texts: USB-C Configure for Sourcing power, UFP port without PD

texts:
My goal is to design a USB-C Dock that is Sourcing power, while being a device, preferably without using USB-PD.
I am aware of this Question Can Type-C device be configured as “Sourcing Device” without Power Delivery protocol?. In the answer it is mentioned:
"You can achieve Sourcing Device and Sinking Host only using USB PD. USB Type-C State-Machine-Based Role Swapping (the method that utilities only pulling resistors at connection) is described (misleadingly) as power/data role swapping mechanism, but in fact it is limited to only two final states: either Sourcing host or Sinking device (taken from USB Type-C Specification Release 1.3, 4.5.1.4.1)."
My question is does anyone know a way to bypass this and only use configuration resistors as maybe people are more familiar with the USB-C protocol now?
If i have to use USB-PD, is it possible to implement it on an STM32 or STM8, without the use of a dedicated USB chip?


texts: Why does magnet wire need to be insulated?

texts: What is it about having multiple coils that enables the magnetic field? Why can't I just have one big wire or threaded wire on a motor? Sorry, it's kind of a baby question but I couldn't find the answer.


texts: power and fusing for first mains-powered project (100x WS2811 (RGB LED))

texts:
I'm a software guy who's done simple Arduino projects powered by a computer but doing my first project which involves mains/"wall" power.  Working backwards:

2x 50-LED chains of WS2811 addressable LED's will be controlled by a FadeCandy.  (A tiny controller that takes instruction over USB, then tells the LEDs what to do.)  This half I have no problem with or questions about.

But the LED's are power hungry.  18.5mA per color, for 55.5mA per light, x 100, = 5.55 amps.

I've got a S-100-5 power supply that takes in wall power (100-240VAC) and outputs 5V20A.  So lots of headroom there, apparently.

I have a fuse holder and 6A fuses (just say UEC 6A).  Would I put this on the DC side  or AC side?  Or is this unneeded such a project?  I'm OK at soldering in electrical guitars and electronics but I never worked with AC power before and am worried that just one stray whisker of wire will short or arc or something.

Finally, in Japan we don't have polarized plugs or three-prong plugs so I don't know which side is hot and which side is neutral.  Does it matter, as long as I don't touch the power supply?  (And it's in a plastic case.)


texts:
I'm currently trying to setup an SPI link between a Tiva C series launchpad and an LCD screen I've got lying around. I've configured the SSI0 peripheral according to the manual, and I measure the correct values on my pins. MOSI is high, MISO is high, SS is high and Clck is low. However I am unable to view any of the signals on my oscilloscope, I can't detect a clock signal at all, nor can I see any data being written out. The only curious thing is that the SSI Data Register always reads all 1's. The code for configuration is included below, it's written in Mecrisp-Stellaris Forth.
: SPIINIT ( -- )
$00000001 RCGCSSI bis! \ turn on spissi - that works, I can confirm its turned on
$00000011 RCGCGPIO bis! \ turn on GPIOA and GPIOB clock -
$00000001 GPIOBDIR bis! \ set GPIOB PIN 0 to output -default is 2ma drive

\ unlock register and commit register are not needed since SSI0 is enabled by default

$00000000 GPIOAAFSEL bis! \ configure SSI0 peripheral - i THINK this is write, pins 2-5 for SSI0 are supposed to be set to 0 in AFSEL according to the data sheet
                          \ why are the first two 11 though? can I write them all to 1 or do I have to unlock and then use the commit register?
$00222200 GPIOAPCTL bis! \ configure mux register - have the right values written here
$00000000 GPIOADEN bis! \ should be 1 to enable for digital signal but table specs 0 for SSI0, dunno why but I'll leave it
%00111100 GPIOAPUR bis! \ set pull up register for pa 2-5
%00111100 GPIOAODR bis! \ open drain select

$00000001 GPIOBDEN bis! \ turn on GPIOB0  for A0 control

\ must configure drive strength, drain select and pu/pd - appears correctly done w/ default?

\ configure ssi to master role - recall all numbers are in hex.
$00000000 SSICR1 bis! \ must first turn off SSI0
$0000 SSICR1 bis! \ select master
$0000 SSICC bis! \ select clock source - system clock
$01000000 SSICPSR bis! \ apply clock prescaler - divide 16MHz by 64 for 250KHz bus speed, if this works try faster
$00000007 SSICR0 bis! \ set clock rate @ 10 MHZ assuming 20MHz system clock, clock phase captured on first edge, clock polarity low, protocol mode SPI,
                              \  data format 8 bit
$00000002 SSICR1 bis! ; \ enable SSI
: ON ( -- )
$0 GPIOBDAT bis! \ A0 low
%00000000 %10101111 SSIDR bis! \ that string is 10101111 for 8 bit config - this is the right on command - this is currently right justified

;


texts:
I have a B-52 AT100 guitar amp on my bench (naturally, it wouldn't let me attach the .pdf I have of the schematic, so I had to attach it as two .jpegs. The schematic can easily be found online though, if the clarity is too poor). The original failure mode was screen resistors R106 and R105 had melted. Looking around the amp, I also found that R137 and D8 were burnt open. I replaced the failed resistors, measured them out of circuit, breifly turned the amp's standby on and measured the voltage drop across R137 to be 120VDC (100 mA thru it, and 12 W dissipation - which of course smoked it again)!
So my thought is something downstream of R137, like something being fed from B+3 or B+4, is drawing too much current. I can't seem to be able to nail it down though. So far I have:

Pulled all the tubes and checked them for shorts. None found.
Checked DC resistance from plate to ground on all tube sockets. The weird results were Tubes V4 and V11 (being fed from B+4, B+3 respectively), I read very low resistance, then it would jump up into the meg ohm range, then slowly climb back down into the 200 kOhm range.
Checked for shorts across the filter caps. None found.
The reverb tank is not connected, but it has not been connected for quite some time before the amp failed apparently.
When I checked the voltage across R137, I also measured B+1 real quick - 280VDC - which seems low.

Thoughts?


texts: LPC2148 + Eclipse + yagarto + openOCD. Issue with the interrupts

texts:
I'm using 'Eclipse-Indigo' + yagarto + 'openocd-0.7.0' setup for a project on LPC2148.

I've set up the environment properly. I'm able to compile, link and debug the project.

I've configurred Timer0 & UART1 interrupts and I'm facing problems with the same.
I've enabled IRQ interrupts through respective CPSR - IRQ bit.

For timer0 interrupts, the control hits the ISR for 1 or 2 interrupts & then control either goes to:

'Undefined routine' or
program keeps running in the 'while(1) loop' defined in main function.

For UART1 interrupts, the control hits the ISR for first interrupt & then program keeps running in the 'while(1) loop' defined in main function.

I've checked the related register values and found that the interrupts are sensed by the controller(The correspoding interrupt bits are set).
IRQ status is enabled(checked the IRQ bit in CPSR when the code is running).

Still the control does not go to ISR even when next interrupt occurs.

Can anybody tell me the reason?


texts:
I'm trying to replace a faulty DC power jack on a laptop, and having quite a difficult time with it. At this point, I'm not sure if the problem is with my equipment, or my technique.

Equipment:

Weller 50w temp controlled iron (max temp: 850f, ETA tip)
Dremel gas powered iron / hot air gun (this thing)

There are six pads on the underside of the board I need to desolder to remove the old jack. The four on the outside, far as I can tell, only provide mechanical support rather than electrical connectivity.

This is what the board looks like from the top:

And the bottom:

(It's a bit of a mess due to my previous attempts. The black/brown crap is just flux, not char on the board)

It took a lot of messing around to get it out as far as it currently is.

The main problem is that removing the existing solder is proving to be nigh impossible - I've got both some desoldering wick, and a solder sucker.

The sucker has proven all but useless, the moment I move the iron out of the way to get the sucker in place, the solder has already rehardened.
The wick kinda works, but it seems to take a very long time to get very little solder absorbed. As in, you can see the faintest hint of silver color in the copper wick.

My technique was to set my iron to max temp (850f), let it get up to temperature (verified on the digital display), add some flux, hold the wick in place on top of the pad and press the tip of the iron into it.

My understanding is that this high temperature is required due to factory solder being trickier to deal with than the stuff you buy on a spool, and also likely to be the lead free kind, which requires a higher melting temperature.

Now the other option I have is the torch/hot air gun, but I don't want to mess around with it too much for fear of scorching the board. Hence why I'm here, asking someone who's hopefully an expert.

How do I tell when my work area is getting too hot?

Given what I've described here, am I doing anything obviously wrong?

Am I missing some crucial piece of equipment to make this job easier?


texts: Is an led driver needed for simple circuit?

texts:
I have been working on circuits for a while, and when an LED has been needed I have always just put in the LED with a resistor. I have never really understood the need for an LED driver or what exactly it does.

My co-worker recently told me that I was doing it all wrong, that I should absolutely use an LED driver as it is better for the LED and reduces power consumption.

Is this true? Is an LED driver really needed for a simple low-power indicator circuit?


texts: What is the lowest voltage a 12V lead-acid battery in a car could be?

texts:
I'm trying to design a product that is powered from the 12V rail inside the car. In normal driving (engine running, electronics on etc.), what would be the minimum voltage of a low battery?

Reading online shows a lot of forums and mismatched information. The lowest appears to be 11.3V? Not sure how correct this is?


texts: Store data in built-in Flash of PIC at runtime using C code

texts: I am designing PIC16F877a based project that counts the number of people in a room and turn ON the relays in accordance with that number like if 5 persons in a room then One relay would be ON. I want user of the device to set the number according to their need therefore I want to store some integers variables (value defined by user) in a Flash memory on uC at runtime using C code. I have searched on Google but did not find any suitable answer.


texts: How to efficiently charge a capacitor from AC source

texts:
I want to charge a capacitor at 200V DC from a 220V AC power supply (peak voltage = 311 V). Also I want no power disipation once it reaches full charge. This goes inside an equipment that discharges the capacitor sporadically.

The first thing I came up with is a half-wave rectifier diode followed by a resistor voltage divider, but the drawback is the useless power loss in the divider once the capacitor is fully charged.

Another aproach is this: half-wave rectifier diode followed by a ~100 V Zener diode, a resistor and finally the capacitor. I should do this but I don't have the zener diode and I don't like this design because is not very flexible in case I need other voltage.

I suspect that there is another clever way of achieving this in a simpler and flexible way. Does anybody knows one?

EDIT:

Capacitor value is in the order of 1uF.
Charging time is not an issue as long as it is not > 1s.
Capacitive divisor is not an alternative (see my reply to one of the answers).
By "efficiently" I do not mean losing power on resistors DURING charging time; I mean it once the charging is done.


texts: What does blocking performance mean in RF transceivers' datasheet?

texts:
I have encountered two terms, adjacent channel selectivity (ACS) and blocking performance (BP), in TI cc1120's datasheet (http://www.ti.com/product/cc1120).

I found the definition of the former (ACS) here: http://www.telecomabc.com/a/acs.html.

  Adjacent Channel Selectivity (ACS) is a measure of a receiver’s ability to receive a signal at its assigned channel frequency in the presence of a strong signal in the adjacent channel.

However, I cannot find definition of the latter, i.e. BP (blocking performance).

Could anyone explain it in simple words? Thanks.


texts: Separate calibration values from program

texts:
I am working on a device with an internal pump. Due to small differences in the pump's motor speed, I have to calibrate the pump. The result is a value between 0 and 1 (PWM duty cycle). The PWM is generated by an XMEGA32A4U, which I am programming in C++ with Atmel Studio 7.0 and I load the program with an AVRISP MK II. I also have an SD-card in the system to save data on.

My problem is now the following: I have several devices and I am trying to avoid to have to change the source code for every device before programming it. Not just because I am lazy, but it is also error-prone. And also because the remainder of the code is always the same and I don't want to save 10 times the same code containing only one differing number. What can I do? Things I thought of:

reading a unique device ID and thus determining which value to take. But this requires storing a unique ID -> chicken and egg problem. Except if it can be done at programming time with a script (?) or there is a serial number I can read out at boot. The device ID appears to be non-unique as far as I read.
Saving the values on the EEPROM in the microcontroller. I did some research and found that this is also not that simple, since you have to have again several source files to generate the several *.eep files which you have to manually select at programming. Although this is something I only need to do once, it is still 'manual'.
Save a config file on the SD card and read it in the beginning. Probably the easiest part, but the SD card is user accessible and in theory delete- and exchangeable. Checking the file against a device ID would help of course, but then I am back at square one.
Use serial communication to store a config value, which is then written to the EEPROM on the device. I could use LabView or a script to do this ("please enter serial number" -> checking against stored list -> output it via serial)

Does anyone have experience in this? What is the best path to take?
Thanks!


texts: Should thermal pads be connected to GND or not?

texts:
I'm creating a footprint for the TPS2141 (LDO and current limiter) and I wonder if the thermal pad should be connected to the GND plane or if thats a bad idea? Should it just have its own copper zone that´s not connected to anything?

Thermally it should be very beneficial to connect it to the ground plane I guess.


texts:
I am here to clarify doubt on soldermask for non plated holes. I know soldermask is used to protect board from oxidation and prevention of solder bridges and accurate placement of components to be soldered.

But in non plated holes I think it it is not necessary.

is it important of given soldermask to non plated holes or not?
Why so?


texts: Low pass filter giving sine wave ( triangular wave as input )

texts:
so i basically have a low pass filtering that is filtering a square wave and giving me in output :

As far as i know the square wave can be made with the sum of multiple sine waves

So the over/undershoot i have is due to the frequencies that are not being filtered.

The triangle wave i have is this one, i want to know if the same logic can be used to understand the output of the filter


texts: How to work around odd LED strip current limiting?

texts:
I’m a theatre lighting technician (and electronics hobbyist), working on a project involving SK6812 RGBW addressable LED strips & strings. They use an 800kHz single-wire control signal, regenerated by each chip. That is to say, the first chip in the string receives the entire packet of N*4 bytes, takes the first 4 bytes as its R, G, B and W 8 bit PWM values, then regenerates the data packet of (N-1)*4 bytes for the next chip, etc.

The strips work as expected, but I’ve been having difficulties with the pixel strings. Unlike the strips, each diode has a 75 ohm (750 code) current limiting resistor in series with the 5V supply! Using an oscilloscope, I compared the data stream coming into the first pixel from the controller, and what was generated by the pixel. The input stream was perfect, but the output sagged significantly to ~3.3V after ~500 microseconds into each packet. Note that according to the datasheet the SK6812 requires a >3.4V logic high level.
I suspect the timing coincides with the 1.2kHz PWM frequency.

Why would this resistor be added? The strips have no resistor and work just fine. The resistor seems an addition that makes things worse! I haven’t gotten around to measuring the inrush current but regardless 75 ohms seems extreme. Any suggestions on workarounds?

The power supplies are generic (read: low quality) 5V 60A supplies, but there is <1% output ripple, and only sags by 0.5V (to 5V from 5.5V) at 15A current draw (based on tests with a programmable load). The LED strip draws a max of maybe 4 amps with everything at full. The voltage drop was barely noticeable with oscilloscope.

Also worth noting, I have made this pixel string work fine at home on a better power supply, but I haven’t gotten around to checking the difference in output data stream from the first pixel with that supply.


texts: Designing a dental furnace control board

texts: I have a few question about designing a heater control board . Firstly I took a power electronics lecture in the university eon ago but now I try to remember it anew. :)) Regarding my subject, I have an old dental furnace (ivoclar p80) which runs AC 230V and makes heat up to 1200 Celcius degree and it is totally 1800Watts. and I want to design my own control board for this oldy one. Actually I have searched some different boards in term of electronics component but I'm confused. Therefore  may I learn which important points of should I be noted to design. For example which silicon device I should use such as power mosfet,src,IGBT so on. one that shall I use optocoupler to drive the switching device or a filter to prevent signal noise and such different questions :)) also I need to control the temp val sensitively. If you could help me it would be appreciated! Thanks in advance!


texts: Using STM32 to transfer a file via bluetooth

texts:
So far I have been doing projects with Arduino, RPi, ATtiny etc. But now I have project in mind where these things doesnt seem to suit. I need your help.

OK, now on the project:

I have a file on my android device (an image and a .ppt file). I want to transfer it to a SD card wirelessly (bluetooth or WiFi). I will be providing a USB port to access the data in SD card.

Now, I want to assemble/make all the electronics required around the SD card.

(Q1) Which one to choose Bluetooth or WiFi (my requirement is only short range, no internet involved) I want to know what Bluetooth module should I use (I have read that the HC06 is for SPP and I cannot transfer whole .ppt and do a FTP on that).
(Q2) I don't want to use RPi or any ready made development board, I want to make my own minimum development board. Will this be possible using STM32F103 and do the Bluetooth transfer, if not which platform should I choose and how to make my own dev board?
(Q3) Is there a specific bluetooth module for FTP? Or any bluetooth module can be used for FTP.. Because when i see the modules they are specified as being Serial.
Please get me started on this. My question might be incomplete, please ask if any information required. (Please note: I had asked this question else where but I have tried to elaborate the question here, I have deleted the earlier question).


texts: I have some extra fans to cool my Xbox (4). I think that they would drain too much power if I connected them strait to the internal Xbox fan. So I want to know if I have a power suppliy for the extra fans, how can I get them to turn on when the internal Xbox fan turns on?


texts: Why does capacitor value changes when capacitor is DC biased?

texts: I have seen ceramic capacitor value varying under various DC biased levels. Dc biased was a huge factor as capacitor value is reduced by 50% almost? Why?


texts: Common Emitter Stage BJT Amplifier with Early Effect Inclusion

texts:
How can I find Rin, Rout and Gm parameters of a BJT amplifier in common emitter stage without neglecting Early Effect?

We have such homework and I couldn't find the exact same example in Behzad Razavi's Fundamentals of Microelectronics nor Adel Sedra's Microelectronic Circuits. Moreover, I couldn't derive hybrid-pi model parameters(Rin, Rout, and Gm) by myself because things get really complex when I need to deal with this much resistances.


texts: crossing 240 V traces on both top and bottom sides of a 2 layer PCB

texts:
My situation is the same as the crossings encircled in white from Can I place 220V Live traces on top and bottom of PCB?

  Therefore, running Line traces on the top layer and Neutral traces on
  the bottom is fine.

The quote above from the first answer makes it unclear to me whether the same holds  true for Live-Live and Neutral-Neutral crossings. Are they still fine ?


texts:
I have a confusion which has made me wonder that my whole basis of electronics understanding is wrong.

I was looking for an intuitive explanation of the right half plane zero on internet( see link http://tinyurl.com/neg5fe4  <--This is important) and got confused about feedback and feedforward current . So, tell me if I'm right: a capacitor is bidirectional in a sense that current can flow in both ways in the miller capacitor. This is unlike a resistor where current only flows from high voltage to low voltage?

So the net current(in capacitor) = feedforward + feedback .

So, It's a superposition? So when I connect an ammeter with capacitor, i will get this net current right? Also  why does miller theorem only calculate feedback component? It's derivation is very generic, i guess(https://en.wikipedia.org/wiki/Miller_effect)

So how does one determine in which direction current flows in a capacitor?


texts: How to measure current on an electrolytic etcher

texts: I'm building a simple electrolytic etcher to mark steel parts. The set up is a 12v DC 5 amp power supply with the ground connected to on side of the steel part and the positive connected to a brass lug with and insulated handle. The lug is covered in a felt pad saturated with an electrolytic solution (salt water) and then pressed against the steel part. The idea is this will etch the metal part to create a mark. I'm not getting good results and I want to check how much current is being delivered through the lug. When I try to set up a multi meter to measure amps I get a small spark and freak the meter out. How can a measure the current at the lug?


texts: Trying to identify a electronic parts company logo SC

texts:
Have this DC power connector,   and looking for the manufacturer using this logo.
SC text  in a parallelogram


texts: Directly driving 5V source MOSFET H-Bridge with 3.3V logic

texts:
I am trying to design a H-bridge circuit for my project to drive a thermoelectric cooler (TEC). Basically, I am trying to control the TEC with a voltage source driven by PWM.

Now the problem is, I have a 5V DC source but my microcontroller (ESP8266) uses 3.3V logic. Since the space for components is limited, I would like to drive the MOSFET directly from the microcontroller.

I have built a circuit based on some things I have found on the internet but am not exactly sure if it is correct. The TEC I am using is expected to draw up to 1A at 1.7V (maximum); the MOSFETS I am using are ROHM RZR040P01TL (p-type) and RUR040N02TL (n-type) which are rated at 4A, have Vgs(th)~=1.3V and built-in GS protection diodes.

Since I have never designed an H-bridge before, my first question
would be about the design. Does it look like something that would
work or I am missing something here?
When I increased the PWM signal above
zero, there was a high pitch noise coming from the MOSFETs. Is this
something to be expected  or does that signal an issue in the circuit?

I have tried sending low duty cycle PWM from the microcontroller (1-10%) which seemed to be working fine - while the MOSFETs were still buzzing, the TEC was working fine and there was around 0.4V voltage accross the terminals (which you would expect). However, when I increased the duty cycle to 20%, one of the N-type MOSFETs blew out.

I am guessing that this either happened because the MOSFET overheated or because I have done something horribly wrong in my circuit design.

I would appreciate some advice on building MOSFET H-Bridge circuits in general as well as some specific recommendations for this particular design.

Original design

Update #1:

I have redesigned the circuit to have each MOSFET switch separately as @WhatRoughBeast suggested. I also have added two N-type MOSFETs to control the P-type gates which should solve the voltage difference problem. This appears to have solved the noise issue - now buzzing only appears if I reduce the switching frequency to 5kHz or lower.

In the current configuration I am trying to control the direction and voltage by:

having B1 and B2 set to LOW, A2 to HIGH and PWM-controlling A1
having A1 and A2 set to LOW, B1 to HIGH and PWM-controlling B2

While the MOSFETs appear to be working now (as in not overheating and blowing up), it seems I have another problem - with 5V supply, whatever PWM duty cycle I use, the TEG always receives the full 4.5V (using 10-20kHz).


texts: I'm working on a basic h-bridge motor controller. It will be powering a 48v 1000w motor. The FETs I am using are these (Datasheet). When I apply the 5v PWM signal from an Arduino Pro Micro with my power source being 48V I get an output of 3.5 volts or -3.5 volts depending on the direction. They seem to be switching correctly but for some reason the output voltage is significantly less then I was looking for. This is a crude schematic that I drew up illustrating my setup. Could this major drop be due to the gate voltage being too low? The data sheet specifies that 2.7V is the gate threshold but almost everywhere it refers to 10V at the gate.  Your time would be much appreciated.


texts: Backfeed gate output to input with OR gate made out of BJT transistors is not working

texts:
I am very new into electronic.

Can you please explain why looping OR gate output back to input does not work when using BJT transistors for OR gate? but it works with OR gate ICs

Here is the schematic: http://everycircuit.com/circuit/6264984905187328

I am trying to achieve this setup, but wondering why it is not working when OR gate is made out of BJT transistors.

Simulation Screenshot when input is on:

Simulation screenshot when input is off:


texts: What is the use of an op-amp whose output and inverting input are connected to ground?

texts:
I am in first year of Engineering school and I was given an assignment containing this circuit, which drives pressure sensors in a pitot tube :

I am struggling to understand the whole circuit, and more precisely the first op-amp, which output (pin 1) and e- (inverting) input (pin 2) are connected to ground.

What is its use? How can such an op-amp have an influence on the overall circuit, if its output is not used?


texts: Is it possible to control and reverse the direction of a dc motor through a headphone socket?

texts:
Yesterday, I found that it was possible to control a servo using a headphone socket with a fairly simple circuit.
I've got a project where I need to to control a dc motor via a headphone socket. Is such a thing possible? I basically need it to rotate at various speeds as well as change direction quickly. Apparently it is possible to modify servos to rotate continuously but none of them seem to have the speed I require for my project

Here's some context as to why I need this. Yesterday, I had an idea on how to automate the black card technique in landscape photography where you move a black card up and down in front of the camera during a long exposure. I want to build it on the cheap so this is my design:

Animated and annotated versions

The DC motor is stuck to the bolt, which is rotated. The nut is stuck to the plastic cylinder so when the bolt rotates, the cylinder travels up. If you reverse the current, the cylinder travels down. The DC motor therefore needs to work in both directions with the headphone socket circuit. As this is already quite a bulky setup, I'd rather not build a whole arduino into it so if I could get it working via the headphone socket of my phone or music player, that would be ideal!

I've never really done much electronic engineering before so go easy on me please ;)

Any help is much appreciated!


texts: Simple constant current source that doesn't die on voltage spikes

texts:
For testing various laser diodes, I need a constant current source, adjustable up to 150 ... 200 mA or so, down to... well, maybe 1 or 2 mA? (low enough to measure where is the lasing threshold where the diode stops lasing and becomes an ordinary LED). The voltage on these diodes when lasing is pretty low, so I could power the whole thing from a 9 V battery, I guess.

I could do the classic simple design with a LM317 and a resistor, but there's something I don't like about it: the resistor (control pot) that controls the current is in the main current path. I don't want that. I want the control pot to be in a section of the circuit where the current is very low (way, way under 1 mA), so the power dissipated on the pot is minimal, so I could use a higher-resistance pot, and the pot stays healthy a long time.

The reason why I need to keep the pot healthy: with laser diodes it is very important to not have any kind of voltage/current spikes on the junction, because it's so incredibly easy to kill them (*) so a few small 100 nF capacitors should be placed at strategic places in the circuit, such as on the control pot and on the output (I could do those tweaks myself, I just need the basic idea for the circuit, I can only envision complex designs - I need something simple and small).

Any suggestion for a very simple circuit that doesn't suffer from the problem described?

(*) - It's so easy to fry them that most people never disconnect the diode from the driver (the constant current source). They only disconnect the driver from the battery. Otherwise the risk of bricking the laser is too high. I fried that way a very nice 100 mW blue laser, a few months ago.


texts: Calculating the 12V battery requirement for a 240V invertere system

texts:
I plan on powering a 240VAC mobile candy floss making machine from a 12VDC leisure battery using an inverter... the problem is my understanding in this area is rudimentary.

Candy Floss (cotton candy) is made by heating sugar and spinning it. The machines have a heating element to get the device up to temperature - usually around 1200W. Once the device is at temperature they can be dialed down to a maintenance voltage to keep the machine hot.

The machines I have seen have a voltage dial to control the temperature. You'd start them at 240V and then dial down to, say 90V when it is hot.

Here's my reckoning - I'd appreciate it if someone can correct me if I'm mistaken...

Current drawn by the candy floss machine at full power...

I=P/V
I=1200/240
I=5 Amps

Let's say it takes 60 second to get up to temperature...

As = A x t
   = 5 * 60
   = 300 Amp seconds
   = 0.83 Amp hours

Finding the load of the candy floss machine...

R = V/I
R = 240 / 5
R = 48 Ohms

When the machine is running on 90VAC...

I = V/R
I = 90 / 48
I = 1.9 Amps

If we're running the machine for 6 hours at this current...

Ah = A * h
   = 1.9 * 6
   = 11.43 Ah

Allowing for the inefficiency of an inverter, say 75%...

Ah = 4 * 11.43 / 3
   = 15.2 Ah

Assuming a maximum 50% battery discharge...

Ah = 15.2 * 2
   = 30.4 Ah

So I only need to find a leisure battery that can handle 30+Ah.

Am I on the right track here? Something tells me I've missed something important :)

Thanks!


texts: What is the need for any kind of modulation in order to transmit signals?


texts:
I want to compute the current magnitude in a transmission line. The line has properties b (total line charging susceptance, p.u.), x (reactance, p.u.), and r (resistance, p.u.). I'm confused about what value of resistance I need to use in Ohm's law and the difference between b, x, and r parameters.

When I compute the flow magnitude (section 4.1.1) as

\$
|y_{\text{snd},\text{rec}}| \times |V_{\text{snd}} e^{jA_{\text{snd}}} -  V_{\text{rec}} e^{jA_{\text{rec}}}|
\$

where \$V_{\text{snd}}\$ is the voltage magnitude at the "sending" bus and \$A_{\text{snd}}\$ is the voltage angle at the "sending" bus (and rec denotes "receiving" bus), how do I compute the magnitude of the branch admittance, \$|y_{\text{snd},\text{rec}}|\$, from b, x, and r?

I'm confused because if \$y_{\text{snd},\text{rec}}\$= r / (r^2 + x^2) - j x / (r^2 + x^2), then what is the purpose of the line charging b? Or is \$y_{\text{snd},\text{rec}}\$= 1/b?


texts: Configurable size LUT using array in C - embedded systems

texts:
I am working with the STM32F7 MCU in a project where I need to compute and create a LUT with the values of a signal which I will finally send to the DAC.

The problem with the LUT is that the size will be known only at run-time because it depends on some parameters sent to the MCU from a PC.
I was searching info about how to implement that in C and the answer seems to be always the same: malloc().

I also read that  malloc() is not a good way to allocate memory when working with embedded systems so I am wondering whether is there any way to implement such functionality in C not using malloc() (initialize an array using a variable calculated at run-time).


texts: A dual-input solid-state switch that will reliably work in a car

texts:
I need a switch, but with a small twist. If it was operating on normal filtered DC I would know how to make one myself. But since it's for a car, I need help designing it for reliability and surge protection.

The most complicated thing about it will be the description, so please bear with me. Basically, what I need it is a switch with two independent control inputs. Input is active when there is voltage on it as described below, and inactive when there's no voltage (it'll be floating, not grounded). The switch should be shorted when either of the inputs is active, or both.

Control input #1 is from the car's power grid, which means 10 V to 15 V DC + noise and voltage spikes. They say the spikes can be up to 100 V, and can even have reverse polarity, and it's my main difficulty with this design - I don't know how to make the circuit work reliably in these circumstances.
Control input #2 is filtered 3.3V, so that one shouldn't be a big problem.

simulate this circuit – Schematic created using CircuitLab

What the circuit will be switching is also the car's power grid, so I don't know if I can use a MOSFET, for example - will it withstand a 100 V surge, which can have forward or reverse polarity? Current is 2 A with short peaks up to 3 A. The main +12 V input is always present, while the +12 V control input will appear and disappear.

It so happens that I also need to feed the 12 V control input that this circuit receives to a micro-controller's input, meaning I need to scale it down to +3.3 V or +5 V, and I need to remove the noise and voltage spikes in order to protect the MCU and detect the voltage reliably. So it will be beneficial if this switch will somehow filter and downscale the noisy input so that I can feed it to the MCU with no additional circuitry. Or at least filter out the noise so that I can connect the MCU's input via a MOSFET or an opto-isolator without the risk of this MOSFET / isolator being damaged by a voltage spike.

My original idea was 2 parallel MOSFETs with high enough gate-to-source voltage tolerance so that it can throughput 15 V while being driven by 3.3 V. And then I have to devise some kind of a filter for the MOSFET that's driven by the car's power grid, but I have no good ideas on how to do it both reliably and simply (with as few elements as possible). Maybe, a voltage regulator, like LM817? Will it withstand the voltage spikes? Will, like, a high-speed diode bridge for normalizing the polarity and an LC-filter do the trick?
Also, I do not know if a MOSFET will withstand the car's voltage being passed into the source-to-drain channel, with its dual-polarity voltage spikes.


texts:
I'm started working with AVRs few days ago. Started with assembler and simulating in Proteus.

My current goal is to enable Pin Change interrupt on PCINT0, which is PB0 on my attiny13. Right now I'm following problem. I've enabled external interrupt request, but not able to make chip to trigger interrupt on PCINT0 pin.

Code is

.device attiny13
;       --- Code segment ---
.CSEG
.ORG $0     ; interrupt vector table
    rjmp Reset      ; reset handler
    nop     ; IRQ0
    rjmp PCINT      ; PCINT0 (pin INT0 to INT5) PCMSK, MCUCR
    nop     ; Timer 0 overflow
    nop     ; EEPROM ready
    nop     ; Analog comparator
    nop     ; Timer 0 compare A
    nop     ; Timer 0 compare B
    nop     ; watchdog
    nop     ; ADC conversion

.ORG 0x10       ; staring after interrupt vector table

    rjmp  Start
PCINT:
    reti
Reset:
    ldi r16, low(RAMEND)
    out SPL, r16
    sei    ; enabling interrupts

Start:
    ldi r16, 0b000000
    out DDRB, r16
    in r16, MCUCR       ; change triggering edge for the interrupt
    ori r16, 0x03
    out MCUCR, r16
    ldi r16, 0x60
    out GIMSK, r16      ; PCIE
    out GIFR, r16
    ldi r16, 0x01
    out PCMSK, r16

Loop:
    rjmp  Loop

In section after Start label all the registers and flags enabling interrupts are set according to the datasheet pages 44 through 47. These are I in SREG, ISC00 and ISC01 in MCUCR, PCINT0 in PCMSK, PCIE, INT0 in GIMSK and PCIF in GIFR.

Debugging in Proteus however shows that INT0 (second vector) is being triggered, but not PCINT0 (third vector).

Can you please tell me what I am doing wrong?

Update

Several changes to code were suggested in comments and this is how I've altered the code, which is still not cause an interrupt on button press while simulating in Proteus.

Reset:
    ldi r16, low(RAMEND)
    out SPL, r16

Start:
    ldi r16, 0b000000
    out DDRB, r16       ; port B input/output
    ldi r16, 0x20
    out GIFR, r16       ; clearing interrupt flag
    out GIMSK, r16      ; Pin change interrupt enable
    ldi r16, 0x01
    out PCMSK, r16      ; enable PCINT0
    sei

Update 2

I'm using Proteus 8 v8.1 with advanced simulation on Windows 8 (x64), after that I've updated to Proteus 8.4. Result is still the same.


texts: KiCAD merge two different copper planes together

texts:
I have a design with different copper planes, for example, a ground plane and a VS copper, on the bottom size.

But KiCAD overlays both copper planes and throws some design rule errors:

So what is wrong with both copper layers?


texts: Can I simplify this to a 2-to-1 multiplexer?

texts:
I have the following 4-to-1 multiplexer circuit:

simulate this circuit – Schematic created using CircuitLab

With this truth table:

S0 S1 S2 | L
------------
 0  0  0 | 0
 0  0  1 | 1
 0  1  0 | 1
 0  1  1 | 0
 1  0  0 | 1
 1  0  1 | 0
 1  1  0 | 0
 1  1  1 | 1

I can see that I only need 2 inputs to the 4-to-1 mux, but I don't think I can get away with just 1 selector. It seems if S1 = 0 then it wouldn't know to pick d0 or d1. Same with S2 = 0. Is there some way to simplify this circuit to single 2-to-1 multiplexer?


texts: Adding Control Voltage and Attenuation to Op-Amp Circuit

texts:
Quick question here about adding control voltage and attenuation into a circuit.
Say I have a simple op-amp configuration such as below, to vary the gain of an audio signal, where P1 is a variable resistor or potentiometer.
Suppose I wanted to add an input signal, say a ±5V low frequency signal, that would vary the resistance of P1 (i.e. using this low frequency signal to, in essence, turn the knob of the potentiometer instead of doing it by hand). And suppose I wanted to attenuate this input signal as well (for example, having a potentiometer that, when turned, varies the amplitude of the low frequency input signal, say to ±2V).
What exactly would I need to add to the circuit below to make this possible?


texts:
I want to light a normal LED for as long as possible on two AA or AAA batteries. It does not have to blink or so, just stay on. The LED doesn't have to light at the max, as long as it's visible from ~1 meter.

The LED is designed for 2.5V/16mA, however, 1.9V/0.25mA is also still possible. Below that, I don't get enough light from it anymore.

I might not be looking for the fewest power consuming circuit, as some other circuits might work at a lower voltage as well. For example, consider a circuit drawing 20mA for >2V and a circuit drawing 25mA for >1V, then the second would be a better option.

What would be the circuit to give the longest lifetime?

Size is not an issue, nor is manufacturing cost or amount of components. You can use a microcontroller if you want, however, an Arduino would be a dealbreaker.


texts:
The tl;dr version of my question is - how can I trade off ability to hold an exact position for current draw.

The full version - I've got a battery-powered system with a servo. the servo is controlling the rudder of an RC sail boat. As such, precision of positioning is secondary to power consumption, and the amount of resistance the servo will encounter will vary with conditions. Since this is a standard hobby servo, it'll draw a pretty substantial amount of current (for the environment) if it can't reach the requested position. How do I cut off the amount of current it will draw until such time that the amount of mechanical resistance drops enough for it to reach its target?

EDIT: Based on a comment, here's some additional info / measurements

There are two servos at play here, though the question applies to both the same. One controls the rudder, the other controls the sails (the second is basically a winch). Both will experience variable mechanical resistance.

I hooked each of them up to the 5V line on an Arduino and measured the current they draw:

The rudder servo, when moving without resistance draws about 50mA, some amount of resistance pushes the current draw up to 200mA

The winch servo draws about 100mA normal, as much as 500mA when there's resistance.


texts: I cannot relate the power supply topology to any standard topology. It is very similar to Sepic but the Mosfet placement is different.It utilizes one coupled inductor instead of two inductors. Which DC to DC converter toplogy is this?


texts: Can you overcharge a capacitor with a lower voltage power source?

texts: If I have a 5v capacitor and a 3v power source, and I connect the power source to the capacitor will it charge up to 3v then stop, or will the voltage rise above 3v?


texts:
I am trying to build a battery-powered application using the Feather 32u4.
I need a timer to trigger every 120 seconds (although Timer1 with it's 8 second limit would suffice for the beginning), thus I tried using IDLE_MODE, which should save some power.
Connecting the battery's 3V to the feather's 3V pin resulted in about 9mA power draw though, which is way to much.
Considering that the promised 0.3mA current in IDLE_MODE is still too much, what other options do I have to have a 120sec timer with ultra low sleep consumption?


texts:
I would like to start off by saying I have little actual experience in electronics, so bare with me, and for all I know I could be way in over my head. Anyway...

I was thinking of making a rechargeable portable battery charger that is able to keep a smartphone charged for roughly 3 to 5 times the normal complete discharge time of the battery (so I would supposedly be able to make the battery on my smartphone last three to five times longer). I have a Galaxy S4 that I wanted to model the project after. The battery is rated at 2600 mAh, so I had figured I would buy a Li- ion (I assumed their wide use in electronics made them good for this kind of thing [specifically the Lithium Cobalt because of their large capacity]) 8Ah battery or higher, or two 4Ah batteries or higher. Doing a quick search on Mouser and Newark, I saw the prices for batteries rated at that Amp Hour level are expensive ($200 for a 12V 6Ah lead acid battery).

My questions are:
Am I missing something here? Am I looking at the wrong batteries? The cost to buy a "long term" charger for a smartphone seems to be between $30 and $100, half the cost of the batteries I found. Am I approaching this the wrong way?
If I am looking for the wrong thing, what should I buy? Or is it hopelessly expensive to make a portable battery charger, and I should just buy one?


texts:
With the Bode100 from Omicron lab, it is possible to perform different measurement. There are two which I want to discuss. You can find the handbook here.
These are :

Transmission/reflection on page 46

Two port connection. Calibration with through method without DUT. According to the description, the transmission is also a gain measurement.

Gain/Phase on page 52

Three port connection. Calibration with through method without DUT.
Goal is to measure the frequency response of the DUT (operational amplifier.)
Which method is better, and what are the advantages/disadvantages?
In my understanding, the calibration removes the effect of the cable in the first method. In the second method, reflections would eventually also be removed due to the three port measurement.


texts: If I have an obtuse trace, will the complementary acute angle cause issues?

texts:
I was wondering if the complement of an obtuse trace would cause issues when routing, would it be better to have a 90 degree trace or one that comes in like this?

or 90 degrees

EDIT: Added a third photo for clarity here


texts: Is a switch considered an active component?

texts: Most of the definitions of "active" components that I have found define them as components able to control current flow. A switch fits this definition, but I am just curious to see opinions on this.


texts: How should I understand the amount of base current in BJT transistors?

texts: I'm having trouble understanding how much current flows through the base of a BJT. With a MOSFET the answer is easy: 0. How do I calculate the amount of base current in a BJT and am I doing it wrong if my circuit cares?


texts: Run a 3 Phase machine, on 240v with start & run capacitors

texts:
Being a Carpenter & Joiner, I must approach "cap in hand" and ask some proper sparkies for assistance in pointing me in the right direction please?  Maybe someone could take a look at the wiring of my Wadkin 10" AGS Tablesaw and hopefully tell me where to begin or perhaps advise me of a good funeral plan?

Why has it got Red white & blue wires and only 3 (I thought 3 phase had 4 wires)?
Assuming success is possible, what about that foot brake (could I still use it)?
What is the purpose of the coil and does it need molegrip extraction?
Which wire goes where and why?
Which type of capacitor would be the best choice?

All liability is mine and no one who offers suggestions can be responsible, should I fry myself like an overpriced gammon steak!  :-)

Thanks in advance, Kevin Chamberlain.


texts: Confused with photodiode amplifier circuit

texts:
I am a beginner at elecetronic design and i would like some help with this circuit. I cannot understand how it is analysed.I know how an opamp works with a negative feedback as an inverting amplifier but I am a bit confused here with the photodiode. Why is it reversed? Does it serve a specific purpose in the circuit? I would be grateful if somebody could explain how this circuit works.

(This is the full reciever circuit i have to build if needed)


texts: Is 240V to 24V DC PSU to 120V 60Hz inverter a low cost way to convert 240V 50Hz to 120V 60Hz?

texts:
I've been looking at the companies providing step down frequency changing units in the 2000W range, and their enormous size seems to be reflected in an equally enormous price. SO...why can't I just use a 240V 50Hz to (say) 24V DC switching power supply and connect the output to an (equally cheap) 2000W DC inverter to give 120V 60Hz? Seems too obvious to be viable...any thoughts, or anyone tried this?

Thanks!


texts: 3Phase + Neutral, 208VAC distribution and conversion to 1Phase 120VAC

texts:
Question 1: How to convert 3phase+Neutral 208VAC supply to 1phase 120VAC? Can I tap off one (any) leg of the 3phase supply and use that to Neutral to get the 120VAC? Or do I have to use all three phases and load each phase similarly to balance the load of the 120VAC equipment across the three phases?

Question 2: We want to step the voltage up from 3phase 208VAC to 3phase 800VAC and the Step up transformer is wired delta, so we just send the 3 phases to the final load right? Or do we have to continue the neutral line to the final load somehow too?


texts: Differential equation of a RRC circuit as Voltage output/voltage input?

texts:
So in this presentation i have got, there is a RRC circuit, and they get this differential equation, but there is no procedure explained how they have got it. This is basicially a series RRC circuit because current I3 is zero, so it is the same current. Later when we would laplace transform final differential equation we would get transfer function Vo/Vi.

In images input voltage(Vi) is Eu, and output voltage(Vo) is Ui. In Final differential equation i think y should be Vo and u should be Vi.

So final when we laplace differential equation we should get the transfer function in the image where K and T would be equal to RC or something similiar.
Like in this example

My question is how to get the final differential equation with Vo and Vi like this so i can get Vo/Vi, i searched the internet and couldn't find anything. English is not my first language so i couldn't express my self better.

RRC circuit

Differential equations

Final differential equation

Transfer function


texts: Which PCB software has the best autorouter?

texts:
I know that lots of people out there feel that autoroute results are not useable.

I find that the autorouter is a good way to get a good placement. I use eagle. I do a basic placement, autoroute everything and look where my wire crossings are. Where I can reduce wire length.  ripup, repeat.

The thing is, the eagle router really isn't that good. I often get routes that should be doable with a straight shot, yet eagle insists on adding jogs.

I feel that given a good placement, many routes should be obvious. I don't want to click them all by hand.

So I'm looking for something better. toporouter is intriguing. The problem there is I don't know how to write an output from eagle that it reads.


texts:
I´ve done some research but not clear solutions are given to this problem, so I will post my case here in case somebody can help. Thanks in advance.

I want to use a DC power supply to power up 121 LEDs. Each of these LEDs is taking 460 mA, so, mounted in parallel, I need an outcome of 55A for the complete LED series.

The problem comes now, the DC power supply that I have found most suitable (RSP 2000-24) can be configured at 21V minimum, and these LEDS need something in between 19V and 20V, so I need to drop the voltage from 21V to 19.5V with the 55A current flow. (They could probable work with the 21V but these LEDs are expensive and I dont want to screw it up)

I´ve found some resistors which can support up to 250W, so I could use several of them I guess... I suspect is not a good solution. I have also found some voltage regulators but none of them seem to stand the 1000W that I need..

Any ideas would be really appreciated!

EDIT: Thanks for your replies first of all. I will answer here the questions mentioned by Russell McMahon so we can tackle the problem better.

  Why are you using those particular LEDs?

The set of LEDs working togheter will be used as a flash light for camera shooting. There will be 6 camera shots delayed 500ms among them. So the LEDs will be turned on 6 times each 500ms for a duration of just 1ms when the flash signal closes the circuit formed by the PSU and the LEDs. That is why I´m not regarding heat sinking, because they will only be shining for 1 ms.

Since the duration of the pulse of just 1ms, I think we may have problems with the Rise up Time & Setup time of the PSU, I´ve thought about using a capacitor so the current can flow immediately after closing the circuit´s switch and the LED´s can light up sincronized with the camera shot. Any suggestions on this issue are appreciated as well.

  Do you need a high CRI?

Yes. Otherwise object colours will appear distorted in relation to reality.

  How long do you want these LEDs to last?

As much as possible. They will only be flashing 6 times for 1ms each time the camera shoots.

  Do you care or know anything about this manufacturer?

For the specifications I need, this manufacturer resulted to be the cheapest and fastest in delivery. Cree was more expensive and takes longer time.


texts: Determining line-to-line vs line-to-neutral loads in split-phase panel

texts:
I have a split-phase sub-panel, with two 120V legs (red/black) and middle neutral (white). Given Hall-effect current sensor clamps around some combination of red/black/white going into the sub-panel, is it possible to answer the following questions:

Current between red and white
Current between black and white
Current between red and black

For example, if I have 3 amperes being drawn from 120V tools on the red leg, 5 amperes being drawn from 120V tools on the black leg, and 7 amperes being drawn by 240V tools red-to-black, I would have the following possible read-outs from the Hall-effect sensors:

Red:   3 + 7 = 10 amps
Black: 5 + 7 = 12 amps
White: 5 - 3 = 2 amps

Can I get from these numbers back to the three distinct loads?


texts: CANoe communication relais board via RS232

texts:
I am using Vektor CANoe 11.X and want to test a relais board.
How do I set up a simulation to communicate with the relais board?

I am connecting the 9 pole rs232 port via gender changer to vektor 1640a hardware.


texts:
I having a hard time understanding the best way to setup a NIOS II system with external code and the resets and clocks. One of the reasons why I'd like to figure this out is the JTAG system really struggles and it seems that portions of the system never get reset correctly.

First things first: You need a dual rank synchronizer or some kind of ARST sanitation like this here. So I have that in my HDL code

One question I have is what does the Altera Qsys Clock Source actually do? Does it preform the function of a dual rank syncronizer? Or does it need a sanitized ARST signal? Because in a most systems examples from altera and other suppliers they don't sanitize the ARST and run it straight into the Qsys/NIOS block. (Like in Example 1A below)

The other question that I have is: If I have external code that I connect to the Qsys\NIOS II system what reset signal do I use? Does it need to be reset with the Qsys\NIOS II system? Does the Qsys\NIOS Clock Source do something to the clock signal? Do I have export the Clock and Reset signals from the Qsys system?

Which way is correct? Are there advantages to either way?

simulate this circuit – Schematic created using CircuitLab

simulate this circuit


texts: Connecting multiple ultrasonic sensors to one Arduino

texts:
I'm trying to connect five ultrasonic sensors (HC-SR04, to be exact) to an Arduino board to detect obstacles in five directions (four cardinal + one Z-axis). I read the datasheet on the HC-SR04s and the Arduino Uno as well, and found that the ultrasonic sensor draws 15mA when active, and the Uno can supply a max of 40mA through each pin and a total of 200mA from all pins.

Now since I don't have ten PWM I/O pins, I've thought that since I'll be firing the sensors all at once, one trigger pin is enough. The ECHO pins will go to a separate PWM pin for each module.

I have two concerns here (I'm just a beginner in electronics :)):

I'm going to supply power to each sensor off a 5V/2A BEC. So will this cause current overdraw from the Arduino PWM pins? If so, is there a workaround? Maybe a transistor-driven solution? (I've done a basic electronics course in college, but never had a chance to design one on my own.)
The second concern is regarding my trigger pin design. Will one pin be able to pulse five of the sensors, or will the current drop not let them fire (since they're all in parallel)? My guess is that it's only the voltage that's firing them up (assumption) and in parallel it would all be the same so it should work, right?

I searched around, but I only found information on connecting one sensor to the Arduino. I read something about running high-amp motors with Arduino by supplying the current through a battery so I think my first concern should be fine? But I'm not sure, and so I thought I'd ask here. Thanks!


texts: How to monitor data exchange on single wire?

texts:
I have two modules that communicate over a single wire. Where would I even start about monitoring the data without introducing any kind of interference to both modules?

One of the modules has to be deleted/bypassed and my own controller will be simulating that module. However, the second module does not work unless it communicates with first module.


texts: Why should a receiving antenna be impedance matched to 50 ohm instead of a lower impedance?

texts:
I'm in the process of getting to grips with RF design and am having some trouble understanding why we should always match antennas to \$50\Omega\$.

I understand from the maximum power transfer theorem that if you have a fixed source (e.g. \$50\Omega\$) that you cannot change as a designer/user, then the maximum power transfer occurs if you set your load impedance to be the same as your source impedance. Therefore, if you are using an antenna as a transmitter, then you'd want to make the antenna (load) impedance equal to the impedance of the source for maximum power transfer into the antenna - so you match your antenna to \$50\Omega\$.

However, what if you are only using your antenna to receive? In that case the fixed variable is the load impedance (i.e. your receiver) which will be fixed at \$50\Omega\$ as below (I've also drawn the transmission line for completeness):

simulate this circuit – Schematic created using CircuitLab

If \$Z_L\$ is fixed (\$50\Omega\$), then the maximum received power will be when the voltage across its terminals is maximized. The voltage across \$Z_L\$ is (potential divider):
$$
V_{Z_L} = V_s \frac{Z_L}{Z_L+Z_S}
$$
\$Z_L\$ is fixed but we can "control" \$Z_S\$. Maximum voltage across \$Z_L\$ (and hence maximum power to the load) occurs when \$Z_S=0\Omega\$

Therefore, following this logic, you'd ideally want your receiving antenna to have a very low impedance (as close to \$0\Omega\$ as possible).

I'm probably missing quite a few fundamental concepts here but at the moment, the only reason I can think to match a receiving antenna to \$50\Omega\$ is in order to avoid re-reflections back to the load. However, if the load itself is already matched well to its \$50\Omega\$ transmission line, there should be minimal reflections already.


texts: LPF based Differential demodulator design

texts:
I am designing LPF based differential demodulator(LPF_DDM) to retrieve differentially modulated signals, which are on-chip capacitive isolated [shown]. LPF_DDM includes a differential amplifier, LPF, and Schmitt trigger. I designed a two-stage opamp [specification below], as a differential amplifier. Simulation results of the 2-stage opamp matched with desired specifications (GBW, Phase margin, gain, etc ). However when the differential modulated signals are given as input, then opamp does not work.
Is my 2-stage opamp design and/or design parameters adequate for differential modulated input signal?
Thanks.
Design Parameters:
Input common mode range: ICMRmax = 4V; ICMRmin = 1.5V ; Load capacitance =2pF ; Gain = 1000/60db ; Slew-rate (SR) = 20v/usec. GBW=30MHz
Phase margin (PM)>= 60-degree


texts: Convert high voltage AC (10kV, 60Hz) to low voltage DC (5V)

texts: Is there any easy and safe way to convert the high voltage AC (60Hz, 10kV, such as the voltage on the overhead line) to 5V DC that can be used to power up a micro controller (around 1W power)? We do have a ground in the AC system. What is the easiest way? Are there any COTS products or components available?


texts: Is there a specific name for a automotive headlamp controller that when energized, will start at , say 3volts & ramp to 12volts? This would usually be used for HID or high intensity halogen lamps to prolong lamp life.


texts:
I am using Arduino UNO and did a project to sync LED to audio. I am not sure how to read a value from a speaker.

I connected a LED to Pin 9 (PWN) with 220ohms and ground. I connected A0 pin to a speaker pin and ground pin the other pin on speaker. I used the Smoothing example of arduino input and modified the code a bit to output to LED.  The speaker I used was with an old Phillips Music System and had only two pins. I played the music and led synced perfectly and everything worked fine. The project was a success.

Today I wanted to try to connect to a home theater (5.1 Sony HT-IV300 Model). This speakers also have same 2 pins. So I did everything same. A0 to Speaker pin 1 and Ground to Speaker pin 2. But suddenly the Music System went to power protect mode and A0 is stuck at ~1000 (975 - 977). I connected the arduino again with the Phillips Music System (Same setup) but A0 is always gives ~1000 value. Connecting to A1 and changing the code works perfectly fine!

Where did I go wrong? I cannot understand, what happened to A0 pin? What is the correct way to read the speaker values?

Thank You.
Abhi


texts: Doubt in JK Flip flop simplification of boolean expression

texts:
I have following doubt in digital. Please have a look.

From characteristic table of JK flipflop,  I made sop expression . Then I made kmap. Both are giving different answers. Kindly have a look ...


texts: Single input dual output simulation help

texts: Ive been using PSIM and there is a problem with the circle mosfet wont turn on. Ive the correct duty cycle and input voltage is higher than the threshold. Can someone simulate it on another simulator or see my anything wrong?


texts: Atmega8 doesn't enter power-down mode on sleep_cpu()

texts:
I'm trying to put atmega8a to sleep with this code:

cli();
sleep_enable();

// set power down mode - 0.5mkA
MCUCR |= _BV(SM1);
MCUCR &= ~(_BV(SM2)|_BV(SM0));

sei();
// now sleep until INT0 or reset signal
sleep_cpu();

However, it seems the processor doesn't actually enter sleep -- the power consumption does not drop significantly.

I thought that may be some peripheral remaining enabled can prevent Atmega from entering sleep, but upon checking AVR datasheet and PM I didn't find any suggestions of this (except that power down can be spoiled by eeprom write, which is the thing I do not do).

Could you suggest where to look further?


texts: I am making a breakout board for Silabs EFM8BB1 (Busybee). I have made the schematic but am unsure about the C2 Debug Interface. Can someone guide me please?


texts:
Just about every time I use a serial port for anything, I only use 3 pins of the usual 9-pin connector (DB9): Tx, Rx, and GND. And when I wire up my microcontroller projects to these ports, I just cross the Tx and Rx signals in the cable, couple the GNDs and it works.

Looking at the pinout descriptions it seems like a the other 6 pins are used for something like flow control and end-point presence-detection. What kinds of devices require you to actually use these pins in practice these days? Why are there so many signals required (seems like overkill), what's the use case for all of them at once?

Could be that I'm just looking for a history lesson here.


texts: How does an engineer calculate the required power/low-noise amplifier gain after she/he is provided with the link budget of the system?


texts:
I have small question about how bytes move around during SPI reading.
I have a flash memory chip and microcontroller.
Suppose I want to know jedec data from the chip(although it can be any data, this is just example), I found how to do it and it works fine, but I don't get the part when we assign jedec parameters to variables.

From the C code below I can see the possible logic like this:
we send "retrieve jedec" command to chip, then for some reason we start to send zeros to assign values to variables, probably it reads the value by sending dummy-bytes. Question is - isn't it supposed to overwrite bytes we are reading?
I mean - you shift something to the register you want to read therefore you get the value back by replacing it with what you have sent.

Maybe I express my question blurry, ask more info if you are confused, but to sum up everything I have two questions:
1. Why we are sending zeros during value assignments like *b1 = SPI_MasterTransmit(0);
2. If we do it to shift the value from slave device to master - why don't we erase the value from the slave by doing this?

void get_jedec_id(uint8_t *b1, uint8_t *b2, uint8_t *b3) {
    PORTB |= 1<<PINB2; // turn high ss pin(/cs)
    PORTB &= ~1<<PINB2; // turn low ss pin(/cs)
    SPI_MasterTransmit(0x9F); // transmit get_jedec command of this chip
    *b1 = SPI_MasterTransmit(0); // manufacturer id
    *b2 = SPI_MasterTransmit(0); // memory type
    *b3 = SPI_MasterTransmit(0); // capacity
    PORTB |= 1<<PINB2;
    not_busy();
}

SPI_MasterTransmit code:

unsigned char SPI_MasterTransmit(uint8_t outData)
{
// Transmission start
SPDR = outData;
// Waiting for transmission to end
while(!(SPSR & (1<<SPIF))) ;
return SPDR; // return received byte
}


texts: Best way to ground a pin when Power switch is closed?

texts:
I'm using a Particle Electron micrcontroller and powering it by connecting the battery through a power toggle switch. Since I also have a solar panel connected for battery charging, I need to GND the reset pin of the Electron when my toggle switch is in the off position to prevent it from operating off the solar power.

I am trying to make a circuit that GNDs a pin when my battery is connected. I thought I could connect a NPN transistor to the pin, with the battery line as the Base, but that would have the opposite effect of what I need (grounding it when it should stay open). Do I use a PNP transistor instead? Am I going about this wrong? Is there a simple way I can do this?


texts:
In every tutorial I've come across concerning servo motors, no one mentions motor drivers. Instead, they show the servo getting power directly from the microcontroller. Yet, I understand that a lot of current sinks when the torque rises.

So, can I power the servo motor via a power transistor or a motor driver for DC motors, like L293? Or there are any other motor drivers dedicated for servo motors?

Thank you in advance.

EDIT:

Even though it was a general question. this is the servo I have in mind: https://www.sparkfun.com/products/11884


texts: Parts which conduct electricity through a rotating shaft

texts:
What are those mechanisms called which are designed to conduct electric current through a rotary shaft?

In the image below, of the interior of a large mixer, there is a set of brushes tracking rotating contacts.

What is the name of this assembly of brushes and rotating contacts?


texts: Why is there a buffer before an SD socket?

texts:
I'm studying the SD card section of an electronic circuit of Sparkfun can bus shield that I have to connect on a Nucleo STM32F411RE.
In the electriconic circuit, that you can see here.

There is a HEX_CONVERTER before the microSD socket (page 2). Looking at the board, I have seen that this Hex_converter is a 74HC4050 Integrated Circuit.
I really don't know what is its function. Could anyone help me?


texts: Simple and cheap way to control baseboard heater from a microcontroller?

texts:
I'm a total beginner with hobbyist electronics and I'm trying to design a way to switch off/on a mains-powered baseboard heater with a microcontroller. The microcontroller would have access to mains power and would be battery-powered. The pin outputs are 3.3V on the microcontroller. One particular issue is that I want to run the microcontroller on batteries, so I think I want a latching relay like this one.

However, that relay seems to have a coil current of about 200mA, which I think is way too high to be drawn from the microcontroller. And at that point I'm in way over my head in terms of how to switch it on and off.

I checked out an answer here, but the circuits provided there seem reasonably complex and I was just hoping for something I could wrap my mind around without worrying about lighting the house on fire.

Am I missing something more straightforward, or are latching relays the way to go in this case? Single coil? Double coil?


texts: Current source and electromagnetic interferance

texts:
I have a current source which has to be really precise in order to charge a capacitor and count a certain time (about 100 ms.)
If anybody has seen a component which allows to count a time (without a microcontroller) when an event occurs and able to set an output after a certain delay programmed by a resistor/capacitor, it will be a pleasure to know it.
For counting this large time (about 100 ms,) I can't use a big capacitor as the tolerance diminishes with the size of the capacitor and so I have to have a low current source. The current is around 100 µA.
That seems very low to me and I do not know if it is reliable to use this kind of current source.
I imagine that if I have 10A next to this current source, it will be possible to have a magnetic coupling between the two currents, and I think that it is possible to have a lot of other possible coupling that I do not know.
So do you think that it could be reliable if I do a correct layout by minimizing the length of the trace of the current source. Here is my circuit:


texts: How do I connect a pin that is not included on the main symbol or any of the gates of an Eagle part?

texts:
In Eagle, I've dealt with a couple of parts that have pads that don't seem to be accessible from the schematic: HTSSOP packages with a thermal pad that should be connected to a ground pin; a battery holder which is a metal can soldered to pads 1 and 3 but Eagle only knows about pad 1.

How do I tell Eagle to put copper between the thermal pad and the ground pin? How do I tell Eagle that the metal can electrically connects pads 1 and 3, even though Eagle must not put any copper between them?


texts:
Inductors are really not my strong point, and I have been getting a bit confused on the rated current vs saturation current.

I know the rated current is how much current the inductor can handle before the temperature increases too much, and all I know about saturation current is when that threshold is approached and exceeded, the core is filled with magnetic flux and the inductance starts to drop.

I have come across a chip inductor HERE which I am planning on using in a  boost regulator circuit. It is cheaper and smaller than the current inductor I am using, with the same rated current. However, whereas my old one had a saturation current of 900mA, this one is very low at 250mA.

Why is there such a difference in saturation current in chip inductors? My boost regulator chip has recommended inductor values of 2.2uH to 4.7uH, so if my current peaks at 300mA for a few ms and the inductance drops somewhat, will this still be ok to use? And would this change in inductance affect the output stability in any way?

As much as I would love to save money and PCB space, I don't know enough about these parameters to make an informed decision. Any advice on how to proceed is appreciated.


texts: Why shouldn't you use the emitter of a BJT NPN Transistor as a current source?

texts:
Several times here on the EE Stack Exchange, I've seen people say not to connect a load between the emitter of an NPN transistor and ground, but instead connect it between the power source and the collector. In that case the transistor is a current sink, not a current source.

Why shouldn't you draw current from the emitter, like this below?

simulate this circuit – Schematic created using CircuitLab


texts: Is it possible to run a Buck converter with rectified AC supply voltage?

texts:
I know that a standard Buck converter requires DC voltage as input. But if your primary input supply is a high AC voltage, it is not very easy to make a clear DC voltage out of it. For example, if I use a 3rd order passive Chebbyshev filter. Even if I put a single capacitor, it won't last for a long time due to high heat dissipation because of its ESR.

Is it okay to not filter this rectified AC voltage and leave it as is? Can the Buck topology work like this?

(Note: Suppose that the load doesn't need very a smooth DC voltage. It can be a lamp or a heater. It requires 15V DC and maximum 30A current. And frequency of the primary input AC voltage is 50Hz.)


texts: Why do we get only one frequency as output in oscillators?

texts:
I am just into oscillators where I learned \$AB=1\$ for sustaining oscillations in positive feedback. Since \$A\$ and \$B\$ are both frequency-dependent, \$AB=1\$ is true only for a particular frequency.

What happens to those frequencies for which \$AB>1\$ holds??
Will these frequencies keep on getting amplified until the limiter circuit limits them?
Then why don't we get those frequencies in our output??


texts: I started my component orientation when I suddenly see those white outlines around my components. And as I zoom in, they increase in number. Even when I tried to move my components elsewhere, they stayed right where they were. What are these? What's going on?


texts: Low frequency transformer at high frequency

texts: I'm getting interested in high voltage circuits, and I already have drawn out a couple of circuits (I have not yet built anything). However, I'm just wondering as to what would happen if a pole transformer rated at 120V and 50-60 Hz were run at 120V and 50-60 kilohertz? Would the transformer overheat? Explode?


texts: Is it OK to replace a 750 ohm 5W ceramic resistor with a 750 ohm 10W ceramic resistor

texts:
One of four (4) 750 ohm 5w ceramic resistors in a subwoofer's power amp section seems to be open. I want to replace it with a compatible ceramic resistor.

Questions:

Will the 10W one generate more heat?
Is it OK to mix one 10W resistor with three (existing) 5W resistors? (All 750 ohms and 5% tolerance.)

[They are in the immediate proximity of transistors]

............................................................

Added on 2/2/17:

I think I was overlooking the importance of derating factors operating temperature range differences when resistors are used in audio amplifiers because audio amplifiers can get hot.


texts:
What are some recommendations on an ideal WiFi to Serial bridge? My ideal qualities would be:

Simple connectivity, SPI or Serial
Reasonable fast speed, at least 1mbit/sec ideally (though probably wouldn't always need that fast)
Inexpensive, I'm thinking under $50
Low power -- it should use at most 100mA, if we could get it even lower like say 20 or 30ma, even better.
Built-in protocol stack -- I want it to handle the WiFi protocol, along with DHCP, TCP/IP, DNS, etc, so that all I have to do is tell it what IP/port to connect to, and then handle the data myself.
If at all possible, 5V-tolerant I/O's...to make it easy to interface to our old-school microcontrollers.

So far I've found:

Matchport b/g
Rovingnetworks Wi-Fi modules

Anyone have any experience with other possibilities?


texts:
I'm trying to answer following question:

  In the ladder circuit in figure 3, find the current, I, if \$V_s = 7V\$.

  Use the fact that the circuit is linear. This can be done by assuming that \$I=1A\$, and working out the potential drops back to the voltage source. Then use scaling.

I have easily computed the answer to be \$0.125A\$ using mesh analysis (and Maple). I cannot, however, figure out how to answer this question in the way suggested in the hint (exploiting the linearity of the circuit). Frankly it is something useful to know; solving 5 simultaneous equations during an exam would not go well.


texts: Can electronics be damaged by undervolting it?

texts:
I was wondering if there are some particularly important mechanism by which one can break electronics, when undervolting it. Its pretty obvious that lots of electronics will not work properly if undervolted, but what about permanent damage? The question was motivated by repair work. I was wondering about what sorts of secondary effects one should look for when a damaged power supply was involved.

I imagine motors could be damaged if they stalled due to undervolting.

So what are specific mechanisms for permemenant damage due to undervolting (or better put undersupplying)? Are there even any?

To add to the question, what are components or simple circuits that fail when undersupplied?


texts: Designing a 4053 IC robotic control circuit for interfacing with Sabertooth motor controller?

texts:
I am designing a control circuit for a robot and was recommended to use a 4053 IC to achieve analogue multiplexing.

PROBLEM

The Sabertooth 2x60 motor controller I am using is running in analog input mode. This means its control scheme is 0v-2.5v is reverse, 2.5v is stop, and 2.5v-5v is forward. I am using ROS and using a 1208FS-PLUS as the DAC to interface to the motor controllers. Until my ROS software starts, it is at 0v and this is full reverse.

GOAL

The design goal is that I require a 2.5v source until my software is started and able to control the robot. My approach was to use the 4053 IC to multiplex my analog signals. While the software is running it supplies a high and switches the multiplexer to use the signals from the DAC. If it is low it uses a 2.5v source from a voltage divider circuit.

APPROACH

Below is a schematic (and built on proto board). I am using 2x10k resistors to build a voltage divider circuit (as per the relationship). The output is using an RC filter to achieve a smoother operational output (as per the Sabertooth user manual recommendations).

PROBLEMS AND HELP

I have tested this on the bench and it works however the voltage divider produces ~2.8v on average which causes the motors under no load to drift. Could anyone recommend a way to achieve as close to 2.5v as possible. Solution can be active as the 4053 is an active component.
The input is not always 5v despite the specs of my DAC specifying it will be. I was thinking of using an op amp to cap my voltage at 5v? Could anyone please assist me to evaluate the applicability of this?
The Sabertooth manual doesn't specify the control signal currents (I don't imagine they would be too large). Should I use a buffer (voltage follower) to somewhat amplify the current from the 4053?

Thanks in advance for any help :)
-Grant


texts: The right gauge wire for a 12v parallel wiring to LEDS and heat sink

texts:
enter image description here

Hey guys would love your expertise on a project, I'm just a beginner on this stuff.

I'm building an LED panel with a total wattage output of about 480W. My question is, what's the smallest gauge wire I can get away with within the wiring between the LEDs? Does it have to be 20A or can it be smaller since each side is only handling about 10 amps? And how do I calculate the total amps the LED is drawing from the AC power? I am planning to place an aluminum backing to the LEDs as well for a heat sink, will that be enough to dissipate the heat?

Does my wiring look correct?


texts: Is a C2328 Transistor OK to use instead of a 2N2222?

texts:
I have this simple circuit to drive a 5v solenoid. I made it all except that Q1 is a C2328A transistor I pulled out of an old power supply and C2 is a 220uF cap. D1 is just a diode I took out from another power supply, not sure what it is.

Basically the solenoid rings a bell. THis worked for about 2 weeks but now it will ring once (2 rings) then the next time only 1 ring and its dead. The solenoid will just not move anymore  though the program is running and is triggering the transistor.

It works of USB power and is triggered by RTS using a USB to SERIAL dongle. The COM port stays reactive.

I wonder if this circuit is flawed and possibly caused damage to the cap or the transistor?


texts: Choice of sensor for detecting touch (on/off)

texts:
I would like to detect a user's touch on a shop window (at a specific area, there would be a 'call to action' marking on the window, i.e. 'touch here')

Any sensor to detect this must be contained within the shop.

There is a 15cm air gap between the shop window and another internal window (behind which any potential sensor could be discreetly hidden as the internal window is tinted).

Both window panes are made of a roughly 10mm thick hardened glass.
The external window area is roughly 3mx2m whereas the internal is roughly 2m x 0.3m, more like a rectangular panel.

I have been looking at using a capacitive proximity sensor such as the STM8T143, which according to the specs is capable of a range of up to 20cm but I'm not sure how the 2 panes of glass will affect this sensitivity? I know glass has a higher dielectric constant than air, but will the boundary between 10mm glass <-> 150mm air <-> 10mm glass be too much for the sensitivity of this sensor?

If a capacitive proximity sensor wouldn't be possible ,or recommended, in this scenario, could anyone recommend another way of detecting a user's touch, or very close proximity to a target area, which would fit the above use-case? The sensor would not have to be behind the interior window it could be in the air gap, but can't be outside.


texts: How to calculate active & reactive power ripple?

texts:
Some control strategies (like : DPC, MPC...) suffers from the presence of active/reactive power ripples, which requires some additional methods to be taken to reduce those ripples.
But to judge the efficiency of those methods we need to calculate/quantify the value of the active and reactive power ripples, how can we do that ?

In his paper : Low Complexity Model Predictive Control—Single Vector-Based Approach, Yongchang Zhang & WeiXie wrote :

  Table II lists the quantitative comparison of both methods in terms of
  active power ripple, reactive power ripple, and current THD at two
  operating points. The power ripple is calculated using the standard
  deviation function, which is expressed as :

  where N is the sampling number of active power and reactive power in a
  period of 0.1 s.

I didn't understand this method of calculation,

what is this standard deviation function ? what is pi and qi ? how can we implement this calculation in an experimental setup ?


texts: Increase voltage and current with external power supply

texts:
I have an ECU A controlling a relay, in which when there is an activation command I can measure 12 V and 100 mA.

The project I'm working on is to replace that ECU A with an ECU B, but when I send my activation command to the relay, it is only able to draw 12 mA from ECU B due to internal limitations. The voltage I measure in that situation is 3 V, but ECU B has a voltage driving system connected to a 12 V supply.

My question is what kind of circuitry I can use to increase both the voltage and the current to reach the values I got with ECU A. I have access to a power supply of 12 V, which is the one being used for the voltage driving system. I imagine some sort of amplifier would be the necessary component, but then which type and how to determine the specs for it?

My background on electrical circuits is not very extensive, so please bear with me. I could really use your feedback. Thank you!


texts: Why won't solder go around the whole pin?

texts: I'm trying to solder the pins on an Arduino nano but the solder won't go around the whole pin. This happens seemingly no matter how much solder I apply. If it's a lot and it blobs it only blobs on one side. Am I soldering incorrectly or is this natural? Are these pin connections still valid?


texts: Inrush current limiting circuit for a 1.5 MW transformer

texts:
I am looking for help with an inrush current limiting circuit for a 1.5 MW transformer as of now the current can reach as high as 10 - 15 kA.

I would like to keep the current under 1800 A per phase and each phase is 480 VAC at 60 Hz.

The input will be 2.5 MVA I’ve been researching various methods but have yet to come up with a solution.

I do not have knowledge on harmonics so I’m trying to keep it simple, but yet effective,I would like to build the circuit myself and will be doing the testing myself as well.


texts: Should I supply a motor with the same current of its stall speed?

texts: I have a DC motor that has a stall speed current of 6 amps. Does that mean I should be supplying a constant current of 6 amps even when the motor is not experiencing a need for that much current?


texts:
Here's the circuit I am trying to build.

I want to get 5V 3A DC output but it's giving above 7V and 4A.

I have checked it in the multimeter attached in the diagram.

Can any one explain what's wrong and how to overcome this problem?

Circuit diagram:

Actually, I have tried the circuit given in the datasheet to get output, but it didn't give the required output so I tried building my own.

LM2596 datasheet.

LED load diagram:


texts: Can Quartus System Console be used via Ethernet instead of USB Byte Blaster?

texts:
The System Console communicates with the the design inside the Intel FPGA via a JTAG-Avalon MM master. The JTAG connection connects to the Byte Blaster and this is how the debugging works.
Is there a way to use Ethernet based communication so the design being tested just becomes an item on the network and we can sit far away and read/write registers inside it?


texts:
I have a question about a LED array I am designing for a home-made 3D SLA printer. I find the subject of high power led drivers quite confusing but I believe I understand how it works now and I need someone to confirm my findings.

My total LED array will consist of 80, 3W UV LEDs. Their rated direct voltage is 3.2-3.4v and their rated direct current is 700ma.

The LEDs are connected to a large cooling fin with active cooling.

I want to connect them to a 50W constant current power supply at 1500ma, I want to connect them 2 parallel series of 8 LEDs. This would give them 750ma per serie.

I have three questions:

Is my conclusion correct?
Would the LED's be able to sustain the additional 50ma above their rated current?
Would this lead to a shortened lifespan or just kill the LED outright?


texts: Issues migrating from ATmega88 to ATmega88P, with V-USB/AVR-USB?

texts:
I'm working on a V-USB (aka AVR-USB) -based circuit running at 5V (i.e. two 3.6V Zeners across D+ & D-) and at 12MHz.  I tried an ATmega88P instead of the ATmega88 chips I normally use and I can't get the circuit to enumerate.  The Atmel appnotes on mega88->mega88P migration don't describe any obvious gotchas.

Anyone have any experience/tips with the differences in ATmega88P chips?


texts: If a power bank accepts multi voltage input, will the lowest accepted voltage choice cause bad effects on the battery?

texts:
I have a power bank which accepts 12V-24V as input for charging the battery. (It aslo supports 12V-24V outputs. But this is not related to the question.)
Assume that I will charge the power bank only when it's off.
If I use the 12V power supply to charge the power bank's battery, will this cause any bad effects?
All I knew is 24V power supply charging will be faster than 12V power supply. But when I don't care about the charging speed. Does it matter?
Thanks a lot.
Edited:
The user guide says higher voltage will result in a faster charging. It also recommends 14V+ charger because of the charging speed. But I don't care of the speed. Right now, I only have 12V power supply and don't plan to buy a new one if unnecessary.
One more information: The user guide does not have this notice, but I found this notice in the selling description. It says if the charging input voltage is less than 12.8V, the battery might never be fully charged. If this is the case, I guess I am better buy a 14V+ power supply.

Added RMc:  It is likely that the following applies.

The powerbank uses 3S LiIon batteries

The internal converter when charging the batteries is a buck converter

There is a maximum upper input current limit.

The output converter acts as a boost converter or linear or perhaps buck boost in some cases.


texts:
I'm having trouble picking the right drive motor for slow smooth continuous motion combined with motion with regular precise stops. I chose a stepper motor with 0.9 degree steps which works great for quick stops but is not even close to smooth motion with low RPM. The motor also has to be quite strong to move the cargo of 3kg with 1 drive wheel with 2cm radius. I was thinking about 360 degree servos, brushless DC and brushed DC motors. The slow speeds I have in mind are a minimum of about 0.5 - 1 RPM.

Any thoughts?


texts: Can you prove that electricity was generated by a photovoltaic cell?

texts:
I am wondering if it would be possible to build a photovoltaic cell that kept track of the electricity it generated (perhaps with a built-in meter), such that you could not trick the meter without destroying it.
The idea would be to make cheating the meter (by pumping electricity from a different source through it) pretty much impossible.
Does anything similar in a different context (maybe electric meters on the sides of houses) already exist?
EDIT: Sorry for posting an XY question — that wasn’t intentional. But I did not see the value of stating the underlying motive, which is something along the lines of what was pointed out in the comments. I have the idea that in certain contexts where owners of PV cells get paid for the electricity they generate, they could get electricity cheaper somewhere else and fool the wattmeter. My  question was meant to be simple and general. Since I know very little about EE I thought something like this might already exist or be known to be impossible.


texts: why a thermionic valve can amplify an electric signal (for instance, a radio wave or AC), by removing half of its phase? In other words, how is it possible that half-wave rectification can amplify the signal instead of reducing it by half?


texts: Connecting Arduino to a Monster iEZClick Remote

texts:
I am looking to do a project with an Monster iEZClick Remote Control using an Arduino Pro Mini 328.

The Monster iEZClick Remote Control is an RF remote that transmits to an iPod socket connector that attaches to an iPod to control its volume, play, pause, skip, etc.

I am wondering 2 things before I buy this:

(1) if I can open the thing, would it be possible to connect each button to the Arduino to read when pushes?

or

(2) Would it be possible to read the RF signals coming from the Monster iEZClick Remote Control and have the Arduino respond to those different commands as it would it the user hooked up each button to the Arduino?

Feel free to add your own solution if something you think of would be better than the 2 above I posted.


texts:
an aspiring electronics engineer here. I do some electronics design for work and I'd like to know the following:

If I have an assembly of a main board, to which an FFC cable connects into a second board (A), to which another FFC cable connects to a last board.

Some signals flow back and forth between these different boards (e.g. I2C), so I'd like to do some low-pass filtering for EMI.
From my work I've learned you can put a filter in series close to the connector where the signal 'leaves' one board.
Since my signal leaves my Main board, but also board A, does this mean I should put something like a T-filter in the signals in both the Main board and in board A? Or would the two filters -separated by some FFC length and PCB- still function as one filter anyway?

I've also understood you should put a T-filter on signals that are bidirectional like the I2C SDA line, which can be pulled high and low by both the MCU and the chips on board A or B. Like so:

And you should put a half T-filter on signals that are unidirectional (can only be dictated by the MCU) like the I2C SCL line:

How do I design for EMC here?


texts: I have used a 3.3V and a 4.7V Zener diode.  What value series resistor do I need for them to work properly? The test current for 3.3V is 76mA and for 4.7V is 53mA.


texts: How to increase sensitivity of Light Dependent Resistor (LDR)

texts:
I am using LDR sensor in my project. The source of light comes from the different colour of images. As we know, the spectrum of each colour is different and it will produce a different intensity of light. I know, the colour sensor able to do this task but it's not listed as options.

Here I attached the schematics and LDR datasheet as the reference (http://kennarar.vma.is/thor/v2011/vgr402/ldr.pdf)

My question is how to increase the sensitivity of this sensor so that it is able to measure the change of resistance within 200ms?


texts: Stray voltage on all earthed and unearthed objects

texts:
We installed an earth mat on a property to eliminate voltage on earthed and unearthed objects on the property. But after installation it was still there. Surprisingly if you measure voltage between two point on the ground itself , the tester reads 10 v AC at 1 meter distance and 80 v AC at about 6 meter distance . All metal objects installed in the buildings even window frames have voltage on them.
Earth mat is 1 meter by one meter and two meters deep , it is connected on the main earth of the property at the supply box through means of a ferrule.

Residents complained to us about getting shocked when touch metal objects on property , on inspection we found that all over the property the earth had 80v ac, we combined earth and neutral to eliminate the voltage but it did not work hence we installed the earth mat.

After installation of earth mat we found the voltage had stil not gone away, we further investigated and found between the ground and metal objects such as the window frames had voltage on them. We also put the probes of the tester on two points on the ground and again found a varied voltage at different distances. There is a 11 k power line across the road but it is common all over the country and at other locations we did not have this problem, at the power line we dit however see the earth mat for the transformer is not connected.

Also when switching main power supply of on municipal side the voltage on earth does not go away. Hope this extra information helps.


texts: How will an ultra-low leakage Schottky diode affect resistor selection when designing a load-sharing circuit?

texts:
Could you believe it? Affordable charger circuits on the market still don’t come with load sharing components built in these day and age. So I had to build my own. I’m somewhat new to this so bear with me.
Components:

Charging IC - TP4056
P-MOSFET - DMP1045UQ-7
Schottky diode - PMEG6010ELRX

Here’s a schematic of how the load-sharing circuit would look, albeit wired based on the TP4056 rather than the MCP73872:

Load-sharing circuit schematic
When researching which pull-down resistor I should purchase, I ran into an issue due to the PMEG6010ELRX Schottky diode that I have.
This diode is rated with a reverse leakage current(Ir) of 5nA@Tj 25°C; 5V, which is pretty low.
According to a design guide posted here, it is recommended to keep the Rpull resistor at no more than 100kΩ and when selecting the Rpull resistor we should use the formula;
Rpull = Vtarget * RD / (VBATmax – Vtarget)
where, RD= VBATmax / IR.
In this case Vtarget is a range from 1-3V, IR=5nA and VBATmax=4.2V. In most cases including in the example they had in the guide, IR is in the 100-200uA range which yields something in 6-100kΩ range.
However, PMEG6010ELRX has an incredibly low leakage current in the single digit nano Ampere range.
How would that affect my choice of selecting a resistor to pull down the voltage so the P-MOSFET will function normally?
Otherwise I’d get something in the MΩ or even GΩ region which is much more than the recommended 100kΩ. I’m under the impression that this resistor’s rating doesn’t have to be near the actual value obtained from the formula. So long as it doesn’t exceed (<100kΩ) regardless of how small the leakage current of D1 is, will the PMOSFET still work correctly?


texts: Refractive index, wavenumber, and wave impedance of the PEC that a plane wave is normally incident on

texts:
I am trying to find the refractive index \$n_t\$, wavenumber \$k_t\$, and wave impedance \$\eta_t\$ of a perfect electric conducting medium t. Here is my work so far:

The conductivity of the PEC is \$\sigma_t=\infty\$.
The intrinsic electric permittivity of the PEC is \$\epsilon_t=\infty\$.
Effective electric permittivity of a conductor is \$\epsilon_{\text{t,eff}}(\omega)=\epsilon_t\left(1-j\frac{\sigma_t}{\omega\epsilon_t}\right)=\infty-j\infty\$.
Effective refractive index of a conductor is \$n_{\text{t,eff}}(\omega)=\sqrt{\frac{\epsilon_{\text{t,eff}}\,(\omega)}{\epsilon_o}}=\infty-j\infty\$.
Effective wavenumber of a conductor is \$k_{\text{t,eff}}(\omega)=\frac{\omega\,n_{\text{t,eff}}\,(\omega)}{c}=\infty-j\infty\$.
Effective wave impedance is \$\eta_{\text{t,eff}}(\omega)=\sqrt{\frac{\mu_o}{\epsilon_{\text{t,eff}}\,(\omega)}}=\frac{\sqrt{\frac{1}{2}}\sqrt{1+j}}{\sqrt{\infty}}=0\$.

It makes sense that the impedance would be 0 but what about the other two properties?


texts: Safety considerations (for parts) for a beginner building with expensive parts

texts:
I'm building for the first time (for me) a circuit with an expensive part (a $80 DEC J11 CPU) and would like to know some "safety" tips so I don't inadvertently destroy the thing while playing with it.

It apparently has both TTL and MOS pins.

I'm looking for guidelines like "don't connect a pin of type A to a pin of type B without a gate of type G in between", or "be sure to add resistors/caps here and here", or "power up this pin/chip before this other pin/chip" or "use a such-and-such circuit to condition the power" ...

(It'll be a breadboard environment if that has additional considerations.)