texts:
I have some basic doubts about switched capacitor resistors:

With this circuit we get an equivalent resistance equal to (Reference: Wikipedia):

Where f is the frequency of the clock signals that open and close S1 and S2.

My doubts are:

When we switch from S1 to S2 or vice versa, Cs has a certain charge and so a certain voltage, and at that instant a different voltage is applied on it. It is like short circuiting two voltage sources with different voltages. Where does the deltaQ (difference of charge) go, since there are no resistances?
Resistance means dissipated power. So if we get the behaviour of a resistor, there should be dissipation of power. But in this circuit S1 and S2 are ideal, and also Cs. Which is the explanation of this?


texts: How well do relays handle brief overcurrents?

texts:
Unlike solid-state devices, relays often (in my limited experience) do not come with maximum peak current draw, only maximum continuous current draws. In general, how well do relays take pulses of current over their rated continuous current draws?

Is this different between 'traditional' relays (like this one: http://shop.ciseco.co.uk/jqc-3f-t73-5v-pcb-relay/) and reed relays?


texts:
I bought this transformer As I need to convert 230vac to 18vac

As can be seen in the image it has 2x 115V terminals and 2x 9v terminals so I  assumed it would be centre tapped but this does not seem to be the case.

There is no continuity between the top left terminals and top right, the setup is the same for the lower 9v terminals.

My question is, can I safely bridge the 2 middle top terminals and 2 middle lower terminals to form a 230v winding and 18v winding respectively?


texts:
Hopefully this is more of an electrical engineering question than a MATLAB question, but I don't understand a system response I'm getting.
I recently got 2 Arduino Due's and configured 1 in MATLAB Simulink to be a pulse signal generator and the other to loop the signal back:

I have the signal being generated as sample based with the sample time set at .01 seconds which also means the serial read, write and scope block have the same sample time. The solver setting for this board is also set at .01 seconds. I set the pulse widths and period length to the appropriate values to get a 1Hz signal (50 pulse width and 100 period width).
For the first check I set the loop-back board with the same sample time settings but have it running in external mode. I loaded both models to the boards, ran the loop-back board and started the generator board. I got an output that showed a .01 second difference between signals which I figured to be due to the .01 sample time of the loop-back board.
The next check I did was set all the sample time settings (solver, serial read, serial write) on the loop-back board to .1 seconds. I loaded both models on the boards again and ran the loop-back then started the generator and still got .01 seconds. I figured with that a factor of ten less samples per second would cause a greater delay but I'm not sure if its my lack of knowledge/understanding in serial comms, arduino or matlab causing confusion. Even if what I'm getting is expected... still not sure why.
Is the delay a factor of sampling time or intrinsic to the circuit? I understand not meeting the nyquist rate can result in missed data but it my case the the graph was just shifted.


texts:
I have tried searching for an answer and looked online, but I'm just getting more confused.

I have a DMM that measures temperature with a thermocouple lead, with a resolution of 1 degree C (shows 020) for 20 degrees C and manual states accuracy of ±1%+3 digits. I understand the 1% of the reading, but I cannot figure out the 3 digits part.

For 20 degrees C, 1% is 0.2. Does this mean I should add 3 to the 0.2 meaning ± 3.2C or add 0.3 to the 0.2 meaning ±0.5C? Or is it something I am missing?

Also temp reading always flickers between 2 readings. Does this mean temp is in between the two?

Thanks


texts: Avoiding ground loop through d-sub like connector shield over metal enclosure

texts:
I have to pass a couple of analog signals between separately grounded systems over a HPDB68 cable. Ground loops have been a major issue previously, so the signals are passed differentially and recovered against target ground using a differential amplifier. The shield is connected to ground on one side. On the other side, I'd connect it to the PCB ground using a capacitor to short RF but break LF loop.
What bothers me is: what is the common way to do it with the D-Sub connector on metal enclosure? Those connectors are usually screwed right on, which does not allow for the capacitor. Making custom spacer for isolation is doable, but this has to be a common issue? There have to be some off-the-shelf parts and solutions for this? Yet I can neither find nor remember ever seeing such an example?


texts: DC Analysis of this common emitter circuit

texts:
I'm learning about transistor configurations (particularly in relation to audio circuits) and am having difficulty analysing this fairly straightforward common emitter stage from the Instrument input of a Roland RE-201 Space Echo. Specifically, I am confused how to find the DC bias voltages for this circuit. If R3 220k was connected to Vcc this would be a standard 4 resistor setup but with it being tied to the collector (which is connected to Vcc through R8 27k) I am having trouble calculating the voltages. Every explanation I have looked at so far brings in the transistor beta at some point in the calculations but am wondering if it is possible without using this (or even without estimating beta) with the known resistors and Vcc of 17v.

I tried looking at it in terms of a voltage divider but don't end up with the 5v Vc that the schematic shows:

i.e.

Vb = 17 * ( 47k / [47k + 220k + 27k] ) = 2.71v

Ve = Vb - 0.65v = 2.06v

Ie = 2.06 / 560R = 3.6mA

Ic = Ie

Vc = Vcc - (27k * 3.6mA) = wrong!

I think I'm perhaps incorrect with my first line of calculation as there may possibly also be a resistance to ground from the collector through the transistor (?) which I imagine should be considered, but I don't know how to factor this in.

Can anyone offer some advice?

Many thanks in advance

EDIT: schematic re-uploaded to show that C6 / R10 are connected to other audio inputs which go through a separate amp stage and so bypass Q11.


texts: How do I safely connect a light switch button to the secondary side on a board?

texts:
I designed a special light controller board. It has a primary side that is connected to AC 230V. There are a certified AC/DC converter module and a relais, bridging the air gap between the primary and secondary sides.

On the secondary side is a microcontroller and various sensors running at DC 5V. The microcontroller controls the relais wich switches the light on the primary side. See the following abstract layout of the board:

In the next version, I would like to connect the button of a light switch to add some manual control. The button press should be received somehow by the microcontroller.

Which component/method do I use to safely connect the button to the secondary side? Note that it is a light switch. The wires are not connected to the AC power, but they run along the AC wires. By law, there has to be an insulation between them and the low voltage side. E.g. in case of a short, there is suddenly 230V on this wire.


texts: Bugs in Maxim chip MAX3421E (used as USB Host)

texts:
The MAX3421E is an USB client/host chip from Maxim which can be controled by SPI.

Can anybody confirm that there are bugs in the chip or at least confirm that the chip does not always do what the documentation says?

I found several bugs / oddities / misdesigns and would like to know if I'am the only one experiencing this. USB programming is very complex and may be I did something wrong.


texts:
I know that processors perform the tasks in binary. If I give an instruction to the computer, for instance, I have pressed letter "A", which is denoted as 01000001 in binary. How does a transistor perform that task?, more precisely, does a processor use 8 transistors to process this 8 bit of instructions or does a single transistor change its state 8 times to process this 8 bits of instruction?
(It might be a very basic question, but I am not a computer expert)


texts:
int main(void)
{

DDRD = 0x00 ;
DDRB = DDRB | 0b00100000 ;
while (1)
{
     while(!(PIND & (1<<6))){
       PORTB |= 1<<PORTB5 ;
    }
    while((PIND & (1<<6)))  {
        PORTB &= ~(1<<PORTB5) ;
    }

}
return 0;
}

I am trying to create a basic security system by using a switch that when broken is picked up by PIND7, then sets PB5. And Vicd versa, when the switch is set, the low signal is picked up by PIND7 then clears the bit on PB5.
The micro-controller is not having a problem when the switch is set, it clears the bit in PB5 immediately, but when the switch breaks, it takes about 30 seconds for the bit in PB5 to be set.
Thank you for any help you can give, I apologize if my code is sloppy I am just a beginner


texts: ATX Computer PSU: OK to connect loads between positive rails, e.g. +12v to +5v

texts:
I have looked, but haven't find an answer.

Are ATX computer PSUs capable of having a load connected between their positive rails, so that for example, current would flow from a 12v rail to a 5v rail?

Specifically, I need to know:

Does the specification of the standard say anything about this?
If not, what is the likelihood that it would be OK?
What's the worst that could happen?

Thanks

Addition: Same question, but between the -12v and any of the positive rails (paricularly +12v and +5v). Similar question here says -12v to +12v would be OK.


texts: I want to use 4x MicroServo with 9V battery

texts:
I have 4 Tower Pro MicroServo 9g SG90 I want to power with a battery. This is the datasheet I found online.

I have a small breadboard and some resistors laying around (220, 1k, 10k), and a 9V battery.

I hooked up the battery leads on the power rail of the breadboard, and added my 4 servos in there, and they turned on and rotated properly when I issued commands from my Arduino board. The thing is that AFAIK it operates on 4.8V-6V from what I have read.

I did a voltage divider using some of the resistors I had and I could output 5V when tested with my multimeter, but the servos didn't work (probably because low current).

So my question is, can I power my 4 servos with a 9V battery? Should I add some resistors before? Bear in mind I am new to electronics.


texts: Relation between phase angle and current direction

texts:
In a triphasic system (any), is there a way to tell if the current is entering or leaving a phase/line/load just by the angle of the phasor of the source ?

In the following picture we can see the labels IA, IB and IC.
They all point towards the load.

But we know that it's not the actual current direction

What is their actual direction when VAB=380<0, VBC=380<-120 and VCA=380<120 ?

Can I tell this by the angle ?

As can be seen by this graph, when two curves cross, two currents are leaving the load, while another one is entering.
60 degrees later, in any direction, the reverse occurs.


texts:
Sometime early 90s I came across a whitepaper published by an oscilloscope manufacturer that described a custom preamp IC they had developed for their scopes. Does anyone know of this article?

The circuit was something like a differential doubly-cross coupled cascode; the article claimed it balanced settling time, accuracy and drift to do an order of magnitude better than the competition. I believe it was Tek but not their "measurement concepts" series. The article could have been quite old at the time (70s or 80s). The custom IC had a three-digit internal part#.

All these details could be incorrect, it was a long time back. But I still think about this circuit, it was just genius.


texts: How much power can a 7805 voltage regulator dissipate without a heatsink?

texts:
I am using a LM7805 linear voltage regulator.

Vin is 12 V
Vout is 5 V (regulated)

My load is currently 100 mA. Without a heatsink, it's pretty hot.

Could i use a large heatsink to regulate 5 A?

Or what is the maximum output current with a heatsink for a 7805 linear voltage regulator?


texts:
I want to calculate theoretically the current carrying capacity of a cable. I have 24 Awg cable, which is having 8 strands: the overall dimension of the cable is 1.27mm and each strands dia 0.15 mm approximately. What I need is a relation, an equation which enables me to calculate its current carrying capacity.

  Since I dont have datasheet, can someone give me an equation for calculating it, or any chart where I could see relationship between strands characteristics and current carried?

https://oscarliang.com/wire-awg-chart-quadcopter-rc/


texts:
I built a simple full bridge rectifier with AC Mains input, but I noticed that:

When the input is 220 V rms the DC output is only 293 V, but I expected the DC output voltage to be 220 x sqrt(2) = 311 V.
The DC out drifts over the time. eg for Vin = 220 VAC I may get 298 VDC output, but if I disconnect the circuit for a while and then reconnect it I may see  293 VDC out for 220 VC in.

The circuit consists of four RL207 diodes, a 10 uF 450 V capacitor and a 1 MegOhm bleeder resistor across the capacitor.

I use voltmeter UNI-T UT50A on its 1000 VDC range .

Questions:

For 220 VAC input

Why is the DC output voltage not 311 VDC as I would have expected?

Why does the DC output voltage vary as described above?


texts: Can 64b/66b be forced out of DC balance by malicious data?

texts: Unlike 8b/10b and 64b/67b, 64b/66b relies entirely on the scrambler for ensuring DC balance.  This raises the question: can a malicious data stream force the line to leave DC balance?  Or would it need access to information that is not exposed by the NIC?


texts:
The task is to find \$I_L\$ and \$R_i\$ given \$U_L\$ and \$R_L\$.

\$I_L\$ is simple enough but I can't get my mind around how to find \$R_i\$ surely you must have more information?


texts: What are odd-even memory addresses in 8086 and how do they work?

texts:
I have recently started to look more into microprocessors at the hardware level, and i am a bit confused on what are the odd-even memory locations that 8086 uses.
As far as i understand, it has something to do with 8086 being a 16-bit CPU while retaining the ability to access individual bytes at a time of its 8-bit predecessor 8080, but how does it work in detail?
Also, how do other early CPUs like the 68000 approach the problem of addressing individual bytes? They don't have on chip cache to read entire chunks of memory at a time nor do they have a complex MMU after all.


texts:
I was asked to:

Design a combinational logic circuit that has 10 inputs, numbered 0 through to 9, and one output. The output is required to go HIGH whenever any one, or more, of the inputs numbered 2, 5, 6 or 7 go HIGH. The circuit should be free of static hazards.

I know I can use OR of 2,5,6 and 7 and give it's output but I don't  know how to check for static hazards and how to remove it? Please help..

Please check if this circuit has static hazards.


texts: extract technical drawing from pdf into altium

texts:
I have a PDF containing a diagram of a PCB which I intend to include in my system. Unfortunately while some dimensions are indicated on this pdf others are not.

I would like to import this diagram onto a mecahnical layer of a PCB at the correct scale so I can use it as a template for my design.


texts:
Reading an NTC datasheet I have understood the meaning of the power derating plot, which looks like this:

Meaning that below a certain temperature, the resistance is so high that to allow the 100% of power one should apply a voltage higher than the maximum allowed.
But I am not sure on how to interpret this data. This graph is taken from a 10k NTC, for which at 0°C is 32554Ω, but according to the plot I can still apply 100% of power, which is 500mW. To achieve that, I should apply more than 120V, where on datasheet they say no more than 50V.

EDIT: The sensor is the NTCLE100.


texts:
A document states that:

Phase-locked loops (PLLs) provide robust clock management and synthesis for device clock management, external system clock management, and I/O interface clocking.
You can use the PLLs as follows:

Zero-delay buffer
Jitter attenuator
Low-skew fan-out buffer
Frequency synthesizer*
Reduce the number of oscillators required on the board*
Reduce the clock pins used in the device by synthesizing multiple clock frequencies from a single reference clock source*
On-chip clock de-skew
Dynamic phase shift
Counters reconfiguration
Bandwidth reconfiguration
Programmable output duty cycle
PLL cascading*
Reference clock switchover
Drive the analog-to-digital converter (ADC) clock*

I have used PLL only to generate more clocks. For this reason I do understand the uses marked with •. However, the rest are completely unknown to me. What do they mean and why would I ever need to use any of them at all?


texts:
The schematic below is an H-bridge , the high and low mosfets are internal to the two ICs on the right side, their datasheet is here.
What is the purpose of the part on the left, which I googled to be a buffer IC, datasheet here.
Is it for the sake of circuit protection?
My understanding of using a buffer is limited, I have always assumed they where used in cases where something could not source enough current to drive something else, so you use a buffer with higher current sourcing capability. Is this correct and is this the case here?


texts: Need help to analysis & overcome an issue with LM358 OP-AMP

texts:
I want to measure the resistance of a coil which its resistance vary in accordance with its temperature coefficient of resistance, the resistance range of the coil vary between 0.12 Ω to 5.00 Ω, at end to calculate its temperature.

The amplified output from the LM358 will be used by an ADC of a microcontroller to determine the resistance of coil (10-bits).

All system (microcontroller + OP-Amp single supply) will be run on 3.0 volts, and that's restricted as this system is a portable-battery device.

Problem
I have bad luck with the accuracy as the following :
 - Above 0.35 Ω the accuracy is somehow acceptable (of course looking for more accuracy).
 - Below 0.35 Ω the accuracy going negatively in the side that effect the purpose of the system as mentioned in the text on the picture.

The problem is that the 0.01 Ω error in measuring the coil's resistance at 0.12Ω (actual resistance of the coil) means an error of 11.2 degrees Celsius which is not acceptable.

at 5.0 Ω the 0.01 Ω error means only 0.33 degrees Celsius which is acceptable.

The method of measuring the resistance depends on a constant current of 0.299 Amp.

At 5.0 Ω the output from the OP-Amp is 1.495 volts, so I used the below equation to estimate the resistance of the coil.

Coil R = [Vout x 5 Ω] / 1.495

On the picture I mentioned the accuracy problem in numbers as observed.

Note: observation done on Multisim 14.1, not an actual circuit.

So what I missing here ?


texts: Estimating power consumption in cadence RTL compiler with VCD file

texts:
I need to analyze the power consumption using RTL Compiler based on the VCD file generated by ModelSim. I have two files:

gcm.v (This is the main circuit. Module name is "gcm")

tb.v (This is the testbench. Module name is "tb", and "gcm" is instantiated as "gcm_tb")

The command to generate vcd file is in tb.v as below:

$dumpfile ("testb. vcd");
  $dumpvars (1, testbench.gcm_tb);

Here is my script for RTL compiler:

set_attribute lib_search_path /opt/cadence/local/FreePDK45/osu_soc/lib/files
set_attribute library {gscl45nm.lib}
read_hdl -v2001 tb.v
elaborate
read_vcd -vcd_module gcm_tb -module gcm -static testb.\ vcd
synthesize -to_mapped
write -mapped > gcm_synth.v
report power -tcf_summary > power.txt
exit

RTL compiler gives me the same power numbers with and without the VCD file. Here is my power summary in power.txt:

============================================================
  Generated by:           Encounter(r) RTL Compiler v07.10-p004_1
  Generated on:           Mar 28 2013  03:47:17 PM
  Module:                 ccm
  Technology library:     gscl45nm
  Operating conditions:   typical (balanced_tree)
  Wireload mode:          enclosed
============================================================

                    Leakage    Dynamic     Total
  Instance   Cells Power(nW)  Power(nW)  Power(nW)
---------------------------------------------------
ccm           2963 71474.787 535247.155 606721.942
  add_147_11   127  6038.327  11984.664  18022.991
  a_aes          0     0.000  19505.200  19505.200
  e_aes          0     0.000  26450.600  26450.600

-------------------------------------------------------
Total nets in design            : 3865 (100.00%)
Nets asserted                   : 0 (0.00%)
Nets computed                   : 3862 (99.92%)
Default nets                    : 0 (0.00%)
Clock nets                      : 0 (0.00%)
Constant nets                   : 3 (0.08%)
Net does not have TCF asserted  : 3865 (100.00%)
-------------------------------------------------------

I see the nets asserted is 0. Is this the reason why the power consumption did not change?

Thank you!


texts: Information content of amplitude modulation versus single-sideband transmission

texts:
An amplitude-modulated radio signal with carrier frequency C, which includes frequencies from 0 to F, will use output frequencies in the range C-F to C+F, or a total bandwidth of 2F.  A modulation approach called single-sideband modulation omits either the frequencies below C or those above C, and simply transmits the others, on the basis that the frequencies on the other side of C are "redundant".

It would seem, though, that there is information content in the seemingly "redundant" frequencies.  For example, if the signal to be modulated on a 1MHz carrier was a sine waves at 100Hz, an AM signal would contain two frequencies: 999,900Hz and 1,000,100Hz.  Receiving both frequencies and demodulating them would a 100Hz signal whose phase matched that of the original.

If the signal were single-sideband modulated (let's assume upper), then the modulated signal would simply be a continuous 1,000,100Hz signal.  Although a receiver which was tuned to precisely 1,000,000Hz would be able to detect that the signal was a 100Hz signal, I see no means by which it could determine anything about the phase of it.

On the other hand, it would seem like it would be possible to have two signals amplitude-modulated in the same bandwidth if the carrier waves were 90 degrees out of phase, provided that the receiver could discern which carrier wave was which.  If the signals to be modulated were devoid of DC content, one could obtain such a result by having the base level of one carrier substantially exceed that of the other.  The receiver would be phase-locked onto the first signal when the primary (0 degrees) carrier strength was at maximum.

If one can make use of two simultaneous analog communications channels, would amplitude modulation of two signals with carrier frequencies 90 degrees out of phase provide the same level of bandwidth efficiency as single-sideband modulation?  What other tricks exist?

(BTW, I'm pondering the notion of performing spread-spectrum transmission by amplitude-modulating a medium-frequency signal (e.g. 100,000-250,000Hz) on a ~900Mhz carrier.  Most "spread-spectrum" receivers I've seen are limited to receiving a single channel at once, but I would think that using analog modulation and demodulation would allow for a DSP to process many channels simultaneously).  To get optimal results, however, one would probably have to be able to accurately determine the relative phases of the signals one was receiving.


texts: Choosing voltage regulator for 3/4 AA battery powered pack

texts:
I've question similar to another SO question, with some minor differences, which I'll explain below:
I'm designing a circuit which should work with 3 AND 4 AA batteries. Idea is to create two models, one with slightly longer life than the other one (33% more). The circuit uses an STM8L, and would periodically "wake up" to perform some periodic stuff, and then go back to sleep, typical of certain battery powered devices. I'm planning to use a voltage regulator of 3.3 V output. I want to know which kind of regulator would make more sense (LDO vs switching). My use case doesn't require any RF application, so bit of output noise is acceptable (meaning switching regulator should be just fine).
With 3 AA battery system, based on the discharge characteristics, "95% + charge" would be available upto 2.8-2.9V. So, a LDO regulator, will be giving on average 3.8V battery regulated output 3.3V, which makes it around 85% efficient. This is putting it on par with most switching regulators out there. Please correct if wrong.
With 4 AA battery system, based on the discharge characteristics, regulator will be on average 4.5V battery regulated output 3.3V, which is <75 % efficient. Now we are getting into that territory where switching regulator would most definitely start to shine.
Please let me know if my above understanding is on the correct path. Should I use a LDO/switching regulator or design the two circuits separately one with LDO other with switching regulator? Any other suggestion also welcome.


texts: Can we assume 230VAC in 3 phase system between phase and neutral?

texts:
If all devices connected to a 400V 3 phase power system are balanced and have a perfect power factor, can we assume the voltage between each phase and neutral is 230V?

Why: I want to measure real power consumption of a 3 phase air conditioner, but can only use current clamps. If I can make the assumption that the voltages are 230V, then I would measure each phase separately and just add up the kWh together.


texts: Is Electret Mic a reliable component to measure Sound Intensity Level (Decibel)

texts:
I am working on a project where I am using a Arduino Nano to count number of Loud Sound (occurring at intervals) with intensity between 65 dB - 100 dB. I want to put a calibration unit and a digital display unit to calibrate the device within the aforesaid range and display the total count.

I am little bit concerned about the heart of the circuit - the sound sensor. I am thinking of a Electret Mic. Is it a good component to measure Loud Sound Level uniformly? I mean if I employ a electret mic to capture sound and place the output to an amplifier to measure the output analog signal, would it produce same analog reading (with minimum tolerance) for similar intensity of sound everytime? To further clarify it - when a sound is heard with 70dB intensity, if my arduino reads 95 from the sound sensor circuit, would it read something close to 95 everytime 75dB sound is produced?


texts: How should the correct cooling drawing be for the footprint on the d2pac case in kicad?

texts: I have bta16 triac.(Package: d2pac)I want to do heatsink with pcb.Do you have a ready drawing? I want to examine.in kicad.I need to example layout.Thanks


texts: How do I replace or fix this electronic chip?

texts:
I have a device that runs on a 3.8V Li ion battery.
A few days ago it stopped working.
I screwed it open, took out the battery, and could identify this seemingly fried (?) resistor on the PCB:

Am I correct in stating that R8 (R6?)  has been fried?

Is there any way I can fix this PCB without any soldering or other equipment?

In case of no, how can I find out what this is and how to order a replacement if at all possible?

UPDATE: This is a Welch Allyn battery handle component. The chip's gold plate is connected to a push-in metal button like thing that the charger locks into and pushes a high voltage into (~9V). I can't seem to find any spec sheets on the circuitry itself though.

The big metal connectors on the bottom picture (top and bottom) should output the battery's voltage (I checked with a second one of these I have laying around). On this one though, only one side has the proper voltage (when compared to the battery's + pole, which is connected to the metal patch on the right of the bottom photograph.


texts: I've seen that a number of schematics will connect the center (common) pin of a potentiometer to one or the other leg, and it then functions more like a rheostat. Is that how a rheostat is wired internally? What's the difference between a potentiometer and a rheostat? Finally, why connect the common to a leg at all on a potentiometer, instead of just ignoring the unused leg?


texts:
I tried to fix a keyboard that was having some intermittent issues by cleaning the conductors on the ribbon cable. I used an emery-board to rub off the rust and patina on the pins at the end of the ribbon, but it turns out that the pins are really soft metal and I ended up rubbing off the conductors themselves.

The ribbon had a little bit of slack so, I trimmed it to where the first break in the conductors were so that I could insert the remainder into the slot. Unfortunately there was not enough metal left exposed to make the connection (<1mm on some of the pins).

I thought about different ways I might be able to expose more of the metal but considering how fragile it already was, I figured that scraping or rubbing the plastic covering was out of the question. I considered using a chemical to dissolve some of the plastic, but I have no idea (or way of finding out) what to use or moreover, how to control it precisely enough. I figured that using a soldering iron to soften the plastic and push it away would work because I could more easily control the heat (more or less).

Unfortunately, the metal seems to have been extremely fragile (maybe it’s solder‽). Not only did the plastic warp a little bit and not soften easily to be pushed out of the way, but one of the lines even got a hole in it right through the metal.

Now I’m left with a ribbon cable (as seen below) and wondering how I can fix it. Is there a way to fix it as is or perhaps attach an extension?


texts: Understanding the difference of optocouplers vs relays and choosing the right replacement

texts:
I'm a bit overwhelmed by the sheer amount of variations in optocouplers and since I've never used one before in any project I don't really know what criteria to look out for.

A colleague of mine suggested that I should replace the relays in my circuit with optocouplers as they are much cheaper and also smaller in size. I agree with him once I looked into it, but unlike relays, I'm very unfamiliar with optocouplers.

I have this schematics in which I use relays to enable/disable a parallel resistor.

simulate this circuit – Schematic created using CircuitLab

From my understanding, if I were to use optocouplers I could get rid of the TPIC6C596, which I only need due to the high current draw of the relay.

So for this output-schematic I figured I could use this LTV-847 which would replace 4 relays at once.

But there were many other options to choose from and I just feel like I'm making a wrong choice because the above was simply the cheapest 4 channel chip that I found.

It's a simple circuit without much timing constraints, so any optocoupler that uses less mA than a relay and handles 24V could work.

For relays it was a bit easier, because I needed the smallest, cheapest 5V relay that I can get, which narrowed down the search quickly.

But with optocouplers pretty much all of the options are cheaper than the relays, are smaller and also use less current...

Edit:

Would this circuit produce the same result as the relays?

simulate this circuit

Is my optocoupler choice fitting for the scenario, given that I have 24V on the input module and 5V on the control side. Basically just requiring a "switch" solution but in a smaller form factor.

Regarding my schematic:

Originally I used relays because I knew they don't produce a voltage drop on the output.

However, from what I've read, optocouplers do produce voltage drops because of the phototransistor used.

But since I'm unfamiliar with the component itself I didn't know how I could best reproduce the result of a relay with an optocoupler, meaning I can get the ~24mA needed on the output side.

The relay simply creates a parallel resistor, so the total resistance is around 1K ohm.

Would I need to lower the resistance of the output resistor R3 or are there optocouplers with identical results as relays?


texts: Why does this CO detector forbid the use of lithium batteries?

texts:
I have several Kidde KN-COB-LP2 CO detectors installed in my house. They look like this:

They operate on standard AA-size alkaline batteries, and typically last several years on such batteries.

The manual says this about replacing batteries:

  When replacing the batteries, use one of the following approved
  Alkaline brands:

  Duracell MN1500 or MX1500
  Energizer E91
  Gold Peak 15A
  Golden Power GLR6A

  These batteries can be purchased where you bought the alarm or at a
  local hardware store. Use of a different battery may have a
  detrimental effect on the alarm operation.

  NOTE: Do not use Lithium batteries in this unit. (emphasis in original)

While they work fine with other quality alkaline batteries from reputable manufacturers, I'm curious as to why the manual specifically forbids the use of lithium batteries.

Batteries like the Energizer L91 "Ultimate Lithium" use Li-FeS2 chemistry and produce a nominal 1.5 V per cell, just like alkaline batteries. They also tend to last longer than alkaline batteries, so why not use them?

Inquiring with Kidde met with unhelpful responses that basically amounted to "The manual says so." without going into more detail.

The only technical reason I can think of is that the discharge curves for lithium and alkaline batteries are different, and the low-battery warning might not activate at the same level with lithium batteries as it would with alkaline.

I also imagine there's regulatory reasons, such as the detector being certified after undergoing tests with the specific listed alkaline batteries but, having not undergone testing with lithium batteries, those are not allowed to be recommended in the manual.

Are there other reasons?


texts: 1oz copper ok for card edge connector in prototype?

texts:
I'm doing a small prototype system and would like to fab boards at one of the inexpensive Chinese places like:

https://www.elecrow.com/pcb-manufacturing.html

I'm going to bus the boards using ribbon-cable card-edge connectors like:

http://multimedia.3m.com/mws/media/22003O/3mtm-100-in-card-edge-connector-drilled-flngs-ts0012.pdf

... with gold wiping area.

I'm wondering if this will work ok (issues such as poor conductivity initially, failure after a few connect/disconnect cycles, etc).


texts: BJT output characteristics in negative Vce region?

texts: How do the BJT output characteristics in negative Vce region look like? Is it zero current or a reflection of the usual characteriscs in positive Vce region about origin?


texts: Some Arduino starter-kit projects show the resistor placed before the anode of a LED, coming from output, and others show it after the cathode, going to the ground. Is there any difference? Why?


texts: PCB trace length matching for High Speed signals with known frequencies

texts:
I am designing a PCB with High speed video interfaces and I would like to know the way to calculate the maximum tolerance that I can count on while I am length matching all the traces.

When I routed the signals from the DVI driver chip to the connector, there where guidelines all over the internet, but when I am trying to route the bus from the driver chip to the FPGA, it is not that easy to find a guide like that.

So all in all the question is:

I have a bus with a frequency up to 165MHz with 24 signal traces. I would like to know the tolerances that I can count on while I am length matching these traces. I would like also to know how to calculate that.


texts: I am trying to write atmel at28c256 on breadboard so I tied all address lines to ground, and all I/O lines also tied to ground. I untie I/O lines for reading, tie 'WE to high, 'CE to low, and 'OE to low for reading. I am reading all ones at I/O ports, no matter what address. So, when I try to write this eeprom I put 'OE high and with 'WE line I touch to ground so that should write stuff to memory but it does not, all I/O ports were connected. I also made small RC circuit with button on WE but that also does not work. Any toughts?


texts: Connecting 7-segment display to microcontroller

texts:
In the above circuit, what is the reason of connecting transistor to 7-segment display?

What's the difference between the two display with transistors and other two with only resistors?

Also please explain why LED is used after regulator, whether it is simply indication(5V) to the microcontroller, or it is used to reduce the power dissipation


texts: Confusion regarding Biased Clipper Circuit

texts:
When the voltage is lower then the biased voltage its appear in Output Voltage, But just when the voltage get larger than Bias Voltage (Vb) the Diode start Conducting and its acts as SHORT and the voltage gets clipped.

But the thing that confuses me is that i learnt that Short makes potential Difference zero so when the diode was conductiong its act as short instead of clipped voltage which is appearing at output it must be zero voltage, right ?


texts: Can I create a CMOS AND gate with 2 serial n-type and 2 paralel p-type CMOS transistors?

texts: So I know that a CMOS AND gate is made with 2 parallel p-type transistors and 2 serial n-type transistors and an inverter on the output. But can we just make the AND gate similar to the NOR gate -instead to just use 2 serial n-type with 2 parallel p type. The truth table makes up an AND as far as I can see.


texts: How to simulate an AC line filter in LT Spice

texts:
I'm fairly new to LT spice and am trying to simulate an AC line filter, but it keeps giving me the error K1: coupling to shorted out (ignored) inductor L1. What am I doing wrong?

Here's the circuit:


texts: What happens when I use a battery with too much current?

texts: I am working on creating a line-bot from a book and it calls for a 6v, 1AH battery. I have these NiMh AA batteries that are rated at 2.3AH, 1.2v. Is there a way to set these up safely for the bot? What happens if I use too much current but the correct voltage?


texts: 60 Volt array of battery interconnect to Uc

texts:
I am trying to read an array of batteries up to 60V with a PIC. I have made a potential divider to scale down to 5V.

I am worried because my system share the GND from battery system which delivery up to 500KWh and so i think this path of current can damage my micocontroller. Anyone knows a better circuit ? or how can i protect my uC

Also I have seen from another post add a buffer on the Vout voltage divider, anyone knows why? is it for decrease the current on the micocontroller pin?

Thanks Antonio


texts:
I'm trying to find a powerful MCU that has multiple analogue to digital converters. I want around a 14 bit resolution to do some serious audio sampling.
Any suggestions or comments would be great, cheers.


texts: Why would someone tend to use a high-side device instead of low-side device?

texts:
I am trying to understand why someone would want to use a high-side MOSFET to switch on and off a load if they could simply use a low-side MOSFET.  Using a low-side MOSFET requires a much lower VG compared to a high-side device.

In the context of a half-bridge driver, I can see how you would need both low- and high-side devices with a charge pump integrated to the circuitry to charge the gate of the high-side MOSFET.

But my question is: How and why would you use a high-side device for various circuits other than half-bridge?


texts: How to find current through inductor when connected in series with an ideal diode?

texts:
Please help me with this simple circuit, which is creating lots of confusion due to different results from theoretical calculation and SPICE simulation.
Ques: In this circuit switch is closed for time t = 1sec, and then switch is opened and we have to find current through iductor and diode after time t = 2sec when switch was opened.
I solved it using V=L*(ΔI/Δt), and when simulated the circuit in LTSPICE the results were completely different. my calculation gave value of current after time t=2sec from opening the switch as I=7A through inductor whereas in LTSPICE simulation value came out aound 4A.
it's L=1 Henry only, sorry it was typo before
Circuit description: Ideal inductance (L=1 Henry), ideal diode and resistance of R=1ohm.

simulate this circuit – Schematic created using CircuitLab
THIS IS THE SIMULATION RESULT OF LTSPICE


texts: Purpose of anti-parallel diodes in isolated gate driving circuit?

texts:
I've come across this high voltage 'modulator' circuit and the MOSFET gate drive circuit is shown below.  The floating wire on the bottom connects to a duplicate of this circuit at the MOSFET drain (whose source is connected to -V1) with the 'dot' flipped on the duplicate's secondary:

simulate this circuit – Schematic created using CircuitLab

(Don't pay too much attention to the component values -- especially M1 and L1.  There's also a TVS on the MOSFET gate not shown here.)

Here L1 is the secondary winding of the 1:1 isolation transformer.  The primary side pulses +15V at about 1% duty, then -15V at the same duty, and repeat.  This charges the gate of one MOSFET at a time, while simultaneously draining the gate of the other (the other winding will see a negative pulse).  I figured out that C1 and D3 (12V Zener) hold the gate open after the positive pulses, and closed for the negative.

But what is the purpose of the anti-parallel switching diodes, D1-D2?  They appear to be in a clipping/limiting configuration, but I cannot figure out why they're needed.

Much appreciated!


texts: Decreasing Voltage of Power Supply via voltage regulator without using input/output capacitors

texts:
I have a HP laptop power supply 18.5V/3.5A that I intend to connect directly to LM7812 or LM7805 voltage regulator when I need to drop the voltage to 12V/5V. Since the laptop power supply (which is switched mode I assume) should be outputting a filtered voltage to the LM7812...are the input/output capacitors recommended in the datasheets truly necessary? could the LM7812 work in this particular case..without capacitors? what would be the disadvantage?
I do have a couple of generic DC-DC Buck converter boards off ebay and these work, but am utilizing it for other purposes.

cheers,
culain


texts: Parallel Port - Voltage / Current required for input pin

texts:
I am developing a program to send and receive sigal to my circuit and pc. Actually I have to count the pulses or (frequency of high pulse) generated from a 555 timer IC in my circuit. When I connect a input pin of Parallel port to the ground pin or simply to a casing of the system it produce a input signal.
I used transistor in the hardware side which let connect input pin to the ground on the production of High pulse. I think it is not a good method to do so.

Is there any way to do it directly by sending voltage to parallel port input pin?

What amount of current and voltage is required?

I am using 2x1.5 volt AA size batteries to supply power to the circuit.


texts: What does a mobile battery percentage indicate?

texts:
Just curious to understand, what does a mobile battery percentage indicate?

What is the input and output in the percentage formula with respect to batteries?


texts:
Looking to play around with the CREE Xlamp series LED and was wondering what would I need to drive them off 110V household power?

Output current needs to be in the range of 800-900mA.

EDIT: I am looking to do this for creating lighting for a NanoReef tank. I would be combining several of these in series.


texts: Grounding two boards connected to a backplane

texts:
I have a design which consists of a backplane and two boards mounted to this through some headers. The backplane provides a common 5V and ground to both boards and it also has a solid ground plane. Between the two boards there are two SPI buses running at ~25MHz where the connection goes from one board -> down in the backplane -> up to the other board.

Here's a simple illustration of the setup:

My question is how I should handle the grounding between the boards at the data connector. The alternatives I have come up with are:

Connect the gnd in both data connectors to the common ground plane on the backplane
Only connect gnd in data connector 1 to gnd in data connector 2 and don't connect to the ground plane
Don't use a gnd connection for the data connector


texts: Multiple Macs Controlled by single USB IR Receiver

texts:
I am looking to connect a single IR receiver to multiple mac mini computers to advance a slideshow played through front row in sync. I was reading this post below from superuser.com and one of the replies suggested that I post the question here. Currently we use a single IR receiver for each Mac computer and advance the slideshow with an apple remote. Our current method works but IR interference sometimes causes a Mac to not advance. I was thinking that if I could connect a single IR Receiver to multiple macs I could advance the slideshow in each mini from a single receiver without any misfires.

User: Chris Stratton suggests building a "number of usb-slave-enabled micro-controllers (one per PC) to a usb-host-enabled one (for the keyboard) using their serial ports."

I am new to electronics and would like to know if this is a viable solution and if so could you give me some direction as to how I could build this.

IR Receiver: http://twistedmelon.com/mira/hardware.html
Similar Post from: https://superuser.com/questions/367276/would-a-usb-hub-work-in-reverse


texts:
I don't belong to electrical engineering but I am trying to develop a intelligent Ni-Mh battery charger for one of my project. I am using MAX712 battery charging management IC. Reason behind that is:

It's available in DIP format so I can give a try on Zero PCB easily.
Cost factor.

My aim is to build a efficient charger that can find out when my battery is fully charged and cut out the charging after that and at the same time didn't harm the battery life (I find out from some of the forum that fast charging harms the battery life, though I cannot provide the link but I had read somewhere.)

I am not sure about the charging method. As per my study of MAX712 datasheet, there are generally 2 methods to find out when battery is fully charged:

\$\dfrac{dV}{dt}\$ (using the rate of change of voltage)
\$\dfrac{dT}{dt}\$ (using the rate of change of temperature of batteries)

I had prepared a schematic using the available resources on net and from the datasheet. Can any one help me to find out the best possible practice of charging Ni-Mh batteries using MAX712? I have to charge eight 1.2V Ni-Mh batteries. I am including my schematics for battery charging. Need help to be verify this and a possible way to provide trickle charging.


texts: Current in a single terminal voltage source?

texts: I know there can't be voltage without current, but how can I calculate the current in a wire if I only have the voltage and there is supposed to be no resistance?


texts: Determining final value of the output of a discrete system

texts:
I'm going through an exam question where I've been told that the samples f(kT) of the following function
\begin{equation}{\text{F}\left(z\right)=\frac{1}{1-0.819z^{-1}}} \end{equation}
are applied to a discrete system with the pulse transfer function

\begin{equation}{\text{G}\left(z\right)=\frac{C(z)}{F(z)}=\frac{T}{2}{(\frac{1+z^{-1}}{1-z^{-1}})}} \end{equation}

where T = 0.1s. I'm then asked to determine the final value of the output of the system.
I know that the final value theorem states

\begin{equation}{\lim_{k\to\infty}\text{f}\left(kt\right)=\lim_{\text{z}\to1}(1-z^{-1})\cdot\text{F}\left(\text{z}\right)} \end{equation}

but how do I obtain a value of F(z)? I'm not sure how the two equations above are manipulated to obtain the  F(z) I should be using the final value theorem with.


texts: How can I find removable plugs for standard pin headers?

texts:
I'm making a right angle adapter for a module with a 2x10 pin layout that has one blocked.

How can I find the little plastic pins to block a hole, ideally ones that are removable? I realize I could just put glue or something in there, but it would be nice to be able to pull out later if possible.

Edit: there is an existing answer with a minimum order of $1088.78 US - so I would be looking for somewhere that sold in sufficiently low quantities to be under $10.


texts: MC33926 Motor Control Feedback Reporting Too High

texts:
I'm using an MC33926 motor controller that has a feedback pin which current mirrors the motor current.  According to the data sheet the mirror is 0.24% of the actual current, so the FB pin should reflect 14mA when the motor is drawing 6A.

I have it going to ground via a 270 ohm resistor, and connected to the ADC input of a PIC18F45K40.

The motor is unloaded, and my power supply indicates the total circuit current jumps 500mA when the motor is operating.

The datasheet indicates that at 500mA the FB pin should be pushing about 0.775mA.  With a 270ohm load to ground the pin should be at 0.21V.

However, the pin is actually reading about 3.9V, indicating that the motor controller is pushing 14mA - or max scale 6A - through the FB pin.

Hooking up an oscilloscope to the FB pin shows some amount of jitter, but I'm not using PWM - I'm just setting IN1 high and IN2 low and letting the motor run.

I've verified that the resistor is 270 ohms with a multimeter, and that the FB pin, with the resistor load, is 3.9V when the motor is only consuming 500mA.

What am I missing, or what should I look at next to debug this issue?

The attached PIC18 is running at 3.3v, the motor controller at 12v.  Here's the motor controller circuit:

Note that the TP3 test point is grounded, so the chip is enabled (and the motor does run).  TP2 and TP1 are left floating, which turns slew to slow, and turns off input inversion.  The FB net goes directly to a PIC18 pin, and does react to motor current when running, just not at the scale I expect.

I'm hoping I'm just missing something stupid obvious and I can move on.

Also, note that this is a custom PCB, hand assembled, so if this is a symptom of a mechanical/electrical issue feel free to offer suggestions towards that end as well. I can tell you that all the pins are visibly wetted with solder, and there are no shorts from pins to any other pin or ground except by design. I've also assembled three of these units and they all exhibit the same behavior.  I haven't tested the fault output, but since the motor is running the controller isn't in fault mode.

EDIT:

I measured a few more parameters:

Current at the motor: 588mA
Ripple at motor: 200mVpp, 444Hz


texts: I am trying to convert an Arduino PWM signal into variable DC voltage source. This will be done by varying the duty cycle output from the Arduino. My question arises when I consider building higher order filters. Will a higher order filter (Sallen-Key, Butterworth, etc.) work better than just a basic active RC filter? I want the output signal to be as "DC" as possible even at low duty cycles.


texts: Does USB host mode on an STM32 require VBUS sensing?

texts:
I’ve been using an STM32F413ZH Nucleo board as a USB host device. All is working well.
However, I’m in the process of designing my own PCB based on the Nucleo design, but using a full-size USB Type A connector as only need to support Host mode.

Other than having a power switch for the VBUS, do I need to enable VBUS sensing ?

What do I do with the ID pin on the STM32 - the Type A connector doesn’t have an ID pin?

Thanks


texts: DC Connector for medium voltage PSU output

texts:
I've just built an enclosure for a 240V mains PSU that drives an 800W 0-100V DC spindle motor for a hobby CNC machine. Everything's earthed as appropriate, all looks good, and it works.

But I'm struggling to find a good DC connector for connecting the motor's power cable. I really want a panel-mounted socket, so I can plug in the motor cable - the CNC machine is multi-purpose, so the spindle and its PSU are non-permanent fixtures. Right now, the cable goes through a grommet in the side of the box and is wired straight into the PSU (with a small knot for strain-relief).

When I search for DC power connectors, I find nothing rated above 30V. So, first question: is there a standard DC power connector rated for this sort of job?

Now, I suspect they just sell higher voltage/power connectors as "AC" because that's what people use them for, and that as long as the insulation is ok with the voltage and the conductors can handle the current, then it doesn't really matter.

So I'm thinking of finding some uncommon, polarized 240V mains connector, and just using that. I'm looking something no bigger than an IEC 60230-2-2 F: any bigger, and I'll need a bigger box! In principle, I could actually use that socket, but it'd be dangerously inviting to a mains plug - boom! I want something less common. But the smaller IEC ones' current ratings are too low.

Are my "use an AC connector" assumptions valid? Are there any connectors which might do the job? This is a home/hobby application, not commercial - but that doesn't mean I'm ok with electrocuting anyone!

Edit

No sooner do I hit Save on this question, and having spent ages fruitlessly looking for a suitable connector, the Bulgin Buccaneer series suddenly decides to leap out from under Google's rock, where it was hiding!  This looks like the tool for the job?


texts: How to Find Thevenin's Voltage & Resistance?

texts:
I've a hard time understanding Thevenin's theorem.
I know that it is just a theorem to simplify a complex circuit, and to easily analyse that.
My hard understanding is in the mathematics of it.

Given this circuit, we'd take out the R2, because it is the load resistance, right?(Can you explain me why we need to take it out?)
Also, a load resistence just a load, which is just the main thing of the circuit, that consumes the power, right? Is it the core subject, that the circuit is built for to power?
Now, to get the Vthev, we need to calculate the Rtotal, and here we'd calculate it if it were parallel, but here it is clearly in series, because we took out R2, and and there is no current in that branch anymore, so why we need to calculate it as parallel?
Also, when we need to get the Rthev, why we need to short the voltage sources, and why we don't need the R2?
If I imagine a black box:

Does the Rthev basically just the overall resistance of the blackbox between terminal A and B? Therefore this is why we doesn't include the Rload when calculating the Vthev and Rthev?
I don't know if my questions are good, because I'm really confused about it, but can you explain me in simple steps?

EDIT

In this example the solutions are: VTHEV = 3 V, RTHEV = 60 Ω, INORT = 0.05 A
Rthev = 1/(1/100+1/150): Why we ignore the parallel 200Ohms?
Vthev = (5/250)*150: Again why we ignore the 200Ohms, and here why we calculate the resistance as series and(250Ohms) and not as parallel, like in the case of Rthev(60Ohms)


texts: Frequency to voltage circuit with LM339 in KORG MS-20 synthesizer

texts:
This is an extract from KORG MS-20 synth schematic. The purpose of the circuit is to convert frequency into voltage (with Hz/volt implementation, double the pitch and double the voltage).

The part I'm interested in is the one marked in red. I can see the first comparator is used as an amplifier and the following one is a zero-crossing detector but, from there on I don't really understand what's happening.

Could someone explain the circuit and how it performs frequency to voltage conversion?

You can find the whole schematic here, the circuit is at the end of page 5.


texts:
Can I read and save the program from a Xilinx XC9572 and burn it to another blank DC9572?  I have a Needhams EMP30 which has this device on its list. I need the adapter for the PLCC 44 pin to DIP. But before I buy it I need to know if it can be done.

Background:
You know that Coin-op Arcade game Hydro Thunder by Midway Games?  It is about 10 plus years old.  It is a sit down boat racing game.  It runs on a computer that uses a kind of custom 3dfx Obsidian 2 PCI video card.

Both of my games have blank screens and I get the 1 long 2 short beeps.   I have some similar video cards that are used in a different called Gauntlet Legends.  What everyone says it if you swap the Xilinx XC9572 chips the card should work.

So I put a socket on both the Hydro and the Gauntlet video cards and swapped the chips but it still doesn't work.  I confirmed that both of the cards work in the Gauntlet video game but not in the Hydro Thunder.  So that tells me that every part of the video card is  OK except for this chip.

I think this chip has the Video Options BIOS on it. Might there be some other reason why I get this 1 long 2 short error?  I have heard that this is called a secondary video card, what ever that means. But is there some special way to configure a secondary video card?  It gives me the same errors no matter what motherboard I put it in.

They want up to $450.00 for these Hydro Thunder video cards which are worth maybe 20.00 for any version except the Hydro Thunder.  It is either this chip is bad or it needs some kind of configuration.  I don't understand why just this chip would go bad on both of them. Any ideas?


texts: Do you always need to clock out the old pixels when reading from a camera?

texts:
I'm writing a program to work with a TSL1401R-LF Linescan Module. It works by reading in a 1 X 128 array of pixels. I've gotten the camera to work properly and my readPixels() method is able to read in the pixels accurately.

However, I'm forced to run a timming() method prior to my readPixels() method or else the program fails. The timming() pretty much does exactly the same thing as the readPixels() method except it doesn't store the outputted values. When I comment it out and only use readPixels() my image becomes saturated and I only get values of 1023 even when a dark object is in the way of the cameras.

This might make more sense when looking at the actual code:

void timming()
{

  digitalWriteFast(SI, HIGH);
  delayMicroseconds(10);
  digitalWriteFast(CLK, HIGH);
  delayMicroseconds(10);
  digitalWriteFast(SI, LOW);
  delayMicroseconds(10);
  digitalWriteFast(CLK, LOW);
  delayMicroseconds(10);

  for(int i = 0; i < 129; i++)
  {
    digitalWriteFast(CLK, HIGH);
    delayMicroseconds(delayTime);
    digitalWriteFast(CLK, LOW);
    delayMicroseconds(delayTime);
  }

}

void readPixels()
{
  digitalWriteFast(SI, HIGH);
  delayMicroseconds(10);
  digitalWriteFast(CLK, HIGH);
  delayMicroseconds(10);
  digitalWriteFast(SI, LOW);
  delayMicroseconds(10);
  digitalWriteFast(CLK, LOW);
  delayMicroseconds(10);

  for(int i = 0; i < 128; i++)
  {
    digitalWriteFast(CLK, HIGH);
    pixelsArray1[i]=analogRead(Cam1Aout);
    pixelsArray2[i]=analogRead(Cam2Aout);
    pixelsArray3[i]=analogRead(Cam3Aout);
    delayMicroseconds(delayTime);
    digitalWriteFast(CLK, LOW);
    delayMicroseconds(delayTime);
  }

  digitalWriteFast(CLK, HIGH);
  delayMicroseconds(delayTime);
  digitalWriteFast(CLK, LOW);
  delayMicroseconds(delayTime);

  delayMicroseconds(20);
}

TL;DR

Basically what I'm asking if there is a way to get my program to work without having to use the timming() method.

Datasheet: http://datasheet.elcodis.com/pdf/58/61/586128/tsl1401r-lf.pdf


texts:
In Atmel ASF I found this piece of code

enum status_code eeprom_emulator_init(void)
{

enum status_code error_code = STATUS_OK;
struct nvm_config config;
struct nvm_parameters parameters;

/* Retrieve the NVM controller configuration - enable manual page writing
 * mode so that the emulator has exclusive control over page writes to
 * allow for caching */
nvm_get_config_defaults(&config);
config.manual_page_write = true;

/* Apply new NVM configuration */
do {
    error_code = nvm_set_config(&config);
} while (error_code == STATUS_BUSY);

/* Get the NVM controller configuration parameters */
nvm_get_parameters(&parameters);

/* Ensure the device fuses are configured for at least one master page row,
 * one user EEPROM data row and one spare row */
if (parameters.eeprom_number_of_pages < (3 * NVMCTRL_ROW_PAGES)) {
    return STATUS_ERR_NO_MEMORY;
}

As far as I know about enums they are used for variables, then how is it also used to contain instructions in above code.?


texts: ATtiny44 not responding to AVRISP mkII programmer

texts:
It's not responding to the programmer at all in avr studio.

avrisp     attiny44
mosi  -- - mosi
miso  ---- miso
sck   ---- usck
reset ----  reset

Or can it not be programmed by an mk2? I assumed all chips can be programmed by it


texts: SMD-Potentiometer question about Datasheet

texts:
I am a bit confused about this Potentiometer-Datasheet.

http://www.bourns.com/docs/Product-Datasheets/PVG3.pdf

Am I right, that the resistance-range is only +-20% of the resistor value? For example, a 5k Potentiometer has only a range from 4k to 6k Ohm?

Thanks


texts: What type of connector is this Velodyne interface box GPS connector?

texts:
Velodyne VLP-16 lidar's interface box has this connector. What type is it?
Could not find this from the manual.


texts: How does charge redistribute in a capacitor?

texts:
Suppose, you have to capacitor plates as shown:

And, according to the solution key to a problem which I was doing, in the steady state behaviour of the circuit, the charges would  redistribute such that each plate gets charge of equal magnitude. Like so:

Now, this was the method taught to us for solving problems where extra charge is introduced into capacitors but I'm not sure why the charges redistributed such that each plate has average of both plates? Why does at end state the charge  redistribute so that each plate has the same amount of charge


texts:
What will happen if voltage sources are connected to both sides of the transformer?

In case they are different phases and when they are in same phase.

How will the magnetizing current be?
How will the flux in core behave?
Will it be different then the normal case?

The above question was asked in an interview. I got confused and was not to able to able to answer. Please help me with this problem.

EDIT1: This question was asked for a practical transformer.


texts: 555 circuit problem.. could it be broken?

texts:
I've made a circuit that's connected to a 12V+5V power source (attached a gallery. last photo is the schematic)

it is simply a 555 timer that goes off whenever one of the two input pins goes high (that's what the 4070N is for).
I've attached some readings under 5 different conditions:
 - potentiometer at 50kOhms (one input pin LOW and the other NC)

potentiometer at 1kOhms  (one input pin LOW and the other NC)

input pins HIGH and LOW

input pins both LOW

I'm a bit stumped with this one.. could it be that the 555 is not working properly? i can read the 4070 with the multimeter and the only weird thing is that it outputs 2Volts when both inputs are LOW.
and what's weirder is that the frequency doesn't seem to change with the potentiometer..

If any kind soul has time to take a look, take a shot. I think i'll replace both chips in the meantime just in case, because i'm not sure anything else is wrong :/


texts: XOR Gate implemented with BC547 transistors not working

texts:
I have checked and rechecked the wiring on my breadboard against the circuit shown in the schematic a dozen times and can't for the life of me understand why it is not working. Can anyone see a fault in the schematic? The circuit implements an XOR gate, with a red LED as output.

The behaviour I get out of the breadboard circuit is as follows: Q3 is on with both switches open, as it should be. SW1 causes Q2 to turn on and SW2 causes Q1 to turn on. I have checked the wiring to the bases of Q1 and Q2 and they both connect to the correct switches. Q4 and Q5 will not turn on when their respective switches are closed.


texts: Must the air gap in a transformer always be perpendicular to the magnetic field lines?

texts:
The air gap in a transformer seems to always be spaced across the cross section of the core, where the magnetic field in the core has to then flow across it.

Since the core is typically made of stacked laminated sheets, it seems like it would be easier to construct an air gap by putting a sheet of plastic, or some other non ferrous material, in between the laminated sheets when stacking them. As far as I know, this is never done - why not? The stacking factor accounts for tiny gaps between sheets where the lamination material is - what would happen if one of those gaps were made larger?


texts: so i am little confused about inductance in transmission lines. the inductance can occur in transmission lines when two transmission lines(shot long or medium) comes close to each other i-e due to mutual inductance? or inductive effect can be present in single conductor due to self inductance? what is difference between both type of inductance's?


texts:
I am learning Differential amplifier, and it has been fun and smooth, but I encounter a problem here. This is a 10x Differential Amplifier setup, and the voltage drop across R5 (0.01 ohm) is 5mv, so the output should be 50mv, but the simulation gave me a strange 97mv output, almost double my expected result. What is the problem here?

V(n001):     4.55006     voltage
V(n004):     4.54596     voltage
V(n003):     5   voltage
V(out):  0.0972042   voltage
V(vb):   4.995   voltage
V(va):   5   voltage
V(n002):     0.000604282     voltage
Id(M1):  0.49994     device_current
Ig(M1):  -2.31583e-009   device_current
Is(M1):  -0.49994    device_current
I(R6):   0.49994     device_current
I(R5):   -0.499984   device_current
I(R4):   -4.54596e-005   device_current
I(R3):   -4.45285e-005   device_current
I(R2):   -4.54038e-005   device_current
I(R1):   -4.44944e-005   device_current
I(V2):   6.45349e-005    device_current
I(V1):   -0.500029   device_current
Ix(u1:1):    -5.57749e-008   subckt_current
Ix(u1:2):    -3.41455e-008   subckt_current
Ix(u1:99):   -6.45349e-005   subckt_current
Ix(u1:50):   2.00963e-005    subckt_current
Ix(u1:28):   4.45285e-005    subckt_current


texts: Combining solar panel strings with different azimuth

texts:
When combining strings with a different azimuth in an off grid system, lets say NNE facing with North Facing and NNW facing (Southern Hemisphere), you catch the morning and evening sun better, this is called "Virtual Tracking" where fixed panels can start charging sooner in the day and stop charging later in the day enabling your battery dependent period to be shortened.

An example might be 9 panels facing in each of the three directions.

Now my question is regarding the electrical characteristics of this practice, if you were to combine the panel strings facing in different directions in the same sub-array, combiner and charge controller.

One assumes that each panel string (i.e. the ones facing different directions) produces a different current output at the same voltage, if this is the case, I guess their is no problem (although at the very start and end of the day, the voltage might not be the same which could cancel out the benefit of doing virtual tracking in the first place).

I guess that if the panels facing different directions (Azimuth) were grouped together on the same combiner and charge controller (i.e. different directions use different combiners), there would be no problem and everything is telling me that this is the only best practice way to implement virtual tracking to avoid imbalance and any electrical back-feeding between the panel strings.

Lets assume three ±45Voc panels are in each string and three strings are combined into one 150V MPPT charge controller, e.g. Outback FlexMax 80, what is going to happen electrically if we mix strings with panels facing different directions, i.e. one facing North, one facing NNE and facing NNW, will the worst performing string at any time of the day become the common denominator for sub array performance.


texts:
This is not a question about tuning PID loops for stability. I am assuming the output looks stable.

The question is: Do PID loops ever achieve absolute stability, or is there inevitably a periodic oscillation, no matter how small?

It's more a question about the fundamental nature of the equations rather than implementation (which can be analog down to the noise limit)


texts:
I've created a dual source energy harvesting board to store energy from small energy sources, like a 3V 15mA solar panel, into a 3F 2.7V supercap and to power a small wireless node (3.3V, 30mA), but I am having trouble finding the cause of a current leak.
Schematic is below:

The voltage regulator LTC3125 (U1) gets the energy from the solar panel and steps the voltage up to 2.65V to charge the 3F 2.7V supercap.

The supercap is the input for the 3.3V voltage stepup regulator LTC3525D-3.3 (U3) and its output (3.3V) goes to the load (wireless node).

This regulator get shut down when the voltage of the supercap goes below 0.9V and starts if the supercap goes above 2.5V. This is done by the non-inverting op-amp with additional hystheresis, the MAX9015 (U2), that drives the shutdown pin of the LTC3525.

The op-amp is powered by two sources: if the sun shines, it is powered by the 2.1V regulated voltage from the LTC3105 (LDO, pin2). If no sun and supercap >0.9V, the power comes from the LTC3525D-3.3 output . If no sun and supercap <=0.9, then the opamp is off and so is the LTC3525. Usually the supercap is >0.9V.  Min VCC of op-amp is 1.8V.

There is also a connection from supercap to VCC of the op-amp through diode D9, but I did this only to stay inside the "input command mode voltage range" of the op-amp (VCC+0.2V). Without this, I had a current leak, when the sun was not shining  because of op-amp latchup.

Everything works fine except for a current leak that happens when:

1.24V < V_Supercap < 2.5V
Solar input voltage < (V_Supercap + (0.2V or more))
LTC3525 not started (no 3.3V output)

In this situation, the supercap discharges circa (44uA-60uA) instead of charging (0.01mA or more).

If I disconnect the solar panel, there is no current leak. If  its voltage is similar or higher than supercap voltage, the supercap charges.

I suspect the cause is something in the op-amp, as its internal V_REF = 1.24V and I use this directly connected to the IN- of the op-amp. The V_REF output impedance is 35kOhm, and the current leaks is exactly V_Supercap / 35kOhm.
The IN- and V_Ref are at 1.24V as soon as the supercap >= 1.24V.

What could be the cause of this and how can I solve it? Or maybe is the problem somewhere else?

Thank you very much for your help.

U1 (LTC3105)

  AUX  =  1.49V
  V_OUT = 1.49V
  SW    = 1.07V
  V_IN  = 1.07V
  FB    = 0.53V
  LDO   = 1.49V
  MPPC  = 1.39V

U2 (MAX9015)

  REF=IN- = 1.23V
  IN+     = 0.72V
  VCC     = 1.44V
  OUT     = 0V

U3 (LTC3525)

  SHDN    = 0V
  V_IN    = 1.49V
  SW      = 1.49V
  V_OUT   = 0V

PSU (to simulate solar cell):

 1.10V 30mA

PSU current draw = 0mA.

Supercap:

 1.49V discharging at 44uA
 If I turn PSU off, supercap discharges with 12uA.


texts: What does bandwidth mean in general, and in the context of the following examples?

texts:
Some examples :
1.The bandwidth of an operational amplifier
2.The bandwidth of a transmitted amplitude modulated signal
3.The bandwidth of a signal used in coaxial cables / optic fibre cables
4.The bandwidth of a signal used for satellite communication

I was recently reading about the usage of two different frequencies (uplink and downlink) for satellite. The reason that both of these frequencies were in the order of GHZ was because high frequencies mean large energies, so large range, and high frequencies also mean large bandwidths. I'd like to learn what 'bandwidth' generally means, and also how it applies to the examples I've given.


texts: Wien Bridge Oscillator: Why does equating the real part to 0 give the gain equation?

texts:
I am learning about Wien bridge oscillators. Following Experiment No. 9: WIEN BRIDGE OSCILLATOR USING OPAMP, they use the following schematic:

They then arrive at the following equation half-way down page 3:

They then equate the imaginary part to 0 to find the resonant frequency, i.e:

This makes sense, because at resonance the current is in phase with the voltage, hence the imaginary part goes to 0. I don't understand the next part where they:

To obtain the condition for gain at the frequency of oscillation, equate the imaginary part to zero.

which expressed as an equation gives you:

Why can you just equate the imaginary part to zero (i.e. the real part goes to 0) to find the gain needed at resonance?
EDIT: After @TimWescott's great answer I created a re-written version of the equation which shows the "missing link", i.e. Im() + Re() = 0:


texts: Regarding pinout of PCF8574 I2C 8-bit expander

texts:
I need some help understanding the pins of I2C 8-bit expander (PCF8574AT) that looks like this,

https://mbrobotics.es/blog/arduino-lcd-1602-i2c/

In the datasheet for this part, there is a pinout diagram for the 16 pin header but nothing is mentioned about the four pins on the top of the module which is  SDA, SCL, VSS, and VDD but these already exist in the 16 pin header.

Datasheet for the expander,
https://www.nxp.com/docs/en/data-sheet/PCF8574_PCF8574A.pdf

Please help me understand why there are two sets of these pins. Basically, I want to understand how the on-chip IC of the module is wired to the header on its side plus the header on top.

Edit: Added datasheet.
Edit: Clarification.


texts: Capacitor selection - Audio decoupling capacitor for microphone

texts: We are developing a custom application based on the TLV320AIC3111. According to the datasheet, the typical configuration has a 1uF cap on the MIC1LP line, which I assume is for AC decoupling the audio input. However, on the EVM for the same caps they've used 0.47uF. The impedance of the mic we'll be using is around 6ohms and we need a good low-frequency response (our signal can go as low as 100Hz). I need help choosing the right value and type (MLCC or tantalum).


texts: Battery lifetime calculation approach for Arduino + GPS/GSM

texts:
I want an Arduino Nano to send its GPS coordinates via SMS. I'm going to use the GSM/GPS module SIM908. My problem has to do with how many SMS will I be able to send before the battery dies.

I've done some calculations but I'm not sure if I'm doing something wrong or missing something...

I read in this question: What is the Max Power Consumption of Arduino Nano 3? that the max consumption of an Arduino Nano is 280mA.
Then we have the SIM908 module. From this link: SIM900/SIM908 power supply circuit I learned that "The module consumes around 300mA current while under normal operating conditions, and around 2A current during transmit bursts".

The arduino nano voltage is 5V while the SIM908 Operating Voltage is 3.2V to 4.8V.

Then I've done this timeline trying to be really conservative:

Turn on: 3 seconds @ 580mA (280mA Arduino + 300mA SIM908).
GPS data gather: 2 seconds @ 2280mA (280mA Arduino + 2000mA SIM908).
Data processing: 1 second @ 580mA (280 Ard + 300 SIM).
SMS Send: 3 seconds @ 2280mA (280mA Ard + 2000 SIM).
End process + turn off: 1 second @ 580mA.

(I totally made up the durations, I just hope they're upper bounds)

average = (5*580+5*2280)/10 = 1430mA.

That is, the process of transmitting an SMS consumes in average e=1430mA. Then, if I have a battery with a capacity of C=10.000mAh, I could get the battery lifetime as,

    L = C/e = 10000/1430 = 7h.

Since 7h = 25200 seconds and we spend 10 seconds in each gather data - send data process, we could be able to complete the process 2.520 times with a full battery...

Now, some considerations: I know that the voltage is slightly different for the Arduino and the SIM908, and the calculations are assuming their voltage is the same, but anyway my result is an upperbound, right?

This calculations are not taking into account the time interval between executing the process. Actually this will be done automatically once every 12h, so I guess the Arduino should actually be ON all the time and fire an interruption every 12h. I don't know if there's any low-consumption mode for such things... or perhaps there are some other ways to handle this like having really low-consumption specific hardware.

Am I missing some important fact that will drop my battery? The battery is meant to last months with just one charge... the device should just send its coordinates via SMS every 12h (or maybe 8h), and perhaps this long periods of time might cause some other problems.


texts: How do I use the measurements from the datasheet to create a footprint?

texts:
I'm trying to make a footprint for a MPU-6050 6-axis gyroscope and accelerometer.
I've added the first 12 pins (out of 24), but now I don't know how to proceed.

PCB dimesnions:

I've added pin 1-6 and 13-18 but I don't know how to calculate the position of 7-12 and 19-24.

Is there something obvious I'm missing?


texts: is using both Nyquist's and Shannon's Theorem possible?

texts:
For instance, say I have a cable bandwidth of 1 MHz, and a signal-to-noise ratio of 255, how would I calculate the maximum bit rate possible if I were to be transmitting data via this cable using 4 signal levels?
Using Nyquist's I would get the maximum data rate 2 x 1 x log2(4) = 4 bps, and Shannon's would be 1 x log2(1+255) = 8 bps, but how would I combine them if I were to calculate the maximum bit rate possible when transmitting through this cable using 4 signal levels?


texts: How can I find a good (local) electrical engineer

texts:
I'm trying to find a local (nyc) electrical engineer, or electrical engineering company to help me make a small device that involves cell phones and bluetooth - at least I think it will involve bluetooth.

My questions are simple:

Are there any sites devoted to contract jobs for electrical engineers?
How can I find small local EE companies that might be able to help me?
How can I best judge the quality of an EE?

Thanks!


texts:
Bt136-600 is an example of a non-isolated triac, while BTA08 is an example of an insulated triac.

What is the difference between an isolated and non-isolated triac? They seem to have the same symbol which is a bit confusing.

Could an isolated triac be substituted for a non-isolated triac plus an optoisolator? I'm guessing not.

Is there an equivalent circuit to an isolated triac using a non-isolated triac?


texts: (How) can I determine the characteristics of an unidentified SMPS transformer?

texts:
I have torn down a crappy Antec Neo HE power supply that would turn on randomly only. It's rated 430W, amongst these 3.3V/22A, 5V/14A, 3 x 12V/16A.

I'm planning to use it for parts in a home made power supply project. There is an unidentified transformer (marked VRL35W015 on its top, SBI 4.2 E150436 C on its side) which I'd like to know how I can check its features, e.g. frequency range, max current, voltage and whatnot. The SBI 4.2 marker lead me to a Taiwanese company that does unfortunately not publish the specification for that transformer type.

Apparently the transformer has two primary and two secondary windings.
How can I check the characteristics of this transformer? Is there a typical circuitry I can build to check it out?

EDIT: Actually the only code that is specific to this transformer is VRL35W015. SBI 4.2 and E150436 seem to be reference model or something similar. There is a small transformer next to this one, both share the same SBI 4.2 and E150436 but the smaller one has a different identifier: VEE19FRC9.

This transformer also has 6 pins on the secondary, wired together in adjacent pairs on the PCB, the primary four pins, independently connected. The document pointed to by Andy Aka seems to confirm, like the hinted thread, the fact that this transformer has been specifically designed for this Antec Neo HE. Not any reason to ditch this transformer, to me of course.

I will observe (frequency, voltages and apparent ratios) with my oscilloscope how the transformer behaves. This will hopefully give me basic information, which I'll further use in my "quest". Lot of fun ahead.


texts: Why is my transistor accepting power from a base?

texts:
I have a transistor (NPN, to be exact it's a SS9014).  Whenever I run 4.5 V through the base, connect a resistor and LED to the emitter and connect the LED to ground, the LED has a faint glow.  Why is any power being transmitted to the LED when there is nothing connected to the collector?  How can I avoid this? Here's the schematic:

I am actually still in high school and want to major in electrical engineering.  I know this may seem simple for professionals, so thanks for taking the time to help me out.


texts: latched circuit that reverts off when power off

texts: I'm after a circuit that stays on after being temporarily actuated, but when the power is turned off, reverts to the off state.  When turned on again, it is still off, but goes on when re-activated.  It's for a car immobiliser system, wired into the acc switch on the ignition.  I'm assuming a bistable flip-flop could be used, if it was powered from the acc circuit? Or would some form of relay be best? (it has to drive external powered components). I want to activate it with an rfid tag.


texts:
This is the code

// PIC12F1822 Configuration Bit Settings

// 'C' source line config statements

#include <xc.h>
#include <string.h>
#include <stdlib.h>
// #pragma config statements should precede project file includes.
// Use project enums instead of #define for ON and OFF.

// CONFIG1
#pragma config FOSC = INTOSC    // Oscillator Selection (INTOSC oscillator: I/O function on CLKIN pin)
#pragma config WDTE = OFF       //  (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable (PWRT disabled)
#pragma config MCLRE = ON       // MCLR Pin Function Select (MCLR/VPP pin function is MCLR)
#pragma config CP = OFF         // Flash Program Memory Code Protection (Program memory code protection is disabled)
#pragma config CPD = OFF        // Data Memory Code Protection (Data memory code protection is disabled)
#pragma config BOREN = ON       // Brown-out Reset Enable (Brown-out Reset enabled)
#pragma config CLKOUTEN = OFF   // Clock Out Enable (CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin)
#pragma config IESO = ON        // Internal/External Switchover (Internal/External Switchover mode is enabled)
#pragma config FCMEN = ON       // Fail-Safe Clock Monitor Enable (Fail-Safe Clock Monitor is enabled)

// CONFIG2
#pragma config WRT = OFF        // Flash Memory Self-Write Protection (Write protection off)
#pragma config PLLEN = OFF       // PLL Enable (4x PLL enabled)
#pragma config STVREN = ON      // Stack Overflow/Underflow Reset Enable (Stack Overflow or Underflow will cause a Reset)
#pragma config BORV = LO        // Brown-out Reset Voltage Selection (Brown-out Reset Voltage (Vbor), low trip point selected.)
#pragma config LVP = ON         // Low-Voltage Programming Enable (Low-voltage programming enabled)

char blink = 0;
void delay()
{
    int i,j;
    for(i=0;i<10;i++)
    {
        for(j=0;j<1000;j++);
    }
}

void init()
{

       OSCCON=0xF0; //32 Mhz
       ANSELA=0x00; // All pins digital
       BAUDCONbits.ABDOVF = 0;
       BAUDCONbits.RCIDL=0;
       BAUDCONbits.BRG16= 0;
       BAUDCONbits.ABDEN = 0;
       BAUDCONbits.SCKP = 0;
       BAUDCONbits.WUE=0;
       APFCONbits.RXDTSEL=0;
       APFCONbits.TXCKSEL=0;

       SPBRGL = 51;//Baud =9600

       RCSTAbits.CREN=1;
       RCSTAbits.SPEN =1; //Reciever enabled

       INTCONbits.GIE = 1;
       INTCONbits.PEIE = 1;
       PIE1bits.RCIE = 1;

       TXSTAbits.SYNC = 0;
       TXSTAbits.TXEN = 1;
       TXSTAbits.BRGH = 0;
       TXSTAbits.TX9 = 0;

       TRISAbits.TRISA0 = 0;
       TRISAbits.TRISA1 = 1;
       TRISAbits.TRISA2 = 0;
       TRISAbits.TRISA4 = 0;
}

void interrupt ISR()
{

    if(PIR1bits.RCIF)
        PIR1bits.RCIF = 0;
    blink=RCREG;
    PORTAbits.RA2 = 1;
    delay();
    PORTAbits.RA2 = 0;
    delay();

}

void send_data(char a[])
{
    int i;
    for(i=0;i<strlen(a);i++)
    {
        TXREG = a[i];
        while(!TXSTAbits.TRMT);
    }

}

int main()
{

    init();
    while(1)
    {
        if(blink != 0)
        {
            delay();
            send_data(blink);
            delay();
            blink = 0;
            send_data("Dennis");
        }
    PORTAbits.RA4 = 1;
    delay();
    PORTAbits.RA4 = 1;
    delay();
    }
}

I am sending data from the UART of arduino.
the pins Ra2 is supposed to and does blink when it enters the interrupt.
the data Dennis is displayed correctly.
But the data recieved by the PIC is not sent back properly and im getting garbage at the serial port output.


texts:
I'm trying to make a very simple electromagnet. I found a inductor, took it's copper wire and wrapped it around a nail. When I connect my bench power supply and crank it up to 20v, but I can't even pick up tiny metal pieces, it just seems like there's no magnetism. I also noticed that there is no current flowing and I can't figure out why. Is my connection or choice for materials wrong?

I also took super thin copper wire from a DC motor and wrapped it around many times a smaller nail, but same effect - no magnetism.

I would expect it ether become magnetic, or at least short circuit, but I get nether..

Any suggestions on what am I doing wrong? Thanks!


texts: I am working on hall effect based current meter and I run into some troubles running my simulation in LTspice. To be precise I am no sure how to accurately model hall effect sensor. In less accurate models I treated hall effect sensor as voltage source proportional to flux. Now I modelled Hall effect sensor as Wheatstone bridge in order to reflect internal resistance. However not to sure how to relate magnetic flux and change in resistance. I am assuming there is relation between change in resistance and flux as there is definitely relation between change in flux and change in hall voltage. Should I simply apply Ohm’s law?


texts:
Burning Temperature of Copper Winding of Motor.

I Have 3 motors 150watt 0.75Amp 220V in Copper and Aluminum and Copper clad aluminum.

I want to know the maximum internal temperature of these motors so that I can apply a Thermal protection sensor to   avoid burning in   the future.

Can anyone tell me the approximate range of temperature of burning of winding wire.

Someone suggested  that  I     apply 45C temp sensor . I dont think   she is right.


texts: Frequency and Period of a JK flip-flop circuit

texts:
Reposting this question from Electric Engineering. Wouldn't normally do this but I have to figure out this concept by tomorrow. Thanks in advance for any answers.

I am currently working through the problem as shown below.

simulate this circuit – Schematic created using CircuitLab

While it makes sense to me why output signals Q0 and Q1 are set to high aside from pulses which coincide with the dropping of CLK, the answer key states that the frequency and wavelength of the input clock is equal to that of the outputs. This is very confusing to me. Shouldn't the wavelength of output signal be equal to 2*wavelength of input signal?


texts: Adjustable current source 0-20mA for LED dimming

texts:
I have been searching through the site, but I have not been able find an answer.
I have an LED (rated for 14 mA at 24V, the LED is with built-in series resistor) that I need to be able to dim from completely off to fully on (0-14 mA).
A search at Mouser and Digikey did not show any simple current source IC’s that can regulate down to 0mA, so now I am looking for a discrete circuit to do the job. However, all of the circuits that I have seen have a min current higher than 0mA. The dimming/adjustment input should preferable be a voltage.
Any IC’s or discrete circuit implementation suggestions are greatly appreciated.


texts: Simulating a big circuit for a huge number of times

texts:
What is the best way to simulate a big circuit for a huge number of times?

I have a big resistive network (lets say 100x100). I want to run it about 10 million times. What is the best way for that?

I am using HSPICE, but it is so slow and it takes days to run those number of simulations.


texts:
I am curious about the difference between SN754410 and ULN2004 and what are the specific usages of both?
According to data sheets SN754410 is a  is a quadruple high-current half-H driver and ULN2004 is a 7 Darlington array. so how should we select these elements in our circuit designs appropriately?


texts: Is this an Inductor, mystery component 600R/2A?

texts:
I was checking a schematic for work, and I saw this component that I don't recognize, marked 600R/2A.
Since they are marked L and are used in combination with capacitors, I think they are inductors meant to serve as low pass filters in combination with the capacitors.
Why do they have such an odd symbol and why are they marked the way they are?
I assume the "2A" part to be the maximum current, and 600R to be some sort of resistance value. But what is the inductance here?
I read online that it is a type of ferrite inductor/filter.
I need to copy parts of this circuit into another design but I would rather understand what it does first.


texts:
I'm developing a four layer board which is powered by 3 voltages - 1.8V, 3.3V and 5.0V. The board has the following stackup:

Signals
Ground
3.3V
Signals

The ground and 3.3V plane are completely unbroken. No signal or power trace travels on them.
I'm using three LP38690DT LDOs to provide power - here's my circuit.

Click here for larger picture.
My concern is the layout for these devices. The datasheet suggests the following

The best way to do this is to lay out CIN and COUT near the device with short traces to the VIN, VOUT, and ground pins. The regulator ground pin should be connected to the external circuit >ground so that the regulator and its capacitors have a "single point ground".

I was somewhat confused by the term "single point ground" but I tried to follow the advice given in the datasheet to the best of my ability - but I am not sure if I am correct:

Note that the text in red is only there to give clarity to the folks here - I will delete it afterwards. Each regulator is connected directly to the capacitors and the ground pin of the regulator is connected directly to the capacitor's ground pin directly. Is this what the datasheet meant I should do?
The datasheet goes on to say

Since high current flows through the traces going into VIN and coming from VOUT, Kelvin connect the capacitor leads to >these pins so there is no voltage drop in series with the input and output capacitors.

What does it mean by Kelvin connect? I know what a Kelvin Connection is - what I don't understand is what does it mean in context for a LDO.
My third question is regarding all three regulators. As I mentioned, each IC is referencing ground from the same via that connects it's capacitors to the ground plane. However, should I connect all three regulators to the same ground point i.e. should all 3 regulators connect to the "single ground point/via"?
Finally, the input voltage is being fed by a 4-point through hole connector which carries 6V on two conductors and GND on the other two. The GND pins are connected direcly to the ground plane. Is this OK or should I connect the GND pins to the GND pins of the regulators directly via thick traces?
NOTE: the layout picture does not show anything connected to the output of the regulators. This is OK. I still have to connect my ICs to the power. ALSO: the maroon color underneath the regulators is not a net. This is Altium's way to show "Rooms" in PCB layout.
CURRENT REQUIREMENTS
Most of the current is drawn from the 5V supply. The 5V supply connects to a LCD display which will draw a max. of 400mA (when backlight is on) - but normally around 250mA.
The 3.3V supply will draw a max. of 300mA (discontinuous) but normally around 150mA or less.
The 1.8V is the supply for the core of the CPLDs that my board has. I was unable to estimate this but I've measured it. At startup, this was around 30mA but then reduced to 0mA. My meter, it seems, was not sensitive enough to actually measure the current. I reckon 200mA would be a safe bet for this.

UPDATED LAYOUT:

I hope this is what folks here meant. I wasn't sure if I should one large copper pour or three separate ones so I went with 3 separate ones.
UPDATED LAYOUT (again):

I've now made made one giant copper pour instead of 3 independent ones. I was't sure how to connect my 3.3V voltage to my power plane using multiple vias so the above is my attempt. I made a small fill and connected it directly to my output capacitor. From there I have 4 vias, each 25 mill in size, connecting directly to my power plane. Is this a better way to do it?
The clearance between the fills and other objects is about 15 mills. Should I increase this?


texts: Shielding Amplification Stages Separately

texts:
I am currently designing a prototyping board for fast pulse detection with 4 amplification stages at the input. I am currently not able to provide a schematic portion of it as I don't have access to it right now, but I can provide it if requested.

Some info on the amplification stage :

The frequency range I am interested in is between 10 MHz and 400 MHz.
I have 3 different 50 Ohm matched RF amplifier ICs, one having a low noise figure and the other two for general purpose amplification. The stages will be somewhat similar to the following :

FILTER -> A1 -> FILTER -> A2 -> A3 -> A3 -> FILTER
I am planning to make the board 4 layers, with the stack-up SIG|GND|PWR|GND, although I am not sure.
In the layout, A2 and first A3 will be by-passable via alternate routing through 0 ohm resistors.

I have no experience in laying a board like this, although I diagnosed and reviewed some. In one of my DigiKey researches, I stumbled upon some easy to use PCB mount RF shield enclosures and thought they might be a good idea to use. The max amplification will be around 110 dB. Which means I will be mostly amplifying noise. From my understanding those shielding products offer protection against inter-stage coupling of the signals in a layout like this, apart from their EMI shielding capabilities. I have some confusions and questions about this:

Is there a chance that the shield will degrade an amplifier's performance by providing a radiating structure due to a signal leakage under the placed amplifier?
When shielding stages, should I include close-by filters and other passive elements in the enclosure as well?
Would the correct placement and performance evaluation of such shields be hard? I have a very tight schedule and I certainly can't test the effectiveness of them.
Should I instead try to encapsulate all the amplifier stages in one shielding block? I don't mean an outer enclosure for the PCB as I will probably make one.

I am at least willing to try some of this as this will be a complete prototyping board anyway, but I would be very glad if I could gain some insight on the issue. Thanks in advance!


texts: RC bandpass filter, what's first: low-pass filter or high-pass filter?

texts: I want to do a RC bandpass filter can I use low-pass or high-pass at the beginning or does it have a specific sequence? First low-pass then high-pass, or first high-pass then low-pass?


texts: Saturation current in inductor - Definition?

texts: Can somebody explain me what actually is a saturation current of an inductor. You may consider one inductor too and explain the things. This is very much confusing for me. Somebody give me a clear cut info on this.


texts:
I am trying to understand a topic on limits of performance.

So there is a delay of tau between input and output so the transfer function becomes G(s)*e^-(tau *s).

I am unable to understand the statement "The phase contribution of delay is negative and at crossover frequency is -(tau * omega_c) ,where omega_c is crossover frequency"
I don't understand how the phase contribution due to this delay is -(tau*omega_c)?


texts: How can I find a similar circuit design like the one in Chargetech or Omnicharge( DC to AC 85 Watt )?

texts:
I would like to build one 85 Watt DC to AC Inverter for my personal use.

After seeing the designs of Omnicharge and Chargetech I wonder whether the Circuit and component descriptions are available to build the same.

Can someone guide me to build a small signature DC to AC Inverter?

Small Circuit with less heat dissipation
12v 20000mah DC  to 85Watt 230v AC.

Any kind of pointers or guidance in the right direction is much appreciated.


texts:
I have a Micro-controller with ADC input range 0V to 3.6V(12 bit). I need to measure a voltage signal in the range of -10V to +10V. So i chose the option of using an external ADC instead of the internal one. Now the problem is, i need an ADC which has a high sampling rate, say 1MHz.Even though i found many bipolar ADCs with high sampling rate, i came to know that without an internal buffer for storing the converted data we cant achieve the specified data transfer speed i.e effectively 1MHz cant be achieved.

So then i searched for adc with internal fifo.But for adcs with fifo, sampling rate specified is very less.What to do? Kindly help me.(adc should have spi feature too).


texts: Arduino - Calculating Resistor's Power and Resistance

texts:
My Question

I know, for example, that using a LED in Arduino without a resistor would cause damages to the Arduino's I/O (damages the LED too?), right? Resistors as far as I know have the two main properties resistance and power, so if I needed to calculate the correct resistor, what would be the steps?

Why for pushbuttons, for example, I don't need it? Is it because it has an internal resistance and LED has an almost zero resistance?

My Guess

Let's test if I am getting this right, let's say all I want is to turn on a LED so Arduino's voltage is 5V (controlled by the board) and its ideal current is ~20mA (it has to be controlled by me). For turning on the led without causing damage I would do:

$$I = \frac{V}{R} \rightarrow 20mA = \frac{5}{R} \rightarrow R = 250 \Omega$$

But I also have to know the if power is correct then I do:

$$P = I *V \rightarrow P = 20*10^{-3}*5 \rightarrow P = \frac{1}{10}W$$

So the power that would be applied to the resistor is 1/10W and a 1/8W resistor would be enough since 1/8W is the maximum power that can be applied and it is bigger than 1/10?