texts: Using infrared temperature sensor to measure water surface temperature

texts: Not sure I choose the right place to ask the question, but... Can I use infrared temperature sensor (such as TS118-3) to measure water surface temperature? I'm afraid some effects as reflection of infrared waves from water surface and blinking because of the water ripple will make its impossible.


texts: First off, I am aware that plugging an UPS into an inverter is a bit redundant.  The only situation I can think of it being useful is in a car when you want full amps for cranking over the motor but still want to run equipment. Anyhow, besides the silliness of why would you plug a UPS into an Inverter, my question is why it will not work. I have been using a motor master 3000 watt modified sine wave inverter with an APC Back-UPS RS 1500VA. When it is plugged in the UPS gives a wiring fault error. I was thinking it may be that the Inverter is not grounded properly so I tied the earth ground pin from the UPS to the buildings ground and still the UPS say’s there is a wiring fault. I heard people say that UPS’s do not like inverters in the past, but the troubling part that I have is that I had the ups working off a Robin Subaru R1700i inverter series generator without any issues. Anyone out there have any thoughts on this matter?


texts:
Can anyone confirm to me if my calculations are right?
I need to choose  a fuse for a circuit which has a 220uF capacitor on the input, after the fuse. The proposed which I intend to use has 0.17 Ohm resistance.
The maximum input voltage is 5V.
I2t is the integral of current waveform multiplied by time, integrated from 0 to infinity (well, 2 seconds is pretty close to infinity for this purpose).
I use desmos graphing tool for computation.
According to this I2t would be


texts:
Just having trouble analysing the following circuit with the information given.

where k=0.16mA/volt^2, Vt = -1.7V and A = 1V.

I believe you have to first find an expression for V_gs but the capacitor and resistors are throwing me off on how to analyse this circuit as it isn't similar to any of the previous examples I have looked at or anything I can find online. Any direction would be appreciated.


texts: What is the difference between Ethernet and Serial communication?

texts:
All the mouse movements, USB connections and other PC peripherals such as printers etc. are what is called serial communication. One bit per time.

So far so good. But when it comes to TCP protocol, Ethernet and internet it is not called serial communication anymore. But this is also bit per second stuff.

Why is that so? What is the main difference? I couldn't understand why it is not serial communication.


texts:
I have a remote controller whose antenna is de-soldered and it seems there was a capacitor or a resistor (see red circle).
Can anyone help me to understand what component could be the missing one? I thought a capacitor similar to others close but I'm not sure.
Thanks to anyone can help!


texts: Reverse charge protection for parallel primary lithium cells (CR2450)

texts:
First time poster, long time follower here.
I am looking into the safety aspect of using primary lithium cells in parallel. The reason behind using parallel cells is to increase overall capacity. In an ideal world the two cells would be the exact same voltage and capacity, in this case there would not be a problem:

simulate this circuit – Schematic created using CircuitLab
The problem comes when partially or fully discharged batteries are mixed with new batteries, thus creating a situation where the discharged cell could be reverse charged by the new cell. This is a big "no no" for primary lithium cells and could result in explosion. BAT1 in this case is the discharged cell:

simulate this circuit
I need to put some form of protection for the cells. I cannot use series diodes like in the circuit below due to and unacceptable voltage drop (the cut-off for my circuit is 2.2v and it needs to last a couple of years!):

simulate this circuit
I looked at using a PMOS configuration as posted at Protect lithium battery in parallel although this seems to only protect for reverse polarity i.e connecting the cell the wrong way round, not reverse charge between cells.
Are there any other ways of protecting the cells from being reversed charged ?


texts: suggestions for how to implement a weird VFD jog mode?

texts:
I'm a total noob at electronics, but my employer has asked me to try to program a replacement VFD on our industrial stone-cutting saw. Everything works on it now, but I need to figure out how to implement the jog mode that was on the old vfd before it got fried.

As best as I can remember, when we flipped this switch on the control panel, the motor would jog for about two seconds, and then pause for about 20 seconds, then jog again. That would continue automatically until we switched back to the normal mode. There is another dial on the panel that would control the motor speed both in the normal mode and during the two second pulse in the "jog" mode.

Any idea how to implement this back into the new VFD? Unfortunately the old one is totally fried, so I have no point of reference to work from.

As best as i can tell now, that wiring inside was done in a rather unorthodox fashion... there doesn't really seem to be a set of parameters in the advanced manual that really correspond to how it's set up.

I know this is all super-vague, but feel free to ask for any details that I provide for you.

Thanks in advance!

The VFD is a Commander SK from Nidec, and is identical to the original.
PN: 0472-0001-11

Technical data guide: https://inverterdrive.com/file/Commander-SK-Technical-Manual-Data


texts: Relay failure with inductive loads: arcing vs. surges

texts:
What is the primary cause of premature relay failure with AC inductive loads: inductive kickback causing arcing across the contacts or the inrush surge current exceeding the capacity of the contacts?  Specifically I'm trying to find the right relay to control a 120vac, 7.7Amp (1/2-hp) furnace motor.  The relay would be driven by smoke detectors.

EDIT: To clarify, the furnace has a main power switch and is also turned on and off by the thermostat.  The relay itself is not used to turn the furnace on or off EXCEPT in case of a fire, in which case the smoke detectors activate the relay, opening the N/C contacts to shut off the furnace.

An engineer at a major relay manufacturer recommended a model of theirs that would handle the high inrush current but made no mention of any voltage spike suppression.  Discussions on this board, however, focus mostly on RC snubber solutions.

Given the nature of my application, the N/C relay contacts would remain closed in normal operation except in the case of fire, monthly detector tests or the occasional burnt slice of toast.  So there should be minimal (but not zero) arcing occasions.  On the other hand, inrush surges would occur several times a day through the closed contacts as the furnace cycles on and off.

This leads me to think that over-sizing the relay capacity is, indeed, the most important thing.  But do you think it would also be advisable to look at a snubber?

OK, no resolution yet.  But here's another possible approach...  Doesn't a furnace thermostat use a relay to turn the furnace on and off?  If so, instead of using the smoke-alarm-connected relay to cut out the furnace motor directly, might it be possible to use this (new) relay to control the current to the existing relay that's already installed somewhere in the furnace?  Presumably this existing relay is already properly spec'd and/or surge-protected.  I don't have a circuit diagram for this furnace but does that sound like a possibility?


texts: LM311 Op Amp as a differential amplifier to drive a solar tracking motor

texts:
I want to drive a 12v DC motor that will rotate an array of small solar cells to track the sun across the sky.  I intend to use two smaller solar cells as my sun "position sensor" by having them at an angle to each other so as the sun moves West, the output voltage will change with the motor driving the sensor to null.

I think this to be a very sluggish type system where frequencies or other gremlins will be subdued.  Expected cycle time would be about 15 seconds "on" every 10 +/- minutes.

I am trying to use a change in sensor voltage of about 0.015v (between pins 2 and 3) to operate the Op-Amp with a sensor voltage range of about 2.5 to 3.5 volts.  The output of the Op Amp will turn on a Mosfet that triggers at about 3.8V to power a relay to the drive motor.

Pins 1 and 4 are grounded, pin 8 is 16.5 volt supply and pin 7 is the output. I have a voltage divider network on the inputs to reduce gain to 379 = (49300/130) * (.015).  Pins 5 and 6 are not used.

My problem is that the op Amp is saturated to rail voltage no matter what the input differential voltage is.  If I put a pot on the rail voltage to vary the output to the Mosfet, the relay picks up as intended when output voltage exceeds 3.8 volts. Also there is a desired hysteresis effect on the Mosfet varying the output voltage using the pot.

Is it possible that the "sensor cells" I am using do not have the current output to drive the Schmidt trigger?
Any other comments, ideas and help will be appreciated.


texts: Word alignment / bitslip in LVDS Receiver

texts:
I am simulating the Soft LVDS IP core as receiver by passing a bit stream with IP core parameters configured as follows:

Power Supply Mode: Dual (for 10M50DAF484C7G)

Functional mode: RX

Number of Channels: 1

SERDES factor: 8

PLL: Internal

Data rate: 200 Mbps

Inclock frequency: 200 MHz (This value was selected automatically after I entered Data rate)

Enable pll_areset port: checked

Register outputs: checked

In the test bench I am continuously passing a bit stream (consisting 0xAA in a loop) after

asserting the pll_areset for at least 10ns.
checking if rx_locked has been asserted.
but the deserialized output is not consistent with the serial input. I have tried increasing the rx_inclock frequency to 400 MHz, 800 MHz and 1600 MHz but to no avail. Any ideas what could be the issue? Besides does anyone know how the inclock frequency is calculated from the data rate? I also tried other input sequences but didn't get the same data at output. I am not sure if the SERDES IP core is either skipping bits or the word/byte boundary is misplaced. Would appreciate any help also if somebody could explain bitslip phenomenon. Thanks

Note (Added 19 Nov, 2018): The device being used is Altera's MAX10 and the IP core is "Soft LVDS".

Testbench

`timescale 1 ns / 1 fs

module LVDS_Test_4_tb;

integer         i   =   0;

reg             clk;
reg             rx_in;
reg     [256:0] input_bitstream;
reg             pll_areset;
reg             rx_data_align;
//reg               align_data;

wire    [7:0]   rx_out;
wire            outclock;
wire            rx_locked;

initial
begin
        clk                 =   1'b0;
//      align_data          =   1'b0;
        rx_in               =   1'b0;
        rx_data_align       =   1'b0;
        input_bitstream     =   256'h0000000000000000_0000000000000000_0000000000000000_0000000000000000;
        input_bitstream     =   256'hAAAAAAAAAAAAAAAA_AAAAAAAAAAAAAAAA_AAAAAAAAAAAAAAAA_AAAAAAAAAAAAAAAA;
        pll_areset          =   1'b0;
//#10       pll_areset          =   1'b1;
//#20       pll_areset          =   1'b0;
end

always @ (*)
begin
#2.5    clk     <=  ~clk;
end

always @ (posedge clk)
begin
    if (rx_locked)
    begin
        rx_in   <=  input_bitstream[i];
        if (i >= 12'h100)
            i = 0;
        else
            i       <=  i   +   1'b1;
    end
end

LVDS_Test_4 lvds (
        .rx_inclock     (clk),         //  rx_inclock.rx_inclock
        .rx_outclock    (outclock),    // rx_outclock.rx_outclock
        .pll_areset     (pll_areset),  //  pll_areset.pll_areset
        .rx_in          (rx_in),       //       rx_in.rx_in
        .rx_out         (rx_out),
        .rx_locked      (rx_locked)    //,
//      .rx_data_align  (rx_data_align)
);

endmodule

Simulation Waveform where rx_in data is synced at posedge of data clock

Update: (24 Nov, 2018)
So, I changed the testbench design, instead of an always block based on the posedge of data clock, now the serial data is transmitted using a forever loop in an initial block at the same frequency. This change somehow fixes the issue but partially, so I do like to understand why it behaves so? A data stream comprising 8'b11001100 was transmitted as shown in the following figure.

 Post-link training the data was aligned.


texts:
I try to design a circuit, where a LiPo is switched by a PMOS over a mechanical switch. Further, the USB Voltage can also occur and the LiPo should be decoupled. My first attempt looks like this, and it seems to work:

Now, the diode D2 is bad practise, because of the power dissipation, but I don't know how to get rid of it, since the Body Diode of M1 will directly couple the USB voltage into the battery. Has anyone a suggestion?


texts: shutting off power to circuit after a short time from an alarm clock

texts:
I am helping with a middle school project.
The idea is to power a 3 V vibrating motor for about 10 seconds after the alarm goes off.

The cheapest way so far I have found is to get a dual alarm clock and replace the buzzer with the motor. Unfortunately, since the alarm goes on for 30 minutes, or until manually shut down, the motor runs for that long. I just need it to run for about 10 seconds. What can I add/put between the clock and the motor so the power shuts off after the period of time till the next alarm event?

Second, if there's a way to do this with some kind of circuit timer, instead of an alarm clock, that would be ideal.

The goal is to be able to set 2 events within a 24 hours period (every 12 hours, or twice a day); when the even happens, it should power my 3 V vibrating motor for about 10 seconds and then turn off.


texts: Did I hook up this CD4052 Analog Multiplexer correctly?

texts:
Upon reading the data sheet this chip seems straight forward, but I'm having the hardest time hooking up the CD4052.  The chip I'm using is actually a, "CD4052BE".  Here is a link to the datasheet.  I have hooked up the following circuit just to test the analog switching capability:

simulate this circuit – Schematic created using CircuitLab

Problem:  There are two things happening that don't make sense to me when I test this same circuit:

I started off with both A and B grounded.  The DMM measurement reads the value 0.157V, where as when I measure the voltage at R1 (at the output for x0), it reads 0.1179V.  That is actually where I would expect it to be.  Why is there a voltage difference?  It seems like it should just be similar to an open wire between the two.
I soon realized that no matter what combination of A/B inputs I used, the voltage is ALWAYS as described in problem 1.  It is as if the multiplexer isn't switching between x0, x1, x2 or x3.  Why would this multiplexer appear to be stuck on a particular switch regardless of a/B inputs?  While R1 reads 0.1179V, I would expect that the other combinations of A/B would yield: 1.09V at R2, 6V at R3 and 10.9V at R3.  The R2, R3 and R4 all read 0v.

Please let me know if something about this seems incorrect or is I just flat out misinterpreted the use of this chip. I reviewed another post that references the CD4052 here, but it didn't discuss the specific issues I was having.


texts: ENOB and oversampling ratios for delta-sigma ADCs (in relation to CS5343)

texts:
I came across the CS5343 ADC the other day and was impressed with its specs (relative to its cost) but then became confused when I dug deeper and read the datasheet.
It's nominally a 24-bit 96 kHz ADC, but the datasheet lists a dynamic range of only 98 dB and a "-92 dB THD+N". The 92 dB figure gives an "effective number of bits" value of 15 using the normal arithmetic. Even the dynamic range would only correspond to 16 bits worth.
So I guess the first part of my question is: why the heck would anyone choose to market this product as a 24-bit ADC?
I then read a bit more about how delta-sigma ADCs work (along with noise-shaping). I partially understand them now but I clearly have serious gaps relating to the practical details, including the decimation. For example, the CS5343 has a master clock rate of up to around 40 MHz (when digitising at around 100 kHz) - specifically, a 36.864 MHz clock can be used to give a 96 kHz sample rate, using a divider of 384x.
Now, I'm stuck here. My feeble understanding of the 1-bit datastream that emerges from a delta-sigma would imply to me that if you want to achieve 24-bit resolution, you need to count the number of "1s" that occur in each set of 2^24 samples. That would mean a multiplier of 2^24 (i.e. more than 16 million) between the data rate and the master clock rate, not 384. (It also implies a master clock rate of around 1.6 THz!)
So here's the second part of my question: given that this 2^N multiplier (where N is the number of ADC bits) is clearly not present in real-world ADCs, can anyone point out the breakage in my italicised text above, or a link which explains it?


texts:
I am trying to find a strong motor which can deliver a torque at least 0.2Nm and around 130RPM. While trying to find a 6mm shaft geared motor with feedback,the required torque and rotational was already hard enough(at least for me), I've managed to find one very cheap and ROHS certified. According to the FIT0186 datasheet, (https://media.digikey.com/pdf/Data%20Sheets/DFRobot%20PDFs/FIT0186_Web.pdf) it has a nominal voltage is 12VDC, reduction ratio of 43.8, no-load of 251 rpm and a nominal current of 350mA.

However, there is no mentioning of continuous torque and how much current it will draw. It only states a stall torque of around 1.8Nm and a stall current of 7A...

I am planning to drive the motor with a SN754410(http://www.ti.com/lit/ds/symlink/sn754410.pdf) which supports a continuous current of 1Amp and peak of 2Amps. Since there is no diagram, is it calculatable? I don't know if the nominal current, stall current and torque has a some kind of relation(i.e. linear characteristic). Am I able to drive this motor with this current setup? X2 is the input coming from the MicroChip, X3 is the motor.

Sorry for this potentially silly question.


texts: Encoder/decoder for serial connection without separate clock?

texts:
I'm putting together a link where the physical layer is SPDIF transmitters and receivers.  I control both sides of the link (ie it doesn't have to interoperate with any other equipment).  I would like to send data from a microcontroller, essentially treating this as a UART.  The problem: if the output stays low or stays high too long (not sending data on the UART), the SPDIF receiver output becomes unpredictable, and it takes a fair amount of time with regular transitions for it to recover.  SPDIF normally uses Bi-phase Mark Code (BMC) to deal with this problem (the clock is always running so there are always low-high transitions).

What is the easiest way to encode and decode data which ensures the link is always transitioning between states?  I'd like to use the least amount of hardware to implement, and relatively simple software; ideally no hardware, and just using the peripherals on the microcontroller.  It doesn't have to be BMC; 8/10 for example would be perfectly ok.


texts: Relation between THD and spectral leakage or number of samples

texts:
So I'm studying data acquisition and on the lab had to perform an experiment involving sampling a sinusoidal signal of frequency 1100 Hz, 70 samples and sampling frequency 22000 Hz.

Now I can clearly see that I'll have spectral leakage in this case because 1100/(22000/70) is not a natural number. Nevertheless I was able to compute a frequency of 1173 .69 Hz which corresponds to an error of 6.67% using weighed frequency method. I think this a pretty decent result. What is intriguing me is the total harmonic distortion which is evaluated at -14.75 dB. Is this a low value? What exactly is THD measuring here? Can someone help interpret the THD meaning? Thank you!


texts: Does long SPI lanes require extra attention?

texts:
I am designing 3 SPI slave devices that are fairly far away from the host, The SPI communicates at 50MHz (Max) at 3.3v

Slave 3 is an off board device where it is connected to the board by a ribbon cable. The slave devices are just straight up connected to the master exempt for slave 3 which have a tvs diode.
Does the SPI bus needs special attention? is it okay to just straight up connect them ?


texts: Converting a USB C into a Y-split USB A for chaging

texts:
I'm looking to split a USB-C (female) into two USB-A (female as well), strictly for charging.

Would it by any chance be possible for me to solder the four voltage connector pins   from the USB-c to the voltage pins on the USB-a, and then do the same for ground?

I'm looking at something like below:

That would be glued tight into a 3d printed enclosure


texts: How to improve this battery-status (voltage monitor) circuit?

texts:
How could this "Battery OK" indicator be improved, without adding too much complexity (or maybe even simplifying)?

The intended function is to have the LED illuminated at relatively-constant brightness when the supply is above a threshold voltage.  As the supply voltage drops below that threshold, the LED should transition as rapidly as possible to completely off.  Idle current should be as low as possible.
With the circuit as shown, this is a plot the current through the LED for supply voltage up to 10V:

The R2/R3 voltage divider is set so that when the supply is at the threshold voltage, the voltage across R3 is one VBE drop.
R1 sets the LED current above the threshold. (Q3 serves as a current regulator.)  This way there's not a dimming of the LED as voltage decreases from maximum until the threshold is reached.
The Sziklai pair is used so that the transition occurs over a narrower voltage range, and so that Q1 base current doesn't load the divider.  A Darlington pair could be used here, but the divider would have to be adjusted so that the lower voltage is 2 × VBE.
Edited to clarify the specifics of the sample circuit:

The 9V source was just chosen because a 9V battery is readily available for testing.  I would like something readily adaptable to other voltages.
The 2.5 mA current through the LED is also somewhat arbitrary.  Having the brightness be relatively constant is more important than the actual value.
I could replace the JFET and its source resistor with a packaged current regulator diode and it would be essentially equivalent.  (I didn't have a model for one of those.)


texts: Calculating Rs Value for 32kHz Pierce-Gate Crystal Oscillator Circuit

texts:
Edit: My primary objective is to learn the mathematical model to compute the load resistor \$R_s\$ to satisfy a given crystal's drive level, not just fixing the one instance below.

I'm building a Pierce-Gate oscillator circuit using a 74HC4060 and a 32kHz 12.5pF watch crystal.

I'm a novice, but AFAICT the oscillator circuit of the SN74HC4060 is just a buffered CMOS inverter:

My circuit's schematic:

Below the oscillator section on the PCB (the IC on the left is the 4060). The back of the board underneath the oscillator section is clear; no signal traces and no copper pours:

While I get the crystal to oscillate, it's sometimes unstable and varies in frequency. I'm a novice and I'm struggling trying to work out the appropriate values for the load resistor \$R_1\$.

As I understand, the crystal's 12.5pF load capacitance should be equal to:

\$C_{load} = {(C_1 + C_{in})  (C_2 + C_{out}) \over (C_1 + C_{in} + C_2 + C_{out})} + C_{stray}\$

where \$C_{in}\$ and \$C_{out}\$ are the CMOS inverter's circuit capacitances and \$C_{stray}\$ represents any parasitic PCB capacitance. I'm a little in the dark on the values for \$C_{in}\$ and \$C_{out}\$ and I can't seem to find them in the IC's datasheet.

Following online rules of thumb, I've been using 3pF for each and 1pF for \$C_{stray}\$. Substitution then gives:

\$C_1\$ = 20pF
\$C_2\$ = 20pF

What I struggle with is \$R_1\$ though.

The value of 470k in the schematic above was taken from https://www.eevblog.com/forum/beginners/using-a-32-768khz-crystal-with-4060-frequency-divider/ but I don't really understand how it was derived.

I understand it's acceptable for \$R_1\$ to match the capacitive resistance of \$C_1\$ (§6.1.2 from http://www.ti.com/lit/an/szza043/szza043.pdf) which for 20pF at 32768Hz I think is 241k.

Yet, I also understand that \$R_1\$ serves to lower the current through the crystal. The crystal's datasheet lists the drive level as \$1 {\mu}W\$ and 241k would seem too low to achieve that.

My circuit runs at 5V. With \$R_1\$ and \$X_{C_1}\$ both equal to 242k and the crystal's effective series resistance at 35k, how do I calculate the current through and voltage over the crystal?

This is probably where I go off the rails (if I'm not already), but do I approach this as the following equivalent resistor network?

Where Ohm's law would put the parallel resistance over the crystal and \$X_{C_1}\$ at 31k, the voltage at \$V_1\$ at 0.57V, the current through \$R_1\$ at 18\$ \mu A\$, \$I_{XTAL}\$ at ~\$16 \mu A\$ and by extension the power consumption of the crystal at \$0.57V \cdot 16 \mu A = 9 \mu W\$?

How do I approach calculating appropriate values for \$R_1\$ that satisfy the crystal's specifications?


texts: How to shield your microphone the best way

texts:
I hope this is not a too simple question for this forum.
I have an issue with EMI/RMI on a microphone I am building. It's picking up noice from wifi hubs, computer screens and mains.  I do not want to spend 100s on too fancy equipment so I am exploring the simple solutions first, i.e. shielding.
The mic is connected to a USB soundcard.
Is there any significant improvement in putting an extra shield outside the mic and the cable and connecting it to the usb ground, se picture, or am I overdoing this? Could I just as well connect the shield and V- to ground pin on the 3,5mm plug?

In practice this means that mic V+ and ground are in the wires inside the mic-cable and the cable shielding is pealed back and connected to the microphone case (copper pipe with copper mesh over mic) and a homemade shield around the USB card (foil and copper-wire).
And yes, I know: "Shielding is the first refuge of the incompetent" and I will still get noise from the soundcard itself and the computer, but that is something I will have to deal with in another question altogeter.
Edit:
I do not have the ready mic with me to photograp. This is the prototype I cobbled together. It did reduce noise significantly but with varied results. Either the shielding is not good enough or, in some cases, it may act as an antenna. I guess the question is whether I have grounded it correctly or made things worse.


texts: High Current or High Voltage that damages components?

texts:
Very basic question here and I'm only looking for a generic over view, but is it a too high current or a too high voltage that will damage electronics? I assume it will depend on the component in question -

1) For example if you have a working circuit with a 10V battery, fixed 5 Ohms resistance and a current of 2A. If you then swap that battery to 20V, would it be the new current of 4A that does the damage or that fact that the voltage is now 20V? Both values are higher than they should be so which factor will do the  damage, both?

2) Also, if when you swapped to a 20V battery, you also increased the resistance in the circuit to 10 Ohms, could this still damage components in the circuit? The current is now the same as it was in the original (2A), but the voltage has gone from 10V to 20V, could this do damage?

3) Finally, you could take the original circuit and lower the resistance to 2.5 Ohms, now the voltage is the same (10V) as it should be, but the current has risen to 4A, I assume this could cause damage depending on the components in the circuit?

Any help would be appreciated, thanks in advance.

Edit - I didn't make it very clear, I wasn't specifically talking about damaging the resistors, I mean't damage various components that could be in the circuit.


texts: Solder balls and routing out of pad corners

texts:
I was approached the other day by a co-worker who claims he avoided routing out of corners of smd pads due to higher odds of solder balls forming. I have so far been under the impression that it is mostly a function of solder paste quantity, then pad shape secondarily.

Is there any experience (personal) among members here, evidence or literature about this claim. I have not found it myself but i do wonder if others of experience have run into this.


texts: How do CPU, IOMMU and DMA controller interact with each other?

texts: While drawing an interaction diagram involving CPU, IOMMU and DMA controller, I failed to find any authentic document showing how they interact with each other. Is the DMA controller physically a separate unit from the IOMMU, or do they reside on the same chip? Does Intel support IOMMU operation?


texts: I have a Pioneer SX-316-S stereo. It has six speakers. The specification says it consumes 320 Watts.  It also says the continuous power output is 100W per channel. It also says the RMS power output is 144W per channel. When I advertise this thing, how many Watts can I call it? 320 Watts?  600 Watts? 864 Watts?


texts: How do Shelly products detect button presses?

texts:
I've been playing with home automation for a while now (mostly Sonoff) and recently discovered Shelly.cloud.  I'm fascinated by the fact that most of their relays use a mains connected switches to interact with external inputs (see image below) - fascinatingly brilliant as this allows one to leverage existing wiring to retro-fit automation products into existing installations.
But how does it work (the switch part)?
These devices are based on the ESP8266EX (PDF) wi-fi microcontroller that uses 3.3V.  This part I get - from what I can see on photos they use a AC-DC on-chip converter, the Shelly 1 (see FCC entry) uses a LNK304DN (PDF) to convert mains to 12V and then they bring that down to 3.3V somehow (I assume something similar to a PMP4536 (www)).
Having worked on ESP8266 I know that it has IO pins that one can use to measure either digital variance or pull-up or pull-down ... but that's all in VCC (3.3V).  How on earth is the external button press being detected?  And this thing works in both power modes, i.e. 220VAC and 12VDC modes.
This question pertains specifically to the theory of how one would go about detecting a 220VAC ON state and translate that to signal that can be used in a 3.3VDC microcontroller (think in terms of the example of using an Arduino to detect if a light is on or off).

Another of their products (Shelly Dimmer) has two SW pins and from some close up photos each has a 240 kΩ resistor and then a S1M diode ... but I can't see more from just the photo.


texts: PCB manufactoring-There shouldn't be bottom silkscreen selected?

texts:
I use Eagle to create gerber files .
When i am trying to check my zip gerber, in 4pcb.com i get this message :

There shouldn't be a bottom silkscreen selected. If bottom silkscreen is required, adjust the design specifications entered below.

Well, our board has printed values in its top and its bottom, and its 2 layers board.
I dont understand why they say that something is wrong with our bottom silkscreen file.

Here is the gerber file job :

top copper: top,pads,vias,dimensions.
bottom copper:bottom,pads,vias
bottom silkscreen: bplace,bnames,bvalues,
top silkscreen: tplace,tnames,tvalues,
top solder mask: tstop
bottom solder mask: bstop
drill: drills,holes

Maybe i dont understand something basic here, but is this right ? our board is 2 layers board,has components on both side of it, and also values and names on both sides.

What this error message means? is there any tool to check how the board would look like when ready,so i can know its ok ?

thanks!


texts: Should I have had a resistor before my transistor?

texts:
I've recently started playing with an Arduino and learning about circuit's.  I was trying to learn a bit about using some transistors as a switch and I think in the process I ended up ruining one of the pins on my Arduino.  When set to HIGH the pin only outputs 0.5 now rather than the 4.6ish the rest of the pins do.

The circuit I built involved two transistors.  One to control a 12v fan via a PWM signal off the Arduino and another to act as a switch for turning on/off an ATX power supply which I used to provide power for the fan.

Here's an approximation of the circuit.  I'm not really sure how to properly diagram it.

simulate this circuit – Schematic created using CircuitLab

To try and explain a bit, The Arduino was powered via the USB connection to the computer.  Pin 11 is setup as a PWM output to control the speed of the fan.  Pin 12 is setup as a HIGH output to switch on an external ATX power supply when the Arduino board turns on.  I use one of the 12v rails on the power supply to power the fan, and have it's ground connected to the Arduino's ground.

Not shown in the diagram is a simply push button to increase the speed of the fan and a 7-segment led display showing a number representing the speed.  I don't think these are related to my pin problem and I'm fairly certain it was all wired up correctly.

After doing a little more research I think the main issue which caused my pin problems is I should have had a current limiting resistor in between the Arduino pin and the base of the transistor.  Is conclusion accurate?

Any additional comments/criticisms welcome.


texts: Cant open EAGLE Schematic file in Altium10

texts:
Iam using Altium designer version 10 and I cant open a EAGLE schematic file  in this.

EAGLE importer is not in the import wizard.
can any one help me?


texts: What is the expression for collector current (Ic) in function of CTR for optocoupler?

texts:
I'm just asking about expression for collector current (Ic) of optocoupler in function of CTR because my simulation results doesn't fit with the CTR=Ic/If equation.

Simulating the part CNY17-3 with the characteristics described on the following figure:

I get the following results:

Calculating the CTR as (Ic/If):

CTR=Ic/If=169uA/34mA=0.49%

The circuit used to evaluate the characteristics (feedback loop for Vout detection in SMPS)


texts: Doubt regarding Nyquist theorem for sampling analog signals

texts: If for an arbitrary signal H(f) = 1 for 300-f-3700 Hz; 0 otherwise, what should be the minimum sampling rate? 7400 Hz or 6800 Hz and why?


texts: Could STM32 Discovery boards debug STM8 chip?

texts: I know that STM32 discovery boards could debug another STM32 chip. But could it debug STM8 chip too? Is STM8's debugging interface compatible with SWD?


texts: I am having trouble understanding the difference between these two concepts. I know that input resistance is the resistance looking into the input terminals and output is looking into the output terminals. What I don't understand is how to evaluate these. In the image below, are the input and output resistances simply the Thevenin resistances at the input and output terminals?


texts: MPLAB XC16 not generating .HEX file after successful build

texts:
I am new to MPLAB XC16 IDE. I am generating a simple blinking LED code to understand the basics of the microcontroller PIC24FJ32GA002.

The main file is as follows:

#include <xc.h>
#include <libpic30.h>

#define sysclock 96000000UL
#define FCY sysclock/4

// CONFIG2
#pragma config POSCMOD = XT             // Primary Oscillator Select (XT Oscillator mode selected)
#pragma config I2C1SEL = PRI            // I2C1 Pin Location Select (Use default SCL1/SDA1 pins)
#pragma config IOL1WAY = ON             // IOLOCK Protection (Once IOLOCK is set, cannot be changed)
#pragma config OSCIOFNC = OFF           // Primary Oscillator Output Function (OSC2/CLKO/RC15 functions as CLKO (FOSC/2))
#pragma config FCKSM = CSDCMD           // Clock Switching and Monitor (Clock switching and Fail-Safe Clock Monitor are disabled)
#pragma config FNOSC = FRCDIV           // Oscillator Select (Fast RC Oscillator with Postscaler (FRCDIV))
#pragma config SOSCSEL = SOSC           // Sec Oscillator Select (Default Secondary Oscillator (SOSC))
#pragma config WUTSEL = LEG             // Wake-up timer Select (Legacy Wake-up Timer)
#pragma config IESO = ON                // Internal External Switch Over Mode (IESO mode (Two-Speed Start-up) enabled)

// CONFIG1
#pragma config WDTPS = PS32768          // Watchdog Timer Postscaler (1:32,768)
#pragma config FWPSA = PR128            // WDT Prescaler (Prescaler ratio of 1:128)
#pragma config WINDIS = ON              // Watchdog Timer Window (Standard Watchdog Timer enabled,(Windowed-mode is disabled))
#pragma config FWDTEN = OFF             // Watchdog Timer Enable (Watchdog Timer is disabled)
#pragma config ICS = PGx1               // Comm Channel Select (Emulator EMUC1/EMUD1 pins are shared with PGC1/PGD1)
#pragma config GWRP = OFF               // General Code Segment Write Protect (Writes to program memory are allowed)
#pragma config GCP = OFF                // General Code Segment Code Protect (Code protection is disabled)
#pragma config JTAGEN = OFF             // JTAG Port Enable (JTAG port is disabled)

int main(void) {
    TRISB = 0xFFFF;

    while(1) {
        PORTB = 0xFFFF;
        __delay_ms(1000);
        PORTB = 0x0000;
        __delay_ms(1000);
    }

    return 0;
}

The project builds successfully with this build output:

make -f nbproject/Makefile-default.mk SUBPROJECTS= .build-conf
make[1]: Entering directory 'C:/Users/mohsi/MPLABXProjects/PIC24FJ32GA002.X'
make  -f nbproject/Makefile-default.mk dist/default/production/PIC24FJ32GA002.X.a
make[2]: Entering directory 'C:/Users/mohsi/MPLABXProjects/PIC24FJ32GA002.X'
"C:\Program Files (x86)\Microchip\xc16\v1.33\bin\xc16-gcc.exe"   main.c  -o build/default/production/main.o  -c -mcpu=24FJ32GA002  -MMD -MF "build/default/production/main.o.d"        -g -omf=coff -DXPRJ_default=default  -legacy-libc    -O0 -msmart-io=1 -Wall -msfr-warn=off
"C:\Program Files (x86)\Microchip\xc16\v1.33\bin\xc16-gcc.exe"   system.c  -o build/default/production/system.o  -c -mcpu=24FJ32GA002  -MMD -MF "build/default/production/system.o.d"        -g -omf=coff -DXPRJ_default=default  -legacy-libc    -O0 -msmart-io=1 -Wall -msfr-warn=off
"C:\Program Files (x86)\Microchip\xc16\v1.33\bin\xc16-ar.exe"   -omf=coff -r dist/default/production/PIC24FJ32GA002.X.a  build/default/production/main.o build/default/production/system.o
make[2]: Leaving directory 'C:/Users/mohsi/MPLABXProjects/PIC24FJ32GA002.X'
make[1]: Leaving directory 'C:/Users/mohsi/MPLABXProjects/PIC24FJ32GA002.X'

BUILD SUCCESSFUL (total time: 6s)

Yet still the project only compiles .a file in the project folder/dis/default/production folder:

Here are the project properties to show that I am using the correct micro controller using Simulator in MPLAB X IDE using XC16 compiler:

Any help would be appreciated. For context, I need to simulate this microcontroller in Proteus simulator. So need the .HEX file from the project.


texts:
I mean compared to ICs (ASICs) with similar complexity, speed etc. Let's compare Ethernet switches to Kintex FPGAs (note that the most expensive switch from the list is circa as expensive as the cheapest Kintex):

FPGAs are well structured ICs (like RAMs). They can be scaled and developed easily.
The design tools (Vivado, Quartus, etc.) are expensive too, so I think the price of an FPGA is the price of the IC (and development) itself excluding the cost of support and the tools. (Some non-FPGA vendors give free tools whose development cost includes the IC price.)

Are FPGAs produced in lower quantities than other ICs? Or is there any technological harness?


texts: Is it normal to hear the electrolyte flowing or bubbling when charging an AGM SLA 12V battery?

texts:
I plugged a 20A, 8 stage charger into my 2 x 130Ah 12V AGM battery bank and immediately I could hear electrolyte flowing and bubbling inside the battery. The battery bank was full when I plugged the charger in. I was just testing it out when I discovered this unusual behaviour that I have not seen before with other chargers. I usually use a 15A smart charger which charges silently. After an hour the charger had only reached stage 4, the unit was extremely hot and the bubbling sound had escalated. I turned it off but am concerned that this may have overcharged and caused damage to my batteries.

Is this normal behaviour or is it something to be concerned about?

If so, what is the likely cause and what is the likelihood that damage has been caused to my batteries?


texts: Dispersing a static field from a touch circuit - escape room

texts:
I run an escape room, inside a puzzle we have is where players need to hold hands and touch 2 screws to complete a circuit and trigger a switch.

I don't have the exact specs, but it's going to look something like this:
https://www.frightprops.com/human-circuit-puzzle.html

It sits in a wooden box (2x2x4).  It was working fine during the summer.
The problem is, since winter time, the trigger will go off just by walking next to it.  Alternatively, you can touch the wooden box to make it go off as well.

So, I could try and ground it (im not sure if this particular controller has a ground - (cheap chinese box)...but I was wondering if there is a way to just reset it back to how it was.

Any ideas?

Thanks


texts:
This board is from a Rhyne UC7067RYE remote receiver for a ceiling fan/light fixture.

I blew the transistor “Q6” (that’s the piece that broke off in pic 3).

The fan circuit still works fine but the light circuit does not (manual).
The only markings I could identify were the ones shown in pic 3: VF08SB RH03.
I know that the package is a TO-126. The numbers do not follow any transistor marking code standards that I know of (JEDEC/JIS/Pro Electron).
My google searched have not turned up anything that looks promising. I suspect this is a custom number from the OEM and I am not optimistic I will figure out exactly what it is but I was hoping someone might have some tricks for discovering what type of transistor it is so I can at replace it with something similar at least.


texts: VHDL - how to use inout as inout and as normal out?

texts:
I wanted to ask if it is possible to use an inout pin as inout and normal out? The two behaviours should be switched through a MUX. The reason for this weird looking implementation is that I have two boards and I want to use the same bitstream. On one board, the same pin is connected to a LED through GPIO and on the other it goes to my I2C bus connection. The software tries to detect the I2C and if successful it sets a register. If not, it clears it.

LED_or_SDA      : inout std_logic; -- port definition

process (register)
begin
    if ( register = '1') then -- software sets this register
       LED_or_SDA <= I2C_SDA; -- here I want to use it as inout
    else
       LED_or_SDA <= gpio_reg; -- here I want to use it as normal out
    end if;
end process;

This implementation throws the error "bidirect pad net is driving non-buffer primitives" during translate. Is there a solution for this?


texts: Can software defined radio be used as noise generator?

texts:
I'm working on solving an issue in a metal detector that generates false detects when subject to electrical interference.
The electrical interference usually stems from devices such as shortwave radio (walkie talkies) when being used in proximity, HF fluorescent lighting, Variable Frequency Drives etc.
I want to design/buy a system that can produce these frequencies with low energy. The idea being that I can repeatedly subject the metal detector to noise to understand the behaviour of the metal detector and in turn design a solution that mitigates the effects of the environmental noise.

Could I achieve this with a software defined radio?
If not, could I achieve what I want with a signal generator, a power
amplifier and an antenna?

I understand that there may be concerns about intentionally generating radio frequencies but I'll ask that in an other question.


texts: Grounding balanced secondary isolation transformer for EMI suppression

texts:
simulate this circuit – Schematic created using CircuitLab

Which is the best secondary connection to clean the main line power from EMI, line noise and HF harmonics by using an isolation 1:1 230/230VAC transformer with balanced outputs:

1) A floating (C1 and C2 are enough)

2) A to C to ground via a small capacitor

3) A to B ground directly

After having determined that connection for EMI suppression purpose ONLY, how to connect D ground output just for safety purpose (D to A, D to B, D to C, D to nothing)?

FYI: the transformer is multi shielded and each shield is connected to B ground. It has also a copper belly belt, currently floating.


texts: Is it possible to copy this RFID fob, and if so what device would I need?

texts:
I've been reading up on this a bit but am having a hard time knowing exactly what I would need to be able to make copies of this specific key. I just know I am going to lose it and I don't want to have to pay excessive replacement fees each time I do, when it only opens an exterior gate. I know I am not savvy enough to build my own RFID reader and writer, but it appears I am not savvy enough even to know what one I would need to buy online.

Any help would be appreciated.
While my query is in my case specific to my product, information on the means of replicating RFID tags is liable to be of ongoing interest to others.


texts: Can I use a p channel mosfet as reverse polarity protection but still charge a Li-Ion battery?

texts:
I want to design the following reverse protection circuit:

The gist of the design is that I want to run a SIM808 chip from a 3.7V battery. I understand that the circuit as such will protect if the user connects the battery the wrong way. But,

The Sim808 chip has a neat built in battery charger and one connects it as follows:

My question is this. Assuming the user connects the battery correctly will the mosfet above allow the SIM808 to charge the battery? Or will it block it?


texts: Strategies for troubleshooting buck converter

texts:
I'm trying to troubleshoot a tps65261rhbr triple synchronous buck converter from 12V producing 1.8V, 3.3V and 5V.

The 3.3V and 1.8V are stable and well-functioning but the 5V is not. An oscilloscope here shows the 5V (blue) next to the 1.8V (red) for reference:

The 5V hovers around 620mV with occasional spikes to 2.9V, but the calculations from the datasheet to select component values, and the simulation I've run from PSpice suggest that these components should work correctly. The voltage divider uses the exact resistance values specified in the datasheet for 5V.

Does anybody know what might cause this behavior in a SMPS?

My current best guess is that I'm tripping the over-current protection circuitry as the 5V comes online, causes a delay for several switching cycles, then tries again. I think the oscilloscope behavior seems to match this description from the datasheet:

  The TPS65261, TPS65261-1 is protected from overload and over temperature fault conditions. The converter minimizes excessive output overvoltage transients by taking advantage of the power good comparator. When the output is overvoltage, the high-side MOSFET is turned off until the internal feedback voltage is lower than 105% of the 0.6V reference voltage. The TPS65261, TPS65261-1 implements both high-side MOSFET overload protection and bidirectional low-side MOSFET overload protection to avoid inductor current runaway. If the over current condition has lasted for more than the OC wait time (256 clock cycles), the converter will shut down and re-start after the hiccup time (8192 clock cycles)

However, I don't think the loads I have on the 5V should exceed the 2A that the SMPS supports on this power line. Currently the 5V has several loads: a raspberry pi CM3 VBat (700mA), a LDO driving a 4G cellular radio (maximum 500mA during transmission), a ZED-F9P GNSS circuit (130 mA), 4 relays, and some other assorted circuitry that should consume negligible current (e.g. USB switch). In total if everything was consuming the maximum current I believe it should be around 1.7A. So unless I've miscalculated somewhere, the only reason I could see enough current draw to trip the overcurrent would be a short circuit.

What I'm really looking for are suggestions for finding and proving root cause. I'm currently trying to rule out a short circuit, after that my next idea is to cut the 5v power trace and measure current over the gap and see if if I can power it with a bench power supply.


texts: Ltspice2matlab error: Bad tag name found!

texts: Hi I want to convert the raw data generated from LTspiceXVII to variables in Matlab. I am using the LTSpice2Matlab function.data= LTspice2Matlab('netlist_whole_network.raw'). But I get Format error in LTspice file "C:\Users..netlist_whole_network.raw" ... Bad tag name found! Could you help me diagnose the source of the error? Also, what is a tag?


texts: Should I use superposition if there is a sine wave current source and a DC voltage source in a circuit?

texts:
simulate this circuit – Schematic created using CircuitLab

The DC voltage source has an angular frquency of 0 rad/sec.

Do I need to:

short circuit the DC voltage source
calculate I(t) in time domain
open circuit the AC current source
calculate I(t)
And finally, add the two together

Or can I just do a Kirchoff Voltage Law in the right loop? $$(1.6-0.8j)I+12+(8+4j)I=0$$

This is the original circuit before I simplified the impedance:


texts: How to measure True Power (Not Apparent Power) consumption in Alternating Current using ESP8266-12F Microcontroller?

texts:
Currently, I am using the ACS712 current sensor module for measuring the peak current then computing RMS Current and thus the Apparent Power (Vrms × Irms = Apparent Power).

Currently, I am not using any method for measuring the Vrms, I am measuring Vrms directly using the Digital Multimeter and putting it in the calculation.

Now, the factor missing is the Power Factor for the calculation of True Power (Vrms × Irms × Power Factor = True Power) which is producing an error of about 20%.

I am facing problem in the measuring the Power factor of the appliance using ESP Microcontroller.

Following is the circuit diagram I am implementing, Please have a look at it and let me know if I am making any mistake which is also responsible for the error.


texts: How to apply the Barkhausen criterion in order to know if a system will oscillate?

texts:
How to analyze or apply the Barkhausen criterion for oscillation of the astable multivibrator below?

The criterion talks about the magnitude of the products in a loop must be equal to 1 (ideally)
The phase must be multiples of 360 starting from zero

I really tried to solve this from my own but I'm not getting anywhere with results that are not meaningful to me in order to understand this.

Also I already obtained the equations for the period, frequency, and time on, for the output waveform taking an initial assumption or state and developing further fulfilling the previous assumptions I've made. Which are correct because I've simulated the circuit on Multisim and I get the same results.


texts:
From what I've read, the spectral properties of the modulation largely depend on the rate of change of the signal phase - "a signal in which the phase changes stepwise has a broad spectrum, well beyond the allocated radio channel". I don't know if I understand this correctly.
An example of the spectrum of QPSK modulation with a random signal causing step changes in the output signal is shown in the figure below:

The book I am using says that "if we assume that the bandwidth of the radio channel allocated to this emission is \$B_k = 1/T\$, then a significant portion of the signal power (approximately a quarter) is emitted outside the bandwidth of that channel. The appearance of such strong interference in other radio channels is unacceptable (moreover - the band in which 99% of signal power is transmitted is approximately ten times wider than \$B_k\$)"
What does it result from? Why ~1/4 of the signal power is emitted outside the bandwidth of this channel? How do phase spikes affect this? And why is the bandwidth in which 99% of the signal power is transmitted approximately ten times wider than \$ B_k \$?


texts: How do you determine the approximate frequency where the magnitude starts decreasing -40dB/dec for complex pole?

texts:
I am stuck at drawing the approximate Bode plot for the complex pole transfer function as below.

Please see the question and problem in the picture.

How do you determine the approximate frequency where the magnitude starts decreasing -40dB/dec as the figure?

PS:

Sorry I made some silly mistake. Actually I want to say that these poles are in the LHS of the complex plane but I got it backward.
Please assume that they are in the LHP now and the system is stable.


texts: can a PC parallel port produce interference?

texts:
Please forgive me for crossing wires on top of IC's but I wanted to get things done, yet still have no luck. Let me explain the circuit.

I created a circuit in which three parallel port data lines are connected to three status lines through buffers (74HC125). The status lines are also connected to a sub-circuit (not shown) through a 3 inch 10 conductor ribbon cable.

The sub-circuit contains a radio module which won't work at 5V (which is why I included 3V on the connector). It also contains a microcontroller (AT89C4051) in which the three lines (DI, DO, and ICLK) are connected to its port pins.

Also, on the sub-circuit, I included LEDs for debugging. I setup my microcontroller program so no LED goes on until ICLK becomes low then high again.

So I did a loopback test of each pin. I plugged this circuit in my computer and tested each line one-by-one with Quick Basic. Yes that program comes in so handy, all I had to do was run these instructions:

out &H378,&Hx0 ;where x=number representing what bits are set or cleared
print inp(&H379) ;if high nibble except MSB is same as what was put in then everything works

So this particular circuit works even with the parallel port connector metal shield removed.

Here's where strange results happen.

As soon as I plug it into the PC port with no external power, some LEDs glow dimly yet I never asked for this.

Once I apply the 5V power after, sometimes the circuit works and sometimes it doesn't. Sometimes a light goes on right away.

I could suspect ground loop issues but I have not spot any of them in either of the PCBs

So the only thing I could guess is the parallel port producing interference?

The circuits are very close to the computer.

This tempts me to ground every unused input of the parallel port in an attempt to cut interference but then again should I?

The only other option for me is to ditch this circuit and make one with a few buttons and press them a million times to run tests which is what I don't want to do.

I setup my port on the PC to AT compatible (SPP mode).

If not that, is my PC completely guilty?


texts: Are USB hubs that backfeed power upstream bad?

texts:
Most USB hubs and active/amplified extension cables allow you to connect an external power supply to the downstream USB port so you can run devices that need more power than the upstream USB port can supply, and/or avoid any voltage drop from the lengthy cable.

Many of the cheaper devices however, simply connect the external power connector in parallel with the power lines in the USB cable.  This means the external power supply can backfeed power up the USB cable and into the source device (such as a computer.)

Is this situation bad?  I am guessing that if both the computer and external power supply are switching PSUs then they will simply adjust the amount of power each puts on the line and it won't cause any problems, but is this thinking correct?  What if the external power supply is not of the switching variety?

Are there any situations where this could cause real problems?


texts: What is an antenna amplifier ? How does it add gain?

texts:
I don't know what exactly does antenna amplifier mean.
Is it possible to increase the gain of a Tx antenna ? Where do I connect the antenna amplifier to it ?

If, for example, the Tx has a power of 20 dBm , antenna has a gain of  10 dBi & antenna amplifier "repeater" has a gain of 60 dB "like common cellular repeaters" , what does  this gain mean ? Does it mean the antenna gain will be 10+60=70 dBi ? Or does it mean the Tx power will be 20+60=80 dBm ? I am confused !

Another example for Rx antenna, if we have a receiver with a sensitivity of -114 dBm and Rx antenna has a gain of 10 dBi  & we  connect it to a 40 dB amplifier, does it mean  the total sensitivity will be -114-10-40= -164 dBm ? (please ignore the SNR)

What is the weakest possible signal at Rx antenna to be amplified  ?

Last  example , just to  understand what the rule of repeater and its gain is.

If we use a Tx that has a power of -30 dBm at 1000 m, antenna has a gain of 10 dBi, & at 1000 m distance there is a repeater that has a gain of 60 dB, how do I calculate  the total gain in this situation ?

Should the total gain at repeater be   10 "antenna" +60 "repeater" ?

Or should we just calculate the resulting power at repeater instead of its  gain ?
Do we write (-30 "Tx"+ 60 "repeater")"total power" + 10"antenna" ?

Sorry for my long question,  I am a beginner , I want to understand .

Thanks.


texts: How electronic components keep synchronized?

texts: So, voltage travels super fast right? Still, there has to be some lag between voltage traveling from one transistor into another. How is a circuit kept synchronized then?


texts:
Update/significant change:

The question below is based on a false premise: taking into account that an IDC with keys pointing out from the cable on both ends swaps the front and back rows, simply rotating one of the connectors gives a 1 -> 1 mapping (thanks @DiBosco for pointing this out). The only remaining difference is that the notch of the connector on one of the footprints has to be on the opposite side relative to pin 1 as compared to the other.

I do believe that the fact that I readily made such an error in my thinking, which would have led to a pair of incompatible boards, shows that the following question is relevant:

When making connectors between PCB's, given the orientations of the connectors and the PCB's, and optionally the type of cable used to connect them, how does one make sure that the pins in the connectors are mapped correctly, before manufacturing the boards? For an example where the mapping is non-trivial, if I use two double row SMD connectors, one male the other female, using the same footprint on both PCB's (i.e. same pin numbering when viewed looking into the connector), and directly connect the PCB's (no cable), I do need to swap even/odd numbered pins on one connector relative to the other.

Also, related to the original question: now I still need to have two footprints, or I have to specify externally for assembly that the relation between the notch and pin 1 is different between the connectors on the two PCB's. Is there any neat way to deal with this?

Original question

I need to connect about 24 signals (give or take, depending on how many pins to dedicate to ground and power) between two PCB's. My current idea is to use a 0.050" ribbon cable with IDC connectors on ends (although see the end of this post).

When in use, the two PCB's will be laid side to side, and if I then place the connectors in the same position, and I want them to be keyed (say, a shroud with a notch on the side of the odd numbered pins), and connect the ribbon cable, I get something like this is wrong, I'm leaving it here for reference:

simulate this circuit – Schematic created using CircuitLab

i.e., pin 1 goes to pin 23, pin 2 goes to pin 24, ... and so on. The notches on the shrouds are on the side of the odd numbered pins.

My question is: while I can of course figure out the correct pin mapping by simply finishing the picture above, I feel it is a bit error prone (since there's no ERC or DRC checks across the two PCB's in my EDA). Also, I would imagine I'm not the first one to come across this problem, or one of a number of related pin mapping problems (say, stacking boards with connectors on facing sides). So I'd like to find a resource which would give the correct pin mappings for this, and preferably other related problems, but my google-fu has not been strong enough. Is there such a web site?

P.S.: any suggestions on better ways to connect the PCB's are welcome. PCB space is at a premium, I was just able to fit a 0.050" SMD -connector, but on the other hand the connection will be made by the end-user, so it must not be too fragile or difficult to connect. The device is a eurorack modular synth, so the user is familiar with connecting 0.100" IDC for the power, which is why the smaller IDC would at least bring some familiarity to the user. Currents and frequencies are rather small, < 50mA and < 1MHz.

Update:

an optimal format for the answer would be a footprint file (let's say KiCad, since that's what I'm using) that would give two footprints with differently numbered pins such that 1 -> 1 would give the correct result. The next best thing would be a table of mappings, which while error prone, would save one step where mistakes could be made.


texts: How to analize an ideal diode circuit with sinusoidal sources and storage elements (inductors and capacitors)?

texts:
In my first Electronics classes, we learned how to analyze a circuit with AC sources and ideal diodes but with only resistive elements. In such cases, the currents and voltages respond instantly to inputs (I mean, there's no lag). What we did was that, during the positive half cycle of the AC voltage source, we assumed the current was exiting from its positive terminal, and from there we imagined how the current would divide in each node as it traveled through the branches. I think this is the common way taught. However as soon as a capacitive or inductive element is added, currents and voltages can have lag, and a transient response exists. Therefore, in the positive half cycle of the AC voltage source, the current doesn't necessarily exits from its positive terminal at all instants during the half positive cycle. The \$i\$-\$v\$ characteristics of an ideal voltage source is \$v=v_s(t)\$ and \$i=\text{any value}\$.

My question is how can we analyze/solve a circuit with ideal diodes, AC sources, resistive elements, and energy-storage elements (L, C), in order to analytically obtain the expression for a voltage or current? I wasn't taught about that. My goal is to obtain an exact expression for a voltage or current. While I know using the ideal diode will actually give an approximate value, I'm asking for that model to simplify calculations. As an example, consider the following circuit, where each diode is ideal, \$R = 1 \text{ } \Omega\$, \$L = 1 \text{ H}\$, and \$v_s(t) = 12 \sin {2 \pi t} \text{ V}\$ (\$f = 1 \text{ Hz}\$), and the inductor is initially discharged. Let's suppose we want to solve for the inductor's current.

The current through the inductor, choosing the reference direction from node 2 to 4, and the current through D1, are the following according to LTspice.

Proposed solution

What I'm thinking to do is the following. In BJT circuits, in order to find its operating region, we initially assume the BJT is in active region, therefore we substitute it with its DC equivalent circuit in active region, then solve the circuit and compare if the assumption is correct. If it's correct, the analysis is done; if it's incorrect, we substitute it with the DC equivalent circuit in saturation region or cut-off region. Here I explain a bit more about this method.

So, I suppose that for diode circuits, we can also make an assumption and prove if it's correct or wrong. This answer describes the procedure I have in mind. However, since the source is AC and not DC, I think the solution we obtain will be valid only for half a cycle. So, we can not obtain the complete response for all \$t\$, but only up to the cycle we analyze. Is that correct?


texts:
I am currently struggling to determine some parameters of a stepper motor I am using. I am trying to calculate the number of pulses per second I can deliver to the motor reliably. This is relatively new topic for me and am having trouble understanding where this value is determined.

The data sheet for the Motor is here:
http://docs-europe.electrocomponents.com/webdocs/157a/0900766b8157a734.pdf

If this value is determined by what drives the motor, the driver is here:
https://www.sparkfun.com/datasheets/Robotics/L298_H_Bridge.pdf

The MicroController I am using is the BeagleBone Black.

EDIT:
Perhaps a better way of asking my question... I already know that the step angle is 0.9, therefore the steps per revolution (SPR) is 400, thus 400 pulses per revolution. However, my true question is how do I determine the number of pulses I can deliver to the motor per second?


texts:
My question is can I use a diode in series with a MOSFET, instead of pusing it as a flyback diode.

simulate this circuit – Schematic created using CircuitLab


texts:
I'm just a beginner, trying to understand an antennas and transistors as an amplifier, I'm studying, please correct me.

Here we have a voltage source, PNP bipolar transistor emitter-base-collector from left to right, speaker and an antenna (just a wire). All these stuff is connected as shown below. Red curves are electric components of EM waves.

As I understand the original signal (from the antenna) plays a role of a switcher in transistor, as a result we will have something like this:

So, will the scheme work?

My doubt why it will work or not:

This is not an antenna, hence the required "minus" on the base will be too low.


texts:
I'm working on a sensor project which uses TelosB based on CC2420 and MSP430F1611 running TinyOS.

The aim of the project is to measure the distance between two devices. I was thinking to measure the time needed by a signal to go from a device to another and return. To have some precise values I need to find the exact moment when the transmission starts and the reciving starts. I think these can be made by triggering an interruption on the SFD pin(which changes it's state at the start of transmission,end of transmission, start of recieving and end of recieving).

I use the component component(HplCC2420InterruptsC) with CaptureSFD interface which returns the timp of the SFD change but the precision is only in 32Khz timer:

async event void CaptureSFD.captured(uint16_t time)

this is the event triggered.

I need microseconds, that's why I search for a way to trigger an interrupt, so I can save a time value in microseconds (the event from the above interface is asyncronously triggered so the time difference is too big).

So how do I trigger in this system (TINYOS) a syncronous interruption whenever the SFD pin changes value(1 or 0)?


texts: Generating a high speed single-ended voltage output from differential currents

texts:
I'm working on a signal generator using a high speed DAC, which has balanced current outputs (two outputs, each 0-20mA, 180 degrees out of phase). The DAC is 250MSPS, so I'd like the analog frontend to handle up to about 100MHz. The output needs to be a single-ended voltage signal, with 10Vp-p.

For the same application with slower signals (a 16MHz DAC), I've used an architecture like this:

A simpler variant that should still work is to use resistors to ground in place of the transimpedance amps to convert the current to a voltage for the difference amplifier.

However, all the high speed amplifiers I can find, such as the THS3202 from TI, are current feedback amplifiers. As a result, their negative input has a low impedance, which - at least as far as I know - makes them unsuitable as differential input amplifiers.

How can I convert differential current outputs to a single ended voltage at these sort of frequencies, given the seeming unavailability of high speed voltage feedback opamps?


texts: Is it possible to add GPIO pins to an old desktop/laptop for use as a development board?

texts: There are many projects online that make use of old computers by turning them into servers etc. I wanted to know if it's possible to turn an old pc/laptop into an x86 development board like the Udoo or lattepanda etc. It looks as if the only thing missing is the GPIO pins. Can one make use of ports like USB or thunderbolt etc to add GPIO capabilities?


texts: Connecting Analog GND and Digital GND of ADC

texts:
I'm trying to make a simple line tracing robot, however I couldn't figure out how to connect AGND and DGND of A/D converter(MCP3208) on a simple perfboard design. I need some guidance how to smooth out the noise for AGND and how to connect these two grounds.

The A/D converter that I'm using(MCP3208)

Thank you!


texts:
The referenced article over on http://www.instructables.com/id/4V-Lead-Acid-Battery-Charger/
indicates a Li Ion charger for mobile phones may serve to charge a low AH SLA.

I held the impression a Li Ion charger actively interacts with firmware aboard the mobile battery to control the charging.

Is the mobile charger capable of charging an SLA? In the absence of necessary firmware, is there risk of damage to the charger, or the SLA, or the target mobile Li battery after the mobile charger is used to charge an SLA?


texts: Interfacing with (Two) Full-Bridge PWM Motor Drivers to Control a Stepper Motor

texts:
I am working to interface with an existing PCB with on-board Full Bridge PWM motor driver chips, which drive a stepper motor. The interface lacks any kind of standard step (clock) or direction signals and I can only use the input signals that are there. There are two chips to drive each stepper motor, they are Allegro A3959. I want to keep everything as is, so I can only  work with what is broken out, but I can add an interface chip  using the available inputs.

I would like to add a new controller to drive the chips, which can only provide the standard 'step (clock) and direction' outputs. How can I accomplish this? I have thought about using a L297 Stepper Motor Controller chip as an intermediary, but with only limited inputs (and no access to sense resistors) I don't believe I can use it. Even if I had access to the sense resistors, I don't know how I would interface it.

For simplicity's sake. I have created a very generalized diagram of what I do have available to me (the pin outs are generalized):

As you can see, I only have the following pins available:

Phase A (direction)
VREF A (current regulation)
Phase B (direction)
VREF B (current regulation)
Sleep (this controls many chips on the board and can't be considered for pulsing)

It is my understanding that I can easily control the direction through the Phase A/B pins. Digital signal 0 for one direction, digital signal 1 for the opposite direction. How do I control the VREF with a clock input signal though?

The datasheet for the A3959 states the following:

  "Current Regulation. Load current is regulated by an internal fixed
  off-time PWM control circuit. When the outputs of the DMOS H bridge
  are turned on, the current increases in the motor winding until it
  reaches a trip value determined by the external sense resistor (RS)
  and the applied analog reference voltage (VREF):

  ITRIP = VREF / (10 * RS)

  At the trip point, the sense comparator resets the source enable
  latch, turning off the source driver. The load inductance then causes
  the current to recirculate for the fixed off-time period. The current
  path during recirculation is determined by the configuration of
  slow/mixed/fast current-decay mode."

Is this similar to a clock signal? (Note: ITRIP is already calculated perfectly for the motor current when VREF is a full 5 volts.)

If I were to supply 100% VREF, would it build up to 100%, produce one single step, trip and then wait the fixed time off before going again?

Would a constant VREF keep the motor going, pulsing automatically?

Full settings for the chips in current configuration is as follows:

Enable pin is held constantly high.

  "If enable is kept high, the current will rise until it reaches the level set by the internal current-control circuit."

EXT Mode is held constantly low. Decay = Fast.

  "With EXT MODE low, fast decay mode, the opposite pair of selected outputs will be enabled during the off cycle."

Internal current-control Mode pins are held constantly high. Decay = Fast, %tOFF = 100%.
PWM blank timer is held constantly low. TBLANK = 6 / FOSCILATOR.
FOSCILATOR is to have a typical value of 4 MHz.
Fixed off time is typically 24 μs with a 4 MHz oscillator.
Sleep logic is used to minimize power consumption. It is not to be used as a substitute to enable.

I normally have a really great understanding of stepper motor drivers. However, all stepper motor drivers I interface with pretty much always have step (clock) / direction as a standard input. Since this is an phase / enable chopper circuit, it will require more expertise (or a specialized controller chip) to figure out.

What is the best approach?


texts: Can closed metal box work as a wave-guide for wireless transmitter?

texts: I am using NRF24L01 and ZigBee modules for wireless communication. I kept the modules in the tapered closed aluminum cylinder for sensor data transmission. The signal was being received when the module was placed at some specific positions (closed to the center). It stopped/slowed down the transmission when it was at other locations. Does this mean it is working as a waveguide?


texts: Help identifying a board edge press-fit contact

texts:
I'm working on a project involving a Becker car radio from the 1980s and I need some help identifying a part that is used inside. It's the gold press-fit contact shown below and it's used to make a right angle board-to-baord connection. The extruding part on each contact is pressed into a plated through hole on another PCB. The contacts themselves are through-hole soldered onto the host PCB with 2 pins each. The pitch on the board seems to be 2.5mm, but they are each a separate piece.

The project is to create a modified replacement board for the one pictured, so I have some flexibility for a different part, but it has to provide the same function.

I'm not sure if I'm searching the wrong thing or this is an obscure part, but I'm not having any luck finding a similar contact online. Any part numbers, names, or pointers would be appreciated, thanks!


texts: Can I (ab)use a transistor as an ESD protection diode?

texts:
The MIDI specification suggests a fast switching diode to protect the optocoupler's LED against ESD that could exceed its reverse voltage:

But this is the only diode used; I could simplify the BOM if I could replace it with some component already used elsewhere in the circuit.
So why not use a PN junction of a general-purpose transistor?

Compared to the 1N4148, the 2N3904 has smaller reverse breakdown voltages, but this would not matter in this application because the LED clamps such voltages.
Other parameters like capacitance or maximum current are comparable.
So this looks as if the transistor would work, wouldn't it?

And which junction should be used, base/emitter, base/collector, or both?
And what to do with the unused junction?


texts: How to check if the pin headers are soldered well?

texts:
I don't have much soldering experience. I soldered 5 level converters, they seem to work and look about the same as this STM32 as I soldered.

However, after a closer look I see not all pens 'shine' and some don't have a good form. Probably used too much soldering, because it was quite hard to determine (using too less cause nothing but heating pins which I also wanted to prevent more than needed).

How can I best test if all soldering connections are ok? I don't have any STM32 experience, so I don't know if there is a general way to do this except for writing programs/testing for each pin?

Or is it visible directly from the pictures that this will not work (I hope not).

(btw it's hard to make pics, they are all from the same STM32, the first pic shows soldering connections which are much darker than the second, the second looks more like the real thing).

Edit: I think I know what I did wrong ... since I didn't have much space the solder tip and solder tin sometimes might have touched directly, also during that the pin itself might not have been heated enough. Next time I really should make sure the tin and tip are on opposite sides of the pin.

Update: Used aceton/alcohol

I used a mixture of 50% 96% alcohol and aceton and got the following results:
It seems to leave some white residue ... wondering if that is a problem.


texts: Why does the current enter the negative terminal of this element and it is still absorbing power?

texts:
Hi there, I am learning the kirchhoffs-laws, according to the passive sign convention if a positive current enter through the positive terminal of an element and exits out of its negative terminal, then the element is dissipating power.
So, in this diagram the current enter through the negative terminal element with 3 ohms resistance. The calculation shows that the voltage across it is the same sign as the voltage across the 2 ohms resistor. Why do they have the same voltage sign although the current enter through different polarity of terminal, is there any element that has such properties in real life?


texts: Dual variable power supply with LM337 and LM317

texts:
I am making this circuit:

C1, C2 2200 μF 50 V Electrolytic Capacitor

C3, C4, C5, C7 2.2 μF 50 V Electrolytic Capacitor

C6, C8 100 μF 50 V Electrolytic Capacitor

R1, R4 5K Potentiometer

R2, R3 220  \$ \Omega \$ 1/4 W Resistor

D1 to D4 IN 4007 Diodes

U1 LM317 U2 LM337 T1 24 0 24 Center Tapped 2 Ampere Transformer

the goal is to create a power supply that can give a variable supply of -15V -to-0  and 0-to-15V

I have already placed all the components in the breadboard and tested the output.
The problem is the readings on the positive side is from 1.6 V to 30 V when I turn the potentiometer from he left most to the right most same with the negative side( but the sign is negative)

What can I do to get the specific range I need of of -15V -to-0  and 0-to-15V


texts: 0 or 1 as desired output after certain threshold

texts:
I'm a high school student, making a project which uses LDR, as we know resistance across the terminals varies according to the amount of light falling on it, but in my project I just need two definite states, either high or low as output, i.e after certain threshold the output should high/low.

Problem is that, I can do this with an Arduino but I want to keep it as simple as possible, so I'm looking solution of this problem in form of any combination of logic gates available in market.

I'm not still in college and don't have anyone around me capable of helping me with this matter, so I'm here looking forward to you guys.

Thank You


texts: PCB Layout Optimization Regarding VCC and GND

texts:
I have two questions regarding routing power and ground.

With respect to power, is it generally better to flood copper planes and have one via per pin/pad connecting directly to the plane under, or is it better to branch out from one via with a star topology? Pardon the sloppy layout, but see the below images where I have three bypass capacitors and a single via in the bottom picture compared to the individual vias for each pad connecting to a pour on the top one.

Secondly, in regards to ground, I was viewing some board layouts based around RF chips that flooded all the empty spots with GND pours on top and bottom layers- what is the purpose/benefit of this? Free real estate for possible noise to couple onto?


texts: creating a differential amplifier for low voltages (current shunt)

texts:
I'm trying to create a "precision" fully differential amplification stage, to measure uA on a 10R shunt, and mA on a 0.01R shunt. shunt resistance values are set at those values for burden voltage reasons. thus the voltage would be ~10uV/uA and ~10uV/mA.
my topology of my frontend is two sets of Shunt -> x10 differential amp -> PGA -> Muxed input of 24 bit ADC (LTC2442).
my question here pertains to the x10 stage amplifier. I've come up with the circuit shown, but it does have its downfalls, mainly requiring 2x 8$ resistor packages each. Cost is not the issue, I just feel that I might be overlooking a simpler solution. I might add a potentiometer to adjust the CMRR, but I'm hoping the resistors match closely enough.
My question is whether or not my design is a good implementation, any improvements to my design, or a solution requiring less matched precision resistor packages.
Pictured is a "clear" picture of what I'm considering using (NOT the one used). the one actually used has two packages of 4x 5K and 4x 1K resistors, as the 4 values need to match closely, but the ratio is software calibrated. VREF = 2.5v. SENSE flags are connected directly to shunts.


texts: ATmega168 TQFP vs. 28DIP - different behavior after programming

texts:
I have developed a program for ATmega168 using Atmel Studio 7.0 and Atmel-ICE as debugging interface.
The development was done on a 28DIP package, since it's easy to work with it on a breadboard. Moving from the prototype to PCB, I chose a 32pin TQFP package instead of 28DIP (please see the part numbers below).
I can program the PCB device with Atmel-ICE without any warning or issues after reading its signature. The device gets flashed, however it does not do anything afterward as if the program isn't there. I wonder if anyone else has seen this?
ATMEGA168-20AU-ND, TQFP 32pin package.
ATMEGA168-20PU-ND, 28DIP package

The default TQFP package had HIGH.WDTON (Hardware Fuse Watchdog always on) and that was not the case for my prototype where I did compare and match in Timer1 to write an interrupt driven delay function.  Turning watchdog on was messing up my delay function, and when I turned it off, the 32 pin package also did what I expected. Thank you all for your responses.
Hamid


texts: Pls help by answering.Thank you.Need to understand before proceeding further

texts:
I have some doubts and confusion. Please clarify by explaining the science behind it. Thank you. I have no knowledge in electicity. Regardless what i put as voltage and current is just example, just want understanding on it.
Hypothetically, a charger output 5V 2A, device input 5V 0.5A will it work? I read that if input is lower than output will work because device draws what it demand from charger and current is low so preventing cable and charger heating up which may lead to fire.

Everything should be fine because communication exists between charger and device due to the circuitry component thing of device and charger (please clarify). Device has a charging controller component in it and so do charger. Device can be phone, tablet, laptop, electric fly swatter, etc. whereas charger can be power bank and power brick or corded wall wart.

However, someone pointed despite working fine its damaging charger due to heat building up at charger and will die at point (please clarify) and

some say by charger will supply its stated current in this case 2A than the needed 0.5A it will cause battery to swollen (please clarify). Does this has to do with the circuitry thing?

On the other hand, if a charger has output 5V 2A, device input 5V 3A will it work? I read that if input is higher than output will not work because device draws what it demand from charger and current is high so it causes the charger to heat up and oversupply which may lead to fire in cable and charger and blown fuse in charger.

Everything should be fine because communication exists between charger and device due to the circuitry component thing of device and charger (please clarify) mentioned above because

I read charger will only supply up until its stated current output so no blown fuse and device just chargers slower? (please clarify)

What if the voltage and current output is different from required v and I input? Will it work? I read it should because regardless voltage higher or lower it wouldn't work cuz too high device swollen and heat up while too low device wont charger or work. (please clarify)

How about current how does current gets affected in this situation when voltage and current is different?
I just know (no knowledge about it, just informed about the words) is depending on device and charger intelligence and the communication circuitry thing,are there more? Please clarify help understand things. Thank you.

I hope you understand what I'm talking about.


texts: Why are these capacitors needed on the USB-C CC lines?

texts:
The reference design for this USB-C chip recommends capacitors to ground between 200 and 600pF on the CCx lines. I have never seen a capacitor to ground on a digital signaling line. Does anyone know what these might be for? Other similar chips also seem to include them.

Datasheet Link


texts: How to write KCL and KVL in these circuits?

texts:
I want to use KCL on this circuit. I have
\$i-i^{i}_{D2}-i^{i}_{D1}=0\$.

Are the correct currents:

\$i=10V/R_1\$?

\$i^{i}_{D2}=V^{i}_{D2}/R_2\$?

But that is \$i^{i}_{D1}\$? I have no resistor.

On the circuit below I want to use KVL, but how should I do that? I don't know how to include \$V^{i}_{D1}\$ in KVL.

I guess this is wrong
\$10V-R_1i-V^{i}_{D2}-R_2i^{i}_{D2}-(-10V)+10V=0\$?

Thanks!


texts: Understanding the basic common emitter amplifier

texts:
I'm struggling to understand intuitively this basic circuit:

simulate this circuit – Schematic created using CircuitLab

I know that out is \$k\cdot\mathrm{in}\$. What I'm struggling with is to understand intuitively what all those resistance are making. Everytime I think about it, everything seems too intricate and coupled.

What I'm asking is an intuitive explanation of how to solve this circuit, but it is maybe a bad question for StackExchange, I'm not sure.

EDIT: I'm using the ground symbol from CircuitLab for +5 because I didn't find any better suited symbol.


texts: Is Joule Thief a constant current source?

texts:
Wikipedia describes Joule Thief, shown below, as a circuit that can be used to provide constant load even when voltage of a battery decreases. At least that's what I think the article means.

simulate this circuit – Schematic created using CircuitLab

The question then is: Is this circuit a (mostly) constant current source? Or does it maintain constant voltage? How does one calculate the current/voltage at the load given a resistance RLOAD?


texts: How to view and customize beta of a transistor in LTspice

texts: If I need to set beta to a custom value, is it possible to make a customized transistor with a beta of my choice? In other words, can I edit a ready or generic transistor's beta and save it as a custom transistor? How can I do that?


texts: What happens to an electrical system at its pole?

texts:
Pole is defined as the value at which value of a function becomes infinity.

Let's say I have one LTI system with transfer function H(s)=1/s+1.

How the system will behave when s=-1.

From Bode plot I can see at pole the slope of Bode plot changes at pole frequency.

Can someone clear this thing?


texts:
i need to be able to update this memory storage device 1000 times per second via MCU in small 8 byte of data chunks trasnfers, and then read back the data into the PC. Should I go for the USB SD card reader - easily r/w from both MCU dev board and PC, or is it too slow for such small and fast transfers ? in the latter case - any cheaper-than-flash-programmer way to read it back into PC ?

edit

The data comes from sensors -> MCU algorithm, 8 bytes each milisecond. I need to store no more than 5 minutes of such data ~ 2.4 MB, but having 1-2 hours of it might prove useful later. I shall then transfer it on a PC in order to plot it on a graph or otherwise analyze it.


texts: Frequency Modulated Continuous Wave Radar based sensor module

texts: I am designing a frequency modulated continuous wave radar  sensor module, I want to know as the level of IF signal is low at output, what level of amplification would be required to analyse the output by a microcontroller later.


texts: What does address like 0xABCD_EFGH means in a memory map?

texts:
What does an address like 0xABCD_EFGH means in a memory map?

I am new to programming microcontrollers, so please excuse me if its a bit lame.

What does one mean by "123 Data Input Registers (GPDI0_3–GPDI120_123)"?


texts: Power consumed by an LED in a simple circuit

texts:
I am in the very beginnings of studying circuits and am a little confused on calculated Power.

If I have a 9V Battery, 4 x 10k Resistors and a single LED, how would I calculate the power consumed by this LED?

I have measured current of the circuit and voltage measured at the LED anode/cathode.

If I am reading my book correctly, is it really as simple as P=V*I?

simulate this circuit – Schematic created using CircuitLab


texts: Is it possible to wire up a cellphone screen to work with a different device?

texts:
I'm trying to find out if it is possible to send video to a cell phone screen (just the screen, not the phone) like this one from something like a video-mp3 player or even from maybe a mac-mini, or something simpler like a microcontroller with the video stored on an SD card perhaps. Additionally, if it is possible, how would I go about doing something like that?

It doesn't necessarily have to be a cell phone screen, but it needs to be around that size, with a very dense resolution for its size. This is why a cell phone screen seems optimal for the job. I've been trying to find other alternatives, but the screens from hobby electronics sites fro things like the Arduino seem to be very small resolution and low color depth (ie 8 bit).


texts: I want to ask a question about transformers. Primary and secondary parts are isolated  electrically and there is only a magnetic coupling. If there is a short circuit in the secondary part, is our primary current affected by this problem or not? Because there is not any electrical connection.


texts: What waterproof temperature sensor do I need to measure water temp using an arduino mega?

texts: I consider myself a complete novice when it comes to electronics.  My current project consists of measuring water temperature using an arduino mega.  What parts will I need to complete this project?  So far I searched sparkfun and arrived at this: http://www.sparkfun.com/products/11050. Do I terminate the leads directly to the arduino or to a breakout board to calculate the Dallas 1-wire signal?


texts: How make a dual +-12V supply from a 24V SMPS

texts:
I'm trying to power a home-made load cell transmitter using a 24V single SMPS. I need to make +12, 0 and -12 Volts that are capable of 50mA. I wish to power multiple channels of opamps and bridges.

I don't have much budget and availability of components in India.

I have an idea to use 1 LM7812 an 1 LM7912(negative) linear voltage regulators and a voltage divider setup to do this as per the circuit below.

simulate this circuit – Schematic created using CircuitLab

Would this work? I've modified it from the suggestions and articles elsewhere.

Somebody suggested me one other circuit but I am concerned about the current capabilities of the opamp.

simulate this circuit

Would this work? If yes, please suggest suitable op-amp.

Are there any other techniques that would do the job economically?


texts:
I’m making a BLDC motor controller application. The motor control IC (Allegro A4931) uses low side current sensing (R7,R8,R9) for controlling the motor. Unfortunately the motor IC does not output a amplified version of the SENSE voltage. I would like my MCU to measure the current with the use of the same resistor. Is there anyone that can help me pick out the right components to do so? I would like the MCU ADC to measure 0V at 0A and Vcc (3.3V) at 5A through the resistors. There is no need for a super accuracy (+-0.25A is ok).

Thanks!


texts: Where can I get a small cheap linear actuator?

texts:
First, I should clarify: I am not looking for much power or much precision. I am looking for the cheapest thing I can plug into an arduino. I am just looking for stuff I can use for prototyping/proof-of-concepts.
I was taking apart an old CD drive when I noticed there was a linear actuator being used for controlling the head. It seemed perfect for my purposes. When I came across this article I realized that this thing was actually quite precise.
This raised a lot of questions, but the most important one to me is:
Do I have to buy a CD player every time I need a linear actuator?
Where do I get those particular linear actuators found inside a CD player? I assume they are cheaper than the CD player itself.


texts:
In my set up I have a scope (high end Agilent scope), a PC with a USB port and Device Under Test. The DUT is powered from the USB port of the PC. PC and Scope is connected to the same power strip.

When DUT is powered and when I touch the ground pin of the DUT with the ground lead of the probe, I often see a small spark which means I have a potential difference between the probe's gnd lead and the GND of the DUT.

Is this common? I am surprised to see a potential difference between grounds given all powered from the same power strip. I cannot trust my measurements. What I am doing wrong? Why there is a potential difference between grounds?


texts:
I am investigating the accuracy of a crystal mounted on a MCU. The API provided by the MCU manufacturer has a TimeGet48 function that returns a 48-bit number indicating microseconds elapsed.

What I did is to configure the MCU to output its internal clock every 10 seconds via UART.

'19:15:18.830 Time: 0000, 947edfeb',
'19:15:28.829 Time: 0000, 95177715',
'19:15:38.829 Time: 0000, 95b00e3f',
'19:15:48.828 Time: 0000, 9648a569',

Above is a portion of the log. Each line of log consists of PC's clock time, high 16 bits of the 48-bit timer, then low 32 bits of the 48-bit timer. I plotted t_crystal - t_pc vs. t_pc below:

This plot shows the time deviation over a period of about 14 hours. I was expecting monotonous increase or decrease but this figure really makes me wonder how this is possible.

I am thinking of the following factors:

PC clock (I use Windows 7) might not be accurate. Probably PC will sync to a global time server once every few hours. However, when I investigate this in Task Scheduler. My time synchronization was set to 1AM every Sunday of every week. This log was captured on Tuesday so PC time would not change due to synchronization.
PC clock and crystal time were both subject to truncation or rounding obviously.
Temperature changes due to aircon. I logged these data over night (6pm to 8am next day). Aircon in my office shuts down after 6pm and turns on at 8am.

These factors would definitely impact the crystal deviations. However, none of these makes the zigzag-shaped fluctuation sensible.

[Update]

I tried Brian Drummond's suggestion and let it run for 4 hours and it indeed worked. Here is new figure.


texts: How much power (amps) through 5.5mmx2.1mm power jack? Through a DC switch?

texts:
I am in the process of building a DSLR cooler (I use it for astrophotography) using a couple of TEC1-12703s (12V 3.3A) or TEC1-12704s (12V 4A). The ultimate idea is to run the TEC's at a higher power when initially cooling to the target temperature, then throttle them back to maintain the temperature as best as possible.

The bulk of the cooler will use an Arduino (~15mA), a power-on LED (~20mA), a couple of sensors (~1-1.5mA each when measuring, ~40µA standby), and a couple of fans (~65mA). So total power draw from most of the parts won't be very high (<200mA).

A couple of the PWM outputs on the Arduino will be used to switch IRBL8748PbF N-channel MOSFETs to deliver power to the TECs. The TEC power will be LC filtered, and a schottky diode will be used on each filter to make sure I don't fry the FETs (not sure if that would really be a problem, but I threw them in just to make sure I don't have weird voltage spikes at the FET drains). Ultimately the fan speed would also be controlled with PWM outputs the same way as the TECs are, with a MOSFET, however to start they will just be connected to the main 12V source and run at full power.

With two TECs, that is potentially up to 8.2A of total current. Even with the lower power TECs, that is still 6.8A of total current. I am beginning to wonder if I can send that much power through a standard 5.5mmx2.1mm power jack. I am also beginning to wonder if I can find a DC power switch that could handle over 8A.

If finding a switch that could handle that kind of power is unlikely, might it be possible to power the TECs directly off the power from the jack, and put the switch after that power line? Since the TECs won't actually power up until the MOSFETs are switched on, they should remain off until the power switch is flipped. At that point, only a few hundred mA would be pulled through the switch. Which would leave only the power jack in question.

Thanks!


texts: What is an appropriate silkscreen pattern for upright through-hole diodes?

texts:
I'm currently using this:

as a pattern to indicate a through-hole diode with anode touching the top pad and cathode in the air.

Is there a more standard way to indicate this?
Is there a standard as to which orientation is preferred for upright diodes? The only thing I've found on the internet is a lead-forming company which shows both options ("band-up" and "band-down").


texts:
LT3080 documentation states under absolute maximum ratings:

  SET Pin Voltage (Relative to OUT) ±0.3V

(http://cds.linear.com/docs/en/datasheet/3080fc.pdf page 2)

In the documentation there's also figure named "Lab supply" (bottom of page 18) with 2 LT3080s. I simulated this circuit in LTspice and it seems that in constant voltage mode the current limiting LT has SET about 1V higher then OUT. Similar thing happens with voltage setting LT in constant current mode.

green trace is OUT, blue is SET (both on U1), circuit set to 10V 1A, load draws 10mA

Is this how this should work?

Note 7 about SET pin current states:

  SET pin is clamped to the output with diodes. These diodes only
  carry current under transient overloads

How is this situation supposed not to damage these diodes (in steady state)?


texts: Can I connect an analog sensor like ACS712 to a digital input pin on Arduino?

texts: I want to know that if it is possible to connect an analog sensor like the ACS712 Current Sensor to a digital input pin on the Arduino to determine only HIGH or LOW values instead of the analog values (0-1023).