texts: What is need of transmission modes in Serial Peripheral Interface

texts:
I am going through SPI transmission for implementing in FPGA, While researching, In few articles such as
 https://en.wikipedia.org/wiki/Serial_Peripheral_Interface and this   https://web.archive.org/web/20150413003534/http://www.ee.nmt.edu/~teare/ee308l/datasheets/S12SPIV3.pdf
 Which says in Section 4.4.1

  Using two bits in the SPI Control Register1, software selects one of
  four combinations of serial clock phase and polarity.

  The CPOL clock polarity control bit specifies an active high or low clock and has no significant effect on the transmission format.

  The CPHA clock phase
  control bit selects one of two fundamentally different transmission
  formats. Clock phase and polarity should be identical for the master
  SPI device and the communicating slave device. In some cases, the
  phase and polarity are changed between transmissions to allow a master
  device to communicate with peripheral slaves having different
  requirements.

My question is What is the need of specifying the different modes in SCK, Though the last line tries to reason out, It sounds vague and doesn't specify actual reason,
What is the actual reason is for specifying the SCK polarity and Phase in which mode is determined.
Thanks.


texts: How to tell a common cathode vs a common anode full color led?

texts: Is there a way to visually tell if it has common cathode or a common anode on a full color LED?


texts: Electrical connection during car jump start

texts:
I have seen the procedure to jump start a car when the battery is dead.

What I don't understand is that why is one end of the cable connected to the metal frame chassis of the car which has the dead battery?

Why don't we connect the positive negative of the working battery to the positive and negative of the dead battery and start the car?

Can someone explain why do we do this connection and what's wrong in shorting the both battery terminals? How does the battery get charged during the correct procedure?


texts: Clarification about USB receptacle and plug

texts:
I need clarifications about which USB receptacle and plug I have to use for an embedded product.

I looked on line and I found a lot of documentation like this or this and I understood that:

If I want to realize an embedded product with device role, I have to use mini or micro USB B receptacle. So I can connect my device to an host using a cable with a mini or micro USB B plug and a USB A plug.
If I want to realize an embedded product with host role or OTG, I have to use mini USB A or micro USB AB receptacle. So I can connect a device like a PenDrive at my embedded product with a cable with mini or micro USB A plug and a USB A receptacle; if my embedded is an OTG I can also connect its to an host with a cable like previous case (and checking the ID pin).

That's right?

If yes I have 3 questions:

If with mini or micro USB B receptacle my embedded product must to have a device role, why in the receptacle connector there is also the ID pin that can be tested by microcontroller (and so switch from device to host role)?
Only the cable with mini or micro USB A plug and a USB A receptacle are USB compliant?
If I'm not mistaken, many smartphones a few years ago had a receptacle mini or micro USB B but, with a particular OTG cable, they could take the role of host and read for example a PenDrive. In this case all these smartphones are not USB compliant?

Thank you in advance.


texts:
A am working on an FPGA based function generator and I am aiming for max frequency to be higher than 10 MHz, hopefully 30 MHz. I have implemented most of the functionality except amplitude control. Ideally I'd like to have a way to digitally control the amplitude. I have thought about using the following: digital attenuators, feedback amplifier circuits, some sort of FET used as variable resistor and not using any specific device at all and just changing the values I pass to the DAC.

Changing the DAC values seems the easiest however, it would negatively affect the resolution of the waveform on lower amplitudes.

Using a feedback amp seems to me like a good way to precisely control the amplitude  however the frequency response of many opamps and the whole circuit that would need to be designed makes for an uninviting option.

Similar stuff with using some sort of FET, say JFET. Something tells me that it wouldn't be as easy as sticking a resistor to a JFET and not expecting any degradation in signal fidelity.

I have no opinion on digital RF attenuators, I think that might be a way to go.

The question is if any of those approaches are better suited for operation at specified frequencies that the other, and what are the most frequently used approaches in the field?


texts: Adding power components in frequency spectrum

texts:
I was doing some problems and I just had some doubts regarding adding up powers in the frequency spectrum.

Let's say I am designing a track and hold system for an ADC and I have a requirement of a 60dB signal-to-noise ratio (SNR). Let's say the input signal is at 0dBm.

Now let's say our clock jitter gives a noise component at -65dBm and we are asked to find smallest capacitor (giving thermal noise) that will allow us to achieve a 60dB SNR.

So my question is, do I now assume that my thermal noise can contribute 5dBm of noise so that when I add it with the jitter power (of -65dBm), I get a total of -65 + 5 = -60dBm? If so, then my capacitor will be extremely small (5dBm = kT/C)?

I feel like that's very incorrect because now my dominant noise component will be at 5dBm.

My question is, how do you guys think about this? How do you add the powers up?


texts: ddr: Is there any significant delta between the different strobes?

texts:
In a DDR memory, during a read, output data from the DDR is aligned on the strobe. There is one strobe per 8-bit:

UDQS/LDQS for a 16-bit-wide DDR
DQS[0-3] for a 32-bit-wide DDR

Is there any significant delta between the strobes of the same DDR chip? 'Significant' means: can I use one strobe for all the bit? I have a custom-made DDR controller in a FPGA and I would like to use one strobe for the entire data set.


texts: Making a electrical signal detector (Inputs from multiple source)

texts:
I am working on an electrical project that, actually works something like a touchscreen digitizer, where I have to generate multiple inputs from over 50-100 sources, and I need to check from which sensor or a group of sensors (probably 3-5) are giving the signals, and then which sensor among the group has the highest electrical signal.

So I would like to know, if there is some way to do this. It has a lot of resemblance with the a resistive touch-screen digitizer, where there are many points that can send the signals, but the digitizer works by detecting exactly where the pressure has been exerted, and then it is sent to the micro-processor which calculates it according to the actual lcd screen.

A basic diagram, or a similar microprocessor reference will be appreciated.

-------------------Edit (More info added)--------------------------

My sensor are basically LDR's (or probably Photo Diodes), and I need to sense light intensity on a specific group of sensors. I am working on an academic project related to robotics.

The LDR's are placed at a distance of 10 mm from each other and arranged in the form of a matrix. So if I take a laser pointer and point to a specific LDR, I should get the reading (may be in number, count) of the active LDR sensor.


texts: What determines the frequency range of a current transformer?

texts:
Per the title, what physical or construction parameters determine the frequency range of a current transformer?  I happen to be looking at these two from mouser, but I'm sure the question is generic enough to apply to a large number of these things...  What causes there to be a thousand-fold different in the minimum frequency?

Also, what happens if you attempt to measure a frequency well outside the rated range?  For example, if you tried to measure a 50-60Hz residential power waveform with one of these KHz-range devices?

CT #1 : ICE CT08-1200 - listed as 40Hz - 200KHz

CT #2 : Murata 56200C - listed as 20KHz - 200KHz


texts: High voltage Flyback transformer polarity

texts:
This circuit is a high voltage generator using flyback transformer.

It works well, but i thought it shouldn't working by this polarity of the feedback winding !

I mean when the voltage on the primary side increasing(before
saturation) the voltage of the feedback coil should be minus to force the transistor switch OFF.

But by the dot convention that shown in the circuit the transistor should be stay ON for ever (because there are no 180 degree phase shift between primary and feedback winding).

So how this circuit can works by this feedback winding polarity?


texts:
Why are there no "even" harmonics in AC machines?
In Chapman's book, he says it's because of symmetry of the flux density wave but I don't get it...


texts:
I want to use the 555 time to control the timing on the power pulse of a spot-welder using a foot switch.

I have seen a few 555 mono-stable circuits, but am having trouble finding the values of the resistors and capacitors in order to get times below 1 second.

Also, I want to connect this circuit to a spot welder in a safe way, because of power difference. My spot welder is made of a MOT, and have a pedal switch to do the switching.

How should I connect these parts together? What kind of pot/cap combo for sub 1 second timing with a 555 timer?

I wanted to add the image at the bottom of the page, but didn't know how.
So, i have to put over here.
Please let me know any modifications that i should do with the connections.
Also, i would like to add a POT in the 555 timer circuit in order to adjust the timing. Where should i put it?
Thank you for any help...


texts: What is the difference between a solid state relay and a transistor?

texts:
Along with the difference between a solid state relay and a transistor, I'm also interested to know if there are transistors that act a lot like the typical relay modules you can find on ebay (where you only need a 5V signal from the microcontroller to toggle the state of the transistor...)  A lot of transistor datasheets I've seen so far have wildly different saturation specifications (where the collector/emitter value is highly influenced by how much voltage is applied to the base), but this saturation idea doesn't really apply to a electromechanical relay...

https://www.fairchildsemi.com/datasheets/2N/2N3906.pdf
https://www.fairchildsemi.com/datasheets/TI/TIP31A.pdf

Doing a search on Digikey's website for solid state relay gave me a list of components that all have input voltages close to 1.25 V... Am I correct in believing the solid state relay is a lot like what I just described?


texts: Trouble understanding this voltage divider for a non-inverting Op Amp

texts:
I'm going through the Op Amp section in The Art of Electronics and I'm having trouble understanding their derivation of the gain for the following circuit:

So by the properties of Op Amps \$ v_A=v_{in} \$, now the way I understand this circuit is that since the potential at A is \$ v_{in}\$ and \$ R_1 \$ is connected to the ground there will be a current flowing through \$ R_1 \$ towards the ground. Since another property of Op Amps is that the current going into them is essentially 0 we know that this current must also pass through \$ R_2 \$ so we can find \$ v_{out}\$ and hence the gain by using \$ v_{out}=v_{in}+iR_2\$ where \$i=\frac{v_{in}}{R_1}\$.

However in the textbook, it is explained as "But \$v_a\$ comes from a voltage divider: \$v_a=\frac{v_{out}R_1}{R_1+R_2}\$", I'm just having trouble seeing why this is valid, this comes from current being \$i=\frac{v_{out}}{R_1+R_2}\$ and then going from the ground to point A through \$R_1\$, I suppose I am confused by the fact that this finds a different current through the resistors than my method and it still works.


texts: Interfacing 3V TI MSP430 to PC serial port

texts:
I am scratching my head to figure out a possible soloution for this scenario:

I am developing a simple application using TI MSP430 microcontroller. The microcontrol part is powered by 2xAA batteries. I want to send/receive data from the chip to my PC's RS232 port.

I already made a level matching circuit by using MAX232N. My problem is, since the MSP430 is powered by 2xAA, it can not reach the +5 volt required for CMOS to RS232 conversion to happen, considering that the voltage from those batteries is around 2.8 if they are fresh and gradually drops down.

Can somone please point me into a good direction?


texts: I'm trying to make a circuit using tc4427 and some other components to make a fast switch for a 24V valve using a signal from a microprocessor. I've modeled the signal from the processor as a pulse of 5V shown in V2 and the valve is modelled as a resistor R3 and a coil C1. Do you think this circuit will work fine?


texts: Signal lines from transducer made common by op-amp

texts:
I am trying to amplify the difference between signal lines off of a Wheatstone bridge based force transducer. I've wired up an LM358N Op-Amp as shown below in a differential amplifier.

With R1=R2=100Ω and R3=R4=3.3kΩ, the gain should be about 33. The op-amp is given a single supply (Vcc) of +12V. The load cell is powered with this same voltage.

When not connected to the circuit, the load cell behaves as expected when its output is measured with a multimeter. However, when connected to the circuit (to V1 and V2 on the diagram), the multimeter measures a difference of 0.0mV between the signal wires.

I have measured the resistance between V1 and V2 when the load cell is not connected, and it is in the low MΩ without power and around 200Ω with power to the op-amp. This makes it seem like the inverting and non-inverting terminals become common when powered.

Is this possible? Would higher values for R1 and R2 get around this?


texts: Any published designs for time-of-flight laser distance measurement

texts: Does anyone have any references/examples for detailed circuitry for time-of-flight laser distance measurements - schematics, appnotes etc.?


texts:
I am designing modules for radio controlled aircraft. Most of the  time I have to read a PWM pulse and produce a PWM pulse between 1000 - 2000 microseconds.
When I use an Atmega328 (@16 MHz with crystal) there are no problems but if I use an Attiny85 (@8 MHz internal oscillator) I get servo jitter (due to PWM pulse timing problems).
My question is;
Can this behaviour be explained with the difference between a quartz and an R/C oscillator?
Thank you...


texts: Programming my ATmega8 board using Arduino IDE

texts:
I made a board with an ATmega8A (SMD-TQFP package). I installed the minicore library in the Arduino IDE. Now I'm able to flash the hex file using Atmel Studio 7 and able to read serial well.

But my problem is reading the digital pin status. It doesn't work well. I searched the internet and in the minicore library, I found that in the ATmega8, pin 14 (PORT B.2) is digital pin 10. So I wrote my code, however the pin does not change its status when toggling it.

Is it a mapping problem? If so, how can I map it?

#include <TimerOne.h>

int setbit = 0;//timer 2 isr
int setbit1 = 0;
int flag=0;
int flag1=0,k=0;
int flag2=0; int Light_CMD_J6=9;
int Button_Status_J6=10;

void setup() {
    Timer1.initialize(100000); // set a timer of length
    Timer1.attachInterrupt( timerIsr ); //
    Serial.begin(19200);
    pinMode(Light_CMD_J6,OUTPUT);
    pinMode(Button_Status_J6,INPUT);

}

void timerIsr()
{
    setbit1=setbit1+1;
    if(setbit1==10)//2 seconds
    {
        setbit1=0;
        flag2=1;
    }
}

void loop() {
    if(flag2==1)
    {
        Button_Status_J6=digitalRead(Button_Status_J6);
        Serial.print("BUTTON 6 STATE IS   =  ");
        Serial.println(Button_Status_J6);
        flag2=0;
    }
}


texts: A hole in middle of a capacitive touch screen

texts:
I'm thinking about using a capacitive touch screen (the touch layer only, no display) to detect the position of two moving parts. Each part would have its 'stylus' just above the screen to mark the position. Unfortunately, such a use-case would require a rather large (1.5cm hole in 7cm screen) hole in the middle of the touch screen.
Have you tried to drill a hole into a capacitive touch screen? Will it work afterwards?


texts:
After a research on MOSFET use, I've found that I'm unable to connect load on Source in N-type without additional consideration.

About this component CPC1002N http://www.ixysic.com/home/pdfs.nsf/www/CPC1002N.pdf/$file/CPC1002N.pdf

I've a MOSFET driven by a LED, N-Type. This component is described as Relay, in this case should I take in consideration that load still need be on Drain becouse there's MOSFET inside?
Or can I put load where I prefer since Vgs is given by an optocoupler?


texts: What OP AMP spec should I be checking to assure this behavior

texts:
Recently, on the advice of others on another thread, I tried to migrate a dual supply OP amp circuit to single supply version. I needed a quad OP AMP, and the logic was that since my final circuit only needed to provide 0 to about 3.5 VDC, an LM324 would do just fine. Well that was easy to try because I had some on hand, but the result wasn't so hot. It turns out that my circuit must drive the equivalent of about 10K tied to +V, as in this simplified test diagram...

The result with the LM324 was that the output under these circumstances was a dismal 650 mVDC, a very LONG way from the hoped output of near zero.

This makes sense... the LM324 uses ordinary bipolar transistors for its output stages and that's about the best you can hope for. So I poked around and found a Texas Inst. quad OP AMP, the TLC274. It uses FETs for all its internal circuitry and its data sheet actually DOES mention its output includes the negative supply rail.

Unfortunately it certainly won't go to the negative rail with any load. In the example shown the best the TLC 274 could do was about 90 mV. Granted that is hugely better than the LM324, but its still a LONG way from zero. To be practical, I'd like the output in the situation depicted in my schematic to be 20 mV or less. Had I stuck with my earlier dual supply OP amps, of course this would not be an issue. But a negative supply is not available without a charge pump oscillator or similar trick requiring more parts so I'd like to stick with a single supply OP amp if I can. I'm just at a loss as to what OP amp specification I should be looking at so I don't keep running into his same problem. TI is pretty fast at sending samples, but ask them for support on a question like this and you can expect to wait a month.

Addendum:

The answers I received here have really enlightened me, and I want to thank those of you who chimed in. I have pored over the specs of several so called "rail to rail" op amps and have requested a few samples, but what I've really learned here is that "rail to rail" is a relative term, and a single supply OP amp may not be the best choice for my situation.

It is indeed a stretch to expect even the best CMOS drive OP-AMps to have an effective resistance low enough to ensure a 20mV or less output against a 1mA pull up load, and even more a stretch to think it would be sufficiently consistent between parts. The truth is that if I want precision control down near zero, a dual supply OP-AMP is a much better choice, if only because "0" really is not "0" with a dual supply, but only a "reference point" between +/- V supplies. Such a reference point can always be adjusted or trimmed as close to zero as necessary.

So since I don't have a V- supply available in my case, I have two choices. Either find a way to alter the circuit I am driving to eliminate the 10K pull up to +10VDC, or revert to a dual supply OP-AMP. To make this work I'll need to add a second OP amp package configured as oscillator and charge pump, to develop a negative supply for the second package. I've done this before and found that just a few volts of V- supply is usually sufficient to build up a good DC amplifier with good accuracy around 0 volts, with a little attention given to the source of the virtual "0" reference.

In any case I now understand that for such a precision DC amplifier, with good drive around 0 volts, it is nearly futile to expect a rail to rail OP AMP to automatically be a good solution. Its not the conclusion I'd hoped for, but win or lose its always good when you come away more educated.


texts:
I'm trying to build a guitar delay effect based on this schematic:

(https://i2.wp.com/cdn.makezine.com/uploads/2009/09/echobenderrev02.jpg)

I designed and oredered a pcb : https://easyeda.com/editor#id=7e588f25fbf742a5b97965476faa0c72|5b4e3f8fb2d04a0993a5a7e7a2797ad2

After waiting for few weeks, and hours of soldering I can't get it to work... All I   Can hear is noise, nothing close to guitar. I double checked (I think) every component and its pinouts..
Can you help me somehow? It's my first project with pcb's...


texts: What is the maximum voltage drop on an LDO?

texts:
I'm a long time lurker :)

How do I tell what is the maximum voltage drop an LDO can handle?
My mentor explained adjustable LDOs like this to me (paraphrased of course):

  "An LDO is essentially a high precision, low range, voltage controller
  that requires a slightly higher input voltage to function.  For
  example, even though an LDO is rated at (1.24-26)V if the input is
  25V, it will only be able to output (24.2-24.8)V."

How can I find these boundaries in a datasheet?

Considered components:

MIC29150/29300/29500/29750 High-Current Low-Dropout Regulators
LT3015 Series - 1.5A, Low Noise, Negative Linear Regulator with Precision Current Limit

Sorry if my English is not good.  C++ is my native language.


texts: RF: Do I need a resistor at line driver output for impedance matching?

texts:
I have a digital RF signal (~50Mbps max) passing through SN74BCT25240, a 25-ohm octal buffer/driver. This is on a 4-layer PCB with a ground/power planes and proper bypassing, etc. I was wondering do I need 50-ohm termination on the output of the buffer, to avoid ringing or over/undershoots? i.e. maybe a series 50-ohm resistor, or ac termination? Because I'll be driving 50-ohm cables and a 50-ohm load. The cable can be quite long (up to 25feet).

I was told by an engineer at work that 'this thing is designed for >25ohm loads -- no termination is necessary, you're just going to divide the voltage for no reason' - yet I've seen at least one design from a colleague with this part using a series resistor. Now, even if I decide a series resistor is needed; how do I choose it? There is no spec for the output impedance of the driver. My earlier guess of a 50ohm resistor was assuming this buffer has 'low' output impedance.

Thoughts?


texts: How can implement a low pass filter with this PWM signal? (Deadstop Fan won't start error)

texts:
I want to low pass the signal to the fans in this circuit.

PWM frequency is 35khz and I calculated that I would need C = 10 µF and R = 10 Ω

But no matter how I place my capacitor and resistor, I get 12 volts and loose the PWM.

I basically tried a lot of options, I just give up :)

EDIT: here's what I tried (but I get 12v on the fan):


texts: Rechargeable 1.2V AA Batteries vs Alkaline 1.5V?

texts:
I wonder about the power output of rechargeable batteries vs alkalkine, as there is a slight difference in voltage.

I have some heated gloves that use 3xAA batteries each. In alkaline they add up to 4.5 volts. If I go rechargeable it'll add up to just 3.6 volts.

But the alkaline (Duracell) are expensive over time and don't even last 2 hours. Whereas I'm looking to get 3800mah rechargeables that will last longer and be reusable.

But will they heat the gloves as much? These particular gloves are super cheap and the heat barely works. But they do work! At least enough to stave off my hands from freezing. I'm worried if I get the rechargeables, even if they last longer, they might not run the gloves as warm? What do you think?

I really want to get some expensive heated gloves that run a custom battery pack at 7.2 volts; I'd get them if I could but they are over $100. Whereas the rechargeable batteries and charger are less than 1/3 that price and I can use them for other things too.

As a cyclist, I'm desperate for a solution. I have Raynaud's Phenomena so no matter how effective regular gloves are, once my brain signals that it's cold, the hands will go ice cold and stay that way. Putting heat at the source is the only thing that works, and I can't use mittens with heat packs as I need full finger control.


texts: An impossible task? Reverse current/short circuit protection not only for load but also for power supply

texts:
This is a magnetic phone charger.  It's a USB cable that plugs into a standard 5V phone-type charger.  The magnetic "plug" has a (+) center-pin and a (-) round metal as the ground with a magnet behind it.  The receiving load-side "socket" mirrors the power-supply plug by having a spring-loaded (+) center-pin and also (-) metal ring as the ground with a magnet behind it.  Has no (D+/D-) data lines, only power.
Unfortunately, (with some deliberate effort) I have discovered that the physical design DOES ALLOW for an inadvertent short-circuit by having the "plug's" center-pin touch the round ground metal of the mating "socket" while at the same time it's own round metal ground touching the center-pin of the "socket".
I can protect the receiving load circuit with a diode, or a MOSFET, or other common reverse-current/voltage protection.  But is there any way to prevent the power-supply itself from getting shorted out?  The 5V power-supply/charger can be anything, since this is just a USB cable.
The only way I can think of protecting a connected 5V power supply/charger (let's assume it does not have one built-in) is to somehow channel away/absorb the short-circuit current somewhere on the receiving load side of the circuit by offering a lower path of resistance, while also making sure that the load-side of the circuit is not damaged either.
What say you?


texts: Does a SIM card consist of only Flash memory or is there a microprocessor inside as well?


texts: I try to explain how a n-channel mosfet works. But as I try to explain there is an ambiguity that I can not understand. As I read many books and searched in the internet does not say anywhere clearly about from whom it is constructed. When we apply the positive gate voltage the holes present under the oxide layer with a repulsive force and holes are pushed downward. Thus, only negative ions in that area left and the layer acquires negative charging. Other books say that this area is derived from the electrons which are attracted. My question is ultimately, of what the channel is created? by the negative ions that remain in the layer or by the electrons which are attracted; And if it is derived from electrons ,from which atoms they come from ?(for example from silicon;)


texts: Understanding the gain in an RC circuit's transfer function

texts:
I am learning about 1st order transfer functions, and I am trying to understand it with practical examples of systems, because it still looks weird to me how a same function can describe various physical systems. I am currently looking at the transfer function of a simple RC circuit.
It is denoted as

lookig at the standard function, we can tell we have a gain of 1 in this function, as explained in this post

I am ok with the fact that the time constant tau is equal to RC in this particular real world example, as a resistance multiplied by a capacitance can be simplified to time units, a little bit like a speed multiplied by a distance.
however, I am not sure how to look at this and, set apart all the math, intuitively understand why the gain should be 1, rather than anything else. I need help understanding what is the concept behind the gain here, because I am completely lost.
Thank you so much!


texts: Generating various emission modes via DDS

texts:
I know it is common to generate sine waves via Direct Digital Synthesis (DDS). What I would like to know is if it is possible to generate a modulated signal via DDS and if so what would be a practical maximum frequency to do so?

Is this a technique being use in practice for emission modes like A3E or F3E?


texts: How to use nonstandard audio sample rate data with audio DAC?

texts:
In Table 1 the CS4334 data sheet states that it accepts standard audio sample rates in kHz of 32, 44.1, 48, 64, 88.2 & 96.

What does one do to get correct output if the audio data sample rate is not one of these number or is less than 32kHz?


texts: voltage drop over IRF9540 = IRFZ440N H-Bridge

texts:
I am trying to build a simple H bridge as part of a learning curve.  At the moment it is on a breadboard.
I am using 2 P-Channel MosFets (IRF9540) and 2 N-Channel MosFets (IRFZ440N).  They are tied to a 3.6v screwdriver motor.  I've tested the current draw on this at stall when powered by a 6v lantern battery.  The max current I have recorded is 0.8A.  When testing on the breadboard it is not under any stalling load.
At the moment I am not using an MCU controller - i'm just jumpering the control wires (going into the gates of each side) straight into the power line.
The P-Channels are getting very hot; which is somewhat to be expected as the P-Channel RDS is relatively high at c200mΩ.  (but I have to say that I am surprised by how high the temp is getting.  ambient is c.25C.
However this question is more aimed at the fact that the motor is running very slowly.  It looks like somewhere in the circuit I am getting serious voltage drop - it appears to be random but sometimes the motor will not turn at all, sometimes it turns slowly and gradually gets faster, but never achieves anything like the speed when directly connected even to a small LiPo 3.7v cell (900mAH).

sometimes I am reading no voltage across the motor pins, sometimes 1-2v.  but nowhere near the 6V across the battery pins.

is this all down to poorly balanced fets?  how can I really be dropping 4+V?
when the gates on the right hand side of the H bridge are brought high I am getting the following voltage drops across drain and source on each of the fets

Q1 3v
Q2 1v
Q3 4v
Q4 4v

(note annoyingly my normal multimeter is on the blink so I am using one that is granular only as to 1v).

the circuit schematic is here: https://www.dropbox.com/s/ih7bx6hlj40vxtf/Screenshot%202015-05-18%2018.24.49.png?dl=0

a photo of the breadboard assembly can be found here (fwiw): https://dl.dropboxusercontent.com/u/194358/IMG_20150518_183350.jpg

(please forgive the absence of colour coding in the wiring).

I am using jumper cables which for sure can't take multi-amps but they should be ok with smaller currents - none are getting hot in any event.

many thanks in advance for any pointers you can give me.

Justin


texts: Mimicking the output of a piezo sensor with a membrane potentiometer

texts:
High level
I'm trying to use an electronic drum pedal as an electronic drum trigger. My specific e-drum unit has only one pedal input, so I need to repurpose a drum trigger input in order to use more than one pedal.
The main issue is the pedal uses a membrane potentiometer, while the drums use a plain old piezo sensor so the outputs don't match.
The Pedal (Membrane Pot)
The pedal has a resting voltage of 256mV and uses a 33.2K membrane potentiometer. As you press down, the resistance approaches 0 ohm and voltage goes to ~6mV. From my research I've determined this is likely a voltage divider circuit? I've mocked it up and messed with the resistor values to get an approximate idea of how it works numbers wise -- no idea if this is correct, so it's just to give you an idea of where my head is at:

Here's a screengrab of an o-scope measurement of the curve from resting to fully pressed down:

The Drum (Piezo)
The drum appears to have a resting voltage of 0V, and when the sensor is activated it produces a negative voltage between 0V and -600mV which depends on how hard you strike -- lower the voltage the harder you hit.
Here is a screengrab of the curve from resting thru the strike and back to resting:

Summary
Basically I need to have the membrane potentiometer produce a negative voltage? Negative voltage is a new concept for me, so hopefully you can clarify what it actually means.
The naïve approach would be to slap a resistor in series to bring the pedal resting voltage down to 0V, and thus pressing it will produce negative voltage -- it makes sense to me from the standpoint of basic arithmetic but I'm sure things don't quite translate that way to the real world.
I'm a software engineer who is quite obviously green when it comes to electronics -- I think I know how to get the numbers, but not what they mean or how to manipulate them -- so any insight at all will be very helpful.
Thanks for your help!


texts:
I am using an AVR at90usb1286-based Teensy++ 2.0 to periodically read data from a few sensors. In its final form, my project will act based on the sensor inputs. For now, I log the results to the USB port.

Because the measurement interval is relatively long I am placing the microcontroller in powersaving sleep between measurements and using the watchdog timer to wake up periodically. This works just fine, but after waking up the USB connection does not work anymore and I have found no way to get it back

I am using PJRCs Debug Only USB library together with their host-side component hid_listen.exe.

Because of its debug function, I would like the solution to impact as little as possible the structure of the code.

I have tried three strategies so far:

Entering powersaving sleep (SLEEP_MODE_PWR_SAVE) without any special precautions. I get an "USB Device Not Recognized" error from windows7 and no additional communication is possible.
Entering a sleep mode that keeps the USB active (SLEEP_MODE_IDLE). In this mode the USB keeps functioning, but the sleep is interrupted pretty much immediately.
Entering powersaving sleep (SLEEP_MODE_PWR_SAVE) and trying to re-initialize the USB afterward by calling usb_init(). This does not seem to have any effect.

Here is a simplified application that shows the problem, adapted from this lesson 13

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/wdt.h>
#include <avr/power.h>
#include <avr/sleep.h>

#include "usb_debug_only.h"
#include "print.h"

ISR(WDT_vect, ISR_NAKED){
    _WD_CONTROL_REG = _BV(WDIE); // must reset interrupt after trigger
    /* do other work inside the watchdog interrupt? */
    PIND = _BV(PD6); /* toggle the pin */
    reti();
}

int main(void){
    DDRD = _BV(PD6);
    PORTD = _BV(PD6);
    /* watchdog setup goo */
    wdt_enable(WDTO_1S);
    _WD_CONTROL_REG = _BV(WDIE); /* generate watchdog interrupts */
    usb_init();

    sei(); /* enable interrupts */

    while(1){
        set_sleep_mode(SLEEP_MODE_PWR_SAVE);
        sleep_mode();
        print("a");
        usb_debug_flush_output();
        /* Do stuff after the watchdog wakes us up */
    }
}

Questions

Considering the given hardware, what are good strategies to put the controller into a sleep state while maintaining some form of debug output capability?

I am not concerned about power consumption, as the USB will be inactive in battery-powered production mode. However, I do wish to be able to get some debug output while I'm writing the program...


texts: Single-ended vs differential measurement of high-impedance voltage sources

texts:
I'm designing a low-cost multi-channel DAQ device with target resolution above noise of 30-50uV DC and +/-2V range. For this task I've selected ADS1220 ADC ICs: it has a 2.048V internal reference, bipolar output codes, an integrated PGA and decent enough noise performance. Also it features differential inputs, so my first thought was to take advantage of it, especially since the sources are 1-2m apart from the device and EMI environment around is questionable (at best).
However, my application involves measuring sources with internal resistance as high as 100k. This complicates common-mode biasing, since I can no longer apply simmetrical biasing (even using 1M resistors), because it will load the source and cause a voltage drop outside noise margin. Moreover, the input offset current of the ADC amplifier is ~2nA, and therefore (2nA*100k=200uV) I have to consider designing an extra preamlifier stage with pA offset current, and trying to maintain differential measuerement becomes increasingly expensive.
So, the question arises: maybe I should switch to single-ended measurement? Given two circuits, are the benefits of differential measurement significant for my application (assuming that 5V supplies are equally low-noise, like TPS7A4901, and cutoff frequencies of the LPFs are ~1Hz)?


texts: NOR Gate is Working Correctly with Vcc Pin Disconnected

texts:
I modified my Sega Master System to have a pause button on the actual controller. To process the signal, I soldered a quad NOR gate to the I/O and CPU circuits in the console. The idea is that the controller pause button sends a combined UP/DOWN signal, and the gate processes it and sends an NMI to the CPU, which is what the Pause button on the actual console does. This is the procedure recommended at the SMSPower forum, and I followed their diagrams.

Here's the thing: I installed the gate upside down, so that the packaging is resting on the circuit board, and the pins are sticking up in the air. I did this so it would be easier to solder the pins to the console, reasoning that the package is non-conductive anyway. When I tested it out, it didn't work correctly. As I was troubleshooting with my logic probe, I accidentally dislodged the Vcc connection, which I had soldered to a +5 Vcc solder point on the board. All of a sudden, it works correctly! I've checked the pin assignments over and over, and I'm positive that the Vcc pin isn't connected to anything; yet, the chip has power, and works as it is supposed to.

So, what is going on here? Was it a bad idea to install the chip package so that it touches the board? And why is the chip working when the Vcc pin is disconnected?

(edited to add requested information)

The gate is a CD4001AE Quad NOR; the datasheet is here:

http://www.datasheetlib.com/datasheet/1478457/cd4001ae_harris-corporation.html

The schematic is here, at the bottom of the page:

http://www.smspower.org/Development/JoypadPauseButton


texts: Analog sensor nonlinearity near the rails

texts:
I am looking into a 0-5V analog sensor. The problem with this sensor is that it

  will typically swing within 15 millivolts of the power supply rails with no output load.

(datasheet p. 4)

This means that the last 15mV of its ideal 0-5V range are unused, so its range is really 0.015-4.985V.

I have two questions about this:

Is this common to all analog sensors?
If so, why is this the case?


texts: how to program BMI160 inertial measuremen unit to latch detection flags

texts:
How should BMI160 registers be set to enable detection flags to be set in INT_STATUS?

For example, how to get TAP_STATUS byte-0 bit-5 s_tap_int to set if XDK110 is tapped?

I don't need actual interrupt, I just want a poll loop to periodically read flags in INT_STATUS to check for detection of the various motion events (tap, shock, etc.)


texts: Old Inductor, replace with newer current-production?

texts:
I'm forced to rebuild a 'magnetic amplifier' circuit and PCB. This circuit was originally designed in 1968, and my PCB was assembled in 1972. It's all resistors and caps, with a few small transistors.

Since I have to rebuild the whole thing, I'm having to find current-day items for the components used bade then.

Everything's been easily replaced, except for one item.

An inductor. On the schematics, it's listed as:

L201
0.975
1.025
HY

And in the parts list, it says (sic):

Inductor, Variable 0.975-1. 025 H

The component is cylindrical, about the size of a quarter round, and about 1.25inches high. The only markings on it are:

AE
426-908
7203

The AE is the manufacturer logo, and the 7203 is the date code, obviously.

So, while trying to find a 1H inductor, through-hole - they don't exist. All the 1H inductors I've found are essentially small transformers, and definately not possible to mount on a PCB. Searching for the 'AE' and part# yeilds no results, unfortunately. I can transfer these off of the old boards, but would rather find a suitable replacement.

Is it possible they meant mH or uH back then? (Similar to how caps were all listed using the MF symbol instead of uF..?)

Edit: Here's a link to a picasa album. This has three images of the inductor (two of top, one with a 27C020 EPROM for size comparison, and one from the bottom). A GIF of the schematics is also in that album. This circuit takes a signal from a cassette tape player head, magnifies it for use with a handful of gates on another board (not pictured, not in schematics). Point T on the schematics is the output. The lead coming in from the top above T, above R226 is +16vdc input. The R and B inputs at the bottom left is the input from the magnetic head. (With shield connected to B, common.)

Looking closely at the inductor - it looks like it's dual-wound, and only one winding is used - I believe, since the middle terminal is not tapped/used, the adjustment isn't even used. How strange.

Edit 2: The resistance (DCR) as measured by my beat-up Fluke 177 is 190ohms. This was measured with the inductor taken out of the circuit.


texts: Anyone know the purpose of these two inductors around a metallic ring?

texts:
So this link on ebay shows a power board that I have taken out from my microwave.

What is the purpose of these two wrapped around a metal ring? Also in general what is the purpose of this power board it takes in an input voltage of 120V AC but what does it output?

The circuit diagram shows the inductors without the toroid. The inductance is incorrect, I am not sure that the Henry value would be for them.


texts:
I have some problem with this circuit, the summering is not right and I should get 8 voltage at the output, but get 13.968 V. I need some input to solve it. Thanks for your help.

I use LTspice, to simulate.


texts: Is there any way to remove and replace a single 1212 (3030) LED from a heat-sink board as shown in the images?


texts: Measure Lithium ion battery voltage (thus remaining capacity)

texts:
What I am working with: I am running my self-made Arduino board (in the sense that I use the Arduino bootloader and code editor) at 3.3V, and powered from a Lithium ion battery, which is USB-charged by a corresponding Microchip charger IC.

What I am trying to achieve: I want to measure battery capacity once every minute or so. I have an LCD attached, so the idea is that the overall setup lets me know how the battery is doing at a given moment. The datasheet of the battery has a voltage versus discharge-level curve, and so by measuring the voltage of the battery, I can estimate the remaining capacity (very roughly but enough for me!).

What I did:

(EDIT: Resistor values updated and P-MOSFET switch added based on @stevenvh and @Jonny's suggestions).
I connected a voltage divider from the battery V_plus, with the larger "portion" going to an analog-read-pin (i.e., ADC) on the Arduino/Atmega chip.
The divider is 33 KOhm-to-10 KOhm, thus allowing measurement up to 4.1 Volts maximum of the Li-ion battery from my 3.3V level microcontroller.
Also, using one of the I/O pins connected to an n-channel MOSFET, I can switch the current through the divider only when I need the measurement.
Here is a rough schematic (updated for a 2nd time based on suggestions of @stevenvh and @Nick):

My question:

How is my current setup?
My only constraints are: (1) I would like to make a rough measurement of the battery capacity based on the voltage reading, as described above. (2) I would like to prevent the voltage divider from interfering with my charging IC's reading of battery presence (in my original setup, the divider sometimes caused the IC to misread presence even when the battery was absent).


texts: Is it possible to infer a floating-pt multiplier in hdl coding without instantiating the IP?

texts:
My architecture details

FPGA Implementation
Floating-pt format (IEEE 754)
At least 17 to 18 arithmetic operations (adders and multipliers) involved.
Currently instantiating the floating-pt IPs of multipliers (ALTFP_MUL) and adders (ALTFP_add_sub).

I was wondering if it's possible to infer these floating-pt multipliers and adders the way I can do for fixed-pt implementation!

By infer, I mean directly writing equation e.g. y <= a*b; rather than writing verbose port-mapping text.

I use VHDL. The design has to be synthesizable.

PS:

In a fixed-pt implementation, it was easy with some type casting and data-type conversion

e.g.y <= signed(a) * signed(b);

If possible, it will help me immensely in the development and I would be able to focus more on functionality.


texts:
My oven started displaying an error code E11 that indicates a "shorted key".
These chips are on the back of the oven touch panel. They don't seem to be the Atmel chips. The marking on the SOT23-6 packages is B2PE.
Any info would be appreciated.


texts: Role of capacitors in electric guitar's output to phone mic input converter

texts:
I want to build this electric guitar output to phone mic input converter:

(source: altervista.org)

From my limited knowledge on the subject, it looks like a simple JFET preamplifier (actually, I've simulated the circuit in LT Spice and it seems to attenuate the signal, not amplify), but I do not understand the role of the 100pF (gate to ground) and 470 pF (drain to ground) capacitors, are they used for some kind of filtering of the signal ? Will it work without them ?

The circuit I used for simulation in LT Spice is:

(the parts in the red rectangle should be the circuity inside the phone, I used the reference circuitry for soundblaster mic input thinking the phone has something similar inside)

So, my question is: what is the role of C2 and C3 ?


texts: Which RJ45 pins should I use for power supply?

texts:
I'm somewhere in a process of creating mini automation system for hobby use.

I've already put CAT 5e cables with RJ-45 connectors in walls. They are somewhere between 5 - 30 meters long.

On one side of the cable there is a host device, on the other a few client devices connected in parallel.

I want to use differential communication (probably RS-485 or CAN) over one pair (A, B) and deliver power through the same cable.

I picked 24V DC as optimal voltage (reduced on devices to 5V by step-down converter). To reduce the resistance I want to use two wires for +24V and two wires for GND.

Now I'm facing a problem of choosing which RJ-45 pins should I use for those signals.

In my first prototype I assigned them:

1 - +24V
2 - +24V
3 - GND
4 - A
5 - B
6 - GND
7 - NC
8 - NC

During hot-plugging, there was a possibility that RS-485 / CAN could make contact before GND pins, but after +24V pins, causing the transceiver to blow.

I also want to make it more "not expirienced user" proof and protect both sides when device or host gets connected to Ethernet (possibly with PoE).

My second idea is to do this:

1 - A
2 - B
3 - NC
4 - GND
5 - GND
6 - NC
7 - +24V
8 - +24V

However on many solutions I have seen using 4 and 5 pin for data transmission is recommended.
I have also seen numerous documents where 4 and 5 pin was left unused.

Which approach should I choose and why? Maybe ther?


texts: At what input frequency of an LCR meter should I measure the inductance of a solenoid valve?

texts:
I wanted to measure the inductance of a solenoid valve that I have: Airtec 2P025-08. I took it to the university's electronic valve. There was an LCR meter and I measured this values:

@ 120hz :  R = 33.6 Ω, C = -33.7 uf, L = 52.5 mH
@ 1000hz : R= 126.4 Ω, C= 4.458 uf, L = 15.93 mH

Which one should I use for a solenoid valve. The guy in charge of the lab told me that I should use those for 1000hz. I think he said 120 hz is for measuring inductance of motors (if I am not wrong).

I read this and it says use 200khz for measuring inductance: How to Measure Inductance

Which one should I use? If I should use those that belong to 200khz, how much are they different comparing to the values at 1000hz?

And one last question: if I want to simulate it with LTspice, Should I enter the values in the Solenoid block like this:

Or do I have to add a resistor and capacitor manually like this:

I am baffled... because I get different simulation results!

I am a beginner in electronics and LTspice,

Thanks :-)


texts:
Is it possible to do a speedo meter with an accelerometer ?
I am working with Arduino hardware.


texts:
bit of an amateur looking for some advice. Have done quite a bit of web searching but want to validate my proposed design. The project is a water control system using a raspberry pi.

I have a water purifier with a tank, and i need to move the water to 4 printers when they need water.
However, the printers contain a water tank so i need some kind of precision.

I tought about this design :

Thanks to the precision needed, i don't think i can use the gravity to move the liquid. That's why i tought about using a pump. But i think that might cause some troubles. Will it be troublesome to active the pump when all valves are closed ? if i open the valve one at a time and then active the pump will it work ?

Maybe another design will work better ?

I need advice ...

It works like this :

the printers send a message in a database . For the moment i send the error message to a raspberry pi with sockets .

Now i want to use these messages and when one of the printers need water , i want to refill it automatically.
When i receive the message , i know that the printer need, for example, 4L of water. That's why i need a pump so i know i need to active the pump for like 30sec and approximatively 4l of water will be refilled.

But i'm afraid, il will cause problems with the pump and the solenoid in series ...


texts: Why put a step-down transformer after a vacuum tube in an a valve amplifier?

texts:
I'm researching valve amplifiers. I found this schematic for one:

So the input is amplified by the first valve, and then the amplified signal is amplified again by the second valve, right?

My question is, why is the voltage being stepped down before going to the speaker? It seems pointless to me, increasing the voltage with the valves and then decreasing it again. All the schematics I can find online do this. Why?

(Is the 300V rail at the top related to the transformer? If not, what's it for?)


texts: Convert voltage controlled switch into ngspice

texts:
I have a circuit file ADA4691 from Analog Devices and it has a different .model V SWITCH versus SW in ngspice with a VON And VOFF instead of VTH for one switching voltage.

How could I approximate the two voltage conditions around the ngspice version?

The models inside are

.MODEL SOPEN  VSWITCH (VON=2.0, VOFF=0.8, RON=1e-01, ROFF=1E+09)
.MODEL SCLOSE VSWITCH (VON=-1.0, VOFF=-1.8, RON=1E-01, ROFF=1E+09)


texts:
The single most important thing I miss in LTspice is the ability to plot things of multiple runs on top of each other. Cadence Virtuoso calls that "Append Plot".
What I mean: I want to plot one node of my circuit, hit "Run" and plot. Then change the topology and run again and plot the result on top of the first one. This makes it easy to see the impact of multiple blocks/parsitics/changes directly in the waveform.
I know I can export the plot after each run and plot them on top in MATLAB for example. I also know I can use .step. But this does not (easily) allow for topology changes. None of these two are solutions.


texts:
I am doing a clone of my Honda's dashboard circuit. Everything is fine except I cannot find the tiny backlight bulbs (see photo) that are used for the dashboard button illumination. Are they standard bulbs that can be bought on Ebay? What would be the correct search term / part number for them then? Any help is appreciated!

Also, a few detached pics, they seem to be just glued on top of two contacts (source - Lexus forums):


texts: Thermal relief pads with through holes shall be soldered on top and bottom

texts:
I would like to know what is the right and correct process for Thermal relief pads for double component sides PCBA.

Should the Thermal relief pad fill with solder on the opposite side of the components?
If solder fillet is done from second side (as being requested) creates a reliability problem by entrapping flux inside the vias. This flux is highly corrosive & will damage the PCBA & cause a failure.
Can those via holes and pads fill with solder paste?


texts: Compensating for power loss through resistor in high/low pass filter circuit?

texts:
Circuit design of a Low-pass filter borrowed from Wikipedia Article on the subject:

Circuit design of a High-pass filter borrowed from Wikipedia Article on the subject:

I'm thinking of implementing an electronic filter Circuit that will pass certain frequencies and attenuate others. It is for the purpose of adding an effect to an audio signal. I notice that such a circuit uses resistors to function. My question is, will there be a reduction in amplitude to the signal after it passes through the Circuit, and is this strictly desirable?

If not, is there a way to actively compensate for this loss with some sort of amplifier that operates proportionally to the resistance in the Circuit?
Is this perhaps what "First order active Low/High-pass filter Circuits" do, using op amps?

Additionally, if I were to implement the resistor as a potentiometer, what should I research in order to actively 'measure' the current resistance in the resistor and amplify proportionally?


texts: My homemade variable power supply burns potentiometer

texts:
I have designed my Power supply using this schematic
And this is my pcb

Everything is connected right but the potintemeter burned twice

Onething i am suspicious of are the parts
C1 1000uf 35v,
C2 0.1uf,
C3 470uf 35v,
C4 10uf 35v but unfortunately I couldn't find it 35v so i bought 10uf 50v which i think is the problem

Is the Pcb okay and if so what is the problem causing the potentiometer to burn ?


texts: What is the PIC micro controller naming scheme?

texts:
I've been dealing with the PIC micro controller for a while and as the question says I want to understand the naming scheme for each PIC line (8- 16- and 32-bit PIC).
For example what is the difference between
PIC24FJ128GA010 and
PIC24FJ256GB110

and the numbers in pic32mx795f512l what do they mean ?


texts: How is damage by pulling sideways usually addressed in connectors?

texts:
Looks like the primary goal of Magsafe is to prevent damage to the connector (both the mobile part and device-attached part) from pulling the connector sideways. Wikipedia cites a patent issued in 2007.

That puzzles me. Isn't the problem at least several decades old? For example, Micro-USB seems to be designed for mobile devices and is super tiny and it's a result of many years of connectors evolution, so I guess the problem of pulling sideways should have been addressed there.

What are typical ways to mitigate risk of pulling sideways in connectors design?


texts:
I'd like to drive the XTAL input to a chip with a logic signal (3V3, 32kHz square) instead of using a real crystal. In general, is this okay, or does the signal need to be filtered/attenuated? At the electrical level, are there any particular things that need to be considered?

(In particular, the chip whose XTAL input I'd like to drive is a Bosch BNO055.)


texts:
Continuing along on my PIC32 adventure, and using my PIC32MX210F016B.   I have some configuration data for another IC that I have to program over SPI.   I want to store that confurgation data, about 2K in the PIC flash.   I'm not to clear how to do that though.  I was trying to find some documentation or example about it.

In TI land for an MSP430 I remember I had to specify the flash page I was going to use in the memory map and then CC studio kept erasing it every time I reloaded code.

I feel like since this is static maybe I can declare it in my code, I just don't want it to end up trying to take up 2k of ram.

Any advice or references on the best way to accomplish this?


texts:
I want to use Multiple Bit Error Detection and I have read a lot of sites but no one shows how to implement it using code and how the receiver performs the error correction to the received data.

The most important part is this Error Detection code needs to detect and correct the error. Just like Hamming Code, but for multiple bits.

Can anyone help, with providing books or any form of information that will help me to write up a program?


texts:
I Recently started building a SEPIC converter using the TL494 and a BJT-based MOSFET gate drive circuit. When testing the gate drive circuit, I noticed something peculiar. I tested the gate drive circuit in this manner:

And this was the waveform at the gate of the MOSFET (yellow: Vgs; green: Vds):

Needless to say, its hideous. So I did some measurements and came to the conclusion (which I later found was incorrect) that the BJT Q10 was at fault. So I obviously replaced the transistor with what I thought was a 2n3904, but was actually a BS170. The waveform at the gate then became acceptable:

Once I realized that it was a BS170, I replaced it with another 2n3904, but the gate drive voltage was just as bad as it was the first time. I retested the circuit with another 2n3904, but I got the same result. The gate drive circuit worked perfectly with Q10 being the BS170, but not the 2n3904. I'd like to know why.
PS I removed the main MOSFET Q4 and tested the unloaded gate drive circuit with the 2n3904 again, and it spat out a beautiful square wave. When I loaded the driver with a MOSFET, the output collapsed again. It seems that this circuit only works with a small signal MOSFET as Q10 for some reason. Also, an LTspice simulation showed that the gate drive circuit works with the BJT as Q10, but it doesn't on the breadboard!


texts: How to protect long (low voltage) cables from EMI?

texts:
I'm designing a new product that will have a uC board in a plastic box, powered by a 12V mains adapter. I'm choosing to use a COTS adapter rather than designing a mains device to reduce certification issues.

On the main (uC) PCB, there will be a 5V regulator powering just the uC, and there will be connectors for three types of external devices. The tree devices are; a 5V sensor, a 12V actuator, and a toggle switch.

The 5V sensor will have its own regulator on the main PCB, and connect to 2 digital inputs on the uC, the 12V actuator will be powered from the 12V adapter via a relay or MOSFET on the PCB, and the toggle switch will be connected to ground and a digital input of the uC.

The sensor is likely to be on a cable less than 2m long, the actuator will probably be on a cable between 2m and 8m long, and the toggle switch will be on a cable between 8m and 20m long.

I have not really got any experience of designing system with long cables, and would like to understand how to design and implement this system to minimise the likelihood of incorrect readings of the toggle switch and sensor due to EMI on the cables.

The type of connector that I would ideally like to use would be 3.5mm jack plugs, and I have identified some cable that I think may be suitable. I am trying to keep the cost per meter of cable down to a reasonable price (<£1/m)

https://www.cse-distributors.co.uk/acatalog/CY-Flexible-Control-Cable---3-Core-1mm2-CY_3C_1.html#SID=174

My assumption is that with the above type of cable, (for the 5V sensor) I can use one core for the 5V power line, two cores for the digital signals, and the shielding for the 0V reference? Is this correct, and will this help to reduce EMI from affecting the integrity of my signals?

For the toggle switch, I assume I can use a single core shielded cable, and use the shielding as the 0V? Is this correct?

What about the actuator, can I also use single core for 12V and shielding for 0V?

I assume that it would be beneficial to use strong pull-ups for each of the digital inputs I am using (~200Ohm?). And that I should place capacitors between 0V and input signals on the main PCB? What values might these need to be?

For the toggle switch, perhaps I would also need a ferrite bead around the cable? At the PCB end? Would ferrites be useful for the other cables?

An example of the setup that I may have is, 12V 2A mains adapter, powering my uC board in a plastic box. a 4-pin jack cable (2m long) connecting to a rotary encoder with 2 digital lines pulsing < 100Hz, a (2pin jack) 5m cable connecting to a maglock (12V <200mA), and a 2-pin jack, 15m cable connecting to a toggle switch in another room.

The maglock would normally be locked, moving the rotary encoder to a particular position would cause the maglock to be unlocked, or closing the toggle switch would also cause the maglock to unlock.

There may be multiple of these systems in one room. There is no high powered machinery nearby, standard mains equipment may be present in the room, and there may be maglocks deactivating/activating periodically.

So my questions are?

In such an environment, what types of EMI would cables of the lengths I describes be likely to pick up?

Is the use of internal cores of shielded cable for power and signals, and the shielding for 0V (connected at both ends) suitable? Will this reduce EMI and likelihood of incorrect values on signal lines?

What interface should I provide on the uC side? e.g. capators between signal and 0V, strong pull-ups, etc.? Should I use these, is there anything else that I should use?

Are ferrite beads suitable for putting on any or all of my cables in this situation? Do I need them at both ends, one end, or not at all?

If ferrite beads are necessary, how might I choose appropriate spec?

Are there any other sources of interference that may be likely to cause me problems?

Should I be 'seperating' ground planes on the main PCB. If so how?

Is there any other general good-practice advice for designing such a system?

Thanks.


texts: Can I use more than one antenna with a radio module (say rfm69) and switch between those antennas electronically, say by a transistor

texts:
I need to know the approximate direction of the radio signal coming to my module, and I have to use very simple hardware and software for this. (Just a microcontroller and one module)

What came up to my mind was using more than one directional antenna with the module, each looking at a different direction, and have a rough idea of where the signal is coming from, by comparing the RSSI of the arriving signal for different antennas.

Is this possible? If so, how can the module switch between different antennas without using mechanical means?


texts:
I am trying to put together a power circuit which will take a 24vAC supply to the following DC supplies.

+24vDC (700mA) - Powering DC relays and OpAmps.
+5vDC (500mA) - Powering MCU, Ethernet etc.
+3.3vDC (150mA) - Powering MCU.

I'm thinking of using the following setup

24vAC -> Bridge Rectifier -> 24v MC78M24BTG Linear Regulator ->
                          -> 5v LM2596 Switching Regulator -> 3.3v LM317 LDO ->.

Is this the best way forward for my application?


texts: Without converting the secondary side to "Y", how would one solve this question?

texts:
The question:

"A three-phase 230 V, 27 kVA, 0.9 PF (lagging) load is supplied by three 10 kVA, 1330/230 V, 60 Hz transformers connected in Y-Δ by means of a common three-phase feeder whose impedance is  0.003+j0.015 Ω per phase. The transformers are supplied from a three-phase source through a three-phase feeder whose impedance is 0.8+j5 Ω per phase. The equivalent impedance of one transformer referred to the low-voltage side is 0.12+ j0.25 Ω. Determine the required supply voltage if the load voltage is 230 V."

The way I did this was to first define the load as a delta load, so that each load takes 27000/sqrt(3) VA.  Then, through KVL, the line currents can be found.  From the line currents, it's just a matter of working backwards by multiplying the line current by two times the line impedance and one times the transformer impedance.  Then, this voltage would be transformed to the primary side (along with the current) in order to find the input voltage (line-to-neutral);  this would then be multiplied by sqrt(3) to get the line-to-line input voltage.

However, my answer is wrong, and I'm not sure why (I believe it has to do with the line currents)...

If somebody could help me work this out, it'd be mighty appreciated.

Regards


texts:
I'm implementing a read-only I2C slave on a PIC18F4620. I have made a -working- ISR handler for the MSSP module:

unsigned char dataFromMaster;

unsigned char SSPISR(void) {
    unsigned char temp = SSPSTAT & 0x2d;
    if ((temp ^ 0x09) == 0x00) {
        // State 1: write operation, last byte was address
        ReadI2C();
        return 1;
    } else if ((temp ^ 0x29) == 0x00) {
        // State 2: write operation, last byte was data
        dataFromMaster = ReadI2C();
        return 2;
    } else if (((temp & 0x2c) ^ 0x0c) == 0x00) {
        // State 3: read operation, last byte was address
        WriteI2C(0x00);
        return 3;
    } else if (!SSPCON1bits.CKP) {
        // State 4: read operation, last byte was data
        WriteI2C(0x00);
        return 4;
    } else {
        // State 5: slave logic reset by NACK from master
        return 5;
    }
}

This is just a port to C from a part of the ASM code in appendix B of AN734.

In my main loop, I'm checking if there is new data, like this:

void main(void) {
    if (dataFromMaster != 0x00) {
        doSomething(dataFromMaster);
        dataFromMaster = 0x00;
    }
}

This gives a problem when the master sends bytes very fast, and new data comes in before the main loop gets to doSomething. I therefore want to implement a buffer where data from the master is stored. I need a 16-char null-terminated array (the null won't be used as a command for the slave). The ISR has to write new data to that array, and the main loop should read it from the array in the order it was received, and clear the array.

I have no idea how to implement this. Do you?


texts: How to find pinout of DC geared motor with encoder?

texts:
I have a DC geared motor with 1 hall effect encoder and I'd like to find the pinout to use it.
Unfortunately I don't have the data sheet and since all motors have different pinout, the only option I have is to find it via multimeter.
I know the ground pin, but don't know which ones are Motor A B, +5V, and encoder output.
Is there a way? Thanks!
Edit: Adding photos of the motor

Edit2: Diode and resistance readings between Gnd Blue and Orange pin(5V and encoder output, which is which unknown)
gnd to blue: connected, 662ohms
blue to gnd: not connected
gnd to orange: not connected
orange to gnd: connected, 1641ohms
blue to orange: not connected
orange to blue: not connected


texts: Help understanding the contact ratings in a Schneider electric Zelio relay specification

texts:
I'm struggling to find clarity on some of the listed specs of a relay, in particular the difference between all the voltage terminologies used i.e. nominal  voltage, coil voltage, contact voltage, switching voltage, control circuit voltage etc.

My understanding is as follows (please correct me if I'm wrong):

Nominal voltage = coil voltage = supply voltage = input voltage
Contact voltage = secondary voltage = switching voltage = control circuit voltage = output voltage
The voltage listed in the name of a relay (like below) is the output voltage

If my understanding is correct then my confusion comes from when the relay such as the relay above is labelled a 24VDC relay, but then its maximum switching voltage is listed as 30VDC and its rated operational current is listed as 5A @ 30VDC as can be observed here

The reason for my concern is that I'm trying to power a 24VDC solenoid valve with this relay, but I don't want to be switching 30VDC to the solenoid valve as it's only rated at 24VDC. Therefore, if someone could help clear this up for me it would be much appreciated. Thanks


texts:
I have been trying to understand why the following astable multivibrator works, but I've hit a wall.  Before I explain what's confusing me, I should mention that I don't have a background in electronics (though I'm trying to learn). My knowledge of electronics does include the following, though: (a) I know KCL/KVL, (b) I can set up and solve the differential equation that describes the voltage across a capacitor in a series RC circuit, and (c) I know that npn transistors act as closed switches if \$V_{BE} >= 0.6V\$.
The most useful explanation of the circuit that I've run across so far is this website.  Ray's website helped me understand that we're basically dealing with two RC circuits, and the oscillation is driven each time by a capacitor turning on a transistor (when that transistor's base-emitter voltage crosses the 0.6V threshold), which induces a negative voltage across the opposite transistor's base-emitter junction and turns off that transistor.  (That's my best rough description of the mechanism at play, anyway.)
A few things are still confusing me, though:
(1) I still don't fully understand the bit about a transistor turning on inducing a negative voltage.  Is there a simple way to set this up with KVL/KCL or something along those lines to see this mathematically?
(2) One reason I've struggled with this circuit is that I feel like I should be able to write down some equations to fully describe this circuit, which I can then try to solve.  Is there a simple way to do that here?  Ray's page talks about the differential equation governing a series RC circuit, which I understand, but I don't get how that applies straightforwardly here. Don't we need to take into account all of the voltages and currents in the circuit here?  I guess I just don't get why we can zoom in on one sub-RC circuit and analyze that.
Any help would be greatly appreciated!


texts: How to derive an exact 10Hz clock from the generated clock?

texts:
How do I go about getting an exact (or as close as possible) 10Hz clock from the generated clock? The master is 100MHz. I have used this 32-bit register to make a clock as close as possible to 10kHz which is done by toggling the output when bit 13 is set. LED is my generated clk which of course is just contantly on at that rate, but I plan on changing the output LED to the 10Hz clock, and verifying on an o-scope.
module Clock_Divider(
input clk,
output reg LED
    );

reg [31:0]big_reg = 32'h0000_0000;
    always @ (posedge clk)
        begin
            if (big_reg[13] == 1'b1)
                begin big_reg <= 32'h0000_0000;
                    LED <= ~LED;
                end
            else
                big_reg <= big_reg + 1'b1;
        end
endmodule


texts:
I made a PCB with several capacitive pads to be read by IQS127.

They work, but any material I put close to the PCB surface will trigger the output, even the 8 mm glass I'm going to use.

The pads diameters is 20 mm, no copper below nor aside (just the traces needed for IQS127).

The problem is just too much sensitivity or perhaps there are some other serious mistakes in the design?

EDIT:
Added schematic and layout.


texts: What are my less expensive options for getting started with CPLDs

texts:
I would like to goof around with some CPLD stuff and I see I have a couple options out there. I don't have a particular application in mind; it just seems like there a lot of possibilities, some of which are easier to use than others.

The main manufactures have development boards, some more expensive than others. They also have programmer cables that generally seem... not cheap. Doing some digging, I've come across several options and I'm looking to understand the pros/cons of each.

Is it fair to say that CPLDs with X Macrocells are more or less the same?
Although the JTAG interface is standard, for the purposes of programming the part, there is no standard previous JTAG Question. Is this a matter of the vendor software talking to the programmer? Do things become more standard if I use some other utility to dump a binary file?
Some of the platforms have cheaper alternatives. I'm wondering what the catches are with these in terms of USB/parallel port, Linux/Windows.
Assuming I get comfortable with a development board, how difficult is the transition to
just using one of the base parts directly? My impression is that in the major options, it's just a matter of some header pins and a couple diodes/resistors. Am I far off on this?
How would I program the devices in my own designs? If I have a development board or starter kit, will I then have to go back and buy an expensive programmer? Why does a dev board sell for cheap but the programmer runs hundreds of dollars? Presumably the dev board comes with the ability to program.

Here are some of the options that stand out for me. I list the prices only to differentiate them from the multi-hundred-dollar options. All of them are in the ballpark for me. I'm looking for the hiden costs in terms of ease of use, software issues and so on.

Xilinx is a popular path. I could do:

Digilent C-Mod board for $17:
http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,400,798&Prod=CMOD
and one of their programming cables (parallel for $12 or USB  for $48)
http://www.digilentinc.com/Products/Catalog.cfm?NavPath=2,395&Cat=5

The Digilent cable requires using their software which is currently windows only, so I'd need to go the $48 USB route.

Another Xilinx possibility is

a Bus Pirate board ($28)
http://www.seeedstudio.com/depot/bus-pirate-v3-assembled-p-609.html?cPath=61_68
and a Coolrunner development board ($15)
http://www.seeedstudio.com/depot/xc9572xl-cpld-development-board-p-799.html?cPath=174

Switching companies to Lattice:

they have a breakout board development kit ($29)
http://www.latticesemi.com/products/developmenthardware/breakoutboardevalkits.cfm

I like the idea of using Lattice parts as Mouser.com carries them (I don't see much Xilinx there). I tend to order more from them. Once I get comfortable with their stuff, I'm guessing that I could hack up a programmer cable based on the schematics of this board. It looks really straight forward. Could I use the eval board as a programmer? The do expose the JTAG header?

The Lattice MachXO2 Pico kit ($29) also looks to be a great value, though the part that it's showcasing is more expensive.

Altera also has good offerings.

A programmer can be had from EBay for ($15)
A demo board can be had from EBay for ($28)

Alternately, Altera has

A starter kit for ($50)

Which of these is the better route for a beginner that is easier to get working (drivers and such), has some staying power, and perhaps offers the most flexibility?


texts:
I'm trying to connect an ADC with an FPGA via JESD, but I'm not able to set a relevant parameter on in. Here is the link of the datasheet, where in the page 92 there are several parameters. In order to configure some of them, in the page 28 of the same datasheet, there is the description of which address corresponds to each parameter. Anyway, the Number of samples per convertor per frame cycle is a parameter that I need to modify (also named as "S" in the datasheet), but I can't. How would it be possible to modify it?

Any help is appreciated!


texts: problem : find the coefficients of linear system used to build a digital oscillator ..?

texts:
Please can one explain to me

I having difficulty on how to start

Thank you all

*** can anyone correct me if anything is wrong !


texts: Amplify signal with extremely low S/N-ratio

texts:
Is it possible electronically to amplify an expected signal with a S/N close to 1, or 1? If yes, how? I already tried to use an Lock-In-Amplifier, but that was not useful after the noise itself is also chopped. Are there other possibilities?
Clarification: I have a photo multiplier tube which detects reflected light (shape is depending on sample which reflects light). The noise is the dark current. If I reduce the light on the sample, the dark current goes down, but so does the signal. If I reduce the amount of reflected light by slits, both signals are also going down. The dark current is random, and therefore not predictable.
Concerning the signal itself: I do not know where I can expect the signal, and I do not know the shape of the signal.


texts: What is the max current consumption on bus side of isolated RS485?

texts:
application -
10 nodes 1 meter apart
120 Ohm terminating resistors at last node and 1st node
i hope to use ADM2486
data rate 10-17Mbps
vdd1 5V and isolated vdd2 5V
what is the max current consumption on vdd2 side is it 58mA at 20Mbps?


texts:
So, one thing I've been reading about is Sparkfun's tutorial on transistors,focusing on BJT (specifically NPN, but a bit into PNP). I'm super new to transistors and such, so please bear with me.

https://learn.sparkfun.com/tutorials/transistors

Looking at the switch applications they all utilize an Arduino to provide control at the Base (LO/HI (0V/5V)).The first circuit concerns controlling an LED  in the framework presented for Saturation mode ("On") and Cutoff mode ("Off"). Vc  is at 5V.

VE > VB < VC; Drive the Arduino pin low, the transistor will be in Cutoff mode.
VE < VB > VC; Drive the Arduino pin Hi,  the transistor will be in Sat mode.

However, if VB = 5v, and Vc is 5V, wouldn't that violate the condition that Vb > Vc?
Ve < Vb checks out, because Ve is on the GND side of the circuit.

They only mention that Vb has to be above a certain Vth to saturate the transistor (this part makes sense in that Vb - Ve > Vth), but leave out Vb > Vc.

Is it because Vc isn't really at 5V then due to voltage drops from the resistor and LED BEFORE the collector terminal???


texts: Maximum voltage and current input of this circuit?

texts:
I am looking to assemble a power supply with an output of roughly 600 watts. One of the components required for such an apparatus is a 40 kVDC, 20 mA flyback transformer that I managed to find and hack in order to work for this specific purpose. I noticed that in this process, many people were calling for a transistor based circuit that seemed to be for transformer feedback. This was the circuit that I was considering:

https://qph.fs.quoracdn.net/main-qimg-b6b61f0253f7c878d9e9a8507053aa42-c

Thus, I was first of all curious if such a circuit would be required for the flyback. If so, I was also curious if the shown parts and their descriptions would be capable of withstanding an input of 60 VDC and 10 A. Thank you.


texts:
Photovoltaic panels can have 20 or 25 year underwritten warranties with a guaranteed remaining efficiency of 80 % of the new panel. That means, that photovoltaic panels seem to degrade somehow.

Why do they degrade? What exactly is reducing their efficiency?
How can this process of degrading be slowed down? E.g. if you don’t need your PV panels, is it possible to conserve them by covering them with a black, opaque coverage like tarp? If not, what else?


texts:
Further to my previous question, I also noticed that the crystal there was a 12MHz where this should have been 6MHz (due to an inventory error - the wrong part was fitted).  I've removed the 12MHz crystal and fitted a 6Mhz crystal using a hot air tool but now it doesn't oscillate.  It kind of looks like it's trying - the scope shows a fair bit of noise and occasional flashes of what looks like about 6MHz waves but it doesn't oscillate stably.

This is the datasheet for the 12MHz crystal that produced a stable sine wave and this is the datasheet for the 6MHz crystal that doesn't.

As far as I can see, the major difference is that the 12Mhz crystal has 40 ohm ESR while the 6MHz crystal has 80 ohm ESR.  As far as I can tell, my rework hasn't damaged anything - the load caps and series resistance are still doing the right things - but it's a bit hard to tell if I've damaged the crystal or the IC.

What is my most likely problem here?  Is the higher ESR of the lower-frequency crystal likely to be a problem?  Or is it more likely that I have damaged a component with my rework?

The crystal has a 1.5k resistor in series with it (cribbed from the TUSB2046B reference design).  I'm tempted to short this out to try to reduce the losses in the oscillator and see if that improves things - is this a useful thing to try?


texts: Saturating magnetic field in an inductor without heating

texts:
I am building an RL series circuit with a toroidal inductor that I am winding on my own. The toroid is made of steel (low carbon, I believe, but not 100% sure) and has about 280 turns of 22 gauge wire. The inner diameter of the toroid is 4.25 in. and the outer diameter is about 5.25 in. The resistor is 0.6 ohms. The circuit is diagrammed below.

simulate this circuit – Schematic created using CircuitLab

I know that according to Maxwell's equations,
$$\mathbf{B}=\mu(\mathbf{H} + \mathbf{M})$$
where B is the magnetic flux density in Teslas, \$\mu\$ is the permeability of the material, H is the magnetic field strength in Henries/meter, and M is the magnetization of the material in Henries/meter. Note that
$$\mu = \mu_0\mu_r$$
where \$\mu_0\$ is the permeability of free space and \$\mu_r\$ is the relative permeability of steel, which I take to be about 1000 at DC. I also know that, in ferromagnetic materials, permeability is a function of the frequency of the input signal as well as of the magnitude of H (link 1, link 2).

A few questions:

How can I calculate/experimentally determine the minimum voltage/current with which I need to drive the circuit in order to saturate the magnetic flux density inside the toroid? I want to be able to run an AC signal (< 100 Hz) through my circuit for several minutes such that the magnetic field reaches saturation but without causing the circuit to overheat.
Is it possible to apply such a high voltage/current that the relative permeability decays to 1? If so, does this mean that at very high voltages, the field wouldn't saturate since the permeability is too low?


texts: What types of mechanical switches are appropriate for a 200 V DC 20 mA circuit

texts:
I have looked at many switches, most recently I considered snap action switches (micro switches). What I prefer to use is a PCB mounted switch, but I cannot find any that can tolerate the V DC ratings requirements.

What are some other options I should consider?

Or is it not a big problem to use a switch rated for 250 V AC in a DC circuit, especially if the number of times the switch will be actuated with an energized circuit is low (few dozen)?

For example, this D2S-10L13D...datasheet. It is rated at 250 VAC 10 A.

Also, will two switches in series allow for double the switching voltage capacity?


texts:
Is there a standardized female DC jack designed to provide power, much like AC female wall outlets? Typically devices that require a DC power input are powered by individual external power supplies (like wall-warts) with hardwired cables that can plug into the load device. I'd like to build a DC bus that is powered by one large power supply and offers multiple female DC jacks so each device requires only a cable (ie. a DC analog to the C13 to NEMA 5 cables used to power many AC devices) and not its own external power supply.

Is there a connector designed for this? Of course a female barrel jack would work, but that seems like a very bad idea because: 1.) the live center pin would be exposed and 2.) it breaks the standard convention of female barrel jacks as inputs and invites someone to connect a second power supply to the jack.


texts:
I am trying to solve following problem which I try to find the signal is periodic or not.

However, as it is different from traditional examples I do not know how to solve it. Can you please give me clues or solve it?


texts: How do I solve for Capacitance in this circuit?

texts:
I know that the equivalent resistance of this circuit will be

$$R_1-j/(\omega*C_x)+L_1+(R_2-C_1)||L_2$$
$$(3+.814j)-j/(4737*C_x)+[(4j)(30-8j)]/(30-4j)$$

I don't know what to do from here; I could set the top equation equal to Z, but Z is not given. I think I have to use the power factor given, but I have no idea what to do with it. Can someone tell me how power factor comes into all of this?


texts: I'm a software developer (C, C++, objective-c, java ...) and I am interested in learning to program FPGAs. Now the question may appear simple to you but please do take time to help me on this one as I'm kind of stuck right now. My company has asked me to get familiar with the technology and work on a lattice product. My question is where to start? After some research I found that I could choose between VHDL and Verilog, I have never used any of them. Is there any specialist who could suggest me where should I begin? Learn a language, learn about the hardware components and then lattice product? Or directly start with Lattice product (as I read that programming methods are very different between FPGA vendors)?


texts: Can a Single Supply Powered Op-Amp Handle Negative Input Voltage?

texts:
I have an input sine wave at 300mV peak to peak. I want to filter this sine wave to eliminate noise and distortion.

I am planning to use the LMx58-N op-amp family, powered using a single supply: 3V to 32V.

Circuitry proposed will be based on the Multiple-Feedback Topology, as shown:

Considering the input signal to be at 100kHz +-10%, I want the filter to work adequately and without any damage to the op-amp. I also want to adhere to good electronic design principles.

Can I pass the signal directly into the above circuit, or should I bias the input signal ?

Any tips and/or suggestions would be greatly appreciated.


texts: Resistance between data/Addr pins and GND ranges from 1k to 1M, is this normal?

texts:
After soldering a 132-pin surface mount DSP, I checked if there are short circuits or not using "GreenLee DM-110" multimeter. I found that the resistance between data or address pins and GND ranges from ~1K Ohm to 1M Ohm.

I know that I should measure an open circuit or several (hundreds!) mega ohms. Why is the resistance too low? Can this cause any danger to DSP operation?


texts: Looking for simulation corner model of 230VAC lines

texts:
I'm searching some sort of worst case model of the main electricity 230V-AC.
The most simple source is a sine with 50Hz and 325V peak.

But we could have disturbance on the main electricity, and I'm also interested to know if there is a sort of list with "corner model" that can happen?

I can give one disturbance case: Imagine a high power load controlled by a triac (that switch on/off properly at 0 current/voltage). Because the line have a resistance and an inductance, the switch on/off of a high power load will have an impact on the main electricity voltage (325V could become 320V or worst?). If this load is connected an odd number of times, then the injected disturbance will generate a sort of DC voltage/current on all transformer connected on the main electricity line. I want to simulate this with LTspice.

After my example, is there a database of corner model (with this type of disturbance) that can happen on the 230V-AC? A sort of international standard where all tools connected on electrical outlet should pass?


texts:
simulate this circuit – Schematic created using CircuitLab

I'm using this circuit to detect if a car engine is running. I tested it and it is working however there is some kind of a problem where in my code (running raspberry pi) I see a lot of interrupts regardless of whether the output is high or low. I don't have a scope to tell an exact number but by eyeballing it I can say it's well above the hundreds if not thousands of hertz. My pi blew up like 10 to 15 minutes in after I hooked this part of the circuit and I'm guessing this has something to do with it. Then again there's always the possibility I accidentally shorted something but I'd be thankful if someone with a better understanding can have a look at this before I blow up another Pi.


texts: Is it possible to use Microchip's ZCD (Zero cross detect) circuitry in an isolated SMPS?

texts:
Let's say you have a device which is fed by AC line voltage and features an isolated SMPS. The switcher outputs 5 VDC, and that powers a PIC micro. I'm curious how is the Microchip's ZCD (Zero cross detection) module supposed to work here? In the technical brief (TB3138), they give the following diagram:

However that assumes the AC and the PIC share the same ground, which is not the case. Probably they assume the PC will be on the non-isolated side, or that the isolation would be a 50/60 Hz transformer. I've searched Microchip's app notes on this topic, and I couldn't find any mention of this scenario.

Any ideas about how to interface the AC to the ZCD pin, is it even feasible?

(And yes, I know those opto-couplers cost pennies).


texts:
I'm trying to implement a XY table using 4 units of these motorized potentiometer, controlled by an Arduino. Since I have other uses in mind, I'd like to use as few pins as possible, wich would imply multiplexing both motor control and potentiometer reading.

I assume I could use a 4:1 multiplexer to use the potentiometer in a feedback loop, but how exactly could I multiplex the motors? I am planning to use 4 H-bridges to drive each motor, but even assuming I don't want to control movement speed I would need 8 pins (enable + direction). Can I achieve that with a shift register?

On the other hand, what gain could a XY table possibly have by controlling the speed of the motors (either all of them or individually)? Would I get more precision/resolution/speed?


texts: Compiling code for AT91SAM3U and a basic USB stack

texts:
I am about to start working on some small application that has to run on an AT91SAM3U ARM Cortex-M3 processor.

What good tool suite / development kit should I use?
Is it possible to find code for a basic USB stack which allows EP links for sending control and bulk transfers using a driver we develop using libusb?


texts: How to associate multiple symbols with one footprint in KiCad

texts:
I made a schematic for a 5 band analog EQ. I used OP Amps to make active bandpass filters for various frequencies within the human hearing range which means when I made my schematic I drew 5 OP Amps in total (one for each frequency) as shown here:

The actual IC I'm using for the OP Amps is the LM 833 which actually has two amps inside it per chip:

I made a custom footprint for the LM833 but I want to associate it with two of the OP Amp symbols I made on my schematic so that when I generate the netlist only 3 LM833 ICs are generated and the correct connections are automatically made according to my schematic. How do I do this?


texts:
I am given to understand that there exists software for tuning PID controllers. I haven't had much luck finding references, though. Pros/cons for algorithms, and references for them?

ADDED: I'm specifically looking for a description (scholarly or otherwise) of how automatic tuning software does its job; not references to automatic tuning software or packages. My use case is not "I have a PID control loop I want to automatically tune" but rather, "I wish to write a piece of software to automatically tune PID control loops for particular pieces of hardware, so that others do not have to do the job manually."


texts: when i turn on the circuit, the AND (74LS08) gate keeps sending signal to the 4 outputs, even without signal from the inputs. I may have broken it because i applied 7,5 volts before correcting the circuit voltage.


texts: How do I deploy PIR sensors to track people's entrance and exits of a room?

texts:
I want to deploy sensors to the door to a private room in order to track people's presence in the room. These are the requirements:

sensors must be outside of the door;
it should detect both entrance and exit or whatever it takes to know there are someone in the room;
due to the nature of the room, it can be assured that at most one person will be in the room at one time;
the sensor should be able to communicate with a computer using either wifi or other wireless medium.

It has been pointed out by this post (What sensor to choose to track human presence indoors?) that PIR sensors can be the solution. However, I know very little of electrical engineering. I'd really appreciate it if you could explain this in details, e.g. what components to buy, where I can buy them, how do I collect the sensor data from a laptop using wireless media, etc.

I have a background in computer science, so the actual coding should be less of a problem.


texts: Need help for making differential equations of following excercise

texts:
I've trouble to find correct set of equations to solve in Maple.

My set of equations with all resistors and caps identical:

\$  0 = \frac{V_i}{R} + V_x \times s \times C + \frac{V_0}{R} \$
\$  0 = \frac{V_x}{R} \$
\$  0 = V_o \times s \times C + \frac{V_o}{R} \$

I presume that the second equation is mistaken, can someone help me?


texts: Why don't we measure electrical consumption in joules, instead of kWh? Aren't they the same measurements, but one is more "proper"?


texts: How can i make an always statement run with initial values in verilog

texts:
I am trying to use this MUX in a MIPS Datapath design that i'm trying to create, but since i use an initial for these, they don't change and the always block is never triggered in the first clock, stopping the execution.

module MUX21(A, B, controle, S);
  input[31:0] A, B;
  input controle;
  output reg[31:0] S;

  always@(A or B or controle)
    begin
      case(controle)
        0: S <= A;
        1: S <= B;
      endcase
    end

endmodule

My question is, is there a way to trigger the always block in the first clock without changing the values?


texts: Calculate op-amp input voltage with potential divider and series resistor

texts:
I have managed to confuse myself when it comes to calculating the voltage drop over a series resistor connected to a potential divider (See below):

The op amp non-inverting input is connected to a 20K resistor which is then connected to the output of a voltage divider (Top resistor is 56K, bottom is 7K). The input voltage to the potential divider is 12V.

I would like to calculate the voltage "seen" by the op amp (set as a voltage buffer) on its non-inverting input (in this case pin 3).

The input resistance for an ideal op amp should be infinite, however in practise there is a very minute input leakage current. This gives me the following questions:

1) Is the resistance "seen" on the potential divider output branch, equal to the sum of the op amp input resistance and 20k resistor? Or would it be equal to the equivalent parallel resistance of 7k||20k+op amp input resistance?

2) As the input resistance of the comparator is very high, (and I don't have specific values for it) could I somehow calculate the potential divider output voltage drops over the 20k resistor and op amp without calculating current draw?

3) Related to the previous questions, can I "split" the problem into two parts? i.e Calculate the potential divider output voltage and then calculate the voltage drop over the 20k resistor and op amp?

4) Would an equivalent circuit without the op amp (i.e 20k resistor is left floating on one side) help me calculate the voltage drop over the 20k resistor?

Thank you for your help- I've been driving myself mad for days with this problem...


texts:
Hello I am looking for an M-bus level converter. It has to support rs232 for hooking it up to a raspi. I have 5 slaves so 20 unit loads should be sufficient. I am not able to find a suitable product on the internet which costs max. 100 euros. Has anyone a hint or a link?
This is what I found in another question here. But I don't know if they sell to private customers.


texts:
I have a problem with this "knock sensor". Piezo disc is glued to a wooden surface and it's signal is amplified by a factor of k=1M2/51k + 1 and then compared to a reference voltage on R12 using comparator.

Both op amp and comparator are in the same package, in this case LPV802.

The problem is I don't ever get high output at RB0.
I suspected that maybe 1M2 for R12 is too big so I put fixed voltage divider using 10k resistors so I have 2,5V fixed voltage reference at comparator.

I measured expected output voltage from the first op amp, in the range from 0V to 3-4V depending on the force on piezo but when that 3-4V is compared to the 2,5V reference I don't get high voltage, I only get cca. 100mV when "knocking" and around 20mV when not.

I also tried combination of R11 and R10, 600k - 51k, and 600k - 25,5k.
Also I replaced LPV802 dual op amp with some other opamp that are both input and output rail to rail like MCP6002 and MCP6232 but the behaviour is identical.

Zener diode is here to limit the piezo voltage to around 4,7V and it tested OK.

Also, I now know that I should have used separate comparator IC rather than op-amp but the PCB is already made and as I don't need very high speeds I don't think that should be a problem here.

Does anybody have a clue what might cause this strange behaviour?


texts:
I have to install a 1500W single phase motor 200m away from the main supply.
I have a question about how to make an earth connection to the motor.
Is it ok to earth the motor chassis with a grounding rod at the motor location itself instead of laying a 200m 10sqsmm earth cable to connect the motor chassis to the main ground rod at the main supply to save the earth cable cost?
Thank you


texts:
In my neighborhood, this Antenna setup is installed. I think that this is LTE/4G Antenna. What do we call the objects encircled in 3 colors in the picture given below.

I believe that the objects encircled by Blue and Green colors are Antennas and Object encircled in Red color is some control panel having wires going inside it.

Please identify the names of these Antenna.