texts: Help with or hints for decoding an IR protocol

texts:
Some time ago I bought a simple and cheap little IR-controlled toy helicopter (same as this one - it's called "Diamond Gyro" or "Diamond Force"). For fun, I've been looking into controlling it via an Arduino.

Update: Got the protocol figured out; see answer

Others have already shared their results on hacking a different IR toy helicopter and decoding its IR protocol. Really cool, but unfortunately my helicopter uses a different protocol. One that I can't quite figure out. (I should add that electronics is purely a sometimes-hobby for me, so I may have overlooked something obvious).

Much like in the 2nd link above, I took the controller apart, located the IC pin controlling the LEDs (the IC's markings have been erased, by the way), and hooked up a logic analyzer.

Got lots of good data, but I still can't figure out the protocol. This site is a great resource, but none of the protocols listed seem to fit. And nothing else I've found seems to fit the signal I've captured either. I have to imagine, though, that it's a simple, off-the-shelf protocol, only because it's a cheap little toy.

So I'd appreciate any ideas you may have. Maybe I'm just looking at it wrong.
(More info below the image)

Signal/protocol characteristics

I captured this at 16MHz with the controller set to channel A; should be accurate, timing-wise. (There are 3 IR channels you can pick from, but using the two other channels don't change the characteristics, only parts of the packet itself.) The timings are very consistent (+/- 10µs max). Packets are repeated with varying intervals but at minimum they're about 100ms apart.

Carrier: 38kHz @ 50% duty-cycle

Lows:
 - Short: 285µs
 - Long:  795µs

Highs:
 - Short: 275µs
 - Long:  855µs

Always 17 highs per packet.

Controls/inputs

The heli's got 3 controls: "Throttle" (i.e. lift/rotor speed), pitch (forward/back), and yaw (rotation around the rotor axis) all controlled with 2 thumbsticks. They all have some kind of range (not just on/off) and are, as far as I can tell, all being transmitted in a single packet. The left/right inputs are only sent if something else is being sent, so I applied max throttle when sampling that. Throttle and pitch input on its own trigger packets being sent, as soon at you push the thumbsticks past some threshold/deadband (in the graph below the "min" label is for first packet sent when slowly pushing a control past its deadband).

It's also got buttons for trimming left & right, as the heli's not a precision instrument (at all) and tends to spin slowly otherwise. The left/right trim buttons unfortunately don't seem to send a signal that's incrementing/decrementing something for each press (which would be handy for figuring the protocol); it seems to just be single command, telling the helicopter to trim left/right, and then it keeps track of it.


texts: Nexys2 - any luck getting it running on a virtual machine?

texts:
So I have a Nexys2 500K board that works when connected 'directly into the os', when I'm running Win7. However, as I use Mac OS X (10.8.2) mainly, I don't want to reboot my PC just to use the board for a moment. So I made a virtual machine (V: VirtualBox), and I set an USB filter to automatically connect a device with

Product ID: 0x0005
Vendor ID:  0x1443

However, although iMPACT and adept detect the board as Nexys2, they always fail to initialize chain with following error (from iMPACT)

GUI --- Auto connect to cable...
INFO:iMPACT - Digilent Plugin: Plugin Version: 2.4.4 INFO:iMPACT -
Digilent Plugin: found 1 device(s).
INFO:iMPACT - Digilent Plugin: opening device: "Nexys2",
SN:10054D236487 ERROR:iMPACT - Digilent Plugin: failed to open device (DmgrOpen, erc = 3072).
AutoDetecting cable. Please wait.
*** WARNING ***: When port is set to auto detect mode, cable speed is
set to default 6 MHz regardless of explicit arguments supplied for setting the baud rates PROGRESS_START - Starting Operation.
Connecting to cable (Usb Port - USB21).
Checking cable driver.
Source driver files not found.
The Platform Cable USB is not detected. Please connect a cable.If a
cable is connected, please disconnect and reconnect to the usb port,
follow the instructions in the 'Found New Hardware Wizard', then retry the Cable Setup operation.

I tried installing the cable drivers from digilent site, but for some reason, Impact cannot detect them (I can only see those two default cable drivers from xilinx).

So, anybody had found a way to get it running through a virtual machine? (Tried installing ISE on Win7, Win8, and newest CentOS, all can't detect anything)


texts:
Below is the image of a pull push circuit but I'am exactly not familiar with it . May be class A or B or AB . But I was hoping if someone could tell me the name for this configuration

I'am known the voltage sources , output power , input impedance , voltage gain and the low frequency bandwidth cut off . My task is to find the values of RC components in the circuit above that will make the circuit behave according to the parameters given . Can some one tell me the equations to solve this circuit or more importantly a link at which I can read more about it . Thanks

Data :
Supply voltages ± 9 V
Voltage gain >20 dB
Low frequency roll-off point < 100 Hz (Lower bandwidth limit)
Rin > 2k ohms

Hint : Choose a suitable
input signal voltage to achieve the specification


texts: Is it really a good-practice disable optimizations during the development and debugging phases?

texts:
I've read Programming 16-Bit PIC Microcontrollers in C, and there is this affirmation in the book:

  During the development and debugging
  phases of a project, though, it is
  always good practice to disable all
  optimizations as they might modify the
  structure of the code being analyzed
  and render single-stepping and
  breakpoint placement problematic.

I confess I was a little confused. I didn't understand if the author said that because of the C30 evaluation period or if it's really a good practice.

I'd like to know if you actually use this practice, and why?


texts: Can voltage across an inductor change instantly?

texts: If current is passed through an inductor, there will be a voltage across it. If that current source is disconnected, the voltage across it reverses. Does this happen instantly?


texts: How to build a FSK modulator and demodulator?

texts:
I want to build a FSK modulator and demodulator, the center frequency is 4.234MHz +-175kHz, FL is 3.951MHz, FH is 4.516MHz, mean data rate will be 564.48kbit/s.
After searching the web, I found that FSK modulator can be build with DDS or PLL, demodulator can be build with PLL or complete software(DSP). Honestly, that's all the information I got.
Do you have better recommendation on how to build this kind of FSK modulator and demodulator? Thank you!


texts: Can a composite video line doubler be made using simple hardware components? (composite -> progressive scan)

texts:
I have a lot of old analog video equipment and my trusty Apple IIe Color Monitor is finally dying. Since CRT's aren't produced anymore, and because I just am interested in how it is done, I obtained a decent plasma monitor (I can't get enough of those deep black tones). I want to know if an analog signal can be deinterlaced without resorting to a FPGA or similar overkill.

Can something to get rid of the interlacing effect on non-CRT's be made with components like 74-series IC's and proc amps (and maybe a AVR microcontroller), or do I need to go out and get some specialized chip from some specialized producer? All I want for output is progressive-scan composite video (although a better signal would be acceptable, I would prefer composite).

The most complex digital video generation hardware I have ever worked with was that of a Commodore 64 (converted it to PAL by swapping IC's with a european one, and replaced a few caps). My other experience was just adding a analog filter to a NES system. So digital isn't really my thing. I hate to think this is a dumb question, and hopefully, even if there's no answer, I am not the only one who wants this.


texts: Using CCM (Core Coupled Memory) in STM32F4xx

texts:
STM32F4xx microcontrollers have 128KB of SRAM + 64KB of CCM SRAM. CMM SRAM is hardwired to data bus so it is impossible to use it with DMA.

What is the reason to add additional SRAM as CCM?
Does it increase performance and if that it's the case why it's so?


texts:
If I can just call on you again to help me advance in a project.

My infrared beam breaker circuit is lacking in range. I would need it to be able to bridge a doorway, so about a meter.

On the receiver side, I am using TSOP1236, which can be triggered by my TV's remote control from across the room. The problem thus lies with the transmitter.

This is the exact schematic that I followed (one modification: using a 9V battery with a LM7805 voltage regulator):

I'm using this exact IR LED.

The 555 timer works in astable mode.
The output frequency of this circuit is about 35.2KHz.
Currently the range is a couple of centimetres.

Could anyone point me in the right direction to increase the range?
Will bringing the output frequency closer to 36KHz do the trick, and provide for a range of about one meter? If so, could you tell me what capacitor and two resistors I would need for that?

Reading this forum and others, something tells me I should connect the output of NE555 to the base of a BC 547 transistor which would act as an amplifier. Maybe this schematic is the way to go? Maybe it is overkill.

Very curious about your replies.


texts: Schmitt Trigger Oscillator - How does it work?

texts:
I have seen countless times the following diagram for a Schmitt trigger oscillator.

As shown in the picture, the slow-rise wave-form generated by the charging and discharging capacitor is translated to a square wave-form at the output, as a result of the Schmitt trigger. However, I have no idea how the capacitor even charges up in the first place. I don't see any "input voltage" other than the upper and lower bounds on the actual Schmitt trigger. How is the capacitor charging up in the first place?

I'm sorry if this is a very dumb question.


texts:
I'm looking at using the RS485 to communicate between two Arduinos. I'm trying to wrap my head around the current requirements though... If I connect a driver to a receiver through a differential pair, then what concerns do I have regarding current sourcing and sinking, as the datasheets I've seen all seem to point to negative currents somewhere along the line.

Am I not interpreting the datasheets correctly. Is it more of a case of a small amount of current will flow from the arduino to the driver. Likewise, a small amount of current will flow from the receiver to the arduino, but for the most part the driver and receiver will source and sink current from their relevant power supplies?

I have included the relevant parts of the datasheet as follows. For the driver (datasheet):

The relevant receiver (datasheet) extract is as follows:

Edit (example circuit)

To clarify the given answer, if I had a circuit below (it cannot be simulated) and had a driver and receiver wired up with the diode it would work okay as the driver and reciever would not attempt to sink current to their respective control pins?

simulate this circuit – Schematic created using CircuitLab

Also, the driver I can see sources 200mA from VCC, but sinks a minimum of 200mA into GND, which is a standard forward voltage circuit... Is this correct? (I'm not too familiar as yet with reverse voltages, sinking current etc...). However the input current (assuming that is what I'm calling the 'in' port that connects to the microcontroller) has a +- of 1 uA, which I am assuming means it can sink or source current from the microcontroller. If this is the case, it would seem to me the diodes would stop this circuit working?


texts: Parameters affecting high-speed PCB transmission line design

texts:
I am designing an I/O board for an NVIDIA Jetson Nano SOM module. The board contains the HDMI, USB2.0, CSI, SD card and power system and GPIOs.
As I am beginner with high-speed designs, I have a problem, please help me to understand.
So for USB 2.0 90 ohm impedance is required, so I calculated the following:

There I have selected 1 oz copper thickness and FR4 material. My PCB manufacturer has a capability of minimum 0.15 mm spacing and 0.15 mm track width. So after entering all the details, I got 0.77 mm as track width and 0.15 mm as track spacing.
For my reference I have downloaded the official Rpi CM4 IO board Kicad files, which are using 0.15 mm as width and 0.25 mm as gap. I have verified the copper core thickness is 1 oz.
So could you please help me to understand, what's the parameter which is causing the difference in width and gap?


texts: How to read potentiometer input from dsPICDEM MCLV-2 Dev Board - dspic33

texts:
I have very little microcontroller knowledge so please bear with me. I am trying to figure out how to use all of the inputs on the dsPICDEM MCLV-2 Dev Board. Specifically, how do I read the potentiometer input in C code using MPLAB X IDE. I want to set the potentiometer from 0-100 and be able to turn it and see an output of the value it is at. All reference material I have read for this board does not contain the actual function used to read/write to the potentiometer. If someone can point me to the right reference material or knows how to use the potentiometer and can help I would greatly appreciate it.

Not asking for anyone to write code for me, just want to know how to access the potentiometer on dev board.

Thanks!


texts:
I am trying to make my first PCB, an would like to program an ATmega328P-PU using my Arduino and a breadboard and transfer it to my printed circuit board.

My problem is that either I will make a mistake, or need to reprogram it in the future, so permanently soldering it is not a great idea.

I am going to buy a microcontroller socket, but I am wondering if it is specific to the model and if the eagle schematic is different from the MCU's.


texts:
I want to learn all the basics about making a simple radio project.

The project is simple... One transmitting device (which only sends out analog signals of some decent frequency.. say 50MHz) and one receiving device which will have an LED and it will light up only when it receives the signal that is produced by the transmitter.

The project is simple.. I wish to learn everything from scratch and implement it using discrete semiconductor components (No not IC's)

I have searched most part in the internet and almost all of them just show only finalized circuit and thus there is no learning process involved.. I wish to learn the entire electronics/physics behind it as I implement it.. Any Book/link will will do...


texts:
I have notice that PICs have the 16F88 and 16LF88 version, after some researching i tought the LF is for chips that work at 3.3V, in other places it says i can still use the 16F88 at 3.3V, the datasheet clearly says :
Wide operating voltage range: 2.0V to 5.5V

Can i power my 16F88 with CR32-3V battery and will the I/Os work at the supplied 3V voltage ?


texts: Attenuation of em waves, when they travel over a surface, happens because the em waves induce a current in the surface and loose energy. EM waves travel farther over sea/ocean. Conductivity of sea/ocean is high. Please explain the connection between high conductivity and longer ranges.


texts: ARM + FPGA board for industrial Product development

texts:
I am using mini2440 board with external FPGA board, I am looking for one ARM+FPGA board with GPIO support.

As of now I am using mini2440 board with GPIO to control the hardware and sometimes using USB FPGA board to control the hardware. I am looking for the board with has ARM+FPGA support so that I can connect my hardware to the board to reduce the hardware.

Please let me know If you know any ARM+FPGA board in whcih i can port Linux and use it for industrial application.


texts: PWM using XC8 compiler and peripheral libraries

texts:
I am trying to run the most simple example of PWM using a PIC18F4550, XC8 compiler and the libraries plib/timers.h and plib/pwm.h

My code is the next:

#include <xc.h>
#include <plib/timers.h>
#include <plib/pwm.h>

//CONFIGURATION BITS...
#pragma config PLLDIV = 5, CPUDIV = OSC1_PLL2, USBDIV = 2
#pragma config FOSC = HSPLL_HS, FCMEN = OFF, IESO = OFF
#pragma config PWRT = OFF, BOR = OFF, VREGEN = OFF
#pragma config WDT = OFF, WDTPS = 32768
#pragma config MCLRE = ON, LPT1OSC = OFF, PBADEN = OFF
#pragma config STVREN = ON, LVP = OFF, ICPRT = OFF, XINST = OFF

#define _XTAL_FREQ 48000000

void main(){
    TRISCbits.TRISC2 = 0;
    unsigned char prescaler = T2_PS_1_16;
    OpenTimer2(prescaler);
    OpenPWM1(0x95);
    while(1){
        SetDCPWM1(300);
    }
}

And the diagram of my PIC is:

But I get an error message when trying to compile:

C:\Program Files (x86)\Microchip\xc8\v1.40\include\pic18f4550.h:4426: error:    (1098) conflicting declarations for variable "_TRISCbits" (C:\Program Files   (x86)\Microchip\xc8\v1.40\include\pic18f4550.h:3829)
(908) exit status = 1
nbproject/Makefile-default.mk:125: recipe for target   'dist/default/production/PWM_code.X.production.hex' failed
make[2]: Leaving directory 'C:/Users/Delfin/Pictures/PIC18F4550   Basics/PWM_code.X'
nbproject/Makefile-default.mk:84: recipe for target '.build-conf' failed
make[1]: Leaving directory 'C:/Users/Delfin/Pictures/PIC18F4550   Basics/PWM_code.X'
make[2]: *** [dist/default/production/PWM_code.X.production.hex] Error 1
make[1]: *** [.build-conf] Error 2
make: *** [.build-impl] Error 2
nbproject/Makefile-impl.mk:39: recipe for target '.build-impl' failed

BUILD FAILED (exit value 2, total time: 1s)

I have already downloaded and installed the periperial libraries from here: http://www.microchip.com/mymicrochip/filehandler.aspx?ddocname=en574973 and also linked them in my code as I show in the following picture:

So, why is not compiling? When I comment the line:

OpenPWM1(0x95);

works fine. I would appreciate any suggestions. Thanks


texts: Implementing certain sequence of JK flipflop to the circuit using tinkercad

texts:
I am a beginner when it comes to electronics and what I'm trying to create is a circuit in which it outputs to the 3 LED (3 bits) the following sequence below using JK flip flop.

This is the picture  of the one I'm doing. I'm using tinkercad
You can access my work here if you want
Also, here's my computation which I'm pretty sure as I've triple checked it.

Though I'm very much familiar on how to arrive at the needed expression for each JK what I'm not familiar with is how to apply it to the actual circuit (in my case is the tinkercad).
Update:
The circuit diagram would be like below where the values of [J0,K0] to [J2,K2] are indicated above.

Also, someone sends me a picture of their schematic diagram and upon checking it, my tinkercad work seems identical to that.

How do I implement the "t", "en" and "0" on tinkercad 74HC73? Do you have any idea? I'm pertaining to this part of the circuit.

It seems that all the "t" and "en" from Q2 to Q0 are 0 while "en" is set to 1.


texts:
Could somebody please explain how to find the address space for the RAM, Sensors, Alarm and ROM? :)

The answer is supposed to be

ROM: 0000-1FFF
RAM: 2000-3FFF
Sensors: FFF0 - FFFF
Alarm: FFFE


texts: How to drive segment display and sens button press at the same time? Understanding this schematic

texts:
I have a very simple board that has been designed by the Italians back in 2001.
It has 3 7segment common anode displays, 2 buttons, and a few LEDs.

I have to interface with it but I don't know how it works.

P3 is just and IDC connector that used to connect to the CPU board.
LED[3..5] are the display modules.

I guess the PNPs are switching the anode of the displays, driven by Cathode[a..f] pins, the LEDs use the same principle, but I think i got that right.

What I don't understand is that how can I sense if the switch S[3..4] has been pushed if it is connected to a pulsating Output. I am planning to use a TM1637 to drive the displays but I am very lost on how to find out when the button has been pushed with a simple ESP32 module.

Can you please help?


texts: DC/DC converter from 9V to around 180V - LTspice simulation

texts:
I am trying to simulate circuit from link: Nixie power supply, but I have come into some problems. I downloaded MC34063 from this forum and example in package is working perfectly. Below is my circuit in LTspice. But for my circuit there is no oscillation on swe output so Q1 and M1 is constantly in one state. As output voltage I got 3.6 V.

Here is digital version of my schematic file: circuit + mc34063 model

What am I missing? Not working is caused by wrong components, different from schematic? I don't get something about LTspice?

I am new to electronic and just pick this as exercise.


texts: Verilog modules: estimating power consumption before physical design

texts:
What can a designer do to get an idea of how much power a various module with consume? It seems like there should exist some decent heuristics to go about doing this, else we would have to wait until deeper into the physical design stage.

A basic idea might be some linear combination of regs + gates + wires, like say:

P = x*numRegs + y1*numANDgates + y2*numORgates + ... + z*numWires

And perhaps the coefficients could come from a standard cell library. Which unfortunately I don't know where to find, for free at least.

Really though, I just want to be able to do back-of-the-napkin calculations to compare similar modules to each other. Any suggestions?
EDIT - by all means, share any free CAD tools that may help =)

Thanks


texts: maximum collector-emitter voltage in BJTs

texts: I am reading BC817 datasheet. According to the datasheet, maximum collector-emitter voltage at open base condition is 45 V. In typical applications we don't use open base configuration. My question is that how can I find maximum collector-emitter voltage when the base is biased. I could not find relevant information in the datasheet (Maybe I have not enough knowledge about it). Many thanks for your time.


texts: Help dimensioning resistors in a two NPN transistor current limiter circuit

texts:
I'm trying to design the current limiter circuit shown above which I saw on this website:

http://electronicdesign.com/power/current-limiter-offers-circuit-protection-low-voltage-drop

I'm using 18V - 24V supply and 2N2222A transistors. It must limit the current to 0.12A - 0.15A to the load so I have calculated that \$ R_{SENSE} \$ must be 3-4 ohms. I'm just unsure how to determine what the value of \$ R_{1} \$ should be.

I'm relatively new to electronics.


texts: Open loop gain - understanding the simulations

texts:
I tried to simulate a non inverting amplifier, to see the differences from the amplification up to the unity gain, just to learn to be more confident with the LT Spice tool.

Then I saw this video describing ho to analyze the loop: http://www.linear.com/solutions/4449

And is doing the analysis by checking the bode plot, where it become 0dB you can of course find the phase margin and so on. I did the simulation with the two resistor set to 1000 as in the example (DC gain = 2).

The problem is that with their amplifier LT6016 is fine, or reasonable:

When I change with the LM324 (a model found in internet), it never starts from gains greater than unity:

My thoughts and questions:

May the LM324 model be wrong? Seems to work with a simulation with a conventional signal.
With other opamp, the gain may still be greater than 1 at DC so you can determine the phase margin, but with a different magnitude: what is telling to me this magnitude? I know that according to this value, the phase margin and bandwidth can vary, but is it proportional to the open gain loop, so is it the GPB?
When is lower or equal than 1 at DC, if it is correct as in the example with my LM324, how can I proceed for the stability analysis?

EDIT:

This is the test circuit, for which I tried negative VEE (like in the video) and as shown, the result does not change:

This is the famous result of all of three op-amps:

EDIT2:

These are instead the plots with the negative supply CORRECTED. Now is meaningful.

And this is the simulated circuit:


texts: How to measure pulse width of an IR signal using an 8-bit PIC?

texts:
My friend and I want to design a universal learning remote controller, like this one, for learning purposes. What we want to do basically is store and replay infrared pulses.

We want to detect 36kHz, 38kHz and 40kHz signals. A 40kHz signal will have a period of 25\$\mu\$s.

We want to use an 8-bit PIC microcontroller, for now we have selected PIC16F616, that will run at 20MHz high speed crystal oscillator. We have two options available:

Use the Interrupt On Change module.
Use the capture mode of the CCP module.

First option will be as follows:

Assume a register is set as: unsigned char _10_us = 0;. This register will hold the time. TMR2 module with period register is set to create an interrupt every 10\$\mu\$sec. When an interrupt occurs, it will increment the _10_us register and  exit. This will give a maximum time of 2.55msec. If more time measurement is needed, additional registers such as _1_ms can be defined and incremented as needed.

Now, every time an interrupt is generated by any kind of change ( high-to-low or low-to-high), the program will note the current time, that is the value of _10_us register. After a while, when the next interrupt is generated, the program will subtract the saved value from the _10_us register, and thus will now the time that is taken in the meantime, with a unit of 10 \$\mu\$seconds.

This option make me scratch my head; TMR2 interrupt will occur about every 50 instructions. Interrupt handling will take about 20 instructions. I am left with 30 instructions to calculate and save the period to an array. Will this method work?

Second option will be as follows:

Set up the capture mode of the CCP module so that it will generate an interrupt when an event(high-to-low) occurs on CCP1 pin. In the interrupt routine, it will set a flag so that a task in the program can calculate(if needed) and save the value of CCPR1H (probably will not be needed) and CCPR1L. Then we will change the configuration of the capture mode so that it will trigger the interrupt when a low-to-high edge occurs. And then it will wait for the next event. I cannot estimate the performance of this method since I've never used it.

Another option?

We can use an infrared demodulator IC such as TSOP17xx series. That would solve our problem completely. However some questions come to mind.

Our reading distance requirement is not much; 1 metre (~3 feet). If we select a TSOP1738 that is meant to be working in 38kHz, how well will this work with 36kHz and 40kHz signals?

Page 4 of the datasheet of TSOP17xx series shows "Frequency Dependence of Responsivity" graph. As far as we understood;

40kHz, which is ~1.053 of 38kHz, will give a relative responsitivity of ~0.6.
36kHz, which is ~0.95 of 38kHz, will give a relative responsitivity of ~0.65.

What do these values mean? Can we use a TSOP1738 and be fine?


texts: Difference between Test mode and Functional mode in JTAG

texts:
Hi while reading the datasheet for an ethernet controller chip, I came across the terms functional mode and test mode in relation to JTAG.

Can someone kindly explain these terms.


texts: Is it safe to touch the return rail on the London Underground?

texts: I had always been under the impression that return rails for electrified rail systems were safe to touch, since they are at ground. Certainly this has to be true for systems that use the running track as the return as these are crossed all the time at level crossings. But I'm confused about how this works on the London Underground. I understand that that system uses a fourth rail for the return (for various reasons, primarily so that the return can be properly insulated from the old cast iron tunnels) and had always assumed that these rails were grounded (at their "ends") like running rail returns and thus safe to touch; but I read recently that the return rail is at "210 volts below earth". Doesn't this mean that that rail dangerous to touch?


texts: Best layer stack strategy for a 6 layer PCB with mostly SMD components

texts:
I am doing a design in a 6 layer PCB where both sides are populated. 95% of the components are SMD. The design is not "High Frequency" in terms of signal speeds....the fastest thing here is a MCU with 80MHz internal clock and digital signals up to around 48Mhz.

I searched around to come up with a efficient layer stack strategy. First thing that pops on google is this article which claims the best would be something like:

If I understand correctly...the whole point is to have minimum amount of cut in the ground planes for best return path. So, one would always try not to route signals in the ground plane at all.

Now my question is, since majority of my components are SMD...then I will require a lot of vias to connect SMD components to the ground layers. This will make a lot of wholes in the board and not only disturbs the inner ground planes but also mhy increase production cost.

From my understanging, the same article states that if top/bottom have also planes for ground, it will worsen the EMI because of increased loop area:

  Some people say that adding additional ground planes helps shield against immunity and emissions. The truth is that it reduces the LOOP AREA!

My own strategy is to follow this layer stack but also pour top and bottom layers with GND to minimize number of vias and just connect top and bottom ground pours with 2nd and 5 layers. If the pour on the top or bottom can not reach some components I will use vias for those particular components.

So the question is...adding GND pours on top and bottom layers in addition to the 2 inner GND layers is a good idea or not? does it make a big loop area and worsen the EMI? I can not make head and tails of this situation really.

Does this make any sense? please let me know what you would do in such case!


texts: What is the feedback mechanism behind this motor?

texts:
I would like to play around with this servo motor but I'm not sure what the feedback mechanism on it is or what the interface is.

The mechanism has 3 wires leading to it (yellow, orange, brown). It consists of a hard black disc (I think the disc is metal or possibly a ceramic?), a PCB behind it that has a square wave pattern around the circumference of the board, and on the board itself there are a couple resistors, ceramic capacitors and a single 8 pin IC (I can't see what is on the IC, I don't want to take the mechanism apart).

The motor came from an old photocopier.

My best guess is that it might be a magnetic resolver but I've never had any experience with them.

So the question is: What is the mechanism in the picture and how would I go about interfacing it (ie, if it was an encoder, I'd do quadrature decoding ect).


texts: Device to measure current in the range of pico Ampere (pA)

texts:
I am working on an electrochemical quantitative sensor and considering the reaction rate I can predict a current output in the order of 10-1 pA (pico Ampere).
I was wondering if there is any device or way to measure a current of this order of magnitude with accuracy (without being too expensive).


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Really, I have been writing codes for embedded application for a while. But this question struck me, and I seem not to give more answers to it myself.

Can I get more details on the reason for selecting an MCU with a particular frequency XXhz. For example when you say ARM® Cortex®-M3 revision 2.0 running at up to 48 MHz, what is the implication to the over-all performance of the Chip and connecting circuit as a whole? Why should I choose this Frequency and not a lesser or higher frequency instead?

I can understand that it determines the speed of the MCU, but could that be that all?

Also, what effect does the external crystal oscillator have on the clock Frequency as well.

Thanks
Paul.


texts: Sine wave shows up on oscilloscope but keeps moving

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I'm fairly new to electronics and new to using an oscilloscope.  I followed a youtube video to setup a sine wave using an Arduino Uno and a capacitor to detect on my Tektronix 2235.
https://www.youtube.com/watch?v=ojkUaCSFM30
However, the scope seems to constantly "move" through the sine wave like a bouncing ball instead of just displaying it like on a graph.  When just doing a simple digital 5V generation using the Arduino and no capacitor, it just shows a stable graph.
https://drive.google.com/file/d/1ZjEv1hedKXllJgSrIjcxXV_FHNsyUWqc/view?usp=sharing
Is this based upon the rate of change of the voltage or something?
Here's the code I'm using:

int f = 2; //signal freq
float fs = 500.0; //sample freq
int sig[500]; //store signal
float t;  //time value

void setup() {
  // put your setup code here, to run once:
  pinMode(10, OUTPUT);

  for (int i =0; i<500; i++) {
    t = (float) i / fs;

    sig[i] = (int) (127.0 * (sin(2*3.14*f*t) + 1.0) );  //127 is 1/2 of 255, the max voltage value
  }

}

void loop() {
  for (int i = 0; i<500; i++) {
    analogWrite(10, sig[i]);
    delay(2);  //sampling interval
  }

}

The scope is set to 1V / div and 10 microseconds.


texts: Is it possible to have a register with multiple drivers?

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This is just a theoretical question I have. Imagine we have a register (a reg signal in Verilog for example) and two possible inputs that have to write to that register. I am assuming all signals are synchronous to the same clock. Normally in these cases I guess that you need a multiplexer to decide which signal actually go to the input of the register. But, it is possible to connect both signals to the input without any multiplexer? I am assuming that at all times only one source wants to write to the register. I have this question because I'm wondering if it is possible to avoid using the multiplexer and thus reducing resource usage in the final circuit.

Thank you in advance


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I have some ideas for Arduino Nano projects I'm throwing around that I would like to power only with a solar panel and I'm wondering if I am going about it the right way. I have: A 7.2V 100mA solar panel, a couple of AAA rechargeable batteries, my NANO(s), and external components. This seems like a complicated project to a noob, so I'll try to list just a few concerns.

Is the 7.2V solar panel compatible with five 1.5V rechargeable batteries?(7.5V when put together in series). I'll just connect + to + and - to - and it will slowly charge?
Should I be concerned about my power supply slowly dropping voltage every night for weeks or months (hopefully years) and charging in the morning, and messing with the circuitry of the nano? I would assume that at night it would die off after a couple of hours, but that may depend on how much power my external components are dissipating.
This may have to be found out experimentally, but does the solar panel produce enough power to at least keep the Nano on and charge the batteries?

I'm thinking it should be a simple circuit, solar panel→batteries→Vin & GND (5V regulator is built in, of course). But if the low voltage while charging and dying off is a problem, I was thinking about using a low-voltage indicator circuit to tell when the power drops below 6.5-6.9V:

Hand drawing:

YouTube video: https://www.youtube.com/watch?v=Z0cOO0TNjNA

and some logic gates, maybe a NOT gate and replacing the positive side of the LED from the circuit above with the input for the NOT gate, with the output going to Vin. Hopefully a transistor NOT gate can withstand the 7.2V.

Please tell me what I should change and anything I should be aware of. Thanks in advance.


texts: Accidentally knocked a capacitor off a laptop motherboard seemingly related to USB

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I accidentally knocked off a capacitor from my laptop motherboard (Lenovo Thinkpad S540, VIUS6 LA-A171P board). According to the circuit diagram, this capacitor (C2434) was something to do with the USB 3.0 circuit (perhaps the VBUS). See the pics attached. The C2434 capacitor is toward the top-right of the second image

My question is should I be worried? Everything seems to be working fine right now, but I'm worried this will come back to bite me in weeks/months from now. I don't really care if the USB port stops working or something, but don't want a more serious issue to arise.


texts: EAGLE - put "symbol" and corresponding "packages" in the "schematics view"

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So in EAGLE every library has "devices" which usualy have one "symbol" and more corresponding "packages" available for that "symbol". So EAGLE only shows a symbol part in the "schematics view" and only package part in the "board view".

But how can instruct EAGLE to draw a package part in "scheatics view"? I would like to put it right next to the "symbol".


texts: Why is it better to use this Opto-coupler to drive the gate of a FET than using other methods?

texts: What significant advantage does using this HCPL3180 opto-coupler have to drive the gate of an FET over using other methods, such as using an op-amp or BJTs, and also does it have anything to do with ground bounce?


texts: Where does the Panel Mount BNC Connector make the ground connection to my PCB?

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This may be a dumb question, but where does the PCB make a connection with the signal ground on this BNC connector? All I see is the signal pin that is soldered on (via solder cup) and no where is there the possibility to solder to a reference ground.
The part is Digikey PN A32342-ND

Thanks


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I have seen a wide variety of different estimates for the maximum current rating for copper wire.  For example, for 24-gauge copper wire, the Wikipedia article about "American wire gauge" claims that a copper wire will fuse after 10 s if carrying a current of over 29 A.  On the other hand, this page claims a maximum current of only 3.5 A for chassis wiring and 0.577 A for power transmission.  What is causing the disconnect between these wildly divergent estimates of the maximum current?  Moreover, which of these estimates is most useful for estimating the maximum current that is safe for use in an electromagnet (both with and without insulation)?

Thank you.


texts: How does an outlet know what wattage to put out?

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In the UK, if that makes any difference, I was wiring a motor and then I wondered (and kinda needed to know), how does a plug socket know how much power to put out? because all the input ampages on all the plugs sad different things but can all be plugged into the same socket.

How does this madness work?!? XD


texts: EBike Controller - Does 'current' affect driving speed?

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I wanted to ask if a brushless controller Current actually affects electric bicycle speed.
At the moment I have a 48V 250W brushless controller, rated current of 5A and maximum current of 10A. protection voltage is 42V.

Here is a more detailed picture about my controller plugs, etc:

So my main question is: if I switch to a same brushless controller but just this time with lets say a maximum Current of 17A, will it make any difference in any way?

I also tried talking with the manufacturer and I didn't get a flat answer; they said it won't affect on the speed but I read in a few places that it might.

My Battery: 48V 13Ah
My Motor: 48V 250W ( model: bafang swx02 )

Also another question, is there any way to make my ebike drive faster than 25 km/h without switching the motor?


texts: How are size of caps determined/calculated for use in smoothing voltage?

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I'm reading this great book (AVR Programming: Learning to Write Software for Hardware by Elliot Williams) and setting up my arduino atmega328pu, usbasp programmer and using avrdude to program the chip.

The book shows the following setup to power the chip off the computer's USB port via the USBASP programmer.

The author explains that you should use a 100 nF (0.1 µF) across the VCC to ground to smooth the voltage.

How is that value (100 nF (0.1 µF)) calculated or determined?  I know 5V is coming off USB port of computer and I'm wondering how that factors into the calculation.

What Does That Do?

Does that basically "short" certain voltages directly to ground -- when voltage spikes?

Part 2 : A Similar But Different Example

There is also a similar set up of a mintduino but the author is using a 9V battery so the voltage is different but in that case the writer/experimenter shows it hooked up like the following*:

Of course you can also see that this experimenter is setting up the atmega328 to use an external crystal (16 MHz) but he uses two smoothing caps of 22pF and he puts one serially on each pin (XTAL1, XTAL2), each connecting back to ground.

Basic Explanation?

Can someone provide a bit of an explanation of how these are similar or different?

General Formula?

Can someone provide a general formula for calculating the cap values I should use in instances where the voltage is different?

*You can see the entire mintduino article at: https://makezine.com/projects/build-a-mintronics-mintduino/


texts: Initial Conditions and Parallel Resonant Circuit Problem

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simulate this circuit – Schematic created using CircuitLab
I already did my own solution but I just want to check if I got everything right, especially in determining the initial conditions. Here is my own understanding:
So, for t<0, the current source and capacitor  is an open circuit and the inductor will be a short circuit. Hence, all the current will flow to the short circuited inductor.
$$ t<0: $$
$$ i(0) = 3A; $$ $$ v(0) = 30; $$ $$ \frac{di (0)}{dt} = \frac{30}{4} = 7.5 $$
Now, at t > 0:
We could do source transformation with the 30V source and 10 ohm resistor, hence, everything will be in parallel. I combined the 6 A and the 3 A to get 9 A current source and combined the two resistances to get:
$$ t>0: $$
$$ i(0^+) = 9A; $$ $$ R = 10||40 = 8; $$ $$ resonant freq. = \frac{1}{√LC} = 5 = 7.5 $$
$$ α = \frac{1}{2RC} = 6.25 $$
$$ s_1 = -2.5, s_2 = -10 $$
Here we can see that we will have an overdamped response hence our solution would be of the form:
$$ i(t) = I_f + A_1e^{-2.5t} + A_2e^{-10t} $$
To get A1:
$$ i(0) = I_f + A_1 + A2 $$
$$ 3 = 9 + A_1 + A_2 $$
$$ -6 - A_2 = A_1 $$
To get A2:
$$ \frac{di (0)}{dt} = \frac{30}{4} = 7.5 = -2.5A_1 + -10A_2 $$
$$ 7.5 = -2.5(-6-A_2) - 10A_2 $$
$$ A_2 = 1 $$
$$ A_1 = -7 $$
So my final equation would be:
$$ i(t) = 9 -7e^{-2.5t} + e^{-10t} $$
Did I do everything right? I feel like my initial conditions analysis is wrong but when I checked using LTspice, im getting the current inductor to be almost 3A for t<0 and 9A for t>0. But when I check for voltage on the node of Vc, im getting 3mV which I don't understand.


texts: How do I simulate the above circuit in LTSPICE? The way I have it set up right now gives me a singular matrix error which I don't understand. Vi is a AC signal with a frequency of 100kHz and a small amplitude of less than 10mV.


texts: FCC certification for multiple transmitters

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Need help in understanding FCC certification for a IoT device with a Bluetooth module and a WiFi module.

The Bluetooth has its own FCC ID, so does WiFi. Both are certified to be modular FCC certified. So I presume that my product needs to have a single FCC ID, whose tests would involve simultaneous transmission.

Is there a way to do only few additional tests (simultaneous transmission), without going for product level FCC, and still sell the product?
Also, does anyone have an idea on how do phone manufacturers handle this, because they have BT, WiFi, LTE as well?

Thanks!


texts: Output Data Rate for this gyroscope is way lower than the clock rate?

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I was planning on using an L3G4200D gyroscope in a project to align manufacturing rollers. I've been looking at the datasheet and it says that the clock rate is 10 MHz but it also has something about a "Output Data Rate" and it can be set to 100, 200, 400, and 800 Hz. That's way lower than the supposed clock rate so I was hoping someone could clear this up. I also don't understand what they mean when they say "Cut-Off" along with the ODR.

This is the product page, it has a link to download the datasheet (PDF)
http://www.st.com/web/en/catalog/sense_power/FM89/SC1288/PF250373

The ODR is on page 29. The clock rate info is on page 12.

Note: We are using the SPI interface. (Almost forgot to mention that).


texts: I searched a lot and saw many videos and every time it get's more complicated..what is the difference between time domain and Freq. domain and phasor domain in circuit analysis ? when should we use each one ? and how we transform a Fn. from one domain to another ?


texts:
Before I work on the simulations, I am struggling to understand the voltage regulated circuit theoretically. I try to vary the V1 DC supply, V2 provides a constant DC voltage of 12 V. The zener (D1) breakdown voltage is 5.1 V, while the forward voltage drop of D2 is 2.2 V.

I am trying to analyze the effect of varying V1 on the circuit voltages and currents, and I would appreciate if you could let me know whether my understanding is correct. All transistor references are made to Q1.

If V1 = 0.5 V DC, Ir1 = 0 A, Vbase = 0 V, Vemitter = 0 V, Iemitter = 0 V. This is because 0.5 V is less than the turn-on voltage of transistor (Vbe = 0). SO the transistor is in cutoff.

If V1 = 1.3 V, Ir1 = (1.3 - 0.7)/220 A, Vbase = 1.3 - (220 x Ir1) V, Vemitter=(1.3 - 0.7) = 0.6 V, Iemitter = 0 V because 0.6 V is less than 2.2 V, so D2 is off.

If V1 =4 V, Ir1 = (4 - 0.7)/220 A, Vbase  = 4 - (220 x Ir1) V, Vemitter = (4 - 0.7) = 3.3 V, Iemitter = (3.3 - 2.2)/220 A.

If V1 = 7 V, Ir1 = (7 - 5.1)/220 V (because the zener is not in breakdown, so the voltage at the node is 5.1 V), Vbase = 5.1 V, Vemitter = (5.1 - 0.7) = 4.4 V, Iemitter = (4.4-2.2)/220 A.


texts: understanding how a motor is controlled with an L293D and raspberry pi

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See update, picture of robot below.

So today I hooked up a motor and made it spin with my raspberry pi and an L293D by reading this tutorial.

This is what the circuit looks like (larger pictures):

It work's and I'm pretty happy. My end goal is to understand this and build something that can control two motors and I'm set to build a small bot :)

My issues:

If I'm not mistaken in this circuit, the enable pin on the L293D is getting a PWM signal for the speed of the motor it drives.

From the software page I can follow what the python is doing but I don't see where it says that pin 18 on the raspberry GPIO should be enabled as PWM?  The docs say that Pin 12 supports PWM ? How does this work?
What if I didn't care about speed? Can I just use an regular GPIO pin for output a high on the enable of the L293D? With the Pi I'm assume that would out a 3.3v? And if I'm looking at the datasheet correct the enable pin can take upto 7v as a high? (What speed would it run on?)
Also again, if I didn't care about speed control, I could hook another GPIO to the second enable and control another motor also right. And I can then control each of they're directions?

Update:

Thanks @Passerby and @JImDearden I got it to work. No PWM, but just two motors. Like @Passerby says, I need three GPIO's for each motor. One for enable/disable and two for direction.

Here is what I made :) And it's wifi network controlled (with a wifi dongle attached) The cable is just a USB power cable :)


texts: Controlling 3-pin pinhole camera from drone using Arduino

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I've got a pinhole camera from an old drone that I dismantled a few years ago. It has a built in MicroSD reader, and 3 pins (red, black, and yellow). I'm wanting to repurpose the camera for use with an Arduino, but not sure how to communicate with it. If I recall correctly, the drone had the option to take a photo or video. I've connected the red wire into +5v, and black into GND, but not sure what to do with the yellow wire. I tried just writing a high signal with an Arduino to see if the camera would do anything, but it didn't work. An LED came on inside though, so it is being powered. Is there some common communication protocol for cameras like this I could use, or any advice on how I could initialize video recording with it? The drone is no longer functional, so I can't use that to determine the communication. Thanks!

Edit: Here is a photo of the camera with the plastic housing taken off


texts: DC supply for control circuit of a DC-DC converter?

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I have a switch mode DC-DC converter assignment which is supposed to convert 36-72V input DC voltage to 9V DC voltage. The circuit I'm working on contains a control circuit (implemented with a custom and multipurpose microcontroller) which requires 5V DC supply (and drains 55mA current from it) to run.

I feel myself in a paradox; a DC-DC converter is needed to run a DC-DC converter. How do I simply obtain a 5V supply for the control circuit? How do other practical and commercial circuits do this?

Since the input voltage can be up to 72V, I can't use a 7805 directly. Is there any way of using it by making a puzzle-like connection out of it, or cascading two 7805 in a smart way? Also, I can't convert the 9V DC at the output to 5V, because in my design, without the control circuit creating PWM signal, the output voltage will be 0V.

I'm working on a scientific assignment in which I can only use the most simplistic semiconductor devices, like (BJTs, MOSFETs, 78xx, etc). So, please don't offer me using a high level IC for this purpose.


texts: Internal pull up resistors in a micro-controller vs external pull ups

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Micrcontrollers such as PIC describe their pull up resistors as weak pull up resistors, what does weak signify?

When/why would I want to use external pull-up resistors on I/O pins that support internal pull up?


texts: High-side switch for 24V controlled by logic level

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I mainly use this high-side switch design for 5V and with low current loads (under 100mA).

Based on the VDSS (-50V), I thought I could energize this design with 24V as well. Apparently, I am making a mistake by interpreting the VDSS.
Even there is no load attached (Drain is only connected to voltmeter), when I connect to 24V source, Mosfet doesn't response to I/O input change (High or Low) anymore and always stays ON. Even I connect to a 5V source again, it still stays ON, another saying I believe the mosfet is gone.

Would you please tell me what is wrong here?


texts: How do I draw a PCB antenna in Eagle without DRC errors?

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I'm designing a board that should contain an antenna I found in an application note. I'm using Eagle and I tried to create a library part for the antenna. However, since the antenna is basically a fancy-shaped short circuit, Eagle tends to report DRC error for it.

Is there a way to draw a PCB antenna in Eagle in such a way, that the DRC errors wouldn't show up?


texts: Not sure how to use Half Bridge Gate Driver (LIN being in/out of phase and more in general)

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I am relatively new about semiconductors and I recently realized that driving MOSFETs requires a middle circuit for most microcontrollers. I followed schematics shared in this tutorial, except I couldn't find IRS2001, instead I bought IR2103. I carefully compared datasheets of both and they seem mostly identical or close enough for me. After trying to set a test circuit though, it didn't worked and I have noticed that IRS2001's LIN pin is labeled in phase, whereas my IR2103's is out of phase. ( I connected MOSFET's gate to LO, and triggered from LIN, while supplying 9V to VCC to driver.) I don't know what that means and couldn't find any helpful sources. I noticed that when I connect LIN to 3.3V or 5V nothing happens, but when I connect it to the ground MOSFET starts to conduct, maybe that's related.
If anyone can lead me to something I'd appreciate that. All the other Half Bridge Gate Driver example circuits consisted of two MOSFETs, why is that? Are those two MOSFETs work dependently to each other or independently? What is the actual use of HB Gate drivers? Can I use my IR2103 to drive as shown in the Instuctables link? Also, is it healthy to use common small BJTs as gate trigger circuit instead of a gate driver?
( I'm using IRFZ44N N-Channel MOSFET, which's load will pull around 10-20 Amps. It needs to respond relatively quickly, my guess is around 100 milliseconds at worst. )


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I am in the process of learning about DC DC converters.  What I am trying to figure out is whether inrush current is needed to maintain the input voltage at the DC-DC converter input while getting its normal operation.
Say, if I have 4-5A inrush current expected for a few tens of microseconds in my setup, can I use my power supply clamps to limit the inrush current,without impeding DC-DC converter operation? I have a few feet of cable from my power supply to my fixture to test the DC-DC converter, with a Kelvin connection on my power supply.  I don't yet know my load capacitance seen by the power supply at the input of the DC/DC converter.  Understanding that the few long cable from power supply to the DC/DC converter has some series inductance, how can I calculate the response time of the power supply to an overcurrent situation?  Please help.


texts: Why do the Duga-1 dipoles look like an array of birdcages?

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Looking for sources for the question What Soviet signals attempted to scramble communication and sabotage Apollo missions? I ran across the Wikipedia article for Duga Radar. Below are cropped and rotated bits from the images in the article.

The BBC video The secret Soviet radar hidden in Chernobyl’s shadow has some related information as well, and you can hear the "woodpecker" sounds well known to short wave listeners of the time.

Rather than simple half-wave dipoles, each radiating element consists of a pair of "pointy bird cages" with their apexes almost touching. It's hard to tell however if they are driven from that point, there's no external connection where you'd normally expect to see a balanced transmission line connected to the points.

Question: What is it about this shape that was important, and why the cage-like structure? Any information on how they were driven is also appreciated.

above: Cropped, rotated and flipped from here

above: Cropped and rotated from here


texts: Finding capacitors with low soakage (dielectric absorption)

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This technical note from Analog Devices indicates that low dielectric absorption is a prime requirement for choosing a capacitor for a sample-and-hold circuit (see page 11).  It also suggests to look for capacitors advertised as low dielectric absorption.

How do I go about searching for capacitors designed for low dielectric absorption?  On Digikey and Mouser, it's not one of the listed parameters.

I also tried searching based on dielectric type, based on information from Kemet and Wikipedia linking dielectric absorption to material.  In this case, it seems like film capacitors are the best candidates (still can't find any datasheets that actually report absorption), but they have very low capacitance.  Ideally I want 1uF or more capacitance, to limit the effects of charge injection from the analog switching logic.

What terms and parameters should I use to guide my search?


texts: Reactive Input Impedance for Current Noise

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I am reading about op amp noise in the app note here. Page 3 mentions:

"Current noise is only important when it flows in an impedance, and thus generates a noise voltage. Maintaining relatively low impedances at the input of an op amp circuit contributes markedly to minimizing the effects of current noise."

For the source impedance does this take into account only real R or complex impedance Z? If my source is 1 MegOhm in parallel with 1 pF capacitor do I take the equivalent impedance of both to calculate current noise?


texts:
Let's say I have 1m of 2,5mm² copper wire, insulated with H07V-K.
The wire carries 40A and environment temperature is 25°C.
The wire is suspended in free air. How hot will the wire get? And how can I calculate it for other values?

The use case is a 12V-230V AC converter I want to hook up to my car and determine the minimum wire thickness required. Because it's only used from time to time and not buried in a wall I suspect I can use thinner wires. This is a temporary thing and doesn't need to be up to code.


texts: My Arduino UNO board is powered with external 5V SMPS through the DC input. On measuring the 5V pin on the Arduino board pinout, I find the voltage to be around 3.7V and the L13 onboard LED glows quite dimly. If I connect an additional USB cable over this DC voltage, the pinout reads 5V and the the L13 led glows bright. Is my Arduino cooked or I doing something wrong?


texts: Can we form any circuit using half adders only? (assuming we have as many half adders as we want)

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Using various combinations on half adders I get these outputs:

{0,1,1,0},{0,0,0,1},{0,0,0,0},{0,1,1,1}

And I also know that we can form any gets using NAND gates or AND and NOT gates but I am not getting any output of the form  NOT so should I assume that we can't form universal gates using half adders?


texts: How would one calculate how efficient a pair of headphones is?

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I'm trying to get a better feel of how exactly the drivers in headphones work.

Specifically, I want to know if it's possible to calculate how much electricity being sent to the drivers in a pair of headphones or speakers is turned into waste heat vs actual motion of the diaphragm.

For example, in a pair of ATH-M50s, the drivers have an impedance of 38 ohms with a maximum input power of 1600 mW at 1 kHz.

I don't know what else would be needed for the calculation, but could anyone give me a general sense of how efficient such drivers would be with their power?

Also, as a side question, what happens to the energy in the vibrating diaphragms? Is most of it dissipated as sound, or is it converted into heat as well through the flexing of the material?


texts:
I'm new to electronics and I have a couple of simple questions on how to safely and reliably power a LED strip.
My goal is to have an individually addressable LED strip lamp.
For the strip I've been researching and I've decided on the SK6812 LED strip for its separate white channel. It's powered using 5V and it uses the 5050SMD LED's which consume 0.3W of power each. I have the choice of 30, 60 or 144 LED's per meter and I was thinking of going with either the 60 LED's or 144 LED's. Ideally I'm planning to use 1.5 meters, so I think I would need:

For the 144 LED's/meter - 144 LED's * 0.3 W / 5V * 1.5m = 12.96 amps of power
For the 60 LED's/meter - 60 LED's * 0.3 W / 5V * 1.5m = 5.4 amps of power

The microcontroler would use some of the power and I've read somewhere that there should be somewhat of 20% surplus of power for the LED strip so that it's not underpowered, so around:

15.5 amps for the 144 LED's/meter
6.5 amps for the 60 LED's/meter

Now it seems to me, by looking at the power supplies that are available, this is quite a bit of power needed. Especially since my project is not too ambitious and I only want to power a simple 1.5 meter LED strip. If I was to go for the 144 LED's/meter - it seems that it would be a hassle of finding a power supply like that and there might be issues with other components.
I'm planning on using the Aircookie/WLED and I would need to split the power from the power supply to the  microcontroller and the LED strip (based on diagrams at https://github.com/Aircoookie/WLED/wiki). Now I want this "LED lamp" to be somewhat aesthetically pleasing and I don't want to split and solder the cable from the power supply to the microcontroller and the strip so I was planning on using a female 1 DC to 2 male DC splitter (2.1mm x 5.5mm) that are advertised for security cameras (for example this) and I've noticed on one of these that the maximum rated power is only 5 Amps.
This low power rating worries me. What if I were to go with the 144 LED's/m strip, using a higher power supply? Do I need to worry about other components such as the microcontroller? How do others power long 144 LED's/m strips? Does injecting current every X distance reduce the power needed? Should I go with a strip that uses 12V? If so - are there any recommendations for and individually addressable one that has a separate white color channel?


texts: How does earth ground complete the circuit?

texts:
I just started reading a book on electronics and currently reading some concepts of earth ground. I came across a section that mentions practices about grounding as follows:

  The ground terminal of the supply is tied to case of the instrument,
  which in turn is wired to the mains earth ground system. A common
  mistake for a novice to make is to attempt to power a load, such as a
  lamp, using the positive and ground terminals of the supply. This,
  however, doesn't complete a current return path to the energy source
  (supply), so no current will flow from the source; hence, the load
  current will be zero. The correct procedure, of course, is to either
  connect the load between the positive and negative terminals directly,
  thus creating a floating load, or using a jumper wire between ground
  and negative supply, create a grounded load.

Quote from Chapter 2, Theory of Practical Electronics for Inventors 3rd Edition by Paul Scherz

My question is:
If the circuit doesn't complete just using positive and ground terminals of the supply, how does it complete then in the case when the ground is actually used correctly (in case of a accidental shock etc.)?
When the hot wire comes in contact with the chasis, the electrons flow from the less resistive path (instead of passing from the body) to the ground. Why can't they flow then when one end is connected to a positive terminal and the other to a ground terminal?


texts:
Consider the following system-level diagram of an AM receiver:

I'm currently focusing on the baseband amplifier stage, which is used to amplify the audio signal. Its corresponding schematic is:

The amplifier shown in the schematic is a TL084. I have few questions about the design of the baseband amplifier:

1) What is the purpose of C1 (1 micro Farad)? I believe it is included to act as a high pass filter, that is, it keeps any DC signals from affecting the circuit.

2) What is the purpose of R1 (150,000 Ohms)? Is R1 the input resistance of the circuit? It makes sense to have a large input resistance since we will be connecting another stage before the baseband amplifier stage.

3) What is the gain equation of the baseband amplifier? Is it okay to assume ideal operational amplifier conditions for this analysis (virtual short between the two inputs of the circuit and no current going into the amplifier)? If it is, then it is easy for me to find the gain equation.

4) Choose values for R2 and Rpot (0 to 10,000 Ohms) that will achieve an in-band gain of 150 V/V to the nearest 5% accuracy.


texts: Is a multiplexed signal same as a composite signal?

texts:
Used to StackOverflow, this is my first question here. So please bear with me if the question is too simple and obvious to you as I am not good in Electrical Engineering stuff. I really need to understand this as part of a Computer Networking course:

I read that a composite signal can be thought of as a combination of simple sine waves and multiplexing is a method by which multiple analog message signals or digital data streams are combined into one signal over a shared medium. Now here are my confusions arising from this:

a) Can multiple composite signals be multiplexed, transmitted and then demultiplexed into the original composite signals? Or only non-composite, single-frequency signals be multiplexed and then demultiplexed into original non-composite signals? If the former is true, does demultiplexing entail separating the constituent frequencies of individual composite signals and then combining them to get the original composite signals? Is that a complex procedure?

b) Can a multiplexed signal be called a composite signal, more so if it is composed of separate composite signals? Can it certainly be considered a composite signal if it is composed of non-composite, single-frequency and separate signals?

c) Does data communication mostly involve composite signals (with many constituent frequencies), or are non-composite, single-frequency signals are also used in communication?

Your answers will be helpful.


texts: What are the seeback specs for common production peltier elements

texts:
I been hunting for weeks for the seeback output for the most commonly sold peltier elements. I found one set of specs for the TEC1 - 12704 branded by HP

rated at 49mv 11ma per degree of temperture differential.

But I can"t find anything for 12706 and above to 12715. I have read 3 dozen datasheets but none contain info on seeback effect output

12706 seems to be the most commonly sold peltier


texts: IRFZ44N is not working properly.its Vgs <1v. So how to make it completely on


texts: How to connect one Android mobile audio output to the microphone of another Android mobile?

texts:
This question is to help the "hard of hearing community" so that they can READ the phone/mobile call because they can not hear it.
Android has some really good (and free, too) apps which can convert voice to text with high accuracy and in many languages (Google Live Transcribe, SpeechNote etc.) Unfortunately as of now there is no feature to transcribe a phone call on Android (Google is working on it but it has a lot of complexities ranging from technical to privacy.)
To transcribe phone calls, I need help from experts.
A hard of hearing person will get call on his mobile phone. (Let us call this mobile "Mobile1.") A mobile headset will be connected to Mobile1 which will have left and right audio and a microphone.
Something like this:

How can I remove Output2 and feed this output to another Android mobile (Mobile2) microphone as input so that Mobile2 can transcribe the caller's voice successfully? A picture of that case is given below where Google Live Transcribe on Mobile2 is translating the voice (which it gets it from its microphone) to text.

I read on the internet and learned some basic terminology about the headset, so based on my limited knowledge, please guide me on how to connect the left or right audio channel wire from one headset to the microphone of another mobile.
Can you please give me a YouTube video demonstrating the making of that adapter or cable or some photos of how to make it so that I can connect with some local shopkeeper for the same because I am not an electronics engineer. I just want to help the deaf community around me and want to see happiness on their faces.

The answer to an old question gave me that idea that we can achieve what I was thinking but that I think the answer is not complete.

If I did not explain myself clearly please ask so that I can do my best to clear it. Please help to support the noble cause of making someone happy.

Edit 1 - Adding a rough diagram as per the suggestion by David.
@David - Can you please confirm whether my understanding is correct about the connectivity of different adapters from source to target mobile? If anything needs to be changed please let me know.


texts: Is it possible to solder a USB cable directly to a board?

texts: I'm working on a design for a PCB carrier for Raspberry Pi Compute Module 4, and I need to connect by USB 3.0 a wire to this carrier board. Is it possible to solder it directly to the PCB in order to save space?


texts: Effect of Pi Filter on the Output of LDO

texts:
Similar to my previous question on +5V Sneak path, I ran into another question now.

I have this circuit as shown.

I have an Pi Filter at the Output.
ATT has 600Ohm Impedance at 100MHz and 0.1Ohm DCR.

This 3.3V goes to the MPC5606S Micro.

My issue:

If I remove the Output capacitor C2, I get the output voltage but All my micro functions are down. Board doesn't get up.

However, If I remove the Attenuator ATT along with C2 (Short the ATT pads), I get the output voltage and my Micro Functions are up. Board is UP.

What effect is this? How come removing the output capacitor plays this type of a role?
Can someone tell me the concept behind this.

Thanks.


texts:
For the B) part, I don't get why is it that for calculating voltage between collector an the emitter (Vce) I take into account diode on base (0.7V), whereas for part A) it's ignored?

Why is Vce in part A and part B are calculated differently? Why is it that in part A voltage of 0.7V isn't taken into account? I get that if βf = infinite, and βf = ic/ib ib -> 0


texts: How to calculate magnitude and phase different of impedence

texts:
How can I use a calculator to find the phase difference and magnitude of a circuit if the circuit has an impedance of, for example, \$Z = 5 + 3j\mbox{ }\Omega\$.

I have the answers \$|Z| = 5.83\$ and \$\theta = 30.96^{\circ}\$.


texts: Relationship between optical power and drive current/voltage?

texts: For a project I'm working on I've got a laser diode whose spec sheet lists the optical power and operating voltage of the module. Unfortunately, the parameter I need most is the drive current. Can the optical power be reasonably approximated as P = VI?


texts: How to use PoE to power an additional device?

texts:
I have an Ethernet (100 Mbps) camera powered through PoE by a PoE enabled switch. The camera is turned on and shut down by configuring the switch to cut the power on and off on the given port.

I want to have a visual indicator that the camera is on. So I did the following:

Assembled a 9V-120V to 5V step down module, a resistor, and a LED.
With a multimeter, determined which wires are used by the camera to get its 54V (which weren't, by the way, the commonly used wires 4 and 8, but rather wires 2 and 6).
Connected the step down module to the wires 2 and 6.

However, it doesn't work. The switch doesn't seem to detect anything. If I unplug it, unsolder one of the cables leading to the step down module, and plug it again, the switch does detect the camera.

What can I do to find where's the problem?


texts: A DC current through a inductor does not create electric fields

texts:
While studying about electric fields and magnetic fields I came across this picture:

and this:

from this website and it indicates that there is an electromagnetic field around the loop of wire, while it gets powered from a battery.
Now correct me if I am wrong but:
As far as I know, since the current is DC, there is a magnetic field (since current is moving), but there is no electric field around the wire (since current is constant, and all the atoms are neutral while electrons/holes move along the wire loop).
There would be a electric field along with the magnetic field in two cases:

if the current was not DC, (if it was either AC or voltage pulses).
When the battery first powers the coil, until the voltage on the coil reaches from 0V to X volts, there is a electric field since the current is changing.

In addition, Wikipedia's electromagnet page does not state anything about electric fields or electromagnetic field. It only talks about magnetic field.
Am I right?
EDIT:
This question and replies here also helps understand how an electric field is created on a coil, if you think of it as a resistor.


texts:
I have made following project using a Holtek HT-12D decoder:

My problem is that when I press any switch on the transmitter and cut power to the transmitter by holding push switch, the receiver end is still showing a LED output. I want it to go to the default state of all LEDs off whenever transmitter goes out of range or power to it is cut.


texts:
Does the change in slip (s) have any impact on load torque in an induction machine/motor? I know it affects the motoring torque. But do the load torque also get affected by the slightest measures if not more?

.
Now my question is if the load torque is independent of slip, shouldn't be BC (the graph for load torque) a straight line parallel to y axis rather than increasing slightly as slip tends to 0?


texts: Confused about determining super mesh or not

texts: This is an easy question related to Mesh analysis. It is a beginners question. In the figure that I have attached there is a 5A current source between two loops and there is common register of 5 ohm as well. In this case should there exist super-mesh or converting the current source into voltage source by 5*5 i.e 10 V works or there is no need to use super-mesh. Sorry if there is the repeated question. I am really confused.


texts: Call member function from interrupt in STM32

texts:
I have created a new STM32 project using cube. I have changed main.c to main.cpp and enabled --cpp in the compiler. If something complains I add extern c so c++ can see it.

I have c++ code running "fine". However now that I started using interrupts I'm experiencing some problems.

I am using UART and HAL. I have defined HAL_UART_RxCpltCallback as extern "C" void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart). When there is a new character in UART the interrupt is executed and the function called correctly. As far as I understand my code is running in c++ in the callback and should be able to access my objects methods.

I want to execute m.onReceiveCharacter() from the callback where m for now is a global variable in the main.cpp file. The object has the method I try to call. I add that line to the interrupt and I can see with the debugger that the function is called and I can go trough it correctly.

However what happens is that sometimes (I still haven't found the logic) some of the members of m change for no apparent reason. For example I have a private member UART_HandleTypeDef* huart that is pointed to the right huart at the beggining when I initialize and after an interrupt (before even the m.onReceiveCharacter() is executed) changes "randomly" to another address.

Usually, if I have a function in the main loop doing some operations on m and the interrupt comes then suddenly the value of huart is changed. The value of huart is never changed in any way in the code and this happens before the interrupt code inside the function is called (but the callback function already entered to). I have seen similar issues with other variables that are also not to be changed.

Any ideas?

Summary: Some of the members of my object change "randomly" to new values when an interrupt comes. What are the possible causes? I am using STM32F030R8, with a project generated by Cube, in Keil compiler version 5.


texts: Design Considerations for a dc motor drive circuit?

texts: I'm planning to develop a control circuit for a 24V, 500 RPM (@no load), 2A, 4 kg-cm brushed DC motor. Motor has to run only in one direction. I plan to use IRF44ZN MOSFET with a proper driver to drive the motor and a PIC 16f873a to generate PWM. But the challenge is, the motor has to be continuously operated for at least one day (24 hours). What are the things that I  should taken care of when designing a drive for such an application?


texts: Audio signal trying to go back to zero zeroes

texts:
I created a two differrent signals on my android phone, one to act as the clock signal (lower signal), and the other to be the data signal (lower signal), but the problem is that the audio the signal always drifts towards the "ground"

Why does it do this? Note that my signal isn't really a square wave it's more of a PWM.


texts: What's the difference between PLA and PAL logic devices? Is there one?

texts:
I've seen both PAL (which I understand is Programmable Array Logic) and PLA (I don't know what this one stands for. Programmable Logic Array?) used to refer to certain types of programmable logic devices that came before modern PLDs, CPLDs, and FPGAs. Is there a semantic difference between the terms, or are they two words for the same class of device?

I was originally going to ask about GALs as well, but I found a question on here that already answers that part.


texts: What are the typical limitations for capacitors integrated into silicon chip?

texts:
This question is a bit premature as I don't have any intention to create any silicon chips right away. But I have an idea of an integrated circuit which depends on what I will be able to squeeze into one.

And the main thing I have doubts about is a HV capacitor. My simulation shows that I will need to have 350 (or 400 even better - 230 VAC + 10-15%) Volts with 100 pF capacitance.

Unfortunately I don't know which limitations are applied to capacitors integrated into silicon chips. Does anybody knows?


texts: What is the value of the given resistor?

texts:
I tried checking with 5 band color code but was unsuccessful.
Resistor is blown hence the value cannot be determined using multimeter.


texts: Difficulty understanding group delay concept

texts:
I’m having difficulty understanding the concept of group delay. The mathematical definition is not difficult, since it says it is the negative derivative of Bode plot’s phase curve wrt frequency. Most often qualitative definitions are easy but the math is difficult. In this case seems the opposite or it is due to my ignorance.

I have read some similar questions but still did not get the reason for such a concept. Is it possible to illustrate this concept with an example in elementary level. I know the meaning of Fourrier transform, frequency domain representation, and basic filter theory. Also a bit of modulation. What would the derivative of a phase frequency plot tell us regarding a low pass filter for instance? Im completely lost on the meaning of it so I cant even pose the question well.


texts: Help me find a component based on its label

texts: I have an SMD component containing two pads. There is a label on the surface of the component: 200A in one row and 06A in second row. I suppose the component is a diode but I don't know what kind and how I can buy it.


texts: Arduino yielding different results when plugged to USB and not

texts:
I'm programming a control system for a motorbike powered by a 68V battery. From this battery I have a shunt resistor whose voltage is amplified by an op amp and fed into an analog pin of the MEGA2560, this works fine.

I then connect the battery to a basic voltage divider with 2 resistors (33k and 430k for a x14 division). This is where it behaves "weirdly". I want to use a voltage regulator to power the op amp and the arduino and make it all standalone. When I close the system to the ground of the battery with the regulator powering the arduino and the op amp I get a fixed reading from the voltage divider (should be oscillating a bit) on the Arduino which is wrong (Using a LCD screen).

I checked the voltages between the ground of the battery and the divider's output and it is fine. The arduino is not sensing the input voltage properly from the divider. Now, when I plug the arduino to my laptop using a USb cable and keep everything plugged as is (regulator+ op amp + divider), it works perfectly fine! I am not sure what is the cause of this, if anyone has any idea it would be greatly appreciated!
Thank you for your help!

TO sum up: When my system is not plugged to the USB laptop it gives out wrong readings when its inputs apear to be correct. As soon as it is plugged on my laptop it all works fine!

EDIT:

This is the schematic of the circuit where the arduino returns the wrong value for the voltage divider (A4)

simulate this circuit – Schematic created using CircuitLab

This is the schematic where it all works fine:

simulate this circuit

Don't hesitate to tell me if this is not clear enough, I will draw them again.


texts:
I need to know how find the correct wires on a transformer with multi pri taps.
I have a transformer that can work on PRI 120vac, 220vac and 250vac.
There was a switch to select the proper input voltage but the switch was removed and now I am stuck. I would like to know what to do to get the transformer working on 220/250 vac.
The colour of the wires that goes in on pri side from main is:

  ORANGE
                                                                 WHITE
                                                                 BLUE
                                                                 RED
                                                                 BROWN
                                                                 YELLOW

I hope this could help in a way.
The transformer is in an audio amp.
The transformer is a TAMRADIO.
I don't find any data about it.
I'll appreciate help.
Thanks


texts: Problem writing to MCP23017 I/O Expander registers (i2c)

texts:
I am creating a basic cable tester device and using I2C to interface with two MCP23017 I/O expander chips.

In my code each MCP23017 slave has its own address and I can communicate with both of them properly via I2C.

The idea is that both ends of a "cable" will be placed in the two sockets. Currently I've programmed it to operate on only 8 wires (Using only GPA7-GPA0 on both chips). Basically the idea is that a logic high pulse will be sent individually on each wire (looping 8 times) from the first MCP23017 chip (pins configured as output and is Slave 1) and received by the second MCP23017 chip (pins configured as input and is Slave 2). Now the LEDs light up just fine indicating that the connection exists however I can't get it to write to the registers on Slave 2.

I am writing to the first chips OLATA and reading from the second chips (Slave 2) GPIOA register. So if OLATA is high on GPA7 (first chip) I wish to read GPIOA GPA7 pin on the second chip. Via these reads I can perform bitwise operations to determine the cable types etc.

My problem is that even though all the LEDS light up as expected nothing is being written on the second (bottom most) I/O expander chip. This is no good for me as I need data writes to the registers to occur so I can read the value on these registers to perform operations on. The relevant I2C code for the I/O expander is provided below, these three functions are each run 8 times in the order shown, one for each GPAx pin:

http://pastebin.com/c3H2pbZp

Now the problem is that nothing is being written to the ReadPin variable, it's empty for all 8 GPAx pins on Slave 2 (bottom most I/O expander chip). Also uint8_t Value is 1<

Any ideas? Please help as this is the only main issue I have that is preventing me from proceeding with writing other program logic.

Thanks!

PS: FYI none of my interrupt pins on both MCP23017 chips are connected to anything and the reset pins are connected to VCC. Also the GPAx pins that are setup as inputs on the second slave don't have resistors connected to them. Just the pin and then the LED to GND.

EDIT: Schematic: (right click to view full size)

http://www.avrfreaks.net/modules/PNphpBB2/files/cable_tester_schematic_107.png

Also yes I know on the Schematic theres no GND connection in VSS for Slave 1 but please note that I have my present setup on a protoboard with all connections inc that VSS connection correctly wired.


texts:
I've just had my first go at getting a shift register to work with my Arduino.. it was almost flawless, but I seem to be missing my first bit.

I followed the guide here, but using only one shift register:
http://arduino.cc/en/Tutorial/ShiftOut

It took a little while to figure out, but it appears as though pin Q1 on my shift register is lighting up when I send the number 2, Q2 is high for 4, Q3 = 8 etc.. when I call shiftout() with the number 1 no LEDs come on.

I checked my wiring and it seems fine.. then I double checked and it's definitely fine.

The only things I can think of are:
1. My shift register is slightly different to the one they're using.. it's a 595N, not a 595.
2. I've done something wrong in the code..

In loop():

  digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, MSBFIRST, 1);
  digitalWrite(latchPin, HIGH);

Does anyone have any tips on debugging this issue?

Cheers,
John


texts:
I want to use a pair of N and P channel mosfets in a totem pole arragement to shift a VFD display on and off using a 74LS247 decoder/driver. I would put the P channel with the source pin on the top and connected to the 25 volts the VFD requires. The P channel drain pin would be connected N channel drain pin. The junction of both drains would be my output (25 Volts). The source pin of the N channel would be connected to ground.

The gates of both the P and N channel mosfets would be tied together and powered from the "Open Collector" output of the 74LS247 decoder/driver to turn on and off the appropriate mosfet. I plan on using a Fairchild FDS8958A mosfet complementary pair.

Questions:

Do I need a series resistor in series with the LS247 output and the two gates?
What value do I need?
Do I need pullup / pulldown resistors between the source pin and gate pins?


texts: Why the power supply of a CPU needs to have fast transient response? When the current loading of a CPU changes?

texts: In my understanding, a CPU power supply is usually implemented by of a Point-of-load (POL) converter which is usually a buck converter. And this POL converter is required to have a fast transient response. It implies that the POL converter can adjust the output voltage to the required level whenever the current loading changes. However, I don't understand under which situations would a current loading of a CPU changes. Could anyone explain and give examples? Thanks.


texts: Amplifying a nV signal across a small resistance

texts:
I am interested in the feasibility of amplifying/measuring a nV level (or otherwise assumed very small) signal across a small resistance.

The SNR of this signal isn't so bad in itself because of the very small thermal noise, due to the small value of the resistance. My main concern is that commercially available low-noise amplifiers seem to inevitably add input noise on the level of a few nV per square root hertz, obviously swamping the signal.

Do I have any other option? I was thinking that due to the small resistance, I might not need an amplifier with such a high input resistance, which might partly cause the noise? I'm not sure.


texts: How does this two opamp relaxation oscillator function?

texts:
How does the following circuit  with two TL082 opamps function?

Where should we start thinking the logic of this above oscillator circuit? I named the nodes in red color as A, B, C and D.

1-) How can we explain the output oscillation in terms of voltages at nodes step by step? In a manner like: "Voltage builds up at D then this happens so forth and so on..."

2-) In my simulation I don't get +-5V pulse output I get around +-3.5V output and the output starts oscillating very late, why? Here is what I get:

※ Btw does this circuit have a specific name in literature? It is an oscillator with negative feedback. But other relaxation oscillator examples I have seen have positive feedback.


texts: how long will a 12V 5W solar panel take to charge a 12V 1.3Ah `lead acid battery

texts: i wanted to know how long will it take for the 12V 5W solar panel to charge a 12V 1.3Ah battery. and also whats the maximum voltage that the panel can produce


texts: Best value Lithium ion/polymer cells/batteries

texts:
I've built a sound reactive, android controlled, wearable RGB LED matrix/suit which I'm currently powering with a rather heavy 12V 3Ah SLA battery. I'm looking to switch to lithium or ni-mh packs and leaning toward lipo for weigh/size/easy of charging/low self discharge etc etc. The suit's current draw is 500mA - 1000mA average and about 3000mA peak @12v depending on mode, and I'd like it to last a night out parting ( ^-:D-^ ) so atleast ~5 hours, I also think it would be best to have the battery rated 14v or above and run a switchmode buck regulator to 12v to provide full brightness over the runtime of the battery and also reduce the direct current draw from the battery and thus ESR losses (although I think these would be low with decent lipos but maybe if I get really cheap cells I'll get better capacity from drawing less current? ) thus I think I'll need about 5000mAh capacity @ ~14v

Now the crux of the matter what are the best value cells to go for in terms of cost per energy density (or cost per capacity/weight)? I don't mind buying packs or building ones from single cells. At the moment I can get 10x 18650 lipo cells off ebay for ~$17 shipped and a 5S2P arrangement should give me ~5000mAh @ ~18.5V which should buck down nicely even if the cells don't have a great ESR? opinions welcome :)


texts: How to get rid of shift and logical operations

texts:
I am trying to upgrade an old firmware of a 32-bit MCU. The fw has many macros in it which uses various operations eg., logical shift etc. I want to replace these shift and logical operations. An example is the following macro.

#define ERROR_BIT(x)  ((x & ( 1 << 10 )) >> 10)

The main reason to get rid of these operations is to improve the code readability. What can be a good alternate approach here?


texts: RF frequency synthesis - how low power can I reasonably go?

texts:
I'm an undergrad working on the analog frontend for a student-developed cube satellite. After looking at the options, I've decided to use the CML Microcircuits CMX994 for the receiver and the CMX998 for the transmitter.

I chose the 994 for the RX because it's a direct conversion receiver, so I don't have to worry about external crystal or SAW filters for selectivity (they're kind of hard to find in small quantity for the frequencies I'd be interested in). Power consumption based on the datasheet seems reasonable, at less than 200 mW in low power mode. I chose the 998 for the TX for similar reasons - it does closed-loop predistortion to linearize the PA I designed, saving me from doing my own complicated digital predistortion setup.

I now need to decide how I'm going to do frequency synthesis. The 994 has an onboard frequency synthesizer, the 998 does not. The 994 has a buffer output to feed the 998, but that only works for half-duplex systems - I'm doing a full duplex setup (435 MHz RX, 144 MHz TX), so I need a separate frequency synth for the TX.

I'm not super concerned about the efficiency of the TX LO. When transmitting I'm pumping about 3.6 watts into the power amplifier (according to my ADS sims it'll be about 2W output at ~55% PAE). So, if I use a clock gen chip like the LMX2571 the added power consumption (100mW) next to the PA is pretty much negligible.

I'm more concerned about power efficiency for the RX LO, which will be running all the time. My options for generating the RX LO are:

Use the 994's onboard PLL and design a tank circuit for its VCO. This should take about 70 mW or so.
Use an off-the shelf low-power frequency synth with an integrated VCO like the LMX2571 from TI. This would take about 100 mW, but I avoid having to design a varactor-tuned tank circuit for the 994's VCO and potentially get a cleaner clock.
Use a PLL without an external VCO and design a low-power VCO from scratch. There are some seriously low power RF PLLs out there, but naturally they don't include the VCO.

So my question is basically this: if I sink 2-3 days into designing a very narrowband VCO, can I reasonably expect enough power efficiency improvement to make option #3 better than option #1? My frequency requirements for the VCO are pretty loose, I only need about a 20 MHz tuning range centered at 870 MHz.

I figure if I can cut LO consumption for the receiver to 50 mW or less, it'll be worth my time. As the LO buffer amp for the 994 takes 5mA when using an external clock, this means that the PLL + VCO together should consume less than about 30 mW - ie: 9 mA consumption at 3.3V, or less.

Given that I have only an undergrad level education (I'll be graduating in a few months), and access to design tools such as ADS and Genesys, is this something I could reasonably do, or should I focus my attention elsewhere?

Thanks for your help!


texts: How can I use SPI and I²C at the same time?

texts:
I have a couple of A/D converters and am reading them every 100 µs over SPI, using the timer interrupt routine with SPI clocked at 16 MHz.
Additionally, I have five digital temperature sensors using the I²C bus in a timer interrupt routine executed every second. With a 100 kHz I²C bus and two bytes per temperature sensor, it takes almost 1 ms to read the temperature.
Obviously while reading temperature values I cannot use the SPI bus, missing almost 10 A/D readouts while I²C is active.
How can I use slow and fast peripherals and have timely readouts?

Thanks, these are all great answers!
I am actually using Teensy 3.2 development board and would be nice to have a solution with ready-to-use Arduino IDE libraries. There is a library for Teensy 3.2 for I2C communication with DMA.
I think that the simplest solution is to read A/D converters using 100 us timer interrupt and increment a variable inside the interrupt routine to initiate I2C communication in the main code every second (Microchip TC74 temperature sensors).
I have never used DMA before and my question is what happens when I2C bus is active (reading), and 100us timer interrupt comes. Will it be accepted right away or uC will wait until the byte readout is finished on I2C, or interrupt will be accepted and I2c reading will continue independently?


texts: Applying a forward bias to a photodiode to shift output

texts:
I am using this TIA circuit and photodiode in photovoltaic mode.
I'd like to modify the circuit such that at zero light a positive voltage is produced at Vout. And as more light falls on the photodiode, the circuit would produce a greater negative voltage.

I can add a bias voltage to the positive input to the op amp to achieve the desired effect. But I am not sure about the downside of applying a positive voltage to the photodiode. I have added C4 here to reduce the resistor noise of the bias circuit.
The photodiode is expected to generate 100uA at the maximum light level


texts: Discharge of a load capacitor through a cascode

texts:
How will a cascode effect the discharge of the load capacitor? I would expect that the discharge trough the cascade is slower since the cascode has higher output impedance.

simulate this circuit – Schematic created using CircuitLab

simulate this circuit


texts:
I am trying to implement a cardioid pattern with two microphones.

I was reading this paper titled "Digital Filter Array Optimization for Directivity Pattern". The link to download the paper is this.

The premise of the paper is

"Two microphone arrays are used for producing a specific  directivity pattern by a time delay between the two microphones. Directional hearing aids are examples of the two microphone arrays application. In this paper, the conventional time delay method was replaced with a digital filter method for directional digital hearing aids."

On the second page of the paper, it states,

"If DF1 and DF2  are  optimally  designed  so  as  to  produce  the  same  magnitude   response,   but   the   constant   phase   difference   response  between  DF1  and  DF2,  the  resulting  y[n]  in  figure  2 should be the same as x[n] in figure 1. "

I'm guessing the above statement should instead read "so  as  to  produce  the  same  magnitude   response,   but   varying   phase   difference   response"

My guess is by keeping the magnitude the same between the two signals, but varying phase should be equivalent of causing a time delay between the two signals. Am i right?

If so, how can I calculate filter co-efficients to vary the phase between the two signals in order to produce an exact time delay of few micro seconds?


texts:
I'm a total beginner so I'm sorry for stupid question(s).

I want to design a circuit and I'm stuck. Here's the description:

Photosensor outputs 0V until the ambient light decreases below certain level, after which it outputs 5V. With that signal, I want to turn on 24 V light bulb (draws 250 mA).

I have a few questions:

I definitely need 24 V battery or 24 V DC voltage source in my circuit right? I can't do much with just 5V?
In LTspice there's no photosensor. Can I use 5 V DC voltage source instead? (As far I understand, photosensor acts as switch, right?)
Do I use MOSFET or BJT?

If you check the picture, I tried to do it like this: The 5 V DC on left side activates the MOSFET. I need resistance of 93 ohm (since 24-0,7=23,3 and I want 250 mA). But it's not working. I think that left DC voltage is destroying my circuit.

Any help would be appreciated.


texts: Design of attenuators in microwave systems

texts: A thin dielectric strip is coated with a resistive film to attenuate microwave signals. However, the dielectric strip is tapered at both ends to reduce reflections. Why does the dielectric strip even reflect the microwave signal? Is this because of impedance mismatch? And if so, why does tapering reduce the reflection?


texts: I am going to be soldering in an enclosed space, so I am building a fume extractor via ducts. My eventual plan is to have one fan near the vent, and another somewhere near the inlet to help the fumes get to the ducts. So my question is how powerful should the first fan be, preferably in CFM, and if I need the second fan. Thanks in advance.


texts: How to find threshold voltage of an NMOS with BSIM3v3 model in LTSPICE

texts:
I want to determine the threshold voltage of an NMOS from a bvsim3v3 model in LTSPICE(Not a specific one I'm asking generally for this model). I can't get it directly from the parameters so I want to know how to. It doesn't have to be the exact value, I know it can be changeable but a good approach would be sufficient for me.

One way I thought of is to obtain it from the drain current equation. I set Vgs, W and L myself and measure the drain current with simulation. So this leads to a sub-question: How can I obtain oxide capacitor(Cox) and mobility from the model parameters?


texts: Can I connect this LED drivers Signal and Power Grounds?

texts:
I am using a LDH-45 LED Driver (datasheet) with an I2C DAC as dimmer on the analog DIM pin.

The DAC uses the same power supply as the Driver (with a linear regulator), so they share the same GND.

The datasheet clearly tells me NOT to connect the DIM- pin with VIN- (PSU Ground), however when I measure the resistance between these pins with the Driver disconnected it reads Zero Ohm.

So.. I'm a bit confused since it tells me not to connect them while it seems they are indeed connected. How should I lay my PCB out? Should I leave the DIM- pin "floating" and use the VIN- as a star point for the DAC..?


texts: Are there any filter design tools that can design an LC low pass filter with unequal in/output impedance?

texts:
All the tools I have used so far design for matched impedance. I need something, preferabely free, which gives me this option.
The requirement is for a higher ( >=4) order filter, lossless, for a 8 ohm (or more)  load, and very small source resistance.
Changing the values works (in ELSIE) for up to 4th order, with a little bit of adjustment, but for higher orders I do not get reasonable results.