texts: Finding a lower-power WS2812-like RGB pixel (or identifying the one I have...)

texts:
I'm looking to build an application with some WS2812 or similar addressable RGB pixels. Since this will be battery-powered, I'm planning to run these pixels at low-brightness most of the time. However, it turns out that the WS2812 pixels have a fairly high base/idle power usage (i.e. with the pixel off), between 0.75 and 0.85mA per pixel. I'll add a transistor to cut power to the pixels when they're completely off, but when running at (very) low brightness, this base power usage dominates the total power draw of my project.
So, what I'm looking for is a type of addressable RGB pixel that has a lower base power usage. I've looked at datasheets for a few types, but most of them just specify <1mA or do not specify anything at all.
Question 1: Anyone know of a type of these pixels that has a low base power usage (either from datasheet specifications or from actual measurements)?
Then, among the stuff I collected are a few different kinds of pixels. Most of them draw around 0.8mA idle. These are by Adafruit, so I'm assuming they're genuine WS2812S, WS2812B and SK6812 LEDs. But one particular board has pixels that only draw 0.4mA in idle! That's a significant saving, so I'd like to identify this particular pixel and see if I can order separate pixels of this type.
This LED is on a LED ring module made by CJMCU:

However, all sellers of this board (ebay/ali that kind of thing) just specify "WS2812", which this is probably not. The CJMCU website is full of Chinese and MySQL errors, so not really helpful either.
I suspect that this is some WS2812 clone, but since these leds have no markings, it's hard to identify them. I've found this post and this imgur album it links to online that shows how to (maybe) identify some types based on the layout of the LEDs, shape of the chip and the bond wire configuration, but this particular LED is not listed there. So I'm hoping maybe someone here knows which LED I have.
Here's the LED itself:

Note that it looks very similar to the SK6812 as shown in the imgur album linked above, except that a defining feature of the SK6812 seems to be a driver chip that's rotated 90° (compared to the WS2812B), but my LED seems to have a square chip...
Question 2: Can anyone identify this LED?
Edit: Since it looks so much like the SK6812, I looked at the website of what seems to be the manufacturer of those and found that the SK6813HV-09-4P and the SK6812MD look like they have a square chip, but the images are too vague (and I cannot find datasheets) to tell for sure...


texts: What is meant by the signal energy to alias ratio and how is it quantified?

texts:
Below solid black curve is the bandwidth of a signal(a 4kHz RC low pass filter). And when we sample the signal at 8kHz rate due to folding the blue dashed line shows the aliasing:

1-) It looks very symmetric but how can we calculate the overall shape of the original bandwidth plus the aliasing? Should we add or multiply these curves?

2-) And from here I found the above curve which the author is able to quantify 50:1 signal energy to alias ratio. What is meant by that and how can that be calculated?


texts:
I'm an industrial designer with limited knowledge of electronics and was looking for some help. I am in the process of developing a dementia care product.

The idea is to manage the access residents have to each others rooms, currently they can wander in and out of rooms sometimes; sleeping in beds, trying on clothes and moving possessions around. This causes distress to residents confrontations between family and care home owners as well an extra work for carers and staff. It is not acceptable to lock the rooms as residents cannot use keys so it would be seen as an infringement of their rights.

I am considering using RFID UHF technology to trigger an electromagnetic door lock when a resident approaches their own door. Based on race timing systems, I am considering placing an antenna under the carpet in front of the door which reads a unique passive tag placed under the insole of all their shoes and slippers.

There are the following considerations:

Each tag must be very cheap ($0.50) and almost disposable, so no batteries.
Residents may not always wear their own clothes but tend to always wear their own footwear around the home.
This is not a security device and only intended to improve the current situation.
Dementia sufferers will not be able to wear bracelets or lanyards.
They will not be able to swipe a card.

Although RFID UHF technology appears to be the best solution, before I 'plough on' does anyone have ideas for a more appropriate technology?


texts: ATmega16u4 and ATmega32u4 i2c bug in Proteus AVR model?

texts:
I am trying to use i2c with ATmega16u4/ATmega32u4 in Proteus (version 8.5 SP1) and in my i2c code the following code line hangs the MCU:

while(wait && (TWI_MTX == twi_state)){

It never gets past this. Doing some debugging I verified that TWCR never changes in the Proteus simulation, so it is impossible to enable i2c, which is the cause of this hang.

I tried setting it directly, with TWCR=0xFF just for testing, but register value never changes, it is always 0 during the entire simulation. If I do the same thing on ATmega328p the register does change successfully.

If I upload the code to a physical processor it works fine. If I use the same code on ATmega328p simulation in Proteus, it also works.

This is not a pull up resistor or communication issue. I have 4.7k digital pull ups connected, but the thing is, the pins never get to change states in the first place, because I cant get the MCU to set i2c enable registers.

This looks to me like a Proteus model problem or bug. Has anyone got ATmega32u4 to work with i2c in Proteus simulation?


texts: Altium : vias under pad for power drawing and thermal dissipation

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On my design, a TO228 mosfet will conduct much power.
Under it, I put two Fills (one on top and one on bottom layer). I plan to
link them with vias in order to conduct better power and to user the bottom one for thermal dissipation.

With altium, I added a via stitching on these fills. I also checked the option
"Allow vias under SMD pads" in design rules.

The issue is that stiching is not applyed when under the pad of the mosfet.
The option "allow vias under SMD" does not seem to affect via stitching.

I saw on other components design that those vias are added in the component own design.

I would preferably add the vias if I assume it is needed and only. I mean at board design time. Is there a way to ?

Thanks


texts: I am completely new to EE. I have ABB S203-C25 curcuit breaker installed. My question is 25A is per line (i.e. total 75, or 25A is total limit)?


texts: Why many (resistor - LED)s connecting in parallel, current of each LED is not stable?

texts:
simulate this circuit – Schematic created using CircuitLab

My circuit is like this, 40 lines of R - LED - LED (total 80 LEDs).
When the count of LEDs is less, LED's brightness is stable.
As the count of LEDs increases brightness becomes unstable (But brightness of all LEDs is same at any point).
So I measured voltage around resistor when the count of LEDs is many, and it was also unstable. Why this occur?

Edit:
Power supply is Apple iPad(second model) Charger.
LED's color is red.
'unstable' here means 'brightness goes up and down'. There is no shutdown. And unstability is not severe. I can observe it only when in darkness(all other lights off) and the front of LED.

Edit(2):
I tried other power supplies(phone charger(5V 1.2A), 3x AA alkarine battery) but result is same


texts: Where should an increase in harmonic frequencies go in the Nyquist formula?

texts:
From the Nyquist formula that \$ Capacity = 2 \times Bandwidth \times log_2(L) \$, where \$L\$ is the level the signal represents, the total number of possible bit combinations the signal can represent.

Say I have these current values of \$Bandwidth=8Hz\$, \$L=8\$, then based on the Nyquist formula, I will get \$2 \times 8Hz \times 3 = 48bps \$ as the capacity.

Suppose I decided to increase (should I use the word "increase" or "add"?) 5 harmonics to the frequency, then my bandwidth would be \$8 \times 5=40Hz\$.

Now, if I insist to let the signal level, \$L\$ remain constant at \$3\$, then the equation will force the Capacity to increase: \$2 \times 40Hz \times 3 = 240bps\$. But, since the frequency increased was due to the number of harmonics which would "form" a more precise signal "shape of the digital signal, it hasn't increased the frequency of the whole digital signal, has it? That's, I should still get \$48bps\$ but with a better quality of digital signals. But in this Nyquist formula, it seems that my capacity is increased immediately if I insist to let my \$L\$ remain constant.

Where should the extra bandwidth value be in the Nyquist formula if the signal level is constant? The capacity shouldn't increase, should it?


texts: How to use TM1637 on a PNP driven 7 segment display

texts:
I am trying to get this 20-year-old board working again for a few days now, constantly feeling I am close to the solution, but I can't get it to work.

The segments Led[3..5] are wired to connector P3 trough the PNP (BC327) the LED's are also wired as a 4th digit

I'd like to get it wired up to a TM1637 as I have that at me, and only have 2 free pins left on my design. (Datasheet_TM1637)

My problem is that the PNP's are inverting the Common Anode input so none of the screens ligh up.

What I tried:

I pulled TM1637 anode output to GND (10K), and now all of them light up, but some segments are brighter than others, none are totally off, and the output shows up weirdly.
Also, the driving signal is pulled up. (Pictures below)

I found some logic IC's on an old board and Recycled them.

I wired it to an HCU04 but the screens go blank(it's not
open-collector)
Also found an SN7405. It's open-collector, but it won't get any
output if driven by the TM1637.

If I wire it to the HCU04, than that inverted output to the SN7405, I get back to where I started with the pulldowns. (also can drive the screen)

To be honest I'm not even sure now if the inverting is the problem anymore.

What could I do to get this working?

P.S.:

I can not change the circuit that is below as it is already on the
board. I can connect to it by P3 IDC connector.
I drafted the schematic, so VCC might be something else. I labeled it
based on the PNP's.
Some current limiting resistors are placed on the cathode lines
(other side of the IDC) I'm not sure if they are needed when using TM1637.
S[3..4], and D[2..3] are buttons for a weird input but that's a whole other story.
The Italians who designed the baord back in 2001 used a 74HC374 to drive this screen

I made a sketch of the circuit:

The board:

Sorry for the lame scope

Unconnected Output:

Pulled Low:

Screen Connected:

Negate:

Negated Open Collector:


texts: Electromagnet connected to a blade to cut a piece of thread

texts:
I am new to the site and have an idea that I would like to implement at my work place. I do not have electrical knowledge but I know people who will be able to implement an electronic system.

I have a small manufacturing company that stitches material together using sewing machines. The machines are old and I do not have funds to invest in new machinery.

I would like to create a scissors/blade that is able to cut the threads after each piece is stitched. The machine is fixed onto a desk and the thread from the sewing machine needs to be cut underneath the machine, so not visible from the top. So my thinking is the having a 2 blades underneath that is connected to a electromagnet and the operator of the machine can press a button using their foot to turn the magnet on and it would close, once the foot is released the blades open. The threads are strong but are thin, less than 1 millimeter in thickness.

I would like to keep the system very simple and cheap to create. I understand that the blades will need to be changed regularly.

Does anyone have advise with this?
Thank you


texts: Using PLC for more over than 200 relays application?

texts:
Hi im currently building an application to control over 200 device in a building. Originally i want to use an arduino and bunch of relays to control them. After asking some questions and such in this forum, people suggest me to use a PLC instead(concerning safety and such). My new problem is that, i dont really understand how PLC works for a lot of devices, what do i do if i want to control 200 relays with a PLC? most PLC only got 8-16 Relay output? how can i extend it?

++

Im not asking a recommendation on which product to buy and such etc (as i know it against the sites rule), im just asking on a appropriate approach to my application. Thx for the comment and replies !


texts:
As a preface: I have 0 experience in interfacing with peripherals other than keyboard and mouse, but am willing to learn, just don't know where to start.

I would like to write a software in python (if C/C++ would be needed or is the easier way to go I can interface that) running on a PC, that can be manipulated by two external buttons (it will be an experimentel setup for small children, so we need big easily identifiable buttons, that are easy to push, so the keyboard/mouse is out of the question). The easiest would be to buy two USB buttons, that can be easily accessed, but I've been told these do not exist, and that I would have to build an interface myself (microcontrollers and stuff). If this is not true that would be great, if it is, I would like to invest my time into something that is not horribly hard and long to learn to use, and both the knowledge and equipment easily reusable if other issues like this come up. What would you recommend?

Thanks in advance:)


texts: PIC16F1503 resets during relay switching of 1HP motor

texts: I am totally new to this stuff. I have connected a 1 HP induction motor through a relay and it is switched by a PIC16F1503. I have connected a 10 uF 25V electrolytic capacitor with VCC and GND pin, is it OK to not connect any ceramic capacitor across because it's already connected to the 10uF capacitor?


texts: Li-Po battery leaking current when connected to TP-4056 charger

texts:
I've been using a Nokia BL-5C 1020mAh, 3.7 Li-Ion battery to power up my SIM800l GSM module. Everytime I used the battery for testing out the various AT commands for maybe 30 mins or an hour, I'd check the voltage, and it'd still be at around 4.2 volts. Not much drain.... But the next day (overnight), the battery would be dead. At around 3 volts (Thanks to the overdischarge protection of the TP-4056). This happened a couple of times.
So I decided to check if the battery was leaking current when connected to the TP-4056 without any load connected to it.
And... I was right. Around 25mA!
Why could this be happening?
Is my TP-4056 module bad?


texts: Independent voltage sources using voltage regulators?

texts:
I'm trying to design a variable power supply, and need some clarification regarding using voltage regulators in parallel as independent voltage sources.

As this is a power supply, one of the outputs may not be used.

My question is, if say V2 is set to 1.2V (the minimum voltage), will it sink too much current so that V1 will not be able to draw 10W (ideally)?

The voltage regulators will probably be LM317's and not intended to be tied together.


texts:
I have two high-q band-pass filters with TI op-amp OPA2376 (http://www.ti.com/product/opa2376) in series of each other. Here is one of them:

My objective is to center the band-pass around 40kHz. On the input, I have some strong noise around 15kHz. Therefore, I want to have a good gain slope that filters such noise (everything below 25kHz is really cut-off) and still gains a lot my signal (everything above 35kHz is gained up).

On the other (upper) side of the band-pass, I have more flexibility. I know that the two stop points are not equally spaced above and below the center frequency but they will look equally spaced if plotted on a log graph. Once again, the upper band is about to be safe so the cut-out frequency can be higher if needed.

What values would you recommend?


texts:
I want to power an Arduino (Wemos D1 Mini) with 5 or 3.3 V from my garage door opener, which has 24 VDC available.

As far as I understand, this can be solved in the following ways:

Step down buck converter
Linear voltage regulator
Voltage divider circuit

What are the pros/cons of each of these?

I'm concerned about heat, and I don't want to burn down the garage. I haven't measured how much current my Arduino draws, but I guess it's very little like 250 mA or less(?). I'm only using the built-in Wi-Fi module and no external sensors/relays.


texts: Buck converter drops only keeps Vout if no traces are connected

texts:
I wanted to try to use a buck converter to get 3.3V from a LiPo battery and found the Analog Devices ADP2108. Exact part number: ADP2108AUJZ-3.3-R7. Farnell/Element 14/AVNet link.

I've populated the PCB step by step, first the charger (MAX1555) and checked that it functioned as expected. Then I added the ADP2108 and checked whether the output voltage was 3.3V and clean after the coil. This was all OK after I added the pull up resistor that I forgot on the layout and have since added in the schematic, so the enable pin is pulled high.
I did not yet have the PIC delivered, but did have all other components. So I populated all the passives around the pic and the TI TLC59116 LED driver.

After doing so, I checked the Vout of the ADP2108 and found a clean and constant 1.01V instead of the expected 3.3V. I cut the supply traces to the TLC59116 expecting a short there, but that didn't help.

After some searching, I found that I could only get the converter to output 3.3V if I cut all traces (where the red lines are in the layout screenshot). If I connect one of the traces (even the trace with only one of the bypass caps to the non-existent PIC), the output goes back to the same 1.01V.

I've measured and found no short between Vcc and GND.
I have also tried to add a load to the output (tried a 470R resistor to ground and a 100mA load on a load bank), to no avail.

I've probed around on the output with a scope and can supply screenshots/descriptions if useful. When the output is 3.3V it runs at 2.7MHz, which is within specifications. If the output is at 1.01V, it also seems to run in PWM mode (with spikes to its input voltage), but the output voltage is too low.

I have no experience with these devices (so far only used LDO's that required no external components apart from caps), but thought it was time to try. Hence, I have no idea where to look next. I tried to measure the total output capacitance between GND and the output, but seem to measure unexpected values (I expect the total capacitance on the output about the sum of all the caps to GND, which is not the case).

I have replaced the coil (I originally used Murata LQM2HPN1R0MG0L as it was described as "high frequency" and had a low ESR) with one of the recommended coils(the Coilcraft LPS3010-102MRB Power Inductor, 1 µH, Shielded, 1.6 A), and did the same with Cin and Cout, to no avail. Also replaced the converter, just in case. All traces are kept as short as I felt possible.

Apart from the issue with the converter, any recommendations on good layout practice is more than welcome.

Requested traces (when unexpected behaviour is shown):
CH1 before L1, CH2 after L1. Marker shows PWM pulse length (around 2.9MHz)

CH1 before L1, CH2 after L1. Marker shows length in between PWM bursts:

Traces with 10uF added to the output capacitor after cutting the traces to the loads. So about 20uF in total.

CH1 input to switcher, CH2 before L1, CH3 after L1. Max1555 Powered from DC bench supply.


texts: What size crimp connector for 2.54mm headers?

texts:
I have a few pin headers on my board which are the standard 2.54mm spaced pins (datasheet), and I'm trying to find the appropriate female crimp connector which will connect to it, exactly like the one below:

However, I'm having trouble determining the size of the crimp connector. The datasheet says that the male header is 1.1mm, so 17 AWG.

What is the size and shape (and hopefully if known, the name) of the crimp connector I need?


texts: Is there any difference between Electronics book in UK and Europe

texts:
I want to know if there is any difference between UK and Europe about teaching electronics. e.g. conventional current flow and probably units and stuff?

Thanks.


texts: Using modern electrolytic capacitor's can as a conductor?

texts:
I have a project cominig up where it would be benicical to have the large input decoupling cap's top surface be a touch contact point for Gnd for the circuit.

I know that in the Old Days of yester year (tube era) the aluminium cans of large caps were one of their primary conductors (Gnd)

I'm not considering standard electrolytics (with srink wrap) that have the X,K,Y relief cuts in the top.

What I'm planning on using is the all metal (japanese) style caps as seen on performance Motherboards, Videocards, etc. As this style of cap has its value data printed on the top so I may have to sand/scuff to top surface to be a better contact.

The space I have to work with is so small and oldly shaped it would be very advantageous to do this. Also the currents are small in the tens of mA.

So my question is; is this something that is done, can be done, or really bad? Would standard electrolytic s be better?


texts:
Hi I've been trying to look online for RGB 5630 LEDs strips but I can't find any. All the strips I've found carried 5050s which give a max of 1020 lm/m more or less..

Any idea if strips carrying 5630s cannot be RGB for some reason?


texts: Can I use the FFT to recognize musical notes on a piano?

texts:
I want to create a tool which recognizes a few musical notes (I know this is re-inventing the wheel). So I would play middle C, D, and E on a piano and it should be able to classify those notes. Here's how I think I should approach it:

Record a sample of me playing a note
Convert the signal to the frequency domain using the fast fourier transform
Find the frequency that is most present (basically argmax of the frequency domain data)
Assume that frequency comes from the note played and use that to classify the note

I haven't tried any of this yet because I don't want to start down the wrong path. So, theoretically, will this work?


texts: Dual Rectified 12V 5V Tapped Power Supply Safe?

texts:
Is the following regulator valid, safe and efficient?

The transformer is a dual 7V output toroidal. So B1 is supposed to rectify out 14v and B2 taps the "center" to produce 7V.
INAE and I've never used dual bridges in a tapped arrangement like this so I thought I should ask before playing around with mains like this.
UPDATE:
The following is the circuit corrected as discussed but without the regulators:

This is supposed to model the Amgis L01-6310 14V/7V transformer to see what sort of voltages might be supplied to the 12V/5V regulators (because I should have used a 12V/6V part since Vpeak of 14V is *1.414 = 19.8V. Secondaries have 7 ohms series resistance per datasheet. I have never modeled a transformer in LTSpice before but I reasoned the turns ratio is 120 / 14 = 8.57 squared = 73.5 but this seemed to be off by a factor of 2 so I figured the primary is wired in parallel for 120V mains so I doubled the ratio to 147 / 1.
Green is the 14V tap. Blue is the 7V tap. Red and light blue shows the load on the outputs.
So it seems I get 16V and 7.2V which isn't too bad. If it comes out to 16V thats only a 4V drop. But I don't think the 12V load will be loaded much. If I only load it with ~25 mA, I get 18V which is 6V * 0.025 = 150 mW.
INAE so this could all be wildly wrong. IIWAE it would probably still be wrong.


texts:
I'm working with a Zedboard and I'm printing to the screen memory addresses of consecutive 32-bit float numbers.

So the print generates this:

Result 0: 5374.557617
Memory is A000000
Result 1: 5474.651233
Memory is A000004
Result 2: 5574.557129
Memory is A000008
 ....

So memory is incremented 4 each time.I can't understand why a memory with 4 more bits can keep a 32 bit number. The only way this makes sense is is hexadecimal is convertible to bytes and so +4 bytes=+32 bits.

However this isn't the way I learned, everyone says that hexadecimal shall me converted to bits

Surprisingly I haven't found anything on the Internet about this question in particular.


texts: Can a dc motor be damaged if I change the direction of the motor while on full speed?

texts: Can a brushless dc motor be damaged if the direction suddenly changes while the motor is already spinning in another direction?


texts: NXP KEAZ64 microcontroller fault on power on (harsh/sharp switch on)

texts:
I have a problem with a design that uses 2 S9KEAZN64AMLC microcontrollers. I have encountered an issue, where it seems that if the device is turned on with a switch i.e. with a very fast rise time on both the supply voltage and the 5V rail, then the device can fault out. Whereas if the device is powered with a more gentle rise time it always boots correctly.
I thought this was a closed case and to fix the issue I would add capacitance to slow the turn on. This does seem to fix the fault. But I want to understand it more. Not all of the units I have exhibit the fault, perhaps 10% do.
See below plots, where:

Blue = 12V supply from the power supply, switched with a relay.
Pink = 5V rail powering the microcontroller
Green = Non-maskable interrupt (NMI) (PTB4, Pin 10)

Microcontroller operating ok

Microcontroller not operating

You might then say that it is due to the NMI pin being driven low during start up. And that I should comply with the final point of the Errata about the VDD ramp up.... perhaps.

However I then tried to recreate the fault, by removing as many decouple/bulk capacitors on both the 12V and 5V rails. This brought the rise time down to 3us, so I was expecting a fault condition, however it never faulted out.
So in summary, I think I have a solution to my problem, increased capacitance on the decoupling capacitors near the microcontroller and on bulk capacitors on 12V/5V rails. However I don;t understand the different result between different boards.
Any thoughts? If you want any more information, drop a comment and I will add information.
Further Info / Schematic


texts: Is this SNR change related to aliased common mode noise or some other phenomenon?

texts:
Below time series offset value of a force transducer amplifier which is sampled by a 16-bit single ended earth grounded data-acquisition board at 500Hz (red plot) and 12kHz (green plot). Before I was having aliasing noise so I implemented 200Hz LP filter using 1u cap and a 1k resistor at the output of amplifiers. The amplitude of the noise decreased on scope test. But the noise level still changes with different sampling rates. So below is the time series of the same output at 500Hz and 12kHz sampling rates:

I couldn't figure out whether it is still due to aliasing or SNR being related to sampling rate regardless of aliasing. As you see below for the FFT of the same output, there is like between 12dB to 15dB difference between 500Hz and 12kHz sampling rates:

So now when I sample with 12kHz it seems I get better SNR.

In my previous question someone answered:

  Your signal adds coherently, giving you 6dB of gain for doubling the
  sample rate. Your noise adds incoherently, giving your 3db for the
  same doubling. You just got 3dB SNR improvement for 2X the samples. Of
  course you have to sample at 4X to get 6dB improvement, and 8X for
  9dB, so there's practical limitations.

I have couple of questions:

How can I verify this dB difference is due to aliasing or just the result of another phenomenon?
Regarding suppressing common-mode 50Hz and its harmonics, unfortunately I cannot use differential ended receiver and I'm also using coaxial cables. If this is still due to aliasing, can I still use common mode chokes to suppress high freq. noise; or will it be useless since the system is not balanced and not diff ended?


texts: Voltage regulator middle pin not soldered to the board

texts:
Today I noticed that my Arduino board only has two of the pins of the voltage regulator hooked up. I thought I understood how it worked, but I must be missing something.

Why isn't the middle pin hooked up to anything? Was it always like this or did I break it? The board seems to work just fine.


texts: Pulsed DC current measurement using arduino and shunt resistor

texts:
I am currently working on a project ( to develop a constant current pulsed DC supply)
in which current has to be measured using Arduino's analog input (Upto 20A) passing through a variable resistance RV1(shown now as 145 ohm).

Current through this resistor is measured using a shunt R1 of .0035 ohm.
Capacity 20A-AC/70 mV max.

For that, an IC4559 Difference-Amplifier is used as shown below.
I have set the gain to 70.
as 70*.070 Volts gives 4.9 Volts, reaching to the Arduino analog input port's capacity.

Question: This configuration works, but in my original circuit there is no grounding near the Diodes (highlighted).
When I remove the ground port near the Diodes, the value read by Arduino become absurd, is there any way to measure the load current without grounding the diodes by using the similar configuration?

Arduino Code:

void loop()
{
  lcd.clear();
  volts = analogRead(A0);
  lcd.print(volts);
  Serial.println(volts);
  delay(500);
}


texts:
I'm using a Micrel KSZ8051 Phy in a 100mbps design. The datasheet specifies that it should have a small ferrite bead feeding the power.

However, the datasheet doesn't suggest any specifications for the ferrite. What should I consider when choosing a ferrite? Do I simply select the component with the highest impedance at 100MHz which can take the current?


texts: Should I use a resistor between an input pin of MCU/CPLD and VCC/GND?

texts:
Some times, I want my MCU or CPLD to input a static logic. So, I choose to tie it to VCC or GND. The problem is that should I put a resistor in series to limit the current? I just think by myself for a while and get my own answer: no!
Take STM32F103（datasheet） for instance,on page 86:

From the 'input leakage current', I know that when applied VDD the input resistance is at least 1 M ohm so that I do not need a resistor in series to limit current. Is that reasonable?


texts:
Good evening.  Sorry for my grammatical errors, or any other errors that have connection with English grammar and language in general. I have a little problem to solve. I think that these two BJT's are in Darlington pair. I have to find Zin, Zout, Au and Ai, common BJT characteristics. Problem is I think that this first transistor is in cut off, or am I wrong? If it is in cut off the     second transistor isn't connected to the AC source, and the    second BJT is in active regime. Then circuit doesnt  make any sense. In general:"Can BJT conduct if it doesn't have any DC voltage source connected with it's Base connected through some resistors?

Info: Vcc=12V,Vdd=8V,Rc=1.8k,Re=5.6k,Rb=390k,ro(output resistance for ac)=infinity,betaforvard=120...

I don't expect that someone solve this for me, just answer me if I am on the right path with this conclusion about regimes of this BJT's transistors.
Thanx ...:D


texts: PIC16F877A PORTA RA4 not working as ouput

texts:
I have used RB state change interruption to turn on two LED connected to portA (pin4 and 5). The probem is when interruption occurs LED on pin5 turn on, but not LED on pin4. When I change pin4 to pin3 it works normally, but I can't use this pin, because my circuit is already printed.

I've read the datasheet, and I understand that PORTA pin4 is multiplexed with Timer0, is that causing the problem? How do I disable that?

XC8 compiler code:

#define _XTAL_FREQ 20000000

#include <xc.h>

// BEGIN CONFIG
#pragma config FOSC = HS // Oscillator Selection bits (HS oscillator)
#pragma config WDTE = OFF // Watchdog Timer Enable bit (WDT enabled)
#pragma config PWRTE = ON // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = ON // Brown-out Reset Enable bit (BOR enabled)
#pragma config LVP = OFF // Low-Voltage (Single-Supply) In-Circuit Serial
                            Programming Enable bit (RB3 is digital I/O, HV
                            on MCLR must be used for programming)
#pragma config CPD = OFF // Data EEPROM Memory Code Protection bit (Data
                             EEPROM code protection off)
#pragma config WRT = OFF // Flash Program Memory Write Enable bits (Write
                            protection off; all program memory may be
                            written to by EECON control)
#pragma config CP = OFF // Flash Program Memory Code Protection bit (Code
                           protection off)
//END CONFIG

int main()
{
   TRISA = 0x00;    //set portA as output
   TRISB = 0xFF;    //set portB as input
   TRISD = 0xFF;    //set portD as input
   TRISC = 0xFF;    //set portC as input
   ADCON0 = 0x00;   //disable AD converter
   ADCON1 = 0b10000110; //disable AD converter
   OPTION_REG = 0b00000000; //disable AD converter
   INTCON = 0b11001000;     //enable port b pullups
   PORTA = 0x00;        //turn off LEDs

  while(1)
  {
  }
  return 0;
}

void interrupt isr(void)
{
   if (INTCONbits.RBIF) {
   if (PORTB) {
      asm("nop");
   }
   INTCONbits.RBIF = 0; //clear interrupt flag
   PORTAbits.RA4 = 1;   // turn on bottom LED
   PORTAbits.RA5 = 1;   // turn on top LED
   }
}


texts: How to implement a transformer into a boost converter instead of an inductor

texts:
I am trying to build a boost converter that would output a high DC voltage (several hundreds). My concern is that I should use a transformer, but how should I implement it so that DC voltage input is possible? Do I need to use an DC/AC inverter before the transformer?

I've been told that an isolation transformer can take DC voltage..

Thank you in advance.


texts:
I am interested in making a small circuit that could sense the vibrational frequency of the object that it is attached to. The resonant frequencies would be in the audible range (likely 5kHz to 10kHz) Imagine a small circuit attached to a tuning fork, I would like to 'ping' the tuning fork and have the circuit be able to output what frequency at which it is resonating.

I have read that Piezo devices would be capable of this but I haven't been able to find anything suitable. Does anyone have any suggestions of what I could use?


texts:
I’m working on DIY project for my home to detect the harmful gases like CO, CO2. I have to design a PCB in which I have included MQ7 for CO and MQ135 for CO2 and nitrous oxide. I am using Eagle software and I have chosen ESP8266 MCU. My questions are:

The MCU I have chosen is good for my project?
Can these two sensors work together in the same PCB board?
I didn’t find the till what distance these sensor can sense the gases in the environment.

Please help me in designing the board.
Thank you

mq7-https://www.sparkfun.com/datasheets/Sensors/Biometric/MQ-7.pdf
mq135-https://www.olimex.com/Products/Components/Sensors/Gas/SNS-MQ135/resources/SNS-MQ135.pdf


texts: DC motor causing project to work unexpectedly

texts:
We have developed in protoboard the following schematic for driving a DC motor with transistor for Arduino, but instead of using the PN2222 transistor, we are using a MOSFET IRF540, and instead of flywheel diode 1N4001 we are using 1N4007. Also we have a LED strip connected to Arduino.

When we were developing in protoboard we were able to control the motor kickback when switching off with an 1N5819, but when did the PCB the diode is not enough. Trying different diodes didn't solve the problem, finally we are using a 1N4007 but still having issues when the motor switches off. The issue is the LEDs animation is affected: we paint in one color but sometimes when the motor switches off, some LED is painted red and the code is not programmed for that. So I guess is something related to the motor.
We can't connect the motor to an alternative power supply, and also we can't solve it because what we did to solve it when using a protoboard was using a diode, and we don't understand well the problem.

We have been researching, searching on the internet but we don't understand snubber schematics, we tried with ferrite and concluded is something related to the motor when switches off and we can't control with this diode. Also we have tried SR5100 because we saw here he is using an SB320 and when I bought the SB320 I received SR5100... also, reading in this web about this topic, I tried to develop an snubber circuit, but I don't understand this video so I can't try it.

Also tell you that the motor is a vibration motor, and when I set less power with a potentiometer it is not making trouble with LEDs. The difference between the first link and our project is also that the motor is not turning free, it is a vibration motor and the implementation of an ArduinoToBreadboard.

EDITED:

The diode is soldered in the motor and is not shown in the schematic because when tried it on the breadboard didn't work, only worked when put the nearest to the motor possible.

EDITED:

Added decoupling capacitor.

EDITED:

Moved decoupling capacitor to correct place (closest to MCU as possible).


texts: 9v lighter/igniter/heater is not working

texts:
Hey guys, I'm new here and I want to make a 9 V lighter/igniter.

I used a short nichrome wire from our broken oven toaster, locked it in with two short bolts and hooked it up to a doorbell switch since its hard to find a proper small switch where Im from. I used a 9 V battery to power it. When i turned it on it did feel warm but the nichrome wire didn't turn red hot.

Is there anything wrong that I'm doing? Should I turn the nichrome wire? I was hoping to used a straight nichrome wire instead of using loops. Am I using the wrong kind of wire? I'm using 0.30mm^2X2C speaker wire. Should I up the power by using two 9 V batteries?


texts: In a three phase choke, is the rated current per phase or for all 3 together?

texts:
In a 3-phase choke, for example here: https://katalog.we-online.de/pbs/datasheet/744839010400.pdf

What is the current rating?
For the inductance it says 3x10.5mH, so its 10.5mH in each phase and if I parallel these together it will be 1 third of that.

But for the current rating it just says 40A, is this also per phase or with all 3 paralleled together?


texts: How to convert battery powered roller blinds to be solar powered?

texts:
I have some battery powered roller shades that I'd like to convert to using rechargeable batteries using a solar panel as the charger. My blinds are Norman Pro-Lift 25 CE blinds. They run off a long tube of 8 AA batteries in a series (so 12V when fully charged).
I found a 12V solar panel that seems made for this purpose on Amazon:
https://www.amazon.com/dp/B07J5B7RFS
I purchased one unit so I could test with it. From my the inside of a window it actually got up to 19V output. For amps it's supposed to get up to .08, but I'm seeing .01 so far but it's pretty cloudy today.
Questions:

Would it be as simple as replacing the AA batteries in the tube with rechargeable AA batteries and then connecting the battery tube to both the solar charger and the roller blinds motor?

What type of batteries are best?

I am unable to get an answer on whether the solar charger shuts off when the batteries are fully charged.  Assuming the charging does not shut off and is exposed to sunlight 6-8 hours a day, would it be reasonable to expect the batteries to last a year?

I can't find any details on the above solar charger, so I don't know if it has an integrated diode to prevent the batteries from discharging into the solar charger at night, how quick will the batteries discharge?  Perhaps this would actually be helpful to prevent batteries from getting overcharged?  Or will the batteries be completely drained after a single night?

Any other tips on how to make this project would be appreciated. Thanks!


texts:
I want to build a simple voltage inverter, just using two diodes and two caps to get a source of negative voltage.

The problem is, that my micro is running at 3.3V and I need at least -6V and about 10-15mA. I have a +8V rail availible in my circuit, so I need a way to use the 3.3V to switch the +8V. I tried simulating this in LTspice:

But it did not work very well, and it has the problem that when the mosfet is open, it is just wasting power on R41. How to do this correctly? I think I need more than one mosfet/bjt...


texts: I an troubleshooting my chiller because I fried my compressor. I have done clues of what could go wrong, but want to discard over voltage. I have a Mitsubishi VFD. That I take 240 and convert to 240 3 phase. But when I measure 1 get 176 and between lines I get 380. But the VFD is program to 240 60 Hz. Do I need a diferent meter?


texts: How to measure the frequency of vibration of an ERM motor?

texts: I´m part of a team developing a device to produce a mechanical vibration whoose  frequency we can vary between 45 and 130 Hz. We are using an arduino with a potentiometer in order for us to vary the supply voltage in an Excentric rotating mass dc motor.Using a transistor as a switch we use the reading voltage in the potentiometer to supply  the base of the npn transistor. My questions are how can we measure the frequency of vibration knowing the voltage supplied to the motor? Do you have suggestions besides the ERM motor? And where to buy a specific motor for this purpose?


texts: I’m trying to identify the kind of connector I need for a few DC fans, but can’t track them down on digikey.  Pictures attached.  Pitch is 2.00mm, wire is 26AWG.  The replacement fans I possess have bare wires so I also need to attach the little metal clips (I guess?)


texts: How to stop a ZN-tuned PID controller from decaying

texts:
How do you diagnose a PID controller that seems to work perfectly for a few minutes, then decays?

I've tuned a PID controller using the Ziegler–Nichols method. I found my Ku of -1 and Tu of 1.142. I then plugged these values into the classic ZN PID formula. My process variable is a target speed, and within seconds of starting it, the controller maintains this speed perfectly. However, I log the errors for each component, and after a few minutes, the integral error slowly builds. When it reaches around 7, after about 15 minutes of running, then the controller quickly decays, and the velocity drops to zero.

I've tried adjusting my Ku and Tu, and re-running through ZN, but the same thing happens. I'm not sure what I'm doing wrong, especially since it runs virtually perfect at the start. It has almost no over or undershoot, but yet the integral errors builds up. Is this a rounding error? Should I reset this periodically or would that be a hack? What might I be doing wrong?


texts: AC Current sink with op amp and transistor

texts:
I want to create an AC load for testing high capacity battery (200Ah) using the circuit below:

Can I put an AC voltage at Vin and get a AC load current through the FET? And why do they need LT1492 with 55mA output current capability while the FET gate current is micro-Amp small?

Another thing that trouble me is that why Iout only depend on that 1 Ohm resistor and not RL?

V+ is connected to the battery.


texts: conventional current flow and ground plane

texts:
I'm a student.
I cant understand why we design ground planes to have a easy (low resistance) path for return current.....
If the real flow of electrons is from battery (-) to battery (+) we should place a plane in the (+) side of circuit to let the charges flow back more easily...

can someone explain this to me ?
i run across an old PCB with a "power plane" instead of "ground plane" and this make more sense considerind the real flow of electrons.


texts: Trying to understand how they got equation for Vzo

texts:
this might seem like an easy question but I'm still new to circuits and I'm trying to understand how they got the equation for voltage.

They have the solution as 6.8=Vzo+5m(20), but when I looked at it I thought It was Vzo=6.8+5m(20) because for the circuit Vzo comes first then comes 6.8v, so why not go in that order?


texts:
I've got a remote control transmitter, with a segmented LCD display.  The MCU has an integrated LCD driver that is driving the display.

I've got the MCU interfacing and working with the LCD. The LCD is only powered from the MCU. I have the LCD contrast and frequency set to where it looks nice.  I can press buttons and update segments and everything works great.

However, when I turn on the TX IC to transmit (it sends a message in 100ms) it draws so much current in the whole circuit that the LCD doesn't have enough current for all the powered up segments.  They go from 100% contrast to say 30% contrast.

It is not like the MCU drops out, just the current being provided to the LCD.  As soon as the TX IC turns off, the display comes back to 100% contrast.

If I hook up the board to an external power supply when the TX IC flips on the current draw goes from 3mA to ~15mA.  The external power supply is set to provide up to 100mA, so it isn't like there is a power shortage.

There is more than enough current available to all the components on the power, for when the TX IC flips on.

If the MCU acting as a sourcing output provides enough current to drive the segments normally, why when the TX IC turns on it would it cause that current drop at the LCD?

Does anyone have any ideas how to correct this?  I've tried adjusting the contrast levels and bias resistors on the LCD driver on the MCU, but that doesn't seem to be what is causing the display "sag".

We have used this segmented display on a PIC16 with an LCD driver, and don't experience anywhere near this much display "sag" so I don't know if this is an issue with the integrated LCD driver, the TX IC doing something crazy, or something else with our design.

I appreciate any help!

I'm actually starting to think it is trace width issue.  Even though my traces are sized correctly for 1oz copper pours, it could be my Asian board manufacturer maybe is not pouring true 1oz copper on the outer layers of this board, so the board is current starved when the TX IC turns on.

There is no reason my power source can't provide the 20ma max the MCU & TX IC use.  I don't see any distortion of the AC waveform going to the LCD, it is just a voltage sag in the entire system.

I traced the voltage going from the battery and power jack, and you don't see them sag when the IC activates.

You only see the voltage sag where I drop the battery voltage across a diode, and it runs to the MCU and TX IC on the board.

One thing I notice, is that my battery charging IC on a 650mA rated trace, only provides 250mA (the resistor value it is set for should provide 400mA charging current) when it tries to charge the battery.  Which makes me think there is not the specified amount of copper on the board.

One board mistake I see is that I used a 400mA rated trace from the diode to the power plane.  If there is less copper, it seems like a stretch that 20mA is causing the system to choke from that trace to the power plane... but I don't see much else.

I'm going to re-confirm with the board house, and increase the main power supply trace widths and hopefully this will not be a further issue.


texts:
The LM3914 IC has a divider that works over 10 LEDs.

Does this IC enable using less than 10 leds and does it automatically adjust the scale based on the number of LEDs (eg 5)?


texts:
I am an EE student and can write [at least simple] programs in more languages than I have fingers. I have just started learning VHDL and I was wondering what a good project would be to really get to know the language and the relevant tools? I am having trouble coming up with one because it is a really different style of programming for me.

I have made simple things like adders, but I am looking for a more long term (ie a month or so) project.

In case it is relevent, I have Xilinx Webpack and a Digilent Spartan3 board.


texts: What is the difference between capacitative and inductive coupling in a twisted pair?

texts:
I'm learning about networking and there is this passage:
"Twisting cancels out inductive coupling, while the shield eliminates capacitive coupling."
What kind of effects are these, qualitatively speaking? For example, if I have two wires which aren't twisted around each other, how would they affect each other? Or if I have two twisted pairs, which aren't shielded from each other, how would they affect each other?


texts: Why are LEDs on most embedded designs inverted?

texts:
I noticed, that on all my evaluation boards that I had up to this point in time. The LEDs were all connected in active low to the Microcontroller Port.
I understand that from a safety view it's better to have active low RESET lines and such. But why LEDs?


texts: In Charging Circuit with battery detection

texts:
The circuit is charging the battery with Vcharge and VCharge also power up the circuit operation. Battery will serve to power the circuit when main power supply VCharge cut off.

A switch is added to connect battery to the circuit with led indicator.

simulate this circuit – Schematic created using CircuitLab

The led is act as indicator to show the battery is connected to the circuit. It is operated as expected when the switch is turned on without Vcharge. However, when VCharge is applied , then the led will also light on regardless of the switch turn on or not where it is needed to charge the battery.

Is there any method to make the led light on only when the switch is turn on even when VCharge is applied?


texts: AVR microcontrollers, who initilizes assembly `data` segment and what is the purpose to have this directive?

texts:
I am new to assembly and microcontrollers and am trying to figure out how they work.

Now, I have read a lot how in assembly text and data segments are for storing program code and initial data for it.
Everywhere people say[1,2,3] (if they say something) data segment stores values preinitialized for the program.

But in AVR, as I understand, data means SRAM.
And to have it initialized you need to instruct your microcontroller to put some actual values there.
Only having instructions under .dseg somewhere in your code  does not magically put values into SRAM. The microcontroller has to reach the initializing instructions by its pace, following the program as usual: starts at 0x0 of the program segment, which is flash in AVR, and follows the instructions.

For instance, in this question the guy examines the code, produced by avr-gcc from C, and finds the routines initializing SRAM from flash, i.e. the program segment of the code.

If it is so, then what is the purpose of having .dseg?

Maybe it is for different assemlers or other tools (like avr-gcc in the referenced question, or avrstudio in the link 1), which would add necessary initialization instructions when processing the code with .dseg?

But if you work with "bare bones" the microcontroller starts from 0x0 (or somewhere else, according to the datasheet), this is where your program starts and there is nothing more to it, is there? (Of course, you put a vector table there for the interupts, if you want to handle them. And 0x0 is the address where RESET brings the microcontroller to. But it is not essential.)

PS

I thought .dseg/cseg could imply different address spaces: when you write an address in .dseg it is for SRAM, in .cseg -- for flash.
But it seams addressing depends solely on instruction definition: ADD a1, a2 -- a# are registers, RJMP a -- a is flash (i.e. program), the SRAM is accessed indirectly via registers -- LDS R1, 0x0060.

Here again, can it be so, that the code under .dseg label like in 1:

 .DSEG                        ; Start data segment
 var1:  .BYTE 1               ; reserve 1 byte to var1

substitutes the indirect access to SRAM via registers?
Probably this information should be searched within the documentation for the particular  assembler at hand? Again, "bare bone" AVR instruction set doesn't provide any of such?


texts:
Tripath made some clever digital amplifier ICs in "class-T" as they called it. Seemed to have a better performance than class-D at a comparable price. Went bankrupt in 2007, but I think this had more to do with mismanagement than product quality.
I thought I heard a rumor than the technology was bought by Cirrus Logic, but they don't seem to have launched Tripath products yet, so I don't know if the purchase went through.
Does anyone know what the status of Tripath and class-T is?


texts:
The selected stepper motor not enough to make required torque.
So, I think its better to replace the stepper with higher torque.
But, new stepper motor has 2.8mH  phase inductance,Old one has 1.2mH.

How this inductance effect to the same stepper driver? Is there some advantages or disadvantages?


texts: Voltage Divider Equation with Load on output

texts:
I know how to calculate the resistance values for a voltage divider without a load on Vout.

I would like to know how I would like to calculate the resistance values of a pot (Example 500kΩ pot) used as voltage divider with a load on it.

With No Load

$$
Vo = V_i*\frac{R_2}{R_1+R_2}
$$
Is this the correct equation to use? With a load across Vout and 0V
$$
Vo = V_i*\frac{\frac{R_2*R_L}{R_2+R_L}}{R_1+\frac{R_2*R_L}{R_2+R_L}}
$$

If
$$
V_o=10V
$$
$$
V_i=12.2V
$$
$$
R_L=150,000Ω
$$
$$
R_1+\frac{R_2*R_L}{R_2+R_L}=500,000Ω
$$

Then
$$
10 = 12.2*\frac{\frac{R_2*150,000}{R_2+150,000}}{R_1+\frac{R_2*150,000}{R_2+150,000}}
$$

I input all of this in to Wolfram Alpha here and I get $$R_1=90163.9$$$$ R_2= -236593$$

How can $$R_2$$ be negative? Does that mean that it is not possible to get my desired out put with a 500kΩ pot?

ETA:
$$
10 = 12.2*\frac{\frac{R_2*150,000}{R_2+150,000}}{500000}
$$
$$
R_2 = -236593.059936909
$$

simulate this circuit – Schematic created using CircuitLab


texts: How do I size the coupling capacitance for a SEPIC converter?

texts:
The app notes I've seen for a SEPIC converter1 all tell me to size the coupling capacitor for ripple currents and voltages. I haven't seen one that tells me how to size the capacitance. Obviously there's some minimum; zero capacitance means no coupling, so the input has no effect on the output. To make the switching effects couple from input to output, we need enough capacitance to overwhelm any parasitic capacitances on the output side of the converter. Maybe 1000 pF should do that, I think, depending on what else is going on in the circuit. But the reference design I've inherited uses a 1 uF cap, which seems like it may be overkill for that purpose. Which makes me think there's more going on for sizing that capacitor than just overcoming parasitic capacitance.

How do I properly size the coupling capacitor in a SEPIC converter?

1 For example, this Texas Instruments AN-1484 Designing A SEPIC Converter.


texts: Linearization of Simulink nonlinear state space models with Linearize

texts:
States of the system in Simulink Conttrol Design are identified at the output of the integrator blocks accross the system.
If a model is already developed in a state space form, and specifically, integrators are already implemented in, for example, forward Euler form, how can one "inform" linearize command on what the states of the system are?
In simple words, how to use linearize for a high order dynamics system that does not contain any Matlab integrator block?


texts: Current limiter for NiMH battery charger

texts:
I am trying to learn about electronics by making my own MCU controlled battery charger for standard AA 1.2V NiMH and NiCd batteries. The supply voltage is 5V from a USB battery pack.

I did a lot of reading on http://batteryuniversity.com/, as well as studying Energizer and Panasonic battery charging guides. I now have a very crude working prototype which controls the current input into the battery by stepping down my 5V down by burning some energy through a transistor and a diode. I have expermentaly found the amount of voltage step down required for 700mA into the battery, but this is highly variable depending on my power supply (which is highly annoying).

Now that I have the proof-of-concept working, I'd like to do the power circuit right. Controlling the voltage can obviously be achieved better with a switching voltage regulator, except that I am not really looking to hold the voltage constant. What I really need is constant current (let's say 700mA), and the voltage can vary as needed.

I have no idea how to build this kind of circuit. Are there "current regulators" that I can buy just like voltage regulators? Is this something I can build by measuring the voltage drop on a sense current resistor?

I am looking for suggestions on how to solve this problem cheaply, as well as any relevant reading material.

Thanks!


texts:
Wire coils can be used to 'pick up' alternating magnetic fields as described by Faraday's law.  I want to do this in multiple axes around a single core.  How could I do this in practice at a reasonable cost?  I have seen 'transponder coils' that do this in a small package (e.g. Premo, Neosid, Coilcraft, Murata):

I realized that placing the core on a simple coil winding machine will not work after the first axis if the winding axis has to go through the bobbin:

Therefore, I am considering either making a rotatable "end cap" that the end of a simple coil winder can be pressed against, or possibly winding each axis on a single-axis bobbin and then transplanting to the multi-axial bobbin.  However, in the latter case I am skeptical that dimensions would match up well and that the coil would stay together.  (Assume 1000 turns of 32 AWG wire.)


texts: Altium doesn't show traces when interactively routing

texts:
When I try interactive routing, the traces don't show up until after I leave the interactive routing state. I've tried resetting desktop layouts, and showing all connections, but nothing I've seen works.

I'm running altium 13.3 in windows 7 in virtualbox (base os is Ubuntu 14.04)


texts: Why is retimer circuit provided for HDMI TX lines?

texts:
I am exploring a Zynq ultrascale+MPSoC design. While looking at the reference design of XCZU9FFVB1156 SOC evaluation board, in the HDMI interface there is a retimer IC in the transmitter side of Bank 128, which converts the HDMI signal to TMDS along and routed to HDMI output port.
But in the receiver side, no such signal enhancing or TMDS to HDMI circuit is used.
I have attached the snapshot of my observation from the evaluation board design for reference.
Why is there no retimer or similar circuit in the HDMI input port? Please can you clarify the concept.


texts: Crystal circuit works in breadboard but not in perfboard

texts:
I'm a beginner and I'm trying to build a digital clock. My clock generator looks like this:

circuit http://img189.imageshack.us/img189/855/tempgd.png

It works perfectly on the breadboard, where I can see the LED blinking at 2 Hz. However, when I try to solder it on the perfboard, it blinks much faster. I don't have a way to measure, but I'd say something like 10 Hz.

I tried to mount three times on the breadboard and three times on the perfboard, and always get the same result. I checked and rechecked the connections, and everything seems to be fine. I have no idea where the problem might be. What could be wrong?

EDIT

I tried replacing the two 15pF capacitor for two 22pF, but it didn't help. Unfortunately, I don't have access to a oscilloscope to see what's happening inside.

Here are the photos of the circuit. The first one is the component side.

photo1 http://imageshack.us/a/img405/5062/dsc07884v.jpg

The second one is the soldering side. Please excuse my bad soldering, I'm a beginner, and it's a little messy from all soldering/desoldering. However, I tested all connections and the connections are correct.

photo2 http://imageshack.us/a/img132/9470/dsc07885l.jpg

Additional question: I'm using a 10K resistor. I saw a similar circuit on the internet that uses a 220K resistor in its place. Could that be the problem?


texts: Block diagrams can be different and still works for the same system?

texts:
I am an telecommunications engineer who is working now as a programmer. At university we took a class on digital filters, Laplace transformation and working in the frequency and time domain. At the time, no one told us what is the practicals that we can do and benefit from the course as we've been working with Math all time.

After 2 years I read an artical that this course is an integral part of control system engineering and remembered that I loved the course and pass it with A+ grade. So I decided to start learning deep with it and make a project at the end and apply for jobs in this domain.

I bought Norman S. Nise book: Control System engineering 6th edition. I was afraid to not study it after seeing the 800 pages of the book.

Luckily I got the courage to start with the first chapter and fully understand it. It was about the design and analysis process. And the exercises was about building a block diagrams.

An exercise was about the following:

A temperature control system operates by sensing the difference between the thermostat setting and the actual temperature and then opening a valve of fuel with an amount proportional to the error (or difference).

The following image represent the author solution, compared to mine. Does mine correct ? And in block diagram, there is only one solution for a control system design ?

The solutions:

https://imgur.com/a/pgs4Ynb


texts:
Here is the circuit of pre-amplifier which makes the weakest signal compatible for power amplifier to take for further amplification.

I literally can't understand this circuit's working. Which class is this? And how it takes the weakest signal from microphone and making it good enough for the amplifier to take for further amplification? And why the signal from microphone is so weak?


texts: connecting a hp laptop charger adapter three wire output to a two wire cable

texts:
My laptop charger adapter broke and I a have this other old adaptor in the house. They both have the same voltage(19V) and 1.58A. The first adapter(The one that broke) has three wires (black, white, and red) going out which then connect to the laptop charger pin. The second adapter however, has three wires going out. I have read that an extra wire is used as some kind of a sensor. In another forum someone identified the sensor wire and left it out in the connection. What does the three wires represent each(which is neutral or positive)?

I simply need a easy fix for my charger. While you attempt to answer please note that I do not have a multimeter or any tool for checking current and voltage except for a tester screw driver and that Except for high school physics I do not know anything else in electricity. I also hope that this is the right place to ask this question.


texts: Can output current of buck current more then input current?

texts:
I want to power a bulb from solar panel(17V/.9A) but due to low resistace (2 Ohm)of load i have to reduce the input voltage to 5.5V @ 2.75A for max power.
I am using generic buck converter (not any mppt module)to lower voltage but as i studied buck converter has not more output current than input current. So is there any way to increase output current?

Some days ago i found that increasing input capacitance at buck converter can let you increase o/p current. Is it true?


texts: ARM Cortex-M4 VFMA (fused multiply-add) performance? 3, 2 or 1 clock? Forwarding?

texts:
I am working on some performance-critical DSP code destined to run on an ARM Cortex-M4. One particular section of the code (a sinc interpolation function) is dense with multiply-accumulate operations and I am trying to ensure that performance is as good as possible so we can clock the MCU slower and save power.
Now, I have inspected the code emitted by arm-none-gcc-eabi for my interpolation function and it was not performant enough, so I have unrolled and rewritten the inner loop in assembly to use a string of VFMA fused multiply-add instructions like so:
VFMA.F32  S8, S24, S16
VFMA.F32  S8, S25, S17
VFMA.F32  S8, S26, S18
VFMA.F32  S8, S27, S19
VFMA.F32  S8, S28, S20
VFMA.F32  S8, S29, S21
VFMA.F32  S8, S30, S22
VFMA.F32  S8, S31, S23

To my surprise, however, the Cortex-M4 Technical Reference Manual says something strange about the performance of the VFMA instruction. While properly scheduled VADD and VMUL operations each take a single clock cycle, the CM4 TRM says that VFMA takes three clock cycles! On that basis, one would conclude that the fastest unrolled loop should consist of interleaved VMUL and VADD instructions, rather than half as many VFMA instructions.
There has been some discussion online about this issue but information is sparse as well as inconsistent. Some say that VFMA is aimed at code size reduction rather than speed improvement and that 3 cycles is normal. Others report observing a 2-clock execution time in a long unrolled loop, contrary to the CM4 TRM. One copy of the TRM says that when multiple VFMA operations are executed sequentially, the results are forwarded and the execution time is only 1 clock cycle. Some say that many of the slower VFMA measurements posted online suffer from additional slowdown due to flash wait states or improper configuration of the MCU's prefetch engine.
Can anyone shed some light on what factors influence the timing of VFMA on the Cortex-M4?


texts: Detect if the load is present on this circuit

texts:
Is there a way to detect if the load is conected on the circuit above?
(The other load should be connected to the F Pad, sorry for the mistake).


texts: Is safety certification required for an electronic board that interfaces to LED driver?

texts: LED drivers come with safety certification. If a company wants to build an electronic board to control the LED driver (say, on and off), does it need to be safety certified as well?


texts: Reducing current consumption in deep sleep mode

texts:
This is in relation to the question I asked about deep sleep mode. I'm using PIC18F and it says in the datasheet that in deep sleep it would consume only few nA. But when I configured for deep sleep mode with port set as input, it shows 50uA, which is far more consuming than the limit in data sheet.

It says (under Core Features, page 3):

  Power Management with nanoWatt XLP

  Deep Sleep mode: CPU off, Peripherals off, Currents Down to 13 nA and 850 nA with RTCC

  Able to wake-up on external triggers, programmable WDT or RTCC alarm
  Ultra Low-Power Wake-up (ULPWU)

  Sleep mode: CPU off, Peripherals off, SRAM on, Fast Wake-up, Currents Down to 105 nA Typical
  Idle: CPU off, Peripherals on, Currents Down to 2.3 μA Typical
  Run: CPU on, Peripherals on, Currents Down to 6.2 μA Typical
  Timer1 Oscillator w/RTCC: 1 μA, 32 kHz Typical
  Watchdog Timer: 0.8 μA, 2V Typical

Why is it consuming much more current than specified in datasheet?

And what all things should I be careful of when using deep sleep mode? I have found one similar question.

I would like to have input from those who have played with deep sleep mode in detail. The controller is PIC18F46J53.


texts:
I want to build a simple edge detector that triggers an interrupt once the power adapter is hot-plugged.
Therefor IN will be around 18V and on the output I need 1V8 logic.

The generated pulse does not need to be accurate but should be around 50-100ms long.

I read that a simple RC-circuit can archive this and from a bit of experimenting in circitlab I found following values to work.
However two questions:

The BUF signal becomes negative on falling edges. Will this be a problem for the buffer IC? And how can I avoid this?
What do I have to look for when selecting a part for the NOT gate. I read about schmitt-triggers, do I needs this? E.g. will something like SN74LVC2G14 work?


texts: Which signals does a 3-pin mouse switch allow to differentiate?

texts:
I am wondering, which signals does a 3-pin mouse switch send. Does it only send

"signalled", and
"non-signalled"

or is it able to differentiate between 3 states:

"clicked signalled",
"unclicked signalled", and
"neither clicked nor unclicked signalled"

Here is a diagram of such an (Omron) switch:

The 3 pins are labelled "COM TERMINAL", "NO TERMINAL", and "DUMMY TERMINAL". What are their purposes? Can they be used to differentiate between the 3 states mentioned above, or only to differentiate between the 2 states mentioned at the beginning?

Here is some further explaination from Omron's website about some of the terms, but I'm afraid that I am unable to understand it: Basic Switch: NO, NC and COM Contact Terminal

To illustrate once more what I am trying to understand: The following image (which I've borrowed from a website and modified) shows an Omron switch in the unsignalled/unclicked state (The metal spring makes contact with the connector at the position indicated by the red line). When it is signalled/clicked state, the metal spring makes contact with a different connector at the position indicated by the green line. The metal spring can also be in between the two connectors and not connect to any of them, but float in mid-air (indicated by the dashed yellow line).

The question is: Can the switch differentiate between all three of these states, and can the user of the switch read out those three different states, or is it only possible to differentiate between 2 states?

I'd ask you to explain with easy terminology, since my background is almost purely software engineering. I have only very little electrical engineering knowledge. Thank you!

Update:

Thanks to the first answer to this question by Andy aka, I am able to state more precisely, what I really want to know:

Does such a mouse switch (or this Omron switch in particular) support short-circuiting two separate circuits so that it allows differentiating between whether the metal spring is currently making contact to the connector at the red line (i.e. short-circuiting the 'normally closed' circuit) or whether the metal spring is currently making contact to the connector at the green line (i.e. short-circuiting the 'normally open' circuit)?

If it did support short-circuiting two separate circuits, a user of the switch could differentiate between 3 different states (short-circuiting red, short-circuiting green, not short-circuiting any => yellow).

If it didn't support short-circuiting two separate circuits, it does only provide two differentiable states, but which ones? Is it
1) short-circuiting red and not short-circuiting red; or is it
2) short-circuiting green and not short-circuiting green?


texts: Raw RGB from CMOS image sensor to grayscale conversion

texts:
I am trying to produce an image with OV7740 color image sensor. As far as I know, the sensor is configured by default to provide 10bit parallel RAW RGB data (due to an on-chip Bayer filter). How should this data be processed/scaled in order to obtain a grayscale image data?

EDIT:
I guess, the discussion of my issue can be found here.


texts: How to Power On Texas Instruments Tiva launchpad?

texts:
I am attempting to power on a Texas Instruments Tiva TM4C123GH6PM with an external power supplied by the VCC pin from a generic ESC.

In the board, there is a non-soldered pin named VBUS which I wonder is available for this purpose. So the question is this point: Can I connect my VCC/GND pins from the ESC into the Tiva so the board will work out? I did not find it very clear in Tiva's datasheet.


texts: I have an 8s7p Li-ion battery with a fully charged voltage of 29 V, a nominal voltage of 25.9V and capacity of roughly 20.5 Ah. This battery was used to run a brushed DC motor (rated no-load current 0.8 A) using a motor driver circuit(IBT-2) (which I assume helps prevent back EMF charging of the motor), and then stored (not at storage voltage owing to the fact that the battery is to be used occasionally every 3-4 days or so). The battery is now showing an open circuit voltage of 30.3 V. Is this possible? What steps should I take to amend this and prevent this in the future? Thank you.


texts:
I have a lamp, with the usual built-in switch, which is powered via a wall-mounted socket. The socket is switched itself with a normal wall switch. So, both switches operate in series, the lamp lights only if both switches are on.

I am looking for a way to flexibly switch the lamp on and off: from the lamp switch regardless of the wall switch and vice versa.

I am thinking about replacing both switches with push-buttons which would power the wires, execept one button is pressed. Then I would need some device the lamp which is able to detect a button push (voltage drop), to survive the short power outage while in operation and to actually switch the lamp.

Any ideas how such a device could look like?

I have rather limited space in the lamp body for installing additional components. I am in Europe with 230V AC. I have no means of adding another wire between the two switches due to in-wall mounting of the cable between socket and wall switch.

I am prepared to build something myself, just don't know in which direction to think.


texts: How to prevent design compilation if generics are not acceptable?

texts:
For a UART that takes baud as generic, I want to prevent design compilation in modelsim and quartus ii if the baud rate is not in specific range. The baud rate is passed as a generic.

One option is to enum for baud rate so this problem does not arise. But provided that I use the natural type, how do I prevent design compilation using assert if the baud rate is wrong?

I could write a function that will determine if baud rate is correct.


texts: Why does the voltage of a lead-acid battery drop with load?

texts:
My solar power system contains a lead-acid battery but as soon as I use the inverter to power some load, the voltage drops instantly by 1 volt.

Why does this happen? And is it proportional to the load (bigger load = bigger voltage drop)?


texts: How can we preserve Printed Circuit Boards without causing any damage to the boards in any conditions (air, cold, heat) while we are not using them for a long time?


texts: Why can a MOSFET be used as an amplifier?

texts:
This is a fundamental question which I am struggling to answer after familiarizing myself with the MOSFET and analyzing different circuits containing MOSFETS.

In terms of GDS channels, what enables a MOSFET to be used as an amplifier?

I know that

Transconductance relates the output current to input voltage.
Voltage gain of a MOSFET is directly proportional to the transconductance and to the value of the drain resistor.
Gradually increasing the positive gate-source voltage VGS, the field effect begins to enhance the channel regions conductivity and there becomes a point where the channel starts to to conduct.
We can control how the MOSFET operates by “enhancing” its conductive channel between the source and drain regions.

However, I am unable to form a logical analysis as to what really goes on in the Gate, Drain and Source channels to enable a MOSFET to be used as an amplifier.


texts: Is it possible to guess a reasonable Kp and Ki based on motor parameters for speed PI control

texts:
Regarding motor speed PI control, there are tons of articles about it. However, I searched many and noticed that most of them just tell you how to tune Kp and Ki following different methods. But they seldom tell you how to get the very first Kp guess, i.e., for my motor, should it start with 0.1, 0.01, or 0.001?

Since we already have all the detailed parameters of the motor, back-emf constant, torque constant, inertia, rpm/v, speed range, PWM duty cycle range of the inverter, etc., and the controller spec such as sampling time, max acceleration, etc., what I want to understand is that, can we estimate at least Kp based on those parameters and give a good guess of it that could be close to the optimal value as the start point for tuning?

Edited
To make it clearer, I added the picture of motor and its transfer function of voltage vs speed. (pictures from http://ctms.engin.umich.edu/CTMS/index.php?example=MotorPosition&section=SystemModeling)


texts:
I bought an LED bulb, W5W, to replace the position lights, number plate lights and maybe the interior reading lamps. However they stay dimly lit when they're off.

I am thinking that the current is already flowing through the wires when the lights are off and the key is out.

So the circuit is closed, but with an incandescent lamp, not enough current exists to heat the coil, but with LEDs there is enough of it to light it.

Some people advise to put a resistor before the bulb, to fix this.

Will these LEDs drain the battery if they stay partially lit (i dont mind them staying like this)? If I add a resistor, won't that one drain the battery too?


texts: Smallest PIC which the TCP/IP stack can be implemented

texts: What is the smallest (size) PIC with internal oscillator available which the TCP/IP stack can be implemented (and used) successfully? Also, what is the smallest (size) PIC with internal oscillator and Ethernet stack implemented?


texts: How to get desired current on output of relay's module

texts:
I'm building automatic garden watering system using

Arduino Uno
5V relay module - this one https://www.amazon.co.uk/2-channel-trigger-module-JQC-3FF-S-Z-RBTMKR/dp/B01NAJ67ML, here are technical details https://www.generationrobots.com/media/JQC-3FF-v1.pdf
Solenoid valve, I bought this one https://www.banggood.com/12-inch-DC-12V-250mA-Electric-Solenoid-Valve-Flow-Switch-p-91741.html?rmmds=myorder&cur_warehouse=CN

First of all, relay module contains in itself transistor and kick back diode included, so no need for those.
I'm concerned about the current passed to valve (I'm afraid of burning it :)), so I have a few questions:

On a page I posted above for valve, it said current is 250 mA. However, on a valve I got its written 12V 4.8 W. How come that current is 250 mA? We know that I = P / u = 3.8 /12 = ~ 400 mA

Now, I know that valve and relay should have resistance, but I could not find it. In a page I posted above for relay module it says coil resistance if 70 ohm at 5 A. Does this mean that current that comes to my valve will be 12V / 70ohm = ~180 mA  ?

3 I connected diode in place of valve Arduino - Relay module -> 1k resistor -> diode
However, when I measure  current with multimeter before the resistor (output from relay), it is around 50 mA.
I found  in Relay datasheet (posted above) that its coil power is 0.36 W. Does it means max output current from it is 0.36W/5V =  ~ 72 mA ?
Or do I divide relay coil power with 12 V since its the external voltage I'm providing to solenoid valve using Relay?
In a case 72 mA is maximum, I would still need to use a transistor with proper resistor on base to get desired current for solenoid valve...
Thanks in  advance


texts: Matching impedance network for an LC ladder network

texts:
Let's say I have a 5 stage L-C ladder network with L= 4.7 micro Henry and C= 60 pF. The characteristic impedance of the network becomes 280 ohms (square root(L/C)). However, from circuit analysis, the impedance of the circuit becomes j*561 ohms at 25 MHz. If I want to drive a load of about 50 ohms which will be placed at the end of the L-C ladder network what impedance of the ladder network will come into consideration for matching? Will it be 280 ohms or j*561 ohms for maximum power transfer? The source is a 50 ohm AC source. I want to pass a signal of about 9 MHz through this ladder network.

Thanks in advance.


texts: Why do people waste time using a SPICE .NOISE analysis for circuits with resistances with significant excess noise?

texts:
Refer to Resistor Current Noise Measurement

Excess noise in a resistor is the electrical noise which is in excess of the value predicted by the well-known Johnsson-Nyquist-Thermal noise formula. Excess noise is created as a voltage impressed across a resistor causes electrons to flow through the resistive material.

In some types of resistors, the increase in noise is so significant that the circuit is useless.

Even in "very good" resistors the voltage noise density can increase by 50% over the Johnson-Nyquist-Thermal formula when 1V is impressed across the resistor. More over, the voltage noise density spectrum takes on flicker (1/f) shape as the DC voltage across the resistor is increased.

To the best of my knowledge, there is no SPICE variant with a .NOISE analysis which accounts for excess noise. Is this true?


texts: While going through some datasheets of  tdc's (time to digital converter ) there is this parameter which is called 'measurement range', could someone please explain what exactly it is? If the measurement range of a certain tdc state "0 to 40 us", does this mean the measurement range is inclusive of 'ns' too?


texts:
I have put together a circuit with TPS2115A, it's feeding a camera from two 5V 20Ah (USB) power banks. The IC (TPS2115A) is used in automatic mode, i.e. whichever supply is higher is sourcing current, hysteresis is between 0.1-0.2V.
I added two LEDs on the inputs so I would know if the batteries are alive but also to keep them alive, since I knew the power banks shut down after 30min if not used.
Resistors used in series are 220Ohm and the current through each LED is about 13-14mA.
I set everything up yesterday and today the camera was still on and both LEDs are on, indicating both power banks are still on. Was pleased to see it worked and I left everything on, letting the power banks drain themselves and see how it behaves.

Meanwhile I was thinking that maybe I could use larger resistors to the LEDs and minimize current consumption. I have a third power bank that is identical, so I started to experiment what current draw is needed to keep it alive. Started with 470Ohm and the current was appr. 7mA, after 30min. the power bank shut down. Ok, so I tried a 220Ohm which I was sure would keep it alive since it works in circuit feeding my camera, but no, to my surprise the power bank shut down after 30min. I have tried several times.

Since my camera setup with power banks is in a garage about 20min. drive from home, I currently do not have access to it, but I have started to try to figure out why the power banks are alive, or that in fact only one is alive and the LEDs are fooling me.
I checked the LEDs and they are bidirectional, green when connected as normal and red when polarity is reversed, however, they are giving off green light, I'm wondering if putting these LEDs on the inputs can mess with ICs intended operation. What do you think, please look at the schematic below:

Thank you.

Edit: I tried to figure out what was going on yesterday. Turned out that the both power banks were feeding current to the camera. Total current appr. 400mA, one power bank sourced 330mA, and the other 70mA (LEDs were disconnected). It (the IC) used IN1 (input 1) when camera was off, but as soon the camera was switched on and thus a larger current needed, the IC switched to using IN2.
I had a small LED connected to the STAT input to see which input was connected to the output.

There was some horrible ripple and noise on both input and output when both power banks where connected and OUT was connected to IN2, if I forced the IC to use IN1, through the logic inputs, the ripple disappeared. The same happened when using only one power bank, no ripple.

See pictures below. I tried every combination but I couldn't get it to function properly so I gave up on it. The IC is in a TSSOP-8 package which I hand-soldered to a DIP-adapter, it's possible it got damaged, although I'm careful. I'm now going to use an evaluation board of the LTC4370, which shares and balances the current/load between two sources, which conveniently also keeps the power banks alive. This one.

Oscilloscope inputs are AC coupled in pictures. The first one shows one input (yellow) and output (blue) when IN1 (forcing it through logic) connected to OUT or whenever only one power bank is connected, camera is on in both pictures. The other picture shows the default mode when IC is in automatic mode; it selects IN2 as soon the camera is turned on. Any idea what could cause these ripples? I used heavy filtering at the end of the evening.

I should add that a small current was being fed to a small peripheral device through a 1W DC/DC-converter, which was the primary suspect, it only draws about 30mA and uses an input LC-filter. Naturally, I had it disconnected in the beginning, but it made absolutely no difference.


texts:
I created an Eagle part that has several holes to solder 0.1" pitched break away male headers to, such as the one below.

However the pad has a hole thats too narrow for the header! What drill size should be used? I used the default of 0.03149606


texts: General questions on Timers [STM32 & CubeMx]

texts:
I'm learning by myself how to handle timers in CubeMx. I've got some simple questions.

First question:

In the clock tree, I see APB1/APB2 peripheral and timer clocks bus frequencies. I thought that when I set a prescaler, the APBx timer clock frequency is the one divided by the prescaler, but actually is the APBx peripheral clock frequency.

What's the real difference?

Second question:

I've set timer 2 in PWM input mode to measure the period of an input signal. So, in the interrupt callback I can say:

period = HAL_TIM_ReadCapturedValue(&htim1, TIM_CHANNEL_2);

Does this say the period in milliseconds? Or is this the right way to ask for the period?

Third question:

I read in an app note:

The TIMxCLK frequency is set to 72 MHz, the prescaler is 0x0 so the TIM2 counter clock frequency is 72 MHz. So the minimum frequency value to measure is 1100 Hz.

How do I calculate that minimun frequency?

When setting the PWM input mode or input capture mode to measure an external signal, how do I choose the prescaler and counter period effectively in CubeMx according to my frequencies range?


texts: Use of a bulk capacitor with a 5V MCU controlled motor circuit

texts:
I have a circuit as such that will ultimately be used for a remote controlled race car:

I have a 5V power regulator (SMPS) to take 4 AA batteries to 5V. With this, I will power a Raspberry Pi, a DC brush motor, and a Servomotor. The construction of this circuit will be pretty modular, as the regulator, the Pi, the H Bridge circuit are all their own self contained components, and of course plus two motors - I will primarily be connecting leads together.

The race car will ultimately weigh 2 - 3 pounds, no more than 5.

My questions are:

If I can count on my power regulator to have a filter capacitor to keep the voltage ripple to a minimum, do I need a bulk capacitor additionally for a 5V circuit?
Do I gain advantage in having one bulk capacitor adjacent to each motor? Or would one be sufficient?
Granted that this is a 5V circuit, how do I choose the capacitance for my bulk capacitor(s)?


texts: LM2776 is it normal to have the oscillations in "bursts"

texts:
Is it normal LM2776 to oscillate in "bursts":

The frequency of the oscillation is OK, but they come in the 8 oscillation bursts every ~9us.

Is it normal? The board design and the schematic is exactly the same as in the DS.

The LM2776 is giving me the correct negative voltage and I draw about 50mA from it


texts:
I have a device (laser diode), rectangular, with pin rows of 7 pins in horizontal rows, spacing 2.54 mm, on the longer sides. Now I am looking for a mounting possibility to make mounting for the diode as easy as possible, while retaining the possibility of removing it without damage. Is there something I can use for mounting the device on a PCB with the properties mentioned above?

Image of the device:


texts: Please tell me the use of high-side floating supply voltage (VB) and high-side floating supply offset voltage (VS) in the IR2101 (datasheet) driver circuit and also the use of capacitor between them.


texts:
I have attached the image of a theoretical question with its explanation given in my book. can anyone please explain this ?

I am not able to start from anywhere so I can't show my work. I am posting this to genuinely learn about faults.


texts:
I am trying to connect STM8L052C6T6 microcontroller using SWIM interface (STM8 port) on ST-Link/V2 programmer and it just doesn't connect.

Power comes from outside power source (target is powered) because doc says Pin1 of the programmer is just for getting voltage reference.

Could someone please point what kind of settings should be inside ST-Link Utility ?

I have tried all combinations of Mode and Reset mode, cannot figure what I am skipping?


texts: Since the slave addresses are 7 bits long, why is it that the number of slaves can be only 127? Is one of the addresses reserved for some special purpose?


texts: I want to export an assembled PCB to the USA. Is there any label, for example FCC, that has to be on it in order to pass the customs?


texts: How to get out of edit mode in CircuitMaker?

texts:
When I edit a PCB in CircuitMaker, I start laying out tracks on both upper and bottom layer.
So far so good. Sometimes, I want to stop, and press Escape. Mostly this works, sometimes, I have to press twice, or three times.

When selecting an item, sometimes trace mode is still enabled, sometimes not.

But I had already twice in a few hours, that I cannot get out of a mode that keeps creating tracks. I cannot get even out of the black screen (see below). I cannot reach the menu, the left pane, or the window below. It just keeps scrolling.

Actually, as I'm writing this (using Alt-Tab I had to change application), it is still scrolling, and it will do so until I with TaskManager kill the application and lose (again) some work.

How can I get out of edit mode when the Escape key does not work?

(If I keep getting problems with CircuitMaker, my next question might be: how to convert a CircuitMaker to KiCad?.)


texts: Deriving 5 V and 3.3 V from 12 V using single IC

texts:
I am making a college project which requires me to use a 5 V LCD display and a 3.3 V microcontroller.

I am using a 12 V power adapter to power to complete circuit.

I am using LM7805 and LM3940 to generate 5 V, and 3.3V, respectively. Is there any IC that takes in 12 V and spits out 2 or more voltage levels like 3.3 V, 5 V, 9 V etc?

If such ICs exist then what is the IC classified as? (like 7805 is a linear voltage regulator).

The IC I require should do something like this:-


texts: How to connect rows and columns in a keyboard matrix

texts:
I want to build a keyboard from scratch, so I started by designing the schematics.

I have found several ones on the web in which the switch - diode direction is connected from row to column, and other in which the switch - diode direction is connected from column to row.

I think that it works fine with both methods, I just wonder if there is a special advantage for the first or the second way.

By the way, for what it matters, I am going to use a Teensy 3.2 M/C with the assorted keyboard libraries. The keyboard columns should be approx. 15 and the rows should be 7.


texts: Why is a broken ground plane not as effective as an unbroken one?

texts:
I did a two layer board a few weeks ago which had a dedicated ground plane. I routed 90% of the signals on the top layer and for the last 10% I had to route them through the bottom (ground) plane.

I was told that, generally, it's a bad practice to have a broken ground plane as it is not as effective as a solid one. Why is this so?

Does this also apply to power planes? Should I only route signals through my Vcc plane as a last resort? What do I sacrifice if I do so?


texts: Circuit to tune multicolor LED colors with a variable knob (rheostat?)

texts:
I am looking at getting some multicolor LEDs, which have Red Green and Blue inside of them. I'm doing this for space saving, rather than using 3 different LEDs--I am using just one.

What I want to do is to use a multicolor bulb to produce all sorts of colors, mixing the channels (if you call it that) so I can the full color rainbow. I need to be able to use a single rheostat to do that, rather than using 3 independently so I can twist just one to change the colors up and down. If I need to use a small transistor, that's ok (I'd prefer to keep it simpler if possible) but I need the ability to use a variable controller knob to tune the colors.

I can't seem to find any circuit design that can do this 1) for a multicolor LED, and especially 2) for a variable control knob in it. Sure, I can do this with an Arduino but I'm trying to use this in way more simply.

I'm not set on using PWM or not using it, I just want the ability to set it up and be able to 'tune' it with a knob. If I can get away without using a transistor or having to program it, that would be ideal.

Thanks!

G


texts:
I have a microcontroller with an active low reset pin. This pin is connected to a timer that periodically triggers a low edge and resets the microcontroller.
What would be the best circuit that would allow me to also manually trigger the reset pin through an external circuit while the pin is connected to the timer? Shorting the two together would obviously not work.


texts: Where is the Ground in a Simple Electronic Circuit

texts: I am rather new to electronics, and I am reading up on the topic. I came across the term ground. I get the large scale applications like the wires leading into the ground from power lines, but how is ground applied to smaller, simpler circuits? Imagine a circuit with a battery and an LED. Wires lead out of the positive and negative side of the battery and connect to the points on the LED. Where would the ground be on that circuit?


texts: LED lighting with incandescent spectrum?

texts:
Is there any reason why they don't produce LED lights with a spectrum closely matching that of an incandescent bulb. Incandescent bulbs produce a nice warm light, while LEDs (even warm white ones) produce a kind of harsh light.

I think it should be possible to mix several LED dies (maybe 5-10) together to build up a spectrum closely matching an incandescent spectrum.


texts: Automatic charging and power switch between USB and LiPo battery

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I am designing a board which can be powered over USB and includes the use of a LiPo battery along with its charger circuit. When the USB is connected, it charges the battery as well as powers the microcontroller. When the USB is unplugged, the microcontroller is powered by the battery.

I was studying the Adafruit Feather boards as they incorporate this feature into their designs. They have implemented this in a couple different ways. The Feather 328P had a MOSFET and a diode such that when VBUS was present, it will override VBAT via the diode and when it wasn't power from the battery would flow through the MOSFET body diode:

Then there is this variant, as present in the Feather 32u4 or the M0 boards where they put the diode across VBUS and VBAT with the anode on VBAT, and skip the MOSFET altogether:

They both perform the same function but in seemingly different ways. What is the difference in the two implementations and what are the considerations for choosing one over the other?


texts: How do I tell whether if it is my oscilloscope or circuit catching mains 50 Hz?

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I see that my oscilloscope has some 50 Hz when the probe only is connected to the oscilloscope, which is normal. But I want to know if my circuit is catching the 50 Hz main from e.g. the power supply. Is there any good way of doing this?
I have a Siglent SDS 1052DL+ oscilloscope and I am measuring the output of a load cell connected to a board.
Edit: Measurements using Jerry Coffins and EforDogsFan methods.
Probe tip connected to probe GND: Showing no significant 50 Hz.

Probe tip connected to probe GND and PCB GND: Showing no significant 50 Hz. Rather some 330 kHz noise from a switching voltage regulator on the board.

Probe tip and probe GND not connected (open): Picking up significant 50 Hz noise, obviously changing in amplitude depending on how the probe wire is put on the table.

Measuring output of load cell: Showing significant 50 Hz noise compared to the DC voltage output of the load cell.

Measuring output of load cell with extra weight compared to previous measurement: Just to show the DC offset when adding significant weight.


texts: How to design Aluminum Clad PCB panel - how is the panel separated after assembly

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This might sound trivial, but I only have experience with standard PCBs. I need to design LED tube PCB and is only 20mm wide, so there will be at least 10 pieces next to each other on one panel.
My question is, how are these made to be separated? The tubes I took apart have all boards with smooth edges. The assembly house warned me, that it is not the same to separate these as it is with standard PCBs.
Maybe I will need a special equipment for this?


texts: Centroid from calculated root locus is different to the one from MATLAB

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Hi all hope someone can help me here.

My problem involves the transfer function

 G(s)=(s+32.8)/((s+2.8)(s+5)(s+27.8) )

As far as im concerned the centroid is calculated using

σ_a= (Ʃpoles - Ʃzeros) / (# of poles - # of zeros)

From my calculations

σ_a=((-2.8+-5+-27.8)-(-32.8))/(3-1)=-1.4

However when i input the following code into MATLAB the solution from the graph shown the centroid will be -1.55

s=tf('s');
G=(s+32.8)/((s+2.8)*(s+5)*(s+27.8));
rlocus(G)

Im not 100% whats the issue but if im doing something wrong could someone please correct me and help me understand.

Thank you for taking your time out to read this.


texts: How to implement "NO solder paste" pad in Altium

texts: I'm designing a footprint for J-Link 10-pin Needle Adapter. The pads need "no solder paste". I've looked around all configurations for the pad but didn't find a method to remove solder paste, so my question is how to design this kind of "no solder paste" pad in Altium efficiently?


texts: Does an electrocardiography recorder put current/voltage on its electrodes?

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(I do hope my question is not off-topic)

Currently learning about ECG recorders (Our 7-months old daughter has to have one during her sleep), I wonder whether this is a pure "passive" measuring device (like a multimeter) or not.

I do think I understood that it measures heart activity by comparing potential differences between 2 or more body-connected electrodes.

But I did not understand whether this works purely by getting signals from the heart and processing them or whether the device actively sends some signals through the electrodes and measures what comes back.

So my question is:

Does an ECG recorder send signals trough the electrodes or not?