texts: Interface 24V signal from one device to 3.3V signal on another device

texts:
I have a device A that sends a signal through an optocoupler, this signal travels through a 7m cable and is used by another device B that has a SN74LVC1G17SingleSchmitt-TriggerBuffer powered by 3.3V, its maximum input voltage is 5.5V. I already have an interface circuit with 24V available on the device B side, so I'm thinking on putting the pull-up resistor on this side, together with a voltage divider and a security zener diode.

The circuit is:

And the result of the simulation:

Will this work in real life? Or do I need to also send the 24V through the cable and place the pull-up resistor on device A side, using a 3 wire cable?


texts: I don't understand how Sedra/Smith got \$R_{id} = 2R_1\$. Why doesn't any of the current go through the grounded \$R_2\$?


texts: Cable shielding through 4 pin GX12 connector, is it possible?

texts:
I'm in the process of making a custom USB cable. I have some GX12 4 pin connectors lying around so I figured I'd use those, but I'm not sure if they will work or if an additional 5th pin is needed.
One end of the cable will attach to a 5 pin JST connector, where one of the pins is attached to the shield of the cable that came with the device originally.
This is what the cable would look like: [USB Type A] --> [GX12 Male] --> [GX12 Female] --> [5 pin JST]
Would it be a bad idea to route the shielding through the GX12 connector housing or is this totally fine?


texts: Driving a 2.4v stepper with higher voltages?

texts:
I went on a drunken online shopping spree around a month ago and today I'm the proud owner of a NEMA17 stepper and a dual H bridge L298N based motor driver.

The motor is bipolar and rated for 2.4V. The driver is 5V - 35V though, somehow I was under the impression that this would be OK.

From what I can understand is that I can use PWM to control the max amps of the driver board and I found some online comments claiming that as long as I limit the average current to what the motor can handle, I can run it with as high voltage as I want. Is that correct?

Normally I'd just hook it up and try it but it did take a whole month to ship here so I don't wanna kill it on first test with just 5V or something.


texts: as we all know in order to work the JFET correctly, we need to have a Voltage across R_s which should be greater than the voltage across R_2. now I can make the voltage across R_s of my choice by using simply voltage divider rule, but how can i set the voltage across R_s of my choice? so that it would be larger? do I need to have the transconductance curve?


texts: Why modern oscilloscopes inputs are not fully differential (i.e. floating)?

texts:
This question is somewhat related to this other EE.SE question, and some hints are given there, but are not completely satisfactory for me.

I've understood that, besides safety considerations, the biggest obstacle to making a fully differential, i.e. floating, input stage is that it is far more difficult (hence costly) to design a wide band DC-coupled differential amplifier than to design a single-ended amp having the same bandwidth (or the same performance, in general).

The usual answer could be "OK, you need a differential input, so buy a (costly) differential probe like this and be done with that".

On the other hand, oscilloscopes are constantly dropping in price, with companies offering ever more functionalities and performance at lower prices (heck! In the low-end market the venerable Rigol DS1054Z has had 4 channels and lots of features for years and now is getting competition from Siglent and others Chinese manufacturers, too).

So, my question really involves answering to the following points: why embedding the differential probe circuitry in a scope is not deemed a right step to do to gain market share? Wouldn't it be beneficial to the average user to be able to use a scope input like a floating multimeter input? Surely the circuitry of the diff probe would become less expensive once embedded in a bigger device and mass market production dynamics kicks-in. Am I wrong in assuming this? Is there something in a differential probe circuitry inherently so difficult to design/build that makes it not quite amenable to cost reduction by volume production?

Note that I know that there are some rare models that have differential inputs, but my question is really about why, with the continual production cost reduction of oscilloscopes, this has not become the rule among manufacturers.


texts: Tiva C PWM pin connected to counter and XOR gate changes pulse width

texts:
I want a slow enough programmable clock for my circuit which I am generating using Tiva C PWM pins. Its a Tiva C 123GXL. The current frequency I have set is 200kHz and 50% high pulse (duty cycle).

When I connect the binary counter (A series of JK flip flops - IC 7473) everything works well, and clock division happens well and I can see 100kHz 50kHz etc. on the various flip flops.

But as soon as I connect the PWM to a XOR gate (IC 7486) also, the pulse width at the output of first flip flop keeps changing per cycle.

Any idea what is happening? Is two fanouts distorting the CLK input to the flip flop? In that case how do I use this generated clock in multiple places?

EDIT:

The Tiva C is being powered by a USB connected to my PC and the 7486 and 7473 have a DC supply of +5V-0V (yes, I have grounded both together)

EDIT2: My apologies, the problem is in output of the flip flop and not the PWM output. PWM output stays same.


texts: Why is amplitude-modulated radio broadcast (AM) still active?

texts:
In my country (Germany) we have frequency-modulated (FM) and amplitude-modulated (AM) radio broadcasts. However, the reality is that no one ever listens to the AM since you just don't hear anything (I don't need to explain to you the downsides of amplitude modulation). :)

So, I asked myself why the AM part is still active? Does amplitude modulation have any huge advantages over frequency modulation that it's worth keeping the hardware alive?


texts: Charging a low-voltage high-C capacitor. Efficiently

texts:
I'm currently upgrading my wind-up torch - upon opening it, I found the manufacturers had been quite sneaky in that the circuit is EITHER windup OR battery powered - worse, the batteries are non-rechargeable, so there's no way to store the windup energy.

My plan is to change that. I have 10F, 2.3V capacitor. It's perfect, except for the fact that the dynamo produces a voltage of ~4V.

The first option is of course a zener. I actually have a bunch of 2.2V which would protect the capacitor fine. The problem is, of course, half the energy is going to be wasted across the diode short. Is there any way I can regulate the voltage below 2.3V without reducing the efficiency so significantly?

EDIT
I've seen a few suggestions elsewhere that suggest putting a high-ohm resistor in series with the zener, presumably to minimize current through it (therefore maximising it into the capacitor). How effective would this be?


texts: How can I modify a USB cable with a voltage-divider to provide 3V?

texts:
I want to power a small device, that normally uses 4 AA/R6 batteries arranged in 2 pairs (so the device requires about 3V DC and drains probably 100mA or less).

Is it possible to cut an old USB cable, keeping the type-A connector to plug into an adapter or a computer, and solder the +5V and GND wires to a couple of components (to divide the voltage) then to the + and - of the battery compartment of the device?

The answer to this question suggests to avoid resistors to divide voltage. Is is still the case in the above example ? Is there another simple solution?


texts: Batteries in series discharging unevenly

texts:
Hi I am quite new to electronics, I had a project powered by 3xAA batteries in series (~4.5 V) with an LDO dropping it to 3.3 V.
It went flat quicker than expected but what was very surprising to me was that the voltage of the three batteries was so different ~0.5 V, ~0.6 V and ~1.5 V total ~2.6 V.
 Is it normal for a battery pack to discharge so unevenly?
Can someone explain why?

If it is relevant it sat most its time in the μA range with hourly very short spikes to ~150 mA.


texts: capacitor ripple current in buck converter

texts:
I'm designing a step-down buck converter and I'm a little bit worried about ripple current which flows through the output capacitors.

In my research on the internet I found that ripple current is given by Vrms_output/ESR. If Ι have 3.5A maximum output current and I want transient responce this mean, 0A to 3.5A = 3.5A ripple current. But this value (transient step), Ι think isn't my normal ripple current.

In my calculation corresponding to equation above if I want a ripple 10mV and select ceramic capacitor which gives me low ESR (< 5mΩ), this is equiavalent to 2A ripple current and I think that isn't normal!

If that is true, can a ceramic capacitor handle this magnitude of current?

Is this amount of current (ripple current, Irms) identical with Inductor ripple current of regulator?


texts:
A previous question on doppler shift velocity sensor make me ask this question. @Chris_stattron provided an insight but I was too curious to leave it at that comment hence the question.

Assume, I am trying to build a device that works at 40Khz and I am trying to understand doppler shift to measure the displacement of the object in concern. The movement of the object creates some doppler shift and everything static doesn't.

Now, my initial, software driven approach was to sample this at say 100Khz and look at the shift digitally but Chis suggested an analog cancellation approach using a receiving mixer. Essentially, what he said was that the local oscillator frequency is used for the receiving mixer and the signal, so that the return signal could easily be sampled with a simple ADC as opposed to expensive ADCs.

Could one of the masters could enlighten us about this approach and probably provide some pointers?


texts:
I am currently working on a project to create an amplifier which can use both physical and digital inputs to change the resistance of a potentiometer.

Is this possible without using sliders?

I know this sounds like a pretty odd question but I'm not sure how else I could do it as all the Pots I've found are either Digital or Analogue.

Thanks for your time.


texts: Why does a IRFZ44N turn fully on on my battery discharger while a IRFZ46N doesn't?

texts:
I've made a simple MCU controlled NiMH AA battery tester a while ago and it works just fine. The schematic below is its discharge circuit for one NiMH AA cell.

Q3 is a IRFZ44N MOSFET. Signals to ADC 1 and to ADC 2 are used by the MCU for measuring battery and MOSFET voltages, respectively, while the from MCU is a 5V signal that turns the MOSFET on and off to control the cell discharge through R8.

The tester discharges two cells independently (thus it has two independent instances of the above circuit).

To cut a long story short, today I replaced one of the IRFZ44N by a IRF46N and the respective discharger circuit stopped working. I inspected the IRFZ46N with a DMM and verified that it doesn't turn on with the 5V MCU signal: the 1.2V from the battery shows up across source and drain.

Then I inspected the original IRFZ44N on the other discharge circuit (on the same board) and it turns on fully. Its drain to source voltage is about 15mV when on and the rest of the battery voltage is across on R8 as intended.

What I find strange is that these MOSFETs are almost identical, the Z46 being just a little beefier than the Z44 (56A max current on the former versus 49A on the latter).

I know that I'm probably using the wrong MOSFETs. They both have 2 to 4V threshold voltage (Vgs-th), so they probably fully turn on at higher than 5V (maybe 9 or 10V?). I should have picked one with 1V Vgs-th, but I'm now curious: why does the Z44N turn fully on while the Z46N doesn't?


texts: is the pickit4 compatible with PICkit 44-Pin Demo Board (PIC18F45K20)

texts:
can I use the pickit4 with the PICkit 44-Pin Demo Board (PIC18F45K20), is it just a matter of aligning the pins with the arrow ?

thanks


texts: Terminal resistor function on JTAG SMT2 schematic

texts:
I'm studying the Digilent JTAG-SMT2 datasheet, in particular the schematic of Example 3 (Interfacing a Zynq-7000 while retaining the Xilinx JTAG Header).

I have a doubt about the function and value of the highlighted resistors. Can someone help me to understand it?


texts: Do I need an impedance controlled connector for RS422?

texts:
I've never implemented RS422 before (crazy right?). Since the impedance of the line is controlled to 120Ω do I need an impedance controlled connector for that? If anyone has implemented RS422 which connector did you use?

I was thinking I'd use a standard 0.1" connector or a molex connector of simmilar size, would this change the impedance of the line to prevent me from getting the full bandwidth of the RS422 line?

If I remember right on industrial equipment people use screw in terminal connectors.


texts: Any reason I cannot just switch a transformer from a 555 to generate high voltages?

texts: I had an idea to finally start using my nixie tubes and thought why not just switch a mosfet which switches a transformer to generate required high voltages for nixie tubes from a low voltage supply. When I googled all I found was these boost converters using inductors. Now is there a reason for these being used?


texts: Amplifying signal from the copper wires of two type T thermocouples

texts:
My apologies if this is too localized, but I am really in a bind.

I am attempting to amplify the voltage difference (so to be read on an arduino) between two thermocouple's copper wires, as pictured here:

thermocouples as sap flow http://www.cens.ucla.edu/pub/EnvironmentalSolutions/SFimages/install_schematic.png

The temperature difference between these two probes is very small, no more than 20 degrees C

I have had little success using both an INA122 and LT1920 on a breadboard to amplify this signal, following the thermocouple schematics in the datasheets.

Is there a simpler amplifier to use for this signal?

EDIT

For those who might have my problem in the future:

The easiest method of reading these small voltages on an Arduino for someone who might not be adept with analog circuitry is to use a separate ADC.

A great example of interfacing one with an arduino can be found here:
http://forums.adafruit.com/viewtopic.php?f=31&t=12269&p=58824


texts: Time domain reflectometry (TDR), pulse shape

texts:
Considering this coax cable open end reflection. What are the correct explanations for the flatter rise time, the rounding of the first reflection, and the much smaller what I assume to be secondary reflection?

EDIT:

Cable: ~100m 50ohm "m17/028-rg-58"

Scaling is 500ns/div.

Signal: 100kHz square wave.

EDIT 2:

Suggestion:

EDIT 3:


texts:
I would like to build a simple RC filter for a PWM input.
I have used this tool:
http://sim.okawa-denshi.jp/en/PWMtool.php

to get the math done :)

I have a 1000 hz pwm input, I can stand to a rather high settling time.
I end with a 2k resistor and 100u capacitor.

With this params (2k 100u at 1000hz) I got
0.006 ripple
0.460s settling time
that are fine for me, I think.

Now, back to question:
Is there ny difference for capacitor type with a simple 1 resistor + 1 capacitor or i can use any type of capacitor? (there is no polarity inversion or anything, so I can use electrolytic as well)

Does the type of capacitor affect the RC filter at all?
Is it the correct approach to try to have low resistor to have low impedance on the output and having a big capacitor instead of the opposite?


texts: Why do power companies never bother residential customers about power factors?

texts:
I recently bought a Kill-a-Watt meter to measure power consumption of my devices. This was just a fun project for me. I put this on my Mac-Mini to see power consumption during various usage states - idle, MATLAB bench mark, starting an application, screen-saver etc. and discovered that the power factor my my Mac-Mini was 0.2 when on standby and .80+ when up and running. However, while shutting down and before login the power factor was .45

I also measured this for my:

Raspberry pi with a 5v 3A power supply (PF=0.68)
Dell Laptop 90W charger (PF=.98)
2006 Compaq Charger (PF=.55)
CFL Table Lamps (PF=.52)
Tube CFL Lamps (PF=.55)
Power PC Late 2005 (PF=)
A 40W Audio Amplifier (PF=.66)
Vacuum cleaner (PF=.97)
Samsung phone charger (PF=.58).

From what I learned in my classes, 0.9+ is a good power factor and utility companies fine industries if they have power factors less than this. But most household equipment seem to have terrible power factors. Yet I have never heard of utility companies fining residential users? Why? Do they correct the power factors at the transformers at our residence? Or is residential usage too meager to bother about?


texts: Designing an audio amplifier, problems with bandpass filter

texts:
I am trying to build a Audio amplifier for a university project, I think that most of my circuit is done but I have an issue with my filter as my sine signal is not symmetrical after filtering to eliminate the offset, Instead of having an interval of aprox. +-5V I get an interval of +5 -> -7. I have used 3 opamps for amplifying the signal and a potentiometer at the first one so that I can increase my interval to 8V(maximum that I need to output).

As my input data I have:

Ai = 700µV
Bandpass freq = 32 -> 512 Hz
Ao = 5-8 V
Rl = 40 Ohm

Below is the circuit and simulation(transient of 10ms w/ step of 10u)
I've tried using Chebyshev filter or a Active Butterworth Filter using some online calculators but I am getting from the computations two resistors with negative values and that's not ok.

Bode plot:

I've tried using a active band pass filter but that also didn't work out; I can provide the project if needed.


texts: 100kHz PWM Motor driver PCB/cable consideations

texts:
I am designing a board to drive a DC micromotor which requires a 100kHz PWM signal. The board is mainly a digital design board, with very little analog signalling. I am planning on driving the motor with the STSPIN240 motor IC via an STM32 MCU. The supply voltage is 6V, I need a motor voltage of 4V98, i.e. drive the motor at 100kHz PWM at a duty cycle of 0.83 for the desired torque/speed characteristics at max load.

The signal tracking from the MCU to the motor IC will travel approximately 70mm. The motor IC PWM output goes to a daughter board via two male/female kk connectors + cable. It then goes from the bottom to the top of the board, ~30mm tracking, and comes off this daughter board via two male/female kk connectors + cable to the DC motor.

The board is a four-layer board. Signal, signal ground, power, signal. The steps I plan on taking for these signals:

MCU PWM signals will be given dedicated tracks, will not use vias and will go as direct as possible.
The ground plane in the PCB will provide the path for the the MCU PWM path.
Any time a PWM signal crosses a signal it will cross it perpendicularly.
The MCU output and input will be tracked directly to the connector (distance of <10mm)
The MCU PWM output cables will be twisted, length of 30mm.
The tracks on the daughter board will be tracked and via'd to the top layer for the second connector with <30mm of tracking.
The cable to the motor IC is a ribbon cable, should this made into another twisted pair?
When the signal goes to a connector the connector will be surrounded by via's to ground.

Do these layout considerations sound sufficient?


texts: Please explain this circuit (CNY70, Zener diode)

texts:
I am trying to build a new (Arduino based) controller for a machine that contains a circuit that uses a CNY70 to detect RPMs in a motor.  The circuit takes a 5V input and I accidentally gave it 24 volts and likely blew something out.  My controller is not just for this machine, I will be making them for others as well (this is not a "how do I repair" question). And to get the controller working, I need to understand this circuit.

Here is the circuit diagram:

simulate this circuit – Schematic created using CircuitLab

Again - I didn't create this circuit, just trying to understand it.

The correct behavior is that it will output 5v normally, and will output 0v when a reflector on the wheel that the motor turns passes over the CNY70.

I am an electronics newbie, and can't make sense of how this works.  If I measure VCC vs GND on my voltmeter, I read 1.6 volts when the voltage is connected to this circuit, and 5 volts when not.  So it's being fed 5V in VCC, but the circuit drops it to 1.6V.

I have actually wired up a different CNY70 circuit myself, but didn't have the Zener diode in there.  That's the part that I'm struggling with the most.  The writing on the diode says "3V9" and "BZX".

Here is a section of the logic PCB this connects to.  On this, pin 24 on the DB25 connector is VCC (yellow wire), 25 is signal (green), and 10 and 11 are GND.

Update: to answer the question 3 below:
When I measure the current between yellow and white (vcc and gnd), with this circuit disconnected, going through a 60 ohm resister as requested - I get 1 milliamp of current.  When I connect the resistor directly between VCC and GND, and measure the voltage, I get 1.379V.

Update - regarding R2.  When I created this schematic, I was going by the readings I got when examining the components on the blown circuit, which I did a couple of weeks ago.  If you look at the picture, I know the "blue thing" (R2) looks like a cap, but I had convinced myself it was a resistor that just looked like a cap based on reading resistance off of it (100k ohms).  Now after examining that component on the working machine, I'm not so sure.  What it says on it is: "XK 104".  So that would indicate it's a 100nF cap?  If I read the capacitance on it, I get 171nF.  For grins, I measured the resistance, and that's 13 mOhms.  So - sorry!!!!  It is a cap, isn't it.  I am so sorry for adding to the confusion here.  Please confirm my mistake, and does that clear things up?  Certainly not for me, I don't know what a cap would be doing in this circuit.

Update: Regarding the zener diode.  If I diode test the one in the working machine, I get .7 volts, and 1.056V Zener voltage (putting the positive lead of my voltmeter on the cathode side).  Shouldn't it be 3.9v?

Dave


texts: In an RLC circuit,what criteria could be used to decide whether the system is overdamped or underdamped? Could we compare the maximum energy stored during one cycle to the energy dissipated during one cycle?


texts: Calculating drain current with series N-channel MOSFETs

texts:
When two N-channel MOSFETS are connected in series, with common gate connections, then how can I analyze this circuit to determine Id through these MOSFETS, as a function of Vgs and Vds?

simulate this circuit – Schematic created using CircuitLab


texts:
I want to make an auto transmission circuit using a magnetic pickup sensor with output 0-3.5 AC Volts.

My device has 3 gears (1, 2, 3) and the one that's activated depends on sensors output. For example, if the output is 1.5V, then the first relay is activated. If voltage is increased, the circuit should deactivate the first relay and activate the second one and so on.

How do I do that? Any ideas?


texts: More equations than unkowns in amplifier circuit

texts:
I am trying to find the Magnitude Response of the gain of this amplifier circuit.

The gain formula is: $$ H(\omega) =  \frac{\tilde{V_{out}}}{\tilde{V_{in}}}$$

My amplifier circuit is as follows:

I am trying to find the magnitude response:
$$ |H(\omega)| =  \frac{|\tilde{V_{out}}|}{|\tilde{V_{in}}|}$$

The end goal: to get both V_out and V_in as functions of ω (with the resistor and capacitor values treated as constants). I will then use a tool (i.e. MATLAB, Maple, or other graphing software) to plot the magnitude response as a function of ω, and I will keep adjusting the values for the resistors and capacitors until the plot shows that the cutoff frequencies at both sides of the pass band are right where I want them.

How I am trying to get the equation:  Before working with the absolute value, I am trying to get the equation V_out/V_in as one fraction with the only variable being ω and the constants being the impedances of the resistors and capacitors (ZR1, ZR2, ZR3, ZC1, ZC2).

The problem: I have way more equations than unknowns! The circuit is way over-defined. I have tried to use substitution to solve the problem, and was taken in circles. I tried to plug the equations into a matrix, but the calculator returned an error. How can I solve this over-defined system of equations? For now, please treat the impedances ZR1, ZR2, ZR3, ZC1, and ZC2 as constants (i.e. don't plug in the capacitor formula ZC=1/jωC or the resistor formula ZR=R just yet, I'd like to get an expression with just Z's first to keep things simple).

What I'm stuck trying to get: An expression V_out/V_in = [expression with only Z's]. This means that Vm, I1, I2, I3, and I4 have all been substituted out.

Equations:
$$\tilde{V_{out}} - 0V = (\tilde{I_{1}})(Z_{R2})$$
$$\tilde{I_{1}} + \tilde{I_{2}} - \tilde{I_{3}} - \tilde{I_{4}} = 0$$
$$\tilde{V_{out}} - \tilde{V_{m}} = (\tilde{I_{2}})(Z_{C2})$$
$$\tilde{V_{m}} - \tilde{V_{in}} = (\tilde{I_{3}})(Z_{R1})$$
$$\tilde{V_{m}} = (\tilde{I_{4}})(Z_{R3})$$
$$0V - \tilde{V_{m}} = (\tilde{I_{1}})(Z_{C1})$$

To reiterate: I want to find ( V_out / V_in ) = [expression with only Z's]. All Vm, I1, I2, I3, and I4 have been substituted out. Then I can finally plug in the capacitor and resistor impedance equations and get an expression with R (resistance) and C (capacitance) constants as a function of ω. But this hasn't been working (6 equations, only 5 unknowns: Vm, I1, I2, I3, and I4). V_out and V_in are not unknowns since they will be shown as a fraction on the left hand side of the equation.

Thanks in advance.


texts: Designing a High-Voltage Bidirectional Square Wave

texts:
I want to create a signal to send through an electrode that my senior design group is designing. The signal is very well-defined because our electrode is going to be compatible with a very specific machine that serves as a waveform generator that we don't have access to. The electrode needs to deliver 800 mA regardless of the impedance of the system, which will be on the order of 220 Ohm, which will bring the voltage up to around 180 V. Unfortunately, our waveform generators only reach 10 V. Here is the description of waveform (bidirectional square wave):

Here are some of my ideas:

1) Transform a 120V sine wave from the wall to 180V. Then use an Op-amp to quantize it to a square wave. Then use a digital timer controlled switch to clip the duty cycle.

2) Create a bidirectional square wave on LabVIEW at the max voltage (10V), then use an analog boost converter to boost the signal to 180V. I understand that the boost converter is used for DC signals, so perhaps after stepping up the signal, we could send it through a capacitor and voltage divider to convert it to AC

I haven't taken any power electronics or digital logic classes, so let me know if I'm going about this the correct way. Also, I would love an exact solution instead a general one like "make a boost converter" because I don't know the details of devices like that :)


texts:
I'm building a little circuit to handle two 5m led strips with an ESP32. ESP32 is a d-duino-32 OLED clone you can find in ebay/aliexpress sites.

Also bought a 5v 20a power supply. One path powers the esp32 with a 1000uf capacitor and a 1ohm/5.1v zener diode. The other path goes directly to both strips with a 2000uf in the middle.

The first time I turn on, I see on OLED display info I programmed. Leds are off because didn't programmed the code yet. If I turn off and on again, I can measure the correct voltage but ESP32 does not start.

If I turn off again, wait some minutes and turn on again, works again.

If I remove the led strips, works always.

It is supposed the 20A power supply should be enough to handle the 300 leds x 60mA each = 18A plus ESP's 500mA although all leds are off initially.

What can cause this to fail?

EDIT:

Circuit:
Photo:


texts:
So we assume to have proper bias currents flowing in both of the two transistors. What is claimed by books is that a capacitive coupling will not change the bias parameters.
But, we know that a capacitor will charge and hence gain voltage across it. Now this capacitor voltage is applied back to the transistor, in our case the voltage will be applied to the collector of the first and the base of the second transistor and hence will change the bias parameters!

What is wrong in my reasoning?
Thank you in advance.


texts: Can a transistor be used to switch two loads with different voltages?

texts:
For example I have a microcontroller running at 3.3v.

I want one GPIO pin to switch a 12v relay and a 5v load. Do I need to use multiple transistors? Or would something like this work?

simulate this circuit – Schematic created using CircuitLab


texts: Why this stabilisation issue occurs for this waveform?

texts:
I'm using this simple wave folding schematic:

This would be best described with two short videos. Both videos have triangle input into wave folder, and I am changing the amplitude with trimpot.
First video is how it looks straight out of buffer without any load attached on output.
The second video is what happens when I attach small audio speakers with built in amplifier.
This module is additional output to my audio oscillator, none of the other regular wave shapes (triangle/pulse/saw/sine) behave this way. I'm sure I could clean it up with higher stabilising capacitor value 33p-75p, but I would like to understand why this is issue for this particular wave-shape.
ADD due comments:
The transistor stage at the left looks at first idiotic because it distorts the triangle wave. But that distortion  is the actual clou of the whole circuit. I's needed to make the triangle wave richer sounding due the generated harmonics. The question was why the system isn't stable if a speaker is connected to the output? The circuit starts to oscillate with high frequency as the video 2 shows.


texts: Controling steppermotor with raspberry pi

texts:
For a school project, I need to control a stepper motor with a raspberry pi or Arduino. I was thinking about a NEMA 17 or NEMA 23 motor. I study mechanical engineering so I don't have much experience with programming Arduino or a raspberry pi.
The motor has to move a carriage 450mm linearly with a variable speed between 50 and 250mm/s. I will use a leadscrew with a lead of 25mm/rev. torque is not a big problem. I calculated the max motor speed to be 600rpm for 250mm/s.

my questions are:

what motor should I use?
can I program the speed to be adjustable?
is this even possible?
how should I start to program this?
Is 600rpm posible with a nema 23 or 17? on google i find anywere from 400 to 1500rpm max
I hope some of you can help me with some of the questions. if you think you have something you can help me with, please respond.


texts: How do I adjust the brightness of a 3 V bulb?

texts:
I need to adjust the brightness of a bulb for my GCSE Product Design project and I can't find an easy way of doing that.

I've researched and found potentiometers and resistors but it just seems to cut power to the bulb as soon as I adjust it less than full.

All resistors and potentiometers have been in the voltage and current range by checking the description of the components i was purchasing and compare them to the description of the bulbs that i am using. I'm using a simple series circuit and need the options to be very compact as in needs to fit in a 1cm x 1cm x 3cm space.


texts: Driving DC motors with MOSFETs and a microcontroller?

texts:
I'm developing a nano quadcopter using an Atmega328 microcontroller, powered at 3.3V, and very small brushed DC motors. The average current used by these motors is about 800mA @ 3.7V.

Initially, to drive them, I used an L293D motor driver but this component was quite inefficient. The current measured when the motors ran at max power was about 500mA and so the thrust was much lower then it should be.

Now, to solve this problem, I would replace that motor driver with 4 logic level MOSFETs.
After a long search, I find this one (2SK4033).

Do you know if it should work?
Do I have to use it in conjunction with a diode? If the answer is "yes", what about this one (MBR360RLG)?

I chose these components also because I can buy them from the same online store.


texts: Why does my Atmega328 clock seem to be off by a factor of 2?

texts:
I have an Atmega328 chip I am trying to debug. I have a sketch that blinks an LED and echoes back things received over the RX/TX pins. I am using the "Import Arduino Sketch" feature in Atmel Studio 7. I want to use the internal 8 MHz clock.

The timer seems to be too slow by a factor of 2. I tell the LED to blink every second, but it takes two seconds. When I send text over the serial port I receive back gibberish, which is probably due to the baud rate not being the 9600 I want it to be.

I looked at the memory fuse to verify that I am using the internal clock. I also tried setting the clock prescaler to 1 in the sketch code.

Here is the section of the data sheet related to the clock frequency:
http://ww1.microchip.com/downloads/en/DeviceDoc/ATmega48A-PA-88A-PA-168A-PA-328-P-DS-DS40002061A.pdf

My fuse settings seem to be OK, I disabled the 8x divisor and specified to use the 8MHz internal clock:

The clock prescaler information is on page 47, essentially it says I need to make the most significant bit a 1 to allow changes to the rest of the bits, then I change the other bits to 0 to set a prescale factor of 1. If I try setting it to a factor of 2 the time delay is made worse by a factor of 2 and has a total of 4 seconds delay when the code wants 1 second.

void setup() {
CLKPR = (1 << CLKPCE); // enable a change to CLKPR
CLKPR = 0; // set the prescale factor to 1
pinMode(greenLED, OUTPUT);
Serial.begin(9600);
analogWrite(greenLED, 15);
delay(1000);
analogWrite(greenLED, 0);
}

void loop() {
    analogWrite(blueLED, 15);
    delay(1000);
    analogWrite(blueLED, 0);
    delay(1000);
    String text;
    if (Serial.available()) {
    text = Serial.readString();
    Serial.println("Echo: " + text);
    }
delay(30);
}

What other settings could be affecting the internal clock?


texts: Why is a low resolution ADC (e.g. 4-bits) a bad idea for a Zero-IF GPS/GNSS RF front-end?

texts:
This is another follow-up from this fascinating question (the other follow-up question is here) for the design of an RF front-end for a GPS/GNSS SDR receiver.
In a comment to the accepted answer, it was noted that:

Zero IF is a bad idea with a 4-bit A/D. Remember you get a rounding error for every sample and for zero IF, this error will also have low frequency. This is what I call beating.

My (clearly incomplete) understanding was that in the absence of interference, GPS only required low-resolution ADCs in order to be effective - I seem to recall the degradation in C/N0 for a 3-bit receiver being in the order of 0.1-0.2dB.
On this basis, why would the MAX2769 and MAX2771 (shown below) provide I- and Q-mixers, but only 2-bit ADCs on the I and Q channels?  Is this configuration only intended to be run with an external ADC? If so, what resolution would be required?
Otherwise, it would seem that the sensible solution would be to choose some IF frequency, and take advantage of the 3-bit I-only ADC resolution.


texts: How to wire headphone switch correctly in audio amp (LM4875) circuit?

texts:
I'm working on a circuit for a small audio device and I'm a bit confused about the headphone jack wiring, I hope someone can shed me some light. I'm using the LM4875 because I have a speaker and a headphone jack in the circuit, so when the headphone is connected the speaker output will stop, switching to the headphone output with the correct amplification.

I want to use a standard DIP stereo jack for the output, but I'm not sure how to wire it.

Below I'm attaching an image of the example in the LM4875 datasheet, with added arrows for indicating pins:

And below an image of my stereo jack's symbol:

I understand that P1 is connected to ground (sleeve), but in relation to P2 and P3 I'm not sure. I'm not familiar with the schematics for audio jacks. I imagine that P2 that is carrying the signal could be the ring and P3 the tip, but if I connect it like this wouldn't the output go to a single channel, to the right earpiece only? This same signal has to output to the two channels of the headphones.

I appreciate any help, thanks.


texts:
I'm trying to explain some LED-lighting phenomena, that we (me and my family) have observed, while changing light bulbs into LEDs. I've had some courses in semiconductor physics, and I've had a basic course in electronics, but I still have some difficulties in explaining these phenomena.

In our living room, there are 4 light sources, each of which consists of 4 light bulbs. I assume all of those (16 in total) light bulbs are in parallel, because when one of them is broken, all the others (15 bulbs), still shine. We can turn those light bulbs on with a slider. So it is possible to let them shine on f.i. half the intensity.

We now tried to replace those bulbs with LEDs. The first thing we noticed (when replacing one bulb), is that the LEDs intensity can't be gradually changed by the slider. The LED is shining on full intensity or isn't shining at all. Furthermore there were no problems in changing 15 of those bulbs into LEDs, but when we changed the 16th bulb, for some reason all LEDs start to flicker. Furthermore if we just remove the last LED, there is no light at all. Finally if we replace the last LED again by the light bulb, we noticed that all LEDs are now shining (at full intensity), while the light bulb (which isn't broken) does only glow (and refuses to shine).

I hope someone can help us to explain these phenomena:

1) The intensity of the LEDs can't be gradually changed by the slider.

2) When changing all light bulbs into LEDs, all LEDs start to flicker. Nevertheless they work fine when changing only 15 or less bulbs.

3) When just removing the 16th bulb, there is no light at all.

4) When replacing last LED by a bulb, all LEDs are shining, while the bulb doesn't.

I have some guesses at how this results could be explained (for instance I think the LEDs flicker, because the offset voltage dropped to lower voltages, the LED will then get only in some part of the voltage period enough current to shine). But I have problems in seeing the bigger picture. I think my main problem is that I can't guess the electric circuit, which is the main reason I post this question here. Any attempt to solve these questions will be greatly appreciated!


texts:
I wanted to use a tiny Linux computer to read data from I²C bus. I knew there was Picotux, and I was thingking about buying one.

But the website is down, so I guess there's no Picotux anymore. :(

Since Picotux is gone, are there alternatives around, that house a Linux computer in a tiny package, such as Picotux?

I need a tiny package, it should run on batteries and consume little power, and have a I²C or USB bus available. Bonus points if it has WLAN (which Picotux had as an option).

It should be able to run a webserver (a tiny one, not a behemoth as Apache) and RRDtool if possible.

Picotux was available at the now defunct website: http://www.picotux.com/


texts: Why do we need an (adaptive) equalizer when we have a matched filter at the receiver?

texts: When both can perform the same task of reducing the effects of ISI, why use both and not just one at the receiver end?


texts:
How do you tell the difference between speakers and microphones?

I pulled the following two components out of an old cell phone
and cannot tell them apart.

Each have two metal contacts on the back.


texts: Will there be any issues connecting 2 loads to a single DC power supply?

texts:
I am working a project that involves 2 loads, a battery and an electronic DC load. The battery is connected to a charger which allows a power path from the battery to the DC load when the battery is discharging. The charger is also connected to a power supply which provides power to recharge the battery.
When the battery is recharging, power is not directed to the DC load from the charger. I wish to create an additional path from the power supply directly to the DC load so that during charging, the DC load will still receive power from the power supply.
Some parameters:

DC power supply of maximum 30V and 100W
DC load drawing constant power <100W
Input voltage to the charger of 8.4V or higher
LIPO 2S battery, 930mAh

Will there be any issues if I create the additional split by creating a Y split from the cable connected to the power supply?


texts: What is the origin of on and off power switch symbol?

texts:
I know I (line) and O (circle) symbols are used to specify a switch that turn on and off the power supply.

My question is What is its origin?

Because I thought that it represent a power line that can be plugged (on symbol) and a closed line (and thus without power supply) but seen that in Wikipedia said that it can come from 1 and 0 used in binary to represent on and off bits, I don't know what is the correct answer.

Note: In Wikipedia, it didn't have verified sources, so I need other source.


texts: Why is Cp here not part of the equation?


texts: Accelerometer gyrometer for radxa board - i2c configurable addresses vs spi

texts:
I am looking for an accelerometer/gyrometer that has configurable address.
It should run on a radxa rock board using i2c,
or
some spi solution.
I am using that board (PRO)
http://radxa.com/Rock/specification
History:
I've tried that sensor for the last three days http://www.pololu.com/product/2468/resources until I noticed that the radxa already uses most of it's i2c addresses from all of the 4 busses. It's the first time I am working on a "non software only" project. Already got some experience but not many. That's why I was looking for the error in my code/checked if the sensor was broken etc.
In the end I noticed that the the radxa already uses the address that the sensor has. (It uses most of the address)
Outprint from i2cdetect (i2cdetect -y BUS_NUMBER)

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10: 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
20: 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
30: -- -- -- -- -- -- -- -- 38 39 3a 3b 3c 3d 3e 3f
40: 40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: 60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f
70: 70 71 72 73 74 75 76 77

That's why I am looking for a sensors that have completely configurable address (not just high and low for one bit) or some device that I can put in front of sensors to change the addresses.

If I want to evaluate the data in 1kHz I might should go spi anyway?
Cheers :)


texts: Transfer Function [ the transfer function of the feedback stage? (Optical sensor and the lm2917) ]

texts:
I have to make a control system that maintains a constant speed of a small car prototype using a DC Gearmotor regardless of external disturbances such as slopes (small slopes).

For the development of this project, the control system will consist of a PID controller that affects the speed of a DC motor. I am not able to use a microcontroller.

I will measure the real RPM of the motor by using an optical sensor which is going to give me pulses, and then I'll use the lm2917 that will transform pulses to a certain voltage value going back to the sum point (operational amplifier adder circuit). And this is how I will do the feedback of the system.

My question is: What is the transfer function of the feedback stage? (Optical sensor and the lm2917)

Thank you.


texts: SMPS regulator blows up, could it be a layout issue?

texts:
I have a curious problem which I have been trying to solve for a few days now and I just can not understand what is going on.

I have designed a SMPS which takes 24V input and outputs 5V (which is then further down regulated to 3V3, and 1V8 for circuitry). The IC I am using is a LT3680, and the schematic is below this post.

I have this circuit on a 4 layer PCB with proper grounding and heat dissipation features and  it works like a treat - no problem whatsoever. I also have this exact same circuit on a homemade single layer PCB with very poor grounding and crap layout. This is a PCB I put together in a few hours just to test some things out.

I apply 24V through a relay to the SMPS circuit on the crappy homemade PCB and the regulator IC IMMEDIATELY pops with a loud bang and it blows a hole in its package. I apply 24V through the same relay, but jump it to the well designed PCB with the regulator, and then jump the 5V output back to the crappy PCB with other (3V3, 1V8) linear regulators. I switch the relay to apply power and everything works well. I tried it hundreds of times without issues. I desolder the LT3680 IC from the well designed PCB, and solder to the crappy PCB (or take a new IC from the box), apply power, and it blows immediately. (I desoldered the known-to-be working ICs just to eliminate the possibility of a bad batch of ICs).

Basically, LT3680 blows up every time on the homemade PCB, and works under the same conditions on the well designed PCB. I have compared the schematics of the boards and there are NO differences in the SMPS circuit (I have designed both of them). The only difference that I can see is PCB layout (very crappy compared to very well designed as suggested by the datasheet).

The question is could poor layout (in particular poor grounding), cause such SMPS IC failure (and why)? Or should I keep investigating, although I am desperate at this point as there seem to be no differences between the boards and the conditions I use them except in layout.

Thanks!

EDIT2: Added both sheets of the schematic
Sheet Two:

Sheet One:

EDIT: Added layouts of the two boards

Crappy Board Layout (U201 is the SMPS IC):

Good Board Layout (note this is a 4 layer board with GND plane):


texts: Why do phase-shift oscillators appear to use high pass filters rather than low pass?

texts: I noticed that a lot of designs of phase-shift oscillators use a sequence of high-pass filters to get the phase-shift. Is there any reason why one couldn't use three low pass filters instead? I realize that the maximum phase-shift for a single high-pass filter is +90 and for a low-pass filter -90. Does this difference influence the design?


texts: How can USB extension cords affect of USB charging?

texts:
I want to use USB extension cords to extend the USB power cords for various devices (specifically, an iPad and Android phones).  When adding a USB extension cord to a closed system where the manufacturer power cord/adapter connect a device to a 120v outlet, how might charging behavior change and what are the effecting factors?  (The "charging behavior" I am most interested in is charging speed and long-term effects on the device battery.)

Sidenote:
I thought this question might be too "end-user" for this site.  But I think it adheres to the site guidelines, as it concerns "modifying [consumer] electronics for other uses" and the answer would concern their design.


texts: Shut off a low-current circuit beneath a certain voltage

texts:
I have a circuit that requires only 2mA of current. I need to turn it off when my LiPo drops below 3.5V. The LiPo is not at risk of overcharging, because the charging circuit is separate from this circuit.

What's the best way to turn off this half of the circuit when the supply voltage drops below 3.5V? Can I just use any old diode?


texts: Will this LM317 Circuit work for my application?

texts:
I am attempting to design a circuit to charge lithium 18650 batteries is a 3S configuration. I understand that a BMS is recommended, but I am not concerned with that. I have built this LM317 circuit (pictured below) and seem to be having some trouble.

When I connect a multi-meter to the outputs with no load attached, I get a full range from 1.27 V up to 18.06 V when I adjust the potentiometer, just as I had intended. But the problems start when I connect a small load to it (12 V, 0.15 A computer fan). Once the fan is attached, I can't get more than 11.5 V on the multimeter. I can adjust the fan speed just fine from 1.27 V to 11.5 V, but once it's at 11.5 V, continuing to rotate the potentiometer does not increase speed or raise voltage level.

So overall I am just concerned that once I connect my battery as a load, it will not charge it to a full 12.6 V as needed.

So my questions are:

Is there a reason I cannot adjust fan speed beyond 11.5 V?
Is there a flaw in my design?
If I set it to 12.6 V while unloaded, and then attach the battery pack, will it fully charge it?
Is there an easy modification I could make to my design to make it work properly?

Here is what I have already tried in order to fix the issues I'm having:

Originally I had R2 at 220 ohms, but increasing to 840 ohms gave about 0.25 V more on the fan test.
I have tried removing D1 to avoid voltage drop, but that only increased Vout by 0.1 V

Note: I have no formal education with electronics nor am I very experienced. I am simply an at hobbyist who finds this interesting and fun and am trying to learn more.


texts: Does a LiPo balancer board need switching for external power supply

texts:
I have 4 18650 LiPo batteries in a battery holder that I am connecting a to a charging balancer. According to the description it comes with charge protection and does proper balancing for the 4 cells. Sadly it does not come with a datasheet or even a model number, all I know is that it is typically used for power drill chargers. Since all the pins are properly labelled the wiring is not really a problem. See below an image of the module.

I am going to use an external power supply (generator driven by a small combustion engine) that supplies 17ish volts to the module. The pins in return are connected to the poles of the batteries inside the holder.
As far as I understood how those modules are working they are basically capable of "turning off" the charging of a cell, if it is full before the others are full and "wasting" that energy by generating heat in a resistor. Does this mean if all batteries are full it just starts "burning" power through the resistors for all cells? Apart from longevity and heat, are there reasons why I would need to switch off the power to the module when the batteries are full? Also how would I typically notice, that the batteries are full? I am assuming the 16.8V on the module always supplies the 16.8V independent of the charge of the batteries? Typically my batteries are only used shortly to power the system before the ignition is activated, then some power is drawn to engage the starter DC motor, after that the external power takes over. So usually the external power supply will run much longer while the batteries are charged than charging them.
In addition to that I am also trying to use the external power supply to power my outside system while charging the batteries and use the batteries when the engine is not running. Do I need to create a system like in this question: Li-po Charging circuit question (switching between battery and power supply) or can I "siphon" directly from the 0V/16.8V connections on the module?
edit: I think my second question can be achieved by 2 diodes, I can get significantly higher voltage out of the generator, so using one diode directly from the generator to the buck converter and one diode from the 0/16.8V outputs of the LiPo module should work. When the generator is offline the 0/16.8V are outputting from the battery, when the generator is running the power is taken from the generator diode. Since I am aiming for 5V the voltage drop from the diode should be irrelevant.


texts: What happens if an interrupt callback execution is interrupted by the same interrupt?

texts:
I have a microsecond timer (generates interruption every microsecond) for which I implemented a "HAL_TIM_PeriodElapsedCallback" function. What occurs if the execution of the callback function takes longer than a microsecond?

PS: I'm using an STM32F030F4Px mcu with st-link v2 debugger.


texts: MSP430 Stack pointer and frame pointer behavior

texts:
While trying to analyze a simple Assembly file generated through the msp430-gcc, I stumbled upon a set of instructions that I don't understand dealing with the frame pointer and the MSP430's stack pointer.

C Program:

#include "msp430g2553.h"

int main()
{
  int i;

  for(i = 0; i < 3; i++);

}

Assembly minus directives:

main:
        mov     r1, r4 ;Stores address of stack pointer in r4(frame pointer)
        add     #2, r4 ; ?
        sub     #2, r1 ; subtract 2 to allocate int i
        mov     #0, -4(r4) ; assign 0 to i
        jmp     .L2 ; start loop
.L3:
        add     #1, -4(r4) ; Adds one to int i
.L2:
        cmp     #3, -4(r4) ; Compare to #3
        jl      .L3 ; jump to .L3 if true
        add     #2, r1 ; deallocate int i
.Lfe1:
        .size   main,.Lfe1-main

I tried commenting the code to trace the program's execution, but I don't understand the line add #2, r4. What exactly is happening here, and why is int i being referenced at -4(r4)?


texts:
I am building 3V3/5V source for my breadboard. The actual voltage will be selectable by the switch. I would like indication, which voltage is actually selected by lighting green LED for 5V and yellow for 3V3. Treshold for 2N7002 is like 2V, so my idea is like that:

simulate this circuit – Schematic created using CircuitLab

But there is problem, that both LED would be lit on 5V, can I somehow simply cut off the yellow (3V3) LED when the green one (5V) gets lit?

Is this schema valid (maby after some resistor adjust)?

Thank beforehands

EDIT: it is just small part of testing environment, meant to anable by jumper 5V or 3V3 output on VCC (or none, if jumper missing). There will be more such device on one PCB and there will be jumper array to configure each, so I would like indicate, what is actually on which VCCxx.

Mode of operation: set jumpers, switch power on, do something, switch power off, reconfigure all the thing, set jumpers ...

It is also possible, that the jumper will be off (SW1 not connected here) and the VCC would be else not connected, or externally driven to 3V3 or 5V. Those internal sources would be on anyway (and would provide power).

So desired result is:

VCC around 5V (say 4.5-5.5) = green led on, yellow off
VCC around 3V3 (say 3.0-3.5) = green led of, yellow on
VCC unconnected or around 0V
(say 0-0.5) = both leds off


texts: Reducing AC/DC adapter (SMPS) output voltage

texts:
I have  a AC/DC adapter P-1650-22 (used to power a notebook) laying around.
I would like to use it for other purposes, i.e. as a constant voltage source for LEDs.
The problem is, that the output voltage is set to 19 V, though I would like it to operate at 11 V - 12 V. The power rating would not exceed the actual rating of 65 W. It would be even less (45 W).
Currently I have no schematic, but I opened up the device already to take some measurements.
Simultaneously I searched the web and have already seen similar products and also some schematics and block diagrams. Please excuse the bad quality of the schematics, but I couldn't find a better one (relevant information is visible though).

From the information I have gathered so far I assume this is a flyback converter.
Would you say that it is worth to tweak some components in order to reduce the output voltage of this device?
For sure I would need to:

Adjust feedback resistive divider for the shunt voltage reference
What else to think of?

What about the need of adjusting the compensation loop (if there is one)?

Circuitry around the LNK6777E (the IC connected to the second winding)

Concerning point 3, I am not really sure what the LNK6777E exactly does and where to tweak (please see the block diagram):

What is the purpose of the "FB" pin? I am aware, that it serves for the regulation of the second winding. So the LNK regulates its own supply voltage. But how is the feedback coming via the optocoupler incorporated via pin "CP"?
So my question is:
What should I consider which I have not already written about?
1st edit:
@Bimpelrekkie, why dou you not recommend changing anything? There are safe ways of working on circuitry connected to mains, i.e. isolation transformer, etc. BTW, reading your answer again I think you missunderstood me. My question about the "FB" pin relates to LNK6777. I am well aware this is the feedback niput but I wanted to know, relating to the block schematic I have posted above, how exactly the regulation works, etc.


texts:
I am performing a simulation of an eletronic circuit using Pspice and OrCAD. I want to know how the circuit will behave for long periods of time (in this case, 500s). After the simulation this weird plot appears.

I don't know if it is because of the settings of the simulation which are the following ones:

If someone knows what is wrong I would be very greatful.


texts: scope - how bandwidth of scope affects what signals you can see

texts: I was wondering if a scope that only has 20mhz bandwidth and the signal you're probing is say 120mhz, can you you still use the same scope to see if a clock is present? Or do you have buy another scope?


texts:
I am looking for an official reference for "gate equivalence".  I have 2 conflicting values for gate equivalence for a flip-flop from 2 different books, and no GE for a mux.  My question: Is there a standard table for this anywhere?  In a paper I'm reviewing, I'm trying to figure out how a FPGA implementation of an algorithm has a lower "gate equivalence" than a custom CMOS version.

As gate equivalence is based on a NAND.  Can I just take the number of transistors, divide by 4 and get a gate equivalence number?  This whole metric seems totally meaningless to me as I cannot find how this comparison is officially made.  Google failed me so I figured I'd try to crowd source the answer.


texts: What is the meaning of a battery's "cycle life?"

texts:
I started to read about batteries, I am interested in lithium batteries, I found a description regarding the stability and capacity/weight, but I read some unclear descriptions like "cycle."

What does "cycle life" mean?
What are the charge/discharge numbers?
What if the battery is discharged to 60% and then charged to 80%, Does this count as a cycle?


texts:
I can't seem to get the op265AB infrared LED from OPTEK to light up. I'm using my phone's camera to look for light. This works with Radio Shack part 276-0142 but the OP265AB just isn't lighting up.

I've tried with 100 and 220 ohm resistors, and with 3.5V, 5V and 9V power supplies. Normal LEDs work at the same spot, as does the Radio Shack part.

The docs say that it is 850nm wavelength.

My hope is to use this as part of a model train detector.

What could I be doing wrong?


texts: Dynamic energy and dynamic power in microprocessors

texts:
In a class I'm learning about dynamic energy and dynamic power and the notes seem to be incomplete.

• Dynamic energy
  Transistor switch from 0 -> 1 or 1 -> 0
 0.5x Capacitive load x Voltage2
• Dynamic power
 0.5x Capacitive load x Voltage2 x Switching Frequency

I've seen simillar formulas used in other places, for example I've seen other formulas that don't have 0.5 but require the value of a constant. Is 0.5 the average or something? Also what is switching frequency in the context of computer hardware? Is that the speed the CPU operates at (e.g. 2.5GHz)?


texts: What linear voltage regulator alternatives are there for use in IOT applications?

texts:
I had been having problems auto-uploading reliably to a ESP board that I have designed. It would sometime upload the program and sometimes it wouldn't. Seemingly completely at random.
The issue was solved when someone advised that the issue might be a power problem.  That led me to question the HT7333 I used in the circuit, because apparently it had horrible transient response which was the reason why the auto-upload wouldn't work well.

That small fall on Vout is actually a drop from 3.64V down to 2.76V. Which isnt that so small what so ever.
The solution was to install 100uF capacitors at its input and output. The same problem exists also with some DOIT Devkit ESP32s, which shows me that the AMS1117 that they use should also have the same issue. The gentleman that pointed this out recommended that I may use AP2112 instead.
What other alternatives are there to the well known HT and AMS1117 for 3.3V and 5V voltage levels respectively? I would very much appriciate it if you would share your experiences.


texts: Can anyone tell me what an 0R-Jumper Varient C is?

texts: I found this component in a schematic I am looking at and have searched the internet far and wide to find out what it is, alas to no avail. If anyone could explain this component and why one would use it that would be awesome. Here is the link to it: https://www.diymodules.org/eagle-show-object?type=std&file=jump-0r-smd.lbr&package=C0R-JMP


texts:
I would like to use a QFN chip but soldering it is difficult as the required tools are unavailable. After searching online, I found that there are sockets available that provide pins for those chips, such as this one .

However I saw on the title that they are called programmable adapters. My question now is, what are the main use of these sockets and can they be used to connect the QFN chip to a breadboard and interface with its pins?


texts:
I'm looking into using a set of IN-12B Nixie tubes in a clock design I've been working on.

If I tie my anode to the 170V striking voltage and use ~16kOhm to limit the digit current to 2.5mA then we're fine. However, I don't know how I am supposed to achieve the 0.3mA current limit for the comma cathode.

I'd like to think that I can just add another resistor in series with my cathode in order to meet the current spec but I've been having trouble finding any examples of people using the IN-12B without ignoring the comma cathode entirely.

What is the right way to go about this?


texts: How to determine whether two ICs can be clocked from the same source

texts:
When there are two integrated circuits clocked on the same frequency it should be possible clock both ICs from a single oscillator. My understanding is that the first chip is connected to the external circuitry (crystal or resonator) as usually via two pins - first is output from oscillator (inverting amplifier) that drives the crystal/resonator and second is input to the oscillator (feedback). The second chip has the oscillator output bypassed and only the input is connected to the crystal or resonator.

How can I verify that both ICs can be clocked reliably like this? What problems might arise?

Thank you,


texts: Is there back EMF in an induction motor?

texts: I noticed that in deriving the equivalent circuit for an induction motor in the rotor component, that a "variable" resistance was introduced. This really confused me as I didn't understand how power was equivalent when they divided everything by slip in the derivation. Is there a back EMF being induced that forms the $$\frac{(1-s)}{s}R$$ portion of the circuit or something along those lines. Is this like an "induced resistance" or a voltage drop depending on slip that would form the component being converted to mechanical power?


texts: Reasons of why the signs of the capacitor of the diagram is correct?

texts:
I've written the following diagram.

The text book says the following.
As the voltage \$V\$ is given between the nodes, it is assumed that the charges \$Q_1,Q_2,Q_3,Q_4,Q_5\$ are charged at each applying capacitor.
My dought came from the diagram.
I can intuitively get the signs of the \$C_1,C_2,C_3,C_4\$ however currently I can't get why the signs of the \$5\$th capacitor is correct of the diagram.
In other expression, why the upper sign  of \$C5\$ is minus and the other is plus, is incorrect.
Can anyone tell me some hint(s) or the website(s) which describe(s) it? so that I can get it in my own.


texts:
I've posted this question to TI E2E forum here. I'm cross-posting it here in hopes of casting a broader net.

I'm writing an Arduino library for the LMP91000 (github), and I'm apparently having some trouble getting the writes to succeed. I know there's a lock bit that has to be cleared before writing certain registers, but I can't seem to get it to change the value. Here is a logic trace of a write followed by read to the LOCK register (0x01).

It looks to me like I'm compliant with the datasheet to me, but the write is not actually taking hold. I've checked an the clock is 100kHz as well. The LMP91000, I think, is acknowledging when it's expected to. My controller is, I think, doing the right things with start, stop, ack/nack for it's part.

Furthermore, when I just go in and read all the registers, I get the following results, decoded for convenience (logic trace attached to e2e forum post):

STATUS: 0x01
  ready
LOCK: 0x01
  Registers 0x10, 0x11 in read only mode (default)
TIACN: 0x03
  RLoad selection = 100 Ohm (default)
  TIA feedback resistance selection = External resistance (default)
REFCN: 0x20
  Reference voltage source selection = Internal (default)
  Internal zero selection = 50% of the source reference (default)
  Selection of the Bias polarity = Negative (VWE - VRE) < 0V (default)
  BIAS selection = 0% of the source reference (default)
MODECN: 0xFF
  Shorting FET feature = Enabled
  Mode of Operation selection = Temperature measurement (TIA ON)

I'm struggling to see what I'm doing wrong, and would appreciate some help figuring it out. Thanks!

Update #1

I should give more context. I have three LMP91000 chips (logically) on one I2C bus. The chips themselves have MENB hardwired to GND. I've put an I2C repeater with an enable (PCA9515ADP) on each to isolate them from each other. I know I could have used MENB for this, but I have another I2C ADC chip with each sensor so I wanted a single point to enable/disable the entire address domain.

I've got two hardware setups now and writes seem to be working on one of the setups, and the other (original) setup is acting as described above. So this appears to be some kind of unit specific issue related to one of my boards at the moment.


texts: Full Spectrum LED(400nm~840nm) vs Grow Light LED (RED+BLUE)

texts:
I'm planning to buy lights for my planted aquarium tank. After a small research I found that regular lights are not suited for growing plants.
Beacuse they need BLUE for Leaf Growth and RED for Stem Elongation.
In stores I found 2 variants of this lights. One was actually a combination of both the LED's and other was simply called Full Spectrum LED.
Can any one please suggest me which one is good for my 6 gallon tank?

I got
Eleocharis Paravula (Japanese)
Ludwigia sp Mini Red
Elatine Triandra

For Ref:
 Full Spectrum LED  : http://www.ebay.in/itm/10-Pcs-3w-Full-Spectrum-LED-Taiwan-Epistar-Indoor-Plant-Grow-Light-400nm-840nm-/172421286248?hash=item28251c0968:g:AMwAAOSwz2lXCiSw
 Grow Light LED         : http://www.ebay.in/itm/LED-Full-Spectrum-IR-UV-Grow-Light-14W-28-SMD-LEDs-E27-Plant-Flower-Grow-Bulb-/252917131903?hash=item3ae3092a7f:g:TG4AAOSwjqVZCYfK


texts:
I have here an interesting piece of hardware, a CD74HC125E that someone gave me. This chip (can I call this an IC ?) is able to set its outputs to high voltage, low voltage or high impedance.

Do I need to put a resistance in series with the chip if I set an output to either high or low voltage, or is there any current-limiting function in it?

If not, how much current can it take before it burns? I could not figure out where to look in the datasheet.

The datasheet can be found at http://pdf1.alldatasheet.com/datasheet-pdf/view/27005/TI/CD74HC125E.html


texts:
I'm using the Arduino Encoder library to keep track of my motor's encoder counts. I need to calculate the motor's speed so it can be compared to a target speed and subjected to PID.

I've thought of one approach:

1) Calculate counts per timestep - Let's say we have a timestep of 100ms and we desire a speed of 50cm/sec. Determine speed in timestep units, 50/10.

To calculate speed motor is traveling at, simply calculate how many counts since last timestep, which will give speed in timestep units, which can be directly compared with desired speed;

speed = counts - prevCounts;
prevCounts = counts;

The advantage I can see with this approach is that it doesn't require us perform division (i.e. speed = (counts - prevCounts) / 0.1 ) in each timestep.

Is this a sensible? Are there any flaws in my method?


texts:
I recently purchased a new soldering station (Aoyue 936). This is my first relatively good quality soldering tool, so I want to ensure I maintain it properly.

My question relates to tinning the tip once I am done using it. The manual which came with my product says:

"When you are not using your iron, make sure you leave a large lump of solder on the tip. This maintains the tinning of the tip, and the tip will last much longer."

However, after substantial reading around the internet, I can't find any such suggestion for tip maintenance. So my question is, when I'm done soldering and am putting it away for storage, do I simply melt a big glob of solder on the tip and put it away, or melt solder on the tip, wipe it off on the sponge, and then store it.

Note: When I try the latter method, the tip initially looks shiny, but after a minute, it gains a slight copper colored tint.


texts: How to model a Schottky diode based on datasheet?

texts:
I have a question about how to model a non-linear a Schottky diode based on available datasheet in ADS. Should I just assign Rs and Cj values from datasheet?

http://datasheet.octopart.com/DMK2790-G4D-Skyworks-Solutions-datasheet-23706700.pdf

The diode will be used as a switch. Could anyone help? Thanks


texts: Classic multivibrator circuit and LTSpice, why is there reverse voltage on base even with diode?

texts:
I had fun today learning the basics of LTSpice using a variation of the "classic multivibrator" (*). I have also built a working version with real components. There is a significant difference between LTSpice and what I see on my cheapo (10Mhz) scope, and that is the voltages on the NPN transistor "protection" diode. As you can see, I put a diode in line with the base to prevent negative current flowing from the significant Vcb the circuit develops. As expected, when I view the NPN bases voltage with my scope, the diode clamps the negative voltage at about -0.6v. But LTSpice shows the full negative Vcb, shifted by 0.6V, at both the anode (node 004) and cathode (node 010). LTSpice shows the diode current at zero, though, except for the (expected?) spike when the voltage goes from forward to backward.
My question is, then: I can see why LTSpice is showing the negative voltages on both sides of the diode. If there is no current flow, is the negative base current still potentially harmful even if the current is near zero, except for leakage and the spike that occurs before the diode switches off?
I am inclined to believe the results on my scope, showing the reverse voltage limited to 0.6V, presumably because all of the high pass filtering from the various components' inductances and capacitances, yes?
Significant gotchas, maybe: In my real version, the PNP transistor of each Sziklai pair is a germanium PNP power transistor, Hfe probably on the order of 30. No germanium models exist in LTSpice; I've used the "generic" PNP model. (**) Also, the output of the circuit are two 400ma, 6V incandescent lamps, which I have simulated by 10 ohm resistors.

(*) I'm baffled why this circuit is so widely used as an example of how to generate badly formed square waves. It really belongs in a Horowitz and Hill "Bad Circuits" section :-)
(**) My Dad brought home some Ge power transistor samples from his job at TI when I was a wee lad in the early 60s. I thought I would finally do something interesting with them after all these years.


texts: BJT Transistors: understanding Vbe measured (model "DCIL TIP 112 N2")

texts:
On my protoboard have a BJT CDIL transistor TIP 112 N2, working in the way that on base I have a Vbb = 5V and Rb = 450  Ohms. On Collector, Vcc  24V and Ic = 0.13A. A gearmotor is working properly on that way, (covered by a diode and a capacitor).
So I tried to measure voltages on BJT just for verifying everything is ok, and then simply do some other calculations. If I assume Vbe is approx 0.7 V, then I should expect Ib have an approx value of (5-0.7)V/450 Ohms = 9.5 mA... However when using the multimeter, a current of 7.8 mA is measured.
The fact is when I measure voltage between base and emitter I notice that Vbe = 1450 mV (!!!)... I was expecting a value near 700 mV as I had learnt, but there's no way to let it down (tried replacing the gearmotor for a cooler, increasing Rb, etc). That value of Vbe reamains pretty constant. Is it ok?? Why is Vbe >> 0.7V?
PD: other measures Vce = 0.71 V and Vcb = -0.75.
Thanks a lot (not an electronic here, please be patient :)


texts: Types of Battery Charging - Trickle Charging

texts:
I have gone through various materials online to understand the concept of trickle charging and other types of charging. I have a few queries which were not clarified.

From what I understand, trickle charging helps the battery to reach 100% by providing very low current upon reaching 90-95% of the battery level. So, it always provides some amount of current despite the charge level of the battery, right?

My query :

Is trickle charging property of the charger that I plug into the wall socket and connect to the phone? Or is the property of the phone to support trickle charging? Is the charger an intelligent device to provide trickle charging? From what I observed, chargers only have power components and circuitry to deliver the required amps at the mentioned voltage, say 5V.
Can someone also help me to understand what is Float charging? From what I understand from the Wikipedia section on float charging, it charges to the required battery voltage continuously at the mentioned voltage and the current and then stops upon reaching 100%. After the battery drops to some threshold (which is set by the phone or the charger ? please tell this ), say 95%, the charger wakes up and provides charge to increase the battery to 100%? Am I right?
How is fast charging different from the above two types of charging? Are there any other types of charging apart from this?

Please help me understand my queries.


texts: What micro controllers or microprocessors are capable of high resolution video but are not BGA?

texts:
I am looking for any chip that I can use to display video at a high resolution (at least 720p). There is no need for

I know of the Blackfin processors, but they are all BGA.
The PIC24FJ256DA210 is capable of only 640 x 480 sadly.

I am guessing that FPGA's are the last option that I have in this situation, but am more curious about anything that would require me to do less work than having to make the entire video system on an FPGA.


texts: Unable to compile STM32F4 code sample with Eclipse

texts:
I'm trying to compile a simple STM32F4 sample using Eclipse with the GNU ARM Eclipse plugin from http://gnuarmeclipse.livius.net/blog/.

I'm getting the following errors:

and the structure is as follows:

and the source code from main.c

#include "main.h"

/**
 * Main application entry point.
 */
int main() {
    init();

    do {
        loop();
    } while(1);
}

/**
 * Application initialization.
 */
void init() {
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);
    GPIO_InitTypeDef gpio;
    GPIO_StructInit(&gpio);
    gpio.GPIO_Mode = GPIO_Mode_OUT;
    gpio.GPIO_Pin = LEDS;
    GPIO_Init(GPIOD, &gpio);

    GPIO_SetBits(GPIOD, LEDS);
}

/**
 * Application loop.
 */
void loop() {
    static uint32_t counter = 0;
    ++counter;
    GPIO_ResetBits(GPIOD, LEDS);
    GPIO_SetBits(GPIOD, LED[counter % 4]);
    delay(250);
}

/**
 * Delay by given ms
 *
 * @param ms
 */
void delay(uint32_t ms) {
    ms *= 3360;
    while(ms--) {
        __NOP();
    }
}

Any ideas what these errors mean?


texts: PCA9685 (12-bit PWM I2C LED controller) and Arduino

texts:
I tried to get a PCA9685 to work at the moment I am using an Arduino with this library to test it but I can't get it to work. I have the Arduino Uno rv3 I wired the scl of the Arduino with the scl of the pca the same goes for the sda all the address pins are on the ground same goes for the ext clk and the oe.

Can someone see what I did wrong?

As requested more information:
I connected the leds directly to the PCA9685 as shown in figure 15 from page 28 of the datasheet

At the moment the led always burns but with the example code from the library it should blink.

edit 2/8/2014
here is how i connected the arduino with the pca9685

I used the example program from the library but the leds don't change in brightness.
(Just to make it clear i have 16 leds connected to the ports and not just one)

I hope its more clear now what I want.
edit(2) 2/8/2014
Be course I have the uno r3 I use the 'special' sda and scl pins that are near the connector.
(when i connect a led to these pins it blinks softly so there is a signal on the pins)


texts: Confusing equivalent AC circuit (analysis)?

texts:
Context

I'm doing some analysis on a dummy circuit. I've been explicitly told that the current generated by the source is a sinusoid:
$$I_{0} = I_{p} cos(\omega t + \pi/2)$$.
It also have been shown an equivalent form with some impedances. The problem is I cannot understand how they arrive at this equivalent. I explain why after the diagram

Circuit:

Analysis

The problem starts when I try to figure out the overall impedance of the circuit so that I can find the overall voltage across the circuit. I compute the impedance ($Z_{0}$) for a capacitor in parallel with a series of components. So in other words:

$$Z_{total} = Z_{C} || (Z_{R1} + Z_{L} + Z_{R2})$$

But before I solve this, I realize that the equivalent circuit I'm given has two impedance 'nodes' in series. How can this be? I don't understand how (supposing that the voltage $U$ marked in purple remains the same in both images) this is possible.

Ultimately I am confused about the circuit and cannot make sense of the equivalent circuit.


texts: Reverse Polarity Protection, External Circuit

texts:
I'm trying to figure the best way to protect the external circuit from a short if a user mistakenly connects the sensor in the wrong polarity. I use a green object in the diagram to represent the second circuit.

The simplest polarity protection is a single diode on the positive side, but i'm considering what would happen if they connect the positive side to the ground on my circuit? Both circuits will share common ground. I'm not sure if what I have below would protect against anything or even work. Then again i'd have to contend with diode voltage drop (maybe use schottkey? i dunno). What do you think?


texts:
I checked a piece of library code intended for encryption/decryption with AES, CBC,  256 Bit Key length.

To check the results I consulted the following website:
https://www.devglan.com/online-tools/aes-encryption-decryption

Since AES uses a block size of 16 Bytes, it is clear to me that input data longer than 16 Bytes will be padded to 32 Byte and also produce an output of length 32 Bytes.

What I don´t understand (and what is also the problem in my code under test) is that for an input length of 16 Bytes (exactly one block length), it seems that the output (encrypted text) is already padded to 32 Bytes.

I read that padding in this case is more of a convention and not a necessity of the algorithm. Is that correct? If so:

-> What is the benefit of use padding if the input is perfectly in the right size

-> How do I decrypt a 16 Byte encrypted text?


texts:
I am currently "investigating" FPGAs, what they can do, how they do it etc.

In more than one place (for example here) I have seen projects that implement a simple microcontroller with FPGA.

So my question:
I would like to know, what is the purpose of doing such implementations? Why use a microcontroller implemented in FPGA instead of having a micro on board? What are benefits? And perhaps also what are downsides?


texts: Can I use a transistor to turn on a 10/12v supply with a USB cable, like this?

texts: simulate this circuit – Schematic created using CircuitLab


texts: Why are my components unconnected in the middle of the breadboard?

texts:
I have this breadboard:

And I need my Integrated Circuit to be connected exactly like this (Don't pay any attention to the wires. Let's focus on the IC in the middle of the breadboard itself):

However, when I connected the power, it didn't work. Then I found out that the IC was pushed up from the breadboard. I tried to push it down and it worked, but when I released my fingers, it stopped working again. That was like the legs of the IC was not long enough to be buried deeply into the breadboard. I had problems with not only the IC but the pushbutton as well.

Did anybody face that kind of problem like me? Please show me the trick to bury the components deeper in the middle of the breadboard. Thank you.


texts: What lamps are out there that don't flicker and give off warm light (like incandescent)?

texts:
In the past few years several countries stopped producing 100W incandescent lamps, and in a few years they may disappear to be succeeded by fluorescent lamps. I really don't like the flicker and the color most common fluorescent lamps produce.

Are there any other kinds of lamps that do not flicker and produce about the same warm light as incandescent lamps (that might not be banned from production in the nearest future)?


texts: Getting the transfer function of a parallel RC circuit. Am I allowed to simplify/remove the component I am trying to solve for?

texts:
simulate this circuit – Schematic created using CircuitLab
Say we have that simple parallel rc circuit and we were tasked to get the transfer function of V_c(s)/V_i(s). We were told that it is not advised to remove/simplify the component of what you are trying to solve. But the I cannot seem to find out what to do without combining the capacitor and resistor to get the transfer function. This is my attempt with the solution:


texts:
I have designed a schmitt trigger circuit using an op-amp where the output switches from 0 - 5V based off an input hysteresis from 2.2 to 2.8V.

My circuit correctly switches at the correct voltages however the output magnitude is 3.6V instead of 5V.
What would be the best way to resolve this, I have tried using a non-inverting amplifier after the output stage, but still get around the same output voltage of 3.6V.


texts:
I am working on a project to make a circuit for machine vision project. Basically, the circuit needs to take a picture (320×240), search for some features, and then give a command based on the features.

For example, if no red arrow is found, then a "clear" command will send. If a red arrow is found, then the circuit needs to send out the direction of the arrow.

My question is: if I want to finish each cycle (from taking a picture to direction outputting) in 2 seconds, would it be possible to use a PIC microcontroller? Which PIC controller and camera would allow me to do that?

NOTE: my boss needs an ACAP (as cheap as possible) solution.


texts: What function does the Inductor and Resistor serve?

texts: The image attached is the circuit of a SMPS with primary side regulation. I am not sure about the purpose of inductor L1 and resistor R5 in this circuit. I figured it has something to do with noise reduction. Is it to reduce ripple caused by the full bridge rectifier or reduce the switching noise from the MOSFET? Would appreciate a concrete answer with frequencies being attenuated.


texts: Is Microsemi Libero supposed to have many arithmetic cores inside its catalogue?

texts:
Here is a screenshot of the Libero catalogue tab in my machine.

I am using Libero 11.9. There are only 3 design blocks which frankly are trivial. There is no divider, no floating point maths blocks, no square root or complex number maths blocks. Do such IP cores exist at all for the Microsemi devices? I am using IGLOO2. What am I missing?


texts: Electric wiring color codes: BROWN, BLUE and BLACK

texts:
31.01.2018 16:40 start /
Thank you all for the answers, because this is not a standard wiring plug, i need assistance wiing the wifi adapter in the middle of cable which connect the energy master expert lcd display to the energy master expert plug.
 Is this correct?

WIFI ADAPTER LIVE IN = Energy master expert PLUG BROWN live wire

WIFI ADAPTER LIVE OUT = Energy master expert LCD DISPLAY BROWN live wire

WIFI ADAPTER NEUTRAL IN = Energy master expert PLUG BLUE neutral wire

WIFI ADAPTER NEUTRAL OUT = Energy master expert LCD DISPLAY BLUE neutral wire

WIFI ADAPTER EARTH IN = Energy master expert PLUG BLACK wire

WIFI ADAPTER EARTH OUT = Energy master expert LCD DISPLAY BLACK  wire

\ end 31.01.2018 16:40

31.01.2018 16:36 start / Update from customer service:
**The Ground Line is bridged in the connector
The meter does not require a Ground Line in the cable.
Blue is the Null Line  and black and brown are the Live Line

Should you have further questions, please feel free to contact us via email.

Yours sincerely

ELV Elektronik AG

Technical customer service department** \ end 31.01.2018 16:36

Which colors are Ground Line, Null Line and Live Line?
The standard says the Ground line is always green-yellow.
None of these wires is green-yellow. Thanks.

update
If black is Earth, then why the on off switch button is using the black wire?

Because the cable is too short , less than 2 meters, i want to extend it. I also want to join the cables with a wifi adapter SONOFF® POW 16A 3500W DIY WIFI Wireless Long Distance APP Remote Control Switch Socket Power Monitor Current Tester For Smart Home 80-160MHz AC 90-250V Support 2G/3G/4G Network.
 That is why i need to know exactly which colors are Live, Null and Earth.


texts:
I'm trying to include an SD card slot in one of my designs. The whole SD format seems confused at best, and I can't seem to find a definitive answer to what I need to wire up.

Apparently the easiest way to do it is with MMC (SPI) on my microcontroller. There are already prebuilt libraries for this use.

In hardware, I'm planning on using a socket from Yamaichi Electronics , FPS009-3202-BL, along with a TXB0104 level shifter to handle 5 V to 3.3 V signal conversion. The microcontroller is an ATtiny4313, which has MOSI on pin 17, MISO on pin 18, and SCK on pin 19. I'm not sure what to do with SS or even if I've wired it correctly. Here's a screenshot of what I have so far:

How can I proceed from here?


texts: To what is this capacitor connected? (OP-amp)

texts: I'm a little bit confused. Is the capacitor in parallel with Vs+?


texts: The purpose of I and Q channels in RF communication

texts:
I have searched both dsp and electronics stack exchange but I remain confused about the reasons why information is sent in I/Q channels.

For a while, I thought that the main reason for sending I/Q channels was so that you can send 2 independent channels on the same bandwidth and since they were orthogonal to each other you could demodulate them independently as well. Effectively you could double B/W, if one channel was multiplied by cos (for example) and the other by sine. On the receive side you you again mix with carriers that 90 degrees offset and retrieve the information you want. I understood this as QAM. Am I correct? I.e. is QAM two independent channels that mixed with carriers of different phase or are the channels related?

From what I read, I/Q are also used for image rejection. Basically as explained here:
Can somebody explain what IQ (quadrature) means in terms of SDR?. Furthermore, from what I have read I/Q modulation is important in SSB/SC but not exactly sure why.

So is I/Q done for both or specifically for one case? Or are there multiple uses for it and you pick it based on application?


texts: Do servo motor specifications take into account the gear ratio inside?

texts:
I know this question may not belong here but I assume this is most likely where the most well informed people can help me.

I am looking at buying a servo motor for a an application that must be able to lift 4-5 lb at a rotational speed of approximately 1rpm. The servo motor listed here http://www.robotshop.com/ca/en/hitec-hs755mg-servo.html states a stalling torque of 200 oz-in. Is this torque rating at the horn of the servo motor or the torque rating of the actual motor before any gear reduction is done?

Is this motor sufficiently strong for my application?


texts: Logic design to circuit -- how is it generally done?

texts: So I've designed this CPU with purely logical components (basic logic gates), now how would I go about converting it into a circuit? I know that logical gates can be implemented using transistors, but it seems pretty cumbersome to do the equivalent conversion for every gate (there are a couple hundred). In addition to this, adding the required resistors and other passive components due to physical constraints seems a bit cumbersome. Is there a secret to how this is generally done?


texts: Connecting a decoupling capacitor straight to the ground plane

texts:
I had always thought that if an IC is grounded to the ground plane then connecting a decoupling capacitor to VDD on one side and straight to ground plane on other side as shown below is acceptable:

However as I understand this poorly spelled guide from the depths of the internet tells me I was wrong all along and the correct way is to run a trace from the IC ground pin to the capacitor and THEN connect to the ground plane:

I believe I was using d) which is somehow wrong. Can anyone more experienced shed some light on this topic, which one of these is the preferred method? Thank you.


texts: Are there cases where a transistor acts bilateral?

texts:
Some places mention an ideal transistor is unilateral. But is that the case in reality?

For example for a BJT we say that the base current or Vbe controls the output port such as emitter current or Vce not the otherway around. I guess this is what they call unilateral.

But in a common emitter amplifier if we change the load between Vcc and the collector wouldnt the base current change? Isnt that behaviour bilateral?

And is Early Effect is an example of bilateral behaviour?


texts: Why there are two communication standards, Bluetooth and WIFI? Why not used just one, when they both works in the same 2.4 GHz band?


texts: Connecting copper and aluminium wires though a board

texts: My g430 headphones recently broke and I narrowed it down to the wire that connects the left speaker to the right. The video I was watching recommends using a spare RCA cable to replace the wire, my only problem is that every wire in the headphones is aluminum but the RCA I took apart is copper. I understand that connecting them directly would be stupid but the connection would be going through the little PCB (image) they have in the headphones. Would this still be safe and durable? I don't know much if anything about electronics I just have a soldering iron and youtube.


texts: How to shield microcontroller from electromagnetic interference

texts:
I'm working with high voltage circuit (2.1 kV for defibrillator capacitor testing) and I'm controlling power supply with arduino, reading required information from laptop using serial interface. Most of the time circuit works fine, but once in a while during capacitor discharge after the test, circuit triggers by itself without operator pressing the button. Also sometimes serial monitor fails. I figured it does so because Linux stops seeing USB port for short period of time USB itself reappears under different name. I assume it happens because, during discharge, electromagnetic field induces voltage in my circuit, so my question is how to shield my circuit against such influence or maybe I'm totally wrong about the reason.

Point of this test is to measure charge time of capacitor. Charge time defined as the time from power On to the time when current supplied by power supply approaches 0.Connecting enable1 and enable2 using relay enables power supply, current Read out provides information when power supply outputs approx. zero Amps . During the discharge, discharge resistor is manually connected to DUT.


texts: Is there a way to make an integrated circuit at home (without using expensive parts?)

texts:
I've seen lots of people like Jerri Ellesworth build integrated circuits at home from silicon wafers, but she used a massive furnace to do it, and not all of us have a huge 2000 degree furnace at our homes.

I want to build my own integrated circuit; building a transistor or logic gate from a disc of silicon is one of my dreams. Is there any way to build an integrated circuit at home without purchasing thousands of dollars of material?


texts:
I've made a turn signal system for my bicycle that uses power generated from the wheel. The wheel puts out 0-9v and is irregular depending on the speed. My lights take 3v, originally from two 1.5v batteries. I used a step-down board from ebay and the system works well, but when I'm stopped at a red-light it is unpowered. I would like to store a few seconds of power, a buffer, and I can think of two ways to do it.

I could add a super capacitor after the step down (or would before be better?) the step down. Or I could add a rechargeable battery.

Which solution is easier to set up? Which solution is better suited to my application?


texts: How do I smooth current dips on a USB charger?

texts:
I've got a USB charger that I want to use to charge a phone.  For about 35 seconds it outputs enough current for the phone to detect it and start charging, then for an instant (no equipment to read the length of time, let's call it a quarter second) the current drops to 0, then picks right back up.  This is verified via a small USB flashlight that exhibits the same behavior.

This is a problem because the phone detects it as the plug being removed and reinserted which jolts the screen back on, resulting in a loss of charge.

Is there a relative simple and small footprint way to smooth this out so that I get steady current?  My fuzzy memory of hanging out with EE people in college makes me think the answer is capacitors, but I have no idea how to do this or how large of a capacitor I need.


texts: Design of a 1-bit adder-subtractor with additional carry/borrow input

texts:
I have to design a 1-bit binary adder/subtractor unit that can both add or subtract two input values A and B depending on a control input C (it is assumed that two's complement is used).

Also, the adder/subtractor has an additional input \$C_{in}\$ for a previous borrow or carry. When subtraction is to be performed and the borrow input is 1, an additional subtraction of 1 is to be done. There are two outputs, one for the borrow/carry and one for the sum.

How would the corresponding circuit look like?

I thought that (because in two's complement \$ A - B = A + (\bar{B} + 1)\$),

\$ A - B - C_{in} = A + \bar{B} + 1 - C_{in} = A + \bar{B} + \overline{C_{in}} \$

So is it correct that when doing subtraction, all I have to do is invert B and \$C_{in}\$ and feed these inverted values to the inputs of a normal full adder?

Also, how would I construct a 4-bit adder/subtractor from those single 1 bit adder-subtractor cells?


texts: Can you identify this soldering station or its tips?

texts:
Some years ago I bought a store-branded soldering station (because it was cheap). I soon regretted my decision as the store only carried two kinds of spare tips: one conical and a huge chisel.

Recently the store stopped carrying the model and while they say that spare parts are available for at least 5 years, there will eventually be a time when I'm all outta tips.

So if you recognize the manufacturer or can recommend suitable tips based on the dimensions, that'd be awesome. I've tried a Hakko 900M tips and they're slightly too thin and fall off.

The station: http://www.clasohlson.com/fi/Juotosasema-Cotech/Pr408341000

The spare tips: http://www.clasohlson.com/fi/Juotoskärjet-Cotech/40-8342

The tip dimensions: outer diameter 6.4 mm (upper end) to 6.7 mm (lower end), inner diameter 4.6 mm, hole depth 24 mm, and finally the outside length 26 mm.

The heating element diameter is 4.5 mm.


texts:
I have an application where I need to measure the voltage drop over a resistor that varies between 10 ohm - 50 kohm. As I have this set up as a voltage divider, with the result being read by an AtoD, I thought the best way to be accurate is to switch in different resistors, depending on the resistance of the variable one:

simulate this circuit – Schematic created using CircuitLab
Something like the above. This needs to be controlled by a microcontroller, and my initial thought was to use a multiplexer to switch in the different resistors. This seemed like a good idea at first, however, when looking through the datasheets of these components, the ON resistance was a problem. For the higher ranges, it was negligible, but if the 100R resistor was in, the on resistance of the MUX was significant enough to affect the result.
This is a budget controlled design so all of the very low on resistance MUX/decoders etc. are out of the budget (I am not in control of this).
My next thought was to perhaps use MOSFETS to switch in the resistors as these can be extremely low with on resistance, however, this takes us more port pins on my microcontroller. 4 rather than 2. This would leave me with only 2 I/O pins left, which doesn't leave much room for adding anything else that may be requested in the future. This method also means more components, which slightly adds to the placement cost.
Is there a better way to do this that I am missing? Or are the MOSFETS perhaps the best way to do this?


texts: I'm trying to decide on a safe input power to a power amplifier. The amplifier in question is SE5004L. The datasheet specifies that the amplifier output 1-dB compression point has a minimum value of 30dBm and a typical value of 34dBm. The small-signal gain is 32dBm. Without making any further adjustments in my design, the input power to it would be -1dBm, putting the output power at about 31dBm. However, this is close to the 1-dB compression point and the datasheet specifies a 26dBm output power at 3% EVM. I have a 6dB attenuator that I can use, which would bring the output power about to the typical range in the datasheet. I'd like to get as much output power as possible, but not if it significantly distorts my signal. Is it generally ok to operate near the 1-dB compression point, or is it better to stay 5-10dBm below? This is for a FMCW radar operating at around 6GHz.