texts:
I have experienced, and read in several articles that LED’s get dimmer “over time”. I’m looking for a clarification: is it really over time, or is it hours of usage?

So if I put an LED bulb in a cabinet (with no power on it) for 10 years, and then power it on, will it be noticeably dimmer than when it was new?

All the articles I’ve read (even one that gave a pretty good laymen’s description of how LEDs work at the electron valence level) simply say “dimmer over time”, and not “dimmer with use”, so I’m guessing that the answer to my question is “yes”, I just wanted to verify that.


texts: What are the waveguide modes of twisted pairs as discussed here?

texts:
From the recent Lightwave article ASSIA exec touts terabit-speed DSL:

In a keynote address delivered earlier this week at the G.fast Summit in Paris, Dr. John Cioffi, chairman and CEO of DSL management optimization software supplier Adaptive Spectrum and Signal Alignment, Inc. (ASSIA) and Emeritus Professor at Stanford, asserted that his company has figured out a way to support terabit speeds over 100 m of existing twisted-pair copper lines. The techniques also can enable 100-Gbps transmission at more than 300 m and 10 Gbps over 500 m, according to the company.
The secret to such high speeds is the use of significantly higher frequencies than currently employed 300 GHz or higher, potentially. "Fiber-like speeds of 1000s of gigabits/second are possible by using the previously unexploited waveguide modes of current copper infrastructure," stated Dr. Cioffi via a press announcement. "Waveguide-mode use is similar to use of millimeter-wave transmissions in advanced wireless and 5G. Waveguides can enable use of frequencies above 100 GHz for extraordinary speeds."  (emphasis added)

At current speeds, "existing twisted-pair copper lines" can be treated as standard transmission lines as is covered in many RF and communications texts.
I'd like to have some idea what the "previously unexploited waveguide modes of current copper infrastructure" refers to. There are dielectric waveguides, hollow conductor waveguides and coaxial waveguides, and those are also well described in standard texts.
Is there a twisted pair waveguide mode?
Is it possible to find a link, reference, or even a sketch of the fields of such modes?
Note: Leakage of signal between adjacent paris due to spatially overlapping modes would be a problem, but not necessarily lethal. Just as in multi-core optical fibers, there are mathematical techniques to even exploit this phenomenon, but that's beyond the scope of this question.


texts:
After reading the FAQ page of Neo generators, I became incredulous of this particular part (translated from Spanish):

  HOW DOES IT WORK INTERNALLY?

  Our optimized system collects the
  abundant radiant energy from the atmosphere and the system is excited
  using a plasma reactor also manufactured by NEO. The ensemble performs
  the operation to capture the radiant and it is magnified by the
  reactor. The key part or element of our system is the reactor and it
  is the element that after its utility life deteriorates itself and
  makes the system unusable.

Radiant energy of the atmosphere and excited trough a plasma reactor?!

And in the patents page they say the utility life of 35 years! Is this believable?

By the way, the top-level domain (.sx) is at least strange!

The question is: Is the Neo generator a credible product?


texts: FET to be controlled with less than 1V Vgs

texts:
I have a simple switch circuit that is powered with a single 1.5V alkaline battery. I want to find a MOSFET(or other device) that will switch on when the  battery voltage is applied. I can find plenty of FETs with a Vgs of 1.5V but none that seem to switch on properly if the battery is a bit flat (ie 1V).

So I'm after Vgs of less than 1V, drain current is less than 100mA, Vds is the battery voltage, ie 1 to 1.5V.

Any ideas?


texts: Input and Output Impedances of Single to Differential mode converter

texts:
I have this circuit that converts a single ended input signal to differential output signal. I want to understand how to calculate or find out its input and output impedances?

The two op-amps are in inverting and non-inverting configuration. Will this circuit work correctly as single to differential mode converter or should both of the op-amps be in the same configuration?


texts:
I am trying to drive a 3-phase BLDC motor with FOC and have some questions about obtaining resolver offset angle. In the driver I used ABC notation for phases and FOC accepts A phase as 0 angle electrical. The motor cabling uses UVW notation. The motor has 5 pole-pairs. There is a resolver for angle detection and the logic uses Angle Tracking Observer to calculate the speed and angle. Logic treats the rotation in CW direction seen from the front of the motor shaft as positive.

Now, here comes the issue. The motor operates fine with ABC phases connected to VWU respectively. In this case, the offset is set to -11.5 degrees, meaning that we subtract 11.5 from the angle we get from the resolver and use that as rotor angle. Through the serial port, I get some debug data on the calculations inside the FPGA and through this data I verified that FOC actually produces a field that is 90 degrees ahead of the rotor angle (in magnetic field domain of course).

To obtain the resolver offset for any motor and for any phase connection scheme, we prepared a calibration algorithm. The idea is to command the motor with basic SVPWM vectors and get the angle from the resolver and calculate the offset between them. To test it, I switched the phase connection to ABC-to-UVW respectively and run the calibration algorithm. What I expected was, since I rotated the phase connection in negative direction by 120 degrees, I would get -11.5 - 24 = -35.5 degrees for the new offset value. Because the magnetic field that is produced should move in the negative direction in mechanical world by 24 degrees because of the number of pole pairs. To my surprise, I actually got 12.5 degrees which is -11.5 + 24 and that would mean that magnetic field moved in positive direction. This doesn't make sense for me.

The logic with 12.5 degrees offset and the ABC-to-UVW phase connection also works, and it actually creates the magnetic field 90 degrees ahead of the rotor angle. The power consumption is the same in both cases, so the efficiency is also the same.

I was wondering what might be the cause of 24 degrees change in the offset? Am I missing something? I added a drawing of the phase change that I did to give you a better sense of my understanding of the system.


texts: What damage occurs in an ESP32 when you power it with 5V

texts:
A colleague flashed the PIC MCUs on a batch of boards. However he didn't pay attention to set the Vdd when programming to 3.3V and used the default (5V). This caused the ESP32 on board to experience 5V briefly. The 5V was supplied via a PicKit3.

Now the ESP32 datasheet specifically says 3.6V being the absolute maximum supply voltage.

The chips seem to be still working fine, as far as I can tell. The problem is that I don't know what to test more specifically - what kind of damage occurs in a chip that isn't 5V-tolerant? Anyone with some experience with this part and this kind of misuse?

I know that the usual answer to this type of questions is "if it's outside the datasheet specs, all bets are off", and if it were a board or two, I'd just shrug it off, but it's a whole batch which I don't want to write off unless absolutely necessary.


texts: Looking for reed relays for high voltage commutation

texts:
I need to chose a reed relay for connecting a point to high voltage (probably between 7000V:15000V) or to GND signals.
System will have 8 channels (pins). Some of 8 pins will be connected to high voltage signal throught a relay. The rest ones will be connected to GND signal throught its related relay.

As you know relays could be Single or double.

I was searching in digikey, mouser, farnell, etc.. providers and I can only find high voltage single relays (SPST). However, it seems not to be other kind of relays (ie: DPST) for high voltage available on these sites.

I have two questions:

Does it mean that DPST or DPDT are not manufactured? Do they exist?
What is the difference between Isolation and commutation voltage parameters?


texts:
In my signal processing chain, the first stage is an inverting gain stage using Op AMP LT6200CS8-10.

My output DC operating point is 1.24 V. I am providing an exponential signal (Amplitude 1mV) as the input. This is my schematic:

C43 is not populated. The layout is shown below:

This stage is driving another op amp gain stage using AC coupling cap C38 shown in layout above.

When I don't apply a signal, this is how the output (net op_amp_1) looks:

When I apply an exponential signal with 1 mV amplitude high and 0 mV amplitude low, the output (net op_amp_1) looks like this

The flat portion shows oscillation:

How I can reduce this oscillatory behavior of the output?


texts: How to convert counter status to some non-electrical quantity, so that I can see the status without power supply

texts: When I place the instrument in the central unit, it'll get power and increment the counter by 1. But when that instrument is removed from the central unit it has to display what was the last count. When the instrument is removed from the central unit, it will not have power. So how you can decide, how many times the instrument is used? Is there any mechanism by which I can convert my counter status to some non-electrical quantity?


texts: How to remove the baseline of sensor output?

texts:
In my project I am using a CO2 sensor that output voltage in range 30mV ~ 50mV. The signal will then be amplified and filtered and be sent to a microcontroller for ADC.

My tutor suggested that I should get rid of the baseline (30mV) and only amplify the difference (50mV - 30mV = 20mV). But I can't think of a way to remove the baseline with electronic circuit.

Can anyone give me a hint or a reference to read so I can achieve this?


texts: Is it possible to get the current in this circuit?

texts:
I have tried to solve this diagram shown above to get total current:
Since $$V_B = V_1 + V_2 + V_3$$
$$12 = V_1 + 4 + V_3$$
$$V_1 + V_3 = 8$$
$$V_1 = 10I$$
$$V_3I = 12$$
$$I = \frac{V_1}{10}$$
$$I = \frac{12}{V_3}$$
$$\frac{V_1}{10} = \frac{12}{V_3}$$
$$V_1V_3 = 120$$
$$V_1 = \frac{120}{V_3}$$
By substituting in $$V_1 + V_3 = 8$$
$$V^2_3 - 8V_3 + 120 = 0$$
I got stuck here and I couldn't complete the solution because I solved this equation with calculator I got imaginative numbers.


texts: What's the purpose of the 'positive feedback resistor' in the circuit

texts:
There is a 1M Ohms 'positive feedback resistor' in the 10mA current source below:

What's the purpose of it?

Update:

Some people just think it's not a 'feedback' but simply a resistor tied to ground, but why it is draw like a 'feedback' resistor? However, if it's only a resistor tied to ground, then what's its purpose?

Just see another figure below:

Here the 10Meg resistor is a 'positive feedback', right?


texts: I left my lead acid battery in my scooter and have not touched it for last 3 months. Now the open circuit voltage is only 6V. Is my battery permanently dead, or is there a way to repair it?


texts: What makes "quality" analog AV cables better than cheap cables?

texts:
I want to upgrade my retro game setup from a mix of composite and RF to a mix of S-video and component, with some composite for the really old stuff that doesn't support S-video. How can I distinguish the high quality cables and switch boxes from the low quality stuff? What physical properties make these cables and switches better than others?

Edit: I don't think this question is off-topic. It's about determining, without using an O-scope, impedance tester, or other tool, how to buy cables that will faithfully transmit an analog signal and protect it from interference. This has applications not just to my situation, but to hobbyists and tinkerers who don't have access to these tools and doesn't want to spend too much money on expensive cables. This is even more of a hobbyist question because it's mostly focused on RCA cabling, which in the US is still a very common find at garage sales and flea markets.


texts: Voltage drop when driving voice coil OpAmp gain stage

texts:
I'm driving a voice coil with a PID controller. So far, I've set the gain (P) stage, which is composed of LM358 opamps and a dual +-4.22 rail with 1.5V AAA batteries. This is the schematic, where you can see the difference between Vref and Vi is 1V, so Vout should go to -1V (3.2 from ground). It works like that until I attach the voice coil to Vload. Then, Voad drops to -0.25V.

Vload won't go further than +-0.25V no matter the the difference (Verr) between signals.

It seems like it's a current issue but, isn't the last buffer supposed to be able to source enough current to drive the voice coil which I can drive if I just plug it to the rail?

Thanks!


texts: Copper oxide on cables after tinning w/ no clean flux

texts:
We just found a problem with some (translucent) speaker wire.

We have been tinning wires for a year by dipping the stripped end in no clean flux and then dipping again in lead free solder. We have a new customer that gave us translucent wires to tin and solder, one day after tinning the first batch we noticed that there was a greenish color for about 1/2" where we have tinned and soldered the wires.

We follow the dipping procedure as directed in the flux PDF.

Has anyone seen this issue?

If it has happened before we did not notice because we were using colored wires.


texts: Need help figuring out the percent operation/sleep time a battery should use per amount of time

texts:
Hoping this isn't a dumb question. I'm really new to this stuff..

I have a battery with 1000mAH, it consumes 20mA when it operates and 0.05mA when it sleeps. If I need the battery to last for a certain amount of time, lets say 8000 hours. How can I figure out the percent of time the battery will need to be operating and sleeping to total 8000 hours? Does anyone know of a formula to make this math easier?

Thanks in advance anyone who helps!
-F


texts: Altium: All connection lines going to absolute origin

texts:
Problem
Sometimes all the connection lines go to the "absolute origin" in the PCB layout.  It is rare enough that I never remember what sequence I took to get this to happen.  In the attached image, I did route->auto route->component and then all the connection lines went to the absolute origin.  It's possible to work with the lines but they're obviously annoying and "wrong".  I can view->hide connections but they will come back eventually.
Work around
The only way I've been able to work around this is to copy the PCB, create a new one and paste the components, etc., into the new PCB.  That usually works.  I would prefer to not have to do that.
I've had this problem with many versions of Altium.  It doesn't come up often but it does come up.  Any ideas would be welcome.


texts: 741 Op. Amp.: Inverting input connected to output (pin 2 connected to pin 6). What does it mean?

texts:
simulate this circuit – Schematic created using CircuitLab

I am a newbie electronics students.

My question is, what does it mean (what happens) when you connect pin 2 to pin 6 on a 741 op. amp., meaning the inverting input to the output (just a jumper cable).

For some reason my circuit works now when I did it, I just did it on accident. Nothing is connected to pin 2, not ground or anything, just pin 6. To pin 6 it's just pin 2 and another cable just to measure the output compared to ground.

Of course I have some other stuff connected to the op. amp., which is a variable resistor voltage divider to pin 3, -15V to pin 4 and +15V to pin 7.

My assignment is to find a linear relationship between the distance to a light source (using a LDR), and the output voltage (or current) of the op. amp.

But yeah, if someone knows anything about my question that would be really helpful, I will probably rebuild my circuit though.

I'm using a myDAQ if that's relevant.


texts: Simple and inexpensive battery heating and cooling in a harsh environment?

texts:
What are your recommendations for methods or devices that are neither complex nor expensive to keep batteries warm and cool in a harsh (hot/cold/moist/dusty) environment, to ensure long cell life?

I'm designing a small solar-powered camera product and I have my choice of battery types: lithium, lead, nickel, etc. The camera would sleep most of the time so for average hourly use I estimate around 10mA x 12V (120mW). The environment could be very dusty, humid, hot, or cold. I cannot require constant maintenance, so a fan with filter does not seem to be a good idea. I can go with a larger pack to reduce the charge/discharge rate, if that is necessary.

Since this is for the outdoors and the initial sales would be in the United States, I expect ambient charging temperatures to be between -18°C/0°F in the winter and 38°C/100°F in the summer. Discharge temperatures could be as low as -34°C/-30°F in the winter and 38°C/100°F in the summer. Humidity can be as much as 100% but 87% is more typical in locations like Florida or Louisiana.

I was asked to supply the following info:

How your device looks: Imagine a security camera with a solar panel.
What it might cost: Less than USD $100 with parts cost less than $50 would be ideal. Any more than that and I might not consider creating the product.
What amount of field failure you can tolerate: Not sure how to quantify this. A life of 5 years would be fantastic. No less than 3 years.
Where it's going to be mounted by whom: Eaves, trees, walls, by non-trained personnel e.g. homeowners, farmers.
How heavy it might become: Small device, so about 1-2kg/2-4lb.

Is this even a concern? On my house I have these solar-powered security lights that have no heating or cooling. Just Ni-Cd batteries in a black plastic enclosure. I live in a climate with hot summers and cool winters. The devices are mounted in the sun and have been going strong for years. I see from reviews on those devices that they are installed in both very cold and very hot locations, and perform admirably. Yet the typically-recommended charge/discharge temperatures for Ni-Cd cells is 0°C to 45°C and -20°C to 65°C, respectively. Cells in an uninsulated black plastic box exposed to sun and snow surely must reach temperatures outside of that range, right?

And there are solar-powered trail cameras that hunters use in cold and hot weather.

Am I over-thinking this? Should I just drop some Ni-Cds in a black plastic enclosure and be done with it? Or are there some inexpensive temperature management solutions?


texts: Can I use this op amp to scale 0-3.3V to 0-5v?

texts:
I recently came in to a voltage meter 0-5v. I want to use it with esp8266 as a humidity display for my weather information station.
the exp8266 model I'm using (wemos/nodMCU) is 3.3V, I can use PWM to set the needle, but it won't use the full range of the meter. I need to scale the voltage up to 0-5v.

So, after reading a bit I decide what I need is an op amp. I order one that seemed like it would work from the data sheet... but I don't really know how to set it up.

https://cdn-shop.adafruit.com/datasheets/tlv2462.pdf
Here is how I've hooked it up.


texts:
I found a strange 6-pin chip with a barcode and SA20 imprinted on the back of it, The front has a hex shape deeply engraved on it. I looked up the chip online and I couldn't find any information on it. What is this chip and what is it used for?

Back of the chip.


texts:
I having an issue. I have a basics 2 pin push button switch I bought from a hardware store to power on my 3- 3V mini LED lights.
I use a 9 V battery to power through the switch and I noticed when I keep the switch pressed down for two days (my application project calls for that) it kills my 9v battery dead, which I need the battery to light the LEDs at least one month while staying lit.
So I thought of maybe reversing my project with the same 2 pin switch so when I press the switch down, the light turn off instead on on, hoping to make my 9 V battery last a lot longer maybe longer than one month since the LEDs lights are off now while switch is pressed. THAT WAS WRONG!
Please help me figure out both ways, or if I need a resistor for the regular way of the lights on when switch pressed or I prefer, when switch is pressed, light stay off until switch is released and light come on. It killed my battery 10x faster than the other regular way. I am so confused and I thought it would be easy to just use a 9 V to power 3 - 3 V LED lights, with a push button momentary switch.


texts:
I am trying to model a li-ion battery. I have checked the generic battery model on Mathworks webpage. However, there is something that confuses me. In the given charge and discharge equations, we are expected to sum different terms with different units.

In this equation, 'it' is defined as extracted capacity, with unit 'Ampere-hour', whereas 'i*' is given as 'low frequency current dynamics', with unit 'Ampere'. How these two terms with different units can be added? Am I missing something here?

Same problem can be seen in this paper as well. This time, 'i*' is defined as 'filtered current', with unit 'Ampere' again.


texts: Spanning high voltage between capacitors in series

texts:
first of all thanks for your time.

I've studied a lot before to make this post but theory and real world rarely make a good marriage.

I have 20kVAC of spike coming from an ignition coil (the one used for making the sparks in a car engine).

The spark is made through an oscillator and so I can modulate the frequency, the amplitude and the duty cycle.

At the output of the coil I put an HV diode bridge to make it DC and, after the bridge, I have a long series of electrolytic capacitors (50 units, SAMWUA 400WV HE 105°C (M), rated at 400VDC/82uF each) put in series.

I made a simulation with PSPICE and the software says that, at each spark, every capacitor is fully charged at each pulse (once put in series the capacitance of each cap is only 1,64uF).

Before to apply the 20kVDC to my capacitor's bank in the real world I would know if I can do it safely or I will risk a dangerous explosion or to damage the bank (I will make particular attention to the polarization, of course).

The second question is: is it true that - in the real world -, at the terminals of each capacitor, I'll have 400Vdc?

What about the first and the last capacitor of the series? Do they have to withstand 20kV or simply, like the others in the series, they will carry only 400V?


texts: Replace LED chip with reversed polarity pin-out

texts:
I want to upgrade the LED chips of a projector.

Red: PT-120-R-C11 --> PT‐120‐RAX‐L15
Green: PT-120-G-C11 --> PT‐120‐G‐L11
Blue: PT-120-B-C11 --> PT‐120‐B‐L11

But the red LED chip (PT‐120‐RAX‐L15) has reversed polarity pin-out.
Swapping black and red cables should solve this problem, am I right?
Do I also have to swap these cables?

Another picture:

© cine4home


texts: How to estimate a value for IC capacitance in a I2C bus?

texts:
What is a reasonable value to use as the capacitance a I2C device adds to a bus if so is not stated in the datasheet?

With this value I intend on calculating the pull-up resistors to eventually use in a PCB.

I need to append to the bus the following devices:

L3G4200D gyroscope

LIS331DLH accelerometer

HMC5883L compass


texts: Is it possible to generate light with an antenna?

texts:
An antenna (e.g. a dipole) is able to radiate at a certain frequency thanks to the EM field generated by a current provided by a signal generator at such a frequency.
So, for instance:
Voltage source at frequency f (representing an amplifier) + Antenna made of conductors = Radiation at frequency f
My question is: is it possible (or, maybe will it be possible) to generate light by using a voltage source at frequency of light (480-750THz)?
All light sources I've seen are realized by using mechanisms different from EM radiation, like LEDs, LASER etc.


texts:
I have a 40W ceramic heater, which needs to work with 24V but I only have a 12V power supply.

Will the heater work with 12V?


texts:
I am searching for a bidirectional buck boost converter evaluation board for charging and discharging the batteries.

Input= upto 30V DC
Output= upto 10V to 20V DC
Current= less than 10A

I always find bidirectional buck boost controllers (ISL81601EVAL1Z, DC2719A) rather than converter. I use a microcontroller to generate the PWM signal to control duty cycle of the converter there by maintaining constant output voltage.
So, if I buy the buck boost controller can I control it with a microcontroller?
When I read its user guide it says no words about using a microcontroller for generating PWM.
Can anyone please help me in this?
If you know any boards please inform me.


texts: Current transformer not sensing currents

texts:
I have made a current sense transformer to sense primary current maximum 2A(of my electric iron) and secondary output is 1A but there is no current in the secondary. I have used a iron "Nut" as a torroidal core(I suspect this may be the problem) and used normal wire with plastic insulation for winding. I took 2 turns for secondary, and burden resistor is 1.4 Ohm. As a newbie I am getting problems, experts please guide me.

update: Thank you experts for helping now I can develop a CT for me.


texts: What is the point of a small mark on a DIP IC opposite the pin 1 indicator?

texts: I have seen an unusual mark on an IC. Can anyone tell me does it have any functional or testing significance?


texts: Low cost high precision linear position sensor

texts:
I am trying to find a low cost high accuracy linear position sensor that can be used in a hobby 3D printer. Almost all current 3D printer designs rely on stepper motors to provide positioning but I want something that works on positioning info rather than assuming the motor will do what it's told. After a few hours of searching I have found lots of technologies that provide high accuracy sensing but they are all sold by companies who tailor make a whole system for application and require that you request a quote. I am assuming that things are probably insanely expensive and not something for a hobbyist. I am obviously not a professional and would just like to find out if any of you know of a technology I can use that should not really be more expensive than stepper motors?

PS. The type of accuracy I am looking for is about 0,01mm.


texts: What will happen if two different size generators are paralleled?

texts: What will happen if I Parallel two different size generators of different manufacturers without a synchronizing panel. Both generators have the same voltage and frequency.


texts:
Assuming that the diode is rated for 20 kV and the pulse is only 250 V, will a 250 V 8 kA pulse that lasts 0.2 uS break a 20 kV 1 A diode? This also assumes that the diode recieves 10 of these pulses every second for 5 seconds.

For reference, terminal are axial leads and the diode is a HV rectifier diode.


texts: I'm still new to PCB design so don't mind this question if it sounds silly . What exactly is the function of the oscillator in the arduino board? Is it clock speed ? If it is, why doesn't it come inbuilt the IC? (The avr chips) what if I have two ICs that require an oscillator of same frequency on one board, can I use the single crystal for both ICs or do I need two ?


texts:
I'm having a lot of trouble finding wifi enabled arduino shields. All the places I've seen them are out of stock for some reason.

Would this thing work? How would I hook it up?

http://www.rovingnetworks.com/wifly-gsx.php

Basically I want to build a network enabled (wireless) robot with the arduino. So you can see it's clearly better if I can get a wifi shield.

Edit: To follow up on this post, I did end up getting the Wifly shield from Sparkfun. I was unable to get it working with the Arduino (Duemilanove) I had, and I ordered an Uno on a hunch, and it works on that! Connects to APs and can host an ad-hoc network. Unfortunately no security options exist for ad-hoc. But I'm okay with that.


texts: Is it customary to use a transistor at the end of a string of logic gates when powering something such as a relay?

texts:
I have a pretty simple circuit - a clock (555 timer), counter, some logic gates, and a relay. Essentially, the clock's state, combined with some logic, will determine if the relay is on or off.
My question is if I need a transistor (or if it's just best practice when driving something in general, and why) to run the relay. The 555's max output current is 225mA, and the relay's coil current is 71-90mA, so in theory I think it's fine. I'm still an EE student, so I'd like to learn to do this "correctly."
Edit: Here's a basic logic schematic from Logisim (also if anyone has suggestions for more advanced digital logic simulation software, go for it).
Basically when the relay LED is illuminated, I want the relay to be on. My question pertains to whether or not I can hook the output of that OR gate directly to the relay, or do I need to insert a transistor between the two?


texts:
i can't understand how, in a MOSFET N, to get an expression of the voltage Vds with respect to time if Vgs > Vth (closed circuit) and if Vgs < Vth (open circuit).
I saw many equations with current, but none of them was like

\$\ Vds =  a(1-e^{-t})   \$

I wrote an expression like this because it seems to fit with this kind of curve. Is anybody know how can i get this Vds without the current ?
I'm not a pro with circuits then sorry for my missing knowledges.


texts: How can I test whether my 3 wire electric motor is broken?

texts:
I have a motor that I'm trying to work out if it's faulty or not. The motor make and model is EMC RB2C-190-060 K010 (photos below) -
230V
~ 50/60 Hz
2μF-450V
65/90W
0.3/0.4A
The motor has four wires coming off it: brown, black, blue, yellow&green. I have tested the resistance between them with a multimeter as follows:

Blue to black = 1 (on all Ω settings)
Blue to brown = 1 (on all Ω settings)
Black to brown = 380 (on 2000 Ω setting)
Blue/black/brown to yellow&green = 1 (on all Ω settings)

Is this enough information to tell? I'm happy to test by wiring it up to power, but I'm not sure what the capacitor to use and how to wire in the capacitor. Any help appreciated, thanks.


texts:
A signal with PSD \$S_x(\omega)\$ is passed through a channel with frequency response \$H_1(\omega)\$ and at the receiver, it is passed through an equalizer with frequency response \$H_2(\omega)\$. The PSD for AWGN is No/2.
My question is, does channel frequency response affect PSD of noise?
For e.g. output PSD of signal here is
$$S_x(\omega)\cdot |H_1(\omega)|^2 \cdot |H_2(\omega)|^2$$

but what about output PSD of noise, will it be No/2 \$|H_1(\omega)|^2\cdot |H_2(\omega)|^2\$  or only equalizer will change noise PSD to No/2 \$|H_2(\omega)|^2\$?

I encountered a question where they considered only equalizer frequency response to get output PSD of noise.
Please help.


texts: How to connect voltage protection relay to contactor?

texts:
Could you help me connect a voltage protection relay (VPR) to a contactor? I'm not sure how to connect the relay output terminals (NO, NC, COM, etc.) to contactor control terminals A1 and A2 in the wiring diagram below.

VPR (voltage protection relay) used is 3 phase type. Manufacturer said L2 and L3 can be shorted to L1 for use in single phase.
Contactor is single phase, NO type.

I would like the contactor to close when there is no fault detected and for it to open when there is a fault.

VPR datasheet
Contactor datasheet

Thank you.


texts: How can CPUs operate at such a low voltage with billions of transistors?

texts: From what I understand, the voltage drop across a transistor is something like 0.5V and the minimum voltage for (conventional) current to pass from the emitter to the collector is 0.1-0.2V. If that is true, then how can CPUs operate at voltages as low as 1.5V if they have billions of transistors? Wouldn't current only get past the first 3 transistors?


texts: How to calculate voltage drop with internal resistance and load values

texts:
Is there a way to calculate voltage drop with internal resistance and load values in the equation? Or is it somehow connected to ohms law? If so, how is it done? I have this test circuit below to illustrate what I mean.

simulate this circuit – Schematic created using CircuitLab
The following is what I mean when I say internal resistance:
When designing a circuit with a battery, we often assume that the battery is an ideal voltage source. This means that no matter how much or little load we attach to the battery, the voltage at the source's terminals will always stay the same.
...
In reality, several factors can limit a battery's ability to act as an ideal voltage source. Battery size, chemical properties, age, and temperature all affect the amount of current a battery is able to source. As a result, we can create a better model of a battery with an ideal voltage source and a resistor in series.

(from learn.sparkfun.com)

Stated in my previous post: electronics.stackexchange.com I understand that a batteries internal resistance + a resistor will reduce voltage by small degrees. I also know that with no internal resistance, voltage is unchangeable, except from the battery itself. If this phenomenon is somehow linked to ohms law, how is it linked? or is there a separate "law" that covers this?

My second question is very basic: Is the voltage the same thru an entire series circuit?


texts: Creating high speed clock by power grid frequency via PLL

texts:
I need to take exactly 200 Samples per 50Hz whereas the samples do not vary in phase. Thus, I thought about using a zero-cross detector and a PLL. The ADC is a sigma-delta ADC with an oversampling rate of 256. Therefore, the required clock is 2_560_000 Hz for driving the ADC.

The CS2000-C from Cirrus Logic seems to fit that purpose but is quite expensive. Does anyone have a cheaper solution to that problem?


texts: Implementing a Boolean function using NOR gates

texts:
The task is to implement a Boolean function using NOR gates only. After minimization what I end up with is the following equation:

$$f(a,b,c,d) = {\overline {b} \overline {c}} + {a \overline {c}} + {c \overline {d}} $$

I tried to do something like this:

$$f(a,b,c,d) = \overline{\overline{\overline {b} \overline {c}}} + \overline{\overline{a \overline {c}}} + \overline{\overline{c \overline {d}}} $$ using De Morgan's Laws:

$$f(a,b,c,d) = \overline{b+c} + \overline{\overline{a} +c} + \overline{\overline{c} +d} $$

Textbook solution suggested to deduce the minimized CNF form and transform it a bit:

I wanted to find out is my solution any good, but Logic Friday created two different truth tables for the two expressions:

What interests me is where did I go wrong in my solution? Do we generally must use CNF to get to the function with only NOR operations?

EDIT: The function is given by:
$$f(1)={1,2,6,9,10,13,14}$$ and $$f(*)={0,8,12}$$

For minimization I used a K-map.


texts:
I am wondering if a PID controller is the correct way to implement a stabilizer for a camera or any device. If I were to shake the device up and down and want to cancel out the movements by accelerating in the opposite way using a motor and linear actuator, would a pid controller work? I can collect real time data in Arduino or input a giant array of acceleration data.

I wanted to base it off of this lab.
https://www.pdx.edu/nanogroup/sites/www.pdx.edu.nanogroup/files/2013_Arduino%20PID%20Lab_0.pdf

Its a circuit which uses a pid controller to keep the dimness of a light bulb the same brightness regardless of the amount of resistance you apply with the potentiometer.

The code confuses me because it changes the set point everytime. I thought a pid controller has an input , a desired output, and the output each iteration. why would the set point change?

Thanks for any help! I made sure to read every pid thread on here.


texts: Xilinx FPGA and DDR3 Memory. Confusing Impedance combinations

texts:
Currently I'm planning on doing a PCB with DDR3 memory and an Artix7 FPGA. During my research a few questions accumulated.
When looking at the reference manual of the Arty7 board, I see that I have to configure DDR3 output drive strength and On-die termination to RZQ/6. Using a 240 Ohm reference resistor, RZQ/6 equals 40 Ohms. On the other hand, the manual states, that all traces are 50 Ohm traces (100 Ohm differential) and that the FPGA's termination should be configured to 50 Ohms.
Another thing is, that the Address/Control signals are all terminated with 40 Ohms according to the schematic.
The schematic of the arty7 board can be found here. The DDR3 memory and its 40 Ohm termination resistors are shown on page 9.
To me, it would be more logical to use 40 Ohms everywhere. Why is this impedance mix used?
I know, that for higher speed DDR3 applications 40 Ohm systems are typically used. However, to me, it seems completely unlogical to go with 50 Ohm traces, when you can't even configure the ODT to 50 Ohms: RZQ/6 = 40 Ohms, RZQ/4 = 60 Ohms, assuming 240 Ohm RZQ. (I've never seen another value besides 240 Ohms).

Can someone clarify this impedance stuff?

Technically, the DDR3 device using 40 Ohm output impedance on a 50 Ohm trace and load should't affect signal integrity, but affects the signal amplitude.

Don't you get overshoot when driving a 50 Ohm net with a 40 Ohm driver?

How is signal integrity guaranteed, when using a 50 Ohm line impedance in combination with 40 Ohm termination resistors?

For my design I initially intended to use 40 Ohm traces, 40 Ohm termination resistors on address lines and an ODT setting of RZQ/6. for a 1000Mb/s transfer speed DDR3 device. Unfortunately, this is a hobby project and I don't have access to SI simulation tools to verify this using the IBIS models.


texts: Eagle project wont open, "Error reading file"

texts: I'm working on a board layout with Eagle.  I tried to open the file today and get a message "error reading file".  No other info besides that and I haven't been able to find anything about this.  It does this with both the .sch and .brd files. Any ideas?


texts: led voltage and current relationship via a driver

texts:
I am trying to understand what happens to the voltage supply to a high power LED when using a Constant Current LED Driver.

Things I (think I) Know:

-An LED has a certain range of operating voltages/currents that it is designed to use.

-When the voltage increases the current increases exponentially.

-Because fine adjustments in voltage and mean large changes in current it is best to use a constant current driver.

So lets say I'm driving a Cree CXA1512 with a Meanwell LDD-1000, a constant current driver.

Looking at the data sheet for the CXA1512 (assuming the led has warmed up and is running at 85 degrees)it states that @1000mA the voltage required would be just under 19V.

The data sheet for the LDD-1000 states that the voltage difference between input and output is -3V.

So to my way of thinking i'd need 19V (for the led) + 3V (to compensate for the driver) which would give me a total 21V required to operate the circuit.

Is this correct?

For my application I'd be powering the driver/LED with 5 lithium cells.
These batteries when fully charged can be up to 4.2V and when discharged can be a low as 3.2V.

So given that the current is going to be @ 1000mA, what happens to the voltage supplied to the LED as the batteries discharge and the led is going to want 19V.

Would a voltage regulator be required to power the circuit and keep the voltage in at a constant 21V or does the demand of the LED @1000mA somehow compensate for the varying voltage?


texts: 22uF 0805 SMD capacitor for voltage regulator?

texts:
I'm trying to use some part of this circuit dual power supply circuit:

http://embedded-lab.com/blog/multi-purpose-dual-power-supply-5-0v-and-3-3v-regulator-board/

Credits to embedded-lab.com.

I would like to use all SMD components (as I'm short on space).

I'm intending to substitute 1N5400 to 1N4001
AMS1117, resistors and the LED is no issue
100 uF capacitors in 0805 I also have

However, I'm doubting about the electrolytical 22 uF capacitors. I ordered the SMD 0805, but I wonder if those can be substituted.

(for my project I need < 100 mA of 3.3V power and about 50-200 mA of 5V power).


texts: Stability of crystal and crystal-less oscillator transmitters

texts:
I have stumbled upon this very cheap so called "crystal-less" RF transmitter:
http://www.mouser.com/ds/2/368/Si4012-35123.pdf

It says there on page 5 the Carrier Frequency Accuracy is 250 ppm while crystal-less. Does this mean that for a 433 MHz carrier there will be 250 x 433 =

108.25 kHz

maximum drift above or below the nominal carrier frequency ? Does this look like enough for the FSK receiver not to be able to tell the signal any longer ? A few tips on how to program the receiver and whether or not I can get away with a non-crystal-less SiLabs paired receiver would help.


texts: Powering a load with specified maximum current of 300mA. Is it safe to use a matching voltage power supply with a higher current rating?

texts:
I just bought a guitar amp that can be powered by a 9v battery or a 9v power supply.  The instructions that came with the amp specify that the power supply should deliver 300mA maximum.  As far as I understand, the load determines how much current is drawn, so why would it be dangerous to use a power supply with say, 1A?  I don't want to fry the amp, but I also don't want to go track down a different supply.

Here's my guess.  I think it's probably not safe.  I noticed that when I turned the volume up while using a 9v battery, playing a note loudly would cause the amp to die for a moment, which I assume means it's trying to draw more current than the battery can supply.  This seems to imply that louder volume equals more current draw from the power source.  If I plug in a power supply with a current rating of higher than 300mA, there's the possibility that the amp will attempt to draw in more current than it can handle when playing loudly and fry itself.  Is this what's going on?


texts: Solar panel and mppt / battery system advice

texts:
I got a free solar panel with specifications:

Voc:   62.00 V
Vmpp: 43.00 V
Impp:  1.17 A

My question is can I hook-up a 12V / 24V mppt charger and charge a 12V battery pack with no effort?

If not, how can I approach this? I'm a bit new and need a good direction.

Solar panel
Mppt
Battery


texts: How to charge 18650 lithium ion cells together?

texts:
How can i charge 6 pieces of 18650 lithium ion cells together using a laptop power supply with auto cut charging when fully charged ?

LGDS318650
H3314903243
KK264D9S3

This is printed on each cell. My cells are in 3S2P order and my power supply is 19v and 3.9 amp. Is there any possible way of charging them.


texts:
How to design a circuit (only using transistors) which takes  0V to 3.3V step at the input and generates a negative 1ms pulse at the output.

Input : ______|‾‾‾‾‾‾‾‾‾‾‾‾‾

Output: ‾‾‾‾‾‾|______|‾‾‾‾‾‾
                1 ms


texts: wave form of the diode current of a rectifier circuit and difference between the transformer and the AC source

texts:
So I have two questions I hope you would answer it, the first one is about how would the current Id of this circuits be? I mean his waveform.

and my second question is these two circuits who are in the same picture, one with a transformer and a circuit with an alternative source. my question is the difference between the two in the representation of Kirchoff's law is to use the U2 in the transformer circuit and the Vs in the alternative source case, right??
thank you.


texts:
I am having a hard time simplifying this logic function:
\$ f = \overline{x_3}\cdot\overline{x_4} + \overline{x_1}\cdot\overline{x_3}+\overline{x_2}\cdot\overline{x_3}+\overline{x_1}\cdot\overline{x_4}+\overline{x_1}\cdot\overline{x_2}+\overline{x_2}\cdot\overline{x_4}\$
I found out on wolfram that it simplifies to :
\$ f = \overline{((x_1(x_2(x_3+x_4))+x_3\cdot x_4))+x_2\cdot x_3\cdot x_4)}\$
but no matter what I tried I cannot get to this result.
Any help would be appreciated!


texts: Is a cross-correlation property of Gold code independent to modulation?

texts:
Gold code is known to have a good cross-corrleation property, i.e., a high cross-correlation value shows iff two sequences are the same.

I wonder whether it is independent to modulation, e.g., BPSK, QPSK, M-PSK, M-QAM, when Gold code is applied to wireless communication.

My naive guess that, since mapping from a binary Gold code to a modulated signal is 1-to-1, so the answer is yes, independent to modulation.

P.S. I'm a bit confused whether this question is proper to EE.stackexchange or math.stackexchange.


texts: I believe in Europe the letter U is commonly used for voltage in (eg.) Ohm's law \$U = I × R \$. I think I understand where the letter V came from, commonly used in North America. But what's the story with U?


texts: Why a wave does not enter a cable? Understanding TDR (Time Domain Reflectometry)

texts:
I have been doing some TDR (Time Domain Reflectometry) measures which involves sending gaussian pulses through a cable and measuring the s11 (reflection) parameter.

In this measure, I could see that from some frequency on, most of the pulse was reflected in the beginning of the cable and it didn't (or it didn't seem to) enter the cable. This reflection happens due to the difference of the impedance of the cable and the impedance of the source but it seemed to be more important at higher frequencies.

The effect of the wave not entering the cable, was also partially because of the higher attenuation at higher frequencies. Anyway, the peak of the reflection in the beginnig was also much bigger in higher frequencies.

So...

Is it because the wave cannot be difracted (or refracted?) into the cable for its small wavelenght?

Or is it because the difference between the impedances of the source and the cable has gotten bigger, so the reflection coefficient has grown bigger? If both impedances depend on frequency, the difference shouldn't grow that much, or what?

25MHz

250MHz

1GHz


texts: I found this display in this cheap chinese handheld tetris. It doesn't have any connectors on itself and is just sitting on small PCB with some kind of gum between them. What kind of display is it and how can I power it with eg. arduino?


texts: Schottky diode polarity attiny85 dev board

texts:
This dev board, forgive my second question on it today.
My question is regarding the Schottky diode. It looks to me like the USB 5V is wired to the cathode. Wouldn't that mean it would only allow reverse current in the micro-amp range through? I would've expected the diode the other way around, to prevent back-feeding the host port.
Edit: Here is another schematic, seemingly of one of a million knockoffs, with the schottky the other way around. Seems to be a schematic error in the Digistump schematic.


texts: Copper-core PCB with BGA: X-Ray inspection?

texts:
When mounting BGAs, X-Ray is necessary for inspection of the ball soldering.
But what if I have a BGA on a copper-core PCB?
Are there exisiting inspection systems covering this?
Or would I have to cut out the copper under the area of the BGA?


texts: I'm going to use a 5V relay ( DIP05-1A72-12D Datasheet), and my supply voltage is 5V, do I need a resistance in series with the relay coil not to burn the relay?


texts: RLC circuit: how to find voltage/current derivatives and derive differential equation

texts:
Trying to resolve differential equations for RLC-networks, I'm always stumbling upon the voltage/current derivatives. Here I would like to give two examples from the same textbook and explain my problems.

Please consider the following circuit:

The author asks to find out the value of vL(0+). Let's follow proposed solution (https://www.slader.com/textbook/9780073380575-fundamentals-of-electric-circuits-5th-edition/361/). For t<0 under stable conditions vL(0-) = 0 because it is a simple wire. iL(0-) is 50V/(40+10) = 1A. vC(0-) is defined by a voltage drop on 40-Ohm resistor, so it is 40 V. At t=0 a 2-A current source is switched on. According to KCL,

2 = iL(0+) + iR(0+);

Axiome 1: inductor current cannot change abruptly. Thus, iL(0-) = iL(0+) = 1 A. Axiome 2: capacitor voltage cannot change abruptly. Then vC(0-) = vC(0+) = 40 V. Then

2 = 1 + iR(0+);
iR(0+) = 1 A;

Now let's calculate vL(0+). According to KVL,

vL(0+) = iR(0+)*R + vC(0+) = 1*40 + 40 = 80 V.

LTSpice confirms it.

Now please consider next circuit:

The task is to find out v(t) for t>0. Step 1: define type of response. Answer: underdamped. Step 2: pick up a general equation from the textbook and find out coefficients A and B:

v(t) = vS + exp(-alpha)*(A*cos(omega*t) + B*sin(omega*t));

In order to find out A and B, we need initial conditions, namely voltage and derivative of voltage at t = 0. It is not difficult to find out vC(0-). Let's focus on the derivative:

iC = C*dV/dT;
dV/dT = iC/C;

And here comes the problem. The author of the solution writes:

iC(0+) = iL(0+) = 0.

Indeed, a current through the inductor was 0 A at stable conditions. BUT, now there is a 50 V source which is switched on. And there is a current through 2 and 4 Ohm resistors. And since all these resistors are in series with capacitor, I can logically write:

iC(0+) = iR(0+) = 50/6 A.

The first circuit was cited in order to show the concept: at t = 0+, the current from the second source cannot be neglected. However, the solution for the second circuit neglect it.

Can gurus of the electrical engineering explain subtleties of the logic?


texts:
I just began being interested in electronics and I got my hands on a Chinese bench power supply APS 3005 that didn't work - only CC red led was on.
I didn't find a schematic for this PSU, but it's the same as on this video.
I found a shorted diode, which I changed with a new one and I also found that there is a LM7812 voltage regulator where I measured that it ouputs only 7V, but between input and ground, there is 18V.
I disconnected the output terminal from the circuit and output was still the same value. So I bought a new LM7812 and to m surprise when plugged in again only 7V was at output.
Why is that it never outputs 12V? Could it be that both the old and the new LM7812 are bad?
Here is a picture of the regulator with output disconnected from rest of the circuit and between input and ground is 18V.

Edit: So I apologize, the problem wasn't the 7812, but my multimeter which showed lower values. When I tried another multimeter it showed 11V, which is fine, since the multimeter is for higher voltages.
Now I have to find why the power supply is always only in CC mode.


texts:
I have ordered a Reed Relay with a diode and electric shield, but I am not sure how to connect the shield to the rest of the circuit because I do not know what the shield does and how does it work in the context of the DIP Switch. Does anyone have any insights on this?

This is the data sheet with more information:
https://docs-apac.rs-online.com/webdocs/1398/0900766b813980c8.pdf


texts: (Convolution Integral): What does it mean to have an impulse response before t=0?

texts:
Context: I am currently learning about convolution integrals as they apply to circuits (LTI specifically, if I understand it correctly.
(For the following, continue under the assumption that \$\theta(t-c)\$ is always used as the Heaviside step function.
Let's say we have a simple step input: \$x(t)=\theta(t-2)\$ (step input, delayed by two seconds.)
But I am provided the impulse response \$h(t)=\theta(t+3)-\theta(t-3)\$
The short version of this question is this: How should I work with an impulse response defined before \$t=0\$ (with regards to convolution)?

Some more details:
The only way I get the same answers is to do it in a way that seems wrong as I understand these concepts.
I understand that to find the output \$y(t)\$, I am interested in the convolution
$$y(t)=x(t)*h(t)\equiv\int_{-\infty}^\infty [x(t)-h(t-\tau)]d\tau$$
$$\equiv\int_{-\infty}^\infty [x(t-\tau)-h(t)]d\tau$$
When I do this using the response as the translated function, I end up with a function that is defined on the boundaries of \$t<-1\$ (no overlap), \$-1\leq t<5\$ (some overlap), and \$5\leq t\$ (full overlap.)
This does not make sense to me, as I am showing output before an input is applied over the period t=\$[-1,1)\$
I also understand that I have the option of utilizing the Laplace transform to solve the convolution.
$$y(t)=x(t)*h(t)\equiv X(s)H(s)$$
(Where X(s) and H(s) are the Laplace transforms of x(t) and h(t), respectively)
This is where things start to confuse me as if I take the Laplace transform of the impulse response, it will include the following step:
$$\mathscr{L}[\theta(t+3)](s)=\int_0^\infty\theta(t+3)e^{-st}dt\equiv\int_0^\infty e^{-st}dt=\frac{1}{s}$$
As \$\theta(t+3)=1\$ over the interval \$[0,\infty)\$.
When you continue on with the product in this way, you get
$$y(t)=(t-2)\theta(t-2)-(t-5)\theta(t-5)$$
If you ignore the one-sided restriction, you get:
$$y(t)=(t+1)\theta(t+1)-(t-5)\theta(t-5)$$
The first appears unrelated, the second perfectly matches the response from earlier (when you ignore that the input starts at \$t=2\$

So my understanding of the 'impulse response' doesn't currently fit with something that is defined before \$t=0\$, and I think that is reflected in the results. I'm trying to figure out what I am missing to understand these cases where I am provided impulse that is provided with a definition such that \$h(t)\neq0\$ for \$t<0\$


texts: Altium Designer: Design Rule Check didn't check for all my nets?

texts:
I'v been using Hierarchical Schematic Design. In my design, there were 76 nets as shown below:

here is my Design Rule Checker:

But when I run DRC(Design Rule Check) while I left all the connections as shown below:

DRC didn't check for all the nets, only 22 nets was checked:

Whyyy? Did I miss something? Or when I'm using Hierarchical Schematic Design i need to enable something??, Because i can not check for all my net connections after i finish.

Any help would be appreciated!!!


texts: When is it considered that too much is too much when it comes to copper fills on DC-DC switchers. I am currently laying out a Buck, 3 Amp max output. Every literature that I have scanned before advises me to pour and fill solid regions on the input node, the switch node(where the maximum peak currents happen in a Buck) and the output. But when should i start backing off?


texts:
Are the dies made for a BGA package any different from the dies for a QFN or a DIP Package? Do BGA dies have connections on the lower side of the die? In the substrate?

How are terminals put in the package under the die?

I came across this picture. Are BGA packages actually PCBs? and are signals just taken off the die edge and routed to the bottom of the package? If so, how does this help in decreasing inductance at high frequencies?

I also came across the image below which makes it look like the BGA packages have connections from the bottom side - from the substrate.


texts:
I found a old RC Car. I'm electronic begginer, so my question might be dump, but I can't figure out how I can do this. I Separated the remote and connected it's power to the Arduino board.

At this time the project looks like this: ( It's working )

My goal:

The Problem:

The buttons are connected to the chip and to the ground. If the button was connecting the 3.3v to the chip, it was going to be fine, I was just going to do as the picture ( My goal ) above, but now I don't know how I can accomplish my goal. My question is how I can switch pins between ground and "chain breaker" ?


texts: I am reviewing a value engineering proposal consisting of downsizing the main feeders to the moveable bridge. for the voltage drop, they calculated the total current draw for the worst case scenario feeder, consisting of miscellaneous equipment (transformers, brakes, receptacles etc.) and 2 100 hp 3-phase motors (fed from VFD's). In their calculation, they used the running amps (55.8A ea) for the motor current draw. shouldn't they use the full load amps (124A ea) ?


texts:
I'm trying to implement a UART on a dsPIC33E microcontroller to communicate with an industrial controller (cRIO by National Instruments) over RS485 (2-wire, half-duplex).

What I want to know is should I implement a delay before the first start bit and the last stop bit of the whole message? If yes, is there any recommendation (standard) how "long" this delay should be?

Here is a waveform of a message recorded at a serial port of the industrial controller:

For easier referencing, let's say that the far left vertical line denotes t=0 ms, whereas time division is set to 1 ms. Since the serial port is configured in a half-duplex mode, data direction can be either transmit or receive. At t=1 ms it can be seen that the port is set to the transmit mode, and at t=7.2 ms it releases the data bus, i.e., it is set to the receive mode. However, I'm concerned about these delays before the first start bit and the last stop bit. Should I also implement these delays on my microcontroller? Is this defined by any standard - hardware or software standard?

Thank you in advance!


texts: Can a reverse battery be considered a resistance?

texts:
In a simple circuit with 2 batteries and a simple load, one of them supplies 10V and the other 3V. The 3V one is reverse, in a way that the total output of batteries is 7V. Can this 3V battery be considered a resistance to the 10V?

I'm asking this cause I'm trying to get a better understanding of bipolar junctions.

Thanks!


texts: All sorts of fail converting Schematic to Bread Board

texts:
Schematic:

Fritzing BB View:

Total n00b: I am trying to layout my breadboard based this schematic, but I'm not sure if I've even come close.  The LM34 in the graphic is actually a SS494B hall effect sensor.  The schematic view in Fritzing is all sorts of wrong, and I assume the PCB view is as well.

Basically I wired all of this up, and I still get millivolts at what should be the Pin 7 to Arduino.  I don't seem to get any amplification at all at pin 1.  My assumption was that i translated the Schematic to the BB completely wrong.  How off am I?


texts: How can you visually model voltage vs. current?

texts:
I'm trying to wrap my head around Voltage and Current. I saw this analogy on a post from another site that seems to make sense:

  For circuits I tend to mentally use a "plumbing" analogy. The voltage is like the water pressure, and the current is like the flow.

Reference https://www.physicsforums.com/threads/visual-model-for-voltage.200937/

My struggle is understanding how this analogy would describe something like using a number of lemons in parallel as a battery. I have seen example people provide where a few lemons can be coaxed to produce around 3 volts of energy.

2 AA's can also be coaxed to produce roughly 3 volts of energy. Yet the current from the Lemon batteries is minuscule compared to that of the Alkaline batteries.

So in this analogy applied to those. The Lemon battery has 3v of pressure and low flow (current) and the Alkeline batteries have roughly the same 3v of pressure but considerably faster flow (current).

Is that difference in flow due to resistance in the lemon? I heard if you squish the lemon you get more current out of it. Could just the juice outside of the lemon produce similar Voltage/Current?

How could one using the same analogy above incorporate the cause of the difference in current between the two?


texts: LCD user-defined graphics how to send instructions?

texts:
I've got a LCM1602C 16x2 liquid crystal display which I'm experimenting on using switches (without a micrcontroller) to understand how it works (I know that it is much more easier with arduino and using the liquidcrystal library).

I was able to send different instructions like display clear, setting address, changing character entry mode and changing cursor and shift direction, I was also able to enter data and show different characters on the display without problems. However I wasn't able to create a custom graphics using CGRAM commands.

In my book it says that first I need to clear the display, then I need to send a set CGRAM command which is anything between 0100 0000 and 0111 1111, then I need to enter the data row by row total of 8 rows. So I did the following:

send clear instruction by setting D7->D0 0000 0001 while RS input is set low, then initiate command by making the transition low-high-low on E enable input.
set the CGRAM command by setting D7->D0 0100 0000, RS low and E low-high-low transition.
send custom graphics rows D7->D0, RS is low and each row is followed by low-hight-low transition on E input:

0000 1110
0001 0001
0001 0001
0001 0001
0000 1110
0000 1010
0000 1110
0000 0100

But it didn't work, all that happened was that the screen was disabled and the cursor got hidden. What am I missing?


texts: In a DC motor, is there one commutation point that is optimal in all respects?

texts:
This recent question got me thinking about commutation timing, and why advancing it can be desirable. However, I wanted to consider more deeply the underlying phenomena, and I'm pretty sure my understanding is incomplete, so I thought I'd try a new question.

The stator and rotor fields combine to make a rotated overall field, and some motors advance the commutation timing to reduce commutator arcing. Here's an illustration, from this article on submarine electrical systems:

The section where this appears is discussing generators, so the arrow labeled "rotation" is backwards if we are thinking of this as a motor. If this were a motor, with the currents and field drawn, we'd be expecting it to turn in the opposite direction, counter-clockwise.

Since at the point label "new neutral plane" the rotor is not passing through any magnetic lines of force, there is no induced voltage, so if commutation is performed here there will be minimal arcing.

But, by moving the commutation point, have we sacrificed some other parameter? Have we reduced torque? Efficiency? Or is this the optimal commutation point in all respects?


texts: Is Automobile Power Viable for Electronics Projects?

texts: I have some project ideas that would be targetted for use in a vehicle. I would like to consider the possibility of tapping into the car's 12V battery to power the projects, for example through the cigarette lighter port. I would put the input power from that port through a linear or switching regulator (e.g. a 7805 or similar), to give me 5V power. Am I likely to face any challenges in that approach? Are there front-end circuits that are a 'must have' for consuming automotive battery power in low voltage / low current embedded applications? Specific circuits and/or part recommendations are encouraged.


texts:
I need to create a custom square wave at the hardware level.
It's a 3.3 V signal at 100 kHz but the high portion of the form needs to be 9.78 MicroSeconds and the low portion needs to be 220 NanoSeconds.
I assume this is a solved problem, but my google fu has failed me thus far, as has my search for a programmable clock device with this capability.
Thank you for your help,
(Update, edited to clarify units)


texts: Multiple analog inputs on A0 pin (ESP nodemcu) with PCF8574

texts:
I am trying to read out several analog values on one analog input on the nodemcu.

As sensors I am using two potentiometers which are connected to GND via a PCF8574 8-bit I/O expander.

With the code shown below I get for both sensors always the same value.So if I change the value of Poti 1, the value for Poti 2 (shown in serial monitor) will also change.

What am I doing wrong? Any help is appreciated.

#include <Wire.h>
#define analogPin A0

void setup() {
  Serial.begin(9600);
  Wire.begin();
}

void loop() {
  measurePotis();
  delay(1000);
}

//Measure Soil Moisture
void measurePotis(){
  Wire.beginTransmission(0x027);
  Wire.write(0b01111111);
  Wire.endTransmission();

  int sensorValue;
  sensorValue = analogRead(analogPin);
  Serial.println("Poti 1: "+String(sensorValue));

  delay(1000);

  Wire.beginTransmission(0x027);
  Wire.write(0b11101111);
  Wire.endTransmission();

  sensorValue = analogRead(analogPin);
  Serial.println("Water Poti 2: "+String(sensorValue));
}


texts: Does a silkscreen text or line over pads/mounting holes give problems?

texts:
I'm intending to create a PCB and let it manufactured (just a few, for a hobby project).

I added some text on the silkscreen layer very close to mounting holes/holes for pins/vias.
Also I used lines over such holes.

Could this cause a problem for a PCB manufacturer? I expect the text/lines will just not be displayed, or will my PCB be rejected because of this?

I'm using KiCad for the design.

Below is the picture... meanwhile I fixed the texts, but the diagonal lines at the bottom through some pads and holes I would rather keep.


texts: Why is the LT1054 circuit providing far more than double voltage?

texts:
I created a LT1054 bipolar doubler circuit. I am using Linear Technology's chip.

My supply source is measured at 6.1V. My finished circuit is providing -16.2V and +21.5V.

Besides being far beyond double, there is quite a difference.

I have never worked with charge pumps before, so I am unsure if this is to be expected, or did I do something wrong. I have went over my circuit several times and it looks fine to me.

UPDATE

Read the accepted answer for the solution. With tantalums, I now achieve -12v and +13v from the unregulated circuit under 15mA load on each rail using a 6v source. Entirely sufficient for my needs. Below is the final layout I used on perfboard (in case anyone wants to use it!)


texts:
I was answering probably a simple questions and I dont match the same result using the different method to solve that circuit below:

My 2 resolutions:

KVL:

\$\frac{30-V}{4}+2\cdot I_x-\frac{V}{6} = 0\$

\$I_x = \frac{30-V}{4} \Rightarrow 90-3V + 180-6V -V = 0\Rightarrow 10V = 270 \,\,\therefore\,\, \boxed{V = 27 V} \$

KCL:

\$ 30 = 4\cdot I_a + (I_a - I_b)\cdot 6\$

since: \$ I_a = I_x\$ and \$I_b = -2 \cdot I_x\$

then,

\$ 30 = 4Ix + 3I_x \cdot 6 \Rightarrow 30 = 22I_x\Rightarrow I_x = 30/22\$

\$ V = 30 - 4.I_x = 30 - 120/22 \Rightarrow \boxed{V \approx 24.5 V}\$

So, what I am missing on my analysis specially on KCL method?


texts: Modifying Interrupt Vector Table of Atmega32

texts:
A project that I'm working on involves a cycle accurate interrupt service routine. This routine is written in AVR Assembly where I just wrote:

.org oc1aadr
rjmp INTRP

(to set up the IVT)
And it worked perfectly well. However I had to use both C and assembly for this project, so I switched to GCC and after looking up some documentation, found that I just have to write the routine with a label:

TIMER1_COMPA_vect:

Now the interrupt is working fine too, but the thing is that it now takes 3 cycles to enter into the ISR. On looking up the disassembler code, I saw that the IVT is like this:

+00000000:   940C002A    JMP     0x0000002A       Jump
+00000002:   940C0047    JMP     0x00000047       Jump
+00000004:   940C0047    JMP     0x00000047       Jump
+00000006:   940C0047    JMP     0x00000047       Jump
+00000008:   940C0047    JMP     0x00000047       Jump
+0000000A:   940C0047    JMP     0x00000047       Jump
+0000000C:   940C0047    JMP     0x00000047       Jump
+0000000E:   940C0049    JMP     0x00000049       Jump
+00000010:   940C0047    JMP     0x00000047       Jump

The JMP instruction takes 3 cycles unlike RJMP, which takes only 2. I've tried writing:

.org 0x0E
rjmp INTRP

But still it won't work, I've also tried writing (.section .init0) before .org, but still no effect. So, is there any way I can change the instruction to RJMP?
Note: Only the interrupt routine is written in assembly.

For my second question: Is there any difference in the clock cycles required by an instruction when using different compilers/assemblers?
MY entire routine takes 3 clock cycles less using GCC compared to AVR Assembler. I don't know whether GCC depends on AVR Assembler or not, but is there a possibility of this happening? (I'm asking this based on the AVR simulator output).


texts: How do you check your schematic before passing to layout

texts:
I am working with Altium.

What verification do you particularly do when going from schematic to layout in terms of electronic and in terms of capture ?


texts: If A = 1 and B = 1 what is the output of the logic circuit below?

texts:
I have labelled the transistors Q,R,S,T,U,V,W,X.

Suppose A = 1, B = 1.

Q will be open.

R will be closed.

S will be open.

W will be closed.

I am not sure about T. Since S is open, that means T recieves a 0 input, and since it is a not-transistor, is will instead be closed? From W's input, I think U is open, and V is closed. Then there is not a direct path from Vcc to X output, so I think the output is 0. Is this correct?


texts:
I have a PCB that I put together and it works pretty well so far. My big issue now is I would like to power it from the cigarette lighter on my airplane.

The cigarette lighter inside a car sits on a somewhat "well-regulated" bus. But, inside a 1975 Cessna 172, the cig lighter sits on a bus that is a very unclean power bus. There are strobe lights going off, the avionics put surges on the bus. The power bus in the airplane is pretty basic.

My circuit uses an Analog Devices LT8640S step-down converter to take a wide range of power and regulate it down to 5V. It works well.  I've been powering this from my bench-top power supply.

But, I'm concerned about how to properly protect my circuit from the main power bus. I'm thinking a crowbar circuit to protect against an over-voltage situation on my side would be helpful.

But, how does on handle decoupling noise and other transients on the bus before they get to my step-down converter?


texts: Unusual opamp topology: driving a dummy load and using supply currents to drive common-source

texts:
Instead of having the output of the op-amp drive some subsequent stages, it uses a dummy resistive load, supply currents to the opamp are cascoded and drive the subsequent stages in a push-pull fashion. The real load is the 4.7u cap. Is this op-amp topology common? Does it have a name? What are the advantages/disadvantages of doing this?

The other question was about the feedback path specifically. This one is about the topology of using supply currents to drive amplification stages. Yes it's the same circuit, but completely different questions.


texts: How to place MOV when you have a center tapped transformer 127V 220V

texts:
I am building a circuit that gets power from AC. I have a center tapped 220V transformer, so I added a switch for 220V or 110V (the three wire sockets)
I added two MOVs, one S20K230 for 220V and a S20K140 for 127V, but when the circuit is running with 220V, the S20K140 will have voltage across it from the central tap, I don't think that is a problem since the voltage will be below the limit, but is this ok? I never worked with AC Mains before, thanks and sorry for the silly question.


texts: Why do my push-pull driver drains ring so much?

texts:
I have read What is killing my MOSFETs which seems to present a similar circuit to mine (my secondary is center tapped as well and has 2 high-speed diodes rectifying into a 10R / 400uF load)

The transformer is 12:1, my power supply voltage is between 10v and 25v at ~300mA.

The transistors are heating due to what I believe is avalanche breakdown. I have used 50V devices and the scope shot shows ~200V devices. In each case, DS voltage rings up to breakdown (if there is sufficient energy in the circuit). I would like to push 10 and ideally 100W through this circuit. I realize the breadboard is not feasible for a 100W design, but it should do 10.

The ringing is at 2.x MHz. The power supply input capacitors are not low-esr or particularly high valued.


texts:
I want to model phase noise. Code below shows how I am adding phase noise in the signal. However, i am not getting correct output. That means, the signal sprectrum shoud be spreading in the frequency domain however, its not changing the phase of the signal. please, anyone can tell me how to model phase noise.

sigma = 0.5;
t = 0:0.01:1;
sig  = cos(2*pi*4*t);                                                        % original signal
A = sigma *randn(1,length(t));                                          % standard deviation of phase noise
sig2 = (A) .* cos(2*pi*4*t + sigma*randn(1,length(t)));           % signal with phase noise & amplitud4e noise
figure,plot(t,sig,'r',t,sig2, 'b');
figure, plot(abs(fft(sig,10*length(sig))));    %%% takin absolute value of fft and zero padding
figure, plot(abs(fft(sig2,10*length(sig2))));
return


texts: Using a PIC to perform switch on and timed shutdowns in automotive environment

texts:
I would like to build a circuit to perform a timed shutdown, based on logic inputs from headlamp wires and ignition wires.

I have decided on PIC10F200 (datasheet)  to perform the logic.

I also have many spare 7805 linear regulators, so thought I'd use those to perform 12V->5V regulation before connecting directly to PIC pins configured as inputs.  Is this a terrible idea?  I have added pulldown resistors so that the PIC input pins can read defined values.

Using Fritzing, i've created a circuit:

I'm still tinkering at the moment, and this being my first PIC circuit, I want to make sure I can avoid all the possible traps when working in an environment like this.

So basically, is the circuit okay, or have I overlooked things?

All and any help appreciated, please go easy on me.  I'm new!

Update:

Following advice from Olin and Wouter, I now have this:

Is this ok?

Olin says making use of the weak pullups on the PIC could save on component count, yhis is how i've interpreted him:

This works in the simulator, but I've no idea if my pile of BC547 are suitable!

I also don't know which to choose, or why?

Thanks again guys.


texts: MT3608 DC-DC converters in parallel with common output

texts:
I'm thinking to use two DC-DC MT3608 converters in parallel with a single potentiometer.

Has anyone experience with these converters?, Any advice?.

Thanks


texts: How to decrease the sensitivity of a sensor (accelerometer)

texts: The accelerometer in this kit are very sensitive. Even a small touch changes the values very rapidly. I want to lower the sensitivity of the sensor. What is the way of doing this?


texts: Digital Optical Volume Control with LED and photoresistor (light to seperate circuits, optical pot)

texts:
Story

At first, I know the existence of a digital pot. 'Problem' is you need an IC to achieve this and also want to keep the circuits completly separated (and simple). Also want to use it with an Arduino audio project without external IC (got already a MCU that can do the 'settings' job). So I came up with the idea to use a led and a photoresistor to seperate circuits and avoid fixed 'digital' steps, just like a normal pot resistor, keep it smooth and natural but without the analog fail/aging problems.

Made two (quick!) drafts, one with simple hardware like an opacity wheel and one with use of an Arduino:

I figure out the basics of this idea using light to control volume is not a new one, found this:
http://www.tortugaaudio.com/evolution-of-ldr-volume-control/
And the Lightspeed Passive Attenuator:
http://diyaudioprojects.com/Solid/DIY-Lightspeed-Passive-Attenuator/

Try to find the component they are using, a led with a photoresistor but could not find it. I started to experiment with existing components, like this one (made an experimental board of an old canon printer, a board with two optical sensors, cut in half and added to audio sockets) to figure out it will work anyway:

The experiment succeed really well, very intresting to see it is actually working. The volume reduces when you put an object between the optical sensors or limit voltage input does the same. Except ...... one side of the amplitude is chopped off. Because there are only four pins, the receiver could be an opto-resistor, however it seems to be a diode? Just listen to this soundtrack what happend:

Wave file: https://drive.google.com/file/d/0B2l-eQoHefcVdXRlUkM1bXJYek0/view?usp=sharing

Wave file (left+right combined): https://drive.google.com/file/d/0B2l-eQoHefcVVzZ3aWVrZ0hMVjg/view?usp=sharing

Question

Althought I can make the component myself by replacing the opto-resistor-diode with a photosensor I wonder if these components are available somewhere. Because available space is an issue, it would be handy it is a compact component (with four legs) sized like a opto-coupler for example. Any ideas? Any partnumbers?


texts: What kind of failures can be explained by this fix?

texts:
My Dell PowerConnect 2324 is normally plugged in 24/7. At some point it stopped working (no connectivity, power light out) and I disconnected it from the network and power. Recently I opened it up and started to test it with a digital multimeter:

Initially I checked the 5V supply directly from the AC converter. This was accurate within 5% but the power light was still off.

There are three circles printed on the board (bottom semicircle shaded white, top half empty/PCB) with a positive and ground contact. These look like they could be test points, so I next measured voltage at these points. Initially all three showed 0.00V. I thought this was odd because one of them was very close to the power connection. I tried again at the closest circle to the power connector and saw a flicker of 5V decreasing quickly to around 3V and then 0V again. I tried the other two circles and found 0V again. Back to the first one: steady 5V. Second one: steady 3.33V; third: steady 2.5V. I looked at the front and the power light was on. The device now functions properly again:

Can someone explain what could have happened and how it was fixed?


texts: How to eliminate the wrong direction torque of stepper motor

texts:
I want to eliminate the wrong direction torque of stepper motor during super fast decelerating.

The wrong direction torque is that: When you suddenly decelerate the input pulses of stepper motor's controller, and if the load on the shaft exceeds the maximum electrical torque, the stepper motor will "slip"(lost sync with the drive circuit). Once the motor has rotated past the current "step"(the motor slips), the current driven into the coils will try to push the rotator ahead toward the next step, at this time the torque is in the wrong direction as you want to decelerate the motor. If the motor is turning rapidly, the torque in the wrong direction may cancel out some of the effect of torque that would be in the right direction(which is to decelerate the motor), so you should not suddenly decelerate the stepper motor controller's input pulses.

But I think with positional feedback, the controller can eliminate this wrong direction torque of the stepper motor in super fast decelerating.

The positional feedback can tell the controller the absolute position of the rotator. Once the motor has rotated past the current "step"(the motor has slipped), the controller can change the current driven into the coils so it won't push the rotator ahead toward the next step, it can only continue to stop the rotator when it has passed the so called "current step", it will continue to try to stop the rotator with its electrical torque even the motor has slipped.

There are many closed-loop stepper motor in the market, the vendors didn't explain the details of operating principle, only said:

Due to closed loop control, the ES series easy servo systems can always implement 100% torque of the motor, and do not need the huge 50% torque reservation in normal open-loop stepper systems.
The built-in rotor position detection sensor constantly monitors the motor movement. If synchronism is about to be lost, closed loop control is used, eliminating concern over loss of steps.

Can those closed-loop stepper motor in the market eliminate the wrong direction torque during super fast decelerating?


texts: Why does LED dim when adding second LED in parallel with a single resistor

texts:
If I have a led hooked up to a 12v DC supply with a single resistor it runs nicely as you would expect. If I add a second LED in parallel the brightness drops, slightly, the brightness on both is (to my eye at least equal). My antiquated primary school knowledge tells me in parallel they should draw more current and stay the same brightness.

What's more if I add any number of additional LEDs the brightness doesn't drop again, its only after the second one.

I've found some questions and answers that indicate that running multiple LEDs with a single resistor isn't a good idea because the current will be different on each LED and that makes sense. However I'm keen to understand what is actually happening to cause the LEDs to dim.

What is wrong with my understanding of bulbs in series vs in parallel and why does a second bulb cause the brightness to drop and additional bulbs not?


texts: I'm using the high side of an IR2110 driver. If I set the duty cycle to 100% the circuit burns out, I haven't how can I calculate the max duty cycle for the driver in a given circuit?


texts: I have a Board and need help using it. Wlan module. model K30356

texts:
Can anyone help me with this board? I pulled it from a cannon computer and correct me if I'm wrong from the very little time I have spent on this but I believe it's a wifi module and I'm wanting to hook it up to an Arduino.
Any ideas or ways I can find out info on it?


texts: Use of Field Programmable Analog Arrays for analog computation

texts: From what I have read it seems that FPAA could provide a way to design a "programmable" analog computer, but are there any online resources on how to implement such a system?


texts:
I had a bug (yes, a literal bug) decide it would be a good idea to crawl inside my printer and short itself across two pins on my printer's power supply board.

I have pulled the board in the hopes of repairing it and I am stuck trying to identify a particular IC so I can replace it.

Could anyone identify the chip and/or suggest an alternative that I could use in place to repair the board?

Printer is a Brother HL-2135W. Board is a Delta EDPS-52BF. Brother part number for the board is LV0848001. I have managed to find a circuit diagram for a very similar board (came from a service manual for the Brother DCP7055 - see below).

Visible markings on the mystery IC are:

DAP?
PVA?
G?

'?' denotes obscured letter/s - unsure how many are obscured.

Images and schematic in link below. Relevant component number is IC31.


texts: Why does the amplitude of a filtered signal decrease when higher order FIR filter is used?

texts:
I am having a signal of frequency range 0-2 Hz. I want to remove baseline wandering (very low frequency drift) for which I found the cut off frequency — 0.0245 Hz — and a FIR filter of order 91. The output signal has no baseline but the amplitude of the output signal is reduced.

Is this common? If yes, what could be the reason?


texts: Why is a 0.001uF capacitor in parallel with the base-emitter of this transistors?

texts: I am trying to analyze a digital circuit. In this circuit, there are several BJT transistors, some for back-light LED driving, some for switching and etc. Almost all of transistor has a 1nF MLCC capacitor connected from base to GND. It seems they are decoupling capacitor, but I am not sure. I really need a reason for this type of design. I asked some people. One of them said this capacitor protects the base of transistor, specially for preventing of unknown switch operating or BCI protecting. (Highlighted capacitors in below picture)


texts: VL53L1X Time of flight sensor field of view implications

texts:
VL53L1X is a Time of Flight sensor, it measures distance via pulsed laser or so I understand. But upon reading its specs it has a field of view of max 27 degrees which is quite confusing for me. I thought it uses laser should only read objects that are relatively straight ahead, it is even has a wider field of view than some ultrasonic sensor.

Does this mean that I can get the angle of the location of the object? It would be great if that were the case or I can only get the distance and I won't be able to identify where in the 27 degrees is the object.

This line:

The VL53L1X also features a programmable region of interest (ROI), so the full field of view can be reduced or divided into multiple zones

I don't understand what this line implies

I was planning to buy 3 of them so I can arrange them in a straight line and be able to track an object.


texts: Addressable ICs similar to WS2811 for monochrome LED

texts:
For my home decoration, i want to individually address the led strings . Since one string is of a single color, i need an ic with serial communication similar to WS2811 ic but monochrome to control them.
I'll use a mosfet or whatever required driven by that .


texts: What does 6kV , 5MW 90% efficiency at full load with 0.9 Power Factor lagging represent for a motor?

texts:
I am confused with I see such a statement like the following statetment:
 Motor with 6kV , 5MW 90% efficiency at full load with 0.9 Power Factor lagging.

Could anyone explain it in simple words ?


texts: Why do chips not always "meet the grade"?

texts: During manufacture, integrated circuits are tested at varying frequencies and temperatures to categorise them into speed grades. However, why don't all ICs come out the same and work the same? They all come from the same photolithographic mask, right? Am I missing something?


texts: How can I build a battery load tester that switches between 0.8 and 2.0 ohms?

texts:
I would like to build a load tester that switches: 2 seconds at 2.0 ohms and 1 second at 0.8 ohms and back to 2.0 ohms to repeat.

I gather that I can have a circuit with two resistors and a switch between them or between one and both.

What kind of device can switch in this way?


texts:
As I tried to derive the transfer function of the boost converter(peak current mode control) in CCM and DCM as Vout(s)/Verr(s) using the CC-PWM switch model accordingly to the book of Pr.Christophe Basso, I am currently facing some issues regarding the PWM switch model in Current mode. because in the Voltage mode I can derive the equations however when it comes to the current mode I cannot really derive it as I am completely confused about the PWM switch itself how is it derived.
If I want to structure my questions, I will start first by showing you the model on the picture of the Pr.Christophe Basso ;

and now the transfer function I want to get in:

and:

my questions are:
as he derived his PWM switch model; I am wondering where is the term Verr and instead I find the term Vc which I don#t understand how he derived it?
How do I replace the Vap and Vcp here, it seems to me for example in boost converter I have to use just the average value?

in the reference given, I checked the Dissertation Of Dr.Cuk but I found out that he was using state space machine and I want to learn to do it in PWM switch model for current control mode.

I have uploaded the small signal PWM switch model for boost converter as below

best regards,
Yaakov


texts: What is the purpose of negative frequencies?

texts:
Below you can see the frequency spectrum of a square pulse. But what exactly is the purpose of the negative frequencies?
Lets say I have a square pulse with a width of 10ns (f=100MHz) and I want to pass it through an opamp, I want most of the energy to be preserved, so I will look for an opamp with a good bandwidth . Lets say the op amp has a bandwidth of 100Mhz. Does this mean I get the whole energy between -100MHz to 100MHz or just the energy between 0 and 100MHz?
It is probably a dumb question but I want to be sure.


texts: Flyback NE555N driver and mosfet overheat

texts:
I have built a small and very simple flyback SMPS based on NE555N IC. The circuit
exactly I did built from is shown below:

It works nicely for small loads.

However I have some issues with it:

Despite NE555N datasheet says output (pin 3) voltage is only about 2 volts lower than Vcc, I have only +6.3v on pin 3. Is it a digital multimeter misreading?
The MOSFET used there is IRF3205, but currents beyond 6-7A force it to heat up, and 10A (with 100-110 Watts on secondary) even more (heatsink is ready to boil water)
Some answers here and some sources on the web (and this circuit) recommend using logic level mosfets. Can I avoid using them (probably until I get some of them)? Will logic
level mosfets work perfectly compared to regular ones I using now if their properties (Vdss, Id, Rds(on), Qg) will be relatively same?

Impulse transformer was salvaged from old dead 200W ATX SMPS, its sizes are (WxHxD) 36x42x16 mm. Its main problem that it's cracked (but still works without noises).
Primary has 8 turns of 1mm wire, secondary has 160 turns of 0.3mm wire; another secondary has 3 turns for 5 volts source (also 1mm wire).

Heatsink sizes are 32x39x14 mm probably aluminum (also from old hardware). Larger heatsink is avoidable because of limited space where circuit will be stored.

Supply is 12V 19Ah Lead-acid battery pack.

I strive to minimize thermal losses on this circuit, so I am seeking ways to minimize power losses on MOSFET.

Does MOSFET overheat due to undervoltage on gate (hence not fully opened) or cracked transformer core? Do I need some other enhancements for this circuit?


texts: How to create an embeded system for LCD GUI design? How to choose an MCU?

texts:
Okay so here is my exact problem.... I want to design an embedded system with a micro controller at it's heart that I can use to control various peripherals all powered by a batter that can be plugged in and charged. To me, that is the "simple" part. Now the problem is, I want to be able to connect a nice LCD screen, say 3-4 inches viewing size, and create a NICE GUI.  I've already been able to hook up a simple 16x2 LCD and control it nicely with a micro controller, but I don't want my projects to feel like they are out of the early 90's! I am used to nice graphical user interfaces.

I've come to the conclusion that the best way of doing this would be to use a Linux embedded system. The issue is, how do you go about designing something like that? Are there any helpful guides? Looking at other answers people suggest using processors like this one. I've also seen this chip that helps simplify GUI design, but the software costs 500$!! I don't want to spend a fortune but I DO want to be able to design stuff like this into a CUSTOM embedded system. I do not want to just go out a Raspberry Pi for this (I already have one anyway)...

So what solutions exist for a problem like this and are these any good resources with tips??


texts: Does anybody recognize this automotive connector?

texts:
I'm trying to repair a wiring harness, and I'd rather pin and install a connector than splice into a junkyard pigtail.  Does anyone recognize this and know where to find them?  There's some serious connector-identifying wizards here.

edit:

I know what the usage of the connector is (camshaft for a second-gen Ford Focus).  I'm trying to make my own pigtail for it, so I'll need a blank plug and uncrimped pins.  That's what I'm having trouble finding.


texts: Solder to positive end. It stays for a second and unsticks from the board. What can I do? I'm nervous about burning the board.


texts: Polarity Question for Powered Home Subwoofer

texts:
I picked up a powered home subwoofer at a garage sale.  It did not have its power adaptor.  All it shows is 12V DC (by the symbol) 2.5A.  But it does not show the polarity anywhere on the subwoofer.  Is there any way a rookie can figure out what the polarity is?
The subwoofer is a Granger Bessel brand.  It was probably part of a home theater setup, since it does not show a model number on the subwoofer.
Thanks for any suggestions you can offer.  If I can't find out anything, I will just try + polarity.  It was just $10, so no real loss if I smoke it.


texts:
Can I power the Redboard Arduino board (basicly the same as Arduino Uno) from the + 12 V output from my ATX power supply? The specifications says the input voltage needs to be at least 7 V.

Is there anything I haven't thought of?


texts: Large button to power on/off items for disabled son

texts:
My husband and I have a disabled son.  We are going to build him a sensory panel wall.  We would like to have large buttons that he can push to power on/off moving toys/lights/etc.  However, we cannot find any that do this.  We have tried this:
https://www.amazon.com/gp/product/B012E8D7XW/ref=ox_sc_sfl_title_18?ie=UTF8&psc=1&smid=A2M1GBFESN1F7H
But the button is too small and hard to push (he has spastic quad CP with dystonic and choreathetosis movements.) The target has to be large and easy.
My husband also tried making a wooden round spring piece over it. It is very difficult for our son to put enough pressure to turn it on.

He needs something like this with extension cord:
https://www.amazon.com/gp/product/B00CYGTH9I/ref=ask_ql_qh_dp_hza
However, this button is momentary. It only sends power to it while he is pushing it.  We need a big button like this that will turn the power on once pushed.  Second push would turn it off.  OR if it automatically went off after a minute or two of turning it on, that would be wonderful.

I searched the internet yesterday for hours and found nothing.  Any ideas/help would be greatly appreciated!!


texts: Why break a PCB trace plane into multiple parallel traces?

texts:
I have a vehicle battery maintainer (20A) that was overloaded and stopped working. On inspection I found a group of traces blown, however all the traces are connected at both ends. It looks like a plane that was divided into 4 traces with the coating removed and solder spread across the traces. There are other traces like these in the surrounding area.

I could easily bridge these point with wires, but my Question is why would they design the board like this? Is it done for RF cancelling or as a safety precaution in case of overload (such as what happened)?

EDIT: It looks like the traces are from the transformer to a diode bridge and a coil.


texts: Converting a galvanometer into an Ammeter

texts:
I am 12th grader just in case.
Anyway, I do understand how a galvanometer is converted into an ammeter but it's logic doesn't seem to add up.
This is what I know so far.
Galvanometer is too sensitive therefore is modified to be used to measure current instead of only detect it.
The current for full scale deflection through it is lets say Ig.
Its resistance, Rg.
Now, a shunt resistance is added in parallel. The maximum current that the ammeter produced can measure is lets say I and shunt resistance is Rs.
Now Rs is of such a value that Ig passes through the galvanometer and the remaining current (I-Ig) passes through the shunt resistance.
I understand why the shunt resistance has to be of a smaller value and the resistance of voltmeter has to be of a really greater value but what I fail to comprehend is how can we successfully measure current when the deflection of the needle is going to always be maximum due to the passage of Ig current (which is the current that causes maximum deflection). Ig is always passing through the galvanometer so how does the ammeter really work and give us current in amperes?


texts: A little clarification regarding voltages, and "real" current movement

texts:
To my understanding, the voltage supplies the potential, and free electrons are taken from ground? This makes somewhat sense to me, for example if something has a "positive" charge then it will attract negative electrons to it - which works out, however I am unsure if negative charge (relative to one specific point) means more free electrons.

Another question, so mains line provides the potential of 120/240VAC (ignoring AC) and the current does not actually "come" from it, only from ground?

This subject seems to be just taught quickly, it would be very nice to have an understanding that "works" in all aspects I throw at it.


texts: Watching some of the restoration videos of old tube/valve devices by Mr. Carlson's Lab, I've heard him describe a circuit element called a "reactor" on several occasions - for instance here, where the circuit includes a "saturable reactor". So far, I have not come across a component of that name. What is a reactor, how does it work and what is it used for?


texts:
I am using a WWVB receiver for a project I am working on. The ferrite antenna that the receiver came with has terrible gain and I want to make one that is several times larger.

I know how to make a loopstick antenna resonant for a frequency I want...

What I am concerned about is if the receiver IC has an input impedance that the antenna needs to match. I would assume the inputs just feed into an opamp or a transistor and it doesn't matter.

I remember in my Antenna class constantly talking about impedance matching but I'm pretty sure that was in regards to matching to a coax feed line.

Thanks


texts: How to calculate right current to charge 2 cell series 8.4V 4000mAh battery lipo?

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I have 4000mAh 2 cell series 8.4V lipo battery

I need make a custom charger I am thinking of using LT3650-8.4 2A charging Ic

if I set 2A
how long will it take to charge this fully /if timer is disabled timer?

is it (1st cell 4000mAh  + 2nd cell 4000mAh)  / 2000mA = 4h ?

if I set 1A
how long will it take to charge this fully /if timer is disabled timer?

is it (1st cell 4000mAh  + 2nd cell 4000mAh)  / 1000mA = 8h ?

What is the maximum capacity of 2 cell battery this IC can charge properly? without a timer?

as I know we have to manage the full charge cycle (5.6-8.4) within 4h at least, so to charge it within 4h with the set current to 2A as in the figure, how long will it take to fully charge a 4000mAH 2 cell battery?

I think everybody has misunderstood the question I am asking. now everybody should be able to understand the question


texts: Has anyone had any succes with converting a ST link v2 to a Jlink using the software that Segger provides? I have not had any success, even with using instructions they provided and was wondering if any one had any succuess/ guidance.


texts: Finding solder pad sizes for capacitors / resistors based on density level

texts:
I found out that there are differences in the sizes of soldering pads for SMD components depending on the required reliability and available space.

For resistors (805) I found good sizes (datasheet from Vishay).

Now I'm trying to find sizes for capacitors (805). In datasheets I did not find the size difference depending on the Density level.

Tell me, is there a table where recommended sizes for various SMD components are indicated depending on the density level? Or a special library for Eagle.

Thanks!