texts:
Regarding something I read in a Xilinx manual saying this:

  Because floating-point operations use considerable resources relative to integer/fixed point operations, the Vivado HLS tool utilizes those resources as efficiently as possible.

I was thinking about the following option:

If that is true about floating-point cores utilizing more resources, why can't we convert every float we have to u32 with a union like this:

union converter{
     float f32;
     unsigned int u32;
}

do the operations always with the u32 and then in the end convert everything back to float?

I saw some examples of people doing this in really small designs, but never in big ones with lots of float operations.


texts: How this current mirror act as a replacement to resistor Rc?

texts:
In this differential amplifier:

The PNP transistor Q6 acts as an active load resistor and as a current mirror. Since current source Q6 has nearly infinite impedance, we will be able to have very large voltage gain Rc/r'e in which Q6 is the Rc.
However, intuitively speaking, I don't get how this current source will generate large gain.
For example, if v1(noninverting input) is at its negative peak, current passing through diode Q5 will decrease and this decrease in current will be mirrored to Q6. At the same time, Q2 collector current is increasing. How will that generate a negative peak AC voltage at Q2?
I mean, the Q6 has only a voltage drop of Vce at that point, and I believe that won't be a sufficient drop to decrease the Vout to its negative peak. Just how does this current source act as a replacement to a normal resistor RC?


texts: Any clue? Or is it just there for better visual?


texts: amplifying 555 astable multivibrator output

texts:
I am using  555 as astable  multi-vibrator and its output is a square wave of 7 V and frequency is around 800 kilo hertz.But i need to increase the voltage to about  40 V . What should i do?
Actually ,i want to make a wireless power transmission system.So i need to give the square wave signal(amplified) from output of 555 to a circular loop made of copper wire and generate emi in a secondary coil placed at some distance.


texts: RS232 serial output: confusion with wiring

texts:
Brace with me as I am new to electronics, but am also eager to learn. I have a sensor which has 4 un-terminated wires:

1) 12V to 24V

2) RS-232 TxD

3) RS-232 RxD

4) Ground(and serial connector return)

I'm trying to get the sensor and my computer to talk but have faced nothing but failure. I have an RS-232 to TTL converter followed by an RS-232 to USB adapter. Here's where my real question starts. I understand that TTL has VCC, Tx, Rx and GND pins. Can my sensor talk to my computer using only the Tx and Rx wires? From my understanding, the two other wires need to be connected to an external battery since it draws so much power...but that leaves VCC and GND empty on my converter.

I've come to realize this morning that my RS-232 to USB adapter was out of date and not supported on my current version of windows. I have a new one on its way but still feel something is not quite right with my setup. Any help is greatly appreciated.

Thank you!

EDIT: Some extra information about my sensor: Digital output is RS-232 as ASCII chars, runs on 12-24 VDC(30mA@12V), configuration is 115200,8,N,1. I've also come to realize I probably don't need my TTL converter. How then would I communicate with only Rx and Tx? (Also, I know that Tx must go to Rx and vice-versa)


texts: Best way to emulate network switching on PCB

texts:
I'm interested in wiring up some Raspberry Pi Compute Modules together on a custom PCB board with DDR2 SODIMM connector interfaces.

http://www.raspberrypi.org/raspberry-pi-compute-module-new-product/

I want to use the compute modules together in a N-body-type simulation where each module acts as a planet or something and interacts with all other modules via MPI. Ideally each module should be able to asynchronously communicate with any other module in the board without interrupting the processing on the other modules.

What is a good hardware solution to high-bandwidth switching for PCB components connected in this fashion? Normally with standard Raspberry Pis I would use an ethernet switch to route packets between the nodes but I'm not so sure here. Would it be feasible to build switching logic + processors directly into the board (or have several of the compute modules serve as switching logic)?

Some research seems to indicate that Blue Gene node cards (it has a similar design to the tray I am proposing above) are connected via tx+rx 12-channel optical fibers, but I'm not sure if that is what I need, as that seems to be missing some kind of switching capability.

Thanks!


texts: Filtering and Delay Compensation in Matlab and Simulink

texts:
I have built a FSK modulator and demodulator in Simulink.

Everything is working fine except the received signal after the channel has short spikes, which are introducing a short pulses in the regenerator output.

The plot for the graph after the demodulation and regeneration,

My demodulator design is:

My regenerator design is:

AIM: I would like to remove those spikes. Those spikes are introducing delay. Which can be confirmed by comparing them with my input bit stream.

Input bit stream:

The PLL filter parameters are:

I am a beginner in Simulink and I would like to know the ideas that you guys would employ in this situation. I would welcome both Matlab and Simulink solutions.

But as my implementation involves Simulink, it would be great if one guides me in Simulink.

Here is the complete plot of all the blocks output:
1. Input bits
2. Modulator output
3. Channel output
4. Demodulator output
5. regenerator output

I am using the carrier frequencies of 2*pi*8 rad/sec and 2*pi*12 rad/sec.


texts: What happens if I change the value of a coupling capacitor in a tube pre-amp

texts:
I own a Blackheart BH1H amplifier and am considering making modifications to change its sound.

The schematic can be found here

One change I have seen suggested is to change the value of C2 from it's current .022uF value to a much smaller 390pF or 500pF cap.

What effect will reducing the value of that capacitor have on the frequency response of the amplifier? Currently there is too much bass response for my taste, will a smaller cap change that? Can the frequency response be calculated easily?


texts: Transistor Driving Flyback Failing Below Ratings

texts:
I'm fairly new to the world of electronics, and transistors are still a bit confusing to me.  I'm trying to build a flyback transformer driver based on the schematics at http://www.powerlabs.org/images/schematic1.gif and https://youtube.com/watch?v=0jWpQ8HEYgk .  I'm using a 2N3055 transistor rated for up to 15 A on the collector with power dissipation up to 115 W.

At 4 V, the system draws about 2 A and I get several thousand volts out of the flyback, as expected.  The transistor gets a little warm, but not too hot to touch.  As I slowly increase the supply to 6 V, the current draw rises to 3 A and then the flyback suddenly stops outputting any voltage.  When I examine the transistor, it shows only a few ohms of resistance between any pair of pins, which I assume means I killed it.  Replacing the transistor fixes the circuit.  Hooking the circuit up to the 12 V, nominally 2 A laptop supply that I hope to use once I'm done prototyping also causes the transistor to instantly blow.

My question is, what would cause the transistor to die at so much less than its rated specifications?  After reading something about voltage spikes caused by inductance in the transformer, I added a diode from ground to the feedback coil as shown in the video above, but it doesn't seem to help.  These transistors are about $3 apiece, so I'd prefer to go through as few of them as possible.  Any ideas?


texts:
I'm looking for a schematic to control LM317 and LM337 from Arduino via digital Pots MCP42010.
I'd like to build this schematic (input dual 30V, 500mA transformer per coil)

However, with digital pots instead, so it will allow me to control voltage from a microcontroller.
However, I must add opAmp in order to use digital pots and I can do it only for positive voltage

But for negative voltage, I didn't find any schematic yet.
Could anyone post me a link for schematic where could I control LM337 and LM317 at once with digital pots or opAmps?


texts:
I would like to build this:

https://www.youtube.com/watch?v=UjlHtHAN0DU

I.e. a programmable stamp/printer that you slide along a piece of paper. I would like for it to use easily obtainable cartridges, such as HP.

I looked around and found this: http://spritesmods.com/?art=inker&page=1 which is really cool and all, but I would like to better understand and control the cartridge. (The way he discovered how to control the cartridge was to cover some parts with sticky tape and "probe" to see what part does what.)

Does anyone know of some commercially available electronics that allows you to control the cartridges?


texts: What is the purpose of the resistors in this schematic?

texts:
I’m looking into using a CD4021B shift register with an Arduino Uno, and found a schematic online detailing how to use it. However, I am confused as to what the point of the 10kohm resistors is, would the current not just pass straight through from the 5V to the shift register when the switches are closed? To me it seems like the resistors are pointless, however I am rather new to this all so if someone could enlighten me as to their purpose it would be much appreciated.

Schematic:


texts: what is the maximum output voltage from an opamp in general case?

texts:
In general, what is the output voltage that an amplifier (not rail-to-rail output type) can provide,if it is supplied for example Vdd=+24V and Vee=-24V which is the maximum value I can get "for sure" from the output, can it reach +24V and -24V? in datasheets they always mention the minimum and the typical output voltage in some cases but never the maximum one.
http://www.ti.com/lit/ds/symlink/opa2604.pdf


texts: Light sensors sensitive enough to detect for PWM from CF and LEDs?

texts:
I have an extreme sensitivity to PWM light sources such as computer screens and light bulbs. This can make it very challenging to make a purchase as I end up having to do lots of guesswork with cameras and other methods to try and identify whether PWM is present.

Is there a photo sensor that I can use to obtain a sine wave of a light source and calculate its modulation?

There are several apps already available to do this for mobile devices such as this one:

http://www.visosystems.com/products/flicker-tester/

But the reviews suggest that this isn't a reliable testing method due to the range of hardware. There's no guarantee that one phone's sensor will product the same results as another. Different cameras are calibrated differently and have varying degrees of sensitivity.

Is there a light sensor I can use to build a detector like this? It would have to be in the kHz range. The higher the better.


texts: Normally closed SSR won't work with grounding out a magneto's primary to ground

texts:
I've been trying to find a device that will ground out a magneto's coil (primary kill wire) in a normally closed state without using a mechanical relay because I want my circuit to be all solid state.

I began to search for normally closed solid state relays, and thought I found one that would work: Vishay LH1501AB This works fine for keeping a 120V light bulb on until I apply voltage to pins 1 and 2 (LED) of this SSR. Now I tried to do the same on an internal combustion engine, except I put the magneto's grounding wire to pin 6 and then pin 4 went to the block of the engine. No matter what, spinning over the flywheel by hand, the spark plug would still spark (I don't want it to until I apply voltage to the SSR's LED).

I believe this has something to do with the contacts of pin 4 and pin 6 aren't really closed, because there isn't a voltage applied to the SSR's FETs, whereas with my lightbulb experiment, the voltage was present.

I'd appreciate any help to get this working using a normally closed SSR and not a mechanical relay, or any other solutions you may have; I couldn't find a normally closed triac.

Overview pic of what I'm trying to do:


texts:
X: std_logic_vector(3 down to 0);
c : Std_logic;
d : bit;
s : std_logic_vector(1 down to 0);

In architecture

x <= c&d&s;

so is this signal assignment in Architecture is correct or wrong

IS bit and std_logic having same condition and is it possible to assign the same to std_logic_vector as in assignment?


texts: Why non repeated poles at imaginary axis makes LTI system marginally stable?

texts: I understand that stability for an LTI system is defined with respect to Bounded input bounded output condition. However I'm not clear on why non repeated poles on the imaginary axis makes the system marginally stable. For a unit step input, a single pole at origin produces an unbounded ramp output [Unbounded Response] and non repeated conjugate poles on the imaginary axis produces a bounded sinusoidal output [Bounded response]. Then why are both these Marginally stable systems?


texts:
I work with a lot of field equipment in a university lab; much of this equipment requires GPS signal to work properly. Unfortunately, we have zero GPS reception in the lab where we do all the testing. I'm looking for a way to produce a valid (not necessarily accurate) GPS signal in our lab.

I've seen that GPS repeaters are available, but I think it would be an ordeal to install an antenna on the outside of the building and run a cable through the wall to our lab. (It's a university building and they would have to approve this and make it happen...probably not worth the effort/money.)

I was thinking that it should always be possible to simulate a GPS signal for a known location and broadcast it. Does anyone know of any "GPS simulators" that calculate what the GPS signals should be at our lab (or anywhere, really) and broadcasts it in the room?

Or, does anyone have any other ideas?


texts: Easy way to tell if a low power MCU supports external memory?

texts:
Please forgive my ignorance, as am very new to this. I am looking to build a custom PCB and have found several low-power modules with internal MCUs.

Is there an easy/quick way to determine whether these MCUs support external memory? From my research, they tend to have embedded RAM/ROM, but my application will require 4 - 8G.

This chips in particular are:
1. http://www.ti.com/product/cc430f5137
2. http://www.atmel.com/devices/AT90USB1286.aspx

Thank you!


texts:
I tried to make an AC / DC power supply and it worked perfectly fine,by changing the switch it would either provide DC from the middlle wires or AC from the wires on the sides.Here is a picture of the circuit:
diagram1 http://8pic.ir/images/kmwfgdyppyvsex9o1ire.jpg

I wanted to have only two output wires so I added another switch to totally disconnect the capacitor and the bridge rectifier like so:
diagram2 http://8pic.ir/images/3alk4npyh1synwqriomn.jpg

While I switch it to DC it still works just fine.Then I discharged capacitor and changed the switchs positions to AC and powered it up again,this time the diodes started to heat up really fast despite the bridge was disconnected and I also noticed that the capacitor was charged again.

Am I missing something here? Why is there current in the DC part of the circuit and why is there not an AC output? Im a bigginer so please explain in simplest way possible


texts: How to sense touch on a diffusing sheet?

texts:
I want to build a combined diffused light and touch-button around 3x3cm. LEDs could be diffused with e.g. a polycarbonate sheet or diffusing fabric, and touch could be sensed e.g. through capacitive touch sensing.

But how could I combine these two for the same button? I haven't been able to find a diffusing material that is also conductive, which (if I've understood correctly) would be necessary to use capacitive sensing. I could have a tiny copper lead in the middle of the button for touch sensing, but I'd like it to be possible to touch not just in the dead center, but on most of the button.

How could I solve this problem?


texts:
I'm using IRM-30-12 for power supply for my PCB. This SMPS doesn't have an earthing connection pin as it has Class 2 isolation protection.There is an AC potential is generated at the circuit GND which is initially found out by using a tester.
When I'm connecting the earthing pin(The earthing of the supply is left open as I'm using a plastic enclosure)directly to the circuit GND the AC potential is no longer exists. Is it the correct approach?

My question is
1. What might be the cause of the generated AC potential?
2. As I have gone through some possible solutions I have found the following LINK;

I have connected the circuit ground to a metal and again connected the earthing wire to the metal. What impact will it have on my PCB?


texts:
In binary, bitshifting is pretty straight forward for example, a binary number of:

10000001

with a left bit shift of 1 becomes :

00000010

However in Hex, a hex number of:

1051

with a left bitshift of 1 becomes:

20a2

Is there an intuitive way to calculate bitshift in hexdecimal, or is it simply easiest to convert from hex to binary, apply the bitshift, and convert from binary back in to hex decimal?


texts: In jfet, why Vgs is half the cutoff voltage when the source resistor is same as the ohmic resistance of the jfet?

texts: \$R_{DS}\$ is the resistance of jfet in the ohmic region.  When the source resistor is matched to this value,  my textbook seems to say that \$V_{GS}\$ will be half the cutoff/pinchoff voltage. Why is this so?


texts:
I have a charge & a drain circuit connected to a Li-ion cell. As only one circuit can be connected to the cell at a time, I believe I need some diodes. My questions are about when the drain circuit is on and the charge circuit is off.

(In the pic attached, charge circuit on the right, drain circuit on the left.)

As far as i can work out, I only need one diode stopping the battery current flowing back into the charger. Is this correct or are some required at the negative side too?


texts:
Background

I am trying to build a USB Bridge circuit as part of a larger project.
What I mean by that is, I wish to control a parallel out circuit based on information transmitted by the host computer.

Application Details

The idea behind the project is to have a USB powered Nixie Clock. A Nixie Display unit has a high operating voltage of about 150V. The power supply part of the project will take care of stepping up 5V DC (up to 500mA due to USB limit) to 150 V (Vdc), 5mA (0.75W).

We want our initial design to have no onboard clock circuitry, instead, we want the time and date information to come over a server lookup from the USB host computer.

Parallel Pin requirement:

Due to a power limitation, our design will rapidly switch between the 6 Nixie Tubes (HH MM SS) such that only one is lit up at a time. This is where the parallel out requirement stems from.

We need 6 pins to select the tube whose anode is pulled up to Vdc and 10 pins to choose the digit that currently glows. These final outputs can come from a decoder, so there is a net requirement of 3 + 4 parallel out pins going into 2 decoders.

Solution of choice

I am trying to use the FT232R bit bang mode for this task as suggested by in this answer to a question I had asked earlier.

My Question

I am having some trouble going ahead with using the FT232R Bit-Bang mode. I referred to this application note by FTDI on using the Bit Bang mode. The notes mention that to use the synchronous and asynchronous Bit-Bang modes, only the D2XX drivers are required. So I visited this link to download the driver but was unable to do so since the linux 1.4.8 version refused to unzip on my system.

An alternative to the D2XX drivers for FTDI devices is the VCP driver (In built to linux)  so I decided to use that.

Unlike the D2XX driver API which has functions to use the Bit Bang Mode, I could not find an equivalent API for the VCP drivers.

All I could do using the VCP drivers is to toggle individual pins one at a time using the IOCTL() system call of linux.

However, this will not be suitable for my application since I would be at the mercy of the Operating System as to when the toggling occurs. This could lead to unreliable and inconsistent timing which would not be suitable for my application.

Is there such an equivalent API based on VCP drivers that I could use? Feedback on the thought process will be appreciated.


texts: Can we prepare any ICs similar to decoder or demux , but for selecting multiple pins simultaneously?

texts: It is possible to select the output pins sequentially using decoder or demux. But for selecting more than 2 output pins at same time, they don't work as the decoder /demux are single output selector ICs. Can someone suggest as to how to select more than 2 outputs simultaneously? And the factor of limitation being that it should be compatible with Arduino or similar Microcontrollers.


texts: Control the stop/start of a conveyor belt using a sensor (proximity or photoelectric)

texts:
I am not too familiar with electric systems so sorry if this is a dumb question. I was wondering if there was a method to stop a conveyor belt using a DC moor with 115 vac 1 phase input using a proximity or photoelectric sensor. Once the sensor detects an object, power to the conveyor is cut.
Thank you for your help!


texts:
I have a couple of deep cycle lead acid 12V batteries (Kirkland Brand), 125 amp-hours each.

I want to run a 120 volt dryer-blower off a 2000 watt inverter for 20 minutes.

I calculate 2000 watts/120 volts = 16.6 amps on AC side,
16.6 amps X 120/12 volts = 166 amps on the DC side.
166 amps X 20 minutes = 55 amp-hours.
Add efficiency losses and we are still under 75 amp-hours.
So, the capacity is there, even with just one battery (and I have 2).

Question: If I am drawing that much power from the battery, are there any problems or concerns? Overheating? Safety?

I realize that this will shorten the battery life somewhat, but I only expect to do this a few times each year.


texts:
Please could someone suggest a suitable battery for a specific project.

I need to power a 40 W  12 V car headlight bulb for 10 sessions of 3 or 4 h each time, recharging after each use.

I have tested with a 7Ah battery and only got 1 hr and I am interested in the difference between the projected mathematical time and real world experience.

Also I need to provide a cost effective solution not only for the battery but also the charger as there will be multiple instances of the set up.


texts: HC-06 bluetooth module working as slave device

texts:
When we say that the HC-06 is a slave bluetooth device it means that this device is connected to a Master bluetooth device. But i am a little confused regarding to the data transfer between Master and Slave since there is also HC-05 which is used as a Master or Slave. Does this have anything to do with data transfer or is this irrelevant?

For example a master (laptop's bluetooth) can send data to the slave device (HC-06) so as a uController connected with the HC-06 can use the received data but can the slave device send data back to the master device? For example if i want to measure some analog voltage from the ADC of a uController and send this value back to the master (laptop) through the HC-06 module, can i do this?

Thank you


texts: LEDs seem to automatically self-regulate to achieve ideal voltage across terminals

texts:
Note: the key question is now in bold at the bottom, for the people who have had trouble figuring out what I'm trying to ask. Sorry about the meandering explanation.

I've been experimenting with resistive droppers lately, and designed the following very simple circuit:

To clarify, this is not just theory. I did this in the real world. The simulator screenshot is just to show how the circuit is arranged.

The input is 120v AC, 60Hz. I used two generic high brightness white LEDs (rated for 30mA, 3v). I didn't do any rigorous calculations, and just made ballpark estimates. And yet, somehow, when I measured it, there is exactly 3v across the LEDs. How on earth does this work so well? Are the LEDs somehow self-regulating their resistance so that there's as close to 3v across their terminals as they can get? Or was I just somehow really lucky?

I later measured the current traveling thru the circuit, and it's around 2.4mA, which is exactly what you'd predict according to ohm's law (120 v / 50000ohm = 0.0024A = 2.4mA). (All measurements were done with a okayish digital multimeter. I don't have an oscilloscope, sadly.) I've tried running thru what I know, and so far have figured out that the LED does not have a linear resistance curve, which is, of course, no surprise. At 30mA and 3v, it has 100 ohms of resistance. But when I try to use that figure to predict how much voltage drop to expect, I end up with around .23v. I've tried looking up the electrical characteristics of my generic-y LEDs, but the distributor didn't give a part number, let alone a datasheet.

(I later actually tested the current draw at 3v, and it was actually 15mA, which gave me a nominal resistance of 200 ohms (3v / .015A = 200ohm). Which didn't help matters -- that just predicts a current of 0.47v. I've also tried plugging everything in at once without rounding, which unsurprisingly doesn't help either.)

I thought maybe there was some sort of AC black magic here that somehow involved the minimum forward voltage of the LED, but I tested it and it's around 2.5 volts... besides, I see nowhere for voltage to build up.

So... is this normal? Are the LEDs somehow "self regulating" their resistance so as to get 3v across their terminals?


texts: Regenerative braking at any speed below maximum - how is it done?

texts:
My mobility scooter has a motor controller with regenerative braking - but regeneration seems to take place even at low speeds, well under the maximum! I know it does this because if I reduce throttle at low speed going down a hill, I see the current reverse on the ammeter and the battery voltage start to climb - considerably higher than with no load.

How does the controller achieve this? Normally, charging can only take place when the motor's generated voltage exceeds that of the battery - and this cannot happen at low speed. I ask because I want to build one from scratch.


texts: Is the capacitor drawn or wired wrongly?

texts:
In my recent study of electronics, I chance upon a guide on building a line-following robot. In one of the diagram shown, I realized that the capacitors, namely, C1, C2, C4 and C5, all marked with red arrows, are connected with the wrong polarity. This is from my recent understanding of capacitors. I have listed my observations and reasoning below.

Kindly help verifies if my understanding is correct. I have tried contacting the author but to no avail ;(

My observations:

The symbol indicates electrolytic capacitors in use, which are polarised capacitor. The flat side of the symbol should be the positive terminal. However, the curve side(-ve) is connected to the power source(+ve) instead.
C3(marked with green arrow) is connected correctly, at least IMO(beginner).
I think this is important as the reverse voltage in electrolytic capacitor will cause self-destruction of the oxide layer and fire.

Here is the link to the guide: http://www.circuitstoday.com/line-follower-robot-using-8051-microcontroller


texts:
I know VDD,VCC,VEE and VSS and what they stand for. But when I came across this circuit:

I saw this. Those PVDD and AVDD terms?
What to do they convey or stand for?
This circuit is amplifier circuit of PAM8403 DS.


texts: Why are the output voltages way too high on this stacked LM317 circuit?

texts:
I'm making a circuit that is intended to "simulate" a stack of 6 Li-Ion cells, for testing a BMS. Here's the schematic:

Schematic of cell simulator circuit

The ICs in red boxes are LM317 voltage regulators. The resistor-potentiometer network replaces the single resistor R2 in this reference design (page 1), to limit the output voltage range. Each LM317 is referenced to the output voltage of the regulator beneath it, to achieve the following:

each differential voltage (measured between adjacent terminals on the connector to the right) is adjustable
adjusting one voltage does not affect the other differential voltages

But when I build this circuit, the following happens:

most of the time, the differential output voltage (Vout2-Vout1, etc) on the regulators at the bottom of the stack is way too high (~8-10 V), and the regulators at the top of the stack drop out
on the regulators whose voltage is too high, the reference voltage Vout-ADJ is much higher than it should be -- around 3 V instead of 1.25 V
adjusting a potentiometer lower in the stack will change the output voltage and the reference voltage of the regulator(s) higher in the stack

This is confusing me.

I added load resistors to the design, and I believe that an appropriate load current is passing (~10 mA). At one point I had the entire circuit working properly, but then I unplugged it, plugged it back in again, and the voltages were way too high again. This made me suspect a loose connection, but I have checked my solder joints and resistances and nothing seems obvious.

Is the design of this circuit sound? Can the LM317 be used this way (stacked to produce high output voltages)? If so, why are the '317s in my circuit misbehaving?


texts: Simultaneously using 4 MIMO cellular transceivers on a single antenna - feasible?

texts:
I have a set of four commercial cellular tranceivers that support 3G and 4G(LTE).

These phones have two antenna connectors (for MIMO/diversity) in an embeddable industrial form factor (eg. just bare electronics, not a handset).

I have been asked to see if there is a way to reduce the necessary number of antennas from the obvious 8, down to 1 or 2 while still keeping all phones fully utilised simultaneously all the time (e.g. all 4 phones are running 90% duty cycle or more, all the time).

My question: Is this possible, and if so how?

My thoughts on doing this (I am not a radio engineer so please forgive my ignorance) are as follows:

Use one 4-into-1 bidirectional combiner for the 4 "Main" antennas and a second 4-into-1 bidirectional combiner for the "Aux" antennas.  This would leave me with the requisite 2 MIMO antennas on the roof.  But would I need additional amplifiers?  Do such combiners exist?  I don't really know how to search for such things due to my lack of knowledge.

Is it possible to achieve all this with a single antenna?

Notes:

The main reason for thinking about this problem is that we don't want to route out 8 antennas when we can get away with 1 or 2.
This whole idea sounds REALLY expensive to me, but lets ignore that minor issue for now, I'm mostly after a feasibility check.
Personally I'd rather just run out 8 antennas (nice and cheap and definitely works) but this system needs to be scalable up to perhaps 12 phones (24 antennas would look like Cthulu's grandma!).


texts: Is there a typical "Active Directivity" for LDMOS components?

texts:
Active Directivity is a measure of how much an amplifier's source match potentially affects its output impedance, or its load match affects its input impedance. High active directivity is a good thing.
What is the typical Active Directivity of LDMOS amplifier components measured in dB?  Is it typically high, low, or does it vary widely between manufacturers and models?


texts: Purpose of the logic gate configurations on the Kenbak-1

texts:
I was just looking through the schematics of the Kenbak-1 computer (long story), and I found this:

simulate this circuit – Schematic created using CircuitLab

I hurt my brain a little bit trying to figure out what that flip-flop does, but mostly why those two NAND gates aren't just inverters... and why the one on the bottom (and the inverter next to it) are even there.

What's the point?

(Note: I haven't had my coffee yet.)


texts: Determine if a heatsink is required (Darlington TIP120)

texts:
I'm planning to switch 1A load at 5V with a TIP120.

Looking at it's power derating graph I see that at 5W case can be around 140C, but how can I tell if it will get hotter than that?

In the datasheet I see that thermal resistance junction to ambient is 62.5C/W so does this mean that it will dissipate 5 times that = 312.5C. That seems like a bit too much for such load.

If power dissipated is VCE * Ic (VCE is 4V for TIP120 at 5V collector voltage, right?), then this means 4 * 62.5 = 250C which is still a lot. I'm getting a feeling that this can't be right.

Also if I dissipate 4W and still provide 5W for my load, then that's almost 50% efficiency, thats horrible. I'm probably off on my calculations, I could really use some help..


texts:
My instructor has been insisting that the multiplexor in the picture above is a 4:2 mux not a 4:1 mux and that my textbook (Digital Design and Computer Architecture by Harris) is incorrect and that there are typos in the text. From what I have learned, this is indeed a 4:1 mux, because there are four inputs and one output.

He also says that a 4:1 or (4:2) mux has four data inputs and one two bit selector. However, from what is shown above it also seems that it should have two separate 1 bit selectors.

I am asking which is correct because I would genuinely like to know and also because I need to implement one in JLS.


texts: Smoothing capacitor for half wave rectification

texts:
I'm trying to implement a half-wave rectifier using just a diode. I'm using a unity gain opamp for isolation from the mains. At the output of the opamp, I'm using a smoothing capacitor to get a DC voltage across 1K load resistor.

But for some reason, I can't get rid of the ripples. Any idea why?


texts: How to pass high current through photo interrupter sensor

texts: I am currently trying to build a coil gun that uses a high current to create a strong electromagnetic attraction. I'm using a photointerrupter sensor to detect when the projectile begins to leave the coil and want to use it as a switch. If nothing is interrupting the sensor, the current will flow through and power the coil but if the projectile is blocking the sensor, current should no longer flow through. However, an issue I have come upon is that photo-interrupter sensors are only able to have very small amounts of current pass through them so if I use the amount of current that I need to power the coil it burns out the sensor. Does anyone have any possible solutions or ways to approach this problem? Any help is appreacited.


texts: How high do you overspec your resistors?

texts:
I have a resistor in a circuit that I've calculated will dissipate 225 mW, worst case, calculated for tolerance variation.

Most resistors are rated to dissipate 250 mW. This seems a bit close to the spec, but is the spec already given conservatively? How close to the spec do you allow before you jump up to 500 mW resistors?


texts: Power of motor needed to carry 2kg of weight at speed of 10 kmph

texts:
I need to make rc car which can carry a weight of 1-2 kg and can give speed upto 15kmph, can anyone please tell me what should be rpm and torque of motor for this purpose ?
Thank You !


texts: Difference between Multiplexer/Demultiplexer and Analog Switch

texts:
What (if any) difference is there between mux/demux IC's and analog switch IC's?

I'm comparing this in the context of chips with the same IO lines (for example a 1:2 or 2:1 mux/demux vs. a SPDT analog switch).


texts: Why does my iPhone / electronics still work even when dropped in water?

texts:
I was wondering why does an iPhone that has been dunked in water still work afterwards even though it hasn't fully dried. While some other electronics stop working completely after touching water.

I am curious to understand why and how this works as I was faced with a dilemma of do I turn on my phone even after its been wet or do I NOT turn it on and risk losing everything from corrosion after 24 hours of drying with an inaccessible battery?


texts: How to find SMT equivalents of TH parts?

texts:
A lot of times hobbyist circuits are designed with thru-hole components since they're easier to solder. What approach do you take when attempting to find the SMT equivalent of a TH part?

For example, I'm trying to find the cheapest SMT diode that is equivalent to the extremely popular 1N4001. In my attempt to do this, I went to digi-key, chose the correct product category, and started using filters for things like current, voltage, etc. I ended up finding the Diodes Incorporated S1J-13-F.

1N4001 Specs:

Voltage - DC Reverse (Vr) (Max) 50V
Current - Average Rectified (Io)    1A
Voltage - Forward (Vf) (Max) @ If   1V @ 1A
Speed   Standard Recovery >500ns, > 200mA (Io)
Reverse Recovery Time (trr) -
Current - Reverse Leakage @ Vr  5µA @ 50V
Capacitance @ Vr, F 15pF @ 4V, 1MHz
Thermal Resistance  100°C/W Ja
Operating Temperature - Junction    -65°C ~ 150°C

S1J-13-F Specs:

Voltage - DC Reverse (Vr) (Max) 600V
Current - Average Rectified (Io)    1A
Voltage - Forward (Vf) (Max) @ If   1.1V @ 1A
Speed   Standard Recovery >500ns, > 200mA (Io)
Reverse Recovery Time (trr) 3µs
Current - Reverse Leakage @ Vr  5µA @ 600V
Capacitance @ Vr, F 10pF @ 4V, 1MHz
Thermal Resistance  30°C/W Jl
Operating Temperature - Junction    -65°C ~ 150°C

Since the specs for both seem comparable, can I assume this SMT device will "just work" when I put it in a circuit with a 1N4001 shown?


texts: Can a device with Zigbee Light Link ZLL connect to a Zigbee Home Automation HA network

texts:
Zigbee Light Link is a subset of Zigbee Home Automation. My question is : is it possible to add a device with ZLL profile to a Zigbee Home Automation Network?

UPDATE
I have a ZLL based device in the form of Mesh Bee, When I query available networks through the AT command it lists the Mesh Bee that has been set as a coordinator.

I have another device that is using Home Automation Profile and is a coordinator, But it doesn't get listed in the list of available networks!


texts: Can `ADD` create a control hazard while in the `MEM` stage?

texts:
Imagine there is a machine that has shared memory for both data and instructions (which means a control hazard can occur between the MEM and IF stages). Can instructions such as ADD that do nothing during the MEM stage cause a control hazard with other instructions that are in the IF stage?

ADD $1, $1, $3 :       IF  ID  EX  MEM WB
SUB $4, $5, $6 :                   IF  ID  EX  MEM WB

In the example above, is there a control hazard between the MEM stage of the ADD instruction and the IF stage of the SUB instruction?

Edit: Description of the each instruction.

IF  - Instruction Fetch
ID  - Instruction Decode
EX  - Execute
MEM - Memory Access
WB  - Write-Back


texts: What is the simplest sound-reacting led circuit?

texts:
A few years ago (around 3 years) I've made a very basic circuit to make a led blink to the sound.

The circuit a single regulator connected to a USB port to extract 5V, with a 3.3V led, conected to a simple 3.5MM cable connected to the sound card, using the left channel.

This circuit worked great, but it was too weak and the sound would be very bad.
This is probably because the electrivity was being mixed with the audio signal.

I don't remember which regulator I've used, but it was one from an old TV, which would lose 0.5V below 12V, and worked with a minimum of 3V.

Posing this, what is the simplest sound-reacting led circuit?

To be a simple circuit, it must require the minimum amount of parts and must be easily assembled without a breadbord or prototype board.

My budget is incredibly low, so, I can't afford to buy and learn how to use a soldering iron, but if it is required I will try to find one.
If it isn't required, I would be really happy.

Optionally, this circuit may be made to work with a Molex connector, on the 12V rail, which I can easily find power supplies and cables to test it.


texts:
My first question here:

I want to make a simple adjustable current supply for some LEDs I have (approx 3 V and up to 3 amps).  I've decided against just using a single FET to control current as it would have to dissipate as much as 9 W of heat.  For such a circuit I don't mind a bit of ripple (above say 10 kHz) in the current since its driving an LED which is driving phosphors anyway (the LEDs are white).

I'm not a power engineer so I have the question:

Would the circuit below (which I pulled from my behind) work?  I haven't seen anything too similar online. Aside from some ripple equal to whatever the hysteresis (divided by R1) are there any problems?  Are there concerns with setting the right oscillation frequency?  Should I choose component values to target a specific frequency (I was just going to go with >20 kHz in case something vibrates)?


texts:
Noob question coming up...

I have connected a digital output pin on my Arduino board to the base of an NPN transistor (BD135). There is a 9v battery connected between the collector and emitter, along with a resistor and LED.
The Arduino simply switches pin 6 on for a few seconds (sending 5v) then off for a few seconds and repeats. I have noticed that when using a lK Ohm resistor that even if the 9v battery is not attached that the LED will still light up (though not quite so bright). I thought that the transistor was a switch and I don't understand why power is getting from the base to the LED; I'd be most grateful if someone could explain what is happening!

If I swap the 1k resistor for a 47k resistor then the LED only lights when the 9v battery is attached.

[EDIT] I've noticed that if I put the LED and resistor on the collector side that it only lights when connected to the 9v battery (even using the 1k resistor on the base side)... is this how transistors should be used?


texts: Existence of input signal to LED at photodiode output

texts:
I try to make simple LED/photodiode circuit by arduino and 741 op amp. I used mid-IR LED by 200mA current and suitable photodiode for it. I wanted make pulsed signal by digital output of Arduino UNO
but the generated signal does not turn off (LOW state) and input signal to led observed on op amp output even when the LED is not in front of photodiode.
Where is my mistake?

simulate this circuit – Schematic created using CircuitLab


texts: How to ground the below circuit when I use USB?

texts:
I am constructing the circuit given below:

The problem, however, is that when I connect the electrodes to my skin, I get a mild shock. I am powering the Arduino using an USB cable. I connected the grounds in the image to the Arduino's ground. I am guessing that the USB power is causing problems. Any suggestions on how to properly ground the Arduino? Also, I am not using any batteries in this circuit. The only power source is the USB cable that I use to power the Arduino. The +5 volt go to the Arduino's 5V pin and the ground ones go to the ground pin on the Arduino.


texts: Shift value to some point in binary number

texts:
I wonder if it is possible to do the following.
For instance, I have a number 00001110. I am shifting it left. -> 00011100....
But the question is if it possible to start setting value in carry flag not from the seventh bit but from the sixth. There is a command - ROL it shifts a seventh bit into C flag, and than stores this value in the zero bit.
But I need to do like this ,but don't do anything with seventh bit, and store sixth bit in C flag and than also store it in zero bit. I mean when the value is 01110000 the next value should be 01100001.
Is it possible to do like this. I would be grateful for any help.


texts:
I have a AD9253 ADC connected to an FPGA. I want to verify the design, so I use the ADC in PN sequence short mode. (See p.28 in the datasheet.)

Here is a table (from the data sheet) which shows the 4 first output.

My problem is that I cannot create the same sequence (even the 4 first output) with my PN-sequence generator.

I have read the ITU 0.150 standard, but I didn't get the solution.

I tried to implement based on the following schematic from this document.

I like to model digital stages in Excel. Here is my solution. (Which fails.)

The time elapse from top to down, and each row shows a snapshot of the shift register. I hoped that the column I results the PN-sequence.

Cells in the first column has the feedback formula. (Eg.: A2: =IF(OR(AND(E1, NOT(I1)), AND(NOT(E1), I1)), 1, 0))
All other cells gets its value from the top left cell. (Eg.: The B2 cell formula is the following =A1)


texts: How can I identify an IC like this NXP microprocessor?

texts:
The code that is impressed is :

SC120541VLQ6

0N13E

QKE1544N

It seems to be a NXP microcontroller (because of the symbol of Freescale). So, I was suspecting it would be a MPC5606S, but I'm not sure, the conections seems not be consistent with datasheet.

I don't know how to discover it. Has someone a tip or an answer?


texts: Switch a 12 VDC circuit from a 0.6 volt signal

texts:
I need to switch a 12 VDC circuit (automotive ignition coil) with a .6vdc signal from an impulse coil. I am trying to replace the ignitor box for this engine; they are extraordinarily expensive and cannot be tested. From what I have read, this may require a germanium transistor to increase voltage sufficiently to perhaps use a MOSFET for the twelve volt circuit. This ignition system fires the ignition coil by interrupting the path to ground for the primary circuit of the ignition coil as opposed to the circuits with which I am familiar, i.e., interrupting the power side of the primary coil. I know just enough about electronic circuits to get into trouble.

Not a model t; oddly enough, I would have no trouble with that; I've worked on many. No, this is an EZGO utility cart I use around our property with a two cylinder Robin engine, 9 HP. I am disabled and depend upon this cart greatly. I understand the circuit diagram provided, thank you.
The impulse coil by factory spec is from 433.5 to 586.5 ohms.  The primary winding resistance of the ignition coil is negligible; 0.5 ohms according to my meter.
I understand the output would be weak; would it be sufficient to drive a MOSFET (or similar switching device) that would provide a ground path for the ignition coil?
I really expected a much higher output from the impulse coil, but that is why I am asking experts. Thank you very much for your help and responses.


texts:
I am developing a portable device embedding sensors, Bluetooth, MCUs etc.. At present I'm at a prototype stage and I'm starting thinking about production.
What kind of certification steps do I need to follow in order to produce and sell it?


texts: PIC + L6203 (Driver) problem (PIC Resetting)

texts:
I've created an electronic board to control a joystick (Yoke) using a PIC18f4550. The uController communicates with the computer via USB and send/receive all necessary data information to control 2 DC motors (2 axis). It's working fine and the control circuitry is self-powered. I have in the same board a couple of L6203 to control each DC motor. Also I've put a separated supply to the motors (24v) but with all with common ground.

The problem is that whenever I turn ON or OFF the 24v power supply, the PIC resets. It's not always but most of times it does reset. I've already made all sort of tests and modifications but nothing seems to change. With an oscilloscope I did not see anything in the PIC +5v line. It remains constant. WDT, BOR and MCLRE are all OFF.

Here are some pics of the main blocks:

As you can see the uC generates two different PWM signals which goes through 4081 logic ports. There I can choose whether the driver turns the DC motor to the left or to the right. There is also another Driver block but its just the same of this one.

I've already tried to add some filters on the 24v supply and also on the USB line (+5v). I've tried to put some decoupling capacitors (0.1uf) in both VDD-VSS pins of the PIC. I've tried changing the DC 24v power supply from a switched one to a linear one. Even turning the power supply with low voltage (adjusted to 1v) does not seem to make any difference.

Also, sometimes playing the game with it, the joystick stops responding (freezes) without disconnecting. I dont know if has something to do with the first problem.

I've already tried to add extra +5v line to the circuit so it does not depend on USB supply. Does anyone know what could it be?

EDIT:
Another funny thing: if a leave VCC jack disconnected (no 24v in the circuit). Then if I just TOUCH the positive pin of the jack with the red probe of my power supply TURNED OFF, the PIC disconnects from USB and reconnect just after. It does not reset but the USB loose connection for a moment (i can hear that USB disconnected sound). Strange that the power supply is off and I just touch one of the terminals (positive) to the board and it does that.


texts: The best control strategy to determine the 0 position of a hall sensor linear actuator

texts:
I am using a TA29 Timotion, with hall sensor as a feedback. To determine its position, the actuator should be in position 0, before it starts counting. What is the best way for me to do this without using an external switch?
https://www.timotion.com/en/product/detail/linear-actuators/ta29-series?upcls=1481269298&guid=1535388333
My controller for this is Arduino Mega 2560.


texts: Baking SMD integrated circuits for prolong time

texts:
I recieved samples of AD7175-2 and AD5684R with an instruction:

  If these samples are to be subjected to solder reflow or high temperature process, they must be baked for 24 hours at 125°C prior board mount. Failure to comply may result in crack and/or delamination of critical surfaces within the package.

Is it done in a reflow oven? Otherwise how?

I am confused because Elektor qs-5188C reflow oven in our lab seems to lack an option, that would let it run for such a long time.


texts: What is the result of deviating from the Kelvin layout when designing a current sensing PCB?

texts:
For a two terminal current sensing shunt resistor with a layout that deviates from the symmetric Kelvin layout, what results should be expected?

For example, with this layout, what result would be expected on the sense leads when the resistor is subject to a 3A current?


texts:
I was trying to figure out if ISI in time domain is similar to aliasing in frequency domain?

Are these two phenomenon dual of each other?

It would be of great help if someone could explain this.


texts: What to look for in a processor for a DSP project

texts:
I am working on a Digital Signal Processing application and I am a little lost in all the information included with giant processors that are labeled as Digital Signal Processors.  I started wondering, "Do I really need this huge processor just to analyze music?"

My project is to store fourier transform data in a EEPROM chip that communicates through SPI.  What do I need to be looking for in a processor to do real-time analysis and store the data in the EEPROM without the processor missing any analysis work?

EG: How many MACS do I need?  What kind of operating frequency should I be looking for?  How much RAM (for say a fourier transform sample size of 512)?  would i be better off using a codec?


texts: How to treat un-used input pins for the Rin/RS232 side on MAX3232?

texts:
I have yet to find a definitive answer or best practice on how to tie the un-used input (RXin) RS232 side on a MAX3232E transceiver. I do know that, say for a TTL logic device for example a buffer/driver one would want to tie the un-used inputs to Gnd or VCC and let the un-used outputs float but with RS232 levels swinging above and below 0V to tie an un-used input on the RS232 side could serve no benefit or even perhaps force the device to consume more current/power.

To my question/s. What is the best practice to do with the un-used input pins on the RS232 side? In addition, what would the consequences be if I were to tie the un-used input pins on the RS232 side to Gnd?


texts:
Has anyone had good/bad experiences with particular PCB-mount thermocouples?

I need to design a circuit board with a connector I can plug a standard thermocouple connector into.

(and yes, I am aware that when you connect thermocouple wires to copper traces, you create junctions of dissimilar metals that can cause errors if the junctions are at different temperatures)


texts:
I was trying to design a data logging application using something like a www.ruggedcircuits.com gator+ board with some sort of rugged zigbee module
for measuring principally steam pressure (to 110 bar) and temperature (to 380 C).

Of course this is a development project with limited funding so I am trying to design a low cost R & D system rather than a big iron industrial control system as this stage.

Does anyone know where to get or have suggestions for:

A rugged zigbee module similar to the rugged circuit gator+ board approach?
Good bomb proof enclosures for connecting sensors that would house the board, zigbee module and power supply?
Pressure and temperature sensors to cope with this sort of environment?

I know that there are really expensive sensors for plant installations, but they are not likely to be in budget as we will need lots of them.

Any ideas or leads would be appreciated.

Harley


texts:
Using the following schematic, I am charging a supercap (3.3F, 3V) via a solar panel and would like to keep a downstream microcontroller in reset mode until the supercap has charged a bit.
To do so, I am charging a separate 100uF capacitor via a 1MOhm resistor (according to this, it would take 100 seconds for 1 tau).
I am worried about the leakage current (according to this, it's about 6.3uA).
Does this mean that the 1MOhm resistor is too big and the charging current would just get leaked away (3V /1000000Ohm = 3uA current < 6.3uA leakage)?
Circuit:


texts: DC bus inversion to 3 phase AC modified sine wave using IGBTs

texts:
I'm working with a variable voltage inverter.

I have 3 phase AC voltage coming in at 480V RMS line to line. It hits a full wave SCR front end, has a DC bus link, and is inverted with IGBTs to created a six step output wave form.

The IGBTs are firing in 180 degree conduction mode and I'm measuring the output waveform with a true RMS meter.

Here's my confusion:

With a full wave SCR front end I'm aware that I should be able to approach Sqrt(2)*line to lone RMS incoming, and I'm seeing that on the DC bus.

But I can't seem to find the equation that dictates how to calculate the conversion from my DC bus voltage to line to line RMS voltage of my six step output wave.

I've found a million different equations about converting from DC to 3 phase AC but none of them seem to match what I'm seeing.

The output waveform line to line voltage in my tests is always right around .816*DC bus voltage. This conversion factor stays accurate from low voltage all the way up to max DC voltage at ~680V DC (480*1.414).

No where in my research have I found where this number comes from. The closest I've come is an equation on the wiki page for RMS voltage

If I divide peak (DC bus) voltage by the sqrt(3/2) I in fact get the conversion factor I was seeing in my tests. But I have no idea where this comes from. And if I'm not mistaken in what I'm seeing this means that with 480VAC RMS in I can get around ~554 VAC RMS out (480*1.414= ~678. 678*.816=~554).

Since we obviously can't just create energy out of no where would this higher voltage come with a reduced current compared with the incoming? Or can someone explain what's going on here and where this Sqrt(3/2) conversion factor comes from please.


texts: Measuring distance sensor in short range to soft materials like wool, fabric and hair?

texts:
I need a type of sensor for my project to measure distance with average precision and between 0 up to 10 centimeter to soft materials like fabric, wool and hair? I looked a lot but unfortunately no success!

Thanks,


texts: How to know whether addition has been done in a parallel binary adder?

texts:
I am little new to electronics and getting some high level overview of digital electronics. The question is that how to know whether addition has been performed in a logic circuit.
For example I have a adder and want to add two numbers (say all zero) how can I know whether the calculation has been done. Say I want to save the result in some small flip flop only when the calculations are performed but since the default state of all logic gate is zero and our result is also zero so how can I differentiate between default zero and result of zero.


texts: Replacing a sensor in an old Logitech Cordless MouseMan Optical mouse

texts:
I have this Logitech Cordless MouseMan Optical mouse which is probably 16 years old. I really like the ergonomics of it and also it can be taken apart easily (lots of screws, every part accessible and big enough) which allowed me to replace malfunctioning micro-switches for particular buttons.

I have a problem though - I'm using it on an old mouse pad which is falling apart. Unfortunately the mouse doesn't work well at all on other mouse pads available these days on the market (I tried at least 4 with different types of materials.) The sensor "gets lost" after I move the mouse too rapidly and stays in one place instead of moving accordingly, or it ends up slightly away from a position on the screen you'd expect it to be.

Would it make sense to replace the sensor, or a diode at least? I'm not really experienced or don't have professional equipment, just a regular soldering iron.

The sensor is on a separate PCB:

Same thing flipped upside down:

This PCB is then attached to the rest of the mouse through this connector on the main board:


texts: Analog Equivalent Circuit of an easing function

texts:
I am trying to wrap my head around wether and with which circuit it would be possible to emulate the behaviour of a digital easing function like output += delta_to_target_value * easing_factor as it is illustrated in a 2D-version here.

I know basic rise-/fall slew circuits, but I expect this is different.

My thoughts:
Let's assume the target's value is a steady stream of random DC voltages, straight out of a Sample-and-Hold. I'd need to find the difference (delta) between target and final output. I then need to attenuate this delta with a easing-factor (< 1). In the digital loop I would then set the output value to equal the current output value plus the attenuated delta value. Somehow I am afraid It would not work that way in a time-continous system. Do I oversee anything here?

Edit:
Nevermind, I had some trouble wrapping my head aropund this. I ran a Circuit simulation with random stepped values and a RC-filter which yielded this result:

Simulation of RC Filter

And then used the same step values and programmed a the easing function I mentioned, which yielded a very very similar result as you can see:

Simulation of Easing Function

What I hoped for:
I hoped for a read curve which does not appruptly change it's direction, maybe as if it had some sort of inertia. The delta in the mentioned easing function is way bigger with growing differences which results in a speedup at value changes. I would definitly know how to fix this in the digital domain, but I am not sure about the analog domain.


texts:
I was reading an Article of LC-Tuned Oscillators in Microelectronics Circuits (By Sedra Smith).

I came across the the Colprit Oscillator. I did the simulation of the circut given in exerciseto understand it.

I dont understand How Colprit Oscilator Satisfy Barkhausen criterion?

The book says "Detailed analysis of amplitude control, which makes use of nonlinear-circuit techniques, is beyond the scope of this book". Does their is any reference to understand it in simple way.


texts: Any diode to protect an optocoupler with low voltage drop?

texts:
I have this design.  By a possible mistake from user, the circuit would receive 12 V AC, and may destroy the optotransistor on reverse voltage cicle.

I can put a diode D1 before the resistor, but the diodes I already know, may have voltage drop or resist just small currents (300 mA), but the AC source can have 2000 mA.

I need a Diode with Low Voltage drop.

The low voltage drop is required to can handle the logical input at right side.

The 5.0 volts is not a source, it comes from a switch connected to a device sealed. When optocoupler gets on, the logical inputs receive a signal and the device acts.

Which diode can I use?


texts:
I need to replace a 5k mechanical potentiometer with a digital one. The hang up is that it will have a maximum of 14V across it. That's too high for most digital pots on the market. The max current should be less than 10mA, so that's not an issue.

These are the main three parts I've narrowed it down to:

AD7376 - 128 positions, volatile, 10k, 28V range, TSSOP $2.86
AD5290 - 256 positions, volatile, 10k, 30V range, MSOP $1.92
AD5292 - 1024 positions, non-volatile, 20k, 33V range, TSSOP $2.62

I think it would be helpful to have it be non-volatile, but it seems like it would be able to initialize to the correct value pretty quickly after initialization, so I don't know if that's too important.

My main question is related to the size. The 7376 has 10k/128 = 78 ohms/tick precision. The 5290 is slightly better at 39 ohms/tick. Finally, the 5292 has 19 ohms/tick.

I'd like to have it be as smooth as possible, so it seems like the 1024 position one would be a good choice. Is there any disadvantage I'm missing with going with a 20k pot when I'm only ever going to use it from 0 to 5k?


texts: Difference between fuse diode and diode - is there is any?

texts: I have a BSA motorcycle with a couple of lucas 1 and 2 amp diodes in the electrics. It is hard to find the original 2 amp lucas diodes so I am thinking of using a standard 2 amp fuse diode instead. What is the difference between a diode and a fuse diode. I am thinking a fuse diode fails safely if overloaded with current whereas with an ordinary diode the whole circuit will get hot and possibly burn out the wire in any random place. Or is there no difference between the two.


texts:
I am using a MCP45HV51 digital potentiometer for gain control. (Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/20005304A.pdf)

I set up the device according to the datasheet and control it with a Raspberry Pi via I2C.

The poti has the address 0x3e.

For some initial testing I use the console with

i2cset -y 1 0x3e 0x00 0xff

The poti goes to its max. value: 5k

i2cset -y 1 0x3e 0x00 0x00

The poti goes to its min. value: ~0.25k

When I read out the registers of the poti with

i2cdump -y 1 0x3e

there is no noteable change.

I don't understand, why the poti reacts but the register does not change its value. Can anybody help me with that?

Thanks in advance!


texts:
How could I choise the break point on the feedback loop of an oscillator (goal: evaluate the loop gain \$\beta \space A\$)? The Sedra-Smith said that it is convenient to break the feedback loop at the aplifier output. I found a case in which this not works: a phase-shift oscillator with an inverting amplifier. In this case, if a break the feedback loop at the amplifier output Vu, i obtain Vu=0 because the "+" terminal of op-amp is at 0V and hence the loop gain \$\beta \space A\$ is 0 (Vp is the voltage source on the opposite side of Vu):

$$\beta \space A=\frac{Vu}{Vp}=0$$

In figure there isn't inverting amplifier.

Thank you for your help.


texts:
simulate this circuit – Schematic created using CircuitLab

Schematics above is a parts of AC Voltage Meter. I know there are several related questions such as "Determining DC gain of single supply op-amp (no AC component)" and "Calculating gain on Op Amp with AC voltage". Things that caused my confusion are:

Both question above use a single resistor instead of potentiometer (see R4)
The presence of double-anode zener (D2 and D1), as limiting circuit
Two variables (SW1 and R4)

Can someone help me on the formula to calculate the gain (such as when the wiper on R4 is on 0%, 10%, 20%.. etc) or point me to the subject that I should be looking? Thanks in advance :)

Edit 1

Thanks for inputs from @analogsystemsrf , I add ground to + input of Op-Amp to remove floating input.


texts: Mock a I-V characteristic of a solar cell?

texts:
Is it possible to create a mock up of a power supply that would mimic an I-V graph of a solar cell?

The graph below shows what I'd like to achieve. Once the load tries to pull more than 200uA the voltage should start decreasing drastically.

I have the following components available:

battery
resistors
capacitors
inductors
different types of diode and transisotrs
op amps


texts: Modify Si4703 FM Tuner evaluation board to add an external antenna

texts:
I have this Si4703 evaluation board which I would like to modify to attach an external antenna. The board usually uses the plugged in headphone cable as the antenna.

Here are the relevant schematics:

One of the comments on the linked page claims this:

  The antenna connection is Pin 2 of the SI4703. It is connected to the shield (ground) of the headphones via C5. This keeps the low frequency audio out of the chip. You would need to cut the trace between C5 and L1 and solder the antenna wire to the free end of C5. Keep C5 between the antenna and the chip.

Is this advice correct? Can I simply desolder L1 and solder the antenna to one of the free ends (the one that is not attached to GND) or should L1 be kept? Will any of this effect reception?

Here's the circuit with C5 and L1 marked:

P.S.: all images are from https://www.sparkfun.com/products/retired/10344, CC BY-NC-SA 3.0 (same as this page), modified to point out items relevant to the question.


texts: solder wire makes solid & glassy residue

texts:
I know using flux makes some residue which makes unwanted contacts between components pins. I dont have any washing liquid or spray to remove it so i simply decided to not use them.

But my solder wire has a solid flux layer. while soldering with it, some melted flux splashes around, makes some white smoke too.

After soldering is done, two separated material remains on board

First a glassy solid residue which will break under pressure like sugar!

Second some greasy appearance around soldered areas.

Unlike lotfett soldering grease its residue is not conductive. However i don't know much about it just tested myself.

I need to know about this material. Shall i remove it? Is there any way to remove it from the board?.

I created this question to be some kind of reference for the mentioned product.


texts: What's the formula that relates capacitance, permittivity and geometric coefficient in the ring capacitor?

texts:
I find it hard to calculate the geometric coefficient of a capacitor with two cylindric electrodes and a tiny distance between them, exactly like this one :

Does anybody know the exact formula?

Thanks in advance.


texts: Why is it said that for efficient transmission of radiation, antenna size should be comparable to wavelength of the radiation?

texts: I have found it across many texts but I am confused about the reason why is it so? Is this related to radiation resistance?


texts: Trade offs between adc range and amplifier gain design

texts:
Edited on 15th,Aug
Tradoffs between ADC range and amplifier gain
If I want to measure a very small signal with 16 bit ADCs，say 10kHz sine waves with amplitude ranging from 0 to 1uV, I have to amplify the small signal first. The signal should be amplified with peak-to-peak value equal to the range of ADC. Then the signal will be shifted up by half of the ADC range by an ADC driver(with level shifter).
My questions is: What are the trade offs between amplifier gain selection and adc range?
Should I use a 2.5V range ADC(16 bit) with 1,250,000 gain amplifier, so the peak-to-peak value of the largest sine wave(1uV) will be amplified to 2.5V?
Or should I use a 5V range ADC(16 bit) with 2,500,000 gain amplifier, so the peak-to-peak value of the largest sine wave(1uV) will be amplified to 5V?
What aspects should be concerned in the decision?
How to choose ADC number of bits?
Also a question, how should I decide the number of bits to use? The noises are fairly large, but I am going to use signal processing techniques, which can reduce noises greatly. It means that more bits should still be useful. (Thanks to gbulmer, you made me realize that I did not really think about this question..)


texts:
I want to convert a 10 MHz train of square wave, 3.3 V to a Gaussian pulse train of the same frequency and amplitude. This Gaussian pulse will be sent into an electro-optical modulator where it modulate continuous wave laser (single frequency 100kHz linewidth) into optical pulse. (See figure)

Can anyone recommend me an available IC that can do the job?

I found some Gaussian filter circuit online. However, I am not sure how to know the timing jitter of the pulse train created by the circuit. My squarewave jitter is low (200 ps) and I would like to keep it as low as possible.

[


texts: How do mains voltage LED filament bulbs work?

texts:
What are the filaments inside a bulbs such as:

https://www.amazon.co.uk/Bonlux-Dimmable-Filament-Incandescent-Replacement/dp/B01AL1WT4C/ref=sr_1_3?ie=UTF8&qid=1481966120&sr=8-3&keywords=led+filament+bulb+6w

What is the circuit?

Are there capacitors or resistors involved?

(LEDs normally drop 0.7V, not 230V.  Typically, they are powered from DC, not AC.  It would be very inefficient to drop the remaining 229.3V through a resistor, and a heat sink would be required, which I do not observe on these bulbs.)

How do LED light bulbs work? mentions the presence of a heat sink, which these bulbs do not have.  These bulbs also seem to have no space for electronic components.


texts: Effect of doubling clock frequency on computer performance

texts: If we double the clock frequency of a CPU, does that translate to a doubling of the CPU performance? Assuming that the number of instructions and CPI are constant, we have an inverse relationship between the clock frequency and computer performance. Thus a doubling of the clock frequency will half the computer performance. Is this correct?


texts: How does the thickness of a dipole antenna affect the gain and the field strength?

texts:
I was asked this question on an exam and I couldn't answer it. I've searched the web and looked in my books but I can't find any information about gain and field strength vs. dipole thickness.
I know that for linear dipole antenna thickness should be much less than the length. Other than that I've found some information that the thickness affects the bandwith and Q.
The question is asking only about the point where the field strength is maximum.


texts: How does an IIR filter change depending on the approximation used?

texts: What are the main differences between the filters when using Butterworth, Chebyshev type I, Chebyshev type II or Elliptic aproximations.


texts: simple RC circuit corresponding differential equation

texts:
I have an RC circuit as shown below

unfortunately I have no knowledge about RC solving but I want to obtain corresponding differential equations for V1, V2 and V3. Having in hand differential equation for V1 is enough for now, if anyone can tell me it!!!


texts: How to customize the 'write' to instrument?

texts:
I'm communicating with Power Supply RIGOL DP832A via Ethernet.

from vxi11 import Instrument
dev = Instrument('192.168.1.186', 'inst0')

answer = dev.ask('*IDN?').strip()
print(answer)

channel = 3
channel = str(channel)

volts= 22
volts = str(volts)

current = 2.3
current = str(current)

selchannel = 'CH'+ channel
mypass = 'APPL ' + selchannel + ','

mypass = mypass + volts + ','

mypass = mypass + current

print (mypass)
dev.write(mypass)

In my expdp832a.py all the stuff with channel, volts and current I'm doing because later I'll be taking channel input, volts input and current input from the user and setting it to the values passed by him say via a function like set_powersupply(channel, volts, current).

When I'm printing the value of mypass, it's string with the value APPL CH3, 22, 2.3 but  still my PowerSupply displays invalid command.

Instead if I directly pass it as dev.write('APPL CH3, 22, 2.3') Everything works properly and Power Supply Channel 3 is set with volots and current values.

What is wrong in the earlier method? If I want it to be user-selectable, I need to pass channel, volts and current values as input from user and not as hard-coded values.


texts: I am unable read register values in ADS1282

texts:
I am interfacing ADS1282 with LPC1768 through SPI. Currently I am not onnected analog supplies. Only digital supplies connected.I am trying to check whether communication is happening or not.But I can't read the register values.

These are the steps I followed.

1.sent 0x11 for - Stop continuous reading.

2.sent 0x20 for - Reading 1st register.

3.sent 0x00 for reading only on e register.

4.Dummy write 0x00 for reading data.

Given delay 100 microseconds in between instructions.
I am getting only 0x00.
I checked different registers.
SCLK = 3 MHZ


texts:
Here is my task:
Periodical signal is given (only one period of signal is shown):

Calculate value of voltage K so that average power of this signal equals 1.5W.
Power of signal can be calculated as $$P=\int_{0}^{T}u^{2}(t)dt$$.
My idea is to express u(t) and solve equation $$\int_{0}^{T}u^{2}(t)dt=1.5$$ (after solving integral I will get some function of k, f(k), and solve f(k)=1.5).
But u(t) is piecewise defined, it is k+2*(1-k)*t/T in interval 0 to T/2
and 1 in interval T/2 to T.
What to do here?


texts: SMD vs. Through-hole components in high vibration environments

texts: This is more of a opinion question than a information question. I am designing some boards that will be working near decent sized actuators, so I ask you, what is more resistant a 0805 SMD or a 7mm thru-hole resistor?


texts:
Can any one tell me

If we rotate a DC motor(1800w) in its full speed how much electric power(as a generator) it will generate?


texts: Signal filtering, what's wrong with the circuit?

texts:
I have this circuit where I receive a protocol signal:

The +L_IN signal is this:

This signal has a 28V DC voltage.

The signal at +Loop_Protocol:

(this signal might not be the best measure, because the ground was connected to the ground oscilloscope with a wire, it might have a 50Hz its not supposed)

The +Loop_Protocol goes to two other circuit parts:

The protocol filtering circuit, which is supposed to strip the DC part of the protocol:

It will go to a pin port of a pic.

The signal at the protocol filter from central, at DATA_IN is giving a signal that doesn't seem right:

And the other circuit is the one that provides 3V3:

The signal at DATA_IN needs to be clean, only without the DC.

The strange thing is that if I remove the capacitor C24 in the circuit 3.3V Regulator from Loop, the signal turns out good. The reason I put the diode BAV70 in this circuit is because that same capacitor was destroying the signal.

Anyone know what can be done to solve this?

Note: When taking the pictures with the oscilloscope I accidentally left it with the option to measure AC only and to invert the signal.  I don't have the possibility to take new pictures now.

Note2: About the BD9G101G it has a high impedance in EN pin, about 550kohm, about Vcc I haven't seen it mentioned on the datasheet


texts: If I pull the power on my computer and IMMEDIATELY restart it without booting OS, will RAM contents be preserved?

texts: I have DDR3 RAM in my computer. My computer is frozen and I have important unsaved work open. I've already dealt with the problem of how to recover and read the contents of RAM. I just need to be able to restart the computer with memory intact. If I lower the temperature of the RAM to do this, memory will be almost entirely preserved. However, this is a last resort. I'd prefer to do it through a quick reboot.


texts:
I'm designing a large adjustable bench power supply (up to 250W per channel, 50V max).  My current thoughts about the design are three stages:

A unregulated supply at ~60VDC, up to 5A out. Using a mains transformer to generate the 60VDC.

A buck converter that takes me from ~60VDC, up to 5A, to ~1.5V above the requested (adjustable) voltage.

Finally, a linear regulator to take me from the output of the buck converter to the requested voltage.

The linear regulator has to be able to operate at 50V, 5A.  Because of this, I'm designing my own.  (I'm not aware of any off the shelf solutions).

I know that you can get close to linear regulator noise levels using this topology (unregulated to buck to linear regulator), however you have to pay attention to the noise in your buck regulator and match it with the power supply rejection of your linear regulator.

What are the things that I should pay attention to when designing this system?  I know you can reduce the noise in a SMPS by turning on the FETs slower, and that typical linear regulators are better at rejecting low frequencies than higher frequencies.  I also know I can use a low pass filter to help filter out the high frequencies of the SMPS, at the cost of ~.5V and some heat.

Are there other things I should take into account?  Does synchronous vs. asynchronous matter?  Should I design a PI filter after the SMPS to filter out the high noise?  Does the op-amp or MOSFET selection of the linear supply change its PSRR frequency response?  I would expect the op-amp matters, but the FET less so, what are the figures of merit I should be looking for?


texts: Reading datasheet addresses for base and offsets

texts:
OK, so for myself and others out there I wanted to clarify I am correct on how I am reading datasheets such as the one in the image below. The thing is the data sheet of this MCU says it is 16-bit registers but it looks to me like it has 32-bit addressing space.

The base address 5 hex values and if I were to just replace the offset with the last three hex values that would be 20-bit addressing which seems totally wrong to me. Whereas if I add the offset to the end of the base I get a 32-bit address, 4 bits per the 8 hex values. But again this is a 16-bit MCU so I am confused as to how to get a 16-bit address from what I am looking at.
If someone could should me what is wrong with the way I am reading this that would be great!


texts:
I'm trying to build a small synth with two pots to control tone and volume, i got the tone one working but I'm not sure how to control the volume since I'm planing to send it to an amp and just setting the second pot in series with the output didn't work.
I saw this picture and it seems like this is what i want but flipped so that it starts silent and becomes louder.

i tried to follow this schematic but i got no sound

So how am i supposed to do this?

Edit: As it turns out, I'm stupid.
it was not a second pot but it was instead a force sensitive resistor and that got me confused.
So i suppose the real question is how do i get the force sensitive resistor to control the volume


texts: How to add an internal signal to the waveform viewer in Aldec HDL for a Lattice Machxo3

texts:
I'm absolutelty no FPGA expert, but designed a device with Quartus and used Modelsim to simulate it. I was then told to modify the design and make it work with a Lattice device as they changed their mind about Altera (mainly down to Lattice devices being a bucket load cheaper I think).

Unfortunatelty (for me) Lattice Diamond comes with this Aldec-HDL program instead of Modelsim. After stuggling for a couple of days I have managed to finally work out how to be able to tweak my workbench and re-run the simulation without having to relaunch [Active HDL] from Diamond. However, after a further couple of days of trying, I just cannot work out how to add internal signals to the waveform viewer.

On Modelsim one of the few intuitive features is that you can select an instantiation of a particular component, pick one or more of its signals and just add it to the waveform viewer. On Active-HDL I can't even find a way of picking a particular instantiation of a module. I can find a way of picking a module, but its signals just say "Unavailable". That doesn't seem particularly helpful anyway as you need to be able to select an instantiation of a component, not just the component definition.

I assume this must be possible, otherwise it's a pretty useless simulator. Can anyone enlighten me on how to do this please?


texts: The Envelope detector is over 100 years old .In its classic form it is a simple half wave diode that peak detects the carrier with the load resister and load capacitor time constant chosen to allow the output to follow the envelope of the carrier .The Envelope detector is well documented elsewhere.Would an averaging type of detector be better in terms of noise performance ? Was the peak detector chosen for simplicity or maximum output voltage or was it the first thing that worked?


texts: In the below circuit, do Rbias and R2 both affect the cut-off frequency? Or is it simply 1/2*pi*R2*C2


texts: Arduino - Controlling Electromagnets/Solenoids

texts:
I'm a French student and today I have to control some magnetic things with an Arduino.
It seems to be electromagnets, but I'm not sure, since I'm a complete novice to electronics.

I saw some StackExchange answers that helped me a bit, but I can't really figure what to do exactly without frying my Arduino.

The datasheet of the magnetic thing is here.

Wired to a AA battery, it worked, and I don't need much more power, so I think that the Arduino could power it, nope?

Do I have to make a montage like this, or can I make a more simple one?  If you do need precisions.


texts: Using Single-Phase and 3-Phase Equipment?

texts:
Let's say I have a single-phase facility and I plug in a piece of 3-phase equipment, what happens?

Is it dangerous?
Is it less efficient (if so, approximately how many percent less in efficiency)?
What kind of adjustments, if any, would I have to make to make this setup work?
Would it increase or decrease the number of amps I use compared to a piece of single-phase equipment?

Likewise, if I have a 3-phase facility and I plug in a piece of single-phase equipment, what happens?

Is it dangerous?
Is it less efficient (if so, approximately how many percent less in efficiency)?
What kind of adjustments, if any, would I have to make to make this setup work?
Would it increase or decrease the number of amps I use compared to a piece of 3-phase equipment?

The power company charges based on wattage, so how would I calculate to find out which setup would be most cost-effective?

Are there any basic ground rules that I should follow when trying to work out these relationships?


texts: 7 Segment Common Cathode LED Digit Display Circuit for Arduino

texts:
For the first time I am going to make a digital clock with 7 segment displays with Arduino Multiplexing. I am about to use the following circuit to run 4 large Common Cathode 7 Segment LED Digit Displays. The circuit diagram shows only 2 digits with 4 of their anode pins connected. Hope you understand the full schematic from this diagram.

simulate this circuit – Schematic created using CircuitLab

My Questions are:

Is this schematic correct?
These are large 4 inches displays, run on 9V, Common Cathode type and consumes approx 200mA current total for all eight segments of each display.
Programmatically, I am going to multiplex digit by digit, not
segment by segment. Do you think BC337 is the right choice for this, considering in parallel that I will turn the digits on and off as frequent as once every 1 mS?
Base resistors 1K Ohm. Is the value ok to supply enough current to transistor base and lit up the LEDs with Arduino's
digitalWrite(Dn, HIGH) method?


texts: Can I improve the high-frequencies absorption of a ferrite inductor with two opposite winding directions?

texts:
A choke if effective against common mode currents by having two windings in opposite direction around the same core. Currents common to both wires produce opposing magnetic fields and get cancelled.

A ferrite instead works by coupling and dissipating high-frequencies as heat.

Would a toroidal ring be more effective for reducing high-frequencies if a single wire is wound in a direction (right-hand) for half of the circumference and then in the opposite direction (left-hand) for the second half, and then coming out of the ring next to the point of entrance?


texts: Why is there a resistor bridge before the amplifier?

texts:
I really fail to understand what the resistor bridge before the amplifier does. Can I just connect my inputs to the - and + ports?

This was taken from the datasheet for INA125, and they use this configuration in several of the applications, and I really can't understand why...


texts: How to debug reset caused by WDTCTL security key violation in MSP430F1611?

texts:
I'm working on a sensor project which uses TelosB based on MSP430F1611 running TinyOS. My program is reset some time after boot up. After the PUC reset, IFG1 is found with WDTIFG bit set, indicating the watchdog timer initiates the reset. This can happen under two cases:

1) Watchdog timer expiration when in watchdog mode only.
But watchdog timer is never started, so this cannot happen.

2) Watchdog timer security key violation.
There is no place that my program explicitly writes WDTCTL (i.e., 0x0120h). So there must be some memory access bug in my code, which illegally writes WDTCTL and causes security key violation.

Is there any debug tool to help locate where this happens? Or any any suggestion on how I should proceed to locate the bug? My program is of thousands of lines, so manual check is non-trivial.


texts:
I am reading through a HIPOT / Dielectric Strength requirement that states in no so many words: "withstand damage when 1KVac is applied between all mutually insulated circuits"

I search every where and it must be my English but, I am not sure I understand what is meant by mutually insulated circuits.

Let's say I have a connector with the following pins going outside an enclosed box:

120Vac Phase A
120Vac Phase B
Chassis Ground
Sensor 1 (0-5Vdc)
Sensor 2 (0-5Vdc)
24Vdc
24Vdc_Return
208Vac "Line" Load
208Vac "Return" Load

What would be considered mutually insulated circuits?

Since I have surge protection on sensor lines a 1KVac will trip those and fail the test. If I remove the protection a 1KVac it might kill the circuit, and perhaps that is OK as long as it doesn't fail short?


texts: Does waveform shape affect transformer eddy current loss as frequency changes but peak voltage is fixed?

texts:
I'm trying to figure out how eddy currents change with frequency. While learning about this its occurred to me that eddy currents might be impacted differently as frequency changes, if the voltage is a square versus a sine wave. (Assuming the peak voltage reached does not change).

A square wave with a negligible rise time is essentially a DC voltage applied to the transformer (for this discussion really just an inductor) for half a period of the operational frequency. As frequency changes, the amount of time the voltage is applied changes, but the resultant slope of current, mmf, H-field, and B-field, is the same regardless of frequency. di/dt = V/L .

Since eddy currents are a result of induced voltage across core resistance, and induced voltage is proportional to slope of flux (V = L * di/dt), then eddy currents remain constant as frequency of a square wave driving voltage changes.  (The peak flux reached changes but that does not result in a higher induced voltage.)

But with a sine wave, the slope of the applied voltage actually changes with changes in frequency, so therefore the slope of the flux changes, and this would changes in induced voltages which create eddy currents. For instance higher frequencies induce higher voltages and therefore higher eddy currents.

Is this correct?


texts:
"The intensity of the field radiated at a distance r >> λ from a current element Idz is given by the magnetic filed intensity $$\hat{H} = \frac{I }{2\lambda r} sin(\theta) dz$$ Find the electric field strength in free space at a point 1km from a λ/2 dipole in a direction normal to its length when fed with a current of 0.1A (rms) at its center. Given that the radiation resistance of the λ/2 dipole is equal to 74 ohm."
I was given this question as an assignment, but I'm struggling to find an accurate solution. Could anyone outline the methods used to solve this problem?


texts: Multiple inductors in series/parallel, flyback diodes required?

texts:
Considering the following setup, 4 equal inductors (4.5V DC, 90 mA pager motors of unknown inductance values) in both parallel and series connection, how many flyback diodes should be used? Is one enough for the entire setup? Or one per series pair or one per parallel pair? Or should each get their own flyback diode?

Or is it completely dependent on the voltage and current through the inductors?

simulate this circuit – Schematic created using CircuitLab


texts: Should I get CE mark on my Arduino project?

texts:
I just finished my big Arduino project after 2 years. I would like to start selling it, but I am not sure if I need CE certification or not. I used the below components:

Arduino Nano-oled 0,96"
keypad
simple buttons
TP4056
2-5V DC-DC converter
NRF24L01 2.4 GHz module

I am not sure if I need a CE certificate. Can somebody can help me, please?


texts: Can I use an off the shelf electromagnetic lock to repel?

texts:
Can I take an off the shelf electromagnetic lock such as this https://www.amazon.com/SKYZONAL-Electric-Magnetic-Electromagnet-Fail-Safe/dp/B01LE95P7I/ref=sr_1_11?keywords=electromagnet&qid=1583007323&sr=8-11&th=1 and use it to repel rather than attract? Can I vary the current to affect the magnetic field strength?

Based on the information provided, I can't tell whether there is some special circuitry built in that only allows it to be on or off, or only allows the current to flow one way in these types of devices. I am looking for a moderately powerful electromagnet for a project and I need it to repel.


texts: Take first edge or level of the wave and ignore rest until reset

texts:
I have a pulse train of fixed frequency of 30kHz. when I connect it to the LED I get LED blink at 30kHz. What would be the way to detect the first edge/ level of the pulse train and ignore the rest, so i get the led to be lit without blinking. LED should turned off when a reset pin is activates.  A parallel capacitor will just smoother the oscillation, but a very large value will case delayed switch off which is undesirable. A digital circuit is expected.

Actually the TSOP receiver gets an modulated waveform to reject ambiance IR. So I want a way to connect the TSOP as a binary switch., with minimum possible components. No Micro-controller (as the person i am suggesting solution don't have experience)

i tried with RS flip flop but it is not working.
Schematic


texts: Signal decimator/down-sample with lowest propagation delay

texts:
I would like to frequency-divide a 10 MHz digital signal by a factor of 8 or 16, with the lowest possible propagation delay. I need a propagation delay that is at most 5-10 ns. The best solution I thought of is to simply use a flip-flop counter. This seemed to be a good one, but the propagation delay can go up to 70 ns in that chip!

Is there a chip that is better suited with my timing requirement? Alternatively, is there a better way to achieve this?

More details if you're interested:

The reason for all this is that I'm trying to use a 10 MHz signal to control an FTM counter in a microcontroller (Teensy 3.6) in input capture mode with some interrupt control used as a phase-lock to keep sync with the 10 MHz signal. The problem is that the FTM counter is not sensitive to that kind of very high frequency, so I need to frequency-divide it before using it.


texts: What does means 'indiscriminate' in RF systems

texts: The RWS-371 RF modules work as at the 434 MHz  band, the documentations states: "These modules are indiscriminate and will receive a fair amount of noise".I guess they at least have some kind of bandpass filter, so what does 'indiscriminate' means? How does this compares with the RF24L01 were you need to specify and pipe address?.


texts:
Maybe I don't quite understand how zener diodes work but, I thought that they would block a reverse voltage until it reached a certain threshold (the zener voltage) and above that, they would allow the current to flow. This diagram shows my circuit:

simulate this circuit – Schematic created using CircuitLab

When the switch is flipped to 5v, I would expect Vout = ~0v because current would flow through D1 instead of R2, but instead, I get Vout = ~3.5v.

When the switch is flipped to 3v, I would expect D1 to block the current and so Vout = ~3v. I get Vout = ~2.7v which is close enough.

I don't have a zener diode to test this with a physical circuit. I wanted to simulate it first so I would know what parts to get.  I have tried it in both iCircuit and CircuitLab and both produce the same results.

I also tried putting the zener diode directly between SW1 and Vout like this:

simulate this circuit

This gets me sort of what I expected. When switched to 3v I get Vout = ~0v but when switched to 5v, I only get Vout = ~1.2v.

How do I get Vout closer to 5v when switched to 5v?


texts:
Has anyone used this data logger (or similar) with v-usb to collect data?

http://www.sparkfun.com/commerce/product_info.php?products_id=9147

If so, what is the maximum times per second voltage data can be sent at HID messages? (I can't understand the spec sheets)
And can it work with an ultrasonic rangefinder (or similar) also from sparkfun?

Thanks


texts: How to prevent peltier power supply from oscillating

texts: I want to use a DAC to control the current to a Peltier device. The Peltier will typically be running at about 0.25A, and this requires less than 100mV. I have tried this circuit, but it oscillates at about 100KHz. The Op amp is fed from a separate 3.3V power supply. The darlington has an Hfe of 2000. How can I stabilize it?


texts: Buck converter: what determines the inductor voltage?

texts:
I am studying buck converters and have nearly grasped their ideal workings in the Continuous Conduction Mode however there is one last bit that I can't get a confident grasp with.

When the transistor switch is OFF, what makes the inductor voltage go negative? Is it that at that instant the diode is not in forward bias mode, it has therefore undergone a large negative
\$ di \over dt \$ according to

$$
V = L { di \over dt }
$$

and therefore a negative voltage is applied across it from say 5V to say -0.6V which is a typical diode forward voltage.

What restricts the maximum value of this voltage?


texts:
I have 4 standard mild steel foil strain gauges bonded to a steel bar in a wheatstone bridge arrangement. They are implemented into a circuit with the INA 125P amplifier. I only manage to use about a fifth of the actual arduino resolution (200 of 1023), and I am assuming that this is because the signal is amplified to around 1 volt or less, where the arduino supplies 5V to the circuit.

I tried swapping arbitrary resistors to set the gain for the INA 125P amplifier but they either failed to make a difference or completely removed any signal to be read on the PC from the COM.

The question is, what else could I try to do in order to get a better (higher) signal?


texts: Switch on and off an electronic device within a time range e.g: 8am to 3pm

texts: i am wondering if anyone know how to adjust an electronic device so it can work on a specific timeframe, I have a water pump, I would like to make it work only within a determined time range, for example 8 am to 4pm, I was thinking to use raspberry pi but I think that's beyond the need. Thanks!


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I have an audio mixer with the following circuit (I omitted the input stage):

I removed the mono instrument output and used the jack connector as an alternative line-output.

However, while doing so, I removed the DC path to ground (through R31) from the opamp outputs.
Was the only purpose of R31 to form the voltage divider to obtain the instrument level signal? Or is it important that a DC path to ground from the opamp outputs exist? In most mixer designs I see online there's no such path.
Secondly, when I turn on my modified circuit there's a DC signal on the outputs that exponentially fade's to 0V in about 3 or 4 seconds. This is strong enough to make my loudspeakers pop quite hard. What can be causing this? Is this related to the missing DC path to ground?


texts: Wiring DPDT switch to add parallel resistor

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folks,

I'm a relative novice at electronics, I've done some guitar stripboard projects and things like that, and I'm currently making some modifications to an old synthesizer. I've done a few of the mods sucessfully, but I think the instructions I got for one of them are wrong, and I'm not sure what to do.

I was going to get into the sonic details but realized it's not necessary to answer the question. I have two separate circuits, and I want to add a parallel resistor to each, and toggle both circuits at the same time. One position would put the parallel resistor in the circuit, the other just leaves the original resistor. The instructions call for a DPDT ON-ON switch. The drawing is here, in the first post:
https://forum.moogmusic.com/viewtopic.php?f=1&t=22856&start=30

I did it as he suggested, it's not giving me the expected sound. When I contacted the guy who did it, he said he never actually did one like that, so he wasn't sure it was correct.  Am I supposed to wire this differently than what he had indicated? I almost feel like something should go on the bottom two posts.

Thanks


texts: How to connect a LED G13 Tube directly to a power socket?

texts: I am trying to build my own cheap lighting for my greenhouse. I have found a couple LED tubes that would be perfect for the task, only they are supposed to be mounted on a lamp of some sort. They have two G13 plugs, one on each side of the tube. Since I'm very ignorant in electronics, how would I connect them to the power socket? I suppose I would have to buy a power plug and some wire, but that's as far as I go.


texts: Why can the DLC (data length code) be 0 in CANBUS?

texts: In a lot of document I found out that the DLC can be from 0 to 8, but they don't say what purpose is of DLC being 0.