texts: Power of supplied by generator when it is loading

texts: I have a cummins generator which is having capacity in name plate as 803 kw. While running the load test, each phase current shows 153 A, 53 A, 120 A and neutral current 27 A or something. How can i calculate the power supplied by the generator using equation. Should i take the max current and use 1.73 x Vl x Il x pf or should i sum up all current and find. Please help with the equation, like which current i should take as I. This meter is showing phase current or line current. If in case of phase current what should i do or in case of line current what should i do?


texts: Differential pair impedance vs temperature

texts:
Does anyone know if the differential impedance, say of a PCIe bus, can be affected by really cold temperature, like -50 °C? I have a wifi card that does not work from -30 °C and colder. I am wondering if somehow the differential impedance of the bus is changing from the temperature.

This is a 12 layer board, 1/2oz copper, FR-4 and the differential pair traces are on the top later.


texts: How long will 12V DC 8 Amps power supply work on 13 Amps load

texts:
I know that I should use 12V DC and at least 13 Amps.

And that I can use power supply with even more amps.

But I am interested if I use only 8 Amps, what I have available, how long it will last ?

Will it be like in minutes days, weeks, months ?


texts: How to dim one of these cheap 5mW laser modules?

texts:
I used to have an old 3x LR44 lithium cell laser pointer for presentations. With the batteries slowly dying, the outputted beam also went dimmer.
Recently I bought one of these cheap 650nm laser modules off eBay. They seem to be designed to work with 3 AA/AAA batteries connected as they are rated for 3-6V. I tried and connected 4 batteries and got a very bright beam @ ~4.68V. I then reduced batteries to 2 and surprisingly, to my estimate, got an equally bright beam @ 3.12V. Then, with only one battery @ ~1.56V, I got no output at all.
From reading and my guess, I now assume that in these metal housings is a driver board, probably similar to this. My second guess is that the Chinese manufacturers build (and sell!) these laser diode modules  only with such drivers primarily to make really sure that overpowering the diode doesn't result in an output over 5mW (even for a fraction of a second, until it would burn out) to protect users like me from stupid accidents.
For my application, the outputted beam is too bright at all tried voltages. I'd like to have the beam more in the 1mW brightness range - I say 1mW as I assume that's extra safe.
(FYI: I assume 5mW lasers are "only mildly dangerous" and 1mW lasers "quite safe" - but correct me if I'm wrong - I'm not going to willingly look directly into them either.)
So, please, can someone explain me why lowering the power alone doesn't work?
Bonus question: I found that using PWM modulation might be the solution, where I "switch a fixed voltage on and off very quickly" instead of "lowering the actual voltage". That would result in a very frequent (thus unnoticeable for the human eye) flicker. (Using a 3 or 5 volt Arduino for that.) Will the installed driver accept that? (Is this driver maybe actually designed to be driven by a PWM supply? ..or will it blow up?) And will that make the laser beam appear less bright? And be safer?
Update:
Using the collected knowledge from the answers, I was able to dim the module: My mistake was: I was only lowering voltage! With two AA batteries connected (measured 3.12V) and a 70 Ohm resistor (to limit current to the module), the beam appears severely dimmed. No PWM required. A 60 Ohm resistor yields my required output (visible, but not irritatingly bright). I can't say what laser wattage equivalent that is.
WARNING notice: 5 mW lasers (Class IIIR or IIIa) are dangerous under bad circumstances! Even 1mW (Class 2) lasers with a focused beam into a non-blinking eye can cause permanent damage over several feet away. Compare this chart or this summary.
Connecting the laser module without a resistor was probably dangerous. A laser diode without driver would've been even more. Without the resistor, the module is able to draw a high current (compare) and may output the full 5mW which may not be what you want. Luckily no direct reflection happened, the beam is not very focused on the module I own and it is spread into a line. So do get a lower powered module (you probably do not need > 1mW, sadly Chinese sellers don't offer them like these 5mW ones) or dim the output if you're operating these lasers with people around! Does it need to be laser? Consider projecting with common LEDs and lenses.


texts: Using unsuitable relay in transistor switching circuit?

texts:
I'm trying to make use of this relay which operates on 5 volts, in a circuit powered by +9 volts. I'm kind of new to electronics, so bare with me. The schematic can be seen on the image below:

According to page 3 of the datasheet the maximum voltage the relay can handle is about 6.5 volts, if I understood correctly.

I have 3 ideas on how to solve this:

Using a voltage divider to divide V. How would I go about choosing the resistor values (kOhms, MOhms..)? Do I need to take care of how big the current through the relay's coil is?
Adding a few basic crystal diodes antiparallel to the diode D11 to drop the voltage, but this solution seems a bit clunky. (edit, meant to say: in series with the relay's coil, but differently oriented than the diode D11)
Using a 7805 regulator, by simply connecting its pins as follows: $ V_{in} = V$, $V_{out}$ to the upper side of the coil, and GND to GND. Do I need to take care of anything when using this solution, or am I safe to just plop i into my circuit mindlessly?

If you have any better or more elegant solutions, please share them with me. And why are my Tex edits not showing up correctly?


texts:
Why function call to clogb2 is not being executed in the following code. I don't get any compilation errors but still parameter adder_width is not updated with the value from clogb2. In fact, that function doesn't return any value.

See http://www.edaplayground.com/x/Pxc.

module ram_model ();

   parameter ram_depth = 8;
   localparam adder_width = clogb2(ram_depth);
   initial begin
      $dumpfile("dump.vcd");
      $dumpvars(1);
      $monitor("%d",adder_width);
   end

   function integer clogb2;
      input depth;
      integer i,result;
      begin
         for (i = 0; 2**(i) < depth; i = i + 1)
            result = i + 1;
         clogb2 = result;
      end
   endfunction

endmodule


texts: LM78xx Reverse Polarity and Reverse Bias

texts:
I'm building a circuit that will use a LM7805 and LM7812 to produce 5VDC and 12VDC respectively, with the input power being ~16VDC from an external wall wart.

I already fried one of each regulator because I'm apparently not capable of keeping track of polarity.

I figure I might as well prevent that. I see in the datasheets that I can use an 1N4007 diode across the LM7812 for reverse-bias protection, which I understand is intended for transient states basically during shutdown.

I also read that I can use a Schottkey diode for reverse polarity (e.g., if I connect the p/s incorrectly again) protection.

Can I do both? Is there anything I need to know about selecting either the regular diode or the Schottkey? Overall, I'm sizing the circuit to handle ~1A of 12VDC and <100mA of 5VDC (just enough to power an ATTiny and one DO). I've literally never bought a diode before, so do I just find a Schottkey diode rated >20V and 1A then call it a day? I don't believe I care about forward voltage drop in my application...anything else?

simulate this circuit – Schematic created using CircuitLab


texts:
I have a ticketing device with an ARM9 CPU, more specifically a NS9750 module.
In the datasheet, its operating grades/ambient temperatures are listed as follows:

125 MHz: 0 to 70ºC
162 MHz: -40 to +85ºC
200 MHz: 0 to 70ºC

Why is the operating range much wider at 162MHz?
If it were linear, I would guess it has to do with the frequency of the crystal changing according to temperature. But this? No clue.

Also, (this is important) what would happen if I were to run it at 200MHz in sub-zero ambient temperatures (up to -10ºC)? Worst case scenario.


texts: How to reduce power consumption in level shifter

texts:
I need to level shift a 3.3v digital signal to 5.8v at around 1MHz. The circuit below works but the power consumption is very high. Can anyone suggest a modification which will still allow the bandwidth but bring the power consumption down?

Adding resistors to the PFET VCC input and NFET GND output does reduce it but I can't find the right balance between slew rate and consumption.

I've looked at the internals of some off the shelf level shifters but am struggling to understand how they manage it.


texts: Criteria behind selecting pwm frequency for speed control of a dc motor?

texts:
I'm working on a speed control circuit for a brushed dc motor (24v, 500rpm, 2A, 4kgcm).

The main components that I plan to use are PIC16f873, 4n25 optocoupler, IRFZ44N MOSFET, BY 500 - 800 diode(for free wheeling).

What is the criteria behind choosing the PWM frequency?
What are the effects of very high & very low PWM frequencies on the system?
What are the drawbacks and improvements to be made in the hardware provided here?


texts: Why do I get gibrish output to the serial monitor of my arduino mega 2560?

texts:
All -

Why does my Arduino 2560 report text that looks like this:

I©ä

I©ä

!11<]=I1)!11<]=I1)!11<]=I1!11<]=I1)!11<]=I1©ä
é
©ä

I©ä

I©ä

I©ä

I©

Every time I execute "spi_dev_test" from my raspberry pi?

I have been trying to follow the instructions on this website :

http://mitchtech.net/raspberry-pi-arduino-spi/

But these instructions are for an Arduino Uno whereas I am using an Arduino 2560.

I looked up documentation for the 2560 here:

http://www.jameco.com/Jameco/Products/ProdDS/2121113.pdf

and it has indicated the SPI pins are SPI: 50 (MISO), 51 (MOSI), 52 (SCK), 53 (SS).

I wired them like so:

RaspberryPi-MOSI ======>> 51(MOSI) on 2560

RaspberryPi-MISO ======>> 50(MISO) on 2560

RaspberryPi-CSO  ======>> 52(SCK) on 2560

RaspberryPi-GND  ======>> GND(just next to 53 on 2560).

According to the website I'm supposed to see "HELLO WORLD" output to the Arudino's serial monitor console.

The serial monitor baud rate is 115200.  I have Tools >> Programmer set to "Arduino as ISP" but I've tried all other options with no success.

Would appreciate all / any advise.


texts: Which 18650 battery connection layout is best?

texts:
I am building a 5S6P battery with 18650 cells.
I have limited space so the geometrical layout is constrained.

I can think of 2 "optimal" ways to layout the cells connections but I don't know which is best.

]1

(the drawing only shows the top view of the pack. Left and right are two different connection configurations)

The left layout has more parallel connections, while the right one has more series connections.

Which should be favored and why? (svg file of the drawing can be D/L here https://easyupload.io/1b2eup)


texts: Relays vs. thyristors: What is best for swiching 230 V lights on and off rapidly (~ 5 Hz)?

texts:
I am building my own disco/party lights. 230 V/60 W bulbs, and ideally I would like to switch them on and off at 5 Hz.

I was planning on a simple setup with an Arduino controlling the lights. My original plan was to use relays, more specifically SRD-05VDC-SL_C (datasheet).

It says "Max electrical ON/OFF switching" is 30/minute, which is too slow for what I had in mind. This seems like a common theme with relays, since after all there is a mechanical switch inside.

After some research triacs/gate turn-off thyristors seems like a possible alternative. I had a look at TIC226m (datasheet), but I could not find any max switching rate.

Are these usable for my setup? Any other tips and suggestions are greatly appreciated.


texts: Figuring out the protocol of an SPI device without a datasheet

texts:
I am pondering about interfacing with the iPad Mini 2 touch panel. It seems that no one has successfully done this and/or published anything about it, so I want to take a stab at it.

As far as I understand the device uses a custom touch screen controller IC, meaning I can't get a datasheet for it. Luckily someone at least made a schematic for the device and we can see that the controller seems to talk to the uC through SPI.

Given that I don't know the protocol for the IC would there be some way to find out the protocol by spamming the input and seeing what comes out of the output?

Thank you!


texts:
Is it possible to build an SSR relay circuit for controlling 240VAC (using TRIAC and other components) with NC configuration?
The idea is to keep the AC circuit closed, even when there are failures in the driver side (like a power supply failure or some control side failure)


texts: Problem with simulating LC filter with N channel MOSFET used for PWM

texts:
I'm trying to simulate an LC filter for a PWM output and I'm having problems with MOSFET used for controlling the voltage. I'm using LTSpice for simulation. When I filter the PWM output directly, it works OK, nicely smoothing out voltage. The schematic looks like that in that situation:

simulate this circuit – Schematic created using CircuitLab

When I want to use N channel MOSFET, however, it doesn't work at all, ie. I only see noise on R1 resistor. The schematic in this case looks like that:

simulate this circuit

What's wrong with the second schematic? And if it's not a proper way of handling PWM with MOSFET, how should it work? I saw similar circuits for filtering PWM output in an H-Bridge and it looks like the same situation - in H-Bridge PWM is supplied to lower side MOSFETs.


texts:
I want to build an IoT device which has the primary function of an alarmsystem. The IoT device will be used outside and has to send data to a smartphone app.
If the IoT device is destroyed or the connection is lost the app has to know it. Therefore the IoT device needs to send a small datapackage every minute or so.
I looked for a suitable communication protocol and found NBIoT. In the first column you can see that it says 6MB inclusive data volume 250 SMS inclusive.
My question is does the 250SMS and 6MB count separately, it it possible to only send one byte 6 million times?
Or does it mean I have 250 SMS with a total volume of 6MB?


texts: Having two variable voltage sources, how drive current only from the larger one at every time?

texts:
Suppose I have a circuit I want to power, nominally 6V DC, 500 mA max. The circuit could be modelled as purely resistive (an incandescent bulb, for example).

Let Vx and Vy be two different voltage sources. Each of these sources might oscillate around 6.2V and 0V (just an hypothetical value, meaning "slightly above nominal, but not much").

I would like to drive current only from the highest voltage source at every time, while turning the other off. The switching between them should be transparent to the powered circuit, so as it doesn't get voltage drops.

I have seen similar problems being solved with two diodes, but my proposed circuit could not afford the voltage drop, since most the time the max available voltage would be very near 6V or slightly below it.

I have thought about using an operatioal amplfier, perhaps combined with, say, some Mosfet(s), but I don't know how exactly that would be done, or if this problem has some better solution.

Also I would like a simple solution with "a handful of readily available generic components" instead of some pre-made module.


texts:
I'm designing a Mosfet based switch that uses a low current reed switch to control either 24V or 12V LED strip lighting. Having some issues with the protection circuits. My specifications are as follows:

12-24V DC input
2A Max output current
Reverse polarity protection
Short circuit protection

My current circuit diagram:

Operation as follows:

Input & output at the bottom left, MSTBA4.
Switch connected top right SWT1
Zener D1 ensures the gates are not driven above 15V to protect them from high voltage damage
Q1 is connected in anti-series (drain to ground) and serves as reverse input protection, when reverse input the gate is pulled to ground through R1 turning Q1 off. During normal operation Q1 is turned on and bypasses its internal body diode.
Q2 is the main switch, when the switch closes then Q2 is turned on and connects the load. (Low side switched)
F1 is a Bourns MF-R250 PTC resetable fuse rated 30V 2.5A (trip current 5A) This is a problem as I will explain shortly.
D2 is a Bidirectional TVS diode to absorb any transients.

The design works but there are a few issues I would like to improve, mostly with the current protection. The PTC takes about 5A to trip in a reasonable time, the 'fets are ok with this as they can handle 10A (thermal considerations aside). The problem comes with using a supply with current limiting such as a lab supply. For example with a current limit of 3A on the supply, the input voltage drops before the PTC kicks in. Once the input voltage is low enough the gate voltage on Q2 drops and causes it to leave saturation and enter triode region. Now Q2 starts to dissipate all the energy itself and fails!
When working with a 24V Meanwell PSU this isn't an issue (NES-50-24), however I'm worried about this switch being used with other supplies...

The goal is to keep the cost and complexity as low as possible. I've considered some options:

Add a comparator circuit for undervoltage protection. i.e. when input is <12V, pull Q2 gate to ground. > Problem here is even with hysteresis this causes the circuit to oscillate as the PSU recovers and then trips the protection again.
Add over current protection with a current shunt and small op-amp + comparator to turn Q2 off. Again same problem with oscillation, also increases complexity.

Any suggestions?


texts:
I have problem with PCF8754 component. The PCF8754 is connected to stm32 MCU and PINS A2, A1, A0 are connected to GND. It means, that 7bit address is 0x20. I want read pin state(P0 to P7), and write state(P0, to P7). I use HAL library. Function for write:

HAL_I2C_Mem_Write(&hi2c1, 0x20, MemAddress, 1, &val, 1, 1);

Function for read:

HAL_I2C_Mem_Read(&hi2c1, 0x20, MemAddress, 1, &data, 6, 100);

I don't know MemAddress(register) for read and write data from/to pcf8574.
Where to find it?


texts:
My system use only line and neutral connection from mains (no ground.) Inside this system it is converted to
   5V using SMPS.

My enclosure is metal, I need to ground this enclosure. Since I do not have ground wire coming in my system I am going to connect my circuit return ground (5V return ground) to the enclosure,
   How effective the shield will be on enclosure by doing this.


texts: Volts to decibels using microphone's transfer function

texts:
I'm attempting to convert a voltage signal originating from a microphone to decibels. However, I do not have the "microphone sensitivity" in terms of dBV/Pa which is used in this previous conversion. Instead, I have the microphone conversion factor as sensitivity.

Given the details below, how would I go about converting this voltage to decibels?

Approximate sensitivity: 250mV/Pa

Pre-amp gain setting: 12 dB

Approximate input-referred self-noise Level (bandwidth: 30-50 kHz): 18 dB SPL

Link to microphone


texts: Does a capacitor regulate voltage when power is off?

texts:
I'm playing with a strip of APA102 LEDs.

When VCC is disconnected, but GND, Data, and Clock are left connected, some of the LEDs faintly blink red, which I'm guessing is due to residual power from Data/Clock coming from my microcontroller.

When I add a capacitor however, this completely goes away.

As I understand it, capacitors help regulate power by filling in gaps in voltage should they come up.
But how does it work when there isn't any power flowing?


texts: How to protect my 12 V, 10 A circuit? I am using a fuse but it failed

texts:
simulate this circuit – Schematic created using CircuitLab

My first question and first project.

I have a circuit. It works on 12 volt & 10 amp circuit. I need to protect it from OVER CURRENT & OVER VOLTS. I am using fuse of 10 A rating.

It is suppose to be plugged in car battery to operate.

I thought that fuse is enough. But for some reason, a friend connected it with the jump start battery kit (not regular SLA battery) and it blew up the first component (12V to 5V step down) in line. I thought that it is just a malfunction and I replaced component and again he attached and it blew again.

I think car jump start battery kit is designed to provide high current/voltage in start and that fried my component and fuse is not protecting.

Do you think fuse can help in both amp and current?


texts: Calculating Junction Temp of Switching Regulator

texts:
I was looking at TI web bench to find a regulator, my question is my calculation is correct and if it is why we have different value on webbench.
The IC is TPS565208

P = (Vout - Vin)*Iout   =>  (12-5)*4 = 28

For Switching Regulator P =  (Vout - Vin)*Iout *(1- %Efficiency)  => 28(1-%90) = 2.8 W

Thermal Junction = 95.9C/W X 2.8W = 268.52C

But let take look at Webbench which it said 80.42C

Link to webbench (I dont know if it works)


texts: How can I display a scoreboard on stage for a play?

texts:
I am part of the team who makes the scenery for a theatrical play at school. What is needed to be done is to have a scoreboard in the middle of the room, that one will control from backstage. The scoreboard will have two 3-digit numbers, controlled individually. Whenever the score changes, a little irritating sound should ... sound.

What is the easiest, more efficient and cheapest way to do this? I have found how to make the scoreboard (MANY LEDs, some resistors, transistors, shift registers, an external power-source and an Arduino), but I have almost no idea about the rest. What should I do?

I already have the Arduino, a Basic Stamp, a Raspberry Pi (to play the sounds) and a PIC (PIC16C63, but I have no way of programming it)s and an OlinuXino (Yes I am desperate) lying around. I have 3 weeks to finish it. My budget is very low (30 euros). What is the least minimum I need? Where can I buy it?

If you mention a shop, please take into account that I live in Greece, so the e-shop should ship internationally.

PS
After some researching, I ended up to the following configuration: arduino with scoreboard (shift registers,transistors, LEDs,2 AA batteries and some resistors), connected and controlled by RasPi, via serial (via UART, using a CD4050, because arduino's USB wasn't preferred by me :)). A wifi dongle will be connected to RasPi, which will connect to a wireless network. The raspberry pi will be powered by a 5V 1.5A voltage regulator. A small speaker will be connected to audio jack. All this on the middle of the room. Backstage, there will be a wireless modem, used as a hotspot. Now either I from my android smartphone (connected to the hotspot) via an ssh client, or my teacher from her laptop (same configuration) will control the setup. Now I end up with a software related problem (of how to program everything
Flawlessly), which I will soon ask on the correct stack-exchange. Thank you all for your answers and your effort!!!

PS2 this way I am using many items that I have lying around, so the actual cost is 9 dollars, plus 3 dollars for shipping


texts: Bias tee with very small low cut-off frequency

texts:
I need to measure the noise spectrum of a diode under certain bias.
The noise frequency I am interested is in the range of several Hz to tens or hundreds of kHz. I am thinking of using a bias tee with fairly small low cut-off frequency. But the low cut-off frequencies of bias tees I am looking at are still a little high (for example, in  http://www.picosecond.com/product/category.asp?pd_id=2 the minimum low cut-off frequency is 3.5kHz). I am also thinking of DIY such a bias tee. For example, the post I need to design a Bias-T circuit for a diode laser - help choosing component values discussed how to design a bias tee working around 10MHz with 25kHz bandwidth. However, in my situation, I at least need it to go from hundred Hz to tens of kHz.

My questions is : 1) is there a commercial product available somewhere else that fits my needs? 2) If there is no such commercial product, how to DIY?

Thanks.


texts:
Let's say I need to power a 9v device with an input power source that is either AC or DC and changes almost randomly. Is there any way for me to detect in a circuit when AC changes to DC or vice-versa and have the circuit switch itself? Ideally I'd like to be able to design two circuits that would maintain power to the device constantly regardless of the input type and voltage.

Is there some circuit wizardry I can do that would be a pseudo switch or is it not possible?

I'm more a software guy but I'd like to know a bit more about hardware, hence the almost noobish question.


texts: Place cells certain distance apart using Design compiler (DC)

texts:
So as an example for self-learning, I am trying to place two Flip Flops (FFs) at a certain distance apart.
Except for these two FFs which must be at a certain distance apart, other cells might occupy any place (in between, etc.).
The two FFs are "FSM_reg_3_" and "FSM_reg_4_" in the following example.
In order to achieve that I wrote this TCL code using create_rp_group, but getting this unknown command error shown in the DC.
Does anyone know the reason?


texts: Implementing Bne in MIPS Processor Circuit

texts: I am trying to include BNE instruction in the following circuit without introducing a new control line. I have thought of many possible ways like adding muxes or and gates etc to implement it but after implementation, a problem always occured with any of the three instructions, PC+4 , BEQ and sometimes BNE itself. Now I need a little advice from the experts on how can I implement bne without introducing a new control line.Here is the circuit:


texts:
So my previous question here confirmed what I thought, to calculate the power dissipated in a component, take the voltage across the device and multiply by the current.
But why do some devices have a current limit and some a power limit?
For example, Low Drop Out Regulators such as this one: LDO40L, do I have to be concerned about power, or as long as I am within the voltage and current specs will I be ok? For example, could I run this at 37V at 380mA with an output voltage of 3.3V?


texts: How do I identify this component? It just says 0 on it

texts: Can anyone help me identify this component? It just says 0 or D on it (I think it's a zero). I tested it for conductivity with a multimeter - doesn't seem to have any (tried both polarities in case it's a diode). Tested for resistance: nothing (i.e. infinite resistance), although I'm not 100% sure I was touching the contact points correctly, so don't take this as an ultimate measurement. Thanks in advance!


texts: Source a really big LCD character display

texts:
I'm looking around for a large LCD character display (metre-ish long, 10-15cm high), and on the cheap side (of course)

Any suggestions?

Actually I think I meant LED display, max $150ish


texts: I have a project that involves deriving a square wave from sine wave at high frequencies, so how can I convert a sine wave to square wave at MHz frequencies? I want a circuit using an op amp that can tolerate high frequencies, 30 MHz max.


texts: Can lipo and Lithium-ion batteries be used together?

texts: Lithium ion batteries have high specific energy and lipo have high c rating (high power).  Is it possible to put lipo and lithium-ion batteries in parallel if they are at the same voltage and protected by charge control circuitry?  This would give you a battery that has high energy density,  but can also deliver short bursts of high power.  The lipo would charge up from the lithium ion then deliver high power when needed the way capacitors are commonly used.  It would be isolated from the circuit by transistors which would control charging and discharging.


texts: Determining the Impedance of the antenna on a known circuit

texts:
I am stuck on how to approach the following problem:

I have a graph with both the response of a short-circuit and an unknown impedance antenna.

The only information I have from this graph is the amplitude of the response and the distance between the minimas of both the antenna and the short circuit on the same circuit.

I worked through the different parts of the schematics of this circuit, but the only question remaining is how to determine the impedance of the antenna.

The vertical axis is the normalized amplitude of the response and the horizontal axis is the distance of the reading on the slot line.

My first reflex would be to use the SWR of the antenna response, but since it's already a normalized amplitude, can I do that? If I can use the SWR there, I can find the reflection coefficients with the rest of the known circuit, but the teacher told us that there is no complex calculation to be done : we can use the figure above to find out the impedance of the antenna.

I asked a few questions to my teacher, but since this is a graded work, he can't give me all the answers I am looking for to complete my work.

Thank you for your help.

edit : following the comments I received, I forgot to give the Z of the slot line which is 50 ohms.


texts: Filtering and latching comparator output on STM32

texts:
I have an STM32F301, and plan to use the COMP2 to compare a hall sensor against the DAC output to check if a current is under the set limit.
Now I'd like to ignore very short bursts from inrush current, and glitches due to EMI, and also latch the error signal as raising the error status turns off the power, which should resolve the overcurrent situation.
My current idea is to feed the COMP2 output into a timer as a trigger signal (which allows me to use the timer's filter to wait for the signal to be stable for up to 16 cycles), and then count down from 1 to 0 in a one-shot timer, and use the underflow output as the outgoing error signal.
Reset isn't time critical, I can do that from the MCU.

Is that a feasible approach?
Can I expect the timers to behave sensibly with values this small?
Can I expect the underflow signal to remain asserted in one-shot mode?
Is there another method to implement a filter and a latch that isn't timer abuse?


texts: Why is there a different load current in two identical DC generators in parallel operation?

texts: I am a university student. While we were performing the experiment of parallel operation of two DC generators, we noticed that the load shared by the two generators was different. The total load current was about 21 A. The first generator was delivering 20 A and the other was delivering 1 A. Despite fulfilling all the necessary conditions of parallel operation, why is the load current so different? I think that it should be equal in both generators.


texts:
The beaglebone uses TI AM335X SOC which has a SGX530 3D Graphics Engine.

I wish to know if there is a single open source operating system available in the world wide web capable of using the beaglebones GPU.

Currently I believe the DRM graphics calls are processed only by the CPU and the GPU is standing there doing nothing.

I have a need to clarify this information.

Thank you very much for your views and answers.


texts: Driving 3 digit seven segment using Arduino Uno R3 and a Demux

texts:
I have to light up 3 digit 7 segment displays using Arduino Uno R3. I have got myself 3 BCD-to-7 segment display decoders. I figured I need a 4-to-16 Decoder, so I bought one and it turned out that it is actually a 4-to-16 "line" Decoder, or precisely, a 4-to-16 Demux. The Demux has output with only one is HIGH at one time...which I can't use with the BCD-to-7 segment display decoders (some combination of input into them cannot be created).

Is there any workaround on this?

the circuit diagram. If you have time, do clarify these configuration is correct? Thanks


texts:
NOTE: I most probably have lack of information on this topic. So rather than reacting furiously or deleting my post; you can inform me, so I can edit/update my post.

I want to start learning to design MCU (I want to be able to use different brand's ARM chips) boards on programs such as Proteus (I'm open for other program suggestions.).

First; If you can advice me an info source about this, I will be more than happy if you provide them.

My main question is this:
I wanted to add schematics of "MKE02Z64VLD4" chip (NXP Brand) that I have under my reach. I reached NXP's website and downloaded a ".bxl" file that they provided and opened in a software (also provided by them). The software does the conversion of that file for various programs (excluding Proteus).

As I mentioned before, I want to be able to work with different brand chips. So I might need to learn to manually add designs to the program.

1. Is there a procedure that you use for such purpose (adding unlisted chip to design)? Or is there a source (other than Google) where you can find libraries?

2. Should I use another program (Such as Altium, Eagle OrCAD etc)?

3. If I manually add a chip to the design program, will I be able to simulate it?

I'm so confused that I might be asking wrong questions. If I do, please correct me.

Thank you,


texts:
When attempting to debug a STM32L471RGT6 chip over SWD, I encounter an ACK_FAULT whenever sending an AP request to halt the core.

I've implemented the following sequences which all work correctly, getting an ACK_OK for every relevant DP/AP request:

Select SW-DP on the SWJ-DP interface
Assert the IDCODE value on the debug port
Set the CxxxPWRUPREQ bits on the CTRL/STATUS register and assert the respective ACKs
Assert the IDR register value on the AHB-AP

The next step is to halt the core, enable halt-on-reset, and reset the core to get it into a known state to reprogram the flash memory. When I send the halt command by writing 0xA05F0003 (DBGKEY | C_HALT | C_DEBUGEN) to 0xE000EDF0 (DHCSR register in AHB-AP), I get an ACK_OK.

But then, when attempting to read that same register to check the S_HALT bit, instead of an ACK_WAIT or ACK_OK like I was expecting, I get an ACK_FAULT (0b001 LSB). I retried the entire initialization sequence, but instead, reading the CTRL/STATUS register on the debug port immediately after the AP request to halt the core, and the STICKYERR flag is indeed set.

Does anyone know why this AP request is faulting and how to resolve it?


texts:
Consider the circuit below where R1=R3=200Ω, R2=400Ω, Vs=8v, and is=100mA.
Question 1: Use superposition to solve for the value of V1 in volts due to \$i_s\$ alone.
Question 2:  Consider the same circuit. Now, solve for V1 in volts due to the contribution of \$V_s\$ alone.
Question 3:  Solve for the total value of V1.

To apply the superposition principle, independent voltage sources are converted to shorts and independent current sources are converted to open circuits.
Question 1:
Since we are dealing with the current source, \$V_S\$ is shorted out so that R1 nd R3 are in parallel with each other.  Since they are in parallel, I thought that this would create a current divider and:
$$ i_1= \dfrac{R_3}{R_1+R_3}i_s$$ and
$$v_1=i_1R_1$$
Solving those equations gives you \$i_1 = 0.05\$ and \$v_1=10V\$.  But this is incorrect... why?
Question 2:
In this case, \$V_s\$ is left intact and \$i_s\$ is replaced with an open circuit.  This creates a voltage divider such that:
$$v_1 = \dfrac{R_1}{R_1+R_3}v_s$$
$$v_1 = 4V$$
Question 3:
Values from question 1 and question 2 are summed, but I can't get question 1.


texts: How does the capacitor in a debouncing circuit work?

texts:
On the following circuit (a debounced push button that turns on a LED):

simulate this circuit – Schematic created using CircuitLab

I'm trying to understand why the LED will not light up as the capacitor looks like it's bypassing the switch. When the capacitor is full, it doesn't transmit/conduct electricity?

You'll notice that I'm very beginner, but after 20 hours of reading various tutorials, I still can't really figure out something very simple; how does the full capacitor act differently than a simple wire? If I replaced the capacitor with a wire placed a wire instead of the capacitor, the light would always be on.

Edit:
Some people pointed out that the debouncing circuit made no sense (bad voltage, etc.) Here's my 2nd attempt to make more sense. R5 and R6 could be the same, but I thought keeping them separate would help to keep 1 job to each component.


texts:
Good Day

I used internal power planes for the first time (Altium), and I now want to generate fabrication outputs in the form of Gerbers.

The gerber below illustrates my internal GND plane, to avoid confusion with the fab house I would like to invert the gerber? Currently the voids are supposed to be copper and the copper is supposed to be voids? It looks to me like the whole gerber should be inverted.

Where do I change the settings for this?

Thank you!


texts:
I see that often commercial radio devices go through EMC tests and attain FCC approval. Do all commercial radio devices need to be approved by the FCC though? According to this:

  The radio frequency device is being imported in quantities of 4,000 or
  fewer units for testing and evaluation to determine compliance with
  the FCC Rules and Regulations, product development, or suitability for
  marketing. The devices will not be offered for sale or marketed.

It seems that if fewer than 4000 units are imported, FCC approval is not required if the imported units are not resold. So if an Amazon seller ships <4000 non-FCC approved radio devices directly from China to a US customer, so long the customer won't resell the device, it'd still be legal. Am I reading it right?

Any thought appreciated.


texts: Which quantities and formulas are counterparts to each other for electrical and magnetic quantities?

texts:
Changed from original question: Which quantities and formulas do you think are counterparts to each other for electrical and magnetic quantities?
If any of you are familiar with physics where some sources make a deep comparison between translational and rotational quantities in order for students to be able to see that the rotational takes some form based off the translational quantities, I want to be able to achieve something like that for electric and magnetic quantities. Like for example, magnetic field and electric field quantities.
I would really want formulas or a source that actually does what I am saying, but having regular concepts like electric field and magnetic field be explained side to side even though they do not have a formula would be fine. I think they do though, I did not check yet.
My point is I at least want a basis on which quantities are counterparts to each other so I can do further research. Like for example resistance can be a counterpart to reluctance. I want clear answers. I am aware not every quantity can be put in a table and I would expect it to have a counterpart. I am fine with also people saying that this quantity is like that.
Edit: No, I don't want to relate it to motion. That was just an example.
Another example I could point out is comparing formulas between differential and integral calculus. I just really want an analogy between concepts.


texts: A question about common mode voltage protection of a device

texts:
This datalogger manual has a warning about excessive commonmode voltage on its 5th page.

  ...data acquisition device you have purchased and are about to use is
  NOT an ISOLATED product. This means that it is susceptible to common
  mode voltages that could cause damage to the device.

I'm planning to use a metal enclosure which will include some power supplies couple of amplifiers and this logger. Basically two amplifier's will be connected to this logger as single ended. The signal to the amplifiers will come from two transducers 15 meters away from the enclosure by BNC cables. The system already prepared and has its own protection and earthing. I just need to move the system to a new enclosure plus this datalogger.

My questions are following:

1-) If I measure the commonmode voltage as they suggest and warn on 5th page and find out it is alright is there still a risk in another environment for the same setup? I mean I will check comonmode in workplace but some other technicians will install it to a harsh environment for measurements. So should they also check the commonmode voltage there before setting and powering up?

2-) The manual says the common mode voltage might damage the logger. How about if I add 15V zener clamps before the inputs to the logger, wouldn't that protect the logger? Or if there is common mode voltage how to eliminate it?

3-) The transducer amplifier system (the signal source) must be earthed because of lightning protection ect. But logger also in the manual says to be earthed. I'm wondering in that case would there be ground loops. Is this logger's earth connected to its analog ground or analog ground and earth are isolated? Can I verify it and be sure by continuity test?


texts:
We have a quite complicated device which runs on Atmega328PB MCU which is incorporated on the analog of Arduino Nano board. User deflects joystick, and MCU controls stepper motor drivers accordingly, also communicating by Bluetooth. Device consists of the following parts:

12V@2A wall PSU (MeanWell) connectet to Vin of Arduino with 100 uF bypass electrolytic capacitor
Industrial APEM joystick with 0.5-4.5V analog outputs (X and Y axis, connected to A0 and A1 analog inputs accordingly).
I2C OLED LCD (20x4)
Two HC-06 Bluetooth modules
Two Allegro A4988 drivers from Pololu connected to a couple of bipolar stepper motors. Vref of drivers is set to 0.25V rendering maximum current of 460 mA.
A button, connected to digital input pin D9.
Indicator LED, connected to D10.

5 volts for all consumers are supplied by AMS1117 installed on the Arduino board.
We have a repeating problem, that after some time of successful operation, A0 input begins to read strange data. We measured the following resistances:

A0 - GND: 210 Ohm
A0 - 5V:  1700 Ohm

This resistances are reached gradually from normal several M ohms, not in a single step.
Our only idea was that protection diodes on the input were fried.
DMM shows the following voltage drop:

D1: 0.155V
D2: 0.55V

On normal pins values are 0.75V and 0.62V accordingly.
Moreover, we noticed that two other input pins (A1 and button D9) are also damaged, but to a lesser extent. All output pins are OK.

What can possibly be a reason of such failure? And what actions should be taken to find it out?

ADDED SOME PHOTOS

General view. Power (12V) goes to the gray box, from there goes to the main PCB, where onboard AMS1117 regulator provides 5V, which goes back to joystick. When fully assembled, main board with motors and screen are located in a large plastic enclosure. Big rocker switch provides 12V to Arduino regulator.

PCB inside gray box. Connects joystick, button with LED, 12V power and a cable going to the main PCB.

Main PCB. That's where Arduino, drivers, motors, BT modules and screen are connected.

THANKS TO EVERYONE You've guided me to right direction (so I hope). Below are oscillograms recorded during various conditions.

Output of AMS1117 5V regulator after turning on main switch

Same for 12V

Voltage in analog input after turning on main switch. That's probably the perpetrator: undershoot down to -1.28V

Even worse if I disconnect joystick output from the analog pin. Voltage goes down to -5V. I believe that when connected to MCU, protection diodes are dying while trying to clamp this voltage.

If I power up a standalone joystick (not connected to anything), signal on it's output demonstrates normal behavior.
When system is under normal operation, both 5V and 12V show very high stability under any circumstances (motors idle or running at full speed, BT transmission on and off).

What is causing such dreadful behavior of joystick output, and how to combat it???


texts: Can I charge a 12V/4Ah sealed rechargeable battery with a 13.5V/500mA charger? If so, how much time would I need to charge it to 100%? If not, how can I charge the battery?


texts: Arduino shield - what should I solder to the pin mounts?

texts: Picked up my first Arduino shield today and I was surprised to see that it doesn't have any pins on it - just empty mount holes.  What's the cusomary thing to solder to the shield to get it to mount to my arduino?  From what I understand these shields should be stackable so I need to solder something to both the top and bottom sides of the shield.


texts: Why / how does reactive power help improve voltage quality?

texts:
This question is related to my previous question that Olin provided a great answer to.

Note that this question is about transmission and distribution systems, not electronics. I believe the claims I make in the question are known to most power system engineers and I have therefore not included citations and external sources.

The following quote regarding the 2003 blackout is taken from the report  "Preventing Voltage Collapse with Protection Systems that Incorporate
Optimal Reactive Power Control", PSERC Publication 08-20:

  By performing the optimal reactive power control after contingencies,
  the system voltage profile, the voltage stability margin at load
  buses, and the relay margins were improved to insure that system
  operating criteria were met after any of the contingencies.

Reactive power is used to control the voltage in transmission systems, and is said to increase the voltage stability.

Why and how does the reactive power help improve the voltage stability?

The previous question was about why reactive power affects the voltage. This question is indeed related, but it's in my opinion a completely different question and answers to the previous question will not be applicable for this. Therefore, in my opinion, this is not a duplicate.


texts: Holding components without bending leads when soldering upside down?

texts:
I am gaining experience in soldering components onto PCBs. I'm working through some one sided through hole PCBs and one thing that I'm having trouble with is holding components once I flip the board. I generally tend to not like bending the leads when I flip the board. There are two reasons -- one being that they still don't seem to fit tightly, not to mention you can't bend the leads of some components (e.g. short lead capacitors) and the second being that they don't solder on nicely. With bent leads, they can even sometimes be touching other soldering points in some cases (after cutting excess off).

The only thing stopping me from attaching all the components and then flipping it and soldering all the leads is that

as soon as I flip it components fall out
the components which are taller than others (e.g. electrolytics) dictate the other components to fall to that height.

The components falling out when I flip the board I can overcome by using a bit of card to hold them while I flip it. I experimented with some sponge to hold the components in their respective heights when I solder but not much success.

The best I can come up with is soldering in 'layers' with the shortest components first (resistors etc) and slowly building up until reaching the layer of electrolytic capacitors.But again, ideally I would like all the components on the board together and then just solder them all in one swipe.

Any better ways of doing this? Any pointers?


texts: When using multiple capacitors for decoupling or bypassing, should they be placed as close as possible to each other?

texts:
It is often recommended to use multiple capacitors in parallel in bypass and decoupling applications, especially when working with frequencies above 50MHz.

There is some argument whether its better to use several of the same value capacitors or use capacitors of different values.  Aside from that, is there any negative impact of placing the capacitors as close as possible to each other and the IC?  Or should there be "some" trace between the capacitors?

Assume capacitor size are all 0603 or 0805.  Is it better to place the capacitors side by side, or some alternate arrangement that leaves more trace between the capacitors?


texts: Analyzing a circuit with diodes connected in series

texts:
This is a problem with its solution:

What I don't understand is how he replaced the three diodes with the voltage sources in DC-analysis or with the resistances in AC-analysis. What assumptions did he make to do that?.

For DC-analysis: if it was one diode then it's ok for me but the problem is with the three connected in series.
For AC-analysis I have the same problem as with DC plus two questions:

Using small signal model, we replace the diode with a resistor rd and then we solve the problem and if the current id was negative then our assumption that the diode is on is wrong and it should be off. Is that right?
If the diode is on in DC-analysis, does that mean that it should be on in AC-analysis?


texts: How to calculate total ADC error after adjustment/calibration?

texts:
I’ve some different ADC channels, extended/standard channels and Precision channels.

So far I know should the TUE (total unadjusted error) be calculated like this:
\$ TUE = \sqrt{e_{offset}^2 + e_{gain}^2 + e_{DNL}^2 + e_{INL}^2} \$

For  the 12bit ADC datasheet, that gives:

\$ TUE = \sqrt{(6^2+4^2+1^2+3^2} = 7.87 \$
(If looking at the datasheet it must correspond to the extended channel without current injection)

and for the 10bit:

\$ TUE = \sqrt{0.5^2+0.6^2+1^2+1.5^2} = 1.96\$ (If looking at the datasheet it must correspond to the precise channel without current injection)

This is confusing me, but my guess is however that the stated Offset error, Gain error, INL and DNL corresponds to different channels in each of these datasheets.

The 10bit Datasheet (see page 80-87)

Now if I’ve thought right above : I do wonder how I can calculate the compensated maximum error after adjustments/calibrations for the Offset error and Gain error?

My guess is that I could just simply take away the offset error and gain error for the TUE equation for the 12 bit “extended channel without current injection” and the 10 bit “precise channel without current injection”.

But how do I do for the other channels which don’t have  the Offset error, Gain error, INL and DNL stated? How do I calculate the maximum error after calibration/adjustment for them?

I hope someone can be kind and help me.

Best regards


texts: Why is it easier to implement bytes as 8 bits rather than 9 bits?

texts:
From book to book I always find the same sentence. For example:

8 bits is an even power of 2, which makes it somewhat easier to design computer hardware with 8-bit bytes than with 9-bit bytes.

The Computer Book (Sterling Milestones) by Simson L Garfinkel & Rachel H. Grunspan
I cannot find any circuit or detailed explanation why that statement is true.
The perfect answer will be a circuit that shows why it is easier to implement.
I know about all other reasons i.e., BCDIC, ASCII, IBM System / 360 and etc. But it's just words, I need a proof with circuit. If one say that it is easier to implement, it means nothing without proof.
It's like to say 1 + 2 + 3 + ... = -1/12.
This statement is true, but it is complete nonsense without proof. Same thing with byte. Show circuit and I will believe.


texts:
I have a mature product (designed by me) on a PCB. For science, I would like to induce Electrostatic Discharge (ESD) damage to the board so I can see how it behaves afterwards. This test would be purely academic.

One idea that comes to mind is to apply triboelectric effect using a vacuum cleaner. That seems like a plausible idea, since some users really use a vaccum to clean their board. What are other "average Joe"-methods (for example: wrap the board in plastic) to inflict ESD-damage?

What are some exaggerated methods to inflict damage? (Like using a raygun or something other silly method)


texts: Connecting multiple DC sources in parallel without the use of diodes

texts:
Obviously to have more current is there a way to somehow connect multiple DC sources together not by using trivial series Schottky diodes, but using mosfets and LDO(Low dropout) circuits? To somehow use the mosfet body diode forward voltage drop as a one way "valve" as long as it's within 0.5V or less between any 2 sources in the array? I don't think it's possible. But I'm not sure... That's why I'm posting this question. I don't think it's possible because the mosfet is not a unidirectional switch but bidirectional? I think the N or P channel is symmetrical in the manufacturing of mosfets. I'm not sure...  I don't know. But if the substrate is connected to the source then it's not symmetrical...I'm not sure...I don't know...I have many questions and very few answers and self-confidence.

I'm almost sure the circuit in the picture does not work, but can somehow be made to work? Can two mosfets in anti-series be used somehow? I don't know...I don't know anything. Can somebody help me?


texts: How to drive +-10V Gate-Source N-MOSFET from 30 V

texts: I have N-MOSFET with maximum +-10V Gate-Source voltage and I need to drive it with 30V signal. Is voltage divider way to go?


texts: Permission Denied on Arduino serial stream

texts:
I'm collecting data with a serial stream from an Arduino microcontroller.

I'm using Cygwin my recording sometimes randomly stops and I get a 'tee read error: Permission Denied' message.

The way I'm doing the recording is that I navigate to the folder I want to store the data file and I enter in a command like

tee </dev/ttyS2 Data.txt

However, in the middle of recording, the recording stops and I get a 'tee read error: Permission Denied' error. Does anyone know why this is happening and how to solve it? It's not like I suddenly have lost my permission to the folder I'm saving my data in.


texts: Help to ID a 16 pin IC, damaged by carelessness

texts:
I need help with the ID of a 16pin IC.
In an act of 100% carelessness, two cables were incorrectly inserted into one of the controls, which resulted in a 16pin IC getting hot and virtually destroying the ID printed on the IC.

Along the bottom I believe I can make out XNAH0828, and the latter part of the top line is perhaps one of these
 ????  8084CPE         ?????  3084CPE       or even  3Q84CPE  but I think the latter unlikely…

Via Google I haven't been able to identify the specific IC. The circuit board was made or designed by I.T.Solutions 2010.

It links to a small LCD display and sends signals to the stitch regulator system.

I also Googled I.T Solutions, there is a company with that name but not sure it is the correct one.

The IC is in a base and although damaged, I have sufficient skill to de-solder and replace the base.

I know I am asking a lot, but at the moment we are waiting to see if Tin Lizzie (Utah based) who make the machine can find a replacement board.


texts: Voltage of Different Voltage Sources in Parallel with Diodes

texts:
I am working on a project in which I will have two different power sources, which I will have to dynamically switch between to supply power to devices. These two power sources will likely be similar in voltage, but may vary slightly.

I figured that the best way to approach this would be by putting the voltage sources in parallel, but if there is a difference in voltage, current will flow between the sources, which is not what I want. I then had the idea to place a diode in series with each source before they are connected, to ensure current does not flow between them (Both sources are DC). I don't see why this wouldn't work, but what would the voltage be of the sources in parallel?


texts: What's the name of this electrical connector?


texts:
I have question abouth parametric spectrum density (PSD) estimation using Yule-Walker (autocorrelation method) equation, which relays on autocorelation:

And it's mention: "However, since the autocorrelation method applies a rectangular window to the data, the data will be extrapolated with zeros. As a consequence, the resolution of estimates is lower…"

Another parametric PSD estimation is covariance which relays equation:

And it's mention: "The advantage of the covariance method over the autocorrelation method is that no
windowing of the data is required in the formation of the autocorrelation estimates
rx(k,l)."

So I don't understand from where this window for data.


texts: 16 channels relay control with 3.3v pins

texts:
I'm going to buy two 16 channels relay boards from Sainsmart : http://www.sainsmart.com/16-channel-12v-relay-module-for-pic-arm-avr-dsp-arduino-msp430-ttl-logic.html

I want to control it with a SBC66EC (modtronix.com/sbc66ec.html?sef_rewrite=1&currency=EUR) which has 32 3.3V I/O.

The relay board must be powered with an 12v alim. My question is : can i control the relay board with 3.3V GPIOs because of the Optocouplers of the relay board ? There is a lot of different theories on the web ... I'm a bit lost as i'm not specialized in electronic/electricity.

Here is the schematic of the relay board : https://www.dropbox.com/s/pm2p3q04sj65x5e/16ch%20schematic.pdf?dl=0

Thanks !


texts:
From the data sheet of the LFCN-490 radio filter, the chip is marked with RF in, RF out and GND, but what is defined as RF in/out? I have seen some circuits using the rfm-22b with pin 1 (RF in) directed towards the antenna and RF out towards the circuitry, but I can't find how to be certain.

EDIT: Datasheet: https://www.minicircuits.com/pdfs/LFCN-490.pdf
Looking at the internal schematic, it looks like it's bidirectional, but then I don't see any reason for marking pin on and naming them in/out


texts: What IF amplifier configuration can I use in my receiver?

texts:
I am making a superhet SSB CW receiver with a crystal filter on the input after the mixer.

Do I have to use IF transformers as the coupling method (1) or can I use capacitor coupling with resistors as the collector load (2) or are RFC better (3)?

Can I use the simple biasing arrangement (B) or the normal bias (A)?

I am aiming for low noise, high sensitivity and ease of construction, this receiver is meant to be reproduced by other people as an relatively easy project.

Is 50 voltage gain per stage good enough? I calculated I need 3 stages for 0.2 µV signal to be translated into a 25 mV signal that will feed the diode mixer detector and AGC detector.

IF is 455kHz. Should I control all the IF stages (AGC to the base) or some different solution?


texts: What is role of R9 resistor at input to OPAMP in this circuit?

texts: I guess it has to something with offset nulling but not getting how .Circuit shown is of instrumentation  amplifier.


texts: Preventing power loss with battery backup

texts:
I would like to use a battery to power Arduino when the power is out, however I am not sure how to do it.
The first simplest solution that comes to mind is using a usb powerbank, but I am not sure if they are a good fit, because I do not think they were designed for that use. Could you explain why that is not a good idea?
The second thing I am thinking of is using a charge controller, but I am not sure if it will stop charging the battery when it is fully charged. I am not sure how much they differ from power bank charge controller. I realise that there can be many different kinds, but I am not sure what to look for. Could you point out some key characteristics to look for?
So it should work like a laptop, not overcharging the battery when plugged in. Also do laptops stop charging the battery when the battery is full, I recon they do, but I am not sure?
I am looking for solution that would work reliably for years. I am thinking there should be off the shelf solution for this, am I wrong? Does this need a dedicated circuit?
Thanks in advance.


texts:
I need a component which is small and light-weight, but which can emit a loud sound. I don't care what sound it makes - only that it be loud enough to hear outside from 20+ ft away.

Unfortunately, my brief searches didn't come up with anything, and I'm assuming this is because I don't even know what the name of the component I'm looking for is. (It's not "speaker", or "siren", I suspect).


texts: How to power an 220v AC bulb from 1.5v dc from an LED

texts:
Friends,
I have 4x4 led arrays. At one time 4 leds can be lighted and at another time it may be 8 or even 12. This I am doing with a help of software and pcb. Say like Letters displaying in an led panel.

I have 100Watts bulb (220v AC power supply) on the other side. I want to light these 100W  bulbs as according to the LED panel.
If 4 leds glow, the corresponding 100W bulbs must glow.
If 12 leds glow, the corresponding 100w bulbs must glow.

Please give me some idea.

I worked with 3v dc relay switches. But in vain. I am not getting above 1.5v dc in the led panel. I have searched for 1.5v dc relay, but is not available (only SSR's are available, which is costly)

Can I use a transistor.
Please help me.
Thanks.


texts:
I am looking at the Digilent Chipkit boards.  What compatibility issues have any of you run across?  There are too many weasel words in the descriptions...

Compatible with many existing Arduino™ code examples, reference materials and other resources.
Pin-out compatibility with many existing Arduino™ shields that can operate at 3.3V

Anyone familiar with any issues using regular Arduino code on these boards (via the custom programmer/UI, of course)?

I like that there are more I/O pins and features exposed.  And though I do not need it today, the idea of increased performance could become important down the road as well.

Also, FWIW, it looks like Digilant's custom shields are NOT compatible with  standard Arduino boards, as they appear to use these extended I/O capabilities.


texts: Help identifying mysterious communications tower

texts:
There's a tower near my house that I thought was a cell tower, but I noticed it's not registered on the FCC map.  Can anyone help me ID what type of tower this might be?  I was thinking it was a cellular base-station, but it seems kinda small.
Thanks in advance!
google maps link


texts: Non Inverting Op Amp output near power supply voltage when input voltage is at 0V

texts:
I have a simple non inverting op amp circuit.

I am using this to amplify a DC voltage. The positive input voltage will vary from 0V-5V.
My problem is that regardless of the input the output is about 22V.
The exact op amp I'm using is here.
Datasheet here
It seems to me that regardless of the input voltage that the output is the saturated max voltage based on the specs.

I'm 100% positive that the op amp is connected correctly, as I've checked the connections too many times to count. I also rebuilt the circuit on a different part of the bread board to be sure.
Voltage at the negative input = 3.6 V
I also replaced the op amp with a different op amp, datasheet here and got similar results where 0V into the positive input resulted in about 22V output.


texts: AC to DC conversion using without neutral

texts:
I have a project to replace my wall switch with my smart switch which can be controlled by ESP32. Needed to use AC to DC conversion to get 3.3V from 240V/50Hz.

Some of the walls have only phase and neutral always directly connected to appliance. In that case I cannot install AC to DC converter for smart switch replacement.

I have seen in a product which I bought recently have only phase for AC to DC conversion and they were able to provide smart control also.

Question is, Any possible way to get step down 240V/50Hz to 3.3VDC without using neutral? and Would it be reliable if we do that?


texts: AVRISP mkII can't connect with target when using an AVR on a breadboard

texts:
I'm having a problem with my AVRISP mkII. I'm trying to program a ATMEGA328P on a breadboard using AtmelStudio 7. The problem is I can not make AVRISP detect the target. Whenever I try to program the uC, I get the warning "target not detected." The read voltage on the target is always 0,0V, and the programmer LED is always red.

I thought the AVRISP was malfunctioning, but measuring the voltage directly at the VCC and GND pins on the AVRISP board, and got the 5V supply voltage.
I tested the programmer through the ICSP connector of an Arduino board, and it was automatically detected, and worked perfectly, then I think the problem is not in AVRISP.

This is the circuit that I'm assembling:

I'm also using 100nF decoupling capacitors on Vcc pins and the Vcc Pin of AVRISP is connected with power supply.

I would like to know if there is something wrong with the schematics, or some setting to be done in AtmelStudio. I'm actually a newbie, and I'm feeling totally lost.

I've already followed the guidelines of some similar topics here, but without success...

Thanks in advance


texts: Eliminating ground loop in Bluetooth speaker circuit

texts:
I have built a Bluetooth speaker (based on this Instructable), which works except there is a faint clicking noise in the background. This is a basic diagram of the circuit for the speaker:

I am almost certain that the problem is caused by a ground loop, because I have tried using a separate power supply for the Bluetooth adapter and this fixes the problem. However, I need to be able to power the speakers and the Bluetooth receiver from the same battery.

I read online that someone else fixed a similar problem by adding an audio transformer to the left and right channels. I tried using an NTE1 1:1 audio transformer, and this did not help. With the transformer connected the speaker was actually worse, because it only made static noise and did not play audio.

If the problem is indeed a ground loop, I would not really expect an audio transformer to fix it because the problem is with the power wires rather than the audio wires. I think a ground loop isolator would solve my problem, but when I researched them online, the only products I saw were adapters made to be used with audio systems like this.

This is probably a really noob question, but I am not sure how to fix the ground loop problem with just small circuit components. How would I go about this?


texts: Difference between external and internal switch mosfet?

texts: I'm on the Digi-Key website and they list both external and internal switch MOSFETs. What's the difference?


texts: What happens when supplying an LED with too low voltage? Will it just emit less light? I'm making an octocopter, and need to cut away as much weight as possible. I need to run the LED without cooling if possible.


texts: Drill size for thermal via (and how many)

texts: Following my previous question, I'm putting via's under an SOIC-8, the thermal pad is 0.12 x 0.09". So how big a drill and how many thermal vias?  I was talking to a smart guy at work today.  And he said, lots of small holes.  'Cause I gain more copper that way.  (Better thermal conductivity.)  I was thinking maybe just two big holes, and fill them up with solder.  The thermal conductivity of solder is only ~1/10 (a bit better) that of copper.  So a big slug of solder beats a lot of thin rings of copper.  The first batch of boards will be hand soldered.  What do you think?


texts: What is the intended use of high current SSRs and triacs?

texts:
I answered a question recently regarding power dissipation in solid state relays. This is the calculation:

Consider this 40 A rated triac - BTA40.

Vto = Threshold voltage = 0.85V = Voltage drop across triac.

Rd = Dynamic resistance = 10 mohm

Assume IT(RMS) = Current through the triac = 25 A

Power dissipation = [0.9Vto X IT(RMS)] + [Rd X {IT(RMS)} X {IT(RMS)}]

Where 0.9 = 2*sqrt(2) / pi

Putting the values, we get P = 25.375 Watts

For 1A current, P = 0.775 watts which seems to be a tolerable value without any heat sink.

Besides this calculation, I tried testing a few triacs rated 4A to 40A. All of them get pretty hot after 2-3 amps of current. Even after putting a heat sink (approx 5cm X 5cm X 2cm) the condition didn't improve much.

As such, I am wondering what might be the intended purpose of these solid state relays? Is it just used for high ampere switching at a very low duty cycle where the triac could get ample time for cooling itself?

Because, for continuous currents above 5 amps, I think I will better off with an electromechanical relay rather than going for solids.


texts: Calculating the frequency of data lines?

texts:
I read a calculation about determining the bandwidth of USB https://www.edn.com/electronics-blogs/all-aboard-/4425691/Rule-of-Thumb--2--Signal-bandwidth-from-clock-frequency

Roughly what was said is:

USB 2.0 = 480 Mbps
Thus the clock = 240 MHz
Multiply by 5 to get Bandwidth and get ~ 1GHz

So trying this for USB 3.0 I think I'd end up with this:

USB3.0 = 640MBps
clock = 2560 Mhz
Bandwidth = ~12Ghz

As far as I know however, USB 3 noise runs somewhere in the 2.5Ghz range. Is the formula given in the article incorrect? Or is there a different way I should be going about calculating the frequency of different signals?


texts: At college we have to use a colophony-free solder, but over heating the solder leaves the flux residue on the boards(light amber in colour). Multicore recommend there own Multicore Prozone cleaner(this is some datasheet on what it is) to remove this residue from the board, but I can't find it on RS, Farnell or Rapid Electronics. Is there another alternative? Is there another industrial alternative as it looks like a generic PCB cleaner.


texts: Does analog time division demultiplexing need any additional sample and hold?

texts:
Quick general summary:  In analog time division multiplexing, after combining several continuous signals into a single line, do you generally need to use some form of sample and hold to reconstruct the continuous signals on the demux output side?  Or do mux IC's do this automatically?

My specific application: I'm collecting 256 voltage signals from tiny wires embedded in brain tissue, eventually collecting them on a DAQ card and doing online analysis.  The multiplexer (perhaps ADG1606 on both mux  and demux side) is intended to reduce the wire-count in the long, expensive cable bundle that connects the on-head signal buffers to the rest of the amplification and digitizing hardware (please see figure - I hope the size is appropriate).  From the answers I've gotten so far, I drew what seems to be the necessary general idea, and I'm wondering about specifications and unforseen limitations.

For the sample-and-hold, I'm considering this setup, except that the droop rate (2mV/ms) and sample time (3ms) seem bad for my application.  Maxim seems to offer inexpensive SH packages with better specs (DS1843 DS), would you recommend using those instead of making SH stages from opamps and switches as the tutorial outlines?

Am I right in imagining that independent SH circuits synced with the mux timing will reconstruct the original independent pre-multiplexed signal (at least the lower-frequency parts that I care about - 0.1Hz to 9kHz)?  Or does the SH switching introduce periods of corrupt output data?

May I skip my late 5000x amplification step (256 channels) by 5000x amplifying the 8 mux lines just before demux?  This would save me some space and money.

And, do I need to lowpass filter the brain signal BEFORE it gets to the mux?  I have not done this in my current setup (which doesn't have any mux), but with mux I think I may need to worry about aliasing?

You may be able to tell that I'm new to this, so clues that may seem obvious to you are still very much appreciated!

Recording setup diagram here  and below


texts: Communication between two AVR microcontrollers over SPI with different power supplies

texts:
I have two ATMEGA32 microcontrollers. First one has the following power supply: 220VAC-line filter-transformer-bridge rectifier-filter-voltage regulator-5VDC. Another one is powered by USB 5VDC. So they have different grounds.

I want to connect them over SPI.

How can i do that?


texts: I am trying to develop a product that requires a 12 V portable rechargeable battery that can output at least 2 A. Since conventional LiPo battery runs only on 3.7 nominal voltage, is it advisable to series-connect 3-4 of these batteries to achieve 12 V? What chip should I use to charge the battery?


texts:
I am interested in controlling the speed of multiple small DC motors that will draw at most 1 amp each.  I only need to run them in one direction, so an H-bridge IC like the SN54410 seems like the wrong choice.  However, for my application, weight is a premium, and the SN54410 is the lightest method (per motor) for controlling motor speed I have found.

When I have looked into using individual transistors, they all seem to require a heat sink (either an external one or a metal back), which makes them heavier than the SN54410.  In fact, I don't understand how the SN54410 is able to drive two motors at 1 amp each without a heat sink (but it does).  Can someone suggest a good component for the job?  I am hoping for either an IC that is designed for unidirectional motor control or a small (TO-92) transistor that could be used to control an individual motor at 1 amp.

EDIT: BTW, I am going to be using PWM to control the speed.


texts: Any reason not to bend the pins on TQFP and VQFP packages

texts: I have an FPGA with a VQFP package, and I need to bend some pins back and hand solder them to fine gauge wire. Is it likely that this will damage the device?


texts: BJT sample and hold circuit for 50 MHz clock

texts: I've designed a sample and hold circuit (as shown in the snapshot of the circuit attached) but i'm having slew rate problems, if I try to adjust the slew rate (by adjusting the capapacitor and resistor values), the output wave gets noisy and has overshoots. In the circuit, Q1 is used as a switch, Q2 and Q3 have complemetary clock cycles to turn Q1 ON and OFF by adjusting the voltage across Q1's base-emitter. Q4 acts a buffer. I have used NPN transistors BFP280W and PNP transistor BFT93. Ihave attached the schematic, the schematic with annotated dc solution and the output waveforms. I need help to fix the circuit to minimize the errors or maybe suggest a better design if this design seems to be not fixable


texts: Altium - Linking Sheet Entries/Ports with Net Labels

texts:
I am struggling to find a way to get the compiler in Altium to see a Sheet Entry/Port (tried with both) and a net label on the same sheet to link.

This redacted schematic page shows what I have (this all on one page, with the relays themselves and drivers etc. all on a second page):

But when compiled, it complains of two nets with the same name (that's sort of the point...)

And in the PCB, it wont link the two together:

I have found a workaround and that is to add the net label next to the off-sheet connector/port:

The problem with this however is that there's not always space to have each net name written out twice.. For the relay1 and relay2 signals used in this example, the off-sheet connector sits right next to the title block for the schematic sheet. It can't move any further to the right to accommodate what would be useless duplicate text.

Anyone know of any settings to allow net labels and off-sheet connectors/ports to connect on the same sheet?

EDIT:
I've though of another workaround, though it's much more of a bodge - a tiny Net label that's basically invisible:


texts: How to realize these transfer functions through op-amp circuit?

texts:
How to synthesize the follwing tansfer function using analog circuit:
$$\frac{(1+sT_1)(1-sT_2)}{as^2+bs+c}$$


texts: How to rotate a part/device in Eagle (schematic view) using keyboard-hotkeys only?

texts:
I'm fairly new to eagle. So far i was unable to figure out how to rotate a selected part in the schematic  editor using keyboard shortcuts only. Please, do not answer with suggestions by using the mouse or the context menu, because I'm not a fan of using a mouse. Also you could suggest an alternative EDA-Software, which fulfills common use cases, like "keyboard-shortcuts for basic operations" OR marking "already placed" parts "in a common" way as a favoured/preferred part.
I'm using Windows 10.


texts: What are the names of all possible logic gates with 1-or-2-bit input and 1-bit output?

texts:
This seems to be a silly question, but the fact is that when I tried to search for related information, none of the search results gave me satisfactory answer.

Logic Gates with 1-bit Input and 1-bit Output

Since the input has \$B=1\$ bit, the truth table has \$C=2^B=2^1=2\$ rows. Since for every row in the truth table, there are \$2\$ choices (\$0\$ or \$1\$) for the output, there are \$2^C=2^{2^B}=2^{2^1}=4\$ different truth tables in total.

Here is a table of truth tables (each truth table is written as a row):

$$
\begin{array}{|c|c|c|c|}
\hline
(0) & (1) & \text{Name} & \text{Formula} \\
\hline
0 & 0 & \text{Constant Zero} & 0 \\
\hline
0 & 1 & \text{Identity} & X \\
\hline
1 & 0 & \text{NOT Gate / Negate / Invertor} & \overline{X} \\
\hline
1 & 1 & \text{Constant One} & 1 \\
\hline
\end{array}
$$

Logic Gates with 2-bit Input and 1-bit Output

Since the input has \$B=2\$ bits, the truth table has \$C=2^B=2^2=4\$ rows. Since for every row in the truth table, there are \$2\$ choices (\$0\$ or \$1\$) for the output, there are \$2^C=2^{2^B}=2^{2^2}=16\$ different truth tables in total.

Here is a table of truth tables (each truth table is written as a row):

$$
\begin{array}{|c|c|c|c|c|c|}
\hline
(0,0) & (0,1) & (1,0) & (1,1) & \text{Name} & \text{Formula} \\
\hline
0 & 0 & 0 & 0 & \text{Constant Zero} & 0 \\
\hline
0 & 0 & 0 & 1 & \text{AND Gate} & XY \\
\hline
0 & 0 & 1 & 0 & \color{red}{\text{Gate-0010}} & X\overline{Y} \\
\hline
0 & 0 & 1 & 1 & \text{Identity on X} & X \\
\hline
0 & 1 & 0 & 0 & \color{red}{\text{Gate-0100}} & \overline{X}Y \\
\hline
0 & 1 & 0 & 1 & \text{Identity on Y} & Y \\
\hline
0 & 1 & 1 & 0 & \text{XOR Gate} & X \oplus Y \\
\hline
0 & 1 & 1 & 1 & \text{OR Gate} & X + Y \\
\hline
1 & 0 & 0 & 0 & \text{NOR Gate} & \overline{X + Y} \\
\hline
1 & 0 & 0 & 1 & \text{XNOR Gate} & \overline{X \oplus Y} \\
\hline
1 & 0 & 1 & 0 & \text{NOT Gate on Y} & \overline{Y} \\
\hline
1 & 0 & 1 & 1 & \color{red}{\text{Gate-1011}} & X + \overline{Y} \\
\hline
1 & 1 & 0 & 0 & \text{NOT Gate on X} & \overline{X} \\
\hline
1 & 1 & 0 & 1 & \color{red}{\text{Gate-1101}} & \overline{X} + Y \\
\hline
1 & 1 & 1 & 0 & \text{NAND Gate} & \overline{XY} \\
\hline
1 & 1 & 1 & 1 & \text{Constant One} & 1 \\
\hline
\end{array}
$$

Questions

What are other names for these gates? As shown above, the NOT Gate is also called the Negate function, or the Inverter.
From my research, I know that the name XNOR Gate is more popular than NXOR Gate. However, the gate is equivalent to a NOT XOR Gate . Why does the X come before the N then (unlike other "NOT something" gates)?
Are there widely used names for the gates marked \$\color{red}{\text{red}}\$ above?

In this question, \$\color{red}{\text{Gate-0100}}\$ is also called SAND Gate, which stands for "Single-inversion AND Gate". However, I am not sure if this is widely used in the field.
In this answer, \$\color{red}{\text{Gate-1011}}\$ (in fact, it is a "NOT SAND" Gate) is called Inclusion Gate or IF-THEN Gate. Again, is there a proper name for this gate? How do IC user manuals refer to a gate with the same truth table?
In this reference, \$\color{red}{\text{Gate-1011}}\$ is called Logical Implication.

== Edited: 2019-04-10 ==

I just found this Wikipedia article by chance, which names all 16 gates (operations).


texts: Extreme long settling time (6 ms) of the DAC on STM32F4?

texts:
I encounter a problem with the DAC on both STM32F4/STM32F429 Discovery boards and hope someone can give me a hint.

The DAC (using DMA with output buffer enabled) generates a FSK controlling signal sequence with only two steps, which looks like as follows

As can be seen on the screenshot, the settling time of the voltage step is about 6 ms! Since the signal sequence controls a very sensitive VCO, this long settling time results in a corresponding segment of output freeuency that is unusable for my application.

I am wondering, is this a problem of settling time?
If yes, is there a way to alleviate it?

Updated:

The probe connects directly to the DAC pin, which is the only pin used in the measurement.
I have calibrated my scope's probe.
The STM32F4 discovery board is powered via the USB port.

With this setup, I tried to capture the rising edge of the step from 0 to 4000 using different time scales.
The results are as follows:

Compared to the above screenshot, the overshooting amplitude seems to be proportional to the step-voltage.

Due to my low reputation, I cannot post more than 2 links, but the zoom-in view shows a similar rising edge as @Arsenal's measurement. I think that is the real settling time.

I hope this update could lead to some new suggestions.


texts: How to calculate maximum power supply rail current (Maximum load current of a system) based on datasheet current values?

texts:
I am designing a DCDC Buck regulator for 12V to 3.3V system power supply. My controller; bluetooth & some other peripherals have following nominal currents on 3.3V rail as per datasheets (Details given below).

There is a required parameter of Io(max) for DCDC regulator. How to calculate maximum required current for circuit?

CAN Transciever:  Nom: 40mA  Max: 70mA
Bluetooth LE Chip (+5dbm Transmission): Nom: 21mA  Max: 32mA
Microcontroller(@ 16MHz): Nom: 10mA  Max: 28mA
GPS: Nom: 46mA  Max: 100mA

I would like to know which value should be taken to calculate maximum load current on this rail? Is it nominal current or peak current?

We generally follow: Io(max) = I(nom)*1.5. Is it OK?
Because calculating with Max current ratings in datasheet will generate very high & way off current value for regulator current calculations as number of peripherals on line increases.

E.g. Here in this case: Nom (Total) = 117mA & Max(Total: 230mA)

**It is also observed that system current never reach to Max (total) current with full load on system.

Hence I would like to know which current value from datasheet should be generally considered for power supply rail current calculation & How to calculate Maximum rail current based on it?


texts:
I am using an STM32F745VGT6 user board with Keil µVision 5. I want to use the internal RTC calendar with the internal clock (LSI).

My question is: first power on clock start 02:00:00 then time is going. For example, when time is 02:05:00 suddenly I power off the energy (cut off energy for Vdd, not for VBattery) then wait 10 minutes. After power on, the clock is still 02:05:00. I am stuck. It is so annoying.

I supply to uninterruptible 3.3 volt BIOS battery to STM 6.Pin (VBatt), as in the attached picture. If I remove the battery, each power off and power on start with 02:00:00. So I believe VBatt is working.


texts:
I have a fully digital implementation of a PLL.
The problem that I have is the white noise coming from the PFD (you can view it as input jitter). I would like to filter it a lot, but an implementation with a PI controller lead to a slope of just a -20 dB/decade of noise rejection coming from the PFD.

Is it possible to improve it? The constrain that I have is on the rejection of the VCO Noise, which should have a slope of about 40dB/decade below the control loop bandwidth

The digital model is composed by:

PFD = Kpfd

VCO (include a delay of 1 sample) = $$
\frac{Kvco * T_s}{z-1}\
$$

PI = $$
\frac{(K_p+K_i)*z - K_p}{z -1}
$$
L = PFD * PI  * VCO

The input noise rejection function is $$
\frac{L}{1+L}
$$
The VCO noise rejection function is $$
\frac{1}{1+L}
$$

The currently used values are Kp=1500, Ki=20, Kpfd=2600 and Kvco=0.15 with a Ts=250us.
I would like to have a  L/(1+L) response above the cut-off frequeny above -20 dB/decade

Thank you!


texts: Should I power my device using USB 5V or PC ATX PSU 5V? Crazy idea: use both?

texts:
I am designing a little device to use inside my PC. My circuit contains a microcontroller which needs to communicate with the host system, and I wanted to do that via a USB port. The microcontroller will be powered by 5V, but my circuit also contains components that need 12V, so I want to add a 4-pin Molex connector to get power from the PC's PSU.

The question here is: to power the microcontroller, should I use the 5V that the USB provides or the 5V that the PSU provides? Is there any difference between the two in terms of amperage or how clean/stable/reliable the voltage supplied is?

Additionally, I wanted to ask someone more experienced about the following potentially crazy idea (I am almost certain this is a bad idea, but want to ask anyway): could I maybe use both? (connect the 5V pin of the USB to the 5V pin of the DC power connector?) Would there be a noticeable potential difference that could cause currents to flow between them (afaik, both of them fluctuate slightly, not exactly perfect 5V)? Would it be safe?

I am asking this because I don't know yet exactly how much power my device will eventually need to draw, and if merging the two 5V inputs is safe and doesn't lead to bogus power consumption, it could be an easy way to increase the current available without needing to add a second connector for more power from the PSU.


texts:
Hypothetically say I want to transfer different wattages: 5 W, 5 kW, 5 MW, 5 GW, 5 TW, 5 PW, 5 EW, on a power line.

Let's assume I have the ability to choose specific voltages and amps for each power line, and I want to minimize the size of the power line. I imagine there'd be a cross over point, where it makes more sense to isolate the wire to avoid sparking and arcs, rather than increasing the wire gauge (as it makes more sense to increase voltage rather than amperage).

Is this point and known and set one, or are more vague approaches used to determine what kind of wire to utilize?


texts: How to trigger a latch solenoid valve from an Arduino?

texts:
I received a sample latching solenoid valve:

https://www.alibaba.com/product-detail/Top-Quality-Dc-5V-Latching-Solenoid_60415603817.html

I want to control it using an Arduino Pro Mini, running a 5V. AFAIK, I can't control it just connecting it to a digital pin since the absolute max current is 40mA.

As per the description pulse width should be 25ms. Not sure how to do that with the Arduino.

Setup is powered by a 18650 battery + MT3608 boost module (5v).

09/04 - More info from the manufacturer:
Valve opens on (+) pulse, closes on (-) pulse. It can be powered with 5v and a pulse of 25ms. The current is 0.23A.

It definitely looks like I need an NPN BJT (will a 2N2222 or equivalent work?). How do I send a negative pulse?


texts: How does synthesis tool handle the ports either driven by or to a module that is empty(Black Box)?

texts: I have a design that instantiates a Memory and a Ring oscillator which I am excluding from synthesis by making them black boxes.(Not specifying explicitly, but instantiating an empty module with only port directions). I know I need lef and lib for the two blocks finally but I only need netlist for the surrounding logic to simulate. I know that synthesis tool will remove any logic that doesn't end in an output. But what about the paths that are coming out of and into these black boxes? Will it see them as no logic and remove them. If so what should I do to preserve them?


texts: Using Dual [High Side/Low Side] Isolated Gate Drivers

texts:
When in general is it easier, even preferable, to use a dual isolated gate driver on an H-bridge with IGBT power transistors, rather than separate high side and low side drivers; what if any are the guidelines?
For example, I want to use an IGBT H-Bridge module as the main component of a switch in a 12V DC circuit to an array of electromagnets whose polarities require periodic alternation at a rate of around 4 to 8 Hz only (with the aim of creating a rotating magnetic field).  In that case, would a dual gate driver for each half of the H-bridge -- such as an ISOdriver from 'Silicon Labs' etc. -- with a bootstrap circuit* be simpler and more straightforward than using separate HS/LS drivers, or even superior? *Vgs 15V required.


texts: Why do germanium transistors and silicon transistors have different conditions for cutoff region in common emitter configuration?

texts:
The textbook I currently read defines cut-off for PNP germanium transistors like this:

  For germanium transistors, however,
  cutoff for switching purposes will be defined as those conditions that exist when \$ I_C = I_{CBO} \$

and they continue saying that:

  This condition can normally be obtained for germanium transistors by reverse-biasing the base-to-emitter junction a few tenths of a volt.

whereas for silicon transistors it is said that:

  Since \$ I_{CEO} \$ is typically low in magnitude for silicon materials, cutoff will exist for switching purposes when
  \$ I_B = 0 mA \$ or \$ I_C = I_{CEO} \$ for silicon transistors only.

where $$ I_{CEO} = I_{CBO} / (1 - \alpha) | when I_B = 0 $$

and where \$ \alpha = I_C / I_E\$

So, my question is why is the condition for cut-off \$I_{CEO}\$ for silicon transistors and \$I_{CBO}\$ for germanium ones, even though both of them are operated in the same configuration (Common Emitter).

And also why are they talking about reverse biasing germanium transistors when cut-off already means base-to-emitter junction is reverse biased?

My initial thoughts are that for germanium \$I_{CEO}\$ is high, so that's why \$I_{CBO}\$ is needed.


texts: Is it possible to use DC-restoration as a half-wave rectifier?

texts:
A simple DC-retoration circuit:

seems to do the about the same job as a half-wave rectifier, is it standard to use these two circuit instead of each other ?

I tried to increase the capacitance of the capacitor to make this circuit serve as a full-wave rectifier but so far my attempts led me to the exact same results as above, Is there anyway (change diode type ...) to make a full-wave rectifier of this circuit ?


texts: How to find gain and phase crossover from a Nyquist plot?

texts:
Note: I need to do this by hand which is why I'm struggling. I'm only using MATLAB here to show the nyquist plot, and I was also using it to try and check my answer.
Edit: There are poles at -50, -10 and 0. So none on the RHS but 1 on the axis. I know this implies marginally stable, but I need to provide an explanation based on the Nyquist plot and I thought using crossovers and margins would be the best way to achieve this. (Since the pole explanation is easy to obtain just by looking at the trasfer function and doesn't relate to the Nyquist)
Using this Nyquist plot, I need to determine the stability of the system. I know that I can do this by comparing the phase and gain crossover frequencies, and gain and phase margins. The margins are calculated using the frequencies, so I need to find them to carry on.

Phase crossover is the frequency when the plot crosses the negative real axis
Gain crossover is the frequency when magnitude is 1

I need to be able to do this by referring to the Nyquist plot, but I'm not sure how to do this. MATLAB doesn't provide any frequency data at the crossover points as it only shows certain data when using the data tips, so how could I estimate the frequencies?


texts:
I have a question:

If I charge a capacitor through a resistor and remove it from the circuit, the capacitor will be charged for a certain amount of time (eventually the voltage across the capacitor will become zero volts.)

What will happen when I do the same with a coil?
I charge the coil with a certain amount of charge (through current.)
What will happen if I remove the coil from the circuit?
It is charged with current so it will not stay in the coil I think, or does it?


texts: What's the Actual Speed in GHz of RapidIO or RocketIO serial interfaces?

texts:
When reading about high speed serial interfaces like RapidIO or RocketIO, I find data rates of 3.125 Gigabits/second and more.

My question is: 3.125 Gb/s = ?? GHz

What's the relation between Data rates (in bits per second) and Frequencies (in Hz) ?

I want to route these high speed signals and want to know its actual frequency on trace so that I can take care of signal integrity.


texts:
How do I build a circuit to operate a 220 VAC power supply from USA AC mains?

I couldn't find this question anywhere else, so please forgive me if this is a duplicate. I need to run a power supply unit that needs 205 volts to start up. However, I live in the USA, so I don't normally have that type of voltage. What do I need to do to be able to power this PSU?

Power Supply BITMAIN APW3-12-1600-B2

Input Voltage Range - 176-264 VAC
   Starting Voltage - 200-205 VAC
    Frequency Range -  47-63  Hz


texts: Comparator with two noninverting inputs?

texts: On page 7 of the LTC3631 datasheet, the diagram shows a comparator with two noninverting inputs. What does such a comparator do?


texts:
In Slide 6 of this PDF, it says that the performance of binary signaling is as follows:

I can understand the approximation for high SNR in the incoherent FSK and DPSK case, but how do we get the approximation for the coherent BPSK and FSK case?


texts: Does a high voltage power supply need a ballast?

texts:
I am currently trying to build a power supply for multiple kV. According to Wikipedia an arc has about the same resistance as Metal. I am building my power supply with following parts:

frequency modulator to 42kHz rated for 250W
flyback transformer
(voltage multipliers for DC and increased voltage)

So if i were to create an arc between the outputs, the circuit would have to supply tremendous amounts of power and melt unless i connect a ballast, right? I found this video on youtube: at 0:58 you can see how they only have a halogen transformer connected to a flyback transformer and are creating continuous arcs.

So how are they doing it and do i need a ballast for my setup?


texts: Cannot read accelerometer values from MPU6050 Interfaced with STM32F303RE

texts:
I m working on a "self-balancing robot" with STM32F303RE.I m using STCubeMX to generate the MCU configuration code and then I added the main() to get the values from MPU6050 from the following code :

#include "main.h"
#include "stm32f3xx_hal.h"

/* Private variables-----*/
I2C_HandleTypeDef hi2c1;
uint8_t i;
uint8_t i2cBuff[8];
uint16_t ax,ay,az;
float Xaccel,Yaccel,Zaccel;
#define mpu6050Address 0xD0

int main(void)
{
   HAL_Init();
   /* Configure the system clock */
   SystemClock_Config();
   MX_GPIO_Init();
   MX_I2C1_Init();
   /* USER CODE BEGIN 2 */
   for(uint8_t i=0 ; i <255;i++)
   {
       if(HAL_I2C_IsDeviceReady(&hi2c1,i,1 ,10) == HAL_OK )
       {
          HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
          break;
       }
    }

    /* USER CODE END 2 */

    /* Infinite loop */
    /* USER CODE BEGIN WHILE */
    while (1)
    {
       i2cBuff[0]= 0x3B;
       HAL_I2C_Master_Transmit(&hi2c1, mpu6050Address, i2cBuff, 1, 10);
       i2cBuff[1] = 0x00;
       HAL_I2C_Master_Receive(&hi2c1, mpu6050Address, &i2cBuff[1], 6, 10);

       ax = -(i2cBuff[1]<<8 | i2cBuff[2]);
       ay = -(i2cBuff[3]<<8 | i2cBuff[4]);
       az = -(i2cBuff[5]<<8 | i2cBuff[6]);

       Xaccel = ax/8192.0;
       Yaccel = ay/8192.0;
       Zaccel = az/8192.0;
      /* USER CODE END WHILE */

      /* USER CODE BEGIN 3 */

      }
      /* USER CODE END 3 */

   }

But, when I add ax,ay,az or Xaccel,Yaccel,Zaccel variables to watch it is always showing 0.What can be the problem?


texts: What do these forward currents at specified wattages mean?

texts:
An LED I'm looking at has various specs listed that I can't make heads nor tails of. It is listed as a "3W LED" supporting a 2.5V minimum and 3.6V voltage. However, "Forward voltage" is listed as 3.4V-3.6V. Which makes me wonder what the 2.5V minimum means.
Also, it lists "Forward current" as "350mA@1W 700mA@3W". Now, if I take those values I get respectively 1W/0.35A = 2.85V and 3W/0,7A = 4.28V - totally different ranges than listed under the supported voltages. Besides, I would imagine that a 3W LED running at 3.6V would have a forward current of 833mA. Why are they listing two of them?
Is this just a mistake on the seller's specifications or am I missing something?


texts: Understanding the CNY70 Reflective Optical Sensor

texts:
As far as I know, TM4C123 LaunchPad safely accepts voltages values up to 3.3V . I got a CNY70 reflective optical sensor and want to connect it to one of the analog input ports safely as in the attachment. (each of +5V comes from 5V AC to DC adapter)

The main problem is that I don't understand much from the CNY70's datasheet.  (I couldn't find anything about the ON state resistance of the transistor, which could make things much easier for me)

Could you please explain what calculations should I do, or which figures should I check in the data sheet in order to calculate the X resistance value for safe operation.

P.S: Please keep in mind that, I'm quite a newbie in electronics

Thank you


texts: Is there an inexpensive multi-pole, multi-position relay?

texts:
One of my projects consist of being able to redirect audio output from one among several PCs to one among several audio devices such as headsets, speakers or audio recording devices. The redirector can link only one input to one output. For instance, audio from PC 1 can go to the headset, or audio from PC 2 can go to the speakers.

The essential characteristic is that when a link from input to output is removed, all three connections (GND, left channel, right channel) should be cut, and only then new link should be eventually established. In other words, I don't want, for instance, the GND of multiple input devices to be wired together.

This can relatively easy be done with two rotary switches. A 3-pole, N-position rotary switch will make it possible to establish a connection with an input or output device and break the connection with GND and both channels at the same time.

However, how is it possible to do inexpensively if I want to be able to switch from a device to another not by manually turning a knob, but by sending a signal to an electronic device (for instance with an Arduino)? From what I can find, there are DPDT relays and even 3PDT relays, although they don't seem quite common, but triple pole triple throw ones don't exist, or at least I haven't found them. I suppose, therefore, that the problem like that is not solved with 3P3T or 3P4T relays, but something else.

What exactly are the options?

Combining multiple relays is possible (and eventually any configuration could be achieved by SPDT relays assembled in a form of three parallel trees), but this seems overly complex and quite expensive.

Should I use a series of bipolar junction transistors for that? Or something else?