texts: Battery monitor for a camper van electrical system

texts:
As one of my first DIY projects, I'm going to build a battery monitor for the DC battery/solar/inverter system in my camper van.

The van has 440 Ah of lead acid batteries and DC currents up to 200A to the inverter, although more typical currents are in the 0-5A range. During the day, the current flow from the batteries often reverses as the batteries get charged from the solar panels, with the maximum charing current being around 10A.

A battery monitor basically provides the state of charge of the battery at all times. The typical design seems to be coulomb-counting (i.e., integrating current over time), combined with a bit of math to approximately adjust for the peukert effect. The monitors will generally try to "zero" themselves when they detect the battery is completely charged, usually by examining the battery voltage (ideally at rest) or the current acceptance rate, or some combination of the two.

I'll (probably) be using a shunt resistor to measure the current flow, either at the positive or negative terminal of the battery.

I'm wondering what type of circuit I need to best amplify and measure the small mV drop across the shunt. A typical 200A shunt is going to have something like 0.25 milliohms of resistance, so the voltage drop across the shunt will be something like 0.1 mV for small currents (which are still important).

I'm planning on using an arduino for as the MCU for the monitor, so I could use the existing ADC (which works between 0V and R, where R is the full scale reference voltage and must be between 2V and 5V). So some specific questions:

1) What kind of circuit do I need to amplify the voltage drop so it can be processed by the arduino ADC? I've looked at instrumentation amplifiers, but I'm not sure if they are the right tool.

2) How can I deal with the fact that current can run both ways? That is, I'll need to measure both positive and negative drops across the shunt. Most differential amplifiers seem to work in the case V+ > V-, but not the other way around.

3) Does it make a big difference whether I put the shunt on the high side or the low side? For the physical layout that I have, a shunt on the high side may be more convenient, however that means a few mV (or less) signal riding on a ~12 volt common mode voltage. Does that make things harder? I can't tell if CMRR etc would even apply here (and I asked a bit about it over here).

4) The DC current may be as high as 200A (e.g., when I'm using the space heater), but typical currents are much smaller. I want to have at least 0.1A resolution for the low currents, and more is better. 200A full scale at 0.1A resolution implies an 11-bit DAC, at least, but the arduino DAC has only 10 bits. I'm interested in a dual range solution where I amplify the signal with two different gains - one giving full scale at 200A, and the other at say 10A, and feed those into separate ADC inputs. When the current is below 10A I can use the much finer resolution I get from the 10A input. Is it feasible? The main problem I see is that I don't know how to "cap" the 10A input so that it doesn't put a damaging voltage to the ADC when currents are higher than 10A.

5) I'm fine with off-the-shelf chips that will do much of the above (up to and including the ADC stage) and then the adruino can just do the integration and UI logic, but I haven't found anything suitable. Anyone know of anything?

Looking back on this question, I realize it could be five separate questions, at least - but this early in the design they are kind of all related. If any of the topics are big enough I'll split them out.


texts: Necessity of a current mirror circuit - MOSFET/BJT?

texts:
I am studying the current mirror circuit.

I already went through similar questions and answers
on this forum. But I was unable to get clarity from the answers. I am just a beginner. I request if you can answer in simple terms in steps for my benefit.
I myself had asked similar question but I was not able to understand the answers. I went back and tried to understand and still was not able to get clarity. So, please help.

What is the purpose of using a diode connected BJT? Won't a normal Diode be sufficient in place of BJT?

I understand it is a very simple circuit but I am not able to understand how does this circuit establish current in Q1 and Q2 to be same?

Can someone explain me the basic concepts to help me understand this?

What is the necessity to establish a constant current using this method? Why can't we use a single transistor and control the Vbe and Ib of it to produce a constant current? Why do we need two transistors to complicate this? Please help me understand this.
While considering Q2, proper biasing is giving by Q1. Vbe of Q1 and Q2 are same. But should it mean that collector current of both the transistors are same? I understand that both are identical transistors in their geometry. But how does the current be same?
I also understand that Q1 must be in saturation and for Q2 to establish a constant current, Q2 should be in active region,right? So that, if the voltage Vout is increased,Q2 will vary its Vce to provide constant Iout. Is this correct?


texts:
I have a microcontroller with a program that remains in "sleep" mode 99.9% of its life. During this sleep mode, it drains less than 1 microamp with an operating voltage of 2.0V to 3.5V. When it finally is awake, it has a short burst of 2.2 mA consumption that lasts about 10 ms.

Elsewhere in the circuit, I have a 12V battery being used. I'd like to save physical space by eliminating my 3V battery and just tapping off the 12V battery with a 12V to 3V converter.

It seems like most linear regulators and switching converters I've found have very very awful efficiency at low current consumption.

Does anyone have a novel solution to regulate a low power device, relatively efficiently?


texts:
I want to build a simple device with 2 inputs and 1 output, all TRS 1/8" audio jacks. The device picks one of the inputs to pass through to the output depending on the time of day (at night, it chooses B, but for the rest of the day it chooses A).

How would I go about doing this?

For completeness, it's for a stereo that is inaccessible almost all the time. By default it plays (through speakers) from the radio. I want to attach this device between the stereo and the speakers, and plug in a simple FM receiver (configured to some unused frequency), so that at night I can transmit over FM to control the speakers. If there's an easier way, please do tell, but consider the stereo+speakers locked away after I install the device, so I need to be able to transmit audio wirelessly to the speakers while falling back on the stereo's output.


texts:
I am designing a small PCB which I want to power using a CR2032 coin cell. The circuit will include a 555 timer, a 40xx TTL and a few small LED's. I chose both IC's with a minimum supply voltage of 2V to make it work with the coin cell.

What are the conventions with powering circuits with a coin cell? Do I need to use a (linear) power regulator for this or can the battery be hooked up straight away?


texts:
See the attached schematic.
     As I test this out, I will occasionally see the K1-B contact remain closed after I open the "External System Enable" switch. The relay contact will "stick" even if the motor is not running as I open the "External System Enable" switch. So the only current through the contact is that of the power supply. Note that I had run the motors before opening the "External System Enable", I am simply stating they are not running at the time I open the "External System Enable" and see the N.O. remain closed.

My thinking is this relay cannot handle the inductive load, period. As I look at the spec for it and it only lists "resistive" load. But I'm not sure about that.
Also note, these motors are NEVER running at the same time.

Can anyone shed some light on what might be causing this to happen? Could it be too low a current from the power supply? I've see other threads stating you need to properly "wet" the relay contacts? Regarding ample load as relay closes, as I understand it.

Relay Data Sheet <--- http://www.mouser.com/ds/2/307/omron_en-g5la-548280.pdf


texts: How does a step-up voltage converter work? I am talking about DC amplified to DC.


texts: VHDL code works well in ModelSim and strange behavior in Altera FPGA

texts:
I'm trying to understand a strange (for me) behavior of a simple VHDL code. I have realized a stupid code that works well in ModelSim and doesn't work in a real FPGA (Altera MAX 10).

Library IEEE;
use IEEE.std_logic_1164.all;

entity test is
port( CLOCK_50:     in std_logic;
        SGN_IN:     in std_logic;
        RESET:      in std_logic;
        SGN_OUT:    out std_logic
        );
end test;

architecture beha of test is
   type state is (ST0, ST1);
   signal NEXT_STATE, PRESENT_STATE: state := ST0;
   signal Y: std_logic := '0';
begin

listen: process(SGN_IN) is
begin
    case PRESENT_STATE is
        when ST0 =>
            NEXT_STATE <= ST1;
            Y <= '0';
        when ST1 =>
            NEXT_STATE <= ST0;
            Y <= '1';
    end case;
end process listen;

state_output: process(CLOCK_50)
begin
    if(rising_edge(CLOCK_50)) then
        if(RESET = '1') then
            PRESENT_STATE <= ST0;
            SGN_OUT <= '0';
        else
            PRESENT_STATE <= NEXT_STATE;
            SGN_OUT <= Y;
        end if;
    end if;
end process state_output;
end architecture beha;

In simulation, the process 'listen' is triggered every time 'SGN_IN' changes. The trigger changes 'NEXT_STATE' and the output 'Y'. If 'SGN_IN' is idle the process is never executed and the output doesn't change.
In FPGA the process 'listen' is executed independently of the 'SGN_IN' signal and the output signal 'SGN_OUT'changes at a frequency equal to \$F_{clk\_50}/2\$ (half the frequency clock).

Could you, please, explain me the reasons of this behavior? And why in the simulation everything works well?

Thank you


texts: I am designing a 12000W voltage stabilizer transformer. I saw in another design that they use on the AC neutral a 10W resistor linking on the branch on relay contacts so that the neutral is taken from the relay. After some reading I realized that they might use it for transformer surge protection. Any help about this. And if there is any one know this circuit can you provide me with it so I can use it in my design.


texts:
I'm trying to convert a linear voltage to a 21kHz PWM signal using passive and active components.

Do you have any idea how I can achieve this ?

I tought about comparing my linear voltage to a sawtooth signal at 21kHz with this scheme:

but making this signal with passive components is really hard and not accurate.

I can use any comparator, amplifier etc..


texts: EEPROM Fatigue - Does it affect only the cells being written excessively, or will it cause global failures?

texts:
We have an EEPROM with a 10,000 cycle life duration - Our application may write more than 10,000 times.
If we write to the same location over & over, is it only that single location that potentially fatigues and fails?   Or would the failure extend over multiple cells?
I'm thinking an easy way to get round the limit is to dedicate 10 memory locations and use a rotating pointer.  That would (I think) increase my potential write cycles 10x before it becomes an issue.
Am I heading down a good path, or is this totally the wrong thing to do?
Many folks are wondering why I don't just use another part, or one that's better documented.   The EEPROM is built-in to this one.  In our business, we're locked into a few suppliers who make very specialized ASIC's and who don't document their chips such that I can just read this in the datasheet.  Their engineers all speak English as their 3rd or sometimes 4th language, so asking this kind of question is usually quite difficult and answers always taken with a grain of salt.  They make up for these annoyances by selling stupid low cost chips.  We have micro's available to us that cost about 3 cents each (no exaggeration).   Most of our IC's are about $0.15.


texts: Microphone output resistance, why this value?

texts:
I would like to sample the output of a microphone. I am using the following set-up in order to tune the DC offset at the microphone output.

simulate this circuit – Schematic created using CircuitLab

The aim is to get exactly 1.65V (half the follower supply voltage).
This is why I used a 100k potentiometer (measured value is 97k) in parallel with the microphone.

While using this set-up, I got a kind of surprise. Without the microphone, I get \$ V_{out} = 8.8 \cdot \frac{P x}{R1 + P}\$, where \$ x \$ is the potentiometer wiper value (0 = wiper to ground), which leads to \$ x = 0.205\$ to get 1.65V at the output.

When the microphone is connected, the output voltage drops down to 1V, which is correct if I suppose that the microphone acts like a resistor \$ Rm\$.

Given the equation \$ V_{out} = 8.8 \cdot \frac{P x}{R1 + P\left( 1 + \frac{R1}{Rm} \right)}\$, which I suppose to be correct, I get \$ V_{out} = \$1\$\,\$V when \$ Rm = 17.5\,\$k\$\Omega\$.

Then, I changed the potentiometer wiper position in order to get 1.65V at the output when the microphone is connected. Following the previous equation, this gives me \$ x = 0.315 \$, which is correct when I check the potentiometer value using an ohmmeter.

So, finally the microphone parallel resistance seems to be 17.5\$\,\$k\$\Omega\$.
However, I (of course) do not get the same value when I use the ohmmeter directly connected to the microphone (without polarizing its FET). I get about 1\$\,\$k\$\Omega\$, which seems to be normal.

My questions are: Why do I get this value of 17.5\$\,\$k\$\Omega\$? What does this value means? Is it relevant to assume the microphone acts like a parallel resistor? (I suppose it can be, because this is like considering the DC component of the microphone FET drain current).


texts: Is the amplitude of a sine wave increasing or decreasing in this phase?

texts:
I'm new to electrical signal, sorry if my question sounds dumb.

Below is a picture from my text book:

It says a sine wave with a phase of 0° starts at time 0 with a zero amplitude. The amplitude is increasing.

I am little bit confused here, shouldn't that be decreasing? If you watch this simulation (choose oscillate) below:

https://phet.colorado.edu/sims/html/wave-on-a-string/latest/wave-on-a-string_en.html

The single point at time 0 is decreasing.

Is my understanding of how waves propagate incorrect or is the textbook wrong?


texts:
For a cost sensitive application we need a 4V supply for a GSM module and a 3.3V supply for a STM32 MCU and couple of sensors. Would it be possible to use a diode like 1N4148 to drop from 4V to supply these parts?
We can make sure not to put the MCU or the sensors in sleep mode and keep the current draw constant. Or add another resistor to keep drawing a couple of mA to keep the drop. Any issue with such a design?
Thanks.


texts:
Seeking help to identify the following common mode choke. The best guess is it a part from Sumida Corporation.

This part is from a refrigerator.
Any of the following information is greatly appreciated

Datasheet
Manufacture
Specification

Based on research it was assumed that following part might have similar specification. Currently not too sure.

SU9HD-40006 from Kemet

Following are results form searches.

Results from google search
Results from Digikey search
PZ-UU10.5-Series 0.5~50mH Common Mode Choke Line Filter Common Mode Inductor
UU Series Common Mode Chokes


texts: Is a matching network needed if the antenna feed line is very short?

texts:
When designing PCBs with RF functionality it is considered good practice to place pads for a matching network immediately before the antenna (or antenna connector). This allows you to compensate for any impedance mismatch arising from design and/or manufacturing issues in the PCB:

A different rule of thumb is that you don't have to worry about RF propagation complexities if your trace is shorter than 10% of the highest frequency component wavelength.

Does this imply that I can omit the matching network if the feed line is very short, electrically speaking?

For example, would the following layout be OK? This is for 915 MHz, with 2mm between the antenna and the edge of the ground plane. The IC is a filter/balun from Johanson Technology. (The 2mm distance was dictated by the antenna datasheet).

(The design isn't completed; I still need to add stitching vias, pull the ground back from the differential microstrip, etc.)


texts: Need some suggestion on 220 - 3.3 volt 500 mA power supply (Or 12 volts maximum)

texts:
I was planning to make some 220-3.3 volts,5 volts & 12 volts power supplies. I tried the configuration above in proteus (0.47uF, 275 volts RMS, Polypropylene film capacitor in series with a small ferrite core transformer). But the output is very low.

The output can be increased by placing a resistor in parallel. But there will be a heating effect. Plus if there is a 1K resistor in parallel with that tiny capacitor, I guess there is no point in placing that large Polypropylene film capacitor.
Even 1uF multilayer ceramic (650 volts) capacitor makes 1.5-volt peak. What should I do? Will this configuration work in practice? I haven't tested practically yet as the products are in shipment from china and it usually takes 15 days. So I am planning to place an order in JLCPCB. So I checked the proteus simulation result.

Most probably I'll use this bobbin and cores.


texts: Using audio amplifier speaker output to drive an electromagnet

texts:
My first time here as a poster so forgive me if I make a misstep...

I am building a coil (22swg enameled copper wire, about 500 ft), some 4in inner diameter of the bobbin, 1" wide, will have ~ 450 turns. I am using lacquer to make sure wire is wound tightly and does not move to avoid heating. I am hand winding it, so it is not the neatest coil... hoping that does not matter so much.

I want to give it a lot of power, and wanted to use an audio amplifier for that. According to some online calculator, the coil I am building should give about 8ohms of resistance, which is perfect for my audio amp as it can do both 4ohm and 8 ohm output (automatically adjusts itself).

The reason I want to drive it with an audio amp is:

Building my own amplifier is not easy, and good power supplies are not cheap; the cost of this audio amplifier (used) is lower than some power supplies.
I need to drive my coil with some frequencies, rather than just constant signal, so planning to use audio frequencies for that generated with my audio software (sine, square and such).

I am not very educated on these matters so I would like to hear what your thoughts are on this setup:

Generate frequencies using my audio software and output that to a pre-amp. It will be a mono signal
Feed from pre-amp to the power amp. I will make sure that all signal strengths are the way they should be (I am aware that pro audio equipment has different line level values than amateur one for instance).
Connect my coil to the speaker terminal for one speaker. Even though the amplifier has two channels, it can be bridged, to give me more power. I am hoping that since a speaker is essentially a coil, connecting my coil should work too.

I count with dumb luck and increasing volume on the pre-amp very slowly and checking the heat that my coil produces. If it stays only warm to the touch, I am thinking - it is OK.

Am I being too optimistic or can this setup actually work?

Also, given the above info, what would it take to get the maximum power out of that coil and the whole setup? The goal is to produce as strong a magnetic field as possible.

Thank you for any guidance, and if I am too clueless, I will appreciate pointers to articles or books that you think I should study to understand my idea and its shortcomings better.

ps. Power amp specs:
800W at 8ohms in bridge mode or 250W at 8 ohms in stereo mode
It can also do 400W in stereo mode at 4 ohms and 600W at 2 ohms in stereo mode.
Max power is 1200W at 4 ohms, bridged.

EDIT:

There would be no ferric core, only a coil.
The goal of this experiment is to see what the biological effects are of such a magnetic field, using various frequencies, around 200-2000 Hz, with most of them around 300-700 Hz. This would be similar to Rife experiments who used radio frequencies to, allegedly, kill viruses. Apparently, or hopefully, microbes have a frequency at which they (may) die, and it is with that in mind that I am building this coil. Naturally, for a test under a microscope, the field does not have to be very strong, but for a real biological effect, "in vivo", the field would have to be stronger in order to penetrate the tissues.
I always thought that the stronger the magnetic field, the more power the coil would consume, which means - more amps or watts, right? (probably wrong :)  )
Voltage gain of the power amplifier is 32.5V/V or 30.25 dB.
Slew rate is >50V/microsecond or >100V/ms in bridged mode.
Current slew rate is > 32 A/microsecond at 2 ohms
Geometry of the coil is not critical, I just built a round one, by hand, and used plenty of lacquer to make sure wires are fixed and cannot move (to prevent losses to magnetic field due to heat).


texts: USB-C laptop charger / circuit breaker device

texts:
Is it theoretically possible to build a device that connects to a laptop via USB-C, receives battery level information and connects laptop to a charger only if the battery level is in certain range?
I am totally inexperienced in electrical engineering, hence also (if the above is possible at all):

Is it something complicated / platform specific (on a hardware level) or relatively easy to do having some basic knowledge?
How is it different with Thunderbolt 3?

Assumptions:

Laptop supports USB-C power delivery charging.


texts: Do MEMS accelerometers have a lower frequency limit?

texts:
Being a higher level programmer by education I have no deeper knowledge of electronics and electromechanics, so feel no obligation to answer this.
I'm wondering about MEMS accelerometers. I heard a claim from a coworker the other day that MEMS accelerometers have a lower limit to what acceleration frequencies they can pick up.
Due to the ODR, (Output Data Rate), we have a finite rate at which we receive distinct samples of the measured accelerometer waveform. Usually (or always?), these accelerometers also employ some sort of lowpass-filter. Thus, we have an upper limit of what wave-frequencies we can reconstruct with the data gathered (due to the Nyquist theorem, at most half of the ODR.) This is known.
But is there any lower limit to what frequencies the accelerometer can pick up, at least to an extent that we can isolate and/or reconstruct it?
Intuitively, my best guess is that it can pick up arbitrarily low frequencies, as long as we have a sufficiently high ODR, and there are detectable forces acting on the accelerometer, - I mean, it can pick up static "forces" such as gravity, so why not low or really low frequencies as well?


texts: Adding a Short Circuit Alarm to a Power Supply

texts:
We have a lab type 3 channel bench power supply. (2 adjustable channels and a 5V channel.) It already has short circuit protection on it. Although I want to add a buzzer alarm when the short circuit protection is active. It just has an indicator LED, and sometimes students won't realize that they short circuited the channel. All three channels have the protection independently. So I can feed the alarm from the 5V channel when one of the other two channels has a short circuit.

My question is how to trigger the alarm?

Power Supply Front Panel:


texts:
Hello I have attached a circuit of a Field Strength Meter that I came up with, my target frequency is around 500Mhz.

I was wondering if a design like this will even be able to tune to 500Mhz.
I am also wondering if I can swap the Ammeter with a current amplifier and then connect that to an LED instead to show the presence of the target frequency.

If there is something horribly wrong with this idea, please do tell.

Picture of a transistor based current amplifier that I was going to connect instead of the Ammeter.

Note: sorry these are not BC547 transistors but 2N2222A


texts: Minimum number of NAND gates required to realize EXOR function

texts:
While trying to minimize the number of NAND gates for realizing EXOR function,
\$A\overline{B} \ \cup \ \overline{A} B\$,
I used De Morgan's & got the expression
\$\overline{\overline{\left ( A\overline{B} \right )}\cdot \overline{\left (  \overline{A} B \right )}}\$
and hence ended up with \$5\$ NAND Gates.
But my book shows it can be done with \$4\$ Gates only.
What should be a good approach towards this minimization problem?
Should I avoid using De Morgan's Law here?


texts: Why Doesn't This Op Amp Preamp Circuit Amplify?

texts:
I have the following circuit as part of a class D amplifier:

simulate this circuit – Schematic created using CircuitLab

I couldn't get the amplitude of Vsig to display, it is ~.447Vp, to simulate a line level input. The goal of this circuit is to increase the amplitude of Vsig to 2Vp to feed into a comparator for the class d amp.

The problem is, as configured, I get no output. I initially used an LM324, and tried two of the 4 op amps on the IC with the same results. I also tried an LM1458, same results. When connected to an oscilloscope, Vout is flat, there is no output signal, not even an unamplified signal.

I checked before and after C2, and still get the same result.I'm not sure how to further troubleshoot this circuit.


texts: Is the HSync and VSync signal level kept high after data period or are they present only during single cycle

texts:
I'm trying to understand HDMI specification for my toy project on Zybo. I'm trying to understand when I get HSync and VSync signals.

I get them once. That means I don't need to look back on previous value - if I read the signal it mean that I get a new line
H/VSync is kept high through the whole period after end of line

Also will I get a VSync without HSync or will they be separate?


texts: Preventing ground spikes while operating a solid state Tesla coil

texts: With a Tesla coil being a high-frequency, high voltage device, and the secondary coil connected to ground, is there a way to prevent the high frequency signal from interfering with other electrical devices when connected to mains ground, such as some sort of low pass filter? I know I can simply avoid this by connecting it directly to the earth or some sort of piping that connects to ground, I am just wondering if there is an alterantive. Thanks in advance.


texts: Where to find the data sheet for Huawei Honor 6 smartphone?

texts:
The smartphone seems to have bq24190 chip for power and charging control (according to /sys/), for which the data sheet specifies that it can be powered not only from USB's 5V, but also from up to 18V.

Does it mean I can charge my Huawer Honor 6 directly from 12V? Where to find the absolute maximum ratings for a smartphone?


texts: Design 2 JK Flip Flops without Switch Input to K

texts:
I have a lab for my Intro to Hardware Course due today. We use TTL. (True= 5v, False= 0v)

Design a 4 bit register using 2 D Flip Flops(Chip 7474) and 2 JK Flip Flops(Chip7473).
Only use 4 Input Switches. Using a Pushbutton for Clock, and another Push Button for
Clear, which will go to all Flip Flops. The output of the register will be measured using
LEDs.

So we can't use a Switch Input for the K of the 2 JK Flip Flops. My teacher gave me the hint of looking at K on the JK Flip Flop Truth Table/Characteristic Table.
K is like Z on it, where it's always alternating between 0 and 1.

My thought is to connect it to the Clock. Can someone confirm or deny this thought process?


texts: Eagle: How can I connect a Polygon IFA to GND

texts:
So I've just completed my Inverted F Antenna (IFA) as a polygon in the brd view on Eagle, I can connect the input section quite easily with an wire.

Whilst the GND section of the IFA I'm having a bit more difficulty with.
As according to the datasheet I'm following GND section on the IFA requires a via which connects to the GND. Now if I add a via and set the name to GND suddenly the part of the polygon that was situated where the polygon is disappears.

Likewise if I name the via as to the name of polygon in this case its called "ANTENNA_2.4GHZ" then the bottom layer for GND will disappear.

As an alternative option I have created a footprint of the IFA for an Antenna library with pads within the input and GND sections of IFA, wondering if this would work instead or if not what would I have to change on it?

Don't judge me on the symbol, will get a better one later.


texts: Inverting op-amp does not give expected result

texts: I am using this op-amp LMC6482 and trying to invert the input. In the diagram below I show how I have wired it up. With this wiring I expect to have an output of 5V (supply is 5v. But just get floating around .75v if input is grounded or 5v.


texts: Bluetooth speaker works only when aux is plugged in

texts:
Plot

Recently got this Bluetooth/FM speaker with a built-in microphone from my friend to try repairing it. He said that it's battery was swollen up so he dumped the battery and never used the speaker again.(old phone battery 3.7V i guess.) I believe it's "something" X6 by a Chinese manufacturer.

Problem

I plugged the USB cable, without a battery, just to saw that it goes on and off, constantly. No sound comes out of it except speakers powering on and off.
Then I tried to plug my headphones to it's AUX input, voila! I heard the Asian chick going: "Bluetooth device is ready to pair."
Paired it with my computer, played some tunes, then I plugged my headphones off and it was still working.
When I powered it off and turned it back on, it's all over again. Constantly going on and off.

By the way it have some low buzzing noise all the time(grounding issues, maybe?).

Here are some pictures of the circuitry and components:

I'm kind of a newbie in here and electronics, I try to repair before throwing stuff away. And I'm curious, what is the reasoning behind this? Thanks in advance.


texts: How to estimate current consumption by ICs

texts:
I'm using an Arduino Due (3.3V) which has a maximum current for all pins 130mA.

How to estimate consumption for a number of ICs?

For an example i use multiple MCP4822 (2channel DAC)

On the datasheet I read "input current" 415-750 μΑ.

But what current the SPI clock signal and the MISO signal consume?

If i connect several ICs does this drains more current?

Does this DAC consumes so small current that i connect as many as i like?

EDIT:
or please only a general guidance: how many ic in general (op-amps, digital pots, transistors) to stay below < 130mA?

About ten or about fifty?


texts: Automated voltage measurement: Tradeoff between PLC and averages

texts:
I am setting up an automated voltage measurement of a precision device. In my case, I am using a Keithley 2000 and controlling it over RS232 from MATLAB.

The voltages I am measuring have to be quite precise (more than 16 bit precision, resolution of tens of \$\mu V\$ on a \$\pm4\ V\$ signal). As such, I need to use some method to get low noise in my measurement. At the same time I need the measurement to be fast enough, since I need to repeat this measurement for every one of the boards \$2^{16}\$ possible outputs.

There are a few ways I can try to lower the measured noise, but I am not sure which is the best. The Keithley 2000, just like most bench multimeters, allows the user to set the measurement time (in number of power-line cycles) and apply filters. I want to work in multiples of a power-line cycle, so all noise from mains hum is canceled out as much as possible. Should I then use as much power-line-cycles as possible and lower number of measurements before averaging, or just 1 power-line cycle and then do a higher number of samples for averageing? For example, 3 measurements at 10 PLC versus 30 measurements at 1 PLC.


texts: Which is the Best power management to maximize runtime on battery?

texts:
I have 3 circuits
Circuit 1 8V 400mA
Circuit 2 5V 700mA
Circuit 3  3.3V 40mA
Battery 4.2V lipo 3000mAh
Option 1 – 4.2v to 8V booster 1.2A and 5v regulator, 3.3v regulator
Option 2 – 4.2v to 5V booster 750mA,3.3 regulator and 4.2v to 8v booster 400mA
Circuit 3 is always operating
Circuit 1 and 2 do not operate continuously


texts: Simple speaker crossover 1st order filter design

texts:
Opened up an old speaker and am trying to figure out what is going on with this capacitor.

The gray cord leading to the larger 16cm speaker cone is an 8Ohm/6.3W capable load and then there is a 1uF capacitor in line with the audio-in line and leads to the smaller 8Ohm/4W speaker cone. So we should be able represent this like so:

simulate this circuit – Schematic created using CircuitLab
I assume this is supposed to be a crossover filter, so a first order high pass filter. However, if we say the -3db-point is 1/(2piRC), this would be around ~20kHz. Wouldn't a tweeter want to remove anything above 20kHz, not vice versa?
This also makes me wonder about the print on the outside of the speaker box that simply states that the entire speaker box can handle a maximum of 6.3W, even though the smaller cone is only rated at 4W. Does the capacitor and the other speaker "soak" up some of the current so it's fine for the entire enclosure to be rated at a higher power?


texts: Can AM and FM signals at the same frequency be separated?

texts:
Suppose one radio station emits an amplitude modulated (AM) signal at 100 MHz, and a nearby station emits a frequency modulated (FM) signal at 100 MHz.

Is it possible to separate these two signals, and listen to only one at a time, or is there irreversible interference between them?


texts: How to measure open-drain vs. hi-z with multimeter

texts: I have an output pin configured to be either open-drain or hi-z. How can I use my multimeter to tell which mode it is in?


texts: Inversion Coefficient Based Design in CMOS amplifiers

texts:
I have designed amplifiers, using potential division method.

What are the steps to design differential amplifier using inversion coefficient  based design methodology?

Please provide links/references of designs with this technique.


texts: What does "case" mean exactly for this three-prong photodiode?

texts: I'm very interested in measuring the the precise amount of amperage coming out of a Si photodiode for an experiment of mine while under illumination. We use Gamry potentiostats for these measurements. I'm looking to purchase a photodiode from thorlabs, such as those listed here. The FDS100 and FDS1010 are both attractive candidates for my application, but for the FDS100 there is an anode, cathode and "case." Should I treat "case" as a ground and wire it to my potentiostat's ground? Why doesn't the FDS1010 have a "case"?


texts:
When using a mini servo (3 wire) for RC models, I've found both designs which connect the signal wire straight to a 555 chip and some that do it via a simple transistor off the 5V line.

I haven't seen the required current mentioned anywhere at all in specs I've seen actually. If it is mentioned, it's only something like "this is signal pin, it uses almost no power".

So is it safe to assume that I can control a servo directly from an output / PWM port of ATTiny working at 5V? (servo power is supplied separately)


texts: Avoid in-amp common mode and ADC input protection

texts:
I'm designing a temperature measuring circuit using a PT100 on a wheatstone bridge. In the temperature range I'm measuring (0-45C) I should get 0-25.5mV from the bridge and then amplify the signal to 0-5V using an instrumentation amplifier (I was thinking on something like the AD8221) so I could read it using a PIC.

Then here comes two problems:

1- Amplifier common mode:

I cannot afford any common-mode voltage. My main supply is +12V so I was thinking on using a charge-pump in order to provide +-12V supply to the in-amp and avoid output clipping.

2- Analog input protection
The  +-12V supply solution forces me to protect the PIC's analog input from voltages below 0V and above 5V using clamp diodes at the analog input but I don't actually know if this is valid solution or it affects the readings in any way.

I don't know if I'm in the right way with this approach so any insight or tip is appreciated. Thanks


texts: Decoupling setting of specific bits (transfer mode, stream, channel) from the generic DMA_Init() function

texts:
So with regards to DMA drivers, what's the approach for configuring certain bits generic inside a function which could be reused for both TX and RX calls which would require different stream parameter at least (On STM32F4, USART RX is on stream5 and TX is on stream6): there are bits including stream#, channel number, transfer modes such that they're decoupled from the generic DMA_Init() let's say?
I decoupled the peripheral/memory addresses along with transferModes from the init function which I can reuse for RX, TX but does it make sense incorporate the rest inside dma_start() as well? Currently, I have:

dma_init();    // set other bits i.e word length, fifo/direct mode, fifo threshold etc
dma_start(sourceAddress, destinationAddress, transferMode);

The examples I've seen online do define transferModes and stream inside the init() function and I'm not clear on this.

So maybe I'm looking for something like:

dma_init();
dma_start(stream5, sourceAddress, destinationAddress, p2m); // rx from peripheral to memory

// process the data now stored in destination buffer, and send out a response
dma_start(stream6, sourceAddress, destinationAddress, m2p); // tx from mem to per


texts:
I'm working with a Zedboard and I'm trying to optimize some functions in Vivado HLS.

However, when there are functions like the following where I don't know what to do.

E.g:

for(i=0;i<end;i++){
    sum+=i;
}

I can't pipeline this because each cycle depends on the previous. Is there any workaround to make the Pipeline directive function?


texts: Reading the data from a glucometer externally with a microcontroller or arduino board

texts:
What would be the easiest way to read data from a USB glucose meter externally with a microcontroller or arduino board and not with the software that is provided. So how could I incercept the digital signals that are being sent out? I don't have a particular glucometer in mind has I want you guys suggestions in buying one.
Thanks for your anticipated response.
Best regards,


texts: Linear magnetic field position sensor output: PWM vs. Digital

texts:
I'm looking at the AS5311 magnetic field position sensor.

The IC presents a couple ways of getting the absolute position of the magnet in relation to the sensor. You can either read out a 12-bit value from the serial port, or use the 244Hz PWM output.

The datasheet says that you should average/filter the values to obtain an accurate result. Does using the PWM output make this easier or something?

In what situations would I want to use the PWM output instead of the simple digital interface?


texts:
I'm using that sensor http://www.analog.com/media/en/technical-documentation/data-sheets/AD7814.pdf

but after reading the datasheet, there is a table for temperature conversion. I can not understand it. Would someone please tell me how to convert the temperature from that table to float point ?


texts: What is the relation between the gain and range of a data-acquisition amplifier?

texts:
A data-acquisition amplifier has different ranges. The board amplifiers a voltage sample and ADC converts it to a digital code. There is probably a reference voltage inside the board so it compares with it and produces a code.

But how can I figure out in which range the gain is 1 or more? For example if I set the range to +/-10V does that mean the gain is 1? Whats the relation between the gain and the range and why? Lets say I set the range to 1V. Will the gain increase in this case comparing to 10V range? I couldn't figure out the logic here.

Here is the board:
http://www.mccdaq.com/PDFs/manuals/PCI-DAS6023-25.pdf


texts: Why is this a Moore and not a Mealy FSM?

texts: Can someone please explain how I can tell which FSM type I have? In my textbook I read that output in a Mealy FSM is based on both the input and the present state, but in a Moore FSM it is based only on the present state. Then why is the circuit in the figure below a Moore FSM? If I change the "In"-signal, then "Q0" and "Q1" will also change, so output depends on input. Does that not make it a Mealy FSM?


texts: What voltage do we use for battery cut off voltage?

texts:
I have a battery that states a 2.75v battery discharge cut-off voltage. Is that voltage measured at the poles of the battery while it is connected to the load or they are talking about the electromotive voltage?

For example. A Sony battery I have, when I measure it with a multi-meter it displays 3.61v EMV but when connected on the load it only gives 1.81V at the poles of it. Which voltage I should consider to stop discharging it?

Why such a large difference in voltage?

EDIT: Since you asked, the battery is a Sony US18650GR - O7.
It is connected on a custom made circuit with 2 parallel 4.7ohm (5 watt) resistors (2.35 in total) plus some mOhms (maybe 0.5-1 Ohm) due to cables, shunt resistor (current sensing) and connectors resistance. At start it draws something like 1.2 Amps and when the voltage dips at something like 1.81v it draws 600-700 mA. No cut-off (over-discharge) circuit.


texts:
I'm using a FXLS8471Q accelerometer for a project using the SPI interface. The chip uses the same pins for SPI and I2C. To detect which interface the user desires,  the chip samples the SA0 pin on power up according to Table 11:

I have two questions.

To make the SA0 pin appear floating, I connected it directly to the input of a CMOS buffer. The buffer I chose happens to be of the 74LVC series. Since the input to a CMOS device is basically connected directly to the gates of MOSFETs, am I correct in assuming that a CMOS input will "look like" a floating pin to this chip?
What is the internal circuit that the manufacturer likely used to detect a floating pin? One thought that comes to mind is a simple 50/50 resistor divider between power and ground. Sampling the middle of the divider with an ADC or two comparators could tell the difference if the pin is tied high, low, or floating. Is it much more complicated than that?

simulate this circuit – Schematic created using CircuitLab


texts: What files/directories are needed to recreate a Xilinx PlanAhead project?

texts:
I wish to make sure the input files are checked into source control so I (or others) can build, recreate, branch/modify a design. However with PlanAhead, the same suffixes are used for both input and output files.

Yes, I did ask Xilinx in a WebCase, but didn't get a good answer. I don't wish an answer on the lines of "all of these directories" where that includes many output files. Some of the suffixes are in this question but that answer isn't sufficient since xml files are used for both inputs and outputs.

Knowing what files/directories aren't needed would also be helpful. Then I could ask Xilinx about those files/directories that aren't known.


texts: electron affinity and measuring open circuit voltage of insulators through rubbing

texts: I am rubbing two insulators, polyester and teflon on each other. Teflon has more electron affinity than polyester. I need to know exactly how much charge is transfered to teflon and polyester in the process of rubbing and the open circuit voltage.


texts: How to implement Serial port RS-232 from 2.5V IO signal?

texts:
I am playing with a Xilinx Spartan-3A development (XC3S50A-TQ144C) and then I tried to implement RS-232 serial port by following the guide here: http://www.fpga4fun.com/SerialInterface.html

I bought a DB-9 port and connect RxD,TxD,GND of DB-9 port to three pin of my development board. (Of coz GND is connect to the GND of my board)

I tried to send a signal of one character every second from the pin to TxD. I checked the signal with a scope. The signal should be correct.

But I cannot see any character shown on my terminal by reading from /dev/ttyS0 (Serial port on Linux).

The scope show that the signal is sent using +2.5V and -2.5V respectively. I think the problem is that serial port should be sent with at least +5V / -5V. How can I modify the board (or construct an amplifier circuit) to send signal in higher voltage?

I have a photo capture of my scope here:


texts:
I'm trying to register an SPI device to my Angstrom Linux (kernel version 3.10) in order to use an ADC chip (LTC2258) for my custom board. Processor that I2m using is Cyclone V, and FPGA handoffs seems correct (SPI Master 1 is given to HPS). So, I edited my .dtb file like this:

        spi@0xfff01000 {
        compatible = "snps,dw-spi-mmio-15.0", "snps,dw-spi-mmio";
        reg = <0xfff01000 0x100>;
        interrupt-parent = <0x3>;
        interrupts = <0x0 0x9b 0x4>;
        clocks = <0x21>;
        #address-cells = <0x1>;
        #size-cells = <0x0>;
        bus-num = <0x0>;
        num-chipselect = <0x4>;
        status = "okay";

        spidev@0 {
            compatible = "spidev";
            reg = <0x0>;
            spi-max-frequency = <0x5f5e100>;
        };

    };

At kernel boot, it only says this about SPI:

root@cyclone5:~# dmesg | grep -i spi
[    0.652554] dw_spi_mmio fff01000.spi: master is unqueued, this is deprecated

But spidev0.0 entry appears under /dev. With default spidev_test program, I see this output:

root@cyclone5:~# ./spi_d -D /dev/spidev0.0
spi mode: 0
bits per word: 8
max speed: 500000 Hz (500 KHz)

FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF FF FF FF FF
FF FF

And there is the thing: SPI interface of that ADC is used for configuration. So, the test case for me is to write configuration values to registers with given addresses, and successfully read them back. So, I modify the tx buffer from the source code; I write and read back the registers. But it gives me the same result, full FFs.

In ADC's datasheet, it says:

Data is written to a register with a 16-bit serial
word. Data can also be read back from a register to verify
its contents.
The fi rst bit of the 16-bit input word is the R/W bit. The
next seven bits are the address of the register (A6:A0).
The fi nal eight bits are the register data (D7:D0).
If the R/W bit is low, the serial data (D7:D0) will be writ-
ten to the register set by the address bits (A6:A0). If the
R/W bit is high, data in the register set by the address bits
(A6:A0) will be read back on the SDO pin

So, I modified the code accordingly. I use my modified spidev_test with these parameters:

./spi_d2 -D /dev/spidev0.0 -b 16 -s 100000000

But as I've said before, result is full ones. Also, changing bits per word parameter does not affect the result.

How can I debug this? Where should I look? Any help is appreciated. Thanks in advance.


texts: How to generate and/or improve this power distribution for these 4 subsystems?

texts:
I am trying to design a system that is powered through a 28V wall adapter and a 6S cells LiPo battery. The system has a subsystem that takes care of the balanced charge, coulomb counter, charge control and protection, automatic power selection from adapter or battery, etc.

The output voltage of this subsystem is up to 28V (when the system is powered by the adapter) and at least up to 18V when it is powered by the battery (and it is about to run out). The maximum current that can provide this subsystem is at least 8.5A. The system works through the wall adapter and when it is removed, it automatically powers through the battery (the behavior is similar to that of a laptop).

Starting from the output of this subsystem: Vout_min = 18V, Vout_max = 28V, Iout_max = 8.5A, I have to design the power of the following subsystems:

Subsystem 1: Vin=24V and consumption less than 1.75A
Subsystem 2: Vin=24V and consumption less than 0.75A
Subsystem 3: Vin=19V and consumption less than 2A
Subsystem 4: Vin=5V and consumption less than 1.5A

In addition, it is necessary to power two  24V fans but as they have a wide range of operation, they will operate with MOSFETs working as switches.

I had thought to use this configuration:

For the subsystems 1 and 2: a DC-DC switch converter with a buck-boost topology. Vout=24V and up to Iout=3A. And then, with a pair of MOSFETs as switches, to control the power of subsystems 1 and 2.

For the subsystem 3: a DC-DC switch converter with a buck-boost topology. Vout=19V and up to Iout=2.5A.

For the subsystem 4: I had thought to use a DC-DC switch converter with a buck topology. Vout=5V and up to Iout=2A.

simulate this circuit – Schematic created using CircuitLab

It would be interesting to maintain an efficiency above 90% and try to minimize the number and cost of components.

My questions are related to the power distribution:

Is it minimally acceptable?
If not, how would you do it?
How can it be improved?

Thanks!


texts: Tesla coil produces AC or DC spark output?

texts: In a standard AC Tesla coil, the output spark from the dome (torus) at the top appears to come out in a steady, constant stream. However, since the AC on/off/reverse function of the AC current in the primary coil causes a similar on/off/reverse induction in the secondary coil, does that mean that 60 times a second the electrons in the output spark are shooting out, stopping, and then experiencing a reverse "pull" back into the dome, or is something else keeping the electron stream constantly pouring out only one way (sort of DC style) into the air?


texts: Understanding Voltage/Power line arrows in complex schematic

texts:
I have some understanding of general electronics but now I want to learn about actual electronic schematics. For this I look at some complex reference designs to somehow get an understanding because like this I usually learn best.

I came across this reference design where I cut out a part that I simply do not really understand. This shows the actual power/dc-connector input to the circuit.

However what I do not really understand are the voltage line arrows (like DC_IN). Since there is already the dc connector (PJ1-021) where pin 1 should be the voltage/power-in line why is there another red DC_IN arrow that points into the circuit (on the upper left)? I would understand if this arrow would point out of the schematic to show that it is used somewhere else. Is this arrow direction a mistake or am I understanding something completely wrong here?

And if this is not a mistake where does this 12V come from if not from the dc connector (PJ1-021)?


texts: Circuitry to measure sub-nano ampere current

texts: Is there a well known methodology to design a IC circuitry to measure sub-nano ampere or even pico ampere currents within a very short delay of nano seconds? The SNR could be assumed to be fairly good above 20dB.


texts:
I have built and tested an active band pass filter, with the intention of creating a speed detector, whose lower and upper cut off frequencies are 48 Hz and 1591 Hz respectively. During testing I confirmed attenuation of voltages out-with the bandwidth above and subsequent amplification. This was using a signal generator where of course, I could send the desired frequency through the circuit.

When I began using the radar module, transmitted frequency is 24 GHz (https://shop.bb-sensors.com/out/media/Datasheet_RADAR-IPM-165_DBE_Rev01.pdf), the received frequency was around 80 MHz and of course, voltage at this range even after amplification was extremely small.

Is there any way I can control the received frequency so I can analyse the frequency? If this isn't something that is possible, is there any other way I can analyse the received frequency?

I'm completely running out of ideas and thought this almost feels like last chance saloon.

I've added pictures of the circuit, radar input and circuit input and signal generator input and output.

As can be seen from the circuit diagram below, the radar is the input to the entire circuit. Both oscilloscope images display inputs and outputs. The outputs appear to be similar when a very large frequency is applied to the circuit, much larger than that of the upper cut off frequency.


texts: Finding the impedance of a distribution line from R,X,C values

texts:
I have real industry data of distribution feeder with line data consisting of r ,x and c values as shown in the attached figure.

I want to write a script in python to calculate the impedance of line based on the above parameters. To achieve this, I tried the below script. Do I calculate it correctly?

import numpy as np
l = 80                                  # Line length [km]
C = 0.00048 * l                         # Line Capacitance [H]
R = 0.0754 * l                          # Line resistance [Ohm]
F = 50                                  # Frequency [Hz]
w = 2*np.pi*F                           # Frequency [rad / s]
z = np.sqrt(R**2 + (w*L)**2)            # Impedance (magnitude) [Ohm]

print("Impedance:",z ,"Ohm")


texts: Emi Filter Design with Tracopower isolated power supply in railway application

texts:
I'm designing, for a railways application, the power supply circuit on a pcb board that supply 5Vdc starting from a 24Vdc(coming from a not clearly defined source, sure a 24Vdc line).

I'm using the TRACOPOWER TEN 40WIR isolated DC/DC converter(railways compliance):
(https://www.tracopower.com/products/ten40wir.pdf)

My questions concern the EMI filter circuit. I'm reading the application note from Tracopower (ten40wir-emc-consideration from Traco website) where I find this figure with suggested filter to comply EN50155 Immunity:

Can someone help me, giving me indications on how to design and size an EMI filter that satisfies the en50155?

Maybe there is a commercial solution that is suitable for railways use?

Thanks you


texts: Are flyback diodes needed for this op-amp voltage controlled inductor?

texts:
I understand the need for flyback diodes when trying to change inductor current abruptly with a mechanical switch or when using a BJT/MOSFET as a switch.

Now, assume I (linearly) control the voltage across a coil with this op-amp circuit:

simulate this circuit – Schematic created using CircuitLab

It seems to me that a flyback diode should not be needed at all with this circuit, even if we imagine that the op-amp has no internal diodes between its output terminal and its power terminals.

Let's say the circuit is steady at Vin = 4V so the coil current is 6A (from right to left). Let's then step Vin to 7V, which should decrease the stored energy in the coil. In my mind the op-amp should simply reduce current flowing through the lower transistor of its output stage at a rate which causes the EMF of the coil to result in 7V at the op-amp's output (when Vin is stepped the 6A through R1 mean that the right side of L1 is at 4V so the induced EMF across L1 would make it's left side 3V higher than the right side at that instant). This current change then ends when 3A are going through the inductor.

My question is: Is my understanding correct and theory dictates that a flyback diode is not needed for this circuit? If yes, is there anything missing from this simplified model which would require a flyback diode in real applications?

Note that this is more of a theoretical question aimed at improving my understanding and mental model of op-amps, so answers along the line of "just throw a diode in there to be safe" are unnecessary. This is a simplified version of my actual circuit which has dual-supplys and regulates current (using a current sense resistor between inductor and ground), so any explanation which allows extrapolation to more complex circuits is welcomed.


texts: A-D conversion: effect of adding more bits

texts:
Say you have a digitizer that's converting an analog signal and feeding it to a microprocessor for whatever you'd like to do to it. How would increasing the number of bits of the digitizer affect the signal? I feel like it would have something to do with the resolution of the signal but that's just a guess and I have no idea how to explain this concept. Also, I feel like there should be a mathematical relationship between these two but I don't think I've seen it anywhere else online.

Additionally, how would the sampling frequency that was first used to obtain the analog signal be related to the number of bits. Are there any precautions that should be taken?


texts: I have a problem with a circuit that transmitts a video signal(PAL 1.0 Vp-p) through a coaxial cable of around 200m.My problem is that the high frequency content is really attenuated by the cable.I need to build an equalization circuit but I don't understand how I will do it because the attenuation doesn't appear only at a certain frequency,so i will need to correct every "frequency".Could somebody give me some advice about this,where do I need to put the equalization circuit(transmitter/receiver) and how do I suppose to do this ?I thought at an active high-pass filter but this will work only for a certain frequency.


texts: Can 85V 35W ballast support a 85V 50W bulb

texts:
I am having PHILIPS MPXL DL50/740 85V 50W PX32D but not having a suitable ballast to test it. I am not able to find suitable ballast but ran into a 85V 35W ballast will it support?
Is there any other way to test those bright bombers


texts:
I've connected a servo(AS-18 acoms) to my arduino and I've uploaded the sweep example onto it. But nothing happens  .  Here's a pic.
I've connected the positive terminal of the servo to 5V on the board, negative to ground and the pulse wire to digital pin 9. Is that right?

#include <Servo.h>

Servo myservo;  // create servo object to control a servo
            // a maximum of eight servo objects can be created

int pos = 0;    // variable to store the servo position

void setup()
{
  myservo.attach(9);  // attaches the servo on pin 9 to the servo object
}

void loop()
{
  for(pos = 0; pos < 180; pos += 1)  // goes from 0 degrees to 180 degrees
  {                                  // in steps of 1 degree
    myservo.write(pos);              // tell servo to go to position in variable 'pos'
    delay(15);                       // waits 15ms for the servo to reach the position
  }
  for(pos = 180; pos>=1; pos-=1)     // goes from 180 degrees to 0 degrees
  {
    myservo.write(pos);              // tell servo to go to position in variable 'pos'
    delay(15);                       // waits 15ms for the servo to reach the position
 }
}


texts:
I am trying out the following circuit, I want to use the Arduino so that I can more easily program pulses to drive my load. I was previously using a function generator (FG), but for some reason it won't save my programmed pulses and it's time consuming to have to individually program 100+ points each time I turn it on.

The previous circuit driven by the FG used two MOSFETs, as the FG had a higher output voltage, to switch the first one. So I switched it with the BJT thinking it should be similar, but I think I have over looked something.

As when I probe node A, I see 5 V from the Arduino for each pulse. However when I probe Node B, I see slightly less than 5 V.
When I expected a value closer to 10V.

simulate this circuit – Schematic created using CircuitLab

I am using the D13 pin on the Arduino as digital out, the other connections are the Vin and GND.
Admittedly the R1 may be a little high, could that be the cause?

Is this the right way to set up such a circuit, or have I missed or misunderstood something?

I saw another question where something similar was asked, and they were using a "push-pull configuration" with an N type and P type BJTs before the MOSFET. Would I need to do something similar or could a single BJT work?

The load (if relevant) is taking a 40V, with 20 A current, at a 2% duty cycle. Occasionally pushing it to double 80V, with 40 A at 1% duty cycle. Its to drive a coil to produce a magnetic pulse.


texts: What would the output impedance be if R5 And R6 were not in the circuit?

texts:
If R5 = R6 = 10 ohms then I think that the output impedance would be 10 ohms.

What would it be if R5 and R6 were not in the circuit?

Thanks


texts:
I'm studying AC analysis of FET: Self bias configuration without bypass capacitor.
I'm not getting how Vrd = Vo + Vgs. My main problem is with KVL. I'm new to the subject.

Reference : Boylestad


texts:
Newbie to electricity here, quick question:
I want to run electric over existing LAN cable (not POE), which of the following is better or workable:
Scenario:

5 CCTV cameras, each requires 9V DC 0.6A
LAN cable length varies from 5m to 20m, 26 AWG copper cladded aluminum cable for each pin (8 pin in each cable)

Method 1: 240V AC to 9V 10A DC power supply > cable > cameras
Method 2: 240V AC > cable > original AC-DC adapter > cameras
Shall I convert AC to DC before or after the cable? Will any of these method works? since the load is very small.
It's almost impossible to run new cable, will my preferable method 2 works in this case?


texts: Capacitor as voltage source but why not as current source

texts: I have read from so many articles that capacitor acts as voltage source if it has some initial charge in it when connected to load. But why we consider capacitor as voltage source , why not consider as current source?


texts: I bought a BX700UI APC UPS for my linux arm server setup (40 watts) to protect it from power cut. - I have the server in the bedroom is it dangerous to have such an Ups in a small bedroom? - Thinking of gases?


texts: Improve recovery time of discrete bjt monostable multivibrator

texts:
How can you improve the recovery time of a monostable multivibrator build of discrete pnp BJT transistors?

I can't use integrated circuits like 555 timer since I need to tolerate voltages up to 36V.


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I am using Keysight MSOX3102T oscilloscope which has 1 GHz bandwidth. At these frequencies, \$1~M\Omega\$ input impedance is not suitable due to reflections. Therefore, it has the possibility to select \$50 \Omega\$ input port.

simulate this circuit – Schematic created using CircuitLab

Assuming the configuration shown in the figure in which I measure a RMS voltage of \$V_{rms} = 2.2V\$ on the oscilloscope, is it correct to compute the power provided by the signal generator as:
$$ P = \frac{V^2_{rms}}{R}= \frac{2.2^2}{50}= 0.0968 W$$
where \$V_{rms}\$ is the RMS voltage measured on the oscilloscope and R the input port impedance?

UPDATE: Thank you everyone for the replies. Maybe I have not been clear enough explaining my doubt. It can be summarized as, setting the input impedance at \$50 \Omega\$, can I take the load impedance as just \$50 \Omega\$ or does it not work that way in an oscilloscope?


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I tried to follow docs, and here is my implementation for triangle pulse:
V1 0 1 PULSE(-0.75 0.75 0m 8.335m 8.335m 0 16.67m 0)

but the result is:

although the Rise time is 8.335m at appears as 0, can someone explain what’s the issue?


texts:
I'm trying to do a problem for revision and I'm running into problems calculating the resistance of this circuit used to approximate a twin-core wire.

It's used later in the question with the middle resistors being treated as a plastic layer, but I'm struggling with the first part of the question which is to calculate the total resistance R across the terminals on the left. What I tried is to treat the sections individually, that is:

This section has resistance \$ R_1 = 2r_a + r_b \$. I then considered adding another loop to this as essentially adding another resistor \$R_1\$ in parallel to the first loop, so this would have resistance $$\frac{1}{R_2} = \frac{1}{R_1} + \frac{1}{R_1} $$
so $$R_2 = \frac{2r_a + r_b}{2}$$

Following this logic, the resistance of \$n\$ loops would be $$R_n = \frac{2r_a + r_b}{n}$$
I don't think this makes sense since for \$n \rightarrow \infty\$, \$R_n \rightarrow 0\$. Am I missing something with this? I assume I did something wrong with the parallel/series treatment but I'm not sure.

The full question is:

  The network of resistors shown in the Figure below contains a large number of identical segments and has an overall resistance \$R\$ as measured across the terminals on the left. Segments are added to the front of the network until eventually adding extra units makes no difference to \$R\$. Find \$R\$ in terms of the resistances \$r_a\$ and \$r_b\$.

  1: Use the result to estimate the ultimate resistance of an infinitely-long twin-core cable made of copper wires (area 1.2mm, conductivity \$σ = 6 \cdot 10^7Ω^{−1}/m^{−1}\$). The 2mm gap between the wires is completely filled with plastic (resistivity \$ρ = 10^{13}Ω/m\$). Assume that the effective dimensions of the plastic layer are 1mm x 2mm.

  2: *Roughly estimate the length of cable needed to establish this resistance.


texts: Capacitor Replacement - Markings: 622JA - GD 1000

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My tube light choke was not working, I tested its circuit using multi-meter and found that a capacitor (labeled 622JA on first line and GD 1000 on second line) was short-circuited so I pulled it out and tested, same result.

There is no documentation or information available online for that part number. Is there a replacement for that part or where do I find it on existing circuits that I have?

Update Image and Dimensions:

Update - Solved
I replaced it with 1600v 7.32nf capacitor (a red giant one), it is working fine.


texts: I need to detect very low amplitude sound in air (typically 0dB), in an enclosed space of less than 100 cubic centimeters, in the low ultrasonic region ie 20kHz to maybe 50kHz.  I will be narrow bandpass filtering it in any case. The frequency is fixed. Temperature range 0degC to about 90degC. What microphone type is most suitable?


texts:
I'm employing a Varistor in a simple circuit that will be used in a car. The Varistor is there to ensure that any load dumps / vehicle transients will not result in catastrophe for the circuit.

My question is this: Should I pass VIN through the Varistor, or should the Varistor couple VIN and GND?

Circuit A has VIN passing through the Varistor:

Circuit B has the Varistor tied from VIN to GND:


texts:
I have 60 watt LED strip I want to control with an Arduino (the Genuino Mega 2560 actually). I found this tutorial which shows you how to do it for a white LED strip, but I am not sure whether I can just connect the same circuit three times or whether there is a better way. Also, the web store I wanted to buy components from said some parts, the BC639 in particular, are "outdated", suggesting the BC63916 instead.

The article's circuit:

Schematic of my (probably very bad) attempt:

As you may notice I am quite inexperienced and I doubt that my "just slam everything together" approach above will work. My questions:

Is it even smart to use the totem-pole driver recommended in the article or should I stick to a more simple solution?
If so, how can I connect three of these circuits together for my RGB strip (or how can I adjust my attempt)?
Finally, are the components and resistor values named in the article sufficient?

  "For the transistors a BC639 NPN and a BC640 PNP do the job. R is 3.3Ω. RB is 22Ω. RGATE is 4.7Ω. C is a big 1000μF electrolytic."

I have one last question, but it is not as important. I could buy a 12V power supply, but the power supply of my PC (which I intend to control the Arduino with) can also deliver this. Is this a good idea or will I destroy my PSU?


texts:
Hello I'm routing PCB of my circuit using Altium and encounter a problem.

My PCB is multi-layer(4) board with two signal plane on each surface and two internal plane (Power Plane and Ground Plane)
the stack order is as follows :

Top layer signal plane
Power Plane
Ground Plane
Bottom layer signal plane
from top to bottom
One thing makes me a little bit confused and I'm stuck with it (Maybe it will be very simple question to you)

Suppose I want to add blind via from top layer to ground plane(1-3)
Then, the via will physically pass through power plane as well.
On some area, it will pass through split plane which is already conncected to other blind via as a net (As shown in the following figure)

Then, Should I avoid this area? My expectation is that : If I go ahead, two via get shorted and ground plane connected to 1-3 via will be 3.3 V plane
If I split the plane again and make no net plane and place 1-3 via on it, is it okay?

Does "no net" split plane means the plane is insulated?
Is each split plane electrically separated ? If so, can I make small
split plane on power layer for signal transmission?


texts:
we have a switched power supply with a sw frequency at around 70Khz

In our DAC pcb , we use LDO with a pssr of about 60db reduction at 70Khz

We are thinking to add a LPF (LC or PI) before the LDO to attenuate even further at least 30db at that frequency (all this because we want to clean the power supply thus having better sound at output)

Is it a good practice to add LPF (lc or pi) before the LDO ?
Will the PSSR add of LDO and LPF ?(the LPF and LDO are in series)
What LPF filter is recommended (pi , lc) or only depends on how many db of attenuation we want to achieve ?


texts: I was going through timers in pic and found that there are so many timers available in micro controllers. For example a PWM time base is driven by Timer2. My doubt is why there are so many timers? Why cannot be there a single timer for example just timer1 alone for the complete micro controller.


texts:
I tried to dc sweep V3 in my circuit and measure the gain.
But it does not give a correct result.
What I am trying to do is actually recreating some measurements from the datasheet.
Maybe there is a simulation techniques that I do not know yet.
Appreciate any suggestion.


texts:
I am using an IC 74162 (decimal counter) and I know that both enable inputs ENT and ENP must be on so that the counter works, but I am not sure about the difference between them, and their relation with the output RCO.

Thank you!


texts: How to find 3 dB bandwidth of any transfer function?

texts:
Suppose we have a transfer function

$$
G(s) =\frac{2(s+3)}{(s+6)(s+1)}
$$
I want to know how to find out the \$3\textrm{ dB}\$ bandwidth of this transfer function?


texts: How "slow" is a Class T "slow blow" fuse?

texts:
I have a DC inverter that's rated for 3kw sustained with a 6kw peak (for up to 5 seconds).

Per the Inverter manual, the manufacturer recommends a battery fuse rated for "at least 350 amps".

How can I determine what size fuse would be ideal in order to accomplish the following:

Never blow at 3kw/250amps (inverter's nominal rating)
Allow surge currents of up to 6kw/500amps for up to a few seconds
Blow pretty darn quick after the 6kw/500amps threshold

I was considering a 400amp fuse, but I'm not sure how to determine if it fits the bill without trying.  Frankly, I'd rather have a breaker with similar characteristics since these fuses are upwards of $50 a piece, but it is what it is.

This is a photo of the fuse: http://ecx.images-amazon.com/images/I/71FMkor8t7L.SX355.jpg


texts: In a Voltage Regulator, what is it that decides the maximum resistance of the resistor and why?

texts:
I need to find the maximum resistance that R can have. This is what I know:
10V<=Vin<=15V
Iz>=0.2mA
0A<=IL<=1A
Vz=5.7 V.
hFE=50

I have derived the equation \$R=\frac{Vin-Vz}{I_z+\frac{I_L}{1+hFE}}\$

But how do I know which value is the biggest R can have and why is that?
I read on Wikipedia that
\$R_{max}=\frac{Vmin-Vz}{I_Zmin+\frac{I_Lmax}{1+hFE}}\$
but I just don't understand why.

Thank you!


texts: Ultra simple circuit (2 Resistor, 1 Voltage, 1 Current): Kirchhoffs Laws don't give the solution; Superposition, but how?

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I am doing a course on Coursera "Intro to electronics" as electronics always was my weak point.

Now we discuss npn transistors and I have simplified circuit  diagram (see below) where I am supposed to solve for VB. I am feeling really embarrassed to ask this but I want to understand this...

Given are
Rb1=15000, Rb2=82000, Vcc=15 and IB=40 mA

My idea was to to a KVL and KCL and I came up with these equations:
$$
V_{cc} - I_{b2}R_{b2}-I_{b1}R_{b1}=0 \\
I_{b2} - I_{b1}=I_{b} \\
and \\ V_{b}=V_{cc} - I_{b2}R_{b2}
$$

and this becomes

$$
I_{b2}R_{b2} + I_{b1}R_{b1}=V_{cc} \\
- I_{b1}+I_{b2}=I_{b}
$$
$$
\pmatrix{
R_{b2} & R_{b1} \cr
- 1 & 1}\pmatrix{I_{b1} \cr  I_{b2}} = \pmatrix{15 \cr  0.04}
$$

When I solve this for IB1, IB2 I get 0.04 mA and 15 mA. This gives me VB = VCC-IB2*RB2 = 14.5055 V

... which incorrect!! :-(

The solution's hint is to use superposition.

My two question:
1. What's wrong with my solution way?
2. How do I go about with a superposition?

EDIT:
ad 2:
after some more thinking: can superposition in this case mean that I

a) have one circuit without IB.

AND

b) one circuit with both voltage set to ground. Thus I get RB1 and RB2 in parallel?


texts: Heat transfer tape, or paste, or nothing

texts:
I am installing a bunch of LM317 and LM337 regulators in TO-220 package. They will have 2 heat sinks on them each.
Occasionally they will have to run close to their maximum continuous rating and can get hot.
My question is about the heat transfer between the regulators and their heat sinks.
Using nothing is easiest.
I would like to know how much better either the tape or paste is over using nothing.
3M has many Thermal transfer tapes. I am not sure which one would be good for this application.


texts: In the given question, I see figure 3 has a common terminal which is more likely to be a full wave rectifier and figure 4 has 4 terminals which resemble that of a bridge rectifier, am I correct in saying this, can someone identify the components.


texts:
I have worked on many electronic DIY projects like MIDIbox (http://www.ucapps.de/), it always was fun and working but at the end, the problem was that I ended with a cool gear, but in a poor casing, for example : wood very roughly cut (by myself!).

What are the best solutions in 2014 in order to make a custom plastic case, with labelling, some round and square holes ?

Example :

Is 3D-printing adapted for this purpose ? Are there other solutions ?

As the desired quantity = 1 unit, are there some companies that propose such a service ?


texts: Detect the state On/Off a DC 12V single coil latch relay

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A LiFePo4 charging/discharging circuit (12 V, 200 Ah, 100 A max) is protected by a single coil latching relay with manual override. This relay is controlled by an ATMega328 (through a FET with flyback diode) but does not have state contacts. For safety and operational reasons, I would like to detect the open/close state of this relay and feed information back to the micro controller.
I have been so far considering measuring the differential voltage accross the contactor (<1 milliohm). This is somewhat simple but may fail if charging voltage equals the LiFePO4 battery (quite unlikely as CV/CC chargers will drive to ~14.4 V in absence of load). Contactor would be declared closed if voltage difference is less than 100 mV for some amount of time (~250 ms).
I am not certain of the type of differential amplifier and protections to use in these conditions:

differential voltage range will be within -20 V/+20 V
50 V transients (+/-50 V) may exist during switching and load dumps

I would be very grateful if anyone could comment and criticize the approach and maybe advice on the kind of differential amplifier to select.
Best regards,
Edit:

Manual override : the relay has an external push button to On/Off manually
Schematic


texts:
I´ll be clear and fast in what I´m asking once my last question did not have many views.

So,
a couple days ago I was at the bench switching a IRLZ34N with a 555 timer, powered by a 15V, @ 50kHz, \$33\Omega\$ gate resistor. As I started changing the drain resistor values, I could the see the mosfet, when switched off, would increase its drain voltage in a speed which relied on the drain resistor.
To bring some numbers, @ \$R_{drain} = 47k\Omega\$ it was really slow to build up that 15V again, @ \$R_{drain} = 3k\Omega\$ it was able to reach 15V within 2us. @ @ \$R_{drain} = 330\Omega\$ it reached 15V in about 400ns.

Although I´ve not uploaded any image to clarify, I searched for what could be the reason why it has such behavior and realized it has to do with drain-gate capacitance (\$C_{DS}\$) and gate-source capacitance (\$C_{GS}\$) though I really don´t get how it affects the switching like that.

I know \$C_{gs}\$ affects the circuit in increasing \$V_{GS}\$ and switching the transistor on and off but I don´t understand how to relate that to the drain voltage as I just mentioned.

Why does the mosfet behave like that after all?


texts:
I have wired this circuit up on a breadboard, replaced the zener with a constant 2.5V supply. I have also replaced R3 with a poteniometer wired as rheostat (varaible resistor)

The lowest output I can get is obviously 2.5V because thats my reference voltage.

My Vout (voltage across the load resistor) is given by what is basically the gain of my op-amp times the reference voltage. What confuses me is how the output of the op amp is being used to control the transistor (NPN). how is it that my op amp out which is going to the base of my transistor also turns out to be my Vout across the load? There is no mention of base current or anything else really to do with the transistor. I thought maybe it was over simplified and i was not expecting it to work, but it does indeed hold a steady output voltage even when I vary the load resistance.
So again I ask how is that the op amp non-inverting amplifier equation happens to give the transistor enough base current to make the output also equal the result of said equation.

Vout = Vref * (1+R2/R3)


texts: Decoupling capacitors introduce more noise on transmitter power amplifier

texts:
I have an issue that I can't understand and looking for your help to give me some insight to solve it.
I'm using a module named dw1000 that is used to measure distance using UWB at 6.4Ghz, 3.95 Ghz...etc.

The IC block diagram looks like this:

The pins VDDPA1 and VDDPA2 on the left side of the block are used to power directly the Tx/Rx power amplifier and since the module is power hangery ( 150mA @ 3.6V) plus the noise that this amplifier generates.  3 decoupling capacitors are recommanded on each of these pins (12pF,330pF and 100nF) and they should be placed as close as possible to these pins as any decoupling capacitors.

I followed the recommanded values, placements, etc. The module has a continuous transmisison mode where the central frenquency is observed and tuned so I use this mode to check out if my device is working or not.

PCB layout of the decoupling capacitors:

First tests gave me the following RF ouput:

As you can see in the image above there is no central frequency and it's obviously very noisy.

So I put the 3 decoupling capacitors on top of each other:

To get them as close as possible to the pins and it did work for one board or 2 but not all.

Then I added a ferrite(BLM15AG601SN1D) on each pin just before the piled capacitors and like magic this fixed the problem in all boards.

The output signal when everything is clean and working looks like this:

Is there an explantation for this and how can I fix it?


texts:
I need some help to make sure I'm design it correct
I want to designing a pcb board for the pi-zero-W so it will connect to my system that works on 24-30V.
the pi-zero-W use around 350mA according to the datasheets , but they recommend power suplly of 1.2A in order to work without problems .
raspberrypi- power
So I found this circuit here
Simple 24V to 5V converter circuit
I have some questions:

what does D3 needed for ? just to prevent "noise" in the input voltage?
what does D4 needed for? in case of mailfunction on the 7805 , it will prevent the input voltage to go to the output? and "save" the 5V device (pi-zero-W)?
does the C1,C2 will do the work for my neededs? or I need bigger C?

in my case the distance is more than 3 inches
or it will be best to use this device ?
P7805-2000-S
and build a sutiable circuit around him also ?
this is what they recomand in the datasheet:

or can you suggest another device ?
Thanks ,


texts: How to determine the value of a decoupling capacitor across a Peltier device?

texts: I have a TEC device (Thermoelectric Cooling device/peltier device), and I have seen several datasheets recommend placing a bypass capacitor across the TEC device (i.e. parallel to the TEC, and in addition to the second order low pass filter on either side of the TEC).  Why is this needed? Does it act as an HPF to provide a low impedance path for ripple in order to increase efficiency of the TEC device? Also, how do I determine the value of this capacitor?


texts: Any good resource for MOSFET op-amp design?

texts: I've been trying to design a two-stage op-amp for a week, but I haven't been progressing much. Does anyone know good resources that teach you how to design an op-amp (transistor level), preferably with examples?


texts: How to identify the polyfuse used in this RS-485 module

texts: This is the popular RS-485 module found in the market, how can I identify the polyfuse/heat recovery fuse in it? Also its manufacturer or electrical ratings?


texts: Calculate the parallel value of resistors at base of common emitter amplifier

texts: I don't know if questions can be asked like this here but if they can I want this question. In an exam paper I saw a question to determine the parallel value of the R1 and R2 resistors in the image below but I am not sure how to do this. I tried using the bias equations for a common emitter amplifier but I have not been able to get the answer. I put the exact question in the image below so you can see how exactly it was asked. I am only asking for question c as I have done the first two(I may or not be correct). You do not necessarily need to solve it but if you at least know formula or method I could use it would be very helpful.


texts:
I am currently moving to a location for work that has a 110v electrical connection but no water connection. I was attempting to use an RV water pump in order to create a plumbing system for my sink but my pumps run on 12V DC current (I have them for use with a future build I'm working on and would rather not get AC pumps at this time if possible). The maximum rating for the pumps is 7.5a, which comes out to 90 watts.

I have come across the possibility of using a 12v battery but I'll only be in this location for a few months so having to purchase a battery as well as a charger that will stay inside seems like overkill for what I'm trying to do, especially because I will not have a use for that battery for any projects in the near future and would rather it not go to waste.

I've also thought about using a transformer to convert from 110V AC to 12V DC but was having trouble understanding the specifications and which one I should get. When looking at batteries, it seemed to me that hooking the pump directly to the battery would be fine as long as there was a fuse between the battery and the pump (either 7.5 or 10 amp?), but that doesn't seem to be the case when using the transformer.

Is this because the pump will just draw however many amps it needs from the battery while something like an LED controller is actively pushing power toward the machine, or am I totally off base here? Is using an LED controller a viable option for controlling the pump as long as I get a 90w controller, or is there a maximum controller wattage that would be safe?

Explanations or resources are also welcome, I'm definitely interested in deep-diving into this subject but currently have no idea what I don't know so I'm not sure where to start. Thanks!


texts:
I'm currently using an N-channel MOSFET (PSMN0R9-25YLC to drive a load as shown below:

The Arduino is providing a PWM signal with a voltage from 4.2V-2.5V depending on the charge of the battery and driving the gate at 490Hz. The voltage between the drain and the source also reflects the voltages above as well. I'm also pulling about 5 Amps at any given time.

After about 30 seconds of use the MOSFET is extremely hot to the touch and I can actually hear it switching the load. Looking at the specs of the MOSFET I believe it should be able to handle this no problem, so what could be wrong?


texts: ESD protection for pH measurement electrode input

texts:
I want to puild a pH meter, which uses a normal glass electrode. Such an electrode behaves as a pH dependend voltage source (<+-500mV) with very high internal resistance (10MOhm - 1GOhm, depending on the electrode). As a consequence, the voltage measurement needs to be performed with very low current. Further, I read that current flow can have a significant impact on the lifespan of these electrodes, so keeping it as low as possible is crucial.

I looked around and found a few promising amplifiers with input currents in the femtoampere range - e.g. the INA116, LMP7721, and LMC6001.

However, I'm wondering now how to protect these amplifiers against ESD, since the device will have to pass standard EMC tests for household appliances. Some of the amplifiers have limited protection built-in, but as far as I understand, this is not enough to protect against the tests that are performed on external device connectors. Adding diodes to the power rails or a TVS diode seems to be out of the question due to the substantial added leakage of even low-leakage types.

However, since the voltage source I want to measure has a very high resistance anyway, would the amplifier be adequately protected by a very high resistance (e.g. 10MOhm) series resistor? Or do I have to use a connector / electrode design which mechanically prevents direct contact?


texts: How to calculate the gain of the op amp in this circuit?

texts: This op amp operates as a difference amplifier and VR2 is for feedback, But I can't figure out how to calculate the gain of this circuit, Any ideas?


texts:
I was looking at RC in parallel (at the bottom of the page at the link) to understand the transfer function \$\frac{V_{out}}{I_{in}}  = \frac{R}{1+SRC}\$, in the case that the input is a constant current.

Given that the nodes of the input and output are shared, \$V_{out} = V_{in}\$, I came to the conclusion that the transfer function is equal to \$\frac{|V_{out}|}{|I_{in}|}  = \frac{|V_{in}|}{|I_{in}|}\$. Then, from Ohm's law, I decided that the transfer function is just equal to the absolute value of the total  impedance.

As far as I know, the total impedance is \$ \frac{1}{Z_{tot}} = \frac{1}{R} + i\omega C \$. Hence, \$Z_{tot} = \frac{R}{1+i\omega CR}  \$ and \$  |Z_{tot}| = \frac{R \sqrt{(1+ \omega^2 C^2 R^2)}}{1 + \omega^2 C^2 R^2}\$, instead of what they have on the wikipedia page, which is \$\frac{R}{1+\omega RC} \$.

Did I miss something?


texts:
I'm an enthusiastic amateur when it comes to electrical engineering, and have been looking at using the HT16K33 matrix driver. What confuses me is on page 6 of the datasheet where it references IOH1 the row source current and provides two typical values, one for VOH=VDD-2V and one for VOH=VDD-3V. Does anyone have any pointers on how to interpret those two different values? Do they relate to the forward voltage of the LED somehow?

I'm just keen not to blow up the first LEDs I connect to this IC. Thanks.


texts: I need to buy a servo motor and need high accuracy control. A sales engineer tells me that the servo motor has 1024 encoder, and its servo drive has interpolation technology which can make the resolution go to 1 million discrete steps (pulses) per turn. I Googled encoder interpolation, but not many websites talk about that. There are only some papers which I could not understand. Would anyone please give a brief explanation of what it is?


texts:
I'm reading from Hayt's Engineering Circuit Analysis and, in it, it says that

  Two other methods have a certain appeal because they can be used for any of the three types of networks considered. In the first, simply replace network \$B\$ with a voltage source \$v_s\$, define the current leaving its positive terminal as \$i\$, analyze network \$A\$ to obtain \$i\$, and put the equation in the form \$v_s =ai+b\$. Then, \$a=R_{th}\$ and \$b=v_{oc}\$.

I'm curious as to the logic here. Ultimately, I understand that this arises because any linear circuit (circuit with only linear circuit elements) must have a linear IV characteristic. I'm wondering if someone can step me through this specific statement though, and why it works.

I get that I can mechanically say that any linear circuit has, at its output nodes (if I can call it that) an IV characteristic of \$V=V_{oc}-R_{th}*I\$ and so this equation in Hayt is simply a restatement. I'm just wondering if someone can step me through the why of this fact. Apologies if this isn't clear, it's not even that clear in my head!


texts: Add Ethernet Switch chip to project based on PIC18F97J60

texts:
We developed an Ethernet-connected device that uses the Microchip PIC18F97J60 controller.  This particular PIC contains the PHY that allows us to simply connect the chip to Ethernet magnetics and then to the outside world.

An added complication is that this device is PoE powered.

Our customer now wants us to provide a pass-through port that allows multiple units to be daisy-chained without them (the customer) needing to install an Ethernet switch.

The data rate is quite slow - significantly-less than 10 Mbps.

Obviously, we now need to integrate an Ethernet switch within our device.  Been searching for simple options and one that bubbled to the top is the Micrel KSX8863 family.  This is a 3-port switch that has two PHY interfaces built-in as well as a Mii port.  The thought was that we might be able to connect that mii port directly to the PIC controller.

Unfortunately, what I know about Ethernet hardware would fit on the head of a very tiny pin.  Consider me to be a complete newbie in this regard.

However, I suspect that because our PIC controller already has the PHY built-in and does not appear to provide direct access to the mii port inside the PIC, a direct connection between the PIC's PHY and the KSZ chip's mii port is not possible.

I'm asking for clarification on this: do I need to be looking for either a different PIC controller (that does not include the PHY) or a different Ethernet Switch that has three PHY ports?

Or: is there some way that I can indeed directly connect the PIC18F97J60 to the mii port on the KSZ8863 Ethernet Switch?


texts: Minimum Clock Period from setup and hold time

texts:
I found several different answers to how setup and hold-time of Flip-Flops influence the minimum time between two rising clock edges.

tclock >= Propagation delay + tsetup + thold
tclock >= Propagation delay + tsetup
tclock >= Propagation delay + Max(tsetup, thold)

Which one of them is right?
From my understanding, it should be the first version, but I've found some answers that say that hold-time doesn't change the clock speed.


texts: How to use two encoder sensors with an Arduino Uno?

texts:
I have the following problem: I must use two encoders to measure the speed of two DC motors at the same time, using just one Arduino Uno. But the Arduino only possess two interrupt pins, and I need both of them for just one encoder. There's any workaround that I can use to get my two encoders running at the same time?

Any hints will be helpful!


texts: How to calculate capacitance analytically?

texts: Im developing a capacitive sensor of concentric cylindrical plates type.I know its dimensions(length & diameter). How i can calculate its capacitance without using any multi-meter or LCR-meter?


texts:
Welcome back on this subject :
I would like to simulate an inductance which varies linearly in function of the current which flows through it. Suppose :
$$L(t) = I_{L}(t)$$
In the simulation for simplicity I used a current source which has a slope of current equal to :
$$\frac{dI_{L}(t)}{dt} = 1$$
So :
$$U_{L}(t) = L(t)\frac{dI_{L}(t)}{dt} = L(t) = I_{L}(t)$$
Finally the expression of the Flux for L should be :
$$Flux(t) = x^2/2$$
Refere to this link for the expression of the flux : LTspice - Simulation of a variable inductance
So here is the simulation :

And here are the result :

What is weird to me is that I have to add a minus sign in the expression of the flux of the inductance. Why ?
Thank you very much.


texts: What makes an alternating-current electric motor rotate in a preferred direction?

texts: Intuitively, from a position of ignorance about the design of AC motors, I would have expected the direction of rotation to vary randomly with each start-up. This appears to be the case for motors driving the turntable in microwave ovens. However, for most applications, it is important that rotation is only in a designated direction. How is this achieved?


texts: Am I exceeding maximum ratings for the power rails of the opamp?

texts:
This  Dual Rail-to-Rail opamp :

I implemented a circuit with this dual rail-to-rail opamp on a breadboard and used a ±15V dual supply. The outputs saturate either to negative or positive rail which I'm not expecting as outputs. In simulation everything works fine but in real I checked the wirings ten times I couldn't find the problem.

My question is regarding the following absolute max ratings for the power rails:

Does 16V above mean that the max supply rail for the opamp is

Vcc<16 and |Vee|<16V?

As I mentioned I use +15V for Vcc and -15V for the Vee. Am I exceeding limits?


texts: On a printed circuit board, I see lots of tiny letters and numbers. Is there some kind of standard that dictates what letter indicates what type of component?


texts: Designing flyback converter - multiple isolated outputs

texts:
Can I treat 2 secondary coils with dual voltage output as one with double voltage for the purpose of calculations?

This seems to be OK for all formulas based on output power as technically the secondary IS a single coil with tap in the middle.

However for LT converters that use flyback in primary as feedback the formulas for feedback resistor(s) are based on Vout and turns ratio. How do I apply these?

UPDATE:

Allow me to clarify the question. Let's say I used all the right formulas and made myself a nice stable converter that puts out +50V at 100mA from isolated secondary coil and uses flyback voltage on primary as feedback.

Now, what happens if I tap the middle of secondary coil and convert this into dual voltage supply? Will I get a nice stable converter with dual +/-25V at 100mA outputs (minus drop on second diode, of course)? Without any changes in the feedback circuit or re-calculating the whole thing from scratch?

I am about 95% sure tapping output coil will not do anything to the functioning of converter, because the transferred power did not change. Except for that feedback resistor that according to LT8302 datasheet is calculated as:
Rfb = Rref * Nps * (Vout + Vf) / Vref
The Vout part of it is confusing, since now I don't have 50V, I have 2x25V.


texts: Using a DC battery to power 20 V AC, 1 A circuit

texts:
and thanks in advance for not blasting me for this question.

I am trying to find a way to power a 20V 1A Ac circuit. using 12vdc Li-on or LI-po cells. The device has a 120vac to 20v 1 amp transformer, So I was thinking I could use a dc-ac converter and just tie into the primary circuit of the transformer, but I am assuming that using a dc-ac inverter will have a lot of wasted energy in the conversion, so I think that the dc-low voltage ac would be an easier and longer running circuit.

Any thoughts? any Ideas?

thanks all

So i ordered a replacement 20v AC 1 A transformer, didnt realize but it has 2 primary leads and 3 secondary, so i powerd the primarys and check the leads to see which two had 20V AC. Soldered them into the board and fliped the switch and pop went the fuse. Tried the 11V circuit of the other leads and no fuse pop, but the amp does not produce any sound and it appears one of the transistors is getting very very hot. Any ideas?

Additionally i took the old transformer apart and found the parimary lead wires to the coil burnt but rhe secondary seems intack can i check the se ondary windjngs in anyway to make sure we specked the transformer properly?

Thanks for all the help everyone!


texts:
I'm using a powered device controller (PD is what they call a device that receives power over Ethernet), and its pins and way of connecting things is really weird. This part, LTC4265, takes in power over Ethernet (POE), negotiates how much power POE can provide to it, and then outputs that power.

What I'm really curious about is why its GND pin is called "input voltage positive rail" and its Vout is "output voltage negative rail". If you look at the data sheet at http://cds.linear.com/docs/Datasheet/4265fa.pdf, page 2 will show a typical application circuit. Also, pin definitions are on page 5. Anyway, it shows Vout outputting negative voltage. Essentially, the positive POE voltage is connected to GND pin, which is then connected to ground, and the negative POE voltage is connected to Vout. Why do they do things this way?

Thanks in advance for the help!