, and I also know the two resistors should have the same voltage drop because they have the same resistance and same current (because the branch with the opposite diodes in series should have a current of almost 0). Knowing that I can calculate that the resistors drop 4.3V and the 2 forward bias diodes drop 0.7V, and I expected the other diodes to drop 0V. But simulating this circuit on CircuitLab gives the following voltage drops:

I don't understand why the opposite diodes in series drop 2.5V each. If anything I would think the forward biased diode should drop 0.7V and the reverse biased diode should drop the remaining 4.3V, but that doesn't seem to be the case. Why is this?
These are "ideal diodes" on CircuitLab but I assume they will behave the same. Is this a correct assumption to make? If not, what would change if they were silicon diodes in real life?


texts: I am trying to design a PCB with AC mains which is going to be controlled using relays to turn on fans and heater. I have never designed PCB for AC. What should I look out for and what should I be doing when designing for it?


texts:
Analog newbie here and first time on this forum... thank you for reading!

What I have is a control for pyrotechnics. I have all the digital control stuff figured out, but analog bits are not my forte.

Car battery supplies this rig, and output channels will be switched using SCRs, IGBTs, or just plain automotive relays. I want to limit current such that those components are not abused, and so that many channels can receive high current even if some have a resistance quite a bit higher than others.

Most circuits I see are around battery charging, or are much lower current. So this is the most simple thing I have come up with so far:

Basically I am using the current gain of each part of my darlington pair to limit current into the load. I'd like feedback on this design or pointers to something more appropriate (which as I said has been difficult to locate given the idea that the load can be a short).

Minor issues include:

I believe I need a snubber diode (or caps?) around my load and diode near the switch somewhere.


texts: How do i control a 6 V supply output based on a 5 V input?

texts:
I have a signal from a microcontroller that varies from 0 V to 5 V. I also have a separate 6 V supply to power a motor. I'm trying to design a circuit that allows the microcontroller signal to proportionally control the amount of voltage the 6v supplies to the motor. So when the signal is 5v, the motor receives 6 V, when it's 2.5 V, the motor is getting 3 V from the 6 V supply.
Vsig = 0 < Vsig < 5
VMot = Vsig * (6 / 5)
How do implement this relationship as a circuit?

All I have so far is a basic NPN amplifier circuit that doesn't do anything I want it to. R1 represents the motor resistance. Vsig is a sine wave with amplitude 5 V and is offset 2.5 V (oscillating between 5 V and and 0 V). Am I along the right lines and what do I have to add to make the functionality I've described?
EDIT: The 5 V controller signal is a PWM signal acting like a 10 Hz sine wave. Motor does not go in reverse. 0 V is stationary to 5 V is full speed.


texts: Acceleration calculation from ADC raw data

texts:
We have interfaced PCB393B12 accelerometer with MSP430F5438A board, by using 8-bit ADC.

We receive raw data in 0-255 range with 0v to +2.5v as reference.

How we can obtain corresponding acceleration(g) from ADC raw data?

Note: Our sensor has a sensitivity of 10000mv/g.


texts: Will 2000A Inrush Current Damage Outlet Circuitry?

texts: First time building an AC control system complete with motors, PLC, sensors, power supplies. All this is sourced from a 220VAC outlet. I have calculated the total current draw of all motors, powers supplies, etc, to be about 38A at full load. What I am concerned about is my 2000A inrush current calculation. Would it be safe to enable the 220VAC line to the control system when connected to a 220VAC wall outlet that can output 60A? Is this kind of inrush current value normal for industrial control systems, therefore it is alright and outlet circuitry can safely handle this event?


texts: the response of wireless channel to an input

texts:
I am reading the wireless of David Tse. In the 2nd chapter of this book there is a discussion about the response of the channel due to an input. It has said that since the channel is linear its output can be written as

\$ y(t)=\int_{-\infty}^{+\infty}h(\tau,t)x(t-\tau)d\tau\$

which \$h(\tau,t)\$ is the response at time \$t\$ to an impulse transmitted at time \$t-\tau\$ and can be obtained through the following formula:

\$h(\tau,t)=\sum_{i}a_{i}(t)\delta(\tau-\tau_{i}(t))\$

in which \$a_{i}(t)\$ is the amplification or attenuation due to different propagation pathes and \$\tau_{i}(t)\$ is its relevant delay. Now I have several questions that I will be thankful if someone helps me.

1- Does "an impulse transmitted at time \$t-\tau\$" means \$\delta(t-\tau)\$? (since in this case the author must wrote "an impulse transmitted at time \$\tau\$")

2- Due to this fact that we know the output concerned with an input can be obtained through the formula \$y(t)=\sum_{i}a_{i}(t)x(t-\tau_{i}(t))\$, how does formula of \$h(\tau,t)\$ have been derived?


texts:
I'm trying to find a battery which can power two 24volt motors. They each use 12amps, so I think collectively they will use 24 amps. I want the battery to at least last an hour.
This battery I'm considering supposedly has 42980 mAh but I'm not sure because it says 3.7/42980mAh. Is this normal or am I being mislead into thinking it has 42980mAh when outputting 24volts. If you need more information, it can be found at the listing https://www.amazon.com/TalentCell-PB240B1-Rechargeable-Batteries-Smartphone/dp/B07SWBS55F/ref=cm_cr_arp_d_product_top?ie=UTF8.

If it can provide 42980mAh it should provide more than hour because:
Approximate Running Time(h)=Battery Capacity(mAh) / Operating Current(mA)
=42980/24000 = 1.79; So it should provide roughly 1 hour 48 minutes
The main two things I am concerned is if two 24volt motors drawing from the same 24volt battery will cause a dramatic voltage drop and if I am correct in the assumption that the battery indeed has 42980mAh.
Here's the main question: Am I right in the assumption that this battery can power both motors?
As you can probably tell I'm new to electronics and any help would be greatly appreciated!
I'm not sure if it's helpful but here are the motor stats:


texts: What is inter-lane skew insertion in display port

texts:
I am reading the display port specification facing some issue in understanding some terminology
1. What is inter lane clock skew
2. In the  fig 2.8 what is bus steering ?


texts: Connector name for angel eyes CCFL inverter

texts:
I have a CCFL inverter for  my car's headlight angel eyes. It seems they all respect some standard connector, but apparently the manufacturer of my headlights didn't get the memo :P, so until now I've been cutting wires and stitch them together on my car. I decided this has to stop and want to make a proper plug-and-play solution.

The problem is I can't identify the type of connector they use.

This is the connector that I want:

This would be the female connector, that I don't need but I thought it may help to identify:


texts: Ethernet Phy Rx developed in a FPGA to send data to an ethernet Mac

texts:
I'm trying to send data from a FPGA to the Ethernet Mac port of a SoC which has the stmmac Synopsys IP.

I'm using the MII protocol at 25MHz for 100Mb/s (4-bit per clock cycle).
I'm sending the following fake ethernet frame:
FF FF FF FF FF FF       Destination Mac (broadcast)
58 00 E3 5B E8 41       Source Mac
00 2E                   Type with size (46=0x2E)
01 02 03 ... 44 45 46   Packet
CF C7 1F CC             FCS

The whole frame is valid and checked at http://packetor.com. The FCS is correct.
FF FF FF FF FF FF 58 00 E3 5B E8 41 00 2E 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 CF C7 1F CC

My FPGA code looks like this:
reg [20:0] count;
reg ctl;
reg [3:0] d;

wire clk;
wire clk90;
pll pll_inst(
    .CLKI   (oscInternal),
    .CLKOP  (clk), //25MHz
    .CLKOS  (clk90) //25MHz shifted phase 90 degrees
);

//Packet is 8+6+6+2+46+4=72 bytes long, so 576 bits.
wire [575:0]val = 576'h55555555555555D5FFFFFFFFFFFF5800E35BE841002E01020304050607080910111213141516171819202122232425262728293031323334353637383940414243444546CFC71FCC;

always @(posedge clk) begin
    if (count < 72 * 2) begin
        ctl <= 1;
        if (count[0] == 0)
            d <= val >> (576 - 8 - 4 * count);
        else
            d <= val >> (576 - 4 * count);
    end else begin
        d <= 0;
        ctl <= 0;
    end
    count <= count + 1;
end

assign rxd0 = d[1];
assign rxd1 = d[0];
assign rxd2 = d[2];
assign rxd3 = d[3];
assign rxctl = ctl;
assign rxclk = clk90;

I send 4-bit by 4-bit, first the lower 4 bits then the higher 4 bits of each byte. This is done at each clock cycle.
The rxclock is shifted of 90 degrees so that data is valid when the 25MHz rx clock is rising up.
I have checked on a digital analyzer and it looks good, similar to the traffic sent by a Realtek PHY.
In the kernel DTS, I have:
phy-mode = "mii";
fixed-link {
    speed = <100>;
    full-duplex;
};

When I boot, the kernel is correctly setup with the stmmac Mac. The kernel driver is here:
https://elixir.bootlin.com/linux/v4.4.230/source/drivers/net/ethernet/stmicro/stmmac
In dmesg, I see eth0 up and configured at 100Mb/s. ifconfig eth0 up is good.
I can send traffic via a Realtek PHY in a similar setup and it's received by the kernel.
But I don't see anything when I'm sending through my FPGA. Is there anything I'm missing or doing wrong?


texts: Is boost converter enough to provide pulse currents without drawing too much current from a coin cell

texts:
I am making a RF circuit which could operate using a 3V coin cell battery like CR2032 or CR2450. In sleep mode it consumes around 10-20uA but during Tx/Rx which lasts for 10ms it consumes ~300mA-ms. My circuit works in 2.8-3.6V range. To supply this surge current I have tried using a 1000uF capacitor and it has performed well except when handling the startup inrush current.

Now to increase battery usage I am planning to use a boost converter with low Iq like : http://www.ti.com/lit/gpn/tps61322. I couldn't use 2 coin cells (6V) and an LDO as I want to keep the form factor smaller and battery replacement easier.

My doubt is if I am using a boost converter, would I still require a capacitor parallel to the battery so that battery is not subjected to high current surges or a boost converter can inherently take care of such surges without drawing too much current (~10-15mA) from the battery.

More details:
Attached is the graph showing current vs time during the Tx/Rx operation. In total it lasts for approx 10ms and consumes about 300mA-ms. Once this Tx/Rx is done the circuit goes to sleep and consumes 10-20uA

The overall current profile of the RF circuit looks like:


texts: Will this short range AM transmitter constructed using crystal work?

texts:
I have designed a circuit as follows:

simulate this circuit – Schematic created using CircuitLab

There are a few corrections in the circuit. I couldn't do it in the editor because I don't know. The corrections are:
1. The input is audio input.
2. The capacitor is electrolytic.

Now my question is whether this circuit will be able to generate the carrier frequency to transmit the audio input. If not, then what are all the required additions and corrections?

Also can anyone explain how to design the receiver to receive the signals.


texts: Is there a more economical version of this powersource prototyper the CADET

texts:
This is what I want....problem is that they are expensive, really expensive ($500). Is there a more economical version?

http://tequipment.net/ELCADET2.html

http://tequipment.net/ProductImages/E&L/CADET2_mid.jpg
Features:

* Expanded Removeable breadboard area
* Two open collector pulsers
* Built-in multi-waveform function generator
* Quad voltage power supply: Three DC & one low voltage AC
* Functions with optional electronics trainer boards
* Built-in logic probe with pulse capture
* BCD to 7 segment decoder/display
* 8 channel logic indicatorsSpecifications

The C.A.D.E.T. II is a Complete Electronics Trainer that includes all the functions needed to teach basic AC/DC, Linear and Digital Electronics courses. The unit contains all the functions of our highly acclaimed original C.A.D.E.T. plus frequently requested features from educators worldwide.

The breadboard area is 33% larger than original C.A.D.E.T., holds up to 32 IC's and comes standard as a removable socket plate with velcro. If you prefer, it can be ordered withour bread boards for use with the extensive line of E&L Trainer Boards. The built-in logic probe will detect narrow logic pulses and eliminate the need for extra lab equipment. The BCD to 7 segment display/decoder saves students time when constucting circuits. The Quad Voltage Power Supply has +5 VDC, two variable DC outputs, and a fixed 12.6 VAC center tapped output. The trainer also includes 8 TTL compatible logic switches and two pulsers.


texts:
I've a question related to digital logic which is:
Why if I have 2^n possibilities for n bits then the indexes of the bits itself are from [0:2^n -1 ]? I'm not understanding why we must initialize the indexes from zero... Who said that bits are primarily indexed at first by zero? Why are we not initializing bit indexes from 2 or any other number? Sound weird for me. Any illustration please? Is that an axiom (starting from index zero till 2^n -1) that PC works with?


texts: Is the Gummel-Poon model useful for explaining AC transistor amplification?

texts:
Let me be clear: By amplification I am talking about the process of boosting the strength of an AC signal. Thus, where the output power to input power ratio is greater than 1.

Now suppose we have a simple Common Emitter amplifier with a voltage divider base(and a positive collector supply voltage).A capacitor is an AC short and a DC open. Now when we add an AC signal to the base, the capacitors experience a change in voltage and began to conduct, causing a surge of current to flow from points E' to C' on the circuit diagram. There is also current flowing through C(BC'). Thus small changes on the base voltage(due to input) control larger changes in the emitter-collector current. And that's how transistors can be used to boost AC signal power.


texts:
I've got a circuit diagram I'm working from, this one:

And I'm currently trying to breadboard it, as seen here:

I've been trying to search google on how to wire a Relay, and am not yielding any viable results. I've got a omron 5VDC with 5 pins, 2 on the bottom, 3 on the top.

I think I've figured out that the bottom 2 pins are for power, and the top 3 are for output, in some way. :S I'm going to be connecting the output of the relay to an AND gate to test if a switch is on, and act if both inputs are ON.

Two questions?
How do I wire up the relay? and
Is the circuit so far matching the diagram? (if you can't tell from the instagram image, forget this question!)

ALSO: I did change it slightly, there is no variable resistor, instead there's an 'average' 100Ohm resistor.

Thank you very much!
Cheers,
John


texts:
I am restoring a Sunn Beta Lead amp and I need to replace one of the pots on the reverb channel.

According to the schematics it’s a 30k s curve 4 pin pot.
I can’t seem to find a replacement.

Anyone knows what to do?


texts: What justifies simplifying the integrands in this Ampere's law problem?

texts:
I'm looking at the author's solution for a problem using Ampere's Law, but his steps are very terse, and two steps slip by without a justifying remark. I've added my guesses below with question marks.

Problem

What is the magnetic flux density inside a conductor wrapped into the shape of a torus with radius 2cm, 50 turns, and a constant 1A of current flowing through it?

Solution

\begin{align}
\oint H \cdot dl &= I_{enc} + \int\int_S \frac{\delta D}{\delta t} \cdot dS
\end{align}

Noting that the current is constant (?), $$\frac{\delta D}{\delta t} = 0$$

$$I_{enc} = (50 \textrm{ turns})(1A) = 50A$$

Assuming the material is homogenous,

\begin{align}
\oint \frac{B}{\mu} \cdot dl &= 50A \\
dl &= r d\theta \\
\int^{2\pi}_{0} \frac{B}{\mu} (2cm) d\theta &= 50A
\end{align}

With the knowledge that the flux density is rotationally symmetric (?),

\begin{align}
\frac{B}{\mu} (2cm) \int^{2\pi}_{0} d\theta &= 50A \\
\implies B &= \frac{50A\mu}{(2cm)(2\pi)} = 500 \mu T
\end{align}

Justifications

Is the constant current statement correct?
Is the rotational symmetry the reason for removing the flux density term from the integrand? If the element were something more interesting than a torus, would that step be disallowed?


texts: Basic electronics: input currents of multi-port sub-circuits

texts:
I am simulating, with PSpice, the transient behavior of an analog circuit that contains several multiport sub-circuits.
When I probe the current on all inputs of a sub-circuit, I see that the sum of all input currents is different from zero.
Is it possible or is it just a modeling issue of the sub-circuit I am analyzing? Should't the sum of all input currents be equal to zero?


texts: Extending a PTC voltage rating with series resistance

texts:
PTCs come with a maximum voltage rating which, according to the answer for this question is essentially because of instantaneous power across the device.

Usually, a PTC is placed across a low-resistance voltage source. However, in my case, the PTC is in series with a resistor which is much greater than the R1max of the device, and the possible voltage across the circuit is greater than the nominal Vdc of the PTC I would like to use.

Whilst the PTC is conducting, the voltage across it does not violate the Vdc, since most of the voltage will be dropped across the resistor.  Once the PTC trips, most of the voltage will be across the PTC since it will be in a high-resistance state, which would likely violate the Vdc rating of the PTC.

Is it safe to operate it in this configuration? My theory is that it might possibly be safe, since the power dissipated is limited by the in-line resistance, but I don't know what calculations I might be able to use to show this is/isn't true.

For a concrete example, the PTC is a Bourns MF-NSHT016KX with a Vdc of 30V, an I_trip of 0.8A and an R1_max of 6R, and is in a circuit with a series resistance of 22R, meaning the PTC will trip somewhere about Vin=20V (as desired).  I would like to be able to expose the circuit to Vin=40V.

(p.s. choosing a PTC with a higher Vdc rating introduces other compromises that I am not willing to make. Similarly for resistor power ratings).


texts:
Perhaps a simple question, but from the Wikipedia page, electric current is defined as"...a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire." (https://en.wikipedia.org/wiki/Electric_current)

So my question is then, how is it that AC current has amperage at all, if there is no net flow of electric charge? Is it caused by an equivalent power being generated somehow? If so, what is/are the equation(s) for finding that?


texts: How can I add reference return path via (ground via) in a symmetric way in PCB Editor?

texts:
I would like to add symmetric via (return path via in the middle) using PCB Editor as shown below.
I can add via manually. I just wanted to make sure it is symmetric to the two diff-pair fanouts as shown in the figure.


texts: Help me build an autonomous remote wind station + camera

texts:
I'd like to build an autonomous remote wind station + camera that I can install near my favorite kitesurfing spot so that I can

Know in "real-time" both speed and direction of the wind
See what's going on there (it's mainly to know whether the spot is crowded)

As I have little knowledge of electrical engineering, I'm asking here for some help designing this remote station.

Here is what I've come up with

Objectives

Learn - I'm doing this to learn new things
Cheap - I do not exactly have a budget, but price will be an important factor
Autonomous - It has to work 365/24 without human intervention

Main subjects

Microcontroller
Communication
Power
Sensors (camera, wind speed, wind direction)

Microcontroller

It has to be programmable, so I can update/improve the behavior of the station if needed.

Any programming language will do - I'm a software engineer, that's what I do ;)

I was thinking something like the Arduino, but I have no idea which model is the best fit for this station.

Communication

As the spot is 50km away from my home, I've found that the only communication protocol/network usable is GPRS/GSM (please, correct me if I'm wrong).

Sending the values read from the sensors (wind speed + direction) can easily fit in a SMS.
I've found a SMS gateway that let me receive SMS for free. It appears to be exactly what I need.

But sending an image (even a 320x240) every minutes (or less) requires a data connection. Indeed, transferring 320x240 = 76 800 pixels will take about 590 SMS (at 140 bytes per SMS minus 10 bytes for the overhead).

Again, there's way too much choice here. Do I need a dualband, a quadband or a 3G/GPRS shield?

Note: I like the 3G/GPRS one as I can easily attach a 7€ camera. But 140€ is kind of expensive.

Note II: I am aware that using GPRS/GSM/3G requires a SIM card with unlimited SMS and/or data. But in France, they are pretty cheap (~15€ per month)

Power

Solar powered appears to be the best (only) choice.

This solar module looks like what I need but I have no idea if that is too much or not enough?

Is there any way it can be cheaper?
Have you got any advice regarding the installation of the solar panel in order to maximize its efficiency?
Is there any warnings regarding the rain?

Sensors

Camera

Apart from the cheap camera (which goes with the 3G/GPRS shield), there are plenty of cameras available.

Again, way too much choice here. I don't even know where to begin... What do I have to consider?

Wind Speed + Direction

I've found these weather meters and even a tutorial (in French) with some help regarding how to connect the sensors to the board and read both values.

There is also some code for Arduino.

This appears to be the easiest part (at least for me) of the station.

Reading values from the Wind Speed sensor is as easy as incrementing a counter and reading values from the Wind Direction sensor is as easy as doing a modulo.

Some other questions

How do I prevent the station from being struck by a lightning?
What is the best material to use for the support? Wood? Steel?
What kind of enclosure can I use to prevent the station to heat too much?

Thanks

Note: I plan to update this post with your answers and hopefully a full tutorial on how to build it


texts: Identity of electronics component needed

texts: I can not figure what the white colored component labeled "5W3K9J" is. The "3K" part seems to indicate a 3K resistor. Could some one please verify this?


texts:
The equation below states the following:

P = G * v^2(t)

W = Integral (P) over all time

Paverage = W/(time period)

Can someone explain the time period (1/2t)? Why is it not 1/T (T = period of the time varying signal)?


texts: LED RGBW Lighting, Will this Design work?

texts:
I've got this schematic for a very small lighting setup for my basement. The goal is to have two fixtures that have red, green, and blue lights that can be controlled with knobs on a Separate controller, (one brightness knob for each color on each fixture) and also a set of white LEDs in each fixture that can be strobed at different speeds (one brightness knob and one speed knob). The plan is to use potentiometers for all the brightness and have the output of each go to 4 LEDs in parallel with a resistor for each one.
      For the strobe I was going to use a 555 astable circuit with a very small capacitor so it goes fast, then link the output to a transistor so to impose the on/off signal to the output of a  brightness potentiometer.

Any help with why this wouldn't work, what pots to use, or how to hookup the transistor right would be great.

LEDs are rated to have a 200 ohm resistor at
9 volts, Thats all I know.

Here is a rough sketch of the schematic.


texts:
For some reason when current biasing a very simple BJT common emitter circuit in ltspice, the current source needs to produce a massive amount of voltage. Why would this be? I'm biasing it at a Q point of 3mA

Here's the circuit
https://www.dropbox.com/s/is0iqjgewsd9lrk/currentbias.asc?dl=0

Here is a picture of the circuit


texts: Differential pairs or single ended signals for 1m cable

texts:
I have one control board and 3 additional boards for the power electronics, that send and receive data from the control board over a distance of ~1m (3ft). All signals are single ended.

I have to design the boards, but I'm not sure about the best connection method.
I could use D-Sub cables, ribbon cable and so on. That's not the problem.

Each of the 3 additional boards receive following signals from the control board:

10x PWM @12kHz
CLK @16Mhz
4x digital signal lines @low frequency (turn on the boards etc.)
+15VDC @50mA
-15VDC @50mA
+5VDC  @200mA
Ground
Analog Ground

And in the other direction, every power electronics board send following signals to the control board:

10x 1bit stream @16MHz
5x analog signals -10V to 10V @2mA

Now I'm unsure if I send them as single ended or use differential line drivers and receivers. What would you do?

That would be at least 34 lines as single ended with one ground and one analog ground connection. Where would you put the ground lines, between each signal? Then we're talking about ~70 lines per board. And could I use a differential pair cable or should it be straight ribbon cable? Or do know a better solution? 2 cables per board would be also okay, but not ideal.

If I use differential drivers and receivers for the PWM, CLK, analog and 1 bit stream signals, we're talking about 52 signal lines (26*2) + 4 slow digital lines + power and ground per board.
3 68 pin D-Sub cables with twisted pairs should work in this scenario or not? In my opinion this is the best alternative. But also the most expensive one, because I need 15 differential line drivers and 15 differential line receivers. 3 drivers and 12 receivers (each 4 channel) on the control board and on every power electronics board 3 receivers and 4 drivers, if I make every signal as differential pair.
So is it necessary to use differential pairs? Maybe just for particular signals to reduce the number of ICs?

Thanks for every advice and your help :)


texts:
I want to use an atmega328p with nrf24l01 + wireless module and communicate it with an arduino nano with nrf24l01 +.

My question is this, if I use different frequencies in the microcontrollers, will there be a problem?

Arduino nano goes to 16MHz and the atmega328p I want to put 8Mhz internal or external or maybe 12MHz since I feed it with a battery to [4-3] V.


texts:
As a newbie to hardware design, I'm having some trouble picking components. I want to switch a 24V AC Solenoid valve using a triac.
According to my research/experience, transistors heat up during use. However, I can not figure out what is causing this heating. Is it the small current at the Base that gets converted into heat? Because the collector and emitter will just act as a closed switch and no power will be lost there right? If not, what is causing energy to be converted to heat here?


texts:
hi for NPN transistor normally Collector will be connected with Vcc, resistor then LED.
and Emitter will be conencted to Vss. So whenever voltage applied to base LED illuminates.

however when Vcc connected to Emitter and Vss to Collector (the rest remains, LED polarity changed) LED illuminates too when there is a base voltage.

any idea? as far i know NPN conducts from C to E only.

thanks.


texts: How can I design a 12V DC UPS circuit using NMOS?

texts:
I have an NMOS with me so I tried to design this 12 V DC UPS circuit after looking at another similar PMOS circuit, but when I open the dc switch, the output is 18kV!! What is the problem with this circuit?

Update:
I remove a pull-down resistor, and now there is no simulation error. I also tested it on the breadboard and it seems to be working with a 9V battery. I have yet to buy a 12V battery.

Background:
My apartment has an automatic generator backup (yay!), but the power goes down for around 10s before it powers up. A similar thing happens when the power comes back online. On a few days there is a large number of power cuts and comebacks. I use a direct fibre router which takes around 3-4 mins to start up and so I wanted a circuit like this. The router uses 12V power, so I plan to use a non-rechargeable or small lead-acid battery.

Similar PMOS circuit:
P channel mosfet battery charging/power selection circuit help

Circuit I made:

Multisim Live: 12V DC UPS


texts: Produce a signal on a wire with a limited range

texts:
Given a setup such as the following:

Is there a reliable, cheap (say, around £20 in parts for each node) way to produce a signal at S, so that detector 1 can see the signal but 2 cannot? The distances involved are not huge - say 10cm between each detector.

I have a couple of thoughts on how this might be possible, but I can see downsides with both:

Some kind of TDR measurement - while this could be ok with long distances, with distances of a few centimetres the timings become ridiculous (and thus very expensive.)
A high frequency carrier that becomes suppressed after a short distance due to the skin effect. This sounds much more promising, but the frequencies I would need are in the hundreds of Mhz, which again become expensive to produce and detect.

It may of course be that what I want to achieve here isn't possible with these constraints. I'm happy to accept that as an answer if that's the case, but wanted some other input in case I was missing anything in particular!

(For those interested in the specific application, it's a model train track. I'm trying to devise a system of determining if a particular locomotive is in a particular section of track without resorting to the traditional method of isolating the track into blocks. S here would be some form of device clipped to the track, and 1 and 2 would be the locomotives.)