texts: Reliability FPGA depending on its number of gates

texts:
I am currently working on a little project and the goal is to find a new model for calculating FPGA's reliability.
I have been working with the MIL-HDBK-217F+N2, but when it comes to the complexity (number of gates) of a FPGA, it goes only until 60,000 gates. But nowadays the complexity can go to several million of gates.

Now my question is, is there any link between complexity and the reliability of a FPGA? Is a FPGA with a lot of gates not as reliable as a FPGA with less gates? And how is Moore's Law affecting reliability?

I have been trying to analyze data from FPGA manufacturers, in their reliability reports, but it seems that the only determining parameter of how they calculate the reliability (in FIT) of an IC is the "Device Hours". The longer the device is tested, the lower the FIT. Unless there is a failure of course. So I can't really compare different FPGAs because they don't have the same duration of testing.

I hope someone could clarify this for me! Thanks.


texts: Building a pH meter circuit - is it feasible?

texts:
Let's say I have a budget of $15-20 to build a pH meter. I will then read the analog values from a microcontroller or such, but I want to first focus on somehow getting a reliable pH value on a shoestring budget.

First of all, is this even possible for an electronics hobbyist? I see existing pH meters out there but they are quite expensive.

There are commercial options running into the hundreds of dollars to cheap ones like these: http://www.sparkyswidgets.com/product/leophi which still require an external probe.

Ideally I want to build a pH meter circuit that has electrodes that simply dip into water to measure its pH.

I also found this:  http://overskill.alexshu.com/cheap-ph-meter-hack-for-arduino/ but it's based on hacking an existing pH meter. I'd first like to hear opinions on whether a complete DIY sensor circuit is possible to do.


texts: How to access the data from RAM and ROM(Flash)

texts:
I have a two-part question based on the memory of the Microcontroller (Common Platform not to any controller specific).

How to access the data/variable stored in RAM and flash. I know the about the RAM access for both static and dynamic in RAM, but I don't know how to read the data from flash/ROM. For example: If I am allocating dynamic memory in RAM using malloc and is allocating from the address 0x0303, will this address and ROM/Flash Address conflict?
What is 'Memory Protection'. It is only for reserved and accessing Permission for specified address or any other use. It is possible in both RAM and Flash.


texts: Are there any caveats to running a boost converter at zero duty cycle?

texts:
Following up on a previous question, I've implemented the following scheme:

simulate this circuit – Schematic created using CircuitLab

The normal buck converter in the dashed box is used to charge a Li-Ion battery (of course, I've omitted irrelevant details). Its required power, factoring converting losses, is less than 5W.
In order to extend the input voltage range of the L6902 to include 2.5…8V, I've prepended it with a custom boost converter, so the complete system behaves like this:

When Vin ≤ 2.5V, no power is drawn from the generator (duty cycle of the boost converter is 0, and U1 is in under-voltage lockout);
When Vin is in [2.5…8.5V], the boost stage is active and U1 sees around 8.5V at its input. The battery charging current is ramped up as Vin increases in a way that the L1 peak current doesn't exceed ~0.9A; the output current of the boost stage is less than 0.6A.
When Vin ≥ 8.5V, the boost converter is in a "pass through" state, duty cycle = 0%, and we have Vstepup = Vin - diode drop. Again the current thru L1 and D1 is less than 0.6A (and usually much less due to the constant power load).

Since the device may work in 3) for extended periods I'm wondering are there any caveats to this mode. Of course there's D1 losses, which I can live with. I also reckon that if the load current changes suddenly (e.g. battery disconnected) the inductor in the power path may introduce some ringing, but given C1's value these should be well damped.

Since I'm far from an expert in DC-DC converters, I wonder whether there may be any caveats I'm not currently aware of?


texts:
I need to read 16 color sensors(TCS3210) one after another. So I am thinking of connecting all the outputs to a single atmega32 i/o pin and selecting a sensor using a demux  showing low on the output enable bar of the sensor to be read. So only one is putting output and rest all have their output disabled.

The output is a square wave whose frequency is to be read (I use the hardware timer/counters of the atmega32 to count number of low to high transitions in 100 milli secs to calculate the frequency). So is this is a good idea? Can I connect all the lines together or should I have something in between?

Also I will be connecting a single I/O pin of microcontroller to input pins of all sensor?Again can I do this?

Datasheet link of TCS3210-https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CEUQFjAA&url=http%3A%2F%2Fwww.taosinc.com%2Fgetfile.aspx%3Ftype%3Dpress%26file%3DTCS3200-E11.pdf&ei=fMpFUY69NITorQfgoIGYAg&v6u=https%3A%2F%2Fs-v6exp1-ds.metric.gstatic.com%2Fgen_204%3Fip%3D117.195.154.23%26ts%3D1363528317182144%26auth%3Dbuy4ggbxloq4plgn33fqat3v75rhqior%26rndm%3D0.48476632428355515&v6s=2&v6t=5038&usg=AFQjCNEQMV_HabUav8aoZYdwWuB5_q9rbQ&sig2=C6l6s2CHkczkSQOrI1ezOQ&bvm=bv.43828540,d.bmk


texts: Type of capacitor for feedback / external compensation

texts:
Referring to the capacitor between the output and the inverting pin in an op-amp, in parallel with the feedback resistor --- should I use ceramic (NP0), or thin film?

We're talking bandwidth in the order of tens or low-hundreds of MHz.  Capacitor value in the order of a few pF, maybe up to 10pF or 20pF.  Ceramics seem to offer higher frequency response; however, their non-linear characteristics presumably make them unsuitable to be part of an analog signal path, and I'm thinking the feedback capacitor qualifies as "part of the signal path", right?

What about other types?  Anything other than ceramic or thin film that is recommended for this?


texts: Capacitor selection drives voltage fluctuation from TLV700 LDO

texts:
I am building a wireless charger based on bq500212A (datasheet here)
However, I have an issue with the LDO: It fluctuates the voltage by about 400mV in a wave.
Blue is where I put my oscilloscope probe. Green is where I put the oscilloscope GND. Green squares represent the installed components.

Here are some oscilloscope images:

Added AC coupling:

It's my first time using the oscilloscope for this purpose. This is what I could find on the internet. I also checked the 5V line and it does not present these fluctuations.
Could you tell me what am I doing wrong and why I don't get a stable 3V3 output?


texts: Why is my 180v dc motor circuit not working?

texts:
I bought a "Johnson" treadmill motor that I know works well, it's 180v, 10amp, 2.5hp.
I decided to go with the cheap setup, so I powered it through a 10000w 80amp max scr, going through a full bridge rectifier.
I have wired it correctly but every time I switch it on it blows the fuses. Could anyone give me any ideas as to why?
I am fairly sure it is not a short circuit.


texts: i intend to use WF101FSYAPLNGO display model of winstar, in its data sheet AVDD, VGH,VGL VDD, VDDT voltages are given, can some one help to find the difference between AVDD and VDD, is AVDD meant for back light control? i am using conga ma-5 n4200 processor for my project, its design guide specifies that back light can be controlled by PWM or analog voltage via a i2c DAC. in the said display's datasheet they don't specify about back light control method.


texts:
What is the best way to power off a dual supply op amp (LM741)? Should I cut the positive, negative, or both? Thanks!

I’m building an audio oscillator using four op amps, and I’d like to be able to turn the oscillator on/off by cutting power to the entire circuit. The four op amps are configured in a feedback loop, so I believe that when I cut power there is no input signal to any of the op amps.


texts: Raspberry pi B+ internal power supply ckt?

texts:
I have just started to study about raspberry pi B+ (data sheet)

Can somebody explain the working of power supply circuit (individual component wise) starting from pg 14. How and why it is advantageous. I guess the implementation of a wildar current mirror in the diagram..


texts: Localized RAM readback errors: chip or timing issue?

texts:
I'm currently testing the hardware of a prototype board using DDR2 memory,
and I get RAM readback errors when performing a memory test.

The errors happen in this fashion:

# Next iteration
ERR@ 00fd4ad4 got ffda0540 not ffda0560
# Next iteration
ERR@ 00dc9601 got 0042af73 not 0046af73
ERR@ 00f3bec8 got 002f862c not 002f86ac
ERR@ 00fd4ad4 got 0025fa80 not 0025faa0
# Next iteration
# Next iteration
ERR@ 00dc9601 got 0042af74 not 0046af74
ERR@ 00f3bec8 got 002f862d not 002f86ad
ERR@ 00fd4ad4 got 0025fa81 not 0025faa1
# Next iteration
# Next iteration

I have roughly the same thing on 2 boards, and I wonder if it could be a voltage/timing error or if it's definitely a chip issue.

What's your experience on this ?


texts: Why the inductance become L/D'^2 in buck-boost small signal model?

texts:
The slide presents a buck-boost converter's small signal model, with source disturbance set to zero. Now the effective inductance in the second figure turns out to be L/D'^2 --- why?
It makes sense the transformer affect voltage source, (Vg-V)d-hat(s) with D':1 ratio, but why twice that for the inductor?


texts:
I have recently bought a new car and replaced the number plate bulbs with leds. The Leds work; however when the lights are switched off, the car does it's own electrical check of all the bulbs by sending a pulse down the particular line.

With normal bulbs, this doesn't do anything but the leds flash.

I have came across a video where someone used a 12 V relay to fool the car when it's doing its self check, but he had to leave the bulbs connected to this circuit which he then fixed behind some interior trim.

I don't want to be driving around with bulbs knocking around behind trim panels, so was going to use a resistor in their place.

I'm having trouble with deciding on the value of the resistor.

The bulbs are 12 V, 5 W and gave a resistance of 3.5 Ω. There are 2 of them wired in series.

So would I need a 7 Ω 10 W 12 V Resistor?

Or a 7 Ω 5 W 12 V Resistor?

Or would I be better with some sort of diode?

Or am I way off with it all?

EDIT...

The vehicle diagnostic does its check on cold bulb only. I want a Resistor that will mimic the cold bulb. Once the lights are switched on and they get a full 12 volts the relay will come into play and divert power to the leds which work no problem. Issue only occurs when lights are off


texts: Dual port, serial interface, buffered, shift register

texts:
I have an "interesting" problem.

The proposed design, for a system I'm working on, needs to use 16x 16-bit serial ADCs and I need to interface the results of all 16 ADCs to a synchronous serial stream running at 40 Mbits per second. There will be a frame size of 289 bits comprising: -

A 17-bit header followed by
16x 17-bits of ADC values

17 bits are allocated per ADC even though the ADCs are 16 bit. This means a frame rate of 7.225 microseconds. Fairly easy using an EPLD from the normal vendors.

By the way, the 17th bit inverts the LSB of each ADC to keep the data scrambler ticking over - it reduces "dead" periods in the data stream by about 50%. Also note that the 16x ADCs are "converted" simultaneously (an important part of the spec).

The problem starts when you look at potential ADCs - most take about a microsecond or two (e.g.) to "convert" leaving approximately 5 microseconds to stream the data from them and this is the root of the problem. In those 5 microseconds we would need to extract 16x 16 bits of data, add the extra 17th bit on and this means we would need to transmit (in order to avoid stupifying EPLD complexity), at a data rate (for those 5 microseconds) of 54.4 Mbits per second. It has to be 40 Mbits per second unfortunately (damn those bureaucrats)!

So, what I'm looking for, are ideas and hence the title of the question - If we extract the data from the 16x ADCs and stream it in a serial "holding" register, when that is complete we can transmit at the more leisurely pace of 40Mbits per second. This, as I see it requires a serial shift register that is 272 bits long (16 x 17) that once full is instantly transferred (parallel mode) to an identical shift register for outputting the data at a more constant rate. One shift register fills at one rate whilst the other is transmitting the previously stored data.

So my main question is - does such a device exist and if not, what are people's recommendations - maybe use a bespoke EPLD to do this. It would need at least 544 flip-flops of course and this is bigger than most EPLDs. I've considered (for about ten minutes) using an FPGA but power drain might be a serious issue on this design. Most of these designs I do are powered across "a gap" because the module fixes to rotating machines.

This is not my specific area of expertise (analogue is my area really) so if I've missed an obvious solution please be kind. There are a couple of ADCs that can just about convert in about 400ns but these are rare devices and expensive and physically a bit bigger than an 8-pin MSSOP. All 16-bit ADCs that fit the bill in size and cost (i.e. under $20 each and little 8-pin devices) take over a microsecond to convert.


texts: What is wrong with this attempt at an SDR RAM in Verilog?

texts:
I have a Spartan-6 FPGA wired to the AEMIF memory interface on a TI DaVinci DM365 SoC that I control. The AEMIF is set up in Select Strobe mode. I'm trying to implement memory read/write on the FPGA over that interface, but it's not working. The hardware does work and this functionality has been working before written in VHDL (not written by me). I'm new to HDLs so maybe there is something obviously bogus here.

It's hard to tell what's actually going on as the clock is 60MHz and my scope/logic analyser struggles to go that fast.

Edit: I have since got this working. Setting drive_data in a combinatorial way meant
that on read, the old memory value was driven out on the data bus, then later the sequential logic would pick up the new address and change the data during the cycle.

module main(
    input EM_A_3,
    input EM_A_7,
    input EM_CLK,
    inout [15:0] EM_D,
    input EM_nCE1,
    input EM_nOE,
    input EM_nWE
    );

wire [1:0] em_addr;
/* temporary storage for emif "registers" */
reg [15:0] mem [0:3];
reg [15:0] em_outdata;

supply0 rst;        // reset always 0 for now
wire drive_data;

initial
begin: FOO
    integer i;
    for (i = 0; i < 4; i = i + 1) begin
        mem[i] = 8'b0;
    end
    em_outdata = 8'b1;
end

// drive EM_D when CE1, OE are low, and WE is high
assign drive_data = !EM_nCE1 && !EM_nOE && EM_nWE;
assign EM_D = drive_data ? em_outdata : 8'bz;
assign em_addr = {EM_A_7, EM_A_3};

// clocked version (not working yet)
always @ (posedge EM_CLK)
begin
    if (!EM_nCE1 && !EM_nWE) begin
        mem[em_addr] <= EM_D;
    end
    if (!EM_nCE1 && !EM_nOE && EM_nWE) begin
        em_outdata <= mem[em_addr];
    end
end

endmodule


texts: Simplest schmitt trigger with fewest part count for microcontroller

texts:
I own several AT89C4051 microcontrollers and I'm currently trying to read signature bytes of the micros that I probably broke (by applying 7.2V to the VCC pin before noticing the 5V regulator became a short circuit between input and output) and I want to read signature bytes of the good micro.

Currently I use an RC setup (1uF pull-up electrolytic capacitor + 10K pull-down carbon-film resistor) on the XTAL1 pin and short the capacitor as attempt to increment the clock by one pulse but I feel this isn't the best approach because the voltage at XTAL1 would slowly fall in voltage and that might confuse the micro.

I read how schmitt triggers and flip-flops might rectify this, but I'm looking for something simple without alot of part count. I mean I could go with a 74HC14 but I'll be wasting 5 out of 6 gates in the package.

Whats the simplest way using the fewest parts to create a clean clock signal without relying on an ultra slow oscillator? I want to increment manually with a button.


texts: Having a hard time identifying some FET's in a blown amplifier

texts: I'm trying to repair an amp thats protection light stays on full time. Using the a multi meter I've determined the problem to be  2 large FET's on the power supply side of the circuit and 2 smaller FET's on the output side. My problem is I can't find out what kind of FETS the larger 2 are. I've looked up their numbers and found nothing then I got into researching numbering charts for FETs and I think I've figured out it's numbered in the JIS system. However even adding the missing informaiton to the numbers on the FET's I'm unable ot find any information about them. I've included the best picture I could get of them and I'd really appreciate it if someone could help me figure out what replacements I need. At this point I'd really just like to know why I can't find any information on them at all as well.


texts: programmer is not responding with stacked shields

texts:
I keep getting the following error when trying to upload my code with the Arduino IDE:

avrdude: stk500_recv(): programmer is not responding

I stacked the following shields:

Sparkfun ColorLCD shield (shieldlist reference)
Libelium XBee shield (shieldlist reference)

on top of a Arduino UNO.

I first thought it could be coming from the shields draining too much power from the USB port, but connecting an external power supply hasn't changed the situation (I had to set it up to 7,5V/600mA to avoid overheating).

I'm kind of lost here, judging from shieldlist I should only be worried about the power supply, which is obviously not the case.

Any idea about my problem?


texts:
i have 12 - 5v car USB charger and inside have chip BD8043S 8 pin chip two capacitors, one diode and ferid. i looking for datasheet but for this chip i cant found. there no resistors like MC34063, it is possible to change Vout to 3.7v on it.

Thank you...


texts: Best-practices for potting a high-voltage circuit

texts:
Can someone recommend best-practices for potting a passive DC high voltage (<20 kV) circuit? I'd like to eliminate a micro-discharge problem we are seeing.
Details of our use-case follow:
I have a a DC high voltage system (<20 kV)  which passes though a low pass (RC) filter to eliminate ripple and other noise before passing into a vacuum chamber.  I can monitor the AC component to see its effectiveness
I can get good results from the filtering component; however we potted our most recent build and are seeing micro-discharges: these appear as 1V+ dips in the output voltage. The number of these per unit time increase substantially above about 15 kV, until at 20 kV they appear every 20 ms or so.
I am wondering if there is any surface-prep we can do to the resistor/capacitor leads and or if someone can recommend a specific potting compound that would work better.
We did a thorough mix and vacuum degas the compound before pouring it into the enclosure.  I didn't use a primer however.  We used Krayden DC170 compound for the potting


texts:
I'm building a computer, and I want to add LED lighting to the case.

However, here in Finland, LED strips are too expensive, and I found this: http://www.tinydeal.com/15w-360lm-6000k-60cm-12v-flexible-led-strip-lamp---green-light-p-107477.html

It's cheap, and it would be excellent for me, but I'm not sure if it's possible to cut it into smaller pieces. It's waterproof, so it has a silicone coating, but that can be peeled off.

Does it have soldering points? I'd rather not order a 5M strip, if I didn't have to. Or if I have to, can I cut this into smaller pieces? http://www.tinydeal.com/dc-12v-24w-300-x-3528-smd-blue-led-flexible-strip-lamp-p-93945.html


texts:
So I am setting up an automated test environment for an electronic product and one of my needs is to simulate a user pulling the cable from the product. Since only 4 wires of the RJ45(T-568B) cable are used  (https://www.iplocation.net/rj45-wiring), I am soldering these 4 wires (1,2,3,6) on a relay (S4-5V) and controlling them with a micro controller, and I have grounded all the other wires on both ends of the cable (the one coming from the router and the one that goes to the product being tested).

                 T-568B
Pin    Color             Pin Name
 1     Orange Stripe     Tx+
 2     Orange            Tx-
 3     Green Stripe      Rx+
 4     Blue              Not Used
 5     Blue Stripe       Not Used
 6     Green             Rx-
 7     Brown Stripe      Not Used
 8     Brown             Not Used

I have checked the connections on both ends of the cable with an multimeter (using the "noise on short circuit" function) and the wires 1,2,3 and 6 were connected as expected when the relay was closed and the other ones were grounded. So I assume my cabling is right, only problem is the device still can't connect to internet with the relay closed. Does anyone has an suggestion of why could that be?

Thanks in advance,


texts: Is there any tool that can create a logic circuit equivalent to some Verilog code?

texts:
For the purpose of learning, I would like to know if there is any tool (free or commercial) that can synthesize some Verilog code and produce the equivalent logic circuit.

Example :

assign z = (a & b) | c;

I am not interested how to see how it is implemented in a FPGA (which AFAIK is specific for each model and usually use LUT's and blocks interconnected together) but rather a logic circuit which is equivalent of some Verilog code.


texts: Need help understanding my voltage measurements

texts:
I have a device connected to a power source (2 AA batteries hooked to a DC-DC step down buck, set to 2.5V).

When the device is connected, I read 2.2 V on the output of the buck. When it is not connected, I read 2.5V on the output.

Now, I need 2.5V for my device, which reading is correct?


texts:
I've seen this packaging used by many companies, specifically in mobile equipment, automotive ECU's, marine, and other harsh environment applications.  I doubt all these manufactures are making the packaging for themselves, so it must be some sort of standard format that I can purchase.

To describe the packaging, I would call it a rectangular box that's a solid plastic housing on 5 sides but one, that normally has a single PCB counterpart that slides down in and has a 'cap' on one side of the PCB.  Sliding the PCB into the until the cap 'clicks' into place gives it a watertight seal.  The cap usually has 1 or 2 Deutsch style or other automotive connector.  Additionally the main housing usually has 2 tabs off it for an M8 / 1/4" bolt to secure it to a flat surface.

Some examples:

Any info on this would be appreciated.


texts: What are the methods to encode Finite State Machines?

texts:
I'm a bit confused about these topics. I already studied combinational systems, and went for Karnaugh Maps and Quine McCluskey methods, so now I studied sequential systems and I'm supposed to study the equivalent methods which are actually related to Finite Machine States.

I read some about tabular method, and partitions in one book. Also, I read that Karnaugh Maps can be also used... And even I think it's possible to generate Finite State Machine in both Moore and Mealy models?

I really need to understand this but I'm confused cause the bibliography at my reach is not consistent and some are related to the higher lever computer science view.


texts: If power lines are properly insulated, why do we see sparks/arcs in videos these days?

texts: I saw a video where power lines touched due to high speed air and created huge arcs. In another video, a person throws a wire in air, it touches a wire and he gets shocked. Also it is said that birds are not electrocuted because they do not short +ve and -ve wires. Why shouldn't the answer be power lines are insulated by rubber?


texts:
I'm trying to run some basic code from my textbook onto a PIC18F4321, using the latest XC8 compiler. It's supposed to turn on an LED after 10 seconds, but the LED never turns on. I've checked my wiring and tested the port and it should all work fine. I try debugging via Pickit 3 and running it as a simulated version and the interrupt never triggers, which leads me to think something is wrong with the timer. Any ideas on what might be causing the interrupt to fail?

#include <pic18f4321.h> //include necessary header
#pragma config OSC = INTIO2
#pragma config WDT = OFF
#pragma config LVP = OFF
#pragma config BOR = OFF

unsigned char count;
void LEDON();

#pragma code T0ISR = 0x08;
void T0ISR() {
    asm("GOTO LEDON");
}

#pragma code
void main(void) {
    OSCCON = 0x60;
    TRISC = 0x00;
    PORTCbits.RC0 = 0; //start LED off
    INTCONbits.PEIE = 1; //turn on peripheral interrupt
    INTCONbits.GIE = 1; //enable global interrupt
    T0CON = 0x07; //16 bit mode, normal prescale, internal clock
    TMR0H = 0x67;
    TMR0L = 0x69;
    INTCONbits.TMR0IE = 1; //enable timer 1 interrupt
    INTCONbits.TMR0IF = 0; //clear the timer interrupt flag
    T0CONbits.TMR0ON = 1;

    while(1);

    return;
}

 #pragma interrupt LEDON
 void LEDON() {
    PORTCbits.RC0 = 1;
    INTCONbits.TMR0IF = 0;
}


texts: STM32F405 Setting Clock Freq Less than Max 168 MHz

texts:
For STM32F405 the max system clock frequency is 168 MHz. I want to run it at marginally lower frequency only for the sake of safety and reliability because my application will run non-stop through out a year without going into low power sleep mode. Should I select a value for SYSCLK or HCLK as a power of 2 (example 128 MHz) or can I select any value (example 150 MHz or 148 MHz etc)?

Edit:

Jitter info added below:


texts: Generating a circuit that match a given boolean function using bi-decomposition

texts:
I am looking for an step by step explanation of how to get the circuit of an given boolean function using bi-recomposition.

I have a given function like:

  f(a,b,c,d)=abc~d+ab~cd+a~bcd+~abcd

The normal ways I know are:

A.) Karnaugh plan:

k-map:

result:

DNF: f=~abcd + a~bcd + ab~cd + abc~d
KNF: (~a+~b+~c+~d) * (a+b) * (a+c) * (b+c) * (a+d) * (b+d) * (c+d)

DNS in Gates(a~bcd):

B.) Second method: minimisation by Quine & McCluskey:

The rsult is also: f=(~abcd)+(a~bcd)+(ab~cd)+(abc~d)

(tool) with input 1: a,b,c,d and 2: [7,11,13,14]

13 logic gates

C.) Simplifying the function on Wolfram Alpha

The result is: f=(abc)XOR(abd)XOR(acd)XOR(bcd)

11 logic gates

(tool used for visualisation: logic.ly)

D.) With bi-decomposition I found this result:

7 logic gates (performance has to be tested by benchmarks)

But how to get there? A step by step explanation / pseudo code is what I am looking for.


texts: How do the areas of the emitter, base and collector affect their respective currents?

texts: I want to know what will be the effect on current if we change(increase or decrease) the area of the emitter, base, and collector. For example, if we double the emitter area what will be the effect on emitter current, base current, and collector current?


texts:
I have 4 electret microphones for a project, each going to an AC channel. On the general case each mic has to be processed individually but in one particular case, I would like to have an image of a sound being made in front of all the microphones, as faithfully as possible.

Would it make sense in this latter scenario to average electrically the amplified output of all the 4 mics, to reduce the noise of each of them (at least white noise, I'm not talking about for example crosstalk from the ADC clock or this kind of correlated noise)?

Something like that for example :

simulate this circuit – Schematic created using CircuitLab


texts: What's the difference between a 74LS05 hex inverter and a 74LS04 hex inverter?

texts:
It looks like the 74LS05 has "open collector outputs" (not sure what that is) and the 04 does not.

Plus, it appears the 05 is more expensive?

Can someone tell me the difference between the two and when would you use one vs. the other?

Thanks.


texts: How do generate a negative supply for op amps ICs?

texts:
I know if you reverse + and - on a voltage supply you can measure a negative voltage using a multimeter, but for an op amp they only have one negative pin so I don’t think reversing + and - would work because you would be connecting the - voltage terminal to ground, I’m a little bit confused about how to achieve this, could you please explain how to get a - supply rail
Thanks,
Be


texts: How to access the selectmap pins (both hardware and software) in Virtex 5 development board?

texts:
We are trying to interface a Raspberry Pi with an Virtex 5 dev. board to read the configuration memory. We have decided to use the selectmap protocol and we understand the signals involved and sequence of commands.

But where are these pins on the board, is it hardwired or should we set the pins in ucf file? Or is there any other to access these pins at all?

We can't find the answer in any of Xilinx's resource documents. The board in general is Virtex-5 development board, in particular XUPV5-LX110t


texts: How can electrons in a tungsten filament release infrared light photons?

texts:
I have a question regarding electric circuits, specifically when it comes to converting electromagnetic energy into light in a light bulb (tungsten)filament. How can an electron in a tungsten atom of the filament release infrared light photons once it comes back to its original state, after being excited by kinetic energy from the electric current. Where do the infrared light photons come from?
“When heat is transferred to an atom, it starts to vibrate more quickly. This vibration is a form of kinetic energy. Some of the kinetic energy is transferred to the electrons around the nucleus. This makes them “jump” from their usual shell into a shell that is further away from the nucleus. When an atom’s electrons move out of place like this, it is said to be in an excited state.
This excited state is very unstable, and the electron quickly falls back down to its normal shell, and ground state. When this happens, the electron releases the extra energy it had gained in the form of infrared light photons.These photons are invisible to the human eye.”
From https://letstalkscience.ca/educational-resources/stem-in-context/what-causes-hot-things-glow


texts: I want to send a simple 5V signal to the usb port. The USB cabel's insulation will be removed and connected to a relay which is connected to an electric door system. I think I should write this code in C. Can somebody give me a hint?


texts: SN74LVC1G123 Monostable Multivibrator IC

texts:
Good afternoon,

I was hoping someone could help me understand some of the terminology in this data sheet and how I translate that into a basic one-shot multivibrator that is retriggerable.

http://www.ti.com/lit/ds/symlink/sn74lvc1g123.pdf

Page 11-13 are the description and application portion of the datasheet. My questions are

1)The pins A and B, and how you work with them to trigger the one-shot. My interpretation is that either A or B must be brought HIGH by a transient signal and the other must be LO(grounded) to trigger the one-shot.

2)the term "gated" with regards to retriggering the one-shot while it is still HI to extend the duty cycle by restarting the RC constant (how to retrigger the one-shot before the duty cycle ends).

Any help in understanding the involved circuitry would be greatly appreciated.

Thank you!


texts: Calculate the electric bill of a phone charger (AC adapter input or output?)

texts:
I need to calculate the amount of money I pay for charging my phone with this charger

I know that I need to calculate the watts then kWh, so I multiplied 5 V by 1.55 A to get 7.75 watts and then use that to calculate kWh. I'm so confused though because whenever I asked anyone in my school they would say, "you don't pay for the output, you pay for the input, so what you did is wrong".

Are they right? Why or why not?
What is the correct method?

Note: I'm not looking for a very accurate number because I don't wanna use a Kill-a-Watt. In addition, I watched a video of someone using it on their charger and it gave a number around 4 or 5, that makes me think my teachers are wrong.

Phone battery
I'm adding info about the battery since some of you asked for it.
It's a Samsung secondary Li-on battery. Nominal voltage 3.85 V / 11.55 Wh. Charge voltage 4.4 V / 3000 mAh.


texts: Trying to understand relay power limits (strictly for DC)

texts:
Let's say I had three batteries in series with two SPDT relays such that the circuit goes relay1->battery1->relay2->battery2->relay3->battery3->output, such that the relays either connect to the next battery in series or bypass it and connect directly to the next relay. This would allow me to turn the relays on and off to change the voltage of the output, such that it could see any combination of batteries 1, 2, and 3 - for example, if relays 1 and 3 were active, the output would "see" batteries 1 and 3, while if no relays were active the output wouldn't "see" any of them.
If each battery were rated for, say, 10 amps, how would I go about determining what DC power the relays need to be able to handle in order to operate safely? Would it be as simple as the voltage of the next battery times the current limit (in this case, 10 amps)? Or do situations such as having relays 1 and 3 active without relay 2 mean that relay 1 would need to be rated for a power equal to the voltage of batteries 2 and 3 times the current limit?
If the latter, is there any way to achieve this functionality if I had a long string of batteries in series? It seems that the power requirements would scale fairly quickly. I'm not really sure how I'd go about speccing relays for a situation such as this, as I'm fairly new to them, so help figuring out what exactly I should be looking for would be appreciated, as I'm pretty sure I couldn't just pick any "10A DC relay" and call it a day.


texts: How can I determine the inductance of transformer winding given a specific power parameter?

texts:
I am searching for a way to determine the inductance of a transformer, either primary or secondary. Example: I have a isolation transformer  that can carry
1000VA 115(primary) to 230(secondary) VAC.
Which means that the transformer is capable of delivering 4.3Amp RMS at 230V.
Is there a way that I can determine what is the inductance of the secondary of that transformer. I looked at the other question posted,
titled: "How can I calculate the inductance of the primary of a transformer given a specific load on the secondary"
The answers given are a bit off subject and do not supply an adequate answer.
Thank you for your help.


texts:
I'm working on a project that involves reading battery voltage via a headphone/microphone jack.  The batteries will vary between 3.0 - 3.6V.  I'd like to convert that voltage to a frequency (linearly if possible) and perform an FFT on the signal to pull read the voltage from it. Since the headphone/microphone jack uses a sampling rate of 44kHz, I'm limited to an upper bound of about 20kHz.  This is the maximum output frequency I can generate from the headphone outputs, or read in with the microphone.

I first looked at a LM331, but it cannot operate at the low voltage I'm using.  Next, I looked at the AD7740, but its input clock requires a 32KhZ minimum input reference clock, so I could not generate that using my system.

Since it's looking like I cannot get a continuous mapping of voltages to a range of frequencies, I'm deciding upon using a series of high precision zener diodes that will enable different resistors to be used in a LMC555 astable oscillator circuit.  This way, I'll know if the battery voltage is 3.0-3.2V, 3.2-3.4V or 3.4-3.6V.  Each Zener will have a different resistor, and the resultant 555 square wave will be filtered to eliminate higher harmonics, then fed into the microphone and a FFT will be performed.

Example: 3.0-3.2V = 1kHz.
3.2-3.4V = 2kHz.
3.4-3.6V = 3 kHz

I've come to stackexchange to ask if anyone knows of a better way, such that I could achieve my original goals of a linear map of voltages to frequencies?  (keeping in mind the constraints)


texts: Mysterious noise of a CAMAC based digitizer

texts:
I'm trying to find out the cause of noise of a CAMAC based digitizer, which converts analog signal to digital signal. It basically functions as an ADC.
The input of the digitizer is connected to a sinusoidal signal from a function generator. Data aquisition is initiated using a trigger manually each time. I show two example outputs in the figures.

As shown in the figures, the noise seems to appear at a random time during data aquisition. Before the initiation of noise, there is no siginificant noise.
What kind of reasons can cause this type of noise?


texts: Connecting a battery powered circuit to the earh ground

texts:
In the following circuit what would be the effect of tying a circuit to the ground from the -2V rail ? I know that no current would flow to the ground since there is no closed loop formed, but assuming the ground is at zero volt level, would the ground pull the -2v rail to zero and change all the node voltages in the circuit accordingly ? And does a setup like this have any usage in real life applications ?

simulate this circuit – Schematic created using CircuitLab


texts: Altium off sheet connector vs net vs ports

texts:
I have difficulties to understand what are the differences between a net, a port and a off sheet connector.

I particularly don't understand when to use a port and when to use a off sheet connector when there are multiple sheet.

I see sometimes people use port and sometimes they use off sheet connector, while I still read that only net can be used in some situations.


texts: I am repairing some ozone generators and one of them has a tower with a discharge path I can't seem to get rid of.  Back in the heyday of television, my dad ran a side (hobby) business repairing bw tv's.  Occasionally, he would use what looked to me (a 5 year old) like red varnish labeled "Corona", not the beer.  Bing isn't giving me extreme happiness finding the product, so I assume it is now history.  Does anyone have recommendations as to what to use?


texts:
I've never seen a capacitor that looks like this, and I known blown ones are either in pieces or typically bulging. This looks like compound I've seen on CRT rings and pots, put there by the factory to show something has been calibrated and not moved since, but why would they put it on a cap like this? Just to show it's original?

I'm assuming of course that I'm not way off base and this cap is blown. This is a 100V power board that I'm reasonably sure has been connected to a 220V source at some point, the fuse to the left is clearly blown.


texts:
Voltage across emitter and collector of QA is 0.7V.

In a current mirror, why is it such that when the voltage across the collector and emitter is different for Qb than QA the value of Iout increases whilst Iin is constant?


texts: Low voltage LED bulb or jump into line voltage?

texts:
I'm not even sure if this is appropriate StackExchanage community for this but I wasn't sure where else this sort of question would fit.

So I tinker with electronics here and there and primarily it has been with DC power (batteries for the most part). I have in a mind project for a simple dimming lamp and I would like to use it introduce myself to AC power although I'm unclear about a few things. The basics of the project I have in mind requires a power source, a dimmer, and a light bulb but I'm struggling to figure out if I should go with an AC adapter as the power source (a wall wart) and use a low voltage dimmer/LED bulb (12V or something of the like) or just dive into full line voltage using the proper dimmer/LED bulb.

I understand that line voltage is more dangerous but it does remove the bulky wall wart and the require for low voltage components. I'm looking to use a LED bulb that imitates an Edison style bulb I don't think I have found one that is more low voltage use (I could simply be mistaken).

Would it be a large pain to do this using an AC adapter and much simpler to use the line voltage provided by my house? Lastly, are there any good resources I could look at around tackling projects when using AC power (especially higher voltages and amps as are provided by households)?

Thanks again and sorry for the odd question.


texts: Strange voltage reading on ungrounded system

texts:
On a small scale off-grid PV project I received a strange voltage reading and I am hoping that some folks here could possibly shed some more light on what exactly was going on and why. Here is the background:

375W pure sine wave inverter outputting 220V.
Ungrounded system
I have left out all other extraneous details and circuits from the attached drawing.
One lighting circuit that that was roughly 100m in length with a switch controlling four lights.
With the switch open and no bulbs in the sockets I received a voltage measurement of roughly 28V. I understand that on an ungrounded system with no bulbs in the socket and an open switch the length of wire that I was taking a voltage measurement to effectively had no reference to the system.

My questions:

why 28V? Why not 0?
Can you steer me in the right direction to be able to understand this better?


texts: Driving two large 7-segment displays using Arduino and shift registers

texts:
I recently started a project in which I want to control two 7-segment LED displays using two shift registers (74HC595) and my Arduino. I thought I had the basic ideas mastered, but I ran into some complications and I could use some help.

For this project, I wanted very (physically) large digits. I purchased two of these giant 6.5" 7-segment displays from Sparkfun. They are common anode.

The first thing I realized is that these displays likely need more than the 5V that the Arduino will supply. So, I'm guessing a different source will be needed. I'm hoping that a 12V battery would do it, but I'm not sure. I'm also a little uncertain what that implies for my circuit... does that mean I'm going to need a relay?

I also realized that I'm uncertain about the resistors I need here. I'm not sure if I'm reading it correctly, but the specs seem to indicate that there are 12 individual LEDs in each segment (five in the decimal point, which I probably don't even need for this).

The specs indicate 20mA forward current and forward voltage of 11.6-12.4V, but I don't understand if that's per LED, per segment, or for the whole display.

One other point - I intend to use multiplexing (or charlieplexing?) to cycle through and turn on individual segments to reduce power consumption at any one time. (I was thinking that if I did one segment per display, that means only two segments, at most, need to be lit at any one time.)

I'd really appreciate any advice here. It would be great if someone could put together the entire wiring diagram, but I'm happy to take a crack at it myself if somebody can answer some of the key questions. (i.e., power source, resistors)


texts: Protecting a relay/SSR when driving AC window cover motor

texts:
I'm having trouble switching an AC motor. Relays spark and glue contacts, and SSRs start to flicker and not pass the full input after a while.

The motor has 3 terminals for 230VAC mains. One is common, one is UP, and the last one is DOWN. common and one of the other ones has to be connected to mains for the motor to move.

The SSRs I tried are rated for 2A 240VAC (FINDER 34.81-8240), use a triac (So inductive kickback should not be a problem), and have zero-crossing turn-on (So inrush current from the motor and it's kickstart capacitor should not matter)

Having ran out of ideas, I tried to switch the SSRs to mechanical relays (rated 8A). Unfortunatelly, they seemed to get stuck after a while. I could see no sparking on closing of the relay, but a massive spark when opening it. (Sometimes, I guess it depended on the phase of current).

So I tried putting 2 RC snubbers (120Ohm, 0.1uF), across UP-common and DOWN-common, parrarel to the motor (To protect two relays), but that didn't seem to change the sparks at all.

I cannot use a bigger relay and would rather not use any unstable components like MOVs, as this setup resides inside walls.
I thought of zero-cross current detection for opening the mechanical relays, but apparently they are too slow.

How can I protect the relays/SSRs so that they don't fail?

EDIT:
I should also propably mention, that the relays are controlled directly from a PLC's digital output module (Unitronics IO-TO16) connected to A2 on each SSR/relay. The only relevant part of the program, esures that they are never on at the same time. (Though, I didn't really see any damage with stuck relays in such condition). Also, I had some other SSRs, which failed differently. Some would start flickering, but more interestingly, some would work normally themselves, but cause SSRs AND relays NEXT TO them to flicker, as long as they had mains connected to one terminal.

simulate this circuit – Schematic created using CircuitLab


texts:
As a tinkerer, hobbyist, wannabe-'maker' (as in the protagonists in the Make magazine), sometimes I feel the lack of better tools in some projects, although for most, I can make-do with my DMM for test/measurement. Have been considering buying a basic 2-channel DSO, because I am having some timing issues which I'd like to investigate. I have used a DSO back in school for a semester, as part of an Analog electronics elective, so I think I can manage to refresh and learn.

The latest project for which I felt motivated to buy a DSO, involves some RF based sensor network. The RF in question is the 315MHz/433MHz kinds, with the prototyping being done around a 80MHz Cortex-M3 MCU based board.

Other than that, at the moment, I do not foresee much analog projects. Given my nature of requirement, can someone confirm if a 50MHz 2-channel 1Gs DSO would be good enough ? I am not very keen on used CROs, since I believe there is a bit of gamble with used stuff, and chasing for returns/refunds is no fun, especially for online transactions.


texts:
I am reading this document : https://www.nxp.com/webapp/Download?colCode=AN3869
I got this link from NXP support, but I did not get a precise answer to my questiosn and I would like to be sure :

The NXP support told me that link training exists between MAC and PHY over SGMII. By reading this document, I assume that the link training is about auto-negotiation. However, link training is usually not about auto negotiation, but about having a proper signal on the cable, so I am a bit confused
MAC does necessarily have a MDIO connexion with PHY if SGMII is used. Indeed, auto negotiation is based on the 1000BASE-X standard and capabilities ares exchanged over the SGMII cable. But there are plenty of other registers in the MDIO that you can/should configure. How do you do this ? Does the information go through the SGMII connexion too, or is there ALWAYS a MDIO connexion between MAC and PHY?

Thank you for your time!


texts: Designing light blinkers using 555 timer ic

texts:
I need to design light blinker which are mostly used on road side for indication purpose. Their main purpose is to blink with a rate of 500ms or 1sec. These type of circuits contains two PCBs, one is 555 timer circuit and another one is led circuit. Now I have studied about 555 timer and have calculated the values of resistance and capacitance required for 1sec blink. Following is the circuit for timer:

So I have used a R1=1K R2=150K C=10uF. At the output pin I connected a led via 330ohms resistance and led was blinking with 1sec delay. Now I need to design the led circuit for blinker. Total leds will be around 170 and I need to control all the leds with this 555 circuit and blink them with 1sec. Now I am confused how to design this circuit. How to connect all the leds(parallely or in series) to avoid voltage drop. I will be using 5MM led with 330ohm resistor. I guess I need to connect them parallely to avoid voltage drop but I am not sure. Is there any other circuit I need to add to avoid voltage drop. Does anyone has already made such kind of circuits. Any help or reference guide please. Thanks


texts: What is the use of 'import' in SystemVerilog?

texts: Once a package is included the file is compiled. Then why it is required to import same package ?


texts: Low voltage signal passing through microcontroller

texts:
Can microcontroller work like switches for low voltage analog signal. I mean when press the button
signal (less than 300 mV, very low amperage) pass unchanged through microcontroller (one analog input,
one analog output), than by software disable input and output or simply turn off power (same button)? I want to
solve that without external switches and relays. Thanks.


texts: Do I need to tie every ground pins of esp32 wroom 32 to the ground

texts:
Which is the proper way of grounding for the module

To avoid the ground loop I think fig. A is the best.


texts: How to use a TL431 for PMOS based reverse polarity protection?

texts:
Consider the following illustration:

I wonder if it possible to replace the zener with a TL431. The usual application of TL431 supplies specific voltage to next stage but the zener here supplies voltage Vin - Vz to turn the pmos on.


texts:
I am using a 555 IC to produce a sound in a small 8 ohm speaker. It works just fine, but the square wave sounds rather harsh. I am wondering if there is a simple way to round out the corners to make it sound better. All the circuits I have found online are rather complex. It seems to me that a simple RC circuit should do the trick, but I have not been able to figure out how to position it.

Any help would be greatly appreciated.


texts: PCIe DIY protocol analyzer / packet spy / monitor - project

texts:
I'm interested in making a device that I can plug into a PCIe slot that can capture PCIe protocol packets.
Along the same lines find a low cost solution so a hobbyist can make their own PCIe interface devices.

For now would start out with a x1 or x4 and work up to an x8 lane device.
(With a x1 lane monitor would it still see x8 packets?)
Is there a low costs solution for this, some DIY logic analyzer that can be tapped into to the PCIe bus?

There are commercial solutions for this but they are somewhere in the $10,000 to $40,000'ish range for a x8 or x16 system.
I'm assuming that they are either terribly complex, and, or to stay in business, to be profitable, they need to be in this price range for the relatively small market they probably have.

In perspective though, I can go to the electronics store and buy a card (network or USB adapter, cheap sound card, etc.) that has a PCIe x8 controller that costs just ~$50.

There has to be a solution where I can buy a PCIe controller chip, and, or one of these said product boards and hack/repurpose it for a protocol analyzer/packet spy/monitor system. In particular if any of these controllers (if "smart") can be reprogrammed/flashed.

Maybe an existing FPGA prototype board can be used for this? They might be in the $1,500 to $5000 range, but at least that's getting closer to a hobbyist budget.

From a ground up DIY solution I see some kind of circuit that takes a PCIe prototype board (seen them in the $500 range), has any required minimal bus buffering/interface, hooked up to an FPGA that is programmed to stream the high speed PCIe packets onto onboard buffer RAM, setup so the RAM can be streamed over USB where a second computer (or microcontroller, etc.) can read and store them.
Then yes I'd have to write the user interface software for it as well.

Any suggestions, anyone make their own DIY solution for this already?

Thanks,


texts:
During RS485 transmission, what is the absolute voltage change in the TXD+ and TXD- pins in RS485? Do they swap value (IE if TXD+ is sitting at 4V quiescent, then it goes 4v 0v 4v during transmittion) or do they just move "differentially" (IE TXD+ goes 4v 3.5V 4v and TXD- goes 0v 0.5V 0V)?

Background - but not my actual question:

I'm trying to understand a problem that is being debugged (not by me) on a project that I'm associated with.   I only get to hear about it from the side.

The explanation for the problem that I am hearing is that one RS485 device is using voltages (absolute) that are too far apart for the other device.   That is to say: that the "master" has it's TXD+ and TXD- sitting at (say) 4v and 0v, wheras the "slave" can only cope with these being at 3V and 0V respectively.

This got me wondering how does the "differential" transmission work in the first place?   When this master transmits alternating bits, does it swap TXD+ and TXD- between 0 and 4V, or does it do some small differential change on them, like dropping TDX+ to 3.5V and raising TXD- to 0.5V?   Would that be valid?

If it's the latter, then I can understand the explanation.   But if its the former, then the explanation makes no sense...


texts: Why is there a huge difference between Is2(peak) and Is2(rms) in flyback converter?

texts:
I try to design a flyback converter which has two outputs.
First output is main output 24V/1A and second output is for Vcc 18V/0,02A.
Total output power -> Po = 24,4W
Efficiency = 85%
So, input power -> Pin = 28,7W
Input voltage is changeable -> VminDC = 70V & VmaxDC = 140V
PWM frequency -> fs = 470kHz
Reflected output voltage -> Vro = 48V

Calculated Dmax = 46%
I selected ripple factor -> Krf = 0,5 for CCM

Primary inductance -> Lm = 60µH
Because of this inductance value;

Problem begins here.
When I tyr to calculate secondary peak and rms value, I'm getting some results that I don't understand.

Turn ratio for main output (Is1) (24V/1,5A) = 2:1
turn ratio for Vcc output (Is2) (18V/0,02A) = 2,7:1

Ip(peak) = 1,51A
So
Is1(peak) = Ip(peak) x Np/Ns1
IS2(peak) = Ip(peak) x Np/Ns2
Is1(peak) = 1,51 x 2 = 3,02A ( output current is 1A )
Is2(peak) = 1,51 x 2,7 = 4,03A ( output current is 0,02A )

What does it mean?
There is a huge difference between Is2(peak) and Is2(rms), although the Is1(peak) and Is1(rms) values are close to each other.
How can I calculate the secondary peak and rms current in generally. What is wrong thing here?


texts:
I am using task in my module in verilog coding, and facing problem,  in passing the argument values. actually The variables defined in the task block as input are not receiving the values that are passed to them while calling this task.
Here is the code

module carry_addr(Cin,A,B,Sum, Cout,rst_n );
parameter width=3;
parameter bits=1;
input [width:0] A,B;
input Cin,rst_n;
output reg [width:0] Sum;
output reg Cout;
integer k;

reg [width+1:0]C2;

task fulladder;
input A1;
input B1;
input C4;
output reg Sum1;
output reg C0;
begin

        Sum1=0;
        C0=0;
      {C0,Sum1}=A1+B1+C4;
end
endtask

task automatic ripple;
input [bits:0] A2;
input [bits:0] B2;
input C1;
output reg [bits:0]sum2;
output reg cout;
reg [bits:0]sum3,sum4;

reg [bits+1:0] C,C3;
begin

            sum2=0;
            sum3=0;
            sum4=0;
           cout=0;
            C=0;
            C3=0;

            C[0]=0;
            C3[0]=1;
            for (k=0;k<=bits;k=k+1)
            begin
                 fulladder(A2[k],B2[k],C[k],sum3[k],C[k+1]);
                 fulladder(A2[k],B2[k],C3[k],sum4[k],C3[k+1]);

            end
            if(C1==0)
            begin
                cout=C[bits+1];
                sum2=sum3;
            end
            else if(C1==1)
            begin
                cout=C3[bits+1];
                sum2=sum4;
            end

end
endtask

always@(rst_n or A or B or Cin)
begin
    if(!rst_n)
     begin
            Sum=0;
            Cout=0;
            C2=0;
     end

         C2[0]=Cin;
         for (k=0;k<=width;k=k+bits+1)
         begin
              ripple(A[k+:bits],B[k+:bits],C2[k],Sum[k+:bits],C2[k+bits+1]);

         end
         Cout=C2[width+1];

end

endmodule

in this specifically, A,B 's values are not copying in the A2,B2 variables in the ripple task.


texts: Vref value and Vref shunt ICs for an ADC

texts:
Hello i am building an ADC circuit, this is my first time building a proper adc that is higher performance. The adc is the ADS131

The ADC will be powered by an isolated 3.3v and I would like to know what would be a good Vref voltage value would 3.3v just be fine. What is the popular convention for this stuff.Where i plan to use this adc is to measure low voltage AC differential signals. The adc is 24 bits and would like make effective use of as many of those 24bits

I am also planning of placing a voltage reference IC but there are several types and do no know which ones are the best. Since the ADC is powered by 3.3v i would most probably need to use a reference voltage below 3.3 because of tiny voltage drop out would that be okay? or i have to find another supply for the Vshunt IC. Is there any notable difference in using a fixed like this one and and adjustable version like this one


texts: Bluetooth communication with smartphone, options?

texts:
I am working on a device which I may want to consider mass producing. The device connects to a smartphone over a Bluetooth connection. For prototyping purposes I have used the very common HC-05 module which makes life very easy. But I do not expect that this device would be ideal for mass production as I can't find a good source for a lot of them and they are expensive (perhaps I am wrong about these arguments) as opposed to a SoC. I was considering the NRF8001 but the problem is that it seems to be a Bluetooth low energy chip, so a lot of older smartphones won't support this. I read somewhere that this chip supports both BLE and Classic, but can't find out about this definitively. I pretty much read through the entire data sheet, and am quite happy with the way this chip is expected to work otherwise and am ready to purchase the $99 dev kit.

I also found the CC2560 from Texas Instruments, but I can't find a lot of information on it aside from the TI website, so am not sure if it's the best solution. I'd rather use something popular so that I can get more support.

I am relatively new to the world of embedded systems, and I definitely do not intend for this to be a shopping question, but I would like to know what you all recommend (i.e. are any of the above solutions viable, or are there other chips/modules out there I should consider)? I find the SPP (Serial Port Profile) very easy to use, and substantial for my needs.

I don't have any intense technical requirements. If I can send a byte of data every second or so, I am more than happy. The range does not need to exceed 5-6 meters. I am interfacing the Bluetooth chip with an AVR microcontroller. I am fine with using the USART, SPI, or I2C to communicate. In terms of cost, it should be a cheap solution ($3 - 7). Using things like Rn-42, JY-MCU, etc. are fine for proof of concepts, but don't make the cut for mass production.

Please let me know if I need to add any more information.


texts:
I am making a drone with an Arduino Nano.
To power my brushless motors and my ESC (Electric Speed Controller), I use a Lipo battery which is connected to a PDB (Power Distribution Board).
I did not find a way to get the voltage value on my Arduino.
How can I get the voltage value of my Lipo battery (in a float value for example) on my Arduino ?
Like the module "1S-8S LIPO ALARM VOLTAGE TESTER" for example but that will return the value and not display it to me.
My material :
Brushless Motors DX2306 2400KV 2-4S :

ESC BLHeli_32 Bit 35A 2-5S :

Lipo 4S 1800mAh 14.8V 80C :

PDB Matek 6 ESC Output : (The manual of how my PDB works in a link)


texts: Transformerless Power Supply High Current

texts: Is there any way for Transformerless Power Supply to output a High Current like 10A to 15A at 12V to 24V. I found highest of 500mA current output for Transformerless Capacitor Power Supply. I wanna use it for Lab requirements for an Electronics Engineer. Like running an Amplifier at 7Amp .


texts: Adding power to a circuit and voltage regulation

texts: Does the power provided to a circuit affect the voltage regulation? For example, if I have a circuit with a LM7805 regulator, how does a 15V power supply compare to a 20V power supply powering the circuit?


texts: How is electromagnetic interference possible when measuring voltage difference?

texts:
This question is primarily concerned with audio but it's probably applicable to other areas as well.

As far as I understand, EMI is caused by electromagnetic waves adding power to wires as they transmit a signal. Let's say you are transmitting an audio signal and the reference voltage wire is at zero watts and the signal wire is at one watt.

Now imagine you have the world's worst EMI and it causes an extra watt to be added to the signal wire and the reference voltage wire. The difference between the wires is still two so the signal hasn't changed. What gives? Why does EMI cause nasty noises at the other end when it would presumably be changing both wires' power equally?


texts: Weird H Bridge measurements: BJTs of Mosfets?

texts:
I'm trying to use the H bridge on the main board of a robot whose microcontroller I removed.
It is connected to a small motor and contains 4 SMDs named 5CW and 6CW. After painstakingly soldering small copper cables to the control traces and powering it at 6V, the current limit kicked in. It actually draws around 1.4V (looks like the positive rail is connected through 2 diodes to the negative).
Now the board contains other but few components (3 leds, couple of resistors and 2 BJTs) so I can't be sure what causes this "short" circuit. Using diode measurement on the Vcc-Ground gives 570 and G-Vcc 474.
This is the H bridge diagram:

simulate this circuit – Schematic created using CircuitLab
Diode measurements for the H bridge:
Q1:  BC: 936, CB: 450   BE: 1260, EB: 450    CE: 880, EC: 565
Q2:  BC: 933, CB: 428   BE: 1263, EB: 448    CE: 884, EC: 564
Q3:  BC: 457, CB: 920   BE: 456,  EB: 1245   CE: 568, EC: 881
Q4:  BC: 456, CB: 918   BE: 456,  EB: 1243   CE: 568, EC: 880

From the BC and BE measurements I thought these were BJTs (Q1, Q2 PNP and Q3,Q4 NPN). But the CE and EC measurements are weird. Perhaps they are correct for mosfets?
Note:

There are two H bridges including this one that have the same measurements so I find it hard to believe that every bridge and BJT was burned. I believe only the original microcontroller, which I removed, suffered the burn.
While testing Q1,Q2,Q3,Q4 the motor was disconnected and as such all collectors are not part of any circuit except that of the bridge. Also all the gates are disconnected.
My multimeter just shows a value when measuring diodes. I never understood what it meant (drop voltage?).

It's hard to do any diagnostic on such a board. Nevertheless, with this data, does the H bridge behave as it should measurement-wise?


texts: Why is the current before one end of a resistor the same as the current after the other end?

texts:
I know that resistors are used to limit the value of the current flowing in a circuit. But why is the value of current the same before it enters the resistor and after it leaves it? I do understand that it creates a congestion for current flow. But why do they have the same values?

In the above circuit, the value of current flowing Between \$B\$ and \$C\$ is 0.5 Ampere, and the value of the current flowing between \$C\$ and \$D\$ is also 0.5 Ampere. Why and how is it that they are equal? Shouldn't the current flowing between \$B\$ and \$C\$ be greater than that flowing between \$C\$ and \$D\$?

Thanks in advance.


texts: How might I find the pinouts for a bluray laser assembly, or figure it out in the absence of one?

texts:
I'm not sure if this is the right place to post this question, but I think it is!

I have a bluray player (HLDS BN20) that stopped working.  I know the lasers inside are reasonably powerful (and dangerous to one's eyes), but I thought it would at least be worth a shot to get some eye protection and then fire up the bluray laser to see if I can melt sugar with it.  The problem is, the assembly is very well sealed and I don't want to risk damaging anything.  There is a FF cable attached to it with many wires, and I can't possibly think of why there are so many.

Here are a couple of pictures:

All posts I have seen on the web from people hacking lasers out of drives just hook them up to batteries -- why don't they use the power circuitry in the laser housing?


texts: EagleCAD symbol shows 4 leads for 3 lead voltage regulator

texts:
I'm curious as to why the following image of a MCP1827S-3302E/EB voltage regulator, which has three legs shows up with 4 legs in EagleCAD.

I noticed that there are two ground pins, GND and GND_2 in the schematic, why is this?


texts: Connecting hifi sterio speakers to my pc

texts: My computer speakers have finally packed up( 12 Years old...Is it possible to utilise and connect to pc my large sterio speakers from hifi system( No longer used )  It seems a shame to discard these big speakers.


texts: Why do we need biasing components for an RF switch if it is based on active components?

texts:
I would like to know why an RF switch need biasing components if it is based on active components.

Thank you very much.


texts: How would you get the bandwidth of a MIMO system

texts:
I found online that:

(SKOGESTAD; POSTLETHWAITE, 2005, p. 81) bandwidth of a MIMO system is the frequency where the maximum singular value of the sensitivity function matrix crosses 0.707 (-3 dB) from below.

For SISO systems the bandwidth was w.r.t. the bode plot of the closed-loop transfer function, which got me a bit confused.


texts: Type of Wideband Transformer for Measuring 120 V AC signal + EMI

texts:
I'm looking to measure line EMI on a standard 120 V AC power circuit using some kind of transformer or other sensor. The device I'll be using to measure the waveform is an Ettus Research USRP N210, which has a very fast ADC (up to 50 Msps), but very limited input power capability (-10 dBm max). The USRP has an input impedance of 50 Ohm, so I'd want a transformer with a turns ratio of about 6000 or more (gives me a 10 dB safety margin). Wide bandwidth is also a requirement, as we would want to see as many higher harmonics as possible (frequencies up to 10 MHz would be ideal).

Is there a type of measurement transformer that is ready-made to do this kind of thing? What are some search terms I would use to narrow my search on Digi-Key, for instance? Also, having some protection against sudden voltage spikes would be nice as well.

I recognize that the USRP is not really made for measuring power signals, but this piece of the system cannot be changed-- the only thing we can change is the transformer. The main reason we are using the USRP is that we need the high sample rate provided by an RF device for the types of signals we will be analyzing, and this is all that we have available in our lab that can do that.


texts: Can I replace one with the other? L7805CP, L7805CV

texts:
Are those chip equal in a circuit?
L7805CP,   L7805CV
Can I replace one with the other to try to fix a broken circuit board?


texts: Difference between different resistor configurations with optocoupler

texts:
I have 2 resistor configurations for an optocoupler.
The first one (on the left) is the one I've used in some previous circuits.
The second one (on the right) is something that I saw on the internet while doing my research.
If I'm not mistaken, the second one is based on a voltage divider. Though the first one works well enough for my circuit, I wanted to know which one is correct or incorrect.
If correct, which one is:

More efficient
More reliable
Adds longevity to the optocoupler's internal LED.
Finally, which one I should prefer (apart from the additional minimal cost on the second one for extra resistance.)

Schematic showing different resistor configurations on an optocoupler:


texts: I/O voltage compatibility checks as part of design rule checks during schematic design

texts:
Schematic design programs have concept of design rule checks. What exactly does this feature check?
Can it check if the input voltage on different pins of an IC is compatible with its I/O voltage? For this the schematic design program would need to have concept of I/O voltage, power supply voltage and be able to work out if they are compatible or not. This means that one can find out if we are driving a 3.3V input buffer from a 5V net or driving a 5V input buffer from a 1.2V net.


texts: 5V UPS circuit with NiMH joule thief backup

texts:
I'm trying to design a UPS circuit for microcontroller backup. Require 3.7-5V, and less than 50mA for 10 seconds every 15 min. Power cuts in my area are never longer than 3hours, and occur rarely.

I'm wondering if the inductor of the oscillator drive part of the joule(!) thief can be made any simpler.. i.e. can be replaced with something else that I do not have to wind myself, or maybe a capacitor...

The simulated output shows 4V at about 70% efficiency on battery. Trickle charge is continuous and fixed at about C/100. Should take 100 hours to charge the cell, which can supply power for a week of downtime. I'm guessing the NiMH will always be above 1.2V, and should not be damaged at 10mA charging current. Joule thief part draws about 2mA with no load, or when powered from mains.

I pieced together this circuit from things on the web, so all suggestions will be appreciated.

added:
I was going with the single NiMH because (as has been pointed out by Jasen), there would not be an issue of polarity reversal. Also no fire hazard, no complicated charging circuit (as in lithium), and cheaply available (even older used NiMH would be fine as they would all hold charge for at least a day).

Q3 ensures fairly accurate constant current. I was unable to fix that confidently with a resistor, since I don't know beforehand the voltage and resistance of the NiMH cell. Especially so, since the input voltage after the diode may vary from 3.8V (4.5V USB - 1n4148 drop) to 4.8V (5V USB - 1n5819 drop). But maybe a resistor is possible, as you say. I don't want to let the trickle charge current increase too much as it's always on.

LT1073 costs a dollar, and not readily available (I'm in India). Parts in my circuit cost 5-10 cents and available everywhere. The coupled inductor does mean that I have to wind it by hand everytime though.

I was of course looking for a solution with a single coil inductor (for the boost circuit), and something else to drive the oscillator. That would allow me to use a cheap off the shelf inductor (like they do in the LT1073 and all other chips). But maybe it is too complex to make with a few simple discrete parts...

Another option is the dirt cheap HH004F, but I have been unable to find any complete datasheet (in English or even Chinese).


texts: How can removing a piezoelectric speaker/buzzer damage a circuit?

texts:
According to a comment at DIY stackexchange:

  "...disconnecting a passive piezo speaker that is fed via a transformer could theoretically upset or even damage the electronics feeding it."

How could the lack of a piezo speaker cause damage?
How could a person silence the piezo speaker without simply "muffling" it with tape or similar tactics? (Perhaps replace it with a dummy load? If so, how would one ensure an appropriate load?)


texts: battery life of rechargeable lithium battery

texts:
I am trying to determine the life of a lithium rechargeable battery (approximation) before a complete replacement is required. From Panasonic's datasheet, I see that at avg. 10% discharge, it is rated for 1000 charge cycles. The nominal voltage is 3.1V and the capacity is 5mAh. Assuming this is connected in circuit and will remain near fully charged (won't be using it as backup often), what do I need to determine the life of the battery in hrs/years. From Wikipedia, I see that we can do cycles x Ah x nominal voltage to get total energy delivered by battery over its life. I also see from the datasheet that the cell is rated for ~2%/yr self-discharge rate, but don't know how to use all this information to get an idea of how long the cell will last.

I'm not concerned about an exact answer as I'm aware this is a huge area of research, I just want to get an idea of how to calculate approximately how long it will last with the info I provided above along with the things I haven't been able to figure out I need.

This is a Panasonic ML621 Manganese-dioxide on the anode (I think) and Lithium/Aluminum on the cathode (I might have swapped the nodes).


texts: Arduino audio output via R-2R DAC - biasing output for piezo speaker

texts:
I followed a tutorial on 8-bic DACs using an R-2R resistor ladder.
I am outputting a sine-wave using data from 0 to 255 on pins 0-7.  This goes through the pins into the R-2R DAC producing an analogue signal.

Now I would like to convert this signal into something that can be used by a piezo speaker.  I understand (perhaps incorrectly) that the speaker cannot play this signal because it needs an AC signal, whereas the DAC output is 0 to +5V.

I've read that now I need to "bias" the DAC to electrically subtract 2.5v from the output to make it -2.5 to +2.5 volts.  This signal should then be able to be fed into the speaker. Is this correct? How do I bias this signal, with a capacitor in series?


texts: Issues with simple NiCd battery charger circuit

texts:
Inspired by this circuit, I'm trying the following one for charging 2 NiCd batteries:

simulate this circuit – Schematic created using CircuitLab
There is a current limiter part, with a red LED (D3) indicating that the charging is in progress. The overvoltage protection should be provided by a 2.7 V Zener diode (D1).
The current limiter part is working as expected, delivering about a constant 120 mA current. The problem comes with the overvoltage protection, since the zener appears to conduct enough current to turn on Q2, with the batteries still at 2.7 V. More precisely, I measure a current of 0.35 mA on the zener, with a voltage drop of 1.9 V on it, and so D3 is always off.
My try to fix this was to replace R3 with a lower resistance, namely 20 Ω. With this new configuration Q1 is turned on, with the zener conducting 15 mA over a 3.3 V voltage drop on it (this Zener diode is pretty far from being ideal, isn't it?). Voltage drop on R3 is then 0.45 V, not enough to turn on Q2.
Based on these experiments, I suspect that the value of R3 can probably be arranged in order to turn off Q1 at an appropriate voltage of the batteries (e.g. 2.9 V). Yet, this seems to me too much dependant on the particular components I'm using, and so difficult to predict and calculate. Also, I wouldn't like to rely on such fine-tuning arrangements in order to prevent overvoltage on my batteries.
My question is: is there a way to properly fix this circuit, or is it simply wrong by design?
Thanks


texts: What will happen if I press the GFCI button on an electrical tester when it is connected to a regular socket?

texts:
I know that the GFCI button on the tester engages the safety mechanism on the GFCI protected wall outlet.
My question is: suppose I have a regular wall outlet, which is not GFCI protected, and is only connected to a normal breaker in the panel. The breaker is not GFCI protected, but will trip on shorts or huge current withdrawal.
What will happen when I try to test the GFCI button on the tester?
Will it burn the tester?
Will the breaker trip?
Will I see smoke and sparks from the tester as long as I am pressing the button?
I don’t want to risk losing the tester.


texts: Cleaning with less than pure IPA (isopropyl alcohol)

texts:
I want to clean a SO-DIMM memory that was contaminated with bottled drinking water. This was not "mineral water" intended for drinking. It was the high volume bottled drinking water from one of the world's largest "soda" companies. This device stopped working after the contamination. Obviously this water is not very dirty but the malfunction is strongly associated with a single contamination event.

Will it be effective to use 70% isopropyl alcohol available in common drugstores or must I use a 99.9% product which is certainly available in my area but less convenient.


texts: If my product uses a certified RF transmitter, is it treated specially by the FCC?

texts: So I have a product. It uses the Particle P1 as the microcontroller and WiFi RF setup (with onboard antenna), which is pre-FCC certified; it has a ("Contains Transmitter") FCC ID that you put on the case of the final product. When I go to certify the entire product, do I still to get it tested as an intentional radiator? Does the fact that the "Intentional Radiator" portion is pre-certified make the device an unintentional radiator from a certification perspective?


texts: Accelerating a stepper motor without it making noise

texts:
I am having some issues moving my stepper motors without it making noise.

I read somewhere that ramping the frequency of the pulse modulated signal would help, but seems to have same issues as well.  Is the "acceleration" to steep..?

The stepper motor i am using is a PK244-01A, and it is connected to a driver board, which has requires the input signal enable, direction and step => which is the one i am ramping. Driverboard

HEre is the code:

    void setup()
    {
      Serial.begin(9600);
      pinMode(9, OUTPUT); //Step
      pinMode(12,OUTPUT); //en
      pinMode(13,OUTPUT); //dir
      TCCR1A = _BV(COM1A1) | _BV(COM1B1) ; // phase and frequency correct mode. NON-inverted mode
      TCCR1B = _BV(WGM13) | _BV(CS11);     // Select mode 8
                                           // Prescaled by 8 on main clock.
    }

    float count = 1000; //

    void loop() {
      // put your main code here, to run repeatedly:
      //output_freq = CPU_clk/(2*8*ICR1_value)
      //ICR1 = CPU_clk/2*8*output_freq
      digitalWrite(12,HIGH);

      delay(1);

      digitalWrite(13,HIGH);

      delay(1);
      ICR1 = count;
      OCR1A = int(count/2);

      while(1)
      {
         if(count != 20)
         {
           count -= 10;
         }
      }
    }

The ICR1 value is computes using this formula $$ICR1 = \frac{(cpu_{freq})}{(2*prescaler*desired_{freq}))}$$

Updated the code with @jms answers:

void setup()
    {
      Serial.begin(230400);
      pinMode(9, OUTPUT); //Step
      pinMode(12,OUTPUT); //en
      pinMode(13,OUTPUT); //dir
      TCCR1A = _BV(COM1A1) | _BV(COM1B1) ; // phase and frequency correct mode. NON-inverted mode
      TCCR1B = _BV(WGM13) | _BV(CS11);     // Select mode 8
                                           // Prescaled by 8 on main clock.
    }

    int count = 200000;

    void loop() {
      // put your main code here, to run repeatedly:
      //output_freq = CPU_clk/(2*8*ICR1_value)
      //ICR1 = CPU_clk/2*8*output_freq
      digitalWrite(12,HIGH);

      delay(1);

      digitalWrite(13,HIGH);

      delay(1);

      while(1)
      {

        int freq = (16000000)/(2*8*ICR1);

        ICR1 = count;
        OCR1A = int(count/2);

        Serial.print("freq: ");
        Serial.println(freq);
        Serial.print('\n');
        Serial.print("count: ");
        Serial.println(count);
        Serial.print('\n');
      }


texts: Low cost/complexity bus for expandable modules?

texts:
I'm trying to pick a bus for an expandable system. Requirements would ideally include:

Unknown number of modules (potentially up to a couple dozen).
Multiple identical modules are allowed (giving modules unique IDs ahead of time might be difficult)
Small and cheap to implement (each module can contain a cheap MCU)
Does not need to be long distance, a couple inches at most, but they not necessarily on the same board.
> 1Mbps would be nice.
Shared bus. No per-module select lines, etc. Ideally needs to handle branches and cycles in the bus.

Leading candidate seems to be I2C, but having multiple identical modules is tricky.

I was thinking I could come up with some scheme layered on top of I2C. For example: the master polls for slaves that aren't assigned an address by sending a message to a predetermined "broadcast" address, and modules that don't have an address randomly respond after a certain number of polls to avoid bus contention. The module will respond with a random number + CRC, so if there's contention the master can tell them to retry later. After some number of polls with no responses the master assumes all slaves have responded and can continue with initialization. I think this scheme could be compatibile with standard I2C devices. I don't know whether I2C support built into MCUs is compatible though.

Is this unnecessarily complex? Are there other simple bus protocols that can handle this scenario?


texts: How does a non-FPGA (ie a PC with a CPU, RAM, hard drive) mimic logic gates?

texts:
I know that an FPGA uses look-up tables (LUTs) to synthesize logic gates. A LUT is a block of RAM that is indexed by a number of inputs.  The output is the value stored at that memory address.   The magic is that the LUT can be programmed to display whatever you want for a particular input.  So, a LUT can be programmed with the truth table of any logic gate in order to mimic it! That's how an FPGA synthesizes the logic gates that you specify in your HDL code.

I was thinking the other day, how does a normal computer mimic logic gates?  As far as I know (which is not far), if I write a program in C++, first it must be compiled to machine code so that the CPU can read it.  Then when I press "run", the machine code goes to memory to await processing by the CPU.  I'm not real clear on what happens next, but at some stage the CPU must have execute the logical operations that my program contains, right? Unlike an FGPA, the CPU can't just synthesize whatever resources it needs. So how does it execute the program?

My Guesses:

The CPU has a number of pre-built logic gates. When it encounters an
AND statement in the C++ code it's executing, it uses one of its AND
gates. If it sees an OR statement, it uses one of its OR gates; if it
sees an IF statement, it uses one of its IF gates; etc.
Or, logic is implemented in memory in some way similar to a LUT. This makes more sense to me since it doesn't rely on a limited
number of gate resources. If my program requires tons of OR logic
    for instance, the CPU won't get bottlenecked by a lack of OR gates.

So, how far off am I?

Edit: Thanks for the answers everyone, I learned quite a bit about CPUs and ALUs. Also, the "IF gate" in my first guess is a typo, that should be "OR gate" (although it's just an example, any logic gate would do). Sorry about that confusion.


texts: Feeding 2 stage discrete pre-amp to LM386 to add gain

texts: I need about 20 V/V or so of additional gain for a pre-amp I am making which currently consists of two transistors and is shown below. I was wondering if I can simply feed the output of the transistor network into pin 3 of the LM386 circuit below. I am tempted by the simplicity of the solution and I am wondering are there any considerations I should have in combining the two circuits?


texts:
I'm trying to pin down this component

Googling has got me to these two but I can't work out the difference or if they match.

SN74AHC373DW

SN74AHC373DWR

Really appreciate some help IDing it. Thanks


texts: How can I plug an arbitrary USB device into two computers?

texts:
Ultimately, my goal is to have a "keypad" with between 5 and 10 buttons, where pressing one of those buttons effectively presses some key on two computers simultaneously.

In the ideal scenario, the "keypad" would just plug into both computers, sending whatever signal I generated out over 2 USB lines. As far as I can tell, this flat doesn't work (a single USB device cannot connect to two hosts).

I saw online some instructions for connecting a USB keyboard to a hacked-together pair of PS2-USB adapters (connecting the PS2 side, which apparently is happy to have multiple "hosts" with a single device). Even without doing the hacking part, my current keypad won't work when plugged in via keypad->USB to PS2->PS2 to USB->computer. Cutting apart connectors to allow it to be keypad->USB to PS2->2 x PS2 to USB->computer isn't likely to improve that any. I'm not clear if Windows no longer supports PS2 (saw that somewhere online), if the hardware keypad doesn't send the necessary signal to be "converted" to PS2, or what.

Are there any other approaches I'm missing? Any intelligent ways to do it with software (so the keypad plugs into one computer and that computer sends the signal to the other computer)? Immediacy is pretty important, but that route seems to have some legs.


texts: what is the Relation of Motor Starting capacitor with Motor speed?More 2 questions in Desc

texts:
Pre-Knowledge:
I know we use capacitors in Single phase induction motor because with one phase the the net torque is zero and Rotor won't rotate so we add another winding perpendicular(with capacitor) to that so that net torque is non-zero.

I have celling fan after some years celling fan max speed is not what it used to be so electrician change its capcitor and replace it with the same value new one and fan is back on its speed.

My question is that:

By time what made fan to lose max speed(how is it related to capacitor)?
What is the relation of capacitor value with the speed of motor?
What are the capacitance limits for a certain winding on motor how much higher and lower value capcitance i can install.

Sorry for long question but i had to state things straight forward that are messing up my mind.


texts:
I am trying to design an image processing system on an FPGA to do Canny Edge Detection.  The design is shown in the image below.

I have a large block ram to store my image. then i have smaller line buffers to read only the lines i am processing. I have 3 lines in use at a time ( with 1 other line as a pre-fetch for the next row of processing ).

The challenge I am having is that filter 1 looks at a 9 pixel box and outputs a value for the center pixel. so for a 10x10 image, the filter only outputs data for 8x8 pixels in the middle.

Once filter 1 has finished 3 rows, i want filter 2 to start on the modified pixel values. To pipeline this design, i am having a hard time figuring out how to deal with the 'missing' pixels that filter 1 does not output. what would be the best way to load those for Filter 2? should i have a way to bypass the first+last row and first and last pixel of each other other to my 2nd line buffer? or is there some other way i can do this?


texts: Ultra low power arduino wireless sensor : care of battery discharge

texts:
I'm prototyping an ultra low power wireless sensor.
To consume less I run an Arduino Mini Pro at 1.8V at 8MHz with sleep 99% of time.

The power comes from a LIR2032 coin cell and the 1.8V is generated from a LDO regulator HT7318. I use the regulator because my NRF24L01 will not support such as 4V voltage and cause an atmega328p consumes less with a lower voltage.

I want the consumption to be as low as possible (nA/pA if possible.)

But to preserve battery life I have to know when voltage goes down.

I'm interested in the Nick scheme:

Measure Lithium ion battery voltage (thus remaining capacity)

But I have some problems:

A direct battery measurement is fully stable but drain battery.
With Nick scheme it doesn't drain battery but I would like to reduce the measurement time needed because of the capacitor C14. (I added a capacitor to the Arduino output to cut off the measurement a short time after switching)
If I remove the capacitor from Nick scheme, the measurement is absolutely not stable, but I don't understand why.

I read there are some all integrated solutions like LTC4150, are they better or worse considering ultra-low consumption?

Other links I found:

Low power battery voltage monitor

Zero or low-current voltage divider for switch identification

Which MOSFET to use for battery voltage measurement?

Reducing Voltage Divider Load to Extend Battery Life

Topic: Battery monitor/sensing ratio calculation on MotionMote/WeatherShield

Power saving techniques for microprocessors

Arduino Pro Mini: Power consumption


texts: Spring PCB terminal block for stranded wire

texts:
I am planning to use this spring terminal block:

Voltage and current requirements: 220 VAC 5 amps max

Wire type : Multi strand wire - 1 sq mm to 1.5 sq mm like this:

Datasheet says that I can use 0.2 sq mm to 2.5 sq mm:

I have never earlier used spring terminal blocks. Online reading suggested use of ferrules for multi strand wires in some articles but other articles and youtube videos were fine with directly stripping and inserting the stranded wires.

What is the preferred way to use such connectors with multi strand wires?


texts:
The circuit consists of a 12V DC supply, there is a GPIO to turn on the solenoid rated at 12V 500mA. Also, a manual switch is there to turn on the solenoid when needed.
The placement of LED and 1K resistor is such that LED would turn ON whenever Solenoid is turned on, be it either due to GPIO high OR by manual switch. My requirement is to Turn on a LED if Manual Switch is ON irrespective of GPIO level.

Manual ON , GPIO ON : LED ON
Manual ON, GPIO OFF : LED ON
Manual OFF, GPIO ON : LED OFF
Manual OFF, GPIO OFF : LED OFF

How can it be accomplished?
NOTE: TIP122 is transistor used. The diode is flyback diode


texts: ADC Amplifier Exhibiting Incorrect Behavior

texts:
I am designing a system that incorporates the ADC12DL040 ADC. Page 27 of the datasheet gives the following example schematic for converting a single-ended signal into a 1V +/- 0.5V differential signal as required by the inputs to the ADC:

With the following table for the values of the unspecified resistors:

My signal input ranges from 0-0.5V, so I used the resistor values in the second row. I am trying to simulate the amp in LTspice with the following schematic:

However, the simulation produces the following output, rather than two 1V +/- 0.5V signals:

Any idea where the circuit is going wrong? Thanks!


texts: BLDC does not start on its own using trapezoidal commutation

texts:
I am trying to control a brushless motor using trapezoidal commutation. I read the signals from the Hall sensors and switch the FETs of each motor phase accordingly. I run the commutation task at 1KHz. To modulate the speed I use PWM at 20KHz.
It all works fine in both directions at different speeds.
However, the motor only starts moving after I give it a little tap with my hand. It cannot start on its own from zero speed. What am I doing wrong?
The commutation sequence seems to be correct because if I modify it then the motor does not run at all. Also, if I swap two phases or two Hall sensors the motor does not move anymore. So I guess the current wiring setup is the right one.
I don't know for sure what kind of winding the motor has, but checking phase-to-phase voltage on a scope shows very smooth sinusoidal curves, so I'm guessing that could be an issue? I will try to implement sinusoidal commutation as well, but shouldn't trapezoidal also be able to get the motor up to speed from its standstill state?


texts:
I am trying to interface micro SD card with PIC MCU using SPI-mode of SD protocol.

Being a beginner, I tried to get the R1 response from the SD card by sending the command '0' through SPI ie.,

0x40
0x00
0x00
0x00
0x00
0x95

But I am not getting the response as 0x01 (in Idle mode)..

The source code is as follows (the PIC MCU I am using is PIC32mx360f512l)

/*********************************************************************
 *
 *                 PIC32 - SD card interface
 *
 *********************************************************************
 *
 * Dependencies:    p32xxxx.h
 *
 *
 * Processor:       PIC32
 *
 * Complier:        MPLAB C32
 *                  MPLAB IDE v8.0+
 * Company:         Microchip Technology Inc.
 *
 * Software License Agreement
 *
 *
 ********************************************************************/

#include <p32xxxx.h>
#include <plib.h>

// Config settings
// POSCMOD = HS, FNOSC = PRIPLL, FWDTEN = OFF
// PLLIDIV = DIV_2, PLLMUL = MUL_16
// PBDIV = 8 (default)
// Main clock = 8MHz /2 * 16    = 80MHz
// Peripheral clock = 80MHz /8  =  10MHz

// Configuration Bit settings
// SYSCLK = 80 MHz (8MHz Crystal/ FPLLIDIV * FPLLMUL / FPLLODIV)
// PBCLK = 10 MHz
// Primary Osc w/PLL (XT+,HS+,EC+PLL)
// WDT OFF
// Other options are don't care
//
#pragma config FPLLMUL = MUL_20, FPLLIDIV = DIV_2, FPLLODIV = DIV_1, FWDTEN = OFF
#pragma config POSCMOD = HS, FNOSC = PRIPLL, FPBDIV = DIV_8

#define SYS_FREQ            (40000000L)
void initialize();
void delay(double k);
void write_byte();

int delay_count,loop;
double d1,d2,d3;
int loop_var01 = 0;
int loop_var02 = 0;
int loop_var03 = 0;
int success_flag=0;
int i , j , k , l , m , n , o;
unsigned char  char_01,char_02 , char_03 , char_04 , char_05 , char_06 ,char_07, response_01;
char read_byte();
void toggle_clock();

int main(void)
{
    int delay;
    delay = 250;
    SYSTEMConfig(SYS_FREQ, SYS_CFG_WAIT_STATES | SYS_CFG_PCACHE);
    initialize();
    if(TRISDbits.TRISD2 == 1)       // if rd2 ie., DO is 1, check for flags

    while( 1)
    {
    }

}

void initialize()
{

// initialize the port pin directions
TRISDbits.TRISD0 = 0;
TRISDbits.TRISD1 = 0;
TRISDbits.TRISD2 = 1;
TRISDbits.TRISD3 = 0;

// initialize the SPI card to SPI mode
delay(10);
PORTDbits.RD3 = 1;
PORTDbits.RD1 = 1;

// do this a minimum of 74 times
for(loop_var01=0;loop_var01<80;loop_var01++)
{
 toggle_clock();
}
PORTDbits.RD1 = 0;

write_byte(0x44);
write_byte(0x00);
write_byte(0x00);
write_byte(0x00);
write_byte(0x00);
write_byte(0x95);

response_01 = read_byte();

if (response_01 == 0x01)
    success_flag=1;

else
    success_flag=0;

}

//write byte ++++++++++++++++++++++++++++++++++

  void write_byte(char_02)
  {
    for(n=7;n>=0;n--)
    {
      if (char_02 & (1<<n))
         {PORTDbits.RD3 = 1;}
      else
         {PORTDbits.RD3 = 0;}
      toggle_clock();
     }

  }

//read byte +++++++++++++++++++++++++++++++++++

  char read_byte()
  {
    while(PORTDbits.RD2)   // read the DO input till the the bit becomes 0
    {
     toggle_clock();
    }

    for (n=0;n<7;n++)
    { if (PORTDbits.RD2)
         { char_03 |=(1<<n); }
      else
         { char_03 &=~(1<<n); }
      toggle_clock();
    }
    return char_03;

  }

//toggle clock +++++++++++++++++++++++++++++++++
void toggle_clock()
{
delay(100000);
PORTDbits.RD0 = 0;
delay(100000);
PORTDbits.RD0 = 1;
delay(100000);
}

//delay ++++++++++++++++++++++++++++++++++++++++
void delay(double k)
{
  for(k=0;k<delay_count;k++)
  { for (l=0;l<1000;l++){}}
}

Please help me to figure out why I am getting junk or no response

Sub-Question:

How to pass the next command (say command24)?

I mean what is the hex value for command 24? I learnt that every command should begin with 01 followed by 'six bis' corresponding to the command number(in this case it is 24)??

What should be filled inside the quotes 0x"" for command 24??

how to pass arguments?? what is its hex value?? Is it 0x00 again or something else??


texts: Rewriting a boolean expression only using NAND

texts:
So I had a truth table and using a Karnaugh map I simplified a function. I obtained.

\$ f = \overline{A_3}A_2\overline{A_1} + \overline{A_2}\overline{A_0} + A_3\overline{A_0} \$

Then using the distributive property of boolean algebra:

\$ f = \overline{A_3}A_2\overline{A_1} + \overline{A_0} (\overline{A_2} + A_3) \$

Ok, with this we have the minimum of logic gates to use.

Now I need to convert this to NAND.
What seemed easier to me was to take the logigram (or electrical scheme) and directly change the gates to their equivalents with NAND. I obtained:

\$ f = \overline { \overline{\overline{A_3}A_2\overline{A_1}} \cdot \overline{\overline{A_0} \overline{A_2 \overline{A_3}}} }\$

Now I have two questions about this:

How should I proceed algebraically to pass to one expression to another (I know I need to apply DeMorgan laws or use the complement of the function... I would thank if someone can give like a tip or something on how to start doing it.
I'm thinking if there is any way to simplify the NAND expression... I see that I have \$ A_2 \$ twice and also \$ \overline{A_3} \$ twice... I'm thinking if there is any way to go even further in the simplification... If someone could also give a tip on how to proceed to not ruin the rule of using NAND only. Thanks very much!


texts: What is the purpose of the RG10MEG Resistor in this circuit? Why is it there, I can't see any difference in the simulation when it's missing. PS: U_IN = 3V DC + 1.5V sinusoidal at 1kHz


texts: Is DC motor model give similar output to BLDC motor model with identical parameters?

texts:
As in title, I would like to know if DC motor should give similar output (motor speed) to BLDC motor with the same parameters (omitting fact that in outputs of BLDC motor occurs ripples due to electronic commutation)?
Based on following paper:
http://webfiles.portal.chalmers.se/et/MSc/BaldurssonStefanMSc.pdf (page 39 of pdf file)
both DC motor model and BLDC motor model should give indentical motor speed, but in my implementation of simulations that is not true, so I would like to know if there is something wrong with my simulation or maybe with this similar outputs information.


texts:
I have a 330w alternator, it is a washing machine alternator rating at 220V and 1.5A

I am trying to make Windmill to charge my battery UPS system (24V Sys), what I want to know is can I get a 24V 15A out of the alternator? And can the alternator handle it? Also how can I do it?

I am new to electronics, I barely have electricity and no teacher nor anyone would like to teach our help me (the people here are quite stingy even though they don't know much) so it ids a real pain to learn this.

What do I need to know? Where can I find few schematics I can relate and learn from? And is it ok to do what I want to do?

I am guessing that the alternator would be outputting AC power so I knew I will have to rectify it (am I wrong? And how can I know?) But I don't know how to step up amps nor if it had any effects on the alternator, I also need it to push as much amps as possible and not wait for the load take what it needs (in this case a battery)

Please help