texts:
I’m planning low-side sensing with the Allegro Two-Wire Hall-Effect Switch (A1190LUBTN-T) and I’d like to confirm my resistor selection for Rsense.

Current is 2-17mA and my ADC range is 0-3.3V.

V=I*R:  3.3V = (.017A) * (Rsense) gives Rsense = 194 ohms.

P=I*V:  P = (.017 A) * (3.3 V) = .056 W

So, this 220 ohm 1/8 watt SIP-11 resistor array 4611X-101-221LF should be just about perfect?

Thanks!


texts: Metastability error propagation with flip flop

texts: I do have a confusion regarding the metastability resolution  using flip flops , I know that I should add synchronizer of two or three d-flip flop to guarantee a safe transmission  at clock domain crossing boundaries, but  my confusion is that  the output of metastability is unpredictable, it might lead to high or low level, and that output then will be propagated to the  rest of the circuit, so how can the second or the third flip flop catch the right value to be transmitted , if the first flip flop is always at metastable state and might settle in a wrong level ?


texts: Newbie transistor question, trying to understand

texts:
My background: I have years of programming experience and have always tinkered. I own lots of components and have built many a circuit using various arduino microcontrollers (love them because I can program them with a C-like language!) - but most of the circuits I've built are because I've read a tutorial, and followed directions, without ever understanding the "why's" of most parts I've used.

I understand the concept of a relay - powering a relay to switch a higher load power on and off (basically).

I also understand that transistors can be used in the same manner, although to a much much lower degree. I've used them in the past, again, following online instructions or guidance.

This time, I'm trying to go off script and build something of my own, and I'm at the limit of my knowledge and googling has stopped giving me any help. So, asking some experts here to help me understand the how and why of it.

I'm building a toy for my cat, which uses an accelerometer to detect when it's moving, and after it stops moving for a bit, it is to jump/move/shake/etc. I'm doing this by mounting a shaft inside a cylinder, and using a tiny DC motor, spinning the guts of the toy around the shaft, in essence, turning the entire thing into a large vibro motor, but with much more force.

The motor pulls 60mA of power, more than my Arduino can supply on one pin. So it needs to be switched. Enter my transistor.

The code runs, the toy "works" but the motor never turns on. No tools to build a schematic so here's a simple text breakdown of the circuit.

Powered by 2 LR44 button batteries, about 3.1v total.
Battery + goes to power arduino, and splits off into the collector of the NPN 2222 transistor.

The emitter of the transistor connects to the motor. The other lead of the motor to the battery ground.

Arduino pin 3 connects to the base of the transistor, with a 560ohm resistor in between. I found that value using an online calculator.

When the arduino turns on pin 3, testing with my multimeter, this is what I find:

Voltage into collector from battery is about 3v

Voltage into the resistor leading to the transistor base is about 3v.

Voltage out the resistor into the transistor base is about 1v, which seems right given the numbers the calculator was showing me and the saturation voltage for the transistor.

Voltage out of the emitter to the motor? I see it peak at about .3 volts or so. The motor is only on for short bursts (half a second) so its hard to say, but it's obviously nowhere near enough to run the motor.

What am I doing wrong? I'm obviously fundamentally misunderstanding something and either have something wired wrong, or... I don't know?

Thanks for any input.


texts: How to use a Piezo ShockSensor and an op-amp practical integrator?

texts:
I have made this circuit :

Once I apply a shock to the sensor, I get this result on the scope :

CH1 (yellow) : piezoshock output
CH2 (blue) : LTC6240 output

Here is the spec of the piezo sensor :
https://www.murata.com/~/media/webrenewal/products/sensor/shock/healthcare/pkgs_spce_00gxp1_en.ashx?la=en-us

What we know :

The piezo has a 390pF capacitance (+/-) 30%.
The piezo gives 0.35 pC/G (0 to 50G)
The LTC6240 has a 3.3V+ to the Power+ and 0V to Power-

Now I am trying to understand how to calculate the gain of the integrator from the circuit above and figure out what are the G's from the mV at the output.


texts: Contour (curve) selection in the Ampere's circuital law

texts:
I need help understanding Ampere's circuital law. Consider a square shaped iron core with an N turn coil on one side. Let each side of the core has the length a an has equal cross-section. The textbook approach is to take a closed contour passing through the middle of the core. All magnetic flux is inside the core, so we have (given the coil current I)
NI = aH + aH + aH + aH
But what if I take a contour that pass inside the coil and then goes outside? Outside the core there is no (or very little) magnetic field, so
NI = aH + 0
The two equations do not match. What is wrong?

Update
After reading comments and thinking on the problem I have advice for future readers.

Magnetic flux concentrates inside the core. This is true enough to assume that flux is constant along the core, but not enough to assume that field in the air is zero.

From Ampere's circuital law we may conclude that H field must be stronger in the surrounding air that in the core to satisfy the law for different contours. B field on the other hand is much stronger inside the core than outside because it is proportional to the flux.

I have modeled the problem in the FEMM and attach supporting figures below. If someone wants to model it himself, be careful not to saturate the core; otherwise you'll get disturbed field distribution.


texts:
I bought a variac at a garage sale a few months ago and I've played with it since then with a 40W incandescent desk light.  Now I want to use it for the incandescent house lights in a small theater.  About 1000W total at 120V.

I don't have any official specs.  Any guesses on maximum power capability?

Edit:


texts: Reconnecting a rewound 110vac motor to power

texts:
Motor is (about) 5hp 110vac and powers a a table saw.
Motor was recently rewound but previous owner did not reconnect to the power cord.
There are no info plates on the motor to help w/ reconnecting.
There are 4 wires coming out of the motor in two pairs. One pair is 1 black wire and 1 white wire, the other pair is 1 black wire and 1 green wire.
The wires on the power side of the connection are a typical black, white, and green which go to the power via the on/ off switch on the front of the machine.
So I need to know which wires on the motor (right in photo) connect to which wires from the switched power wires (left in photo)
Motor wires: (on right in photo)
black, white, black, green.
Power wires from switch:
(On left in photo)
black, white, green.
Any help appreciated!


texts: Obtaining a triangle wave from a square wave using a LM324N op-amp

texts:
I am generating a square wave with a 555 timer chip and I am trying to obtain a triangle wave from the 555's output by using an op-amp (LM324N) as an integrator. The op-amp is in single power supply mode with pin 4 (V+) connected to Vcc (+5V) and pin 11 (GND) connected to GND. At first I thought it might be because I am saturating the op-amp's inputs, but then I measured the 555 output with a digital multimeter and it indicates that when the 555 OUTPUT goes HIGH it puts out about 3.5 V. In the initial configuration (blue in the drawing) the LED1 pulses as it should along with the 555 OUTPUT but the LED2 (op-amp output) is constantly off.

Then I inversed the polarity of the LED and wired it to Vcc instead of GND (as seen in red) and it stays always on, regardless of 555 output.

The Op amp inverting input is connected via a 220ohm resistor to 555 OUTPUT and via a 10 nanoFarad capacitor to op-amp's output (pin 1), the non-inverting input (pin 3) is connected to ground.

What am I doing wrong here? And how can I get a triangle wave with an op amp from the square wave output?


texts:
The wired wall control panel in my garage has only 2 wires connected to it.
Yet somehow it acts different when I push the big "door" button than when I push the "light" button or the "lock" button.
That pair of wires is connected to the overhead automatic garage door opener.

Many different overhead automatic garage door openers and many different wall control panels are all compatible with each other.
I suspect they are compatible because they all discriminate between the buttons in the same way.
What is the name for that way?
If there are several different, incompatible ways or protocols, used in actual garages, what are the names of those ways?

(It shouldn't matter which particular door opener I have, because I would like to know the name(s) of the way(s) used by most door openers, even if that's not exactly the same way my particular door does it. But just as an example, I currently use a
Chamberlain LiftMaster garage door opener
).

Here's a picture showing some examples of apparently compatible 2-button and 3-button wall control panels from 2 competing companies (and a few incompatible ones),
from the BlueMate.com website:

Like many other people, I'm designing and building a gadget connected to those same 2 wires that tells the automatic garage door opener to roll down my garage door for me when I drive away but forget to roll it down.
(
Debugging a garage door opener circuit with an optocoupler and mosfet ;
Activate garage remote via an Arduino ;
shorting a remote control pushbutton with GPIO and a transistor ;
etc. ).
It would be nice if my gadget uses a standard method that works with many or most garage doors.
It would be nice if my gadget could also activate and deactivate the overhead light the same way the wall control panel does it.

What is the name of the protocol(s) used to let an automatic garage door opener know which button I've pushed on the wall control panel?

I'm looking for an answer more like "It's called the HART Communication Protocol; the main varieties are ..." and less like the well-meaning posts that suggest something like "Just look at the signals with an oscilloscope, and assume that if your prototype works in your house in an ActiveX control in Mosaic Netscape, it will work for everyone".


texts:
i tried to calculate the cuurent that flow into 2 trnsistor that conect in line. the drain of the first is conect to the source of the other. and they conect to the same Vd.
one of them is l1=1010^-4 cm but the first is short l2=0.510^-4.
i need to find the equation between Vds( the total of the 2) to the cuurent(that coomon becuse they in line). and to guess that after the Threshold voltage the current is steady.


texts:
I had a question in mind. I was reading "Design and Analysis of Integrated Circuits" by Gray and Meyer... In the edition 5 there is an analysis of a Low power OpAmp NE5234...
In the second stage of Amplification an unbalanced differential pair is used. I wanted to know why is that? Although it might not have any effect on voltage gain but it might introduce some other voltage offsets...
Designer could've used a symmetrical structure, why it hasn't been done so?
Thanks in advance...

P.S. There is a picture from that second stage.


texts:
I am designing a footprint for the UJ2-AH-SMT female USB connector for use on a PCB. I have been following their datasheet for the recommended PCB layout drawing. There are two small holes underneath the pads, I assume to help line up the connector on the board. For the dimension of the holes, it says "2-⌀1.30". How big should I make my drill hole/pad size so that it is the best fit for the connector?

Picture of PCB layout:

-Ben


texts:
The input is a current source (photomultiplier), and the output is connected to a charge amplifier (I belive).

I tried to draw the schematics from the circuit board, but I don't know what the three-leg grey components are (transistors I suppose ?) and I am not sure my schematic is right.

I suspect it is a transimpedance amplifier, but I don't understand how it is powered.

Schematics and picture link


texts: What are the odds of a miscalculation in an Arduino?

texts: I am running an experiment using an Arduino that requires several million calculations per second to be performed by an Arduino. I was wondering the odds (if any) that one of these calculations is wrong, and how I could prevent such an error?


texts: Can capacitors be exposed to temperatures above the max. operating temp?

texts:
I have an NVIDIA GeForce 7300LE graphics card that's having problems (see here), and I heard about baking the card to restore old solder joints.
The thing is, this involves putting the card in the oven at 385 oF (200 oC) for 10 minutes and the capacitors on the board are rated to 105o C operating temp and I don't know if they would be damaged by the high temps.
Would the 385o temps damage the caps or plastic connectors on the board, or would it be fine?

Thanks!

EDIT: Well, since I needed to replace that card anyways, I figured I would try it and see:

I heated it in my toaster oven, to a max temp of 250o C for about a minute, and an average temp of about 200o C (not counting warmup and cooldown)
the board was not damaged in any way, and all the plastic connectors survived, but...
when I plugged it back in my computer, I got crazy patterns of flashing lines across the screen

I think that the temperature might not have been stable enough to keep the capacitors from frying (it was a toaster oven, I guess I should have used something with more of a good temperature gauge) Ah well, I guess it was worth a try. Time to go to the local computer parts shop and get a new graphics card :)


texts: Why won't zones flood into vias or other plated through holes that are part of a footprint in Ki-CAD

texts:
I am using KI-CAD.  Visible in the picture is a GND_USB plane (yellow) on layer 2, and also the top layer (red).  I have a QFN package with an exposed pad in the center.  For some reason the ground plane won't flood into the thermal vias.

In the picture you can see that the ground plane floods over some other vias.  It just won't flood over the ones that are part of the SMD footprint.  In general I can't get zones to flood over any plated through holes in any footprints.

Each via in the footprint shows what net name is assigned to it from the schematic.  They all say they are assigned to GND_USB (the same as the plane).

The vias are defined in the footprint as plated through holes, and exist on all copper layers.

What might be possible causes for why the ground plane won't flood over vias that are part of a footprint?

Note that the plane is staying exactly 20 mils from the vias, which is the clearance setting for the plane (zone).  I confirmed this by reducing the clearance and watching the flooding get closer.  So apparently the zone thinks it needs to maintain clearance from those vias even though they are the same net.

EDIT:

Well Seth found the setting.  The problem was in the pad properties in the footprint.  For some reason the "Pad Connection" property was set to "none" by default.  I changed it to "Solid" and it works now.  That was a little confusing because all the SMD pad types do connect by default so I never bothered to notice that setting.


texts:
We're trying to set up ThreadX for the first time and we're trying to understand all the timer settings that.
Although there are basically two constants that we need to set, they are not really clear to us...

Our MCU is the STM32H7, and we're using CubeMX to generate the initial code. We've set the core clock to 400MHz, and the Timebase Source was set to Timer6 - Timer6 Interrupt Period = 1ms

ThreadX timer setup is defined in tx_initialize_low_level.s, and there are two settings:

SYSTEM_CLOCK: Should be the same as the core clock
SYSTICK_CYCLES: ???

In the manual there is no clear information on what this setting should be, only that by default it is 10ms.

Should we set the SYSTICK_CYCLES to 1ms like the timer interrupt? What is the purpose of the setting? Is there a difference between this setting and the hardware timer interrupt?
Are there any 'best practices' for ThreadX timing settings?

Thanks in advance,
Trout


texts: How to know the size (W/L) for a circuit to source or sink a minimum of 4 times as much current as a minimum sized conventional inverter?

texts:
Consider the tri-state NAND below (i.e. if EN is high, output is NAND of A&B; if EN low, output is
floating. Assume EN and ~EN always track). Show work.

a) Label each transistor with a size which would allow the circuit to source or sink a minimum of 4
times as much current as a minimum sized conventional inverter through its output Y.

I dont know how to know how to get the sink or source, is there a formula for that? like if the size (W/L) = 2, then what is the current?, would size = 4 double the current of size 2?


texts:
I've been using the AD620 to offset and scale up a tiny AC signal for my project.

The AD620 is set up in the following way:

Rg= 6.8kOhms (between pins 1 and 8)
Vin = 0.123V rms AC signal (pins 2 and 3)
REF = 2.5V (pin 5)
+Vs = 5V (pin 7)
-Vs to Ground (pin 4)

Even though the gain is supposed to be G=49.4k/Rg+1=8.26 and I'm supposed to see an output (pin 6) of: V=0.123*8.26=1.02 V-rms, I get no AC output signal at all.

What I'm getting is a DC 1.6 Volts signal (which, I suppose, comes from Vref).

Do you guys have any idea of what's going on?


texts: Schematics for device, which reacts to water?

texts:
After failed attempt to combine a resistive wetness sensor with a multivibrator
( How to trigger multivibrator (or similar) from collector? ), I'd like ask a direct question.

What could be schematics for simple device, which has parallel wires in a textile with approx. resistance of 1MΩ when wet (and zero conductance when dry) as a sensor and some sound generator as a 8Ω speaker output? If possible, done with discrete transistors and other widely used cheap components (no ICs)?

Working voltage no higher than 5v DC.

I will still try answers to the above mentioned question, but I have a feeling,
that the design I tried there is badly flawed.


texts: N-Channel Mosfet has full Voltage on all Pins (IRFZ44N)

texts:
I recently wanted to use a IRFZ44N N-Channel Mosfet (up to 50V) to control a 50 LED Panel with a current of 35V.

The Panel itself uses 230V AC which goes to a rectifier (?) which outputs 35V DC and powers the LEDs successfully.

I then cut the cable going to the negative terminal of the rectifier, connected the part coming from the LEDs to the Drain and the rectifier to Source.

Problems I have and things I found out:

When I power the lamp, I can't control the state of the LEDs (LEDs always on)
When I measure the power, all 3 Pins (Gate, Drain, Source) measure the full 35V (full output of the rectifier)
When I tested the Mosfet with 3v pins from my Raspberry Pi, it worked so I guess the Mosfet itself is not broken. Also tested 3 of the same Mosfets all with the same results
I added a 10kOhm resistor between the gate and the source. It didn't change anything and the LEDs stayed on
The Mosfet itself is rated for 50V so it sould be able to handle my 35V

I am obviously missing something, but what?


texts: How to calculate the variance of a discrete signal?

texts:
Explained as:
'the variance of the signal is the mean of its squares minus the square of its mean'

The mean of its squares (average of instantaneous power of all samples) minus the square of its mean (all samples added together and squared).

$$
\sigma (x) \equiv E[x^2] - (E[x])^2
$$

Im not sure if my script correct?
And what is E in the equations for variance?

%%
clc
clear

%% Signal
x = [ 0  5  5  0 -5 -5 ];
fs = 6;

%% Power Calculations

% Instantaneous power of each sample:
ins_pwr = x .^ 2;
disp(['Instantaneous Power (w) = ' mat2str(ins_pwr)]);

% Average power of signal:
avg_pwr = sum(ins_pwr)/length(x);
disp(['Average power (w) = ' num2str(avg_pwr)]);

% Variance of the signal:
var_pwr = (sum(ins_pwr)/length(x)) - (sum(x)^2);
disp(['Variance (w) = ' num2str(var_pwr)]);

Output:

Instantaneous Power (w) = [0 25 25 0 25 25]
Average power (w) = 16.6667
Variance (w) = 16.6667


texts:
Consider an IGBT chip within a power module.

The top surface of the chip is often metalized by aluminum (with approximately 5 microns thickness) to bond some aluminum wires into the chip; I am hazy about the chip bottom-side metalization.

Which material is used to construct the bottom-side metalization and how thick is it?


texts: How many SMD 5630 LEDs can I power with 12V 1A power supply?

texts:
I am new to this and have what is probably a newbie question.

I am using SMD 5630 LEDs from a strip that I am cutting off and wiring each LED individually. They will be wired in parallel and I am trying to understand how many I can power with a 12V 1A power supply. (Edit: The power supply converts to DC current.)

From the specifications I found each LED requires 3.6V at 50 mA and using an Ohm's calculator I found I need 22 ohm resistors. I just don't understand how to figure out the maximum number that I can support. Could someone explain, speaking slowly and using small words? :)


texts: Corrupt, unreadable sectors on an SD card

texts:
I have several SD cards with a damaged filesystem. As I analysed them with different hex editors (active diskeditor, wxhexeditor, and bless) I found unreadable sectors at the beginning of the filesystem especially in places where you don't expect a high write endurance.

One card has errors after the FAT boot sector (>243), and another one has errors in the hidden sector area (150-230). These sectors seems to have a hard error since I can't even read data from them. Neither with the command sudo dd if/dev/sdd bs=512 skip=249 nor with hex editor tools.

The main concern I have is when I format the SD cards with the SDFormatter V4.0 in quick format mode, the bad sectors are gone and everything works fine. This disagrees with the assertion that the concerned sectors had hard errors since the quick format mode only initializes the filesystem without initializing the card on low level.

Bad sectors only can be excluded from the S.M.A.R.T register on the SD card, and this requires low level formatting.

What can cause such a failure? The signal integrity seems to be OK. Voltage, threshold levels, and the timing are also fine. One thing I can’t really check is the firmware. Is it possible to get the SD card goes bad only by messing with the firmware?

One of the cards was sent to the manufacturer. They found out that the card has no errors. But they could not tell me what the problem could be. Has someone an idea how to find out what problem it could be? Has anyone dealt with a similar problem?

Operation Mode:

CLK=13 MHz
SPI
FAT16

Here are some facts about the SD card and its usage:

Supports wear leveling
High Level Cell 2 GB
Hyperstone S6 Flash controller
Used at normal conditions (room temperature)
MTTF weeks to several months
Only a few gigabytes (approximately 3 GB per month) will be transferred to the card.


texts: What NAND gate chips should I use to create a simple computer

texts:
I have been reading the bool 'The Elements of Computing Systems' and I have designed a circuit for the computer that will use 1232 NAND gates, which assuming that there are 4 on a chip, is 308 chips. I believe that this number of gates, whilst still a large amount, is in the realm of possibility.
The issue if that I do not have much knowledge in the electronics, I am more into the computer science side of it, and i know that these logic gates are, unfortunately, not perfect. What should I look out for on the datasheets of these gates for my uses?
Any help would be greatly appreciated!


texts: Using Microchip's dsPIC33E USB Starter Kit

texts:
I'm a student and I'm starting a project in which I'm working with the Microchip's dsPIC33E USB Starter Kit.
I used some samples taken from this site
for initiating, sending and receiving packets. There is no screen in this board, so I'm printing what I need on the computer screen with a terminal software IVT VT220.

My first problem is printing more then one line to the screen - if having 2 print commands in the same code, it'll print only the first, then will do the rest of the code, just without the second printing command.
For example this code:

// some code
putrsUSBUSART("first print");
putrsUSBUSART("second print");
//the rest of the code

will print "first print", and then will do the rest of the code.

The second problem I have is sending and receiving messages in different modes. When I'm using loopback mode, I'm able to transmit a message and then receive it. By checking the rx register it looks like the message has been transferred correctly. However, when changing the mode to normal mode and doing exactly the same process, it still looks like the message I've received is valid (although working with one device only! So it suppose to work fine only in loopback, not in normal mode. or maybe it doesn't work at all in both modes?).

Any suggestions why this things happen???


texts: Capacitor Ripple Current - Frequency coefficient

texts: I am designing a motor controller with a 11A max start load and 3A max continuous load. Looking for capacitors I found in this datasheet a "Frequency coefficient for ripple current", what is that and how am I supposed to use this in calculations.


texts:
I'm messing around with some servos and one by one they stop working.

I've got a Raspberry Pi to which I connected a pca9685 servo driver board which in turn connects to 3 of these cheap servos. I got it running with this example code in Go. I've edited the example code to my liking, but I didn't change the basics of moving the servos. I kept the same minimum and maximum pulse width.

Now after messing with them for maybe 15 minutes one stopped working. I rebooted the pi and switched the connectors of the servos around to be sure it wasn't a fault in the code, the pi or driver board. One servo just stopped working. I figured it was just bad luck and moved on. After another 15 minutes of moving the other two servos around I disconnected and stored everything.

So a week later I'm trying it again, and now only one is working. Again I checked whether it was really the servo which doesn't work anymore. I switched connectors around and one out of the original 3 servos is now working on any connection, while the other ones never work, whichever connection I connect them to.

I'm powering the servos with 5v straight from an external charger (so not from the pi) and I never attached any weight to the servos (they just move in the air).

Following this trend I guess it's only a matter of minutes until my last servo will die. I don't care about these servos too much but I wonder why they break. I thought of any one or a combination of the following reasons why they could break:

I powered them with a too high voltage. This doesn't seem to be the case though. According to the product information on AliExpress they have an operating voltage of 4.8V-6V. The 5V from the usb connected charger should therefore be perfect.
I chose a wrong minimum or maximum pulse width, which breaks them. This could be. I just kept the default values as they were in the example here. But how would I know what are the correct values?
They are simply really shitty servos so it's only expected that they break within an hour. I guess this could be, but 2 out of 3 breaking within an hour is quite extremely shitty. To me at least.

I guess the most probable is that my code somehow breaks them. is there a way to know whether my code harms/breaks my servos?

Or do you have any other thoughts on this? Are there other reasons which could break them? All tips are welcome!


texts: Consistent Current Output From Batteries To DC Motors

texts:
I'm new to ECE and as a beginner project I've taken apart an RC car and attached an Arduino to the DC motors with an L298N module for control. The goal is for the car to drive a certain path with pre-programmed instructions. Everything is working, but I've noticed a constant drop in current (measured with a multimeter) as the motors run. This results in a lot of variance in the path the car takes. I'm powering the L298N with 8 double A batteries and powering the Arduino with a separate power supply.

Is there a way I can ensure that both motors receive steady current? If there is a better way to have the RC car consistently follow a set path or just tips you have for a beginner I'm open to any suggestions.

Thanks in advanced!


texts: Why reverse connected MOSFET start to turn on at Vgs<Vth?

texts:
The circuit shown below is implemented using two AO3400 N-MOSFETs.
AO4300 datasheet here.

The right-hand MOSFET is connected with normal polarity (Vds is positive),
while the left-hand MOSFET is connected with reverse polarity (Vds is negative).

The graph at below right shows the relationship between Vgs and Vds simulated by LTSpice.
The blue curve is for the normally connected FET, and
the orange curve is for the reverse connected FET.

At low Vgs  (<< Vgs(th)), the reverse connected MOSFET is conducting due to current in the body diode, resulting in a Vds value of about 0.6 V. As Vgs increases to above 0.4V , Vds starts towards GND level.

Why does the reverse connected MOSFET starts to turn on from about Vgs = 0.4 V when this MOSFET has about 1.1 V threshold?


texts: Can I2C protocol employ differential signalling for a longer distance?

texts:
As far as I understand some serial protocols use RS485/422 differential signalling to be immune to noise for long distances. We also know that differential signalling is about voltage levels and inversion i.e. it has nothing to do with the protocol itself.

Now I'm wondering why I2C communication link not extended by using two RS485 transceivers. I never saw any example of it. Is there a particular reason why I2C is always single ended?


texts: Are both of my SSRs broken or am I doing something wrong?

texts:
I have one side of a 125VAC panel-mount indicator connected to the AC load points of a solid state relay. The control points are hooked to a microcontroller with a basic program that switches the indicator on and off depending on characters that arrive on the UART.

The problem is that even when no voltage is applied to the control points, the indicator light still glows dimly. When I engage the control points, the indicator lights up brightly.

At first I thought the SSR had failed, so I ordered another one from a completely different company, but it's doing the exact same thing. Is it just a coincidence that I got two broken SSRs in a row from different manufacturers or (more likely) am I doing something wrong?

EDIT: Here are the SSRs I've tried.

ECE ESR5102401000 24-240VAC/10A 3-32VDC
SHZHE SSR-25DA 24-380VAC/25A 3-32VDC


texts:
I want to built a varying resistive load in LTspice. I tried using a resistor with Value defined as V=V(Vresistance) where Vresistance was the netname of the voltage source (pulsed). But this had some error shown below.

I want the value of resistor to follow the voltage waveform. Is there anyway to achieve this in LTspice.


texts: Finding resistance of unknown resistors in 2 pairs of parallel circuits

texts:
If you are given two pairs of parallel circuits, with three unknown resistors and one 4ohm resistor, with the total resistance totaling 3/4 ohms ; how are you supposed to find the resistance the unknown resistors? Do you just use the parallel resistor formula : rt = 1/r1 + 1/r2 + 1/r3 ... But using that formula will simply give you the total of the three unknown resistor's resistance, not the resistance of each resistors. How do you go about to solve for the unknown resistors. Note that the only numbers given are one of the resistor and the total resistance.
Thanks,
There's a picture below of the diagram

simulate this circuit – Schematic created using CircuitLab


texts:
We have had some issues with resonance overshoot from our 10W wall supply to a products LDO. The theory is that this overshoot will destroy the LDO once in a while rendering the product useless.
While investigating this I examined the difference between having the wall supply plugged in the wall first and then into the product and the other way around.
So when having the wall supply plugged into the product first, and then into the wall I will get this static on the supply input of the product (see first picture). Down to -5 V for a short time . Second picture shows how long before this small static event is before the voltage ramps up to normal on the product.
Is this problematic for an LDO with Absolute maximum input -0.3 - 6 V? Is there any way to mitigate this in the future?


texts:
I am trying to find the correct potting compound for a device that will sit on top of lead acid batteries. It will have SMTs, and we would like it to tolerate temperatures as low as -40. Because of this we need to make sure whatever compound we select won't break the solder joints when the device and potting compound get very cold.

What is the more important value to be concerned about when potting SMTs; Tg or CTE. I was recommended a very low CTE epoxy for our solution but am interested in hearing other opinions.

Options that I have considered are:
Hotmelt (fear it won't last)
Silicon (acid resistance??)
Epoxy (will it break SMTs off?)
Urethane (Acid resistance, will the higher CTE effect SMTs)


texts: How can I install mini aluminium heatsink to wireless card?

texts:
I am thinking about increasing txpower of the my wireless card. But I am worrying about the heat can damage my wireless card. My solution is installing aliminium heatsinks on the wireless card.
My wireless adaptor is TP Link WN722N V1.X. And I don't know that if my card support heatsinks.

Example for mini aluminium heatsink : https://imgur.com/a/hBvIeAK

Question: I don't know how can I install these mini aliminium heatsinks because my circuit card does not have holes for heatsink installation.

How and where can I create holes for heatsink installation at the following wireless card?

Or is there any way to install those mini aliminum heatsinks without creating holes on wireless card?


texts: What happens if a 12 V DC, 7-ampere-hour battery is installed instead of a 12 V DC, 4-amp-hour battery in the Schneider APC PRO550?

texts:
I have UPS APC Pro 550 and need to change its battery and its battery had capacity 21W @ 15 min-rate to 1.67V per cell @25°C (77°F), and what I found in local market is 7 amp hour and 9 amp hour.
First, I need to know 21W @15 min, etc. means what Amp hour?
Second, what are the consequences if a higher or lower capacity battery is installed?


texts:
As part of my current workflow producing a PCB layout I open my gerber files using gerbv. This allows me to switch on and off layers and check things are as they should be.

However I need to present the layout to some others in my team, preferably without needing gerbv. Currently I do this by offsetting all of the layers so they can be seen individually and then print to PDF.

This is pretty tedious and I cant help thinking there is a better way, so are there any gerber viewers that support the following.

View a stack of layers from each side of the board (Would be great if this was something like the graphical view OSH park creates - example)
Display each layer separately, without manual offset adjustment
Output to PDF


texts:
I measure a network's transfer function using a network analyzer and therefore have a set of complex data points, representing the network's gain and phase. I wish to fit a continuous, rational transfer function to my measured data to create a model of my network.
To find a discrete-time model, there is the "Frequency Domain Least Squares" algorithm:

http://robotics.itee.uq.edu.au/~elec3004/2014/lectures/Precise%20Filter%20Design%20(chapter).pdf

Several months ago, I found a PDF which presented a very similar method to estimate a continuous transfer function, but I don't remember where it is nor do I remember its name. I only remember that it was also a simple least squares algorithm as in the above link. Does someone have a hint for this?

Update:
Meanwhile I was able to recover the paper I mentioned. It is called 'Practical Transfer Function Estimation and its Application to Wide Frequency Range Representation of Transformers'. In my application, I am not dealing with a transformer but with some other passive electrical network involving RLC components, and I try to fit a transfer function to that. The network analyzer gives me some complex data for logarithmically spaced frequencies. I tried to use the method presented in the paper, but since my frequencies range from several Hz to several 100 MHz, the algorithm is unable to converge because the matrix A involves \$\omega\$, \$\omega^2\$, \$\omega^3\$ and so on - which leads to an ill-conditioned equation system, and therefore it cannot be solved. I wonder whether there are better algorithms than this, or whether this algorithm could be used, though, perhaps with some pre-processing of my frequency data.

Link to the paper I mentioned:
https://ieeexplore.ieee.org/document/252689


texts: I received a schematic with many inductors marked "600". These are small chip inductors for filtering spikes on audio and GPIO lines on a sound chip. The default value for the resistor is simply the Ohm. It would not make sense for the inductor to be 600 henries though. What value can I assume of these?


texts: How to connect five flex sensors to on esp8266?

texts:
I’m using a lolin nodemcu 8266. I was wondering if it is possible to connect 5 flex sensors to one node (to make a glove which detects finger gestures).

I’m an experienced programmer but new to electronics.


texts: Can you help me identify this resistor please? Is it 1.91 ohms resistor? In such case where would I find such resistor to replace this burned one?


texts:
What is wrong with the calculations below?

*This is not homework.


texts: Will this P channel Mosfet switch work from a 3v3 GPIO

texts:
I'm designing a circuit that I can reuse over again to switch loads of different kinds from around 8-30v and from around 0.5-15amp. Like a universal Solid state relay but I want my own custom circuit so I can put it on different PCBs.

I plan to interface this with a 3v STM32F GPIO

Here is my circuit:


texts:
I am trying to stop the RTC clock by setting the CH bit in it's second register.
I read the second register, mask the 7th bit to 1, rewrite this to the second register. But for some reason, this approach is not working.

I want to stop/start the RTC according to my needs. Can you guide me in this problem?

The schematic is:

My code is:

// LCD module connections
sbit LCD_RS at RB2_bit;
sbit LCD_EN at RB3_bit;
sbit LCD_D4 at RB4_bit;
sbit LCD_D5 at RB5_bit;
sbit LCD_D6 at RB6_bit;
sbit LCD_D7 at RB7_bit;

sbit LCD_RS_Direction at TRISB2_bit;
sbit LCD_EN_Direction at TRISB3_bit;
sbit LCD_D4_Direction at TRISB4_bit;
sbit LCD_D5_Direction at TRISB5_bit;
sbit LCD_D6_Direction at TRISB6_bit;
sbit LCD_D7_Direction at TRISB7_bit;
// End LCD module connections

unsigned short read_ds1307(unsigned short address)
{
  unsigned short r_data;
  I2C1_Start();
  I2C1_Wr(0xD0); //address 0x68 followed by direction bit (0 for write, 1 for read) 0x68 followed by 0 --> 0xD0
  I2C1_Wr(address);
  I2C1_Repeated_Start();
  I2C1_Wr(0xD1); //0x68 followed by 1 --> 0xD1
  r_data=I2C1_Rd(0);
  I2C1_Stop();
  return(r_data);
}

void write_ds1307(unsigned short address,unsigned short w_data)
{
  I2C1_Start(); // issue I2C start signal
  //address 0x68 followed by direction bit (0 for write, 1 for read) 0x68 followed by 0 --> 0xD0
  I2C1_Wr(0xD0); // send byte via I2C (device address + W)
  I2C1_Wr(address); // send byte (address of DS1307 location)
  I2C1_Wr(w_data); // send data (data to be written)
  I2C1_Stop(); // issue I2C stop signal
}

unsigned char BCD2UpperCh(unsigned char bcd)
{
  return ((bcd >> 4) + '0');
}

unsigned char BCD2LowerCh(unsigned char bcd)
{
  return ((bcd & 0x0F) + '0');
}

int Binary2BCD(int a)
{
   int t1, t2;
   t1 = a%10;
   t1 = t1 & 0x0F;
   a = a/10;
   t2 = a%10;
   t2 = 0x0F & t2;
   t2 = t2 << 4;
   t2 = 0xF0 & t2;
   t1 = t1 | t2;
   return t1;
}

int BCD2Binary(int a)
{
   int r,t;
   t = a & 0x0F;
   r = t;
   a = 0xF0 & a;
   t = a >> 4;
   t = 0x0F & t;
   r = t*10 + r;
   return r;
}

int second;
int minute;
int hour;
int hr;
int day;
int dday;
int month;
int year;
int ap;

unsigned short set_count = 0;
short set;

char time[] = "0000:00:00 P";
char date[] = "00-00-00";

char toggle = 'P';
char str[10];

void main()
{
   I2C1_Init(100000);                 //DS1307 I2C is running at 100KHz

   CMCON = 0x07;                      // To turn off comparators
   ADCON1 = 0x06;                     // To turn off analog to digital converters

   TRISA = 0x07;
   PORTA = 0x00;

   Lcd_Init();                        // Initialize LCD
   Lcd_Cmd(_LCD_CLEAR);               // Clear display
   Lcd_Cmd(_LCD_CURSOR_OFF);          // Cursor off

   second = read_ds1307(0);           // To stop the ds1307 oscillator
   second &= ~(1 << 7);               // Setting CH bit
   write_ds1307(0, second);

   Lcd_out(1,1,"Time:");
   Lcd_out(2,1,"Date:");

   do
   {
      second = read_ds1307(0);
      minute = read_ds1307(1);
      hour = read_ds1307(2);
      hr = hour & 0b00011111;
      ap = hour & 0b00100000;
      dday = read_ds1307(3);
      day = read_ds1307(4);
      month = read_ds1307(5);
      year = read_ds1307(6);

      time[2] = BCD2UpperCh(hr);
      time[3] = BCD2LowerCh(hr);
      time[5] = BCD2UpperCh(minute);
      time[6] = BCD2LowerCh(minute);
      time[8] = BCD2UpperCh(second);
      time[9] = BCD2LowerCh(second);

      date[0] = BCD2UpperCh(day);
      date[1] = BCD2LowerCh(day);
      date[3] = BCD2UpperCh(month);
      date[4] = BCD2LowerCh(month);
      date[6] = BCD2UpperCh(year);
      date[7] = BCD2LowerCh(year);

      if(ap)
      {
         time[10] = 'P';
      }
      else
      {
         time[10] = 'A';
      }

      Lcd_out(1, 6, time);
      Lcd_out(2, 6, date);
      Delay_ms(100);

   }while(1);
}


texts: What is the meaning of fault_reg = ram [address] in verilog?

texts:
input [3:0] address;
reg [3:0] ram [7:0];
reg [3:0] data, fault_reg;
fault_reg = ram[address];
data = fault_reg;

If the value of ram is 1010 and the value of address is 100, what is the value of data[0], data[1], data[2] and data[3]?

Does it mean data[0] mean bit No.0 = 0 of ram, data[1] mean bit No. 1 of ram = 1, data[2] mean bit No.2 = 0 and.....?


texts: What assumptions does the solenoid force equation make?

texts:
$$F = (N⋅I)^2⋅uA/(2g^2)$$

F = Force
I = Current
N = Number of turns
g = Length of the gap between the solenoid and the magnetizable metal
A = Area

Does it assume a solenoid of zero length and does it also make assumptions about the magnetic susceptibility or permeability of the metal it is attracting?
And is g the gap between the metal and centre of the solenoid or the end.


texts: I am trying to obtain the transfer function for a photodiode. Since I couldn't find any standard result online, I figured I would try to obtain it from the circuit equivalent shown below, but I am having some trouble with this. From what I understand, Ri and Ci are dependant on the incoming signal so I wouldn't be able to model this using set values for Ri and Ci. Is this true? Is there a standard result that I just haven't been able to come across?


texts: How to switch to a second power source if the first loses power

texts: I am trying to wire two power sources to one led strip. I need a switch or relay to switch between each power supply depending on which one has power coming to it, then once the first power supply loses power it will automatically switch to the other?


texts:
I'm finalizing my plans to make a physical control panel to interface 2 of my 3D Printers to an embedded Linux device.  (Just minimal physical controls since 95% of the controlling will be done via a web browser rather with physical buttons.)

Each printer will have it's power supply controlled by the mCU, and about 20W of LED lighting.

One printer is powered by an ATX power supply that is also powering the mCU with it's +5V standby power.  The other printer uses a non-ATX SMPS that has a PWR_ON pin similar to an ATX PWR_ON pin.  (IOW, floating or high = PSU off, low = PSU on)

My main concern is whether simply connecting everything to a common ground is sufficient to keep each PSU and the mCU safe as the two power supplies kick on and turn off.

Am I missing anything needed to keep the three main components reasonably safe?


texts:
I want to use MCP73833 as a charger IC with the ability to route STAT1, STAT2, PG to RaspberryPi GPIO.
Those are open-drain outputs and should be pull-up, according to datasheet. The datasheet also says that PG can't be pull-up to the MCP73833's output but only to the input due to IC's internal schematic.

My question: how should the pins be pulled-up correctly keeping in mind that GPIO has 3.3V level and MCP73833's input is around 5V?

RESOLUTION

Below is my final schematic. Thanks to Maple.


texts: Generating a midi signal from switches or digital logic

texts:
I have a control board I have wired up consisting of various buttons and momentary switches. (For an art project)

There are enough for exactly two octaves (C3 to C5). I want to connect these control voltages to some off the shelf board that will generate the correct midi notes for me, which I can then connect to a synth to generate the actual sounds.

So my flowchart is:
control board -> ? -> synth -> PA.

What exactly is the board called that goes in that space? Basically something that can convert switches / logic into a midi signal?

There must be something off the shelf that can do this.


texts: Oscilloscope ground clips sparks while connecting to power supply ground. I do understand The clip is connected to earth ground. But why does it not spark when I am powering a circuit of the supply?


texts: Standard parameters of a second order transfer function with some zeros

texts:
We already know that we can derive the parameters \$\omega_{n}\$ and \$\zeta\$ from a second order system which adopts the canonical form:

\$ H(s) = K\frac{\omega_n^2}{s^2 + 2\zeta\omega_n s + \omega_n^2}\$

How can I find the damping ratio and the natural frequency of a second-order system with one or two zeros:

\$ H(s) = \frac{K_1s^2 + K_2s + K_3}{s^2 + K_4s + K_5}\$

\$ H(s) = \frac{K_1s + K_2}{s^2 + K_3s + K_4}\$


texts:
I'm trying to read an analog input on a PIC18F65J11, and I'm having trouble. I don't think the pin is set up correctly because I'm getting a 0 for the value I read in, and the input is measured to be about 1V (but can get up to 3V). I want to use Here is my code:

#include "p18f65j11.h"
#include <adc.h>

/**CONFIGURATION **************************************************/
/* Device Configuration */
#pragma config XINST = OFF  // Turn off extended CPU instructions
#pragma config FOSC = HSPLL // HS oscillator will PLL that multiplies oscillator frequency by 4 (system clock is running at 16 MHz)
#pragma config FOSC2 = ON   // System clock selected by FOSC1:FOSC0 (used #config to set FOSC to HSPLL)
#pragma config DEBUG = ON   // Background debugger enabled; RB6 and RB7 are dedicated to In-Circuit Debug.
#pragma config WDTEN = OFF  // Disable watchdog timer.
#pragma config WDTPS = 8    // Watchdog timer poscaler select bits is 1:8 (not important b/c watchdog timer disabled).
#pragma config STVREN = OFF // Reset on stack overflow/underflow disabled.
#pragma config CP0 = OFF    // Program memory is not code-protected
#pragma config IESO = ON   // Oscillator Switchover mode disabled.
#pragma config FCMEN = OFF  // Fail-Safe Clock Monitor disabled.
#pragma config CCP2MX = DEFAULT // ECCP2/P2A multiplexed with RC1 instead of RE7 pin (doesn't matter b/c not using ECCP, which is pwm output)

int myVoltage;

void main(void)
{
    myVoltage = 0;

    // Configure clock registers (FOSC is set to HSPLL)
    OSCCONbits.SCS1 = 0;    // SCS1:SCS0 = 00 means use primary
    OSCCONbits.SCS0 = 0;    // clock source (CPU divider output) if FOSC2 is on (FOSC2 is indeed on from the #pragma config above)
    OSCCONbits.IRCF2 = 1;   // IRCF2:IRCF0 = 110 means the internal oscillator is set to 4 MHz
    OSCCONbits.IRCF1 = 1;
    OSCCONbits.IRCF0 = 1;
    OSCCONbits.IDLEN = 0;   // on SLEEP instruction, device enters sleep mode instead of idle mode
    OSCTUNEbits.PLLEN = 1;  // enable PLL (4x multiplier), so system clock is 4 * 4 MHz = 16 MHz
    // Basically, I've just set it to use primary oscillator, told it the oscillator is
    // 4 MHz, and told it to enable PLL so that my system clock is 16 MHz.

    // Initialize Port A
    TRISA &= 0;             // set Port A as outputs
    LATA &= 0;              // all pins outputting 0
    TRISAbits.RA0 = 1;      // set pin AN0 as input to read voltage

    while(1) {
        OpenADC(ADC_FOSC_8 & ADC_RIGHT_JUST & ADC_12_TAD, ADC_CH0 & ADC_INT_OFF & ADC_VREFPLUS_VDD, 0);
        Delay10TCYx( 5 );
        ConvertADC();               // initiate conversion of sensor1 @ AN0
        while(BusyADC());           // waiting to complete conversion
        myVoltage = ReadADC();      // read the result of sensor1 @ AN0
        CloseADC();
        printf("%i volts \n\r", myVoltage);
    }
}

What am I doing wrong or missing? I suspect it's the OpenADC() part that may be wrong. I've got it using Fosc/8, result in least significant bits, 12 Tad, channel 0 (AN0 pin), interrupt off, VDD as the highest limit, and 0 so that all analog pins are analog.


texts: Source of 5.5 Hz Noise showing up on ADC

texts:
I recently bought a ADS1115 ADC to use with my raspberry pi. It's getting signal from an amplifier, and I've been seeing this strange 5.5 Hz sinusoid (as noise).

As seen in the picture above, its about 5.5 Hz, roughly sinusoidal. A few observations:

Noise (5.5 Hz sinusoid) is present in my signal when ADC is connected to amplifier
When ADC is disconnected and input floating (with wire), noise is present (still 5.5 Hz sinusoid, less in amplitude).
When I ground the ADC input, I don't see the waveform

Any idea on what could be causing this? It's so low frequency and I'm totally stumped... I'm trying to figure out the source and then how to get rid of it... would appreciate any ideas!


texts: How do I program 2 CAN nodes to transmit continuously in succession?

texts:
Suppose I have three CAN nodes: A, B and C. We know that when two nodes transmit at the same time, the node that has the least SID will prevail over the bus and the other node will have to give the bus to the first node. What I would want to do is that node B and C will continually send CAN frame to node A in succession (e.g. node B -> node A, node C -> node A, node B -> node A). Can I just assign a lower SID to B than C and just do the following code snippet?

Node B

while(1) sendCANmsg(data, NODE_A, sizeof(data), RTR_OFF);

Node C

while(1) sendCANmsg(data, NODE_A, sizeof(data), RTR_OFF);

Inside of the sendCANmsg, here is the snippet:

TXB0CONbits.TXREQ = 1;  // Request Message Transmission
while (TXB0CONbits.TXREQ); // Wait until message is sent.

By the way, I'm using PIC18F25k80 in implementing this. I was just thinking that after node B sent the message, when node C is about to send its message. Node B will again win the bus arbitration thus giving node C no chance of transmission. So I remedy that I can only think of is to insert a small delay like:

while(1) {
    sendCANmsg(data, NODE_A, sizeof(data), RTR_OFF);
    delay_us(10);
}

Or am I wrong? :)


texts: "Chip Select Bar" - proper jargon or a place to have some beers at?

texts:
Today, I came across a data sheet for an ADC (cf. p. 2) including a pin list with the "barred" (i.e. overlined) letters CS, indicating negative logic for the Chip Select pin, followed by the name that had the word "Bar" spelled out.:

\$\overline{CS}\$ = Chip Select Bar

This seems strange to me. To this day, I have always called this pin "Chip Select" - and in writing, I might use "Chip Select (negative logic)" or something similar, and the only time I would probably spell out the word "Bar" would be when talking to the person who typesets the data sheet. Outside the context of typesetting, this rather sounds like a funny name for a bar where you can meet EEs after work. But - I'm not a native speaker.

Surprisingly for me, searching for the term "Chip Select Bar" produces tons of results, the first one being an application note by a reputable company where you can not oly read the words "Chip Select Bar", you even find a pin labeled "CSB" where I would have expected "!CS" in case the typesetting software wouldn't allow \$\overline{CS}\$. It's the very first time I see the letter B as a symbol for negative logic, and this surprises me even more than the spelled-out word "Bar". And in the application note, they are talking about an active low signal, aren't they: "CHIP SELECT BAR (CSB) - CSB is an active low control ..." (cf. p. 3).

Now... is it possible that spelling out the bar in the symbol for negative logic has really become a synonym for negative logic and even replaces "‾" or "!" as a symbol when a pin name is abbreviated, as in CSB? It appears that this habit might cause more confusion than it helps, doesn't it? Is the word "bar" really a commonly used synonym for "active low"?

Loosely citing The Doors: "♫ Well, show me the way. ♫ To the Chip Select Bar. ♫ Oh, don't ask why. ♫ Oh, don't ask why..."

P.S. Please excuse the title and my idea that I might get some beers at the Chip Select Bar; I actually intend to ask a serious question about proper jargon.


texts:
I am referring to CC2531 reference design from TI (http://www.ti.com/tool/CC2531USB-RD)
In the schematic diagram (and in the BOM), it is saying ‘ Not Mount’ for some components (resistors, capacitors, testpins etc.). I am new to PCB design and wondering what that means. How it impacts the PCB design?

Please suggest.


texts: Why is my half-wave rectifier output in mV when the input is AC 10Hz 100V?

texts:
I have made this circuit a handful of times in real life and it is giving me a positive cycle waveform.
Why is it not working now?
The input is taken from the IP Test point and ground and output is taken across output load resistor and ground.
The second image is the reference transformer with IP p-p 20V and OP p-p 60V.


texts: How to equalise highly asymmetrical rise and fall times?

texts:
This question is kinda similar to highly-asymmetrical-rise-and-fall-times, but I think that the data sheet is already suggesting that I'm at the optimum design.  Resistor changes were the answer to that particular question.

I have this:-

which produces this output that's fed into an Arduino digital input:-

with 1 V and 200 nS /div settings.  It's clear that the LM311P comparator is being thrashed beyond it's slew rate which is okay.  You can see the relatively slow rise time in comparison to the fall time.  The data sheet suggests a 500 Ohm pull up resistor.  That's about 10 mA of current which seems a lot for a logic circuit.  I'm assuming that as they've used the 500 value for their timing diagrams, this is the optimum value and maximises speed.  I realise that the rise /fall times are different on the datasheet, but is this the only reason for my asymmetry?  And if so, is there no solution to equalising them any better?  Even if a solution eludes me, I'd be happy with an explanation.

The reason for the output pulses not reaching the full 5V level as been asked.  The inputs to the comparator are white noise from the Zeners, which looks like:-

I don't think that it's oscillations, it's just too fast for the 120 ns switch time.  The Rigol's FFT display is naff so I can't accurately measure the spectrum /frequency.


texts: AVR-ATmega256 What is the use of PORTxn?

texts:
In AVR ATmega2560 microcontroller, there're 3 register for I/O port: DDxn, PORTxn, and PINxn

DDxn decide the direction of each pin while other two, according to the datasheet

PINxn toggle the value of PORTxn by written 1 into PINxn
If pin is input (DDxn is written 1), written 1 to PORTxn turn on pull-up resistor and written zero turn it off
If pin is output (DDxn is written 0), port pin is driven high (one) if PORTxn is written 1 and low (zero) if PORTxn is written zero

I don't understand what these term means: pull-up resistor, driven high and low. What is the difference between 2 terms. What do they do with I/O port and what is the use of them? Can anybody give me explanation and example.

I also don't know what is register used for store address for I/O. I means for input and output there must be some address tell where input data is stored or address tell where data is ouput. Furthermore, if 8 pin of one port is configured to be mixed between output and input then how the data of each bit of each pin is organized to be store in a register (which contain 8 bit)


texts: When to Remove the Ground Plane under SMD components for High-Speed Signals?

texts:
I'm reading TI's recommendations on routing high-speed signals. Most of the guidelines are common sense, but there's one guideline that I haven't read before: It recommends completely removing the ground plane below the mounting pad of a SMD component for high-speed differential signals.

I knew similar techniques are used in RF designs to minimize unwanted coupling and the impedance discontinuity it produces, so it certainly makes sense in digital designs. But in digital designs, this concept is not commonly mentioned. Correct me if I'm wrong, but my impression is that, in most digital design and EMI/EMC books, the most important concept is to create the most continuous ground plane possible - removing ground planes under SMD components isn't really an emphasized topic - so my assumption is that it's not always needed.

Question: When should I remove the ground plane under SMD components for high-speed signals? How common is it in digital designs? Is it always needed? Is it worth doing on every digital board?


texts: Can a voltage stepper work on "negative" voltage?

texts:
I'm working on a project in which I need to supply 2-7 V using a 5 V micro controller in order to power a torquer for a satellite project.

Since I want to be able to use the same torquer to turn in both direction I'm using a H-bridge (l293d) in order to reverse the voltage.

Now for my question, as the title says, will a step-up converter (Pololu U3V12F12) be able to step up a "negative" voltage?


texts:
I want to design something like this:
There is a button, an input pin, an output pin, a voltage input, and a voltage output.
If the button is pressed once while the device is off, it won't do anything.
If the button is long-pressed while the device is off, it will set the voltage output to high (it will short the voltage input and output together).
If the device is on and the button is pressed once, it will send a pulse to the output pin.
If the device is on and the button is long-pressed, it will turn off the device (cutting the power on the voltage output).
If it receives a pulse on the input, it will also cut the power.
I found the stm6600 chip but it does not quite do what I want it to do.
While searching online, I found a lot of advice about using microcontrollers. The thing is, I don't want to. I have the knowledge and the equipment to do so, but I don't want to use a uC just for this.


texts: Which is the most recommended sensor for sensing humans inside a rail passenger car?

texts:
I am thinking of an application which is necessary to know if there is and where someone is located, inside a rail passenger car or bus, for example, the problem there is many external factors such as external sunlight or temperature that could disrupt thermal sensors, creating many false positives. In case of cameras some objects, like seats or other objects difficult to "see" people in a determined place. Another point is it is a real-time application, it means, the amount of generated date from cameras would be almost impossible for processing.

I am thinking to use ToF sensors or mm-Wave sensors, however, I do not know if the seats or some objects could difficult or even make impossible for sensing human.

Someone has some idea or advice which sensor could be used in such an application?

PS1: It is necessary to sense someone before he/she seats, I was thinking to set some ToF sensors on the ceiling of the wagon, in order to see when someone is passing through, however, I do not know if the same ToF can see someone while they are seating.


texts:
I am trying to use Eclipse ARM plugin but it seems that there is no HAL library support for anything other then stm32f4.

Is it possible to add support for stm32f1 somehow.


texts: Why does attaching the case to the PCB ground plane cause the audio to cut out on my cassette player?

texts:
I bought a NIB (new in box) cassette recorder on eBay recently but have had problems with the audio from the start. The issue was that touching the dials could cause the audio to crackle, go quiet, or cut out entirely.
It took some time and a lot of triage to narrow the issue down to something unexpected. The problem is with the screw that connects the PCB ground to the case. The reason it appeared to be the dials was because the PCB was being nudged slightly against this screw (it was very confusing to locate this problem!).
Here is an overview of the PCB:

This is the point at which the PCB ground plane connects to the metal inside (the housing is all plastic):

The issue is when I add the screw here and begin to tighten it. Screwing it in enough to achieve continuity between the case and the ground plane does not create any noticeable distortion. But if I continuing to tighten it then the audio will begin to crackle, become very quiet, and then cut out entirely. This only affects the audio signal; the tape continues to play as the motor spins.

I tried adding a steel washer to ensure a good contact with the ground plane but it made no difference with the previous description:

I made sure that this was not a fault of the PCB due to pressure or flex. I flexed the board manually and applied pressure to the location where the screw would be with my finger as well as the back of my plastic screwdriver. The audio is perfect without the screw being present but this also remove all continuity with the case:

What I don't understand is why this only happens if the screw is tightened. Simple continuity with the case does not cause the audio to cut out. For example, the tape is playing just fine as I bright the ground plane with the case here:

This issue occurs whether the cassette player is powered by batteries or the DC barrel jack. The player also has an option to be powered by AC with what I think is an AC/DC converter inside (not visible in the photos).
I could use a non-conductive screw or a plastic washer to "fix" the problem but then the case is no longer grounded.
I am interested in a solution that solves the problem safely but I also want to u the audio cuts out only when the screw is tightened and not just from achieving continuity with the case.
I am new to electronics. Shouldn't the case always be connected to ground for safely in the event that it somehow becomes live?
UPDATE
I added a small piece of heat shrink between the screw and the ground plane contact to test for sure whether or not this was a mechanical issue. I was able to tighten the screw fully without any of the previously described issues. This does not appear to be a problem with mechanical stress around the area. Continuity between the screw and the case was confirmed as well as no continuity between the screw or case with the ground plane of the PCB when the heat shrink was used.

UPDATE
The answer provided by JRE indicated the cause of the problem. Sure enough, there was a large filter capacitor on the reverse side of the board that was just barely touching another metal standoff. The degree of which it touched probably changed as I handled the board but it would always short itself when the ground screw was fully tightened.
I bent the capacitor back and the problem went away. It was probably some kind of filter capacitor that connected up with the speaker; grounding it caused the audio to cut out.
I'm glad that I tested it only with batteries or my fused power supply connected. I guess that means that the chassis could have been live if I'd used the AC adapter?


texts:
I'm using the following VFD for a 3-phase AC motor:
ACS550 user manual

I want to monitor the power consumed by the motor and the actual rpm.

On page 28 and 78 it meantions:

• Analog output AO1: Frequency

• Analog output AO2: Current

It seems I can use these outputs to monitor the current and the freq.

But what is AO2 here in mA? Is this the indicator for stator current in mA?? If so how can I convert it to the real current??

And similarly is Analog output AO1 the actual rpm?? And how can I convert it to the real rpm?


texts: Which formulas do I need to calculate current of a 3phase induction motor

texts:
How can I know the current a motor would require to run at a given RPM.
Here are some values:

160 HP motor
325 volts
2300 RPM
311 ft/lbs of torque(not sure how useful this is)
induction motor
using a IGBT inverter to control PWM
3 phase

I don't have a extensive background with electrical engineering and I am not quite sure where to start. I found a Tesla Motors data which was logged it seems it uses about 1000 amps but this is in MPH not rpm. I am not sure what is the drive ratio on the Tesla drive train to calculate RPM. Furthermore I am not too sure how would RPM variance affect current (hence why I wanna know which formulas are use to calculate this)

Tesla Motor data: https://drive.google.com/open?id=0B_bX3Zu4zvgYX1RYYmR1RnZVUG8

Do I need to get somebody to measure Tesla winding resistance to be able to calculate it for Tesla Motors? Is there any other number I need that can only be gotten from a real/already built motor?


texts: Why aren't there any 400V ultracapacitors?

texts: I thought that ulracaps could be better than electrolytic ones for filtering after a bridge rectifier in a compact switching power supply due to their higher energy density. But, for some reason, I can't find any high-voltage supercapacitors on ebay or amazon. I could, of course, put a bunch of low-voltage ultracapacitors in series but that would defeat the whole purpose of a power supply being compact. Is there any reason why there are no high-voltage supercapacitors? There already are 5.5V ultracapacitors, which are basically two 2.75V caps in series, so why they can't go higher? Did I miss something? Are they hard to manufacture?


texts:
I have problem with identifying a SMD component. This component is a part of automotive module. It has 2 pins. One of the pins is attached to Vcc 12 V, and the other is attached to the circuit parallel with a capacitor.

I have tested it and has any continuity. So I assume this part is broken. On this part there is written ST E CH C632.

Can any one help me to identify this part?


texts:
Recently I ordered some tiny SMD MOSFETs (AO3400) I never paid any attention to ESD. After soldering several MOSFETs on SMD to DIP conversion boards for prototyping I noticed they didn't function correctly after some searching I found out that it is because of ESD.

I understand the gate pin is the most sensitive but what about drain and source, how does the sensitivity different pins compare? if I finally solder them on PCB and the drain is to be an output (to be connected to LED strips) do I have to provide ESD protection for this pin? What about touching the board? Is putting some glue or epoxy on the MOSFET any good?


texts: How can I build a 2 input AND gate 24VDC PNP inputs and 24VDC output?

texts:
I'm trying to build an AND gate that takes two inputs from standard 3 wire 24VDC PNP sensors and provides a 24VDC output.

I was thinking using some sort of diode resistor logic (link to circuit: http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/diodgate.html).  However, I can't get this to work because when the sensors are off, the output of the sensor does not pull the inputs of the gate to ground.

What is the best / simplest way to to this?


texts: Does this rfid reader work with the nfc ring?

texts: I bought a rfid rc522 and hooked it up with an arduino nano. The rc522 reader says it reads at a frequency of 13.56Mhz. The nfc ring is also at 13.56MHz but i can not get it working with it. The reader reads a card that came along with it so i know the reader is working. Any help?


texts:
This is another LED pixel project that I'm looking to power in a slighty different way. It's 110no. 5050 SMD pixels on a 300mm x 300mm board.
The long and short of it is that I'll use USB-C Power Delivery to supply 3A at 20V. The logic side of the circuit is all 3.3V, while the LED pixels are 5V. In total I have an absolute maximum of 6.6A worth of pixels.
To keep the PCB low profile, and to allow for better/easier heat disspiation, my idea was to use 3 or 4 integrated buck modules (e.g. TPSM84209) to power groups of pixels.
Is my understanding correct in that:

I can tie all of the grounds together (of the µC, USB-C and buck modules)? In that way, they all share the same reference and it means logic to the pixels will work?

The particular module I've linked (TPSM84209) will output 2A at 5V? My reading of the graphs (for Vin = 24V) suggests that at 2A it's about 80% efficient. Does that mean that if I draw 10W on a buck module, the module will draw 12.5W from the 20V supply, or 1.6A?

What additional drawbacks might there be with using multiple buck converters (aside from increase in cost and complexity)?


texts: What is this component, labelled as "RT" on the PCB?

texts: Can someone tell me the name of the below component? It is labelled as RT on the PCB:


texts:
Being able to thermally stabilize an LED is useful for any sort of high accuracy sensing application. I was looking for an LED module that would incorporate a thermistor and something to adjust the temperature like a TEC.

I was able to find this company: https://www.laserscom.com/products that have the three packaged together with a fiber optic connector coming off of it and am wondering if I can find more convenient options (In terms of location/availability). But overall, I'm finding it surprisingly hard to find anything like it. I tried looking in the different optoelectronic categories at digikey and looking at the product list for some big LED companies but really didn't find anything like it.

It seems like something that would exist based on reading application notes and datasheets of PID controllers intended to work in tandem (http://www.analog.com/media/en/technical-documentation/data-sheets/ADN8835.pdf). Am I just not using the right search terms to find it or are LED+thermistor+TECs typically bought separately and put together?


texts: 433 MHz Transceiver - understanding OOK demodulator parameter 'OokFixedThreshold'

texts:
I would appreciate some help to understand a parameter for this device https://www.semtech.com/products/wireless-rf/fsk-transceivers/sx1231h. I'm far from an expert at RF matters and this question has left me stumped - not even google has been able to help me out.
Section 3.4.12 of the data sheet speaks about the OOK demodulator. In order to effectively set-up the demodulator the noise floor of the receiver ('OokFixedthreshold') should be programmed into register 0x1D 'RegOokFix'. There's a simple procedure to determine the value to be programmed in reg 0x1D. I've followed the procedure, everything works fine, no issues with the receiver. The value I use is 0x60 / 96 dB.
However, I have no idea what this value represents. The description of the reg in section 6.4 says the value of the reg is in dB. A dB is a ratio. So, my question is, from what reference point? The noise threshold is 96 dB up or down from where? There's no clarity in the data sheet to help.
I'm hoping there's somebody out there that is an RF expert and can help. Not understanding this is bothering me ;-)
Many Thanks
Thanks for the comments. I should probably have stated. The RSSI value with no transmissions is between -80 dBm and -82 dBm. The device is in continuous receive mode and reg 'RegRssiThresh' is wound right down so the received goes straight into 'RxReady'.


texts: what is logic power, signal power and clock power in FPGA?

texts:
I am measuring power of my design in spartan3e kit. When I use Xpower Analyxer, it shows me some thing like the figure below

I don't know what is clock power, logic power, signals power and IOs power. And to what I know, power is estimated on a particular cell, not on signals or wires. Am I right?


texts:
I have a power supply based on VIPer22a. It is an isolated supply with output 17V, 400mA. The input voltage ranges from 100-240V, 47-63Hz. It drives the LED Array module perfectly. I have attached the circuit for that supply as well. But I am designing other product which requires Dual outputs. Here are my specifications :-

Output 1 :- 17v, 400mA
Output 2:-  3.3v, 1A
Constant current and voltage

The circuit I have attached can help identify what exactly I need because it is working fine. I just want to improve on that or may be make it better. I don't know whether it is constant voltage & constant current or not, please let me know that after going through the circuit.

Please recommend me some design for my application or any improvisation on this.

Update :-

I just found ST's eDesign suite which helps in designing power supply. I filled up my requirements and it displayed all the information I require for my supply.

I just want to confirm the completeness/accurateness of this design and if it fits my purpose.

Here it is :-

Schematic :-

Summary :-

Parameters :-


texts:
So, I'm generating a 1280x1024 (native screen resolution) VGA signal using a Lattice HX8K > Yosys, according to these timings, and a PLL of 107.812Mhz of Pixel Frequency. I then pass it through a simple scaler to achieve an effective pixel resolution of 320x256.

All signals are being buffered through a 74HC245 and some resistors. I would like to use the 74ALVC245 variant, but I'm still waiting for the order to arrive.

simulate this circuit – Schematic created using CircuitLab

The monitor detects and displays the correct image, but there is noticeable "ghosting" in the bottom of the image (something that is quite absent in the top):

What could possible be the culprit? Would the ALVC solve it?

Addendum: Per channel ghosting:

Addendum 2: Some curious findings:

Ok, here's something I wasn't expected. While disconnecting the ~500Ohm resistor in the green channel (to test a different one), I was expecting to see the image completely black. Instead, this is what I saw:

After which I tried to leave the green channel on, and directly connect the red and blue channel to ground:

Could this be bad cable shielding? I tried this cable with a raspberry PI and a HDMI -> VGA adapter, and I couldn't see any artefacts resembling these images.

Addendum 3: If I just disconnect the red and blue channels (leave them floating), then I get a perfect green image. Could this be noise in my GND lane?

Addendum 4: So many new things after going through an oscilloscope. Let's start from the beginning; measuring the freaking 3.3V source from the PMOD connection of the FPGA:

You would imagine a stabilised 3.3V source, right? Guess what:

That's 306mV of noise measured right at the PMOD. There's definitely some internal coupling going on with a ~1.4Mhz signal which I can't even begin to identify.

Now the easy things. Is the 74HC245 introducing more lag than it should? Let's compare IN vs OUT at the VSync pins:

These don't seem to be a problem; the 3.5V Pk-Pk seem inside range, given the oscillations of the power supply. But zooming out on the HSync:

Green is after the 74xx245, yellow is before. There's so much noise going on when the signal is high, that it actually pushed the envelope to 4.06V! How's VSync side-to-side with HSync?

Not bad; but not a pretty signal, though, considering I'm filtering both of them with a couple of 22pF capacitors.

And what about the individual pixels? Well, being this a 70Mhz oscilloscope, I don't have enough resolution to capture individual pixel measurements. But zooming in on a very fine region of the red channel:

Which gives a 600mv envelope; very nice for the 0.7V VGA target input, right? What happens when I zoom out?

OMG... It's like, there are two signals superimposed on top of each other (with lots of added noise), and an offset of some hundreds mVs, enough to push the envelope to 1.61V Pk-Pk. This seems crazy, and I bet this is the the probable source of the ghosting...

Now what? I'm completely out of my comfort zone, so all your help would be appreciated guys :)

Addendum 5:

After reading a lot here about wires, and also here thanks to @Peter Smith, I decided to cut the cables that connect to back of the monitor to about 1/3rd of their size (they had around 1m, and are 24AWG). The ghosting is way better now, but you can still see some weird superposition:

Here's the physical setup photo, as some requested (sorry for the xmas-themed table towel):


texts:
I designed a integrator op-amp on pspice. I want to get triangular waves for output and square waves for input.

Input is OK, but I can't get triangular waves.

What is wrong, should I use a second op-amp?

thats the schematic. red one is the input green one is the output


texts: Implementing an op-amp based circuit that has a given transfer function

texts:
I have this question but I am really confused about how to start, can you please give me some helpful hints.

Let us assume we have a DC voltage measured in a circuit, called \$V_{\text{in}}\$. We intend to build a circuit such that it has a transfer function defined as

$$H(s) = \frac{V_{\text{out}}(s)}{V_{\text{in}}(s)} = \frac{s^2+s+1}{s}$$

Draw this electrical circuit. The circuit can be composed of resistors, inductors, capacitors and op amps only.

I tried op amps with resistors and capacitors in a few different forms, but I didn't get the same \$H(s)\$.

Also I tried a few filters but non of them gave me the same answers.


texts: Combining a bootloader and user program into single flash-able binary

texts:
I want to flash the UF2 bootloader for SAMD21 MCUs together with a compiled binary of a user program onto a SAMD21 MCU.

From what I understand how any bootloader works, the bootloader sits in a specific address space in the flash (in case of UF2 it seems to be 0x0-0x00002000) and then after that address space the bootloader will flash the user program and execute it.

Now it would be great if I can program my board with the bootloader and the default user programm all in once without needing to flash the bootloader with the programmer first and then connecting the board via USB to flash the user program.

Can I somehow concat the binaries so the programmer can flash everything at once in a single operation?

I planned on using https://github.com/adafruit/Adafruit_DAP with a Teesny for flashing. This works great using only the bootloader binary.


texts: TDA2030L Audio distortion at high volume

texts:
I am using a TDA2030L audio amplifier to make my own subwoofer at home. The amplifier works well with the sound input (from a PC) at around 14 percent. The power input is 19V and 2A which is about 38W and the gain for my amplifier is 50 since am using a 100k resistor as feedback between pin 2 and 4 and I have grounded pin 2 with 2k resistor grounded with 22uF capacitor (25V).

When I increase the volume beyond 24% in my PC the output of the amp at the  speaker (4 ohm) is ok while playing in high frequency. BUT when I increase the bass the output gets distorted with the speaker playing in "PULSES", (some audio is not heard and it only booms at certain points with diaphgram of the speaker vibrating in a large displacement).

I have tried using a filter capacitor at the output to avoid DC output into the speakers but it doesn't help. When i use 20V, 1A source the problem still persists.
Below is the circuit that I am using (I have not included the bass and volume control, but I am basically using potentiometers of 10k)

The output from the pc at 100% Volume is about 0.5~0.7v with a current of about 0.02mA


texts: How can I show the variant of a device in a symbol in EAGLE?

texts:
I am creating a device with multiple variants in EAGLE. The associated symbol should show the variant as well, so that it will be directly visible on the schematic.
I know how to add e.g. >VALUE or >NAME to a symbol and how to show attributes, too. But I can't find a way to show the variant name.


texts: Turned arduino 5vdc analog pin to 0vdc (gnd) in order to mimic a momentary switch

texts:
I'm just wondering how I would go about getting the normal 5vdc that comes out of the Arduino analog/digital pins to a 0vdc signal? I wanting to mimic a push button (momentary switch) so that it acts as if I am pushing a button on a remote.

I'm sure I could use a resister of some value in order to get it down to 0vdc but I am unsure of that value nor am I sure that's the best way to go about doing something like this.

Any help would be great! Thanks!

update

Would using a TLP592A work doing it this way:


texts:
I designed a Colpitts oscillator with a single transistor amplifier stage. I now have to connect the antenna to the circuit through a coaxial cable. Do I have to redesign the output impedance of the circuit to match the impedance of the coaxial cable? Or is it better to just add a buffer stage and design that to match the coaxial?
By match, I mean Input Impedance = Output Impedance.


texts: How to use a NPN-Transistor to get status LEDs for an ATX power supply?

texts:
There are many instructions "How to Convert a Computer ATX Power Supply to a Lab Power Supply". Often they suggest they suggest to place to staus LEDs to indicate it the power supply is turned on or in standby-mode or without electricity. The purple wire is on +5V if the power supply is connected to electricity (this includes standby and power-on) and the gray wire is on +5V if the power supply is turned on:

(Sorry, this is in German, there is no other public domain picture available.)

Instead of having a green and a red light at the same time turned on (e.g. doing it this way), I wanted to a red LED for standby and a green LED for power-on (this could be even nicer using a two-color LED). To do so, I used a NPN transistor (a BC547B, PDF datasheet) and some resistors to build a NOT gate:

It actually works: when you connect the power supply, the red LED lights up and when you connect the green wire to ground (not in the circuit diagram) the power supply turns on, the greed LED lights up and the red LED goes off. However, there is a strange voltage on the gray wire, which I cannot understand (and it might be the cause why the LEDs are not very bright). Between the gray wire and ground there are 2.5V. How does that happen?

Note that I verified that the gray wire is on +5V if I disconnect the right part:

I am not very sure about the the resistor R2. In the beginning I used 1kOhm. But after playing a bit on the breadboard, I noticed that the green LED gets a bit brighter if I increase the resistor. I cannot explain that, maybe I made a mistake somewhere...


texts:
How can I calculate the transfer function with nodal analysis?

I tried it with the system of linear equations but it doesn't seem to work:

\$I_{R_1} + I_{R_2} = 0\$ and
\$-I_{R_2} = 0\$

with

\$I_{R_1} = \frac{u_e-u_d}{R_1}\$ and
\$I_{R_2} = \frac{u_a-u_d}{R_2}\$

I get the wrong answer.


texts: How to convert a voltage source into a current source when resistors are in series?

texts:
I am following the diagram that is attached below:

Now, say I have the following circuit:

And I apply this theorem and end up with

Then, even though the current was the same in Circuit B for R, R1, R2; it is generally different for R than for R1 and R2 in circuit A. Why is this?


texts: Soaking phone motherboard in isopropyl to fix potential corrosion

texts:
Is it advisable/safe to soak my phone motherboard in an isopropyl alcohol bath?

I dismantled it after water damage occurred and it now powers on fine but my cell signal isn't consistent.

I was advised to soak the MOBO in a bath of isopropyl to remove any potential corrosion on the antenna/board.

Is this sound advice?

Here is the component in question.


texts:
Are there power consumption benefits between a discrete timer: astable multivibrator or some other; and an integrated circuit?

I have a time dependent circuit in a project and I went looking for the simplest, as in component complexity, discrete circuit I could utilise to allow my project to self regulate its timing and I came across the astable multivibrator

I built it into the project but now that the whole thing is up and running I am starting to wonder if my interest in simple components is hurting my greater interest in lowering power consumption.

Would an IC like the 555 consume less power than a discrete astable multivibrator designed to meet my circuits specific needs?

..also, suggestions on lower power consumption discrete timers other than the AM, or discrete timers with less components than the AM, as well as any direction on how to accurately measure power consumption of the circuit would be greatly appreciated.


texts: Will the use of an AC relay keep my power supply isolated?

texts:
An isolated power supply is used to convert 120 VAC 60Hz power from mains to 12V. A linear voltage regulator then converts the 12V to 5V.

A 5V micro-controller is then used to switch on a 12V relay (with the use of a transistor) to power an AC device.

The relay allows the AC current from the main power to flow to the device. The 12V is used to switch on the relay.

Will the use of the relay cause the low-voltage side of the circuit to lose it's isolation or does it depend on the relay?


texts: Can't understand a variable in the formula used to determine CDTY to set duty cycle of PWM on cortex M3 (SAM3X8E)

texts:
I want to generate complementary PWM on an Arduino due. For that purpose I am programming the cortex M3 using the PWMC library. In order to set the duty cycle I have to set a value in CDTY channel register of the Cortex M3.

The formula for calculating the duty cycle of a center aligned PWM is given in the SAM3X datasheet as,

Now I don't know what is the value of the variable "fchannel_x_clock" in this formula. If I get to know that, I can easily find the value of the CDTY to get my desired duty cycle using the above formula.

Link to the complete datasheet: http://www.atmel.com/Images/Atmel-11057-32-bit-Cortex-M3-Microcontroller-SAM3X-SAM3A_Datasheet.pdf

The formula above is in the PWM section of the data sheet.


texts: How much power can transit through a power line linking generation and load?

texts:
First things first I am not an electrical engineer at all so please bear that in mind when you reply/comment.

I am looking at the following problem, I have a power line which connects a windfarm to a consumer.

I make the assumption that the consumer will always be able to consume the power provided by the windfarm.

I assume that the windfarm actual power generation capacity varies between zero and a maximum that is exceeding the capacity of the power line.

My question is: How can I determine the maximum amount of power that can transit through the power line from the windfarm to the consumer before curtailment in required ? or the transmission line upgraded.

So far I have used the following:

where I(Amps) is the maximum current that the line can handle before melting. Vphase is the voltage of the line (lets assume a transmission rated at 400 kv). and pf the power factor of say 0.8.

Using this equation and assuming I is 1000 amps, Vphase 400 kv and pf 0.8, I find that the maximum power that can transit through the line is 692.8 MVA or 554.2 MW.

If that is true (which I suspect it isn't), am I correct in thinking that if the wind blows hard and the windfarm could produce over 554.2 MW then all that excess power capacity would have to be curtailed ?


texts: Replacement for MC12149 (Voltage Controlled Oscillator)

texts:
I need to build up a VCO from 250-350 MHz. I have found an interesting IC called MC12149 from Motorola. However, it seems to be archived and no longer manufactured. Looking at the datasheet, it looks very simple configuration. I have been searching here on Stack and in many stores yet I have not found a substitution for such IC.

Do you know any suitable IC?


texts: Why can some products take 110v 60hz and also 240v 50hz?

texts:
Most modern chargers can go into any output across the world. I believe this is because of low powered "Switch mode" technology it uses rather than transformers, like they used to.

To go from high AC to low DC is pretty easy now.

But my main question is about other products that may use a motor. Is it possible to design a circuit that regardless of the input (110v or 240v 50/60hz) it can function the same way without a toggle switch?


texts: Wi-Fi controlled light; 230VAC - 12VDC/3.3VDC

texts:
I try to connect an ESP8266-12 and a 12V RGB LED strip to 230V AC. Based on this link, I've came to the following scheme. This will also be the first time I will etch a PCB myself.

The partlist will be as following:

Part      Value

C2        0.1uF
C3        0.1uF
C4        0.1uF
C5        0.1uF
D1        1N4004
D2        1N4004
D3        1N4004
D4        1N4004
F1        1A will be sufficient?
JP1       screw connectors for 230V AC
JP2       jumper for connecting GPIO15 to ground
LED_STRIP the rgb leddstrip
Q1        TIP120
Q2        TIP120
Q3        TIP120
R1        220 Ohms
R2        220 Ohms
R3        220 Ohms
S1        switch to reset ESP8266-12
SERIAL    header pins for connecting over serial
TR1       transfo
U$1       ESP12
U1        L7812
U2        LD1117V33

I'm still unsure about what transfo to use? I was thinking about the MYRRA  44090  TRANSFORMER 1.5VA 24V. I'd like to get some feedback on this pick.

Also I'd like to gain some feedback if this scheme is safe to use. I assume the ESP8266-12 will be isolated from the net since I'm using a transfo?

For completeness I add a link here to my GitHub repo where the eagle files can be found.


texts:
I've just replaced my smoke detector.  It was manufactured in 2006 by BRK.  This is an ionization-style detector. I took it apart and the track side of the circuit board is covered with a thick waxy substance.  It's clearly part of the manufacturing process, and not  a by product of nesting spiders.  It's 1 - 2 mm thick and fairly uneven, translucent and soft.  You can scrape it away with finger nail pressure.  Applying a match flame to it causes the substance to melt and drip off just like candle wax.  It's not flammable in it's liquid phase.

For all intents and purposes, it looks and behaves just like candle wax.  Can we still really be using candle wax to protect pcbs this century?  And if so, why?


texts: What are some inexpensive easy to use SPI devices I can experiment with?

texts:
Introduction

I'm completely new to EE, but have decades of software development experience. I want to learn to interface with multiple SPI devices on a single SPI interface on a Raspberry Pi. I'd like to start cheap and easy. I only know about complex and/or expensive devices like LCDs and radio interfaces.

Question

I'd like to compile a list of device options (they don't have to be specific device models or where to buy them) that a budget constrained kid looking to escape a coal mining town in Appalachia could start with. (Even though that is not my situation now, it was a few decades ago and that is always who I think of.)

Specifics

My ultimate goal is to read multiple MAX31855 chips. Before I go investing in 4 of these $8 chips and 4 $26 thermocouples, I'd like to try connecting a few cheap (<$1?) SPI devices so I can work on the python code to interface with SPI.

If I totally fail at this, I'd rather only be out a few dollars.

What so you recommend?


texts: What is preventing using a CAN bus chip and SD card on a shared SPI interface?

texts:
I am interfacing with an SD card and a CAN interface chip (the MCP2515) on an SPI interface. For speed of writing, I am using a FAT library and opening a file to stream to. If I temporarily stop streaming data to the SD card to gather data from the CAN chip, resuming the card writes causes corruption of the file.

I cannot see why the two interact with each other. If at the lowest level there is no overlap in pulling the CS pins low for each device, surely the SD card would effectively be blind to what was happening on the SPI bus. I have confirmed releasing the CS pin of the SD card is not causing any issue, nor pulling the SC pin of the CAN interface chip. It is only with an SPI transfer that the SD card writing becomes corrupted.

Is this a problem of electronics, or is this more likely a firmware/library issue that I am facing?

Further information:

Microprocessor: ATmega2560
CAN Interface: MCP2515
SD Card: Transcend 4GB C10 MicroSD HC
SD Card level shifter: 74hc4050

The writes are done in complete 512 byte chunks, aligned with the blocks on the SD card. The symptom of failure is that the next block written returns a failure to write. I have not been able to decipher the meaning of the fault yet, though two codes are returned for each failure. These may be generated by the SD card itself bud I do not know yet:

0x13
0xFF, 0xE0, 0x7F or 0x3F

Once the SD write completes, its CS pin is pulled high before the CAN CS pin goes low. Once the CAN operations are complete and the CS pins are swapped. Though this is when the fault occurs.


texts: H-bridge with MOSFET's stops after 2 pulses

texts:
A H-bridge (12V) driven by a 555 astable multivibrator (about 2Hz) and using 2x p-channel (RFU9024) and 2x n-channel (1N60) mosfets starts up fine, on half period 1 the bridge conducts one way, then the next half period it conducts the other way, but then it stops and the side that does not switch over starts to overheat.
The 555 is decoupled with a 100nF and a 47uF across the 12V supply rail; pin 5 is connected with 100nF to ground.
When breadboarding this circuit it works fine, a custom built pcb does not work. All traces have been checked and re-checked for shorts, open sections, wrong connections, wrong parts, defective parts,... no errors there.

The load is resistive.

Question: what makes a h-bridge stop its oscillation after just 1 period (and in fact short circuits on one of its legs)?


texts: Can a MTS 101 2 pin ON-OFF switch rated for VAC be used in a DC circuit?

texts:
I'm currently looking at buying a bunch of MTS 101 rocker switches which are rated for:

AC 125V 6A, AC 250V 3A

For DC the rating is not available

http://www.massuse-relay.com/details/MTSSeries.pdf

The selection was purely considered on "cool factor"

I read something about "arcing" of AC switches in DC circuits, but does this apply on such low voltage circuits as well?
Can I buy and use this or should I really not bother with AC switches in DC circuits (even low powered ones)

The switch would be used to make an 'on/off' toggle for a small electrical device (a small Electric Piano Organ Module which runs on 5v)
- uses 555 IC
- 3x 0.1uF Electrolytic capacitor
- 1x 4.7uF capacitor
- 4ohm 2W speaker
and a bunch of momentary switches and transistors to make sounds.

The other option is SS12D00 or something similar, but even though they work just fine, they look a bit dull in my opinion.
But hey safety > cool factor?

Thanks in advance!


texts: Electrical Component Degradation Over Time

texts:
I have a brand new 5-Disk CD Carousel Player.  It was never used except for initial test about 20 years ago.  It was stored in original box with all packing materials including desiccant in basement.  I have not tested it yet.
Question:  What, if any, electrical components could be compromised by this lengthy storage? Or, could the unit operate "good as new"?   Thanks.


texts: AC out to DC output 90 amp flux core wire welder

texts:
As stated above I have a welder that I wanted to change from AC output to DC output. I got a 150 amp 3 phase rectifier and two 82000mF capacitors. I hooked the capacitors together in parallel then the two capacitors and rectifier in parallel. I wanted the electrode (i.e. gun, wand) to be negative and the ground clamp to be positive so I hooked them up accordingly. I got everything together and turned it on. The wire feed motor was running sluggish and then I heard a couple of popping noises and and a bubbling sound. The capacitors are blown. I want to know if capacitors that blew in that type of circuit can destroy a rectifier because now the wire feed motor works, but there is no electricity flow through the gun or the ground clamp.
Also since my capacitors are blown does anyone know of a good electrical parts supplier that sells large capacitors.


texts: Has double (green) protoboard benefits when using this way of soldering?

texts:
I'm intending to use the same soldering 'technique' as in the picture below (just an example), by using wires and solder connections.

I am wondering if it has benefits by using the green double sided protoboard (I have quite some of them), or using the cheaper brownish (bakelite) ones like below?

The only advantages of the green ones I can find of (for this way of soldering) is that they don't small bad and they are a bit thicker.

Do I miss some more important benefits?

(I checked google but the double layer doesn't seem useful with this technique).