texts: why don't we see more snubbers in schematics?

texts:
Introduction
Let me start by saying that I know what a snubber is and how to implement one. I learnt how to use them when developing power electronics. Needed to reduce EMI in switchers, but they are even more needed in order to not have exploding power FET's. Also often a trade-of between clean and efficient.
Example
So while being aware of the usefulness of snubbing, I was thinking about a filtering schematic that is used often in one way or another:
power supply -> Pi filter -> buck converter for point of load supply.
In the schematic below it's represented with a ferrite bead equivalent on the left hand side and input cap of buck on the right hand side, with an equivalent load of the buck of 1.5W on 12V supply rail. There's the 1nH inductor in between to represent a PCB track.
Just look at the terrible 20dB peak, smack in the middle of the audio band. I wouldn't like anything like that feeding audio circuitry.

Add 2 snubbers and look how clean it can be:

Question
Other than accross switching elements with parasitic capacitance (mostly FET's and diodes), I don't ever see mentioning of snubbers. Why is that? Am I overcomplicating things, being paranoid, or do I have a blind spot somewhere that would render the snubbers in above example useless?


texts:
I tried using the PTM 14nm model file on LTSpice. I realized LTSpice does not support BSIM-CMG models. Is there any alternative like LTSpice, which can simulate FinFET models?
Thank you.


texts: Is it possible for two different systems to have the same step response, and vice-versa?

texts:
Every time I have had to tune a controller (PID, usually) to a process, I have first matched an equivalent first order or second order model by doing some curve fitting on the step responses; and then tuned the controller to the identified model. It has worked well so far, however I wonder if that will always be the case.

Hence my question: if a process is an excellent fit with a model, does that necessarily mean they are nearly equivalent (and therefore controllers tuned to the equivalent model will always work on the real process to some extent) or are some aspects of the system not captured by the step response?

To illustrate, I have recently fit the sum of two different first order systems to a process, because neither a first order or a second order fit. It's a very good fit now, but I do not want to leave anything to luck.


texts: Voltage buffer with ideal Op-Amp (positive feedback) - Instability

texts:
I know that the circuits which employ negative feedback are stable, whereas those which employ positive feedback are not stable.

How can I prove that a voltage buffer (ideal op-amp) which uses positive feedback is not stable?

I know only the dual case ( \$ A=+\infty \$ because the op-amp is ideal):

$$v_u=A \, v_{in}=A (v^+ - v^-) = A \, v_i - A \, v_u$$

$$v_u = \frac{A}{1+A} v_i = v_i$$

If I consider:

$$v_u=A \, v_{in}=A (v^+ - v^-) = A \, v_u - A \, v_i$$

$$v_u = -\frac{A}{1-A} v_i = v_i$$

The last result should be wrong.

Thank you so much for your time.


texts: Do I need pull-down resistor on Enable pin cd74hc4051

texts:
Can I directly connect enable pin to ground? I am not going to use it.

datasheet

Also can I connect all unused pins of LM324 op-amp to ground through single resistor or what configuration does it need?


texts: Changed Op-amp, now signal is not centered

texts:
I'm making a pre-amplifier for my 9mm electret microphone to be read by an Arduino. Here's the schematic:

Note that the resistor I used connected to the output is 1Meg. My supply voltage is 5V.

Initially I used LM358 as the op-amp. When I plotted the output it seems to be normal -centered around 2.5V with a bit of noise (my plot range is 0 to 5V). But when detecting loud sounds, the output gets clipped to ~3.7V.

Because of that I decided to switch the op-amp with a rail to rail AD8051 instead.
Wiring with corresponding pinout from its data-sheet and using the same resistors, capacitor and mic. Now the output I get is somehow centered at 0V and the signal seems to be amplified more than the last time.

Why did this happen and how do I get the output to center back at 2.5V? aren't op-amps interchangeable without having to change resistor values?


texts:
in my application I have an SD Card reader using the NXP LPC1822 microcontroller. It works very good with all SD- and SDHC-Cards I've tested so far. Only thing that does not work is SDXC.

I already contacted some Distributor and NXP FAEs about that problem, but all they could say was "We haven't tried SDXC on a microcontroller yet". So first question: Is there someone in the SE Universe which did that already? Doesn't matter if with NXP or others.

Some more informations about my application:

It is basically a "dumb" SD Card reader. I only tunnel requests coming from a windows 7 machine over USB (MassStorageDevice of LPCUSBLib) and SCSI to the SD Card Interface. Any data requested I tunnel back over USB to the host. So no FAT file system or any data handling on my controller. Just shovelling masses of bytes.
I use LPCOpen (heavily modified to get better performance) to talk to the SD Card interface. This works perfectly as already told.

When I plug in a 64 GB SDXC card, it gets enumerated and is displayed in the windows explorer as an unformatted SDHC card with 32 GB. If I format it, I get a normally usable 32GB SDHC Card out of it.

Next Question:

I am no member of the SD Association, so the only thing I have is the simplified spec. And this does not say anything about SDXC. Because of the behaviour stated above I wonder if there are some obscure status bit flags which identify a card to be sdxc? there is such a bit for sdhc, but I can not find anything about xc.


texts: I think for the first part of this problem I solved for Ra = 13kohm and Rb = 7kohm, but I'm not able to understand or see how to get the voltage at the point V1. Any idea on how to go about finding V1?


texts: ATtiny85 and high frequency PWM for driving a ferrite transformer

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Some background: I have an ATtiny85 running at 8 MHz under the Arduino IDE. I have been gifted a large ferrite transformer and some MOSFETs & drivers to drive it. However I am lacking a suitable PWM signal to actually make it work. I tried using analog write, however the current quickly got out of control due to the switching frequency simply being far too slow.

I know a little bit about programming here and there. I've also worked with the Arduino Uno, which I am also using as a programmer for the ATtiny. However I have a limited understanding of the inner workings of microprocessors. So I looked for a library to make all of this work, and I found this:

https://github.com/micooke/PWM

However, I am still unsure how to actually make this work, or adjust the pulse width with a potentiometer. Think a 4047 with a deadlocked frequency, but with an adjustable pulse width. To keep it simple I don't have a clue how to make this work, and it is driving me crazy.


texts: Replace/Repair Resistor type to drive 5V dc-motor for old toy

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I have an old toy that drives an 5V dc-motor.
The wires around the motor is brittle and suspected burnt.

This toy uses 2x 1.5V batteries or 2x 1.2V Nimh batteries for powering the whole toy. When the motor initialize or reverse in direction, it hung and causes the circuit to stall. This results in the motor to be super hot. From the picture, the resistor is Green-Black-Gold-Silver which is 50*0.1 10% = 5 Ohms 10% resistor (metal oxide)?

I suspect the 3x capacitors and 2x resistors at the motor died.
I notice that there a number of different types of resistor like metal oxide film resistor, metal film resistor, Cermet resistor, carbon film resistor, wirewound resistor.

What resistor is recommended for this application in a humid environment?
Is a fusable resistor advisable to use to prevent motor overheat?


texts: Extension cord to Power strip in old house

texts: I live in a old house that has very old wiring. We got a small upgrade so we now have grounded outlets. I need to plug in a lot of devices into this outlet such as speakers, monitor and a gaming computer. So I bought the longest power strip I could find since I need to stretch it to my desk. But it is not long enough. My question is, is it dangerous to plug a power strip into a extension cord? In a old house that has old wiring and does not have many amps? Would I need a high rated extension cord?


texts: COM port assignments changing for DLP USB232M

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I am working with some legacy PCBs containing USB-to-TTL UART adapters. The adapters are powered via the USB bus with only the transmit, receive and ground pins interconnected to the rest of the PCB. These adapters appear to Windows (7, 64-bit) as COM ports. Intermittently on powering up the system the COM port assignment of one of the boards will change. I'm trying to figure out what would cause that behavior. It seems the most likely culprit is a grounding issue since the port change mostly happens during power up and that's one of the very few electrical connections between the adapter and the rest of the board.

However, for some of these boards, moving the USB cable from one port on the PC to another will also cause a change in the COM port assignment regardless of whether or not the board is powered up.

Where should I be focusing my attention to track down this issue?

The cables are good, the drivers are up to date and the interconnects follow the manufacturers reference design.


texts:
I am in the planning stages of building a motorized altazimuth telescope/antenna mount. I will be using two large stepper motors that operate at 1.75 Volts / 12.7 Amps. I would like to make the mount portable by powering it with a 12 Volt car battery.

What would be the most appropriate circuit and component values to power these stepper motors within spec?

Note: I am not needing details on the stepper motor wiring or switching, just a means of dropping the voltage/current to the appropriate amounts.


texts: Are FPGAs used as Cubesat flight computers?

texts: Are FPGAs used as Cubesat flight computers and are there benefits or drawbacks in using them?


texts:
I have been playing around with some digital microphones, which have an I2S interface. I managed to get it working (Arduino board with small I2S mems board). At least, I think I did.

When reading the I2S specification, or the microphone datasheet, I can not seem to find the answer to the following simple questions;
1. What do the digital values represent?
2. How do you convert the digital values to dbFS (and then later an dbSPL)?

The SPH0645LM4H-B (Knowles) microphone seems to output all negative values (?). I read somewhere you have to "subtract the midpoint" to eliminate the large DC offset etc. (See here: Convert Digital and Analog values to dB SPL ) On the other hand, a support engineer at Invensense explained to me that the ICS-43434 outputs positive and negative values which "represent the amplitude of the signal relative to +/-full scale".

I expected I2S to be a standard; isn't that the case ... ?


texts: Estimating power consumption of GDDR5 chip from data sheet

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I am trying to better understand the power consumption of this 8Gb Micron GDDR5 chip. Specifically, I want to estimate the following:

idle—What is the power consumption when the chip is idling?
max activity—What is the power consumption when the chip is at max activity?
low data rate—What is the power consumption when the chip data rate is low, e.g. at 1.0 Gb/s (the maximum data rate is 6.0-8.0 Gb/s)?
low power modes—"Low power modes" is listed as one of the features and I'm assuming they are referring to the ABI_n and DBI[3:0]_n pins. What are the power savings there?

Can the above information be gleaned from the data sheet or other online sources?


texts:
I am building a sensor which has to differentiate between 6 different objects.
Each object contains an LC-circuit which oscillate at different frequencies (let's say 100kHz, 90kHz, 80kHz, 70kHz, 60kHz and 50kHz).
The sensor contains a coil, which starts the LC-circuits in the objects by creating a magnetic field which induces a voltage in the objects.
Then, it must measure the frequency of the LC-circuit to differentiate between the different objects.
Are there circuits which can easily differentiate between 6 frequencies? I want to avoid using a microcontroller.
If there are better alternatives to this approach, I'd be happy to hear them too!
However, the objects and sensor should be pretty small and inexpensive.
Edit:
Why do I want to avoid microcontrollers?
I need a lot of these sensors, and my objects are small. The LC-circuit in the objects must therefor be small. Because of that, the frequency of these LC-circuits is quite high, and microcontrollers with a sample rate high enough are pretty expensive.
tldr; i would like a cheaper alternative


texts:
I have a DCP010512BP 5->12V DC-DC Converter from Texas Instruments. With a supply voltage of 5.00V on Vin and a 4.7uF ceramic cap across the output, I read the output voltage as 21.0V with a digital mulimeter with no loading applied.

This is obviously way out of spec for the output voltage of 12V +/- 10%.

Could the ripple noise be somehow affecting my multimeter, or is this kind of behaviour expected when unloaded?


texts: Parallel DC Conductors - Need Multiple Grounds?

texts:
I'm working to power a 5m long strip of 60 WS2812B LEDs per meter. I have a 5V 300W DC power supply and am using 14 AWG wire. During my initial testing, the maximum distance between the strip and the power supply was ~2 feet, if not significantly less, so I never really had to worry about voltage drop.

However, my actual final product will have the LEDs ~10-25 feet from the power supply, but I'm working on a tight budget and attempting to be as economical with the wire as possible. (I need to wire up a bunch of strips, so I'll probably be buying more like 250' of wire -- that gets very expensive as the gauge goes up.) Since I have a 5V power supply and the WS2812B are happy with anything between 3.5 and 5.3V according to their datasheet, fiddling around with this voltage drop calculator tells me that, with the following settings, I can expect a final voltage of 3.71V at the strip:

Material: Aluminum (My top contender is CCA wire.)
Wire Size: 14 AWG
Voltage: 5.5 (My PSU has a +/- 15% voltage adjust, so I'm assuming I'll dial it up to maximum and probably get more like +10%. If I actually get +15%, even better!)
Number of Conductors: 2 conductors per phase in parallel.
Distance: 25 feet (The absolute maximum distance I expect to have to run power.)
Load Current: 18A (Maximum full-white current draw of one 5m 60LED/m strip)

I'm looking at buying 14/4 CCA wire for this project, but I'm not sure what the best practices are for running my power over multiple conductors, then combining them both at the PSU and at the strip. (The theory here is that I'm splitting the current over multiple conductors, so less current-per-conductor = less total voltage drop, right?)

For "2 conductors per phase in parallel," does that refer to, in 14/4 wire with individual insulation colors of red, black, white, and green:

A:

Green: Connect to GND @ LED strip and V- on PSU.
White: Connect to GND @ LED strip and V- on PSU as well.
Red: Connect to +5V @ LED Strip and V+ on PSU.
Black: Connect to +5V @ LED Strip and V+ on PSU as well.

or B:

Green: Connect to GND @ LED strip and V- on PSU.
White: Unused/Disconnected
Red: Connect to +5V @ LED Strip and V+ on PSU.
Black: Connect to +5V @ LED Strip and V+ on PSU as well.

In other words, does each positive connection need its own ground/return? I worry that A would create a ground loop, which would be especially bad considering I'm expecting to be working in an environment with a lot of nearby AC lines to induce current. (I'm in a theater, so lots of conduits everywhere carrying power to stage lighting, etc.) If B is the way to go, would I be able to use the unused conductor in the 14/4 as another positive conductor (essentially having "3 conductors per phase in parallel") and reduce my voltage drop even more? Is there an option C that I actually should be considering?


texts: How to interpret the equation \$e=K_e.\omega_m\$ in a BLDC context?

texts:
After researching a while on the subject, I noticed that several sources state that the back-emf constant of a BLDC motor satisfies the following equation:

$$ e = K_e.\omega_m $$

where:

\$e\$ - Back-emf
\$K_e\$ - Back-emf constant
\$\omega_m\$ - Angular velocity (in mechanical degrees, not electrical)

This makes perfect sense to me in the case of a DC motor, where we only have one phase. However, things get confusing to me when trying to understand the above equation for a three-phase BLDC.

When applying this equation in a BLDC context (as I've seen a couple of sources do), \$e\$ is the back-emf in which phase? Or is it an average value, or something else?

I'm trying to get answers from the book Analysis of Electric Machinery and Drive Systems but I have little background in this area, therefore hindering my reading substantially.

Any help would be appreciated, thank you.


texts: is this level shifter a dud or am i doing something silly?

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i am very new to hardware circuitry and am attempting to connect a wiegand rfid and pin code reader to a raspberry pi for door access control logic. more details at: https://gist.github.com/grenade/d7289df5c83172b82052b2b87df9f978.

in the 2nd photo below, there are 3 wires connected to a bidirectional level shifter (5v - 3.3v). from left to right they are connected as follows:

wiegand data 0 - level shifter hv 1
wiegand gnd    - level shifter hv gnd
wiegand data 1 - level shifter hv 4

i intend to connect the level shifter to the raspberry pi as follows:

raspi gpio 04 - level shifter hv
raspi gpio 06 - level shifter lv gnd
raspi gpio 11 - level shifter lv 1 (lower left pin)
raspi gpio 12 - level shifter lv 4 (lower right pin)
raspi gpio 17 - level shifter lv

i am following a related post which describes a schematic which uses similar hardware.

multimeter shows 12v coming from the power supply at the top of the first picture
multimeter shows 6v coming from both data 0 and data 1 on the wiegand reader. i was expecting 5.5v, but whatever.
multimeter shows 6v coming from both lv 1 and lv 4 on the level shifter. i was expecting a level shift down to 3v ~ 4v.

have i misunderstood what level shifters do or is this one a dud since it outputs the same voltage on the lv end as is going in on the hv end?


texts:
I am wanting an at a glance indicator of what voltage level is being supplied by a DC generator (think pedal power).  My general thought is a series of LEDs that light up in sequence as the input level increases, but I am having trouble coming up with a workable circuit.  My voltage level can range from 0-24VDC, and I am looking for something that will indicate the current level in ~3V increments.  The generator is the only power source I have, so comparators that need an external reference voltage or power source are out.  I don’t need precise switching on the LEDs, they can gradually get brighter, but I would like something that only allows one at a time to be “partially” lit.  I think I remember building such a circuit in one of my early electronics classes, but it has been many years, and the details elude me.

So basically the goal is 8 LEDs:
0-3V - LED 1 goes from off to fully on
3-6V - LED 1 is on, LED 2 goes from off to fully on
6-9V - LED 1 & 2 are on, LED 3 goes from off to fully on
etc.

I am thinking this should be possible with a zener/resistor/LED network, but every layout I have toyed with would push too much current through the lower level branches as I move up towards max power.  So far my google skills are failing me in terms of finding a workable solution.


texts: How to power a device (1V, 1A) from a computer's USB (5V, 0.5A)

texts:
I have a wolphram wire that works as a heating element. It's resistance is 1 Ohm.
The wire hits the target temperature when it passes 1A of current. I can achieve this current by applying 1V across the wire. Since the device is powered by USB which outputs 5V I need to step the voltage down to 1V somehow.

I believe one solution would be to use a step-down power supply like this one banggood.

Are there any other solutions?


texts:
I have to model mathematically a motor in matlab and as a state-space and I can't figure out what will be my control variable. I will have a H bridge power electronics.
In order to keept it stable and precise,
Is the current that I need to control in the coils or the voltage ?
Do you have any suggestions for state variables or the model?

Thanks,
John


texts: AT91SAM7A3 not in kit list in Atmel Studio 6.2

texts:
I am trying to use Atmel Studio 6.2 and Atmel ICE to program AT91SAM7A3, but I could not find AT91SAM7A3 in the kit list of Atmel Studio 6.2.
What should I do next if I want to load my code in AT91SAM7A3?


texts: Charging 1S 850 mah battery at low current, 4.2 volts max, potential issues

texts:
On an Atari ST computer (1985 -> 1987), there is an optional battery backup circuit board for the clock chip (6301). The voltage output by the board to the battery cable with zero load is 4.17 to 4.20 volts. Based on measurement of charge time, it appears the maximum current from the board to a battery pack is less than 30 ma. The 6301 clock chip is a CMOS chip, so the voltage needs to be 3.5 v to 5.0 v, and the board's 4.17 to 4.20 volts is sufficient. When running on battery power, it is reported the board pulls about 1.3 ma current.

The battery pack is 3 x AA nicd or nimh pack. If using an external charger, the packs are normally charged only to 4.1 volts, in case there is a potential over voltage issue with the circuit board.

I'm wondering if the 3 x AA pack could be replaced with a 1S 850 mah LiPo battery, which would eliminate the self-discharge issue of a nimh pack.


texts: Voltage conversion between multiple orders

texts:
I have this circuit in which I want to convert the input voltage of micro order to volt. The circuit image has been posted. I have figured out the bandpass filter ( basically everything after the big vertical dotted line).
What I can't figure out is that the input offset voltage of AD620 is 30 micro volt. So it could create a problem. For that I have read that you need to use a capacitor in series with the feedback resistor but I don't know how to calculate the value.
If anyone has a better idea about this please do suggest!
Also another doubt I have is whether the comparator (TL084CN) after the instrumentation amplifier (AD620) will be able to shoot the milli order voltage to near Vcc value or at least bring it into order of volt?
The shape of the signal doesn't matter to me but only the frequency does . So I'm trying to shoot the voltage up before passing it into the bandpass filter.
If you have understood my goal and have better modifications to the circuit please let me know!

Datasheet used:
AD620an

TL084CN

Image of the circuit:
PS: The gain is 883 due to the 56 ohm resistor at instrumentation amplifier (not clearly seen in the image)
Image]3


texts: How to prototype with an 8-pin 'daughter board'

texts:
I've purchased a couple of wireless transciever boards (nRF24L01), and they bring out the I/O pins in an 2x4 arrangement which fits snuggly into breadboard. However (obviously) when you do that the pins are 'connected'!

I think I need to take a breadboard apart and break some tracks.

Without soldering, is this my only option?

Any other approaches appreciated.

Many thanks
Ian Hunter


texts: AC Electrical Safety Guidelines/ Legislation for in-house ATE

texts:
I am designing an in-house measurement and control system and we have decided to use a Traco AC/ DC converter.  We are taking UK mains 240V AC and converting it to 12V for use in powering a number of measurement devices and an industrial PC.

I am using the TXM 035-112 AC/DC converter which means the AC must be wired to the AC/DC converter rather than using a kettle lead, (UK Mains plug to C13 IEC Socket).  It works fine, there are no problems but I am concerned in case we are not complying with the UK electrical safety standards, (e.g. Do we need to earth the control system chassis?  Is an MCB required? Do I need to place electrical hazard stickers)

Does anyone know the standards that must be followed when using screw terminal AC/ DC converters?  (We have been referred by SteveG & Traco to IEC 60950-1 (£620) which we don't yet have, (why do safety documents cost so much?).

Ideal would be an xyz of what needs to be done according to EU law.


texts:
I would like to find a USB extension cord with a switch, a bit like the picture below, but instead of a manual switch, I would like to control it by GPIO of RPi.
I thought it would be easy to find but I tried many keywords in English and French and couldn't find something already built. Should I create it myself with a transistor on the Vcc of the USB (I don't know if it that simple)?

[EDIT]
The reason why I need that is, sometimes I got a problem with my motor driver that is connected in USB to the RPi. The only solution we have to reset it is to unplug and replug the USB cable. That's is why I would do it softwarely and then be able to restart everything from a script.
That's why I don't know if just opening the Vcc is enough or should I open the 4 wires of the USB cable.
Thanks in advance


texts: Solving RC circuits with impulse or unit step input by using convolution integral

texts:
I want to learn the solution of RC circuits by method of convolution with impulse response and input

and find zero state solution.However I couldn't understand clearly the using of the method. For example I have such question

and I wanted to use this method to solve this problem . I obtain impulse response of Vc and convolve with given input

as shown but I couldn't find desired answer.Can you give me insight ?


texts: Heating a box (as a thermodynamics dummy)

texts:
I expect to build a dehydrator and am knowledgeable enough for most of it (fan, timer, power supply and so on), bar the most important part: the heating element.

If you're not familiar with electric dehydrators: you usually seek a 30-70°C (most of the time ~40°C) temperature control for a 5-12h drying timespan.

Problem is, I have absolutely no clue how to pick a heating element. The box will be made of wood (not sure about the door, will be either wood or glass) and its dimensions should be something like 30x30x50cm. The box is partially open so air can pass through (with the help of a fan).

Is there a fairly simple way to guess which amount of heating power I need? To pick a heating resistor which will "roughly" do the job at expected temperature?


texts:
See the video in the following link: https://www.youtube.com/watch?v=olnXy-J48SY

"Variable field magnet motor"

How does this work and is it actually efficient?


texts: Why two Xilinx scripts with different bitgen options yield correct and incorrect behaviors?

texts:
I am really puzzled by a FPGA synthesis problem on Xilinx ISE.

Precisely, it took me a long hour to discover why a same RTL design (set of VHDL files) works like a charm on a board using a synthesis script, while a second one does not yield a correct behavior. I have not seen any error messages, nor differentiating warnings.

The difference lays in bitgen options :

-g binary:Yes
-g DriveDone:yes -g StartupClk:Cclk

Only the second set of options does works.

Could you give me more insight on these two lines ?

Thanks


texts: How to use tri-state buffers to make AND and OR logic gates? I can use an inverter

texts: It's for an assignment where I have to make AND/OR gates using tri-state buffers and NOT gates. Is there any way I can do that without using any other gates?


texts: Use a European halogen electric light fixture in the U.S.

texts:
I brought a halogen standing light fixture home to the U.S. from Europe.  The light worked using an adapter to convert the Euro plug to the U.S. plug, but the light was dim.  I read that the wattage of the Euro bulbs was specified based on the 220V in Europe so i replaced the bulbs with US rated bulbs ( 300 W) and the light worked perfectly for a while. The main torch light stopped working but the task light continues to work.  I tried another bulb in the fixture and it does not work either.

There is a T2.5AH 250V fuse in the fixture that, when removed, turns off the task lamp.

Does the fuse have to change to correspond to the 120V?  Do i have to replace anything else in the lamp to make it work?

Thanks in advance for your help.


texts:
I got a new IR led, emitting light at 850nm.  It says 5v reverse voltage and 1.5 forward voltage.  How many volts should I give it?  I have DESTROYED three other IR LEDs because of giving them too many volts.  What should I do?!

---------------------------------ADDED----------------------------------
Here is the full information on the LED, typed up:

Max. Reverse voltage:5v
Max. Continuous forward current: 100mA
Max. Forward Voltage: 1.5 typ., 1.8V max.@50mA

So, if I give it 3.3v@50mA raw, it will destroy it, correct?  Therefore, I guess I need a 10k resistor?


texts:
I'm currently working on receiving signals from an RC remote. I have used pins A8 to A15 on my Arduino Mega board.

The ports and interrupts are setup with the help of this code:

DDRK = 0b00000000;      // Set port A8-A15 to input
PCICR |= (1<<PCIE2);    // Enable interrupt on PCMSK2 containing receiver pins
PORTK = 0b11111111;
PCMSK2 = 0b11111111;    // Enable all interrupts on receiver pins

Then I have set up an interrupt which finds the pin which interrupted and times the pulse.

// Interrupts whenever a signal is received.
ISR(PCINT2_vect) {
static uint32_t startTime[8];
static uint8_t lastState;
uint8_t mask;
uint8_t changedPin;

mask = PINK ^ lastState;
lastState = PINK;

if(mask & (1 << 0)) changedPin = 0;
if(mask & (1 << 1)) changedPin = 1;
if(mask & (1 << 2)) changedPin = 2;
if(mask & (1 << 3)) changedPin = 3;
if(mask & (1 << 4)) changedPin = 4;
if(mask & (1 << 5)) changedPin = 5;
if(mask & (1 << 6)) changedPin = 6;
if(mask & (1 << 7)) changedPin = 7;

// Check if the changed pin is high
if(lastState & (1 << changedPin)) {
    // Start counting if it is
    startTime[changedPin] = micros();
} else {
    // Save if it has gone down again
    rcValue[changedPin] = micros() - startTime[changedPin];
}
}

This is actually working really good, except for the part when I connect a total of 4 or more pins.

Example:
A8: Working fine
A8 to A9: Working fine
A8 to A10: Working fine
A8 to A11: A9 and A11 working fine, A10 doesn't register any input, A8 jumps up from normal values (1000-2000) to values which are approximately 17000.

My guess is that it may have something to do with the masking and detection of the pin from there, but I have searched all over the almighty internet and it has not given me a clear answer.


texts: High voltage, high common mode current measurement. Any suggestions?

texts:
I asked this question a few days ago, but I don't think I was clear enough, so I'm going to try again.

Here is a rough diagram of my sputtering system:

Basically, a DC voltage supply holds the substrate at a large negative voltage (~-1000V) relative to the chamber chassis (Vs) and a DC current supply pushes a large current (~120A) through a plasma into the chassis and substrate (It).  Only a small fraction of the total plasma current actually goes through the substrate (~2A out of the total 120A).  Most of the current passes directly into the chassis.  So, to clarify, there are two power supplies.  The voltage supply is providing -1000V to the substrate through which ~2A are passing.  The current supply is providing 120A through the target/plasma (at about 20V).

The resistor between the chassis and ground indicates that the chassis is poorly grounded.  Furthermore, the resistor should be taken to be variable as the current flow through the stainless steel chassis fluctuates, meaning that the voltage of the chassis relative to earth ground fluctuate significantly over time.

Here is the problem:  I want to measure the voltage between the substrate and a particular spot on the chassis without measuring any of the voltage due to the large current flowing through the chassis.  The measurement doesn't have to be very precise, it's only used as a check (i.e., +/- 5V is fine).

Right now, this is accomplished using a Fluke battery powered DMM.  Since it's battery powered, it makes a real floating differential measurement.  What I'd like to do is replace this handheld meter with a non-battery powered solution that could also be hooked to a computer for data-logging purposes.  I thought maybe using a 110V AC to 9V DC wall adapter that could hook into the Fluke's battery terminals might be an idea, but I guess there is no electrical isolation and all the current in the chassis would get dumped through the Fluke to the mains ground.

Can anyone suggest an approach?  I'm pretty ignorant about this stuff.  I've tried reading up on it but can't figure out anything that might work.  If I can clarify in any way, I'd be happy to.  Any suggestions (including "you're stupid.  this can never work") would be appreciated!

Thanks a lot in advance,
Brian


texts:
It has been a while since I took "Embedded Systems" course where we studied "Super-Loops", "RTOS", Semaphores, Multitasking (cooperative vs premptive) so sorry for this question.

We have an an application where we have an ADCinterface to a number of signals and where we are sending SMS at the same time. We are using super-loop. The problem is:

  When we are sending SMS's, the rest of application has to wait on it.

My question is: do microcontrollers (32 bit PIC, ARM or 8051 based etc) support threading so that one thread can take care of SMS while we read ADCs in a separate thread, or it is just a matter of using RTOS which supports multi threading vs super-loop which does not?


texts: Explain the internals of digital multiplexers

texts:
We were taught ayt our school about data selectors or multiplexers as basically a OR gate taking input of some decoder (Binary to Decimal,Bin2Hex,etc.) with an EXTRA INPUT Lines attached to the AND gates and the output of AND gate is fed to OR gate
Something along the line of this:

This has confused me (google resources added to that confusion.It put me to conflict between what taught at school and what's there).

Can someone explain:

Why do we need Bin2< desired_base > DECODER
How they help us select a particular input over the others
How the receiver knows what kind of input the given output from multiplexer maps to
Since just a HIGH or 1 can represent different combo of Inputs
In simple words how the DECODER or more appropriately said DEMULTIPLEXER revert/decodes back the INPUT
Applications of MUX and how it used in those applications (can you give a big picture of it)


texts:
I am new to PIC microcontroller programming. I am trying to programming PIC12F629. I have a hex file (size 518bytes). When I am trying to write using PICkit2, it shows memory overflow. Here is my code:

int main()
{
    TRISIO=0b00000111;
   // ANSEL=0b00000000;
    GPIObits.GP0=0;
    GPIObits.GP1=0;
    GPIObits.GP2=0;
    int count;
    while(1)
    {
        jmp1:
        if(GP4==1)
        {
            goto jmp1;
        }
        else
        {
            jmp2 :
            GP1=1;
            __delay_ms(10000);
            GP0=1;
            count=0;
            jmp3:
            if(GP5==1)
            {
                count=0;
                GP2=1;
                __delay_ms(40000);
                goto jmp5;
            }
            else
            {
                count++;
                __delay_ms(5000);
                if(count==60)
                {
                    GP1=0;
                    goto jmp5;

                }
                else
                {
                    goto jmp3;
                }
            }
            jmp5:
            GP0=0;
            GP2=0;
            jmp4:
            if(GP3==1)
            {
                goto jmp2;
            }
            else
            {
                if(GP4==1)
                {
                    goto jmp1;
                }
                else
                {
                    goto jmp4;
                }
            }
        }
    }

   return 0;
}

Flowchart of intended behaviour:


texts: Is it safe to instantaneously discharge 100nF 5V through an HC CMOS gate?

texts:
Consider the classic "pulse stretcher" circuit shown in Fairchild AN-140, Figure 12.

When the first gate drives low, the instantaneous capacitor discharge current will easily exceed the absolute maximum value for the gate sink current. Of course, the absolute maximum value is normally a DC rating, and the gate can actually withstand much higher currents for short periods. I guess this is the effect which this circuit relies on for successful long-term operation.

How can I determine if it's safe to instantaneously discharge 100nF 5V through an HC CMOS gate without a current-limiting resistor? I guess that is what the author is trying to establish with the "BE SURE THAT" equation below Figure 12. However, I don't understand why that equation is dependent on "t", and it seems to fail for any reasonable values of "C" anyway.


texts: Any ARM based microcontroller with integrated WiFi?

texts:
I am looking for a ARM based low cost SoC with an integrated WiFi, tried different search engines and still not been able to locate one.

I would like to know if anyone knows of such device that has an integrated WiFi controller that only needs and external antenna.

I may choose other architecture than ARM, but I would prefer to stay with the CPU architecture that I already have a working SW development environment.

---- Update July 27   -----
I have found a device that has an ARM Cortex M3 plus WiFi interface, the name is Imp, they are selling a small break outboard with their IC here

http://smartmaker.com/en/home/602-electric-imp-002.html

The problem with this one is that all communication with that device MUST go through their servers.
Now, the question is if there are any other companies who have such a product with an open interface rather than a closed one like Imp!

Update 2
REALTEK seems to have created the perfect low cost module for this and the modules are widely available on e-bay and AliExpress like this one:

http://fr.aliexpress.com/item/RTL8710-WiFi-Wireless-Transceiver-Module-SOC/32666025289.html

The module is sold between $2 and $4 depending on quantity and shipment. RTL8710 is based on Cortex M3 and has between 512k and 2M memory available.

There a very well written page about RTL8710 on Hackaday:

http://hackaday.com/2016/07/28/new-chip-alert-rtl8710-a-cheaper-esp8266-competitor


texts: Solving for the impedance and phase shift in a series-parallel AC RCL Circuit with Complex Numbers

texts:
Having a lot of trouble working through an AC circuit, asking for some help.

The circuit is relatively simple - I have a capacitor of capacitance \$C\$ and resistor of resistance \$R\$ hooked in parallel, which is hooked in series with a coil loop of impedance \$L\$ to an alternating voltage source of \$e_0\sin(\omega t)\$.

I'll work through the steps to show you where I'm having my problems.

So, first, solving the parallel combination. $$ \frac{1}{Z_t} = \frac{1}{Z_c} + \frac{1}{Z_r} $$

and we know that \$Z_c = \frac{-i}{\omega C} \$ and \$Z_r = R \$

So $$ \frac{1}{Z_t} = \frac{1}{R} - \frac{\omega C}{i} = \frac{1}{R} + \omega Ci $$

and thus $$ Z_t = \frac{R}{1+i \omega CR} $$

Now, to find the total impedance, \$ Z = Z_t + Z_l \$

$$ Z = \frac{R}{1+i \omega cR} + i \omega L  =  \frac{R(1- \omega^2 LCR) + i \omega L}{1+i \omega CR}$$

Is that right?

Additionally, the next problem I then have is the phase shift. By definition, the phase shift of a complex circuit is $$ \phi = \arctan\left(\frac{\text{Imaginary}}{\text{Real}}\right)$$

How the heck am I supposed to get an imaginary and a real out of that equation? What parts are imaginary and what are real?


texts:
For a visual reference of what I mean by semi-cylindrical plates check the diagram below.

EDIT:
The above diagram is not what I intend to implement. It is just to show anyone trying to answer the problem what I mean by semi-cylindrical plates.
How would one go about deriving the formula for such a capacitor? I could start with something but don't know how to proceed further. Here is what I could come up with.

If we start with the equation of parallel plate capacitor $$ C = \dfrac{\epsilon A}{d} $$
and replace d = f(x), x being the angle shown in the diagram. Then by the formula of chord length $$ f(x) = 2rsin(x) $$
this makes the original equation $$ C = \dfrac{\epsilon A}{2rsin(x)} $$


texts:
Both I2C and SWD are two-wire protocols. I wonder what are the main differences of the hardware layer of these protocols and what are the pros/cons of each one?

It's also interesting that the maximum claimed speed for i2c is 5MHz (version 4, ultra-fast mode) and 50MHz for SWD. Why is the difference so big? Is it possible to achieve the same speed for I2C if same hardware components are used in theory?


texts: Selecting an Arduino for automotive Dashboard

texts:
In an upcoming project I need to design a custom dashboard for a race car (in a student design competition). There would be at least 3-4 sensors that would need interfacing and a graphic LCD to display the stats.

My preferred choice for the processor board is an Arduino because of the number of libraries available, the cost factor and the relative ease and rapidity of development.

Where I am stuck, however, is choosing the exact processor. With 32 kB of flash and 2 kB RAM, the Uno seems a decent enough and a cheaper choice while the Arduino Mega 2560 would be more than sufficient for my needs.
My initial choice was the Arduino Uno (processor: ATMega328) but considering the fairly intensive nature of the application I am giving it another thought.

1) Is there any other alternative besides the Arduino that I might have overlooked?

2) Which is a better choice for this particular application? (Note: cost is a -key variable here)

3) On an slightly unrelated topic, how do you usually estimate the RAM usage of a particular application for choosing a processor (considering you have sufficient flash)?

I'll be programming mostly in C with some Processing-like code.


texts: Should I include a pull-up resistor for this application? simple schematic

texts:
Once the FSR is pressed the output of the comparator should go high. Since there is not really any "delicate" logic behind this schematic I was wondering if a pull-up resistor is really necessary for this application that involves simply turning ON a DC motor while the FSR is pressed. The comparators' data sheet does say that a pull-up is recommended. What do you guys think?

Comparators Data Sheet: https://www.onsemi.com/pub/Collateral/NCS2250-D.PDF


texts: I'm currently making my GCSE project and the deadline is quite soon, but i have a fair amount of issues still.  I am using a Genie C20 chip to programme a countdown that will indicate the start of a race on a scalextric track.  If a microswitch (in the scalextric track) is activated before the countdown is finished (the player has started early), an alarm will sound.  Can someone help me to work out why this circuit is not currently working?  Could it be something to do with the voltage regulator?


texts: Current flow in long channel MOSFET in saturation

texts: Why doesn't the current in long channel nMOS decrease with drain voltage due to pinch off that takes place when gate voltage at a point in the channel is less than the threshold.


texts: What is the purpose of a superstrate above a printed antenna?

texts:
I've seen that there are some planar antennas which are not simply a metal patch above a substrate, but present also a dielectric superstrate.

Some examples of this configurations are:

This planar biconical (aka bow-tie) antenna (taken from here, page 5)

This ring antenna (taken from here, page 3)

According to both articles, the superstrate has the effect of alleviating the resistive losses created by a resistive frequency selective surface (RFSS) which is put under the substrate for impedance matching purpose.
I don't need a precise and accurate analysis of this, but only an intuitive description. Basically, the situation described by both articles is this (in which I've represented the resistive FSS with a resistor):

How can a dielectric layer above the antenna help to reduce the dissipated power on the resistor (resistive FSS)?
A professor has told me that the reason may be that the superstrate may attract more of the electromagnetic field toward itself. Less electromagnetic field goes to the resistive FSS below the antenna, more goes above the antenna, so, less resistive losses.
But, why should a dielectric superstrate enhance the electric field going towards itself?


texts: Home automation protocols to use for wifi

texts: I am trying to zero in on which home automation protocol to use for my embedded device. I have a wireless module which connects to a router. So the protocol has to operate over wifi. I know I will not be able to use Zigbee and Zwave since these dont operate over the 802.11 layer. I was wondering if there is any open source home automation protocol which is a standard and which has been implemented for wifi or is independent of the medium of transmission of messages ? Also I am targeting embedded systems so if there is a C library to use that someone knows about or a open source project written in C for home automation , please let me know.


texts: High-voltage programming of ATTiny13 with AVRISPmkII and avrdude?

texts:
I am in the process of learning on how to program ATTiny13-20pu, and am reading this post: http://www.vk2zay.net/article/211 (archived: http://www.webcitation.org/6Imwjmidx ), which explains how to do serial communication with attiny.

Citing:

  "The fourth ADC multiplexer channel in the tiny13 requires the reset line to be dedicated as an IO pin. Setting this fuse breaks simple serial programming, so I chose to use
  only three of the available four channels. You can alter the code if
  you don't mind HV programming,"

To program ATTiny I am using AVRISP mkII, which I connect using 6-pin Vcc,GND,SCK,MISO,MOSI connector. External DC is 5V (GND and Vcc from avrisp are connected to GND and Vcc of that DC source, otherwise avrdude does not see the target). An example of the command on Linux:

avrdude -p attiny13 -c avrispmkii -P usb -U flash:w:blink.hex

The question is, is it possible to use HV programming in this setting or do I need something else than AVRISP? What to do with external DC source, which is now 5V and is parallel to AVRISPs Vcc/GND?

As I have too little experience in programming chips, I am trying to play safe and understand the consequences of blowing that RESET-related fuse.

If possible, please tell also if I am doing the programming in a wrong way (endangering chip or AVRISP device), or call things by wrong names.


texts: Can I convert 72V to 12V using potential divider?

texts:
In our automation project, we'll be using a buck converter to convert the DC voltage from 72V to 12V. This method of conversion is quite expensive!! We are converting the voltage to power the raspberry pi 3 B+ and some sensors. So first, we need to charge our power bank through a car charger.

I was thinking if we can use a potential divider circuit for this purpose or a cheaper way?

What are the drawbacks of doing this?

it seems like not possible or having critical drawback :)


texts: Paint Can Power Plant {gasification stove, steam turbine, dynamo, batteries}

texts:
thanks for stopping, here's a little update, this is not going to happen the way I'd hoped so I'm going to change my tack a little, it was suggested that I pick up an alternator so I'll do that and rip apart my bike for donor parts. I need to lose close to a hundred pounds so, in addition to the paint can set up, I want to get exercise while charging my batteries, I mean camping is one thing, I have no intention of roughing it.

Here's why I'm doing this crazy stuff, this project is part of my Movember campaign {Link to Sweet Tom Movember page here} I'm writing and trying to raise awarness at the same time. I have too many ideas and not enough time, I leave Monday night after karaoke so this seems like the obvious thing to me.

So I will start with a pedal power unit to start with and then refine my paint can power plant while I'm up there {somehow lol} I will try to post some pictures and test results of my output when I have something to tell.

I really want to thank everyone for their input... Did I mention that I want to generate power while walking too? I'm thinking a 3D printed tesla turbine with a bladder system in my shoes but that's a whole other kettle of fish.

Cheers

I'm writing a book and part of my story includes a wilderness retreat on which I'll be embarking quite soon. It all started with a paint can, a couple of bucks from Home Depot, turned into a highly efficient wood stove. I had the idea to fashion some kind of steam jack to charge a cell phone but then I asked myself, how much power can we generate with wood pellets as fuel?

As a starving artist, this project uses as many found parts and workarounds as possible as well as embracing the designs of Nikola Tesla and those he inspired. Currently working on locating a stepper motor to re-purpose into the tesla turbine

The next step is a dynamo, I was thinking of an old hand blender motor that I have kicking around but I need your collective knowledge to get from there to batteries.

I also saw this today and wondered if it was possible to incorporate this design:
I'm not sure if that's practical or possible given the time and money constraint.

I also need advice on how to control the charge and dump the input once the batteries are full. I was thinking it would be cool to have a Tesla coil to dump to power to... not sure if I could do it safely in the woods.

I hope I can find the knowledge I need, I wish I had more tile to get it ready.

Live, love and stay Wild my friends


texts: Controlling Two Circuits with One Switch

texts:
I'm trying to build a circuit with multiple timers, each with an SPST output relay. I want to connect up my circuit so that if any of the timers reaches their set point, they turn on a beacon.  It doesn't matter how many timers reach their set point, as long as one has I want the beacon to be on. Additionally each timer will turn on its own light when it reaches the set point.

I've drawn up a circuit, but have a question, is it possible to control two lights with one SPST switch? The simplest form of the circuit I'm visualizing is shown below:

(All the Lights and Beacon and Power Supplies are 12V)

The outsides (including the switches) are the timer circuit section, while the middle part is the beacon and its power supply.

I'm particularly confused about what happens in the red path. Would that be bad for the lights? Or turn them on before the timer switches close?


texts:
I want to program the STM32L152C8u6 unit but i don't know how.
Can I use the SWD interface on the STM32F4Discovery development board to program a STM32L152C8u6?


texts: Updating Arduino Uno R3 ATMega16u2 firmware

texts:
Regarding another big problem I have with some of my arduino's boards I start to suspect the ATMega16U2 chip to be corrupted and would like to be sure that he's working fine.

So I've download Atmel Flip and I'm able to connect to the ATMega16u2 through serial with the proper driver installed and the 16u2 passed in DFU mode.

But now I'm a bit stucked. Indeed on the github repository of the arduino project I can only find the 8u2 code. And I can't find any hex file firmware for the 16u2...

As it's the first time I'm doing this, can you help me a bit ?


texts:
I want to set up an experiment exactly as given in this data sheet for the T/R switch that I recently bought (the MD0101):

Every pulser receiver circuit that I’ve found neglects to address what happens during the “receive” portion of the event, i.e., if you’re using a function generator that just pulls the output to ground after sending out a pulse train, how are you supposed to be able to sense any movement in the piezo transducer if both of its plates are grounded?
The only way this circuit would work is if the function generator immediately disconnected its channel after sending out the pulse train, correct?


texts: What happens when an op amp misses one of the power rails?

texts:
I would like to know what happens when a dual power supply op amp misses one of the power rails and what kinds of damage I can expect for op amp.

What prompted this question:

I have a analog PID module from SRS (SIM960). It usually works in a mainframe that supplies the power but because of space constraints I had to supply powers myself (+5V for digital and +/-15V for analog). It worked for a while, but yesterday I discovered that -15V connection had been un-plugged by accident, and the PID module was not behaving correctly. I promptly fixed the connection but now the module seems damaged. At least the input pre-amp section is damaged. The (P gain * error) value does not read correctly, and it seems to be at an almost fixed value, not responding to change in polarity, P gain, or error itself.

The online manual for SIM960 does not show the schematic diagram, and I don't think I can post a copy of the diagram from the paper manual, so the input preamp section looks like instrumentation amplifier followed by some op amps for proportional gain. All the op amps are OPA228/OPA2228.


texts: What is the more frequent error in DDR Memory?

texts:
this is about DDR memory data corruption and not about STUCK address or data lines. If we have a good DDR with no memory stuck issues and we perform lots of writes and reads which type of error is more prominent

0 getting converted to 1
1 getting converted to 0

Where can I get such statistics.


texts: Beginner question: what does it mean for a TinyFPGA BX to be sold without pins?

texts:
This might come across as a really silly question for some of you, but to give more context - I want to buy a gift for someone else and I have found a TinyFPGA BX, but it says "without pins".
What does that mean? As far as I know, pins are quite essential. The description does not really explain what that means. Does that imply it cannot be hooked up to a breadboard,  etc?
Link to the product TinyFPGA BX (Without Pins)


texts: MOSFET Driving /w PWM - Ultra Low Duty-Cycle

texts:
I'm working on an adjustable (0.1 - 60VDC) direct off-line SMPS using UC2843.

Expected minimum output voltage is 0.1VDC in my application, so the minimum duty-cycle ratio (\$D_{min}\$) will be %0.08. Since the gate drive signal is not perfectly rectangular, it will have sharp triangular pulses at such low duty-cycle ratios. I think that it's impossible to drive a MOSFET with such a signal but I'm not sure. Gate capacitance of the MOSFET is about 1.5nF, by the way.

According to the datasheet, UC2843's rise- and fall-times (\$t_r\$ and \$t_f\$, respectively) are about 50ns typical. Putting minimum \$2t_r\$ between rise and fall for proper driving (which means \$t_{on-min} = 4t_r = 200ns)\$, required switching frequency will be about \$f_S=8.10^{-4}/200ns = 4kHz\$. :) Of course the switching frequency cannot be that low. I'm planning that it will be around 100kHz.

Is it safe to drive a MOSFET with a "triangular" pulse? If not, what can you suggest?


texts: Sending messages between CANs FD with different bitrates

texts:
In my team we are performing some CAN FD tests. We are trying to extend our current tests for classic CAN to cover FD and while trying to send message between CANs FD with different bit-rates we have faced a bit unexpected situation. In case of classic CAN the behavior is pretty obvious (different bit-rates - no message sent or received), but for CAN FD it's not that simple. It turned out that our CANs FD can actually send and receive messages when their arbitration bit-rates are the same, but data bit-rates differ. For opposite situation, when arbitration bit-rates differ and data bit-rates are the same then no message is being sent.
This situation occurs while performing our unit tests and when trying to send messages with linux tool - cansend.
My question is: does CAN FD protocol allow frames transfer for the same arbitration bit-rates, but different data bit-rates?
I wasn't able to find answer on my question on this forum nor in official Bosch documentation.


texts: Voltage drop across capacitor in a DC circuit? (Simple question)

texts:
I'm trying to find the voltage drop across a capacitor in a DC circuit. We can assume that the capacitor is fully charged and in a steady state. Therefore, the capacitor is now an open circuit. So this is really an open circuit voltage problem.

My question concerns the following section of the circuit:

Node a -> resistor -> node b -> capacitor -> ground

Is the voltage at node b zero because no current flows through the capacitor \$(V=0R)\$? Or does the voltage at node b equal voltage at node a?


texts: Question about powering ADC to LED board

texts:
My bench power supply died today & I thought I'd salvage the LED displays. Turns out they are on a board which has 2 x ICL7107 3 1/2 digit A/D converters. The datasheet says that the max supply V +6v but also mentions -9V. Does this mean the chips need a dual supply?
I noticed that the board has a L7805CV positive voltage regulator which according to the data sheet gives a 5V output. Prior to this there is a 2w10 bridge rectifier.
So my assumption here is that I can power this from a +5V supply if take out the regulator & the bridge?


texts: Operational Amplifier zero current input

texts:
Can i ask a very basic question please about Op Amps, specifically non inverting op amps with a negative feedback. I know two conditions are present a priori to any voltage input, and that is input current is 0 for both inputs. If input current is zero, how does voltage get applied in the input?
And is negative feedback a constant loop that is constantly fed back until the voltage difference is 0, but isn't this an a prior condition?


texts:
It is said that, though only active power can actually do work, we have to consider apparent power to dimension the source.
But what would seem important to me for that would be to know the maximum absolute value of the instantaneous power, which would be the apparent power plus the active power (S+P, not P+Q (to be extra clear, there is nothing hidden in that notation, it's a pure boring arithmetic sum of two real numbers)).
Is that correct?
EDIT:
As Charles Cowie answered, it is not the peak of the instaneous power \$p(t)=u(t)i(t)\$ which is of any use most of the times. So, why is S important when dimensioning power source and input? What physical value exactly is important and which S represents more or less?
EDIT2:
I said that \$\max(p(t))=S+P\$ which is maybe a bit surprising and unjustified. Let's say that \$u(t)=\sqrt{2}\,U\cos t\$ and that \$i(t)=\sqrt{2}\,I\cos(t+\phi)\$ (frequency or pulsation isn't important for my calculation, so WLOG, let's admit \$\omega=1\$).
Then \$p(t)=u(t)i(t)=2UI\cos(t)\cos(t+\phi)=UI(cos(2t+\phi)+\cos(\phi))\$. You can find that with trig identities. \$p(t)\$ takes its maximum value when \$2t+\phi=0\$, so you have \$\max(p(t))=UI(1+\cos(\phi))=UI+\cos(\phi)UI=S+P.\$


texts: Controling 4 LEDs with 5 pushbuttons and Arduino

texts:
My code:

#define MAX 50
const int LED1 = 2;
const int LED2 = 3;
const int LED3 = 4;
const int LED4 = 5;
int array[MAX];
int old_b = 0;
int val;
int counter = 0;
int i;
int temp;
int L1;
int L2;

void setup () {
  pinMode (A5, INPUT_PULLUP);
  Serial.begin(9600);
}

int readButtons (int pin) {
  int b, c;
  c = analogRead(pin);
  Serial.print("analogRead =  ");
  Serial.println(c);
  delay(100);
  if (c > 1015) b = 0;
  else if (c > 70 && c < 76) b = 1;
  else if (c > 122 && c < 128) b = 2;
  else if (c > 169 && c < 175) b = 3;
  else if (c > 209 && c < 217) b = 4;
  else if (c > 247 && c < 256) b = 5;
  else if (c > 280 && c < 291) b = 6;
  else b = 0;
  if (b == old_b) {
   return 0;
   old_b = b;
  } else {
    return b;
    old_b = b;
    }
}

void loop () {
  while ((val = readButtons(5)) != 5) {
    if ((val == 1) || (val == 2) || (val == 3) || (val == 4)) {
      array[counter] = val;
      Serial.print("In  ");
      Serial.print(counter);
      Serial.print(" saving ");
      Serial.println(val);
      delay(200);
      counter++;
      if (counter == MAX) {
        counter = 0;
      }
    }
  }

  temp = counter;
  counter = 0;

  for (i = 0; i < temp; i++) {
    if (array[i] % 2 == 0) {
      L1 = 2;
      L2 = array[i] / 3 + 3;
    } else {
      L2 = 5;
      L1 = array[i] % 3 + 3;
      }

    if (readButtons(5) != 5) {
     digitalWrite (L1, HIGH);
     if (readButtons(5) != 5) {
      digitalWrite (L2, HIGH);
      delay(1000);
      digitalWrite (L1, LOW);
      digitalWrite (L2, LOW);
      if (readButtons(5) == 5) {
        i = temp;
      }
     } else {
       digitalWrite (L1, LOW);
       i = temp;
     }
    }

  }
}

So I have a function which detects if a button was pressed. Prior to that, I have determined in which range are values for certain button and all buttons are connected on analog pin 5 like this, except I have them 6 and my resistors have 2200 ohms. In the while () {...} loop, while the 5th button isn't pressed, Arduino is "looking" if any of first four buttons was pressed. If it was store it in an array and if not keep "looking". When 5th button is pressed, we brake out and store last known place in array in which value was stored and set the place counter to zero so when starting again, Arduino stores values in the first place of array. Then based on that what is stored I determine which pin/LED will light up. If at any time during blinking LEDs 5th button is pressed again, Arduino stops the blinking and again waits for the presses from first four buttons. That is how it is supposed to work in theory. In practice I still can't get it to stop blinking every time 5th button is pressed again. I have to press it multiple times, sometimes two or sometimes even more presses are necessary if I want it to stop blinking. I don't think using interrupts will help, since I don't know how I should implement them in my problem. Here is my circuit (except I have Arduino Duemilanove Atmega 168). LEDs go 1 to 4 from right to left:


texts:
Assuming I have a complete SMPS simulating circuit using Simplis/Simetrix simulator and all the AC and transient specifications are met. How can I perform an EMI/EMC simulation test using this software?
I have looked around its documentation and I did not find something.

Which software performs EMI/EMC test simulations of power electronics and in that case is there a way to import the Simplis/Simetrix circuit to that software?
I found something that may help me on the following site: https://www.edn.com/edn-access-02-03-97-spice-predicts-differential-conducted-emi-from-switching-power-supplie/

Unfortunately, the images and illustrations are deleted, it seams as an obsolete publication. Does anyone have an update, or the original publication? It’s an important document that might help me.


texts: Determining minimum safe wire width at high amps in a DC 12V system

texts:
In a 12V DC system, given a particular maximum current and length of wire, what is the best method to determine the minimum width (gauge) of that wire?  In particular, what method is best for high current levels and short lengths of wire?

The typical way to do this seems to be to calculate the width of wire necessary to achieve a given voltage drop, e.g. 2%, perhaps using an online tool.  However, if I understand correctly, the % voltage drop is not actually what is relevant in terms of fire safety, but rather the number of watts of dissipated heat due to that voltage drop per unit length of wire.  Running 200A over 1 foot of 10 AWG wire will result in roughly the same % voltage drop as will running 20A over 10 feet of the same wire, but in the first case there will be much more heat generated per foot of wire, so presumably there will be a higher risk of fire hazard and melted insulation.

Is it safe to assume that a 2% voltage drop will not create a fire hazard even for high levels of current over short lengths of wire?


texts: What does "S" pin stand for in power input/output?

texts:
It is probably a pretty basic question but:

What does "S" stand for?


texts: Difference between __I and __IO and __O in CMSIS core

texts:
in core_cm4.h header file defined some thing like this:

#ifdef __cplusplus
  #define   __I     volatile             /*!< Defines 'read only' permissions                 */
#else
  #define   __I     volatile const       /*!< Defines 'read only' permissions                 */
#endif
#define     __O     volatile             /*!< Defines 'write only' permissions                */
#define     __IO    volatile             /*!< Defines 'read / write' permissions              */

What's the difference between __I , __O and __IO while they are defined in same way.

and how they work to specify "read/write only" while they are only defined as a volatile variable ?!


texts: While NGSPICE can compile and run BSIM4 models, I could mot find anywhere reference to LTSPICE being able to run these models. Has anyone tried, and saw that it worked, or knows that this will probably/definitely not work?Thanks


texts:
I have been trying to figure out why my verilog program is not working for hours.  To test it I just added some constants as inputs to my module and I am using the integrated logic analyser to check the outputs.  For some reason all of my intermediate values are 0.0 (64 bit float).  I then used the ILA to check the u and d inputs and their values are zero.  Right now I am using $realtobits to create constants out of float values.  Is this synthsizeiable?

binomial_controller bc(.u($realtobits(1.0025031276057951857)),
                       .d($realtobits(0.99750312239745997367)),
                       .u_v($realtobits(1.0026284483291278971)),
                       .d_v($realtobits(0.99737844229982886013)),
                       .p_up($realtobits(0.49968750024413099986)),
                       .p_up_v($realtobits(99.500999000666340066)),
                       .p_dn($realtobits(0.50031249975586900014)),
                       .p_dn_v($realtobits(0.50035863068484875971)),
                       .int_exp($realtobits(0.99999843750122074937)),
                       .price($realtobits(100.0)),
                       .strike($realtobits(100.0)),
                       .start(start),
                       .clk(cclk),
                       .last_nine_tree_elements(r),
                       .ready(ready));


texts:
Recently I started messing around with controlling RGB leds with the Arduino for a project I'm building, so I built the following schematic:

simulate this circuit – Schematic created using CircuitLab

Essentially what the code does in the Arduino is that I have a 3D array as follows:

int paterns [][4][4] = {{{255,0,255,255},{255,0,51,255},{255,255,51,255},{255,255,0,51}}};

where the first dimension contains arrays that contain 4 sub-arrays.
The second layer array contains 4 int values, the first is intensity (brightness) of the led, and the other three are Red, Green, Blue respectively. This way, when I want to color the 4 LEDs, I access the main array and  Iget the 2D array from it, which contains brightness, red, green and blue values for each of the 4 leds.

Then, these values are writen using the analogWrite function to each pin respectively. Brightness is essentially controlling the transistor as a variable resistor.

Now the problem is that after creating the new circuit (LEDs are connected with solid core copper wires spaced ~9cm away from each other as seen in the diagram), the LEDs appear to flicker a lot in certain colors. For instance, when the following is pulled from the array:

{{255,255,255,0},{255,153,153,0},{255,51,51,255},{255,0,255,0}}

the yellow-ish LEDs flash a lot, whereas the blue and green are perfectly stable, and as far as I can tell the red diode is the one causing the noticable flicker. Having said that, I disconnected the red channel, and although the colors are altered, they only flickered very very little. In fact it was so little that you must pay close attention to the diode to notice it.

Here is the full code:

int oneGround = 11, twoGround = 13, threeGround = 12,fourGround = 10;
int red = 9, green = 8, blue = 7;
int dela = 100;

int paterns [][4][4] =
{{{255,255,102,102},{255,153,51,0},{255,255,255,0},{255,204,255,0}},
{{255,0,255,51},{255,0,255,204},{255,51,255,255},{255,0,204,204}},
{{255,255,255,255},{255,255,0,0},{255,204,0,204},{255,153,0,153}},
{{255,102,0,102},{255,102,102,0},{255,0,153,102},{255,0,255,51}},
{{255,0,153,51},{255,10,231,84},{255,10,231,84},{255,66,120,84}},
{{255,66,120,84},{255,66,41,255},{255,255,143,17},{255,30,186,237}},
{{255,153,0,204},{255,0,0,255},{255,204,51,0},{255,0,102,102}},
{{255,153,255,51},{255,153,153,0},{255,153,153,0},{255,153,153,0}},
{{255,153,153,0},{255,0,204,204},{255,0,204,204},{255,0,204,204}}};

void setup() {
  pinMode(blue, OUTPUT);
  pinMode(green, OUTPUT);
  pinMode(red, OUTPUT);
  pinMode(oneGround, OUTPUT);
  pinMode(twoGround, OUTPUT);
  pinMode(threeGround, OUTPUT);
  pinMode(fourGround, OUTPUT);
}

int c = 0, d1 = 0;

void loop() {
  lightUpValues(oneGround, paterns[d1][0][0], paterns[d1][0][1], paterns[d1][0][2], paterns[d1][0][3]);
  lightUpValues(twoGround, paterns[d1][1][0], paterns[d1][1][1], paterns[d1][1][2], paterns[d1][1][3]);
  lightUpValues(threeGround, paterns[d1][2][0], paterns[d1][2][1], paterns[d1][2][2], paterns[d1][2][3]);
  lightUpValues(fourGround, paterns[d1][3][0], paterns[d1][3][1], paterns[d1][3][2], paterns[d1][3][3]);
  if (c == 2000) {
    d1++;
    c = 0;
  } else c++;
  if (d1 == 5) {
    d1 = 0;
  }
}

void lightUpValues(int groundPin,int brightness, int r , int g, int b) {
  analogWrite(groundPin, brightness);
  analogWrite(red, r);
  analogWrite(green, g);
  analogWrite(blue, b);
  delayMicroseconds(dela);
  digitalWrite(groundPin, LOW);
}

So, how can I stop the flicker of the LEDs?

Notes:

I haven't yet learned C, all I know comes from Java. Sorry if my code harms your eyes!
I'm also a newbie in electronics, I only know a few basics and thats it, I really want to learn more though! :)
The hardcoded color array is created by a program I made, it is not written bit-by-bit...

Thank you for your time!


texts: Selecting a Capacitor for an application

texts:
I have been designing circuits recently,and the way I come to think of a resistor is that it limits the current and I can do the math to get the right value.

With a Capacitor I am aware that it passes AC Through and blocks DC, and it can also store energy, and output it as a voltage. But what is a good way to come to think of a capacitor when doing circuit designs?


texts: RC time constant changes with introducing LED

texts:
I am testing time constants for a capacitor. Practical implementation is almost accurate as theoretical calculation. But the Time const changes(rises) when I introduce an LED in series with R AND C.

cap=1000uF; Res=10K; Vcc=5V;
When only Cap and resistor is present, the Time constant comes out to be 10sec at 63% of vcc which is ~3v1 and practically it comes out to be ~11sec so it's okay.

But when I introduce 2v2 Red-Led in series with it, the time const rises to 30sec. As far as I know, LED has internal resistance in mili-ohms so the R will not be the reason for this much change.Other factor is the LED capacitance, It will probably have some value but that value should reduce the Time constant instead of increasing it because it is in series with the 1000uF so the overall capacitance should be low, hence (RXC) should be low.

Am I missing something?


texts: Is it possible to generated a combinational clock mux that is guaranteed glitch free?

texts:
Can we generated a LUT based clock mux that can be glitch free ?
I would like to switch 3-4 clocks at 100-200 Mhz. The mux can be made glitch free using registers, but can we do away with the registers (depending on certain considerations) and still get a glitch free LUT based clock mux ?


texts:
I need to make a converter to go from RS422 full duplex to my Arduino. I have found lots of different chips which I think can do this, but am slightly confused by the terminology. The RS422 device is a laser distance sensor (Micro-Epsilon optoNCDT 1302).  It has RX+, RX-, TX+, TX-. So I have two lines for input and two lines for output.

I could use two RS485 line drivers to achieve the full duplex comms which I need.  There are a lot of chips to do that.

But then on my Arduino (clone: chipkit max32) would I need to use two UART channels? And then alternate which one I am sending each byte on?

The device uses 4 byte instructions. So if I wanted to send an instruction would I send Serial1(firstByte) then Serial2(secondByte), Serial1(thirdByte), Serial2(fourthByte)?

And then receive data the same way? I feel like I am missing something and can do this on one UART channel but am not sure how.


texts:
I'm looking to hack together a keyboard by taking an existing keyboard and connecting it to switches that I'll assemble separately.

What I want to know: What should be the electrical properties of the switches that I'll buy? I'm new to this so I'm not sure whether I need "mom off", "mom on", SPST, SPDT... Please tell me which one should be used for a keyboard.


texts: Difference between "accelerator" and "microcontroller"?

texts:
I am reading the Intel D1000 micro-controller specs, it says:

  ...Intel® Quark™ microcontroller D1000 target - a configurable and fully
  synthesizable accelerator and microcontroller core...

I am not much of EE background. So:

What does synthesizable mean?
What's the difference between accelerator and micro-controller?


texts:
I do not understand exactly how the below formula has been found. The formula allows to calcul the output capacitor (Cout) of a PFC boost converter working in CCM :

Here is the definition of the hold up time if needed,

The formula for the capacitor is approximately equal to :
$$C = \frac{Ic*\delta t}{\delta V}$$ (I did not suceed in doing the greec letter "delta")
So the hold up time is 20 ms : $$\delta t = 20 ms$$
Then during the hold up time the output voltage must decrease at the maximum from Vo to Vo(min). So $$\delta V = Vout-Vo(min)$$
So we have at the moment :
$$C = \frac{Ic*HoldupTime}{(Vout - Vout(min))}$$
So Ic would be equal to $$Ic = \frac{2*Pout*(Vout-Vout(min))}{(Vout^2-Vout(min)^2)} = \frac{2*Pout}{Vout+Vout(min)} = \frac{Pout}{\frac{Vout+Vout(min)}{2}} = (approximately) Iout ???$$
But why ? Ic would be equal to Iout ?  During the hold up time which is a portion of time during the recitfied line voltage drops, the current will flow into the capacitor and out to the capacitor according to the duty cycle and the switching frequency. Vout is roughly constant even for a PFC, so the average current through the capacitor must be close to 0 more than Iout.
The formula is coming from here https://www.infineon.com/dgdl/an-1166.pdf?fileId=5546d462533600a40153559aabdf1128 (page 9)


texts:
After installing MPLAB Harmony Configurator from the available plugins in MPLAB (v5.05)

i tried to create a new project but it seems that harmony location is not valid?
I doesn't seem to have anything on PC related to it.


texts: Converting 5V from Raspberry Pi to 3.3V at MCP23017

texts:
I am trying to utilise a Raspberry Pi's 5V output to push more current towards sensors connected to an MCP23017 i2c port expander. However, the MCP23017 requires that I down-convert the voltage to 3.3V.

To do convert from the Raspberry Pi's 5V supply to 3.3V, I'm using an LD1117V33 voltage regulator, a 100nF 16V ceramic capacitor, and a 10uF 16V electrolytic capacitor connected as shown in the diagram below.

Pi's 5V output goes into the left pin of the LD1117V33, which connects to the  the + (left) pin of the electrolytic capacitor.
The middle pin of the LD1117v33 connects to the - (right) pin of the electrolytic capacitor, the left pin of the ceramic capacitor, and through to the ground.
The right pin of the LD1117V33 connects to the right pin of the ceramic capacitor. It is supposed to output a 3.3V supply for the MCP23017 (but it does not).
MCP23017 output connects to the ground.
The ground in this diagram connects to the Pi's ground.

The MCP23017 works normally when connected to the Pi's 3.3V output. Why doesn't it work with the power regulator, shown above, connected to the Pi's 5V output?


texts: Considerations when repairing dimmer switch

texts:
I originally asked this question on DIY StackExchange. So far no answers and a suggestion to try on Electronnics, so here goes:

I have an IKEA lamp with dimmer switch which took a knock and immediately started outputting full brightness. I've read a little about how dimmer switches work and that this is likely caused by the triac breaking.

I would like to repair this by replacing the triac (/diac combination?) but want to make sure that I have the right idea and check if there are any risks in doing so.

Photos:

As I understand it the block in the middle with the metal cover is the triac, possible also a unit containing a diac. Then the obvious variable resistor connected to the outside, a fuse (looks like a second fuse attached under the metal hood -- and labelled on the board -- but can't see it properly until disassembly), some resistors (baseline resistance? "taper"?) and finally the inductor and capacitor smooth out the voltage cut, reducing stress/noise on/from the load.

I plan to desolder the triac unit and replace it with an equivalent part (if I can find one). Is there a good way to confirm the triac is broken in advance? Are there any safety concerns?

UPDATE: I have since confirmed that the metal cover in the middle contains a triac (including make/model) and a thermal cutoff.


texts: Switching multiple photodiode inputs to an op amp

texts:
I am playing around with LEDs as (semi)wavelength selective photodetectors and have reproduced the circuit found in Forest Mims' Make article:

I have an operational circuit using an LM358 powered by an Arduino which is also reading the output.  I would like to expand this circuit to allow for multiple LEDs but would like to minimize the amount of components and analog read pins on the Arduino.  For my application, I do not need to measure the response from each LED simultaneously, so I would like to include some type of voltage controlled switch or similar device that would allow for this type of circuit:

(apologies for the image instead of schematic - for some reason circuit lab is hanging on the save and insert button for me)

I do not know if there is an IC that provides the functionality that I am looking for.  Essentially, I would like to use some type of communication protocol accessible from the Arduino that will allow me to digitally control which LED is connected to the op amp.

Questions.

What type of chip or circuitry would I need to cycle through the LEDs in this circuit and
given that this an educational rather than mission-critical project, are there any red flags that pop up with the proposed design?


texts: Why there are several curves on next image (datasheet for 2SK170)? What condition changes to use one or another curve?


texts:
First off i'm using arduino as MCU.
I have two internal speakers inside a box to output the sound from a FM Rádio Module, but i have also an stereo jack in my box, so anyone can plug a external speaker or earphones and listen to music. I want to cut off internal speakers when someone plug a stereo jack. My PCB mount stereo jack is in round format and only have 3 pins (GND RIGHT LEFT) it doesn't include the switching options. How can i detect when the jack is plugged into external jack and cut off internal speakers?


texts: Mod 6 counter that counts 1-6 on a 7 segment display (FIXED)

texts:
I fixed the problem, thank you all for your help, I posted the entire circuit, for anyone in the future who has a similar problem.

[![enter image description here][2]][2]


texts: How do I use a clipping Zener at the input of an Opamp inverting amplifier?

texts:
I have a \$ V_{in} \$ signal for which I cannot guaranty that it would have an upper limit. I want to clip this input signal to a limit (e.g.; 8.2V) with a circuit like above.

Is this circuit alright? Are there better Opamp circuit for this purpose?

This modified circuit is not a standard inverting amplifier. What is the input-output relation/formulation in this circuit when \$ V_{in} < 8.2V \$?


texts: What PWM frequency would give higher torque or RPM for a Brushless DC Motor

texts:
We use brushless DC motors (three phase, star wound, 540 size)in RC car applications, these are controlled by electronic speed controllers (ESC's) which will obviously vary the voltage etc supplied to the motors. They use hall effect sensors on the phases.
We can vary the motors timing on both the motor itself as well as in software in the ESC, we use a combination to acheive the desired power characteristics depending on track size, grip level etc.
We can also set the 'drive frequency' which I believe is the PWM frequency.
The available settings are 1KHz, 2KHz, 4KHz, 8KHz and 16KHz.
Of those available settings, which should give more torque and which one should give higher rpm (if that's even correct)

I understand that the answer is never quite that simple, but this is the only setting I don't properly understand..
The following page gives info on the motors I use, there is a chart at the bottom and I'm interested in settings for the 4.5turn and 13.5 turn motors

http://www.gforce-hobby.jp/products-en/G0005.html


texts: In PIC24 programming, why does AD1PCFGL = 0xFFDF mean assigning analog to AN5?

texts: I know 0xffdf is a hexadecimal number, but why does the instruction AD1PCFGL = 0xFFDF; mean assigning analog to AN5? What has 0xFFDF to do with 5? How are they related?


texts: Simple RC-Circuit (Neuron): get \$u(t)\$ as a function of time

texts:
I am trying to understand how a LIF-Neuron (please take a look) works and how I come from this:

$$
I(t) = \frac{u(t)}{R} + C \frac{du}{dt}
$$

by multiplying the equation by \$R\$ and call \$\tau_m = R\,C\$ the "leaky integrator":

$$
\tau_m  \frac{du}{dt} = -u(t) + R\,I(t)
$$

to this expression if we assume that \$u(t^{(1)}) = u_r = 0\$:

$$
u(t) = R\,I_0 \Bigg[1 - \text{exp}\Big\{- \frac{t - t^{(1)}}{\tau_m} \Big\} \Bigg]
$$

It seems that I fail to do the integration part here. Could somebody help me to get over this?

The according circuit:


texts:
I'm a ham radio operator, but haven't been very active on HF bands for a while.  I have an inverted-V antenna and a long run (approximately 25m) of coax that runs from my upstairs "shack" down the wall, through a conduit that I buried in a trench and up near a tall oak tree in which the antenna is mounted.

Other stations don't seem to be able to hear me very well, and so I am suspecting that the coaxial cable may be waterlogged.  Other than the obvious tests with an ohm-meter, how can I test the coax to see if it is still OK?

I don't have an antenna analyzer, but do have an antenna tuner and a dummy load.


texts: Why do bare die chips (MOSFET) have a maximum storage temperature?

texts:
As far as I understand, a chip in general and a MOSFET in particular has a maximum operating temperature (let‘s say 125 °C or 150 °C for Si) because above that temperature the risk increases of building a thermal runaway that creates a positive feedback and destroy the device.

But why is there a maximum storage temperature? For instance on this datasheet of the 2N7002:

Let‘s say the maximum storage temperature is 150 °C. What happens if a put a bare die chip (not mounted or anything) in a temperature chamber and heat it up to 200 °C for one hour? If the chip doesn‘t conduct current then there is no thermal runaway and since it‘s only the chip then there is no thermal stress with solder and substrate. Furthermore, this devices are normally rated to endure some (around 3) reflow profiles, which have a peak temperature (normally above 220 °C) which is above the maximum storage temperature.


texts: Is there any way of replacing components symbols systematically in KiCad?

texts:
I'm drawing a schematic in KiCad which has a lot of capacitors and resistors. Now i realised that for the sake of tidyness and to make it easier to read it would be nice to have those caps and resistors replaced for the smaller size symbols.
Is there any way to do that without having to go through them one by one?


texts: Voltage dropping capacitor doesn't work?

texts:
I connected a voltage dropping capacitor in series with 220v AC supply and I measured the output voltage and it was 220 v too. I was expecting to get a voltage that is less than 220 volts. Did I make a mistake or the capacitor doesn't work ? I just want to test the capacitor before making the rectifier and load circuit.

One more thing, It is written on the capacitor 822j does that mean it is 8200 pF ?

It is about 0.9 uF when I measure it.

I know it is a dangerous circuit and I should use a transformer but I would like to make a transformer less power supply.

Thank you very much,


texts: Is there a way to step up voltage without consuming power when there's no load?

texts:
Is it possible to take a lower DC voltage, such as the 1.5v from a AA battery, and step it up to a higher DC voltage, such as 5v, which keeps that 5v potential even when there is no load, and which doesn't consume any power when there's no load?

In other words, is there a thing (a board, a component, etc) which can take a AA battery and output 5v without the battery running down when the 5v-needing board is off or in low power mode?


texts: What is the formula for working out the volts, amps and watts of a DC Motor?

texts:
Can anyone remind of the correct way of working out the volts amps and watts on a DC motor?

I know it is something like:

\$ V=I \times R \$

\$ I=\dfrac{V}{R} \$

\$ W=\dfrac{V}{I} \$

or something like that...

So, basically, to get the answer of one you multiply or divide the other two? I forget what order it goes in.


texts:
I'm trying to control a stepper motor with an Allegro A4988 driver with microstepping.

When advancing a few steps with no load, I can see that at full-step mode all steps have equal angle, but in half-step mode there are large differences. At quarter-step I can tell some steps have zero angle, i.e. stepping doesn't move the axle at all. But I'd need my motors to move evenly at 16th-steps.

I've tuned the current control so that the winding current in full-step mode is at 70% of rated current.

I have no datasheet for the motor: I recovered it from some old dot-matrix printers built in the 80s-90s. It has 48 steps and 50ohm coil resistance. It's an unipolar stepper with 6 wires, and I'm using it as bipolar by leaving the two center wires disconnected. Given that the printer would originally be powered at 12V and the coils are connected in series, I assume a maximum current of 120mA so I based my tuning on that.

I'm powering the drivers with a bench power supply, set to 12V and max current 1A. It also powers a Raspberry Pi through a step-down converter; when motors are off the supply shows 210mA, and 310-330mA when on and stepping.

I tried other steppers taken from other printers, hard drives and floppy drives roughly the same age, and they all behave the same. I tried other A4988 modules in the same batch, and the results are the same.

I have no "modern" steppers so I wonder if the stepper age is a problem, but on the other hand it's weird that they all show the same behavior.


texts:
I am currently studying flip-flops.

I understand the purposes of flip-flops, and that they can be made by using NAND or NOR gates.

But what are the reasons for making them these two ways? Does either way work for storing bits? Or is this just for cost consideration?


texts: Hydrogen Peroxide and Hydrochloric Acid Etching

texts:
I am trying to make a PCB stencil by etching thin Aluminum using a toner transfer method.

I am using H2O2 3% and HCL 10% in a 1:1 ratio. I have also tried 3:1 and 1:2 ratios.

The alu has been cleaned with acetone.

I've tried room temp chemicals and putting them in a hot tap water bath.

In all cases the reaction is incredibly slow and weak. After 10 minutes the surface of the alu is covered in bubbles but no pitting.

Any ideas what I a missing? Others have reported this working for them (commonly with copper PCBs) so it seems strange. Perhaps this combination requires HCL at 30%?

Thanks.


texts: How does multimaster I2C work and its significance?

texts:
I am fine with I2C basic communication and implementation?
Need info on Multimaster mode of I2C
How does multi master I2C work? Advantages over I2C single Master?
In what circumstances this multi master is preferred?
Is it possible that a single slave can have multiple masters?


texts:
I started to work on PIC24FJ128GA202 microcontroller. Tried samples programs like LED blink and switch, controller works fine with the coding, then I started to work on UART configured all the parameters  as per datasheet norms. But my PIC is not functioning to my code. I have connected my controller to PC to check the characters transferred . I have posted my code below. I don't receive any character on hyperterminal... Some times I received garbage values.

#include "p24FJ128GA202.h"              // Pic24FJ128GA202 header file
#define led PORTAbits.RA2

void init_processor(void);

void init_processor(void)
{
    /* oscillator configuration is pending*/
    OSCCON = 0x0000;
    CLKDIV   =  0x0000;  //do not divide
    OSCTUN = 0;
    RPINR18bits.U1RXR   = 7; //UART1 receive set to RB7
    RPOR4bits.RP8R  =   3;   //UART1 transmit set to RB8
    __builtin_write_OSCCONL(OSCCON & 0xbf); //clear the bit 6 of OSCCONL to
                                       //unlock Pin Re-map
   RPOR4bits.RP8R = 3;
   //__builtin_write_OSCCONL(OSCCON | 0x40); //set the bit 6 of OSCCONL to
                                        //lock Pin Re-map
    // configure digital pins
    ANSA = 0x0000;
    ANSB = 0x0000;
    //  assign  IO values for ports
    PORTA = 0x0000;
    TRISA = 0x0000;
    PORTB = 0x0000;
    TRISB = 0x0000;   // 7 as receive and 8 as transmitter

    // Init UART1
    U1MODE = 0x0000;
    U1STA = 0x0400;     //Enable Transmission, Clear all flags
    U1BRG = 25;
    U1MODEbits.UARTEN = 1;        // And turn the peripheral on
}

void uart1tx(char in_c)
{
    while(U1STAbits.UTXBF != 0);
    U1TXREG = in_c;
}

void uart1str(char *s)
{
    while(*s!='\0')
    {
        uart1tx(*s);
        s++;
    }
}

char uart1rx()
{
    char c;
    while(U1STAbits.URXDA == 0);
    c = U1RXREG;
    return c;
}

int main()
{
    int i,j;
    led = 1;
    init_processor();
    while(1)
    {
        uart1tx('A');
        led = ~led;
        for(j=0;j<250;j++)
        {
            for(i=0;i<1275;i++);
        }
    }
    return 0;
}


texts: Which is best way to detect external led flashing with ESP8266 keeping circuit power consumption very low?

texts:
I have an external led (color is red) which flash with variable frequency. I need to monitor those flashes, calculating how many time led flash in a minute and log them.

I made a first try with an Arduino + photoresistor + LM358 as comparator (to get ON/OFF signal from photoresistor) and it works.

simulate this circuit – Schematic created using CircuitLab

I use them because I have those components available to make a test, but now I need to create a very small circuit with very low power consumption and wireless connection.

Specs:

microcontroller: ESP8266-01
VDD: 3.3V (coin battery)
led frequency up to (about) 5Hz

What about the light sensor circuit? What is the best way to simplify it and keep consumption very low?

NOTE: I cannot open/modify the device I need to monitor. The only way to monitor its activity is through led activity


texts:
I am using a TBMA1 biconical antenna from TekBox to make emissions measurements on my hardware (datasheet.)
I want to confirm that I understand how the antenna factor plays into dB correction. At 190 MHz at 1 meter the antenna has a factor of 16.71 dB/m. I calculated a gain of -0.91 dBi, so really a loss, using this formula:

If I measure 50 dBuV/M, I have to add 0.91 on top of it, correct?


texts: Why does my home-made capacitor have an apparent polarity?

texts:
The Problem

I've built some simple capacitors to use as pressure pads on the stairs at home - the aim is to light the stairs up as you go up them - here it is in action. But I'm getting weird readings form them, but only when connected one way round.

The Hardware

I've built them by sticking a piece of kitchen foil to each side of a piece of card, then sticking a stripped wire to either side. They then attach to a small circuit board via a molex KK connector ("SENSOR"), schematic below.

DATA_IN and DATA_OUT ports connect to other similar circuit boards. RA0 outputs data in serial format at 57600 baud. RA2 connects to RA1 of the "downstream" board and allows for the devices to self-enumerate and manage usage of the serial bus.

Power is provided by a battery and data is read through a rasberry pi via an optocoupler - so no electrical connection outside of this system.

The Firmware

The firmware on the PIC works by first setting RA4 low for a millisecond to drain the capacitor. RA4 then becomes an input and is attached to a comparator which compares against an internal voltage reference (4/5 Vdd).RA5 now goes high, and we start a timer and measure how long it takes for the voltage to reach the reference. When weight is applied to the sensor, the card compresses and the capacitance increases - and takes longer to charge up.

Results

Most of them work normally, and take about 800 uS to charge up to 4/5 Vdd. But some give really bizarre readings, fluctuating between about 30uS up to 4000uS to charge - and it changes on every single reading. Even weirder, if I take the connector attached to the "SENSOR" header on the board and reverse the polarity of the sensor - it starts working normally.

So in a sense, I have a solution to the problem - reverse the polarity of the sensors - but this is unsatisfactory as I have no idea why these apparently symmetrical sensors should behave so differently depending on which way round they are attached. Why is this happening?


texts: How to scale +15v/-15v signal to +10v/-5v?

texts:
I have a control voltage signal of an audio synthesizer that goes from +15v to -15v and I want to scale it into +10v to -5v.

I want to scale its range.

How can I do that?

I guess a way to do it is offsetting the ground to +2.5v and then dividing the incoming signal by 2. But, is there a neater way to do it?


texts:
I did my first CAN bus design on a prototype PCB. Now I would like to verify if the CAN transceiver is working OK. So I connect a PC-CAN-USB debugger and my scope on the CAN_HIGH and CAN_LOW signal lines and send a simple CAN message from my linux CPU (./cansend can0 -i 0x000).
I can see that the message is received correctly in the PCCAN-USB debugger. But the signal on the scope has a very strange pattern at the end of the transmission (see picture).

In the picture you can see the complete CAN packet of this transmission at 1MBit rate. (Notice the  mandatory bit stuffing '1' after 5 consecutive '0's).
What seems to be strange is the transmission of the last bit(s):

Can anyone explain what is happening here?
What is the meaning of this last bit (is it some kind of acknowledge bit?)
What could be the reason for the last bit looking so strange on the scope?
Does this transmission look 'OK' to you?

Thanks for sharing your CAN knowledge.


texts:
What is the minimum resolution recommended for low acceleration motion control?

Maximum Velocity can range between 2 rev/sec to 50 rev/sec. Acceleration could be as low as 0.01 rev/sec/sec. Precision is important (as the motor will need to decelerate at the right point to reach it's target position without overshooting) and the motion should appear as smooth as possible.

Motor is 12VDC with a 64:1 gearbox. Encoder will attached to either shaft or after the gear box. Motor is controlled via the Arduino PWM pin, with a pin to indicate direction.

As a rule of thumb, is higher resolution required for very slow motion?


texts: What is the difference between software and firmware?

texts: I've started learning about embedded coding. The words 'firmware' and 'software' are a bit ambiguous to me still. My understanding is that software is high level language tailored for user interaction, loaded into the CPU and modified frequently; whereas firmware is low level language, modified infrequently and loaded into a microcontroller for direct hardware control? What are the differences in terms of speed, timers, memory, peripherals, compiler, debugging etc.?