texts: When would it become necessary to use an OS for an ARM MCU

texts:
I take it an ARM MCU can be run without an OS - at which point might it become necessary to install one?

Can the mbed SDK run without the mbed-os or any other mbed for that matter?


texts:
I needed some advice on my first ever PCB. I am trying to build the circuit below (schematic drawn using OrCAD Capture), which is straight out of the datasheet of the flyback controller LT3748.

I did some reading (including some of the posts on this forum), and decided to adopt this plan:

2-layer PCB: All components/tracks go on top, bottom layer has ground plan only
All components are surface mount only.

Ok so my first attempt on the PCB is below (using the ExpressPCB software). This is a class project and we must build our own transformer. We couldn't get the bobbin we wanted and so decided to just lay down the transformer somewhere next to the board and connected it through a 4-pin connector.

We couldn't really mimic the layout suggested in the datasheet, as we're using only a 2-layer design for various reasons. We do realize that a 4-layer design along with a small commercial SMT transformer would have been ideal, but we're working with what we've got.

So based on some of the feedback below (and thanks to everyone who commented), I've made slight improvements to the PCB (as shown below).

I also have some questions:

The datasheet advises to isolate or physically separate the high current ground from small-signal ground. The secondary ground is completely separate, so that's done with. As for primary, the only high-current grounds are those of Vin and R8 (the sense resistor). So, is it a good idea to connect the negative terminals of Vin and R8 with a track and then connect that track at one point to a ground plane that will have all the other small-signal grounds. The only penalty then would be that the R8 to Vin track would be quite long (since I'm using 2-layer only and wouldn't like to break my ground plane underneath, unless it is less worse than running this long track).
As you see from the schematic, I'm running two tracks underneath the IC (i.e. on the same top layer). Do you foresee any problems there? My IC shouldn't get hot, as it works with small current only.


texts: Can one use a conventional microphone as an underground acoustic sensor?

texts: I need an acoustic sensor I can bury to monitor the immediate area acoustically for footsteps. Is it possible to simply bury a microphone and call it a day, or would a more specialized underground acoustic sensor be necessary?


texts: Why most particle accelerators used vacuum diodes instead of transistors?

texts:
HERMES III (High Energy Radiaton Megavolt Electron Source) at the Sandia at Sandia National Laboratories is the world's most powerful gamma ray generator. HERMES-III produces a highly energetic beam that tests the capability of electronics to survive a burst of radiation that approximates the output of a nuclear weapon. It used a field emission diode, instead of a transistor.
I wonder why most accelerators used vacuum diodes instead of transistors. Transistors are much smaller. What are the reasons?


texts: Inner structure of a bipolar stepper motor?

texts:
The classic diagram looks like this with coils just positioned sideways to the rotation

I'm not sure if this is just a schematic or it indicates the actual structure. However I assume the actual structure is more like this

This makes more sense in terms of lining up the motor with more precision, although the first (sideways coil) setup should still be able to control a magnet with a bit more effort.

But finally looking up the actual stepper inside I see this.

How can 4 wires control so many coils. Can someone help me understand what's going on here.

Thanks


texts:
I have noticed that during my circuit design i always end up finding around the net  better ways to improve my designs pic related its an example,

Its a fuse blown indicator that gets improved by using a mosfet, in the left  the led only turns on when there is a load connected and the fuse is blown, but in the right circuit (mosfet one) the led turns on whenever the fuse blows even if there is no load

Even after reading the theory i didnt understand how mosfets worked until i saw this working live

I have been wondering where can i find a huge compilation like this, im thinking about a huge compilation of circuit designs that can be implemented right away, some kind of bible that has a brief explanation of all kinds of configurations for OP amps, all kinds of circuit schemmatics for several types of transistors, in short im looking for a circuit compilation

does this book or something similar exist?


texts: Question about the value of Output voltage ripple mentioned in power modules datasheets

texts:
I am searching for a power module that takes +15V and converts it to -15V but one important spec is the "Output Voltage Ripple" rating. I found this module from TI: PTN78000A

I found that its output voltage ripple is 2% Vout(pp) which is equivalent to 300mVpp in my case and this is not acceptable for me. I understand that the output ripple depends on the filter (caps and ferrite bead for example) at the output of the power module, so does this mean that the 2% written in the datasheet is for the module alone without any output filters?

Also, If I want to reduce this 300mVpp to say 50mVpp, how can I design the output filter so that it can cause this reduction in ripples?


texts: Bypass caps on RF board: why are there three different size caps in parallel?

texts:
Take a look at this evaluation board for a variable gain RF amp (datasheet):

J5-J10 are intended to connect to DC power (with the exception of J6, which is a DC analog control voltage). All of these lines have three capacitors in parallel. Take the trace connected to J10, for example. On your way from J10 to the pin on the chip, you go through these three capacitors:

A 2.2 µF capacitor in a big package (called "CASE A" in the datasheet)
A 1000 pF capacitor in an 0603 package
A 100 pF capacitor in an 0402 package

Why are three parallel caps used instead of one 3.3 µF cap? Why do they all have a different package size? Is the order important (i.e. is it important that the smallest-value capacitors be closer to the chip?


texts: Is there any way to drop 230V AC  to 200 V AC by using resistor? I want to drop voltage before applying to a 12 0 12V 500mA transformer. If yes what will be its rating?


texts: How to set the boost output voltage in this IC?

texts:
I want to use this boost IC to drive an LED string.
I have 9 LEDs. 300mA forward current and 3V as typical Vf.
Can someone guide me on how to set the output voltage of the LED string using that IC?


texts:
Im designing a simple usb application and I used this USBLC6-2 for ESD protection and voltage surge on the Vusb. On the datasheet it says that the breakdown voltage is min 6V, however I did some test for this if this is for real. I input a 10V on the Vusb and I am expecting that the zener diode should clamp the voltage to 6V however I can measure 10V.

Can anybody explain why the input voltage was not clamped down to 6V as it is supposed to be clamp according to the datasheet?
With regards with my PCB layout i just followed what the datasheet says


texts: Over voltage protection on lock-in amplifier input

texts:
I'm performing an experiment in which I send a sine wave into a test device and try to measure its response which will be in the order of a few \$\mu\$V. This response is obtained from the buffered output of a controller box (commercial device belonging to the setup). Because of the available equipment I would like to measure this signal with a lock-in amplifier.
The problem is that due to the nature of the test device's feedback loop, the signal may get a DC offset of +/- 10 V at random moments. While there is a TTL reset available to remove this offset as quickly as possible, I fear that the 10 V will damage the input of my lock-in amplifier (sr830).
Is there an over-voltage protection circuit that I can build in between my device's output and my lock-in's input to protect the lock-in from these occasional high voltages?


texts: Best way to diagnose embedded computer in field problems?

texts:
I'll soon be deploying a new embedded system.  I have a separate serial port that can connect to a diagnostic program.  I also have two LEDs, one I flash to indicate the OS is running, the other that the application is running.  I fear that it's going to be hard to work out what happened if the embedded system experiences a total crash however.  It does have a watchdog so would reboot, but I'd like to be able to work out why the crash occurs, if it does.

The only way I've done this in the past is to have a parallel system back in the lab, give it the same type of inputs, try and trigger the problem, then analyze through debug prints or outputs to digital I/Os to figure out what could be causing it.  Often it is very hard to replicate the problem however.

Does anyone have any advice on good methods they have for debugging in field problems?

Thank you,
Fred


texts: Problem with MOSFET making my current dissapear

texts:
The current of 150 mA has to go around 18 different circuits, one at a time.

Now I am trying to use 18 LDOs as suggested below. But now the problem is that the current that is supposed to be 150 mA drops to 10 mA. I was able to figure that the problem is the MOSFET. I plugged only 1 MOSFET without load and the current stays at 10 mA and when I don't use any load just the regulator connect to ground the current is what I expect, 150 mA.

simulate this circuit – Schematic created using CircuitLab


texts: How to calculate average delay time of circuit having several possible transition states

texts: Is it possible to calculate average delay for all possible states directly without calculating them individually using Xilinx or with Cadence.


texts:
This may be a stupid question, but stupid > dead anyday, so I'll go ahead and ask.

I have a schuko socket and a non schuko plug similar to the link.

The only thing keeping me from sticking the power plug in the schuko plug is the broad sides on the plug, not fitting in the schuko plug. Would it be unsafe to simply cut off the sides of the plug, so it would fit? If yes - why?

thanks!


texts: GY-521 Unable to set PWR_MGMT_1 register - can't disable SLEEP mode

texts:
I am attempting to interface between a custom 8051-based MCU and a new (ebay) GY-521 module (Gyro/Accel chip) using I2C bus.  I have written the I2C bit-bang functions myself and they seem to be working fine.  I can view bus operations (Read/write) on the scope, and I'm seeing ACKs from the GY-521 when they should be seen.

However, in order to read the gyro/accel data, I must clear the "SLEEP" bit from the PWR_MGMT_1 register.

Procedure:
 1. Send START sequence
 2. Send 7-bit address + WRITE bit (0)
 3. Read ACK from slave
 4. Write 8-bit register address (0x6b)
 5. Read ACK
 6. Write 8-bit data value (0x01 = use X Gyro as clock source)
 7. Read ACK
 8. Send STOP sequence.

I can watch the MCU write the new value (0x01) to the register, but then when I Read back the register, the value is back to 0x40 (default).

Any reads of the gyro or accel values return zeros due to the module being in sleep mode.

Here is the spec sheet for the MPU-6050 gyro that's used in this board.
https://www.cubby.com/pli/Spec+Sheet.pdf/_506bd71d53d3454282f06fa698666f04

Here's the register list:
https://www.cubby.com/pli/Register+Map.pdf/_17685da9808c42099c5ebdc1058c63b3

If you wish, I can post the scope output where you can see the value being set, the ACK received, and then reading back the value yielding the default.

Any suggestions appreciated.

Thanks


texts: Using 12v to power two 6v coil relay in series

texts: FTR-J2AK006W (https://www.fujitsu.com/downloads/MICRO/fcai/relays/ftr-j2.pdf) has two 6v coil inside it, does this mean I can connect them in series and feed them 12v?


texts:
I want to control an 5V relay board with an ESP8266 (which operates on 3.3V). Schematic of the board:

IN2 is normally on 5V and must be pulled to 0V for enabling the relay. I saw people using an NPN transistor like this (second image, the relay board has the same pins but is not the Keyes_SRly) and also people connecting IN2 directly to an GPIO pin. Which one is safer/the right way?


texts: Understanding this circuit for getting sensor data from an arduino to a phone via the headphone jack

texts:
I am trying to understand the circuit below which relates to getting sensor data from an arduino to a phone via the headphone jack.

The instructions on this page aren't clear on what the function of the resistors/capacitor is so I was hoping someone here could give an explanation.

Thanks!


texts: Finding RC time constant with a Y connection

texts: I think I have somewhat of a solution to the problem pictured, but I'm not confident in it. What I did was treat the resistor as a load, so I removed it and found the equivalent capacitance of the circuit it was attached to, so I got a time constant of about 10.3ms. Is that right or am I oversimplifying? I'm not sure if I have to do that delta-y stuff (and I'm hoping that I don't).


texts:
Outline:

I'm trying to work with an Arduino and Analog thumb stick to get values for a simple differential drive robot I'm working on. The Keyes_Sjoys Arduino Joystick Module I have in my possession is giving me some strange numbers however.

Following axises Data I have:

X-axis range of 0 to a shaky 470-520 with a center value of 40.
Y-axis range of a solid 4 to solid 1023 with a center value of 605.

Problem

I haven't used analog sensors before but it seems pretty obvious that my X-axis ranges should feel somewhat similar to the Y-axis but they don't. In addition, the X-axis hits zero way way before even coming close to the edge for its operating range.

Is my sensor plain broke (it's new), or is there some way I can recalibrate the potentiometer?

Update 1:
Wiring is the same as in this tutorial, and I used the same code, just added another analog input.
http://arduino.cc/en/Tutorial/AnalogReadSerial

void setup(){
 Serial.begin(9600);
}
void loop(){
  int X = analogRead(A0);
  int Y = analogRead(A1);

  Serial.print("X = ");
  Serial.print(X);
  Serial.print(" Y = ");
  Serial.println(Y);
  delay(3);
}


texts: how to get a clean AC current waveform for power-factor calculations

texts:
I've been doing a project to figure out the power factor of a load by comparing the zero crossings of the voltage and current signals (of a AC signal) and hence finding the phase difference using an arduino UNO.
the application is confidential but i can say that im using a load which can introduce change the inductance in the circuit and hence give me a phase difference and also increase the effective resistance which further decreases to current consumed. i have my voltage signal available through a particular method and im using a ACS712 hall effect current sensor module for current sensing.

Ive been able to get cleaner waveforms  using a low pass filter (from 500ma to 300ma i can get good power factor readings) for currents up till 300mA, but currents lower than that become comparable to the inherent noise of the sensor.
 Hence im looking for other options to get a clean current waveform, i looked into similar sensors with the current ranges and sensitivities that my application desires, but they aren't readily available and may cost a lot on a production level for my company.

I cant use a CT cause my currents are already at very low values, lowering them further through a CT wont help and as per my calculations for 1:50 turns CT will end up with similar low current signals as the ACS712 (dont know about the noise effects though), hence im looking at the shunt resistor method. my questions are as follows:

1) Is there any other approach i could follow to calculate the power factor?

2) can i still use a CT? considering its an isolation method. but how would i measure currents in the range 500ma to 50ma that is required for my application.

3) i have tried using a 5 ohm resistor as a shunt (5*0.2 = 1Vpp) and tried to observe the output, the signal seems to be very noisy to begin with, how do i go about this? additionally how do i make it safer considering there is galvanic contact with the AC lines as opposed to other methods.

4) should i follow any other approach to get this done?

so im in a bind :/ need help!!! :cry:
(sorry for the big paragraph and list of Questions! 8-O )


texts: Why are Ethernet jack center taps connected to VCC?

texts:
Taking this schematic as an example:

EtherTen

Can someone explain to me why the center taps of the transformers (TXCT, RXCT) are connected to VCC? I've seen this connection in many (although not all) schematics on the Internet.

What would happen if they would be connected to GND?


texts: can high speed memory interfaces like GDDR5 or XDR ever become mainstream?

texts:
Given the limited memory on GPUs, I'm wondering why there are no socketed GDDR5 memory modules so that you can install more RAM.

The main challenge seems to be maintaining signal integrity since GDDR5 runs 2.5x faster than the fastest DDR4 (4 GHz vs. 1.6GHz, double pumped). Unlike DDR4, it needs to train links to find the phase offset between bits (to account for different PCB trace lengths) so that they can be sampled together. Also, they need to use CRC.

XDR 2 runs even faster at 800 MHz, x16 pumped! but uses differential signaling which means a lower bandwidth per pin than GDDR5.

So will putting GDDR5 onto DIMMs greatly increase wire length, signal attenuation, and negate the speed advantage?

Or is it lack of interest? There would hardly be a market for just GDDR5 upgrades for GPUs. CPU makers would need to support it too. AMD already has for their APU in the PS4.


texts:
I built a circuit based on this IC.
Link: http://www.mouser.com/ds/2/256/MAX756-MAX757-92691.pdf

It says if you put the 2nd pin to Low, then it switches to 5 v out. That seems to be untrue. I found that if you float the pins and then touch a finger to the 1st pin, then it switched to 5 v. I can also touch it with a jumper wire, paper clip, and also hoover my finger over the pin and it jumps from 3 v to 5 v.

What is going on?

Thanks


texts: Does a device with USB HS Device support necessarily support host mode?

texts:
I'm a beginner in the MCU world, I've been looking at some comparison tables for MCU capabilities and I am a little confused about USB capabilities.
For instance, looking at this Microchip listing https://www.microchipdirect.com/Chart.aspx?branchId=2155&mid=14&treeid=21, MCUs' USB support is always advertised as one of these 4 possibilities: "None", "Full Speed", "Host, Device", or "High Speed".
But none are advertised as "High Speed Device AND Host", not even the $10 ones when for less than $2 you get similar models supporting Device+Host and for less than $3, high speed. And when I look at the capabilities of an ATSAM3U1C, (https://www.microchip.com/wwwproducts/en/ATSAM3U1C#additional-features) for example, high speed capabilities are mentionned, but not USB Host support.
I wonder if it's exclusive, or if it's my current ignorance of the field that's kicking in and that, perhaps through knowledge of the USB protocol, it should be implicit that USB High Speed device support necessarily comes with USB (full speed, at least) Host support and it is therefore not mentionned. Could you please shed some light on this ? Thanks.


texts:
I have a project that uses 2 separate MSP430 microcontrollers. Both of them need to have different firmware uploaded to them. My place of work use the 8-way MSP-GANG programmers to program instruments in production.

The annoying thing with this, is you cannot put different firmware on different ports (or there isn't a way I could see), so I would be forced to program one, change the 'image file' and program the other.

The way I have got around it is to write a script by following the instructions in the USER GUIDE (page 24 - 30). Now, via the MSP-GANG software, I can press the 'GO' button and the script runs, programming the first microcontroller on one port, then the second one on another port. This is fine, but via this software, you can also edit the image files and change memory locations of different images. We would rather the production staff not have the ability to access any of this, so I have been trying to find a way to have the script run on a standalone unit.

I cannot seem to be able to save the script to any image file, and when putting it on an SD card, it just comes up with an error.

Does anyone know if it is possible, and how to run a script on a standalone GANG programmer?


texts: Macro Button for my Game Boy - Master button to press all buttons at once

texts:
So I am trying to add a button on my Game Boy that will "press" A+B+SELECT+START at the same time. I have found the test points for these buttons on the PCB and connected them to a button with the other end to ground, tested it and it worked just as I expected. But then I tried to press B by itself and all the buttons are pressed again, makes sense seeing how all the test points are now connected on one end of the button.

Do they have buttons that are 5 inputs that are not connected until the button is pressed, or is there a way easier way to do this that I am not thinking of?


texts: USB 2.0 full speed audio class max sampling frequency?

texts:
what is the maximum achivable sampling frequency when using USB 2.0 full speed isochronous audio transfer and stereo 24bit format (recording only) ?

when no compression is used !


texts:
The output from an existing circuit gives me 2.5V and .15mA

I have setup the following circuit and it seems I cannot drive the relay. May I know why it is so?


texts: How do I build RAM/CPU with logic circuits?

texts:
I want to build a little 4 bit computer, out of logic circuits. I want RAM and a CPU and all that good stuff. My main problem is, should I work on RAM or CPU, which one would "teach" me more so that I could build the other, and could someone give me a circuit map? Thanks, if you helped!

Since I have asked this question, I have learned much more about electronics. So on October 1st 2015 I will do a live stream where I will be designing a 4-16 bit computer with logic gates, transistors and nothing else really!
Go here to watch.


texts: The Fourier transform is just an operation on certain functions.When the functions are signals, why is it that the variable chosen (w) has to correspond to the frequency of the signal ,when it is just a variable?


texts:
A question so simple I've never thought about it before. Usually I get my PCBs made in standard green, but have been offered a blue for my next revision of an existing (green) board at no extra cost.

What colors are available as standard, and why should you choose one over another. Is there a "best" color?

Would any of this affect color blind tech people who work on the board?


texts: Why do we use one bias (VCC) for transistor amplifier circuits and 2 supplies for opamp circuits?

texts: Opamps are said to have 2 supplies, so that the output can rail between these two points, then why do transistors have only one bias point.


texts: EMC Cable shield used as PE wire, great idea or not?

texts:
In order to save on cabling, our company uses 3 wire EMC cables to connect electric machines to their VFD's. Some folks in our company think we should really use a dedicated ground wire, many are of the opinion that using the shield as ground (at least for wire diamaters < 6 mm²) is just fine.
Recently we had some problems with bearings of machines that were running for 1-2 years: fluting, and a washboard like appearance of the raceways, as described in SKF documentation.
Can this problem be related to the omission of the ground wire? Are there any other compelling reasons to use a ground wire?
We often also don't use load reactors after EMC cabling. We use Danfoss drives (type FC102), which are said to have built in filters that are able to drive about 75 meters of cable without the need for additional filtering.


texts: phasors and differential equation circuit analysis?

texts:
I am having trouble, the steady stae voltage i find by differential equations is no the same as the one i find by phasors, what is worng?

\$V_{ss}(t) = \cos(4t)\$  volts      ........ by diff eq, just looking at thevinin voltage

phasor;$$V = 1\times\frac{-4j}{4\sqrt3 - 4j} = 0.5e^{-j\pi/3} = 1/2\cos(4t - \pi/3)$$

they are not the same, what is the problem?


texts: POV display possibility with ws2812b neopixel strip

texts:
I am trying to build a full RGB POV display. Unfortunately I purchased a neopixel strip (ws2812 144/m), and lately found that its data transfer rate is 800khz that is actually less for POV display. It is rather suggested to use APA102 based strip (adafruit dorstar) that is SPI based and works @6mhz. I am currently in India and I am not able to get a dotstar strip at a reasonable price. So, is there any possibility to use that strip to display at least an image (not some animation) properly. Please note I only intend to use 50-60 leds from that strip to keep the length within 18 inches.
Thanks,
Debojit


texts: Charging a 36V battery set with a 255W solar panel

texts: I have directly connected a 255W solar panel (with Vmpp of 49.5V but can peak at 56V in full sun at mid-day) to the 36V battery set of my golf cart.  This seems to have been working fine for months, as I am a light user of the golf cart (a few miles per day) in a sunny state.  In other words, I have been able go for months without connecting to the grid.  However, my research certainly leads me to believe that there is a risk of overcharging (if there isn't a good balance between my driving and the sun-hours, I pressume).  My question is whether the overcharging would be due to excessive Amps or excessive Volts?  (depending on the answer, I may fashion the correct protection).


texts: Intuition behind transit angle of a klystron

texts:
What I understand is that the electrons get attracted to the anode and during their passage through the buncher gap, they regroup into bunches due to differing potentials imposed on different electrons by the RF signal. Then they reach the catcher cavity and transfer their energy to the cavity therefore amplifying the RF signal.

But then I came across the term buncher gap transit angle \$\theta_g\$ which is equated as

$$\theta_g = \omega \tau$$
where \$\omega\$ denotes the angular frequency of the RF signal and \$\tau\$ is the buncher gap transit time. I don't understand whether the parameter transit angle is really an angle between two physical dimensions inside the klystron or is it a mathematically convenient notation. Is there any intuition which the parameter tries to deliver?


texts: Need help with standalone circuit; atmega328p and WS2812

texts:
I have a problem involving those two modules, can't keep them work together in board for more than 30 secs. Randomly, leds WS2812D-F5 w/ WS2812B-B, starts to turn on when should be off and then all goes on full white making useless the chinese version atMega328P U TQFP32.
Have tested both separately and worked fine, the leds with an external Arduino with welded jumpers on board, and the MC with blink. But... I'm only been able to program, via ISCP, the MC only when the Led module isn't welded.

Why would the MC has been able to program without connecting the signal (digitalPin 10) to leds?
Why would the leds produce such randomness and procede to anihilate the MC only when it is connected?


texts: how to change output impedance of op amp

texts: I have made a non-inverting op-amp using lf351n with gain of 5 and i need to connect the op-amp to a device with input impedance of 50ohm.I want to know how to make the output impedance of the op-amp to be 50ohm


texts:
The other night the corner of a switcher IC in a LED lamp power adapter blew off.

I opened the adapter and "reassembled" the IC case with tweezers to identify the model.

I see it's a LNK364PN and I found the datasheet.

Can I ignore the first and the third line of numbers printed on the IC (0948 and 68089E respectively)?


texts: Enterprise model blinkers - two fast flashes and pause for 3s and repeat LED circuit (with 555 and/or 556 and/or 4017)

texts: I'm building a Revell Enterprise Into Darkness model with LEDs and I need help with circuit that makes two fast flashes, pauses for 3 seconds, then repeats. as seen in the movie.  I have searched and found circuits with constant flashes but can't find the one I need (2 flashes, 3s pause, repeat).


texts:
We have a circuit that has a 6V input for charging. We want to protect the device from ESD on the input, but have some discussion on where to place a resistor. The two differences we are looking at are below.

In the first case, we have the argument that the series resistor will slow the input charge somewhat, making life easier for the ESD diode and thus making it more effective.

In the seconds case, we have the argument that the ESD diode is left alone to do its job, and the series resistor can help absorb whatever the ESD diode doesn't handle.

Is there a common practice where to put the resistor and if so, why?

simulate this circuit – Schematic created using CircuitLab

simulate this circuit


texts:
I don't want an introductory text on timing constraints, nor an application note, an user manual, a webinar. I read them all, already, many times. The concept behind timing constraints is very easy. Still, when I have to code them in a sdc file I can't get through it. I have to spend several days trying and failing to make the Quartus software accept my design. And I know for sure that many other FPGA designers are suffering like me.

Somebody please stop this agony!

Let's try with an example. Consider the following top entity:

entity top is
    generic (
        W : positive := 8
    ) port (
        ser_data_in  : in  std_logic;                      -- Serial data in
        ser_bclk_in  : in  std_logic;                      -- Bit clock in
        ser_fclk_in  : in  std_logic;                      -- Frame clock in
        par_data_in  : in  std_logic_vector(W-1 downto 0); -- Parallel data in
        par_wclk_in  : in  std_logic;                      -- Word clock in
        ser_data_out : out std_logic;                      -- Serial data out
        ser_bclk_out : out std_logic;                      -- Bit clock out
        ser_fclk_out : out std_logic;                      -- Frame clock out
        par_data_out : out std_logic_vector(W-1 downto 0); -- Parallel data out
        par_wclk_out : out std_logic                       -- Word clock out
    );
end entity;

Serial data is transmitted at DDR, clocked by the bit clock (frequency = F), which is center-aligned. Serial data comes also with a frame clock, which is edge-aligned with the first serial bit (frequency = F/W).
Parallel data is SDR, clocked by the word clock (frequency = F/W), which is edge-aligned.

I won't enter into SERDES details, let's imagine that I have a simple shift register that shifts with ser_bclk_in and transfers its data to another register every rising edge of ser_fclk_in. Deserialized data operates somehow with parallel input data and the result is output to ser_data_out and par_data_out. Naturally, the SERDES at the output is specular to the input.

My question is: for a given maximum skew between data and clocks, how do I constrain such a design?
Since I have already all the clocks I need, can I successfully constrain this design without using PLLs?
It is necessary to declare multicycle paths? If so, why?

P.S. I am still willing to read more about the topic, therefore, if you know any uncommonly clear text about timing constraints, please share it too :)


texts: Protecting a 3.3V circuit from 5V power supply

texts:
I'm designing a dev board for 3.3V parts. On the dev board, I will have a header for an "FTDI Friend" USB-to-Serial converter.

The FTDI part can supply Vcc to the target board.

However, FTDI parts are available both in 3.3V and in 5V versions. I want to protect my board against someone accidentally using a 5V FTDI and feeding that into Vcc.

What's a cost-effective strategy for this?


texts: Attenuate and disperse ESD change on USB connector shield

texts:
I’m having problems passing ESD immunity on a device I’m designing. It’s a portable USB device in an aluminum enclosure with a metal USB connector that is in contact with the enclosure.  When the device is hit by the ESD gun, the discharge ultimately finds its way onto the USB connector through the shield and into the ground plane where it causes havoc.
I’ve accepted that there’s no way to stop the discharge from getting onto the USB connector shield, and so I want to try to attenuate and disperse it there.  Can anyone recommend a filter circuit for the USB shield pins?


texts: transient analysis not matching ac analysis for RLC circuit

texts:
I am modeling a simple impedance-matched RLC series resonator. I get a nice resonance at around ~48.5MHz when I do an ac analysis. However, when I try to do the corresponding transient analysis at the resonant frequency, I don't see the ~35bB voltage gain. All waveforms are across the 4.7pF capacitor.
In fact, I don't really understand what I'm seeing in the transient analysis at all. Can you spot anything wrong?


texts:
I would like to understand how a zener diode clamps the voltage.

I1 = I2 + I3, in order to calculate I2 I need the zener's resistance which is not doable since it is not a resistor. However I don't need to make such a calculation because I can just assume that Vd of zener is 5.1V and therefore Vd across R2 is going to be 5.1V, so order to calculate current in this circuit O would just use Vt = 500I + 5.1 which is I = (Vt-5.1)/500

My question is: Why do I need to assume that voltage drop of a resistor in parallel to zener diode will be equal to a drop of zener itself?


texts: Unusual Component Inside Photo Multiplier Tube Base

texts:
I am attempting to diagnose problems with a PMT (Photo Multiplier Tube) in our lab. I have taken apart the base, and begun drawing the underlying circuitry. I have come across a circuit component that I can't find any information on. Image below:

The part in question is the red, boxy thing (i.e. not the capacitors or the resistors). It is symmetric with 6 legs/prongs, three on each side; it reminds me of an op-amp, only with 6 legs instead of 8. The leg labeled "3" is not attached to anything else in the circuit.

After scouring the web, I found something that was remotely close-seeming to this part called an "optical isolator" or "optocoupler" (there are apparently several names for it); basically a device with a transistor and a diode connected in some special way. It seemed to match up pretty well with what this was, however, there is clearly printed on this device the text "2000 uH" (micro-henries), which is a unit of inductance. There are a few other differences which make me hesitant to call this device an optical isolator.

I have image searched for anything remotely similar to this for quite some time now, and even any opto-isolators I can find don't really look like this. I have also done the obvious and searched Google for the text strings printed on the part (i.e., "PE-5768", "7946-IP" etc). So far, nothing has come up to help me identify this component.

Has anyone ever seen this part before? Can anyone tell me what it is or what it's used for?


texts: XBee Pro S2B in AT mode keeps resetting the Arduino

texts:
I have just bought a whole bunch of Xbee Pro S2Bs and Freetronics Eleven boards.

When I set up the XBees in AT mode, the Arduino constantly resets.  At least that's what I think it is doing - the D13 LED keeps flashing (3 times in quick succession, once per second) and the sketch won't run.

In API Mode it seems fine, but I want to use AT mode for simplicity - anyone have any ideas why AT mode would be causing the Arduino to reset?

I have already asked this question on the Arduino forum but haven't got anywhere yet ...

http://arduino.cc/forum/index.php/topic,60285.0.html


texts: What sensor do I need to measure distance from the side along a straight line?

texts:
In a few days I will start to build a hand railing for my stairs out of bamboo with a built in LED strip. I want to be able to indicate the position of a person standing on the staircase by illuminating an LED at the corresponding distance along the length of the hand railing. Of course I will be needing an individually addressable LED strip for this but that is not the issue, neither is the micro controller I will be using (I figured an ESP8266-01 would do nicely, hoping to also being able to switch the led strip wirelessly).

I am kinda stuck on the measuring distances part. The best case scenario would be that the measuring sensor(s?) would be integrated in the railing itself, which would mean sensing from the side. I don't know if this is possible other than using multiple ultrasonic sensors but this would mean that components will be visible through holes in the bamboo and that kind of takes away the magic. It also means that the code will be more complex since I have to check how close the person is to one sensor compared to the other to get a more precise distance. I am looking for the most elegant solution here.

Another option is to measure from the top or bottom of the staircase but the only sensors I came across were either the ones that couldn't measure more than a few feet or this really expensive one:

My questions are: What is the best way to approach this? What sensor(s) do I need in order to keep costs at a minimum?

This is my first post and my drawings are awful so, please be gentle :).


texts:
It's usual to talk about loading a circuit when measuring voltage, with a voltmeter or with a voltage probe and an oscilloscope. It can be seen as putting an impedance in parallel to the element whose voltage is to be measured.

However, I don't understand in which way exactly does a current probe load a circuit. Can it be seen as an impedance in series to the branch of the circuit being measured? What does the value of the impedance depend on?

EDIT:

Thanks to the comments below I realized that the question was not specific enough. The mechanism of the current probes I'm interested in are those which basically make use of a transformer to sense the strength of a magnetic field caused by a changing current in the circuit. Something like this:

How do these load a circuit? Also, if a Hall effect device is added to the probe to detect DC as well, does the mechanism in which it loads the circuit change?


texts: I am operating the buck converter with STmicroelectronics VIPER01 IC to step down the input voltage of 200 volts to 6 volts in continous current mode 300 mA load current. The operating frequency is 120 kHz for VIPER01. My minimum turn on time comes about to be 250 ns for 200 volts input voltage. The minimum turn on time is listed 270 ns in the Viper01 datasheet. Would the Viper01 switch to discontinous mode of operation instead of continous mode due to not able to produce the minimum turn ontime? Or would it still produce the 270 ns at the output?


texts: How can I use a single 74595 to drive two different IC's?

texts:
I'm trying to build an audio circuit with as few parts as possible.  Also, I really need to limit the number of pins used on my Arduino.

I didn't ask this in the Arduino site because I don't think this is specific to Arduino but I wanted to mention I was using it just in case.

Anyway, I have two sound chips.  Each one has an 8-bit data/address bus that I have driven off a 74x595 (can't remember exactly which one at the moment).

When using either audio IC, everything is fine.  But, what I want to do is possibly use the same shift register to drive BOTH music IC's.

Unfortunately, neither audio IC seem to have a way to put them in high impedance mode (SN76489 and AY-3-8912) that I can tell.  Plus, they both are designed to play notes while the CPU does other things so simply resetting (or disabling somehow) one while the other received data would stop their current notes from playing.

My first thought was to use some kind of octal bus transceiver but I've never actually designed a circuit with one.  But if I'm not mistaken, wouldn't I have to electrically disconnect one audio IC from the data bus while the other receives data?

Or, is there simply a better way.  I'm struggling with adding that bus transceiver vs. simply pulling three more pins from the Arduino and using a second shift register.  But if I did that, I would have to use the audio pins for digital logic.  Which I know is technically OK.  I was just trying to avoid it.

Any tips would be appreciated.

Thanks.

EDIT

Another idea I had would be to use a 16-bit shift register and split the bus.  I would drastically have to change my audio drivers but that might work.  Unless there is a better way...

EDIT 2

OK, two shift registers chained together may NOT be a good idea.

Think about this:

The AY-3-8912 requires two 8-bit writes (address then data).  The SN76489 only requires one 8-bit write.

So, if my data were:

$A5 $38   // AY
$78       // SN

Sending an $A5 then $38 would put $A5 on the SN data bus.  Then things would get out of sync.

Plus, now that I think about it, the VGM data format (that I am using) also has non-IC commands like pause commands.  So I could get a pause command that is three bytes long.

Keeping all of this padded/sync'd seems like a nightmare.

Ugh...


texts:
My text book says, "Single Pole amplifiers are always stable,hardly surprising, because in the worst case it can never go beyond 90 degrees."

But it did surprise me and I cannot figure out why a single pole amplifier cannot go beyond 90 degrees.
What is the reason?


texts: Help needed... NPN current flow with 0v at Base

texts:
I'm having a head scratcher:

simulate this circuit – Schematic created using CircuitLab

In my mind this should work flawlessly. The 5v/GND through R1 to the base of Q1 is controlled by a microcontroller (but for testing I am literally connecting to a 5v source or GND by hand)

Applying 5v... The Relay closes, great... but upon applying GND to the base the relay remains closed, meaning there is still a current flow. Only upon disconnecting GND from the Emitter of Q1 does the relay open again.

What am I doing wrong? I thought my theory was sound.


texts: Why electric light bulb more often burns out when we switch from OFF to ON our wall switch, but not during regular work? What happens to it so it burns?


texts: how to choose resistors' value for common emitter amplifier?

texts:
I want to choose the best values of  R1 , R2 , R3 and R4 to get the maximum gain (high performance).

I design the circuits practically, so I don't need to do a lot of calculations. I want the simplest way to calculate the four resistors.

This is the datasheet of the transistor, I think it may help :
http://www.onsemi.com/pub_link/Collateral/2N5401-D.PDF


texts: Do I need to terminate my oscope in a specific way for viewing video signals?

texts:
I'm a novice and have used my Rigol scope to look at small circuits from kits and attempt to diagnose issues on my vintage computers.  I'm at a point where I want to check out composite video (for learning purposes) and I keep reading that a video signal expects a 75 ohm load.

This makes sense, but given my scope only has 50 ohm and 1M ohm input resistance, and also taking into account my probe, do I need to impedance match to 75 ohms, and if so how do I do it?  In my case I would be looking at the composite output coming out of the device.


texts:
Ok can someone explain to me what is considered One Byte Wide or Two Byte Wide? I couldn't find much on it. From what I know 8 bits = 1 byte? So lets say there's 16 bits and it needs to be 2 byte wide does that mean put it into 2 8 bits?

If this is confusing the specific question is 128K memory in 1 byte and 2 byte wide. So would 2 byte wide mean 2 64k? I'm confused and trying to grasp this concept so bear with me.


texts: Can I connect a Raspberry Pi and a servo shield to a single power supply?

texts:
I'm building a robot that requires 12 servos and a Raspberry Pi. I will be using the Adafruit 16-channel servo shield(https://www.adafruit.com/product/1411) and a Raspberry Pi 3B. Of course, if they were both connected to the same power supply, it would be way easier to turn the system on and off.
Is there any way to do it, even with additional pieces or arrangements? If so, how?
Also, could the power supply be a battery? What characteristics should it have?


texts:
Any techniques/circuits/sensors that can determine the open/closed state of a set of contacts, independently of whatever power or signals are being switched by the contacts?

Obviously easy if there's no or a known load; but (for example): three NO switches in series switching 120 VAC to a bulb.. what black box circuit could be connected across each set of contacts and measure the state of each switch?

Ultimately a logic-level output for a uC, and don't need a fast response time (under a second is fine).

Edit: let's assume a few mAs of leakage ok, and a power load: DC-60Hz, < 250v.


texts: I am adding an ATX power supply as a bench power supply to power accessories on my model railroad layout. I prefer to run some lighting accessories at +7v, but obviously a power supply has +3.3v, +5v, +12v and -12v. Someone said getting +7v was as simple as wiring a +5v to a -12v wire. That didn't seem right to me. Is it, and if not, what would I need to use to convert the -12v to positive voltage?


texts: Help needed driving an old PIC programmer from Raspberry Pi GPIO

texts:
I have been trying to use a Raspberry Pi's GPIO pins to drive an old PIC programmer board that used to have a parallel port connection before I started messing about with it.

You can see from the clip of a schematic I found online that the data write/read pin on the PIC is connected to two parallel port pins, one an output and one an input. When programming the chip, the pin flips to become an output after you send a command to read the current word.

I'm not sure in particular how reading back data from the PIC is supposed to work, because it looks to a newbie like me that the output of an inverter is connected to the input of the inverter that leads to the 'read' pin for sending data back to the PC.

Could somebody please explain what is going on at the point marked with a '?' that stops the inverter output 'fighting' with the PIC DATA pin output?


texts:
Please Help with connector identification

Can anyone help me identify this connector type?

I is 2 pin, pitch I think is 0.8mm (I measure it to be 1mm between the outer part of the pins, I do not have the tools for more accurate measurment)
From side to side it is 3mm, and 1mm in height. I initially thought it was a type of JST, but after scouring the internet I have not found any matches. Not for JST or Molex or any other brand.

If anyone could help me identify it, I would greatly appreciate it.


texts:
I'm trying to setup some DIY home automation, and I've run into a bit of a roadblock.  I am attempting to wire an Arduino Uno into a RJ-11 cable in order to connect to a TW523 two-way X10 controller as shown here: http://www.arduino.cc/en/Tutorial/X10.  They provide a diagram to connect the RJ-11 to the X10 interface, however it is not very friendly to newcomers.  The RJ-11 has six wires, so how am I to know which one is the data pin, which one is the zero crossing pin, and which do I ground?

Thanks!


texts: How to increase data through put of RS485 RTU?

texts:
I am using 20 sensor nodes, each has mpu9250 i2c, Arduino atmega328 MCU 8MHz and max485 chip in it,
each slave has a unique id program.

I have Arduino due as Modbus master with max485 chip,
I hope to use Arduino Modbus library RS485 RTU,

assume slave is continually reading data and updating local variable with imu data 12bytes, and ready to send over the bus.

and master is polling data from each slave node.

all sensor are connected the same bus, 1.5ft from the sensor node to sensor node away each (cat 5 cables), the reason to choose Modbus is having higher data rates compared to CAN bus or I2C,

I have a doubtable point,

how long it will take to respond to master with data?

how to calculate request/response time or the time to gather data from all sensors by the master?

in other words how many samples per second achievable?


texts:
I'm trying to make a tone transmitter that can transmit a tone at least one hundred feet in clear sight to any standard radio on a frequency where no one is broadcasting. I understand that the values in my tank circuit are a bit off, but once I am able to transmit to a radio, then I want to adjust the transmitting frequency.

I tried the first circuit. The enable connection point (of course marked enable) works perfectly, but the transmitting distance seems weak.

I'm thinking of doing the second circuit, but I don't want to waste a circuit board only to find out that it doesn't work.

So using only BJT (NPN or PNP) transistors for the RF portion, how should I arrange the parts for maximum transmission power without violating law? I think my limit is 1/4 watt, I'm not sure.

For initial tests, I'll use 9 VDC but in the end I'll use 5 VDC that's generated from a 7805 regulator that the 9V will feed into.

Should I go with the second circuit or would it function better if I changed how the parts are connected?

Circuit 1:

Circuit 2:


texts: Differential voltage to current converter

texts:
I have this circuit to solve:

with \$R_2=R_3\$ and \$R_4=R_5\$. I want to find the transfer function between \$I_{\text{out}}\$ and \$V_{\text{in}}\$ (differential).
I'm trying to use superposition, but the math is very long. Do you have any other idea on how to solve it?
Any hint?

I've divided \$V_{\text{in}}\$ in \$V_1\$ and \$V_2\$, and tried superposition. I've found the current on \$R_2\$ and \$R_4\$, but I'm having a problem finding out a relation between \$V_{\text{x}}\$ and \$I_{\text{out}}\$ in order to solve the system.


texts: Why is LTSpice Bode plot disagreeing with a linear plot?

texts:
Here is a picture of an amplifier that I'm simulating using LTSpice. When I insert a sine wave of 0.01 volts and 314Hz as an input, I get this:

The output is taken from the collector and is oscillating between about 2.65 and 2.35 volts. This would mean that the amplitude of the output is about 150mV. This divided by the input amplitude of 10mV gives a gain of 15.

When I do a Bode plot of its frequency response, using 0.01V again as input, I get this:

Past 100Hz, I get a gain of about -16.4 decibels! This is nothing like the gain of 15 that is claimed by the linear graph. When I convert -16.4 decibels to a gain ratio, I get something like 0.15. So what am I doing wrong?


texts: Lenz Law and Magnetic fields in an Inductor

texts:
Hoping somebody can set me straight on the magnetic fields involved in an inductor when the current is changing. This is how I see it:

The source current has a magnetic field.
This changing flux produces an EMF which in turn produces a current which also has a magnetic field which opposes the change which produced it. The lenze induced magnetic field would have opposite polarity to the inducing magnetic field.

So therefore there are two magnetic fields:

Magnetic field from source current
Magnetic field as a result of Lenz Law (cemf).


texts: Is my approach for the RL circuit correct?

texts: For the image above, i(0+) = i(0-) = 0A, and to get the IL(t) function, you solve for Rth, which is 50ohms. Afterwards, i'm confused with how to approach getting IL(t).


texts:
I recently purchased a radio which unfortunately doesn't have battery option. Its spec is AC 230V - 50/60 Hz and 14 W

Is there any way to use my Ni-Mh rechargeable cell battery with this device.

Regards


texts: My PCB manufacturer only requires eagle board file, and not a gerber file is it fine to go about getting the board fabricated with him?

texts:
It's my first time getting a PCB manufactured.

My manufacturer only requires eagle board file, but not a Gerber file.
Is it fine to go about getting the board fabricated with them? Or should I be concerned about getting a faulty board made and wasting my money?


texts: Comparator on an op-amp in a PT2399 delay pedal

texts:
I am building a guitar effects pedal from a schematic I found online. Unfortunately the schematic is poor quality and hand-drawn, but there is a diagram of it constructed on veroboard (this is generally the way it is done in the world of effects pedal building.

It uses a PT2399 delay chip. From the creator's original post:

  The chip's input stage is set up as a comparator with the aid of the Vref pin, so that gives us an ultra-amplified, squared-off waveform straight away.

The comparator means the input is quite heavily gated, so I only get sound out of it if I play my guitar very hard, or amplifying the signal before it gets to the pedal with an external device. Basically, it's not very responsive or sensitive.

I would like to make it so the required input volume is lower, and I can play the guitar more gently and still be able to trigger the comparator. The schematic:

And the veroboard diagram:

So the vref pin is pin 2 I believe (pinout here) and it is connected to pin 16 (the input) via R2. The audio input goes into pin 16 via a 47nF capacitor (C4) but I'm not too familiar with comparators, so I don't know which values to change. I've experimented but I don't think I'm on the right lines and I'm not getting any change in sensitivity. Can anyone help?


texts: How to know the status of a two way switch through MCU

texts:
My project is this one that I asked earlier (except the fact that I'll be using SPDT switches) Two way lighting
What I'm asking can the MCU detect if the circuit is closed (whether by the physical switch or the MCU triggered relay). I'm thinking some sensor upstream on the appliance/ bulb wire and a ground?


texts: Can 1-wire (One-wire) sensors be used over power lines?

texts:
I'd like to sprinkle my house with 1-wire sensors (temperature - everywhere, humidity and flooding - in the basement), but the only wire in most locations is the power-socket (110V)...

Can a 1-wire microlan simply coexist with the AC power without short-circuiting and without the readings getting lost? If not, perhaps, HomePlug AV devices can be used?


texts: Emulating guitar pickup loading effects with a floating gyrator?

texts:
I'm looking to construct a high impedance buffer which emulates the loading effects of an electric guitar connected to a nonlinear, low input impedance amplifier such as the Dallas Rangemaster (pictured below).

While it's easy to model the frequency response of an RLC circuit in a vacuum, it's also interacting with the nonlinearity of Q1 (both the diode V-I curve and the miller effect in a nonlinear amplifier seem significant here).

One way would be to externally drive a real pickup with a voltage source and connect the other terminal to the Q1 input.  This is a) expensive, b) noise-prone, and c) changes the topology of the quite significant parasitic capacitance of the pickup from series to parallel (as compared to what's seen by an induced voltage in the coils).  Therefore it seems like an undesirable approach.

A more desirable solution would be to build a floating (gyrator) inductor.  While it's easy to find information on grounded gyrators, information on floating gyrators seems more sparse.

Therefore I am wondering

Is the floating gyrator approach reasonable, or am I likely to get poor results in practice?
For my application (audio frequency, ESR must be well-specified but it doesn't need to go below a few kOhms) is there a recommended floating gyrator topology that will have good results?


texts: Series R-L AC Circuit Analysis - Conditional

texts:
Is there a way to get resistance and inductance of a circuit wherein the only given is the source,circuit current and its frequency?

To make it clear, ill give an example:

An impedance coil takes a 3A and connected across 110V 60Hz source. But then the impedance coil is connected across 220V 25Hz source and takes 4A. Find the resistance and the inductance of the coil?

Im getting confused... What will I solve first? What i know is that at first I can get is the impedance of the circuit, and im stuck there, dont know what will solve next.


texts:
I found a lot of tutorial to get counter value from an interrupt timer
something like:

    /* USER CODE BEGIN WHILE */
  while (1)
  {
  count = __HAL_TIM_GetCounter(&htim2);    //read TIM2 counter value
/* USER CODE END WHILE */

Generally, this code is used with HAL libraries and STM32F4
I used the same but the function is not declared in HAL Libraries.
Do you know why? What I'm supposed to use instead?

Thank you


texts:
A quick question,

I have this pulse as an input to some device:

I just need to simulate it in LTSpice. I have the values of voltage obviously, and I know how to simulate that fall time. I just need to know how to simulate that spike at the beginning of the pulse.

Edit: Here is a close up of the spike, measured:

Thank you!


texts:
Library pps.h of PIC32 contains a pre-processor function that directs a peripheral's input/output  to certain micro-controller pins.

The function is:

#define PinSelOutput(grp,pin,fn)   OUT_PIN_PPS##grp##_##pin = OUT_FN_PPS##grp##_##fn    /**<Pin Select output bit*/

What I cannot understand is the implementation of "##_" before "##pin".
It glues the string part before "_" with "_", somehow.

Is there a table with special hashtag combinations that I could check?


texts: Can an optical mouse be used to measure distance down to 1-10μm?

texts:
I am working on a home-built CNC machine that uses stepper motors and MXL timing belt for the machine movement. Because I'm using steppers, there is no feedback to the controller about the actual position of the machine (ie, open-loop). Sometimes when I am making cuts, shards of material fly into the path of the gantry and gum up the track, causing the motor to skip steps. To solve this, I am installing a dust shoe and vacuum to keep the area clean, but this still doesn't address the problem of skipping steps due to any number of various reasons.

Of course, there are solutions that already exist that "close the loop" for the industrial market, but I think they would be out of budget for the homebrew hobbyist. If something as ubiquitous as an optical mouse sensor could be used, it would be a great boon for improving DIY machine robustness, if even marginally. It could also be used for self-calibration if the measurements are accurate enough.

The footprint of my machine is 750x1000mm, so I need something that can measure accurately over that distance. Obviously, the optical mouse can be used to measure distance (that's what it is designed to do!), but what parameters should I be looking for to meet my goal (DPI, CPI, camera resolution, etc) of measuring to a precision of 1-10μm and would these measurements be repeatably accurate?

(Each step of the motor moves the machine about .01143mm, so I guess 1μm precision would be preferred but that might be asking too much.)

Unfortunately, it seems that my best lead and the most discussed family of sensors from Avago (ADNS) are discontinued. For example, the ADNS-9800. Have they sold the technology to another company? Does an alternative exist that is easy to source and has proper datasheets? I'm guessing they have been discontinued because other companies have integrated the USB aspect into the die of the sensor module, making the entire thing cheaper to produce (rather than needing another micro to do the SPI/I2C->USB conversion).

Is there a better way to do this while keeping costs in check? Up to $30 per sensor would be a  target for this kind of market, I think.


texts: Effect of LEDs in series instead of parallel with resistors

texts:
So I have two LEDs with a Forward Voltage rating of 2.65V each. Would I be okay in hooking them up to a power supply of 5v in series rather than in parallel with resistors?

I'm asking mostly because they're currently glued into a model, and if I blow them it will be very difficult to get replaced, but I also don't have any resistors at the moment.


texts: How can I create a theatrical spark ejector?

texts:
I'm involved with an amateur theatre company (I do lighting, audio etc...) and would like to simulate a switch short-circuiting. I have also done a bit of magic in my time and have used "spark ejectors".

Because I would like to build something in to the scenery, I'd quite like to build a custom spark ejector (that I can then fill with flash paper and "sparkle additive" and power with 1.5V AA batteries, just like in the commercial versions). Looking at the commercial hand-held devices, they seem to be a fairly simple coil underneath the chamber that you then load up with the "payload".

Does anyone know of a tried-and-tested circuit diagram which would let me do this? I've done quite a bit of work with MCU's in the past and am well aware of the potential safety issues with these devices!


texts: Is it possible to calculate effective value of a signal from its average value?

texts:
I have a signal which I want to calculate its effective value. The signal is a voltage value read on a 33.3m\$ \Omega \$ resistor connected series to a 220V AC power line. My aim is to calculate the reactive power transferred on the power line.

(Frequency is 50Hz. Vertical scaling is 10 mV/square for both signals.)

I obtained the "Filtered Signal" by the circuit below:

The filtered signal can be assumed to be a DC voltage level. Its value read from the oscillator screen represents 150mA current level through the current sensing resistor. This is the average value of the current flowing on the power line, isn't it so? However, I need the effective value of the current in order to calculate the power. Since the current on the line is not sinusoidal, I cannot calculate the effective value from those simple AC voltage wave formulas.

So, what can I do? I'm stuck at this point. Is there any way of calculating the effective value of this current from these available data, or any way of calculating the power directly?


texts: Circuit modeling a biological cell potential difference

texts:
From a book on Neuroscience, Go to page 12, Box 7-2 (particular image attached below)

The author claims that $$V_m = E_{Na} + I_{Na} / g_{Na}$$ on one side of the equation and then says $$V_m = E_{K} + I_{K} / g_{K}$$ by looking at the other side of the circuit.

But how can this be?  Since the battery is showing a negative side facing V_in doesn't it have to be

$$V_m = -E_{K} + I_{K} / g_{K}$$

Am I misunderstanding something or did the author make a mistake in calculation?


texts: Can I use this MOSFET based on these parameters?

texts:
Motor specifications:

Maximum current: 15 A
Ipulse: 30 A

I am using MOSFET as a switch to drive between 36V (42V maximum and 30V minimum) battery and a motor (15A Maxinum.)

I am not using PWM as a gate voltage to drive it. I am using constant DC 3.3V from my microcontroller and I am amplifying it using an NPN transistor to get 10V as my gate voltage to drive the MOSFET with low Rdson.

Please find the below circuit.

The above circuit explains that when the base voltage is 0 I will get 10V from collector to drive my MOSFET ON. When I give 3.3V as a base voltage my MOSFET will be off. Based on this I am switching the rail between battery and motor.

I am using IPD088N06N3 MOSFET for switching.

Can I use this MOSFET for my application? It has very low  Rdson.

Conduction Loss:

I^2 * Rdson = (15A)^2 * 8.8 mohm = 1.98 W

Total Power Loss:

((max Tj) - (Ta))/ Rthja = (175-25)/62 = 2.4 W

If I see based on the power loss I can use this MOSFET because 1.98 W is less than 2.4 W.

When it comes to switching losses I am confused because I am not using PWM to control the switches the MOSFET will turn off the rail when the charge or discharge current exceeds the threshold values. Until that the MOSFET will be on. How can I calculate switching losses?

Can I use this MOSFET for my application based on losses?

Eon= (15)(42)(45ns)/2 = 28.35 uJ

Can I use this MOSFET based on my application and I will use it for bidirectional purpose based on that so can I use this MOSFET. Please find the datasheet here.


texts:
I am a beginner and I am learning to design and develop a Battery Management System for low voltage applications like E-Bike.

I would like to build a 36 V, 10s, 2500 mAh battery pack. The knowledge that I have gathered are:

3.6 V lithium-ion battery has maximum charge voltage of 4.2 V and minimum of 2.5 V, for safer side 2.7 V.
we are able to charge or discharge the 2500 mAh battery by charging or discharging 2500 mA for one hour, or 1250 mA for 2 hours. That is called battery capacity.
when it comes to maximum output current in C rating:

1C: an electric bike can draw (discharge) 2500 mA for 1 hour

2C: an electric bike can draw (discharge) 5000 mA for 30 minutes

If my understanding above is wrong, kindly correct me.

I have received an E-bike Specification below:
Inquiry: Li-Ion battery 10S1P 36 V / 2500 mAh, for an e-bike template

Li-ion pack 10S1P 36 V / 2500 mAh / 90 Wh 10S1P Consisting of 10 Li-ion cells INR18650A made up according to drawing including PCM.

U-n = 36 V
I-n = 15 A ---> What is this?

I-pulse = 30 A briefly ---> What is this?

Discharge temperature range: -20 to 60° C

Load temperature range: 0 to 60° C

My doubt is: What is the maximum output current a load can draw or discharge, based on the above specifications? How to determine that?

And what is In and Ipuls in amps? Is this the maximum current that an E-bike can draw from the battery pack?


texts: Is the "dc impedance" and ESR the same thing?

texts: In a super-capacitor, what is the DC Impedance? Is it the same as ESR (Equivalent Series Resistance)?


texts: How to measure air dust/particles in kitchen?

texts:
Several Arduino projects use optical dust sensors like GP2Y1010AU0F to measure indoor air quality. I would like to do the same in living room, bedroom and kitchen. I am interested mainly in PM2.5-PM10, but I would be interested also in pollens, meaning up to PM100 (according to Wikipedia). Going below PM2.5 may be difficult and not worth the effort.

However, in the kitchen there is risk of particles sticking to the measurement sensor, altering the baseline: when cooking, it's normal to have some oil particles in the air, even if the sensor is not directly exposed to the cooking area.

The datasheet of said sensor explicitly states:

  Please don’t do cleaning, because there is a case that this device is
  not satisfied with its characteristics by cleaning"

It's probably translated from another language, but it's clear: no cleaning recommended.

Also, the datasheet states:

  Dust adhesion

  There is a case that this product does not detect the dust density
  correctly, since the dust adhered to the inside of the dust through
  hole may project into the detecting space which consist of emitter and
  detector light axis. Please take the structure and mechanism of the
  equipment into consideration to avoid the influence of adhered dust.
  And when the dust is adhered, please consider the maintenance such as
  vacuuming or blowing off the dust by air.  In addition, please pay
  attention to structure and placing location of the application to
  avoid any adhesive particle like oil, etc. to gets into the device. If
  it sticks to optical part, malfunction may occur.

What should I use to measure dust/particles in the kitchen?


texts: voltage monitor using tps3897 - understanding

texts:
Although I have some experience with circuitry it is mainly analog experience.
therefore I can't solve the question i have been given in interview.
I have been asked what does the next circuit do:

Now I only have used dc/dc or LDO to monitor voltage so I guess that this tps3897 supposed to be the digital equivalent to LDO + delay, but the problem it doesn't make sense that this is what this circuit suppose to do.
I tried to simulate it in my had(best simulator in the world or what?) for one of the two devices -
at t0 - sense_out is zero -> pull up works -> se_pwr_up_dly0 =  '1'.
after some time delay (which I guess is 40us+220n*4  = 41us?) sense out is '1' and then again se_pwr_up_dly0 ='1' .
so at all times se_pwr_up_dly0 is a logic 1 , then the same goes to the other se_pwr_up and this circuit ....do nothing?
I mean the only other option I can think in my head(I meant simulator) is that is suppose to detect when se_pwr_0 is different from se_pwr_1 and alert a flag which is the time between 41us to 40.6us ? its just does'nt make sense.
what am I missing here?
would appreciate it if someone could explain and draw the signals in time as response to 5v_Stby rise from 0 to 5v
edit:
thanks to jong I thing I got an hold on it yet I wanted to play a little bit with this circuit so I tried to simulate it and I keep getting error and I cant get why.
this is my simulation:

and this is what I get :

what did I miss?
*I had to put some load at the xor output otherwise it wouldn't work


texts:
Suppose we have an open-loop transfer function $$G(s) = \frac{1}{s(s+a)(s+b)}$$
If we plot the root locus for the closed-loop system we will get roughly something like this :

Now the question is when I add a new zero to the system which is at \$-a\$ then the book says that we should plot the root-locus without cancelling the pole-zero ( \$-a\$ in this case ) .
I have a practical doubt , in real systems suppose we add a new zero somehow obviously it will not be exactly at \$-a\$ but at some \$-a+\epsilon\$ where \$\epsilon\$ is very small , even in that case the root-locus will become something like this :

Because now the aysmptotes will change cause $$n-m = 2$$ . Therefore the new asymptotes are at $$\frac{\pi}{2}$$ rad and $$\frac{3\pi}{2}$$ rad . These two plots become completely different , if I go strictly by the book then my system (even after the addition of new zero ) becomes unstable for some value of gain \$K\$ but if I consider the situation practically then my system is always stable .
Please help me out , which one is correct .


texts: How does a wireless charger work without a magnetic core passing through both "coils"?

texts:
Every time I hear the description of a wireless charging system it goes like this: "remember a transformer? It's the same here - one coil is in the base and another is in the device and when you put the device onto the base the transformer gets assembled and starts transmitting power".

One problem with this description is there's no magnetic core in the system. AFAIK each transformer has a magnetic core in its design. A magnetic core is a huge set of steel plates that goes though both coils and this set of plates in fact conducts energy - the alternating current in the primary coil induces alternating electromagnetic field in the core and that field induces current in the secondary coil.

So looks like the core is a key component and a transformer can't possibly work without a core. Yet I don't see a magnetic core in a wireless charging system.

How does it work without a magnetic core?


texts: What is the magnetic analog of resistivity?

texts: Would the magnetic analog of resistivity be the inverse of permeability?  I ask this because resistivity is defined by E/J, and so taking the magnetic analogs as H/B, I see that this is simply the inverse of permeability.


texts: Multiple ADC readings in Arduino Uno with INA125 problems

texts:
First my system used four cheap resistive load cells (maks 5 kg, input 5 VDC) to measure COG of a quadrotor. The measurement pan dimensions are 60 cm x 60 cm and made from glass (glass weight=2080 gram), each load cell installed in each corner of the pan. The system used to measure weight variance from 0 g - 3500 g with Arduino Uno (custom-handmade) four-channel ADC 10 bit (A0-A3). Later data is transmitted to a PC via a WizFi210.

The load cell gives a linear differential output (after several adjustments with multiturns in a Wheatstone bridge) from 0.1 mV to 0.8 mV, and I need to amplify these outputs so my Arduino Uno can read these, and I used eight INA125s with a dual-power supply configuration.

First, four INA125s are used as instrumentation amplifiers with a gain of 100 and input from the load cell output, and the other four INA125s are used as operational amplifiers (negative Vin connected to ground directly) that amplify the instrumentation amplifier outputs.

The real problems are:

My INA125s affect each other while I changed the amplifier setting of one INA125. Why that can be happen? What should I do?
Between the Arduino Uno ADC inputs and the operational amplifiers I put capacitors (act as low-pass filters, value 9400 µF x2). Can these capacitors affect ADC reading performance?
Why is my ADC reading in Arduino Uno really unstable? While using an oscilloscope it seems stable.


texts: Way to discharge solenoid without (heated) resistors?

texts:
Here is a simple simulation of a schematic for my solenoid:

Once the switch is closed, the solenoid will be activated with ~80mA charge. When it is open (where the screenshot is at) it will discharge via the resisters in a looped path, due to the diode.

Now those resistors are cumbersome. A 100 Ω resistor would reach ~800mW of power during discharge, so for this specific test I split it in to four 25's in series.

I would like to provide a lot more power to my solenoid however (200-800mA), how would I be able to discharge it safely, with minimal current resistance when the switch is closed?

I could possibly use some wire-wound resistor (~5W) as a last resort, however those I do not have currently.


texts: STM32 Built-in LCD Controller Interface?

texts:
I have a bit of a specific question here:

I am the proud owner of an STM32L476 microcontroller. According to the datasheet (page 41), this specific MCU not only has a built-in LCD controller, but it can also drive an LCD in one of the built-in low-power modes. Problem is, I have no idea how to communicate with the LCD controller! I have scoured this datasheet and managed only to find the controller's memory address.

Does anyone know how to use this LCD controller?

P.S. I have searched the programming manual, but the word "LCD" doesn't appear once in the document. I really am at a total loss here


texts: What's the max current for this component?

texts:
I have a switch marked as having a max current of 2A at 240Vac, and 6A at 125Vac.

What would its max current rating be at 12Vdc?


texts: LTI system described by a differential equation

texts:
Lets say an LTI (linear time invariant system) is describe by a differential equation such as this:

$$ \sum_{k=0}^{N} a_k \frac{d^k y(t)}{dt^k}
= \sum_{k=0}^{N} b_k \frac{d^k x(t)}{dt^k}$$

(source)

A differential equation has a solution, it can be a particular solution (given there are initial conditions) or a homogenous solution. Now, what does it mean when a function is said to be a solution to the differential equation of the LTI system?

Mathematically, if you plug that function into the differential equation, the differential equation is satisfied, but what happens in real life (what does it mean when we find a solution to an LTI system)?


texts:
With these antennas; how does the signal flow through the glass?

Is it also possible across other bands; like 2.4GHz Wi-Fi signals?

Specifically tuned for the 4G NextG / 3G spectrum for optimum reception performance.
Operates at 5db gain. Suits: All handsfree car kits / cradles that require external antennas.

GSM 900MHz / 1,800MHz
3G 2,100MHz
NextG 850MHz
FME Connection
Whip 1 Gain 5dB
Cable Length 5m


texts: Calculated output is greater than the op amp can produce?

texts:
I had to analyze a differentiator and integrator op amp. I am now asked the question of what would happen if the calculated output is greater than the op amp can produce?

I am given a hint that it is usually a little less than the magnitude of the power supply voltage.

I think the answer is that the op amp would damped on suppress the output, so that the output is within the range that the op amp can produce, but I can't find anything that can confirm this for me.

Can someone tell me if I'm on the right track or not? Or if I'm going in the completely wrong direction.


texts: Attempting to connect a simple memory chip to a computer

texts:
not too long ago a friend jokingly bought me this simple toy which basically consists of a "push-me button" that creates a laughter sound when pushed.
How the hardware looks
I pulled the speaker out and was wondering how one would be able to access the memory chip which contains the sound, and change it to something else.

So yes, basically, I would like to know how I would be able to connect the chip to the computer, and edit the file which is contained in the chip.

It is important to note that I'm doing this purely out of curiosity in regards to the concept (connecting this random hardware to my pc and how this thing works), so the explanation may be as general as you`d like (I would love to be able to access this specific chip regardless though).

P.S.
I would greatly appreciate if anyone could also direct me to a source of information regarding the subject at hand, as this chip got me very excited about the whole hardware/software interface thing =D

Thanks in advance!


texts:
I am new to programming in ladder logic and am trying to write a simple program wherein outputs Y65 and Y66 follow the sequence:

Y65 turns on for 30 seconds.
Y65 turns off.
Y66 turns on for 30 seconds.
Y66 turns off.
Repeat.

I am using timers and internal bits to achieve this but I am having a few issues: 1) Y65 remains on for the entire time and Y66 turns on and off immediately. I have attached snapshots of my program. X1 and X2 are physical hardwired inputs; C1, C2, C3 and C4 are internal bits; Y65 and Y66 are outputs. Any help would be appreciated.


texts: What is the difference between the triode ( ohmic ) region and the saturation ( linear ) region in mosfet ?? It's confusing since both regions are linear but why does mosfet work as an amplifier in saturation not in triode ? Isn't triode equal to the active linear region in Bjt ? If it is not then what is the triode region and what is it used for ??


texts:
For a 3D scanning project I need to capture a video/snapshots of an object and a projector image that is projected on the object. The projector works (only) with a framerate of 60Hz, the camera supports rates in {3.75,7.5,15,30,60} Hz. I have to work in Matlab, and since it's an IEEE 1394 camera, I can only use the CMU 1394 Camera driver since other drivers are not supported by matlab.

Now, my problem is, that the framerates of the camera (driver) seem to have a tiny non-zero phase-offset that adds up over time such that the captured image gets darker and darker until it reaches some minimum and becomes brighter and brighter again and so on. This is annoying. There are sample applications for 3D scanners that are able to work with different drivers. There, the problem does not exist, so I am pretty sure that it's the driver's fault.

Fortunately, the driver is open source, so putting a little offset somewhere in it and trying to solve the problem by trying out different times, could work. There is, however, one additional idea I had: The camera supports triggering. Is there any way that I can trigger it using the output of the projector? If that would work, that would be much easier and more elegant than fiddling around with that driver. The projector uses VGA. Do you know of any possibility to capture the signal and use it as a trigger? If possible without lot's of additional hardware.


texts:
Is it possible to assert that particular formal port is associated in the instantiation in the VHDL? I have some entity with generic. Based on the generic value one of the input ports must be associated. I would like to achieve something similar to this:

entity tmp is
  generic (
    G_FOO : boolean  := false
  );
  port (
    a_i : in  std_logic := '0';
    b_i : in  std_logic := '0';
    d_o : out std_logic
  );

begin

  assert (not G_FOO) or (b_i is associated)
    report "b_i must be associated in mode FOO"
    severity failure;

end entity tmp;


texts: cny70 with 40106 and PIC, only detects 1 time every time I reset

texts:
I am using a PIC18F2550, a CNY70 and a 40106. (Schematics below)

The problem is that when I turn on the circuit, the first time the CNY70 detects something works perfectly (I have 1 led in every B output, except for B0 that is the interrupt input). The LEDs turn on for a very short time and then turn off. But when I try to do it again, the voltage of the CNY70 output changes how it has to, but the 40106 output only change from 10mV to 100mV. Also, I have changed the CNY70 and I have the same problem. I checked all the connections several times but i can't find anything wrong.

I tried 3 different configurations with the CNY70 and the 40106:

Without capacitor:

With capacitor between 40106 input and Gnd:

With capacitor between Vcc and Gnd: (I can't post more links - the same as the 1º but with a 100nf ceramic capacitor between Vcc and Gnd)

I use a PIC18F2550. The program is very simple, right now is only for testing the sensor:

#int_EXT
void  EXT_isr(void) {
  output_B (0b11111110);
  delay_ms (300);
  output_B (0b00000000);
}

void main() {

   setup_adc_ports(AN0|VSS_VDD);
   setup_adc(ADC_CLOCK_INTERNAL);
   setup_spi(SPI_SS_DISABLED);
   setup_wdt(WDT_OFF);
   setup_timer_1(T1_DISABLED);
   setup_timer_3(T3_DISABLED|T3_DIV_BY_1);
   setup_ccp1(CCP_OFF);
   setup_comparator(NC_NC_NC_NC);
   port_b_pullups(TRUE);

   set_tris_b(0x01);

   enable_interrupts(INT_EXT);
   enable_interrupts(GLOBAL);

   while(true){}
   }

Steps to reproduce the problem:

Turn on the circuit
CNY70 to air (open). it's output is 4.5V
40106 input is then 4.5V so the output is 0V (10mV). (B0 = 0)
Now I cover the CNY70 (close). It's output is 150mv.
40106 input is then 150mv so the output is 5V. (B0 = 1)
B1-B7 output high, turning on the 7 leds for a few ms.
I put the CNY70 to air again (open). it's output is 4.5V
40106 input is then 4.5V so the ouput is 0V (10mv) (B0 = 0)
I conver The CNY70 again (close). It's output is 150mv.
40106 input is then 150mv, BUT the output is only about 100mv. (B0 = 0)


texts: What is the amplitude of output signal in below circuit?

texts:
I calculate the amplitude of output signal by using the formula shown in figure. where R1 = 1 k ohm and Cf = 1 μF and Vin is sine signal. I got my answer is 5 V. Is it right? I want to know that why Rf (feed back resistor) did not contribute here while calculating V(out).

Sorry, previously I post the wrong circuit in which I showed positive feedback instead of negative feedback.


texts:
I’m working on a new PCB design using an Mstar LCD controller (MST9812Q1). I can’t link or post a datasheet as everything has “confidential, for internal use only” plastered all over it.

The controller, among other things, basically takes a HDMI signal and converts it to LVDS to drive an LCD panel.

Mstar reviewed my schematic and told me that I need 0 ohm resistors on the HDMI bus between the connector and the LCD controller to “damp” the signal. Mstar was not very clear as to why they are needed. I’m guessing this is for tuning the impedance should there be a problem or for EMI attenuation?

I’d rather not do this as I want to keep the trace impedance as consistent as possible. I already have a common mode filter with ESD protection (EMI8142MUTAG) on the HDMI bus which adds 6 ohms of channel resistance.
http://www.onsemi.com/pub_link/Collateral/EMI8141-D.PDF

Of all the application notes I’ve read on HDMI, none have said to add these 0 R resistors to the HDMI bus, and other HDMI product’s I’ve inspected have not included them either.

I have talked to my PCB manufacturer and gotten recommended trace widths and spacing for a 100 ohm differential impedance.

My questions are

What function are these 0R resistors meant to serve?
Will the EMI8142MUTAG provide enough damping?
If I am careful about my trace impedance, how likely am I to need to
add “damping” to the HDMI signal?

Below is the HDMI portion of my schematic with 0 ohm resistors added.

EDIT: I’m not using bus elements for power and ground nodes. They are ‘medium’ sized wires. It is a drawing style I was taught at a previous company and have kept because I feel it makes the power rails clearer to identify in the drawing.

EDIT2: I've just had a response from Mstar (well, not Mstar directly as they are forcing us to go through a Taiwan distributor). "There are for EMI purposes. If you do not care about passing EMI then you can take them off." So, considering I already have common mode filters on the port which also have 6 ohms of channel resistance, I guess I can safely not fit the 0R resistors?

EDIT3: I've just had another response from Mstar. They are pretty insistent about adding the 0R resistors. "Please still need you to put back the 0R. It is not just for EMI and it also for impedance test so we can fine tune it when signal is not so good. This recommend from MStar."


texts: arduino IDE isn't able to load skethes to my arduino mega board

texts:
I made a big mistake: I've written a small sketch just to play with my new arduino mega 2560. The sketch worked fine but a bit slow, so I thought that if I increase the baud-rate I will get faster communication to my computer. So I changed the baud-rate to 14400 (in the Serial.begin(); statement).

Now I'm not able to upload sketches any more, and I don't know how to solve this, I tried to burn the bootloader again but I don't know how to do it.

The sketch:

const int pin_in=A0;
const int cols=151;
int value;
int prev;

void setup() {
  Serial.begin(9600);
//  Serial.begin(14400);
}

void loop() {
  value=analogRead(pin_in);
  value=map(value,0,1023,0,cols);
  for (int i=0; i<cols; i++){
    if (i==value){
      if (value==prev){Serial.print("|");}
      else if(value<prev){Serial.print("/");}
      else if(value>prev){Serial.print("\\");}
    } else if (i%30==0){Serial.print("|");}
    else {Serial.print(" ");}
  }
  Serial.println("|");
  prev=value;
  delay(1);
}

When I try to upload my sketch (or any example sketch) I get error while opening /dev/ttyACMX although its present before trying to upload the sketch.

processing.app.SerialException: Error al obrir el port sèrie "/dev/ttyACM0".
    at processing.app.Serial.<init>(Serial.java:178)
    at processing.app.Serial.<init>(Serial.java:77)
    at processing.app.debug.Uploader.flushSerialBuffer(Uploader.java:77)
    at processing.app.debug.AvrdudeUploader.uploadViaBootloader(AvrdudeUploader.java:175)
    at processing.app.debug.AvrdudeUploader.uploadUsingPreferences(AvrdudeUploader.java:67)
    at processing.app.Sketch.upload(Sketch.java:1671)
    at processing.app.Sketch.exportApplet(Sketch.java:1627)
    at processing.app.Sketch.exportApplet(Sketch.java:1599)
at processing.app.Editor$DefaultExportHandler.run(Editor.java:2380)
    at java.lang.Thread.run(Thread.java:744)
Caused by: gnu.io.UnsupportedCommOperationException: Invalid Parameter
    at gnu.io.RXTXPort.setSerialPortParams(RXTXPort.java:213)
    at processing.app.Serial.<init>(Serial.java:163)
    ... 9 more
processing.app.debug.RunnerException: Error al obrir el port sèrie "/dev/ttyACM0".
    at processing.app.debug.Uploader.flushSerialBuffer(Uploader.java:101)
    at processing.app.debug.AvrdudeUploader.uploadViaBootloader(AvrdudeUploader.java:175)
    at processing.app.debug.AvrdudeUploader.uploadUsingPreferences(AvrdudeUploader.java:67)
    at processing.app.Sketch.upload(Sketch.java:1671)
    at processing.app.Sketch.exportApplet(Sketch.java:1627)
    at processing.app.Sketch.exportApplet(Sketch.java:1599)
    at processing.app.Editor$DefaultExportHandler.run(Editor.java:2380)
    at java.lang.Thread.run(Thread.java:744)

Is there a way to reset an arduino mega 2560 board?


texts: Altium Designer board outline and polygon

texts:
Is there a way in Altium to create a rule that will automatically create a recess from board outline when pouring a polygon?

This is tricky to do it with keep out.


texts: How to measure elapsed time using MSP430

texts:
What I want to do is measure the time it takes for a blade to spin round driven by a motor, and I am trying to achieve this using an LDR which detects the change in light each time the blade rotates over it (if there is a better method then please share). Once the ADC value from the LDR reaches a low enough threshold due to the shadow cast by the blade, I would like to register that as 1 rotation, and effectively measure the time between rotations.

I'm aware this can be achieved using Timer_A, although I don't know which mode to select (Up, Up/Down, Continuous), whether to divide the clock and most importantly how to **store the time as a variable in milliseconds*. So it would look something like..

If (ADC_value <900) {            // if one rotation made
  Time taken to rotate = X milliseconds
}

How can I obtain X?

Thanks in advance.


texts: I want to confirm this circuit is going to work and ask how to calculate the zener voltage. The load is going to be driven by 30 volts, and the gate voltage is the same 30v, through an optocoupler.


texts: I need help designing a very simple timer

texts:
I'm designing a very simple led light timer based on the Pomodoro time management technique. For those of you unfamiliar, you work for a set amount of time, take a short break, and repeat.

My end result is to have a 5v USB powered device that lights a green LED for 25 minutes, then switches to a red LED for 5 minutes over and over again. This does not at all need to be accurate...+/- 5-7% isn't going to kill me. Ideally, it'd be small enough of a device, like one of the smaller Altoid tins, to sit on my desk unobtrusively. Though an Arduino-controlled Nixie tube countdown timer does have its charm....

I've found and re-read this q&a, as a start but there are so many options that I'm not sure where I need to start.

From my understanding of the 555, it pulses (I'm thinking of it in astable mode), and triggers something. I'd originally thought I'd need a decade counter to keep TRACK of the pulses, but the page noted above seems to indicate that I can control the time between triggers with resistor and capacitor combinations. Of course, that suggests I'll need some formula to determine proper capacitance and resistance...which I've been unable to find.

Other solutions suggest relays, which I've not worked with yet...so I don't know what I don't know about relays in this solution.

Can someone point me in a good starting direction, or perhaps recommend which schematic on the above page would be most appropriate for my purposes, if any?


texts: ferrite bead selection for GSM application

texts:
I am trying to get a better understanding of a good method for selecting ferrite beads from those available.

I have a CLC filter, with 1uF x7r ceramics for each C, L being a ferrite bead in a 0805 package. Following this a LDO regulator that may need to supply 80mA peak of regulated supply. There is a GSM antenna operating from 850-2100MHz a few cm away, which is why there is additional filtering at the input of the LDO which is a noise sensitive 3V rail (10uF + 1uF + 0.1uF + 47pF on output). Assuming we are not going to change this arrangement, could you make some suggestion on how to select this part?

I have read guidelines of specifying the load to be no more than 20% of its rated current. This is the ferrite bead I am currently looking at. How would this other ferrite bead compare, since it has a very different profile?

Comments? Thoughts? Suggestions?


texts: Solving circuit DEs: derivative of inductor current should be zero, but isn't

texts:
I am in the process of solving a DE for a circuit.

So: the circuit starts with a voltage source of 5 VDC and is allowed to reach steady state. At time t = 0, the source is switched out for a 10 VDC source.

I am in the process of finding the initial conditions: $$i_L(0^+)\ \  \mathrm{and}\ \ i_L'(0^+)$$

Clearly, $$v_C(0^-) = 0\ \mathrm{V}\ \ \mathrm{and}\ \ i_L(0^-) = \frac{5\ \mathrm{V}}{100 \ \Omega}$$

So $$i_L(0^+) = 50\ \mathrm{mA}$$

Now, to find iL', I said $$v_L = Li_L'\ \ \mathrm{and}\ \ v_L = v_C$$

So $$i_L'(0^+)=\frac{v_C(0^-)}{L} = 0\ \frac{\mathrm{A}}{\mathrm{s}}$$

But, if you simulate this circuit and flip the switch, the slope of the current through the inductor is clearly not zero.

Am I doing something wrong, or is there something subtle happening?

Thanks


texts:
Almost all smartphones on the market seem to use a distinct LCD as their display, though most use an ARM processor with a GPU from one of a relatively (compared to the screens) small number of companies (PowerVR from Imagination, Mali, Adreno from Qualcomm, etc). When a company goes about designing a smartphone, I assume their choice of LCD isn't restricted by their choice of SoC (and therefore GPU).

So, once they have chosen their SoC, how do they interface their LCD and GPU? Is there a standard protocol? They don't use HDMI under the hood, so what is it? If they wanted to take for example this display(chosen for no particular reason) and use this driver (purely based on recommendation by aforementioned display), where would they start? Is engineering an interface a whole difficult task by itself?

I have seen a few different interfaces mentioned while researching this before, for example:

SPI - this isn't fast enough to drive 1080p@60, which many smartphones provide
i80 - this doesn't provide 8 bits per colour as far as I can tell, but moreover I can't find a "standard" description of this interface
various parallel rgb interfaces which aren't very well documented.

I feel as though this gap in my understanding in part comes from incomplete datasheets, Chinese datasheets I can't understand or datasheets behind paywalls. How can I gain more understanding on this topic? Or do I need to be "in the business" to even start?

Any advice or guidance for further understanding is appreciated.


texts:
I have this comparator circuit using an op-amp. This is my actual op-amp used in the circuit. I have used TL072 as I didn't have the simulation model.

This circuit is used to trigger the output when the inverting input is less than 80% of the non-inverting input.
But, when I use this in actual circuit, when the inverting input is less than 80% of the non-inverting input, the output is oscillating, even though the circuit is designed for hysteresis.
I read this application note from TI, but I am not sure why the output is oscillating. Can someone tell me the reasons why the output might be oscillating?
In actual circuit measurement, the input at the non-inverting node, has an oscillation of 1.4V peak to peak. I believe this is the reason why the output is also oscillating.
But I am not sure on why the input is also oscillating. I have no capacitors also in the entire circuit.
Can someone tell me the reasons and how to avoid this oscillation?


texts: How to set external clock value for STM32F1?

texts: I creating a project with the microcontroller STM32F101C8t. This microcontroller has an internal clock of 36MHz. My question is how to correctly set the external clock value, ie what crystal value should I use. I already set the external clock pins in the STM32CubeMX, now it is necessary to set the correct value for the external clock.


texts:
I’ve been soldering components to my PCB; all has been good, but recently, after soldering a big electrolytic through hole cap, the power and gnd plane were shorted. This persisted even after removing the cap.

Is it possible that the plated throughole has a gap in between layers where excess soldered flowed through and connected to GND in one of the internal layers? This board was made through OSH Park (it’s a 4 layer board).

EDIT: Solved the problem by drilling through the center of the throughole with an oversized drill. I got to the assumption that the throughole was causing the short by using the suggested method of applying current to go through the power plane/GND and seeing that the lowest voltage was in the vicinity of the hole.


texts: Is this a sensbile way to switch a 12V line with 3.3V logic

texts:
I am just starting to learn about making electronic things, so this may be a foolish question. I think this is adequately different to similar questions here.

As a first project I am working on making a fan controller based around an ESP32/ESP8266 MCU (I'm coming from software development, so this feels like a comfortable route in). The fan is a 4-wire PC fan (SUNON PMD1206PMB3-A 12V 3.4W). I have a working system to send the PWM signal to control the fan speed and plan to work on getting back the fan's tacho, but am having an issue with system stability on start up that I believe is due to power stability caused by the fan drawing current while the MCU is booting. An approach that I'm thinking of is to get the MCU to control the power to the fan and only switch it on when the boot is complete (this has the advantage of allowing the fan to be turned off when the set speed is zero - the zero duty cycle oddly leaves the fan running at 20rpm).

Since the ESP32 uses 3.3V logic I cannot directly switch a MOSFET with a line from the MCU, so I was thinking of using something like this.

Is this a sensible approach? Is there a better way to do this?

Note that the +12V and +5V are already available in the circuit - though from looking at this related answer it appears I could draw from the 12V.


texts: Decreasing amount turns on coils decreased my rpm?

texts:
So after reading link after link of how torque and speed are inversely proportional, I deduced that if I decreased the magnetic flux, my motor should run faster albeit with less torque. However, when I redid my windings from 300 turns each to 100 turns each, my motor barely moved! It went from 2500 to like 400rpm. What gives?

Motor specs: hand made brushless dc motor, 3 coils of 28 gauge wire, 12V, 1 permanent magnet pair, and vex optical shaft encoder used for 6 step commutation