texts:
I'm looking to follow up on a question (asked by another) that wasn't answered to my satisfaction in another question.
RFID Antenna Array

I am successfully using the ID Innovations ID-2 chip to read 125kHz RFID tags. Furthermore, I have sucessfully tested connecting antennas with RG-58 coaxial cables with SMA connectors up to 8' in length. I now need to use need to use multiple antennas to scan in different locations using the same ID-2 reader IC.

I hesitate to use traditional analog multiplexers because the signal sent from reader to antenna is extremely analog, and ranges from a few mV to over 100V and I'm worried that the properties of MUX ICs will destroy the signal to/from the antenna.

I basically need a "2-pole,4-throw selector switch" that i can control with some I/O pins from an Arduino or other microcontroller.

Can anyone point me in the right direction? someone suggested using mosfets in comments on the other question? Thanks in advance!

I will make whatever board i develop to do this available as open source hardware.

ID-2 Datasheet

Update: I would use something like an analog switch IC if it didnt seem like the signal would exceed the maximum voltage of the IC. Am I wrong?

Update2: Found some Solid State Relays that look like they might be the best of both worlds. Im going to go ahead with these for now. http://www.mouser.com/catalog/catalogusd/646/1981.pdf


texts:
Why did he pick the HV to be the side where he applied the voltage? Usually open circuit test voltage is applied at the LV side. So, from the question how can I know which side he performed the open circuit test on?

SOURCE:
Basic Electrical and Electronics Engineering-I
Fifth Edition, 2015
Abhijit Chakrabarti
Sudipta Debnath
McGraw Hill Education (India) Private Limited
ISBN (13): 978-93-392-2204-8
ISBN (10): 93-392-2204-0


texts: Specifying parts for Induction Heater; how to determine current requirements at transformer?

texts:
I'm working on specifying parts for the following circuit:

I intend to have a very large work coil, (like 12" diameter) so I'm expecting to need a lot of power. I'm on a tight budget, though, so power is the tricky part for me right now. What I'm trying to do is figure out how much power I can get to the work coil for under 500$.

Looking at low-profile transformers online to start with, I found several that step-up the voltage a lot, but they have very low current ratings.

I'm not sure if that's an issue, though, because I expect that there won't be a high current-draw from the transformer. I'm thinking that the colpitt's oscillator and work coil will convert the changing voltage into a current for me, so I only need to worry about current on the transistors (or op amp) in my oscillator.

Am I right that I don't need a high current rating at the transformer?
Are my hopes realistic here (financially)?
What's the danger of applying too high voltage to the work coil?

Thanks a lot!


texts:
I have this PCB with led display constantly on consuming all the energy available in the battery I connect.
There is a way to switch it off after few seconds?
Dc-dc Boost Step up Voltage Converter 3v 3.3v 3.7v 4.2v to 5v 2A


texts:
We are designing analog input with RC low-pass filter and we want to be able to disconnect the filter if needed. So we came up with these two options. 1st option has jumper at the right side and has twice as much inputs because you literally have to disconnect the wire of the input and connect it for example from IN1 to IN2.

The second design has only one input IN but we are concerned that if op-amp is used the wire above it might bring a lot of disturbances from the air... Also we are concerned about current which might flow in the op-amp output or (-).

Well what do you think?


texts: SoftConsole VS Keil for Smatfusion2 or any other development environment?

texts:
In order to program the ARM Cortex-M3 processor which is embedded in the Microsemi FPGA board SmartFusion2, I think there is two possibilities (correct me if wrong):

Keil MDK (Microcontroller Development Kit) provided by ARM.
SoftConsole a software development environment provided by Microsemi.

One obvious thing is that SoftConsole is free while the other presents a limited free version.


texts: AMS1117 3.3V regulator outputs 4.2V or 3.3V depent on source of 5V input

texts:
I'm trying to use a AMS1117 3.3V to deliver 3.3V from a 5V input.
Case 1. 5v input supplied from 5V output of usb power supply module pictured below

Works like a charm, 5V in and 3.3V out.
Case 2. 5V input supplied directly from micro usb output.
When the voltage regulator is not attached, the micro usb outputs 5V. When it is attached, this output goes down to 4.9V and the regulator outputs 4.2V.
Can anyone help me understand what is going on? The 5V output from the module passes through a chip with an underlined 4 on it. What does this chip do?
edit: schematic added


texts: Relation between Fast Fourier Transform and Laplace/Continuous Fourier representation

texts:
I am trying to identify a system by means of its differential equation (i.e., Lapace representation). I put together a rather straightforward regression algorithm (similar to Proni's method for ARMA) under the assumption that the FFT of the system response is equivalent to the Laplace transform evaluated at \$ -j\omega \$ (with \$ \omega \$ restricted to \$ (-\pi , \pi ) \$, (but this doesn't seem to change anything).
It converges quite consistently but the poles I get are both positive and negative (i.e., stable and unstable if I interpret them as I intended in the s-domain) and both inside and outside the unit circle (again unstable and stable if I interpret them as a Z-transform instead).
I am no newby to DSP, but it is clear I have some misconception somewhere. Most likely on my interpretation of the FFT as simply a sampling of the Laplace transform on the imaginary axis or in the proper scaling of this axis. I have checked the equations back and forth multiple times, and I can't see what I am doing wrong.

The gist of it is simply to solve the equation:
$$
y(s)*(1 +a_1s + a_2s^2 + a_3s^3) = x(s)*(b_0 + b_1 s + b_2 s^2)
$$
For the values of \$ a_i,b_i \$ that minimize the representation error, setting \$ s=j\omega\$ with \$ \omega \text{ in } (-\pi,\pi) \$ and making \$x(j\omega)\$ the FFT of a known input and \$ y(j\omega)\$ the FFT of the measured output (trimming the edge frequency bins as these are noisy).
I know that the FFT of a finite sampled sequence is simply sampling the Fourier transform and adding the aliased components into it (which in this case can be assumed to be zero, as the data stream is digitally filtered and subsampled).

I want to implement it in the continuous s-domain, as it is modeling an analog system and that would make the results easier to understand. So, before I throw all of this away and model it in the discrete Z-domain as an ARMA, can someone point to where my problem lies?


texts: How does placing cap between signal GND and earth GND solve common mode noise?

texts:
Thanks in advance for your time.

I am reading several articles about differential mode noise and common mode noise. Among which I found the below 2 pretty instructive:

https://www.murata.com/~/media/webrenewal/products/emc/emifil/knowhow/26to30.ashx
https://micro.rohm.com/en/techweb/knowledge/emc/s-emc/01-s-emc/6899

Let me first talk about my understanding as a start point.

Differential mode noise is some noise generated with the propagation of power line, such as noise generated from some on-board chips' operation like source/sink power to GND. This will produce ripple on power line, which is noise. In this case, placing capacitor between power and GND line solves the problem, it conduct the noise current to GND and flow back to power source.
This is illustrated in Figure marked 1 and 2.
Common mode noise is pretty confusing. It is generated through the coupling between your on board signal trace or plane and the Earth GND. The start point is, there is coupling between your on board trace or plane and the surrounding mechanical box which is connected to Earth Ground, so this coupling will generate some current through it. Then this coupling current will flow back to your power supply's Earth GND, which its surrounding mechanical box is connected to, then through its stray capacitance, the noise will flow to both the power and GND lines that the power supply feed to your board. This is the signal flow of common mode noise.

Is my understanding correct?

My questions are:

In the first article, Suppression method of common mode noise (2), it says adding cap between signal GND and earth GND solve common mode noise, why? I understand method (1), using common mode choke, but why method (2) also works? Just because common mode noise is referenced to Earth GND, so placing cap between where common mode noise flow through and Earth GND, can filter it out?
Why doesn't differential mode noise's current go with the common mode noise's path?


texts: Powering an LED with a Thermoelectric Generator

texts:
Can a small Thermoelectric Generator feasibly power an LED?

I want to make a small LED circuit that consists of a coin cell, an LED, and some sort of touch-sensitive switch. The entire circuit needs to be very small (~3cm³), and there must be no moving parts. The circuit is for a jewelry piece so it doesn't need to act within finely tuned boundaries at all times, all I want is for the LED to glow visibly when the circuit is held.

I've never used TEGs before, but after reading a question from earlier this year I would like to know if a small TEG could be used, essentially to act as both switch and power source. I tried figuring it out but I am still struggling to understand the relevant information on this page and the related datasheets.

I would like to use one in the 10mm - 20mm range if possible, using this as an example.
My understanding is that since they work on temperature differences,  if  a temperature gradient of 68deg / 27deg produces 8.8V, then a typical human/room temperature gradient of 37deg / 27deg would produce around 2.2V, enough to power your typical 1.5V LED.

Am I correct in this assumption?


texts: Feeding microcontroller and linear actuators (motors) with the same power supply

texts:
I have already made a diagram using a motor controller.

The details of the actuators are:

Input voltage: 12VDC
Max Load: 750N(168.607lbs)
Stroke Length: 16 inch
Travel Speed: 12mm/s
Duty Cyle: 25%.

Could you please check if it is ok?

Some of my concerns are:

Be sure if the feed of 12 volts for the motors, and 5 volts for Arduino are correct  and can live together as shown.
Be sure if the wiring for the Arduino, driver and motors is correct since it looks kind of simple.

Diagram1

I want to know if this is the natural approach by doing it with a voltage regulator to feed the Arduino and with 12V 10A power supply to feed the motors, or if there are other, better options to make the circuit feed only using one power supply (12V, 10A).

MDD10 Datasheet Link: https://www.robotshop.com/media/files/content/c/cyt/pdf/cytron-10a-7-30v-dual-channel-dc-motor-driver-shield-datasheet.pdf

UPDATE

I have increased power supply to 13A, also changed the linear voltage regulator (7805) to a switching voltage regulator (OKI-78SR-5), what do you think about this approach?

Diagram2

Or I should try with the 12V DC Vin of Arduino(I understand that it works with a linear voltage regulator)? Being this option, it could be maybe with a voltage pre-regulation stage(from 12V to 9V for example) or maybe connecting directly to the jack.

Diagram3

Thanks, Best Regards.

I'm adding a fourth diagram..

Diagram4

The orange color is used to represent a heavy wire which goes from the 12v power supply to the ground of the motor driver, from the ground of the motor driver goes a normal cable to the arduino ground, and from the arduino ground a normal cable to C2 then to the ground of the voltage regulator then to C1.

This is to avoid noise caused by the motor driver to the arduino and the voltage regulator.


texts: Theory behind parallel battery with diode

texts:
In a big simplification of my circuit, will be a situation that capacitor will have more voltage than the main battery. And thus, need a diode protection.

In the current simulation with multsim, this is simple ignored OR I maybe wrongly simulating.

My leader said "until capacitor's voltage is high than main source, so it will flow current and battery no."

My question where is it in theory? Do KVL answer it?

*sorry for my bad english

EDIT:

I think this is the more apropriated


texts:
I am using an Intel Edison with Arduino Breakout Board to communicate via SPI to a LS7366R Quadrature Encoder Buffer.  I am using the QEB as a timer: a pulse that enters the index will shift the counter register to an OTR register for reading.

My problem is with the speed of SPI communication from IE to QEB.  I am programming IE with a mraa library to communicate via SPI in C.  According to a clock speed of 6.25 MHz, it should take 1.28 microseconds to transfer 1 byte.  Instead, it takes 60 microseconds.  I do not know why my SPI communication is slow.  I have already ensured that communication is working properly, albeit slow.

Proof: The following code takes on average .61 seconds to execute.  If I remove line 3, it takes on average .005 seconds to execute.

1. for(i = 0; i < 10000; i++) {
2.     mraa_gpio_write(ss_o, 0);  // ss_o is slave select one
3.     mraa_spi_write(spi, 0x60); // transfer 1 byte via spi
4.     mraa_gpio_write(ss_o, 1);  // end transmission
5. }

My question: How can I speed up my spi communications?

I am using mraa version: v0.6.1

EDIT: After transmitting 5 bytes of data at a time, I found that the initialization may be taking a long time.  Replacing line 3 above with...

3.    mraa_spi_write_buf(spi, write_buf, 5);

... results in .65 seconds, a minute increase of time for 5 times the data sent.  I am not an expert on parsing libraries, so can anyone help me find the bottleneck in the mraa spi library?  I want to see if I can edit it to speed up the SPI calls.

EDIT: CLARIFICATION: I am intending to use the counter as a timer; every time a pulse comes in I want to know when it came in.  Therefore, I need fast repeated reads of the OTR register.

EDIT: added full code:

#include <stdio.h>
#include <time.h>
#include "mraa.h"

int i = 0;
mraa spi_context spi;
mraa_gpio_context ss_o;  // ss_o is slave select one
clock_t start, end;

int main(void) {
    spi = mraa_spi_init(0);
    mraa_spi_frequency(spi, 6250000); // Set frequency to 6.25 MHz
    mraa_spi_mode(spi, 0);
    ss_o = mraa_gpio_init(10);  // ss_o is pin 10)
    mraa_gpio_dir(ss_o, MRAA_GPIO_OUT);
    mraa_gpio_use_mmaped(ss_o, 1);
    mraa_gpio_write(ss_o, 1);

    // Initialize counters
    mraa_gpio_write(ss_o, 0); // Begin SPI conversation
    mraa_spi_write(spi, 0x90);
    mraa_spi_write(spi, 0x1);
    mraa_gpio_write(ss_o, 1); // Terminate SPI conversation

    mraa_gpio_write(ss_o, 0); // Begin SPI conversation
    mraa_spi_write(spi, 0x88);
    mraa_spi_write(spi, 0x30);
    mraa_gpio_write(ss_o, 1); // Terminate SPI conversation

    start = clock();  // For measuring time
    for(i = 0; i < 10000; i++) {
        mraa_gpio_write(ss_o, 0);  // ss_o is slave select one
        mraa_spi_write(spi, 0x60); // transfer 1 byte via spi
        mraa_gpio_write(ss_o, 1);  // end transmission
    }
    end = clock();
    double diff = (double)(end - start) / (CLOCKS_PER_SEC);
    printf("Time elapsed: %f\n", diff);

}


texts: Anomalies while using transistor as switch

texts:
I have started learning Transistors from this Tutorial by Sparkfun - https://learn.sparkfun.com/tutorials/transistors . I understood that while using Transistor as a switch it operates in Cutoff or Saturation region to turn ON or OFF.

However below is a diagram that shows the Transistor in OFF state.

I couldn't understand how voltage drop of 1.3v exists across LED and 3.7v across Collector and emitter terminal. The current flow has clearly marked as 0mA which is true since transistor is in cut off region no current flows from Collector to emitter terminal. Surprisingly when I assembled this in a simple breadboard and measured the voltages there indeed is a drop. Here are my observations.

Vcc : 4.81v ( Not a good power supply I suppose )

VR2 : 0v

VLed1 : 0.68

VCE : 3.55

VBE : - 0.24

IC : 0

There is a voltage drop exists across Led1 and CE terminal of transistor however there is nil in resistor R2. On seeing this, I have been scratching my head with these four questions.

1)  Current being the same across series connections should make the resistor to drop voltage as well isn't it?

2) Besides summing up the VCE and VLED1 does not equal to the supplied voltage Vcc.

3) And why there is a negative voltage exists in Base terminal of transistor.

4) How can there be a voltage drop when there is zero current flowing ?

Am i missing something? Kindly help, thanks in advance.


texts: Does duty cycle have effect on sending pulse train properly for long distances

texts: A system will use coaxial cables to convey pulses to trigger remote systems. The cable lengths might vary up to 100m. In that case, if the duty cycle of a 30Hz fixed pulse train is too low like %0.05 (less than 20us), is there any possible benefits to stretch the duty cycle to around 50%? Is there any relation?


texts: Is there a wireless protocol for 100m-1km range in rural property?

texts:
I am an electornics hobbyist. A friend of mine, who is building an organics farm, wants to wirelessly automate some devices in his property, and asked for ideas.

His problem is to "talk" to remote devices, namely the front driveway sliding door (around 100m away from home) and water pump (200m away from home in the opposite direction). This "talk", that is, sending and receiving commands and data, would be handled by some sort of dashbord or "control center" yet to be devised.

At first, he expressed the desire to use WiFi, but as far as I know, at least the water pump would be too far from the control center.

I am pretty sure this type of scenario is pretty common, but could not find an obvious protocol for the "100+ meters" range, up to, say, 500m or 1km.

What are the protocols commonly used for this, specially in rural areas?

UPDATE: At first, we would not like to depend on third-parties, such as cell-phone operators or similar paid services.


texts:
I have a Uni-T UT139C multimeter. I want to measure the power usage of my Blitzwolf USB charger. Can I just connect my multimeter in series with the charger at the wall and measure how much power the charger uses ?

And how can I calculate watts in AC circuits?  it's same as DC (VxI)? Or it is different than that. I searched about it in the internet and it says we need to know the power factor. Is it true?  if so, what is power factor..?


texts: What's the difference between WLP and BGA (IC packages)?

texts:
I read the following sentence in this Maxim appnote. (WLP = Wafer Level Packaging, CSP = Chip-Scale Package)

  WLP technology differs from other ball grid array, leaded, and laminate-based CSPs because no bond wires or interposer connections are required.

No bond wires? Then how is the die connected to the ball grid? Can anybody explain the difference between WLP and BGA in more detail? They look very similar.


texts:
I am trying to control some power LEDs using a microcontroller. For this I plan to use a transistor based constant current source to protect the LEDs from getting damaged and PWM on the base of the transistor to control the brightness.

The circuit is set to obtain 300mA across the LED. The transistor is 2n2222 NPN.

Problem:
The Vin is 12V. The LED consumes only 3V. This leaves about 9V that drops across the transistor and the resistance in series. The power consumed by the transistor is high enough to burnt it. After a few seconds of working it gives up and the current in the circuit increases to about 1A before it burns out.

I want to understand what can be done to stop this from happening. I also tried using a 5V zener in series to consume 5V before the transistor. This did the job somewhat but the zener got extremely hot (enough to melt plastic) and that can't b good for the life of product.

Some help here will be highly appreciated.

Limitations-

I cannot use a voltage regulator to decrease voltage as there is absolutely no space left on the PCB.
I cannot change the power source from 12V to something less.

Update:

So inspired by @indraneel answer down below, I understood I had to either utilize the remaining voltages in an efficient way or make sure the extra wattage was dissipated in a dafe manner.

What @indraneel suggests is very efficient as you get to actually make use of the extra wattage you have after the first LED and this also won't give too much heat. But it just wasn't the right solution for me as the LEDs are quite expensive. But, this inspired me to understand that the only way is to consume this power. So I decided to use a 5V zener in series. Obviously, the zener diode will heat up too much to dissipate this power. For that I placed the zener on the aluminium PCB where all my LEDs are. That acted as a heat sink for the zener. Now obviously the aluminium PCB does get warm but it neither affects the LEDs, nor does the transistors get burnt/damaged.

I hope this post helps someone. :D

FINAL UPDATE

So earlier I thought that using zener in series was a good way to drop some voltages but it is in fact a bad idea. Eventually the zener gives up, in a day or two maybe. THE SOLUTION WAS TO FINALLY MAKE SPACE FOR AN LM2596 BASED BUCK CONVERTER TO GET RELIABLE STEPPED DOWN VOLTAGE AND VERY LESS HEAT.


texts: Can I generate a clock pulse by using just one SPST switch?

texts: Why can't I get output for IC 7490 by just toggling the SPST switch (to generate a CLOCK pulse )?


texts:
I can't figure out what manufacturer this even is. All I know is that the top side is all connected to 24V and the bottom is all connected in parallel to a bunch of the same chip.

Part says 4614 and BV9K3B on it.

I took a look but couldn't find the manufacturer here:

http://how-to.wikia.com/wiki/How_to_identify_integrated_circuit_(chip)_manufacturers_by_their_logos/A-E

Any Insight?


texts:
I have an active low circuit. I'd like to delay the low signal input when the it gets tied to ground, but allow the input to come up instantaneously when the ground is released.

I've tried adding a capacitor in parallel with the input with a resistor in series with the input on the switch side of the capacitor.

Something like this..

I've also tried moving the resistor around.. and done a few variations of this and nothing seems to be working. I feel like this is something so simple that I'm missing. the component value in the drawing are not accurate to what I tried but i've tried as high as a 22uf cap and 2.7K resistor.

This whole idea seems to be working backwards. I'm getting a delayed high signal and fast low signal.


texts: Male Apple Dock Connector => USB (power only)

texts:
I have an old external battery for Apple devices (has 30 pin Apple Dock Connector), and I want to repurpose it to be an external battery for all my USB devices.

Anyway, I don't have much experience with this kind of thing, so if someone could give me some good advice on how to accomplish this, it'd be great! I only really need to convert it to any kind of USB cable, since I can just get converters from there.


texts: Is rms value of a positive varying DC voltage same with its mean value?

texts:
I know that rms of an AC is totally different than its mean. But what if the voltage is not alternating(DC) but varying by time. For example a noise with a huge offset.

How is varying DC measured by voltmeters? Mean or rms? Or as in my question are they the same thing for a varying DC?


texts: How should be interpreted this note about the floating point?

texts:
In an old class notes I have found something that puzzles me since I don't grasp how it works.
The notes says

  **Floating point numbers representation **
  In general if \$N=\pm(a_{n-1}...a_{0}...a_{m})_{r}\$, then \$N\$ could be written as
  $$N=F\times r^E$$
  where
  $$F=\pm(a_{n-1}...a_{m})_{r}$$
  $$E=\pm(b_{k-1}...b_{o})_{r}$$
  so the fractional part \$F\$ is multiplied by the \$r\$ base raised to the power \$E\$.
  Let \$S_{F}\$ be the sign for \$F\$ y \$S_{E}\$ the sign for \$E\$, then the floating point representation reduced is:
  $$N=(S_{E}S_{F},b_{k-1}...b_{o},a_{n-1}...a_{m})_{r}$$
  with \$S_{F}\$ and \$S_{E}\$ equals to  \$0\$ or \$1\$ for \$F\$ and \$E\$.

  Example
  $$N=(1.650000)_{10}$$
   for \$n+m=5\$ and \$k=3\$,
  \$F\$ and \$E\$  would be
  $$F=+(0.16500)_{10}$$
  $$E=+(0.007)_{10}$$
  Then

  $$N=(00,007,16500)_{10}$$

I'm guessing that its like when you convert a fractional decimal to binary starting to multiply the number by the base 2 but I don't know why the  E and F coefficients, nor what the n,m and k are and how are assigned.

Could please explain how the theory part is applied to the example?


texts: About floating ground and circuit problems

texts:
Good morning,
I have a power supply with floating ground that drives my circuit.
Since the circuit doesn't work as expected (it works fine only if the ground is tied to earth) I did some measures with oscilloscope. I left the ground of both probes (with 10x) disconnected and I did the difference between the two channels connected respectly to gnd and to the input signal of an opamp. What I see (see picture) is that the difference (white band) is not flat but there are peaks
I'm wondering if:
- it's a my mistake in the measure or
- the two points don't float together creating a voltage difference in the opamp input
- there is a way to reduce the float voltage difference

Thanks


texts: What happen to a dff(flip flop) without input?

texts:
I have this question but I don't know what happen to a dff without an input is it always 0 ?? like this picture below the 2nd dff hasn't any d ??? Also, if someone can draw the answer of the question ?
thank you

and I would like t


texts: Wiring transformer output in series to get twice the voltage possible?

texts: I already have a transformer 2x 6V outputs. I was wondering can I these in series to produce 12V? Similar to how you would wire two 1.5v batteries to produce 3V.


texts: TTL or IGBT Output - software switchable

texts:
I am creating a circuit which will be used in an Engine Management system.

Its function is to:
a) either drive a 12v ignition coil directly (using a normal IGBT)
b) or if required, offer instead a 5v TTL 'trigger' output

I have sketched out a diagram.

I believe 'switch' section A can be accomplished by simple logic gates to choose where to direct the MCUs trigger signal - either it goes to driver type B or driver type C.

B - I plan to use a simple AND gate to give the 50mA 5V output when in "TTL" mode

C, is just a simple IGBT (there is a logic driver built in to it etc, that part is fine)

Juntion D is the issue (as only 1 pin can be used for the ignition outputs):
The user may either be connecting to this to a simple 12V ignition coil (which will be using the IGBT part to operate, switching it ground etc

or

An external igniter that requires just the 5v trigger to be there

So the output system (especially the part in (B) need to not be damaged by the connection of a 12v ignition coil, and so forth.

The user cannot open the ECU to for example change physical jumpers.

Looking forward to your ideas


texts: What abbreviation does they use for nominal voltage (Un) in Russian?

texts: I need to translate the "Un" symbol for Russian client.


texts: Can a rotary incremental encoder, count more steps due to interferences

texts:
I have an incremental encoder having differential signals A-NotA, B-NotB I-NotI, that apparently randomly seems to count more impulses. It is possible to have more impulses due to electrical interferences ( IMO not because of the differential outputs ) or can this happen?
The encoder is a Baumer BHK 16.05A.1024-I2-5 and a datasheet can be found here http://www.pdfdoc.ru/process-control/sensors-and-transducers/rotary-encoders/baumer/bdk-min-shaft-encoder-1024ppr-ttl-o-p-bdk-16-05a-1024-5-4-499-7598

The wiring is done by 5m cable with shield connected to ground at a single point ( near the encoder ) and we are not using twisted pairs.


texts: Cape to ease sensor interface on Beaglebone

texts:
Is there a "cape" to make wiring sensors into a Beaglebone easier?

Whenever I read some guide for wiring a sensor into the Beaglebone (like this one) it always recommends attaching wires directly to GND, +V and signal pins, which is horribly messy and unmaintainable. Even for small projects, you end up having several wires connected to the same GND/V+ pins, so if you need to replace or repair something, you end up disrupting the wiring for every other component in your project.

Most Arduino guides assume this bad practice too, but at least I've found various "breakout" shields to help organize GND/+V/Signal pins so I can attach individual sensor cables.

Is there anything similar for the Beaglebone? I can't find anything appropriate Googling "breakout" or "IO" cape.

Edit: The interface I'm referring to called GVS and is popular in the Arduino community. Unfortunately, there's not much uptake yet in the Beaglebone community. I could only find one GVS cape, but looks pretty useless. Out of all the Beaglebone's pins, it only exposes 5 as true 5V GVS. All the other pins it exposes are at 3.3V or 1.8V levels, which are useless for most existing sensors.


texts: Safe to exclude capacitor in this circuit?

texts:
This is a front panel for a piano-keyboard (Kurzweil SP3X), with buttons and button-LEDs. The LEDs did not work at all, and I traced it to a shorted capacitor (C2), which I removed and confirmed it was shorted. Is it ok to simply leave this (C2) open, not replacing the cap?  It's just for convenience as I don't have tools at my current location. For learning it would be nice if you explained why it's ok or not.

Mostly there will be only 4-6 LEDs active on right panel. But during startup all LEDs light up simultaneously for about 0.5sec, as seen here at 12sec-mark: https://www.youtube.com/watch?v=szlCpS0GEhA


texts:
Those days there have so many different protocols in the soc which basically means different clock rate.

In a Soc system, there have CPU which run at some clock speed, then there have memory(dram) to run at some speed. In between, there have a AXI bus which also has a clock. Is there a relationship between those three clocks? If not, does AXI function as an interface between dram and CPU which transfer the data in the two different clock domain?

If so, how about other domain such as EMMC, HDMI, etc? How can one bus bridge all those different clock domain?

Finally, what will generate the clock for each of those sub-blocks? I know CPU will have its own clock as well as memory as its own clock. How about bus, HDMI, EMMC, SPI, MIPI etc?

THanks a lot,

Brian


texts: What is the forward beta of the BJT KN2222A?

texts:
I don't know what is the forward beta of the bipolar junction transistor KN2222A, I'm an amateur and i don't found the value in the data sheet or i just don't understand where.
Please let me know


texts: Control of flow of current usig Tri-state buffers

texts:
Are Tri-state buffers essential to the building of processors?
If we connect the control input of the Tri-state buffer to the Q or Q bar of a flip flop then we can program?


texts: What is the current limit/saturation of series inductors?

texts:
I am currently trying to increase a 12Vdc 30A (from a computer power suppy) to 24Vdc 12A. The circuit I have used is based on a application note for the NCP3063 boost circuit with an external mosfet, but I am having problems trying to find a large inductor which is capable of handling the average inductor current of 25.7A.

So, to increase the current through my inductor, could I simply put two inductors in series? If they both had a saturation point of about 10A, would that then give me twice the inductance and twice the current limit?


texts:
There is a little timer circuit that I just design with a relay at the end of the second cascaded 4017 output for switching on/off power applicants. There is a button to reset the counter to zero. My first question, is there any faults to this circuit? second question is how/where do I add a button to start the counter? last, what is the maximum time for this timer? 10min from 555 X 100= 1000 mins/60=16.6 hours?

Here is the finished PCB design:


texts: Need to map 0-5V DAC output to 0-10V output

texts:
I am using a TLV5618 to take a 16 bit SPI package to produce a voltage between 0-5V with 12 bits of resolution (4 control bits).

Now I need to shift this signals from 0-5v to a 0-10v signal. I do not have negative power supplies, I have 10V, 12V, and 24V supplies available to me. Is there any simple circuit that can do this in a linear fashion?
i.e. 0v = 0v+-10counts and 5v = 10v+-10counts

I am attempting to read these signals by a ADC on a plc so it is important that it outputs voltage from 0-10v and it doesn't have any problems getting to 0+/-10counts or 10+/-10counts, which makes me think opamp circuits are generally not going to be an option.


texts:
I want to build a stereo channel strip, using the NE5532 IC. It should feature 2 mono inputs with volume control, mute switch and pan control going to a stereo output with unity gain. In the schematic you can see where I am with my design so far, however I'd have a few questions:

Are the capacitor and resistor values ok? As far as I understand, the NE5532 is an acceptably low noise IC for summing but doesn't like high resistor values; as for the capacitors, I've determined these values don't affect the audio signal within audible range, as far as I can see on my spectrometer.

Is it better to feed both left channels and both right channels through a resistor each (meaning, 2 resistors going to the inverting inputs of each op-amp) or is 1 resistor per op-amp input enough, as I've done here (R1 and R2)? My thinking was, less resistors, less noise.

Does the order of volume pot and mute switch in the signal path matter?

Is it better to put the pan controls before or after the op-amps?

Any suggestions are welcome, I'd be very grateful.

Thanks in advance


texts: Why is this MOSFET's "pullup" resistor necessary?

texts:
I'm reading an basic electronics textbook, the chapter on MOSFETs, and it has started with a simple model of the MOSFET as a switch (the "S model"). It shows a circuit like this:

And says: Here we see the purpose of the load resistor R -- it provides a logical 1 output when the MOSFET is off.  Huh? Without that resistor (ie, replacing it with wire) the value at Vout would still be 1/high when the switch was off, because there is an open circuit between drain and source.  So why does it need the resistor?

(This is on p.292 of Foundations of Analog and Digital Electronic Circuits, by Agarwal and Lang.  I'm trying to follow the MIT open courseware, first course.)


texts:
My understanding of Intellectual Property (IP) Cores is that they are specific FPGA or ASIC circuit layouts or setups with the intention of being sold for general use.

What are Soft, Firm and Hard IP Cores?


texts:
We are learning about general purpose shift registers.
My professor draws them with like multiplexers connected to the D's of each flip flop. So in an example of a register with a 4 bit input and output, it looks like 4 Flip flops next to each other connected with each of their D inputs to the output of a multiplexer.

Then i watched this video and it shows a diagram of the register at about 2:08
https://www.youtube.com/watch?v=Fc1FF7dVyaU

Why is that one different? Is the registers with multiplexers wrong? I don't understand my professor very well.


texts:
I tried to use timer0 in mode 0 of AT89S52 for blinking a led for 1 second using this code:
#include<REG52.h>

//XTAL frequency is 16.000 MHz

sbit led = P1^0;

void delay(int a)
{
    int z;
    for (z = 0; z < a; z++)
    {
        int i;
        for (i = 0; i < 10; i++)
        {
            TMOD = 0x00;
            TL0 = 0x1f;
            TH0 = 0xa4;
            TR0 = 1;
            while (TF0 == 1)
            {
                TR0 = 0;
                TF0 = 0;
            }
        }
    }
}

void main()
{
    led = 0;
    while (1)
    {
        led = 1;
        delay(1000);
        led = 0;
        delay(1000);
    }
}

But the the delay that generated is not 1 second.
Is there a way to generate a 1 second delay from 13 bit timer mode?


texts:
I am attempting to use a board that performs level shifting from a 5V GPIO pin to a 3.3V RSTn pin on a Decawave DWM1000 Module via a SN74LVC2G17DBVR.

The problem is, as discussed in Section 5.6.3 of the datasheet, the external source of the RSTn pin must be open-drained as soon as the chip has been reset. If it were directly connected to the GPIO pin, then it would simply require that the pin be configured as a high-impedance input after driving low. However, I suspect that the trigger is complicating things.

In order to initiate a reset, the GPIO pin is configured as an output with a low value. It then holds this value for 2 milliseconds and then is configured to a high-impedance input. I think that the trigger cannot allow an output to float, and so the reset can only be driven high or low.

So I guess my question is this: Is there a modification that I can make to the existing board that can address this issue? If not, what component should I use instead?


texts: Unity Gain Op Amp outputting odd voltage

texts:
I have an op amp set up in a unity gain, or buffer, configuration like so:

Unity Gain configuration Op Amp http://img580.imageshack.us/img580/2389/opamp.png

The op amp is tied to 3.3V and GND, I am trying to buffer my 1V (from a resistor voltage divider) through the Op Amp. I would expect to get 1V on my output pin as shown in the above simulation, however I am getting 1.35V.

This is with a TL061CN, however for some reason my other op amp, a TLC271IP does provide me with the 1V output!!

Is there something that I am missing with this first op amp, or is it just broken?


texts: Electrical conductivity circuit help, with two solenoids

texts:
I have a project im working on but cant seem to figure out the basic of the circuit.
The principal of the circuit is two solenoids wrapped around a chemistry glass making a magnetic field. The purpose is to measure salinty of the water in the cup. Plan is to amplify the signal enough to see a clear difference in salinty levels, which shall become proportinal with a 4-20mA signal.
 The two solenoids around the glass.
 Picture is from an pdf.
My question is, what components is needed in the circuit and why? How much Vpeak-peak and hertz would you recommend? Im using an signal generator and  a osciloscope to measure.


texts: Fourier Transform Time Scaling Property using f (frequency) or w (omega - angular frequency)

texts:
The time scaling property for a fourier transform is as follows:

My book shows this property in terms of \$f\$; however, my instructor likes to use \$\omega\$.
I have also seen this property written as:

I am confused because \$f = 2\pi\omega\$. So how can the property be written the same with \$f\$ and \$\omega\$ interchanged?  While using \$\omega\$ in the numerator, shouldn't there be a \$2\pi\$ in the denominator to make that statement equivalent to the one just using \$f\$?
Thank you for your help!


texts: What reduced the noise when multiplying neighbor samples?

texts:
Is this a common filtering technique? I multiplied each sample with it's neighbor.

I was trying to distinguish the spikes from the noise. Low-pass filtering wasn't as helpful maybe because both the spikes and the noise are kind of high frequency.

TOP: filtered, BOTTOM: unfiltered


texts: Why can't the bootloader save and log messages for us to view later

texts:
I have a problem whereby a remote BeagleBone device is taking hours to boot up. When it does, I don't see any problems in the kernel boot logs such as journalctl -b or journalctl -b -1

Without having physical access to the device over the serial interface, we can't see what is happening in the bootloader. Why is it that the U-Boot bootloader logs are not saved to somewhere on the flash memory or even RAM, or somewhere readable from when the kernel takes over? This would be extremely useful.

I understand that the file system is not mounted at that point, but surely there could be a solution? Or am I missing something that makes this procedure very difficult?


texts: What is the voltage source and ground on an antenna?

texts:
I've seen a few diagrams relating to AM demodulation, and I can't for the life of me figure out where the voltage source and ground come from in an antenna.  From what I understand, an antenna can just be a piece of wire.  How can it have a voltage source and a ground?

Here's an example diagram:

Where does the voltage source and ground come from?


texts:
Can someone explain the superposition theorem step by step when applied with phasors (AC circuits)?
I think books and websites mostly include examples of how to solve something with superposition but not enough detailed theory.


texts: What does "no design unit detected in this file" mean?

texts:
I got this error then I tried to add a source file.

Can anyone tell me what this means? What should I do to correct it?


texts: Avoiding thermal noise to enter low temperature while not using dissipative element

texts:
Let's assume that we want to interact with a circuit at very low temperature \$T2\$ to avoid any source of noise. The voltage interacting with this circuit must have a specific target value \$V0\$. Imagine for instance a waveguide terminated by an LC and we want that the voltage felt by this LC circuit matches \$V0\$ the most closely. But our constraint is that the signals are generated at \$T1 \gg T2\$
One issue will be that the Nyquist noise at \$T2\$ might annoy us, and we want to remove it. One way to avoid it is to put an attenuator at \$T2\$. It will dissipate (almost) all the noise at its input (and thus the noise emitted at \$T1\$). The drewback is that it is dissipative by essence and we thus loose energy.
I wanted to know if it is possible to make a circuit that realizes the same goal (isolating the low temperature stage from noise at high temperature) without making use of any dissipative elements. As a constraint we must avoid any unwanted reflection of signal on the low temperature stage so that if one wave has been sent it will only interact once with the low temperature circuit (no extra reflection will come to annoy us).
I saw that for a two port circuit what I ask is impossible. I call \$S\$ the scattering matrix. Assuming a two port device, calling 1 the port coming from high temperature and 2 the one going to low temperature, a lossless circuit will have to verify:
\$|S_{11}|=|S_{22}|\$,\$|S_{12}|=|S_{21}|\$, \$|S_{11}|=\sqrt{1-|S_{12}|}\$
Here, I need to at least ask: \$S_{22}=0\$ (to avoid those extra reflections). And this gives me: \$|S_{11}|=|S_{22}|=0\$,\$|S_{12}|=|S_{21}|=1\$. Thus basically all the signal (including noise) from high temperature is entirely transmitted which is something I don't want.
Are there way to make this work by considering \$n>2\$ port circuits ? Calling \$2\$ the port associated to the circuit I want to control, assuming that all port but \$2\$ are connected in the end to the temperature \$T1\$ we want to limit thermal noise while being able to control it via the port \$1\$ while using non dissipative elements. I cannot just send a huge signal amplitude in the beginning to have a very high signal over noise ratio because I also must match a specific \$V0\$ at the end of my circuit.


texts: Audio transformer: What to do with an unused winding?

texts:
For the purpose of impedance matching and floating a single-ended, ground-referenced signal, I am planning to use an audio transformer like this one.

Here's the schematic from the data sheet:

My source has 150 Ω and I am using an output impedance of 600 Ω. Therefore, I am connecting pins 6 and 7 and feed the secondary (5-8) into my 600 Ω load. For the source, there appear to be several options:

Feed the signal to 1-2 only, connect a 150 Ω resistor across
3-4. This will increase the power that has to be provided by the
load, but the impedances on all windings will match and the desired impedances cannot be achieved: 150 Ω
source impedance matches 1-2, the additional 150 Ω resistor
only appears to matches 3-4 but really messes up everything else, and the output resistor matches 5-(6,7)-8. [edited after Neil_UK's answer]
Feed the signal to 1-2 only, leave 3-4 open. No additional power required for unused winding 3-4, impedances on 1-2 and 5-(6,7)-8 will match, but
any parasitic capacitance across unused winding 3-4 might build a
resonant circuit across this winding and degrade the fairly linear
frequency response of the system. Might be a bad idea (?).
Connect the two primaries in parallel. No additional resistor required, thus
no additional power dissipation. Impedances on all windings will
match: 150 Ω source impedance matches (1,3)-(2,4), and the
output resistor matches 5-(6,7)-8. However, any possible mismatch
between the two primary windings might degrade the performance.
Mains (50/60 Hz) transformers that can be configured for either 115
V or 230 V are usually connected exactly this way to use the
additional copper of the paralleled primary windings, but how about
audio frequency transformers, where stray capacitance is a concern because (a) it is larger due to the high number of turns and (b) it matters more because we're using frequences up to 15 or 20 kHz instead of just 50/60 Hz?

Which option is preferred? Why?


texts:
I have a heavy 14.4V 1.5A heavy battery charger I would like to use to charge my car battery (over time, monitored for heat in a well ventilated area).

When I plug the battery to the charger as is, I believe it turns off as the led doesn't turn on and the Voltage I read is 10.8 which is what the battery is at.  When I measure the charger on it's own I get 13V.

Can someone help me modify it to make it work? I'm comfertable soldering and researching if you don't feel like giving a specific answer :).  Images of the transformer and circuit:

Thanks in advance for any efforts :)

Edit - I sketched a diagram of the circuit on tinyCad, here it is:

I noticed that there is an earth connection for the battery, but only 2 connections to the wall socket. I don't get how it would be earthed, but perhaps the third connection is needed to turn it on? It is directly connected to one of the switch's 4 'legs'.


texts: Different behaviour of batteries with same voltage read

texts:
I am powering an embedded system using one 3V Lithium battery.

Two similar devices were acting very differently: when they both were on, the voltage read across the batteries were different (2.9 and 2.78--and of course both completely the same when not under load), even though both batteries had the same voltage when not under load. I thought the two devices are different because of the tolerance of the parts (LEDs, photodiodes, and such).

But when I exchanged the batteries, the behaviour of the two devices (and the voltage across the batteries) also changed, So I concluded this has something to do with the battery.

Now, my question is, how I can single out such batteries? And why do they act like this? And what are the techniques to make this problem go away or less significant?

The battery has a storage life of 10 years and has been produced six months ago, both of the batteries have also been used the same amount


texts: Series vs parallel for microphones (electric guitars)

texts:
I want to create a passive "mixer", with which I can connect two of my guitars to one amplifier, so basically one with two 6,3" input jacks and one for output.

For passives without a transformer as far as I know I have two options:
Connecting them parallel or series.

simulate this circuit – Schematic created using CircuitLab

Which one should I use and why? If there is no specific, what are the advantages of each?
Won't parallel produce too much voltage and damage my pre-amp or amp?

(PS: I know that the volume knobs will affect both guitars, but that doesn't matter for me.)


texts: Why does reverse supply polarity damage the ICs?

texts:
Assuming you need for example an OR gate for your circuit project, you can use a 4071 IC  or simply use two transistors as shown below:

But I wonder why the ICs are very sensitive to reverse supply polarity (as any other IC) but the transistor version circuit is not sensitive to supply reverse polarity connection (no damage.)

Note:
I found another question which asked about what causes damage when the car battery is connected in reverse (but his question is about the car fuses not logic ICs):
Why reverse polarity causes damage


texts: determining current in individual phase for a 3 phase winding brushless dc motor

texts:
I have an 3 phase brushless dc motor with no neutral wire. I measured the resistance from phase to phase and found them to be on average 0.255 ohms(between A and B, A and C, etc...all the values are pretty close).

These 3 phases are in a star formation. You can see the motor here: http://www.cda-intercorp.com/Products.cfm?cid=1&Data=Design#ScrollTop

I am running the motor on 28V. How do I know what current are running through each phase(A,B,C). To add to this, if I stall the motor, only two of the phases would have current right? What would the current be then?


texts: How to connect multiple AT28C256/AT93C256/AT24C256/24LC512 EEPROMS to have more space

texts:
I want to have more memory say 1 Mega Byte, But I don't know how to connect multiple EEPROMS either in series or parallel

I would like to use either AT28.... or AT93.... or AT24.... series

Also suggest that, is 4x4 DIP EEPROM is better than 16x16 or 8x8?

It seems 24LC512 provides 512Kb and AT24C1024 provides 1024Kb with 2-Wire Serial, How many of them will make 1 Mega Byte?


texts: Programming esp8266 NodeMCU (with Arduino IDE)

texts:
I just got some esp8266 NodeMCU chips, which I want to use for IoT. I understand that these chips are programmed with Lua code. Is this correct?

I found online that I can program these chips with the arduino IDE.

1) Does the arduino code get compiled to Lua?

2) Are there any alternative IDEs for programming these chips?

3) As AVR is used to program Atmel chips on Arduino, is there an equivalent for esp8266s?

Edit

this post is related.

What does the 'NodeMCU' in 'esp8266 NodeMCU' mean, as opposed to plain old 'esp8266'.


texts:
i have the parameters for this linear amplifier
Swell rate >52 V/µs
Bandwidth DC … 5 kHz
Power 3 × 30 kVA
rise time at nominal voltage (230 Vrms) is 5 µs.
and the transfer function is:
$$F(s)=e^{-0.00003s} × 5.5 × 10^{12}/(s^2+ 12*10^{9}*s +1.4*10^{12})$$
the question is how he get that TF


texts: Undervoltage Testing of a LDO or Switching DC-DC Converter

texts:
I am using a Regulator section in - UJA1076 this IC
Input Voltage = 16V
Output Voltage = 5V
Load Current = 0.1A
My question is, I want to test the undervoltage condition 90% and 70% as mentioned in the datasheet.
What are the ways to bring the output voltage below the undervoltage limit of the regulator? Like, I want to check at what conditions does my output voltage drop from the the nominal 5V to some thing like below 4.5V and 3.5V.
My answers - We provide a step load at the output to see the voltage dip. But how much should the load current be and for how long?
And other solution is that we reduce the input voltage till we achieve the required output low voltage of 4.5V and 3.5V.
Are there any other methods to bring the output voltage low?


texts:
I'm about to hook up some LiFePO4 (32650) batteries to solar panels. I bought a couple of noname BMS boards ("HX-4S-F30A") for a 4S configuration for the batteries online, and the specification is a bit thin on details. It mentions a charging voltage of 14.8V, but there is no mention of lowest/highest input voltage the BMS can handle.
Do these kind of battery management boards typically handle voltage regulation, or do they expect to be fed with the exact voltage mentioned as the "charge voltage"?
I understand that the question is a bit broad since it is just a generic no-name board, but what is the typical behavior of BMS boards: can they handle a bit of input overvoltage without getting damaged, without damaging the batteries, and while still charging the batteries?
I'd like to feed the BMS directly with (up to) 20V directly from a solar panel without having to have a dedicated voltage regulator between the solar panel and the BMS, but I'm not sure if that will be a problem*?
*=for the BMS board, for the batteries, or for the fire department


texts: Maximum input frequency of 74HC Logic gates

texts:
I have a clock that is running at 25.175MHz I want to run that signal through some basic logic gates from the 74HC series.
I have looked on the datasheet for the 74HC08 (AND Gate), I can't seem to find any information about the maximum frequency i can run through these gates.

Does anyone know how to find this information, hopefully I am not being too stupid and it's on the datasheet. I have checked 3 times now!

So my question is: What is the maximum input frequency of the 74HC Logic gates?

Thanks


texts: Using a ferrite core transformer as an inductor for a boost converter

texts:
I am trying to make a boost converter.
I'm stepping up 5V to 12V.
I have all the required components, including a power MOSFET(IRLZ44N), a Schottky diode (SR260) and an astable multivibrator that produces a 71.4kHz square wave for my MOSFET.
I just don't have an inductor, but I have a small ferrite core transformer in my parts bin. I got the transformer from an old SMPS that uses one power transistor to step down the AC.
If I use the secondary winding (winding with low resistance) as an inductor:

Will it work?
Will there be a high voltage at the primary that is unconnected?
The boost converter has a feedback. Will this damage the transformer?
Will my MOSFET and diode get damaged?


texts:
I'm using GHDL. After various update of this thread, under advice, I try to do the simpliest configuration of a testbench with only clock signal. The code compiles correctly, but when I run it (command: ghdl -r entity_name) it stucks.
Here is the code:

library ieee;

use ieee.std_logic_1164.all;

 --  A testbench has no ports.
 entity clock is
 generic (
            clk_period : time := 2 ns -- per le tempistiche
        );
 end clock;

architecture clock_0 of clock is

signal clock : std_logic := '0' ;

 begin

-- clock generation

    --process_clock : process

            --begin

            clock<=NOT clock after clk_period/2;

        --  end process;

        end clock_0;


texts: Strange thing with 5mm LEDs and variable PSU

texts:
I have 3 standard LEDs (not COB just the tiny regular ones used in circuits with an Anode and Cathode in epoxy lens), I was just testing them today doing random things with them:

1.9v - 2.1v = red

3.0v - 3.4v = green

3.0v - 3.2v = blue

I think they're about as standard of an LED you can get. Anyway I have a variable power supply when I connect an LED to either the negative or positive (doesn't matter) and touch it to me or touch it to the ground it lights up. I can do this for any color and any polarity. I'm confused? It doesn't work on anything unless it's a conductive thing.. ie me, metal, the ground... but the ground is for AC electricity only? DC goes from positive to negative terminals? My variable power supply is floating, I put it on a bungee cord on my ceiling just to test it out..

So basically if I connect the positive OR negative (Anode or Cathode) to the variable power supply positive or negative (does not matter, any way works) and I touch it, it lights up. My PSU can be on 0 volts 0 amps and it still lights up. The power supply itself doesn't show any amperage draw ... so I am thinking it's leaking AC or something crazy and that is going through me and lighting the LEDs? can they run on like 1 volt AC? I can't imagine 1 volt would travel through my body's resistance? I can't feel it at all, I've been shocked by 15volts AC before and you can feel it pretty decently so not sure if anything lower can even travel through my skin.

I'm ok at electricity, I understand the basics so I've been able to test some things as I said above but still not really sure what to say about this. I have a multi meter that measures no resistance at all as in, infinite ohms or no connection for electricity to flow. It goes insane when I turn it to DC reading, like numbers from -300 to +200 and it sits at 20volts AC when I turn it to AC. But I can touch the power supply end to the ground or to a metal rod I put in the ground and I get no spark or anything.

Thanks...


texts: Is keeping batteries rolling loose inside a drawer a fire hazard?

texts:
Simple question.

At some point I began keeping batteries (AA, AAA, 9V, etc) inside a random drawer in my wardrobe that I use for other electronics (like cables, pen drives, etc.).

And I've started to worry that they might randomly arrange themselves (they roll a lot when I open and close the drawer) into a short circuit inside the drawer and start a fire.

I imagine a lot of people do that, and I've never heard of this causing fires.

Is it a fire hazard?

Extra: If that is indeed a fire hazard, what would be the ideal way of storing batteries at home?


texts: Safely powering Dell laptop from external Li-ion battery with a 11.1V/19.5V step-up converter

texts:
I need to build a power-bank type device for my Dell Latitude 6530 laptop (19.5V, 90W nominal power input).

I have 12 Li-ion 3.7V, 3.35Ah (18650-type) cells, 3S4P configuration (11.1V total output). I also have a 200W, 6-35V/9-55V step-up converter, together with all the necessary wiring and plugs.

I connected the battery to the converter, set-up the right voltage, then connected the plug to the laptop. It worked like a charm, ie. the computer was not draining the battery (I knew and accepted it won't be charging, due to Dell's policy on foreign power adaptors). Everything was working fine until I needed to replace the battery on the boost's input. Apparently right after connecting the new one output voltage has surged far beyond the safety limit of my laptop. I heard a quiet click sound and found the computer damaged. It can only work on batteries now, no more charging, servicing required.

Lesson learnt, I want to avoid this kind of issues in a future. I consider adding a 20V Zener diode on the converter's output (typical cathode-plus setup). To protect a converter itself from over-current I think of adding a fuse between the output and Zener. I believe using a Zener has an additional benefit of protecting the converter in case of inducing a high voltage on the receiver (no matter the polarization).

I'm a passionate, not an expert in electronics - this is the first step-up converted I'm handling. The question is whether the above solution makes any sense and can effectively protect the devices? Are there Zener diodes capable of handling this output power (provided that I won't be increasing the output voltage)? What other measures I can (or should) take to prevent damaging my laptop (or any other receiver) again?

Unfortunately I don't have any schema of the converter itself, but I can try to get it if necessary.

EDIT #1 (2020-04-21 13:17 CEST):
As requested, here's the schema:

simulate this circuit – Schematic created using CircuitLab


texts:
I'm using a LM339 voltage comparator by supplying it 5V, with a reference voltage of 1V.  I have a 3K pull up resistor on the output to 5V.  For some reason, the output voltage is always 2V.  It doesn't change at all when my input signal rises above the 1V reference voltage.  Any thoughts would be much appreciated :)

Edit:  I wasn't clear in the diagram, but the bottom phototransistor is actually attached to a voltage regulator.  Also, I tried removing the top photodiode and now the output is always 5V.  I think it's like this because I have to pull it high to Vcc so I'm not sure how to make this work.


texts:
I'm designing a board for a school project using eagle. I thought I could get away with using the onboard clock of the PIC18 since it's not doing a whole lot (mostly just LEDs), but one of its tasks is RS232 communication, and I (just) learned that the onboard is nowhere near accurate enough for any sort of comms. Since the RS232 link is crucial, I need it to work. So I've had the task of cramming an xtal and two caps on my already crowded PCB. Here's my result at 3am this morning:

I'm sure I've made some experienced board designer sweat a bit. The big glowing trace is ground. I think it's the best I could do considering there was absolutely no room to move the PIC or the two top chips, and very little room to move the bottom one. The board is going to be CNC milled so I can't go less than 16mil trace width/16 mil spacing. I rearranged what I could to make sure OSC1 and OSC2 had no vias. The caps are small little ~20pf ceramics, I just used the cylindrical parts for the pad spacing.

(Also, blue is the bottom layer, red is the top; everything has to be through-hole and connect on the bottom)

I plan on running the chip at 4.9152MHz. If for whatever unfathomable reason it's not enough speed, I'd like the option of 7.2MHz. I know speed affects design.

Any advice would be appreciated. I'm probably going to spin the caps so the trace to the xtal is shorter. I don't see any possible way to have a 'ground ring' which is suggested as there's no room.

EDIT: Here's an updated design. I switched out the caps with a better footprint (still ceramic), and the microcontroller connects to the ground plane at only one point. The dashed lines show where I'm going to put my guard ring (pins 1 and 20 of the TPIC are N/C):

Edit 3: Fatter traces, better shielding, I think this is as good as it can get:


texts: What module do I need, to make a light stay on for 2 minutes and then turn off?

texts: I have a quick question. I am trying to create a box where the button is clicked; the light comes on for 2 minutes. I am using a 12-volt battery to power this. I want to know what module I need for the bulb to stay on for 2 mins and then turn off. Could someone help?


texts: What is meant by shallow diffusion in silicon fabrication technology

texts:
I know this is a google before ask type question, but I didn't find the answer
still on google. Then I went to library and refer some books but my changes were
negative. I've searched more than 20 appendixes of books.

There are specific patents and there's no wiki page written on shallow diffusion.

Could you explain in simple what is called shallow diffusion? I mean in
general.

--Thanks In Advance--


texts: Piezo Buzzer Coil or Resistor oscillator

texts:
I found two ways of working with piezo like a buzzer.

In the first case, we use only a resistor. When we turn ON the circuit, I have my transistor off, With Vc=VDC. When the piezo sends a feedback voltage, we have saturation in the transistor; my Vc = 0.2V ( approximated), and the piezo doesn't stretch and feedback voltage = 0V.

But, how does it work using an inductor? When we saturate the transistor, the coil tries to maintain the current throughout the circuit, and a -EMF voltage appears and polarizes my base in reverse and cuts off the transistor. Does this cause an oscillation in my piezo?

Is there any difference in efficiency of each circuit?


texts:
I am designing a circuit board that has an SPI bus with 32 slaves. I plan to drive the bus at 8 MHz. Another individual on this site commented on a previous post of mine that the total capacitance from all the slaves might limit the maximum rate.

I went ahead and tried that calculation. The capacitance of the GPIO pin on the MCU is 30 pF and the capacitance on the CLK lines for the slave is <10 pF. I compute the resistance of the CLK trace to be 0.6 ohms using an online trace calculator (8 mil, 1 oz/ft, 20 cm total length)

C = 30 pF + (32*10 pF) = 350 pF
R = 0.6 ohm
tau = RC = (350 pF)(0.6 ohm) = 0.2 ns
t_rise = 2.2 * tau = 0.44 ns

I was able to probe a similar board with 16 slaves (predecessor to the board I'm designing) and found the rise time to be 18 ns. I made sure to set the probe to 10X.

So my  question is: where am I going wrong here? Do I need to take into account the output resistance of the GPIO as well?


texts: current loop transmitter with higher regulated voltage

texts: I have a xtr115 in my circuit that is used for 4-20mA current transmitter, the regulated voltage of xtr115 is +5V, but I need +12V and -12V in my circuit, is it possible to connect an external Regulator to XTR115 to build +12V without dependent on the output current?


texts: Meaning of "caps not pop with watch crystal" in a schematic

texts:
caps not pop with watch crystal

You can find this sentence in ADuC 841 evaluation board schematic. Could someone explain what does it mean?


texts: How do I differentiate two distinct frequencies? 24Mhz and 40Mhz

texts: I have these two frequencies fed to the input of the PLL and need to vary the B.W according to the frequency. But before that, how do I differentiate between these two frequencies?


texts: Resistor values for a Voltage- Controlled Current Source Circuit

texts:
simulate this circuit – Schematic created using CircuitLab

Hi Folks,

During my bachelor thesis, I am learning IGBT gate driver cricuits. I am struggling with understanding the following circuit. It is a current sourcing part of a IGBT gate Push - Pull driver and it's sinking part is a replica of it with analogous P-Type devices. I am simulating only the current sourcing part to learn the current control mechanism of this gate driver.

Functionality:

The voltage at Vin is adjusted in such a way that V- = V+ = 5V, so that OpAmp always operates in linear mode. For example, 5A at output >

if Rf = R1, (15 - Iout) - V+ = V+ - Vin

Vin = 0

My problem is:

why a negative voltage supply is being used to maintain a specific negative voltage on Emitter of Q1 ? and How the values of Re1 and Re2 can be calculated?

Thanks in advance for your analysis.


texts: Where should I mount relays on an electronic circuit board?

texts: I'm designing a emergency circuit in which I'll open the circuit of two stepper motors and a three phase motor using an emergency button (or computer interface) and relays. My question is: How should I mount the relays? Should I put them on the PCB or somewhere else? I'll use two 833h relays (one to open 24V DC and the other to open 110V AC).


texts:
Currently, I am creating a custom EAGLE library for a relay that I couldn't find the CAD for.
In the packag stage:
I added the pads as seen in the picture and I'm having second thoughts about adding the holes.
My thinking is that they needed to be added for the milling machine to know where to drill but none of the tutorials I have seen have added them.
What is the way to go about it?


texts: Does an overvoltage TVS for USB hot-plugging connect to shield ground?

texts:
I am designing a keyboard which will connect to the computer via usb-miniB to charge a LiPo battery.  The datasheet for the charging IC I am using specifies overvoltage protection on the USB power line, and I have been looking into various TVS diodes.  I am finding differing information about where to connect the TVS diodes to:

This FTDI doc provides an example to shield ground, and also advocates and RC filter connecting shield ground and signal ground.

This TI part, which is advertised as for USB, provides an example to signal ground.

I am wondering which is the better practice, and whether that practice changes depending on whether it is a TVS intended for OVP rather than ESD protecton.


texts: I'm designing a system in which a MCU processes a PWM signal and outputs a slightly modified version of it. As this signal is extremely critical for the application, I'm looking for a way to output the raw input signal if the MCU fails, bypassing it completely. How could I do this?


texts:
I am new to electronics and trying to make something easy to start with.
Bought one of those voltmeter and ammeter AIO from ebay (LINK , see item #5) and want to hook it to a 12V battery (4Ah) to measure how many amps a 12V monitor draws and to monitor battery voltage.

Specs:

Operating voltage: DC 4.5 ~ 30V.
Measure voltage: DC 0 ~ 100V.
Minimum resolution (V): 0.1V.
Measure accuracy: 1% (± 1 digit).
Minimum resolution (A): 0.01A.
Operating Current: <20mA.
Measure current: 10A (direct measurement, built-in shunt).

It has 5 wires:

Red thin and Black thin;

+

Red thick, Black thick, Blue thick;

Since it says it can measure up to 10A (with its internal shunt) I dont need an external shunt, right '

First question is: Can I power the ammeter (in the red and black thin wires) with the same power source i'm going to measure ?

Second how do I wire the power source, monitor and ammeter without worrying about the external shunt ?

If anyone can provide a wiring and a simple explanation I'd appreciate.


texts:
I've decided to use standard web-camera as a simple spectrograph, being inspired by this website (and this one too).
The device actually works, as you may see on the image:

But you may see on the image as well that the camera is trying to compensate the lack of brightness. Of course I need the input to be non-modified. I tried to use various software settings for the camera but none of them worked, so I assume that the camera does not accept them.
This means that I'll need to either find another camera which does accept the settings from software side or try to modify the camera electronics to prevent auto-exposure from working.
So a few questions can be implied from the text above:

Is there a way to find a proper device for my purposes? (I can't afford buying tons of cameras to test this feature)
Do you think this auto-exposure can be disabled by eg. removing one trace on the camera PCB or something similar? (as soon as I am home I'll provide some info about the camera)

Edit:
OK, so it turns out (after some testing in other programs), that the problem is not the auto-exposure, which can be turned off successfully through the OpenCV, but the automatic white balance correction of the webcam. Which is, sadly, unsupported in OpenCV. Does anyone know of any other way turn it off, be it software (preferred...) or hardware?

The cam is Trust SpotLight Webcam Pro.


texts: RLC circuit magnitude of the transfer function

texts:
I found a lecture MIT, about RLC circuit.
I think there is an error in the formula 1.1.
After all the transformations, I can not get the same formula...
My decision path is the same as in this document.

Tell me please how they get formula 1.1?


texts: My questions pertains to the \$ \beta\$ value of a transistor. On page 162 of this book, it says that \$ \beta\$ increases as temperature of the transistor increases. But it doesn't explain why. Can anyone explain that bit more thoroughly?


texts: So I had a problem with DS3231 not counting time when on VBAT. Also, I had a problem with alarm not resetting after it is triggered. I saw many people on the net having these problems, so below is the solution.


texts: Why is phase of current assumed to be 0 when deriving formula for instantaneous power in an AC circuit

texts:
In two different books I'm reading the authors start the discussion of instantaneous power delivered to a load in a steady state AC-circuit by assuming
\$i(t) = I_0 \sin(\omega t + 0)\$ and \$u(t) = U_0 \sin(\omega t + \alpha)\$\

Then they derive or simply state the formula \$p(t) = i(t)u(t) = \dfrac{U_0I_0}{2}\left(\cos(\alpha)(1-\cos(2\omega t)) + \sin(\alpha)\sin(2\omega t) \right) \quad (1.) \$

I thought it was strange to assume the phase \$\beta\$ of \$i(t)\$ to be zero, wouldn't we want to be able to calculate the instantaneous power for arbritary \$i(t)\$?
When i set \$i(t) = I_0 \sin(\omega t + \beta)\$ and \$u(t) = U_0 \sin(\omega t + \alpha)\$ I reached the formula
\$ p(t) = \dfrac{U_0I_0}{2}(-cos(2\omega t + \alpha + \beta) + \cos(\alpha - \beta) \quad (2.) \$
When \$\beta = 0\$ \$(2.)\$ is equal to \$(1.)\$ but with other values for \$\beta\$ this is not necessarily so.\

So I wonder, what is the point with deriving a formula for instantaneous power only for the case when the phase of the current is \$0\$?

EDIT in response to the two first answers

About my derivation being wrong, I can't see why it would be wrong.
wolframalpha seems to agree that is is correct (I've used \$K\$ instead of \$I_0\$). Here is how I derived my formula:

\$I_0\sin(\omega t + \beta) \cdot U_0 \sin(\omega t + \alpha) \$ =
\$\dfrac{I_0 U_0}{2}(2\sin(\omega t + \beta) \sin(\omega t + \alpha)) = \$
\$\dfrac{I_0 U_0}{2}(2(-\cos(\omega t + \alpha + \omega t + \beta) + \cos(\omega t + \alpha) \cos(\omega t + \beta) ) ) = \$
\$\dfrac{I_0 U_0}{2}(-\cos(\omega t + \alpha + \omega t + \beta) + 2\cos(\omega t + \alpha) \cos(\omega t + \beta) -\cos(\omega t + \alpha + \omega t + \beta)  ) = \$
\$\dfrac{I_0 U_0}{2}(-\cos(2\omega t + \alpha + \beta) + \cos(\omega t + \alpha) \cos(\omega t + \beta) +\sin(\omega t + \alpha) \sin(\omega t + \beta)  ) = \$
\$\dfrac{I_0 U_0}{2}(-\cos(2\omega t + \alpha + \beta) + \cos(\omega t + \alpha - (\omega t + \beta) )  ) = \$
\$\dfrac{I_0 U_0}{2}(-\cos(2\omega t + \alpha + \beta) + \cos(\omega t + \alpha - (\omega t + \beta) )  ) = \$
\$\dfrac{I_0 U_0}{2}(-\cos(2\omega t + \alpha + \beta) + \cos(\alpha - \beta )  ) = (2.) \$

Regarding that only the difference in phase matters, I can't see how this can be. If we only imagine two sine curves being shifted back and forth along the time axis it seems obvious to me that the product of their values at some time \$t\$ will change, and hence the power will change when we shift them even if we shift both the curves by the same phase.

For example if \$\alpha = \pi/4\$ and \$\beta = 0\$ and the amplitudes are \$1\$ then at \$t=0\$ we have \$\sin(\omega t + \beta)\sin(\omega t + \alpha) = \sin(0 + 0)*\sin(0 + \pi/4) = 0\$

but if \$\beta = \pi/4\$ so that \$\alpha = \pi/2\$ we have at \$t=0\$ that
\$\sin(\omega t + \beta)\sin(\omega t + \alpha) = \sin(0 + \pi/4)*\sin(0 + \pi/2) = \dfrac{1}{\sqrt{2}}1 \neq 0\$


texts: How is it possible to create wires/circuits that are nanometer in size?

texts:
This image from wikipedia shows -

  An array of 17 purpose-built oxygen-depleted titanium dioxide
  memristors built at HP Labs, imaged by an atomic force microscope. The
  wires are about 50 nm, or 150 atoms, wide.

How would you explain to a layman how this is done? If I want to drill a fine hole I need a  finer drill. What tools are used to create these 150 atom wide wires? How are these tools created?

If some sort of chemical process is used how is it directed/controlled to achieve such precision? I imagine atoms would run everywhere in a test tube and it won't be easy to take a set of copper atoms and put them in a line.
And then you need to ensure that these wires do not touch each other.

How does one create such circuits?


texts: (THEORY QUESTION) If a diode was not placed in a buck convertor, when the switch is off would the load still be powered on?

texts:
(For Theoretical Purposes and Understanding assume the diode is not in the circuit)

I just have a bit of confusion regarding the buck convertor when the switch is off. Since an inductor cannot change instantaneously, when the switch is powered off, current will still flow towards the switch. Then a charge will build upon the switch terminal potentially causing a flashover etc (i get this is why we need the diode).

However as the current is still flowing through the load when off, it will be powered on still right?


texts: How do I explain current and voltage to a lay man?

texts: A man asked me this question in suburban train when I told him that I am an electrical engineer. Of course I replied him that current is the flow of electrons and in order for the current to flow there should be a potential difference between them. But the man didn't know what electron or potential difference was either.


texts: How to specify a minimum clock to output time in output timing constrain?

texts:
In design, an external clock pin triggers a flip-flop, where the output goes to an external data pin.

Using Xilinx ISE, how can I specify a timing constraint, so the output should be held for some short time after the rising edge of the external clock?

I have looked in the Xilinx Constraints Guide, and it has:

OFFSET = OUT {time_after} AFTER {clock};

But this constraint allows output data to change immediately after the clock, thus with a minimum clock to output time of 0 ps, thereby specifying a duration of {time_after} where the output is undefined.

In compare, for inputs, the constrains is:

OFFSET = IN {time_before} VALID {time_valid} BEFORE {clock};

So here the duration of the defined data can be specified to {time_valid}, but with an independent start time given as {time_before}.

However, it appears that output timing constraints does not have the same flexibility, or I have not found it ☺


texts:
I am studying for my circuits exam and in the review we have this question below:

The output of a PNP transistor used as a switch is normally taken off it’s ____________ terminal.

I would say collector terminal because of the nature of the PNP transistor.

This is a traditional PNP transistor that our professor draws:


texts: Can you guys explain to me how the turning on of Q2 and the charging of C2 increases the vgs of the FET? An equation would be helpful.


texts: Does an op amp needs an Input Bias Current to operate?

texts:
I'm confused about the source of Input Bias Current, is it generated by op amp, where the current "leak" from the op amp. or it's a must to operate the op amp? for example if I have in a data sheet a 1pA input bias current, should I provide a 1pA to the inputs of op amp? I know that the bipolar op amp needs a current to operate, but what about FET and CMOS op amp?

In short question: Should I build circuit to "provide" this current, or it's just given by the op amp itself?

Also, what is the difference between input bias current and the leakage current?

Note: if the type of op amp make a difference, I'm interested in
LTC6078/LTC6079


texts:
For our current design we require overvoltage protection on USB D+ and D-. I am aware that for USB, the total line capacitance of the line should be less than 10pF.

We are planning to use a circuit like this for OV protection, the diodes are schottky diodes such as 1PS10SB82 with capacitance 1 pF. Could you guys suggest that this clamp section will not affect USB D+ and D-.


texts: STM32F1 Can't I use the internal voltage reference as the ADC reference?

texts:
There seems to be a badgap voltage reference built-in in the STM32F1 microcontrollers (on ADCx_IN17).

Coming from AVRs it seems to me very strange that it's not possible to use this reference as the ADC VREF, at least I think it's impossible. Am I right ? Why is it there than ?


texts: Need fast and exact voltage follower or divider cascade

texts:
Intro: I'm designing a makeshift oscilloscope and now need an input cascade for it (it is more fun project for me, rather than industrial-grade tool).

The matter is I want to get something faster compared to popular 200 kSps things based on arduino (atmega). My current approach utilizes TLC5540 adc with stm32f030 controller, giving 8 MSps - quite enough for now.

The problem is: that ADC seem to have input not well suited for using directly:

it is low-impedance, hundreds Ohms, if I got it correctly
it is about 2V range.

Thus I want input cascade with higher input impedance (at least 10-100 kOhms) and either unity gain (with resistor divider) or adjustable 0.5-0.2 gain.

OpAmp voltage follower - usually I use something like LM358 for such case  - but it won't suit the intended frequency; there are others, like TL084 - but they seem to need more than 5V power supply... I can resort to this option if no better available... MC3317x and MC3407 may suit marginally...

NPN voltage follower - no problem with frequency, but it won't work linearly below ~0.7V input as I understand.

I think, I can manage with some shift and gain - e.g. if input 0..5 V range would be mapped to 0.8..2.2 V - but the mapping needs to be linear. E.g. stupid and straightforward approach could look like this:

As about accuracy - it is not an extreme-precision tool of course, so 3-5% error is not critical...

So what better options may I miss? - probably some JFET/MOSFET follower? Thank you in advance for suggestions!


texts:
I am new in electronics and this is old subject but still. I started new Arduino project where I control 4 solenoid valves independently via Arduino 4 chanel 5 V Relay module. From the beginning I put flyback diode on each solenoid to eliminate EMF (1N4002). Everything works fine but when I speed up cycle things get messy (I need speed about 30 Hz). Solenoid coil can't discharge properly that quickly (it has delay). I read some forums and found solution: diode+zener.

What kind of zener diode should I use and how to properly mount it (any additional parts)?

I am also afraid of over-heating due to quite high current. How can I avoid it?

My valves are: 48 VAC, 3.8 VA and 24 VDC, 3.1 W.


texts:
Arm boasts NPU's that have been designed for vision inference:
https://developer.arm.com/ip-products/processors/machine-learning/arm-ethos-n
However I cannot find where to purchase/develop NPUs (i.e. using a development board).
Is there something I'm missing?


texts: How do I verify that my 3.3v power rail meets the requirements for an Ember EM357 SoC?

texts:
I've built a circuit that is going to supply 3.3v to a CEL Meshconnect Mini Zigbee module and now I want to test and verify.  The only two things I know to look for is:
-Make sure it's actually 3.3v
-Find out how much ripple there is

Can any basic oscilloscope tell me how much ripple there is?
How much ripple is too much for a Zigbee SoC?
Are there any other factors(i.e. noise) that I'm not taking into account?
Am I over thinking this?


texts: RC Low Pass filter, capacitor in series or in parallel?

texts: I've seen 2 variations of the RC low pass filter, sometimes with both the resistor and capacitor in series, and more commonly with the capacitor going straight to ground. What is the difference between these variations?


texts: Current sensing on negative 1.1kV DC rail

texts:
I searching for a way to do high side current sensing on a -1100V DC rail.

My HV is generated from the hamamatsu C9619 High voltage power supply module and it powers the hamamatsu R647P Photomultiplier tube together with the E849-90 D-type socket assembly also from hamamatsu.

My current region is up to 500 μA.

Any ideas or suggestions would be extremely helpful.


texts: Common output from two proximity sensors

texts:
I need help wherein I'm using proximity sensors to trigger an event in a device. The device looks for 12V from the sensors and registers it as an event trigger.

There's no problem when I'm using one sensor. However, could anyone suggest a good logic for using two sensors? Both will be connected to the same port of the device as I can allot only one.

The best solution I can come up with is using a timer relay to switch off output from one sensor so that when the other sensor is active, it can then send the trigger to the same port. (Two sensors to detect two different events)

Thanks in advance.


texts:
I know this must be trivial for many... Which are the main reasons why line data is not modulated/demodulated in normal enterprise wired networks (in the sense that discrete voltage levels are used)? I'm not talking about DSL of course. I'm thinking of Ethernet BASE-T (e.g. UTP cable) but also older versions (coaxial cable) enterprise computer networks. I undestand it is the best compromise, but I can't find details.
For example, a sinusoidal carrier wave could help to reach longer distances on a single cable. Also, without a sinusoidal carrier, line data must be scrambled with a non-trivial techniqhe to ensure a constant variation of the signal. Some of the reasons I may guess: higher costs, data rate limitations, less reliable components... Thanks to anyone who will be kind to provide real world details.


texts: MCU Design, maximum wire length per frequency and characteristic

texts:
I'm getting pretty deep into MCU design and I've run into a problem for which I'd like to find a formula.

In circuit path design how can I correlate max wire length to max transmission frequency on that wire/pin?

I'm working with a wide assortment of MCUs and external hardware operating range 16MHz to 160MHz.

For example:
I have a 20MIPS MPU interfaced with an SRAM (parallel) IC. The SRAM has a 10ns access speed which is more than enough speed for the MPU. The MPU takes two intsructions one to write the address and one to read/write the data. The data and addresses are on separate buses so the maximum speed on any given pin in the project is 10MHz.
Currently that works just fine with a 4" ribbon wire for each bus, but I'm concerned that If I swap out MCUs for a 48MIPS or 72MIPS MCU that I will have timing issues.

I read this thread and a few others, but they appear to be mostly single use fixes, where I need a general formula if possible. Wire length, EMI and comms failures

Followup question, does it matter if the signal is part of a parallel or serial bus, or can each pin simply be examined as a single entity?

Alternately acceptable to a formula would be some good reading material on this specific topic.

I also recognize that using larger gauge wire, twisted pair for serial, adding a ground line(s) for noise, and using pull-ups/downs may help the issue. For this question though my primary focus is length v frequency, if that's possible.

Thanks a bunch


texts: Turning water pump on/off using Arduino Uno R3

texts:
I'm trying to build a simple system to turn a water pump every 24 hours for 10-20 seconds. I have 5V pump. When I connect it to 5V, GND it works but when I connect it to pin 12 (or any other digital pin) and GND it does not work. Here's my sample sketch:

int led = 12;

void setup() {
  Serial.begin(9600);
  pinMode(led, OUTPUT);
}

void loop() {
  digitalWrite(led, HIGH);
}

What am I doing wrong?


texts: I'm currently designing a digital audio mixer. One common thing found on audio mixers is a optional 20dB pad on the input. I've seen some attenuator circuits but all of them require you to know your source impedance. However, with mixers, it's impossible to know the impedance of the connected device. How could I create a 20dB pad then? If I try to design a circuit that has large enough resistance values that the source resistance doesn't matter, it gets REALLY noisy.


texts: Converting BCD Truth Table to Output Functions Using K-Maps

texts:
To be honest, I'm just looking to see if I'm on the right track with a certain question.

This here would be my answer for the K-Map for the "H" output function and im just curious if im on the right path here. Any input would be appreciated.


texts: What problems arise when a clock signal is connected to a nondedicated clock input pin on an FPGA?

texts: FPGAs have dedicated pins to input clock. They are supposed to directly connect to clock networks and PLL inputs. However, if we use a nondedicated pin, the design can still compile. Why are we allowed to compile a design that uses clock on nondedicated clock pins and what affects does it have on the design performance?


texts: Understanding and measuring voltage output of chime transformer

texts:
I am interested in replacing my doorbell chime with a new one.  The existing button and transformer work, but I want to make sure that the chime I get is compatible with the output of the transformer.  I'm not sure where the transformer is actually located in the house.  I've taken a voltmeter, set it to 20v AC maximum and set to to 'peak hold' and had a friend push and hold the doorbell.  I measured approximately 10-14 volts that way at the chime.

Most of the doorbell chimes I've seen are rated 16V/10VAC which I understand is 10volts AC.  But, what is the 16volt value?  Peak voltage of the sinusoid?

Was my technique for measuring the voltage output of the transformer reasonable?  Since I've set it for AC voltage reading, the value I'm hoping for is 10V (or close to it) vice 16 volts if I want to purchase one of these 16V/10VAC chimes, correct?


texts: Cooling circuit board for troubleshooting

texts:
I'm trying to troubleshoot an LCD TV. It turns off at random intervals I'm guessing as it heats up with use. I want to determine which PCB is failing with heat, and then even isolate the area on the failing PCB. Is there an easy way to cool the PCB temporarily. A small fan is one idea. Can I spray the board with something to cool it down temporarily? I thought I've heard of that.
PS. I've tested all caps and they are all within spec. Also don't visibly see cold solder joints.


texts: How does this high amperage LED dimmer work while being so small?

texts:
I am trying to make a custom dimmer circuit for an off the shelf LED lamp meant for aquatic plant growth. I found a generic dimmer that many people (in the aquatic plant community) use, and am very curious how they managed to make a dimmer so small.

According to the lights it is supposed to be able to dim, it connects to a 24V@(max)4A power supply (input to power supply is 110-230V). The output is directly used by the LED lamp (which we can assume uses at least more than 2A).

Some ways to dim LEDs that I found are

1.) PWM into a mosfet...but at min 2A, I feel this thing would get much too hot. The PWM would then need another IC (at least a 555) which I don't think can fit in there.

Edit: It also seems somewhat wrong to control LED's at this amperage with PWM...especially given that there is a blackbox driver circuit that comes after this dimmer circuit and turning that on and off at high frequency seems 'wrong'.

2.) Constant current...I'm not entirely sure how to make a constant current source driver. I would imagine that this would be in the actual lamp circuit rather than the generic dimmer circuit or generic power brick. Also this dimmer is adjustable, which I am not sure how you would do in a small space for a constant current driver.

3.) basic buck converter to limit the voltage coming in. The issue again is with how you can dim this dynamically with button presses.

I can imagine building any of the three options above to control high power LED's, but I can't wrap my head around how I would go about making the result so small...

Short of me buying the thing and taking it apart, it would be great if anyone had ideas on this!


texts: How to get the continuous current rating of a power led from the spec sheet?

texts:
I am looking at an Osram OSLON® Black, SFH 4715A Infared LED.

Is this LED rated for continuous operation?

The spec sheet lists:

  Total radiant flux (IF = 1 A, tp = 10 ms) (typ) Φe 770 mW

Does the 10ms mean that this is the maximum on time? Any way to figure out what the maximum continuous current is?

Thanks!


texts: Optimizing signal voltage level for 5V device

texts:
Are there any benefits associated with using lower signal voltages?

For example, if a 5V device has an input high voltage level minimum of 2V, would running input signals at, say 3.3 vs 4.5 or 5v have any significant effects?

I understand using lower ADC input voltages will reduce resolution.


texts: How are system clock and oscillator frequency related?

texts:
My question is given a, for example, a quartz oscillator on a MCU board, how is the system clock generated? I'll break down this question into several parts below:

I always have the impression that oscillator generates a sinusoidal wave. But digital circuits use square wave as clock signal. So is there always some circuit that converts the sinusoidal wave into a square wave with the same frequency?

If the oscillator is eventually used for the MCU to count system time (e.g. the MCU is able to give current timestamp or measure a time duration in terms of its "device time unit"), without using any frequency multiplication or division, does one "device time unit" correspond to the duration of one period of the oscillator?

If there's some constant offset between the actual oscillator frequency and its nominal frequency, how does this error translate into the error in the duration represented by one "device time unit"?

Thank you!


texts: How to fuse wires into single solid thread?

texts:
I'm trying my first real project with an arduino of my own design/idea.
I come from a CS background this EE stuff is both exciting and scary.

I'm trying to wire up a 3.5mm female audio jack to the Arduino, via my breadboard.

I've just finished soldering some wires to the jack (my first time with the solder) but now I have hit an issue I didn't think of: the wire I'm using is made of 10's of little copper wires, this seems normal enough, but I've only ever plugged in larger solid single-thread wires in to my arduino.

Do I somehow have to fuse the little ones together to be able to plug this in? Or can I just kinda shove it in?

END NOTE: Thanks every one for your suggestions!
Thanks guys, and sorry for the lack of proper terminology, as I said, I'm from CS and very new to any thing to do with EE.


texts:
I'm designing a new ISA form factor PC board for a legacy system.  I've looked around the net and found several references for ISA board dimensions, but they don't call out the location of the edge card connector fingers with respect to the front panel edge of the card.

Does anyone know where to find a reliable ISA board outline, including the relative location of the edge card contacts to the front panel edge?

One possible source of the mechanical specificaitons is IEEE P996, a proposed standard for the ISA bus that was apparently never finalized, but it does not seem to be available any more.


texts: Multiple sensors on a single serial port

texts: I want to use a single serial UART port on an mcu to communicate with two different sensors. I have connected both the sensors' TX lines together to mcu's RX line and vice versa. I am switching the sensors ON and OFF in such a manner that at no point in time are both the sensors being powered. Would this configuration work?


texts: Limit direction of "audio" in an aux connection

texts:
I added and AUX connection for my car radio by soldering straight into the audio lines between the CD player and the car radio.
I connected my phone to this AUX connection and added an external mic.
So the 4 poles (CTIA) connect to LEFT, RIGHT, GROUND, MIC where LEFT, RIGHT and GROUND go to the car radio (connection between the radio and the CD player) and the GROUND and MIC go to an external mic.

The problem is that my phone and the CD player share the same lines so basically the cd player "sends" its audio into my phone through the LEFT and RIGHT lines. Of course, this has no effect on sound and also, I play a silent CD, but, I am having problems with my phone (android) where it automatically turns down the volume all the way to zero. I think this is happening because of a feature that turns down the volume when high audio is detected on the lines.
What I thought was maybe there is a way to prevent the cd player from "entering" my phone lines? For example a diode or so..?
I know that audio is achieved from change in voltage, but there must also be current I guess..? Also, could you recommend what I can do to avoid noise from the radio? I guess that it is coming from the GROUND line, so maybe some sort of capacitor on the ground line?


texts: I have a bluetooth module which uses the CC2541 IC. My project is battery powered and so i want to be able to put the device to sleep.i have been looking about trying to find how to do this and it would seem that there is no sleep/wake pin but one has to program the chip itself to put it to sleep. could anyone just confirm this before i start assembling a high side mosfet config. to power the module on/off please? thanks.


texts: MAX9814 feedback from headphones - normal, or faulty device?

texts:
I have a setup similar to this one: amp, 100uF cap leading to headphones, nothing more. Powered from a Pi-Ion battery @3.9V.

It had worked fine with MAX4466, but after replacing that with MAX9814, I get VERY loud high-pitched noise. The mic is responsive, and the noise even dies for a fraction of a second  when I am providing it with very loud sounds myself (like tapping the mic)

The noise appears to be feedback from the (very small) 32 ohm Philips headphone speaker:
Moving the speaker closer and further from the module changes the noise frequency (Doppler effect) Works even at 80cm (my cables don't reach further).
[edit] Tried different headphones, 140cm away - same.

I have tried 2 different MAX9814 modules, replacing caps, even ditching the breadboard and mounting on a piece of PCL plastic (insulator):

No change.

Dropping max gain from the default 60dB to 50dB makes is a little better (until the autogain gets there again) and at 40dB makes the noise cease at distances over 20cm.
Similar with a pair of Panasonic headphones (not disassembled), but there, noise can disappear at over 35cm at 50dB. At 60dB, still appears at 140cm.

Granted, the module was purchased from ebay not from adafruit, but the board design appears to be the same.

The question, again. is whether all that is perfectly normal, or not.
The fact I have not read about it on the sites which decribe how to connect a headphone jack to the MAX9814, on the default gain setting, no less, leads me to expect it is not. The effect happens with the (Panasonic) headphones a full cable length away, after all.


texts: Resistance issue in a triac-optocoupler switch

texts:
I have made the following circuit to control my water pump with Arduino(UNO R3). I have tried many resistors (calculated myself) to limit current in the optocoupler and triac, but failed to carry the load for a long time. At one time either resistor get burned or triac gets too hot. Kindly suggest what resistance I should use in the resistors with '?'. Any other suggestions are also welcome.

MOC3021 datasheet
BT136 datasheet