texts: Simplifying a Boolean Expression with two additional conditions

texts:
Problem:

Given that $$ A \cdot B = 0$$ and $$A + B = 1$$ use algebraic manipulation to prove that:
$$ (A + C) \cdot( \overline A + B ) \cdot (B + C) = B \cdot C$$

Answer:
First, I will rewrite the left hand side without the operator $$ \cdot $$. That is, I will write $$ AB $$ to mean $$A \cdot B$$.

\begin{align*}
(A + C)( \overline A + B ) (B + C) &= ( 0 + \overline A C + AB + BC ) (B + C) \\
(A + C)( \overline A + B ) (B + C) &= ( 0 + \overline A C + 0 + BC ) (B + C) = ( \overline A C + BC )( B + C) \\
(A + C)( \overline A + B ) (B + C) &= B( \overline A C + BC ) + C( \overline A C + BC ) \\
(A + C)( \overline A + B ) (B + C) &=  \overline A BC + BC + C( \overline A C + BC ) \\
(A + C)( \overline A + B ) (B + C) &= \overline A BC + BC + \overline A C + BC \\
(A + C)( \overline A + B ) (B + C) &= \overline A BC + BC + \overline A C \\
(A + C)( \overline A + B ) (B + C) &= \overline A BC + \overline A C + BC \\
(A + C)( \overline A + B ) (B + C) &= \overline A C + BC \\
\end{align*}
I think I am on the right track, but I do not know how to finish solving the problem.
Thanks,
Bob


texts: Can i use another H-bridge for this bipolar stepper motor drive?

texts:
I am driving a bipolar stepper motor with a H- bridge. For this sheet:

source

Can i use my L293DNE H-bridge driver instead of the pictured SN754410NE? Will there be any consequences for this?

I have earlier used the L293D chip for this design:

Needing only 2 controlling pins from the microcontroller it seemed much better, but i have never gotten it to be as smooth in controlling as the top driver sheet, there seems to be software issues when using the arduino library to control it)


texts: Electrical connection that is "AND NOT" gate

texts:
I need to create an electrical switch on normal net voltage (230V) that sort of acts like an "AND NOT" gate.

All I have at the moment is three copper wires and some connectors. Obviously, when I just connect them, I'll get power on C when A or B are powered.
What I need is power on C when A is powered and B is not.

How can I connect my wires to get this, or what do I need to buy in order to end up with what I need?


texts: How many volts can a 1 Watt 8 ohm speaker take?

texts: I am working on an Arduino project and the sound is too low because the output pins on my Arduino UNO is only 40 mA. I can hook up an NPN transistor to amplify the sound, but I don't want to blow the speaker. How much voltage can a 1 watt 8 ohm speaker handle?


texts: How can I prevent incoming calls to two phones?

texts:
I am looking to build a small circuit board that would allow me to prevent incoming calls from reaching a device but still allow outgoing calls to reach their destination.

This is for a standard RJ11 connector I am looking at working with. I have some experience with small electronics but any pointers on where to get started would be great.


texts: Rated power vs. temperature for resistors

texts:
As you know, there is a Rated power vs temperature curve for resistors in datasheets like the image below.

For DC inputs, I think everything is clear about power. My question is that for pulse inputs, should we use RMS power or average power to work with this curve. Many thanks for your time.


texts: How to calculate fuse i2t rating when current is known?

texts: How do I convert the fuse current rating to the i2t value? For example, in this circuit simulator, when adding a fuse, the only values that can be specified are the i2t value and resistance.  The fuse I am attempting to simulate says 32mA.


texts:
If we have a linear power supply, which uses parallel power transistors (NPN) as series element, with emitter current sharing resistors, then which is the maximum acceptable difference of current between 2 parallel transistors?

For example, if the total current is 3A, and we use 3 NPN transistors in parallel each with 0.1Ω emitter resistors, then which is the maximum acceptable difference of current between 2 parallel transistors?


texts:
I have simulated this circuit in Spice and it works as it is supposed to, but I fail to understand the use of diodes D3 and D5.  I know it has something to do with T2 transistor.

Edit:

Correction R22 is 22 ohm and ERR_Out is pulled up to 15V externally (not shown in this circuit.)

Could some one explain it to me?


texts:
The idea is to protect the input stage of a control card from improper power supply connection. The power supply is a standard desktop AC-DC power adapter (Meanwell GST160A12) with inbuilt shortcut, overload and overvoltage protection. Since other models are used (Meanwell GST160A15) the risk for improper connection and operation is high.
The control card needs an input of 12V and draws circa 12 A. How should a circuit be design in respect with efficiency and simplicity?
There is no problem in brutally shorting the power supply adapter. I was thinking in just placing a Zener diode of correct rating that can turn on when the voltage is above 12V and short out the PSU. Would this be a very bad design?

simulate this circuit – Schematic created using CircuitLab


texts: Why do batteries recover after a load is removed?

texts:
I carry a small 2-AA flashlight, and a few times, I have accidentally left it on in my holder.  Each time it dies completely, so that no light is emitted, but if I turn it back off and wait for a few minutes, the light works weakly again.  The longer I leave it off, the longer the dead battery lasts.  I've noticed similar patterns in my mobile phone battery.

Why does this happen?


texts:
In addition to my last post I have more information and details.

I want to run 240V Relay (5V Coil) from my AVR chip (ATmega328P).

My EMR relay takes up to 200mA on it peak.

I have 2N2222 transistor, and I have MOSFET (IRFZ44N power MOSFET).

What is the criteria to deiced which transistor to use?

The BJT can allow up to 800mA (which is ok for me), and the IRFZ44N can take up to 50A (which looks too much), but I also find some MOSFETs that runs 1A.

It looks like the MOSFET is easier, just connect the output pin from the IC to the gate and that's it, while the BJT has some calculations involved. Am I right?


texts:
How can I detect AC 'reverse polarity' (single phase) (without the use of ground/earth) and drive a led when the polarity is reversed?

It should at least detect 230 VAC but it would be cool/informative for future readers if the solution could work in US and EU (approximately 120 VAC to 250 VAC).

I did find this (non-isolated!) circuit, but I can not get it to simulate (the simulator complains that it needs ground or the LED blinks on both halves of the wave).

Source: 1 & 2

My questions are then:

Is the above schematic really functional and how does it work?
Is there a better or alternative way (MCU or perhaps even an IC) that does this?

Update:
Most current answers are leading me to believe one needs a reference. Now I'm thinking, why not create one? Something like a 'virtual ground' or somewhere along that line?

Update 2:
Today I read that older single-phase watt/hour-meters will run backwards if neutral and hot are reversed.. Why is this and couldn't the reason for this behavior be used in a 'equivalent circuit' that detects 'reverse polarity'?
Also, I wonder: could a hall-effect sensor be used to recognize a unloaded 'hot' wire, since a hot wire clearly emits a diversity of electromagnetic fields and elf radiation?


texts: Wire AC/DC Power-Supply to multiple devices

texts:
I plan to power 5 SBC boards through a single power-supply. Each board consumes 5V at 3A max. The power source is ordinary 230VAC (EU). I am uncertain how to connect everything in a sane way.

Power-supply candidate: MeanWell HRP-75-5
DC 5V power connector: Pins or Barrel
Board: Rock64 SBC with attached USB 2.5" drives

I want to operate this 24/7 under normal indoor conditions. Eventually everything should be contained in a box. But until then it has to lay open. The solution has to be quiet and should not produce much heat. The 5 boards should consume power roughly in the same dimension. If one malfunctions or gets plugged off, it should not impact the others.

Main questions

Do I need additional elements between the power-supply and the boards? e.g. limit the max current to 3A.
How to split the power into 5 lanes? Should I build a Stripboard or can it be done as a heat-shrink-tubed bundle of wires?

Side questions

There are a lot of power-supplies similiar to the one I picked. What specs should I look out for except the total Watts?
Does it make sense to use a bigger power-supply in the 100 Watt range to get higher efficiency or lower heat? The pricing seems close.

Thanks a lot.


texts: In the switching from Eagle to Kicad the first thing I was missing are the bend modes. In Eagle you can very quicky change weather you want to prefer a right turn or left on the fly via the "bend mode". Is there something like this in Kicad 5? I'm aware of the quite powerful drag feature, but I liked the bend mode quite a bit.


texts: Can you help me find the voltage drop for R3 and R4 on the following circuit

texts: Circuit:  my teacher says the voltage drop is 1.5V each.  I don’t know how he gets that answer.  Here is my work thus far.  I get 7.5V for each.  Please let me know where I am going wrong.  Thanks!


texts: Time (Propagation delay) taken for adding 3 n-bit binary numbers using Carry Propagate Adders (Ripple carry adders)

texts:
While being introduced to carry save addition technique, I was told that the time taken for adding 3 n-bit binary numbers using ripple carry adders will be (2n+1)t_FA  (Assuming we neglect the minor time difference between a full adder and a half adder),
where t_FA is the delay for a full adder.
Excerpt from wikipedia:https://en.wikipedia.org/wiki/Carry-save_adder
"If you were to add these 3 numbers using conventional methods, it would take you 2 carry-propagate adder delays to get to the answer. If you use the carry-save technique, you require one only 1 carry-propagate adder delay and 1 full-adder delay (which is much lower than a carry-propagate delay) and. Thus, CSA adders are typically very fast."
The reasoning was that it takes n(t_FA) time for adding 2 n-bit numbers using an n bit ripple carry adder
and since the output can have at most n+1 bits, to add the 3rd number and the intermediate result requires (n+1) FAs and hence (n+1)t_FA and therefore total time of (2n+1)t_FA
Can someone show this through a circuit diagram?


texts: Measure an engine valve lift in a fixture

texts:
I work in a company which manufactures engine valves and we have a rig in which valves can be tested for endurance. The fixture in the rig is custom designed for the valve and the corresponding camshaft's lobe is fixed onto the top to actuate the valve. So I am looking for a setup to figure out valve lift (vs crank angle or cam angle) and currently I have an Arduino MEGA 2560 with me. I would like to know what kind of displacement sensor (with precision of 0.1mm) and encoder should I use, will an Arduino MEGA wil be fast enough? The maximum speed at which the camshaft rotates would be around 3000RPM.

This picture has 2 valves but in my case, I would have just one valve and I would have to calculate crank angle from cam angle (sort of).

Any ideas on this would be helpful.

Thanks!


texts: Audio Amplifier which can Supply 20W to 20-40 Ohm Load

texts:
I've looked around for a while, and my question appears to be very specific and I was hoping that someone who knew more about audio amplifiers could help.

I'm doing some research assistance where sound sources with impedances from 20-40 Ohms are going to need to be driven at 20W. Based on some Googling I've done, this appears to be very specialized. Even very expensive amplifiers are only rated with 4 to 8 Ohm load speakers. The amplifiers need to be suitable for audio (passband from maybe 100Hz to about 25kHz), and I've found nothing so far.

My question boils down to this: does anyone know where I might find such an amplifier, or whether I need to construct my own? I'd like to spend less than $100 on the amplifier, which may be impossible.


texts: What is the minimum amplitude level of the input signal to trig the capture interrupt in xmega timer

texts:
Dears
I have a collection of wires connected to xmega256, 8 for porta, 8 for port b where portb used to trig 8 ultrasonic sonsors and porta used to echo that sensors, I have implemented the measurment using two tc0 timer in input capture mode and pulse width mode and every thing is good, but with out any ultrasonic connected to the board and when I trig some pin an echo signal rises at the same sensor pin and this signal fire the timer interrupt
The pins connected directly to the xmega with out pull down resistors and I have check the wiring pin by pin, i dont know the source of that echo, it just appears using the oscillator when I trig the same sensor pin and it is some times randomly appears .
How can avoid that signal to prevent the timer interrupt
Any same problem have faced you
Thanks


texts: Can I use a twisted pair for 5V and ground?

texts: I'm going to use a RS485 modbus connection which requires a twisted pair. Now I also need power, that will be a 5V line and a ground. The distance will be about 3 meters max. Can i use a twisted pair for the 5V and gnd as well? Or will that result in a voltage drop?


texts:
I am doing a project in school for which I have chosen to use stepper motors to drive a conveyor. Reasons I chose these, and not BLDC or AC motors include their low cost, and ease and accuracy of control.

I purchased the Sparkfun Redboard, a 125 in-oz unipolar stepper motor and Brian Schmalz' Big Easy Driver; I am driving the Big Easy Driver using a 12V, 2A power supply. (Redboard runs off computer USB for now)

I have been having a few issues, which I have researched somewhat, but was hoping to get others' input on what I've come up with:

The motor exhibits a lot of vibration and noise, especially when microstepping. This is contrary to my understanding that microstepping should actually smooth things out. Also, when I try to use a pulse width less than 1 ms (the datasheet for the chip says the minimum pulse/delay is 1 ns), the shaft chatters rather than rotates.

Could this be a problem of too low voltage? I tried a 19V laptop power supply, but it fried a driver somehow, so I would prefer to try other solutions first. Also, could the fact that I'm using the default Arduino libraries and not Accelstepper contribute to this? (website is down, can't download it right now...)

Any input anyone has would be much appreciated.


texts:
I have, what I'm sure, is an absurdly simple question:

How do I step up 3 volts to 5 volts using either an OP_Amp or an XOR IC?

Background:

I have a 5volt power supply.
I have a 3volt output from a motion detector (which is supplied by the aforementioned 5volts) .. I have a 5volt circuit that needs to be triggered when the motion detector is tripped (which would, presumably, also be supplied by the aforementioned 5volts).
Currently, I'm using an exclusive OR GATE IC to grab the 3V output from the switch .. I had hoped that this would then pass-through the 5V from Vcc through to the waiting 5V circuit on the opposite end of the circuit.

Additional info:
 - XOR IC : CD74HCT86 74HCT86 QUAD 2-INPUT EXCLUSIVE OR GATE
 - IR Motion Sensor : HC-SR501 IR Pyroelectric Infrared PIR Motion Sensor
 - Circuit needing voltage : array of LED lights.

Let me know if you need additional info.


texts: Why should the bias servo transistor not be placed on the main heat sink for a Sziklai pair?

texts:
The Wikipedia page on Sziklai pairs contains the following statement (emphasis mine)

  Sziklai pairs can also have the benefit of superior thermal stability.
  [...]. [Q]uiescent current is much more stable with respect to
  changes in the temperature of the higher power output transistors vs
  the lower power drivers. This means that a Sziklai output stage in
  a class AB amplifier requires only that the bias servo transistor or
  diodes be thermally matched to the lower power driver transistors;
  they need not (and should not) be placed on the main heatsink

I'm specifically interested in the "should not" part of that statement. I suppose that placing the bias transistor on the main heatsink may be overcompensating, which could create distortion at normal operating temperature? Or is there something else at play? Does this mean that I should make a separate heatsink for the lower power transistors so that they can be thermally connected to the bias servo transistor?


texts: How to generate a file with BOM for multiple schematics - EAGLE

texts:
I've 3 boards each with it's own schematic but with a lot of common components. I want to generate an unique BOM for all this boards to know quantity of each piece I need and make a single order BOM.

For example:
I can extract a single BOM with
run bom.ulp

But now I want to merge this BOMs in a single file with quantities of a common single piece sum togheder.

There is a method in EAGLE or Excel to do this? I want avoid to manually do this becouse of risk to make errors in count or add pieces.


texts:
R4 is thermistor with R25 value of 5 Ohm, Beta is 3150. V should be at most 1V because I want to use internal 1V1 reference voltage. V supply is 5V. I don't really want to use OpAmp to keep it simple. The problem is also to draw as less current from power supply as possible. Accuracy can be 2-3C, range is 20-80C.

I tried to use some Wheatstone bridge calculators, but I don't get the bridge balanced and to draw acceptable current.


texts: Where do I measure the Amp draw of my motor which is connected to a centrifugal fan?

texts:
I just started my job as an apprentice technician. For the longest time, my supervisor have always been measuring the amp draws of my motor from the outgoing cable from the motor to the electric panel (which is below the full load amperage stated on the nameplate), but one of our clients insist that the way we've been measuring it is incorrect, and the correct way is to measure the amp draw from the cable incoming to the motor's panel from the distribution panel, which shows that the motor is drawing twice the amps of the FLA.
The motor is a 50Hz 11kW motor with 25.5 FLA.
I haven't found any specific references or examples in my google search, and the closest I've seen is this website
https://www.hvachowto.com/measure-amps-blower-motor-condensing-fan-motor/
So, which is the correct way to measure the amp draw of the motor configuration?
Thank very much for any help, and I apologize if the question is too simplistic or stupid to begin with.


texts: Controlling the temperature of mica band heaters mounted on extruder barrel very precisely with power rating of 5kW

texts: I want to control the temperature of mica band heaters mounted on extruder barrel very precisely with a power rating of 5kW and 220VAC. What should be the best for the switching purpose of these heaters?


texts: How to generate desired voltage signal in a circuit?

texts:
What I am asking is a design or pulse shaping question.

We learn about analyzing circuits but not designing them in school.

Let's say I have an input signal which is a triangular wave and I want to generate some output signal with some sophisticated shape that are not simple sin or square wave or something we know.

How should we design the circuit in between to achieve that? What I can think of is to write equation of my output signal of desire in time domain somehow and take laplace of it to figure out what components in what order should be placed to achieve this signal.


texts: Best method for sending data over a mono audio channel

texts:
I'm looking for a way to send binary data over an audio channel on a video/audio transmitter. This will be an add-on feature to my product because it already has an audio interface. I'm hoping to be able to reach about 1 kbit/s data rate at a minimum, but higher would be nice. The requirements for any such protocol would be:

High noise immunity - so a signal with some noise and interference on it doesn't cause problems. Ideally, data would be either error free or flagged as having errors, as corrupt data could cause lots of problems. Weaker signals may introduce jitter and other nasties into the signal, so it should be capable of withstanding these.
Be able to work on a bandwidth limited (approx 8 kHz) audio channel. This includes slew rate limitations and variable jitter, including between clocks or bytes.
Be easy to implement, both transmitting and receiving, on a small microcontroller.

The protocol only needs to be one way as data will only be sent. The reason I ask this is because I've gone through lots of possible options (FSK, PSK, duty cycle modulation, Manchester, etc.) but have no idea which would be the best.


texts: I have two signals, say a and b. Signal a has power of 6 Watt. Signal b is summation of signal a and noise n and has power of 7 Watt. I want to normalize the signal b in a way that its power is equal to the power of signal a. Does anyone have any idea on how to carry out this type of normalization?


texts:
I have a problem with perfboard, every time I made a circuit which works flawlessly in breadboard, doesn't work on perfboard. Is it because of soldering distance or am I doing something wrong?

All circuits are 5-12V and low current (200mA max). First one is 7 segment display, second one pwm motor control, last one Ne555 frequency generator. Display circuit's problem is display randomly flickers segment. PWM's problem is MOSFET randomly opening or closing (and heats up). NE555 problem is output is always on even NE555 removed.

It seems like solder or perfboard causing the voltage jump (somehow) but I checked several times and multimeter shows no connectivity, I tried to clean the paste and clean the space between solders but still no luck. Some of my circuits to show the problem:


texts: Pin TX0 -> 1 and RX0 <- 0 on ATMega2560 for USB serial communication

texts:
I am currently working on a project where I have to make my pc communicate with my ATMega2560 through the USB serial port. The ATMega2560 is the receiver.
I have been told that the pins TX0 -> 1 and RX0 <- 0 on the board are used for that:

I am coding in C++ in Atmel Studio. Can I just configure the UART to use RX0 and then it will work? Or do I need to do anything extra, which I don't do when I am using the other RX pins?


texts: Higher KV means lower torque for DC motors?

texts:
I'm in the process of trying to build an electric skateboard. On the websites I visited I read that torque and KV are inversely proportional which does seem counter intuitive. So I'm wondering why that is the case.

I think some beginning of answer can be found in this paragraph:

In summary, a low KV motor has more winds of thinner wire - it will carry more volts at less amps, produce higher torque and swing a bigger prop.

So yeah, lower kv motors have thinner wires. Thinner wires mean more resistance and less current for the same voltage. I don't really understand the rest though. I don't see the relation with more torque..


texts: PIN diode in RF switching vs. PIN diode used as photodiode

texts:
From what I understand, there are traditional photodiode components that are designed with PIN diodes, in which the gate is activated by light saturation.  For a PIN diode component made for RF switching applications, the gate is operated by applying a forward bias current.

How closely related are these two types of components? For example, if I take a photodiode and fully saturate the sensor with light, would it operate in the same fashion as an RF PIN diode? Would an RF signal be able to pass?


texts: Expose SDRAM as a USB 3 mass storage device

texts:
Challenge:
Build a device that can host one or more SDRAMs (e.g DDR2, DDR3) and expose them as a USB 3 (slave) mass storage device.

Goal:
Allow a USB 3 host to mount the device and allow near 5Gbit transfer rates.

Attempt 1:
Use a PC to build the device - fail - PC doesn't come with hardware necessary to use USB in slave mode.

Attempt 2:
Use a micro controller, such as PIC or ARM. SAM9 has support for DDR2, but lacks support for USB 3. Perhaps there're other micro controllers out there which would be suitable?

What other configurations can you think of that might help in solving the challenge?

Note: Please disregard the fact that SDRAM is volatile and somewhat unsuitable for storage.. Also, I'm aware of the existence of i-RAM or HyperDrive, which basically does the same thing but connected over PCI.


texts: Issues with a timing circuit using a comparator and RC

texts:
Above is a comparator circuit which employs RC time constant to control the ON time of the output(please left-click to enlarge the image). Red plot belongs to the momentary-switch voltage versus time, green plot is the output voltage; and the blue is the current through the LED.

The load connected to the output will be a solid-state-relay such as:
https://www.sparkfun.com/products/13015

I'm planning to drive a DC motor with that relay as a next step.

My questions are:

1-) When ON time I want the LED to glow, so I had to use around 270 ohm in the simulation(R6) to obtain a moderate brightness around 11mA. Bu then I had to choose R5 as 470 ohm where I normally choose it 10k in non-loading applications. Is the value of R5 pull up OK?

2-) Regarding C1: Should I use a tantalum capacitor instead of an electrolytic one for stability and long term use?

3-) R5 drives current all the time, so one has to switch off the power. Is there a workaround to prevent that? And LED current never goes to zero. Any ideas about these?

Note: I don't want to use an additional opAmp.

edit:


texts: Why doesn't the STM32f0 go to the interrupt routine? (in the debugger)

texts:
I'm trying to execute my project in the debugger but it doesn't go to the interrupt routine. the project is correct and it works without the debugger nicely.

How do I use it?

Ok, here we go!

at first, I connect the J-link debugger to the board and I click on the start/stop debug session button. now I'm in the debug environment. I go to the Peripheral > System Viewer menu and choose these peripherals to observe them: RCC & NVIC & EXTI & GPIOA and finally GPIOB. the configuration is enough (I'm not sure that these configurations are enough. if there are some other configuration that have to do, tell me).

Ok, lets go to start the debugging. I pass all functions between int main(void) and while (1) by clicking on the Step Over button. well now I'm in the infinite loop and time to show! before push the button in the circuit, the registers are:

Now I push the button and click on the Step button in the debugger environment and the registers for interrupt are:

I expect that if I click on the Step button, it jump to the interrupt routine but when I click on it, it doesn't go! click-click-click-click-...
No, it doesn't go!

Why? What is the problem?


texts: Gigabit transceiver with MHz reference clock

texts:
I've some experience with Xilinx FPGA generating 10Gb/s over SMA loopback with on-off keying modulation (what scope shows) to perform BER test but the documentation shows it uses a reference clock in MHz level.
How is it possible to generate gigabit line rate especially 10Gb and above with MHz reference clock? Someone told me to look at SerDes but I could not make sense with it. Can somebody please navigate me?


texts:
After extensive research and finding very helpful circuits for the rest of the system I still have not found what im looking for. I am building a PoE raspberry pi weather station that will be mounted on a 30 meter tower so access is limited.

The challenge is as follows. The AC source is unreliable so I have a +-2 hour battery backup inside the weather station. The idea is to monitor the AC input, battery voltage, and Pi state ( Shutdown or not). When the AC is not avialable the Pi will run off the battery. when the battery nears depletion the circuit must send a signal to the PI which will run shutdown script.

When the AC supply is restored the "Run" pins on the Pi needs to be toggled to reboot the pi. the issue is the reset circuit cannot just reset the pi every time the AC comes back and falls away. becuase if the run command is given to the PI While still running on battery it has a good chance of corrupting the SD card. my current solution is a Arduino pro micro programmed to check all the conditions and only reset the PI when the Arduino it self sent the shutdown command.

Is there a way todo all of this with simple circuit ?


texts: Bilinear transformation: why does it cause a deformation on my filter

texts:
So I'm designing a Butterworth 4th order highpass digital filter. I developed all my equations (I can put them here if it is relevant) and arrived to this graphs for the frequency response. In red there is the original analog filter and in blue the digital filter.

Can someone please help me understand why I'm observing these differences? I used the bilinear transformation which I know adds up zeros to the transfer function, but I can't understand why these zeros seem to add a 0.4 dB error in the edge frequency of the filter (3000 Hz) and it seems to shift the phase response to the left. Can anyone clarify this to me? Thank you!


texts: Altera Cyclone II JTAG after AS Programming

texts:
I've been playing with FPGA(Cyclone II EP2C5T144C8) with Quartus II 13.0 WebEdition 64bit and Altera USB Blaster.

At first, I was using JTAG mode for programming FPGA into RAM. When I wanted to program EEPROM(EPCS4), so I switched to AS mode.

Since I programmed in AS mode, I can't use JTAG mode anymore. 'Auto Detect' fuction in Programmer window responds with 'unable to scan device chain... bla bla'.

jtagconfig gives:

>jtagconfig -d
1) USB-Blaster [USB-0]
  Unable to read device chain (JTAG chain broken)

  Captured DR after reset = ()
  Captured IR after reset = ()
  Captured Bypass after reset = ()
  Captured Bypass chain = ()

However, programming in AS mode works. Seems like JTAG mode has been disabled somehow..?


texts: Does volts or amps increase the strength of an electromagnet?

texts: I'm trying to make an electromagnet that's strength is constantly getting incremented by small amounts every second. I need to know, which would have a greater effect on the electromagnet's strength, amps or volts? (I know increasing the turns and/or density of the magnet wire will increase the strength, but I am looking for answers other than that particular one.)


texts: Phasor analysis of AC circuits: Which is correct: impedance triangle or phasors as resistors?

texts:
Phasor analysis is convenient with AC circuits when looking for simple quantities like impedance.  After converting capacitive and inductive quantities to reactances, I then treat them like resistors.  It's a convenient way to make AC circuit analysis relatively simple.  However, I found out today that I may have been doing it wrong, and I need help understanding why.  For example, the circuit below:

To find the impedance in this circuit, I would first find XL, then Xc:

\begin{equation*}
{X_L}=2{\pi}fL=52.779{\quad}{\quad}{X_C}=-{\frac{1}{2{\pi}fC}}=-16.579
\end{equation*}

Then I would treat the reactances as resistances, in this case using the simple parallel resistor formula:

\begin{equation*}
Z = \frac{1}{\frac{1}{R}+\frac{1}{X_L}+\frac{1}{X_C}}
\end{equation*}

The result I get this way is Z = 24.75Ω

In studying for the FE exam, I've come across a method which relies on the impedance triangle:

Through some trig on the relations on this diagram, the formula for impedance in a parallel AC circuit with reactive components becomes:

\begin{equation*}
Z = \frac{1}{ \sqrt{\left(\frac{1}{R}\right)^2+\left(\frac{1}{X_L}+\frac{1}{X_C}\right)^2} }
\end{equation*}

The result I get this way is Z = 24.17Ω

As you can see, they both produce a very similar result, but not the same.  One is an approximation, and I have a suspicion based on the impedance triangle that the latter method is correct.

Can someone please elaborate as to why that is or isn't the case?

Thank you.


texts: How do I use i(t) = c^(dv(t)/dt) and c=q/v and

texts:
In this series circuit:

To determine the voltage dropped across each capacitor

The charge stored in a 2 Farad capacitor

The number of charges stored on the capacitor plates

And Determine what value of a new capacitor C that would store the equivalent charge of all the other capacitors


texts:
I have a question about solid state relays.

I am into drag racing and we use a solid state relay/driver to control the transbrake solenoid(large solenoid in the transmission that allows the transmission to be held in place while loading the engine). We use the holley performance 554-111. We use solid state because we want to pulse the solenoid so the car creeps forward under large engine loads. This allows us to creep into the staging beams and then launch the car.

So I was playing with this driver/relay last night and this is how it's wire.
Orange Wire: 16v in
Small Yellow and Black Wire: Ground trigger from ECU
Blue wire: Output to transbrake solenoid

When I check voltage at the transbrake solenoid without the relay being engaged it still shows voltage. When I engage the relay the same wire increases in voltage about .6v(from 16v to 16.6v).

Everything works as it should, but I dont understand how. If the output wire always has voltage why is it not engaging the solenoid even when its activated off?


texts:
I'm going to try to build some throwies soon and am ordering some LEDs and other needed things for the task.
It is my understanding that a CR2032 battery is 2.6-3.1 volts.
Well, I have these LEDs picked out.

660 nm wavelength
1.85-2.5V Forward Voltage, at 20mA current

Would this be ok to use without any resistors? I'm ok if LED life is shortened, but I definitely don't want for the LED to just light up and then be burnt out a second later.


texts: Is there a good replacement for stripboard in the surface mount world?

texts:
More and more components I want to use are only available in surface mount packages.

I can either get a big collection of adapter boards for all flavors of SOIC/WFBGA/QDERP to 100 mil pin spacing, and keep using breadboard and stripboard, or I can try to make the jump to all surface mount.

I don't imagine there are many solderless prototyping solutions for surface mount components, but are there solderable "stripboard" type products for surface mount at different pitches?

If not, would it be a good idea to make some exposed pads in a crisscross network of some sort from a board house and keep around for experiments, or is there some reason that won't work at all?


texts:
I attached some wires to a microcontroller for capacitive proximity sensing of fingers or hands. The sensitive areas are of several shapes.

For a compact shape, I just put some wire in spiral fashion to get a larger sensing area.

But there is a long linear shape (about 400mm) too, so I just spread out the wire this way. Now it has a large idle capacitance, is not very sensitive, captures a lot of noise and is not more sensitive than the attaching wire, so the detection area for a certain threshold expands to the wire between the sensor wire and the controller.

Is there a simple way to get the linear area more sensitive and defined?


texts: Stop EAGLE from wanting to connect all thermal pads together

texts:
So I'm doing a board with a few components that have pads named TH (for "thermal", not "through-hole"). The pads are not connected to anything in the library device, and I haven't done anything special with them. One side of the board has a polygon named TH as well.

After using the autorouter, EAGLE gives me a bunch of airwires in places where it wasn't able to connect all the TH pads together. Now, I don't really care about that - is there a way of telling it not to do that? Just hooking them up to whatever part of the TH polygon is around would be fine for me, it doesn't all need to be connected.


texts: Why are circuit boards not covered in thermal paste?

texts:
A pcb in deionized water may behave differently due to the change in capacitive ratio (leaving obvious problems such as where to get pure deionized water and keep it contaminant free).

However, would covering the circuit with thermal paste have the same effect?

From my understanding, thermal paste is thermally conducting but a good electrical insulator. From basic physics, heat dissipation works better with larger surface area (and a large temperature gradient between two sources, amongst other factors such as materials used etc.

Why is this not used in complex high power circuits where passive power dissipation is required?

Would it be a problem if it was applied only across the copper tracks and on the tops of components, making an irregular heatsink that spans the dimensions of the board?

Obvious use case would be cramped Mobile devices:
This would also increase the surface area, which would increase heat dissipation efficiency significantly.


texts: Op amp driving large capacitive load - do I need to be careful during power off?

texts: I have an LTC6090 high voltage amplifier, with a +140V supply, driving a 200 nF load through a 10 ohm resistor. During device power-off it's possible that the aplifier +ve rail will sink faster than the capacitive load. I have a 1.5M resistor to discharge the load which will take about half a second. In this scenario the load capacitor will be at a higher voltage than the rails. Will the amplifier just discharge the load as it sinks, or could damage occur if the rails drop too fast?


texts:
I am trying to design a device that captures DV (digital video) from camcorder and stores it on sd card. The camcorder produces ~4MB/s of data which the device needs to capture and save to SD card.
What should I take into consideration when picking right microcontroller for this task? How to calculate max speed of IO using controller data sheet? How does running input and output at the same time affect bandwidth?


texts:
I'm studying all by myself, I'm not taking any courses or majoring at something. Last year I had a question about an RL circuit that's been annoying me for a while. Now I'm at home doing nothing but reviewing some exercises that I've already done and this one is a problem, as I couldn't do this one.

The question is: How can find \$i_3(t)\$, that little current right through that inductor?

PS: If you just give me a little start, I'd appreciate it very much.


texts:
I'm building a grow light using 100 rgb leds. I know that I need resistors but I don't know how to calculate which ones to buy.

Also before I buy the leds I have the choice between common cathode and common anode, which would work best for my project?
I've tried online calculators but they only work for normal leds. Here's the technical information:

Forward Voltage / Current: R:2V-2.2V G:3V-3.2V B:3V-3.2V | 20mA (each color)

I intend on using a 6v lantern battery as my power supply.


texts: Positioning a quadcopter using IR signal

texts:
I need to get an autonomous quadcopter above a bucket (60x40 Cm) and deliver a payload inside. The idea is to get near the bucket using the GPS. Then guide the copter by putting some IR emitters around the bucket and receivers on board.

I have an arduino board in the flight controller but I might need another one. I will use Mission Planer software to get near the bucket and control the copter but to find the exact position of the bucket I probably need to implement another code or use another software, any ideas? I guess I need a program that makes the copter to move towards the signal is stronger (keeping the altitude). And when the signal is weaker in all directions, it means the copter is upstairs.

I also don't know the circuits that would do for the emission and reception of the signal and I heard that infrared may not work outdoors...

Once the copter is above the bucket, it won't be a problem to trigger the payload using a solenoid valve and a relay.


texts:
I try to do a CRC-16/Maxim calculation in VHDL.
My current implementation looks as follows

lfsr_c(0)  <= lfsr_q(15) XOR data_in;
lfsr_c(1)  <= lfsr_q(0);
lfsr_c(2)  <= lfsr_q(1) XOR lfsr_q(15) XOR data_in;
lfsr_c(3)  <= lfsr_q(2);
lfsr_c(4)  <= lfsr_q(3);
lfsr_c(5)  <= lfsr_q(4);
lfsr_c(6)  <= lfsr_q(5);
lfsr_c(7)  <= lfsr_q(6);
lfsr_c(8)  <= lfsr_q(7);
lfsr_c(9)  <= lfsr_q(8);
lfsr_c(10) <= lfsr_q(9);
lfsr_c(11) <= lfsr_q(10);
lfsr_c(12) <= lfsr_q(11);
lfsr_c(13) <= lfsr_q(12);
lfsr_c(14) <= lfsr_q(13);
lfsr_c(15) <= lfsr_q(14) XOR lfsr_q(15) XOR data_in;

With lfsr_q initiated to 0x0000.
But this gives me the result for CRC-16/BUYPASS according to https://www.crccalc.com/

What do these RefIn and RefOut exactly mean and how would I change the above lfsr to output the CRC-16/MAXIM? Is my assumption correct that I don't have to manipulate my input so I still can shift in MSB first?


texts: multi-level NAND circuit simple conversion

texts:
i am working on understanding the NAND conversion I have just got the basics of two-level NAND conversion and when i went to the book example for a multi-level NAND coversion it used solved an example until reaching to a level and kept the or gate, although he could replace it with NAND , i have searched on the web I found some people done the same but without reasoning why, i read the text book related-material but also the writer didn't explain why he left it .
the example is :

anyone know the reason why he left the or gates although he could replace it with NAND ?


texts: Op Amp Clipping High when Signal Goes Low

texts:
I'm using a 4558D JRC, and when my amplified signal gets low enough to clip, it goes to the positive supply rail rather than the negative one. Can anyone explain why that is?
It makes a really horrible scratching sound when I'm trying to soft-clip my guitar signal.

I'm powering it with 9V, non-inverting; input biased at 4.5V, as I'm not using a dual-voltage power supply; and a gain of around 501 (Gain = 500k/1k+1).

Datasheet:
https://www.rcscomponents.kiev.ua/datasheets/jrc45584i743ncft874nfdt34ufguygf43.pdf


texts: How to design and build RF amplifier, that work in 450Khz

texts:
I have a schematic, that is a sine generator and mixer that does AM  modulation. How to design and build an RF power amplifier and build a compact antenna. The goal is to transmit signal up to 50 meters. So the amplifier should be enough power.
I plan to use only fixed frequency, that radiate device, it's about 450Khz.


texts: SIM908 Li-Ion charging with 6V solar panel

texts:
So, I want to know if I can hook up a 6V 2 watt solar panel to the Vchg pin on a SIM908 gsm/gps module and trickle charge my 6Ah LiPo battery that way.  A little background...

So, I have completed the first prototype for a new product I'm developing that is essentially a SIM900 GSM modem, and a separate GPS receiving module, all hooked up to a 6 Ah battery that gets trickle charged using a 2 watt 6V solar panel hooked into the Adafruit Solar Li-Ion charging module (which is based on the MCP73871 charging chip).  This charging chip features something called "Voltage Proportional Charge Control", which allows you to set the chip to charge at the max current possible without collapsing the input voltage field below a certain value (the Adafruit board uses 4.5V as this value).  This essentially means that in any light condition, the charger will draw as much current from the solar panel as possible without causing the panel's voltage to collapse below 4.5 V.

Seems to work okay.

For the next iteration of the prototype (version 2.0, if you will) I would like to switch to the SIM908 module, which from what I can tell is essentially a SIM900 module with a GPS unit incorporated.  I should mention that I'm also going to be just getting the SMD breakout board version (not a shield), so that I will have access to all of the pins on the SIM908.

In reading the "Hardware Design" guide that SimCom produced, I noticed that the SIM908 also has a Li-Ion charging function designed into it as well.  Sweet!  That means that I won't need to buy another Adafruit Solar charger (which costs me about $20 plus shipping).
Right?

Adafruit seems to think this won't work very well, and say that setting up the charging circuit this way would result in the charger turning on and off repeatedly as it collapses the voltage coming from the solar panel by trying to draw too much current. Here is their discussion on this where they state:

  Now you can see what happens if you connect a 6V solar panel to a lipoly charger. As long >as the current being drawn by the charger is less than the panel's short circuit current >at that light condition, everything is peachy. The moment the light changes even a >little, and the current the lipo charger wants is higher than the short circuit current, >the charger becomes unstable: it will draw too much current, which will cause the voltage >to collapse, which causes the charger to turn off, which reduces the current draw, which >makes the panel voltage recover, which turns on the charger again, which then draws too >much current, and the cycle repeats.

But would I really lose that much efficiency?  Is there a downside to having the charger repeatedly turn on an off?  Does anyone know how to find out if there is a Voltage Proportional Control Charge function built into the SIM908?  I'm guessing I'm going to have to stick to a solar-specific charger, but I thought I'd ask here in case I'm wrong.

Here is what I'm thinking the SIM908 charging circuit would look like:

simulate this circuit – Schematic created using CircuitLab


texts: Measuring input and output resistance of the hybrid model

texts: I understand that the input and output resistance is calculated using the Thevenins theorem. Thus the output resistance = Rc itself as the current source is open. But what about input resistance? Shouldn't it be (hi + Re)||Rb since the current source is open? What am I doing wrong here?


texts:
How or what are the constraints for deciding factors of envelope detector for AM?
As far as I know that charging time of  the capacitor should be below 20T where T is periodic time of carrier and discharging should not give negative clipping, but I cannot see how to apply them.

Question 2


texts: In my lecture notes I keep reading "do not gate the clock". I tried searching on the Internet, but I'm unable to find the exact meaning of this phrase.


texts:
It's said that impedance is 50 Ohms, and VSWR <2:1. I understand that 50 Ohms mean the input impedance (in that case transmission line or in other words cable)
Does the VSWR < 2:1 mean nominal impedance during the operating bandwidth is betwen 25 and 100 Ohms?


texts: Can't get low pulse from particulate sensor Shinyei PPD42

texts:
I have a Shinyei PPD42 that's connected to my Raspberry Pi B+ using a voltage divider to get the output of the PPD42 to 3.3 V. According to the specification sheet, P1 emits digital output when >1 μm sized particles are detected and P2 emits digital output when >2.5 μm sized particles are detected. Using the ratio of LOW pulses in 30 seconds, you can use a formula to determine estimated pcs/0.01cf, μg/m^33, and AQI. The LOW pulses, according to the specification sheet, are supposed to be 10ms - 90ms in duration.

I've followed some great resources that describe how to physically setup the sensor (vertical orientation, covering the sensor with tape/paper but leaving the air inlet/outlets uncovered, keep away from an air stream, etc).

I've run different projects (written in C) as well written my own code (in Python) to get the calculated values. However, what I'm finding is that regardless of the project I use, P1 and P2 almost never provide a LOW pulse. So, I end up getting a lot of zeros. For example, I ran the previously mentioned project overnight and didn't see a single calculation above 0 for the whole night.

If I remove the tape from the sensor opening, and move my hand up and around the opening, I do start to different values for the calculations. This is obviously just because of the change of light, but it's been an interesting way to make sure that the photo diode is still working.

I've tried to use my phone's camera to see if I can see the infrared LED (as seen in this deconstruction of the PPD42). I can't seem to pick up the PPD42's infrared LED on my camera but I can pickup infrared LED from my TV's remote.

I have a digital multimeter where I tried to debug P1 and P2 without connecting to my Raspberry Pi. I should be able to see the voltage drop from ~4V to ~0.7V when particles are detected (according to the specification sheet). Unfortunately, the multimeter just measures ~4V all the time. My guess on this is that the expected pulse duration of 10-90ms is probably too short for the multimeter to measure? Or, is this further indication that I'm never getting pulses from the PPD42? I have a second PPD42 that behaves the exact same (I just recently purchased them both new from eBay).

Is there anything else I should be doing to debug this sensor and see how I can get LOW pulses? Could both of my units be defective?

Here's some test results from @SamGibson's suggestions:

I don't have an oscilloscope or logic analyzer handy.
I followed the instructions to connect a red LED + 3 K resistor (anode on 5 V end). The LED is OFF by default. Wouldn't this indicate a constant LOW pulse from P1 or perhaps it's the opposite? The LED blinks on/off when I move the box around and wave my hand around the sensor opening (I removed my tape). On its own, I get a small LED blink on/off every minute or so.
I used my multimeter to measured the voltage across the IR LED (back of the board) and got ~1.4 V.
Pointing in my remote control at the photodiode and holding a button does turn on the LED. However, I noticed that it blinks at a fast rate. I confirmed with my camera that my remote control's LED blinks on its own very quickly. I'll have to find another IR source to test with constant IR light.
When I measure the voltage on P1, I get 4.5 V and 4.7 V (I measured ~15 minutes apart so that's why I got 2 different values). This seems to be higher than the HIGH/LOW pulse range according to the spec sheet. If I recall correctly, I previously measured this to ~4 V, so I'm not sure what could have happened to cause a different measurement.

I've confirmed that the IR LED seems to be functioning. I used my Nintendo Wii Remote's IR camera and the Wii U's "Sensitivity" view. I pointed the Wii Remote's IR camera at just the right angle inside the PPD42's sensor opening and was able to see a dot on the Wii U's "Sensitivity" view. So, I seem to be back to square one. So, the unit appears to be functioning but it's just not sensitive enough.


texts: Why is there no voltage drop along a feedline

texts: This page shows a graph of voltage along a transmission line by distance. Considering the case of a simple purely restive feedline of 50 ohms matched to a load of 50 ohms, I would expect the voltage at the source end to be twice that of the voltage at the load end of the transmission line (line and load act like voltage divider), so the VSWR would be 2:1, not 1:1. It seems to me that this transmission line, unterminated, would achieve that 1:1 ratio. Why is the SWR/VSWR considered to be infinite for an unterminated or shorted line? Are these measurements built on the assumption that reactive components to the impedance dominate over purely real (resistive) components?


texts: Can the output of one logic gate serve as input to more than one subsequent logic gates?

texts: NOT gates take one input, AND and OR gates take two inputs. But can any gate have more than one output? I've only ever seen diagrams where each logic gate has exactly one line coming out the right end.


texts: Crosspoint switch matrix for audio frequency signal?

texts:
Modular synths have recently piqued my interest, but patch cords are hell. I have been thinking of some intelligent way to route signals - something microcontroller-driven and remembering different presets. I came across analog crosspoint switches - they are used to switch high-frequency signal, television and the like, and have 16 inputs and 16 outputs. They, however have unnecessarily high bandwidths (60+MHz) and prices ($30+/chip) for this.

I'm looking for a 16x16 switch (or a good way to implement one), suitable for modular synth use, and not having dedicated inputs and outputs - just 16 points which can be freely connected to one another.


texts: How do I cut power inside a main panel when there's no service disconnect present?

texts:
I am trying to install a 50A circuit breaker for a 14-50 outlet. I'd like to put that breaker in the main panel of the house.
Looking at my panel I cannot figure out how to cut power to the whole panel. There doesn't seem to be a service disconnect anywhere. I can see breakers which feed: a subpanel in the garage, the oven, the AC, the irrigation system, and the telephone/TV panel. But no main breaker or service disconnect. What am I missing?
The only other things on this panel are 2 sections: 1 where the meter sits (below the pictured panel) and, next to it, a section that's sealed off by the electric company (PG&E). Could my service disconnect be in the street (there's a bolted down box in my front lawn), or in the sealed box?
Thank you!


texts: How to make 2 or more bluetooth devices(ESP32) get RSSI Values(signal strengths) of each other?

texts:
I am creating a prototype for a Social distancing tracker using bluetooth devices, wherein if 2 bluetooth devices come in close proximity(measured with signal strength), then both modules send their addresses to a Wi-Fi server.
Module used: ESP32(with Wi-Fi and Bluetooth built-in).
Requirement: Each Bluetooth module should be able to get the RSSI values(signal strength) of all other Bluetooth modules in proximity.
I have achieved a BLE server, and also a BLE scanner on 2 different ESP32 modules using Arduino IDE, but am able to only get RSSI values of the server device on the scanner device.
I would like to get RSSI values of both devices of each other(it doesn't matter if they are acting as a server/client/beacon as long as the functionality is achieved).


texts:
I'm trying to make a circuit that have in input a "not connected" or "GND", and the output is a function of input.

For example if there is no connection, the outpur is 3.3V. If the input is connected to GND, the output is 0V.

I only can use analog elements. I have problems to simulte the "open circuit" with ltspice

Do you have ideas?

Thanks


texts: Reading datasheets and applying Ohm's Law

texts:
I have a CPLD that wants +3.3v and has a maximum allowable current per pin of 8ma.  I need to supply a clock signal.  The oscillator I selected accepts 5v and outputs 5v-ish levels.  I'm finding it challenging to internalize the datasheets of the CPLD and the oscillator.

Now, the oscillator's datasheet says for my clock speed (1MHz), it typically likes 10ma (Supply Current, typical).  Which means that as long as 10ma are available at 5v (Supply Voltage, typical) we're gonna have a lot of wiggly fun.

This is where I get confused.  Since the output of the oscillator is up to 4.5v (Output Voltage Levels) and this exceeds the 3.3v required by the CPLD, I need to add a resistor.  But I don't know what the current should be.

I arbitrarily decided that I will allow 4ma to reach the CPLD. This will prevent the smoke from coming out of it. The oscillator will source 16ma (Output Current) so I believe this isn't a problem.    Ohms:

(4.5v-3.3v) = .004R
1.2v = .004a * R
1.2v/.004a = R
300 ohms = R

So a 300 Ohm resistor between the output of the oscillator and the CPLD's clock pin will prevent damage to the CPLD by limiting the current and reduce the voltage to the limits required by the CPLD.

Q1: Does any of this make any sense?

Q2: I assume that when the datasheet says the output current for "1" is -16ma, this means it will source 16ma.  Why does the oscillator's datasheet say the oscillator's "0" current is 16ma?  I'd have expected 0.

EDIT -

Wow, thanks for the great feedback.  I will look for a 3.3v-compatible clock.  While in retrospect it's just a better idea, I am surprised that adding a resistor would be so problematic. They seem to be used frequently in digital circuits.

Reference circuit...  here's the datasheet for the CPLD.  I have not seen a reference circuit as such.  However (boy am I dumb!) I do have a working dev board 3' from me that sports an oscillator having "8.000 G MEC AL8GS" stamped onto the tin. (It's my assumption that's the oscillator.  Looks like one.  The only other thing nearby is a tiny Atmel chip of some sort that I suspect is related to JTAG programming.)

Edit 2 - I'm not married to any particular brand or type of oscillator; for my purposes a low frequency clock is ok.  I believe anything over 500KHz would be fine. Back to DigiKey and Mouser!


texts:
This is a follow-up question to (this question).

Here is the amplifier section in question:

In the answer, the author (@Brian Onn) gives the following explanation:

"Slow vs. fast is not about the gain of the circuit. The feedback is going to be "fast" when it has high enough bandwidth."

I thought I understood this at the time, but after investigation (and it's hard to find any direct references), I realize I don't.  So, the comment warrants its own question.

Here's a brief summary of what I understand so far:

1) The input to the feedback amplifier (meter driver) is the output of the bridge.  It'll be a phase altered AC signal of various amplitudes when the bridge is unbalanced and a signal closer to DC when balanced.

2) There are two feedback paths in the amplifier (one for AC and one for DC).  Each path effects the gain of the amplifier differently. The design objective (as Brian points out) is to make the tracking "snappier" when the bridge is unbalanced and less so as the bridge approaches a balanced state.

3) Negative feedback reduces the gain and broadens the bandwidth. I understand this well enough.

But, what I don't understand is how a change on the input to the amplifier can result in a slower or faster response (from the output) depending on the bandwidth.

I see difficult mathematical references to step response and slew rate and my feeling is that this is where the answer lies.  Can anyone provide a more "intuitive" explanation?


texts: How to get a pseudo-equivalent circuit for a 2N3904 transistor?

texts: I'm trying to analyze an FM transmitter circuit, but it has a 2N3904 circuit. I have just basic circuit analysis tools; how could I get a circuit that does similar things to this transistor using just L's, R's, C's and sources? I know I could apply the hybrid-\$\pi\$ model, but I don't know how to get the parameters. Is not for practical purposes, so I don't care about power and frequencies concerns.


texts:
Is it possible to run code on the ARM Cortex M architecture from locations other than the onboard flash memory (such as another flash chip, SD card)?

If so, how?

If not, what microcontroller architecture does permit this?


texts: Is it sufficient to cool 4 TEC1-12708 (Peltier)?

texts:
Recently I tried to cool water with one TEC1-12706 (waterblock+tec+cooler) but for a lots of reasons (that I am now aware) it didn't cool water (1L in a closed cicle) under or even near 0ºC. I rethinked and made some calculus and I concluded that maybe 4 TEC1-12708 should be enough.

The problem is that peltiers need to be well cooled, so I started to build another water refrigerator (bigger waterblock+4 peltiers+aluminium to dissipate heat+fans) but I realized that is a way more expensive (and i'm student) than buy the sets already made.

My question is if this set that I'm thinking to buy is sufficient to dissipate the heat of the hot side of the 4 peltiers. Peltier set image: https://imgur.com/sEw4UiN (assuming that cool side is turned to wateblock).

If not sufficient what are the other cheap ways to dissipate heat?

Thank you and sorry about my english.


texts: Uninterruptible Power Supply... 110V AC and low current (60 milliamp)

texts:
I have a "smart" lightbulb that requires 110V AC input and uses 7 watts. Due to stormy weather here in Florida I have frequent but minor power outages that last seconds at a time. This smartbulb doesn't have non-volatile memory, so I have to reprogram it every time the power goes out.

I'm wondering how involved of a schematic I would need to ensure that the bulb receives power for at least a few seconds after the power goes out.

I really don't know anything about hardware electronics (I'm a programmer), but maybe I could get away with using some big fat capacitor? I'm not even sure where to begin.


texts: Definition of amperage of non-invasive current transformer

texts:
I want to order a non-invasive current sensor for my little project and need to understand what CT do I need. I have many questions but they all interrelated to each-other. I try to explain what I mean.

I will use a current transformer with 5V Arduino to monitor energy consumption. Speaking of 5V and the alternating current I want to mention that ADC will use only the 2.5V range of analog pins, as measured voltage is an AC. Maximum expected current value is 30A. I came across with a quite affordable SCT-013 series transformers from manufacturer YHDC on Ebay. Interestingly they have different amperages from 5A to 100A. All transformers has a Burden resistor exept first 100A that only have a Zener diode to limit the output voltage. I don't know whether I have to buy 100A CT without a resistor and customise it or just buy a 30A one...

You can just explain those two questions:

Why do those current transformers does have a amerage value? Of course many things evolwed here. But most importantly, they just have different number of turns and different Burden resistors. Build construction could be the same and seems to me the same. Can I not use 100A CT that has no in build resistor and calculate my own resistor value to make it eg. 10A for 5V ADC? What is the reason putting a resistor in instead of letting the people choose their best?
If I calculate the value of Burder resistor for SCT-013-030 that has 30A input current in respect to 5V Arduino, it makes 106 Ohms.

I(peak primary) = 1.414 * 30 A = 42.42 A

I(peak secondary) = 42.42 A / 1800 turns = 0.02356666666 A

R(Burden) = 2.5 V / 0.02356666666 A = 106.082037 Ohm

But why it has a 62 Ohm Burden resistor? Why it has to have a 0-1V output?


texts:
I performed the AC analysis of the following circuit:

This is a simple second order LPF satisfying the butterworth filter requirements. According to me after the break point there will be a continuous decrease in magnitude by -40db/decade but this was not the case as seen below:

The pictures shows that the response decreased by almost -40db per decade but it then started to increase uptill a certain point which according to me indicates the presence of a zero. But there is no zero in the T.F of the sallen-key topology. So please can someone explain why this happens?


texts: Configure STM32F3 PLL timing for ADC read of Power System and FFT

texts:
I am new to the STM32 series microcontrollers. I have a Nucleo with an STM32F303RE device to prototype a project I wish to explore. I got that model because I plan to slave ADC2 to ADC1 and read the voltage and current simultaneously, using DMA and 1024 samples.
I am planning to read the ADCs using DMA and, when the buffer fills, calculate Power, Volts RMS, Amps RMS, VA, KVAR, and do a FFT on both sets of samples to document the harmonics. Once complete, I may push it out the serial port or whatever, and then repeat the process.  I am doing this to learn the modes and limitations of the STM32.
As I am preparing the configuration, I immediately ran into the issue of not being able to configure a clock source of 61440 Hz through any timers, to operate the DMA sampling of the ADCs.  Looking at the PLL, I was using STM32Cube-MX to adjust values in the clock page but I can't get there.
Any suggestions?
PS: I was using 60 Hz * 1024 samples (you have a power of 2 for FFT).


texts: measuring load cell output by a oscilloscope

texts: Is it possible to read a load cell output (0~10mV with 10nV steps) by a oscilloscope? or I should buy an extra high precision Multimeter to read the load cell output?


texts: How to correctly configure dsPIC to receive UART signal?

texts:
I want to use Proteus to simulate UART data transmission, I am going to open two virtual COM ports and connect them.

So I first use Virtual Serial Ports Emulator to open virtual COM ports:

Second, I use tera term to be COM1:

Third, my circuit in Proteus to be COM2:

And I set the COMPIM in the circuit as COM2, baud rate 9600.

The code of dsPIC chip in Proteus:

void main() {
     Unlock_IOLOCK();//unlock
     PPS_Mapping_NoLock(0, _INPUT, _U1RX);//Set UART1 Rx be pin RP0
     PPS_Mapping_NoLock(1, _OUTPUT, _U1TX);//Set UART1 Tx be pin RP1
     Lock_IOLOCK();//lock

     UART1_Init(9600);//Set Baud Rate
     Delay_ms(100);//Let UART initialize
     while(1)
     {
            unsigned receive;
            if (UART1_Data_Ready())
            {
              receive = UART1_Read();
              UART1_Write(receive); //The result should be sent back to COM1
            }
     }
}

Then I started Proteus simulation, then typed a character 'o' in tera term. As you can see, the virtual terminal on Proteus have received 'o', so the virtual COM ports work fine. But dsPIC seems to lose reading the 'o', so it cannot send it to COM1 back.

If I changed the code and restart the simulation

void main() {
     Unlock_IOLOCK();//unlock
     PPS_Mapping_NoLock(0, _INPUT, _U1RX);//Set UART1 Rx be pin RP0
     PPS_Mapping_NoLock(1, _OUTPUT, _U1TX);//Set UART1 Tx be pin RP1
     Lock_IOLOCK();//lock

     UART1_Init(9600);//Set Baud Rate
     Delay_ms(100);//Let UART initialize
     while(1)
     {
            unsigned receive;
            UART1_Write('a');
            if (UART1_Data_Ready())
            {
              receive = UART1_Read();
              UART1_Write(receive); //The result should be sent back to COM1
            }
     }
}

I can see 'a' sent by dsPIC in tera term:

So the UART_Write() seems to be OK, I don't know why dsPIC cannot read data from COM1. Maybe I configured something wrong.


texts: Operation of a simple transistor capacitance multiplier

texts:
According to the text, due to the Zener diode, Q1 is supplied with a constant base voltage.
Any change in the output voltage is sensed at at the emitter of Q1 which brings a change in the forward bias of the transistor. Thus the transistor changes its resistance at the CE junction and compensates for the voltage change at output or input.
Here the transistor is acting as a variable resistor. The total current passes through the transistor hence it is also called a pass transistor.
Q1. What  difference would it make if I replace this Zener diode with a capacitor and how would this circuit behave with a 1 Vp-p ripple  superimposed on 5V DC input signal?
I have multiple queries regarding capacitance multipliers.  I will take them successively.
Source article
Refer to figures 4.34, 4.35, and 4.36.


texts: What is the name of the tiny PCB radio connectors? (e.g. Apple WiFi/Bluetooth antenna ports)

texts:
What is the name of the nearly-flush flat antenna connector often found in laptops/tablets for its external antennas? They are very small and the antenna lead usually has a 90º male plug that snaps in.

UPDATE: now that I know the name I can find pictures of what I had in mind. A better look at the socket and cables can be found in the (presumably) rights-reserved image on this page but here is one I found on Flickr via the component's Wikipedia article:

UFLS-02-M-SMDS-01 by oomlout, CC-BY-SA on Flickr


texts: How does a negative feedback amplifier reach steady state?

texts:
I tried to simulate a negative feedback non-inverting op-amp, and got incorrect results.

I ran the following time-stepping code in python:

A = 100000                      #open-loop gain
B = 0.75                        #the feedback factor
V_out = 0                       #initial output of op-amp is zero
V_in = 2                        #input voltage of 5V (DC)
for t in range(1000):
    feedback = B*V_out
    V_out = A*(V_in - feedback)
    if V_out > 10:                    #saturation
        V_out = 10                    #hits rails at 10V
    elif V_out < -10:                   #saturation
        V_out = -10                   #hits rails at -10V

But this model doesn't behave like a practical op-amp.
V_out saturates at -10V, and feedback goes to 7.5V, and not 2V, thus violating the second summing point constraint.

Why is this happening?

NOTE: I've used the standard general feedback model for reference.


texts: I understand that one needs to consider inductance, current rating and self resonant frequency when selecting an inductor for an LC filter. But it seems like there are so many different inductor package styles out there meeting these three characteristics (some big, some small), are there some to avoid and others that are well suited to an LC filter?


texts: Can I use an adjustable DC power supply to discharge a battery?

texts:
With a typical adjustable DC power supply, I can set the current (typically a mode called I-Set) to provide a fixed current by controlling the voltage. (within the limits of the supply)
When testing a battery, can I do this in reverse?
In other words, hook up the battery to the power supply backwards, and set the supply to draw a fixed current from the battery, instead of supplying current to the battery?(again, within the limits of the supply and the battery being tested)


texts: data storage, FPGA to mass storage device

texts:
For a project I am working on I need to transfer, without loss of information, continous data bursts at a maximum of 48 MB/s from an FPGA to a mass storage device.

An SD card device (with appropriate SD Host controller) could give random delays up to approx. 500 ms.
I don't know the USB standard in detail so I could not argue about possible delays.

In any case any kind of delay implies the use of an intermediate FIFO.

What could be the best solution to achieve this kind of transfer & storage ?


texts: how much current does the 74161 4 bit counter needs?

texts:
you see, i have this circuit

simulate this circuit – Schematic created using CircuitLab

however when i add another more 74161

simulate this circuit

the first one stops working and it just alternates between Qa and Qb LEDS i think it's because of the current needed, however im using a pc 600 watts power supply, any idea of what's going wrong?


texts: what is the maximum ESP32 app code space for 16mb flash?

texts:
I am using esp32 dev kit with 4Mb memory
Arduino IDE

I have noticed when wifi example is running almost 50% of program space is used.

after some research, I have set memory configuration to no OTA/app code 3mb /spiff 1mb

still, I need more memory for app code

if I use a 16mb flash esp32 what is the maximum available/configurable app code space?


texts:
I'm using L293D to control a motor. The motor input pin of L293D is controlled by output pins of HT12D IC. To control the speed of the motor I have a PWM signal from Arduino, but to which pin of L293D should I connect. I think it should be pin 8, right?
Here is a link to the pinout: https://www.rs-online.com/designspark/rel-assets/dsauto/temp/uploaded/learn_arduino_L293D.jpg?w=1042


texts:
The DiSEqC (Di[gital] S[attelite] Eq[uipment] C[ontrol] specification (bus_spec.pdf within https://www.eutelsat.com/files/PDF/DiSEqC-documentation.zip) describes a tone-based serial data bus that can share coax with an RF signal.

The spec mentions LNB/switch power and the legacy 13V/18V legacy signalling method, and mentions a long-term desired/recommended 12V power level.  But in my reading of the spec, despite these "recommendations", nowhere is any DC bias required (using the magic "must" and "shall" words).

Is it legal/valid to couple DiSEqC tones without a DC bias?


texts: Is there some kind of official standard for signal measurements?

texts:
Judging from this question, it seems that different people/sources have different definitions for measurements like amplitude.

I personally encountered people disagreeing on the definition of the rise/fall time, some stating that it should be computed using 10% and 90% of the amplitude, other stating that it should use the peak-to-peak values.

Since this can lead to confusion at best (thinking about contract issues) is there some sort of recognized standard? Or should I explain how each measurement is computed?


texts: Can I buy an ideal diode? How do I OR two power supplies together

texts:
I'm trying to switch over from USB power to external power if it's present. (External power is 6V to 13V). The current is 2A.

To do this I'm using diodes 1 and 3. See image below. ("OR" configuration.)

I'm then using diode 2 as reverse voltage protection in case the external power is connected backwards. (To avoid destroying the computer by raising the 5V USB power line to 13V.)

Is there a better way to do this? The amount of voltage and heat wasted by the 3 diodes is huge (at 2A).

Can I perhaps use 3 ideal diodes? Something like this?

http://datasheet.octopart.com/FR014H5JZ-ON-Semiconductor-datasheet-85537694.pdf

What's the standard way to solve this problem?


texts: Common Emitter Amplifier Problem (Incredibly lower Gain than input, and Distorted)

texts:
I'm trying to create a common emitter amplifier to power a medium sized 8 ohm speaker as a learning experience using one NPN transistor specifically the PN2222A.

Here's the design schematic in LTspice.

The arrow pointing to the 8 ohm resistor is the speaker that I'm using. I put it in the simulator so I can see how much current would be going through it. I run the simulation producing a 400hz sine wave. The results are a clipped sine wave current going from only 1.6mA to 3.2mA. Which is much smaller than what the input of 200mv could produce on its own.

I removed the 8 ohm resistor and ground so I can check to see the voltage of Vout.

The results are normal. The gain is about 7x of the 200mv input.

I then tested this using my breadboard hoping it would yield different results. It did not and what resulted was a quiet speaker that produced a distorted sound. I could push my speaker much louder by just connecting the 200mv input directly into the 8 ohm speaker.

Why is it when I add an 8ohm speaker to Vout which has a normal voltage level gain of 7x of the input, that my current is completely distorted and only pushes 3.2mA through the speaker? Shouldn't plugging my 8ohm speaker into Vout give me something around 300mA?

How do I fix this problem? Please be as detailed and informative as you can. I am new to circuits and circuit design. Thanks.


texts: what does the c stand for when charging li ion batters ie Max. Discharge rate: 2C (6.8A)

texts:
looking to charge a 4 pack of li-ion battery but dont understand what the 2c means
 know the rest. i.e. Max. Discharge rate: 2C (6.8A)


texts:
I used microcontroller for wireless application. Problems arise when I put the microcontroller in high rainfall areas. The microcontroller is often damaged by lightning.

How to protect data lines and dc power lines from DC Voltage Spikes and Lightning?

I expect your suggestions, Thanks.


texts: Why does shading a single PV panel in a series string reduce the current output of the whole string?

texts: I would like to understand how shade on just one panel in a series string reduces the current output of the complete string.


texts:
I'm making a new prototype PCB that unfortunately has some elements that are prone to failure, so I'm trying to design them to be easily swappable.

I'm taking inspiration from this design of using an additional PCB with a socket:

But I'm having trouble finding this or similar.

I could just use any old stacking connector, or 2.54mm headers, but I like the mechanical stability this brings.

If anyone knows a similar part (to the white socket) or even specific keywords I'd greatly appreciate it.

Thanks.

BTW, Pictures came from here


texts: RC snubber on bridge rectifier (capacitor rating)

texts:
I am using a bridge rectifier on the mains and across each diode I have placed a RC snubber for EMI mitigation. (C is rated at 1Kv)

My question is...on the C (from the RC snubber) should I use Y or X rating cap ? (I am planing to pass UL/FCC/CE

Right now I am using regular ceramic cap.


texts:
I am designing the edge detection circuit with predefined output pulse duration. Pulse width will be 18.33 ms, supply power is 5V. Error tolerable is +-1 ms.

There're a number of designs already available. Initially I focused on 4538, called "dual precision monostable". I do not need dual, and datasheet is dated back 1988, and I decided to look for something more recent.

I found SN74LVC1G123, which is declared to work at 5V properly, but I see several things I can not properly evaluate:

4538 is described as "precision", 1G123 does not have this word in it. Logical suspicion - newer device is not precise?
4538 says - use simple formula T=R*C. Great. 1G123 does not give any formula at all, gives plots instead where I am expected to find the matching values. Reading 4538 datasheet more thoroughly I see it talks about error depending on the temperature and supply voltage. So I assume that these datasheets just take different approach with 4538 deliberately making things looking simpler than they are.
I need 18.33 ms (1.833*10^7 ns) at 5V, looking at 1G123 datasheet plots in section 9.2.3 I do not think I will be able to select capacitance properly at the first try. Am I expected to experiment here and find suitable capacitance?

And in overall, do I take proper approach? Is the component type I select a proper one?

I am a gidital guy, and for me it would be much simpler to have CPLD with high speed clock in and some logic inside. But there're no CPLDs with just few inputs and outputs, and they must cost more than 4538 or 1G123 (however this one is questionable).

To give more detail on what I want to achieve in general: I need to detect video synchronization frequency automatically - 50 Hz or 60 Hz, and for this I set timer at 18.3 ms (midpoint between 50/60) and sample the value at the next edge: process not finished means 50 Hz (PAL), and finished is 60 Hz (NTSC). I did not find any dedicated device to give this task to.


texts: Splitting 0-10V Analog signal from 1 AO to two different set of Ventilators to regulate speed?

texts: Is it possible to take 0-10V signal from analog output and split it in parallel to two different Analog inputs ..to regulate speed of two different sets of ventilators? Or do i need some special devices like ..signal conditioners?


texts: Is there a direct to PCB punchdown Ethernet connector?

texts:
I’m attempting to design a small board that splits 802.3af and provides both data and 5v power to an MCU on the same board.

I can find plenty of ICs with reference schematics for the splitter part - but they all expect an RJ45 port, which I understand contains something called “magnetics”. So far as I can tell, this is both about isolation and impedance matching.

My intended application is for outside, where I’d expect just using a reel of solid core cable. Personally, I find it annoying having to crimp a plug, so use an IDC and then a short patch for that.

What I’d really like is somehow to avoid either the plug or IDC + patch, so there could be 8 punchdown connectors directly on the board. Presumably then you’d have to replicate these mysterious (to me) magnetics on board.

I’m struggling though to find anything like this.

Here’s a picture I found of the internals of a PoE splitter; essentially, I’d like to understand what would be needed to replace the RJ45 port with a punchdown connector.


texts: Circuit to remove noise from digital communication line

texts:
Carrying on further from my previous post and drilling down to specifics, I am trying to figure out the right way to implement "glitch remover", or "noise remover", using electronics (i.e. not in software). From one of the answers in my previous post, I learnt that one could use a RC-circuit for this purpose, and the principles seem to be same (I think) as used for switch debounce.

My key objective is to decode RF data, but noise is triggering my ISR way too fast and starving my main loop() of previous cycles. My device being Arduino (atmega328).

Edit: (about the RF module)
I am using this ISM band ASK/OOK receiver module. While the spec page or the website doesn't have a photo of the reverse side PCB, I can tell that it has a miniature white (what looks like) a trimpot. If I had a scope, I'd have tried to turn the trimmer to see if affects the AGC. However it might very-well be for trimming L-C parameters, since same module works for 315 and 433MHz, and the trimmer might just be the factory settings for 433MHz.

At a very high level, the following diagram describes the purpose of "glitch remover". We have a noisy signal on input, but output is fairly noise-free. Noise is any signal transition that is shorter than a certain duration (say 400us).

Edit:
Actually the "glitch-free waveform" shown on right is a fake. I quickly drew it up by cleaning the narrower marks in paint. In fact, the waveform on left is actually all noise. In the midst of the high-frequency noise, the real transmitted signal is quite well formed and easy to make out, as it's frequency is much lower, and there is a 'guaranteed' trailing long-space, marking the end of the packet. The real transmitted signal is 12-bits + 1 sync bit. Each bit is represented by 1 Mark, 1 Space, 1 Mark, 1 Space of, where length of Mark/Space vary, e.g.

0: HHHH LLLL LLLL LLLL HHHH LLLL LLLL LLLL
1: HHHH HHHH HHHH LLLL HHHH HHHH HHHH LLLL
F: HHHH LLLL LLLL LLLL HHHH HHHH HHHH LLLL (Floating address pin)
S: HHHH LLLL LLLL LLLL LLLL LLLL LLLL LLLL

where each H/L has a duration of 100us, and each bit thus takes 3200us. Noise spike are typically 30-40us duration, which is what is causing my ISR to overwork.
Based on what I understood from the answer from supercat in my previous question, and based on a little research, I think this is the schematic of what I roughly need.

Need help to check if the schematic is correct ? And what might be the potential values of R1, R2 and C ?

If I understood supercat's response, then to filter out noise signals less than 400us, I can use a 0.22uF capacitor for C, and R2 of 1K, and probably 100R for R1. Is that correct ?

Or, should the schematic be this (of course, this is closer to supercat's description).

With R=1K and C=0.22uF ?

I do not have a scope, so unable to do fine measurements and see waveforms, but do have a logic-analyzer. This probably limits what and how I can test if I experiment.

BTW, can I expect that such a "glitch remover" to leave the desirable signals completely intact, or would they suffer some distortion of some kind ?


texts: I tried this method but the answer is not matching. Where it all went wrong?


texts: What tests should I perform before I claim my enclosure is Type 1?

texts: I've seen varying definitions of "type 1" enclosure, and most of them are informal. I've also heard it informally explained that I should be able to drop a screw into the top of the unit and not have it contact any live parts, but that's also informal. Is there a defined series of tests I can perform to claim type 1?


texts: Which commercial oil can i use for isolation of a high voltage transformer+voltage doubler?.The output voltage is about max 60kv.


texts: Antenna that can be used for large range of frequences?

texts: Is there an antenna or device that can be used for WiFi, NFC, bluetooth, GSM for use with a frequency counter to measure the frequency of the waves?


texts: How to make a motor capable of resisting physical movement?

texts:
Is it possible to make a motor capable of resisting physical movement?

For example, at the gym you control the resistance to movement by putting more load, more weight. Is there a way to control that resistance electronically? Maybe by using a motor controller adjusting the PWM signal?


texts:
In Multiple Access Protocol for cellular networks, there is this Frequency Reuse Patterns. And I am given a formula to one of the patterns that states: \$\text{Reuse factor }\mathbf{K} = i^2+j^2+ij\$

I know that the reuse factor \$K\$ meant the number of cells that are reusing the frequencies. But what do the \$i\$ and \$j\$ represent? And how can I use this formula?


texts: Can a synchronous regulator "chirp" in burst mode?

texts:
I'm looking at (the millions of) buck regulators available for a project where the board will be a host board for a Gumstix Dual Cortex A9. This can pull quite a bit of current at maximum so I was figuring 2.5A for a good bit of leeway. However it will also be battery powered so, assuming I can get the Gumstix and the rest of the equipment to sleep efficiently, the quiescent current of the regulator becomes important.

I was thinking that would mean I should use a non-synchronous regulator as, traditionally, the synchronous have been poor in low current modes. The non-sync can operate in Discontinous Current Mode due to the freewheeling diode, which the sync can't do. However, there seems to be synchronous regulators that can do it all. Looking at the LT8610 from Linear, it has high efficiency at high power and high efficiency at low power. It achieves this
by using "Burst Mode" at low currents. Apparantly down to 2.5uA which is quite something.

My concern is that there may be a catch. I believe various Burst Modes can lead to chirping - that irritating squeak that comes from the bursting on-off frequency causing the capacitors/inductors to vibrate at audible frequencies. I used to hear that quite a lot, mainly from laptops, and I don't really want the same thing in my project.

The other catch of course is that the LT8610 is nearly twice the cost of a simple non-synchronous regulator like a TPS5420 and is harder to work with (16 pin MSOP vs 8 pin SOIC). I can deal with that if it's has nice features.

It is somewhat mystifying how systems like the Kindle manage to be in sleep mode to the extent that they are. Perhaps they use linear regulators... or some sort of combination


texts:
I have a photo-multiplier going into a preamp then two stage shaping amp (PC250 and PC275 board from Amptek). The photo-multiplier is attached to a plastic scintillator and then a beta emitting radioactive source is placed atop the scintillator, and the number of output pulses is the source decaying.

My question is, if I put another photo-multiplier and scintillator set up on the other side of the source, and connect the photo-multipliers in parallel, will my count rate double, or stay the same but the pulse amplitude increase?

Thanks!


texts: Current mirrors inside an OTA (Operational Transconductance Amplifier)

texts:
let's consider this transconductance amplifier (OTA) (reference):

I have a very basic question. Why do wee need the mirrors M5,M6,M7,M8,M10?
Why is the output taken from that current source? Why cannot we take the output at the drain of M1 and M2 (the main transistors of the differential pair)?


texts: When were "bump / IDC" connectors (2 row, 0.1" grid, mass-term ribbon cable) introduced? By whom?

texts: I am doing a timeline of connectors and I can't place these these connectors.  Who introduced them? (3M?) And when?


texts: Large synchronous buck stage after PFC circuit

texts:
I am working on a fairly small motor controller (2kW).  The power input is AC 110-220VAC, so there is a PFC stage that boosts the initial DC voltage to 390VDC.  After this stage, I require a 160-165VDC stage for brushless DC motor commutation.  PFC and commutation are not a problem.

I have been looking at manufacturers online and they seem to be low on high output voltage controllers (input range as well..)

What is a viable and efficient buck stage for this circuit?

My current thought process is down a path of using a lower voltage, synchronous buck, controller chip and isolating the chip from the input/output via a low power DC supply and external gate drivers.  That all seems very complicated...

What ideas do you have stack??


texts: Making a simple ring with LC tank circuit

texts:
I'm learning about oscillators, but I can't seem to get the tank to oscillate. I have built a very simple circuit using the 555 timer and a LC tank (sorry for the bad circuit layout, this was my first drawing):

My voltage source is 5v, not 2v, I made a mistake in the drawing. According to the formula, I'm getting a 4 hertz signal at 66% duty cycle: 138ms - high, and 69ms low.

I'm trying to produce the following pattern on my oscilloscope every time I get a signal from the 555:. I do not have a specific goal for the  frequency/voltage or any of the other factors, I just want to generate this pattern.

If I remove the inductor, the wave becomes as expected:

But the problem is - if I put back the inductor in the tank circuit, my binary signal becomes a flat line with randomized distortions, I can't even make out where the signal starts or ends, it looks very similar to this:

I thought maybe the inductor is too high of a value, so I tried to use 10uh inductor instead of 100uh, then I can see again my binary wave with slight distortions, but nothing close to oscillation.

I believe my values are totally off for the tank circuit or the frequency coming from the 555 is too high and the 100uh inductor can't work 'fast enought', but I know nothing about eletronics, so it's just a wild guess.

Any hints on where did I go off the track?


texts: Can USB 3.0 SSTX lines be swapped with SSRX lines

texts:
It is given in the USB 3.0 specification that USB super-speed lines support "polarity inversion". That is SSRX_P can be swapped with SSRX_M (or SSTX_M with SSTX_P).

Can we also swap SSTX lines with SSRX lines?

That is SSTX lines can be used in place of SSRX lines and vice versa.

Please help me to get a clear picture.


texts: LTSpice, Current is not the same after going through identical step up and down transformers

texts: I'm modeling my transformers as coupled inductors with appropriate values. I'm stepping up the current from my generator and then stepping it down at the load with identical inductor values (just flipped to represent step down vs step up). Since the turns ratios are identical the current should be the same on the generator side as it is on the load side. But when I am simulating it, my load current has an amplitude of 136ish A versus the generators current of 193ishA. Why aren't they the same?


texts: Export RTL view and Waveforms as images from Xilinx ISE webpack

texts: I think this is really a homework question, but moderators' call. I am trying to export the RTL view and waveforms of my verilog code into an image file (any format). But there doesn't seem any option to do that. What is the proper way to do this?


texts: what do i interpret from these memory labels?

texts:
What do i interpret when i see this configuration for  some cache memory : 512 x 12 or for a main memory with a label 32k x 12 ?

What does these two configurations tell about the memory ?


texts: I have a main buck DCDC 5V that feeds to five different LDOs(3.3V). To create power sequencing, I would like to use a resistor and a capacitor at the input of the enable pin of each LDOs and by changing the value of R and C, introduce enable delay. The input to the LDO's enable pin will be tied to the 5V rail. What are the pros and the cons of using this method to introduce enable delay? Thank you


texts: I am total layman about this topic and I would appreciate experienced users to give me some useful tips and hints. I develop some code for arm cortex m0 which I want to simulate in qemu (it is not a problem cause it is well described). My processor is going to work with external flash, which verilog model I am in the possession of. The issue is that I got no idea what would be the best way to simulate my HW and SW simultaneously. I would appreciate some advice where to start, what programs you would recommend and if it is hard to get into these topics? Thanks in advance.


texts: Microcontroller with embedded radio and wake on radio

texts:
I am looking for a microcontroller that has radio and WOR (wake on radio) feature all in one...basically a system on chip solution with low power consumption.

I was checking suppliers like TI etc... and couldn't find an all in one solution. TI for example has MSP430 as a nice low power uC, and CC1101 radio chip with WOR function. Too bad that they don't provide this as a single product...but maybe they do and I couldn't find it yet.

I wonder if you know a solution with the features I said....please let me know!

The application I have in mind is quite limited in space, so the smaller the solution, the better!

In particular I am looking for a 433 MHZ radio


texts: Finding voltage drop on a resistance using mesh analysis

texts:
How to find out Vx on the specified resistance using mesh analysis?

simulate this circuit – Schematic created using CircuitLab

Here Vx is to be found out on the 1 ohm resistor.

I tried solving it by applying super mesh on the 5A source.I got 3 equations corresponding to the loops.

10*i1 - 11*i2 + 22*i3 - 5 = 0 ----- belongs to the loop containing 5V source
10*i1 - 16*i2 + i3 = 0 ----- belongs to the loop that doesn't have any source
i1 - i3 + 5 = 0 ---- supermesh

The solutions that I got:

i1 ~ 3.28A
i2 ~ 1.943A
i3 ~ -1.718A
Vx ~ 3.661V

But the solutions specified are:

i1 ~ 3.825A
i2 ~ -1A
i3 ~ 0.375A
Vx ~ 1.375A

Can somebody please tell me where did I go wrong?


texts: Connecting USB shielding of two hosts and one peripheral

texts:
I'm making a simple project regarding switching USB connection between two computers. I would like to know if it is safe to connect USB shielding for pc1, pc2 and peripheral together, while keeping the power and data wires separate? For example when pc1 is connected to peripheral and pc2 is not, keeping the shielding connected together is dangerous for these devices?

The setup consists of one desktop computer and one laptop which is connected through a powered dock (all powered from the same outlet). So if I understand correctly desktop PC will have solid ground and by connecting the shielding together the laptop will be grounded by the PC. So overall it is safe to do?


texts: Transition state between 0 and 1 in logic gates

texts:
Logic gates in electronics circuit works by converting analog signal into binary,say 0-3 V.Then accordingly at 0 volts the circuit correspond to low (0) similarly at 3V it correspondent to High.
My question is what happens between the transition state? How the circuit behaves between 1-3 Volts (this intermediate regions)? Why the circuit do not work between 1-3 Volts?


texts:
I have a very limited number of outputs available (4 to be exact) on my existing PLC and need to share 5-7 bits of information to another PLC without having the expense off add-on communication cards.

I was thinking of using a binary coded decimal system to turn 3 outputs into 7 separate messages. The problem is that its not just one message at a time, I need to be able to share a combination of ANY 7 of those messages and be able to decode them without fail.

Is there an existing encoding convention that I can use to achieve this?


texts: Why are polarized capacitors are treated as non polarized in Clamping circuits?

texts:
This semester we studied clamping circuits, but there's rather strange happened when the professor was explaining the working of the circuit, he treated polarized caps as if they were non-polarized. I thought to myself may be he was wrong about that so I searched the internet and found a video explaining it in the same way.

Here's the link to the lecture:
https://drive.google.com/open?id=0B_L71uXbwhG0dC1XaklTZnRaUUU

Here's the link t the video:
https://www.youtube.com/watch?v=LA7c7jenkd0

So what am I missig here?


texts: Differential Opamp: How to cut or reduce current consumption from supply rails

texts:
I built a simple differential amplifier using an LM358:

Please find the datasheet here
I want to reduce the current consumption so my idea was:

Use a GPIO pin of my MCU to switch Vdd supply to the opamp
Use large resistors
Try to also switch V1 and V2 but that is not preferred, I end up using too many GPIO pins and I need additional MOSFETs.


texts: Driving relay with PC serial port fails after few hours

texts:
Ive been trying to use this schematic:

to drive relay (from this answer).

(Components are as specified in schematics, with D2 being 1N4007)

Vcc is 12V from PC standard Molex connector, DTR is from RS-232 DB9 serial port from same PC, and GNDs from both Molex and DB9 ports are connected.

I've completed bottom half of schematics (ending with T1), and wrote a simple software which does DTR ON for 2 seconds, then OFF for 2 seconds, then repeats. I've tested it (by connecting voltmeter between Vcc and output from T1) and it worked for at least an half an hour by happily alternating between 0 V and 12 V (open terminal voltage) exactly as I needed.

I left it doing this ON/OFF switching, and went to work on upper half for few hours. However, when I come back, the lower part of schematics was dead - it's open terminal voltage between T1 collector and Vcc  now alternated between 12V and 10V, and if I connected some load (upper half of circuit, which seems to work OK if I connect it to power supply directly) it dropped to constant about 3.5V

I'll tear it down in few days to examine/rebuild, but in the meantime, can someone:

spot would could be wrong with this, and
suggest what can be changed to make it more robust (it is going to be installed in fairly inaccessible place)?

UPDATE
At the time it was detected not working correctly, T1 or rest of electronics did not seem hot (about room temperature, maybe little higher -- of course it might have been dead already by then)

UPDATE 2
Another thing, when measuring DTR to GND on PC serial port via voltmeter, it seems voltages are -12V for OFF and +12V for ON (instead of 0V and 12V which I'd assume - however it seems valid configuration). Could that have impacted the circuit (and how to protect from it) ?

UPDATE 3
The forensics shows that the transistor T1 died (the E-C measures as 12k resistor), the rest of components are OK. Does that help find the problem? I also note that BC517 has VEBO of 10V - could that have caused the problem (the collector was open at the time T1 died)?


texts: Help with identifying connector for 25 AWG wire

texts: I believe the wire here is 25 AWG. Does anybody know the name of this connector? I need the specification to write up a defect sheet and I currently cannot travel due to quarantine measures.