texts: Does Interrupting a Microcontroller Data Receive with a Higher Priority Interrupt Cause Data Loss?

texts:
I would like to know what would happen if a Serial Terminal were to send a large amount of data to a PIC/AVR, for example over USART interrupt, which was then interrupted by a higher priority interrupt like a timer, which would postpone the data transfer. Would the data be lost? Or does the Serial Terminal have a buffer before sending, and hold on to the data until we go back to the receive interrupt?

For exmaple I am using an atxmega128a1, and am using this interrupt to receive bytes:

//interrupt to receive a byte
ISR(USARTC0_RXC_vect){                      //ISR for when receive flag is set
if(FIFO_Put(&RxFIFO, USARTC0_DATA)){        //put data into receive FIFO
    USARTC0_STATUS |= USART_RXCIF_bm;       //write 1 to clear bit
}
}

If I send a large amount of bytes over a serial terminal at one time, this interrupt will trigger many times to receive every byte.

I also have a timer interrupt of a higher priority which may take a long time to complete:

ISR(TCC0_OVF_vect){
    AXISid n = X;
    static BOOL cycle;
    TimerAxisInterrupt(n, &cycle);
}

To re-iterate, my question is, if the higher priority interrupt occurs during a large data receive transfer, will any data be lost?

If relevant: I am sending the USART data over rs232 using a max3232 logic converter. I have the handshaking lines and RTS CTS lines looped such that i am only using the Rx and Tx lines.


texts:
My understanding is as follows:

A voltage induces an electric field at a capacitor, which is measured in coulombs.  If I wanted the capacitor to leak the charge exponentially, I could model that as a parallel resistor around it.

How would I express the dual of this paragraph for inductors?  Something like:

A current induces a magnetic field at an inductor, which is measured in (Webers?).  If I wanted the inductor to leak the magnetic flux exponentially, I could model that as a (series resistor?)


texts:
I am trying to model a switched mode power supply and I'm working on semiconductor losses now. I discovered how switching looses are affected a lot for diode's reverse recovery charge. The problem now is I can't find good information about this parameter in datahseets.

An example here, this Farchild diode:

http://www.farnell.com/datasheets/1845305.pdf

has this plot

Since Qr (reverse recovery charge) is the area under the curve, I assume I could just multiply 1Amp x 20ns and to get 20e-9 C. However, I assume that the peak reverse recovery current won't be 1A if the forward current is higher than 0.5A. So how could I know it?

Another example, this Panasonic diode:

http://www.semicon.panasonic.co.jp/ds4/DB22306_BED.pdf

has this plot

In this case they put 100mA of peak reverse recovery current with 100mA of forward current.

Does anyone know a good way to know Qr value?

Thank you so much.


texts: Can I make a homemade radio transmitter?

texts:
I got a new HTC one m9 and it has an FM reciever in it, it picks up all the radio channels in my area really well. I am trying to make a very simple radio transmitter for the fun of it. I dot want something complicated that transmits voice, I want to transmit a simple beep, pause, beep, pause etc. I dont have a lot of capacitors so I dont want to make anything complicated. I found this schematic online and built it:

Instead of 1.5 volts i have close to 7 volts though. The site just said it was an RF transmitter(radio frequency) Should my Htc FM reciever be able to pick up anything from this, if so how can I make a noise of anysort that i can recognise it? Thanks.


texts:
I am trying to find long-lasting  items -- to buy in bulk. The idea is to order them for a lifetime. What are long-lasting electronic items? Which items are good idea to stock? I have tried to get ideas from this discussion.

==== YES List ====

No staling

prototyping tools: breadboards

Good idea (?)

1M resistors
1k-10k resistors

No evaporation but better items may be developed, takes little room

ceramic caps
op amps: LM741,
temperature sensors: DS18B20
transistors such as BC547C

==== NO LIST ====

Moving parts, no lubrication, can get jammed

pots

Modern technology

FPGAs

Absorbs moisture, evaporates

rosin (DIY when you need with denatured alcohol+pine cones)
electrolytic caps

==== HEAVY LIST ====

Must be ordered as bulk via sea to ge cheaply, long-lasting

Antistatic mat (55 RMB/1m^2, like this, but 3kg per pc. In Chinese, 防静电台垫 防静电桌垫 防静电胶皮)
solid 1000' 22AWG spools (red and black)
stranded 100' 22AWG spools
PCB stand
Magnifier glass table things such as this (in Chinese,  20倍放大镜 带灯放大镜 折叠式放大镜 台式放大镜LT-86C 20X)
Ultrasonic cleaners (such as these. In Chinese, 数码型不锈钢超声波清洗机)
Cabinets, lockets -- (like these)
Soldering stations such as this (in Chinese, 双数显热风枪带烙铁 热风拆焊台 超)


texts: Component to detect the state of an external LED

texts:
I need to detect the state of an LED in a machine that I cannot connect to in any electrical way. So I would like to measure the light emitted from this LED.

The conditions:

The ambient lighting is low to very low (both the machine containing the LED and the sensing device are inside a box with few and small holes)
The sensing component can be very close and well aimed at the LED (distance between 0 and max 5mm)
The LED is orange (if that is relevant?)
Input will be processed by a PLC

My question is: what component meets the following criteria the most?
Criteria in order of priority (from high to low): reliable detection, simple wiring (few components, easy to wire to let's say an arduino), easy programming the microcontroller, and low price.

I am looking into these alternatives (but maybe there are more?).

LDR (light dependant resistor)
Phototransistor / photodiode
LED as a light sensor (in the same colour as the emitting LED)

Which component meets the criteria the best?


texts: Are GPIO outputs software or hardware controlled?

texts:
I’m trying to diagnose an iPhone 6s that’s stuck in a boot loop. iTunes error points to a baseband issue.

So I’ve compared to a known working board and found that the PMU_TO_BB_PMIC_RESET_L line (at Resistor R2200) should be high at 1.8v but when I measure it’s very momentary high then quickly drops and stays low at 0v

Tracing the line it’s an out from the GPIO section of the main power ic for the entire phone

I have no other literature or information on how the circuit’s supposed to function so I’m here asking to hopefully gather any information that may help me determine what’s going on

If GPIO outputs are software controlled then I need to figure out what parameters are causing it to go low and stay low.

Apologies in advance if I’m not supposed to ask “troubleshooting” questions but I need to get data off this phone and my last resort is seeking help here


texts:
I have to connect 8 optocouplers as shown in the picture with STM32F407 MCU. These are giving 8 digital signals to the MCU.

The supply voltage at the outputs of optocouplers is 5V DC while the STM32F407 power supply is 3.3V DC. Which GPIO pins are safest to connect these digital signals on STM32F407 MCU?


texts: Why is there continuity between the leads of my DC power supply?

texts: I have a power supply that outputs constant 5v DC power. It's not adjustable or anything fancy. Using a multimeter, I found that there is continuity between the 2 output leads. Is this a bad thing? If not, then why does it happen?


texts:
So I've been getting into the world of building circuits with an Arduino controller and a breadboard. I've been working in IT for years, but I'm not super familiar with electronics at this level.

While following a tutorial for building a "knock sensor" using a piezo speaker as the sensor, it connected the piezo speaker from ground to an analog input pin on the Arduino. Then, it connected a 1M ohm resister in  parallel to that. All it said was that doing so protected the Arduino from the voltage spikes caused by the knock sensor.

After asking around, I learned that this resistor was called a "burden resistor," but I can't seem to understand how adding a resistor in parallel to the element that generates the voltage would protect the Arduino board.

Can someone explain this to a newbie like me?

This is the webpage that shows the burden resistor: http://arduino.cc/en/Tutorial/Knock


texts: Help review my first arduino PCB: What did I do wrong?

texts:
EDIT: After taking all what you guys said into account, I edited the pcb into the following. Changed the FTDI while breaking the ground loops and working on the traces a bit, changed the size of the 100uF capacitor and hopefully the new routing is better.Give me your thoughts over thatnearly identical circuit just added the ISP and removed FTDI

So I've drawn an arduino based pcb with the purpose of using a ds3231 temperature compensated RTC to wake up and put to sleep an atmega328p-au which will then control a MOSFET which connect to the ground side of a micro servo to turn it on/off. It's my first design so before I make a prototype I would like to take your opinion about it (attached an online gerber viewer for you guys to take a look Here ).
Board size: 45mm*16mm

so the rtc send signals from its digital and analog pins to the arduino, which use that to drive on/Off the MOSFET gate.
apart from the motor who have a peak of 1A @5V, everything else is relatively low powered (with a maximum of 40-50mA) . What I'm worried about is interference which might trigger or prevent the trigger of the ds3231 to the MCU.
here are more pictures if you don't want to check the gerber:

Sorry for my poor formatting: it's my first time over here.
Thank you for your help!
The servo (mg90s microservo) is going to be off for like 59min each hour and when it turns on it only do so for a few minutes. I started from the pro mini official drawings and went from there. I used the breadboard prototype I did as a reference for connections. I understand I got a lot to learn. The shipset is in sleep mode almost all the time.

I'm afraid of unwanted noise on the digital pins or A4 A5 which might cause unwanted behaviour(early wake ups).It's powered by batteries. do I risk a lot of noise over the long D2 line Due to the ground plane under the IC1? do A4/A5 have a risk of being affected by noise ? how can I fix that in that case?


texts: Adding diodes to easy driver stepper motor driver

texts:
I had an easy motor driver damaged by removing the motor while the drive was energized. I sent an email to Brian Shmalz to see if there was anything that could be done to protect the board in these cases. He replied with the following:

  You can add eight diodes to the four motor lines (one diode to M+ and one to GND for each of the four lines) to help protect the driver in case a user removes the motor while under power.

and

  You'll want Schottkey diodes with a nice low forward voltage - like 400mV or so at 1.5A or so.

I ordered some of the diodes he recommended however I am still learning when it comes to electronics like this and I don't really understand what he is advising to do.

The board has 4 motor pins in a set of A/B pairs. I don't understand where the 8 diodes should be placed in relation to these pins, or which orientation the + and - sides of the diodes should be in. Schematics and diagrams can be found here http://www.schmalzhaus.com/EasyDriver/

How should this be wired to accomplish what Mr. Schmalz has suggested?


texts: What does this mean, "External reset input, active low. Must be asserted for a minimum of 10 µs."?

texts: Looking at this USB Hub controller IC, XR22404, page 5. More confused on the second statement, what does it mean to be asserted for a min of 10 us?


texts: How ST-Link RESETS the MCU by using Reset pin? How to connect Boot0 pin when it is not used and SWD interface is used?

texts:
I am designing a custom PCB based on STM32F401RCT6 microcontroller. I am using SWD interface and STlink to program and Debug the micro controller.

I understood that reset pin is used to RESET the MCU which includes all the registers clocks etc. When Reset pin is connected to ground externally it is in Reset state when it is not connected to ground it is not in reset state.

I also understood that the ST-LINK resets and then sends the program through SWD interface.

Question 1:

My question is how ST-Link resets because as per datasheet Reset pin of the micro controller should be connected to the ground via button switch so that we can manually reset by pressing it. But when I refer to the schematics to connect the reset pin to SWD interface, I saw two connections: one is via button switch to ground and another is directly connected to the SWD connector. Then I got confused like the reset pin is connected to ground via button switch and how STlink will reset the MCU when Reset pin is directly connected to the SWD connector without connecting it to ground.

So when we want to reset we need to do manually reset by pressing button. If it is like that then why we need reset pin for SWD interface to ST link?

Or is it like Inside Stlink Programmer Reset pin is connected to GND. So for automatic reset via STlink we are using RESET pin in SWD interface and for manual reset we are using button. Am I correct? If I am wrong correct me.

And my other question is: I am using SWD interface for programming and debugging since I am using SWD interface and not using Bootloader, should I connect Boot0 pin to ground. Or is there any use of Boot0 pin (Bootloader) while programming using SWD interface?


texts: Using the same input for AC and DC power

texts:
I'm currently exploring a requirement to have a power input to a system which can take both mains AC and DC power. The input would feed the input into a AC/DC converter, or a DC/DC converter, whichever was appropriate. My intention is to use a DC blocking capacitor for the AC stage, and an AC blocking inductor for the DC stage.

simulate this circuit – Schematic created using CircuitLab
I have a few questions regarding this approach;

Would a DC blocking capacitor and AC-blocking inductor suffice?
What additional safety precautions/components might be necessary?
Would I need to use an isolated DC/DC converter?

Any advice would be appreciated.
Technical details edit:

AC and DC will share the same power input connector.
Input will be 110-250VAC or ~12V DC
Desired DC output will be 24V
AC/DC output current of up to 6A, DC output current likely much lower (<0.5A)
An off the shelf AC/DC has already been selected, but could potentially be changed.


texts: Transimpedance amplifier with a non-ground reference

texts:
I'm studying for an exam and as a part of a question I am given a transimpedance amplifier and need to explain/show how the current gets converted to voltage.

That's fairly easy, however, the op-amp has a Vb connected to the non-inverting input, which makes my answer differ from the official one.

My logic says that the inverting input is virtually on Vb, and then when we add the voltage drop over R1, output is V1 = Vb - I * R1.

The official answer just says V1 = - I * R1.

Is my understanding flawed? Does the non-ground reference affect the output?


texts:
I have a complex EMI problem.

There is a RPi Compute Module along with a LAN9512 and GSM modem (M66).

Layout guidelines are strictly following the datasheets' recommendations, I don't think there is anything can be much better around them on the layout.

Now RPi and LAN9512 are connected via USB differential pairs, but when GSM modem is active (i.e. connects to network, receive call etc), the LAN9512 disconnects from usb and comes back only after a full reboot.

This is the main issue which I'd like to solve here.

Console log of the issue:

kernel: [   10.172712] usb 1-1-port1: disabled by hub (EMI?), re-enabling...
kernel: [   10.172750] usb 1-1.1: USB disconnect, device number 4
kernel: [   10.173135] smsc95xx 1-1.1:1.0 eth0: unregister 'smsc95xx' usb-20980000.usb-1.1, smsc95xx USB 2.0 Ethernet
kernel: [   10.175308] hub 1-1:1.0: hub_ext_port_status failed (err = -71)
kernel: [   10.175332] usb 1-1-port1: connect-debounce failed
kernel: [   10.192773] usb 1-1: Failed to suspend device, error -71

What could also help:

I'm seeing that 3.3V and 1.8V power lines do have a square signal which is 400mV higher when the GSM communicates (square length is 500-600us, dV is 300-400mV):

On the board I have DC generators:

5V - MP2359
4.1V - MP2359
3.3V & 1.8V - PAM2306 (common)
2.5V - AP7115

They are wired like this:

18V input DC
 -----> 5V  -----> 3.3V ----> 2.5V
            -----> 1.8V
 -----> 4.1V

GSM modem is powered from 4.1V so it is actually separated from everything else.

These spikes (squares) are only presented on 3.3V and 1.8V which is regulated by the very same PAM2306. Neither on the 2.5V nor the 5V does have these spikes. Also the 4.1V which is actually for the GSM does NOT have these spikes either. There are 100uF, 100nF, 33pF and 10pF decoupling capacitor on the 4.1V rail.

PAM2306's layout (on the top right there is the 1.8V at the inductor's right side):
Please note that this layout is the recommended by the datasheet. I know those lines going around look strange though.

I also tried adding a 100uF decoupling to the 3.3V rail, but did not help.

One thing should be good to know here: could these spikes cause the USB disconnect?

UPDATE1:

I have removed PAM2306 power module and replace with 2 MP2359 for the 3.3V and 1.8V.

Now the boards seems more stable, however the USB disconnects after connecting the GSM:

# pppd call gprs
... lot of pppd messages ...
pppd[2079]: primary DNS address a.b.c.d
pppd[2079]: secondary DNS address a.b.c.d
usb 1-1.1: USB disconnect, device number 3
smsc95xx 1-1.1:1.0 eth0: unregister 'smsc95xx' usb-20980000.usb-1.1, smsc95xx USB 2.0 Ethernet
smsc95xx 1-1.1:1.0 eth0: hardware isn't capable of remote wakeup

So as you can see, after getting GPRS IP addresses, the ETH suddenly unregisters itself.
After changing those power modules the previous 'disabled by hub' message went away so the situation is now better but not perfect.

What would you recommend?

UPDATE2

After an hour without trying to dial up GSM, the USB disconnected from the PI.
So not the power rails were the root of my problems.


texts: I have two 2.5A 12V DC motors running fans at high rpms. When I hook up one to my 10A 12V DC power supply it works great. When I hook both up the motors just pulse, turning a revolution or two every second or so. I would love to know what I am missing.


texts: Prevent a power bank welder from short circuiting

texts:
I have a power bank made of lithium ion batterys. Its 12v and over 10 amp (I can't test it do to a lack of a tester that reads over 10 amps). I am planning on making a welder out of it using 1/16 in welding rods. But I have issues with the batteries heating up do to short circuiting them.

QUESTIONS:

How can I prevent them from short circuiting?
what could I take a thermostat shut-off out of to make sure I don't exceed high temperatures?

MY SOLUTION FROM RESEARCH:

I believe from what I read on the internet that I can prevent my circuit from short circuiting by doing a few things:

Add a fuse to make sure that the max current doesn't flow from the positive to the negative.
Add a resistor or current regulator that will prevent the max current to flow to the negative.
Add a light that can handle the current to prevent it from short circuiting.

I have my two questions under the word questions. And I just added some possible solutions that I need to know if it will help prevent it. If you have any other questions I will be more than happy to edit this post.


texts: 8.6 ohm resistor is decreasing 3.97volts to 2.95 volts which is connected to zener diode i can't understand how it is happening

texts:
i'm trying to pass 3.3v to nodemcu from a 4v battery, For that I'm using a resistor of 8.6ohms and a zener diode of 3.6v. and the circuit diagram is as follows

 but when i simulate the circuit in online simulator 8.6ohms resistor is reducing much lower voltage.But in real time it is reducing 10volts nearly. i can't understand where the mistake is.Please answer me and suggest me other ways to power my nodemcu from 3.7-4.2v battery easily and efficiently.


texts: How much current would you design for the various supplies required for Spartan 6 LX9 devices?

texts: I'm designing a new board based on XC6SLX9-3TQG144C.  There are three supplies required -- VCCINT, VCCAUX, and VCCO.  VCCINT is 1.2V and the other two will be 3.3V.  I'm wondering how much current to design for in the power supplies.  Obviously the current consumption depends significantly on the RTL running inside, but are there any good rules of thumb for this?  In the past I've just over designed the thing to be able to supply something like 1 amp (can't remember which LDO I used, but at the time it was a national part) for the internal supplies and whatever I think I'll need on the I/O side of things (which is much easier to estimate).  I'm trying to minimize area on this board though so it would be nice to not just "shoot the fly with a bazooka" so to speak.  Is there a reasonable way to accurately estimate the current consumption for the internal supplies of an FPGA?  I've looked a bit at xpower, but I didn't see (didn't spend a ton of time looking) a way to enable/disable various portions of the design as one would expect in real life (e.g. memory controllers, actions responding to external events, etc).


texts: How do I solder a LED in place of an earphone?

texts:
I have a super basic bluetooth headset.  I've taken off the earphone, and want to put a very low power, basic LED in its place.  I plan on just soldering the anode to the red wire and the cathode to the black wire.  Will this work?  If not, what do I need to do?

Thanks


texts: What’s the difference between led current draw with and without PWM?

texts:
I have a LED that’s rated for 3W (aprox 3V and 1A max current)

Do I get the same result in terms of current draw and led’s durability if I supply the led with a 1A Led Driver (at full current supply, or full PWM signal) or if I supply the led with a 2A led driver, but only allow to the led half the PWM max current?

Attached is the datasheet for the Cree XP-E neutral white led I’m using. XPE-Datasheet

I found this document about over-current pulsed driving leds of this manufacturer: Cree over-current pulsed driving leds

I’m also using a constant led driver, but it only provides 500mA.

I have another led driver that is set for more than 1A. That’s why I thought of using this one but in a lower PWM setting.

Thanks for reading!


texts: How does “bidirectional” transmission on gigabit ethernet work 2?

texts: I was looking for an answer to the question how the 1000BASE-T transmission works and I came up with this post How does "bidirectional" transmission on gigabit ethernet work? but still a few issues it is not clear to me. If I understand your answers correctly, if on the two sides of the wire you receive a signal, say +1, each recipient will receive a +2 signal. The question remains: what happens if we send two signals say +1, -1 and on the other hand a signal with a value of 0 will be given in the same pair. Is this possible? If so, will the 0 signal meet the +1 signal and then it will meet with the -1 signal, so will the value we get will be 0? From the answers there, we get +1, but I do not know why. I decided to ask a new question because I have too little reputation to add a comment :(


texts: Help me understand this load detecting circuit

texts:
I'm looking at this circuit:

Which has come from here

The claim is made that "it detects a voltage drop across a large bridge rectifier that acts as a high power shunt", which is referring to the transformer wired across D1.

However, that transformer appears to be wired in parallel with the rectifier, so wouldn't the coil on the transformer see a full 120V? I don't get how wiring the circuit this way causes the drop over the rectifier to become the supply for the transformer coil. What's going on?

Edit: From the description given, I am under the impression that the coil on the transformer is supplied with a very low (comparatively) voltage. I don't understand why this is the case. The transformer appears to be directly connected to the mains voltage in this circuit - so it should be supplied with 120v.


texts: Is this a reliable circuit to monitor AC mains voltage?

texts:
I want to design a simple circuit to monitor AC mains voltage and take simple decisions if the voltage falls below a specific reference voltage.

It's important to mention that accuracy isn't an issue at all.

Circuit description :
The input voltage is stepped down to 9 V peak voltage and rectified, the rectifier plus the capacitor is intended to act like a peak detector and the output voltage at C1 would represent the peak input voltage (of course after stepping down).

This voltage is scaled via R1 and R2 then compared to a reference voltage using hysteresis comparator (using LM358 but not found in ltspice).

Is this a valid concept ?


texts:
http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Components/General/RelayBoard-Large-v16.pdf

I'm trying to determine the base current of the NPN transistor but keep getting numbers an order of magnitude higher than the requirement of the 2N3904.

Any suggestions are greatly appreciated.


texts: Why does this UK mains plug have a gap going down the live pin?

texts:
What is the purpose of the gap on the live pin of this plug?

I've never seen this before and was why this gap was their since the plug is only for an alarm clock.

The gap goes down the middle of the live pin to half way down the pin the pictures below show the plug.


texts: DC motor advice for fan (tea leaf blower) - advice

texts:
I'm trying to build a kind of tea leaf blower (the machine will blow cut tea leaves.) I bought a car air conditioner blower fan (link below) and I connected my blower system (technical drawing link below.)
The air flow isn't enough to make the tea leaves fly, so I have to increase the air velocity. What can I do to increase the air velocity? I have 100 watt power limit.
There are 13 nozzles on the tube. Each nozzle is 20 mm in diameter. The tube is 1 meter long, the tube diameter is 70 mm tapering to 40 mm beginning to end.
What I tried and the results:

Motor powered with 12 V:

Fan only:

The motor draws 5 A

Fan connected to tube:

Current drops to 4 A (48 W)
Average air flow velocity in nozzle: 42 km/h (highest value average)

Motor powered with 18 V:

Fan only:

The motor draws 9 A

Fan connected to tube:

Current drops to 5 A (90 W)
Average air flow velocity in nozzle: 57 km/h (highest value average)

Motor specifications:

Brushed DC motor
Factory usage fan RPM is 2700
12V
487 m^3/h airflow (average air flow velocity 49 km/h)

I tried with 18V, RPM is 3700, average air flow velocity 64 km/h.
My project image:

Radial fan image:

Radial fan datasheet: https://1drv.ms/u/s!Ao1QAv8AtzQgo0uh3r90yp1b5lZv?e=ulLm7v


texts:
Having the following diagram, how can I amplify output from pin 3&4 to speaker, using BC547 transistor?

(source: elm-chan.org)


texts: How do volume production manufacturers use contactless JTAG programming?

texts:
Do high volume manufacturing outfits all make a custom made 'bed of nails'?

I have not been able to find a ready jtag contact pattern and spring loaded header other than tag-connect pointed in this answer.

Are there really no common JTAG PCB pattern and pogo-pin parts?


texts: Constant Current of an XL4016 Buck Power Module

texts:
Hi have this buck converter
: Step Down Buck 9A 300W Converter 5-40V To 1.2-35V Power Module XL4016
I've done my research, read some posts and articles but I'm still quite confused, some say a constant current supply "constantly push" the set current, but some say a constant current supply alerts you only when you're about to reach the set current and is current limiting.
Let say my load uses like 1A, and I set my XL4016 Step Down Buck Power Module current pot to 5A.

Will my load receive 5A constantly or will the current limiting
feature kick in once my load reaches 5A?

Edit: I'm gonna be using the XL4016  Buck Power Module to power some motors for my project, and im gonna buy like 1 or 2 converters for a bunch of 5v sensors and loads, etc. maybe a linear regulator one. But for the 12V ones, im thinking of my XL4016. My input is around 18-14V, i want it to constantly be at 12V, and 5V.
thanks a lot.


texts: Two outlets, to power device if either is on

texts:
Basically, I have a 120V device I would like to have powered if either/both of two outlets have power. So both could be on, or just one of them.

The device itself is typical in that it only has one power cord.

Two questions:

How do I wire this correctly?  Assuming I have to use these two 120V outlets and a single power cable into the device.
How could this go horribly wrong?  Although this may sound absurd, for the sake of my learning, say I "split" the power cable and connected it to each outlet.  I assume this would end up providing much more voltage than I wanted and damage the device?  I would get some varying voltage based on the phase of each outlet?  Or am I horribly confused?

Of course I really need #1 answered, but I'd love some insight on #2.


texts: Efficiency of solar panel under warm-white LED light

texts:
I need to transfer power from ground level and from a normal 230 V outlet to up to a test jig which is at high potential. I need about 50-100 mW after all losses to power my circuit. Power is too low and voltage too high for a normal transformer to be viable. Power consumption isn't an issue. No production run, just a test jig. I need to run it for a long time so batteries will eventually be depleted.

Your normal mono-, polycrystalline or even CIGS PV panel is around 13-18 % efficient under 1000 W/m^2 sunlight, but what about you shine it with a COTS warm or cold white LED lamp? I didn't find anything useful online so far. Does it drop down to ridiculous levels or can I expect at least 5 % efficiency out of the PV panel?


texts:
I was wondering how waterproof wristbands are charging. I suppose is a common technique that all vendors are using. For example my wristband has two exposed leads as it seems below.

The charger has similar leads that fits to the wristband and a micro usb for current input. When i am trying to measure the voltage on the two exposed leads i am not getting anything, as expected because the device is waterproof, but these leads are charging the wristband.

Does anyone know how this charging method work?

How these leads are going "active" when the charger is attached?


texts:
The application is high-side current sensing for a battery-operated device. The current drawn from the battery goes through a shunt resistor, the voltage across the resistor is amplified by an INA, which output goes into an ADC (ADS1262). An MCU retrieves the conversion results and forwards them to a computer for analysis.

I tested the circuit by generating a current [0 A - 1.5 A] through the shunt resistor (0.01 A steps from 0 A to 0.1 A, then 0.1 A steps). According to the resistor's value and the amplification, this gives a voltage range [0 V - 4.3 V] at the ADC's input, which has a 5 V reference. I calibrated the ADC before the test (offset and gain respectively at min and max input current). For each current step, I recorded 100 conversion results from the ADC synchronized with as many samples from a tabletop DMM (Agilent 3606) for the ground truth. Then I computed the average error for each step. As shown below, the absolute error between the generated current and the measured one decreases linearly with increasing input. At 1.5 A input, the error is smallest (about 50 μA).

Why is the error larger for smaller inputs? I expect some ADC nonlinearity, but in the ppm range, not several percent. I checked that the ADC's input is indeed linear, so this behavior doesn't come from the amplification stage. Is it a general property of ADCs or is it specific to my circuit?

(This was part of a prior question, where I gave more details on the project. I don't think the details are relevant here, though. This other question shows an error curve very similar to mine, but they used a MOSFET for the current sensing and its characteristic was nonlinear to begin with. So it doesn't help me much.)


texts:
I have a UMFT4222EV, that is a development module for FT4222H. It has 2 jumpers to change the mode from 0 to 3. If I change the jumper settings unplug and plug it again to USB, it is enumarated as expected.
However, I designed a PCB with FT4222H but mode changing doesn't work. It has DCNF0 and DCNF1 inputs. If I connect them to GND, It must have mode 0. But it stays always mode 3 as listed in device manager in windows.

The PCB is working, I mean  all volatage levels are as expected, 12MHz cyristal connected to FTDI chip is also generating oscilation at 12MHz.
Only non-working thing is mode selection.

What is the problem?


texts: How do we define the cutoff frequency in an active Op-Amp filter?

texts:
When we get a circuit such as the following:

How do we define the cut-off frequency? Is it still $$f_c = \frac1{2\pi R_1C_1}$$ since \$f_c\$ is defined for \$X_{c1} = R_1\$?
Or is it defined so that \$V_{out}\$(the one after OA3) is \$0.707V_2\$?


texts: Issues with wireless charging receiver circuit

texts:
Circuit is not functioning as intended, just get repeating pulses Vrect ~= 2.5V. I understand Vrect needs to be above this value but I having trouble getting there.
AC1 PAD 1 & AC2 Pad2 are connected to the receiver coil with part number listed. This is intended to be a WPC 1.2 compliant receiver circuit used with off the shelf transmitters. The BQ51003 chip is to be used as a 5v power supply. The power transmission never gets further than the initial ping. I believe it is due to low voltage at the Vrect pin, as that voltage never gets higher than the undervoltage lockout value.  This leads me to believe the issue is with the resonant circuit and I am needing advice on how to go about fine tuning the resonant circuit to get the required voltage.

Ls' ~= 33uH
Ls  ~= 29uH


texts: z-Transform Methods: Definition vs. Rectangular Rule or Tustin's Rule

texts:
The definition of the z-transform is defined as \$z = e^{sT}\$ where "s" is complex frequency for continuous-time systems and "T" is the sample period.  Why are rules such as the forward rectangular rule, or Tustin's method used instead of the definition?

Forward rectangular rule:  \$s \leftarrow \frac{z-1}{T}\$
Tustin's rule:  \$s \leftarrow \frac{2}{T} \frac{z - 1}{z + 1}\$

Edit to clarify my question:
I am asking about the characteristics of the transform methods.  If I transform G(s) to G(z), then why use Tustin's rule or forward rectangular rule instead of the definition?  I would think the integration rules are just an approximation to the definition.

Edit #2:
What makes any given "s-to-z" map better or worse than any other?  What are the characteristics of these maps and how do they compare with each other?  In other words, if I map G(s) to G(z) using Tustin's method, how/why will this compare with mapping with the definition \$z = e^{sT}\$?  The same question applies to other maps (forward rectangular, backward rectangular, etc).  If I get different pole/zero locations using different maps, then how/why would I select a given result (G(z))?  To reiterate my previous question, why use an approximation (Tustin's method etc) when one can use the definition?


texts: What could cause a gain error in the R-2R DAC?

texts: I was studying R-2R ladders and I still what causes a gain error in the R-2R.  I assume that it could be caused by an error in the R or 2R resistors.  I don't think that a mismatch in the feedback resistor of the opamp would cause any offset error. Also I am unsure how a mismatch in one of the  R or 2R resistors causes a gain error and not just a DNL and INL.


texts: I want to find the pole associated with this circuit design

texts: the result of the pole location is given as 1/(R(C1 series with C2)) ie 1/R(c1||C2). I am unable to derive it, can anyone help me to derive the transfer function to obtain the pole associated the circuit shown in the picture.


texts: Why do these types of inverters produce different output power?

texts:
In induction heating we generaly use single-switch, half-bridge and full-bridge inverters to generate power. Why is it that they can't all produce the same average power?

Single-switch:
Half-bridge:

Full-bridge:


texts:
I'm using a touch LCD whose content I want to change if the user moves toward it. For this I'm looking for an SMT proximity sensor with a 40~50 cm detection range. Space above the PCB is only 3 mm, so Sharp GP2D12 and the like are out.

note - I'm not looking for shopping advice ("where can I buy part xyz?"), but rather design advice ("How can I solve this design problem?")


texts: Why Exactly Car Charger Stop When Car Is Off?

texts: Just out of curiosity, I'm wondering why car chargers can provide no power when the car is off in most cars. Is it because the electrical system that connects to the car chargers is running off the alternator and not the battery?


texts: How to clean my soldering iron tip or how to determine that it's beyond repair?

texts:
First, I've read though questions Soldering Iron Maintenance and Going through Soldering tips quickly and was unable to solve my problem. I have recently (as in less then a month ago) obtained Multitip 25 ERSA Microsoldering iron with 0172BD/10 tip.

From the start I had problems wetting the tip. I tried everything but solder just wouldn't flow over the whole tip. I later found information in one of manufacturer's catalogs that I should wrap solder with flux around the tip and then turn on the iron. After few tries, I managed to get a big part of the tip wet (and it was working great), but one small part wouldn't wet.

After some soldering I decided to try to get whole tip wet and obtained 0TR01/SB tip refresher. After using it according to the manual, the whole tip was covered in black substance which should be easily removable, but it isn't.

Now about half of the tip is contaminated and about half seems to be working (I managed to clean the working part).

My question is: Is there any other way to clean the tip? Two things from questions I linked I didn't use were dedicated tip cleaning mesh (couldn't find a source of them in my country) and flux outside the wire (because I don't have any at the moment) and how to decide when a tip is dead and needs replacing?

Also, how do the tip refreshers feel (I'm assuming that they are more or less all alike)? I often find them described as paste, while the one I got is solid (but melts when in contact with hot tip).


texts:
I am currently working on a system with 4 channels of IF signals (100kHz). Since its a fast changing signal via all 4 channels I have to process all channels simultaneously. I have chosen 2 16 bit dual channel simultaneous sampiling ADCs (ADAR7251) for the 4 signals. (ADC throughput 600ksps) I want to use SPI for data acquisition. But I am not able to decide on which microcontroller will be best for simultaneous data acquisition from 4 channels of ADC using SPI.

I have mostly worked on AVR, so my choice is 32-bit AVR UC3 Microcontrollers from ATMEL (eg. AT32UC3L0128). But I am not sure if simultaneous data acquisition and storing will be possible in the Flash. Apart from acquisition I have to run a sperate process to transfer the data to PC via RS232 or LAN. ARM Cortex M based uC (eg. STM32F407/417) also works for me, if there are better suggestions.

Please suggest a microcontroller that can be used for 4 simutaneous data acquisition with SPI.

ADAR7251: http://www.analog.com/media/en/technical-documentation/data-sheets/ADAR7251.pdf

AVR UC3: http://www.atmel.com/products/microcontrollers/avr/32-bitavruc3.aspx

STM32F407/417: http://www.st.com/en/microcontrollers/stm32f407-417.html?querycriteria=productId=LN11


texts:
When we know the impulse response of a system, we know all the equations needed to find an output of the closed loop system. So, theoretically we can find the perfect or at least a very good PID tuning since we can simulate or predict how the system will respond.

In practice, when we already know the impulse response of a system, is that easy to find suitable values to the PID coefficientes? Or it will only help but we still will need an iterative method or trials to tune it well?


texts:
Let's say I've got a device which requires 700mA at 5V and I want to power it of a capacitor for one full hour. Now if I calculate the required capacity I get: C = I*t/V = 504 Farad. Capacitors like these are quite expensive.

Does anyone here have a better idea of getting 700mAh @5V on a capacitor? Perhaps using an array of lower C capacitors? Maybe a chemical cell?


texts: KiCAD: Triaxial Connector Footprint from Drawing

texts:
I am planning to use a PCB-mount triaxial connector, CBBJR79TL, in a design for a laboratory prototype. Making reference to the "recommended mtg hole pattern" section from the CBBJR79TL drawing, I have attempted to make a footprint in KiCAD. I am new to PCB design generally, as well as KiCAD specifically.

There are 6 pads. The pads are located at (-79,0), (21,0), (129,129), (-129,129), (129,-129), and (-129,-129). Pad Number 1 corresponds to the center conductor, Pad Number 2 corresponds to the inner shield, and Pad Number 3 (technically 4 contacts) corresponds to the outer shield. All units are in mils.

How to interpret the dimensions provided on the drawing?

The pins themselves appear to be 50x40 mil (+-5mil in each dimension), and yet the recommended hole diameter is 62.5 mil. Suppose I add 22.5 mil of pad diameter to account for the annular ring -- that leaves a total pad size of 85 mil. The closest of the two pads (Pad 1 and Pad 2) are 100 mil apart (center to center). With a total pad size of 85 mil, this means that there will be only 15 mil of solder mask between (edge to edge) of Pad 1 and Pad 2. This distance is lower than recommended pad separation distances (50 mil) for through-hole parts that I have come across online.

That being said, I am unsure what Pad Size and Hole Size I should be using. I have a feeling I am missing something – perhaps something related to the pre-tinning note (note 7) on the drawing?


texts:
I’ve designed a PCB that is 50mm by 48mm
It’s a simple 12 LED light board, each LED has its own 36 ohm resistor and is all powered by a 5V supply
each LED runs off 60mA and uses 0.306W
The resistors are 1/4 resistors

Ohms law states that 12 LEDs at 60mA is 3.6W (720mA)
The LEDs are in parallel.
Will this get hot, to hot to run on its own? And is their a chance of it over heating and becoming dangerous?


texts: Dynamo powered by motorcycle to charge a battery

texts:
Hello and apologies if someone has asked this, I didn't see a question quite along these lines.
If you have an electric motorcycle, is it possible to have a dynamo attached to the bike that will charge a battery, so that when you need to stop for a recharge of the bike, you have a charged-up battery to do it from?  Would a battery that could do that be too big to lug on a bike?
IF the battery has to be huge, or multiple, could you instead do this with, say, a stripped-down truck with a group of batteries in the bed?
Not surprisingly, I'm watching 'Long Way Up' and seeing them struggle with the short range/recharging necessities of traveling on electric motorcycles.


texts: Capacitors with an LDO voltage regulator - how necessary is it?

texts:
I’m planning on using an MCP1700 to drop the voltage of a lithium polymer battery from 3.7 V to 3 V. The battery will be connected to the regulator via a charging circuit (https://www.sparkfun.com/products/10217). The data sheet for the regulator suggests a 1 µF capacitor on its input and output for stability. How important is this? I’m currently using a regulator without capacitors, and my device powers on and runs just fine.

Does it simply make the regulator less efficient, due to less stability and it having to “chase its tail” more?

What about on the input? Does the charger circuit take care of any needs?

The device it's going into is a Game Boy Advance which already regulates its voltage a bit (it’s used to being powered by AA batteries), so I was considering leaving the capacitors off.


texts:
I am using a tantalum capacitor of 10 uF rated at 20V as a decoupling capacitor.
It is placed in parallel with a 5V supply. Now when the circuit is powered, the capacitor burns out.

I replaced the tantalum capacitor assuming that the previous capacitor was defective. But when I powered the circuit the capacitor burned out again.

I replaced the tantalum capacitor with electrolytic capacitor of 10 uF rated at 63V. This time the capacitor did not burn after powering the circuit.

I do not understand why the tantalum capacitor burns up?


texts: How does a guitar body affect electromagnetic pickups?

texts:
If the pickups are just electromagnets detecting vibrations in metal strings, what effect does the guitar (size, shape, type of wood, solid body, hollow body) have on the pickups?

Most argue that the pickups are similar to microphones. However, direct contact with the pickup by material other than metal does not produce any significant sound from an amplifier.

How can wood vibrations from the body effectively transfer to the electromagnetic pickup to affect tone in a significant way?


texts: Why is this circuit causing my breaker to trip?

texts:
I'm an electronics hobbyist and I decided to make my own electric heater/kiln thingy. It works fine for a couple of minutes, but then the breaker trips. This is my first project involving AC, so I'm a bit clueless as to what could be happening here.

The circuit is very simple:

I have a coil of wire that is switched on/off by a SSR which is controlled by a PID controller.
The PID and the heater coil each have their respective fuses.
I'm run it off a wall outlet and since I live in Canada, it operates at at 120V AC 60 Hz.
I have it grounded to the heatsink of the SSR, which is housed close to all the other wiring, but definitely not touching.

Edit: I hope I didn't botch this circuit drawing, but here it is.

simulate this circuit – Schematic created using CircuitLab

My thoughts:

The breaker cannot be tripping from over-current because the fuses are never blown, and the wire itself can only handle a maximum of 5 amps before melting. (I think the breaker trips at 10 or 15 amps).
Is it possible that the coil is generating a voltage spike that is arcing over to ground? Like how in DC, the voltage builds up as the field collapses.
If 2. is a possibility, how would prevent that from happening? Like how in DC you would have a fly back diode.

That's all I could think of, and honestly I don't know what to look up so I decided to ask here before turning it back on again.

Thanks.

PS: I decided not to draw a circuit because I don't know what the exact values would be for all of the components. I'm hoping that the circuit is simple enough to understand from the description in words. I can attempt to go calculate everything if it's really necessary, just hope I don't have to haha.


texts: Consider lowering VDD to save power in a static CMOS gate. Also scale Vt proportionally to maintain performance

texts:
Will the dynamic power consumption go up or down? Will the static power consumption go up or down? Explain with proper analytics.
I came accross this question while solving a question booklet issued by my University. Although the answer might be straightforward, I need the steps to prove the statement.


texts: Differentiate between clapping and talking

texts:
I brought a clap activated switch project to practise my soldering. I realised clap activated was really sound activated. Is there a way I can get it to be able to tell the difference between me talking to myself and clapping?

I was assuming I can some how get it to only work within certain frequency.


texts: How to protect reed switches in dual float switch pump control circuit?

texts:
I'm trying to make a dual-float switch control for a pump. I want the pump to come on when the water is at the high level, stay on until water falls to the low level, then turn off and stay off until water returns to the high level.

I am using the circuit described here with some modifications: https://electronics.stackexchange.com/a/74159/99764

The problem I am having is that I keep destroying the upper float switch. I thought adding the diode across the relay coil would prevent this, and the circuit worked twice, then the relay switch stuck closed again.

Sorry for the terrible diagram. Any help? Do I need to put RC protection on the float switches? If so, where? And how do I calculate the values of R and C?


texts: Usually I route my PCBs never making a 90º turn as best practices recommends, but sometimes there are points were 3 traces must intercept, if I always do 45º turns, in this intersection will be a 90º turn, so is it ok, or there is a better way of doing so?


texts: Typical rms values for random jitter in satellite communication

texts:
I'm trying to find typical values for random jitter in satellite communication and I'm not really finding any values in any documents. Most of the time I only find definitions for different jitter types.
Now I thought that someone here maybe knows resources or the right place to search for such information.
Thanks in advance!


texts: How do I drop 19VDC from a 0-60VDC source to get an accurate linear 0-48VDC signal

texts:
I've been using the Stack Exchange website for years, but never asked or answered a question, so first I'd like to say thank you for all of the help over the years. On to the problem:

I want to measure the output voltage of a pair of solar panels that can have a peak open circuit voltage of more than 48VDC. I want to use that with an LM3914N to indicate output between 19VDC and a maximum indicated 48VDC - but I want the circuit to be able to handle up to 60VDC from the solar panels. This means that the voltage divider will "see" from 0-29VDC for a solar panel output in the 19-48VDC range, and divide that by 5.8 to get the driving signal for the LM3914N.

Right now, I have a breadboard prototype that uses a 19V Zener diode (avalanche diode) in series with a ~75KΩ total resistance voltage divider to provide a 0VDC signal at ~19VDC panel output and increases to 5VDC at 48VDC panel output. The current through the zener and resistor voltage divider is <600µA maximum, and the LM3914N input signal impedance is relatively high (~20KΩ), so power dissipation isn't  a problem at these levels.

My question is: Is there a more precise, efficient, SIMPLE, and preferably, inexpensive method of dropping the panel output by (as close as is practically possible) exactly 19VDC under the fairly wide input range from 0VDC to 60VDC? Is there a way to use something like a TL431 in place of the zener to do that? (The TL431/TL431A from TI, OnSemi, and Fairchild are only rated for a maximum cathode voltage of +37V, so that would not meet the specs, but others that I'm unaware of might.) If so, a simple schematic showing how to use a TL431 or similar to do this would be a great help.

What I have now is not as accurate as I would like at the low voltage end of the input range, with the zener not being as linear as I want it to be. It's consistent, but not very linear from ~18-23VDC panel output, improving significantly as the solar panel output voltage increases above 23VDC. I eventually plan to log this data, and I would like the data to be accurate and high resolution; ideally, ≤1mV. I can increase the current through the zener to improve the accuracy somewhat, but I also want to keep the parasitic power losses and coincidental heat production as low as practical.

I am asking for a simple, efficient, and inexpensive solution to this problem, but I'm interested in learning the most accurate practical ways to do this, so any additional information about this is also appreciated.


texts: GPS signal strength issue - route layout problem?

texts:
In my design I use GPS module u-blox MAX-7, LNA MAX2659 and chip GPS antenna. First prototype design shows good signal strength, in 2 minutes from a cold start I have a fix. Here is the picture of PCB layout:

The highlighted trace is RF signal from LNA to GPS module. Under this section, there is LCD display (U7).

Now, I had to significantly modify the PCB layout, because I changed some parts(LCD, GPS antenna etc.) and I want to fit the device into a small enclosure. The size of PCB is very limited, so I came up with this design:

As you can see, because of size limitation I moved the GPS module to the bottom layer of PCB and I had to use via to route the RF signal to the module. Again, there is LCD display next to this section.

My problem is that now the signal I get is really low. I get one message every few seconds. Can via in RF signal route attenuate the signal so much? Do you have any suggestions how to solve this?

PS: I also tried to populate PCB with GPS related parts only. Result was the same.


texts: My understanding of RC circuits is broken

texts:
I asked a relatively simple question. Unfortunately, the answers provoke far more questions! :-(

It seems that I don't actually understand RC circuits at all. In particular, why there's an R in there. It seems completely unnecessary. Surely the capacitor is doing all the work? What the heck do you need a resistor for?

Clearly my mental model of how this stuff works is incorrect somehow. So let me try to explain my mental model:

If you try to pass a direct current through a capacitor, you are just charging the two plates. Current will continue to flow until the capacitor is fully charged, at which point no further current can flow. At this point, the two ends of the wire might as well not even be connected.

Until, that is, you reverse the direction of the current. Now current can flow while the capacitor discharges, and continues to flow while the capacitor recharges in the opposite polarity. But after that, once again the capacitor becomes fully charged, and no further current can flow.

It seems to me that if you pass an alternating current through a capacitor, one of two things will happen. If the wave period is longer than the time to fully charge the capacitor, the capacitor will spend most of the time fully charged, and hence most of the current will be blocked. But if the wave period is shorter, the capacitor will never reach a fully-charged state, and most of the current will get through.

By this logic, a single capacitor on its own is a perfectly good high-pass filter.

So... why does everybody insist that you have to have a resistor as well to make a functioning filter? What am I missing?

Consider, for example, this circuit from Wikipedia:

What the hell is that resistor doing there? Surely all that does is short-circuit all the power, such that no current reaches the other side at all.

Next consider this:

This is a little strange. A capacitor in parallel? Well... I suppose if you believe that a capacitor blocks DC and passes AC, that would mean that at high frequencies, the capacitor shorts-out the circuit, preventing any power getting through, while at low frequencies the capacitor behaves as if it's not there. So this would be a low-pass filter. Still doesn't explain the random resistor through, uselessly blocking nearly all the power on that rail...

Obviously the people who actually design this stuff know something that I don't! Can anyone enlighten me? I tried the Wikipedia article on RC circuits, but it just talks about a bunch of Laplace transform stuff. It's neat that you can do that, I'm trying to understand the underlying physics. And failing!

(Similar arguments to the above suggest that an inductor by itself ought to make a good low-pass filter — but again, all the literature seems to disagree with me. I don't know whether that's worthy of a separate question or not.)


texts: How much of the loss of battery capacity in higher currents is caused by its internal heating?

texts:
For example this page give this data for one AA battery:

0.5A : 1.84Ah
1A   : 1.411Ah
2A   : 1.18Ah

Is it mainly b/c of the internal heating?


texts: Need help decoding part number for SOT23-5 chip

texts:
I have a circuit board that has come out of a smart plug-in lamp dimmer/switch module. I would like to find the part number of a small SOT23-5 integrated circuit chip that is on this board. The SMT code appears to be FW7GE but I have been unsuccessful in a multitude of web searches and visiting manufacturer web sites to locate the actual part number that corresponds to the SMT top code.

Here is a picture of the chip zoomed in as far as I could and still maintain a decent focus. The chip seems to part of a switching power supply

Any help locating he part number would be much appreciated.


texts:
I'm driving a high power load with the BTA440Z (datasheet):
line voltage is Vac = 230 AC, load power is P = 1.33 kW, thus load current is ~ I = 5.8 A.
If i swap the load with another that draws P = 2.33 kW, then I becomes ~ 10 A; in this condition the triac overheats and it doesn't un-latch due to thermal runaway.

To properly size the heatsink, I need to know how much power the triac is dissipating, and I realized that in the datasheet there is no such thing as an equivalent to what in a MOSFET would be "Rds on", and that I don't actually know how to find such a parameter.

The circuit is as follows, taken from this datasheet, without the snubber network:

Initially R1 was 680 ohm, because i thought that it could work anyway and less current would pass through the opto; but i subsequently dropped it to 360 ohm because i figured that more current through the gate would make for a wider channel between the main terminals: is this assumption correct?
Does this current also contribute to the power dissipated on the triac?

Based on what i read, what i know, (electronics-tutorials.ws, link 1 and link 2, and the Wikipedia page about Triacs), and the following image, my guess is this:
for the most part, the power dissipated by the triac is given by the current to the load I, times the triac on-state voltage VT.
Is this correct?

Please note that without a zero-cross detector, my microcontroller won't turn off the opto after the triac has been fired into conduction, so assume the opto is always on.


texts:
I'm making a function generator which works in the audio range for a college project. I'm not allowed to use microcontrollers or any digital chips. So I'm using a Wien Bridge oscillator with a pot to generate variable sine wave. It is followed by a Schmitt trigger to generate square waves and finally an integrator to get triangle wave. I found this schematic on the web for the Wein bridge:

Could you replace the two variable 100k pots by a single pot? If not, is it possible to somehow mechanically (or electrically) gang the two different 100k pots? I'm trying to avoid using a single double-ganged-potentiometer to save cost.

I would like my final design to have only two pots. One for frequency and one for amplitude.


texts: Testing UK carbon monoxide power socket is live

texts:
My Deta 1121 carbon monoxide detector is showing no lights. I'd like to test the ceiling socket to determine if the fault is with the wiring or with the detector.

A separate heat detector is on the same RCB circuit and powered on, so I'm hopeful it's just the CO detector that needs replacing.
I have an earlier version of the Silverline 513121 multimeter and believe these are the correct settings to use when testing UK mains electricity:

My plan to test if the circuit is live is to:

Set the Multimeter to 600V AC ~
Place the black probe on the Neutral (grey wire) screw
Place the red probe on the Live (brown wire) screw

Could anyone please confirm that sounds sensible?


texts: Getting coordinates of a device in a 3d space

texts:
I want to make a device that knows itselfs x and y coordinates in a 3d space, for example in a room. I can move the device anywhere in the room but I just need x and y coordinates. Is there anyway doing this by using accelerometers and/or gyroscopes? If not what is the easiest way to do this?

--Edit--

Here is the details. The device will be a kind of electronic pen. When I draw something to the wall with that device, I want it to be drawn in my computer screen too. The wall size is fixed. So, can an IMU give me the accurate coordinates on the wall during a few hours drawing period. If yes what should the precision or sensitivity of the IMU has to be?


texts: How to calculate phases and power factor of two loads in series

texts: I have attempted the follow question by following the formula to sum up the cosine voltages below, but have had no success, would anyone be able to point me in the right direction? I tried graphing a solution but failed.


texts: Do 240V AC switches only need to open the active wire?

texts:
I want to add a simple inline switch to a small, mains powered lamp (~240V AC, 10W Max).

It's earthed; it has a typical 3-core cable with a 3-pin plug.

I bought a bunch of switches, expecting each switch to have 2-3 contacts per side, but they only have 1 contact per side. In other words, they're only capable of breaking contact for a single wire. They have grooves down the adjacent sides to run/hold the other 2 wires, but it seemed strange.

Is it fine to just open the active wire, as shown below?
Note: Brown = Active. Blue = Neutral.

This is the kind of thing I do all the time with 6-24V DC applications, but domestic appliances aren't really in my wheelhouse. Is there any reason this would be inappropriate or unsafe with 240V AC?


texts: Phase voltage vs line voltage in a delta configuration

texts:
If we have a three phase circuit, where source voltages are in a delta configuration, like the one in the picture:

What is the difference between phase and line voltages in this case?
When generators are in a wye configuration, we know that line voltages are defined as: \$E_{12}=E_1-E_2\$, but here, line voltages are simply: \$E_1, E_2\$ and \$E_3\$. What are phase voltages then?


texts: Help identifying fuse 3.6 x 10mm 125 V, 2.5A cylindrical maybe ceramic?

texts:
I would like some help identifying the type (and maybe brand or model number) of fuse this is and if anyone has suggestions on what might be suitable for a replacement or what terms I can search for to find a replacement.

It is a 3.6 mm X 10 mm cylindrical (cartridge?) fuse in a plug for a 9" fan. The body is white, so I believe it is ceramic instead of glass.

On one end, the metal has "(G) CED c (UL) US" embossed. The items in parenthesis here are actually in a circle on the fuse. I've included best pictures I could below.

The other end, "125V 2.5A" is embossed, so it appears to be 125 volt and 2.5 amps. I do not know what the interrupting rating is.

I don't know for this application if a fast acting/quick blow fuse or a slow blow fuse should be used. I assume fast would be safer, but I didn't know if the motor start surge would blow a fast trigger and thus mean a slow blow is appropriate. I'm also not sure if this is ceramic or not, and if a replacement should be ceramic or if a glass fuse would be acceptable for a fan application.

The best my noob self could figure out and search for was "2.5 amp 3.6 10 ceramic fuse" and make sure it was rated above 125 volts (250 was common). My best find was fast blow 576-087402.5MXEP at Mouser, which, if an appropriate replacement, means the fuse + shipping costs more than buying a new fan (clearance at $4). I'm hoping to find appropriate alternative fuses that might be more cost effective.

Any advice anyone can provide is appreciated.

Thank you very much for your time and thoughts.


texts:
My Understanding
From my previous understanding of stability and op-amps, I know that placing an op-amp in a closed-loop configuration reduces the DC gain and extends the 3-dB bandwidth as seen in the image below:

The DC gain has reduced from $$A_{OL} \rightarrow \frac{A_{OL}}{{1+\beta A_{OL}}}$$
The 3dB point and hence the single dominant pole has moved to $$\omega _{p0} \rightarrow \omega _{p0}(1+\beta A_{OL})$$ where beta is the feedback factor. Thus, we get a bandwidth extension.

What the book says

In Chapter 10 of Razavi's book, he has the explanation above.
My Concerns
Q1:
He says that if we decrease the feedback factor beta, the gain decreases (see the grey line in the figure). But as per my understanding (see drawn figure), decreasing the feedback factor should increase gain (the gain should get closer to open-loop). What am I misunderstanding?
Q2:
In Fig 10.7, even with a decreased feedback factor (grey line), the poles remain at the same location as they did with the higher feedback factor (black line). How? Why are we no longer benefiting from bandwidth extension as my understanding?
Also, I understand he's dealing with a multipole system rather than a dominant pole in my drawn figure but that shouldn't make a difference to my questions (I think).
Apologies for the long question. I had a really long thought about this but the book kept going against my understanding, so I had to post here.


texts: Feasibility of rat-race as RF mixer without active devices

texts:
My understanding is that RF mixers generally use some sort of active device (sometimes diodes) to produce output rich in harmonics, and rat-race couplers can be used to get the sum or difference between two frequencies.
Would a solely passive microstrip rat-race coupler fit my application of 5.8 GHz FMCW radar downconvertion? I'm only interested in the difference between two RF signals that are very close in frequency.
Additionally, I've seen examples(1) of radar systems that use a rat-race structure in conjunction with diodes as part of the mixer stage, what might be the reason for that?
(1) Here is a screenshot from this youtube video. Two diodes can be seen around the rat-race coupler.


texts:
I am in the need for a high-side load switch and came up with the following schematic. High-Side voltage levels and current vary between 5-12V / 2 A max. The high-side PMOS (SI5509DC) is rated for 20V V_DS and 12V V_GS and up to 4A.

A 10V Zener diode D1 and the voltage divider formed by R2 & R3 is meant to limit the PMOS Gate-Source voltage. Diode D2 at the output shunts negative going spikes due to inductive loads towards ground.

C1 controls the fall time when opening the switch. I have not yet found a way to make the turn-on behaviour a bit smoother.

The switch will be closed most of the time and switching frequency is not an issue. However, I need to have negative logic at the input to keept the switch open during bootup when the driving pin of the CPLD is tri-stated and pulled towards 3.3V by internal pull-ups.

simulate this circuit – Schematic created using CircuitLab

My Logic interface is 3.3V @ 20mA CMOS (MaxV CPLD). I need to make the thing as robust and compact as possible and would like to ask for advice and comments.


texts: Help with building a 3 Phase DC Motor Controller

texts:
I'm looking to design the power stage of a 3 Phase DC Motor Controller for use with the Emrax 268 motor.  The maximum input battery voltage would be no higher than 300VDC and the maximum continuous current draw would be 180Amps (with a 360A 2 minute burst capability).

It's listed as a 3 phase sine wave driven motor, but I'm not sure if it needs to be a true sine wave or what waveform would be acceptable to drive it.  If it needs to be a true sine wave, then how would I get that from an IGBT or MOSFET controlled output?  Additionally, I'm not sure if I should go with IGBTs or MOSFETs.  I have a contact at International Rectifier who could get me pretty much anything they make, so cost isn't necessarily a big deal.

This will likely become a part of my senior design project, but I'm a year out from that, so for right now I'm just doing some research and trying to get an idea of what I'll have to do.  So any help or general tips when working with motor drives would be helpful!

Thanks!


texts:
Here is the following assertion :

  Question: Why is it commonly stated that in a flyback transformer, the "air gap carries most of the stored magnetic energy"?

  Answer: We can intuitively accept the fact that the energy stored is proportional to the volume of the magnetic material. And because of that, we also tend to think the ferrite must be carrying most of the energy, since it occupies the maximum volume — the amount of air enclosed between the ends of the ferrite being very small. However, the stored energy is also proportional to \$B\times H\$, and since the \$H\$-field in the gap is so much larger, it ends up storing typically two-thirds of the total energy, despite its much smaller volume.

I actually do not understand the assertion. The energy into a transformer is proportionnal to \$B \times H\$.

The magnetizing force \$H\$ is given in a transformer by the Ampere's law, \$\oint H\,\mathrm dl = I \text{(Amperes)}\$.

So \$H\$ is the same into the core or into the air gap.

However the flux density \$B\$ depends on the core. \$B= \mu H\$ with \$\mu\$ the permeability. The permeability of the air is lower than the permeability of a core. So, obviously the flux density is higher in the core than in the air gap.

As the magnetizing force is constant in the air or in the core, it means that the energy is higher in the core than in the air gap. Where is my error?

Actually, I'm not certain of what I said. What I know is that the reluctance across the air gap is higher than the reluctance across the core. So if the flux density is constant into the air gap or into the core, we have indeed more energy contained into the air gap because \$H\$ is higher. But why my first assertion is false ? and Why the flux density is constant ? Actually if \$H\$ is higher into the air gap it means that the flux density is constant.


texts:
As in the title. What limits most integrated circuits to 150°C junction temperature?

I know it's not good practice to run chips very hot (as it shows you are wasting a lot of energy) but I'm curious as to what actually limits them to around 150°C.


texts: How to charge lithium-titanate battery with lower voltage

texts:
I would like to charge a lithium-titanate battery rated at 2.4V (capacity 50mah, max charge voltage 2.75V), which is lower than the typical li-ion battery (3.7/4.2V).

Most charger ics seem to be fixed at 4.2V, so what is the correct way to do this? If I need a battery charger ic, I would prefer to use a standalone charger ic, instead of a mcu controlled one. Power source will be USB.

*edit:
I found this article on how to change the termination voltage of a charger ic http://www.maximintegrated.com/en/app-notes/index.mvp/id/4520 using an opamp to change the volage to the sensing pins. Does this approach work with other charger ICs as well (do they all function in the same way)? Or what would be the best way to get a suitable charger?


texts: How to determine whether the substrate of an LED chip is p or n type using the bench equipment?

texts: I was thinking that you could use an ammeter and see if there is positive or negative current passing through? Am I right or wrong on this?


texts:
I'm planning to use an ATSAMC21G16 in one of my current projects. But I got a hard time finding the correct pin in the Datasheet for the SDADC.

On page 907 the block diagram shows, that VREFB can be selected as a reference for the SDADC.

On page 920 this is confirmed by the bit for reference selection. Also here VREFB is clearly mentioned

However, this pin is nowhere to be found in the port function multiplexing table on page 30 for the ATSAMC21G version.

I can only find it in the table for the ATSAMC21N model.

Does this mean, that only for the N package version an external reference can be selected for the SDADC? Or is there something I'm missing? If it is not available, why would they design it that way? Because with the internal reference stability and accuracy, the 16bit resolution seems to be pointless to me.


texts: Determine the line phase and line to line voltage

texts:
Three single-phase transformer are connected as a transformer bank rated at 18MVA,
      13.8kV(delta)/120kV(Y) // one side of the transformer bank is connected to a 120 kV
      transmission line and the other side is connected to a three-phase load of 12MVA at 0.8 lagging power factor compute the following

I'm keep confusing with what value is for   13.8kv(delta)/120kv(Y), for (Y) sometimes its V_phase and sometimes its V_line-to-line.. How do you decide this
Is turn ratio  N1/N2 = VAB(delta) / Vphase(wye) ??


texts: How do I find circuit board layouts (footprints/packages) for embedded processors?

texts: I am seeking layouts for mobile processors like the ones in phones. I am not sure which processor I will use yet but I am just trying to get a general idea of where to find these layouts.


texts: Splitting Power Tracks/Planes into Different Layers

texts:
I'm just wondering that, in terms of EMC/EMI, what the effect of splitting a power track/plane into different layers can be.

Assume a power track/plane/pour area (with enough thickness and/or total area for, say, 5A DC) is split into two tracks/planes/pour areas (equally or not) and each track/plane/pour area is drawn on different (i.e. bottom and top) layers then connected with enough amount of vias and/or through-hole components' terminal pads (filtering caps, parallel diodes etc).

Doing so is good or bad for EMI/EMC?

Sorry for my English.


texts:
I'm trying to get USART working on my atmega8-16PU microcontroller. I've studied the documentation and took the examples of code from there. I've managed to transmit the data from microcontroller to PL-2303HX chip which is connected to my computer via USB

The problem is that i receive different data from what i send from mcu. Here is the code:

#define F_CPU 8000000UL // Clock Speed
#define BAUD 9600
#define MYUBRR (((F_CPU / (BAUD * 16UL))) - 1)

void USART_Init( unsigned int ubrr)
{
    /* Set baud rate */
    UBRRH = (unsigned char)(ubrr>>8);
    UBRRL = (unsigned char)ubrr;
    /* Enable receiver and transmitter */
    UCSRB = (1 << RXEN) | (1 << TXEN);
    /* Set frame format: 8 data bits, 1 stop bit */
    UCSRC = (1 << URSEL) | (1 << USBS) | (1 << UCSZ0);
}

void USART_Transmit( unsigned char data )
{
    /* Wait for empty transmit buffer */
    while ( !( UCSRA & (1<<UDRE)) );
    /* Put data into buffer, sends the data */
    UDR = data;
}

int main()
{
    USART_Init(MYUBRR);
    while(1)                      /* run continuously */
    {
        USART_Transmit('a');
        _delay_ms(100);
    }
}

I get 0x80 0x00 at the receiver's side and that is not the 'a' symbol. If it's important a 12 MHz quartz is connected to the PL-2303HX chip. What am I doing wrong?


texts:
I'm using low power MOSFETs (N channel-STP4NK60ZFP and P channel- IRF9530). The aim is to build a demo kit for students to study the thermal characteristics of MOSFET at variable frequencies and duty cycles.
P channel : threshold voltage = -4V ;Drain current (at 25 deg C) = -12 A
N channel : Vt = -4.5 V , Id= 4 A

With a supply voltage of 9 V(sorry ,not 12v) and gate voltage of 10 v, i'm trying to heat up the transistor as fast as I can to save time. I'm using a higher watt resister. But what should be the value of the resister in order to heat up both the transistors?


texts: How do I combine outputs in Simulink by changing a specific parameter?

texts: I am studying a Cruise control system, and I want to change the coefficient of rolling friction and put them together in one graph keeping the remaining parameters the same. How do I store all the data in one graph?


texts: Init code for reading and writing SD card with MCS51?

texts:
Do you know how to interface SD card with MCS51,
AT89S52 with SD card and
code example in Keil if there's any...

Thanks for the info...


texts: Free/Open Source alternative to TekScope Anywhere?

texts:
I'm trying to analyze a signal I got out of a scope on my PC and a program like TekScope Anywhere looks like it will do what I'm after.
How can I get plots and data of the scope?


texts: Total power periodic voltage develops in a resistor

texts:
What's the total power this voltage develops in a resistor of 2 ohms?

What I got: total power is $$S=UI$$ where U and I are both effective and calculated as a square root of a sum of squares of effective values.

Is effective value for a zero harmonic 2 or a square root of 2?

Similar question, what happens when this voltage is superimposed with u1(t)=2V? Is the amplitude of every harmonic increased, or only the one of the zero harmonic?

Any mistakes?
13/4 is what I get.


texts: SD card initialization problem - CMD16 wrong response

texts:
I'm using SPI to interface with a micro SD card 2GB and get error respond in CMD16 response and also CMD17 response. Because of that, I can't also read bytes from SD card. Here is my code:

SD card Initialize function:

uint8_t SDCard_Initialize(void)         {
   uint8_t i;
   //Send 80 pulses to active SD card
   for(i = 0; i < 10; i++)
      SPI_ByteTransfer(0xFF);               //Each byte send = 8 pulses
   GPIO_SPI->BRR = GPIO_CS;                 //Enable SD card CS pin
   SDCard_SendCommand(CMD0, 0, 0x4A);       //SD card go to Idle state
   if(!SDCard_CheckRespond(0x01))
       return 1;                            //Error code 1
   for(i = 0; i < 10; i++)                      {
       SDCard_SendCommand(CMD1, 0, 0xFF);   //SD card active operations
       if(SDCard_CheckRespond(0x00))
          break;
       }
   if(i == 10)
       return 2;                           //Error code 2
   SDCard_SendCommand(CMD16, 512, 0xFF);  //SD card active operations
   if(!SDCard_CheckRespond(0x00))
       return 3;
   GPIO_SPI->BSRR = GPIO_CS;               //Disable SD card CS pin
   return 0;
}

SD Card send command function:

void SDCard_SendCommand(uint8_t cmd, uint32_t arg, uint8_t crc)         {
   uint8_t temp;
   int8_t i;
   SPI_ByteTransfer(cmd | 0x40);    //Transmit 6bit command, transmission and start bit first
   for(i = 3; i >= 0; i--)     {    //Transmit 32bit argument
       temp = (arg >> (8 * i)) & 0x000000FF;
       SPI_ByteTransfer(temp);
   }
   SPI_ByteTransfer((crc << 1) | 0x01);     //Transmit 7bit CRC and stop bit
}

SD Card check respond function:

uint8_t SDCard_CheckRespond(uint8_t res)                {
   timeout = 0;
   Timer_Initialize(3600, 1999);            //Set timer trigger at 100milisecond
   while(SPI_ByteTransfer(0xFF) != res) {  //Loop until get correct respond or timeout
       if(timeout)                  {
           TIM_DeInit(TIM2);
           return 0;                      //Return error if timeout
       }
   }
   TIM_DeInit(TIM2);

   SPI_ByteTransfer(0xFF);             //Add 8 clock after receive respond

   return 1;
}

The response from CMD16 that I got instead of 0x00 really strange: It can't be 0xC0 because the response's MSB in manual must be 0.

FF C0 7F FF FF FF FF FF FF FF


texts:
I've recently been using the Texas Instruments CC1310 LaunchPad for some prototyping and now want to make a custom board. I would like the RF performance of my custom board to be as similar to that of the Evaluation Kit as possible, so I am trying to implement the same Meandering Monopole Antenna

http://www.ti.com/lit/an/swra227e/swra227e.pdf

One think is confusing me and that is the use of vias in the antenna. the antenna is on both layers of my 2-layer PCB, and it looks like the layers are connected with vias. In the images within the PDF referenced above, it just looks like closely placed small vias aling the centre of the antenna.

On the LaunchPad evaluation module, they are staggered and along the edge of the antenna, which you can just about see here:

http://dev.ti.com/tirex/content/ti-rtos_cc13xx_cc26xx/ti-rtos_cc13xx_cc26xx__2.16.00.08/resources/cc1310LaunchPad/project0/images/cc1310_launchpad_explained.PNG

I don't know much about antenna theory, but have successfully implemented PCB antennas from reference designs in the past.

Are the vias necessary to connect both layers of the antenna?

Does poor placement of the vias negatively affect RF performance?

Why are the vias placed differently in the two designs I referenced above?

Are there any rules to follow when placing vias in antennas?


texts: Is my MOSFET-based bidirectional level shifter insane?

texts:
In a moment of cheapness, I decided not to order a 5v to 3.3v level shifter from Sparkfun, but instead to put it together myself.  The original schematic used a BSS138 MOSFET, but since I enjoy surface-mount soldering about as much as root canal treatment, I decided to use a similar seeming MOSFET that is through-hole mounted and easily available from my preferred supplier.

The results of this were sub-optimal.  When pulling the 5v line to ground, all was fine - the 3.3v side went to 0.07v.  But when pulling the 3.3v to ground, the 5v line showed around 4.14v (it was otherwise a touch above 5.1v).  On a closer reading of the datasheets involved, as well as the original Philips application note on the subject, I began to come to the conclusion that the gate threshold voltage was the problem.

By altering the schematic and tying the MOSFET's gate to 5v instead of 3.3v, both sides seem to work fine.  Pulling either side low causes the other side to go low.  I'm not, however, at all confident that this is actually a sane thing to do.  My understanding of the original schematic isn't deep enough to form a sensible opinion.

Will this modified schematic work, or are the current good results I'm seeing mere fluke or a precursor to something releasing magic smoke?


texts: Can I place 220V Live traces on top and bottom of PCB?

texts: Can I place 220V/10A max Live on top and bottom of PCB and let them cross over on 2 different layers. Is it safe? Is there a minimum distance of some rule that we need to follow. Attached image with PCB image. Please advice.


texts:
I would like to make a camera mount where it can rotate automatically around the Z axis, and also make a variable angle against the ground plane.

The camera weighs about 500grams.

Is a servo motor adequate to make the camera make a variable angle against the ground, or is it a better idea to use a stepper motor and a worm drive?

For the vertical axis I believe that either stepper motor or servo will work adequately.

Also, could you suggest a good way to measure the actual rotation that takes place when using a stepper motor?  For a servo I believe measurement is not necessary as it already has feedback from a potentiometer.


texts:
Is it possible to use a HC 12 circuit(https://www.elecrow.com/download/HC-12.pdf) to control a 5V relay?

If yes, can you give me a clue on how to do this?

I've been searching for a while and I found nothing.


texts:
I was trying to solder a new capacitor on my pcb and I had problems. At the end I think I burned the copper under the pcb mask and I am wondering if i totally destroyed my pcb. Here is a picture:

where u can see at the photo the brown stuff used to be a little copper which during the soldering just popped out almost burned.

the brown is plastic.

the up brown is the + of the capacitor and and the down brown is the - of the cap.


texts: Which parameter to use to specify the relay in a CAN line communication?

texts:
I need to use SSRs (solid state relays) to comute lines of comunication to a vehicular OBD-II interface. I will use SSRs to choose wich lines will be used at the pins of the connector. The lines wil not be commuted during comunication. The signals I need to comute are CAN.
The CAN transceiver is the SNx5HVD251, so, In order to specify the SSR electrically, I tried to very the maximum current the SNx5HVD251 supports. In the datasheet says, in the operational conditions, that the driver output current, IOH is at most 50mA or -50mA. But There is another parameter, Short-circuit steady-state output current that, accordingly with datasheet, is 200mA.

So, this is my doubt, wich parameter to use ?


texts: Does the register P1IN has default values? I am trying to test a matrix keypad but in register P1IN-1 and P1IN2 are always high.


texts:
I have a small PSU board out of a defunct DVD player that I'd like to use as
a supply for my breadboards. It has two rails, +12 and +5 with two GND
lines, but there's no current indication. My guess is that it's in the
500mA-1A range, but I really have no clue.

What's the best way to test it and determine a safe limit?

Also, if it requires a load in order to operate, should I just wire in a big
resistor across +12 to ground?


texts: How to connect wires coming from bottom side of a single-layer PCB?

texts:
I intend to use an IMS PCB, that is a PCB with aluminium substrate. It will be a single layer PCB (because of the cost, and heat), so only the top layer.

I need to connect approx. 20 wires to the top of this PCB, which are from another PCB, but I need them to come from the bottom face of the IMS PCB. One solution is drilling holes and soldering them, like this:

But I would need a better looking solution... Do you have an idea? :)

Thanks.


texts: Getting brownouts when using MCU controlled P-FET to switch power to another board

texts:
I have an MCU connected to a logic level P-FET(part no AO3401A). The source is wired to a 3.3V regulator that also feeds the MCU. The drain is wired to an LED and a header that connects to a second board with some LEDs and buttons. When I leave the header unplugged the circuit works as expected, and I'm able to turn the LED on and off from the microcontroller. However when I connect the second board the microcontroller browns out and resets continuously. I don't see any fluctuations on the +3.3 when looking at it with a scope.

Why exactly am I seeing these brownouts, and what might I do to prevent them?

Thanks!
Circuit diagram below

.


texts: Can is use the 2N7000 MOSFET to switch 12v from 3.3v?

texts: I want to control some 12V solenoids (SH-04215-015) from a Raspberry Pi Zero W. I believe I need to use a MOSFET transistor to switch from the 3.3V of the GPIO to the 12V the solenoids need. I'm not sure what MOSFET I need though; I don't understand most of the terms on the datasheets. I was looking at the 2N7000 MOSFET will that work for going from 3.3V to 12V? If not what do I need to look for on a datasheet to determin if a transistor meets my criteria?


texts:
I'm trying to test the 5V version of the relay listed at the web address below.

http://www.mouser.com/ds/2/316/mech_eng_tx-908539.pdf

I have tried applying 6V directly from a battery to pin 6 with ground connected to pin 7, also tried the same for pin 1 and 12, but I don't hear any switching. Checking the resistance between pins 3 and 5 (and 10 and 8) shows an open connection (many megaOhms on my multimeter).

Which coil should close the relay? 6/7 or 1/12? I can't tell from the diagram. And why isn't it latching? I'm certain this question demonstrates a fundamental lack of understanding about latching relays. Please help a novice. Thanks!!


texts:
I have the following bode plot and I am trying to determine the DC-Gain and the Gain at high frequencies

How do I calculate the DC-Gain from this plot? Matlab's function dcgain() says that it is equal to 2. How do determine this?


texts:
I'm new to the community, and new to building electronics in general. I am mainly concerned with grounding of line voltage transformers -- I am sure there is some IEEE standard on this but I have not been able to discover the appropriate regulation.

Does anyone know where to start looking for household electronic standards? I have wired three phase 120V to a manufactured power supply, but I want to start modifying my own power supplies and I wish to do so safely.

Thank you in advance, I know I will have to do my own research I just do not know where to start.

Ben


texts: If I convert 10 V, 1 ampere to 5 V, do I get 5 V 2 ampere?

texts:
I know the current in the circuit is the same.

And also,

Power = 10* 1 = 10 watts.

So,
10 = 5 V * (x) ampere,
X = 10/5,
X = 2 ampere,

With some loss while using a voltage regulator, I will get some loss in current also ... That's not a problem. All I need is: if I reduce the voltage, do I get the same 5 V 2 ampere?


texts: For how long can one hold a soldering iron on a component pin when soldering?

texts:
Somebody told me not to keep a soldering iron on the pin of a through hole package for more than 2 seconds. I am not aware of where he got this number from.

When soldering we come across discrete passive and discrete active components, then we have integrated circuits that connect the die to the package via very thin bonding wires. We have very passive tiny surface mount components like SMD resistors and also really huge power transistors.

How do we know for how long we can keep the soldering iron tip on the component without damaging it?
What temperature does one usually use when soldering, is it the same for all applications?
If this time duration is not enough and we need to put the tip back to complete soldering, how long do we need to wait so we can apply the soldering iron for full duration without damaging the component?
Finally what determines what shape of tip to use when soldering?


texts: Could a bad hdmi cable be the cause of 60hz speaker hum?

texts:
I was at a friend's house trying to help him get his computer/tv/stereo connected in his new apartment. We had some difficulty getting the tv to acknowledge the video signal. The hdmi source option was intermittantly available depending on the position of the cable. So it's a bad cable and needs to be replaced.

But we wanted to do as much diagnosis as possible in case anything else had been damaged or lost during the move. So we carefully placed the cable and backed away slowly and selected the source.... (Wait, wouldn't that be a great opening for a spooky story? Sorry, back to reality.)... Then testing the computer audio through the receiver, there is a very bad 60-cycle hum coming through the speakers. It's still there if we switch to the internal tv speakers and disconnect the receiver.

If the audio is running from the mini-headphone-out (I kept wanting to switch it to line-out, but it didn't ever help) to RCA-ins on the tv, could the bad hdmi cable be introducing this hum even though no audio (in use) is going through that cable? Or does this implicate the stereo-mini-to-rca cable as well? Or is it likely to be something else entirely?

Now, don't let me forget to mention that there's hum in the air already. The apartment is on the side of the building with the A/C pen for 2 apartment buildings (about 20 of them). When we turned everything off, we could distinctly hear the same buzz (maybe a little more pink) from outside. And I could also hear a little bit from the refrigerator in the galley kitchen about 10 feet away from the living room.

So, any ideas, etheric masters?


texts: What does it mean when they say 50MHz oscilloscope with 250MS/s sample rate?

texts:
I want to buy a digital oscilloscope to see how a WiFi module transfers signals and data. But I don't know which specification should I take into account?

Actually I don't know what the difference is when they say, for example, 50MHz oscilloscope with sample rate of 250MS/s?

Now as the Wifi frequency I am interested in is 2.4GHz, does it mean I have to buy a oscilloscope with 2.4GHz input channel?


texts: Frequently used functions, performance improvements using static variables?

texts: Does defining variables (large arrays) as static inside a function have any performance improvements if the function is to be called repeatedly say in the order of seconds?


texts: Reason for choosing SPI based flash devices over I2C ones

texts:
I have gone through the below link which says that u-boot support three type of flash technology

http://www.stlinux.com/u-boot/flash

1.Nand
2.NOR
3.SPI Serial Flash

I would want to know why SPI is choosen to be used as flash devices not I2C .

Why can't we have I2C based flash technology?


texts:
I need the Xilinx System ILA IP core to debug the AXI bus of a design. So I´ve created a more simplier design to playing around with the ILA core and to understand how it works.

With the following software

#include "xgpio.h"
#include "xparameters.h"

int main()
{
    XGpio Gpio;

    u32 Status = XGpio_Initialize(&Gpio, XPAR_LED_GPIO_DEVICE_ID);
    if(Status != XST_SUCCESS)
    {
        xil_printf("Gpio Initialization failed!\r\n");
        return XST_FAILURE;
    }

    while(1)
    {
        u32 Input = XGpio_DiscreteRead(&Gpio, 2);
        XGpio_DiscreteWrite(&Gpio, 1, Input);
        for(u32 Delay = 0; Delay < 0x10000; Delay++);
    }

    return 0;
}

I also enable the cross trigger interface from the processing system to the ILA in the debug configuration.

I set the my breakpoint to the line XGpio_DiscreteWrite(&Gpio, 1, Input); to capture the AXI communication from the processing system to the gpio core. Now I run the debug configuration and open the ILA with the following settings (default settings):

After continuing my application the ILA sample the communication with the gpio core.

But the core doesn´t sample the second transmission (the transmission for the XGpio_DiscreteWrite(&Gpio, 1, Input) line).

I´m quite sure that I´m using the ILA wrong. So how can I improve the usage of the ILA? What is the meaning of Number of windows in the ILA configuration?


texts: Satisfactory Margin for Traces from PCB Edge

texts: I've had problems routing too close to the edge of a PCB before and was wondering if there's a suitable rule-of-thumb that I should use (maybe to put in a design rule in Altium somehow with my keepout)? 25mil, 50mil?


texts: How to calculate input and output impedance of BJT Common-Emitter amplifier circuit

texts:
Why is the input impedance not 260Ω in this circuit?

I calculated this impedance as follows:

\begin{align*}
I_B &= \dfrac{18.7V - 0.7V} {180kΩ} = 0.1mA
\\[1 em]
r_{\pi} &= \dfrac{26mV}{0.1mA} = 260Ω
\\[1 em]
R_{in} &= \dfrac{180kΩ \cdot 260Ω}{180kΩ + 260Ω} = 259.6Ω
\\[1 em]
\end{align*}

Similar question for the output impedance, which I calculated to be:

\[
R_{out} = \dfrac{1kΩ \cdot 30kΩ} {1kΩ+30kΩ} = 968Ω
\]

UPDATE:  Bad answer key


texts: Speed control of single phase shaded pole induction motor

texts:
I have a group project where I have to control the speed of a single-phase shaded pole induction motor. My plan was to use a Triac-based circuit however, all Triac circuits I have seen use a potentiometer to control the speed of the motor. In this project, the motor's speed is dependent on an external analog signal received from another unit. The 3 signals can either be high, medium, or low. How can that external analog signal be received and used to drive the motor at the specific high, medium, or low?
NOTE: No microcontrollers may be used


texts:
I was reading up on parabolic reflector designs ,specifically the prime fed design and I can't seem to understand how this design works so well? Won't a major portion of the power reflected off the reflector  be input to the feed thereby increasing the VSWR ?

Also , would any reflector dish work with a feed . What would be the things apart from gain to keep in  mind while designing a dish given a feed .


texts: connecting ac and dc sources together in series

texts: I want a small signal ac voltage riding over a dc voltage, but when I connect my signal generator in series with the DC power source,then the two sources get coupled.I mean if i try to change the ac amplitude the DC amplitude changes too and vice versa.So  any solutions for this problem?/


texts:
I am trying to use TCS3200 color sensor for my project with De0 nano FPGA board. The output of TCS3200 is a square waveform and i am confused how to use that waveform for a particular task.
I searched over Google and found out that i have to measure the frequency of the output waveform  so how to proceed with the Frequency measurement using Verilog Hdl.
I tried some logics for measuring the frequency like Using the up counter at rising edge and count till falling edge but this doesn't work .


texts:
I am designing a board which include DDR3 Ram, AM335x Series MPU. I have a question at this topic.
How should it DDR Ram layouts at PCB? Can I draw at top layer? Or which layer the best? I want to work with this board without problem.


texts:
I have an audio circuit setup currently in which a microcontroller (PIC32MM) sends PWM signals to an amplifier which is attached to some speakers in order to hear what is going on.
I have attached a diagram of the connection from the micro to the amplifier.
When testing the code, I can hear that sound is being emitted, but it is in a distorted and high pitched way that I cannot make out the sounds, since it should be saying specific words.
I have also attached oscilloscope graph of signal coming from the micro with measurements. I would like to know how I could bring down the pitch of the sound since currently its very high pitched or squeaky and then if it is still distorted how to resolve that issue if it exists.

https://drive.google.com/file/d/1C_dP481wpWxKS-ZUuh4AW5rsz75gSgHD/view?usp=sharing


texts: Arduino. How do I limit the output value of a PID controller?

texts:
I have the following PID algorithm I snatched from a website whose name I forgot and I need to limit the output such that its maximum value is, let's say, 90. How do I do that? I tried using Arduino's map function but I need to know the maximum value of the output in order to use that. Here's the code:

//working variables
unsigned long lastTime;
//double Input, Output, Setpoint;
double errSum, lastErr;
double kp, ki, kd;

void Compute()
{
   //How long since we last calculated
   unsigned long now = millis();
   double timeChange = (double)(now - lastTime);

   //Compute all the working error variables
   double error = Input;
   errSum += (error * timeChange);
   double dErr = (error - lastErr) / timeChange;

   //Compute PID Output
   Output = kp * error + ki * errSum + kd * dErr;
   Output = map(Output, 0, 1500,0,90);

   //Remember some variables for next time
   lastErr = error;
   lastTime = now;
}

void SetTunings(double Kp, double Ki, double Kd)
{
   kp = Kp;
   ki = Ki;
   kd = Kd;
}

The call of the map function was added by me as a inefficient way to limit the output.

If it helps you in any way, I want to use it for a balancing robot but weird things happen when the value of the output goes over 90 (the servo library's write() function only accepts values between 0 and 180).

Thanks in advance!