texts: How does the proposed Microsoft .NET Gageteer compare to other systems?

texts:
I'm a .NET developer interested in the .NET Gadgeteer.  Based on what's public, how does it compare to other devices?

If you're interested, here is a Channel9 video that shows you how to use VS2010 to create an embedded application. It is due to release in Spring of 2011...


texts:
Homework:
I am trying to wrap my head around converting a capacitor circuit into an equivalent capacitor.  I have looked at resources saying that it is the same as delta-wye transformation of resistors, but in reverse.  I thought I had the process right, but I keep getting the wrong answer.

      24       48
a-----)|---o---|(---o
           |\       |
           | \ 4    |
        8 |(  |(   |( 24
           |    \   |
           |     \  |
           |      \ |
b-----|(---o---)|---o
      10       30

I combined the 48 and 24 into one, then took a Delta-wye transform:

      24        16
a-----)|---o----|(----o
            \        /
             \      /
          C2 |(    )| C3
               \  /
                \/
                o
                |
               |( C1
                |
b-----|(--------o
      10

The calculations I used were as follows:

4*8 + 4*30 + 8*30 = 392

C1 = 392/4 = 98

C2 = 392/30 = 13.1

C3 = 392/8 = 49

Plugging in those numbers the equivalent capacitance should be:

Ceq = (24^-1 + 98^-1 + 10^-1)^-1 + 13.1 + (16^-1 + 49^-1)^-1 = 31.7

Unfortunately this is the wrong answer.  I'm not sure what i'm doing wrong, Please help.


texts: How to create a small heater from batteries

texts:
How should I go about creating a heater from batteries (AA/AAA/9V/C/D any will do) that last as long as possible (the longer lasting the better)?

I have seen this post.
But that only lasts 45 mins and doesn't seem very efficient. Is there any way that I could make the heater last long? Maybe by making it not heat up as hot?

I need to have something heat up to \$60^{\circ}\$F deg (for example if a pipe is at \$30^{\circ}\$F deg, I want to heat it up to \$60^{\circ}\$F).


texts:
I'm new to this forum and to microelectronics, my apologies if I don't give all relevant information.

I'm trying to use a FAN3214TMX low-side MOSFET gate driver (datasheet).

Input is provided by a Raspberry Pi GPIO, which delivers a 200 us pulse of 3.3 V in a nice rectangular shape. VDD is provided by batteries (3 x 4.5 V in series). Measurements were performed with a picoscope against GND. The whole setup is on a breadboard.

I expected a rectangular pulse of 200us with 13.5 V at OUTA. Instead I got the signal below.

Any help is much appreciated!

UPDATE:
I soldered the IC onto a SMD development board, glued two SMD ceramic caps (1 uF and 10 uF) on top of it and connected them to GND and VDD. It works as it should, even with the ca. 10 cm each of air wiring:

With a total gate charge of 2.2 uC I get a rise time of ca. 200 ns. Problem solved! Thanks guys.


texts: Can I operate a 120VAC contactor with a DC power supply

texts:
If yes, What would be the voltage and amperage for DC to operate the 120 VAC contactor?
And, Can I connect two contactors in parallel, and actuate both using DC ?
I need it for a project, where I can't use AC and have to work with existing 120VAC Contactors.

edit:
My project involves the use of limit switches, which is why I was using a dc power supply. And the output from the limit switches actuate the contactor that run lines to the AC motor.
Is is safe to run AC through limit switches. The limit switches would be in close proximity with the user. If yes, then I do not need any conversion. And I can run the entire circuit on AC alone.


texts:
I've connected an Arduino to a MOSFET to control a valve.

I've connected the Arduino's GND to the negative lane (word?) on the breadboard (for clarity modeled by SW1 in the circuit diagram).
I noticed that if I don't do this, it does not work (no voltage at the gate) - why do I need to use the same ground?

And: Is my circuit any good or could it be damaging my Arduino?

simulate this circuit – Schematic created using CircuitLab


texts: Questions about RF ground plane and low frequency reflections

texts:
Why do RF signals on a microstrip/stripline require a ground plane to propagate within a circuit? When studying DC and low frequency AC circuits in school, it appears that ground is a particular point from which electrons are flowing, not a plane that provides any added benefit or relevance to the signal traveling forward on the line. Furthermore, why is it that we need coaxial, parallel plate, coplanar, etc. transmission lines in the first place, if a signal can travel down a conductor at low frequency without one?
Also, one more question that has been bothering me for a while. Why do we only care about reflections at high frequencies? Wouldn't low frequency signals see power reflected at impedance mismatches too? I understand that usually this is a question of line length compared to signal wavelength, but it seems that regardless of this, power should be reflected back.


texts: PCB Protection Circuit for LiPo batteries doesn't output a voltage

texts:
I have two LiPo batteries (18650) connected to a 2s PCB protection circuit. I can read a voltage at the b+ and b-, which is about 7.03 V but there's no voltage at p+ and p-. Is there something wrong with my circuit or is my board damaged?
Here some Images of my build. Sorry for the Google photos link, I get an error if I try to attach my photos to this post.

https://photos.app.goo.gl/oVLaHCQpMJgqAEr68


texts: Help identifying IC damaged by wrong voltage

texts:
I accidentally fried an IC when switching out a power supply; sent 12V instead of 5V. I've been trying to find some information on this drive, a Corsair M500 240GB, (CT240M500SSD1) - maybe a datasheet, but I haven't found zilch.

IC below - the damage is pretty visible. Maybe it's some sort of regulator? Not sure:


texts: Whole board design scaling in EAGLE 7.5.0 (free version)?

texts:
I have designed a very simple PCB in EAGLE that should be approximately W: 10mm, L: 30mm in size. This design is repeated 18 times (I need many of them).

However, for some reason, the whole PCB is huge. I simply cannot find a feature to re-scale my whole design to the dimensions that I want. Is this available in the free-version? If so, how do I access and use it?

Any help will be much appreciated.


texts: I'm seeing some weird behavior in a circuit I just soldered up.  I haven't done detailed debugging yet, but it occurred to me that the metal case on the 2N2222A transistors I used might be connected to one of the leads.  It seems that this is often true with some of the larger metal cans, (e.g. TO-3 and TO-220), but I couldn't find anything definitive about the TO-18 package.


texts: Easiest way to generate quadrature signal on PCB

texts:
I have a chip which needs a quadrature LO. Specifications:

Frequency range: 1.7 GHz - 2.5 GHz (wider range appreciated)
Both I/Q differential (i.e. 4 wires in total)
Each wire 1Vpp
DC offset of 500mV (capable of driving 50 Ohm, i.e., 10-20mA)
Matching is 50 Ohm but not perfect (S11 > -10dB)
Jitter: hundreds of fs rms (like 400fs)
Phase accuracy: ~1 deg
If possible: Capability of fast (or even ultra fast) hopping/settling (around 10ns)
Cost: "does not matter"
Power: "does not matter"

For my current revision, I use an external signal generator which goes into a 90 Degree hybrid and enters the PCB via 2 SMA connectors (I and Q). Each of these channels go through an on-board 1:1 balun. An RF choke adds DC offset of 500mV.

However, this setup is clunky, the on-board balun (MABA-007871-CT1A40) does not even meet the specs. For my second revision, I would like to generate these signals on-board to simplify the setup.

An RFDAC (like AD9164: 16 Bit, 12 GPBS) would satisfy all requirements but getting this 165-pin BGA beast with its SERDES interface working takes me forever.

So if I relax the fast settling requirement I would assume there are solutions out there. However, I am unable to find any quadrature generators on DigiKey! (I can find I/Q Modulators or Demodulators but I need the generation).


texts:
I need to accurately measure a narrow band signal (of about 200Hz) centered in a part of spectrum that is many times its band (at about 20kHz). I have only a 12 bit ADC that is relatively fast (5 MSPS).
Can I perform something like this:

Sample & hold the signal at more than 2*B as required by the
Nyquist theorem but undersampling with respect to the center
frequency
Add some gaussian noise (dithering)
Oversample the (alias) signal and filter it in the digital domain to increase the total ADC resolution

Does it make sense?


texts: How much humidity can a microcontroller/embedded device withstand?

texts:
I'm working on a project that employs a microcontroller in an 80-85°F environment with quite a bit of humidity. It's going to be placed directly next to an array of fish tanks. Obviously, the water can damage the device if water is spilled on it but this shouldn't happen.

Would the device be ok if operating in those conditions for days at a time? I've been considering designing an enclosure with a fan(the microcontroller already has a heatsink on the CPU) but are there any other considerations such as rust that I should keep in mind? Thanks for your answers!


texts: problem solving: line level to iphone attenuator buzzing sound

texts:
I'm trying to use the mic input on my iPhone to record line level audio.
I have made a cable with an attenuator as shown in the picture below.

Recording from my macbook pro works like a charm (3,5mm headphone jack).

Recording from my DJ mixer (stereo rca), or UR22 audio interface (1/4" jack). I get a rather loud buzzing sound. audio clip

This is my first time building something like this myself, I'm probably making an obvious mistake, would be nice if someone could help me out.

Update: turns out it was due to a faulty jack, not making proper ground connection on the TRS side.

to anyone wanting to to do the same, use the schematic, it works! but switch R1 and R2 for something lighter if you dont need heavy attenuation.


texts: I'm trying to connect my antenna to my PN532 chip using an SMA connector but I'm not sure about the pinout. I'm using the following as my sample schematic and I want to use the following SMA connector to connect to an antenna. In the schematic you can see how the two load resistors connect to two pins and then a third pin connects to ground on the antenna. However, I'm not sure how this pinout correlates to the SMA connector meaning, which portions of the SMA connector are Pin1/Pin2/Gnd. Can anyone help me understand this?


texts: Difference between an Analogue multiplexer vs ADC chip with lots of channels

texts: Advantages and Disadvantages of Analogue Multiplexer vs a ADC chip. For having more analogue inputs on micro-controller. Thx


texts: Do "True RMS" meters really do RMS if the input is a high frequency signal?

texts:
I'd like to measure the average of a signal which is mostly zero (less than a few nanovolts as best as I can tell) but may have occasional nonzero "blips" of maybe 20-100 nanoseconds (maybe 1V tall).  I can catch them on a scope, but it is kind of hard to figure out how common they are and what their total area under curve is.

Would a "True RMS" meter produce meaningful input from this kind of signal? (RMS current/voltage/power, any is fine)  If yes, how does that work?


texts: Simple Square Wave Amplification Technique?

texts:
I have a square wave that is 5v peak-to-peak. I need a circuit that can amplify this square wave up to any given supply voltage between 9 and 50v. I don't need much current, nothing more than 100ma certainly, 20-50ma would work. My preference is to use components as cheap as I can get. How can I amplify this square wave for minimal component cost? Is there a way to achieve a square wave with a high peak-to peak voltage without in input pwm?

Edit:

The 0-Vsupply square wave will be fed into the following circuit:

simulate this circuit – Schematic created using CircuitLab

Vout will always float 10v above the supply, minus a few diode drops. The part I am stuck on is how to get a square wave at the supply voltage.


texts: How to add value of 5e^(-25/2t)u(t) to a voltage source in LTSpice?

texts: I want add the following value 5e^(-25/2t)u(t) as a Vin to my circuit in LTSpice. However I don't know how to do this - can someone help?


texts: Cutout a polygon from another in any layer in Eagle CAD part creation

texts:
I am trying to create a part with a bespoke pad. How do I cut one polygon (for where the hole will be) from the original pad polygon. I don't just want to make a dimension layer and let the PCB house cut through the pad, or is that the right/only way to do it? Couldn't find any ranks for the polygons nor a restrict layer that works for pads?

Any pointers are greatly appreciated.


texts: Why isn't my load cell detected by openscale?

texts:
I want to measure the pull force on a rope, so I bought myself a Sparkfun OpenScale and this tensile load cell. I just received both of them, so I connected them as described and hooked the OpenScale up to my Raspberry Pi.

I then opened the terminal on the raspi and started the load cell terminal interface using screen /dev/ttyUSB0 9600:

Serial Load Cell Converter version 1.0
By SparkFun Electronics
No remote sensor found
Minimum time between reports: 495
Press x to bring up settings
Readings:
1477,-32780.74,kg,21.75,0,

As you can see though, it says no remote sensor found.

I took out my multimeter and measured the voltage on the black and white connectors. When I connect the openscale to the Raspberry Pi it measures 5 volts for about 2 seconds and then it goes down to zero volts. This is in line with the docs on OpenScale which say that the voltage on the load cell is switched off if no load cell is found.

From this point on I'm kinda lost. Does this mean that the load cell is broken? Or does it mean I'm doing something wrong? Does anybody know what steps I could take to find out what's wrong?


texts: What could be the source of this sine wave distortion, visible as equally spaced lines in FFT?

texts:
I have an MCU controlling a 16bit DAC via SPI (and an additional LDAC output, which triggers the update of the DAC output). The MCU has a precalculated 1120Hz sine wave in a 364-byte long buffer (all calculations in float32, rounded to uint16 for DAC output), sampled at 29120Hz. In a timer interrupt, the update of the DAC is triggered via LDAC and then a new value is loaded from the buffer and sent via SPI. The update to last value is triggered in the beginning to reduce jitter due to memory access races against DMA. Interrupt has a sufficiently high priority to not be delayed.

Althrough visually the sine looks good, FFT of my Rigol DS1054Z behind the DAC (before the reconstruction filter) shows a significant distortion:

The highest peak is the required 1120Hz, others are equally spaced by 260Hz. The right peak seems to be only 5dB below the main!!

The jitter on the LDAC pin is on the order of +/- 0.25us, which I'd consider acceptable against 34.3us sample time. The timer itself runs from the MCUs crystal and should be stable enough.

What kind of a problem would lead to such a distortion pattern? What could be the ways to diagnose and reduce it?

Just in case relevant: the DAC is an AD5686, full-scale reference is 5V, sine amplitude is 25mV which results in roughly the lower 10 bits being "switched".


texts:
I need to declare a bit with the constant value of 1.

What almost worked was:

signal name: bit := '1';

but the value of "name" is always '0' in this case.

How can I do this properly?

Full code:

ENTITY sleA IS
PORT(
    signal sel: std_logic;
    A: in bit_vector (3 downto 0);
    S: out bit_vector (3 downto 0)
);
end sleA;
architecture arq_sleA of sleA is
begin
    sel <= '1';
    S(3) <= ((not sel) and A(3)) or (sel and A(2));
    S(2) <= ((not sel) and A(2)) or (sel and A(1));
    S(1) <= ((not sel) and A(1)) or (sel and A(0));
    S(0) <= ((not sel) and A(0)) or (sel and sel);
end arq_sleA;


texts:
I have looked in the data sheets, as well as the TI article, but I am still unsure of the answer to this question:

  What is the practical difference between a 7446 ("BCD to 7 segment decoder/driver with 30V open collector outputs"), a 7447 ("BCD to 7-segment decoder/driver with 15V open collector outputs"), a 7448 ("BCD to 7-segment decoder/driver with Internal Pullups"), and a 7449 ("BCD to 7-segment decoder/driver with open collector outputs").

To drive a normal 7 segment LED common-cathode display, can I use any of them? If not, what are they for?


texts: Recommend a Serial to USB cable/converter that works with modern OSes

texts:
I'm hacking on a board that has an RS232 interface (via a Max232 chip).  My new computer doesn't have a serial port, which leaves me using USB.  I actually have a Serial to USB cord already, but it doesn't appear to work on any modern OS that I run (Windows 7, Linux).  I'm not 100% positive, but I think it's this one:

http://www.amazon.com/Cables-Go-26886-Serial-Adapter/dp/B000067RVJ/ref=cm_cr_pr_product_top

I still have the driver CD too, which worked fine in XP, but Win7 wants nothing to do with it.

So, can anyone recommend a serial to USB cord/converter that they know works?

Thanks!


texts: TVS diodes configuration for AC differential signal

texts:
I would like to protect an ADC from ESD and Overvoltage by placing TVS diodes. After a bit of reading, configuration B seem to be the way to go for a differential AC signal. But I'm not competent enough to choose the diodes for this and having 6 of them does not help space/cost wise. So I went ahead and looked for an already-packaged IC, but most configurations of the ready-made ICs are configuration C. Such as TPD2E1B06 for 5V AC differential signal and TPDE007 for 12V AC differential signal; which is perfect for my applications.
Also the series resistor also plays an important role, as I have read that it also reduces the current stress these diodes will receive. At the same time I am using them to step down the voltage signal so I can read the 5V and 12V needed in my application. I would also like to know what would the best placement be in A or D or both but with half resistance.


texts: Clamping Constant Current LED Driver Output Voltage

texts:
I want to test a Constant Current LED Driver across its voltage range without using a LED for test purpose.

How can I clamp the output voltage of this driver to required voltage levels?
For Example -
LED Driver Ratings - 800mA Constant Current Voltage Range - 17V to 34V.
Now how do I test this driver at 17V, 18V etc to make sure this driver works under different voltages.

I also tried to clamp the voltage using an Op-amp but in vain. I am not sure if output voltage is stiff enough to clamp LED driver output voltage. Also, current is getting drawn from the output of Opamp whereas opamp is primarily used to just clamp the voltage.

Any thoughts on how this can be achieved?


texts: Storing short, small, intermittent pulses of energy

texts:
I am running an experiment using graphene at the moment to create energy from different chemical solutions. A link to what I am building on is below:

https://phys.org/news/2014-04-team-electricity-saltwater-graphene.html

Amazingly, this does actually work; it is possible to get intermittent pulses of voltage anywhere from 40mV to about 100mV with a period of a few tens of ms when a drop of solution is dropped onto a small sheet of graphene. The reason I say intermittent is that I am dropping the drops of solution intermittently onto the graphene itself, which would be analogous to a real world situation.

However, I am struggling to harness this voltage/energy.

I have tried to put different capacitors in series with the graphene sheet, such that the voltage pulses could be stored in this. However, I think what happens in this case is that as soon as a voltage pulse (presumably) goes into the capacitor, it is just leaked away completely back into the graphene sheet, which is effectively just a resistor when not generating small pulses.

The fact that the pulses are so small means that I can't use a diode. And I don't want to use a transistor switch if I can get away with it, because having to apply an external voltage to this circuit defeats the point of what I am trying to do.

Any comments much appreciated!

Thanks,
Jon


texts: How to use PIC16F84A TMR0 Interrupt as a substitute to the Sleep instruction in Assembly

texts:
I have this circuit:
So my problem is that I'm having trouble using the TMR0 interrupt as a delay or substitute to the SLEEP instruction in the PIC16F84A. I can't quite get the concept of using the overflows to generate a timeout.
What I have in mind is that, I have to put the overflow counter loop inside the TMR0 subroutine, and then loop until it reaches the number of overflows required to generate a 1s timeout. Is this correct? If so, how could I implement it in my code?
Side Question:
How can I initialize variables in PIC assembly? What is the equivalent of
LABEL DB 00H

in PIC assembly?
Here is my code so far:
LIST P=16F84A, F=INHX8M          ; MCU is PIC16F84A, output is Intel Hex
INCLUDE<P16F84A.INC>             ; include this file to use register names instead of addresses
__CONFIG _CP_OFF & _WDT_ON & _XT_OSC ; code protection off, Watchdog Tiemr on, XTAL osc used

 ORG 000H
 GOTO MAIN
 ORG 004H               ; interrupt vector
 GOTO INT_RTN           ; jump to label INT_RTN or the interrupt service routine

 **MAIN**
 ; initialize PIC
 BSF STATUS, RP0            ; set register bank to 1
 CLRF TRISA                 ; clear register TRISA (bank 1)
                            ; sets all bits in PORTA as "output"

 MOVLW 0FFH                 ; load literal value 01H to Wreg
 MOVWF TRISB                ; move data in Wreg to register TRISB (bank 1)
                            ; set ports in PORTB as "input"

 MOVLW 004H                 ; load literal value 04H to Wreg
                            ; prescaler 1:32 assigned to Watchdog Timer (WDT)
 MOVWF OPTION_REG           ; move data in Wreg to register OPTION_REG (bank 0/1)

 BSF OPTION_REG, 6          ; interrupt event during rising edge
 BCF INTCON, INTF           ; clear the RB0/INT interrupt flag
 BSF INTCON, INTE           ; unmask (enable) RB0/INT interrupt source
 BSF INTCON, GIE            ; enable all unmasked interrupt
 BCF INTCON, T0IF           ; clears the TMR0 overflow interrupt flag
 BSF INTCON, T0IE           ; unmasked (enable) TMR0 overflow interrupt
 BCF STATUS, RP0            ; set register bank to 0

 CLRF PORTA
 CLRF PORTB
 CLRF TMR0
 GOTO START
 ; program start

 **INT_RTN**
 BCF INTCON, GIE             ; disables all unmasked interrupt (no interrupt overriding)
 BTFSC INTCON, INTF          ; check the RB0/INT flag
 GOTO RB0_INT                ; jump to label RB0_INT (routine for RB0_INT)
 BTFSC INTCON, T0IF          ; check the TMR0 interrupt flag
 GOTO TMR0_INT               ; jump to label TMR0_INT (routine for TMR0 interrupt)
 GOTO EXIT                   ; exit INT_RTN

                             ; hardware interrupt
 **RB0_INT**
 BCF INTCON, INTF            ; reset RB0/INT flag
 ;code for RB0
 GOTO EXIT

                             ; TMR0 Interrupt
 **TMR0_INT**
 BCF INTCON, T0IF
 ;code for TMR

 **EXIT**
 BSF INTCON, GIE               ; enable all unmasked interrupt
 BCF INTCON, INTF
 RETFIE                    ; return from interrupt routine

 **START**
 CLRF TMR0
 MOVLW 09H                 ; load literal value 09H to Wreg
 MOVWF PORTA

 **COUNTDOWN**  //Countdown timer from 9-0
 MOVF TMR0, W
 BTFSS STATUS, Z
 DECFSZ PORTA, 1                 ; decrement register COUNT, skip next line if result is 0
 GOTO COUNTDOWN                  ; jump to label INC
 GOTO START                      ; jump to label START

;====================================================================
END


texts: VDD Error with 18F24J10 after turning off XINST

texts:
I am using a PICKit2, pk2cmd, and SDCC to program a PIC18F24J10. In the course of troubleshooting some problems I was having with my code, I upgraded to SDCC 3.4.0. Compiling with the latest version gave me a warning,
"The code generated by SDCC does probably not work when XINST is enabled (possibly by default)."
So, I've gone ahead and disabled it via

    #pragma config XINST=OFF

And now it doesn't program with pk2cmd, giving me the following error:

    Program Memory Errors

    Address    Good      Bad
    003FFE     00FFFF    00F000
    VDD Error detected. Check target for proper connectivity.

Without the XINST=OFF line, it programs successfully. I can swap back and forth between having no change with Success and having XINST=OFF with Failure.


texts: In three phase symmetrical fault motors(Induction and Synchronous) become generators(I guess because of the inertia). When do I take in consideration of the motors? Do I even need take them in consideration assuming there are big motors that have impact on the short circuit current or because it has short time impact I do not need to take them in the calculation?


texts: Which wireless communication solution is right for my needs?

texts:
The design involves a single base station that communicates with multiple peripheral units. Peripheral units should be able to communicate back to the base station but are not required to communicate between them.

It would be best if some mechanism exists so that when a peripheral unit tries to send data to the base station while another is sending data it will get into a queue.

The amount of data is not great and not continues, more like bursts of 50 bytes or so once in a few minutes / hours.

The system should be low cost as possible with ranges up to 100m in open space under ideal conditions.

If I could pick a close example from wired bus world I guess it would be I2C where each peripheral has an address.

Thanks!


texts: What happens when you connect hot and cold sides of Peltier device together?

texts:
I would like to know how the Peltier device would act if you heat sink the hot side WITH the cold side. Would it just sit there and consume power?

I need something to consume ~15 watts or more at 14V. Was thinking of other possibilities than a power resistor.


texts: What is the most power hungry component of a air conditioner?

texts: Im taking about those old school air conditioners, which draw around 1200 watts from the wall.


texts:
I read in the book "Serial Port complete, 2nd edition" that the clock of the UART should be 16 times the baud rate, but I have never seen any microcontroller in which we set the frequency of the UART before configuring it for a specific baud rate. So:

1) Why should the frequency be 16 times the baud rate?

2) Can you give me an example of any microcontroller where we set the UART frequency?

3) What is the purpose of setting the clock frequency of the UART if we have timers? Like we generate the baud rate in a simple 89c52 through Timer 1 and we don't set any frequency.

4) What's the idea of setting the baud rate with a timer like we do in 89c5x. How it is linked to the UART frequency?

5) RS-232 is "recommended standard 232" and a UART is physical. Hardware does parallel-serial and serial-parallel conversions. Am I right?

6) Does the UART contain a counter, so that after the start bit it waits for 8 cycles and then after each 16 cycles, the samples are taken from RX line to detect the bit?


texts: VHDL: What does STD_INPUT and STD_OUTPUT appearing in std.textio mean?

texts:
The package contains the following lines:

file INPUT: TEXT is in “STD_INPUT”;
file OUTPUT: TEXT is out “STD_OUTPUT”;

For some reason these remind me of the standard input and output streams from my C language lessons. What do these mean here? Is it really possible to read/write the standard input/output stream by using this package? How?


texts: State Table & Karnaugh-map for Finite State Machine

texts:
I am trying to create a Finite State Machine that is able to check if a number string is valid. For example, it would accept 3, 4.65 or 8.93e-10. So far I have created a transition table for the machine as follows:

This is the state diagram of the machine:

I am having trouble understanding on how to create the state table that I can then use to create the Karnaugh-map for this machine. I understand that I would have to convert the state and transition values into their binary equivalent and then list the inputs and outputs for each state.

I would appreciate if someone could guide me in the process of creating a state table that can then be used to create a Karnaugh-map.


texts: Connector for a certain type of lead-acid battery

texts:
I need to connect some lead-acid batteries together, to form a bank. A fair amount of current will be drawn from them.

However, I haven't seen the terminals used in those batteries before. What should I use to form a solid connection between them?

Thanks.


texts: Why is a relay controlling a roller shutter constantly at ~50°C?

texts:
I have several Shelly 2.5 controllers for my roller shutters. They work great but I noticed that the temperature they report is stable around 50°C.
When reading relevant forums, it seems that nobody is particularly worried about that temperature. I got to wonder where that temperature can come from.
They are only used twice a day for 30 seconds and otherwise stay idle, so no coil current. They do have a WiFi connection that is always up, so this may be the reason. But 50°C seems quite a lot, compared to a phone for instance.
Is there a general reason for such devices to be that hot?


texts: Charge sensitive amplifier operation doubt: Same BNC for two purposes. How?

texts:
I opened a charge sensitive amplifier (CSA) board which is used in radiation detection.

I am trying to figure out how it works.

It is totally confusing me that one BNC is used for two signals. How is it possible?

The operating voltage of the CSA is -20V, and the output of the CSA is square pulses. One BNC (left side in the pic) is used to supply -20v and to take CSA output (square pulses.)

How is it possible?

Similarly, on the right side, just one BNC is used to supply high voltage to the detector and to take the output of the detector (charge pulses- which then go to CSA.)  Again one BNC for two purposes.

How does it work? Any suggestions?


texts:
I need to plot Smith chart, having frequency, VSWR, reflection coefficient and phase. I'm aware there's smithchart command in matlab and as an argument I should use reflection coefficient, but my chart looks not as it should (below the chart you can see my rho values):

As far as I know, as an output I should get something similiar to this:

So my question is: is there any program that will help me with this task, using values that I mentioned in the first line? So far I've found something called Smith, but it would be rather tiresome to manually add dozens of points. Still, if it's the easiest way to plot Smith chart, I'll go with it.


texts:
I am looking for a small tactile switch that works like:

press once -> turn on, press again -> turn off

I only found this model http://www.adafruit.com/products/1683 , but i am looking to buy directly from manufacturer/reference in mouser or digikey if possible, for a small production batch

do you know how can i find this?


texts: How is Frequency related to Kinetic Energy?

texts:
Does producing higher frequency waves require more energy than their low frequency counterparts with same amplitudes? For example, in electronics,  would a 500 kHz wave require higher voltage to produce in comparison to a 50 Hz wave at the same amplitude?

This is to assume in both cases that the material is free from resonant properties, and is not oscillating at its natural frequency. Also assuming the material is capable of producing both of the frequencies in question equally well.

Examples using waves in air, or models using pendulum systems are welcome. if my question is too vague, please let me know, I'll try be more specific. I am looking for a general theory.


texts: How can I boost 1 Volts 30 Ampere input to 5V with maximum Current limit of 5A?

texts: How can I boost 1 Volt 30 Ampere DC input to 5V DC with a maximum Current limit of 5A?


texts: To Fail-Safe or not Fail-Safe on RS485/422 Transceiver

texts:
I'm stuck on a PCB design issue.

I'm designing a new PCB (Daughter board) that will plug (via DB15-F to DB15-M) onto another PCB (existing Mother board) and the design intent is to take (from the Mother board) the existing differential Step/Dir signals and reconstruct them into single-ended TTL Step/Dir signals on the new Daughter board.  After reading the datasheet (several times) for the MAX3095 (pg 11 Fail-Safe Implementation) my interpolation is that with the existing (which I cannot change) PCB using the MAX13443 driver circuit (with the diff lines biased to 2.5V) then the MAX3095 receiver output (Y1/Y2) will/may be undefined during boot-up.  I was not planning on terminating the MAX 3095 receiver's diff input's because the total conductor lengths involved are like 1 inch board-to-board and low baud 250kbps. I was hoping to let the built-in Fail-Safe utility (on the MAX3095) keep the receiver's outputs in a defined state during uProcessor boot-up, high Z state or open.  But now I am 2nd guessing myself.

Because the mother board diff signals are bias equally (when not driven) should I add the external discrete termination/Fail-Safe circuit (instead of relying on the built-in FS utility) on the MAX3095?

If the attached image is un-readable I will do a crash course (schematic tool) on the EESE site.

Thanks.

edit: I just noticed an artifact (or rushing my efforts) from my copy/paste and the diff pairs going to the MAX3095 are NOT RS422 but just TTL/CMOS born diff signals.


texts: Decoupling power supplies, how much should one worry about high frequency noise?

texts:
When using a potentially noisy power supply, how much should you worry about noise above the frequency bands you are interested in?

For example, if I have an instrument amp with a bandwidth of 1kHz, should I be worried about 1MHz noise?

Put another way: is it common for 1MHz noise to downconvert into noise in my frequency band, or is 1MHz noise going to pretty much stay at 1MHz?


texts: Can't write more than one byte to the SST39SF010A Flash!

texts:
I use code composer to program the TMS320C31 DSP (through MPSD) to write to the SST39SF010A flash. I can successfully write one byte to any location of the flash by following the "Chip Erase" then "Byte-Program Algorithm" sequences mentioned in the datasheet.

The problem is when I want to write more than one byte in different locations, only the first byte is written and the rest aren't. I added delays between writes but no difference.

What is the cause of this problem? I searched for drivers (Programming algorithms) for this flash but couldn't find!

Update: 21/7/2013

First:

This is the code we wrote to program the flash:

void main()  {

volatile unsigned int * start_flash = (volatile unsigned int *)0x00001000;
      volatile unsigned int * end_flash = (volatile unsigned int *)0x0001ffff;

      volatile unsigned char * flash_addr1 = (volatile unsigned char *)0x005555;
      volatile unsigned char * flash_addr2 = (volatile unsigned char *)0x002aaa;
      volatile unsigned char * flash_addr3 = (volatile unsigned char *)0x005555;
      volatile unsigned char * flash_addr4 = (volatile unsigned char *)0x010000;

      volatile unsigned int x = 0;

          // Chip Erase

        * flash_addr1 = 0xaa;
        * flash_addr2 = 0x55;
        * flash_addr1 = 0x80;
        * flash_addr1 = 0xaa;
        * flash_addr2 = 0x55;
        * flash_addr1 = 0x10;

        // Delay
        for(x=0;x<=100000;x++);

        // Byte Program

        * flash_addr1 = 0xaa;
        * flash_addr2 = 0x55;
        * flash_addr3 = 0xa0;

        // Data in the first address

        * (start_flash) = 0xba;

        for(x=0;x<=100000;x++);

       // Data in the following address

        * (start_flash+1) = 0xab;

        while(1);
  }

"BA" is written correctly in the first address but "AB" isn't.

Second:

We are using an FPGA in the system between the DSP and the Flash (and all other system peripherals). Data and Address of DSP is bypassed through the FPGA to the Flash, and control signals are generated from the FPGA. I think there is no problem in generating the control signals since we are able to write one byte successfully, is that correct?


texts: Is Epoxy Adhesive Glue (specifically Araldite) a good insulator

texts:
I snapped off a piece of insulating plastic (on a car stater motor) and want to glue it back on with some Epoxy Adhesive Glue (specifically Aradlite) glue, could someone tell me if this is a good electrical insulator or not?

http://www.screwfix.com/p/araldite-2-part-epoxy-adhesive-tubes-opaque-2-x-15ml/2457h

http://www.my-sds.co.uk/Admin/ViewDocument.aspx?ID=9c3084d6-ab98-4f61-bc32-8ab675547ecb&primaryReportId=0


texts: Calculate the finger position on a Capacitive touch slider

texts:
When building a Capacitive touch slider like the picture shows, I know when finger tip touches the metal slider it would create a apparent sensor capacitance is increased by the introduction of a parallel path
to earth through human body.
But how could the exact position of the finger tip on the plate be calculated?


texts:
I have tried implementing a design involving AT90usb646 about four times but in each case the board gets connected and immediately disconnects . lsusb outputs that an Atmel Corp device has been connected so I know that the board is working but it gets disconnected before I can do anything with it . I usually fabricate it with Oshpark and have had no troubles whatsoever but this time I tried etching the PCB at home since this is a hobby project and I wanted to try out things rather quickly . The boards are two layered and I followed every guideline for laying out the USB portion namely keeping the tracks small and components close , calculating the trace width with impedance calculators , not breaking the ground pour underneath the usb data lines and keeping the VBUS and Ground pour away from the usb data lines to prevent noise. This is the image
[![enter image description here][1]][1]  The data sheet from Microchip for AT90USB646 suggests a couple of caps for VBUS and UCAP and I have placed them accordingly . I have rechecked everything and also cross-checked with Teensy ++ which uses AT90USB1286 which is similar to AT90USB646 but can't figure out what it is I'm doing wrong.
Here's the schematic

[1]: https://i.stack.imgur.com/d0bJe.png


texts:
A voltage source is a device that produces constant voltage, but allows amperage and power to vary, in accordance with the laws of electricity. A current source is a device that produces constant current, allowing voltage and power to vary.

Is there a constant power source – i.e., a device whose output power never varies? No matter the nature of what it is connected to, its voltage and amperage would be adjusted to provide constant power. (Its behavior would be undefined for both open and broken circuits.)


texts:
Does voltage drop with discharge? Since voltage is the potentiality between two charges to re-balance (from my understanding).

I mean, once all charges are equally shared between both capacitor sides, there is no potentiality between the charges to re-balance since they are now balanced.

Can we tell that voltage drops when a capacitor discharges?
If yes, does this mean that my 9V lithium battery
loses voltage while being used?
That would also mean that a LED would lose brightness over time, is that the case?


texts:
I am designing a DAQ software, which looses some information during read out. There fore I thought of testing another CAMAC ADC and in particular the Lecroy 3351. Surprisingly I saw that it doesn't have lemo conncectors but ECL.

I found some ecl to lemo connectors like the following

but I feel that it's not practical. Is there another way around this? In addition is it possible to make a home made connector? It the manual it is stated that the left input pin is the signal and the right is the ground. I feel that if I connect the core of the coaxial cable to the positive pin and the shielding to the ground I would be OK. Is this right or I have to reconsider?


texts: Why is there a negative value on the scada when the analog input wire is disconnected from a field instrument?

texts:
I'm an apprentice electrician at an fmcg company.

I've been seeing a trend recently,  at the plant, where the scada actually reads a negative value instead of zero when a field device such as a current transducer or RTD fails, ie the feedback wire going back to the plc analog input card is discontinuous.

Should this value not be zero?

Moreover, a Flowmeter eprom was recently damaged due to an unexpected current surge so the Flowmeter reads 0g/h even when there's flow going through. This value was - 500g/h (negative 500) on the scada...
 I mean,  if the Flowmeter or any other instrument isn't sending any electrical signals back to the plc, why does it not read a zero value?


texts: Finding the Thevenin equivalent resistance in given circuit

texts:
I tried finding the equivalent resistance (between the nodes A&B) for the given circuit, however I can't seem to get it right:

simulate this circuit – Schematic created using CircuitLab

The equivalent voltage is 0, that I was able to calculate, but the answer for resistance is Rt = 16, which I'm not sure how to find.


texts: Solar Panel + Controller + Diode to float LiPos

texts:
I have a few solar panels I wanted to play around with and charge some 18650s till I get a little more comfortable that I won’t blow something up.  My main goal is to understand how to charge batteries, use solar panels, diodes, and learn more about electronics on this side.

The plan is to take come 5v solar panels in parallel, then run them to my little voltage regulator, and from there a diode is run off the + side to a 18650  and the - is bare. I will set the regulator to have a continuous output of ~4.1v so I don't blow anything up or charge too fast.

This brings me to asking things I don't understand, can’t really google, and think I know but I just am not brave enough assume.

1) Battery
a 18650 generally has a low end of 3.6V and a high end of 4.3V.  Outside of that will damage it/catastrophe.

Question - If I set a controller to feed 4.1V from a solar panel continuously, could I damage a battery or cause it to go over 4.2V?  When I think of voltage, I think of it more like the width of a river.  If you keep feeding something 4.2V 100ma, won’t the item go over 4.2V eventually?  It would just take longer to “charge” given the lower voltage? (like a 2mm straw to fill a glass vs a 4mm one?)

2) Diode
I get that a Diode controls the flow making it go only 1 way, so if I use one on the + side then the power cant back feed, but do I need one for the – side?

I can see this being a waste of a diode and you would need to invert the direction to make it useful at all, but I feel like leaving it open like that is bad mojo?  Someone please tell me it would 100% be a waste to use one on both + and – to prevent back feed drain?

3) Theoretical Question
If you had a 12v battery and a 12v solar panel in parallel leading to a motor or device of some sort, and used a diode on the + side of the solar panel (preventing back feed and forcing a charge only situation, would this cause any catastrophes?    In my head, it would work so that when the motor ran, it would draw from the battery and the solar panel.  If the motor were cut, the panel would charge the battery.  Is this how it would work?  I feel like I am 100% wrong and this would cause a short or something having a panel in parallel with a battery.

note None of my batteries have a Protection Circuit, which is why I feel so scared of trial and error with this kind of stuff.

If anyone has any related info to topics I asked about, Please post it, I find it difficult to google anything related to charging/batteries/solar panels on google unless it is raw statistics. Real life applications, experience, and lessons learned are really hard to find.


texts:
I recently acquired a toy that uses this transformer:

but since I live in a 220V area, I cannot use it directly.

I have this generic AC-DC adapter:

which in theory is all I need because it has a 4.5V output and enough amperage.

However, I'm a bit concerned since when measuring the voltage of the ac-dc adapter when it's set to 4.5V output, I get ~10.5V. I know that the voltage measured in a no-load scenario is supposed to be higher than when it actually has load, but it seems a little bit too much.

When set to 9V, it outputs ~16.6V

Is it safe to use this ac-dc adapter with this toy? Or it might be broken and supply more volts than it indicates?


texts: How do I identify Pin 1 on a chip with no corner mark

texts:
I am trying to identify Pin 1 of MAX3222E, the TSSOP variant (See Page 16 of datasheet), but it doesn't have any corner mark!

Could someone suggest how to identify Pin 1 in this type of situation?

I don't have a high-res camera on me right now, but I do have the chip in front of me, so here's a drawing of everything I see on top (the + sign is just part of the full name MAX3222EEUP+):


texts:
I am putting a late model engine into an older model car and need some help regarding the vehicle speed signal.

The car produces a 12v 50% PWM signal for the speedometer and transmission. The engine management system for the new engine requires the speed signal to be 5v 50% PWM.

Rather than fork out $200 for a brand name signal converter box, I would like to find a simple alternative I can put together myself. I believe using 2 resistors to make a voltage divider would work, but I'm worried that it may have a negative effect on the existing signal.
Can someone please help me out with an easy circuit that won't be taxing on the existing signal?

I'm a mechanic, so my knowledge of creating this type of stuff is minimal. Any help (preferably with a diagram) would be much appreciated.


texts: Produce a clock out (5 MHz) with a counter and a clock in (50 MHz)

texts:
I'm trying to solve previous years' tests in logic design and there's this question that I can't really solve..

So, it gives me an 8-bit counter and a clock in (clk_in) of 50 MHz and it asks to produce a clock out (clk_out) of a 5 MHz. How do we do that?

It also says that it has a clear button, when the clear is equal to one it clears and when it is equal to zero it counts.

Any ideas? (It asks us to design the circuit.)

Thanks in advance!


texts: Should I use a current limiter on a battery powered system

texts:
I'm designing a small battery powered system, actually I'm battery powering a module which already has all the switching regulators it needs.  This provides me with a wide input range of 5-10V.   I was thinking of connecting the batteries directly to the module instead of using a regulator because I don't want to pay an efficiency penalty, especially in low power mode.   I was worried about inrush current though when the batteries are first turned on.  I know the internal resistance of the batteries should limit it some but should I add some kind of current limiting or soft-start circuit to protect the batteries from damage or overheating?

That'd be easy to do with a regulator, not sure what I'd use without one.  Maybe a high side switch with some time based control.  Should I even be concerned about this?  Target batteries are LiOn that won't be recharged in the device itself.


texts: Schematic diagram of a double-balanced Gilbert cell mixer

texts:
For the following gilbert cell circuit, I have few questions.

I understand that R1 to R4 as well as M1 to M6 are parts of the double-balanced differential topology which helps to eliminate the DC component in RF and LO incoming signals, such that there would not be RF and LO feedthrough in the mixer output.

1) What is the purpose of the small-signal current source io ?

2) What are the purposes of M7, M8, R5 and R6 ?


texts:
I'm working on the next revision of a prototype PCB board,
and from the first one I learned that LEDs would be very
helpful instead of having to probe each pin/wire for a
certain state.

In this regard I have a design question; how would you add
LEDs for debugging purposes to a PCB, such that they don't
interfere with or alter the voltages and currents, and still
keep the added components to a bare minimum.

As of right now my thought is placing a MOSFET gate on the
wires in question, and then let that control the LED. But I'd
like to know how you would do it, as I am no expert in electronics
and always looking to learn from more experienced people.

UPDATES:

· The signals being debugged are, of course, digital in nature.

· The LED's in question are going to be SMD, of course.

· If you have schematic examples that makes it so much easier to understand :D

— Thanks in advance :)


texts:
Our team now evaluate laser diodes for making LIDAR
At first, we bought SPL UL90_A T08 from digikey
and used lmg1025-q1evm (Ti) board to drive the LD.
We drive Forward direction with 11V (As Datasheet of LD says that)
You can see image below link
schematic

View

Considering that laser diodes also operate similarly to diodes, supplying current to the anode should be able to measure voltage on the cathode side as well.
But as you see upper Figure, cathode of the LD is not showing any voltage when FET is off-state.
It is like a opened-circuit.
Is it the right working situation ?
Edit)
DATASHEET : https://dammedia.osram.info/media/resource/hires/osram-dam-6120373/SPL%20UL90AT08_EN.pdf
FET DRIVER BOARD User Guide : https://www.ti.com/lit/pdf/sluuc20
As shown in the graph on page 15 of Ti's User Guide, when measuring the cathode side with a probe, the signal should move.
Not at all


texts: How to understand the perfomance counter statistics

texts:
Q1. why is it is printing the different stats for the same file.
Q2. According to this
httpss://www.systutorials.com/docs/linux/man/1-perf-stat/ it should print as task clock ticks[the first stat in the output].But for me it is printing as task clock.Are they both same??


texts: Arm mode and Thumb mode makes the PC's bit 0

texts: The ARM and Thumb modes are word-aligned and halfword-aligned. I understand this means that if it's in ARM mode, the start of addresses must be divisible by 32, and if it's in Thumb mode it has to be divisible by 16. But how does this relate to the PC's bit 0 never used for anything? (The instructor said that because of that they used PC's bit 0 to show whether it's in thumb or ARM mode since it wasn't being used for anything else, but before that I'm confused about the relation between alignment and PC's bit 0)


texts:
I have a circuit where I would like to replace standard 10A glass fuses with some resettable solution.
I have looked into polyfuses:
https://lcsc.com/products/PTC-Resettable-Fuses_11042.html?q=poly%20fuse
It seems they don't produce these for larger amperages. Any suggestions?
In size it needs to be around the same as the glass fuse or smaller.
Are these safe btw on the long run? Because let's say I have the device on a remote location if something gets shorted which plugged into it that should remain turned off. As I understand these polyfuses reset themselves I don't see that too safe as if it keeps turning back the device off which had the fault that might leads to fire and other issues.


texts: How to build a blinking 12V indicator LED light

texts:
I attempt to build a blinking circuit using 12V truck light ( like this one: http://www.princessauto.com/pal/en/Tail-Lights/4-in-LED-Stop-Turn-Tail-Light/8126047.p). I have try to build a single LED blinking circuit and doubt that the same circuit would work with this 12V (24-LEDS) indicator light. I'm seeking advices/directions on how to build this circuit. It would be grateful if someone can give me a working circuit for it.
Thank you


texts: Battery isolator reminder for classic car

texts:
I would like to add a small buzzer or led light to the dash of my old MGA which activates only when:

a) the ignition is off

AND

b) the battery switch is on. (i.e., I have forgotten to shut off the battery cut off switch.
This is to remind me to use the cutoff switch-as a safety feature and to prevent battery drain.)

Behind the key switch, I can obviously see if the ignition is off and elsewhere I can see if the cars electrics still have a voltage. I assume some sort of relay would help do this, but unfortunately I have no clue.

Really hope someone can help.

PS I would order any parts in Europe, either eBay or conrad.com or reichelt.de.


texts: Circuit for a coarse and fine setting potentiometer?

texts:
I've tried to find a circuit for a coarse and fine adjustment (two potentiometers) voltage divider, but I don't understand it and/or they don't have a linear response.

Problem: I want to have an adjustable voltage from 0 - 5V using two potentiometers, one for coarse adjustment and the other for fine (10mV if possible) adjustment.

From the datasheets I've looked at (e.g. this) they don't seem to specify the resolution of increments possible of the pot.

Here are three circuits I currently have:

The third circuit's fine adjustment decreases as the coarse adjustment is set higher, so I don't think this is a good idea (unless a logarithm pot is used... no idea how those work yet).

Since the first and second are very similar, I'll consider the first one.

I assumed a 5 degree resolution out of 300 degrees, since I could not find any information regarding this.

This gives me:

0.83kOhm / adjustment with the 50K pot, and a 166mV resolution
0.167kOhm / adjustment with the 10K pot

The equation I obtain is:

$$
 V_{out} = \frac{R_{course} + R_{fine}}{50 + R_{fine}} V_{in}
$$

Plotting this in matlab for 0V course adjustment, I get the following curve:

At the lower end of the pot, there is a resolution of 33mV and at the higher end of the pot there is a resolution of 24.7mV.

For my application, this is adequate. However I'm unsure if there is a better (and linear) approach to a fine and course adjustment.


texts:
Will appreciate if someone enlighten me. I tried searching online but I am still confused.

Considering I have an hour of power - 25380 kW. How do I convert it to kWh (energy)?

I am not sure if I should use kWh = 25380 * 1hr or kWh = 25380 * 24hr

Thanks!


texts:
In Keil IDE Software there are two ways to erase chip before program it.

What does do "Erase Sectors" mode?
When to use "Erase sectors" mode and when to use "Erase Full Chip" Mode?


texts:
I've been looking for ideas on how to launch a ping pong ball a small distance (< 1 metre) for a game. Solenoids look like they might be useful but I'm not 100% on what force/type I need. I can mount it under a base and have the balls roll over it, with a pin pushing the ball up a ramp to it's target.

As it's only a ping pong ball, it should be light. I was considering something like this:
http://www.adafruit.com/product/412

Am I along the right lines? Or should I go back to the drawing board.


texts: Embedded System for a image processing task

texts:
I initially posted this on SuperUser, but I suspect, this might be a better place to post this (sorry for the double post!): I'm quite a beginner to embedded systems, but am eager to learn more. I've used an Arduino previously and quite recently purchased a Raspberry Pi (but not used it as much). I have numerous questions that I haven't found answers to when using Google, thus the post! I'd appreciate any insight (apologies in advance if my questions seem too naive!).

Recently, I've been working on some image processing code using a few image processing libraries. My code is written using C++ in Visual Studio on Windows XP. My program uses multi-threading capabilities at various stages primarily because some of the processing tasks are quite time consuming. My intention is to transfer this working code and install the back-end libraries (OpenCV, Boost etc.) onto an embedded system that is merely connected to a camera.

From my search, it seems that the top of the line, embedded system are at a maximum of 500 Mhz (http://microcontrollershop.com/product_info.php?products_id=3790). This really surprises me, we have i7 Quadcore PCs running at 2.5 Ghz available quite commonly for Laptops/Desktops. Why haven't embedded systems caught up to this increase then? Also they maximum memory I've seen is 500 MB. Again, desktop PCs average at-least 4 to 8 GB commonly. Do we get dual/quad-core embedded systems? What is the top of the line system currently available?
To allow for an initial easy transition, I've heard that XP Embedded or Windows Embedded 7 Standard (embedded variant of Win 7) are alternatives. Here is a difference chart. However, I've read at a few places that Windows Embedded 7 has more RAM support and thus I am inclined to it for that reason alone. Can someone add to this please? I know I could use Linux Embedded or VxWorks as well, but at this point I believe I would run into numerous OS related issues with my code if I continued and perhaps the libraries might not be supported ...
I've come across PC-104 systems a few times in my searches. Reading about this, it seems to be standard. Are there better alternatives? I'm a little confused with the top-of-the-line ARM processors I've found since I don't think they satisfy the minimum hardware requirements to run the OS (1 GHz x86 or amd64 processor).
My main reason to transition to this is to learn something cool in the process and have a dedicated solution that is headless and designed to perform just one specific task (hopefully in a real-time manner).


texts: Filter design for piezoelectric transducer

texts:
I'd like to use a piezoelectric transducer at one of its resonant frequency (4500 Hz). In order to get a clearer signal, I would like to use a band-pass filter.

First of all I calculated the impedance of the piezoelectric transducer. To achieve that, I put a variable resistor at the output of the transducer:

simulate this circuit – Schematic created using CircuitLab

Then I generated an audio signal with a frequency of 4500 Hz, and measured for two different values of Ri the amplitude of the voltage V across the variable resistance.

For both values, I used the formulaRi/(Ri+Z)=V/V1, which allowed me to calculate Z (I found 12 kOhms). Is the method correct?

Now my problem is: I'd like to apply a band-pass filter, with a centre frequency of 4500 Hz, and a band-width of a few hundreds Hz. But according to the formulas I've found for RLC band-pass filters, it seems that I will need an inductance definitely too big to reach such a BW. What would be the best way to implement the band pass filter, preferably with passive components? Thanks!


texts: Can I power a 5V USB hub using 5.33V DC or should I use 7V with a 7805 voltage regulator?

texts:
I'm basically loading up enough batteries to run a USB hub and a webcam. The USB hub is rated at 5 volts. Right now I've connected 8 batteries (these batteries, if relevant)
in series and in parallel to output 5.3 volts. Will the extra .3 volts cause problems for the USB hub? The 7805 voltage regulator requires a minimum of 7 volts to output a steady 5 volts, so I was wondering if I should increase the battery voltage and do it that way? (I've been trying to avoid this because I figured there would be significant power loss, is that so?)

The application is a little 6 volt car/robot with a webcam/raspberry pi/wifi USB.

I realize that the hub will probably draw more amperage than my 8 batteries can currently support, so I plan on stacking more batteries if necessary.

Also, I'm thinking of powering the USB hub/raspberry pi by separate battery packs. Is there any reason to connect the grounds to each other since they are on separate circuits?


texts: What kind of "locking" barrel connector is this?

texts:
I am looking for a replacement for a barrel connector; this is a locking connector (PN: PWRS-14000-260R for a Motorola FX9500 RFID Reader Country of origin: CHINA) however the locking 'fins' (for lack of a better description) are located on the sleeve instead of more commonly (?) nubs on the plastic tip

Even knowing the plug specifics (2.1mm x 5.5mm inline plug (Female)) and providing measurements of these 'fins'(are about .5mm tall x 2.7mm wide and stick out of the barrel sleeve about 7.5mm from the end of the plastic tip) and contacting Digi-Key and Condor Electronics with pictures, I am unable to find anything on this plug type.

I am beginning to think that this is a proprietary plug made specifically for Motorola by LEI and Motorola is NOT good about providing vendor info (I'm finding out).

Any ideas on what this particular connector is referred to as and if they can be found anywhere commercially?

Barrel front:

Barrel side:


texts: Design a Voltage controlled current source

texts:
I have to create a current source (cs) capable of delivering up to 1.5 amps in order to calibrate a IC. The cs must be adjustable through a signal generator.

I thought I could use an op-amp and I have found some from TI (e.g. OPA548 from TI) but it works as a voltage source, which is a mistake and does not function properly.

I have not done anything similar and need some help. The input signal which is supposed to adjust the output is a sinusoidal waveform of 50Hz and IC must not see a signal higher than 500mV.

Can someone please help me?


texts: LED Lighting Project: Components for RGB controllable system using cree® Xlamp® Xm-l color leds

texts:
Experience:  Novice, I know not to touch 220v circuits...
Objective:   LED lighting system for exterior trellis with controllable color, using Cree® Xlamp® Xm-l color leds.
Required:  What is the easiest way, and what components in addition to the Cree LED's are needed to control colors?
Assumptions:  Correct transformer is used, correct dimmer is used, 8 of the Cree LED's (or similar) to shown will be used in aluminum heat sink kits like the one shown below.
Any help will be appreciated and especially help related to controlling the Cree's colors.


texts: Input selection circuitry for USB/battery

texts:
I'm making a development board, and trying to sort out the input selection circuitry, where if a battery (3.7V lipo) and USB is connected at the same time, it doesn't damage the circuitry, by stopping current flowing back into the USB.

So the design I followed was taken from the Arduino schematic: https://www.arduino.cc/en/uploads/Main/arduino-uno-schematic.pdf and I chose the linear regulators + op-amp based on their properties.

Just wanted to ask whether my circuit configuration is correct?

Primarily the questions I have are:

MOSFET Q1 is there to act as reverse polarity protection; is this okay to use?
MOSFET Q2 acts as an ideal diode by permitting either the op-amp to drive the regulator, or the USB, depending on whether the battery is connected. Is this correct?
Is the 5V regulator correct? Other configurations have a capacitor on the output, but the reference schematic for this didn't have one; is it necessary?
The 5V regulator output also goes into the input of the 3.3V buck converter, so it can be supplied by a stable 5V, and thus guarantee a 3.3V output; is this correct?
Is it okay to have my Vbat connection pin where it's at, just after Q1? And to have that connected to the input of the 5V regulator?


texts: ATMEL AT89S52 programmer help finding suitable software for flashing over LPT

texts:
I have this old ATMEL programmer and I'm hoping to start learning about micro controllers on a lower level before I move to Arduino.

Unfortunately the floppy disk that came with it is lost, and the chip (red arrow in the picture) is sanded off. and it's not possible to contact the person who made it.

What software do i have to use? I'm fairly capable in ASM but i dont know how to transfer the program to the microcontroller.

Can i use USB-to-LPT converter? or i have to find an old pc with a LPT port to use this prehistoric relic?


texts: Light bulbs are blinking when controlling powerful heater with PWM via SSR

texts:
I'm creating a diy sous-vide rig using esp8266, a tubular heating element (1.5 kW) and a solid state relay (zero- cross, Fotek SSR-25DA)

I use a relatively powerful heating element, so that the water can quickly reach the desired temperature.
However, once it's reached, I want more granular control, so I use 10 Hz PWM to open and close the SSR.

The problem is, my ceiling lights start to flicker when the duty cycle is not 100%.

I think this is due to the starting current of the heater, but I don't know how to approach fixing it.

Maybe I should increase the PWM frequency? But I'm not sure it will work at all, considering that the SSR is zero-cross.
Or should I add some fat capacitor in parallel with the heating element?

I want to be able to limit the heating power because it takes some time (about 300ms) to get the temperature from the sensor (ds18b20), and leaving the heating element on for that time on full power easily overheats the water.

Here are some specifics:

Water volume is about 3L
The readout time for the sensor is 375 ms
Typical temperature range is 60-65 degree Celsius
I use the following cycle:

    read the temperature (t)
    if t >= target
        set duty to 0
    if t < target - 3
        set duty to 10/10
    if t < target - 2
        set duty to 7/10
    if t < target - 1
        set duty to 5/10
    if t < target - 0.3
        set duty to 2/10
    else
        do nothing


texts: How to make a register in VHDL remember?

texts:
I was given the assignment to implement an 18-bit register in VHDL. I used an example from the book "Free Range VHDL" recommended to me earlier. Here's what I got:
library IEEE;
use IEEE.std_logic_1164.all;

entity reg18 is
    port ( REG_IN  :  in std_logic_vector(17 downto 0);
           LD,CLK  :  in std_logic;
           REG_OUT : out std_logic_vector(17 downto 0));
end reg18;

architecture reg18 of reg18 is
begin
    reg: process(CLK)
    begin
        if (rising_edge(CLK)) then
            if (LD = '1') then
                REG_OUT <= REG_IN;
            end if;
        end if;
    end process;
end reg18;

However, the mentor argued that it doesn't remember the input and something with the VHDL signal must be done. Nevertheless, here's a citation from the same book:

If you have not speciﬁed what the output should be for every possible set of input conditions, the option taken by VHDL is to not change the current output. By deﬁnition, if the input changes to an unspeciﬁed state, the output remains unchanged. In this case, the output associated with the previous set of input can be thought of as being remembered. It is this mechanism, as strange and interesting as it is, that is used to induce memory in the VHDL code.

Can you, please, explain to me how the mechanism of remembering in VHDL really works? Thank you in advance.
EDIT: By signal was meant the VHDL signal that is opposed to the variable. And yes, your comments confirm the citation.


texts: Is a buck regulator the best option for my needs?

texts:
I'm looking at using an MC33063 buck/boost inverter in a QFN package to step down 5-30V to 4.2V. This will be used to power an MCU, some modules, LEDs cosuming about 200mA max, optionally to charge a small LiPo, so the 1.5A is more than enough.
What I would like to know is if this is the correct way to go considering space is of the essence and I need to use as little extra parts as possible, ideally low part heights.
The additional diode, resistors and caps I saw in example schematics could probably be made to fit.
Everything is SMD.
Can I expect to be able to go as low as 5Vin or more likely around 6V?

1.5A isn't mandatory, but I would rather not go down to 0.5A, just in case, so 1A is a good compromise.


texts: Difference between an ideal integrator and a practical one

texts:
I only learned about the ideal integrator design (top circuit), but when I searched for a practical model for an integrator I found it was like the one in the bottom circuit.

Two new elements, Rf and Rs are added to the ideal model. I don't quite follow what their functions are. It would be great if someone can explain what they do and how large their values should be set compared to R1. Thank you.

(I've only just learned about op amps, so I may not understand complicated concepts.)


texts: How to select a DC cable connection type based on current?

texts:
I have a battery and DC-DC converter solution that I've ordered. The solution will output 20A continuously at 5V, and will sometimes pulse up to 30A for durations up to 10 seconds.

I believe voltage is not a big concern here.

How would one go about selecting the appropriate connector for such a battery solution and DC power cables attached to it, given the current that it must tolerate?

From my research, 2.1mm barrel jacks cannot handle this level of current (they typically range from unspecified current to 5A).

For my 20A continuous, 30A pulse requirement, an model SD45 connector was recommended by the battery manufacturer:


texts:
I would like to make sure I'm reading this value correctly as 22.10 ohm. I think the first color on the left is white, but the second color I am nearly certain is gold. The gold band must be the multiplier then, and I am miss-reading the first color which may actually be silver. Let me know what you think, I'd like a second opinion.

Edit: Is it possible for this resistor to be a 220 ohm 5% with a white reliability band?

Edit1: Additional info.

I can't physically measure this component, this is an image of an identical board I received from a supplier of the part.
This is on an oven control board. This resistor burnt up on my board and I would like to replace the part.


texts: how to find drain current and Gate voltage using transfer characterstics

texts:
I am facing problem in analyzing the correct value of Id and Vg from my circuit below, using the given transfer characteristics.

given : Vs = 5V (for symmetrical output)
        Vd = 10V
        Rg1 = 1MOhm


texts: Must FCC-certified modules be labelled with the correct FCC ID?

texts:
The manufacturer of this radio module I bought claims that it's FCC certified, but  there's no FCC ID on it (though there is the FCC logo). If the final product is to be FCC tested, would it then be tested as an intentional radiator since there's no FCC ID on the radio module (rendering the certification invalid)? AFAIK, that costs a lot more than an unintentional radiator test.

Their website has the FCC ID - could I just print it on a sticker and stick it on the module?

Thanks


texts: AT-Commands: Send E-mail with attachment

texts:
I purchased a telit GSM Click (GL865) to use in my project. The architecture is composed of PIC based board with two MikroBUS connectors, I used one for the Telit GSM click, and the second one for the SD card.

I interfaced the Telit GSM Click correctly.
I interfaced the SD card correctly.

I can read and write files to the SD card from within the Pic.
I issue successfully the AT commands to Send SMS and to Send E-mails.

The goal: Send e-mail with attachment, via telit GSM CLIK GL865.

The problem: I can't send e-mail with attached file.
I tried to provide filename to the command, it works without Error, but the received e-mail does not contain the file sent by the Telit modem, in contrast, I get an empty file with the same filename.

Example:

AT#SMTPCL=\"myaddress@mymail.com\",\"testEmail\",1,\"test.txt\",0
then I issue my text (email body)
then I issue the escape sequence ("+++")

Where: test.txt is a text file (containing some text) and stored in the SD card.

The command above works fine, I receive the e-mail (containing email body text) with an empty file "test.txt"

I think that the AT Command fails in finding the file, then it will send an empty file with the same filename.

I think that there is a way to import the file to be used by the Telit modem and the AT commands.

I read the official Telit documentation and searched in the Internet, but I did not find any solution.
I would like to seek your valuable support, and tell me please, how to get it to work, I will be very thankful.


texts:
I'm trying to figure out what the following schematic symbol is:

I'm referring to the "10 NP" with the two vertical bars.


texts: How to sense the zero crossing of current?

texts:
I am trying to sense the power factor angle using microcontroller.

Now the mechanism that I have thought it that

Measure the zero crossing of voltage
When the voltage zero is sensed, start the timer of micrcontroller and then start sensing the zero of current.
But how to sense zero of currrent? By using a zero crossing current circuit

My problem: I have made zero voltage circuit using transistor and opamps. The transistor is dependant upon the voltage applied between the emitter and base.When the voltage is zero, the transistor is off and the collector 5 V pulse is obtained accross collector and emitter.

But what for current? Is there any electronic device that is turned on/off by current ?

So I think the only solution is to convert the current into voltage and then sense the zero of voltage. Is it a viable solution?

@Andy AKA

Convert voltage and current to digital.
Sample the V and I at much much higher rate-more than 2 times of 60hz ('dont stick close to nyquist:-)')  .
Apply low pass filter to the voltage and current.
Apply atleast 6 LP filters,so that I can remove harmonics and get pure 60 Hz wave.
Now I have V and I.
Find Vrms and Irms.
Do cosQ=V*I/(Vrms*Irms).

Doubt: In order to sample current, I must use current transformer(to lower the current) and convert it to voltage and then use a 12 bit ADC or is a ADC avaliable that can directly convert current input to digital?


texts:
I would like to replace a battery pack with a power supply.  I have several Force Fx light savers.  These are powered by 6 AA batteries concealed in the hilt.

I want to create a small power supply that will be enclosed in a wall mount for the light sabre, when the sober is on the wall mount the idea is that it will be mains powered.

I would also like to create a small circuit that detects if the power supply is mains or battery and switches out the sound fx when powered from the mains.

The question is, what sort of power supply would I required to replace the 6 AA batteries?


texts: For loop does not compile in Matlab mcode using Xilinx block

texts:
I have a simple code in xilix type mblock in simulink:

function q = test1( n)
q = 0;

  for i = 1:n
    q = i;
  end;

end

If I run this code naively in matlab console, it works fine. However, when I want to simulate the xilinx block in simulin, it shows the following error:

Does that mean that I cannot have any dynamic loops in there?


texts: Using neighboring traces for PCB return current

texts:
I am developing a 2-layer board for a 3-channel BLDC motor driver.  I am using an IC for the driver (DRV8313).  I will PWM it at 20kHz with around 10% or less duty cycle.  Current is less than 1A.

It seems ideally, the return current for the BLDC power use neighboring (or nearly neighboring) traces, as that is the actual loop.  But those are on the same layer.  The PCB will be a standard 1.6mm thick; the current is low enough that I can make the traces even closer together on the same plane.  Will this keep EMI as low as having an actual ground plane reference, or is the ground plane still preferred?  Is the fact that traces are wide and flat a reason for this?

I want to do this so I can route +12V and GND on neighboring traces on the bottom of the board (which means I need the return current flows of the +12V trace and GND trace/plane to cancel each other out too).  I'm trying to avoid going to a 4-layer board, and avoid running wire jumpers on the top just to feed the IC.


texts: How much capacitance/joule/watt is needed on average household' energy storage system with supercapacitor?

texts: I am on the process of making assumption how much capacitance/joule/watt is required on average supercapacitor as household' energy storage system. I plan the design for energy hub to be charged by electrical grid on night, and by the sunlight on daylight. I've found that for normal household energy use, the power supplied by meter (9.2 kVA on average) should suffice.  In theory, this allows you to simultaneously supply devices with a maximum power of 9.2 kW or 9200 watts. Does it mean that ideal household supercapacitor for renewable energy resource (sunlight) on energy hub is 50% or...? Any help would be appreciated. Thank you.


texts: Industrial flash (LED?) for rolling shutter

texts:
I am developing industrial monitoring system, at this moment with Raspberry Pi and its camera (this might change if it is not satisfactory). The camera will take still pictures of the scene once in a few seconds. Since the objects are moving, it has shutter time max 1/1000s. After some experiments, I determined I need around 10kLux light source which is either turned on all the time (though without producing excessive heat), which is turned on and off programatically, bracketing the camera action, or one which can be synced with the camera shutter using the camera's chip flash sync.

The camera unfortunately has rolling shutter, so xenon flash tubes are out, AFAIK -- their light interval is probably too short, there would be partial exposure -- but that's just what I understand from readings sources, so I will be glad to be corrected here).

What other flash options do I have? I will be glad to use LED-based flash, but need reliable circuitry around it as well. Ready-made industrial cameras systems costing over $4000 are something I would like to avoid, if possible.

I would like to ask for pointer in which way to go, keywords to search for, or even marketed products which would be suitable. I am personally only moderately skilled in low-level electronics, but have colleagues who know that stuff.


texts: What is the best way to limit voltage of a solar panel?

texts:
I am using a 6V 6W solar panel with the Particle Boron microcontroller with a battery pack.

I want to ensure that the voltage supplied by the solar panel does not surpass 6.2V, as that is the max Vin rating for the microntroller.

What is a good and simple way to go about this without sacrificing too much power from the solar panel?


texts: How to choosing the right transistors for active antennas

texts:
I'm trying to build a Mini Whip active antenna that receives 10KHz to 20MHz. But I'm having trouble finding the right components especially the transistors.

It calls for a J310 and a 2N5109, which are both hard to find.

When designing an antenna circuit what exactly is it you need to look for in a transistor? High frequency response? How does one go about choosing a suitable replacement?

I've tried using www.alltransistors.com to find similar transistors, but I'm not too sure what to compare. Obviously: polarity, max power dissipation, max voltages, maybe transition frequency? maybe the noise figure?

Other people have substituted these for a MPF102 and 2N3904 or BF245C and 2N2219A

I've also found other people using these as replacement, but I'm having trouble sourcing these too: BF245A, BF245B, BF245C, BF246 A/B/C, MPF102

I guess that these transistors are all very similar but subtly different, the problem for somebody out of their depth like me is knowing if it matters or not, if I use the wrong one will I end up with a terrible antenna?

On a similar note what being an RF circuit do you think its necceasary to have tighter tolerances on the resistors too? I was thinking about choosing +/-1% resistors over +/- 5% resistors?

Many thanks!

Scroll down the pdf for circuit diagram:
http://myweb.tiscali.co.uk/wgtaylor/PA0RDT-Mini-Whip.pdf


texts: Pull down resistor not pulling current down to 0 V? - Arduino + LED's

texts:
I was recently connecting an LED strand to my Arduino nano using the following wiring diagram:

I was using 10k ohm pulldown resistors in order for the LED's to be off when the Arduino is outputting a low signal but the power is plugged in.
However the LED's are still on (very dim but noticeable).
I was wondering if adding a bigger pull-up resistor would fix my issue?

Also if this helps I'm using the following hardware:
Arduino Nano rev 3
10K ohm resistor
12V 6A 72W power supply
300 LED strand.

Thanks in advance!


texts: what parameter should be noticed in design sample and hold circuit?

texts:
if I want to sample from a pulse with 50kHz frequency, that changing between -5 and +5 Volt, what parameter should be considered in choosing op amp to get high accuracy, and How should I calculate my accuracy of the circuit.
Consider That I use switch with 25ohm turn on resistance,and my circuit something like this :


texts: Generating unipolar and bipolar voltages from AD5752

texts:
The AD5752 consists of two DACs internally.

Can I use one DAC to generate unipolar voltage and another DAC for bipolar voltage simultaneously?

It is a dual channel DAC.

Datasheet


texts: How to bypass continuous input on Trigger pin of 555 IC after some time working in Mono-Stable/ One shot version?

texts: I configured the 555 IC such that it gives the output pulse for 3 Seconds (Approx.) as soon as there is input on trigger pin, but my project requirement is; even if there is input continuously on trigger pin after 3 seconds, the output should not stay HIGH; so how to do it? And another requirement is; if again INPUT detected on TRIGGER pin, the OUTPUT should again stay HIGH for 3 Seconds and after that, it should go LOW; after 3 Seconds.


texts: Best configuration for 400W resistive heating device

texts:
Suppose I wanted to heat a large aluminum disk with joule heating. I would use one of its flat faces, which has a radius of about a foot (30cm, SA = 0.28 sq m) and enough resistors to dissipate 400W of energy.

If I use 12V across a circuit:

P = V^2/R

P = 320W

V = 12V

R = 0.45 ohms

and the current for such a circuit would be I = V/R = 12/0.45 =~ 27 A (which seems very high)

Is this correct? Is this kind of set up "safe"?

--

And if you are interested:

If you were to build this circuit, how would you arrange resistors of any R value while:

Distributing the heat across a large (1ft radius) surface
Remaining under 100W per resistor
Maintaining R=.45 ohm total circuit resistance as closely as
possible

Here is one attempt of mine, using 10 parallel 4ohm resistors (.4 ohm circuit resistance):

simulate this circuit – Schematic created using CircuitLab

If you think it is safe/worthwhile, I am open to setups with higher voltage, but for some reason 12v seems to be the standard.

Also if I wanted to use PWM (DC) to control the output of this circuit, what would be the cheapest and most efficient way to set that up with Arduino?

My disk is about 10.8 kg with specific heat capacity (Al) = 0.9 J/gC

So I chose 320W because this would allow me to heat by 10 deg C every 5 min:

0.9*10800*10/320 =~ 300 sec = 5 min


texts: I thought I understood the basics of DC circuits and Ohm's law but now I'm confused

texts:
So I was taught in school and also read a lot of articles of the basics of DC circuits. I know the formula R=V/I, and therefore that resistance is directly proportional to voltage and inversely proportional to current. So if I increase the resistance the voltage increases too right?

Now I'm working on an old RC car I used to play with. The battery pack consists of 6 AA batteries which provide 9V, but I noticed that there's another output that outputs 4.5V. I guess it's being used to power the driver board.
I tried reading the voltage but I also put a 10 megaohm resistor in the circuit. I was surprised when I saw that the multimeter was reading around 2.2V. Isn't the voltage supposed to be higher because of the resistor?

I am completely confused now and I'm pretty sure that I have a lack of understanding or just confusing some things. Please explain why did this happen.


texts: A current generated from electric generator turbine/motor forced externally to rotate in one direction

texts: How can an AC current generated from electric generator turbine/motor forced externally to rotate in one rotary direction be alternating, as it's just the reversed DC motor process generating force or rotary kinetics?


texts: Potentiometer controlled current regulation

texts:
new one here.

Thing is this;
I have an electromagnet (or a solenoid as I prefer to call it). When it gets energized the plunger inside is pushed out to a certain length (goes back to its original position thanks to a spring). It is supposed to work on 12V DC. It has two leads and the resistance between them is 0.9 Ohm. Assuming the voltage would be constant, max current it can draw would be 13,3 Amps. I need to be able to control how far the plunger can get pushed out. I am led to believe that with constant voltage this can be achieved by varying (limiting?) current to the solenoid.

The question:
How would such a circuit look like? Is it doable with LM317 or something similar (LM350?)? Would a thyristor or a transistor be of any use? I'm really newbie to electronics, but willing to learn. Is there even a proper 'name' to the kind of circuit I am looking for?

P.S. I know current limiting can be achieved by increasing resistance, like with a potentiometer, but the pot might become dangerously hot, right?

Or am I talking rubbish ...

Someone please enlighten me... Thx in advance.


texts: Protecting two layers of PCB with electric tape?

texts:
I have soldered several small PCBs, and I want to stack them together (using hex spacers).

However, since lack of (vertical) space it could be that some components (on the top) might touch the wires/solder junctions (on the bottom) of the PCB above.

What is a good way to prevent this?

I was thinking about thin wooden or plastic plates between the layers, however, this will cost some (vertical) space, especially where the wires/solder junctions from the above PCBs are lower than the top components of the PCB below.

So another way I thought was to use two 'layers' of electrical tape, stick together (with the 'glue' sides towards each other). So it is like a flexible 'plate'.

Would such a thin (< 1 mm electrical tape 'layer') be enough to isolate signals around 5 V, and very low current (DMX512 signals)?


texts: Low-pass filter - choosing R values dependent on the load impedance

texts:
I need to design a low-pass RC filter that is connected to an oscilloscope at the output. The oscilloscope has a load impedance of 1MΩ||20pF. I have to choose values for R and C, taking this load impedance into account.

Originally I chose R = 1kΩ based off another post here (which I can't find now). Then, using the formula:$$\text{f}_c =\frac{\text{1}}{\text{2}\pi\text{RC}}$$ for my desired cutoff frequency of 10kHz, this gave me C = 15.9nF

Then I found this website which calculates the RC values for you if you enter the desired cutoff. It gave me R=160Ω and C=0.1uF

So here's the problem: using my values gives a real cutoff of 10,010Hz, and using the website's values gives 9947Hz. Clearly my values get closer to the chosen cutoff, but I haven't taken the load impedance into account because I don't know how it would affect the values. In a simulator, both circuits behave almost exactly the same, but I'm concerned that the simulator's oscilloscope doesn't have a 1MΩ impedance.

Can somebody explain how the load impedance would affect the choice of values, and which values I should choose? My set, the website's set, or a completely different set?

The circuits and their frequency responses are below, so you can see how they're basically the same.


texts: Is it possible to design a high power wide input supply range boost converter which has to be compatible with single phase as well as three phase power supply? and if it is possible then which analog control technique is suitable for it?


texts:
I want to use a 2s Lipo for a autonomous car built with a Beaglebone and  Motor Bridge Cape from Seeedstudio. The Motor Cape has an built in voltage regulator which steps down 7,2V to 5V system voltage. This allows supplying motors an Beaglebone from same source.

While charging a 2s LiPo charger is supplied with 12V. Is it possible to charge the LiPo under load? Or do I have to supply the Beaglebone from 12V source while charging?

This would mean that there has to be a switch between battery source and 12V source which selects the source automatically. That is not a complicated task, but supplying the system by battery all the time would be easier.

For example the swithing between LiPo and 12V source could be realized like this:

simulate this circuit – Schematic created using CircuitLab


texts:
I need to be able to switch a load circuit off when the output voltage from a buck boost converter is around 3V (or below 4V or 5V).
The converter is powered by a 10W solar panel and the load can draw a max of around 560mA. The converter is set to 12V output, but whenever the panel is in shade and then put in sunlight, the converter doesn't have time to properly switch on because the rest of the circuit is drawing all available current (I understand this is called stall?) at 3V and starts overheating quickly. I then need to disconnect the load for the converter to switch on properly.
I have found a few undervoltage circuits online, but nothing that I can use or adjust. Mainly because I am a newbie when it comes to circuit design. So I can't calculate the values and don't know which mosfets to use.
Any help with part values and advice would be much appreciated. Here are three circuits that look simple enough. If you have any suggestions, that would be great too.

Image source: https://www.powerctc.com/.

Image source: http://s3.amazonaws.com.


texts: How to properly analyse this simple circuit?

texts:
I often get awfully confused when presented with circuits like this, and can spend around 20 mins looking at it trying to figure out exactly whats happening.
So the way i find the voltage across 100M resistor is:
1/ Notice there is a potential diff of 5V between 10V and 5V supplies
2/ Most of the current flow will be through the 1k resistors
3/ because there are two 1k resistors there should be 2.5V at dropped across R1
4/ Therefore 7.5V will be dropped across R3 as it is 5V below the 5V supply
Is this a correct line of thinking? Is there a simpler way to analyse this?


texts: How to determine which connectivity and peripherals are needed in a microcontroller?

texts:
This post goes a step beyond my previous question about microcontroller selection here. In short, I am a moving away from AVR for product development and I want to stick with popular manufacturer uC series that have longevity and a lot of community support around them for troubleshooting.
In this process, I am having some confusion with uC selection based on required connectivity and peripherals. I know that I will need some combination of I2C, SPI and UART connectivity. Also, I know that I will need PWM and timer peripherals. In my current prototype, I have an external Bluetooth module, LCD (OLED), and motor controller. Unfortunately, when I include Bluetooth and LCD as necessary peripherals in my searching, I notice that 1) either the selections to choose from become a lot more limited or 2) often a lot of other peripherals and supporting connectivity are required with the additions.

In industry, do developers generally try to simplify things by including as many peripherals as possible in their uC selection (if cost effective), even if it's an overkill in the sense of potentially adding more uC capability than what may be needed?
Aside from my soft requirement to work with a well supported and popular series, is it more a matter of the cost driving whether to choose a uC with all the needed connectivity/peripherals and then some?


texts: How to explain this solution to the common-mode voltages?

texts:
One of my previous question revealed that a variable voltage test device's power supply which is an AC/DC adapter, and is SMPS type which causes common-mode voltages. A solution given by tying the supply ground to earth ground. This works only if the AIGND of the data-acquisition device is earthed.

Anyway below is about my question:

Now I found another workaround which I cannot explain the reasons. To begin with the issue was due to the parasitic leakage of the SMPS adapter which causes common-mode voltages to appear all the way at the device terminals wrt earth. I show this in Figure 1 below:

Now if I tie the ground of the device to the AIGND of the differential input data-acquisition channel as in Figure 2 below(green line), I still have 50Hz noise:

But if I tie the ground of the power adapter to the AIGND of the differential input data-acquisition channel as in Figure 3 above(green line), 50Hz common-mode  noise completely disappears.

Even more strangely is that: when I make a continuity test between the adapter and device ground(GNDA and GNDB in Figure), they are already connected to each other.

So theoretically tying from GNDA or GNDB to AIGND shouldn't be different.

My questions are:

1. Why does the common-mode voltages disappear when I connect the adapter ground to AIGND?

2. The continuity test tells adapter and device ground already connected. Bu then how would you explain the difference between the results of Figure 2 and Figure 3?

3. Can I safely use this method in this type of situations? I mean tying the power supply GND to AIGND.

I mean I have a setup when the switch above is open. And when the switch is closed the common mode noise-disappears even though there is continuity between the GNDA and GNDB. Can this technique be used safely?


texts: What sample rate do I need to analyze usb 2 with a analyzer?

texts: What is the sample rate needed for a logic analyzer to be able to analyze a 480 Mbps USB 2 bus?


texts: Charging questions, current limitation and voltage

texts:
I'm having few issues with chargers, current delivered to a device etc... just need to connect the dots I guess.

When I connect a phone to a charger for example IPhone which is rated at (5v,1A max), to a charger rated at (5v/2A) The phone will only draw 1A correct? what is limiting the current here? is it a resistor in series built inside the phone?

If I'm Building a PowerSupply that has a charging USB port, do I need a resistor before it? or would it cause a short circuit?
For example
(Voltage source) ---> (LM317 as voltage source) ---> (USB Port) -----> (Phone)
do i need a resistor before the USB port or will the phone handle it?

Also, charging a lipo, let us say 1cell at 4.2v maximum, if i set the LM317 to 4.2v and plug the lipo, am i forced to put a current limiting resistor or will the lipo draw as much as it needs as the voltage is appropriate?
wouldn't the charger stops automatically when the voltage off the battery be equal to the voltage of the lipo? 4.2v ---- 4.2v so no current will flaw?

Long Question short, is the current limiting resistor built in the batteries or do I need to place one?
wouldn’t the charging stops automatically due to Vin = V of battery?


texts: How can I reduce the current draw for a dimmer with a triac for an immersion heater?

texts:
I've been working on variable control for a immersion heater. The problem is that the heater consumes a lot of current, about 10 to 15 Amps. I already have to circuits to control it, the problem is that both circuits overheat to the point that they already burned some components. The heating comes from resistance in the triac circuit while the components support more than 25 Amps (Triac and the Mosfet).

Here are the two circuits that I've tried. I need a way to avoid the overheating of the one or both circuits. How do I avoid overheating in these circuits?


texts: IC has pull-down resistors on SMBus lines?

texts:
The datasheet of TI bq40z50-R2 (Li-Ion Battery Pack Manager) tells that "The SMBus clock and data lines have internal pulldown".

Pin equivalent Diagram is in image below:

Aren't usually the SMBus Data and Clock lines to be connected to pull-up resistors?

I'd like to connect this IC and a Battery Charger IC to same SMBus, but the latter requires pull-up resistors for the SMBus lines.

Would this work anyway?

Thanks


texts: Getting 12V wall wart to power 12v solenoid driven by Arduino

texts:
Scenario: Power a solenoid by soldering on the gnd and pwr cables of a 12v wall wart.

I found this wall wart in my house that I think will work. From what it says I assume it can transform 120v to either 5v or 12v through the "tiny pins" that plugged into whatever device it plugged into.

I'm thinking the steps to use this wall wart on a breadboard to power both the solenoid and Arduino would be something like (with some unknowns?) [This is where I need help - verification and additional info on the steps to take]:

Remove the "cruft" around the little pins so they are free (is there a recommended way of doing this?)
Here is what I don't understand: take 1 of the 12 v little pins and solder a cable that will go from the wall wart to the breadboard's + row (or twist the 12V cables together then solder or crimp to cable) do the same with the GND.


texts: What does that statement exactly mean? ( about dB )

texts:
When you separate the collected signals, each car’s channel must
  attenuate the other cars’ signals at least by 20 dB.

A speaker will be able to generate a sound which contains 3 different frequency values of sine waves. And also the amplitudes of the sine waves will be tunable, so that at each instant;

A(f1) = 0 (meaning does not exist at that time)

A(f2) = above_threshold ( higher amplitude w.r.t f3 )

A(f3) = below_threshold

Note: The f1,f2,f3 will be change their states for different scenarios.
A means amplitude, f_i correspondes to the sine wave at that frequency.

Then a microphone(seperated by 10 cm from the speaker) should be able to collect this sound, distinguish different frequency components by also indicating their relative amplitudes, because "which of frequency components has higher amplitude which one has lower amplitude and which one is non-existing" is an important information that should be obtained.

This information will be used in a next step of decison mechanism, so I will need DC converted signal levels. To achieve that I plan to amplify signals and then full wave rectify them.

So, relating this part, there is a requirement which is quoted above. Please notice that car's signal means one of the three different frequencies.