texts: Using an arduino in below-freezing temperatures

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I intend to use an Arduino in an environment with highly variable weather.  It will be an outdoor project staying outside during the entire year with temperatures ranging from a maximum high of approximately 37C (~100F) to a maximum low of approximately ~35C (-31F).  It is unlikely that these temperatures will actually be reached, but it isn't unheard of.  The temperature will most likely fluctuate between -15C (5F) and 30C (86F).

I have read that the ATmega32u4 and XBee 1mW U.FL (which I also intend to use) datasheets that both of these should operate properly between -40 and 85 degrees Celsius.  Does this mean that the Arduino itself should be able to carry on normal operation? (if it runs a bit slow, that is fine, as long as it functions normally)

Also, I am concerned about condensation.  I intend to use the following enclosure for the project http://www.adafruit.com/products/905 and will need to drill a few holes in it to get wires in and out. Will I get condensation in the enclosure? How big a problem is this? Is there an easy way to prevent it? Also, I'm curious whether the holes I drill for the cables will be problematic? Does anybody have any tips on sealing them?


texts: What switch would replace a series of 6 pins linked by jumpers?

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I've bought a small electronics kit - a function generator which produces a 1kHz signal in various waveshapes - square, sine, triangle and integrator. It's a basic kit on a single PCB (555 timer based) and you select the waveform you want using a jumper between 4 pairs of pins.

I would like to put this kit in a small box to use as a more robust tool for testing equipment. I need a chassis mounted switch which could essentially imitate the action of moving a jumper between these four sets of pins. What sort of switch would I need, and how would I wire it?


texts:
I'm working on a dual H bridge for a bipolar stepper motor. I found these two designs. I would like to know which design would you guys recommend and why? and if there is any component that might be implemented to any of the designs to prevent any damage to the motor or to improve it's performance. The transistor that I will use are 2N7000, SUP90P06 and IRLZ44.The motor will be powered by a Lipo battery (11.1V, 25C, 2200mhA). The motor that I would be using has these characteristics:

Rated Voltage: 3.6V DC

Rated Current: 1.2A/phase

Winding Resistance: 8.8±10% ohms / phase

Winding Inductance: 3.5 mH±20 %( 1kHz 1V rms)

Holding torque: 185mN.m Min (Bipolar)

insulation resistance: 100Mohms Min (DC 500V)

for the first configuration I would have to build two setups like these since it's a bipolar motor.

and the second design is here, for this setup up I would add 100 ohms resistors for each of the inputs coming from the MCU to the gate pins. This design doesn't require the additional 2 N mosfets from the first design.

Thanks!


texts: Is it ok to connect batteries in parallel?

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I've seen some questions about connecting batteries in parallel to increase capacity, and the answers all indicate that it's fine to do. But why? Isn't that creating a short if the batteries aren't at the exact same voltage? I understand there's some internal resistance in the batteries, but is that enough to make this safe?

Is there any benefit to isolating the batteries with diodes? E.g., give each battery it's own diode, with the positive terminal connected to the diode's anode, and then putting each of these battery-diode pairs in parallel?

I'm concerned entirely with off-the-shelf alkaline batteries, like AA, AAA, possibly 9V.

Resolved

No, it's not ok in general, for the reasons I described in the question (creating a short circuit).


texts: Relationship between Conducted and Radiated Emission

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Maybe it's a silly question but I couldn't find any useful info about this. Sorry for that.

I've been asked to design a 72-to-24VDC/6A converter for railway vehicles. I designed one and it works perfect. But our customer wants that the converter should pass railway EMC (i.e. both conducted and radiated emissions defined under EN50121-3-2) tests.

We have a small measurement laboratory equipped with Rohde&Schwarz measurement devices. We perform some pre-measurements on the products so that we can see their performances and make necessary modifications before sending them to accredited companies for actual testing and certificating process. For now, we can only measure conducted emissions in our small lab. Anyway, I performed some measurements in our small lab and made some modifications on the circuit to have it finalized.

After finalizing the test sample, I showed the pre-measurement results to my executives and one of them told me that if I can have the product passed the conducted emission pre-test according to radiated emission limits then it can pass radiated emission test as well (NOTE: RE limits are lower than CE's and as I stated above, we can only measure conducted emissions). When I ask him to explain why, he only says that our other products could passed RE test when they pass CE as well. But this is not an answer for me.

Sorry for the looong story, and finally my question is: How can it be? As you can guess, CE can be thought as the emission conducted via supply (or other signalling, control etc.) cables to other devices and/or battery and it's measured directly from the cable via a spectrum analyzer but RE is defined as the emission radiated by the device itself via its case (or not, doesn't matter) and it's measured via a 10m-distant-antenna. So, is it possible to define a substantial relationship between conducted and radiated emission?


texts:
I am trying to generate a reset pulse in order to wake up an ESP8266 device.

The ESP8266 supports a "deep sleep" function, in which it consumes very little power. However, the only way to wake it up is to reset it (by pulling the reset pin low - the device will restart as soon as the pin goes high again).

So I am trying to use an external event (let's say a normally-open switch) to wake up the device. However, there is a snag - the device should wake up immediately after the switch is closed, even though the switch might remain closed for many seconds or minutes afterwards. So I need a circuit that will generate a reset pulse (low, then high after several milliseconds) whenever the switch is closed.

I thought to myself - "no problem, that should be easy!" (yes, I am that much of a newbie! :) ). And I built this circuit - which performs beautifully in the simulator...

But of course real life does not fit the simulation... I am using a Wemos D1 Mini development board - which adds a whole new level of complexity, including a pull-up resistor on RST and a capacitor between RST and ground. So, of course, this simple circuit no longer works :(

My question is - how can I change this circuit so that it does the job? Or, if that is not possible, what type of circuit could I use instead?

I did consider a 555 as well, but a) I am not sure about the power consumption, and b) that is a 5V device, so it might be more difficult to run on batteries.

Some additional challenges:

The additional circuitry should use as little power as possible (the whole idea of using deep sleep is getting the device to run for a long time on batteries)
Would it be possible to use multiple switches to wake up the device? (I could then run the switches to different GPIO pins, and get the status of the pins on startup to find out exactly which event generated the wake signal)

Thank you!


texts: I am powering a circuit on 4 AA batteries. 6v is not going to hurt the circuit, but it runs more optimally at 5v.  Is there a simple and effective way to drop the supply voltage by 1v to get the best results?


texts:
I have a single FPC1020AP chip as shown in the picture below. The datasheet for FPC1020 says there are 19 pins, of which 15 are used. However, I cannot find the datasheet for this exact chip, which says which pad on the chip maps to which pin in the functional description. Thus I presume this must be somewhat standardized. The chip itself seems to have 34 pads and a marking in the corner, I suppose to indicate pad 1.

I contacted the manufacturer, but until now I did not get a response. I am unfamiliar with this package type, but if you would have to guess, which pad is which pin? Or is this blatently obvious and someone can point me to the specification of this package type?


texts:
I'm working on a project which runs off a 50V DC power supply. There is a high power H-bridge being switched at 250Khz powered straight of the 50V. There's also the analog control electronics running of 12V. The 12V has to be created from the main 50V supply. Like this:

Obviously there's noise being created in the 50V by the switching of the H-bridge which I'd like to prevent making it's way to the 12V supply. Which is the preferred method for this?

Things I've considered:

A low pass RC filter before the linear regulator.
A low pass LC filter before the linear regulator. Hard to damp properly as the analog section's input impedance is obviously not fixed.


texts:
For a silicon diode that starts conducting for 0.7 volts, we say that it is directly polarized when its voltage is 0.7 or greater and we can represent it with a voltage generator (of 0.7V) in series with diode resistance.

If voltage is lower than zero but greater than breakdown it is in inverse mode and it is modeled with current source (saturation current).

When diode voltage is under breakdown voltage, diode is in breakdown region, and is modeled with voltage (breakdown voltage) source and corresponding resistance.

My question is, for voltages 0 to 0.7V
is diode also considered to be in direct mode of operation, if thats the case, can it still be modeled with voltage generator? If thats not the case, then how do we interpret this region of operation of diode?


texts: Why do lower frequency RFID readers have a smaller range for reading tags?

texts:
Low frequency RFID readers only go a few inches. UHF can read much farther (on the scale of meters). As far as I know, lower frequency waves of the same energy actually radiate better/farther.

Is there a reason that the distance scales up with frequency? Is it an arbitrary choice that lower frequency readers only work with low power?


texts: Confusion with impedance matching example using an ideal transformer

texts:
Starting from "The Effective Resistance of a Load Resistance attached to a Transformer" at page 8 of this document there is an example where it demonstrates impedance matching using an ideal transformer. There are sections as the paragraph below:

The document says the winding resistance of the ideal transformer is zero. So far so good. I don't have any problem with that.

But then it writes the equation:

Vo = Ip*Ri + Vp

I have two problems/confusions with this equation:

1-) Vp is across the primary winding. The primary winding is a pure inductive reactance. So shouldn't correct the formula use phasors or simply be?:

Vo^2 = (Ip*Ri)^2 + Vp^2

(I mean why does the doemunet treat Vp and Ip*Ri as they are in phase?)

2-) This is a bit more confusing. According to the definition of ideal transformer it is written:

  An ideal transformer is a theoretical linear transformer that is
  lossless and perfectly coupled. Perfect coupling implies infinitely
  high core magnetic permeability and winding inductances and zero net
  magnetomotive force (i.e. ipnp - isns = 0).

This means ideal transformer has infinite inductance. And if the inductance is infinite, the voltage across the winding at any non zero frequency should become infinite from s*L equation.

But then back to the document, Ip must be zero since inductive reactance of the primary would be infinite. But the document treats as if it not zero. Where am I thinking wrong here?


texts: Design a circuit for given transfer characteristic

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Design a circuit for the following transfer characteristic with diodes(Vf = 0.7 V), resistors and voltage sources:

My try: I think this circuit should work:

In general it behaves like that. Vout is constant for voltages less than some number, linear for an interval and again linear for voltages greater than some number with different slope but I couldn't figure out values for voltage sources and resistors. When I set them so that they fit the transfer characteristic in an interval, in the other intervals doesn't work. I don't know whether I should change everything or there is an elegant way for the determining values of resistors and voltage sources.


texts: Power different types of lamps in single circuit

texts:
As homework, I have to design a circuit (in the form of a circuit diagram) to power three given lamps optimally (so that they receive the exact current and voltage they need) with any number of 1.5 V batteries and any number of arbitrary resistors.

The three lamps are: 0.15A/8V, 0.20A/5V and 0.12A/4V. The designed circuit needs to be optimal in the sense that the power consumption to power the three lamps needs to be as small as possible.

Currently, my best (and only) bet is this one:

+---[3]---[42Ω]---+   [3]=0.12A/4V
|                 |
+---[2]---[20Ω]---+   [2]=0.20A/5V
|                 |
+---[1]---[6.7Ω]--+   [1]=0.15A/8V
|                 |
+-- 6 batteries --+

Can't post images yet, therefore this crappy sh** stuff. batteries 9V indicates the position of the 6 1.5V batteries amounting to 9V.
(As a side note, the resistor values are rounded to 2 significant digits, and could mathematically be \$41\frac{2}{3}\Omega\$, \$20\Omega\$ and \$6\frac{2}{3}\Omega\$. Also, the comma is supposed to be a decimal point.)

Is there a better solution than this one (with a consumption of 4.23W), and if so, how would I arrive at that solution?


texts: Why does my ethernet on my custom board only work sometimes?

texts:
I have a custom designed board that basically functions as an ethernet switch. On it I have 4 ports 3 with magnetics and 1 without magnetics. I could not use integrated magnetics on all of them because the last port is heavy duty and didn't come with that options.
The behavior I am seeing is that if I use any combination of the 3 with magnetics then I can connect to the internet just fine. All of them recognize in seconds. When I use the port with discrete magnetics the internet only works sometimes and without any real pattern as to when it will or will not work. Sometimes I can get connection by unplugging and replugging but there is no consistency.
Things I have tried/check:

Differential pair impedance 0.25mm with 0.2mm between - same as all the other ports
Tx/RX length matching - both pairs are within 5mm of each other.
Changed out ports on board
Tried different cables
Unplugged and replugged on both laptop and board side. Will sometimes fix the problem but not reliably.
Tried another board of the same design without any change.
Inspected board for any assembly defect.

I really have no idea what could be the problem it seems to be a problem with my board but there is nothing I can think of.
EDIT:
More specific details of what circuit entails.

Switch IC KSZ8895MQXCA
Mag Jacks: JDL-0011NL
Magnetics: TG110
Non-mag jack: MRJR-5381

Layout of area of interest

Schematic of area of interest


texts:
I need help with the following configuration , using LIRC for as the source signal  for  infrared led transmitter circuit with raspberry pi .

when putting the infrared led emitter led above the collector , I couldn't get enough range for led ( wasn't bright enough using a digital camera ) even with higher voltage and current ( 5 volt )

so I've chosen the following configuration to get current gain without voltage gain  , the led was bright and got range about 6 meters and even can handle 2 IR leds in series .

my question :
1- I know the emitter follower configuration has a current gain and no voltage gain ( the IR led can handle up to 1.5 A for a short time of pulses ) , so how can i calculate current flowing from the emitter to the IR led .

2- if the emitter follower has no voltage gain , it should have voltage drop about .7  , so vout should 3.3-.7 = 2.6 volt .  I have used a digital mulitmeter between the emitter and ground and shout that voltage is about .2 volt .
so , is it a wrong reading ? how could the led be bright if the IR led typical forward voltage is 1.3 volt ?

how can I calculate current of Ie ?

3- how can I simulate IR pulses  using ltspice (generting squrewave from independent signal source tool)

attachments  :
example for IR pulses http://bit.ly/1N4GHRv


texts: Open Source USB Flash Drive Circuit Anywhere?

texts:
I would like to make a removable USB flash drive from scratch. I would probably start from component selection. And because this is not as exciting as some other DIY projects, I haven't found any reference designs I can follow. Is there a resource you can recommend to find a schematic of a usb flash drive so i can look at it as a reference design

Thank you!


texts:
I am attempting to create a footprint for a Surface Mount Component and I am using the manufacturer's datasheet for reference. They include PCB dimensions but the notation used is a bit confusing. It has a P and I am unsure what to make of it, another is almost an order of magnitude greater than what it should be, and again I suspect it is a notation.

The datasheet states the unit to be mm, which is helpful. But some of the dimensions do not make much sense, and I am certain this is because I lack understanding. I have looked extensively and I cannot find any source about this, to the point that I decided to ask here. If anyone could provide some insight I would greatly appreciate it.

(The images are drawn to scale, and I have circled the confusing parts)

Straight to the point: What do the notations in these red circles (on the images provided, both the P notation and the 10-0.7) represent? The units are in millimeters and one of the P-notated dimensions is nice enough to have an = sign to represent what the actual value is (P1.27 x 4 = 5.08mm) while the other: I have deduced that 10-0.7 = 0.7mm.

Thank you for taking the time to read this! Please even if you do not know the answer feel free to share your thoughts!


texts: What is the correct way to read color codes?

texts:
For example,

The resistor above has four colors. Green, blue, red, gold.

My calculation says its value is 562 ohms +-10%. But this page says its value is 5.6K-1/4W. What is my mistake?


texts: PLC as gateway with TCP/IP communication stack?

texts:
I'm having issues designing an architecture for communication in a vehicle. Currently a PC is connected through a switch to a series of ECUS, each one with a TCP2CAN converter. The PC has to be started prior to the ignition of the vehicle, which is the main issue, in order to keep the watchdog of the master ECU alive.

I'm searching for solutions to do this in an automated way, meaning vehicle's ignition, turns on a device (call it PLC or Microcontroller) which is able to handle this TCP messages (RAW) and send them to their correct destinations  This implies timing limitations in the system, to keep watchdogs alive.

I've found multiple PLCs with Modbus TCP IP protocol, but I'm unsure whether this is equivalent to TCP/IP. I've also search in other questions and answers, but most of the TCP/IP questions refer to a stack in a microcontroller. I'm open to other solutions (not necessarily a PLC), as long as I am able to work as a gateway to interact with TCP/IP messages (read them and modify them accordingly).


texts: Why is ground shared between primary and secondary side in LT3750 circuit example

texts:
LT3750 is a capacitor charger controller IC. The sample (typical application) circuit in its datasheet shows an otherwise isolated secondary side sharing a ground with the primary side. A PCB layout suggestion for the same circuit later also shows that the ground is shared, so this is an intentional part of the design, not a mistake.

What's the purpose of sharing a ground like that? Wouldn't it negate the benefits of isolation and make the lower voltage primary side susceptible to destruction by the high voltage from the secondary side (if the positive rail of the secondary somehow gets close to the primary side or sparks)?


texts:
One of my previous classmates said "Low Drop Out regulator has a minimum load requirement and this is related to stability. It might affect start up overshoot." In the previous school project, my LDO, designed to produce a 1.8V regulated voltage, has a 0.6 V start up overshoot and that was the advice he gave me to improve my schematics by adding a resistor in parallel to my load to achieve some minimum load current even in zero load condition. It didn't improve anything though. He didn't explain further as he was in a rush then.
Today I recalled that statement and tried to search such statements on Internet and find a couple similar statements without explanation. I couldn't find that freindly classmate again as he graduated. Could someone give a detail explanation to me how does the relations of minimum load current and stability hold true?


texts:
I'm trying to understand how the I2C "General Call Address" is supposed to work for implementing in a microcontroller.

According to the I2C Specification (PDF), Section 3.1.13:

  When bit B is a 'zero', the second byte has the following definition:

  0000 0110 (06h): Reset and write programmable part of slave address by hardware. On receiving this 2-byte sequence, all devices
  designed to respond to the general call address reset and take in the
  programmable part of their address. Precautions must be taken to
  ensure that a device is not pulling down the SDA or SCL line after
  applying the supply voltage, since these low levels would block the
  bus.
  0000 0100 (04h): Write programmable part of slave address by hardware. Behaves as above, but the device does not reset.

How is the "programmable" part of the slave address supposed to be set?  Is there supposed to be a third byte in the general-call command?


texts: How Channelization code is shared in HSDPA?

texts:
I am on my way to understand the HSDPA/HSUPA technologies. I have just started and came upon the topic of channelization code. I learned how these codes are generated - Hadamard code technique - and how they are used to transmit and retrieve the information. Further I read upon the 3GPP page that a major feature in HSDPA is that the channelization codes can be shared not only though code multiplexing, as in R99(UMTS), but also using time multiplexing. In time multiplexing one UE is allocated all the channelization codes in one TTI and another may use the resources in the next TTI.

Now I have these doubts, which I am not able to get cleared even after referring various resources.
1) Why are we giving all of the Channelization codes to one UE. Wouldn't just one suffice?

2) What does sharing the code through code multiplexing mean. Is it different from code division multiplexing? How is the channelization code shared between different UE using code multiplexing?

3) Out of Time multiplexing and code multiplexing which is better and why and used in which case?


texts: Can I use C language to program a CPLD/FPGA?

texts: I wanted to know if I can program  CPLDs /FPGAs using C language? If so, is it commonly practiced? What are the steps and the required & tools for the same?


texts: As you could see from the image below i want to understand what is the -V in a switching power supply unit and where i can use it?


texts: Has anyone programmed ATmega8A using USBasp?

texts:
I have failed to program ATmega8A using USBasp. I am sure that the wiring is ok. I have programmed an ATtiny13A several times with the same USBasp. However, no luck with the ATmega8A. This is the error avrdude shows-

avrdude.exe: error: programm enable: target doesn't answer. 1
avrdude.exe: initialization failed, rc=-1
             Double check connections and try again, or use -F to override this check.

I tested without the microcontroller connected and found the same error. Which means I have broken connection. I don’t think so.

Is there any possible reason avrdude shows this error without broken connection?


texts: Can I program a MSP430553 IC using the TIVA C development board?

texts:
I have a few MSP430G2553 ICs. Can TIVA C board (EK-TM4C123GXL) used to program the ICs as I need to buy it for a online class I am about to take ????
If yes, please specify the method to be followed.


texts: How to decide between a TVS or Zener diode for overvoltage protection?

texts:
I'll leave my specific circuit out of this for a more broad question:

What criteria does one use when deciding whether to use a Zener diode or a transient voltage suppressor, for overvoltage protection on a particular application? Also when would one use a bidirectional TVS?


texts:
I have built a buck regulator with a Texas Instruments LM5575-Q1. It was designed to handle an input range of 9-75V and output 6V at 500mA.

When I have no load it does measure 6V but as I increase the load the voltage drops. With a load as the input voltage goes up the output goes down. Thus full load and 75V is worst case scenario.

Any suggestions as to why this might be the case?

EDIT:
The first scope picture is the switching pin with no load, 5V per division.
The second scope picture is the switching pin with a 13ohm resistor for load, 20V per division.

EDIT: picture of the board. It is a battery monitor board, a Particle Photon is powered by the buck regulator in question and measures up to 4 batteries that are connected in series. The issue was first noticed when we added the 4th battery in series the photon would constantly reboot itself. It was determined to happen when the photon tried to communicate via Wi-Fi it pulled more current and the voltage dropped enough to reboot but then came right back on.


texts:
It says 100J and is much bigger than the other components.

It has a resistance of 2ohm when the circuit is without power, and 15 ohm when I attach power to the circuit. It has a 1nf capacitance. So it might be a capacitor, but why is it bigger than the other capacitors, and could it replaced by any 1nf capacitor?


texts: Why is temperature coefficient divided by reference resistance?

texts:
In a book I am following, it is assumed that the temperature resistance relationship is linear.

I would expect, then, that the resistance at a given temperature would be given by the formula

$$
R_{t} = mt + R_{0}
$$

Where m is increase in resistance per unit temperature. Therefore by taking another known resistance at temperature A we could calculate this m

$$
m = \frac{R_{A} - R_{0}}{A - 0}
$$

However the book (and everywhere else) defines the temperature coefficient as the above gradient divided by the resistance at temperature 0.

$$
\alpha = \frac{R_{A} - R_{0}}{R_{0}(A - 0)}
$$

and then the formula for resistance at temperature t as

$$
R_{t} = \alpha R_{0}t + R_{0} \equiv R_{0}(\alpha t + 1)
$$

My question is: what is the purpose of dividing by resistance at temperature 0 just to multiply by it again later, and what does this alpha coefficient actually 'mean' (in the same way I understand gradient m 'means' resistance increase by increasing temperature by 1 unit)?


texts:
I have to access the 'small' part of soldered header pins. Female jumpers cannot be placed there as the small part is too small. So i thought extending the small part of the header pins so they can fit inside a female jumper.

So i removed the metal part of a header pin and tried to solder it with the small part (the bottom part) of the pin header.

It was really difficult to solder with only two hands, but i managed to do it.
The thing is, it has broken two times already. It is too weak. I cannot do it again, only for the frustration it will break again.

So what is the best way to extend a header pin?


texts: Why is there a non-zero phase error in a second-order PLL?

texts: Why is there a non-zero phase error in a second order PLL even though there is an integrator in the loop (type-1 system)? The same transfer function is applicable whether frequency or phase is considered as the input. Why then, under locked condition,steady state error for a step-change in frequency is zero but is non-zero for phase?


texts: Headphones volume controls do not work after 4 pole jack repair

texts:
I have been repairing the jack for my pair of Sennheisers for Android (I have done 3 attempts so far) but I can't seem to make the volume controls work.

To clarify, after the repair, the sound is alright, the microphone also works but none of the buttons work.

I am not sure what I have done wrong. The soldered connections are all ok, at least it seems like they are ok.

There are 6 wires in total, 3 grounds and 1 for right sound, 1 for left and 1 for mic, something like this:

Then what I soldered the mic, right, left wires to the their corresponding positions, and then I soldered all 3 ground wires to the ground position (not sure if the grounding of all 3 ground wires together is correct), the positions look like this:

What have I done wrong?

Many thanks for your help,

Edit 1:

As Chris pointed in one of the anwers, the reason why the buttons were not working was because android uses CTIA specification and I wired things based on OMTP - a comparison is shown below.

After a rewired things based on CTIA as below, everything worked as expected.

Edit 2: Marking this question as answered although there is still one minor problem with the stereo where the right audio sounds very "echo-y" and not normal - for another thread.


texts:
I'm looking to do a quick, cheap, DIY LED project. But not sure what I actually need to shop for.

I'm making this drinking game similar to Plinko from the game show The Price is Right. I would like to add battery powered LEDs to the inside if it's frame.

Here's some specs/ideas on what I'm looking for:

These are for visual effects mostly, with some illumination at night. So, not a lot of voltage. Maybe 3mm?
The frame (inside dimensions) will be about 18x30 inches. I'm thinking maybe 2 LEDs shining down from the top, and 3 on each side.
I want them to blink slowly (like the rate a christmas tree light does). But each one should blink on it's own, not all of them at once.
Looking for white or rotating color. Exact temp isn't important.
I'll be using a plastic battery case to power it. Either D batteries or AA. Case isn't bought yet, so I can still get one that holds a different number.
I'd like for 1 set of batteries to last at least 12 hours.
I need it to be easy to wire up. I say this because I've seen some that look mounted on a tiny disc that needs special contacts. Some soldering is OK, but the soldering gun I own isn't very precise. These will be mounted in the wooden frame (prob through drilled holes).
Will I need resistor(s) as well?

I hope that answers any questions that's needed. Can you lead me to know what I'm actually looking for? Thank you very much.

P.S. In case you need a better idea of what I'm making, here's a rough image. Little circles are pegs. Orange ball is dropped at the top, bounces down the pegs, & lands in one of the slots at the bottom.


texts: Power measurement with buffered solution

texts:
How can I design a power measurement unit for my slow logger?

I want to measure AC current and would like to use a CT coil.

This will give a output of 1 V when 30 Amps are flowing through my cable.

My logger has only the capacity to take a measurement every fifth second. I need some kind of buffered solution to read from, that saves the collected values.

Any ideas how would I design this?


texts: Do cold cathode fluorescent lights (CCFLs) degrade as a function of idle time?

texts:
I have a HP LP2475w display with a cold cathode fluorescent light (CCFL) backlight. It is approximately 8 years old. However, it has only 9041 backlight hours, meaning it has been used for only 12.9% of the time and the rest of the time it has spent idle.

When compared with newer HP Z24i monitors, the LP2475w at 85% brightness will eventually after turning on and waiting be equivalent to Z24i at 90% brightness. However, Z24i at 100% brightness is only 300 cd/m2, whereas LP2475w at 100% brightness should be 400 cd/m2. Thus, I estimate the LP2475w has lost 20% of its backlight intensity. Yet it has only 9041 backlight hours.

Is it possible to lose CCFL intensity just by being idle due to e.g. diffusion or does the intensity of CCFLs degrade only when actually being used?


texts: In the USA, the grid transmits power at/around 60Hz. How big of a frequency deviation can the grid handle before relays trip and cause a blackout?

texts:
I understand that small frequency deviations will result in automatic load shedding or other control actions to restore system frequency, but when does a blackout occur? When the deviation exceeds + or - .05Hz? + or - 0.1Hz?

Power IT Labs has posted numerous simulations that are cool, but I've struggled to fully understand them.

Thanks in advance.


texts: Two 10ampere switch instead of one 16 ampere

texts: I want to use two 10 ampere switchs for my 16amp appliance.What I will do is divide the input wire of the appliance into two,pass it from two individual 10 ampere switch and then recombine them and pass it to appliance input.Can this thing work.Do 10amp+10amp in such a circuit equals 20 ampere or it will be 10 ampere only.I will switch on and off both switches simultaneously so that single switch isnt loaded more than its capacity.


texts: STM32 SPI DMA timings between data frames and multiple DMA profiles

texts:
I'm trying to setup the STM32L432 MCU for SPI communication (24 MHz, 16 bit data size, master transmit only), using DMA.

The slave device is a 32 channel amplifier chip. I need to send a specific string of bits only once at the start, to setup the registers on the slave device, and then continuously send another string of bits to let the slave know to keep sampling and cycling through its 32 channels, until it receives a stop command or powers down.

I've generated a code using CubeMx, with the appropriate parameters setup. I've been using the HAL_SPI_Transmit_DMA command to send the data. I'm getting the correct SCLK and MOSI signals however am not getting the correct timings between successive SCLK bursts. My two questions are:

The timing between the successive SCLK bursts is too short when Circular DMA transmission is enabled (shown in screenshot) I would need it to be roughly twice as big (about ~200 ns) Where can I control the timing of this? If I enable Normal DMA and put the HAL_SPI_Transmit_DMA command within a while loop I get the opposite problem, the gap between the successive SCLK bursts become too big, about 5 us. I've also tried using software NSS pin control using writepin, however get the same problem as with using the while loop, too big gaps between the data frames.
How could I setup two different DMA profiles to operate withing one script, and call them up when required? I would need this as the bit stream dataTx2 only needs to be sent once so would require DMA to be set to normal, while dataTx would needed to be sent continuously using circular DMA.

The code can be found here: https://github.com/varkong/SPI-DMA-Ver-C/tree/master/Src

Thank you in advance,

varkong


texts:
My question is about phasing?

Why phasing is needed in power line? Can't we just use one conductor instead of two or more conductors? I already searched for it, but couldn't get any relevant answer.


texts: How a USB3 device is detected over a USB2 one?

texts:
I've got a hardware platform (setup as host) which it's got a USB2.0/3.0 Micro type B female port.The system is definitely capable to detect and interface USB3 devices (can see in the embedded OS the USB3 and USB2 HUBS).

But in order to plug standard USB3 devices with a "normal" Type A connector I had to use this adapter.

The problem I've got is that all USB3 devices I'm plugging in are detected as USB2 ones instead. I tried different devices as cameras and memory sticks with same results.

I need to understand how an UBS3 device is detected over an USB2 one, I'm trying to dive into the spec and I'm no able to find a clear answer easily....

My initial guess is that this adapter is changing something in the physical layer that makes the USB3 device be detected as USB2...

Would it be possible that the adapter is causing this problem?
What can change at the physical layer that an USB3 device is forced to be detected as USB2?

Any ideas/clues will be appreciated.


texts:
Morning all,
I am toying with the idea of wiring up a small On-Off-On rocker switch which will control which battery will be active in my Airsoft setup. Below is a brief diagram of how I expect this the setup would be wired:

I am looking for some guidance:
1) Would you expect this wiring setup to work, apologies I am by no means electrically competent. This has been drawn up using various other diagrams and forum posts.
2) Previous tests show that during the initial engagement of a airsoft rifle, the circuit can see upwards of 47.5amps. Am I correct in assuming that the Single Pole Double Throw switch would indeed need to be rated approx. 50amps?

Again, apologies if the above is completely incorrect.

Thanks in advance,
Connor.


texts: Powering a 5V LED strip with CR123 Batteries

texts: I bought this 5V battery powered LED strip on amazon for a project of mine. It wants 3 AA batteries. Due to size constraints, I would have difficulty fitting in even 3 AAA batteries. However, 2 CR123A batteries would fit fine. I have heard that LED's are more sensitive to current than voltage. So should I have any problems powering it with CR123 batteries? And also would 1 (3v) or 2 (6v) be preferable?


texts: Brushed or Brushless DC motor for self balancing robot?

texts:
I am looking to balance a robot using a flywheel connected to a DC motor (think of it as an inverted flywheel pendulum). Similar to this: https://www.youtube.com/watch?v=0312BNqIBFI

What I am unsure about is whether to use a brushed or brushless DC motor.

In this case torque control is important to maintain balance (I intend to do this by controlling the voltage and by knowing there is a relationship of voltage to current; and that torque is proportional to current).

The brushless motor seems more complicated to control. I am tending towards using a brushed DC motor (geared) but I am not sure if there is any disadvantage to using a brushed motor for this type of application? I am not concerned about longevity (i.e. brushes wearing out).


texts:
I am parsing data from a Siglent SDS2000X oscilloscope.  The first chunk (0x00 - 0x003) is for wave_length.  The data sheet states that for arbitrary waveform generation, the wave length is "16 Kpts".

What unit is Kpts?  Kilo-Points?  How would I convert that to a wavelength unit such as meters?  Is a value of 3622260667 reasonable?

Specs: https://www.siglent.eu/sds2304x.html


texts:
I'm a beginner and have the following circuit:

http://123d.circuits.io/circuits/201729-pulse

The left LED turns on when you plugin the battery, I'm expecting when I press the switch for the right LED to turn on, and the left LED to turn off.

The left LED should turn off as there will be input into pin 2 of the 74HC02 chip.

Pin 1 is the output

Pin 2 & 3 are inputs to the NOR gate.

Any ideas where I'm going wrong?


texts: How to connect 5 kW electric heater to the weak wiring in house?

texts:
The water heater has a 5kW heater and requires 20A.
Unfortunately, the wiring in our house is old and this allows us to get only 10A.
Is there an easy way to reduce energy/current consumption and connect such a powerful heater to the network with an energy consumption of about 2kW?
I found, that "Triac power regulation" can be used to reduce the power consumption:

I've tested schematic using LTspice and found, that peak current is the same (very big) - 20A:

In this case, power consumption is about 2.5kW, but I am worrying about weak house wiring because of peak current is 20A. I'm not sure if it is safe.
P.S. The voltage at the outlet is AC 220V (50Hz).


texts: Circuit for small level voltage detection (microvolts)

texts:
I have been working on a project lately which help in the detection myogenic potentials (of the levels of micro-volts).
After studying from several places, I finalized the following test circuit.

The initial voltage dividers helps in generating the micro-level test signal from 1V 1.5khz sine wave. Second stage is the instrumentation amplifier, next the second order low pass filter and lastly the non-inverting amplifier.
When this circuit is simulated in TINA from TI, it works as required. But when the same is implemented on the PCB, I am not getting anything close to the Input but a 150-180kHz wave, somewhat in triangular shape.
following are the sch and board layouts

Can anyone suggest how can I go ahead since such small voltages are already very difficult to measure. Thanks in advance.


texts: Im using the polygon tool in Circuit Studio (basically Altium Lite). and I am trying to increase the necks which coonnect the pour and pad to maximize connection area. But having a hard time finding it. Does anyone know how to increase the necks or make them cover the whole pad


texts:
I'm having a problem with this circuit. I am trying to get an LED wash light circuit to be remote controlled via DMX512. The problem is, after I designed the circuit for the RS485 (which will deliver the DMX signal to my LED circuit) my professor told me that there's no time to make it and that I should just buy it. I couldn't find a descent one to buy. I am also not sure if I should connect the LEDs with parallels or using a darlington pair?

I have attached the circuitry for the RS485. Also, the options I have to connect the LEDs, not even sure which microcontroller is the best for them. Any help? It's also 5 - 9 LEDs.


texts:
I'm an electronics engineer, I have primary only worked with digital and analog design, never with RF design. But finding the field interesting, I wanted to do a project mainly to get better RF design skills. So I decided to build a simple spectrum analyzer, using a PLL with integrated VCO, a mixer and some matching circuits. The signal to analyze is feed into the mixers RF port, the PLL(VCO) generates the LO signal for the mixer, and by filtering the IF output signal and measuring the power from DC to some frequency, I should be able to get the frequency content at the LO frequency.
The PLL(VCO) frequency is set using a MCU, so the idea is to just set the frequencies of interest, and measure the power at the mixer IF port from DC to some frequency.

Hope that makes sense. :-)

Now how do I measure the power in the IF signal, from say DC to 10KHz?


texts: Please help identify this vintage component

texts:
I got this item in a bidding lot and have been trying to figure out what it is ever since.
The nearest I can tell it is either an electro shock therapy device or perhaps a remote detonator. It has brushes and a fluted cylinder. Very heavy cylinder with a handle to spin the cylinder and an electrical contact is what it appears to be On one side. Has a ground lug.

I haven't tested for current since one of the brushes is missing.

Has anyone seen One of these and know what it is?


texts:
I'm using an Arduino to control[1] 2 stepper motors [2][3] (both obtained from scraped printers and I can't seem to find datasheets for them). First I used a 12V 0.5Amp power supply, that worked for each motor separately (although [3] lacked some torque), but when connecting them together the motors stalled. I then connected a 14V 1Amp power supply and both the motors ran fine, apart from the fact that motor [2] got extremely hot, I understand that due to it's lower resistance it takes the grater share of the current while it is probably rated for lower current in the first place. As you might have gathered I'm working with a nearly non-existent budget, and my knowledge of electronics is rudimentary at best, I don't have a variable power supply, I'm basically working off scraps...

My question is how do I divert more current to motor [3]?

I thought of placing a resistor (something like 30-40ohm) on the motor [2] circuit, but that resistor would have to have a very high power rating, and, wouldn't it create a voltage drop? I think [2] is rated for 24v, and I'm already providing it with only 14v...

Another option I read about is using PWM to control the current, the problem I have with this is that it would cast me 2 extra PWM pins on the Arduino and I'd rather save them for other things (I have an Uno, so only 6 PWMs).

[1] Using L293D quad half-bridge.

[2] Mitsumi m35sp-9t resistance 10ohm

[3] Malaysia 42sin-15k8na 28ohm

p.s. I expect many people here would wince at my messy, inaccurate, quick and dirty, trail and error approach to electronics, being a programmer, I understand how you feel, but I'm not building a control system for the mars rover, I'm just trying to learn electronics by doing electronics.

Thanks.


texts: Protect voltage level translator from reverse voltage input

texts:
I have a circuit that can interface with an external signal or power. And Those signal lines must be translated to a 3.3v level (and vice versa) because that what the circuit uses. And I would like to protect the the frontline IC from reverse input by the user

Although i have a PMIC power mux and is configured to protect against reverse inputs. The voltage translator IC references the voltage before the PMIC. That is because IN1 of the PMIC either be present or not and if it is present it will have priority on the output, hence i reference the voltage translator on the output of the PMIC

Is it possible to also place a diode at the ground pin of the voltage translator just like the PMIC to protect it from RVP, Im afraid that since it does not have a direct reference to ground the signal voltages will be messed up

Another idea is to place a diode in series on input 2, But wont that cause a voltage drop on IN2?


texts:
I'm unable to understand how the biasing of the 12AX7 Tube in the schematic below works.
In particular, I can't understand how the LM334 can switch on, where does it find the required voltage to switch on?


texts: Embedded Firmware Question - Memory dump

texts:
Ok so the back story is this. I landed an online code interview with a company that shall remain nameless.

I know I am not ready for a job there but I was basically given the chance by an insider. Anyways below is a picture of the question.

I have experience doing  register programming and dealing with micro-controllers, but all of this is on my own so I have never seen "real industry up-to-standard code" so to speak. I most definitely have never dealt with any "memory dump" from a micro-controller , because well I have  never had such bug or even knew it could do that...

My question is two fold.. first is the questions in the picture... if anyone can answer them.... and my other question is...if a micro-controller fails or something goes wrong and it stops working then how does it do a memory dump? seems to me that it would require it to be in working order to execute something like that. otherwise youll just get the memory dump of what things looked like "before" the crash.


texts:
I am having trouble identifying this component. I think its a diode. But I am not sure since I hardly know much about electronic components.

The Component says "22-16 U2" and then has a symbol on it.

I know 22-16 is actually a wire gauge or size. But I am not sure if that is what it is referring to.

Any help would be appreciated.

When I tested it with the diode setting on my multimeter it showed a voltage drop on both directions.
So Me thinking its a diode ... thinks its gone bad... but is it really a diode, and what do the markings mean?

I have a photo of it. But I guess since I am new to this forum I do not have enough reputation points... Bummer But I can email the photo to anyone willing to help.


texts: Multiple inputs for driving a reset (RST) pin

texts: I have an active high reset (RST) pin that is connected to a push-pull output. I am trying to connect another input to this RST pin, but this input is unable to drive the RST line high. Is this not possible because of the other output that is connected to the RST line? Can multiple push-pull outputs not drive a single pin?


texts: Zener diode equation proof (chacteristic curve)

texts:
I'm trying to prove this equation(at least I think that's the correct one):

which produces this graph:

I can prove the one that describes the PN diode but I am not sure what I should do differenly here. Any help would be appreciated!

Note: If anyone can point me somewhere I can find this proof I would be grateful as well.


texts: Multi-feedback active bandpass filter - transfer function derivation

texts:
new to this forum. I have a question about a certain topic I'm struggling with. I have this circuit, C1 and C2 are equal and therefore just described as C:

I want to deduce the transfer function Vout/Vin with the help of node voltage analysis. This is what I have as of now:

Equation 1: Vb = 0

Equation 2: (Va-Vin)/R1+Va/R2+(Va-Vb)/(1/(I*2*pifC))+(Va-Vout)/(1/(2*Pi*I)fC) = 0

I can't seem to get it to work. I define the equations in maple and solve them like a system, but I believe I must be writing the equations wrong. Can anybody give me a helping hand?

Thanks in advance!


texts:
For a friend I'm trying to make a fuzz pedal and found this very flexible fuzz circuit, called "The Fuzz of 1000 Faces," at instructables, credits to Randofo.

However, since it's an old post, I ask the question here (since it's more generic.)

Can someone explain why the 100 K resistor (in the red circle) is used for all transistors under it? Because how I read it, is that it is connected to the collector of the first (2N2222,) and than the emitter is connected to all other emitters. But it seems to me, the first is different (why is it not connected to the emitter of the first for example?).

The original circuit can be found here: http://www.home-wrecker.com/multiface.html (thanks jsotola).

It seems to me, if the  2N2222 is not selected (switch is off,) there will be no current flowing out of the emitter of 2N2222 so all subsequent transistors will not function either.

UPDATE

Because for double checking the complementarory?) comment and answer, I added the following possibilities (changes in Red).

1A Resistor to all emitters

1B Resistor to each switch (collectors)


texts: Do I need to connect a resistor to either one of the 2 input pins of this "and" logic component? If so, what would be the value for it?

texts:
The said component is sn74lvc1g08 from TI, datasheet.

I was planning on connecting 3 1.5 volt AA batteries (in other words, 4.7 or 4.8 volts max in total) to one of the input pins (either A or B) and I'm quite sure although not 100% sure that a resistor is necessary, but I don't really know how to calculate the value of the resistor.

Please give a rather detailed procedure regarding the method of calculation. Thanks in advance.

I'm working on some safe-critical project and I'm ticking in "extremely meticulous" mode so please bear with me.


texts: Is it possible to connect a switching buck converter to a simple transformerless power supply?

texts:
Many cap based transformerless power supplies intended to use with 5V circuits, use a 5.6 zener diode to regulate ouput voltage. I'm using below circuit and the calculator here [which is based on the well known microchip appnote A954] to calculate values. with R1=33R and C1=1uF the current usually is about 45mA which is fine for many things, but a bit too low for my project.

I thought I could use a higher voltage zener (e.g. 35V) and feed the output to a switching buck. with above values for C1,R1 and the 35V zener, the output voltage rises to 34V (while the current is still at 45mA) which is about 1.3W. the 34V output is well in the range of super cheap MC34063 converters in buck configuration (with the circuit provided in datasheet). this way, with the worst case of 70% efficiency, the buck can output 5V, up to 180mA which is enough for my purpose.
one problem is, that the D1 (zener diode) calculated power dissipation is about 2.5W and the suggested real power handling is double. so a 5W zener diode is required which is hard to come by in my local stores.

Is the whole idea applicable?
Is there any workaround to use a lower power rated zener diode instead? my connected device is always on and draws at least 50mA.

-- I'm well aware of risks of non-isolated supply. The project is a remote controlled light dimmer with some added things and is out of reach of people


texts: Under no load condition,what will be the angle between the induced voltage and the supply voltage in synchronous motor?

texts: Can anyone explain what will be the angle be the angle between induced voltage and supply voltage in synchronous voltage under no load condition?


texts: What is burst length with respect to the AXI specification?

texts: I am reading AXI specification, and I am encountering "burst length". Please enlighten me what is it.


texts: Is probability theory useful in electrical engineering

texts:
I have a few days off after finishing this semester and I am hoping to study something. Ideally, I would like to be able to benefit from it in any upcoming courses I might take. I'm thinking of either Fourier Series or Probability Theory. Currently I'm leaning towards Fourier because it's essential to Electrical Engineering, however Probability Theory seems intriguing (also opens up interesting areas such as Machine Learning).

So how relevant is Probability Theory to an undergraduate Electrical Engineering student?


texts:
I haven't done EE for quite a long time. I need to implement some MUX, so I started with a two-way MUX.  But I don't understand how to make the decision:

Wiki- Multiplexer

A truth table will show that

  This truth table shows that when  S=0 then
  Z=A but when S=1 then  Z=B.

I don't get the logic here. The boolean expression is Z = (A and S') or (B and S)

Let S = 0, then each sub expression will become

　　　　　　　　　　　　　　　　z1

A = 0,　　S'　= 1　　　=>   0

A = 1,　　S'　= 1　　　=>　　1

　　　　　　　　　　　　　　　　z2

B = 0,　　S =　0 　　　=>　0

B = 1,　　S =　0 　　　=>　0

Can someone please explain to me how do we reach that conclusion? Thank you very much!


texts: What is the difference between ultrasonic receive and transmit 40khz transducers?

texts:
Having been looking for said transducers, I've come across both receive and transmit versions of seemingly similar products. I would've thought that due to reciprocity, a so called transmitter could receive just as efficiently.

Could somebody enlighten me on the difference please? All I can gather really is slightly wider receiver bandwidths.

Examples
Receiver: http://uk.farnell.com/prowave/400sr100/receiver-ultrasonic-40khz-10mm/dp/1007342

Transmitter: http://uk.farnell.com/prowave/400st100/transmitter-ultrasonic-40khz/dp/1007341


texts: Why are oscillators 'always' AC coupled with 1000pF?

texts:
Most of the time I see oscillator datasheets or datasheets for parts requiring external oscillators, the oscillator output is AC coupled to the part it's driving through a 1000pF MLCC.

This datasheet:
https://www.iqdfrequencyproducts.com/products/pn/LFTCXO073006Reel.pdf
as an example says "A DC-cut capacitor is not built in to the oscillator; a 1000pF DC-cut capacitor is therefore required in the output line."

So my question is where does this value of 1000pF come from?  In particular the above datasheet says "Drive Capability: 10kΩ//10pF".

I'm certain I must be missing something, but if the drive capacity is only 10pF then surely the 1000pF is too large to effectively couple of the 52MHz (in this case) output?


texts: Understanding of coupling coefficient and power transfer efficiency

texts:
I am a bit confused about my derivation to get power efficiency from the coupling coefficient.
The coupling coefficient \$k=M/\sqrt{L_1L_2}\$.
$$
V_2=M\frac{dI_1}{dt}=L_2\frac{dI_2}{dt}\\
V_1=M\frac{dI_2}{dt}=L_1\frac{dI_1}{dt}\\
$$
Therefore,
$$
M={V_2}/{\frac{dI_1}{dt}}={V_1}/{\frac{dI_2}{dt}}\\
L_1={V_1}/{\frac{dI_1}{dt}}\\
L_2={V_2}/{\frac{dI_2}{dt}}
$$
Then I substitute them into \$k\$ to get:
$$
k=\sqrt{\frac{V_1dI_1}{V_2dI_2}}=\sqrt{\frac{V_2dI_2}{V_1dI_1}}\\
k^2=\frac{P_1}{P_2}=\eta_{12}=\frac{P_2}{P_1}=\eta_{21}
$$
So I can say: if there are two coils that one is given power source and the other is receiving the power, then the two coils can transmit and feedback the power to each other with the efficiency of \$k^2=\eta\$. Therefore, the total power received in the receiver coil will be:
$$
P_2=P_1(\eta+\eta^3+\eta^5+\dots)=P_1\sum_{n=1}^\infty\eta^{2n-1}=P_1\frac{\eta}{1-\eta^2}
$$
As you can see, the efficiency of the power transfer here becomes \$\frac{\eta}{1-\eta^2}\$.
Is this correct? Or am I having any misunderstanding here?


texts: I have interesting problem to overcome and seek some advice. I need to test different hall effect sensors and magnetic cores. I am currently stack at issue of bandwidth. I tested sensors at DC using 10 turn coil and 10 A DC supply. This approach proves challenging at 20 kHz due to power capabilities of most signal generators. Considering two solution building oscillators with frequency of 20 kHz using signal amplifier and multiturn coil with compensating capacitor or generating fast step signal to measure 10% to 90% raise time. Not sure which one would be more practical in terms of cost of overall equipment.


texts:
just a couple quick questions. My goal is to make a powerful inductor and I was wondering if it is possible to this by connecting the primary and secondary windings of a microwave transformer in parallel. The question is: this is only possible if the coils were wound in the same direction, right? And what would happen in this configuration if they were wound in opposite directions?
Major noob here, so sorry if these are stupid questions! Any advice is highly appreciated, thank you in advance!


texts: How much current and voltage should be flowing back into my battery?

texts:
I am very new to electrical engineering, and one thing that has been bugging me is short circuits.

Main question:

When I have a circuit, how much current and voltage should be flowing back to my battery, safely (as not to short circuit, melt the wire, or damage components, or throw off voltage source equilibrium) with a load or resistance placed within the circuit?

I have recently spoken with a graduate electrical engineer (he has been out of the field for a while though) and he told me that if I have a circuit that allows voltage and current to flow back to the battery after resistance, then the battery will accumulate more voltage and current, thus sending more voltage and current back out to the circuit...  This is also why a wire connecting both terminals of a battery with no resistance or any components that deplete the voltage and current will cause a short circuit.  So am I supposed to design the circuit so that no voltage or current will be delivered back to the battery?

Example:

I guess a good example would be a circuit with a 5 Volt battery that has a 100 Ohm resistor and .05Amp (50 mA) current.  Would this deliver voltage and current back to the battery after it passes through the resistor?

So then, in regards to the same example, if I have a 5 Volt Battery and .05 Amps flowing through the circuit, but a 50 Ohm resistor - would this short circuit?

Please let me know, as this has been bugging me a bit, and I think the issue is that i am thinking about it incorrectly...

I appreciate the help!


texts: Can electroluminescent (EL) wire used as a conductor?

texts:
I know the El wires have high-frequency AC current running through them, but I have never seen anyone using them to carry power. Can I use them as a conductor for a DC led and power an led lamp using them?
Would connecting the end to led light (drawing more current) break the light?
As far as I understood the light acts as a capacitor and a resistor combination
So driving the 5v DC output of my powerbank at 2khz would provide me 314 KΩ of resistance and 4.7 nF of capacitance (per meter of wire).
Which is as follows:

simulate this circuit – Schematic created using CircuitLab
Could I add an LED source at the end (5v, ~1.8 Amps) as such:

simulate this circuit


texts: How to find Cpi ( in hybrid pi model) of transistor from SPICE parameters

texts:
I have the following SPICE parameters for an NPN

IS=8.11E-14 BF=205 VAF=113 IKF=0.5 ISE=1.06E-11
 + NE=2 BR=4 VAR=24 IKR=0.225 RB=1.37 RE=0.343 RC=0.137 CJE=2.95E-11
 + TF=3.97E-10 CJC=1.52E-11 TR=8.5E-8 XTB=1.5

I am stuck on how to find Cpi ( from hybrid pi model) from the SPICE parameters.

Is the below assumption correct?

Cu = CJC
Cpi = 2*CJE + gm * TF

where gm is IC/VT under standard conditions


texts: Interfacing 20x4 character LCD with LPC54628

texts:
This is the very first time I am dealing with the task of hardware interfacing.
I needed to interface a 20x4 character LCD with an LPC54628 microcontroller.
I am using https://www.sunrom.com/p/20x4-lcd-black-on-yellowgreen which has a built-in HD44780 LCD controller and to connect it with LPC54628 microcontroller I have used I2C LCD Backpack - PCF8574 (https://www.sunrom.com/p/i2c-lcd-backpack-pcf8574) which interface the LCD using the I2C interface.
As I mentioned before the very first time I am dealing with this type of work, so anyone suggests where to start? it will be good if the example is available.
I have gone through the below links but unable to get how to use it in our case.
https://e2e.ti.com/support/archive/launchyourdesign/m/msp430microcontrollerprojects/666684 https://github.com/xreef/PCF8574_library
Note: Here we haven't used the internal LCD controller of LPC microcontroller, as we needed to keep LPC free from it to perform other tasks and even we don't have a high data flow rate on LCD.


texts: I am trying to decode RCMM(philips protocol) using VISHAY TSOP31536 IR Receiver with STM32F207 microcontroller kit. There is sufficient data for RC5 protocol but not even a single site is explaining about RCMM. Even the details of RCMM specified(frame/message details) in documents is quite different from what I extracted from the CRO in lab. Where can I find reliable RCMM documentation?


texts: Capacitor in RS232 level shifter. Data is strictly half-duplex

texts:
I have created a level shifter very similar to the schematic at: http://picprojects.org.uk/projects/simpleSIO/ssio.htm except for the capacitor I use 47nF because the page claims:

  at high bit rates the 100nF capacitor may cause the signal to be distorted to such an extent that it can't be received correctly, in which case try changing the 100nF capacitor to a 47nF or even 22nF. If communication is strictly half-duplex you may not need the capacitor at all.

But there's no mention as to what capacitor value is best or why.

Then I see this:

  If the host transmits a lot of zero (null) data in a stream, the capacitor will discharge because in RS232 zero bits are sent as a positive voltage and ones as a negative voltage.  Since the circuit needs the negative voltage to charge the capacitor, this will also cause problems when transmitting data back to the host.

This suggests that I need a bigger capacitor that many other circuits use.

I ideally want to exchange data in a half-duplex fashion at 115200bps because later I'll use radio modules which restrict my data to half-duplex.

What should I do? Should I remove the capacitor? change its value? or lower my baud rate? and no I don't want to throw my entire circuit in the garbage can only to redo it to the max232 chip. I don't have any of those and they are not cheap.


texts: measure Watts, given only Current in a single-phase AC system

texts:
I live in Greece where 220Volts/50 Hz is in every house's socket.

I need to measure the Watts being consumed by a device (a single lamp), which I hook up in the socket.

The problem is that I can only measure the instantaneous current i(t). I don't know the resistance of the lamp neither the instantaneous voltage. The current is being measured from an arduino, using ACS712-5A, which makes my first question :
Is this safe, for me, my arduino and all my peripherals to measure the curent with ACS712-5A ?

Secondly, this is the "analysis", I did to determine a way to measure the Power. I need you to tell me, if it's valid ?

$$
P_R(t) = V(t)i(t)\\
=> P_R(t) = \sqrt(2)V_{rms}cos(ωt)*\sqrt(2)I_{rms}cos(ωt+φ)
$$
,but φ=0 since I just have a lamp (an ohmic load). So,
$$
P_R(t) = 2V_{rms}I_{rms}cos^2(ωt)\\
=> P_R(t) = V_{rms}I_{rms}(1 + cos(2ωt))\\
$$
but instantaneous power is not so usefull, so I go for the average power :
$$
P_M = \int_0^T V_{rms}I_{rms}(1 + cos(2ωt))dt\\
=> P_M = V_{rms}I_{rms} (t\Big|_0^T + \frac{sin(2ωt)}{2}\Big|_0^T)dt\\
$$
the second term is 0, so
$$
P_M = V_{rms}I_{rms}T \\
=> P_M = \frac{V_{rms}I_{rms}}{f} \\
=> P_M = \frac{220I_{rms}}{50}
$$

So, all I need is calculate $$I_{rms} : I_{rms} = \frac{I_{max}}{\sqrt2}$$
which means that I must determine the maximum current. In order to do this, I need to have a sample rate faster than 50Ηz (ideally faster than 2*50Hz based on Nyquist theorem). On this question : https://arduino.stackexchange.com/questions/699/how-do-i-know-the-sampling-frequency is being said that :

  For a 16 MHz Arduino the ADC clock is set to 16 MHz/128 = 125 KHz. Each conversion in AVR takes 13 ADC clocks so 125 KHz /13 = 9615 Hz.

So, I guess my arduino is capable of that measure. The pseudocode I guess will be something like this :

    max = 0;
    t = millis();
    while (1)
    {
      instantCurrent = readAnalog();
      if (instantCurrent > max)
        max = instantCurrent;
      if (millis() - t > 1/50) //period is over.
      {                        // prepare for the next maximum in the next period
        Irms = max/sqrt(2);
        AveragePower = 220 * Irms/50; // --> THAT'S WHAT I WANT
        t = millis();
        max = 0;
      }
    }

So, what's your opinion ?

Edit :
Missed, the division by T in calculating the average power :
$$
P_M = \frac{1}{T}\int_0^T V_{rms}I_{rms}(1 + cos(2ωt))dt\\
$$
which makes a more reasonable result, independent of frequency, as Anderson mentions :
$$
P_M = V_{rms}I_{rms}
$$
The general problems thought, remains the same :)


texts: Accelerometer IC single/double click event

texts: What are Accelerometer single and double click event, can someone clarify it for me with some theory and/or practice?


texts:
TL;DR : Can I control a servo's torque by PWM'ing a PWM ?

I'm thinking about buying a dynamixel AX18 and I would like to be control it's output torque.

If I modulate the input command, I expect the torque to be linear to the duty cycle. But I don't know if this would work on a servo, as the gears and it's internal controller might get in the way.

I would like to make a closed loop with a force sensor, in order to control the torque. I would have to identify the parameters of the servo to get the Kt gain.

Is this solution plausible or am I missing something?


texts: Long range sensors - Ultrasonic/IR/LiDAR/laser - for microcontroller

texts:
I want to build a sensor module that has a long range.

I was going to use an ultrasonic sensor for my project where I needed to know the exact distance of an obstruction in the path of a moving body (to which the sensor is attached). But I needed a large range (because the sensor will be used in vehicles like trains) and read that ultrasonic waves won't be able to detect the obstruction at a large distance quite as well. Because they spread out, there might be some disturbances (unwanted elements being detected). So I thought I'd ask if there were alternatives to ultrasonic sensors that still have the large range.

About 500m would be optimal, but I think I can settle for anything above 100m if I have to.

Cost is a limiting factor, so it would be best if it can be frugally homebrewed or bought for a low price. Any suggestions?
Thanks.


texts: 74HC377 Octal D flip-flops latching on falling edge of clock

texts:
What would cause a 74hc377 octal D flip-flops to occasionally latch on the falling edge of a clock?
I have several different 74hc chips across several breadboards. I was daisy chaining the breadboard's power lines to distribute power, but this caused the voltage to be inconsistent and certain chips didn't work correctly. So I soldered some wire into a grid and connected the power lines directly to each breadboard. This made every breadboard to have a consistent 5.2 volts, maybe a little high but within spec for all chips. I'm using a cheapo charger power supply if that matters. Anyways, after I did this, the 74hc377 usually works correctly. However, it unpredictably latches a second time at the falling edge of the clock after latching correctly at the rising edge. I don't really see any reason this could happen, so I'm asking here in case I'm missing something obvious. I have decoupling capacitors across every IC (and larger capacitors on the power lines) and all unused input pins are pulled low. I know it's not a bouncing problem, because the push button clock I use is hooked up to a debouncing circuit, and a 555 timer based clock has the same problem. Any ideas?


texts:
Below is an H bridge inverter circuit model I came across in net:

I'm getting Singular matrix Iteration error when I try to run this.

If I delete the circuit on the right things work. Or if I ground the C1's terminal it also works but then it is not the same circuit anymore.

I uploaded the circuit asc file here:

What could be the reason causing this error?


texts: what is this IC and pin on the HC-SR04 which is being used for "Raw Echo" data?

texts:
An article using the HC-SR04 ultrasonic sensor to detect multiple objects at various distances shows a modification to the board of attaching a lead from a pin on one of the ICs on the board calling the data "Raw Echo".
The article is https://create.arduino.cc/projecthub/mircemk/ultrasonic-radar-can-detect-multiple-objects-at-each-ping-7a0f26 which the author says comes from this article https://arduinoplus.ru/arduino-radar/ which my browser can translate into English. The Russian article has the same board modification.

This modification is the same for HC-SR04 and HY-SRF05 ultrasonic
sensors and allows multiple echo signals to be detected. If you have
an HC-SR04, the integral circuit to which you solder the wire is
designated U2.

The image of the board modification is:
A similar modification is done in this lab for multiple object detection using the HC-SR04 https://www.instructables.com/Enhanced-Ultrasonic-Range-Finder/
I would like to understand what this specific IC is and what this pin, which seems to be an output pin from the IC, is doing.
My hunch is that the pin is used on the board to see echoes and some kind of comparator circuit is used so that once the first echo is seen, the board considers job done and the output of the board Echo lead is dropped indicating echo found. Any other echoes that are indicated by the IC pin are ignored. When a Trigger is done on the Trigger pin of the board, the comparator circuit is reset for a new echo detection.
So using the IC Raw Echo pin allows the detection of multiple echoes from a single ultrasonic pulse.
I have found a couple of articles that describe the electronics of the HC-SR04 to some extent including a schematic however I can't understand the schematic versus the physical board.

https://uglyduck.vajn.icu/ep/archive/2014/01/Making_a_better_HC_SR04_Echo_Locator.html
https://www.electroschematics.com/an-ultrasonic-shortcut-getting-the-hc-sr04-transducer-up-and-running-fast/
https://www.davidpilling.com/wiki/index.php/HCSR04
http://www.pcserviceselectronics.co.uk/arduino/Ultrasonic/electronics.php

Several questions about this general topic have been asked:

Sonar HC-SR04 analog output. Multipoint Sonar Radar
Functional block digram of a HC-SR04?
Can anyone identify the microcontroller on an HC-SR04

And this question, which was closed due to lack of clarity, seems to be similar to my question: Analog Signal HC SR04


texts: H-bridge with BJTs: why do IC and discrete solutions differ (or Sziklai vs Darlington)

texts:
I've noticed that [now mostly defunct] discrete BJT combo packages for H-bridges (for example Sanken made a bunch of these, see STA474A schematic below [half-bridge shown]) as well [higher power] hobbyist circuits [that still use BJTs for some reason] basically use an all-Darlington solution.

On the other hand, popular BJT-based H-bridge ICs like L293 or SN754410 use a Sziklai (aka pseudo-Darlington) on the high (=PNP) side, as shown below (half-bridge shown), i.e. where the final output transistor is an NPN even on the high-side:

Also it seems impossible to find any discrete Sziklai packages like you can for Darlingtons.

So I'm trying to understand why this happens. On one hand, I think using PNP as the output transistor for monolithic driver ICs would suck in terms of beta because of the lateral PNP issue. But I'm less sure why apparently there was no market for discrete Sziklai packages. Can someone shed more light on these two issues?

Here a are few more BJT-output ICs I've surveyed:

A3968 and also A3966 use the same source driver solution as the other ICs mentioned above. (Interesting enough they have a patent on their low-side/sink driver, which they call a Satlington™; the U.S. Pat. No. for that seems to be 5,075,568, which Google unfortunately doesn't appear to have scanned/digitized yet. The Satlington's purpose is to descrease the chance of a shoot-through given the totem-pole config of the final output NPN transistors.) However the appnote describing the latter IC does say that the 3966 IC is fabricated in "DABiC4 (Digital Analog Bipolar CMOS, version 4)" which does reinforce my impression that the source PNP/NPN compound is indeed chosen this way for the lateral PNP issue in such a process.
LB1205M. This is not exactly a H-bridge, but instead provides four high-side Darlington drivers, with PNP-style input driving an NPN-Darlington. In some sense it is the "discrete Sziklai" I was looking for, but it is fabricated in a monolithic ICs process; "equivalent schematic" below:


texts: How are loudspeakers able to play many different sounds at the same time?

texts:
I know this is kind of a lame question, but I wanted to know how loudspeakers are able to play so many different sounds at the same time. Like, in a song we can hear the voice of the singer and all the musical instruments at the same time. The sounds come from the speaker at the same time. How is the speaker even able to do it?

Thanks.


texts: How do I find the corresponding level of those audio samples?

texts:
I am trying to self-study this problem for a future exam. The writings in red are solutions to the question. I have a problem in number part e of the question  where they find the corresponding level of the samples from the audio signal's equation.

We have 256 discrete levels, and five samples.

I did not understand in part e why does the value of the sample 3V corresponds to the 255th level. and why -1.248 corresponds to the 74th level, and so on...

Any help?


texts: High Current Pulse Opamp 2.5% Duty Cycle

texts:
I am driving an IR LED (LED914 and LED907) in series at 4.5 A for 2.5% duty cycle, In the 28 V I connect a DC supply and set the current to 150 mA, the idea is to continuously charge the capacitor C17. Based on the calculation $$Irms= 4.5A(.025) = 112.5 mA$$
but I gave 150 mA from the DC power supply \$(\frac{28 V}{0.15 A})\$ just to make sure the capacitor will be replenish I tried up to 500mA just to get 30 pulses which is way away on the calculation.

Channel 3 is the Voltage across the capacitor and channel2 is the voltage across the current sense (R28). As you can see the last 9 pulse voltage across the current sense is less than 0.450 mV, The IR LED \$Vf=4.6 V\$ (during this pulse),I supply 28 V/0.15 A on the capacitor C17 continuesly to charge the capacitor while discharging.

On bench the charge on the capacitor is getting drained. I checked the leakage on C17 and I am getting in \$µA (120 µA)\$, I am wondering why I cannot replenish the charge on the capacitor with the DC supply?


texts: If one resistor is added to a circuit bypassing a longer parallel circuit, will the parallel circuit have current?

texts:
If you took and connected one bulb (the resistor in this case) to the end of a circuit in which the power wire bypasses the parallel circuit with multiple bulbs, would it cause the current to skip the parallel circuit?

Assume all 7 bulbs have the same resistance.

Of course, this one resistor probably cannot handle the power and might blow out quickly. However, aside from that.

See the illustration below:

Update: Here is another drawing of the same circuit (modified from the different drawing from the answerer below):

And here is what it would look like if the bypass was removed like the answerer's second picture:


texts: Avoid using HOLD and WP on SST25VF080B SPI Flash IC

texts:
I have recently purchased SST25VF080B SPI Flash

SST25VF080B SPI Flash Datasheet

I have downloaded the software driver (written in C?)

SST25VF080B Software Driver

Since I want to use it with a Parallax Propeller MCU I will convert/port the driver to the SPIN language.

What I want to ask is;
How do I wire the HOLD and WP pins so that those functions are NOT available?

These are the notes from the datasheet:

  4.1 Hold Operation
  The HOLD# pin is used to pause a serial sequence underway with the SPI flash memory without resetting the clocking
  sequence. To activate the HOLD# mode, CE# must be in active low state.
  The HOLD# mode begins when the SCK active low state coincides with the
  falling edge of the HOLD# signal. The HOLD mode ends when the HOLD#
  signal’s rising edge coincides with the SCK active low state. If the
  falling edge of the HOLD# signal does not coincide with the SCK active
  low state, then the device enters Hold mode when the SCK next reaches
  the active low state. Similarly, if the rising edge of the HOLD#
  signal does not coincide with the SCK active low state, then the
  device exits in Hold mode when the SCK next reaches the active low
  state. See Figure 4-2 for Hold Condition waveform. Once the device
  enters Hold mode, SO will be in highimpedance state while SI and SCK
  can be VIL or VIH. If CE# is driven active high during a Hold
  condition, it resets the internal logic of the device. As long as
  HOLD# signal is low, the memory remains in the Hold condition. To
  resume communication with the device, HOLD# must be driven active
  high, and CE# must be driven active low. See Figure 5-3 for Hold
  timing.

  4.2 Write Protection SST25VF080B provides software Write protection. The Write Protect pin (WP#) enables or disables the lockdown function
  of the status register. The Block-Protection bits (BP3, BP2, BP1, BP0,
  and BPL) in the status register provide Write protection to the memory
  array and the status register. See Table 4-3 for the Block-Protection
  description.
  4.2.1 WRITE PROTECT PIN (WP#) The Write Protect (WP#) pin enables the lock-down function of the BPL bit (bit 7) in the status register. When
  WP# is driven low, the execution of the Write- Status-Register (WRSR)
  instruction is determined by the value of the BPL bit (see Table 4-1).
  When WP# is high, the lock-down function of the BPL bit is disabled.

So the WP Pin I take it has to be tied high?
So I would wire a 10K resistor from the +3.3V supply to the WP Pin
But how I secure the HOLD Pin?

Thank You for reading.


texts: Designing 14.8v Li-ion battery charger + 5v power regulator for Raspberry Pi (of other 5v device)

texts:
The RasPi requires a steady 5V and to this end I build a power regulator circuit using a LM2576T, similar to the one on  page nine of the latest MagPi magazine.

This works great with an external battery pack but does not provide a way to charge the batteries directly. I have to charge the batteries first before using them with my Pi. Ideally I'd like a circuit that can run the RasPi from the mains power adapter while charging the batteries and run off battery when disconnected from the mains.

I have 4x 3.7V 4200mAh 18650 Ultracells batteries and a battery holder with PCM

These batteries have a full charge voltage of 4.2V and cut off discharge of 2.75V

I've done a lot of Google searches looking for examples of both a power regulator and li-ion charger but so far not found what I'm looking for...

Is there a specific name for this type of circuit? Does anyone have experience building a circuit like this? Is there any reference documentation or example circuit diagrams you could point me to?


texts:
I am working with the STM32F767ZIT6.
At the moment I am exploring the QuadSPI peripheral.
After setting up the peripheral with the following configuration I noticed some undesired behavior of the data lines following the dummy cycles.

// PRESCALER    = 160 -> 1 MHz.
// FTHRES       =   3 -> 4 Byte threshold.
// FSEL         =   1 -> Flash 2 selected.

QUADSPI->CR =
        (160UL << QUADSPI_CR_PRESCALER_Pos)
    |   (  3UL << QUADSPI_CR_FTHRES_Pos)
    |   QUADSPI_CR_FSEL;

// FSIZE    = 31    -> 2^32 Bytes.
// CSHT     =  7    -> Chip select 8 Cycles
// CKMODE   =  0    -> SPI Mode 0.

QUADSPI->DCR =
        (31UL << QUADSPI_DCR_FSIZE_Pos)
    |   ( 7UL << QUADSPI_DCR_CSHT_Pos);

// FMODE        = 0 -> Indirect Write Mode.
// IMODE        = 3 -> Four Lines.
// ADMODE       = 3 -> Four Lines.
// ABMODE       = 3 -> Four Lines.
// DMODE        = 3 -> Four Lines.
// ADSIZE       = 2 -> 24 Bit.
// ABSIZE       = 2 -> 24 Bit.
// DCYC         = 8 -> 8 Dummy Cycles.
// INSTRUCTION  = 0x48.

QUADSPI->CCR =
        ( 3UL << QUADSPI_CCR_DMODE_Pos)
    |   ( 3UL << QUADSPI_CCR_ABMODE_Pos)
    |   ( 3UL << QUADSPI_CCR_ADMODE_Pos)
    |   ( 3UL << QUADSPI_CCR_IMODE_Pos)
    |   ( 2UL << QUADSPI_CCR_ADSIZE_Pos)
    |   ( 2UL << QUADSPI_CCR_ABSIZE_Pos)
    |   ( 8UL << QUADSPI_CCR_DCYC_Pos)
    |   (72UL << QUADSPI_CCR_INSTRUCTION_Pos);

QUADSPI->DLR = 64;
QUADSPI->ABR = 0xAABBCCUL;
QUADSPI->AR = 0x123456UL;

QUADSPI->CR =
        QUADSPI->CR
    |   QUADSPI_CR_EN;

Send Instruction (1 Byte 72)
Send Address     (3 Bytes 0x123456)
Send Alternate   (3 Bytes 0xAABBCCDD)
Send Dummy       (8 Cycles)
Send Data        (64 Bytes 0x12345678, 0xFFFFFFFF ... 0xFFFFFFFF)

So after the first glance everything looks good.
But there's one thing that could cause trouble and make me uncomfortable.
After the 8 dummy cycles the data lines changing their state, according to the first data byte high nibble, on the rising edge of the clock.
But I am using SPI mode 0 so the slave is sampling the data lines on the rising edge of the clock.
So there is a chance that the first 4 bits after the dummy cycles gets corrupted.

Did I made some configuration mistake, is it a bug or is this normal behavior and I am wrong?

Reference Manual

Quad SPI description p.407
Quad SPI registers p.423

EDIT:
After looking into the errata I probably found the problem.

  2.12 QUADSPI peripheral limitations

  2.12.1 First nibble of data is not written after a dummy phase Description

  The first nibble of data to be written to the external
  Flash memory is lost in the following conditions:

  The QUADSPI is used in the indirect write mode
  And at least one dummy cycle is used

  Workaround

  Use alternate-bytes instead of a dummy phase in order to
  add a latency between the address phase and the data phase. This works
  only if the number of dummy cycles corresponds to a multiple of 8 bits
  of data. Example: To generate: – 1 dummy cycle: send 1 alternate-byte,
  possible only in 4 data line DDR mode or Dual-flash SDR mode – 2 dummy
  cycles: send 1 alternate-byte in 4 data line SDR mode – 4 dummy
  cycles: send 2 alternate-bytes in 4 data line SDR mode or send 1
  alternate-byte in 2 data line SDR mode – 8 dummy cycles: send 1
  alternate-byte in 1 data line SDR mode

But the workaround is not working for me because my slave needs the 8 dummy cycles to switch between input/output mode.
If I use the alternate byte instead of the dummy cycles there is a chance that the master and slave driving the data lines concurrent which could cause some hardware damage!
So is there a magic trick to getting around this problem?


texts: How to implement delay functions in Keil ARM MDK

texts: How to implement delay function in Keil ARM MDK that waits given time in microseconds that can be recompiled to any reasonable clock speed defined in Keil project settings ?  And all of this without using timers.


texts: Where to connect unused 555 timer ICs pins?

texts:
simulate this circuit – Schematic created using CircuitLab

This question might not have a close answer since I think it heavily depends on the considered pin and IC. However, consider, for the purpose of this question, a 555 timer. Suppose in my design I do not use the discharge pin (pin 7). What should I do with it? Should I use a pull up resistor? Should I leave it float? Should I connect it to GND through a resistor?

More in general, is there a standard practice for what to do when not using some pins of an IC?


texts: Is this the correct way to compute or the resistor for the ATMEGA? and how to compute for the fuse?

texts:
Is this the correct way to solve the resistor for the ATMEGA? The ATMEGA can only handle 6.6mA 4.98v @ 16Mhz but my transformer outputs up to 2Amps of current.
This is my first time that I designed a power supply with a fuse on it, do you guys know how to choose the correct fuse for the power supply in Primary and Secondary winding? I am really confused about the ratings of fuses.


texts: What is the efficiency of a lithium polymer battery?

texts:
I noticed that when charging and discharging a lithium polymer battery, the incoming/outcoming energy I calculated is very near to the specifications of the manufacturer.

How is that possible if any battery has a "real-life" efficiency? In practice, my test data say that my battery is nearly 97% efficient (-3% of the designed capacity or measurements error). I suppose I should give the battery more energy in order to achieve a capacity of 3600 mAh.

The battery has a capacity of 3600 mAh and I charge it with 1 A, which is actually \$\approx\$0.72 A for 5 hours (0.72C). The battery heats only about 1-2 °C. The ambient temperature is 25°C and stable. Battery resistance is < 70 \$\text{m}\Omega\$.


texts: problem with connecting the Arduino with 12V electric door strike

texts:
I followed this sketch to wire my arduino with a door strike.
but when I upload the code on it, the arduino did not control the power goes to the door strike. the door strike opens whenever I plug in its power supply, but I don't want this to happen, I want the arduino to control the power that goes to the door strike. I think the error is with my wiring, can you please help me

components:

1- door strike 12V

Voltage: DC12V

Current: 200mA

Fail secure, NO mode (Locked when power is removed)

2- power supply 12V

3- relay 12V

4- transistor
I'm using the one that comes with Arduino Starter Kit
they did not write anything about it
this is what is written on the transistor: "transistor IRF520 YSK AV"

5- resistor 1K ohm

6- 9V battery

this is the sketch

this is my wiring


texts:
Sure this is a pretty basic question for you guys, but figured I'd start here.  Is the linked LCD screen driven by some type of driver, or do you just supply logic voltage to whatever pin you want to illuminate on the LCD?
https://www.farnell.com/cad/2244525.pdf
So for example, if this were ran off of an Arduino, is there a better way to control the massive amount of pins?  I know some of the Adafruit stuff has I2C and or SPI with library, but didn't see anything for this one.
Is the best way to do that to use an array for each position of the digit in order to illuminate?  For example, if a rotary encoder were used just as a counter, each susequent counter step would be an array to supply voltage to the proper LCD lines?  Maybe this could be done more simply with bit shifting?  Just looking for any direction that someone may know.


texts: Does TB6612FNG require additional circuit to control motor and why

texts:
I am trying to understand the schematic for the TB6612FNG motor driver. I was unable to understand why do we need this additional circuit (marked in red in below diagram) when I can directly connect to the power supply. My other question is why are we using the P-Channel Enhanced MOSFET.
Reference datasheet can be found here: https://www.sparkfun.com/datasheets/Robotics/TB6612FNG.pdf


texts: Can I add 2200µF capacitor to regulator 5V?

texts:
Can I add a extra capacitor ceramic/electronic 2200 µF (actually working perfect from USB port laptop) for the test circuit for L7805 SMD? I need for peak current 2A SIM800C module.

I don't know why they recommend 0.33 µF and 0.1 µF. Maybe somebody has a short answer.

I didn't include the complete schematic, but the system needs to work in 5V and SIM800C is fed by a regulator 3.8V.


texts:
I'm trying to have an area of my PCB with the same geometry on the top and bottom copper layers, but I'm having trouble with the polygon on the top layer. I placed vias on the bottom contacts (which will be soldered to two-lead package), and set the 'orphans' setting on the top polygon that overlap the bottom contacts, but they don't fill when I ratsnest the PCB.

Is there any other setting I'm missing?


texts: Where/How should I fuse this transformer?

texts:
Background: I have a step-down transformer P241-5-36, which is a single mains primary coil to 36V Center Tapped (18-0-18) secondary.  I would like to use this transformer to build a linear regulated dual rail (+15V/-15V) DC power supply for DIY synth work.  I'd like for both me and the power supply to not be destroyed if I happen to accidentally produce a short circuit on the secondary side.  The data sheet says for my particular transformer, "36V C.T. @ 0.35A" under the "Secondary RMS Rating" column.

Question:
Do I place a fuse on the primary or secondary coil, or both and should I use a 0.35A value fuse or something else?  I think the fuse needs to be on the primary coil (though I'm not sure the value), but when the transformer spec identifies 0.35A at secondary, it is confusing me.

Research: I researched linear regulated power supply circuits and found the following schematics:

Example 1
Example 2
Example 3

While these schematics all to very different things, they all share a commonality in that they show a fuse on the primary side of the transformer.  I read through this post asking general safety questions about a PSU schematic.  That individual's schematic showed fuses on both the primary coil AND secondary sides.

Proposed Schematic: Here is the schematic I plan to use for my power supply (up to the linear voltage regulators).  It is dependent upon the correct location and value of a fuse - I took a guess here:

simulate this circuit – Schematic created using CircuitLab

Please note: I included a switch to float ground because I may want to probe with my oscilloscope and connect the probe's ground clip to something other than ground on my circuits.

Thanks, EE Community.


texts:
Could anyone share the internal circuit(transistor level circuit) of GPIO section in a microcontroller?

I am curious to see how a pin can serve as both input or output(of course only one at a time). I understand that there will be switch setting, I would like to see the FET level circuit of the switch indeed!


texts: Difference between capacitor start and capacitor run Induction motors?

texts: All though in both types of Induction Motors, capacitor does the job of phase shifting to produce the rotating magnetic field, their working principle is the same. Then whats the point in disconnecting the capacitor by centrifugal switch for capacitor start, and not disconnecting for the capacitor run motors. I mean is either of the Induction Motor designated for particular power rating, plus i read somewhere that capacitor start Induction Motor has high starting torque. Also when i browsed the internet found this piece of info that capacitor run motor has improved p.f. due to start capacitor, so isn`t it always advantageous to have capacitor permanently to improve motor efficiency.


texts: Power connectors for very long LED strips

texts:
I'm working on LED project at home where I'm installing Neopixels LED strips along the top and underneath my cabinets, so basically in 2 long strips.

Because I may need to disconnect things (e.g. get at the controller) I would like all the connections to have some sort of connector. I was looking at the JST connectors but they are only rated for 3A.

The longest strip is 4 meters long (4meters x 30 leds/m x 60mA = 7.2 Amps) which is way more.

Any suggestions on what sort of connectors/wires to use?

Thanks a tonne!


texts:
I recently bought a wireless gaming mouse and while functionally its great, the battery life is a little less than I would like.

I tried to mitigate this by adding in another rechargable AA battery (as the bay only fits one) but found this wouldn't be possible without grinding away some of the internal plastic, which I'm not prepared to do.

Therefore, I came up with the idea of fitting an induction charging coil within the mouse, with a charger embedded in a custom-built mousemat.

Ideally I would have liked to have made the mat out of aluminium, but after looking into it it seems this would result in interference, preventing proper charging.

What other factors like this are there that I should be aware of going forward with this project?

I'm intending on powering the charger via USB from my PC, would there be current/voltage concerns connecting this? How about in the connection between the receiver coil and the battery within the mouse?

I'm a complete beginner when it comes to things like this, so any and all guidance would be very much appreciated.


texts: Global Variables vs. Pointers in Embedded Design

texts:
I've written a few 8bit embedded systems and the codebase I inherited and have expanded is basically 80% global variables (extern volatile), and than non-global control flags and logic variables as needed.

The end result, is that you end up with a lot void() functions to modify the global variables.

The systems run fine and the software quite readable and easy to work on, but I always have that design nag in the back of my head that I should be refactoring everything and pointer'ize the next design.

I don't have any religiosity about the memory usage aspect, the static memory is there to use as much as the heap is.  It's more a question of as systems get larger, I suspect maybe the globals start to be more of a hinderance than you think.

Do many of you experienced embedded software programmers use pointers extensively in your 8bits systems?

We don't use linked lists or anything sophisticated where you really need pointers and to dynamically allocate memory.  I could see the next system I write, I use structs in place of variables to group information a bit more logically and you would use pointers than to modify the structs.

Also, the functions can get re-used if you pointerize your code, but in one sense the functions are pretty trivial and one off in the embedded systems I've built.  Very application specific stuff.

FOR POSTERITY: Also posted on the ARM KEIL C51 Forum

SINCE THE POST WENT A BIT 8051 EMPHASIS: BEST C51 COMPILER GUIDE EVER WRITTEN


texts:
I want to use the latching relay displayed schematically in the attached circuit diagram.  The designer decided to place the +V (12vDC) on the common (center) for the coil(s) and then requiring the -V on either the R(eset) or the S(et) terminals.
For reasons of circuit design that this relay is to be used in, I want to reverse the voltage polarity.  So, MY QUESTION is:
Can I connect the "V+" terminal to the - side of the power supply and use +12V as the Set and Reset trigger?  I realize that this would require flipping the diodes around and that would make the "R1" terminal the set input and the "S1" terminal the reset.  But that shouldn't matter as long as I wire the output contacts accordingly.
I'm asking whether I'm overlooking anything from an electronic/functional standpoint and also why the designer used the + power on the coil midpoint/common?  I am more used to using +volts to trigger my devices.

Further description from the designer is as follows:
CONTROL TERMINAL BLOCK:
V+: relay coil common terminal.
R: relay reset action signal input.
S: relay set action signal input.
SWITCH TERMINAL BLOCKS:
Rx / Cx / Sx: Switch X.
Ry / Cy / Sy: Switch Y.
When the input trigger signal R is Low(pulse or constant):
Switch X, Rx – Cx is connected and Cx – Sx is disconnected.
Switch Y, Ry – Cy is connected and Cy – Sy is disconnected.
When the input trigger signal S is Low(pulse or constant):
Switch X, Rx – Cx is disconnected and Cx – Sx is connected.
Switch Y, Rx – Cx is disconnected and Cx – Sx is connected.


texts: I am trying to figure out the capacitance seen at each node, given that the source and drain diffusion capacitance is shared in the nmos stack. Given that the fingered layout uses a finger width of W=2 I want to try to find the capacitance at both B and N. I thought that based on the widths in the nmos stack the shared diffusion would be equal to (6+2)/2 unit C but I seems like I am wrong. I also thought that both N and B nodes would experience the same capacitance but I'm not sure. Can anyone explain why my analysis is incorrect?


texts: Cutting a slot in a PCB using a hand file for a USB connector - are the planes exposed and shorting with the connector?

texts:
I'm making a HID keyboard which connects through micro-usb. Unfortunately I made an error in the PCB design and missed including a slot for the usb connector to fit in.

Being the enterprising DIY hacker that I am, I used a hand file, like this one, to cut out the slot and then house the USB connector snugly within it. Here's an image of the finished connector:

I assembled 2 boards and both of them have weird connectivity issues with the device working sometimes, but most times just failing as a malfunction.

The USB port's outer housing is grounded. My question is, is it possible that by filing, I exposed the ground plane and the VDD plane and now the USB connector is shorting with it, thus causing the device malfunction?

EDIT: Here's an image of the PCB layout. Have marked the USB port and the De-coupling caps.