texts: Noise on stereo summing circuit from LED's

texts:
I've been a tinkerer and hobbyist for 20 years now, but mostly in software. I've done my fair share of simple soldering (replaced controller ports on an original Xbox with actual USB ports, for example) but only have the vaguest idea of how electricity actually works.

All that being said, I've got a virtualization setup that I love and for which I'd like to sort out an audio playback solution. Basically, I just want to be able to funnel two analog stereo sources into one amplifier and not damage any of my hardware.

The first thing I did was buy one of these and ran it backwards, effectively. The amp was connected "Amp Input" and my two sources were connected to the A and B channel outputs. That worked fine, but before long I wanted to eliminate one of the (now three) boxes on my desk.

After some googling, I wound up with this (likely often cited) article: http://www.rane.com/note109.html and set to building myself what I understood as the "right" circuit. Enter this fella:

PC 1 is onboard audio on a fairly high-end motherboard, originating as a TRRS 1/8" connector. PC 2 is the 1/4" TS output from a Native Instruments Komplete Audio 2 USB audio interface. The amp takes two RCA inputs.

My solder job really sucked, but the connections were sturdy. I just used some high end(?) RCA cable I had lying around and a few other connectors. Once complete, I wrapped the whole shebang in electrical tape (no heat shrink at hand) and connected everything. And wouldn't ya know it - everything worked!

I have since discovered an issue, however, and I'm nearly certain it's my cable.

If I have the amp cranked, there is a very audible, pulsing hum. It sounds like cicadas, actually. It didn't take long for me to realize the pulses matched exactly with the "breathing" effect from my motherboard's LED controller. I've got two strips of white LED's pulsing, and the buzzing corresponds with the fade in either direction. When they're either fully off or fully on, there's no noise.

Predictably, when I remove the 1/8" TRRS connector from the motherboard, there's no interference. A little more interestingly, the signal noise also vanishes if I disconnect the outputs of the USB sound card.

So... what have I done? What might solutions be other than changing the lighting? ;) What did that little box do that I could replicate, perhaps?

Thank you all in advance for any help!


texts: Using a Computer PSU for its 12V output for high wattage loads

texts:
I'm looking to install some LED light bars (primarily designed for use on off-road cars) as fixed outdoor lighting on my property.  I see they have models that use up to 700+ watts of power (for crazy amounts of light, like 78,000+ lumens) at 12VDC:

If I were to use a 800W+ computer power supply to power the light bar, could the power supply handle a 700W load through a single molex connector?  I understand usually the loads are spread over multiple connectors on multiple 12V rails.  I'm not sure if I can handle a single 700W load.  Should I connect it to both rails simultaneously?


texts: Is a two-element circuit series or parallel?

texts:
Is the voltage source in series with the resistor or is the voltage source in parallel with the resistor? If the voltage source is in parallel with the resistor, then why do they share the same current? If the voltage source is in series with the resistor, then why do they share the same voltage?

They are both in series and in parallel, correct?


texts:
I'm trying to transmit and receive voice to my GSM modem over a 10-meter cable from a handset connected board using TEA1062 line drivers. But when I connect a speaker to the handset, a sine wave noise rides on the line signal, so the speaker tinkles.

I tried using different speakers with different ohm values and realised that when I use a 130ohm speaker everything is okay. But if I use an 8-ohm or 16-ohm speaker, that noise signal noise happens. If I disconnect the speaker, the noise signal disappears.

There is not much information on the TEA1062 datasheet for the beginners since this IC is not used anymore. Are there any basic rules about audio based designs like impedance matching for speakers etc.? I just used the typical application schematic in the datasheet. I couldn't even understand the formulas for changing the line voltage level. This IC was mostly used for fixed telephones so they assume we are using 48V line level etc.

Edit: Sorry, I'm trying to add the schematics for half an hour but there is a failure about imgur. Below is the links for the schematics:

Schematic of the typical application in TEA1062 datasheet

The typical application only shows the telephone side of the 2 nodes. So, I needed to design the first schematic with a local supply.


texts: Simple NOR gate (transistor-level) diagram

texts:
My question here is simple:

I cannot understand how the input flows throughout the circuit.  I understand the P and N type transistors; I could see why if A and B are both 0, and pass through the P-transistors, their value will be 1, and C will be 1.  But I don't believe that's the right interpretation.

So what  I don't get is -- what of the N transistors?  I drew a red and blue path for input A, to clarify.  How do I know where A goes?  What should I take into account for determining the output of C?


texts: Result with Thevenin method doesn't equal node method

texts:
I'm following the MIT lectures on circuits and electronics. They introduce the Thevanin method for solving linear systems in lecture 3 (https://youtu.be/RsJ1eg7XNVs?t=46m49s).
I can't seem to get same results using the Thevenin method as with the node method in this circuit when calculating the voltage e in this circuit:

This is my result with the node method:
$$
0 = (e - V) * \dfrac{1}{R_1} + e * \dfrac{1}{R_2} - I
$$
$$
e = V * \dfrac{R_2}{R_1 + R_2} + I * \dfrac{1}{\dfrac{1}{R_1}+\dfrac{1}{R_2}}
$$
$$
e = V * \dfrac{R_2}{R_1 + R_2} + I * \dfrac{R_1*R_2}{R_1+R_2}
$$
But when I try to use the Thevenin method, I get a different answer.
First, I convert the part of the circuit with R2 and I:

Where:
$$
T_{th} = I * R_2
$$
$$
R_{th} = R_2
$$
Then, after combining the voltage sources, I use voltage divider to find the voltage across Rth:
$$
e = (V - I * R_2) * \dfrac{R_2}{R_1 + R_2}
$$
$$
e = V * \dfrac{R_2}{R_1 + R_2} - I * \dfrac{(R_2)^2}{R_1 + R_2}
$$
I must have done something wrong here. Why do I get different values for e?


texts: Design a MOD-N counter using LS293 circuits

texts:
This is the internal scheme of the LS293 circuit.

I understand that the CP0 frequency will be divided by 2 and the CP1 will be divided by 8, but I don't understand how to use this circuit to build a mod-n counter.


texts: flipping the UART rx/tx pins on an arduino

texts: I managed to flip the rx/tx lines on a project I'm working on. My GPS RX is going to my ATMega's RX, which is clearly wrong. Since the pin map lists the rx2 and tx2 lines as pins D16 and D17, I'm hoping I can work around this for the time being by using SoftwareSerial over those pins and flipping them virtually. This doesn't seem to be working. Is there something I need to do to disable the native UART? Can this work in principle?


texts:
Hello I am picking up a project from someone else who has a built a dipole that is connected to a 1:1 transformer with the intention of using it as a current balun. I have noticed that from documents that the balun is supposed to be built with the corresponding polarity

(source: vk5ajl.com)
From looking at the PCB built I have determined that this isn't how it is wired. It is wired like.

The thing I am wondering is that if this polarity difference is effected my Balun  abilities. I haven't really been able to find a explanation about this.
This is the balun I am using: Pulse CX2147


texts: I have a battery case with a built-in led bar battery level indicator.  The case was made for a 36-volt battery, but I will be using it as a 48-volt pack.  I would like to drop the voltage to the battery indicator by 12-volts so it would be somewhat accurate.  Are diodes the best way to do this?  I do not feel like a regulator would be a good choice.   Thanks!


texts: Can I use a multimeter to measure audio signals by testing amperage or voltage?

texts:
I'm in the process of adding a subwoofer to my car. In doing so I spliced in a T harness to audio wires from the head unit and routed the wiring to where I Will be placing the Amp. I tested the speakers after that using the balance/fade settings from the head unit; all channels work as expected.

In the interest of future proofing my wiring I tapped all four speaker channels, that way if I decide to add a four channel amp I don't have to rerun another wire set. Unfortunately with four speaker wire sets, I didn't keep track of which is which, and need to verify which wire-pair belongs to which speaker channel.

I was wondering if I could use the balance/fade settings on my head unit and a multimeter to determine which speaker wire is which channel. I can set it up so only one speaker is active at a time and test the wire pairs with my multimeter, but I'm not sure if I should be looking at voltage, amperage, or both.


texts: If a device has a metal case should it be grounded?

texts: If a device such as this potentiometer has a metal case, should the case be grounded or left floating? Electrically the case is not connected. Data sheet


texts:
How would I go about finding the gain of this circuit? Here's a link to the datasheet.

Using our test apparatus to create a PWM on the diode, I get 1.16V out of pin 1. I can provide more information if needed.

Thanks,
Luke


texts: What does "NS" indicate as a capacitor value?

texts:
I'm looking at an application note, and it contains the following in the circuit diagram:

What does the  NS in the diagram represent? Or is this just a typo on the behalf of the manufacturer?

Edit: Further down the datasheet, this is clarified as "Not stuffed"

What does that mean?


texts: Using DALI-2 BUS interface(slave) to supply SiLABs EFR32xx

texts:
I am working on DALI bus converter, using EFR32xx MCU(SiLAbs) for home usage. My question is following.. Is it possible to get DC voltage from DALI interface to supply MCU unit(3.3V) to avoid stuff battery or external DC voltage input? If i am not mistaken, DALI bus(master) supply is ISOLATED 16VDC 250mA maximum, it means, my slave device will get around 4mA in case, when all 64 devices will be connected to dali bus controller(master). Does anybody did the same, and if yes - can this connection diagram be provided?
Beforehand thanks
Arsen


texts: Input Attenuation and Intermodulation Products

texts: I am measuring intermodulation using spectrum analyzer. How does the input attenuation affect the power of intermodulation products?


texts: What happens when one of the 3 Phase load is disconnected suddenly?

texts:
I am sorry if I am asking trivial question.
I tried to search previous questions but unable to find it, there is only question on what will happen if neutral line disconnected.

My question this time is about what will happen when one of the three phase loads get disconnected just like the in the figure below?

For (a) which is star-connection, is the phase voltage is still Vline/sqrt(3)? Is Ineutral= -(IR+IB) still valid if IY=0?

For (b) which is delta-connection, is the phase current of still Iline/sqrt(3)?

How do I solve these two questions? I tried to find similar questions online but cannot find any with keywords like '3 phase system, one phase disconnected'.

My answers for part (a) and (b) are as shown below.

If you know similar problems from some other source, would you kindly share with me? I can read there myself. Thank you.


texts: Heating issues with solar charging circuit

texts: I am using the above circuit to charge a 7.4V Li-ion Battery.With input MPPT voltage set at 12V, I have applied 13V input voltage to the circuit. The battery is charging at 1.4A. (according to the calculation it should be 2A). But, the input diode D1, Input capacitor C1, MOSFET Q1, diodes D3 and D4, Inductor L1 are heating too much during charging. What could be the reason of heating ? Any design problem or other?


texts: Weather proof enclosure for Raspberry Pi

texts:
I have built a device based on Raspberry Pi who have to be located on a house's roof.
I use an IP67 enclosure with IP69 pressure compensation element with gore-tex membrane. I add silica gel before closing the enclosure.

I have seen that 3 chips are very hot (+-30°C more than ambient temperature) in normal external temperature (power regulator, ethernet and arm chip). I will add a passive heat sink on those three components.

I will underclock the ARM to match with performance needs.

Do you have another idea to avoid premature failure of electronics due to humidity/temperature?


texts: Magnetic path length for partially wound toroidal transformer core

texts:
According to Wikipedia, magnetic path length is defined as "the effective length of a closed magnetic loop inside a magnetic core made of ferromagnetic material." Thus, for a toroidal core that is wound all the way around, the magnetic path length would be \$2\pi r\$. I'm curious if this definition holds even if the core is only partially wound.

For example, if I wind a coil to drive the core 1/4 of the way around and wind another coil to measure the magnetic flux density on a non-overlapping part of the core also 1/4 of the way around, is the magnetic path length the same as the above or would I divide by 4?


texts: Why so many specs for RCD vs US GFCI (or RCDs?)

texts:
Why are there so many RCD (Residual Current Device) specs and mA tripping thresholds for use in equipments in Europe vs the USA where they were not used (but only 5mA GFCI for personal safety)?

Don't they use any EGC (Equipment Grounding Conductor connected directly to the utility transformer) in Europe that requires such massive RCD specs?

Lastly. Is the RCD in Europe compatible when used in the USA 240v ac (red and black wire)? Has anyone successfully used RCD in the USA? In theory it should work because the toroid only detect imbalances but some people comment that they were not compatible for some reasons. True?


texts: How to reduce current without affecting voltage for powering a fan?

texts:
So I have a 12 v 1 amp power supply. I want to convert the current from 1 amp to 0.08 amp and keep the voltage the same. This is for a power a brushless fan; specs 12 v 0.08 amp. I am not sure how to do this. If anyone can help, I would appreciate it a lot.
Thank you


texts: Insufficient current to drive automotive relay?

texts:
I'm adding a leisure battery to my van so I can run some stuff with out fear of draining the starter battery.

My leisure battery is wired to my starter battery so it can charge from the alternator when driving but is separated by a relay to avoid draw while stationary. I have split a wire from my dashboard which becomes live with the ignition and reads 14.5 volts with the engine running to use to activate the relay, and grounded the other side.

My Problem

When I connect this wire to the relays trigger circuit (pin 86 I believe), it's voltage drops to 0.6 which doesn't seem to be enough to close the circuit.

Any one know what I'm doing wrong?

edit

I'm using this relay

I have wired it up like this;

the switch

pin 30 positive on starter battery
pin 87 positive out of relay

control/coil

pin 86 live from dash
pin 85 ground.

Van is mk6 ford transit, wire is white and green one from display behind the steering wheel which I thought might be alternator warning light...

hope that helps.


texts: Wrong ground reference producing wrong output on ADS1115

texts:
I am currently working on a project, which involves measuring current in a DC circuit and storing that generated data on an arduino microcontroller.
I decided to go with the ADS1115 and a shunt, which is located in series on the low-side of the circuit I want to measure. It is a 0.001Ω shunt, which results in a voltage drop of 1mV per amp.

I have attached a schematics of the wiring (Note that there are multiple other devices connected in parallel on the arduino, which all have very little power consumption; I left them out for better reading)

The issue I'm having are the results the ADS1115 is giving me:
When no voltage is applied to the left circuit, i get a single-ended reading of about -20, which in my application is unacceptable. When voltage is applied and the load draws current, i also get a reading, which is -20 bits off.

The ADS1115's supply voltage is around 4.98V and I am not sure if the problem lies in all the other components that are attached to the arduino's circuit.

I am not an electrical engineer but a software developer, so please take that into consideration when commenting on my schematics and/or wrong wiring. :)

Any help is appreciated!


texts: How do I wire a 9 pin serial connector into a RJ11 4pin connector?

texts:
I am working on a project, the door control system I am using is a bit old, and it works through a serial connector on a 4 pin RJ11 line. I am currently trying to wire an old serial wire into its RJ11 wire, so I can get my raspberry pi to work with it. (I am using a USB to serial connector on the pi)

However, the problem is I don't know which wire goes into what.  The door controller is one I got was from a friend's deconstruction project. Its a Stanley Access Technologies MC521 controller.

The RJ11 has 4 colors on it, black, red, green, and yellow from order left to right. And has the text RS232 near it. A signal was detected on the red wire when it boots on.

any ideas?


texts: When will parallel LED voltage drops become an issue

texts:
The following circuit will cause problems because of voltage drops:

simulate this circuit – Schematic created using CircuitLab

It should be changed to look like this:

simulate this circuit

However if we used both parallel and series resistors in this circuit, there is a potential for voltage drop issues between the LEDs. As we raise the value of the series resistor and lower the values of the parallel resistors, what determines the point at which voltage drop issues start to happen (and at what values?)

In this scenario, all of the LEDs are the same brand, with a 2 volt drop +-2% and are run at 20 mA.

simulate this circuit

Edit----

Practical application: I designed my original circuit with 18 LEDs in parallel, each with a 220 ohm resister. Now, I want to change the voltage to 9 volts (or 12 volts).  Will I need to switch out all of the original arrays or can I add one resistor in series?

...Then I became curious about the limits involved in doing this.


texts: Can I test a DC motor by replacing the brushes with wires?

texts:
I'm troubleshooting the DC motor for a 14W Lucas windshield wiper (from a 1970 Land Rover).  I tried a number of things with no luck so I'd like to see if it's a problem with one of the brushes that is only partially touching the commutator.  Before I buy new brushes (which are hard to find), I'd like to find a way to test whether that's actually the problem.

So I've tried bypassing the brushes by touching the wires from a power source directly to the commutator.  Nothing happened.  But I'm not sure if that should have worked.  I don't have a good motor to compare.  Can I bypass the brushes this way?


texts: Need Help to Determine Quiescent Current in Class AB Output Stage

texts: I am studying class AB amplifier output stage and having Vbe multiplier as biasing to address cross-over distortion. I am able to get good results with no Cross-Over distortion in output. However I am not able to find equation for quiescent collector current of NPN transistor in output stage due to my limited knowledge of circuit analysis. Please help me analyze how the Ic_Q is 19.4 mA, and what equations are involved that are governing this collector current of NPN output stage transistor for the given circuit.


texts:
How does a temperature sensor gather temperature? What is the mechanism used?

More specifically I want to understand how the TMP102 sensor works.


texts: Programmable polarity switch for DC circuit

texts:
My question concerns a future research project in electrocoagulation (water treatment) I am planning right now.

I will have a lab power supply connected to two (or more) plates in water. The operation will run in a galvanostatic mode, meaning I want to have a constant current through the system as one of the major outcome determining factor is the charge density through the plates (e.g. \$mA/cm^2\$). The plan is to procure a lab power supply that can supply up to 30 A, since that is at the higher end of the range I want to test. My measuring probes and the power supply will be programmable, meaning I have the possibility of centrally controlling the electrical inputs and the data collection of experiments from my computer.

One thing that I want to test is reversing the polarity of my electrodes to counteract electrode passivization, i.e. switching the anode and cathode during the experiment. I would like to do this in a programmable fashion as well. For example, either at timed intervals or maybe when a certain voltage drop has occurred due to the increased resistance from the passivization.

Given that I have all required signals connected to the computer, what would be the way to solve my problem? The programmable side will not be an issue for me, I am mostly interested in the best way to solve the problem.

Requirements:

Switching circuit should be able to handle up to 30A passing through the switching side.
Programable

Thanks in advance!


texts: The difference betweem RFM12S and RFM12B

texts: I want develop a board, which should use a wireless interface to send data. I have the RFM12S module and I find only docs about the RFM12B! does anybody know the difference between those two !


texts:
I have designed this basic RC high pass filter circuit in LtSpice IV:

It should have cutoff frequency around 10 kHz. When I perform the ac small signal analysis the output is as expected.

But if I give as input tree AC sinusoidal signals each with different frequency(400 Hz, 4 kHz and 18 kHz), and perform transient analysis, it seems that filter doesn't work.

Here's the procedure...

I made desired input using summing amplifier. Circuit is shown belove.

Then I perform transient analysis. The output and input signals are:

Output signal seems to have all tree frequency components.

Then I have done FFT on both input and output signals and it confirmed that both signals contain same frequencies, just like the high pass filter didn't worked.

By inspecting the magnitude axes (the one in dB) I noticed that the signals have been suppressed, but as it seems not significantly. If you look at output signal in time domain this becomes apparent.

What I'm doing wrong?

How could I design a filter that will keep only 18 kHz signal?


texts: Protecting a laptop from USB connected devices

texts:
In the past couple of months I've managed to destroy 2 perfectly good laptops through programming development electronics through USB. I've been wondering what could be done to prevent this. A couple of ideas I've had (not sure how practical):

USB connector / hub with clamping 5V zener diodes on power and data lines
USB connector / hub with opto-isolators on data lines
supplying the usb connection with external power source plus previously mentioned idea

In combination with these ideas perhaps resistors on both 5v D+ and D- lines to limit current to say 200mA (enough for most of the devices I use).

Just wondered what some more experienced engineers than myself thought about these ideas and their practical implications?


texts: Constant Current Load op-amp ref voltage limit

texts:
I am trying to build a constant current load circuit described in
DIY-Constant-Current-load

I wanted a 20mA CC load, so I chose 4V at R2-pin2 and 200ohm for R1.
After constructing the circuit, i found out Vref (LM358-pin 2) is at maximum of 1.8v instead of 4v, what is the reason behind this?

reference schematic


texts:
So supposedly there is a potential difference between those two rods when the circuit is open. Does this mean theres an electric field present here such that ∫Edl≠0 ?

If I put some random loop of wire in the vicinity (I'm not thinking of Faraday's law, instead just a simple line integral acting on charges), will current start flowing "because theres a potential difference"?

Why does KVL apply to open circuits and how exactly does it?

Is it only true for paths close to the circuit?

Can I take trajectory that goes all the way to infinity and back and still apply KVL?

Can I pick a random trajectory that ends where it started and even if theres a gap, assume that the total voltage drop was the one provided by the voltage source?


texts: Chaining two batteries to achieve a specific voltage range under their maximum

texts:
I'm building a portable 8x8 LED matrix powered off of two CR2450 coin cell batteries. Most of my components ( Attiny85 and LEDs ) can run easily off of the supply voltage range of the CR2450, but the shift registers aren't being as conducive...

There are three shift registers in my design: two DM7495N and one NTE74LS164. All three shift registers have a recommended voltage range of 4.75 to 5.25 in order to operate. If I chained the two batteries, they would supply a maximum voltage output of 6V and a minimum of maybe a little over 5.2V, before the other components become under-powered and the batteries would need to be replaced. That is not within the range associated with the shift registers..;(

Is there a really simple way to step down the voltage to fit the ratings of the shift registers without using a voltage divider? Like maybe with a couple of resistors or some other common electronics component? Something tells me that there is in this case, since I am using two separate batteries... If I have to, I could ignore the recommended ratings, as both registers have a maximum input voltage larger than 6V, but I would like to know if there is an efficient and easy way to step the voltage down in this case. Thanks!


texts: Altium Designer Black Screen in Gerber File

texts:
I am currently working on a project. After everything done, I needed to make a Gerber File. I tried everything on the internet but I got nothing different than a black screen. I do not know which part I'm doing wrong.

I only used Top Layer of PCB. I need your help. Thanks!


texts:
I am trying to calculate the equivivalent capacitance to ground of a 3 phase LCL filter with capacitors to ground. Inductors removed from circuit as I assume they will be ignored by the meter...

simulate this circuit – Schematic created using CircuitLab

Ignoring C3, it`d be simply 2 series networks in paralell with C4. Specifically:

C4 + 1/(1/C1 + 1/C5) + 1/(1/C2 + 1/C6)

This almost fits with measurements of actual circuit (3% less), small enough that could be explained by the capacitors +-10% tolerance. However what effect does C3 have in such a calculation?

Update
Inductors are back in the schematic from comments suggestions, at the cost of a much uglier schematic. I think this is not necessary as the probe should only send a very low frequency current and then measure the change in voltage. And as frequency approaches zero, reactance of inductors also approaches zero, while reactance of capacitors approaches infinity. In effect making inductor values negligible. Therefore I think this simplified circuit is ok to use:

simulate this circuit


texts:
I've been trying to solder an SSOP 0.1" onto sparkfun's breakout board. However Somehow I've managed to short a positive to ground. Are there any tips you can give me in identifying it? I'm quite confused because I've sprayed and swapped with PCB cleaner/ IPA. I can't see any solder bridges on the pins. It doesn't appear to be a dead short as my meter telling me there's some resistance there. It also doesn't heat up right away.

I'm going to have to get a new breakout because I've managed to pull one of the pads off therefore am unable to through hole solder the wire.

Is there anything wrong ?
I do remember having an issue with the usb not registering then after power cycling it worked. I found a short on my circuit across 5v and gnd on the regulator so removed the ft232rl then it disappeared. I found a short between positive and any gnd on the ft232rl while it wasn't connected anything.

I used IPA and a pcb cleaner to clean off the type R flux I used to solder the ssop


texts:
Suppose that there are two periodic signals with particular frequencies. Two signals are then combined into one signal.

Suppose that we take finite samples of these signals. (so, finite time of transform.)

Then, is it possible to figure out the frequency content of the two original signals using any kind of transform?


texts: What is the point of the diode in parallel to the fan here?

texts:
Sorry - no background in EE so this might be a bit of stupid question.
I'm looking at this simple circuit and am trying to understand the point of the 14N007 diode that is put in parallel to the fan in an NPN transistor switch circuit.
I thought diodes were only used if an inductive load were to be expected and thus its used to dissipate any EMF generated.


texts: I2C ADC ADS7830 and Digital Isolator MAX14850 - reading central heating system thermistors

texts:
I want to read the temps from my central heating system.
I have the ADC ADS7830 and the digital isolator MAX14850.

I need help with the circuit.
This are the values of the different thermistors (not all because i can't post more then 2 links):

Thermistor values

I have the Adafruit LM4040 voltage reference here but it has only 4.096V.

The ADS7830 datasheet says on page 11:

  If a +5V supply is used, an external +5V reference is required in
  order to provide full dynamic range for a 0V to +Vdd analog input.

What if i need to read 6V? I guess i need a voltage divider?

Then page 18 the layout:

  The GND pin should be connected to a clean ground point. In many
  cases, this will be the "analog" ground. Avoid connections that are
  too near the grounding point of a microcontroller or digital signal
  processor. The ideal layout will include an analog ground plane
  dedicated to the converter and associated analog circuitry.

They talk about GND and not COM. Not connecting GND to the supply and voltage reference? Do i link GND and COM?

What about the power for the voltage reference? I already have a dedicated power supply for the relay board to have real isolation. But i guess using it also to power the voltage reference is not a good idea because the relays can cause noise and voltage fluctuation?

First draft (not sure about COM):


texts: Why cant I run my file on LTSpice with a library?

texts: I have a circuit using 74HC74 D flip flops for my psuedo random number generator. And my schoolgave us LTspice customization folders to use and we have to import it to the LTspice folder. I did that but when I actually tried to included it in the spice directive it can't find the file. Am I doing something wrong?


texts: PPM/PWM controlled, closed-loop stepper motor?

texts:
(It is easy to misunderstand what I'm describing if you read it too fast)

I've google this for a few days now. I'm looking to make or buy something that bolts onto the back of a stepper motor that makes the stepper motor function exactly like an RC servo. That means it receives PPM/PWM input, HAS A POTENTIOMETER to measure shaft position, and automatically moves the stepper CW or CCW until it is in the correct position according to pulse width. Think of it like RC servo electronics with a big stepper motor in place of the little DC motor that normally is found in the servo casing.

If for some crazy reason this doesn't already exist, one way that it could be made is by buying a cheap servo, desoldering the small DC motor from the control board, making some kind of interface that translates the -5v to 5v DC voltage to stepper pulses, and outputting that to a stepper motor.

A stepper with an optical encoder is not what I'm looking for. A stepper that receives a direction and speed as input, regardless of what is attached to it, is not what I'm looking for. I'm basically looking for something with the physical characteristics of a stepper (The ability to direct-mount other hardware to the output shaft, metal frame), the high torque of a stepper, but with the control characteristics of a RC servo. It needs to be able to be overloaded, externally knocked out of position, interrupted while moving yet still know where it is. Guessing where it is is not acceptable like it is with open-loop control.

Doesn't this already exist? If not, what would be the simplest design, with the fewest separately-bought pieces, for something like this?


texts:
I know that this question won't be too difficult to answer, but unfortunately I couldn't find anything reasonable about it on the Internet.
I have a 1.2V 1500mAh rechargeable battery and want to charge it (without a standard charger, although I have one lying around. I only want to do it for learning purposes.) I know that there are modules like the TP4056 for Lipo batteries and 18650 cells, but I don't know that there is something similar for an AA battery. Can I just connect the battery to 1.2V and limit the current to 150ma? At what voltage is the battery fully charged? I would be grateful for helpful tips or instructions.


texts: Can I solder 4 AA batteries together in series and make my own rechargeable battery pack?

texts:
I've bought my young son a couple of remote control tanks for Christmas. They are supplied with two rechargeable 'battery packs' (4 x AA batteries heat shrunk together). The battery pack supplied is Ni-Cd 400mAh 4.8V

The charger says "Output 4.8VDC 250mA".

The reviews of these tanks say they are great but the batteries don't last very long.

I wondered if I could buy 4 x 2850mAH AA batteries and then solder them together to replicate the supplied battery pack and then charge them with the supplied charger and use these instead of the supplied ones?

I've been reading on the internet how to solder the batteries (i.e. don't apply heat for long and 'rough' the ends up first to help the solder stick). But I also read somewhere about 'balancing' the batteries so that they would charge??

The supplied batteries are just linked together (i.e. nothing in there that I could see that would 'balance' them) so thought I would get expert advice on the best way to proceed with this?

I'm fine at soldering but don't want to make a home-made battery pack and then have it blow up when I try and charge it!

I bought a plastic 4xAA battery holder that links the batteries together but it doesn't fit in the tank compartment so that won't work.

Help appreciated :-)


texts: 5-10 second backup for wifi router during power cut

texts: In India power cut is often. And most houses are installed with Inver-battery, for backup till the power comes back. But since all inverters don't behave as ups, there occour a little gap between the power switching i.e. from main power to battery power. Gap is roughly lasts for 1-2 seconds. And during that gap my router turns off for obvious reason. Can i do something to cover this gap and prevent it from turning down? I've tried using two 220uF capacitors in paralled to power supply input in router but nothing noticable happened. Power supply for router is of 12 V 0.5 A. Please help.


texts: Multiple switches, same function. Can they be wired in parallel to a single I/O pin?

texts:
I'm working on a Raspberry Pi project that requires 30 separate momentary switches to be hooked up to trigger the same function within the software. It's for an art project.

I don't need to distinguish between different buttons - I just need to register any button press - ideally on a single I/O pin for simplicity's sake, if possible.

My first thought is to simply wire up all the buttons in parallel, connected to a single I/O using the internal pull-up resistor.  I know that in theory this should form a logical OR gate, which is what I want.

My question is: might multiple button presses cause unexpected behavior or potentially cause electrical damage to the Raspberry Pi? Or will this work as expected? If the former is true, what's the best way to achieve this?


texts: Can a 1.8V linear regulator be avoided with 5V power and 3.3V?

texts:
This a theoretical question, I am happy with my current design, no intentions to try this yet.
Background:
Some PCB that has requirements of 5V, 3.3V, and 1.8V. The 5V is the supply from some standard linear dropout regulator, and the 3.3V and 1.8V current requirements are low and also fed from some linear regulator powered from the 5V supply.
Let's also pretend maybe our only goal is to reduce the number of components on a board, and that the components aren't particularly sensitive to noise or the exact voltages required.
Theoritically, would it be possible to only populate the boards with the 5V regulator to act as the supply and the 3.3V to act as a supplementary source for the required components. Then for the specific component that needed 1.8V, connect the VCC to 5V and the VDD to the 3.3V plane/source.
Would this not create a sufficient ~1.7V voltage potential across the chip? We could even design say to have a 5.05V source and a 3.25V secondary to get a closer 1.8V approximate assuming the other chips have good tolerance as well.
What would the greatest penalties be and considerations? Obviously a dirtier 1.8V source with power fluctuations and spikes. Also introducing the tolerances in output voltage for 2 regulators instead of one. But if our acceptable input range was 1.65-1.95V, could this work?


texts: Optoisolator with Logic Output - How To Use IC Circuit Example?

texts:
I'm looking at an Optoisolator with a Logic Output..It's an optoisolator with a Schmitt Trigger on the output. I think the datasheet is a little bare for my comfort level, so I'm looking for some advice/confirmation on connecting these.

These are the devices I would like to test:

Fairchild FODM611
Fairchild H11L1M / Fairchild H11L1M(Other sheet with circuit)

This is my interpretation of the datasheets. For devices that are "the same"(for my application) they have different hookups on the output. Also, I've tried to contact Fairchild, but have not heard back.

simulate this circuit – Schematic created using CircuitLab

Using Circuit 3 with 330 ohm pull up
Output RED = FODM611 Output
Input BLUE = 3.3v PWM Signal

Using 100k pull up


texts: Driving a relay directly with a microcontroller?

texts:
Are there any microcontollers on the market that would be able to drive this relay directly?

If not, what is the most cost effective way to have a microcontroller control 5 relays?


texts:
What is the bias stability in degrees/hour of the gyroscope on the BNO055? The  datasheet lists some specs of the gyro on page #14 but I cant find the bias there. There is an item called "output noise" that lists 0.1 degrees/s - is this the bias? I actually am looking for following two values (sample taken from Xsens MTi 1-series):

Gyroscope bias stability: 10 deg/hr
Gyroscope noise density: 0.01º/s/√Hz


texts: How do I get the sidebar back? I minimized it in an attempt to get more screen space but I cannot seem to get it back.


texts:
I am using a microcontroller with flash memory partitioned into two areas (i.e) Primary & Secondary. When a remote firmware upgrade is done, I am writing the received binary file over Ethernet to the secondary (inactive) partition of the flash. If the received and calculated CRC matches, the boot loader will copy the latest firmware from secondary to primary partition.

How to handle the situation in which the size of the binary file exceeds the size of either primary or secondary partition of the flash?


texts:
Are languages like eLua and Micro Python feasible for production level use on an embedded micro like an STM32?

There doesn't seem too be much information outside of their sites. Not looking to do real time stuff in these languages directly, but perhaps linking them into existing lower level C modules could speed up testing and application level development. So I was curious if anyone has had much experience with these in the real world.


texts:
I am trying to build a pulse generator that is triggered on by the leading edge of a clock signal, stays on for one full clock cycle, and is triggered off by the next leading edge from the clock.

Something like:

Clock:  ___-----_____-----_______-----___
Signal: ___----------____________--------

Any thoughts?


texts:
I am motorcycle engineer, I don't know much about CAN bus systems, and I need your advice.

I had searched on this site, and I found this schematic. But in my country, I can't find the components like this. Could I use two 1N4148 opposite to replace them? And do I have to install it on every node (Dashboard, ECU, ABS, and BBS) to protect?


texts: How can I make a L+R+mic audio dongle to record an Android phone's own output?

texts:
I'm looking for a way to wire the stereo output of a device into its own mono microphone input. This will be soldered as a 4 pin 3.5mm TRRS audio jack.
I need to record the output of my smartphone on the smartphone itself (without software modification.) I have screen recording apps available, but they take audio from the microphone.
I tried two circuits:

Android official Audio Loopback Dongle (stackoverflow question about this circuit) - this works but distorts human speech. Perhaps incorrect resistor/capacitor values?
Headphone Output/STEREO MIX To MIC Input For Recording, but wired input and output together, ground left not connected. Android doesn't detect this as an mic and uses internal microphone.


texts: How to allow current over a certain voltage

texts:
I am new on electronics and i was practicing on transistors. I have a working circuit below. The LDR I use allows current and letting LED smoothly based up to amount of darkness. The Voltage after 2.3 k resistor is 0.7 maximum .. All i want to do is to let led run on the darkest moment. So only if it is fully dark the LED must light up .. Not smoothly relative to darkness. What should i do for this ?
FIX: the source voltage is 6 Volts


texts: My daughter's science project is to charge AA batteries with a solar panel

texts:
We bought a 0.5 watt solar panel with 4.5 V, a 4 AA battery holder and a 15 ampere Schottky diode 45V , and 4 lithium ion rechargeable batteries.
We connected the red positive solar wire to the diode. We assumed the end of the diode with the silver line is the cathode and connected that end to the solar red wire.  We then connected the red wire on the battery holder to the opposite end of the diode that was black.  The black wire on the battery holder was placed with the black end of the solar panel.
We placed it in the sun to charge but my daughter said it did NOT charge the 4 lithium batteries.
Please let me know where I went wrong.
Thanks so much for such a quick response!  You engineers are amazing, kind and helpful people.  This world would be a much better place with people like you in government....but I guess that's why you are engineers.
I heeded everyone's comments.
I still used the 0.5 watt solar panel with 4.5 V, a 4 AA battery holder and a 15 ampere Schottky diode 45 V, and changed to 4 Energizer Recharge Power Plus 2300 mAh NiMH AA.  I changed the direction of the diode.  Guess what!?!  It worked.  Thank you for all the warnings about the lithium CoO2/graphite Tenavolts 1.5V AA High-Capacity Rechargeable Batteries with 2775 mWh.  Out of curiosity, because we used a 4.5V solar panel and the lithium batteries were 1.5Volts (x4) the total voltage need to charge would 6V solar panel.  By using a solar panel that was less than the required voltage, would the batteries get charged but not to full capacity?  Would that decrease the risk of fire? How does time of charging come into the equation?
Any books or websites recommendation that are not too esoteric that can explain this to my 12 year old daughter and me would be greatly appreciated.


texts:
I need to intercept a 220V AC line to drive a 3.3v MOSFET that activates (for example) an LED.
Looking around, a solution could be to use an AC/DC converter but they are meant for powering (so mostly higher current than I need) and not signals.
They are costly and inefficient for my application.
Is there an alternative way, schematics or simple /cheaper component to convert the 220V into a 3.3 V signal?


texts: Will there be any voltage drop when connecting load to batteries?

texts: In my project I am planning on using 10 AAA Batteries(to give me 12v as each battery is 1.2v) to power my project. I am wondering if there will be any voltage drop when I connect a load. If so how can it be calculated? This is so that I can account for it.


texts: How does RFID reader reads a passive RFID tag?

texts:
There are different types of RFID tags like active, passive, semi-active ect.

I can see that the active ones emits radio waves which is received by an RFID receiver and hence the data is transferred. This is like a classic radio transmission.

But how can a passive(non-powered) RFID tag is read by an RFID receiver as an overall system? What is the idea behind? Are the passports using passive tags? I cannot sense a sort of battery on a passport tag.


texts: Programming ATMEGA328P with FTDI232 with original 1.8.1 bootloader

texts:
trying to program a custom arduino board, effectively an uno w 328P chip that plays some audio, with a particular board/bootloader, but having some issues.  The wiring is fine, as mentioned below it will program with some board/bootloader combos, but not the one I want.

The board programs over ISP no problem (both bootloading and actual code), but I would like to be able to program via an FDTI232 board for convenience.  I've connected the FDTI232 to TX/RX/power and DTR to 0.1uF cap which has other leg connected to the reset on ATMEGA328P.  So, this works fine - I can write/read serial data fine, and if I load the ATMEGA with minicore bootloader it will happily program via the FDTI.

However, the minicore bootloader doesn't work with my main  program - it induces massive audio noise.  Furthermore, my main program uses extensive libraries that only work with arduino 1.8.1, and also with arduino AVR boards 1.6.20.  More recent boards just create massive issues in the running of the code with extensive resets, noise and instability.

How can I get the board to program via FTDI in this circumstance?  I gather there is an old/new bootloader that if I had the newest version of arduino might help but I am unable to update for the aforementioned reasons.

I've tried changing the board defintion uno.upload.speed to 57600 as thought it might be related to this - however I am actually wondering if this upload speed doesn't actually change the bootloader - is this correct and if so how can I change it/what else should I do?

For reference - the standard arduino 1.8.1 arduino uno bootloader works perfectly with my board - but I want to be able to bootload this onto it then upload code via FDTI.

Thanks very much for your help


texts: Transistor Based Amplifier and DC Only Negative Feedback

texts:
My analysis of Heathkit RLC Bridge continues (previous question here).  This time I've been trying to analyze the feedback amplifier section shown below and taken from the original document IB-5281 (apologies for the poor image quality):

Originally, I considered this a current shunt feedback amplifier and went about re-drawing the circuit after applying a couple of rules: 1) opening the output loop and 2) shorting the input voltage.

Then I saw C17 and it seems like it shorts out the feedback loop at AC.

Is this true?

If so, why would the amplifier apply negative feedback to DC only?  Wouldn't the lack of negative feedback (at AC) make the AC signal prone to all the usual distortions that NF is supposed to solve?

How do the usual rules around calculating the gain for current sampling current shunt feedback change when the AC signal model doesn't apply?


texts:
For a home pet project I want to wire up an electro motor to a Raspberry Pi. I want to constantly reverse the direction of the motor (meaning I want to be able to change the direction of the motor about every second). As far as I understand this can only be done with brushed DC electro motors. Since I need quite some power, I was thinking of buying

1. Motor

this electro motor, which is described as:

200W DC motor is reversing 24V speed control motor 1800 rpm high torque micro motor

2. Battery pack

I then want to wire it up to this LiPO battery pack, which has the following description:

Output voltage:12V-24V
Input voltage: 12.6V
Input current: 1AH-2AH
Output current: Max. 6AH
Output power: Max. 110WH
Material: Li-polymer for PHILIPS 2900MAH batteries
Capacity: 52000MAH(3.7V)

[EDIT]

@MarceloEspinozaVargas told me in his answer that the battery pack has a regulator which is too weak. So how about I buy two of these battery packs (2*12V), serially linking them up so that I get 24V, and then using this regulator, which says it is a DC-DC Automatic Boost Buck Converter 8V-30V to 2V-16V 6A 80W CC/CV Voltage Regulator charging 5v 12v 24v 19v Car power supply. Would that work you think?

3. H-Bridge

I then want to use this H-bridge for reversing the motor direction, which comes with the following info (description below picture):

Double BTS7960 43A H-bridge High-power Motor Driver module:
BTS7960B H-bridge 43A high-power motor driver Module Overview:
This driver uses chips BTS7960 composed of high-power drive full H-bridge driver module
with thermal over-current protection. Double BTS7960 H-bridge driver circuit, with a
strong drive and braking, effectively isolating the microcontroller and motor driver!
High-current 43A

Features:
Double BTS7960 large current (43 A) H bridge driver;
5V isolate with MCU, and effectively protect MCU;
5V power indicator on board;
voltage indication of motor driver output end;
can solder heat sink;
Just need four lines from MCU to driver module (GND. 5V. PWM1. PWM2);
isolation chip 5 V power supply (can share with MCU 5 V);
size: 4 * 5 * 1.2 cm;
Able to reverse the motor forward, two PWM input frequency up to 25kHZ;
two heat flow passing through an error signal output;
isolated chip 5V power supply (can be shared with the MCU 5V), can also use the on-board 5V supply;
the supply voltage 5.5V to 27V;

My Question

Before spending the money on it, I want to be sure that this combination will actually work. I mean; does that seem like a good battery pack for that motor, and can the H-bridge I link to handle the power going through? I see the H-Bridge says

I'm just a bit insecure about spending all this money when it's not going to work. So all tips are welcome!


texts: Tracking rotation with extremely high accuracy

texts:
I would like to track the angular position of a fairly slow motorized rotating arm (direct-drive; see illustration below) -- but require angular accuracy of under 0.05°, and similar resolution.

As @gbulmer noted in the comments, that is equivalent to tracking the tip of the arm positionally along the circumference, with an accuracy of (2×π×10cm)/(360˚/0.05) = 0.08 mm.

Is there any currently realizable sensor or electronic method that can attain this level of accuracy in rotational sensing without spending a fortune?

This is what I've tried so far, from simplest to intricate:

Digital compass/magnetometer: I started with this; but obviously nowhere near the performance I'm looking for.
Rotary encoding: Potentiometer-based / Hall-Effect-sensor-based encoding: Couldn't get sufficient resolution and there is significant linearity error.
Machine vision: Tried placing an optical marker on the tip of the arm (since the tip traces the longest arc) and using camera (OpenCV) to track the marker's position: couldn't resolve very tiny rotations so well, given the arm's rotation spans a 10x10 cm area.
Magnetic encoder: I'm currently investigating the use of AS5048, a Magnetic rotary encoder from AMS, positioned with the sensor's center at the motor's shaft position. Something like this:


texts: What is the purpose of the PCB jumpers in the attached image

texts:
Can someone please tell me what may be the purpose of the jumpers in the attached image? Why not use a PCB trace instead?

Figure 1 The PCB is a part of an old Videocassette recorder (VCR)


texts: When is a fuse used in tandem with a breaker/MCB?

texts:
I have observed that at the input (supply side) of some electrical units, only MCB is used for overcurrent protection; whereas in other units, a fuse is used as well as MCB at the input side.
Why and when are -

Both fuse and MCB required/preferred (as both function to protect against overcurrents)?
Only MCB required/preferred (to protect against overcurrents)?
Only fuse required/preferred (to protect against overcurrents)?


texts: How to interpret Vgs(th) min/max in a MOSFET datasheet?

texts:
This is a screenshot of IRF9640 MOSFET datasheet. Will you please tell me, what is meant by max and min value of Vgs threshold voltage. Also what they mean by test condition.

Whether the max and min values are only applicable for specified test condition?
What will be the threshold voltage for a switching circuit and how the range varies?

My doubt is, for p channel mosfet to turn on Vgs < Vgs(th). For IRF9640 in what volt it will turn on -3 or -5? When i used in my application Vs is 6v and Vg is 3v hence Vgs=-3v but it won't turned on, Why? It turned on when Vgs=-3.3v.

If we consider -2v as threshold, it should turn on when Vgs=-3v. Why they given a range for threshold voltage. Whether we have to test each mosfet to know their threshold. What i am pointing is that, if we have two IRF9640, will Vgs(th) is differ from each other?


texts: Hows does a processor physically do calculations?

texts:
What should I know to understand how a processor performs computations, at the level of the electron (concerning adders,gates,etc.)?

Suppose I already know the logic side of the issue, i.d. how processors do arithmetic by binary logic operations.

I need an overview of the main subjects, perhaps in the form of a diagram.


texts:
I have a simple circuit, where I want to use a MOSFET (IRF8010) as a switch. I have a microcontroller which produces a 3.3V PWM output @ 500Hz and will be used to control the MOSFET. Obviously, driving the MOSFET gate directly from the μP was not an option (very low output current, slow gate charging), and I was told that the best solution to drive the MOSFET was a driver, like IR2104. Having searched the internet, I could only find detailed information about using the IR2104 for H-bridges and Motors.

How should I use the IR2104 in my case?


texts: Is there a colour standard for mains 'signal' wiring?

texts:
Hello I am currently wiring a mains powered chassis. I have relays which use mains voltage levels for controlling other mains voltage relays. I would like to differentiate between the signals by using striped brown-red, brown-blue cabling etc.

This has to go through compliance testing. Do all 'live' mains voltages need to be coloured solid brown?

Edit: This is currently a product destined for the EU market.


texts:
I purchased SN74LS26N quadruple 2-input NAND Gates chips for my circuit. Before I insert any chip into circuit I test it on separate breadboard.

So I did with this chip and I get NO output when my inputs are LOW...

Does it make any sense to you? I am doing something wrong?

simulate this circuit – Schematic created using CircuitLab

I am not the best with schematics so I hope this is clean for you..
I tried adding bypass electrolytic caps 0.1uF but that didn't help

Thanks!


texts: I2C Put One Termination Res at the End or on Each Slave Board

texts:
I Have a system with I2C bus wired just like this:

My questions is which one is better: put the termination pull up res at the end of connection (on the last board), or put pull up res on each slave board?

Because I'm having problem, at initial it can work but after sometimes the I2C communication to board failed and can't be recovered (SCL always stuck low when I observe using logic analyzer)
(on each board there's a chip like PCA9685, MCP3424, PCA9674, etc)


texts:
I was setting up a PIC16F628A for a simple Hello World program (blinking LED) and somewhere in the process, I have failed. The LED stays lit at the specified pin and does not "blink". I am using the Internal Oscillator (which resonates at 4 MHz). This is my code (Using the XC8 Compiler):

#include <xc.h>

__CONFIG(FOSC_INTOSCIO & WDTE_OFF & PWRTE_OFF & MCLRE_OFF & BOREN_ON & LVP_ON & CPD_OFF & CP_OFF);

#define _XTAL_FREQ 4000000

int main() {
    TRISB0 = 0;
    while(0) {
        RB0 = 1;
        __delay_ms(1000);
        RB0 = 0;
        __delay_ms(1000);
    }
    return (0);
}

And my schematic:

I have read that this might be a MCLR problem but I have configured the fuses to set MCLR as an input pin as shown in the code.


texts: Resistor in parallel to circuit is causing VREG to output higher voltage

texts:
I am building a circuit to convert a 300Hz PWM signal to a 30Hz PWM signal with the same duty cycle. It's a pretty simple circuit:

I'm having a weird issue with the R7 resistor though. It's in parallel to the GND_PWM_IN to 12V_IN part of the circuit. I have it there because the system that outputs the 300Hz PWM frequency tests the resistance of the circuit, and if it is shorted or over ~150ohms, throws an error code. In short, it wants the resistance to be about 100 ohms.

When the resistor is put in the circuit, the output voltage as measured on the 5V line of the VREG is actually around 7VDC. When removed, it outputs a perfect 5VDC. I do not understand what is causing this, but it is causing problems for my microcontroller and the rest of the circuit which doesn't like that high voltage.

Any insight into why it would be causing that voltage irregularity, or if there is a better way to fool the impedance sensing circuit without having R7 there, would be greatly appreciated!


texts: Do you have to put a voltage across a PV cell for it to work?

texts:
I'm studying about PV cells and I'm slightly confused. Currently, I'm learning this very simple model.

I'm trying to figure out how exactly it works.

Am I correct in saying that; You apply a voltage across the PV cell using an external voltage source (which would require it's own independent power?) and the PV cell provides current(using energy from sunlight ofcourse), the exact value of which depends on the voltage applied?

Question: If this is true, then all PV cells have external power sources? (albeit small?)


texts: Multiple LED strips and one power supply

texts:
I have been given a purple, waterproof, high intensity (18 LEDs/foot) LED strip. I don't have any spec/datasheet for the LED's because they were acquired directly from a Chinese manufacture.

I can clearly see they are rated for 12VDC but cant find any other data on them. I am trying to lay 7 strips that are 5 feet each in length using one power supply. As of now I am using a 12V, 3A switch power supply that I recycled from an old laptop and the full strip of LED's turn on but they get warm to the touch.

My question is, whats the best way to hook 7 5 foot strips together? Series or Parallel? and how would I calculate the overall power consumption in order to pick a correct power supply? Can I add a 5 watt resistor to each strip and lower the current if necessary?

I have attached an image of the strip.


texts: Will motors cause more noise when connected to a ground plane instead of directly to batteries?

texts:
I am making a small robot using an Arduino and two servo motors. There are two ways that I can provide power to the motors:

1) Run power and GND wires from the battery holder to the motors, then connect the GND pin on the Arduino to the GND wire going to the servos, like this:

2) Run a power wire from the battery holder to the servos, then connect the GND pin on the Arduino to the servos (no GND wire going directly from the batteries to the servos):

One of the concerns I had about 2) is that the motors can draw several amps when stalled, so I wasn't sure if that would be too much current for the GND trace on the Arduino to handle. However, after looking at the PCB layout for the Arduino I see that there is a GND plane instead of a trace, so I assume the amount of current flowing through it is a non-issue?

My second concern is noise. I know that motors generate a lot of noise and so my main question here is whether not having a wire from the batteries to the servos (instead routing the current through the GND plane on the Arduino) will create a lot of noise that could cause problems for the microcontroller and ICs on the Arduino?


texts:
I have a circuit here. For negative output voltages from \$V_1\$, the diode will be off, making \$V_0\$ simple to calculate since the circuit just becomes resistors. When \$V_1 = 0\$ the diode is off since no current flows.

How do I properly analyze the circuit/reduce the circuit to easily let me analyze the relationship between \$V_1\$ and \$V_0\$ for small positive voltages like 1-4 V.


texts:
What is the purpose of a pragma Data_Align in TI emb. compiler.

The datasheet explanation:

http://www.ti.com/lit/ug/spnu151j/spnu151j.pdf

"The DATA_ALIGN pragma aligns the symbol in C, or the next symbol declared in C++, to an alignment
boundary. The alignment boundary is the maximum of the symbol's default alignment value or the value of
the constant in bytes. The constant must be a power of 2. The maximum alignment is 32768.
The DATA_ALIGN pragma cannot be used to reduce an object's natural alignment."

Can someone re-explain it in a different method? I really don't understand the purpose of this pre-compile directive.


texts: Does cooling the NAND chips on an SSD negatively affect its reliability?

texts:
The problem of heat dissipation in high-performance, small form-factor SSDs is well-known, for example, the paper Transient Thermal Analysis for M.2 SSD Thermal Throttling published in 2018 17th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems states:

Solid State Drive (SSD) technology continues to advance toward smaller footprints with higher bandwidth and adoption of new I/O interfaces in the PC market segment. Power performance requirements are tightening in the design process to address specific requirement along with the development of SSD technology. To meet this aggressive requirement of performance, one major issue is thermal throttling. As the NAND and ASIC junction temperatures approach their safe operating limits, performance throttling is triggered and thus power consumption would drop accordingly.

Naturally, if space allows, adding a huge heatsink is a possible solution to this problem, there are many products available on the PC gaming market. I also see many M.2 to PCI-E passive adapters on the market have built-in heatsinks by adding a huge copper pour with connection to the ground plane under the M.2 connector.
But one can find many unsourced posts on random computer hardware forums, which claims that the NAND chips should never be cooled. It is claimed that they are actually designed to heat itself up to an optimum operating temperature, and adding a heatsink to the NAND chips adversely affect its reliability. Here's some examples.
One claim reads,

Don't cool the NAND dies themselves!
They heat themselves up to operating temperature by design, cooling them means they just continually dump out power trying to hit temperature, and will be operating with a lower endurance (simplified: higher operating temperature = lower energy input to set/erase cells = less degradation of each cell per write/erase cycle).

Another claim reads,

Cooling the NAND is bad. You want the NAND to run warm and stay warm. As its temperature fluctuates, and as it cools down, if you suddenly transfer a large file (read or write, I can't remember) while the NAND hasn't had time to warm back up first, it can significantly reduce the life of the NAND.

It doesn't sound right to me. It suggest that the NAND chips depend on the self-heating effect to reach an optimum operating temperature, which is something I've never heard before. The only chips that I know that use self-heating are National's LM199/299/399 "Super Zener" voltage references, and Linear Technology's LT1088 Thermal RMS-DC Converter. But I don't believe NAND chips have anything to do with self-heating.
I tried to fact-check and/or debunk these statement, start by looking for a NAND chip datasheet found in some recent SSDs. I went to Digikey and Mouser, set the filter to the highest storage density and sorted them by prices. Unfortunately, it seems that datasheets are not available (all under NDA? I'm looking at the wrong place?).
Are these strange statements have any factual basis?


texts: Frequency response of output capacitance in an operational stage

texts:
Simulating the circuit shown below:

I found that the output capacitor C3 actually change the shape of the bode Diagram..

look at that:

With C3:

Without C3:

My question is how can I calculate the effect of C3 on the frequency resposnse of my circuit?


texts: My 30A PDU is drawing 20.5A. It's L6-30P plug gets hot (65°C. Ambient: 35°C). Is this safe?

texts:
I have a home server setup that is drawing 20.5A from a dedicated 30A line. The power is supplied via a PDU rated for 30A (240V). The PDU's plug runs a bit hot, and I'm nervous if it would be safe to use this setup.
Here're some facts:

The PDU has L6-30P plug. It's temp is stable at 65°C.
The server room's ambient temperature is about 35°C.
The supply wire (10 AWG) or the rest of the PDU's cord isn't that hot (about 40°C).

Is it a good idea to keep this setup? Or should I split the load to another PDU on a separate line?


texts: How much time does it take to demodulate one OFDM symbol? In 802.11a standard the Symbol Interval Time is 4us. Does this mean that each symbol is demodulated within this period or there is pipelining involved? I understand that the answer may depend on the hardware platform, but I would like to know the range (us/ms) in the fastest implementation. Moreover, a breakdown of time needed at various steps would be nice.


texts:
Link for the System
This is my existing system, I would like to Add a LED indicator which will turn off when the Lamp get burned/damage.

Someone told me to use transistor but am not sure which transistor, where and how to connect them.


texts: How can I get a linear relationship between a voltage divider and an ADC?

texts:
I'm making a small level meter using an ATtiny microcontroller. It uses a linear 5K potentiometer as a voltage divider coupled to an ADC pin. So far it's working except the digital values don't seem to correlate well with the measured voltage.

The schematic:

simulate this circuit – Schematic created using CircuitLab

The relevant code:

#define F_CPU 1000000
#include <avr/io.h>
#include <util/delay.h>

int adc_value;

void ADC_init()
{
    // Enable ADC
    ADCSRA |= (1 << ADEN);

    // Set ADC reference to AVCC
    ADMUX  |= (1 << REFS0);

    // Prescaler /8, 125kHz ADC sample rate @ 1MHz
    ADCSRA |= (0 << ADPS2) | ( 1 << ADPS1) | (1 << ADPS0);

    // Auto trigger enable
    ADCSRA |= (1 << ADATE);

    // Use input channel ADC2 (PB4)
    ADMUX |= (1 << MUX1) | (0 << MUX0);

    // Left shift ADC result
    ADMUX  |= (1 << ADLAR);

    // Start converting
    ADCSRA |= (1 << ADSC);
}

int main(void)
{
    DDRB = 0x07;
    PORTB = 0x00;

    ADC_init();

    while(1)
    {
        adc_value = ADCH;

        if (adc_value < 64)
            // output A
        else if (adc_value < 128)
            // output B
        else if (adc_value < 192)
            // output C
        else
            // output D
    }
}

I measured the voltage at PB4, and noted the points at which the output changed:

Minimum: 196 mV
64: ~235 mV
128: ~500 mV
192: ~770 mV
Maximum: 2.849 V

I expected approximately 1.5 V to be where a digital value of 128 is obtained, not 500 mV.

If I understand correctly, the ATtiny13A has a 10-bit ADC, the values from which are stored in two registers, ADCH and ADCL. With ADLAR (the left adjust) enabled, the value is shifted into the ADCH register and effectively two bits are discarded.

The datasheet indicates:

  If the result is left adjusted and no more than 8-bit precision is required, it is sufficient to read ADCH.

I'm confused about why I am getting a nonlinear conversion on the ADC. Can you explain what I may be overlooking?


texts: 24v 450w DC motor powered electric bike connected to a lith-ion battery pack (56v 6.5a)

texts: How do I prevent the DC motor from burning out using this battery pack?


texts: BJT common-base output resistance derivation

texts:
In Sedra/Smith the following image may be founded that is used for output resistance equation derivation of common-base BJT amplifier. The question is why the gm*v and v/re currents are directed up? Why they are not displayed in down direction?

The equation of output resistance with image current is: R_out = r_o + (1 + g_m * r_o) * Re', where Re' = Re || r_pi.

When I was used down direction in my derivations the r_o current I write as: ix-gm*v, and fount R_out = r_o + (1 - g_m * r_o) * Re'

The update was added to post. The schematic that I use for "ro" derivation is presented below. The equations that I derivate are:

vx = (ix + betta * ib) * ro + v;
v = ix * (Re||Rpi);
ib * Rpi = (ix - ib) * Re;

May anyone check them?


texts: What is the best way of connecting electricity fuse/cut-out

texts: I am talking about home/industrial electrical fuse fitting or correct mointing . Should the fuse be mounted on L(live) wire or N(neutral) wire?.


texts:
I am using these step-down adjustable buck regulators for various purposes (hobby projects and experiments) and they work more or less fine. But I have this little concern - when they convert relatively high voltage (~20V) to relatively low (5V or 3.3V) they tend to get pretty hot (almost impossible to touch them for more than a few seconds).
They still work, and I add some small heat sinks when I actually put them into something more "final". I don't know if they have thermal protection, but they haven't failed me so far.
Still, I've been wondering whether it is a good idea to use them in "series", I mean connecting the output of one to the input of another. For example, the 1st could convert 20V to 12V and the other would further step down from 12V to 5V.
This way they would share the "work" and eventually run cooler.

Will that degrade the overall efficiency?
Will it be twice the losses ... or less ... or more?
There are some cases I would care about efficiency (e.g. if the source is a solar panel or a battery) and others where it is not an issue (mains powered bench top power supply, sorry green people).

Would it actually improve reliability?
Apart from eventually making them run cooler, is there any benefit?
I don't know what happens if one of these fails - but I guess it will either stop conducting (no harm done) or just pass the input voltage to the output (probably frying the electronics connected as a load).
I guess if it is the latter, there is still some (minor) improvement - if the 1st one fails, 20V will come at the 2nd input, which will then regulate them to 5V and the load will survive ... until the 2nd one dies from the same cause the 1st died. At least the load will live a bit longer.
If the second one fails first, the load will see 12V (instead of 20V) and will be a cooked at a lower temperature, so it will taste better :)

Is there any other reason why it makes no sense to do that?

We're talking hobby grade stuff for personal use, mass production cost is not a factor.


texts: Why can't I use solar PV system while disconnected from grid?

texts:
During utility power outages, a simple grid-tie solar PV system is required to auto-disconnect from the grid for safety.  One cannot utilize power from the PV system while disconnected from the grid (or battery backup), because "the excess current needs somewhere to go."  Therefore the panels are disconnected from the inverter as well.  However, while the sun shines on the panels, they will continue to have a voltage differential but no current (What happens to the extra electricity (amps) created by an off-grid solar (PV) array?), like a disconnected battery.  Please correct me if I misunderstand.
If the panels can sit at voltage but no current (like a battery), why does excess current need to be sent somewhere when a small amount of power is utilized (unlike a battery)?  What prevents us from using only part of the PV power generated?
Edit:
Thank you for the answers and comments so far.  With those in mind, please allow me to rephrase my question:
Why does a solar PV system need to be grid-tied or have a battery backup to be usable?  Why can't they just include a 60 Hz wave generator to govern A/C conversion, and use power when the sun is shining?
I understand the Sunny Boy string inverter can do this to a point, but why isn't it a standard feature on most inverters, and what limits it to 2000 watts on the Sunny Boy?


texts: Is it possible to run a stepper motor only with a L293D at reduced current?

texts:
I would like to drive my stepper motor (1.4A rated current, 3.5V, 2,5 Ohm coil resistance). I only own some L293D drivers but I think I will burn it if I just wire the motor to the driver without some sort of current limiting.

Obviously I will loose some torque but that's ok for the moment.


texts: How to adjust PCIE signals using Hyperlynx S- Parameter report?

texts:
I’m using Hyperlynx (MentorGraphic) for Signal Integrity test for PCIE GEN 1 Tx Rx & Clk signals. I imported Altium designed layout file to Hyperlynx. These signals (Tx, Rx, Clk) don’t pass S – Parameters when I run Serdes Batch Wizard, but they pass Channel Verification.

What are the changes I should make, for the design to pass S Parameters? How can I figure out the things which need to be done, using S – Parameter report?
Is it possible to make those changes directly to the imported Altium design?
Why doesn’t it pass S – Parameters and but does pass channel verification?

Here I have attached the parameters which I gave for Serdes Wizard and the results of the report.


texts: Detecting a connection to a distinct circuit with no current return

texts:
I hope the title is informative, and that I'm not posting a repeat - part of my problem here I believe is that I don't know the correct terminology to find the answer on the internet as a whole.

The specific situation here is in the sport of fencing, and the diagram below depicts the circuit created within an epee - with the top button-switch being pressed, and completing a circuit, when the fencer scores a hit with their sword. However, when the hit is on the opponents sword, it's not desirable to score a hit (as it's not a valid one).

I'm wondering how one could detect the condition shown below in Figure B, where a very simple circuit with a closed switch has a conductive connection to a part of another circuit, with no return path for current.

I know that another device can do it, their guide suggests that the green wire (in my diagram) is kept close to each fencers body to provide an 'earth reference'. I'm confused about what this means - would you try to detect some current leakage, or other change in the voltage/current/resistance characteristics, when the circuit is connected to a new ground voltage?


texts:
From the appnote FDMQ8205/A is almost identical to FDMQ8203 except the externa circuitry is no longer required.

I am curious if anyone knows why in the FDMQ8205/A design VOUTN is NOT connected to GND but FDMQ8203 shows VOUTN connected to GND. Was this intentional or just a small mistake in the datasheet?


texts: Why is the usb shield always tied to ground (GND pin)?

texts:
The shielding on a cable is to avoid interference from the outside world however it is always tied directly to the GND pin. Not inside the cable itself but inside a device. Every single device I take a look at, will do this, computer/hubs, usb soundcards, usb bluetooth dongles, usb powerbanks, usb harddrives, arduino's etc.

In my perspective this make no sense at all because the shielding is now acting like a big attenna instead of a faraday cage, or am I wrong? I think this a source of noise and/or ground loop problems.

What is de reason why they doing this?

Example, when measuring resistance between shield and GND pin, it reads 0 ohm:


texts:
I'm trying to use pin change interrupts to detect pressed buttons. Until now I have never worked with these kind of interrupts and there are some problems, so I want to make sure if this is the correct usage.

If I got the datasheet right the following things must be done to use a pin change interrupt:

Set which PINs you want to control in the PCMSK register
Enable the PINs register for pin change interrupt control (PCICR)
Enable interrupts
Use the corresponding interrupt vector

Project: Simple Moodlamp, Colors controlled via 4 Buttons.

Setup:

Atmega168A-PU
4 mini push button switches
MOSFETS to control my 3 Watt RGB LED

Here is the code I'm using which is not working as expected:

#include <avr/io.h>
#include <stdint.h>
#include <avr/interrupt.h>
#include <util/delay.h>

#define BUTTON1 (1<<PC5)
#define BUTTON2 (1<<PC4)
#define BUTTON3 (1<<PC3)
#define BUTTON4 (1<<PC2)

#define GREEN   (1<<PB1)
#define BLUE    (1<<PB2)
#define RED     (1<<PB3)

void init() {

        // enable LED
        DDRB |= GREEN;
        DDRB |= BLUE;
        DDRB |= RED;

        // button pullups
        PORTC |= BUTTON1;
        PORTC |= BUTTON2;
        PORTC |= BUTTON3;
        PORTC |= BUTTON4;

        // pin change interrupts for buttons
        PCMSK1 |= PCINT13;
        PCMSK1 |= PCINT12;
        PCMSK1 |= PCINT11;
        PCMSK1 |= PCINT10;

        // enable pin change for buttons
        PCICR |= PCIE2;

        sei();

}

ISR(PCINT2_vect) {

                PORTB = BLUE;
}

void ledTest() {

                PORTB ^= RED;
                _delay_ms(250);
                PORTB ^= RED;
                _delay_ms(250);
                PORTB ^= RED;
                _delay_ms(250);
                PORTB ^= RED;

                PORTB ^= BLUE;
                _delay_ms(250);
                PORTB ^= BLUE;
                _delay_ms(250);
                PORTB ^= BLUE;
                _delay_ms(250);
                PORTB ^= BLUE;

                PORTB ^= GREEN;
                _delay_ms(250);
                PORTB ^= GREEN;
                _delay_ms(250);
                PORTB ^= GREEN;
                _delay_ms(250);
                PORTB ^= GREEN;
}

int main() {

        init();
        ledTest();

        _delay_ms(500);
        PORTB |= GREEN;

        while(1) {
                _delay_ms(100);
        }
}

Note: The buttons should be debounced. Since I'm trying to this step by step and it shouldn't mater for turning on the LED, I ignored it here.

Question: Is the way I'm trying to use the interrupts correct?

Problems with my setup:

Buttons1-3 are totally ignored.
Button4 is triggering a reset of the atmega

Things I checked:

Buttons are in no way connected to the reset PIN
Buttons are properly connected to GND if pressed
Buttons are not connected to GND if not pressed
Buttons work nicely if I utilize them without an interrupt, e.g.:

if(!(PINC & BUTTON4)) {
                PORTB ^= BLUE;
        }
16MHZ external crystal / internal crystal
Any errors in the routing
I'm using a 100nF capacitator between PWR and GND on the atmega
VCC(7), GND(8), GND(22), AVCC(20) are connected (since I don't need AREF, its not connected)


texts: So I want to experience a bit with with ARM

texts:
I thought about buying one of the following boards:

http://www.micro4you.com/store/lpc1768-arm-cortex-m3-board.html

or maybe

http://www.micro4you.com/store/lpc2368-development-board.html

For studying purposes.

I have experience with Xilinx, FPGAs, Virtex 5 and Spartan 6.

I would have bought there zynq 7000 but it's a bit pricey...

So what do you think about the boards? Do you have a better recommendation?

Thanks a lot.

Assaf.


texts: Connecting any signal route with unused pin

texts:
I am using BGA package type of MCU, and it has ball pins on the bottom side. As I route the signal route, some of pins should be connected with unused pins without build-up method. The pins are not ADC. I wonder it will affect any operation on the chip or not.

I think my firmware will not take those pass-through unused pins, so it is not. But it is not general in artwork. Is there anyone who faced same case?

A is signal route I am using
B is unused pin, but I connect with A for pass-through
Other sides are blocked by other routes.

Jiwon


texts:
i built a clock circuit using ds1307 and atmega328 and it works very fine
but i noticed that the time of my clock is increment by 6 seconds in a day (approx) by comparing to my computer clock
what is the problem could be?? i used the DS because it gives a real time clock
i used the crystal that came with the ds1307 when i bought it?
could it be the ds has a kind of problem ?
or should i but a capacitors on the crystal?

thanks any way


texts: LSM9DS0's Accelerometer not reading correctly

texts:
I have a LSM9DS0 Gyroscope/Accelerometer/Magnetometer breakout board. I am using an Arduino Uno which operates on 5V. The LSM9DS0 is communicating to the Uno using I2C through a Logic Level Converter. The Uno and the LSM9DS0 are connected in parallel to my power supply. The Accelerometer function worked fine the first few times, but when I turn the power supply off and then back on to reboot everything, the Accelerometer seems to fail. Instead of actually getting a accurate number, I receive -1.50; Even if I move the board, I still get that number.

I have researched this and have found nothing. The only thing that fixes this seems to be unplugging the LSM9DS0 and then plugging it back in. I am truly puzzled by this.
Do you have any suggestions or solutions to this problem?


texts:
I am working on a POE design  for the first time that supports 100Mbps. I plan on using the mEZS84801A evaluation board that uses MP8007 as a reference design to do all the signature detection, classification and dcdc converter as shown below. I need an output of 12V to supply the camera which will be the PD it will draw around 8W during continuous run time.

I need some advice for the circuit design before the MP8007, involving the RJ45 and transformer. The main concern is, we do not what the customer will be using for their PSE, is there a way to design for both Mode A and B so that when they plug the cable in with their PSE, the design can accommodate for an Endspan switch or if they decide to use a Midspan and ethernet switch?

The IC is compatible for both modes but I noticed that the magnetic transformer after the RJ45 is different depending on mode. Mode A, the pairs 4,5 and 7 and 8 are left unconnected since power is from the data pairs, whereas Mode B the spare pairs are connected. I am thinking if both cannot be supported at once, I would have population options to select between modes. But ideally if there is a way to make a design that can support both modes without needing to modify the PCB it would be much better. Appreciate any help and/or suggestions. Thanks in advance!


texts:
I got myself a spartan-3an evaluation board in order to learn fpga programming and some verilog. It's taken a little while to stop seeing it in terms of a sequential programming language and to start seeing it in terms of connections between blocks of hardware but I'm getting there.

I've made a small "program" that takes a image defined in "ram" and displays it on the vga port. The ram is just a set of reg's like this

reg ram[4095:0]; // Video memory for 64x64 pixel display

I used the patterns in the help and the compiler has inferred that it should put this into a blockmem and it all works nicely.

My doubt is about timing though.

I have one "always" block incrementing a counter for the vga horizontal position, and one incrementing a counter for the vga vertical position. Then I have another always block that uses that counter to generate an address into a "reg" that indxes the memory.

There is then another "always" block triggered by a clock that reads that memory.

My doubt is this - I'm generating the sync pulses based on the counters. That's fine, but I'm generating the address in the video memory too from those counters to read the pixel. However that read will occur on the next clock pulse so my pixel data will be output one clock cycle later than I'm expecting. I'll calculate the address on one clock cycle but not have the pixel data available until the next one.

Have I understood that situation correctly? And if so, what do I do about it? Ignore it because it won't be visible? I could probably buffer the sync pulses too and delay them in the same way. Or I could pre adjust the calculated memory address to compensate in advance.

What do people generally do in this kind of situation? Or is every case different?


texts: Altium "Update PCB documents", components are generated at the same place

texts:
I'm new with hierchical design in Altium. When I update the PCB, all the components of the multi sheets are generated at the same place.

There is the hiearchy of the project :

I highlighted the problematic sheets in yellow!

There is two "InputAmplifier" sheets in "InputConnectors"
There is eight "InputsConnectors" sheets in "AudioInputs_16"
There is one "AudioInputs" sheet in "TopLevel"
There is eight "OutputConnectors" sheets in "AudioOutputs_16"
There is one "AudioOutput" sheet in "TopLevel"

The components are looking like this on the PCB:

-

And far away all the components of the problematic sheets are generated at the same point:

How can I split all the components? There is a lot of components and moving all of them by hand will be really long.

Thank you!


texts:
If gradually increased from 0 to 100 duty cycle, does PWM on its own take care of inrush current in a motor drive?

simulate this circuit – Schematic created using CircuitLab


texts:
I am building a circuit using a fixed 5V LM1084.

All the circuit diagrams in the datasheet seem to be for the adjustable configurations. To used the 5V fixed should I connect Adj/GND pin directly to ground?


texts:
I keep reading about TCP/IP stack for wifi module. I am having bit difficulty to understand that.

I am working on hobby project in IoT and need to choose wifi module for Atmega328P. I heard about CC3000 module which is very costly. So I thought I should buy raw wifi chip and use that with Atmega328P and use MQTT to communicate with it. This is just a theory. But this stack thing came in between and I don't know what it is?

What is TCP/IP stack for wifi module? I am new to this area. So, it would be great if you can elaborate the answer.


texts: High speed photodiode for laser pulse width measurement

texts:
I want to measure the temporal width of a Q-Switched laser (which should be close to 5 ns) and the delay between two lasers that I send in my experiment. The delay is between 1 ns and 1 µs. Wavelength will be in the visible.

I'm not sure about the device that I have to use. I found the FDS025 photodiode from Thorlabs (low capacitance 0.94 pF and rise/fall time of 47/226 ps but with small area, only 0.049 mm²). Is it sufficient? Since I'm looking directly at the laser, should I suffer from the low current generated by the PD? If yes, what kind of high-speed amplifier do I have to use?

Thank you in advance for your help!


texts:
I have a Sony QX10 camera, with comes with built-in wifi. I want to to connect wired ethernet to it. I was hoping I could find a wifi chip inside the camera, and solder to where the ethernet traces go into the wifi chip. Here's what the motherboard looks like, -- several chips I could not identify, and none that are obviously wifi. I've added labels on the chips that are to small to read in white.

There's also a teardown video of a similar model here: http://youtu.be/aH0_dAtKofw .

I could not find any other chips or antennas elsewhere in the camera that were obviously related to wifi. Should there be an obvious antenna somewhere?

Is it possible that wifi is integrated into the large processor IC itself?


texts: Designing a circuit for active low input relay

texts: How do i modify the following circuit for a  1 form A contact relay such that it has active low input.


texts:
This is scheme of triac control module.
I'm using optotriac MOC3041 (T1 on scheme) and triac BTA140 (T2 on scheme).
Is it possible that my control module doesn't work correctly due to too small capacity C1 (should be 10nF and I have 5nF in one module) or lack of part with capacitor C1 and resistorr R4 (in second module)? I thought, that this part serves only to mitigate overvoltages, but this two modules (with capacitor 5nF and without part with C1 and R4) doesn't work correctly. They allow executive element to work, either the state is low or high on T1 input.


texts:
While using 8085 especially at a different baud-rate ,
DTE being the micro-controller, DCE being any modem/or a Display device coupled with
RS232 db9 or db25 port.
I can understand SBUF can Store upto 8 bit of data when its full, it gives A TI high
ie it hires a transmitter interrupt,
But  Iam confused whether this SBUF (mentioned in program) bleongs to the DTE or DCE,
Suppose there is a program,To transmit at baudrate 4800,
     ORG 00H;
00   MOV SCON #50H;
01H  MOV TMOD #20H;
02H  MOV TH1,-6;
03H  MOV A,#'Y';
04H  CALL PRINT;
05H  MOV A,#'E';
06H  CALL PRINT;
07H  MOV A,#'S';
08H  CALL PRINT;
09H  CLR TI;
0AH  SJMP 03H;

PRINT: MOV SBUF,A;
   P1:  JNB TI,P1;
        RET;

Also during transmission of 'Y' to the receiver of the DCE, REN flag must be enabled,
there is a need for both the sides to understand the tranmission of data(first 8bit has taken place, which this program seriouly misses) and we use TI for that ,
but can we address both ends SBUF in a single program?


texts: What should I use for a 3.3 voltage reference that sinks maximum of 1mA?

texts: I am in search for stable and precise 3.3 voltage reference IC. I am using it for the temperature sensor application which only sinks 1mA at max. Can someone suggest me a best component/IC for this type of application.


texts:
I'm a beginner in the field of electronics, and I have been trying to put together flasher and buzzer circuits together.

this what i did till now :D
but when i finished the circuit on the pcb the leds doesn't blink :(

Notes on the PCB:
between BS4 and BS3 a variable Resistor

between BS6 and BS5 a Button for the flasher

between BS1 and BS2 a Button for the buzzer

can anyone help :D


texts:
What is the easiest way to make a device that can control GPIO pins using USB?

Can I make a device similar to this on my own without any special hardware?


texts: Why does inserting a resistance in the common of my scope probe cause it to pick up AC noise so much worse?

texts:
I'm poking at the inside of a USB oscilloscope, with the hope of modifying it so that the scope probe commons can be referenced to different voltages.

When I use my USB oscilloscope to measure a 24V DC signal with a 10x probe, I get reasonable results.

By my figuring, this 10x probe is a 9 MOhm resistor, in series with the scope's 1 MOhm internal resistance. Thus, a 10:1 divider.

simulate this circuit – Schematic created using CircuitLab

By adding 10 MOhm to the probe, I should turn it into a 20:1 divider. When I insert 10 MOhm into the positive signal path I do get a rough 20:1 effect, but I start seeing AC 60 Hz noise.

simulate this circuit

When I instead put the resistance in the common path, between the signal common and the scope probe common, I see vastly more AC noise.

simulate this circuit

My USB scope is isolated from my PC with a commercial USB isolator. Can anyone tell me what's going wrong, and how to fix it? I thought this might just be a consequence of having all this strewn about my desk instead of pleasantly soldered together with minimum signal paths. But I would have expected the noise to be much lesser magnitude, and much more responsive to physical rearrangement. Moving leads and parts has zero observable effect. And it still wouldn't explain the difference between inserting the resistance in the positive and negative paths.

Why is this happening, and how can I fix it?


texts: Why does analog video signal in computers change?

texts:
I've been told that analog video signal from computer's graphics card changes somehow, and because of that there is an "auto" button on many monitors that connect via d-sub.

Why does the video signal change?


texts: Simple circuit for fading an LED out (no MCU)

texts: What is the simplest circuit you can create which fades an LED in from off to bright, without using any sort of processor or MCU? Would an inductor be of any use here?


texts: How does NVIC know what function to call on an interrupt (libopencm3)

texts:
I'm trying to learn ARM programming on the blue pill and was looking at libopencm (I've HAL but i want to move to an opensource alternative). In the examples for the RTC, it sets up the rtc_isr() function. But what tells the NVIC that the interrupt vector points to that function? Do I have to name my function with **_isr()?  I've tried to go through the documentation for it but it doesn't say anything about how interrupts are handled in the the NVIC.

Thanks for the help!

#include <libopencm3/stm32/rcc.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/rtc.h>
#include <libopencm3/stm32/usart.h>
#include <libopencm3/stm32/pwr.h>
#include <libopencm3/cm3/nvic.h>

static void clock_setup(void)
{
    rcc_clock_setup_in_hse_8mhz_out_72mhz();

    /* Enable GPIOC clock. */
    rcc_periph_clock_enable(RCC_GPIOC);

    /* Enable clocks for GPIO port A (for GPIO_USART1_TX) and USART1. */
    rcc_periph_clock_enable(RCC_GPIOA);
    rcc_periph_clock_enable(RCC_USART1);
}

static void usart_setup(void)
{
    /* Setup GPIO pin GPIO_USART1_TX/GPIO9 on GPIO port A for transmit. */
    gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ,
              GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO_USART1_TX);

    /* Setup UART parameters. */
    usart_set_baudrate(USART1, 115200);
    usart_set_databits(USART1, 8);
    usart_set_stopbits(USART1, USART_STOPBITS_1);
    usart_set_mode(USART1, USART_MODE_TX);
    usart_set_parity(USART1, USART_PARITY_NONE);
    usart_set_flow_control(USART1, USART_FLOWCONTROL_NONE);

    /* Finally enable the USART. */
    usart_enable(USART1);
}

static void gpio_setup(void)
{
    /* Set GPIO12 (in GPIO port C) to 'output push-pull'. */
    gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_2_MHZ,
              GPIO_CNF_OUTPUT_PUSHPULL, GPIO12);
}

static void nvic_setup(void)
{
    /* Without this the RTC interrupt routine will never be called. */
    nvic_enable_irq(NVIC_RTC_IRQ);
    nvic_set_priority(NVIC_RTC_IRQ, 1);
}

void rtc_isr(void)
{
    volatile uint32_t j = 0, c = 0;

    /* The interrupt flag isn't cleared by hardware, we have to do it. */
    rtc_clear_flag(RTC_SEC);

    /* Visual output. */
    gpio_toggle(GPIOC, GPIO12);

    c = rtc_get_counter_val();

    /* Display the current counter value in binary via USART1. */
    for (j = 0; j < 32; j++) {
        if ((c & (0x80000000 >> j)) != 0) {
            usart_send_blocking(USART1, '1');
        } else {
            usart_send_blocking(USART1, '0');
        }
    }
    usart_send_blocking(USART1, '\n');
    usart_send_blocking(USART1, '\r');
}

int main(void)
{
    clock_setup();
    gpio_setup();
    usart_setup();

    /*
     * If the RTC is pre-configured just allow access, don't reconfigure.
     * Otherwise enable it with the LSE as clock source and 0x7fff as
     * prescale value.
     */
    rtc_auto_awake(RCC_LSE, 0x7fff);

    /* Setup the RTC interrupt. */
    nvic_setup();

    /* Enable the RTC interrupt to occur off the SEC flag. */
    rtc_interrupt_enable(RTC_SEC);

    while (1);

    return 0;
}


texts: My ohmmeters don't behave as the book "make: electronics" describe

texts:
Here's the (low end) devices I own. One is an HoldPeak HP-90EPC, the other is an GBC KDM-110

I am following the book "Make: Electronics" by Charles Platt and I am at the very beginnings, where it suggests to:

measure the resistance of two points of my tongue, wet
measure the resistance of two points of my tongue, dry

I get about the same results, or the same range, beacause I don't get a single reading but plenty which change very dynamically every second.
Also,

measure the resistance of two parts of your body, then move the probes closer or farther away and see how the resistance increases when they are more distant from each other

This is not happening. It looks like my body is about 18 megaohm resistant no matter where I touch the skin - either a couple centimeters apart or on one leg and the arm of the other side of the body.

Same goes for water. If I put the probes into water, the reading is ranging apparently random and seems not to take into account the distance between the probes.

Are both my devices junk?
Or, there is a reason why this could actually make any sense?


texts: Making a wireless clicker to use in presentations, suggestions?

texts:
I will be needing a wireless remote/clicker of some sort to use when delivering presentations for projects and assignments (i.e. Powerpoint type). Yeah, I can buy one quite cheap - but really, what fun is that?

The first thing which comes to my mind is to use a small microcontroller like the ATTiny for the receiver, connected via USB as an HID device. Then use something cheap like IR to send it the signal. I've never done this, but I think IR is the simplest and cheapest method. What other cheap alternatives should I consider? The disadvantages of IR are obvious.

In terms of functionality, it needs to have the bare minimum ability to receive a signal as an indication to move on to the next slide. I'll first tackle this first, before adding further functionality. I think if I go the HID device route, it should be pretty simple if I just program the microcontroller to send a left mouse button clicked command.

So should I use a microcontroller, or something else? What is the easiest way to do this, and what wireless technology would you recommend I use?

Thanks.


texts: How does this circuit works for detection of Logic low, Logic High and Hi-Impedance state?

texts: I was working on a design of Li-ion battery charger using LTC4001. Here a pin is called CHRG, which indicates the different state of charging like charging cycle begins, threshold reach(i.e 4.2V or C/10), Fully Charged. I'm bit confused with the operation of this circuit. So can anyone help with this circuit?