texts:
I am making a PCB where I want to have some polygons directly connect to all the components within them, and some to only relief connect. Normally this isn't an issue as I can just set up some design rules.
The problem is that in this specific case the polygons have the same net, so I can't do it by net or by net class. I found one rule called InNamedPolygon which would make sense to use, but when I set up rules to do it, nothing happens.
I know this is specifically the InNamedPolygon, because I have other nets specified in the same rule, and these all connect the way I would expect them to.
TLDR: Is there a way to make a rule that only applies to a part of a net (that happens to be in a polygon), and what does InNamedPolygon do?
I have attached an image of my current rules:

(I also have a lower priority rule that sets all polygon connections to relief and vias to direct so that other polygons have the normal relief connect)
The weirdest part is if I hit the Test Queries button, it highlights all the polygons I want to affect, but only applies the rule to the net class (IsSolidPour) and not the other specified polygons.


texts:
In the paper "The study on electromagnetic compatibility of DC electric motor in HAPS" there is a description for a DC motor model structure :

My problem is with imaging this model as I can't understand, and therefore, imagine this model, specifically the louvers part as it is not illustrated in the figure. Someone, please provide some pictures to illustrate this model. Thanks in advance.


texts: Powering many external 3.5" HDDs (USB) by an ATX PSU

texts:
I have many external USB disks like this one, that I would like to power from a single dedicated ATX PSU, instead of one 12V power adapter per disk. Because each power adapter would take one power outlet, and if we have say 10 disks, that's 10 power outlets required, and it begins to be ridiculous.
The PSU would be dedicated to power the disks, and started using the paperclip trick.
Each external disk is sold with a power adapter outputting 12V 1.5A 18W.
And the end of the 12V power cable looks like this:

My idea would be to cut that cable (which itself includes 2 cables), and connect each of the 2 inner cables somewhere on the PSU connectors.
The questions I have:

How to connect this twin-cable cut from the power adapter, to the connectors provided by the PSU?
By reading the PSU power details (sticker on it), can I get an estimate of the maximum number of disks that can be powered this way?

This is the sticker with the power details:


texts:
Big picture: I want to control a LUXdrive 3023 BuckPuck LED driver (3023-D-E-1000) from a Particle Photon (essentially an ARM Cortex M3 microcontroller). The MCU runs at 3.3V. I have tried a few things but fail to get it to work.

This seems like a very trivial problem to me but even here my very basic EE knowledge seems to insufficient.

The LED driver has a control pin where a voltage of 0-5V can be applied to adjust the constant current the driver provides. At 0V it outputs 1A and at 5V it outputs nothing. The 5V can be taken from the driver's own reference pin or supplied externally, in which case a common ground between that external source and the driver's LED ground pin has to be established. According to the docs, the control pin draws less than 5mA.

On the microcontroller side I have a 3.3V PWM output at 500 Hz. The idea is to dim the LEDs by brining the PWM signal to the driver's control pin and essentially very quickly alternate between current and no current output; I could also dim the LEDs by using the microcontroller's DAC to vary the voltage at the driver's control pin, which would cause it to vary the current. But I have read somewhere that LEDs are happier with being run at their designed current rating and insteads switched on/off for dimming purposes.

Anyway, the question is how to get from the MCU's 3.3V PWM signal to the 5V needed for the driver's control pin.

What I have tried so far:

Switch the driver's reference/control pin connection with a FET
Using a 2N7000 FET where the MCU's PWM output pin is connected to the gate pin, the driver's 5V reference pin to the drain pin, and the driver's control pin to the source pin.

simulate this circuit – Schematic created using CircuitLab

Nothing was being switched though. I am not sure whether I was not able to open the 2N7000's gate with the 3.3V or whether there is a conceptual problem here.

Bring the 3.3V PWM signal to 5V with an op amp
I tried to increase the 3.3V signal to 5V with a LM358 op amp I had lying around. I set the gain to 1.5 with a pair of 330k Ohm and 220k Ohm resistors (giving the ratio 330k/220k = 1.5).

While this dimmed the LEDs, I was not able to fully switch them off, i.e. providing a full 5V at the driver's control pin.

Any tips or recommendations?


texts: Need help understanding a power circuit (caps and diodes)

texts:
I'm trying to repair an old electric piano (Baldwin Piano Pro EP101) and I've gotten advice to check out the filter caps in the power circuit. I've metered out the voltages and I found power where I didn't expect it. Please see image:

Power from transformer coming in the top. Pins "I" and "J" are ground on the bottom. I've mirrored the board so the traces match up with the components on the top side.

Why do I find voltage on the (-) side of the black capacitor?
Why is the (+) of the black capacitor going to ground?
I think both of these capacitors are in series, but why is there ground in the middle of the two caps?
Does it mean I have power coming in through the "M" pin at that bottom that shouldn't be? Or maybe one of the diodes at D9 and D10 (2nd and 3rd from the left) are bad and letting the power go the wrong way?

Am I on the right track? Should I just start pulling parts and testing them out of circuit? If you're interested in the overall problem, see the short youtube video here: Baldwin Piano Pro - Very loud noises

Edit: Thanks for the feedback.Larger picture and my attempt of a diagram. Surprised to see AC and DC volts when I measured. Not sure what that is about.

simulate this circuit – Schematic created using CircuitLab


texts: Calculating forced response in RC circuit

texts:
In one my assignment questions, I need to find voltage across a capacitor. This is the diagram given:

And the conditions given are:
1- Switches A and B are in perfect sync, and when A opens, B closes and vice versa. Also their positions change every 30 ms.
2- Initially switch A is open. Assume steady state is achieved
And the question is to find voltage across capacitor at time instances:

t=0+ and 0-
t=50ms+ and 50ms-
60 ms

So considering the open switch and steady state condition of capacitor (acts as open circuit). I reduced the circuit to this:

The voltage across capacitor will be same as voltage across the 7 ohm resistor.
Applying current division and also taking into consideration the 3A current through the 7 ohm resistor, I got voltage across the resistor as approx 23.205 Volts.
Also as this is a forced response, the voltage across capacitor will be Vc = Vo - Voe^(-t/RC)
So at t=0+ and 0-, i.e steady state Vc = Vo = 23.205 volts.
But I am unable solve for the other parts i.e 50ms and 60ms as I am not sure how to take into account the position change in both the switches. How do I go about it ?


texts: Timing characteristics serial- & parallel input adressing

texts:
Hello I am looking on some analog and digital multiplexers that have high supply voltage along with high amounts of channels and I've found some that are programmable either serially or parallely and I am wondering how I should interpret the timing characteristics in the datasheet.

So for example lets look at these two multiplexer circuits from Analog Devices and Intersil respectively, AD75019 and CD22M3494.

The data load time of the AD75019 is 52µs since the max serial clock speed is 5MHz and 256 bits need to be loaded in order to program it.

On the CD22M3494 however there isn't any load time parameter since it is programmed parallely, so the parameter that I should compare the AD75019 to is what?

I've looked at some other multiplexers that are programmed parallely as well and some of them have a parameter called "Switching frequency" which I would assume is the one parameter that I should look at in this particular case, but on the CD22M3494 however I can't seem to find any parameter for this.

Can anyone help me and point me in the right direction?


texts: Is there any 'switching IC' to replace 'transistor switch' for switching the 12 volts LED array?

texts:
I have created a 12 volts LED array, and used a MOSFET to switch this panel. Do we have any switching IC which can switch it instead?
I will have five LED panels similar like this to switch at the end. I thought an  IC may reduce overall circuit complexity.

LED Panel voltage: 12 volts
LED Panel current: 250 mA
Switching MCU: 5 V AVR


texts: Driving high and low inputs of a MOSFET driver with a single PWM signal

texts:
(A typical circuit from FAN7390 datasheet.)

I have high-side and low-side MOSFETs to drive. I read dozens of MOSFET driver datasheets, all of them have two separate inputs for controlling high and low side MOSFETS independently.
However, my control signal is a single PWM signal. I want the high side MOSFET to turn on when the PWM signal is logic-1, and the low side MOSFET to turn on when the PWM signal is logic-0.

As you see in the circuit above, the HIN pin can be directly connected to the PWM, and LIN signal can be obtained by inverting the PWM by a BJT. But I can make sure that this won't cause a shoot through or any other problems.

What is the proper/best way of obtaining LIN and HIN signals from the PWM signal?


texts: PIC18F66K22 - RTCC with external crystal

texts:
Project details: (though I'm more interested in theoretical answers)

MCU: PIC18F66K22
IDE: MPLAB X IDE
Programmer: PICKit 3
Compiler:   C18
Project:    Real Time Calendar Clock

I've started on getting the intern RTCC from my PIC to work.
I find that there are little tutorials on this subject and none who are theoretical or withouth all too many (microcontroller specific) technical details.
The datasheet, which is specific for my microcontroller, on the other hand, seems to lack information (not sure if it's common knowledge I'm missing?)

How do I set up the Clock/external Crystal and RTCC?

Do I have to set TRIS (Tristate/Datadirection) registers for the Crystal pins?
Do I have to set the input of the Crystal high for it in order to start oscillating? (or a short pulse or something?)
Is the part below the right configuration?

#pragma config RTCOSC = SOSCREF // RTCC Clock Select (RTCC uses SOSC)
RTSECSEL (RTCC Seconds Clock Output Select) should be set to (10)?: RTCC source clock is selected for the RTCC pin (the pin can be LF-INTOSC or SOSC, depending
on the RTCOSC (CONFIG3L<1>) bit setting) ? I have another peripheral connected to the RTCC pin, will this become an output for the Clock Seconds? (Somehow confusing, but I think the Clock Output Select can be used to select the input? :#)

For those who don't like theory

The test code

Maybe a quick error is spotted here. The assembly thing is from the datasheet.

  (datasheet: "For the RTCWREN bit to be set, there is only one
  instruction cycle time window allowed between the 55h/AA sequence and
  the setting of RTCWREN.")

Also #pragma config RTCOSC = SOSCREF // RTCC Clock Select (RTCC uses SOSC)
And TRISC registers are set.

_asm
movlw 0x55
movwf EECON2,0
movlw 0xAA
movwf EECON2,0
bsf RTCCFG,5,0
_endasm

RtccInitClock();
PADCFG1bits.RTSECSEL1 = 1;
PADCFG1bits.RTSECSEL0 = 0;
RTCCFGbits.RTCEN = 1;
RTCCFGbits.RTCWREN = 0;


texts:
I have a couple of potentiometers that haven't been touched in quite some time. In fact, probably not in 15 years. So now they produce noisy output, presumably from oxides or some other crud that has built up on the contact surfaces.

Outright replacement might be an option, but these are quite large relative by current standards, they are in fact about the diameter of a quarter and are probably 1/4" inch thick, real 1970's technology. Might be hard to get the same form factor.

Certain retailers used to carry this stuff that came in a can like wd-40, complete with a little red tube for injecting the stuff into exactly this kind of part. You'd squirt a tiny amount into the noisy pot, wiggle the knob 2-3 times, and no more noisy output. So there's the proof of concept that it can be done, but this magic stuff seems to have vanished from the shelves.

It had to just be some kind of solvent, like xylene or something. Any ideas on what would clean the corrosion (dust? dirt? fungus?) off a potentiometer, without damaging it?


texts: Difference between directional and beamforming antennas

texts: What is the difference between directional and beamforming antennas? From my understanding, a beamforming antenna is a special case of directional antenna. For example, in a 120-degree directional, the antenna transmits homogeneously across the entire 120 degrees, whereas in beamforming an antenna focuses the beam in a fraction, e.g., 30 degrees, of those 120 degrees. Am I correct?


texts: Keysight's Advanced Design System users, what's wrong with this simulation - II

texts:
As requested, I am forking a question as continuity to my previous inquiry from:

Keysight's Advanced Design System users, what's wrong with this simulation?

As such, this is not a duplicate. It is done so that the progrssion of the discussion is not so hard to follow for the readers. Maybe you should start doing it here in SE -- linked posts.

Keysight DC Sweep Problem

Alright, so I here's the DC sweep from the problem of the previous post above. I'm not really sure if I set it up right, since I'm new with ADS.

Here's the new setup:

Here's the output:

Doesn't seem to matter what I initialize VINMAG to be, it shows the identical plots. I can ignore VOUT for now, but why is VINMAG's plot always the same for any initialization? Probably a problem with variable declaration/initialization?

This can't be right.


texts:
I need some help with this basic inductor.

If I have the current in that direction and those values of voltage and inductance, what is the value of $$\frac{di}{dt}$$ ?

I know that:
$$V_L=L.\frac{di}{dt}$$

So:
$$ (2-0) = 2.\frac{di}{dt}$$
So:
$$\frac{di}{dt} = 1$$

but that's wrong because the answer is

$$\frac{di}{dt} = -1$$

What is wrong??

Thanks


texts:
I would like to know if it is necessary to add a base resistor to the Q1 transistor in the below schematic?

The complete schematic: https://ibb.co/kc5QkSC


texts: How to reduce distortion in amp with Tda2030 IC when using at high volume

texts:
This is my circuit diagram.

And also how to gain bass and clarity


texts: PCB Dimensions definition in Altium Designer

texts:
I am designing a PCB to be cascaded to this PCB shown in the following picture.
I wonder how can I define the dimensions in Altium designer. Thank you.


texts: Where (under what name) can I find these breakable female pin headers?

texts:
I'm looking for these pin headers:

They're easier to work with than the regular pin headers because of the grooves.
There are similar headers that are also breakable but with round sockets (I'm not looking for these).

So I'm looking for a name or a search term so that I can find these on typical stores (e.g. aliexpress).


texts:
I'm just wondering how can I drive a speaker with an AVR chip, like Atmega16?

I have a source code for it and I have ran it in Proteus and it worked but I don't know how can I connect it practically. Should I use transistors or not?

How I should bias the transistor any way?

Is there something with my speaker maybe it's power is upper than the chip's power?
(I have a 2W speaker)


texts: What could probably go wrong in PCB if output PAM4 signal my look like this?

texts:
I've been recently testing a self-designed PAM4 transmitter(TX).The transmitter is intended to work at a data rate of 40Gbps,and it really does work in the simulation tool(Cadence)under various PVT,so that I've gained much confindence.

However,I am totally a novice in the field of PCB design,(not to say the high-speed one)and I basically designed this circuit board with some guidelines over the Internet(lol,I promise I read a lot).

Now with some basic measurements conducted,the result is far from good enough:the eye diagram is almost closed at 28Gbps,so I slowed the TX a little bit,to the speed that I am fully confident about(@4Gbps).As can be seen in the pic,it still turns out to be working in a bad state:edges are not clear at all,levels are rough.

So if the IC itself is assumed to work as satifactorily as in the simulation tool(sharp edges and flat levels),what could possibly go wrong from a pcb perspective to cause problems in the pic?

SMA_CLK_BP&SMA_CLKB_BP are the ports which high-frequency clocks (provided by BERT) come in.SMA_TXP&SMA_TXN are the output ports for the PAM4 signals shown in the picture.

There are some bypass capacitors(SMT) and ferrite beads around,mostly on the bottom layer,to serve the supply.

For simplicity sake，some pull-up/down resistors have been omitted in the schematic.


texts: Difference between IEC60309 2P + E and P + N + E

texts: From my understanding the 2P + E contain 1 wire for the line 1 wire for neutral and another line for ground. Then what's the difference between these 2 plug? Are they compatible with each other?


texts: What is the connector type of the Sony Dualshock 4 controller's EXT port

texts:
I'm trying to find information on the connector type for the EXT port on Sony's Dualshock 4 controllers.  It's entirely possible that it's some custom thing they threw together, but I'm having difficulty determining even that.

The female receptacle on the controller looks like this:

A male power-only mate for it looks like this:

The male connector is 6.5 x 2.0mm with pins at the four corners along the length.  Does anyone have information for this connector?

EDIT:  Some additional information.  It appears to be the same jack that Sony uses for minidisc players.  Most MD service manuals reference it as J301 and offer a part number of 1-793-288-62 for the receptacle, but that doesn't seem to offer up any information either.


texts: Wifi Channel vs a Sub 1 GHz channel of same width

texts:
If the same channel-width is allocated for a WiFi channel and also for a Sub-1 GHz channel, would the maximum allowable speed be the same for both channels theoretically?

If they differ, what is the theory behind the same?


texts: MicroSD card performance deteriorates after long-term read-only usage

texts:
I'm using a STM32L432 microcontroller to read data from a microSD card via SPI. In my application, I'm playing a sound file with a length of 10 s in loop.
I found out that after the application ran for approximately 20 - 25 hours, the audio stream gets heavily interrupted by noticeable gaps that occur multiple times per second. This can be observed on 10% of all microSD cards that I tested. It occurs for SanDisk, Kingston and all other brands that I tested. Stopping the application and letting the microSD card rest for some days does not solve the problem. It seems that the flash section of the microSD cards that stores the sound file got deteriorated. Reformatting the microSD card fixes it, probably because the sound file gets stored on another flash section.
A further investigation yielded that the gaps in the audio stream occur because the microSD card takes too long to respond to the CMD17 command. When the microSD card is new, the responds take never longer than 4 ms in our tests. However, after a usage of 20 - 25 hours, the respond time increases to up to 95 ms on 10% of all microSD cards.
I'm a bit confused of this result because I did not expect the performance of the microSD cards to deteriorate if only read operations were carried out. Do you have any experience with that? Would the response time decrease when using SDIO instead?


texts: Bypass capacitor in combination with ground plane

texts:
I read it is advisable that every IC has a bypass capacitor, as close as possible to VCC, going to GND.

However, I'm wondering, as I want to create a PCB with a GND layer as second layer, can I place the VCC pin of the bypass capacitor close to the VCC pin of the IC, and the GND pin of the capacitor directly to the GND plane, or should I create a separate 'connection' directly to the GND pin of the IC?


texts: LTSpice - Voltage Comparator not working

texts:
My question is - why is CMP_OUT not going to HIGH (i.e. to 12V, P12V_IN) when INP_U1 is greater in voltage than INP_U2.

I think I haven't wired the LT1011 right. Do I have to do anything with the "B" and "S" pins?

I am open to using another part for the comparator as long as it is available in LTSpice.


texts: Need help designing headphone amplifier circuit

texts:
I have to design a headphone amplifier circuit. We are told the impedance of the headphones and the minimum voltage they require and also the voltage source. After researching I have found that the LM386 is a popular choice. I've seen many circuit diagrams but what I don't understand is how to pick the voltage gain needed for the amplifier.

I originally thought that you would need to know the input audio signal voltage and when you multiplied that by the gain that would need to give the minimum voltage required by the headphones, but it appears that what matters is the current which I don't get.

And are you able to design such a circuit without knowing about the audio input signal? If you do need to know about it what is it you need to know about it and why?

I would greatly appreciate any help as I am very lost. Thanks


texts:
The book page 12 show the plot of collector current Ic vs temperature at fixed Vbe =600mV.

With the equation: Ic = Is*e^(Vbe/VT).

Where Is = 10^-16A.

Vbe = 0.6V
      VT = kT/q = -8.6173324×10−5*T (V/K)

I tried to plot the function for temperature from -55 to 125C (or 218 to 398K).

However, the result is totally different from the plot in the book. Could you explain?

I understand that Is also varies with temp but I think Is is fixed in the plot.

Thank you.

Book plot:

My plot:


texts: Practical issue aiming non-visible infrared light at a reflector

texts:
I built a beam breaker set-up, with the transmitter and receiver next to each other, and a reflector about two meters out. Basically, the transmitter is an IR LED and the receiver a TSOP. Between the two components, I placed cardboard. I am constantly getting readings from the Arduino terminal on the alignment of the beams (HIGH or LOW).

I believe the set-up or individual devices are not faulty and all is working as should, including range, after extensive testing. When I place a retroreflector in front of the devices, up to about a meter, it works. Further, not so much.

It really comes down to having the IR LEDs pointing the same way, in the same angle. They don't now, and if I move the reflector further away, there logically comes a point that one beam 'falls off' the reflector.

After an entire afternoon of fidgeting, I finally managed to aim, using trail and error, only one IR LED at the reflector two meters further.

Methods I tried, include plain measuring on flat surfaces against straight walls, using a laser pointer, bending and cutting the legs of the LEDs the exact same way, moving the reflector up, down, left and right and finally, keeping the reflector in place but move the IR LEDs up, down, left and right.

The problem is that, even if I manage to align a LED, all it takes is a small accidental nudge to have to start all over.

Does anyone have practical tips on how to aim IR LEDs?

Transmitter

An ATTINY, using a MOSFET to drive the LED near max. capacity despite the limit on the pin, drives the LED. It uses this code to get 36kHz and send bursts as not to overload the TSOP:

// ATMEL ATTINY45 / ARDUINO
//
//                           +-\/-+
//  Ain0       (D  5)  PB5  1|    |8   VCC
//  Ain3       (D  3)  PB3  2|    |7   PB2  (D  2)  INT0  Ain1
//  Ain2       (D  4)  PB4  3|    |6   PB1  (D  1)        pwm1
//                     GND  4|    |5   PB0  (D  0)        pwm0
//                           +----+

void setup(){
  DDRB |= (1<<PB0); //Set pin PB0 as output
  DDRB |= (1<<PB1); //Set pin PB1 as output

  TCNT0 = 0;
  TCCR0A = 0;
  TCCR0B = 0;

  TCCR0A |=(1<<COM0A0); //Timer in toggle mode Table 11-2 - PB0
  TCCR0A |=(1<<COM0B0); //PB1

  TCCR0A &=~(1<<COM0A1);
  TCCR0A &=~(1<<COM0B1);

  TCCR0A |=(1<<WGM01); //Start timer in CTC mode Table 11.5
  TCCR0B |= (1 << CS00); //Prescaler Table 11.6

  OCR0A = 12; //CTC compare value, 36kHz
}

void loop(){ //cycle = 1/36 = 28μs
  TCCR0A |=(1<<COM0A0); //burst on for 10+ cycles
  TCCR0A |=(1<<COM0B0);
  delayMicroseconds(500);

  TCCR0A &=~(1<<COM0A1); //off for 14+ cycles
  TCCR0A &=~(1<<COM0B1);
  delayMicroseconds(1000);
}

Receiver

The receiver is an active-low TSOP that, via a comparator, is connected to an Arduino calling the attachInterrupt() function. There are two LEDs and two receivers to determine direction. The C code calculates direction and spits out the result.


texts: How does VCO in PLL in computer processor work?

texts:
In todays personal computers and notebooks, what is usually used as a Voltage-Controlled Oscillator for generating clock signal for processor?

Is that a crystal rather than RC circuit?
Is it tuned by varicap?
Does it contain reference voltage and comparator?
What is a diagram/scheme of that circuit?
Is frequency of the internal crystal the maximum possible output
frequency?
Does VCO work on clock signal or continuously?
What is the physical principle behind changing the frequency? Can I
see graphs explaining how it works?

EDIT
Let me state, that I have read all the related Wikipedia pages, so please don't send me search through it again. That's pointless. I wouldn't have so many questions, if I haven't read about PLL's for hours and hours. Now I need to put all the information into frame. I'm asking for guidance. I understand it takes a person with very deep knowledge about the subject. So please if you don't have the knowledge, don't spam here. I am really interested in the subject. Thank you.


texts: Powering COB LED with "under-voltage" LED driver

texts:
I have LED Driver
Model: LD-361500-105MPF
Input: 90-260VAC 50/60Hz and
Output: 20-36VDC, 1500mA+/-5%.

I connected it to the LED COB Citizen 1212C4 which needs, according to datasheet (COB's datasheet link, page 6), 37V at 1500mA.

When i power up this circuit i get power consumption of 60W, im guessing 36V and 1.66A. its about 11% of a difference and not 5% that is declared on the driver. I'm cooling it easy with active cooler, temps dont go crazy high (around 30°C?).

My question is can this be ran for a long time without any problems?


texts: high value resistors in optical slave trigger? Why?

texts:
In a commercial optical trigger, for triggering flash units remotely using the on camera flash, there are very high resistors two 30Mohm in series. Why such a circuit would need resistors so big? This trigger works well with old flash units that have an high sync voltage (up to, and sometimes in excess of, 300V when the flash fires) or newer flash units usable with digital cameras that stay in the range of 2-6V (but also slave triggers built from the simplest circuits that have only a photodiode and an SCR work with both if the SCR can take an high voltage)
In series with a photodiode they would be too big, as a divider they would leave nothing to the circuit to trigger the strobe... What am I missing? I cant undertand their function or benefit... (and i dont have one at hand to break apart)
I attached two pictures, the first shows two slaves, same brand, same circuit, one is builtin in an hotshoe adapter the other has a plug at the back for connection to other adapters, cables or directly to the flash unit. The circuit has a  photodiode, SCR, 4.7K resistor, 400V 0.047 capacitor, and two 30Mohm resistors that can be seen soldered in series! I suppose the 4.7k resistor and the capacitor are the RC to filter ambient light. The resistors are very visible in the closeup picture of the peanut slave. Triggering happens when the SCR shorts the negative rail of the flash unit and the positive center pin of the flash unit.


texts:
I have read that bluetooth devices had a built in short range with data rate of 1Mbps with a 2.4 Ghz Frequency, which means that there is possibility of interference between IEEE 802.11b WLANs and Bluetooth.
How can a DSSS Signal (Wifi) intefer with a FHSS? Does WiFi usually operate at 2.4Ghz, since IEEE 802.11ax have both 2.4/5Ghz Frequency for down/up link transmission.

In the reference, it was specified a legacy method to support both in a collaborative mechanism, if any one have any material or answer supported mathematical work, please do share as post. Thanking you in advance.

Referred : View Link


texts: how to go from eagle design to Part list

texts:
I am looking for a maintainable, shareable and scalable process to output a complete part list (as in "Part N°XXX from supplier YYY") From an Eagle project, when it seems to only be able to provides a BOM ("Component type XXX with value YYY").

Is there a way to do that using Eagle alone, or do i have to process the BOM, in excel for example?


texts: Where on a cellphone does the electromagnetic radiation(radio frequencies) come from? the antennae or the transmitter?

texts: I'm an electrosensitive (someone who is sensitive to electromagnetic fields such as radio frequencies). I'm trying to figure out a way in which I can use a cellphone without it's radiation affecting me. What I want to know is if the radiation comes from the antennae because I'm planning on purchasing an external antennae that I will connect to a Samsung Galaxy S3 that has a FME connector.During my research they stated that once an external antennae is connected the internal one will be disabled so I would just place the antennae at a far distance and use an amplifier to boost the signal to the cellphone. Can this idea work?


texts: How to test the maximum secondary current of a step down transformer?

texts:
I got a small step down transformer from my local market which has a total of 6 individually isolated winding in it (1 primary of 230V and 5 different secondary wingding with 5 different voltage).

My question is that how can I find out the maximum output current for the secondary winding? I was told generally these used to be made for "Small Sound Systems". As this from a local market it has no datasheet. Transformer weights about 500 grams and looks well made. The dimensions of the transformer are near about 6cm X 3cm X 5cm and all the secondary wires are less than 1mm in dia.

This is my first question on stackexchange. Thanks in advance for all help and suggestions!

The winding voltages and resistance measured are as follows:

Primary Winding (Red thick wire)      230V with a resistance of 72.6 ohms
Blue Wire                             8.8V with a resistance of 1.4 ohms
Yellow Wire                           11.1V with a resistance of 2.0 ohms
Green Wire                            12.8V with a resistance of 2.7 ohms
White Wire 23.1V with a resistance of 9.1 ohms
Red wire 3.7V with a resistance of 1.8 ohms

  These are all the output voltages when the transformer is given 230VAC as input.

I tried measuring the maximum output current by a short circuit test (Using some high watt ceramic resistance in series with my DMM in amp mode).But unfortunately the DMM is not showing anything, I double checked my DMM for a blown fuse inside but it was working properly when I tested a DC load.

I want to use this transormer for building up a variable power supply circuit, but without getting sure of it's maximum output current of the secondary windings, I can't proceed further.I am not that much experienced of power electronics hence can't figure out what to do next.

Here are some pictures of it

Thanks again for helping me,

Best Regards,

Robbin


texts: How to interpret telephone line for Arduino?

texts:
I wish to built my own "Dialler Capture" using Arduino.

Alarm panels use something called Contact ID, that use the phone line to transfer "packets" (quotation marks are used because they aren't network data packets, they are DTMF sequences).

I know that the phone line uses 48V while the Arduino uses 5V. I don't want to put 48V directly onto a controller!

I cam across the M-8870 chip which appears to convert DTMF to a byte (4-bits). Is this my only option?

Also, the Arduino doesn't understand DTMF. Even if I made a voltage drop to 5V, didn't use the DTMF converter (appears to be obsolete) it doesn't have an analogue input, only a PWM input.

May main question is, programming aside, how can I get an Arduino to understand DTMF using electronic components (that could be built on a breadboard)?


texts: Why do generators have to rotate at a slower frequency if demand outpaces the supply?

texts:
EU residents might have noticed that some of the clocks in their house have been running out of sync with other clocks. Apparently, the cause for this is that power suppliers had to reduce the frequency at which the AC network alternates the current flow. I understand that the speed at which these clocks tick is based on the frequency of the AC network, so thus far it makes sense. The thing I don't understand is that according to reports, the reason the power suppliers had to reduce the frequency was because a regional provider in the Balkan did not provide their fair share of power to the grid. I read the article of the Swiss power grid website at https://www.swissgrid.ch/swissgrid/en/home/experts/topics/frequency.html which states:

  If the consumption of electrical power is lower than production, the frequency is higher; if consumption is higher than production, the frequency is lower. The reason for this is as follows: the electrical generators of an electricity grid rotate more readily and faster when consumption is low. Consequently, they rotate with a higher frequency. Conversely, the electrical generators rotate more laboriously and with a lower frequency when consumption is greater.

So the generators have to rotate at a slower pace if demand is greater than supply. Why? I mean, I don't even understand how the grid remains functional if demand is greater than supply. usually if demand is greater than supply, part of the demand doesn't get fulfilled. I might misunderstand how the power grid as a whole deals with a situation like that. I especially don't understand what the link is between the undersupply on the grid and the mechanical speed of the generators. I know basically nothing about the power grid, so that doesn't help either.


texts: Connection of two identical transformers

texts: I have a substation with two identical transformers 110kv/25kv single phase 50 hz usually one acts as spare. Now for some reason i want to charge my substation from secondary side i.e., 25 kv side from one of the transformer. Let us say My voltage at secondary side is 21 KV, corresponding voltage at primary side will be 120 KV (SAY). Now i want to feed this 120 kv to the primary of second transformer duly keeping the different tap at secondary of second transformer so that out put voltage of second transformer is maintained at 25 KV. Is this arrangement possible? .


texts: What should I do to have both the synchronous and asynchronous serial communications?

texts:
You know that ATmega32 supports Universal Asynchronous Receiver/Transmitter.

with pins :   RXD & TXD

But it doesn't support Universal synchronous Receiver/Transmitter.

with pins : RXD/TXD & CLOCK

What should I do to be able to use both the USRT and UART interfaces on my microcontroller?


texts:
When we initialize a serial communication, we usually have to set the baud rate (e.g. 115200)
I notice that many people assume that 115200 means 115200 bits per second. However, each baud(signal change) can encode more than 1 bit. baud 115200 means 115200 bits per second only if each baud = 1 bit.
If each baud is 5 bits, then having baud 115200 means a bit rate of 115200 * 5 bits per seconds.

If what I said above is true, what is the baud to bit ratio for UART and USB3.0 assuming the baud rate is set to 115200?

It cannot be 1 to 1 because 115200 bits per seconds is 14.0625 KBps (kilo byte per second), which is too slow.


texts: STM32F10x microcontroller debugging problem

texts:
I'm a beginner and I'm using STM32F10x family to learn about electronics.I was using STM32F103 blue pill in the past few months and I can debug it and upload code to it while both boot0 and boot1 are equal to 0.
When I switched to STM32F105 which has only boot0 and exposed since I couldn't find boot1 in the pinout in the datasheet.I have to hook boot0 into vcc in order to flash the elf file.now this also happens on the blue pill I can't flash it wihout turning boot0 into 1.
the problem is I can't debug it while boot0 is equal to 1 i'm getting
Target is not responding, retrying...
Target is not responding, retrying...
Error! Failed to read target status
Debugger connection lost.
Shutting down...
I think its because boot0 is equal to 1.
and when I turn back boot0 into zero the debugger can't flash the file and can't debug.
I'm trying to debug it since I have a problem I done a simple code to toggle led after 1 second but the code only execute for 16 seconds and stop executing. and I want to debug it to see why.
on the STM32F103 the this problem don't happen


texts: Quick question here - I have a circuit that originally used a 2SK30ATM-GR JFET, with an RDS(on) maximum of 800 ohms. Most of the cheap JFETs I can find have a significantly smaller RDS value, generally below 5 ohms. The application for this JFET is just an audio circuit, so is the RDS value going to affect anything if I substitute in a new JFET?


texts:
I have the following Karnaugh map's for JK flip flops. I've attempted to minimize them myself, however whenever I go to implement them I run in to an error. Anyone able to see if I've made an error in my minimization.

(originally uploaded to jsfiddle)

Hope you can help, hope this is the correct place to post!


texts:
While finding the norton's equivalent curcuit,we
1.find the short circuit current through the load
2.Find the resistance between the two points across which load is connected shorting the voltage sources or replacing them with internal resistance.
3.make an equivalent circuit with a current source of magnitude of the short circuit current with the load resistance in parallel.

BUT from where these rules come from?
How can we assure that following these steps we can replace a circuit with the equivalent one.


texts: Atmega Microcontroller interrupt delay function on button press

texts:
I am using Atmega32A and I have 2 LEDs. Here's step by step what I want to do

When the MCU is powered, I have one LED lit (PC0)
When click on a button (PD6) the second LED at (PC1) is lit and the other one is turned off.
A delay function is delaying this state for 10 seconds. After that the first LED (PC0) is lit, too, for 5 seconds. At this time both the LEDs are lit.
Then 3. repeats.

What I want to do is, when I click on the button at (PD6) to be able to interrupt / break the delay.

Here's the code

#include <avr/io.h>
#include <util/delay.h>

int main(void){
    DDRC = 0b11111111;  //Makes PORTB as Output
    DDRD = 0b00000000;  //Makes PORTD as Input

    PORTC = 0b11111110; //LEDs
    PORTD = 0b11111111; //Button

    int pressed = 0;
    int Pressed_Confidence_Level = 0;
    int Released_Confidence_Level = 0;

    while(1){
        if(bit_is_clear(PIND, 6)){  //If button is pressed (PD6)
            Pressed_Confidence_Level++;
            if(Pressed_Confidence_Level > 500){
                if(pressed == 0){
                    if(PINC & (1<<PC0)){
                        PORTC = 0b11111111; //PC0 LED ON, PC1 LED ON
                    }
                    else{
                        while(1){
                            PORTC = 0b00000001; //PC0 LED ON, PC1 LED OFF
                            _delay_ms(600000);  //10min
                            PORTC = 0b11111111; //PC0 LED ON, PC1 LED ON
                            _delay_ms(300000);  //5min
                            /* How to exit this loop on button press? */
                            }
                        }
                    }
                    pressed = 1;
                }
                Pressed_Confidence_Level = 0;
            }
        }
        else{
            Released_Confidence_Level++;
            if(Released_Confidence_Level > 500){
                pressed = 0;
                Released_Confidence_Level = 0;
            }
        }
    }
}


texts:
I have a diode that reads F or 4, 65, B, but I can't find any information about what these markings mean online.

I don't have the original packaging so I'm at a loss.

Does anyone know what this means?

Or know a way that I can test the diode and work out what it is?

I am hoping its a 15V Zener, but that seems unlikely.


texts: Basic wattage and volt conversion when using solar panel

texts:
I have a basic electronic question or two I need to ask.

I want to use a solar panel which delivers 5.2W and is rated for "8V open voltage and 650mA short circuit". If I connect a 5V voltage regulator to lower the volts to 5V, would the amps go up to be 1A after the regulator? (W = V * A)

Another thing I'd like to know is, if I regulate the voltage to 5V and get approximately 1A out of it. How would using different components together work? I.e. I am using an arduino with a servo and a GPS unit and an XBee connected. Would these individual components' amp-usage just be added up (lets say to 850mA) and then the "extra" 150mA would just not be used?


texts: Need help understanding simple oscillator circuit

texts:
I know this seems like a really basic question, but bear with me. The following circuit diagram is given by one of my old electronics kits:

simulate this circuit – Schematic created using CircuitLab

The book specifies this is a "light organ" whose sound output at the piezo transducer varies in pitch based on the light input. I understand that the impedance of the photoresistor drops with more light, but how does this oscillator work? What is the role of the BJT in this circuit? (To simplify, one could just replace the photoresistor with a potentiometer or even a fixed resistor.)


texts: How can I draw a circuit from its transfer function?

texts:
I am new in automation electronics and in this forum.

I have this transfer function: \$G(s) = \dfrac{10}{(s+1) (s+5)}\$ and I was asked to create the circuit with 5 op-amps and the correct resistors and capacitors.

I don't know much about these kinds of electronics and any help would appreciated.


texts: how do we find the Norton equivalent circuit current of the both node ,a-b

texts:
Determine the Norton equivalent circuit current of the both node ,a-b, of 9 ohms resistors

simulate this circuit – Schematic created using CircuitLab

Solution:

simulate this circuit

\$V=RI=(6//6//6)\frac{36}{6}=12\$ , and \$I_N=\frac{V}{6}=\frac{12}{6}=2A\$

1.I want to ask why is \$(6//6//6)\$ ? because i think it should be \$=(R3//R1)+R2=(6//6)+6\$

2.Why will the answer said \$\frac{36}{6}\$,this value should be a current value,but i don't understand why it can just write \$\frac{36}{6}\$,not \$\frac{36-V}{6}\$ or \$\frac{36-0}{(6//6//6)}\$

3.Why do we just ignore the R4?according to what reason?


texts: What is the best instrument amplifier to measure microvolt dc signals from a low impedance differential type T thermocouple system?

texts: I wish to measure 0.02 C difference between two type T thermocouple junctions with accuracy. I need only 1Hz bandwidth. I am looking for small changes in temperature in this apparatus.


texts: How to control a cellphone using an Arduino?

texts:
I wish to control a classic cellphone using an Arduino Nano by connecting the cellphone keys to digital pins, and switch them using a program that I will put on the Arduino. The idea is to make a pseudo-GSM shield, and be able for example to send SMS messages, make a call, or just print a text on the LCD of the cellphone.

The 2 issues that I found :

The cellphone that I use contains 25 keys, but the nano contains
just 13 digital pins, so is there a smart way to use few pins to
control the 25 keys?
To switch on/off a key I thought to use a transistor, where
E(mitter) and C(ollector) connected respectively to GND and V+ of
the key and B(ase) connected to arduino. by setting HIGH or LOW on
that pin it will open or close EC circuit of the transistor.

Question: Is there a smarter way to switch ON/OFF the keys using just few components (because in my case I will use 25 transistors and it's a lot !!)? And should I to use the same power source for the Arduino Nano and the cellphone?


texts: I2C: 3.3V and 5V devices without level-shifting on 3.3V-bus?

texts:
do I really need a level-shifter if I use 5V-powered devices on an I2C-bus that has pull-ups to 3.3V?
In my understanding the devices will only pull the lines (SDA, SCL) low (to ground) and never drive their supply-voltage to the bus. So I don't see a reason for a level-shifter as long as all devices detect the voltage from the pull-ups (3.3V) as logical high. That should be the case with devices using 5V as supply.

In my case I have an IC whose inputs are not 5V-tolerant as master and I could power my slaves with 3.3V but using 5V is easier in my circuit and allows higher (internal) clock-rates for the slaves.


texts:
I am a developer of a cheap product and i have no experience in mass production. Device is fully functional and represents a single sided PCB, a microcontroller, a bunch of diodes and a few passive elements. However, MC is kinda overkill and schematic could be done with some simple TTL/CMOS logic and passive elements. I can easily create VHDL or logic equivalent. I can't use standard logic IC's due to size restrictions. It would be best to use a few hundreds of transistors on a custom chip, if that's possible. I saw a ton of devices that are ridiculously cheap and have some circuitry in COB. This one costs 10c shipped, that's 4 times cheaper than a MC in my PCB
I had no luck finding a suitable manufacturer. I found some MPWs like MOSIS, but that's obviously not what i need.  So, is there a way to create about 10k of devices with cheap custom COB?


texts:
Not sure if this is off topic. I have an old ipod dock with a 30 pin male connect and I want to switch it out to a male micro usb. So that I can use the dock. I don't want to use an adapter as I want it to look natural.

I was simply going to rewire old connector to the micro usb.

Ipod Dock pinouts
I have found the pinouts for both.
http://pinouts.ru/PortableDevices/ipod_pinout.shtml

Micro usb.

http://pinouts.ru/PortableDevices/mini-USB_pinout.shtml

It looks like I can simply connect up the 16, 23, 25 and 27 on the ipod connector to 4, 3,2,1 respectively on the micro usb side.

Just wanna make sure before I do anything.


texts:
I'd like to create a simple circuit for keeping a line "high" for a few seconds after being triggered high, without any external power.

To specify it in more detail: given three inputs, 3.3V, GND and a processor output line that can be driven high, create a circuit that drives an output line high for 5 seconds after being triggered by the processor output line, even when the 3.3V line goes dead. The timing doesn't need to be exact.

Theoretically, I guess this would be easy by just hooking up a capacitor and a thyristor together. However, suitable thyristors do not seem to be easy to find, and fitting together all the component values seems tricky.

This is also similar to all the power-on / power-off delay circuits, but a little different.

So, I am looking for better ways to do this.


texts: How to send ASYNC 8,N,1 serial data over an SPI interface using two Arduino Uno boards

texts:
Need help with sending ASYNC data between two Arduino UNO R3 micro-controllers.

System design follows:

RS232 modem 19,200,8,N,1 --> UNO-1 D0=(rx), D1=(tx). RS232 parameters cannot be changed because the device is hardcoded. UNO-1 runs sketch sending AT commands and parsing data received. Parsed data must be sent to another RS232 modem but unfortunately this device is hardcoded for 9,600, 7,E,2. There is only one USART o the UNO.

My idea is to take advantage of a 2nd UNO R3 to convert the data to 9,600, 7,E,2.

So..  19,200,8,N,1 modem --> UNO-1 -->SPI INTERFACE (mstr) --> UNO-2 --> software serial port --> Device 9600, 7, E, 2.

I've tried reconfiguring the USART on the UNO before sending data to each ASYNC device. Problem showed up that unsolicited and important data is received form the 19,200 modem while the UNO is sending data to the other ASYNC device at 9600,7 ,E, 2.

The SPI interface seems to be my only option. Can any one help?


texts: Analog vs digital wireless newbie questions

texts:
As i try to understand the real difference between analog wireless and Digital wireless i'm asking some questions :
As far as i know digital means more accuracy of data, but require larger bandwith to reproduce same as analog
thats why continuous stream as audio or video are hard to send digitally, but easier with a powerful and calibrated analog rf transmitter.

But for small analog stuff, let say i just need to send an analog "tilt" or simple analog accelerometer ( just motion activated ) wirelessly to engage a led to the receiver side, do i really need to consider it digitally ? Can i make an analog a link tilt sensor/tx to rx/led without mcu in the way?

I'm trying to do a very tiny project where form factor is key, and where data doesn't have to be that accurate, is it possible doing it analog all the way?

Second question:

To the other extreme, what is the best solution to send continuous or large digital data wirelessly ? (lets says 24bits/48khz audio ?)

Third and final question:

How can i calculate easily my needs in terms of kbps if I go digital, or bandwidth/power when doing analog.


texts:
I have several doubts about solving circuits.

Can any circuit be solved using Nodal Analysis?
If some circuit can be solved using Nodal Analysis, can it be
solved using Mesh Analysis too?
Why do we need these techniques to solve circuits?


texts: Reverse current frying a boost converter?

texts:
AFAIK, most boost converters incorporate a diode or some mechanism for ensuring that current flows from the battery to the output. For instance, TPS61030's datasheet says that

  This device however uses a special circuit which takes the cathode of the backgate diode of the high-side PMOS and disconnects it from the source when the regulator is not enabled (EN = low).

MPC6140's datasheet says that

  With the EN pin pulled low, the output of the MCP1640B is isolated or disconnected from the input by turning off the integrated P-Channel switch and removing the switch bulk diode connection. This removes the DC path that is typical in boost con- verters, which allows the output to be disconnected from the input.

Does that mean if current tries to flow from output, these chips (at least these two?) won't be damaged at all? That is, for instance, there are two possible power sources connected in parallel, boosted to 5V. If only one is hooked up, would the current flowing into the other booster in reverse fry it?

What if both could be hooked up?


texts:
This has been driving me crazy for several years now -- my soft touch lamp has been turning itself on most mornings. Some details:
It is definitely tied to sunrise/dawn, as the time each day varies along with the sunrise. This makes me think it could be related to some voltage/current fluctuations that could occur at that time each day -- perhaps street lights turning off? But it does not happen EVERY day.  Also, a second lamp will USUALLY turn on at the same instant, but not always. Note we live in Mexico and line voltage fluctuates more than is normal in the U.S. If I turn it off immediately it will turn itself on again either immediately or within 10 - 15 seconds. This window during which this occurs is 2 - 3 minutes long. I hope someone can explain this, because my fallback answer is that it's haunted...
[Edit]I'm attaching a photo that shows the lamp just after it went on at 7:20 one morning. The alarm clock is NOT connected to the lamp. The lamp is just a simple almost spherical shape. Unfortunately it does not have any model number or manufacturer information.


texts:
What is the highest number of transistors that can be used within a gate? Very open ended and general question, but I'm trying to gain a better understanding for digital logic.

In terms of chips, I'd like to understand what a general ratio is for transistors to gates.


texts:
I have an Ac to Dc switched-mode power supply that looks a bit like this :

Now as you may or may not know, there's the Ac input with a N and a L for neutral and live line. Now I want to know if it's ok to plug the Live line on the neutral side and vis versa. Also how am I capable of knowing wich of the wire I connect to it is the Live or Neutral line. Now I've also been told not to do this, thanks for explaining me why is that..


texts:
I have a Virtuabotix MMA7361 Three Axis Accelerometer Module that I am trying to use to detect tilt. It works, but only for two axes at a time. It doesn't matter which way I try to flip or turn the board, but no matter what, the "Output Axis"(shown in the picture below) will not work. Am I mixing an axis up or messing up the orientation somehow? The spin and and the input axis seems to work no matter the orientation. I've tried twisting it and turning it, but out of X,Y and Z, only two of them work at any given time, with the last one staying near-constant.

The second picture is of the board I have. I am using an Uno to read the values.


texts: Is there a standard symbol for gain margin?

texts:
In the context of control loops, specifically power supply control loops in my case, the symbol \$\phi_m\$ is used for phase margin. I've occasionally seen it with a capital M, but on balance it seems to be pretty consistently the lower case subscript.

My question is: Is there also a standard symbol for gain margin? Like perhaps \$A_m\$ or \$G_m\$? I searched around and could only find instances where it was actually spelled out; of course that could be because I could only search on "gain margin", not knowing exactly what to be looking for :)

It's come up as a value to be stated in my last couple of questions and I wanted to avoid using a phrase if a nice compact symbol would do the needful :)


texts:
I have a fairly simple question. I just want to know if my work is correct, it seems too simple. I'm not sure how current sources work- do I have to combine them somehow? Here's the problem below:

Here's my work:


texts: If a high rpm motor is run at lower rpm, will it produce more torque?

texts:
I did the following calculations:
Max current = 1.2A, Max voltage = 12V
Then power = 14.4 watts = 0.019hp

Rpm = HP * 5252 ÷ torque
I need a torque to 2kgf-cm = 0.144 lb-ft
Gives rpm= 698.

Thus this means if I put load(mechanical) on the motor, it will run at 698 rpm and increase its torque to 2kg-cm?

(The motor is a high rpm motor, i.e 12000)


texts: Pressure sensor without using MEMS chips

texts:
I'd like to figure out how to make a pressure sensor for very low cost (essentially disposable), mass produced piece of medical equipment.
The problem: this can't use any parts which aren't already available in huge quantity.  In other words only parts with > 100k and preferably > 1M in distributor stock.  This probably rules out the obvious approaches of using MEMS pressure sensors for cell phones (or does it? any super-high volume MEMS devices?).  Probably most specialty parts are out; commodity parts only (resistors, capacitors, generic op amps, generic transistors).  It is okay to fabricate components from raw materials (eg - a force sensitive resistor from conductive foam) if the materials are readily available.  It helps if all the parts used are extremely cheap (bom cost < $10).
What the sensor should do is sense pressure differences.  It needs to pick up changes of <1cmH2O (100 Pa) in pressure, and it needs to have response times <1 second.  For this 0.1 cmH2O precision and readings every 0.1 second are great specs.  The typical operating pressure is 0 to 40 cmH2O.  The physical form factor of what this connects to would be a short 20mm tube - as short as possible; 20mm x 20mm is good - with tapered connectors on both sides.  I assume this would need a mechanical component like a diaphragm or piston which is somehow interfaced to a PCB.
It's okay if this doesn't have a very accurate zero, and other specs like linearity, drift, offset, scale error are non-essential as long as roughly 1cmH2O changes can be detected between 0 and 40 cmH2O.  It is okay if each sensor needs an individual calibration.
Idea #1: diaphragm the position of which is read out using some version of capacitive touch - read out capacitance
Idea #2: diaphragm which compresses a force sensitive resistor made of anti-static foam - read out resistance
Idea #3: conductive diaphragm which touches a different number of conductive pads on the pcb depending on how far it's deflected - read out which pads are shorted together
Idea #4: conductive diaphragm the end to end resistance of which is read out depending on stretch
Bounty if rather than an idea, you build a working prototype.  Huge bounty if you do it within the next day or two.


texts: Need help understanding a portion of the Arduino Mega 2560 schematic

texts:
I'm planning to build a custom Arduino Mega PCB, so I downloaded the schematics and design files. For the schematic, I have a fairly good understanding of the connections, components, and their purpose.

However, I'm a bit unsure about the IC7B op-amp, RN5C/RN5D 10K voltage divider, and T1 FET and how they work together in the grand scheme of things. A picture of that part of the schematic is attached below. I also attached the power jack portion of the schematic below as well.

I'm assuming the op-amp will either send a voltage or not depending on the VIN line. That output is connected to gate of the FET that will either close or open the USB VCC line. So either the barrel jack or the USB will power the 5V Vcc line but NEVER both. Is that correct? I see the +3V3 line is the output of the voltage regulator but also the input of the op-amp so that's feedback op-amp right? I'm still not sure what the two 10K resistor voltage divider before the CMP input on the op-amp is for.

If you can confirm my guess and/or explain their role and importance, that'd be great.


texts: Stepper motor getting very hot: wrong driver or power supply?

texts:
I have built a simple driver circuit for an unipolar stepper motor, based on an ULN2003A. The schematic:

The motor is a PM25L. Data sheet is here.

It was salvaged from an old electric typewriter, and the ULN2003A and Zener from the driver board inside the same device. It's a 5 wires motor, but the one in the schematic is 6 wires. I suppose the only difference is that the 5 wire version has the two center taps joined together so that's what you see in my schematic.

The Zener diode is an HZ-361
According to the datasheet the Vz is 34.2, so it's above 2x the power supply voltage.

I am feeding the motor from a laptop variable power supply. The lowest it can run it is 9.5V and it's rated at 3.5A at that voltage.

The motor seems to run perfectly, however after a minute or so it becomes extremely hot. I don't have anything to measure the actual temp but it is painful to put my fingers on it for more than half a second.

As suggested below by Russell McMahon I also did the following extra test:

given the circuit above, add a 25V 100uF cap between COM and GND. operate motor. measured voltage across the cap is around 22V
given the circuit above, remove the zener and leave COM pin floating: nothing bad happens to the ULN2003A, the motor runs well but still overheats
given the circuit above, remove the zener and put a resitor and a 100uF 25V capacitor in series between COM and GND (COM -> R -> C -> GND): the motor runs well but still overheats


texts: Transformers in series in the primary end and in parallel in the secondary?

texts:
I know the basics of transformers and one thing I have never understood is the specification of primary and secondary voltages.
By theory, the 2 parameters of importance is the transformation ratio and the VA rating right?. But then why do transformers have specified primary and secondary voltages?

I have a 120 VAC primary voltage (to 24VAC in sec.) transformer but my supply is 230VAC. So, Can I connect two such transformers in series (in the primary section) to make sure the specification voltage is not exceeded?

But what is the significance of these voltage specifications? Can I connect 230VAC directly and just make sure the current in the secondary output does not exceed the VA rating? Would that work?

The problem is I have two 120VAC to 24VAC transformers and my supply is 230VAC. So can I connect the primary in series and the secondary in parallel to achieve 230VAC to 24VAC transformation.


texts: I'd like to improve this design to support ICSP

texts:
I'm new to electronics and this is my first circuit.  I have some questions about implementing ICSP in this design.  This is a bit of a long post with quite a few questions so I'll apologize in advance for its length.  Unfortunately I don't have a mentor who I can ping questions off of so any help is greatly appreciated!

I'm using an Atmel ATtiny10 microcontroller to drive an RGB LED.
The circuit is powered by two 3V CR2032 batteries in series which provide 6V.
The batteries are connected to a fixed-output voltage regulator which converts the battery power down to 5V for the ATtiny.
Three of the ATtiny's four I/O pins are connected to the LED's three anodes via current-limiting resistors (the fourth MCU pin is unused with an internal pull-up resistor enabled).

So far this is pretty basic stuff, and it works on a breadboard.

I'd like to add ICSP functionality so I can program the ATtiny in-circuit when this is moved to a PCB (for initial loading and later if I want to modify my firmware).  Here are my questions:

Q:  What is the best/preferred way to supply power to the ATtiny during programming (my programmer is an Arduino and not the expensive dedicated programmer from Atmel)?

There seem to be two options:

Supply power through the existing battery+voltage regulator components, or
Supply 5V via the programmer directly to the VCC pin on the ATtiny via a header/ICSP pin.

Q: If I go with option 1, do I need to be concerned about isolating the circuit from my programmer/Arduino?  The Arduino is powered by a USB connection from my computer and I don't want to fry it.  If I do need to be concerned about power isolation here, how is it done?

Q: If I go with option 2, I believe I'll have to put a Shottky diode between the regulator's Vout and the ATtiny's Vin to prevent current from going the wrong way into the regulator (i.e. from the programmer to the regulator's output pin).

A diode here seems to present a number of problems:

It adds an extra cost to the circuit.
It adds another part consuming battery power.
The voltage drop across the diode will cause the ATtiny to see less than 5V at its Vin, which is probably undesirable (due to clock destabilization).

Q:  Are the concerns I just listed about the diode all valid concerns?  I haven't designed anything with a diode yet so I don't have any experience with operational practicalities.

Q: Is there a different/better way to get power to the ATtiny for programming that I haven't thought of?

Q: Two of the pins used for programming the ATtiny will also connect via the resistors to the LED.  What steps should I take to isolate the programmer from the LED?

I ask about this because I've tried to program it with the LED connected and the programmer usually hangs (you can see in the schematic where I connected the programmer, to nets PB0 and PB1).  I had hoped the resistors between the pins and the LED would be enough to isolate the LED but it doesn't seem to do the trick.  Disconnecting the LED allows the programming to succeed, however I won't be able to disconnect it once everything is soldered to a PCB.

Q: In a very general sense, what steps are usually taken by ICSP designers to isolate pins that have to be dual-purposed for programming as well as circuit control?

Thank you!


texts:
I have started learning basics about circuits and I stumbled upon this circuit in which I have to find out what is the value of Vo.
I have thought about using mesh method but it is a bit confusing in this circuit and I couldn't figure it out yet.
Could anyone help out, it should not be difficult for anyone with experience.

Thank you.

This is what I have tried using mesh method:
Starting from left side the loops are 1 and then 2(middle top) then 3(middle bottom) then 4.
Mesh 2: -2Vx + (I2-I3) - Vo = 0
Mesh 3: 2 + (I3-I2) + Vx = 0
Mesh 4: 2 + I4 + Vo + I4 = 0

I am not sure if those three were correct, but regardless of that, the one that confused me which I didnt write here is the first loop (Mesh 1) because it would seem for me that it would simply give 3Vx = 0 which is not correct for sure.

Hopefully this shows enough were I might have done something wrong.


texts: Correction factor for monitor based off orthogonal regression

texts:
I'm seeking some clarity about providing a correction factor for an instrument based off orthogonal regression. Currently I have a machine I built myself, co-located with a reference monitor recording PM10 pollutant data. I want to eventually be able to deploy this station on its own and trust its recording reasonable data, so am looking for a way to calibrate my station against the reference machine. After reading around the topic, it seems orthogonal regression is the usual form of analysis, rather then basic linear, as it assumed random error for both the reference and the built_station.
I have used the below example of data for the purpose of this question, when in reality I have over 9 months of data at 15 minute intervals. Where x= reference_station and y=built_station

What my end goal is to perform orthogonal regression on a data set like the above example and perform a correction factor, so I can re-deploy my machine and say it is, to some degree of confidence, recording suitable data. I'm unsure if the equation is similar for linear regression and am stumped at where to begin.
I'm familiar enough with linear regression and the correction factor I can form based off that, where x=(y-c)/m, but I'm struggling to piece together the information required to do a similar level of analysis based off orthogonal regression.
If anyone could help with some clarity around the topic and how I could achieve a final result, whereby if I apply the obtained correction factor based off the analysis of the two stations side by side, I can use this correction factor for my station and potentially achieve more accurate measurements of PM in my area.


texts: Which SIPO chip is better, 74HC4094 or 74HC595 or something else?

texts:
I want to drive lots of LEDs in a spinning persistence-of-vision (POV) device.
I need one output pin per LED, because matrix techniques don't work right in spinning POV devices.
A serial-input, parallel-output (SIPO) chip is the best way to independently control lots of output pins using only a few pins on my microcontroller, right?
Which SIPO chip should I choose?

74HC4094 used in Doboz
74HC595 used in bicycleledpov aka spokepov
TPIC6595 used in ... (a POV device I can't find the link to right now)
... or perhaps something I'm overlooking?

Does one SIPO chip clearly have more capabilities or easier to use than another, or are they all more-or-less equivalent functionality?
They all can be connected in the "daisy-chain SPI" configuration, right?
If I only have room for one kind of SIPO chip in my box of
"electronics components I always have on hand",
which one should it be?


texts:
I am trying to use the ethernet phy on my FPGA.  I am at the point where I can receive a frame.  The frame I can see using chipscope matches the data of the frame sent from my computer which I can confirm using tcpdump. However the crc I am computing does not seem to match.  The last 4 bytes of my packet as seen on the card are 0x4b504124.  However, both my on card calculation and C++ calculation which match are 0xC3899D7. I thought the c code which I copied from somewhere was correct for ethernet. I checked it against some other c code I found and they match.  Can someone point me to a correct implementation of c code for ethernet crc, or tell me what I am doing wrong?

unsigned int crc32b(unsigned char *message, int sz) {
   int i, j;
   unsigned int byte, crc, mask;

   i = 0;
   crc = 0xFFFFFFFF;
   while (i < sz) {
      byte = message[i];            // Get next byte.
      crc = crc ^ byte;
      for (j = 7; j >= 0; j--) {    // Do eight times.
         mask = -(crc & 1);
         crc = (crc >> 1) ^ (0xEDB88320 & mask);
      }
      i = i + 1;
   }
   return ~crc;
}
...
uint16_t buf[] =
{
    0x3333, 0x0000, 0x00fb, 0x0050, 0xb624, 0x9756, 0x86dd, 0x600b,
    0xa860, 0x0035, 0x11ff, 0xfe80, 0x0000, 0x0000, 0x0000, 0x6191,
    0xd947, 0x7f85, 0xc538, 0xff02, 0x0000, 0x0000, 0x0000, 0x0000,
    0x0000, 0x0000, 0x00fb, 0x14e9, 0x14e9, 0x0035, 0x7e5c, 0x0000,
    0x0000, 0x0002, 0x0000, 0x0000, 0x0000, 0x055f, 0x6970, 0x7073,
    0x045f, 0x7463, 0x7005, 0x6c6f, 0x6361, 0x6c00, 0x000c, 0x0001,
    0x045f, 0x6970, 0x70c0, 0x1200, 0x0c00, 0x0001
};
unsigned char* data = (unsigned char*)buf;
std::cout << crc32(data, sizeof(buf)) << std::endl;


texts:
I’m trying to simulate a half wave rectifier for a -84dBm 2.4GHz AC signal.
The rectifier doesn’t seem to be giving me the correct waveform - the negative half cycle isn’t blocked?
Also sort of confused about how I’m supposed to pick the capacitance value.
Would appreciate any help and guidance.


texts: Compensating for Accelerometer Cross-Axis Sensitivity

texts:
For my inclinometer application, I use an integrated 3-D accelerometer chip that outputs analog voltage.

Before I deploy my device, I submit it collect a bunch of samples with different temperature and angles for temperature compensation.

The problem I am experiencing is that voltage outputs for each individual axis are not completely independent. For the same temperature, if one axis is kept constant and the other changes, the former will output some change as well.

For example, let's say I'm measuring "g" on the pitch axis and the output is zero when the roll axis is zero. If I roll the accelerometer to one side, I get the corresponding roll "g", but pitch will have a slight change (+/- 2 degrees), even though pitch is still zero.

Any ideas on how to achieve better precision out of this?


texts: Any cheap and easy ways to isolate analog signals?

texts: I want to isolate some transducer signals. Everything I've looked up is pretty expense/requires a lot of supporting circuitry which, because of volume, is not ideal. What is the easiest/cheapest way to isolate analog signals?


texts: Electromagnet Options to Vibrate Long String at 80Hz

texts:
I recently completed a popular maker DIY where I recreated a product called SlowDance. You have see the original in action here https://player.vimeo.com/video/262079608

This product functions on the premise that an Electromagnet vibrates the object in the frame at around 80hz and then strobes LEDs lights slightly slower than 80hz producing the illusion of slow motion (the LED strobing is not discernible to your naked eye). For my DIY version I used the electromagnet, Arduino sketch, and PCB available in this kit:
https://www.tindie.com/products/Nick64/jf-slomo-slow-motion-frame-diy-kit/

Now I'm interested in creating a scaled-up version of this frame but lack the know-how from a electrical engineering standpoint.

The intent for the scaled-up version would be to vibrate a 4-6ft long string of unknown composition at 80hz. I would then anchor the string taught at one side of the frame and attached it to the electromagnet at the other.

My question is fairly simple, what type of electromagnet would be best suited to accomplish vibrating a 4-6ft long string at 80Hz and getting an appreciable range of motion out of the string (and any object I subsequently attached to it)?


texts: STM32F4: How to get data from multiple channels sampled from a single ADC?

texts:
So I have searched everywhere for a solution to this problem but I can find anything. I have three channels connected to ADC1 of my STM32F446ZE-nucleo and I want to sample the channels at a rate of 200 Hz each. I set up TIM2 and linked it as the interrupt for the ADC conversion, and this works fine for 1 channel. But I am struggling to get it to work for multiple channels since I don't know how to get the data from each specific channel within the HAL_ADC_ConvCpltCallback.

My setup looks like this:

/* ADC1 init function */
static void MX_ADC1_Init(void)
{

  ADC_ChannelConfTypeDef sConfig;

    /**Configure the global features of the ADC (Clock, Resolution, Data Alignment and number of conversion)
    */
  hadc1.Instance = ADC1;
  hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV4;
  hadc1.Init.Resolution = ADC_RESOLUTION_12B;
  hadc1.Init.ScanConvMode = ENABLE;
  hadc1.Init.ContinuousConvMode = ENABLE;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_RISING;
  hadc1.Init.ExternalTrigConv = ADC_EXTERNALTRIGCONV_T2_TRGO;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.NbrOfConversion = 3;
  hadc1.Init.DMAContinuousRequests = DISABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SEQ_CONV;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
    */
  sConfig.Channel = ADC_CHANNEL_0;
  sConfig.Rank = 1;
  sConfig.SamplingTime = ADC_SAMPLETIME_15CYCLES;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
    */
  sConfig.Channel = ADC_CHANNEL_1;
  sConfig.Rank = 2;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
    */
  sConfig.Channel = ADC_CHANNEL_2;
  sConfig.Rank = 3;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

}

/* TIM2 init function */
static void MX_TIM2_Init(void)
{

  TIM_ClockConfigTypeDef sClockSourceConfig;
  TIM_MasterConfigTypeDef sMasterConfig;

  htim2.Instance = TIM2;
  htim2.Init.Prescaler = 41999;
  htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim2.Init.Period = 4;
  htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  if (HAL_TIM_Base_Init(&htim2) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_UPDATE;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

}

I start my ADC and timer after receiving data on USART3 like this:

// start timer and ADC interrupt
HAL_ADC_Start_IT(&hadc1);
HAL_TIM_Base_Start(&htim2);

This is where I am struggling to get the right data:

void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
{

    // get values
    WE_ADC_VAL = HAL_ADC_GetValue(hadc);

    uint32_t nrConv = hadc->NbrOfCurrentConversionRank;

    // populate buffer
    transmitBuf[0] = WE_ADC_VAL >> 8; // upper 8 bits
    transmitBuf[1] = WE_ADC_VAL & 0x00FF; // lower 8 bits

    // send by interrupt mode
    HAL_UART_Transmit_IT(&huart3, transmitBuf, 2);
}

I thought that hadc->NbrOfCurrentConversionRank should have info on which channel is being sampled, but it is constantly 0 (I thought it would go from 1 to 2 to 3). How would I go about to get the individual channel's data at each conversion complete interrupt? Any help would be appreciated :)


texts: Series/parallel combination of resistance/capacitance in an RC circuit (wrt LCR meter readings)

texts: I have this equivalent circuit I am working on. I have to find out individual values of all components in it. I can measure resistance, capacitance and impedance of the whole circuit. I am not sure resistance and capacitance values I measure with LCR meter are equivalent values of capacitance and resistance in this circuit? If so, how Ra, Rs and Rc are connected in terms of series and parallel to find equivalent resistance? Similarly, for capacitance?


texts: Estimation of swimmer's velocity from IMU sensor

texts:
I am dealing with the problem of estimation the swimmer's velocity. In the same time data from IMU sensor and tethered system are acquired. Data from tethered system are reference data. From IMU sensor acceleration, angular velocity and strength magnetic field data were acquired. IMU sensor was placed on lower back.

Example data from tethered system for the one trial:

The best velocity from IMU that I estimate was:

and for the comparison purpose:

My questions are:

As it can be seen, the curves are not overlap exactly. Is it possible to improve the results for IMU sensor?
Do you have any idea how to pre-process data from IMU?
How improve data from tethered system?


texts: Sharing a USB keyboard between two PCs on a button flip

texts:
The PCB for the task would comprise of a USB connector, two sets of 4 PTH for the two USB cables (one set towards PC 1, the other towards PC 2), shared GND and TX and a DPDT switch for separating the VCC and RX.

Will that do? Could I get away with even a SPDT switch? I doubt I could as I do not have Germanium diodes in order to isolate the two VCCs of the two PCs and neither the parts for a FET and logic gates setup.


texts: I'm trying to replace a couple broken LEDs. They run on 3V, the white case is 2.5mm by 8mm, but there's no markings on the part or the PCB it came off of. Only other thing I can say is they're fairly bright, coming out of a holiday decoration.


texts: Differential amplifier, superposition theorem, output derivation, what is a loop here?

texts:
So based on this article, when V1 is removed/grounded, in this picture.

Is the loop number 1 drawn correctly? Or does R3 and R4 both belong to the same loop? I'm not sure how Vout2 was calculated. It's supposed to be: \$ -V2 \frac{R4}{R3} \$


texts: Battery Wiring - 3 Independent systems with common ground

texts:
Background:  Building a radio control wheel bot.  Using a motor controller that recommends independent power supply for 1.) power to the controller and 2.) power to the motors.  Also want a 3rd power supply for accessories (lights, horns, etc.).

I am using 8 identical lead acid batteries.  6 in parallel for the motors, 1 for the controller power, and 1 for the accessories.  All 3 systems are 12v.

I want to hard wire a solar charger (with controller) to charge the systems, but I will put a switch on all the positive connections to the charger, so I can choose when each system is being charged. I do not want to put switches on the negatives though.

So now the question:  Is it ok to connect all the grounds from all the batteries together?  Then, if I want to charge all 3 systems at the same time, I will turn all the charging switches on, which will effectively put all 3 systems in parallel.  Is this ok?

Is it ok to charge one system while all the grounds are connected?  Most likely i will want to charge the controller power and accessory at all times, but only charge the motor batteries when I'm not driving it (to prevent voltage/current spikes from going to the controller power).

Any explanation is greatly appreciated.  Thank you!


texts: Problems without ground, Amplifier & Exploding surge protector?

texts:
Not sure if this is a common issue, or how to formulate a single question, so please feel free to edit.  I'm just trying to understand the situation and don't know where else to turn.

I have an electrical outlet in my office that powers my computers.  They work just fine, and I never had any issues.

I plugged in a tube guitar amplifier the other day and instantly burned a fuse on the input section of the amp's circuit.  Swapped out a new fuse, same thing.  Took the whole amp (again with a new fuse) and plugged it into a different office in my building.  Worked like a charm (as it did before bringing it to the office).

I decided to plug in a surge protector power strip. It is the type that lights an LED when the outlet is grounded.  I plug it in and it exploded!  Well, it made a huge pop inside the power strip and stopped working followed by a stream of smoke and burnt plastic.  There was nothing plugged into this power strip.

I pull the outlet out, and there are only two wires.  There is no ground wire.  The hot is on the correct side (provided that the black is indeed hot).

Does this sound like a normal string of events considering there is no ground?  Or is there something SERIOUSLY wrong in this scenario?

I've played in an industry where we pop out the ground on amp cords on a regular basis to stop 60hz hum in some installations.  Why would the absence of a ground here cause this problem?

Thanks for any info.  If this seems off-topic, please help me re-formulate the question so that I can understand what's going on.


texts:
I often see the same method for computing voltage distribution in electronic circuits implying components whose V-I curves are not trivial.

For example, in a circuit implying a resistor and a LED having 2V / 20mA caracteristics, we substract 2V from the supply voltage to determine the remaining resistor's voltage, and we assume current in the whole circuit is 20mA to determine resistor's value using Ohm's law. But what about a direct computation? If the resistor's value is too low, the LED voltage would be higher than this ; on the other way, if the resistor's value is too high, the LED voltage will be lower.

Is there a standard way to compute voltage distribution directly, based on chosen components (i.e. the inverse of the method that determines other components)? And more generally, is the voltage distribution always unique?


texts: When considering Zener current, is lower current generally better?

texts:
I'm creating a small assortment for my parts box, and I wonder about Zener currents. For example, a selection of 4.7V 500mW Zeners spans a wide range of Zener current values:

BZX79C4V7 = 5 mA Zener current (80 ohms Zener impedance)
1N5230B = 20 mA (19 ohms)
1N750A = 75 mA (19 ohms)

What are the pros and cons of selecting one over the other, in terms of general utility / substitutability? As a rule, is a lower Zener current generally better?


texts:
Question about rewinding a brushed DC motor:

I've taken apart a DeWalt router to see why I was getting so much sparking (already tried replacing brushes). While testing the resistance between commutator bars, I found a high peak which corresponded with a burn mark. This is my first time doing this and just going off the internet, does this mean the wire is damaged somewhere?

I think the only options are to replace the rotor or rewind the existing one. I know the latter is a bit out of my depth but I'd like to give it a go, especially if the armature I'm doing it on is wrecked anyway - can anyone point me to a good reliable explanation of the winding? I think I've got my head around it, but it would be good to have confirmation from someone who actually knows what they're doing. I've seen a few diagrams that all looked slightly different.

FOLLOW UP:
I've been looking around for a matching commutator to replace the current one. I think this will be easier than trying to solder the wiring into the tabs on the bars with them already spot welded down (i think?). The closest match I have found is 2 mm smaller in diameter (original 33.5, measured worn).  Are there any issues with changing the nominal diameter of the commutator a little? This would bring the distance from the commutator to the brush housing to around 3mm

Thanks.


texts:
For an upcoming ESP8266 project, I need to use a relatively large (or several smaller) batteries and am hoping to get at least 10Ah.  To achieve long life, I will be utilizing one of the ESP8266's available sleep modes.  In the deep sleep mode, it utilizes somewhere between 10 and 70 microamps.

I know that most lithium ion batteries are recommended to discontinue discharge at a voltage of around 3.0-3.2V, for the sake of battery health.  However, do they also have any kind of limitation such that the battery will not supply current if the load goes below, say, 1mA?  I apologize if this is a nonsensical question, but I know very little about batteries, and I want to ensure I can put it into deep sleep while using a battery like this.


texts: Output impedance seen by the load in this emitter follower

texts:
I'm trying to understand what the concept of "output impedance" relates in a simple buffer such as an emitter follower conceptually without digging in formulas.

Imagine the Rload is about to be coupled to the emitter terminal of an emitter follower as shown in the below drawing:

Can we say the output resistance/impedance seen by the load Rload is re(intrinsic emitter resistance)?


texts: Electromagnet is acting perpetual... why?

texts:
Here's what I have - I made it as to be as classical of a electromagnet as possible:

a) Soft iron "U" shaped round bar-stock, ends machined to be flat & parallel. Spool of copper wire slid over one leg of this "U" shape iron.

b) Soft iron flat "keeper" bar to go across the ends of part "a" above

Momentarily connect the wire across a battery: the flat bar jumps to, and becomes firmly attached to the electromagnet.

Remove battery.

Flat bar stays firmly attached...

as long as I don't pull it off...

...for months without losing strength.

Why?

Yet, when I do remove it, there is no remaining "pull" that attracts the flat bar back to the U shape rod... so it's not becoming "permanently magnetized"... which is why soft iron was used.

Also, if a flashlight bulb is connected across the ends of the wire before removing the "keeper" bar, the bulb flashes. (in this case, the "keeper" is quickly smacked with a screwdriver handle in order to get high detachment speed.

This happens no matter how long it's been sitting on my shelf... or even hanging upside-down by the "keeper" bar... with the weight of the electromagnet hanging by the keeper bar.


texts: Voltage divider : using board voltage vs Power supply

texts:
I am using an ncd relay power switch that is capable of reading 8 sensors.

When I use the 5V and GND provided by the board I get a Vo=3.46V.
If i switch R1 to 100k I actually get Vo= 2.7.

When i use an external 5V and GND provided by a power supply I get Vo=2.6, still using R1=10k here.

Question: Why am I getting different voltage values from the two different power sources. Why am I having to switch R1 to 100k to get the proper Vo when using the relay board? Is there some voltage reference I need to take into account?

According to curstomer support "the ADC inputs on that board float(they are not pulled either direction".

simulate this circuit – Schematic created using CircuitLab


texts: Flat panel that outputs light - to be used as a replacement for an EL panel

texts:
I'm trying to create a lit surface similar to a backlight for an LCD display (I'm replacing an EL panel in an arcade machine). For various reasons I don't want to just replace the EL with more EL.

The biggest constraint is that I only have about 0.2 inch of thickness to work with (the old EL panel and it's PCB are slipped into a very narrow space).

My thought has been to edge-light an acrylic panel (I have some very narrow LEDs from LITE-ON), and then etch it's surface somehow so that the light will exit from the face of the panel. My problem is that I don't have a good way to measure the light output to see if one of my ideas is better than another.

Is there some simple trick I could do with a digital camera to get an idea of the light output of the panel? I don't really need an absolute measurement, I just need some way to compare relative to my other attempts.

Also, any clues on an optimal pattern for etching the acrylic would be nice - I've so far tried scratching the emitter surface with steel wool and sandpaper to not great effect. I also tried scoring parallel lines with a knife, and that's been interesting, but I'm having trouble figuring out what's my best bet here.

Should I be trying for good light output from the acrylic then adding a diffuser on top of that?


texts: Do I need to limit the current on the inputs of a parallel load shift register?

texts:
I have a Parallel Load Shift register (SN74HC165)

When connecting the parallel inputs, do I need to add a resistor to limit the current?

And if so, can I use one resistor for all 8 Inputs in total?

This is my intended circuit:

simulate this circuit – Schematic created using CircuitLab


texts: Unidirectional logic shifting (3V3 to 1V8) with minimum components?

texts:
I am trying to bypass the pushbutton of an external device (an LTE Hotspot) and switch it on using a Raspberry Pi. The pushbutton pulls down 1.8V for 2 seconds and then the external device powers on. I'd like to do this using an RPi but since it runs at 3.3V I am hesitant to tie it directly to one of the GPIOs as I don't know if the device is 3v3 tolerant.
Ideally, I could have used a logic shifter but the external device does not expose the Vdd.
Is there a way to perform a unidirectional level shifting with minimum components?
Any ideas are welcomed.


texts:
We have 3 motors each 0.37kW, they are now running on mains power, sometimes mains power cutoffs/fails, in that case we want the motors keep running. The motors are controlled by a PLC which do not have a battery backup. How can we keep motors running with & without PLC, in case if mains power cuttoff?
Control table

Mains    Control
------   -----------------------------
ON       by mains with PLC control
OFF      by UPS without PLC control


texts: GOTO a specific address in HI-TECH C Compiler PIC18F

texts:
I'm trying to jump to a specific address in HI-TECH compiler and the address is given dynamically.

I tried using asm() function but it looks like the argument must be a constant char[]. Is there another solution to jump to an address using goto or another function like goto_address(address) in CCS Compiler?

I tried this:

long address = 0xA20;
char addr[15];
sprintf(addr, "goto %s", address)
asm(addr); // Here argument error.

Thanks.


texts: 6 Band Resistors, which way should the bands be read

texts:
I've just bought a bag of random resistors from Maplin, and can't work out which way round the six band ones should be read.

For instance I have one which is either:

  Violet Orange Red Brown Brown Red

or

  Red Brown Brown Red Orange Violet

The red band at either the right or left appears thicker than the others.

Can anybody point me to somewhere with a clear explanation (or provide one themselves) as searching on Google isn't finding me anything lucid.


texts: Why DC/DC with external mosfet have limited current rating?

texts:
Why does DC/DC converters with external mosfet have current limit?

From my understanding, for components with an integrated MOSFET, the limit comes from the components (less performance, the Rdson is often higher), if a too high current flows through the component it risks to heat too much and exceed the junction temperature.

But if I use a DC / DC "controller" which controls an external MOSFET, no current flows through the component itself. It would then be enough to choose a mosfet with a high current Id

I take as an example the TLE6389, the typical application is given in the datasheet

My hypotheses:
Does the current limitation come from the current measurement function (the internal logic works up to a current value) or does the limit come from the ability to control a more powerful mosfet (the GDRV pin which controls the gate of the mosfet provides an output between 6 and 8 V)?


texts:
Activity: maintenance (installing/replacing hardware parts, like motherboard, CPU, DIMMs, graphics cards) inside an ATX case. Goal: ESD protection and user safety.

Original question: Is 'grounding a desktop PC via the power cable' safe when working inside the case? Answer: in theory, maybe. In practice: NO!

Edited question: Is 'grounding a desktop PC via low impedance (less than 1Ω) path' safe when working inside the case? (Considering the PSU is completely disconnected from live and neutral.) Answer: if a dissipative antistatic mat should be grounded via 1MΩ resistor, then a good conductive surface like the unpainted inside of an ATX case should too.

New question: Is 'grounding a desktop PC via 1MΩ resistor' unsafe when working inside the case? (Considering the PSU is completely disconnected from live and neutral.) Answer: probably not as PE (Protective Earth) is only needed when an appliance is plugged into a wall outlet.

People often advice 2 things to prevent ESD damage:

Antistatic wrist strap, connected to the case of your desktop PC.
The PSU should be turned off, but still plugged into the wall outlet.

I do understand a low impedance path is desirable in case of a residual-current. But when a PC is powered on, you should not be working inside the case anyway.

If the power cable is disconnected, then is a low impedance path to mains earth safe when you are building a PC or doing maintenance (installing/replacing hardware parts) inside the case? Can the case become a shock hazard in a worst case scenario?

After all, you're probably going to touch the unpainted conductive inner surface of the case at least a few times, while (un)screwing things. Should there be another resistor?


texts: How to properly unlock an FFC connector?

texts:
I'm trying to replace a part on my camera and need to disconnect a connector that looks like this:

From what I understand, they're extremely fragile and so I don't want to accidentally break anything (as many others unfortunately did when working on this camera).

Whats the correct way to unlock this connector?

Which part of the connector unlocks? The bottom or the top part?


texts: I have 2 feed through capacitor NFM21PC475B1A3 & NFM21PC105B1C3. These haven't the same capacitance. I want to separate them but I can't measure. Help me what should I do?


texts:
Hi i find in some bloc schematics the following bloc:

I don't have the schematic for this bloc and i want to know what is the linear N-rate circuit ?and what is used for ?


texts: How to stop electric fluctuation while using PIR sensor

texts:
I used a triac to control the AC current to my led bulb  but once the bulb is in on state, it's flickering.
I made a bridge rectifier and using transistor connected to triac, the input is given through PIR sensor
How can I reduce flickering, should I use a relay instead of triac. I just want to ON and Off based on pir sensor detects object
I read somewhere that it's because of small current.
I did exactly same in this youtube video
https://youtu.be/6Bua0g8HDIY


texts: Designing a synchronous counter with d flip flops

texts:
I have to design a counter with two inputs: x and y. If y = 0, the counter behaves like a 3-bit ring counter, and if y = 1, it behaves as a 3-bit Johnson counter. If x = 0, it counts up, and if x = 1, it counts down. I may only use D flip flops, and any logic gates I require.

For reference, here are the state tables of a 3-bit ring and Johnson counter (in that order):

So naturally, I created this big table of states:

Since there are two inputs, and three states, each following state depends on five bits. Therefor the K-maps for Q1+, Q2+ and Q3+ (which are actually D1, D2 and D3 for the flip flops) are maps of five variables, making this somewhat complicated.

The question is: is there a way to do the minimization with k-maps in a simpler manner (perhaps I am missing something)? Or, if there is no way to simplify the minimization, then is it wiser to use k-maps of five variables or perhaps another method (quine-mccluskey maybe, or something completely different)?


texts:
How much can a transformer go without a failure?

For example, let's say that a transformer is designed to work with 500mA. (obviously you should avoid exceeding this limit)
But as I learned with capacitors - their tolerances are up to 20%.  (you can pretty much safely run a 10v capacitor with 12v source)

And now I am wondering - what are transformer tolerances?
In other words, can you run a 500mA transformer at 600mA safely and without failure?  I know this is really subjective as it depends on the transformers quality but there has to be an average number.


texts: Power consumption of LD33CV voltage regulator

texts: Does LD33CV voltage regulator consumes any power when there is no load? I used my multimeter and it shows the current flow as 0.00A without any load. But I feel my battery is draining out because of the voltage regulator


texts: Which STM32 development board is suitable for a beginner?

texts:
I am trying to learn STM32 programming. My goal is make my own embedded system using STM32 chip on separate PCB.

There are several development board in ST. What is the most suitable one for a beginner?

How about STM32F4 Discovery development board?

Your opinions are greatly appreciated.

(This is about product recommendation, However this product is learning tool. I think I'm not violating rules)


texts:
In using an electret mic, I understand that you need to supply it some voltage for it to operate, and that you connect a coupling capacitor at its output to remove the DC biasing component of the signal.

My question is, what would the output be when you don't use a coupling capacitor? Would it be an AC signal with a DC offset when the mic detects a sound? And when it does not detect a sound, is the voltage at the output equal to the supply voltage?