texts: What amperage fan is safe to replace my 0.13A fan?

texts:
Fan on my wine fridge is buzzing, so I'm replacing it with a CPU or case fan off newegg.

Should the replacement fan be rated at more than .13A, or less? I suppose the fridge probably puts less than .13A in, but the replacement fan should have a max of at least .13A. Would it be bad to get a fan with an even higher max, say .15A or .2A?

Edit: Existing fan specs are as follows (from this pdf) and the sticker on the fan.

Model:             RDL8020S
Bearing System:    Sleeve
Rated Voltage:     12VDC
Operation Voltage: 6~13.8
Rated Current:     0.13A
Rated Speed:       2,500 RPM
Air Flow:          27.6 CFM
Air Pressure:      1.7 mmH2O
Noise Level:       30 dBA
Dimensions:        80mm x 80mm x 20mm

I found several fans that have lower amperage, but I'm reluctant to buy them. Finally I found this fan which has .13A rating, but I suppose that means it would always be spinning at its highest setting.

P.S. I realize that almost all computer fans have 3 pins not the 2 that this one has. I figure I'll just splice red to red, black to black, and snip off the yellow one, which is just throttle control anyway.


texts: Can I program a QUAD SPI Chip with a standard SPI microcontroller?

texts:
I have to program a MX25L12835 Quad SPI chip. This is a Quad SPI serial flash. Is it possible to program this using an arduino? Can this be used as a simple 1 channel SPI or can quad SPI interface fall back to regular SPI? Or do I need a microcontroller that supports quad SPI?

Do I need to do anything special to connect the flash chip?


texts:
Why are computer memory capabilities often multiples of a power of two, such as 2^10 = 1024 bytes?

I think it is something related to the binary logic, but I do not understand the precise reason for that.


texts:
So I'm trying to build a guitar amp switcher (and I don't really know what I'm doing =)).

The idea is that guitar out is connected to X4 jack and then switched to either X1, X2 or X3 jack, which goes into amps input.

Then amps speaker out are connected to X5, X6 and X7 jacks and selected output is routed to X8 jack.

S1, S2 and S3 switches are parts of 4 pole 12 way rotary switch.

Currently, I tried a schematic listed below:

However there is a high pitched noise when using it which disappears when I use some kind of guitar pedal before guitar in.

If I connect everything this way I get high pitched noise (everything is connected with TS cables):

And this way there is no noise:

Is there any way to fix this issue?


texts: What does clock/signal speed actually do?

texts:
This is may be a silly questions but I am curious.
I know that in circuits power lines are at speed near light but why are signal lines so different?
Let's say I use I2C(MCP23017) I can choose between

100 kHz
400 kHz
1.7 MHz

while SPI allows up to 10MHz.
For the Ethernet connection I also need a 50MHz Clock signal.
As I know this board doesn't like to many questions at the same time I try to keep my focus on the most important for me.
What does these numbers mean for my circuit (Is bigger always better)?


texts: what does this mark mean on reed switch?

texts: I have some used reed switches with no datasheets. all of them have a black mark on one side. I want to know what does this mark mean?


texts: Analog switch on an instrumentation amplifier input

texts:
I'm working on a project for school that involves a configurable input stage (AC/DC coupling and variable input impedance) connected to an instrumentation amplifier. I am wondering whether I will experience any major DC offset issues if I connect an analog switch to the in-amp's inputs, or if I would be better of using relays.

Here's what my input stage currently looks like:

A few notes on the design:

The 1.3k resistor pair provides protection for the input stage
The resistor network connected to the switch is designed to allow be to select the input impedance

The options are infinite, 50ohm single-ended, 75ohm single-ended, 100ohm differential, and 150ohm differential.

To the left (out of image), there is a mechanical relay-based AC/DC coupling selection circuit
I realize that the analog switch will have no protection, but I'm hesitant to use diodes due to leakage currents
I do not need fast switching

This question is mainly about leakage current: is the leakage of a CMOS switch (such as the ADG409) low enough that it won't produce a significant DC offset at the output? Or would I be better off using relays?

Edit: something like the MAX14778 would be a better option, assuming that the leakage currents are common-mode. The only problem is that it comes in a 5x5mm QFN package, which is not ideal for prototyping.


texts: Is this a suitable sine wave osc? how would I control the frequency?

texts:
Overview-

I'm making a bank of analog sine wave oscillators and I'm interested in keeping the design compact.

I've started by making a Wien Bridge oscillator. As I'm working from a single power supply and I'm trying to keep the design small, I've been using the LM386n-1 IC.

I'll be using the oscillators to do some additive audio synthesis, maybe some FM and I'll probably need some of the oscillators as LFOs.

My questions are-

Is this a suitable approach for making a compact analog sine wave oscillator?

Also, how would you suggest I control the frequency, which component value should be changed to achieve this? - I've tried messing with all the resistors to change the pitch, but they all seem to be interdependent.

Here is the circuit I've been working from, it's from the National Semiconductor LM386 Low Voltage Audio Power Amplifier datasheet-

And this is what my implementation looks like, I don't have a suitable incandescent bulb so I've just replaced it with a 1KΩ pot. I'm still not sure what I'll use in the final circuit as AGC, suggestions are welcome.


texts: Wireless charging with metal plate on back of phone: eddy currents wasting energy and heating up?

texts:
I just got a car mount for my phone which uses a small magnet stuck to the back of my phone. I'm not sure the material, but I'm guessing it's conductive.
My concern is with wirelessly charging my phone.
Finding all of the necessary parameters to calculate the I^2R losses seems more complicated than it's worth. Does anybody know from experience/intuition whether this will cause any issues? I may try wirelessly charging to see if it's slow, or if the plate heats up, but I'm slightly concerned.


texts: DC1601B Demo board input line caught fire during use

texts:
I am using a DC1601B-C buck-boost converter in an automotive circuit to power some various electronics that I have added. It worked fine for a couple months, but under a less-than-normal load of 2.25A (when it should be able to output up to 20A) the input power pin caught fire.
In my circuit I also have a SLD8S17A TVS diode attached between the input power and ground to block the load dump. The diode was still functional after the fire so I don't believe the fire was caused by load dump.
In the DC1601B-C datasheet, the test instructions say not to "hot plug" the board. It also says to start power with the J1 jumper in the "OFF" position and switch it to the "ON" position after input power was applied. I had the board soldered into the circuit and left the jumper in the "ON" position, then applied power by turning a key switch with the load already attached.
I tried to research what hot plugging was and all I could find was hot plugging devices into a computer while the computer was still on, which I am not doing, so I am not sure what hot plug means in relation to a voltage converter.
My question is, was I "hot plugging" the converter by having it soldered into my circuit with the load attached before the power was turned on? And a follow up question is what else could have caused the input line to blow/what other protection circuitry am I missing?
As you can see in the photos below, the regulator caught fire only at the input power pin.
How can I prevent the DC1601 demo board from catching on fire?


texts: Can I achieve a one shot button without a 555?

texts:
I have a complex circuit, but my problem only relates to one small part.

I have a relay, which is energised by pulling the low side low using an NPN. I would like a pushbutton to operate the transistor (and therefore the relay) for a time (500ms ish) then deactivate it and wait for the next push (ignoring the button if held). I understand how I can achieve this using timers (or a MCU), but I was hoping there might be a more simple and compact solution...

The image shows a simplified schematic of the starting point...


texts:
I have come across the following circuit in a datasheet for a battery charger:

I have also seen a similar use of the charging circuit for use as a lithium battery charger, e.g http://shdesigns.org/pdf/lionchg.pdf

But is this circuit implementation actually suitable for a lithium battery? (I know the 6V circuit would require the voltage output of the LM317 (R1 and R2) to be set dependent on the attached lithium battery voltage.)

I have read that lithium batteries need the following order to charge safely and correctly (Assuming the battery is not below  its discharge condition, in which case trickle charging is required first):

Constant Current (CC)
Constant Voltage (CV)

The constant current stage requires the battery to be charged at its max (fully charged) voltage with a fixed current. The max charge voltage is set by R1 and R2 in the top picture (Although would R3 affect the output voltage as it is in series with R2?). R3 and the BJT act as a current control.

The constant voltage stage requires the battery to be maintained at its max (fully charged) voltage, whilst the output current is steadily dropped. The battery is deemed "charged" when the output current is below a very small current limit, which is specific to the lithium battery. This stage initiates when the voltage across R3 gets close to around 0.6V the BJT starts the turn on, which shorts the adjust pin and drops the LM317 output voltage until it is stable at around 1.25V, which then reduces the output current to the battery?

Questions:

Does R3 affect the LM317 output voltage as it's in series with R2?
How does the BJT and resistor precisely work in this setup? Won't the battery initially try and draw as much current as it can, meaning 0.6V would develop across R3 before the battery is sufficiently charged to transition into the CV stage?
Wouldn't the 0.6V developed across R3 mean that the potential "seen" by the battery is approx 6.3V? (6.9V LM317 output subtract 0.6V). Wouldn't this be insufficient to charge the battery fully?
When the BJT turns on, the voltage output of the LM317 will drop to 1.25V as the adjust pin is shorted (which bypasses the resistors). Surely this is not suitable for the CV stage of charging, as the potential drops to way below the battery charging voltage? How is current output to the battery affected during this voltage drop?
Is the BJT even required for the CV stage? If just the resistor was used to limit the current, wouldn't the current to the battery decrease as it reaches full charge anyway?


texts:
I am a beginner and trying to make an IR sensor module for my project. I have implemented the following circuit diagram on my breadboard.

The problem is that even if I don't introduce an obstacle in between the sensors , the LED at the output is still glowing. Where is the error? How do I know that the sensor is still working? Please Help!
Thank you!

[ NOTE: I am using 330ohm resistor instead of 150 ohm mentioned in the diagram ]


texts: Single-supply op-amp behavior with 0V input

texts:
I am confused by how op-amps work. I have a single-supply op-amp: the power rails are +5V and ground. The circuit in the image says the op-amp is an LM741 but it's actually the op-amp built into the Cypress PSoC 4200M chip (data sheet). My understanding is that op-amps generally cannot output a voltage that is too close to the power rail. Therefore I expect that if I configure the op-amp as a voltage follower and tie the positive input to ground, I should get something greater than 0V from the output.

Looking at the data sheet, I think that, assuming I set the power to low and my load is minimal (it's an ADC), the output should range from 0.1V to VDDA (5V) - 0.1V = 4.9V.  Does that look correct?

The reason I'm confused about this is when I simulate the circuit in CircuitLab (with the LM741) and run the DC sweep simulation, I see the LM741 outputting the full range of voltages from 0V all the way up to 5V. It seems to be behaving as an "ideal" op-amp. But what's the point in choosing the op-amp model in the simulator and entering all the parameters if it's not going to simulate correctly? Am I doing something wrong or does CL just not simulate op-amps correctly or do I not understand how op-amps work?

simulate this circuit – Schematic created using CircuitLab


texts:
Let's imagine a regular deep cycle gel lead-acid battery from the building market.

Capacity: 100Ah
Nominal voltage: 12V

Is it really correct to say that the energy in the battery is 100Ah*12V = 1200Wh? Or should I rather consider that the voltage when fully charged is more like 13.5V and when fully discharged much less?


texts: How to calculate power from current and voltage, both of which are sinusoidal waveforms represented by phasors

texts:
I am stuck on working out power consumption when both the current and voltage is represented as phasors.

\$I(motor) = 4.5+j8.2 amps\$
\$V(motor) = 9.4+j5.5 amps\$

The answer I have been given to this question is 43.70 watts, however I do not know how to get to this answer. I've tried
\$Power = Voltage\times Current\$
Which game me -2.8+j101.83


texts:
I'm learning how to use Qucs using the tutorial.

But I have no idea what is DC sweep, AC sweep, parameter sweep, Vsweep, ... and so why to even use them.

Could anyone please help explain what are these "sweep" terms?

P.S. I'm not an electrical engineer, just that basic electronics is a first year subject so highly technical terms will mean almost nothing.


texts:
The Q-factor is often defined as Q=resonnance frequency/bandewith.
Suppose we take this definition and take two LC circuit which both have Q=1 but the first resonnant circuit has a resonnance frequency of 1 and the second one has a resonnance frequency of 10.
This means that the first circuit has a bandewith of 1 and the second one has a bandwith of 10. But if this is the case, I would say intuitively that the second circuit is less selective because it has a bigger bandwith. But the Q are the same so one says the selectivity is the same. It seems weird to me that in the formula of the Q we don't just have Q=1/bandwith. Why is that?

edit

But does it makes sense to say that the Q factor characterises the pic in the frequency domain even though in the figure just down here the shape are exactly the same but the Q factor are different?


texts: Detecting linelaser with photodiode and Arduino

texts:
I'm looking to experiment with a Valve Light lighthouse sort of setup. I've bought line lasers and pin photodiodes (BPW34) and get to successfully detect the laser line. The photodiode is in parallel with a 10K resistor; this seems to give the best results. I've tried with 100k, 18k and 1k for example. The photodiode is connected to an analog port of an Arduino with a reference voltage of 1.1v. The line laser is 5mW and connected to 3.3v. The line seems clear and visible at 5 meters.

The problem I'm facing is that the distance it detects the line is max ~ half a meter. The Valve lighthouse detects 10m easily. How do they get this phenomenal performance?

I think I could improve it with the following methods:

Using a comparator that compares the photodiode line with a low pass filtered line of the photodiode.
Implementing an amplifier using (for example an op amp or transistor).
Using an IR receiver instead. I have some lying around but I didn't get them to work with another laser, so I'm not sure about that.
Or using a different photodiode, that works from 700nm to 1100nm, like BPW 34 FS

Anyone has some ideas what would increase the distance best?


texts: Disassembling pre-assembled JST Rectangular Plug PHR-4 (0.079")

texts:
I'm going to purchase pre-assembled 4-Position Cable Assembly CABLE-PH04 with standard PHR-4 JST connector housing [0.079" (2.00mm) pitch].
The PHR-4 JST connector plug will be connected to mating 4-pos male Connector Header on PCB. For my needs, I need 3 wires connected on PHR-4 plug, so one wire is superfluous, and I need to remove it.
My question is, does it possible accurately pull out the single wire from JST PHR-4 plug without damaging the slight connector housing? If yes, how to pull out the wire accurately?


texts: Inductor selection for obtaining a noiseless analog power rail

texts:
I interface an image sensor, and the design schematic for power supply is:

How do I choose one from the available 3uH inductors based on the specs? I figured the maximum current and dc resistance specs, but how important to consider are the following specs for this particular application?

self resonant frequency
Q minimum

The sensor clocking can range from 5-30MHz.


texts: I wanted to short a solenoid, so   I just touched the wire of two adjacent loops at a point somewhere in between of solenoid, but now I wanted to know  what changes occur in its inductance and resistance?  .   How to draw it's equivalent circuit (i.e shorted L-R circuit) ? so that I can use it for other electrical purposes.


texts: Choosing power supply, how to get the voltage and current ratings?

texts:
Power supplies are available in a wide range of voltage and current ratings.  If I have a device that has specific voltage and current ratings, how do those relate to the power ratings I need to specify?  What if I don't know the device's specs, but am replacing a previous power supply with particular ratings?

Is it OK to go lower voltage, or should it always be higher?  What about current?  I don't want a 10 A supply to damage my 1 A device.


texts: What makes primary batteries leak on very deep discharge?

texts:
From my experience, if a primary (alkaline or zink) battery is left in a device with very low consumption (like a remote control, or a quartz watch) then at some point all the energy is drained and later the battery electrolyte leaks and damages the device.

What exactly makes batteries leak on very deep discharge? Do all primary batteries behave this way?


texts: Why does this washing machine have microprocessor pins directly connected to the main AC power?

texts:
I'm studying the attached washing machine partial schematic at the point in which the main microcontroller activates 2 water elecrovalves.
I would ask:

It seems the microcontroller pins 36 and 40 are connected by the 1k resistor to the main AC "ground" (which means phase or neutral). How is it possible that the 230V phase, and not the neutral, could be connected to the pin? From my experience an optoisolator is the correct choice.
The triac is not provided by a snubber. It is correctly designed?
Why does one of the triacs have a voltage divider with 560 Ohm resistor and not the other?

Thanks a lot


texts: Can a reverse biased diode be driven past its voltage rating but with current limited to few uA

texts:
If, for example, a Silicon diode rated at 100V is reverse biased at 200V (long term, not just very briefly) but in series with a few MegaOhm resistor such that the reverse current is limited to one microAmp (or a few uA), would that change the characteristic of the diode.  I know, from experience, that the diode won't become faulty but, rather, I am trying to inquire whether this is an acceptable practice. Presumably the diode works in Avalanche region but can it recover without any issues?

This question can also be applied to other pn junction devices e.g. transistors (C-E rating exceeded but current limited to a microAmp or two via MegaOhm resistor).
31May'18: WhatRoughBeast, Elliot Alderson and BimpelRekkie have all really made me think harder. Thanks all. I think you all have raised useful points. This question is not a theoretical one since I actually noticed a somewhat similar scenario in one of the circuits used successfully over a number of years, the series (collector) resistor being 470k but the device in question was an NPN transistor (BC547B) rated at 45V, Common-Emitter config. The positive rail could surge well beyond the 45V. Sorry, I can't post the full circuit due to strict NDA with various companies I worked for.
A diode (pn junction), once it reaches its breakdown voltage level cannot "allow" voltage across it to rise further (the I-V graph slope is very steep beyond the Breakdown voltage) so the series R will keep absorbing any further rise in supply voltage (like in a normal Zener diode). So, basically, my question effectively boils down to: "Can a diode (or pn junction in Transistors etc) be damaged, or deteriorate in its standard characteristics, if it sees Breakdown voltage repetitively over long term, keeping in mind it doesn't venture far into the Breakdown region, only slightly i.e. a few uA. If power dissipation is the only consideration then the answer is "No, it won't get damaged", but I had been suspecting a possible problem elsewhere, hence my question. BTW, other external considerations, such as Safety, Creepage/Clearances can be assumed to cope with higher voltage surge.

5 June'18: I have given it further thought and I think the answer also depends upon how rapidly the reverse voltage is applied. For a "very fast" rising (reverse) voltage, when the current is initially zero, all of the voltage will appear across the pn junction.  This raises alarm since there is (internal) di-electric breakdown consideration too (perhaps, at the back of my mind, this is what I had been worrying about). In practice, it may not be a problem since such adverse conditions are not so realistic (?). Anyhow, if anyone of you does manage to carry out relevant tests, perhaps on a Fast Recovery and on a slow recovery diode, then please do enlighten us too. If I ever get an opportunity and time, I'll endeavor to do likewise...keeping in mind, a failure will provide us with a conclusion but a "pass" won't (necessarily....since it's just a one-off test!)


texts: Interfacing Current transformer with PIC16f88

texts: I am trying to interface Current transformer with PIC16F88. I have used 120 Ohms burden( recommended is 125 ohms in datasheet) ,I am using 20:1 A CT with winding ratio 1:2500. The link to datasheet is :http://www.shahelectronics.net/MediaImages/SET2106-2500-20A-20AMP_CT.pdf   So please help me with some techniques for interfacing and coding.


texts: Voltage regulator UA78S09 (9V/2A) supplying only 0,4A of current

texts:
I power voltage regulator by 12V / 8A power supply.

UA78S09 is responsible to convert voltage to 9V for DC motor, which is able to swallow 1,5A at start and under heavy load. Motor however does not start even if specs for regulator states that it should be capable to provide 2A current.

Multimeter shows proper voltage 9V but max current peaks on around 0,4A only (only multimeter - no motor connected).

Why is that so?
 BTW: I have attached heat sink to regulator (if it matters here) and do not use capacitors.

Disclaimer: I am total noob, just started playing with simple circuits. So please be gentle with me ;-)


texts: Why are Samsung NAND flash memory chips so hard to find?

texts:
I'm looking at NAND flash memory chips for a home project I'm working on.
There seems to be quite a few manufacturers available, Micron seems a good choice (even though a lot of their chips, mostly the small ones, are asynchronous).
But Samsung chips seems impossible to find anywhere. Not on Mouser, not on Digikey, not on Farnell. Am I missing something?
Even their website doesn't seem to list anything. Are they only selling in big quantities?
Surely a lot of companies need to get their hands on low quantities for prototyping, right?


texts: Calculating instantaneous and average power

texts:
sorry that this is such a basic question but I need to calculate the average and instantaneous power for the following circuit:

A voltage supply in series with a resistor: V1 = 150sin(wt)V and R1 = 25ohms

I understand that t = time, w = 2*pi*f but what is confusing is that I am not given either time or frequency do I just assume that sin(wt) = 0 and V = 150V?

If this is the case then is the instantaneous power just P = VI (or (V^2)/R)?

How do i calculate average power if Pavg = VIcos(phi)?

Any help to these questions would be amazing.
This is a practice paper for an exam not homework.

thanks


texts: Connecting external 2.4GHz antenna to Intel Edison

texts:
I would like to connect an external 2.4GHz antenna to an Intel Edison.

According to Mouser, there are different Edison part numbers for different antenna configurations (internal or external). However, the unit I have has both an on-board antenna and an external U.FL. connector:

I can't find any relevant documentation, so I thought I'd ask here: what are the practicalities of hooking up an external antenna to Intel Edison? Would I need to remove the onboard antenna first? If I don't, what are the downsides of having both antennas connected?


texts: What is a safe clearance for ground planes?

texts:
I am designing a board and the ground plane default clearance was set to 22 thou. I have been told in the past that a rule to thumb, with signal lines, is to work to "8 thou track and gap"

So is it safe to drop the ground plane clearance to 8 thou?

This means that the ground plane flows between all my signal lines, which I assume is good for reducing cross talk?

The highest voltage on the board is +12V with +/-5 and +3.3V supplies.

There are 6MHz and 20MHz clock signal but these don't run very far.


texts: Replacement transistor for stereo receiver

texts:
Can I replace a 130w transistor with a 150w transistor in a Onkyo receiver.

Looking at this question the first response -

  No, changing the transformer alone is not sufficient. You also have to
  upgrade the switching devices that create the AC that drives the
  transformer. Typically, those are MOSFET transistors, and you then
  have to find bigger/faster MOSFETs. Such MOSFETs, in turn, typically
  need bigger/faster driver chips to pump enough charge into the gates
  to avoid heating up, so you also have to replace the driver circuits.

  Then there's the issue of built-in protections -- often, there are
  Hall current sensors or sense resistors that determine the current
  draw on the inverter, and shuts down in case of over-current, to
  protect both the inverter and the surroundings. Even if you replace
  all the power electrnics, the control electronics will likely not be
  aware of the change, and thus shut down before you reach the higher
  wattage you want.

  So, no. Inverters (and most other electronics) are generally designed
  as matched systems, where each part is good enough for what it does,
  but doesn't have too much wasted capacity. Using a bigger part than
  necessary will just increase price for no good reason. If you want a
  bigger inverter, buy a bigger inverter.

but this was about an inverter. The only reason I'm asking this question because the original transistors on ebay are used. Which to me sounds questionable, but Toshiba recommends a newer transistor but it has a higher wattage and I don't really feel like ripping this stereo apart again.

MY FIRST QUESTION

  I recently burnt up one of the channels on an Onkyo receiver, which is
  the third time that this has happened. The warranty ran out and was
  hoping I could re-solder new transistors in myself. Now the original
  transistors that were in the unit were Toshiba A1962 and underneath
  the part number was  a 0 then 840 which when I look at the data sheet
  0 is a characteristics indicator and 840 is a lot number. When I sent
  it into a professional electronics repair shop under warranty they
  replaced two transistors, 1 with a Toshiba A1962 (0 characteristic 027
  lot no.) and 1 Toshiba C5242 (0 characteristic and 948 lot no.).

  When I looked up the
  A1962
  on Toshibas site they said they are replacing it with new designs and
  the
  2SA1943N
  is recommended. Now the recommended part is rated at 150w while the
  older is 130w I believe.

  All in all I am not an electrical engineer, but I think I can solder 2
  transistors to a board but I'm unsure off which ones are required.


texts: Loudspeaker electro-magnetic waves noise isolation

texts: I read about the  magnetic waves created by Loudspeakers, causes noise in electronics circuit. If a speaker is going to be soldered in-place with all other circuit components, how can the noise be isolated from the circuit?


texts: Connect STM32 FSMC to LCM with 6800 interface

texts:
I want to use STM32 to drive a LCM with a KS0108 controller. Sadly, it has a 6800 interface. Fortunately, ST gives a document: TFT LCD interfacing with the high-density STM32F10xxx FSMC . In p. 12 it gives two methods:

But the http://www.techtoys.com.hk/Displays/JHD12864J/ks0108.pdf, states when write to LCD, the data is latched at the falling edge of "E":

Then, assuming we use the method 1 above, the pseudo-code should like:

gpio_E = HIGH;
lcd_addr = lcd_data;
gpio_E = LOW;

After the second clause, the /CS should goes to high, and the write phase should be end. Then what's the state of the data bus, will it hold the data last output??? Or it will go to high impedance after /CS high? How can we make sure the LCM to latch the correct data?

For method 2, the situation should be similar. In ST's reference manual, it gives the timing diagram when writing:

When the writing phase ends, how long will we expect the data still exist on the data bus?


texts: Why some MAX 10 chips don't support ADC while the datasheet says they do?

texts:
I'm using an Altera MAX 10 chip 10M50SCE144C8G. I want to use its ADC. In datasheet, it says that this chip has a "Single ADC that supports 1 dedicated analog input pin and 8 dual-function pins". However, when I want to use it in Quartus, in the IP parameter Editor, I got an error msg saying that:

  Error: unnamed.modular_adc_0: The selected device part number 10M50SCE144C8G does not support ADC.

I tried different versions of Quartus: 15.1 and 16.0, got the same error.

How do I fix this error?


texts: LC oscillator emitter current doesnt go to 0(class C)

texts:
Im trying to create a 433MHz oscillator with the help of ADS for the simulation. From the lectures i have had on transistor LC oscillators, i know the are forced into class C operation, and that current in the emitter should look like this:

With a nice flat 0mA current in between the peaks.

In my simulation though, it doesn't really reach near 0mA current:

It actually looks like a sinus..

How come? Do i bias the base too much? I have tried to tune it a little, and i can come closer what i believe it should look like, but then there is some high frequency oscillations in between.

(could be worse/more oscillations in between)

Could it be some capacitance in the BJT that oscillates with the inductor?

This is the schematic:


texts: Pull up to 5V on a wire that may occasionally see 60V

texts:
I have a wire that either floats - that's when I want to pull it up to 5V - or it may see up/down to +/-60V applied to it - and that's when I really don't want it to be connected to the 5V rail. Problem is that I can't figure out how to make a switch that will stay off when large voltages are applied to the wire. There are all these different combinations of voltages that can be applied to these wires - I'm only showing the extreme cases in the diagram.

simulate this circuit – Schematic created using CircuitLab

I want the switch to be closed only when the wire is floating (leftmost case on the diagram) and open in all the other cases. All my attempts were along the lines of connecting a BJT between the 5V rail and the wires - but all of that fails when the wire goes negative and the transistor is in the reverse active region.

simulate this circuit

I'm just curious at this point if this can even be done with discrete components, but if there's an IC that can do what I want that's fine by me. Thank you and I really appreciate all the help and advice.

Edit 1: These two wires are inputs to a differential amplifier whose output is fed to an ADC. Input voltages range from -60V to +60V, but the two wires are never more than 60V apart. That means the top wire can't be at 60V and the bottom wire at -60V.

simulate this circuit

Sometimes the input is "dry" in a sense that it needs a connection to the power rails to produce a meaningful input. For example, the output of an open collector tachometer without a pull up will "float".

simulate this circuit

5V is a power rail that powers a lot of things in the circuit - that's why I want to protect it as much as possible. Also, +/-60V signal is an input to the op-amp and I'm worried putting a very large resistor will affect the accuracy of the measurements.

Edit 2: Can the following circuit possibly work? I ran a sim and it checks out.

simulate this circuit


texts: What are typical failure modes of piezoelectric transducers?

texts:
How do piezoelectric transducers in ultrasound probes fail?  I have a machine whose elements are being driven by an amplifier that is very noisy.  The signal I see arriving from the power amplifier has white noise and also a popping/clicking characteristic.

I was wondering if driving an element outside of its resonant frequency would damage it.  In principle, if the resonant frequency is 5MHz and you drive it with 8MHz, could that cause damage?  What if there are multiple frequencies like in white noise... if you drive an element with high power white noise, would that damage the transducer too?

Any other way these elements could fail?


texts: arduino duemilanove why does it have 1k resistors on txd and rxd

texts: I was constructing my own arduino duemilanove, I noticed there was 1K resistor wired in series with the txd and rxd. Why does it need them? It works for me without them.


texts:
I have really no idea about electronics.
I am trying to provide IR lighting for my night camera that I use with the raspberry Pi.
The Pi is powered by a 5v usb power bank. The IR requires 12v.
I purchased these:
https://uk.banggood.com/DC-12V-48LED-IR-940nm-Night-Vision-Infrared-Illuminator-Board-For-CCTV-Home-Security-Camera-p-1280391.html?rmmds=myorder&cur_warehouse=CN
https://uk.banggood.com/48pcs-IR-LEDs-Light-Board-Infrared-Illuminator-940nm-Invisible-Light-at-Night-No-Red-Exposure-Camera-p-1281930.html?rmmds=myorder&cur_warehouse=CN
And thought getting this:
https://www.amazon.co.uk/gp/product/B071X6VYXR/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1
to power from a 5V USB Power bank would work.
But it did not.
I cannot seem to find anything that will power these lights.
I also rather not do any soldering.


texts: Programming the Atmel Mega 328P-AU 32 MLF (QFN) using the Arduino ISP

texts:
I have successfully managed to program both a (DIP)Mega168A-PU and a (DIP)Mega328PU using another (DIP)Mega328P-PU ISP.

This is the configuration that works for both DIP formats (168A-PU & 328P-PU):

No capacitors or resistors required.
Now, following the same logic, this is what I have for the (QFN)328P-AU:

First thing I've noticed is that the QFN version has 2 VCCs and 3 GNDs, so I connected everything to the same PWS and GND. I tried to flush it using the Arduino IDE with the clock option set to both 8Mhz internal and 1Mhz internal - same unsuccessful result.

The avrdude complains about the device signature being 0x000000:

This is what I'd like to know: Do I have all the pints properly connected? Is it safe to assume that if the DIP version works fine using this pin configuration, the same thing should happen with the QFN? Is there something I'm missing? Thanks.


texts: Does Slave Select have to be sychronous with Clock?

texts:
I'm working on the SC18IS600 chip (SPI to I2C converter) and have been having issues just communicating with it. At the moment I am attempting to configure the I2C Address register and set it to 0x3F or 0x00. When reading the address back however, I am getting (afaik) gibberish - it's not even reading back the default address value. While testing I noticed that the CS line goes low much earlier than the clock signal and want to know if the CS line must be synchronous with the clock when using SPI, or if a delay like the below image is acceptable. If anyone has other suggestions as to why this might not be working, please feel free to make them.
Edit for explanation: The 'gibberish' I was receiving was a result of not allowing for an 8us gap between each data word. The SC18IS600 requires this gap, further explained here for anyone else: https://community.nxp.com/thread/461576
Image: yellow = MISO/rx, blue = MOSI/tx, pink = clk. Image taken while trying to read the address. Sorry for the image quality, it's a very old oscilloscope that can't save images anymore.
datasheet at https://www.nxp.com/docs/en/data-sheet/SC18IS600.pdf


texts: How to multiplex 8 pieces of 74141 without transistors?

texts:
I'd like to use 8 pieces of 74141 in order to drive the same amount of Nixies with an Arduino. What approaches will I need to consider?
Update: I'm able to drive 1 single Nixie with a 74141. The problem here is that there are not enough pins on Arduino to drive more so I'll need a solution for this.


texts:
I initially posted this in SuperUser SE Site, but it was recommended that I bring it here instead.  So, here we go :)

We have a 'dated' security system at the office.  It is a model that was made (or at least rebranded) by a company named ATI Access.  The board are stamped as: SA-2000-II V8.0.

As I mentioned before, the company that made (rebranded) the board is "ATI Access", located 30 minutes away from me in Milwaukee, WI.  As of a few weeks ago, they are now defunct.  That means that all my tech support, etc, has gone out the window.  With that being said, I am trying to have a go at a small project, but I am now flying blind.  Here are the details:

On the top left side of the board, there are 5 inputs that can be programmed to do various tasks such as trigger an alert, or open a door by pushing a button.  Looking at the manual for the board, a simple 'dry contact' switch is all that is needed to trigger them.  So, what I have done on one of my panels is connect wires to Input 2 and attached them to a doorbell attached to the side of a table in my IT Closet.  I then programmed the input to open the door on my IT Closet when the button is pressed.  It works great.  Go me, right?

Well, that is not good enough for me.  I want to be able to control it with my PC as well.  Now yes, I could just keep the security system open at all times, and alt-tab to it, right click on the door, and choose Open, but that is a lot of steps.  I figured I would just write my own app that sits in the system tray that I can double click on, which would somehow emulate me pushing the doorbell.

I am not looking to use the PC to control a motor to push the doorbell for me, although that would be kinda cool.  I am thinking that perhaps the serial or parallel ports could act as a dry-contact switch (however I am pretty sure that's not a feasible idea), or perhaps using some sort of dry contact relay that can be controlled via the serial port.  So, the sequence of events would then be:

Click on the icon of my app in the system tray
App sends a signal out via the COM or LPT port (this part I can handle, I love programming)
That signal is picked up by [insert stuff I don't know here] that trips the relay momentarily to a CLOSED position, completing the circuit to the security panel input header.
Security Panel works its magic and opens my door.

As stated, I have this done the manual way utilizing a doorbell button, but I am looking to fancy it up and use my PC instead.  Has anyone done here ever done something similar to this and is willing to point me into the right direction for [insert stuff I don't know here] ?

For bonus points: Does anyone have experience with this type of security panel?  I'd be interested in knowing if there are any alternatives to the software that I am currently using for it (StarAccess Pro is the software that is used).


texts: Is it possible to change the speed of an AC motor(drill press) without losing too much torque?

texts:
I have a drill press as in the image below, it runs from 110V AC 60Hz and has internal belt reduction. Unfortunately however for some materials and hole widths, I need it to go even slower than It's been built for. Is it possible to drive the motors  in such a way that I can slow it even more without losing significant torque?(for example on a lower frequency higher voltage )

I can build a custom inverter if necessary. I'd like to avoid mechanical modifications if possible.


texts: Why do we need to continuously refresh a high resolution graphics LCD while we don't need the same for a character LCD?

texts:
It is very easy to interface an MCU with a character LCD (let say, 16x2, 20x2, 20x4, etc.) because we don't need to constantly refresh what is displayed.
Once we send what we want to see, it is displayed as long as the LCD is powered.

On the other hand, if we want to use a, let say, 800x600 graphics LCD (TFT or whatever with Parallel RGB interface) with the same MCU, we need to refresh the whole frame at a specific frequency, which almost make it impossible to use such an LCD with a relatively slow MCUs whose clock speed is, say, 16MHz or 20Mhz. Even if we choose a faster MCU, the display refreshing process takes most of its processing power.

Taking into account that, I am not going to display a video stream on the LCD, rather than that, I just would like to use the LCD as the information panel of a machine like a CNC machine where most of the things on the display will be constant and only some parameters will change;

Do I still need refresh entire frame continuously?
Is there a simpler way to overcome this without using FPGA, PLA, etc?


texts: What is a good (cheap) way to slow down a fan with a thermistor?

texts:
What is a good (cheap) practice to manage a fan with a thermistor?

Here is what I think to do:

simulate this circuit – Schematic created using CircuitLab

This should work as temperature change to speed up or down the fan, right?

I do not want to make a IC controlled fan controler for it. I need to work in very tiny box beetween actually existing fan wires  (it makes too much noise) so the idea is to lower its speed by few % only.

I may be able to work around with a mosfet "classical" fan drive schematic but then I need to deport that elsewhere in the box.

I mean something like this:

Is first schematic useable or I need to work around second one  (with the mosfet?)


texts: Pin Configuration for Breadboard 3.5mm Stereo Audio Jack

texts:
I have this 3.5 mm stereo audio jack which can be mounted on a breadboard.
Could someone please help me with the pin configuration?

I'm using this audio jack to serve as input to the MT8870 DTMF Decoder.
Here's the circuit diagram:


texts:
How is gain defined for a receiver antenna?
If we look at a radiating antenna, there is a Pin, and the gain in a particular direction would be the radiation intensity Ur, divided by the radiation intensity of a lossless isotropic antenna Ui, in that particular direction. G = Ur/Ui = (4pi * Ur)/Pin.

But, what is the baseline for the receiving scenario. I know it is the isotropic antenna, but in which way? What does Pin (as the very basis for the comparison) translates to in the receiving scenario?


texts: S-curve using linear potentiometer without huge power drain

texts:
The following circuit uses a linear potentiometer and two resistors as a voltage divider to create a very steep non-linear S-curve as the potentiometer is adjusted.
However, the low resistances consume a large amount of current and dissipate quite a lot of power.

Is there a better alternative to this circuit?


texts:
My Answer is as follows:

However, the correct answer is as shown below:

My question is where is my mistake?
So, I added the below as of my understanding is my reasoning accurate or not?


texts:
I have a PCB board which is supposed to be powered of 12V supply.However, now I would like to run this of a battery.

Most LiPo batteries are 3.7V , and 12V batteries are big and hard to get. What is  a effcient way to boost this 3.7V to 12V making sure this voltage conversion has maximum efficiency?

I am looking basically at http://www.onsemi.com/pub_link/Collateral/MC34063A-D.PDF . But converting 3.7V to 12V must be something that is very common. Is there any IC which does the charging and conversion from the LiPo in one package? Something that monitors the amount of electrons in a battery and regulates the current for a longer life(like the IC circuitry on a cell phone)

Also I was looking at Li-ion va lipo here http://www.androidauthority.com/lithium-ion-vs-lithium-polymer-whats-the-difference-27608/ and it says the cycles is 100-400. I thought mobile phone batteries have a much longer life? Any suggestions?

At 5V, I am expecting about 1A to be drawn by the PCB.

In order to be safe I am expecting about 500-600ma to be drawn from this board. Tolerance is not really important.


texts: How to deal with analog pin drivers with output switching?

texts:
I'm trying to figure out if there's any way to affordably improve the performance of an analog pin driver that needs to be periodically isolated from its load, for the duration of self-calibration. The circuit, as it currently stands, is as below, but I'd like to - if possible to do so cheaply - to remove the effects of SW1's resistance on the DC performance.

The circuit is a +/-10V pin driver for an analog output that has to interface with "typical" DAQ cards. They usually offer high DC impedance. Some of those cards are dynamically nasty: they have multiplexer inputs with their fast (10s of nanoseconds) charge injections. It needs to maintain about 15 bits of accuracy across time and temperature (1 part in 30,000). Thus it self-calibrates using an ADC and a stable reference. The bandwidth is about 1kHz.

The loads are assumed to be high-impedance, with a dynamic component. Unfortunately, every once in a while someone will "happily" attach a voltage divider or some other circuit with sufficiently low DC impedance to kill the accuracy of the output voltage with SW1 present. I like making life easier for my customers, and was wondering if this deficiency could be cheaply removed.

There are 10 channels, so per-channel cost is under scrutiny as well.

simulate this circuit – Schematic created using CircuitLab

C2 stores some charge to ease U1's job in presence of dynamic loads. R2 stabilizes the op-amp in presence of the capacitive load. U1 is a 15MHz GBW rail-to-rail output part, running at a gain of 4, with 2V of headroom between output and supplies - it's fed +/-12V. I didn't show the rest of the circuit attached to the inverting input, it's just a 2nd order MFB filter.

R1 closes the DC feedback around R2, taking out its effect on DC performance.

For in-circuit calibration and removal of gain and offset errors, SW1 is opened, SW2 closes, and an A/D converter is attached to the output.

For this circuit has to be affordable, SW1 is a DG411 or similar, with about 30 Ohms of on resistance. It'd be very nice if that resistance could be used in place of R2, and placed inside of the feedback loop.

Conceptually, I'd like something as follows:

simulate this circuit

For calibration, SW1 opens, so that a misbehaving load won't skew the calibration, SW2 closes and SW3 flips. The voltage follower U2 is necessary to prevent SW3's R_ON from influencing the gain of the circuit. Its closed-loop output resistance needs to be under 1 Ohm, worst case.

I'm really interested if it's possible to turn things around to avoid that U2 buffer - it would add about a $1.50 per channel. U1 would also "see" the nasty dynamic disturbances directly on its input. This worsens the settling time from dynamic disturbances on the output.

One solution would be to retain R1 and use very low R_ON discrete mosfets for SW1. This is problematic - most cheap and small mosfets require large gate-source voltage (5V) to maintain low resistance. Realistically I'd use two N-channel devices back to-back. The analog part of the circuit is isolated from the CPU, so I can't use cheap voltage multiplier tricks on a CPU output pin to steer those switches. The switch control signals are threaded through the GPIO outputs on the calibration ADC (this probably spills the beans on what chip I use for the ADC).

I was wondering if there is a discrete solution that would be stable enough to work, but I can't see any. Since R1 is on the order of 40k, I can't see a simple emitter follower at work here - there's just not enough current to keep the output resistance into R1 down to the required 1 Ohm. Is there some field-effect or BJT discrete magic that could be done here in place of a full-blown op-amp U2?


texts: Running microphone signal through stereo jack

texts:
I've recently mounted a 3.5mm connector onto a walkie talkie, so that I can plug in a headset. It works really well, though I've had the idea that since it's a stereo jack and the singal is mono, I could use the second connector pin to run signal from microphone to the walkie talkie. I'm not sure how though. Would connecting the microphone's output to one of the microphone contacts on the walkie talkie be enough? If so should it be + or - ? How do electronics usually handle electret microphones?
Do send a constant current to one pin and use the second as output (treat the mic as a switch) or is it different?
Thanks for any suggestions.

PS: just to clear any confusion I've already attached the microphone output to the stereo jack, I just need to figure out how to attach it to the walkie talkie


texts:
Just wondering how to treat a resistor power rating if the resistor is only getting current passed through it for 1us or less?
Is it reasonable to exceed the power rating significantly (say 10x) for such short pulses or unwise?


texts: Calculating the base emitter voltage increase for an ideal transistor

texts:
For a approximately ideal transistor (η = 1) at an emitter current of = 1μA the Base emitter voltage is = 0.60V. How can I work out how much the base emitter voltage increases if the emitter current rises to 100μA?

I am aware of the formulae relating the currents at the base, emitter and collector as well as relating alpha and beta but how can I relate these to the base emitter voltage?


texts: WS2812B LED Strip Not Drawing Full Amperage

texts:
I recently purchased one of these LED strips. Now I have read all about how these are notoriously known for drawing a lot of current from its power supply so I bought one of these power converters thinking I would have more than enough power to sufficiently supply the strip. The converter is wired to a 12v power source.

However, when I set all of the LEDs in the strip to full white at max brightness I see a reddening of the LEDs as you get closer to the end of the strip, indicating to me that the blue and green diodes seem to be dimming and therefore not receiving enough power.

I then measured the current using a multimeter and discovered that the strip was only drawing around 4.5 amps when in reality it should be drawing around 9 amps. This was calculated based off of 60mA per LED at full brightness from Adafruit's guide to powering the WS2812B's and other research I've done.

In essence, the LED Strip is only drawing 4.5 amps when it should be drawing nearly 9. Any ideas on why this might be? I am also controlling the LEDs using an Arduino Uno.


texts: Identifying and replacing laptop motherboard connector

texts:
My laptop was having cooling issues, to I opened it up to clean the fan. When attempting to start it up afterwards, nothing happened, and soon after I smelled burnt plastic. Upon inspection I discovered that the ribbon cable connecting the power button to the motherboard was burnt. I must have put in a little off, and two connectors shorted. There doesn't seem to be any other damage, so I figure if I can replace the wire and the connector on the motherboard (it's ruined as well) the laptop should return to its former glory.

I've identified the cable as cvilux e208903-5 awm 20706 105c 60v vw-1
How can I go about identifying the connector on the motherboard?
Is it advisable/possible to cut the burnt part of the wire, and strip the remainder? Or am I better off replacing the wire altogether?
I've soldered electronics before, but this a lot smaller than anything I've ever dealt with. Is it doable? What should I be looking out for?


texts: PCB opaque coating for anti reverse engineering?

texts:
Im trying to find a coating for my PCB in order to protect it from reverse engineering. I want it opaque, non-conductive and with a low thermal resistance.
Basically I do not want that someone replicates my circuit easily.
I´ve beens searching a lot on coatings but did't find anything that suits to all my requirement.
Anyone with an idea?


texts: Is it possible to draw diagonal circuit connections in Proteus Isis? I can only seem to get right angles, and a particular bit of my design would look a lot clearer if I used a couple of diagonals.


texts: Identify unknown capacitor and resistor values

texts: How can I find out what the values of R12 and C3 are?


texts:
I came across an online tutorial which has the following category:

As you see SMPS is categorized as a non-isolated power supply.
Or am I interpreting the tree wrong?

But isnt an SMPS isolated through a transformer and opto-coupling(for the feedback)?


texts:
I've been running some tests on USB charges from different manufacturers checking voltagem and current.

I noticed that some usb charges do deliver 4.9 to 5.2 volts and from 500mA to 2.4A.

My manufacturer's charger (Apple) delivers 1000mA @ 5.05v to my phone.

My questions are:

If I use a 600mA @ 4.96v could reduce my battery life?
if I use a 5v at less current (slow charge) will it prolongue the battery life?

Thanks


texts: Verilog: negative value in brackets of vector signal definition

texts:
I am looking at the code in the following website.

https://www.csee.umbc.edu/~tinoosh/cmpe641/slides/05-Memories.pdf

In their code, they claims something like

input signed [7:-12] c_in;

I am wondering what does the negative mean in here?

module scaled_square ( output reg signed [7:-12] y,
input signed [7:-12] c_in, x,
input [11:0] i,
input start,
input clk, reset );
wire c_ram_wr;
reg c_ram_en, x_ce, mult_sel, y_ce;
reg signed [7:-12] c_out, x_out;
reg signed [7:-12] c_RAM [0:4095];
reg signed [7:-12] operand1, operand2;
parameter [1:0] step1 = 2'b00, step2 = 2'b01, step3 = 2'b10;
reg [1:0] current_state, next_state;
assign c_ram_wr = 1'b0;


texts: what is status code "0xC8" in an AVR TWI MCU I2C

texts:
0xC8 is called Last data byte status in Atmel's TWI's Slave transmitter mode, but what does it really mean? If TWEA==0 is for the Master receiver, then a Data byte in TWDR has been transmitted; NOT ACK has been received: 0xC0 status should be received.

Looks like the guy who wrote the application note for Atmel even had no idea what this status is.

#define TWI_STX_DATA_ACK_LAST_BYTE 0xC8  // Last data byte in TWDR has been transmitted (TWEA = ??; ACK has been received

and it's treated as an error code instead, what a shame!

    case TWI_SRX_ADR_DATA_NACK:      // Previously addressed with own SLA+W; data has been received; NOT ACK has been returned
case TWI_SRX_GEN_DATA_NACK:      // Previously addressed with general call; data has been received; NOT ACK has been returned
case TWI_STX_DATA_ACK_LAST_BYTE: // Last data byte in TWDR has been transmitted (TWEA = ??; ACK has been received
case TWI_BUS_ERROR:         // Bus error due to an illegal START or STOP condition
  TWI_state = TWSR;                 //Store TWI State as error message, operation also clears noErrors bit
  TWCR =   (1<<TWSTO)|(1<<TWINT);   //Recover from TWI_BUS_ERROR, this will release the SDA and SCL pins thus enabling other devices to use the bus
  break;


texts: Correct name of a 12v power strip socket

texts:
I'm trying to locate one of these black strips:

I purchased it as a component part in the uk but they don't sell them anymore.

It supplies 12v lights (attached to the output of a transformer.

Any ideas what the official name for one is?


texts: How to get sensor data at fixed time intervals

texts:
I am using a STM (stm32l432kb) microcontroller. In my application I need to get the data from the sensor at fixed interval(based on the selected Mode).
Like I have to select the Modes:-
Mode 1 : which output the data at fixed interval of 5 sec.
Mode 2 : Which output the data at fixed interval of 10 sec.
Mode 3 : Which output the data at fixed interval of 15 sec.

Here I am little bit confused that how to get this data based on modes.


texts:
I have the below circuit and when I turn off the MOSFET (Logic 0 at gate vg) the LEDs (LED1  and LED2) still shine with a small intensity. When I replace the LED with an incandescent  lamp (car lamp) the lamp does not shine at all. Does anyone know why?

Ciruit 1:

Ciruit 2:

MCH6445-TL-E -> Q1 Mosfet's datasheet:
http://www.mouser.com/ds/2/308/MCH6445-D-108455.pdf

MMBF170LT1 -> Q3 Mosfet's datasheet:
http://www.onsemi.com/pub_link/Collateral/MMBF170LT1-D.PDF

Final circuit which works fine:


texts: Possible to convert dead 18v battery into wall-plug?

texts:
Not sure how better to title this... But basically, I want to try to convert one of my old ryobi 18v batteries into a wall plug.  I want to strip the guts of the battery, attach some components and a heavy duty cable to be able to plug the "battery" into the wall so I can have continuous power to a "cordless" tool.

In other words, I want to make a plug-in cord to make any of my cordless tools into a corded tool.

I know Ryobi has tools that have both battery and cord hookups.  I'm wondering if I could just take the guts from one of those and put it into the old battery casing, so everything plugs in just fine.

Question: Is it possible, and is it as simple as creating an AC/DC converter


texts: I'm mostly a software person, so this might be a super basic question. I wanna connect to an SOP8 flash chip. I see many recommendations for the Pomona clips, but that one is labeled SOIC8. I can't seem to find a consistent source as to if these two mean the same thing or if the SOIC8 clip will work for SOP8. Should the Pomona SOIC8 clip work on SOP8?


texts: How to calculate the maximum cable length of fire detection loop

texts:
I have been tasked with writing a software to calculate the maximum cable length of the fire detection loop, I am not a electrical engineer myself and therefore I am struggling with some of the calculation aspects, please help.

So having data:

Wire type i.e. wire with cross sectional area 1.5 mm square has the resistance of 12.1 Ohms/km or 3.688 Ohms/1000 ft. Or for the USA folks 12 AWG.
Vopmin (Minimum operating voltage) 17 V
Voutmin (Minimum output voltage) 24 V
Total devices current consumption i.e. 400 mA

We calculate the worst case scenario, i.e. all of the detection devices are based at the end of the line.

Having this data, how to calculate the Vdrop (voltage drop across the length of the wire). And the maximum cable length of this circuit?

Please if possible provide the formulas with the example calculation, thank you in advance.

Regards


texts: How will transformer efficiency change if the transformer is connected backwards?

texts:
Suppose I have a transformer designed to convert 220 volts into 5 volts and when it works in this mode being 95% loaded its efficiency is 97%. Now I connect the secondary winding to a 5 volts power source and connect appropriate 220 volts load to the primary so that the transformer converts 5 volts into 220 volts and is 95% loaded.

How will the transformer efficiency change? Will it remain 97%?


texts: Can someone explain this grounding phenomenon?

texts:
I went into a conversation with an electrical engineer. Here is what was on the table:
Me: How do you connect a two-phase load to a three-phase delta load? If the loads were Y-connected, then you would just take one line wire and the neutral point and connect them to the load. But in the case of a delta source connection, where there is no neutral point, how will you do it?
Engineer: You connect the other terminal of the load to the ground.
Me: How does this work?
Engineer: Three copper rods are inserted vertically into the ground at with specific spacing between them. [Material] is placed at the ends of the rods touching the ground, i.e. between the rods and the ground to increase conductivity. These three rods are connected to one wire - the earth or neutral wire.
Me: Why does this work? As far as I know, soil does not conduct electricity that well.
Engineer: Deep down into the ground, the conductivity of soil is much better, so the soil at the tips of the copper rods does conduct electricity.
Me: Consider the circuit on the left. The lamp lights, doesn't it? What if I connect the same circuit as shown on the right? Does the lamp still light?

Engineer: No.

Can someone explain to me the final "no"? Why does the underground soil conduct electricity underground, but when the same soil is brought up to the surface it fails to do so?


texts: Why do wall plug power supplies use audible switching frequencies?

texts:
Every plug-in power supply ("wall wart") I have ever used starts off silent, but eventually starts to emit high frequency switching noise. It usually happens only when the charger is on, but not charging anything. I presume it is due to the capacitors failing, or maybe the glue around an inductor.

My question is, why do they all use switching frequencies around 18 kHz which is audible and really annoying? Why not go up to 25 kHz or even higher?


texts: Why 3 phase is preferred over any other phase power transmission?

texts:
Why 3 phase is preferred over any other phase power transmission ?

My instructor was explaining this topic in my Electrical machines class. And he mentioned the following points

In single phase, system there is double frequency oscillating component. So, it is not preferred.
In 2 phase system, there is no double frequency oscillating component. So, it is ok to use it. And it can be used to transfer 1.414 times output rating in the same frame size as single phase. Also, we have return neutral current which is 1.414 times the peak value which is not good.
In 3 phase system, we can transfer 1.5 times output rating in the same frame size as single phase. Also, we have zero return neutral current which is also a good thing.
In infinite phase system, we can transfer 1.57 times output rating in the same frame size as single phase. There is not much improvement from 3 phase so we went with 3 phase.

Now, I am confused with the thing how he got the values 1.414 for 2 phase, 1.5 for 3 phase and 1.57 for infinite phase and what does it mean by saying in the same frame size. Please someone help me with this concept.

EDIT: I want to understand how the 3 phase is 50% more efficient than 1 phase whereas infinite phase will be only 57% more efficient than 1 phase. I am not asking why 3 phase over 1 phase as that I have already mentioned in my question.


texts: What is the purpose of built-in FPGA with Intels new chip

texts: I know that Intel acquired Altera in 2015 and the new Intel chips include a built-in FPGA. But what is it for?


texts:
I read (for instance here) that FM modulation is less affected by noise than AM modulation.

But I don't understand conceptually the reason for that: why is the SNR with frequency modulation higher than the SNR with amplitude modulation?


texts: problems related to buck converter/voltage regulator

texts: In buck converter how should we assign a value to capacitor and inductor for reducing 12 voltage to the 9 voltage or any other voltage to any other.


texts: What are good microcontrollers available today?

texts:
I have experience with assembly and C programming for microcontrollers, but I'm not familiar with the various MCU and DSP families offered by today's companies. (eg: Texas Instruments, Atmel, Renesas)

I'd like to know about the good microcontrollers / DSPs, and what its like to develop with them. Please summarize your understandings about the various MCU / DSP families, one family per answer.

It would be very interesting also if you detail what is(are) the main application(s) for this(ese) microcontroller please.

(This is a "community-wiki", so anyone with >100 reputation can refine and improve answers)


texts: How to digitally "amplitude modulate" an LED

texts:
I am wanting to do some open-air LED communication experiments.

I have a receiver that detects Amplitude Modulated light signals, and then converts that into sound.

Currently, I hook up a series transformer with the LED with an audio source on the primary.

I have heard that if I Pulse Width Modulate the LED, the detector will perceive that as AM.

What type of circuit could I use to convert a sound signal into fast PWM for the LED?


texts:
I am getting started learning more about AVR ATMEGA programming.
Reading an article about the inner workings of Arduinos, I am learning how the shiftOut method is structured. I am kind of familiar with bitwise operations so far, but I have an expression I do not understand yet:

void shiftOut(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder, uint8_t val)
{
    uint8_t i;

    for (i = 0; i < 8; i++)  {
        if (bitOrder == LSBFIRST) {
            PORTD |= !!(val & (HIGH << i));
        } else {
            PORTD |= !!(val & (HIGH << (7 - i)));
        }
        PORTB |= (HIGH << clockPin);
        PORTB ^= (HIGH << clockPin);
    }
}

The line PORTD |= !!(val & (HIGH << i)); is not 100% clear to me. I understand that i set the i-th bit High on PORTD but what das the !! mean and val&(HIGH <<i))

I know this might sound basic, but can you please help me out?


texts: Relay to switch lights on from gate motor

texts:
I'm installing a 24V sliding gate motor (Powertech 500) and was hoping to power two 12V LED wall lights of it as the gate opens.
Unfortunately the motor doesn't have an input connection for lights but does for a flashing light. This connection gives out an alternating voltage as the gate opens/ closes which causes the light to flash. Now with my limited knowledge of electronics and from the guy at the gate shop reckons, I thought I could wire the lights into this connection with a latching relay, which would trigger the lights to come on a stay on for a period of time.
This would be good... but I also don't need the lights to come on during daytime so I'm wondering if there are there latching relays with 24hr timers that will only operate during certain periods? I can't seem to find anything.
otherwise, can a separate timer be included in the wiring to achieve this? I'm not sure what I should be looking for
is any of this going to work? and is there a better alternative??? the motor comes with 2 battery backup but not sure how I could wire into this....
Obviously I come with little knowledge of how this works so any help would be appreciated.


texts: Photo multiplier tube and lock in amplifier

texts: My photomultiplier tube is connected to a Transimpedance amplifier for routine experiments. However for an experiment I need to connect the output of the PMT to lock in amplifier (SR 865A). The manual says that the lock in has inbuilt amplifier. Shall the transimpedance amplfier be removed before the connection between PMT and lock in is made or via the external amplifier is fine.


texts: Electrelet Microphone in Amplifier Circuit

texts:
I am trying to build this circuit with the only difference in my version being 9 volts instead of 12. For my Microphone I used a Electret condenser microphone from here.

It says it runs on 2.2vdc so I put a 330k resistor is series with the microphone. My problem is that the only noise i get to the headphones is if I tap on the microphone. If I blow on it or talk into it nothing comes through to the headphones. I tried it with and without the resistor with a 1m and 1k resistor and checked the polarity of the microphone. Any help appreciated. If needed this link is to the tutorial.


texts:
I have a PSU (wall wart) with a symbol on the label that I don't recognise. I'm curious as to what it means. It's probably some safety symbol of some form, but not one I have ever seen before. I'm sure it's obvious though:

It's printed on the label with all the other safety symbols, ratings, etc.

Underneath it, I don't know if it's related to the symbol or not, is an ambient temperature rating of ta=40°C and an IP rating of IP20.

If you're interested, here's the entire label, so you can see it in context (and yes, I know those current ratings are completely wrong - 0.5A in, 0.5A out?!?!):

Any clues?


texts: How to say whether INL and DNL of a DAC is good enough?

texts:
The DAC has an INL of about 20 or so LSBs. DNL is +-2LSB.
Since it is a 14 bit DAC, is it safe to say that the DAC is monotonic for 13 bit use? (Since DAC is monotonic if DNL is not below -1LSB)

And secondly, what INL is considered good enough for DAC? Of course it should be as close to 0.5LSB, however, is there any other information provided by INL that needs to be considered?


texts: Should we try to match the differential impedance of a CML pair, and if so, why?

texts:
Differential signalling 'traditionally' involves two conductors carrying equal and opposite signals, the data being signalled by the polarity. In this arrangement the majority of the current returns through one or the other conductor and the common-mode current is minimal (noise and whatever is coupled from the conductors).
Current Mode Logic is also a differential signalling technique, but in this case each conductor either sinks or does not sink current. The current never changes direction and returns along the same path.

My question is, why should we try to impedance match a differential pair connecting CML devices? Does differential impedance even mean anything since the conductors will never carry equal and opposite signals?\$^1\$ Would it not be better to treat each conductor individually and match them to the single ended impedance of the devices?\$^2\$

(1) If we take EEWeb's definition that differential impedance "is measured between the two lines when they are driven with opposite polarity signals".

(2) While still taking into account cross-talk from elsewhere on the board, length matching, etc


texts:
Has anyone had any success in using the Rigol Ultrascope software to control a scope remotely via Internet - ie not just on a local LAN?
It works fine on the local LAN and apparently uses port 5555. I set up port forwarding of this port in my modem to the scope, but could not get Ultrascope to work using my public IP address. I am wondering if Ultrascope also uses another port for something?

I was able to use Putty to connect to the scope from outside the LAN in command line mode.

My object is to be able to share the scope screen (and controls) with a colleague at a different location while discussing a problem.

I am using a DS4014, but Ultrascope is the same for all models I think.

While I'm asking, is there any other/better software for remoting a Rigol scope?


texts:
what is effect of capacitor on output voltage of op amp, when we use capacitor on feedback loop?
for example we can use lm358, with 2 resistor for gain (1K and 1K) we have gain=2, okay? But what happened when we use capacitor exchange with resistor in feedback loop?


texts: Arduino Starter Kit, Color Mixing Lamp Project 4

texts:
I just started looking into electronics and circuits. I purchased the Arduino Starter Kit to help get me started. I have a question regarding one of the 15 projects it comes with. Specifically with project 4. Basically the the project introduces photoresistors, in this case 3, and the multi light LED, which I believe is a standard RGB LED.

The part I don't understand is that we have to make a calculation for the resistor readings. We have to convert the reading, which would be in a range of 0-1023 to a range of 0-255 for the analogWrite() function. The calculation is very simple, just divide the reading by 4 and you get a measurement within the 0-255 range.

I don't understand the need for the conversion. What is the need for it? Why is the sensor range 0-1023 and not some other range? All I get from the reading is that it is needed for the function and doesn't go into any more detail other than that. I'm sure it is something fundamental that I am just not seeing.

Any point in the right direction would be appreciated. Thanks!


texts: Extension of Audio Amplifier's Bandwidth

texts:
I am curious, whether extending audio amplifier's BW (bandwidth) beyond 20 kHz has any benefits compared to 2Hz-20kHz audio BW amplifier?

Some say that high-frequency -3dB point should should be 30kHz, others say 50 kHz, some say that it shouldn't go further than 100kHz.

I have read somewhere that low high-frequency roll-off point attenuates higher audio frequencies that cannot be heard by human and that there is "void" in output signal, due to high audio frequencies attenuation (higher than 20kHz).

Is very high BW in audio amplifier a good thing (the higher the better) or is it only asking for trouble? Could the amplifier start oscillating on some high frequency with very high BW?


texts:
I am planning on a 1 cubic inch robot as my next project in robotics and the biggest challenge I am facing is on the battery. Lithium polymer seems to be the best option in terms of weight and the required current output and rechargeable!

The requirement in circuit is around 400mA with 3.5V, After searching a lot in Internet I could best get to this battery which fits my dimension and voltage requirements.

But its still low on current so I plan on using them in parallel. I read that Li-ion and Lipo batteries are very sensitive and might damage the battery or cause fire if used incorrectly So I need some help on this!

Can I use them in parallel ? Is that the right and safe thing to do ?
If I use them in parallel then can I charge them to in parallel ? or do I need some special balancer circuit ?
Can somebody help me with a decent charger circuit for this cell ?
Anybody knows a better battery than this one that I can use in my application?
Any other points/suggestions that will help me on this project that I missed out ?


texts: How to have multiple devices getting measurement from a single thermocouple

texts:
I have a system with redundancy on the control unit using thermocouples.
My question is : is it possible to get from different devices the measurement from a single thermocouple ?

I am thinking about sending the signal after the cold junction is applied into 2 different ADC, but as the thermocouples involves very little voltage, I'm not sure if this would screw up my measurement.


texts: Controlling cardreader numpad input with microcontroller

texts:
I am trying to automatically input a pin code into an electronic card reader so I can automate the process.

First thought was to build a small robot finger and control that to input the code, complexity vs benefits was too high for this option.

Second thought is to directly deliver power to the pressed buttons with a microcontroller.

Assumption: when a button is pressed, a switch is closed so current can flow through the circuit.

Question: how can I measure the current when a button is pressed? Where do I connect the multimeter on the electronics shown below.

Assumption: knowing the amount of current a pressed button delivers to the circuit, I can deliver the same amount directly via a microcontroller.

Question: where - given the layout of the board below - do I connect the microcontroller to each button on the circuit?

I am a computer science engineer with limited knowledge in electrical engineering, so
directions and resources to help me solve this problem are greatly appreciated.

If you think there is a better way to being able to input numbers softwarematically into this card reader, do let me know!

The card reader looks as follows:

Electronics look like this:

With the rear of the buttons looking like this:

The rear:


texts: Using current measurments for smart charging a battery

texts:
I've been doing some reading on smart charging a battery, and I hope to create a system that can charge batteries with the use of a solar panel.

Most of the reading I've encoutered utilises the "Negative delta voltage" on NIMH batteries to determine when the battery is nearing its full charge. But from what I've read this voltage drop is very small and hard to detect, so other failsafes are put in such as timers.

I've also read that as a battery charges, it begins to let less and less current through. So my question is, why does nobody seem to use a current measurment on the battery to determine how close it is to being full for smart charging applications?


texts: LEDs and Arduino Microcontroller, How much Ampere, is it safe?

texts:
If I have 144 leds each requiring around 50-60mA, therefore I need 8amps right?
Where can I get a power supply that does not look like a rectangular rock but is also easy insertable into the typical European wall plug?

TL;DR: 5V and 8amps right?


texts:
For a hobby project that I am doing, I would like to measure the voltage across a shunt resistor with a differential ADC. I am thinking to use the ADS1292 of TI.

However, I have the following question. Since I also expect a negative voltage across the shunt resistor. I would like to generate a bipolar reference Voltage for the ADC

How can I best accomplish that? I have a 4.5V power supply and want to use a rail splitter. Is that stable enough for a precision measurement? If there is a better way of doing that I am open to suggestions.

Best Regards

EmbedWise

Embedded Systems Enthusiast


texts:
My project requires a backup power supply, and I want to include an LED to determine when the backup power supply becomes active. My thought was a voltage divider to limit current to the LED, and allow the excess to bypass the LED and go straight through to the load.Would connecting a BJT as an amplified Zener where the Zener is in fact the LED be relevent?

I am told the correct way to do this would be to utilize a transistor, however I cannot think of a way to connect a transistor where I am not connecting it or an LED to ground(else there will always be current regardless of whether the backup power supply is active), or running the full load current through the gate of a transistor.Would a BJT be better here?

What is the correct way to approach this? I suspect using a transistor would be correct, I have just not been able to create a working circuit with a transistor myself!

EDIT: More info

When the 12v supply is droped it is disconnected and creates an open circuit.


texts:
For a project, I will be using a Avago 2310Z photodetector.

When I went through the datasheet, I could not find the sensitivity mentioned

I also looked through couple of datasheets from other companies, but could not find sensitivity mentioned.

Sesitivity parameter is needed to perform power budget analysis in an optical link.

How is it calculated?

Here is the link to datasheet.

http://www.avagotech.com/products/industrial-fiber-optics/industrial-control-general-purpose/1300nm/afbr-2310z#documentation

Regards,
Abhilash


texts: Reverse voltage protection using a Power MOSFET at low voltages

texts:
I don't know as much about MOSFETs as I'd like to. However, I'm planning on using a Power MOSFET to limit reverse polarity issues on a 3V coin cell, i.e. just above 2.7V. How do I pick a power MOSFET for this application? I'm not asking what the best MOSFET is but more what a good heuristic is for determining what a good component is for this particular use. What would I look at? How do you pick the right component?

(from http://www.ti.com/lit/an/slva139/slva139.pdf).


texts: Using common mode choke in differential configuration for differential mode EMI filtering

texts:
Why is it not popular using common mode chokes in differential mode configuration for differential mode noise filtering?

Mostly when using fly-wire type chokes with filters, where the chokes are simply kept inside the enclosure with its wires connected to X and Y capacitors placed on the PCB (due to its size which makes it costly to be placed on board), can't this kind of arrangement help avoid placing one common mode choke and two separate single winding chokes and go with one common mode choke for common mode filtering and another common mode choke connected in differential mode configuration as shown in attached schematics?

Could saturation be a problem for low current design? If yes, I dont understand why not if two separate chokes are used. I am assuming the core is properly sized to not go to saturation during normal operation.


texts: Why do we need a pull-up resistor when there is a floating connection at the base of a transistor?

texts:
Let's say that the base is connected to any normal PIC. My teacher was talking something like, "There will be a floating output at the base when nothing is connected so we use the R7 (10k) for safety." but i do not understand,
1. Why will the output be floating?
2. Why do we need the 10K if the output is floating?

Thank you for your time :)


texts: I'm sorry I'm totally new to electronics and I get confused of what Vo is in such problems and how to calculate it so can someone explain what Vo is and how to calculate it


texts: Creating a footprint for a component with plastic "bumps"

texts:
I think that I can best describe my question by giving two examples:

This is a TRS audio jack: https://uk.farnell.com/lumberg/1503-03/connector-receptacle-3-5mm-phono/dp/1216980.  It has two plastic "bumps" (I don't know how those things are really called) and the datasheet clearly shows their location and dimensions.

This is a card edge connector: https://nz.rs-online.com/web/p/edge-connectors/6812238.  It has four plastic "bumps" at the corners and the datasheet doesn't mention almost anything about them.

So I assume that in the first case, the plastic things are for mechanical stability, they need to fit inside the pcb, and when I'm creating the footprint for the component I need to add (possibly NPTH?) pads for them.
And in the second case, I assume that the plastic things are for something else (spacing? I don't know?) and I don't need to include them in the footprint.
Is my line of reasoning correct?


texts: Can I use meander antenna as show in below pic

texts:
I wondering will above antenna work properly or not because most of the PCB design layout antenna directed in right side & feed length remain unchanged.

As per as I know, feed length does not affect performance but it's width does.

Here is original antenna layout


texts: I'm currently learning digital logic and have been tasked with building a 5-bit multiplier using only simple gates. I saw it recommended here to use a truth table to help you build the circuit. Unfortunately, for 5x5 multiplication a truth table isn't very realistic as far as I know. Is there another way I could derive a formula that could then be converted to a circuit? Thank you for any help!


texts:
Calculation show  Vin should be 1.02V as no current will be drawn towards  negative terminal of opamp and Vout should be -1.02V. But simulation show Vin to be 114mV and Vout to be -114mV.

There must be something wrong in this simulation schematic.

I would be glad if you could help me out.

simulate this circuit – Schematic created using CircuitLab


texts: Relationship of signal Frequency and the SNR?

texts:
Sincerely, It is not my homework. It was the question asked in one German University's Online Exams.

I went through Google as well but couldn't find a single way out to figure the solution of this Problem.

A Received Signal is filtered in the low pass filter. At the Input of the Low Pass filter the Bandwidth is B=80khz and the SNR is 30 dB. What is the SNR at output of Filter if equivalent noise bandwidth of the filter (low pass filter) is 20kHz.?


texts:
As we know, when we use a thermocouple, we measure mV value.

This is what I wonder.

Why we measure voltage not current?
Like voltage, I think the current of T/C is proportional to temperature too.


texts: Intelligently Charging and Profiling Lithium Polymer Battery Packs

texts:
Lithium Polymer battery packs are widely used in Radio Controlled (RC) airplanes among other things for their charge/weight advantages. These packs typically consist of X series cells and Y parallel cells, and if I'm not mistaken, each parallel segment is ganged across series segments as follows, with taps brought out.

So what I've drawn above as an example is a representation of a 4S3P configuration (4 series, 3 parallel), B+ is the pack positive terminal, where B- is the pack negative terminal, and T1, T2, and T3 are series tap points.

From what I've read you need circuitry to do charge protection to cut off charging voltage when charge is complete (i.e. all cells have reached 4.2V). It's good to have cell balancing circuitry that can selectively bypass series segments to allow the pack to fully charge. And finally it would be nice to have fuel gauge circuitry to monitor / profile the cell / pack state of charge (or equivalently depth of discharge).

There seem to be quite a lot of chips out there for doing "battery management" or "charge management" or "fuel gauge" functions for particular chemistries. What are some tried-and-true techniques? What is the most integrated available solution to this problem? I would think there would be "all-in-one" solutions to "battery management" problem that are equiped to interface with a pack like I've drawn above, why does the landscape seem so varied and federated?


texts: How do I rotate A2212 2200Kv BLDC via 220 V Ac?

texts:
I use Lipo battery (11.1V 25 C 3s) to rotate the motor. But now I want to rotate motor via 220V AC (Home supply).I followed this tutorial and successfully converted 220V AC to 12 V DC. But I am not able to rotate the motor.
I was using this motor.,this battery with the capacity of 3300 mAH and this ESC.. To test the circuit I am using this servotester
I would be highly obliged I am corrected.
Thanking you.


texts:
I hope this is the right place to ask.

I`m looking for a self retaining pcb connector. It should be 2.54mm pitch.
Something like this

I have a lot of boards that have unpopulated serial ports, I need to do firmware upgrades over thi port and I am looking for a cable or plug that retains inside the holes when I let go the cable.

I don`t know how this is called or even if it exists.

Thanks


texts: Why does my LCD screen emit sound when displaying black-and-white lines?

texts:
I recently discovered this page (epilepsy warning; flashing lights), which displays horizontal black and white lines and animates their thickness. Amazingly, it makes my laptop LCD screen emit an audible continuous squeak that changes in pitch. It has a few thousand upvotes on Reddit, implying this is a common observation.

If your screen does not squeak, this recording matches what I'm getting. (Thanks dadooor on Reddit!) Make the page as large as possible—it's louder that way.

For experiments, I created a large image with 1-pixel horizontal lines, and one with vertical lines. Try zooming in. For me, it's loudest at 200%. Interestingly, the vertical one is silent at any zoom level.

drivers99 on Hacker News speculates:

  Without knowing anything else, I guess that there may be a capacitor somewhere that is charging and discharging along with the brightness of the screen as it is refreshed from top to bottom, which is causing it to flex in a way that produces an audible noise.

Is that a workable theory?

Why does it only happen for horizontal lines?


texts: What are the best practicies for a Altium - HFSS workflow?

texts:
I'm a relatively new user of HFSS and Altium.
I'm trying to find the best iterative workflow but I'm struggling a bit.
I have in mind some sort of continuous integration workflow where i change things in HFSS for instance then move to altium, change things and then back to HFSS.
Do you have any recommendations?


texts: Is this quote about interference from wireless charging coils accurate?

texts:
This blog post suggests that apple dropped their promised AirPower wireless charging mat because it didn't pass EMI standards, specifically due to the (unconfirmed) idea that they were using a large number of coils to make the product simpler for consumers to charge multiple devices without having to carefully position them over individual coils.

One quote stood out to me:

  We asked an engineer with experience building wireless charging systems what obstacles Apple was working to overcome. “Over time, these harmonics add up and they become really powerful signals in the air,” explains William Lumpkins, VP of Engineering at O & S Services. “And that can be difficult—that can stop someone’s pacemaker if it’s too high of a level. Or it could short circuit someone’s hearing aid.” If Apple’s multi-coil layout was spinning off harmonics left and right, it’s possible AirPower couldn’t pass muster with US or EU regulations.

Specifically the bolded part surprised me, and I'm not sure if it's just because he's simplifying for a lay audience. I would have thought that the resultant field due to harmonics at any reasonable distance would be established near-instantly since it's just EM waves travelling in free space around the speed of light.

Is there something I'm missing that causes this to be different in the case of wireless charging devices?

Secondly, is this just a power conditioning issue, or do the coils themselves generate the harmonics? That is, if you had a perfect sine generator at the resonant coil frequency, would it also generate harmonics in the emitted EM?


texts: How to calculate consumed energy effects on battery voltage?

texts:
I have 2 3,6V batteries. I want to send a SMS when voltage drops down to 3,4V. I ve chosen a voltage detector which has a 3,4V threshold. What I am trying to figure out is how long does it take the battery voltage drop down to 3,4V from 3,6V... So what are the elements to consider while calculating the time of this 0,2V consumption? What do I need to know? I checked the battery datasheet and there is this figure indicates what I need to know. But if there is not a datasheet, how can I calculate the time? What values sould I know?

Here is the battery datasheet: http://www.farnell.com/datasheets/301017.pdf

P.S I ve search the entire questions and answers but I could not find anything but voltage drop coversations. Sorry if this is asked before.


texts: systemverilog structure initialization with default = '1

texts:
Can someone shed light on what this SystemVerilog code should do:

typedef struct {
 logic [15:0] a;
 logic [15:0] b;
 logic [15:0] c;
} my_struct;

localparam my_struct s = '{default:'1, c:0};

Is this legal? I can't quite figure out the spec well enough to tell. This doesn't work right with Vivado, and I'm not sure why.

This works:

localparam my_struct s = '{default:0, c:'1};

Thanks,
Nachum


texts: Tactile touch button design using pull up resistor

texts:
As you can see on my github https://github.com/mancio/Volante-The-Gamepad I'm designing a gamepad with analog axes and digital touch buttons using pull-up resistors

My pull-up resistor switch works like that:

simulate this circuit – Schematic created using CircuitLab

The 2 MOhm resistor is my dry skin that short the circuit to ground closing the switch. The Idea come from the Makey Makey project https://makeymakey.com and actually works.

I have some issue to fix button flipping. I'm able to partially debounce the switch with with the capacitor, but bigger is the capacitor bigger is the delay of the switch. Total debounce means also too big time delay during switching.

Here you can see my PCB button: one serpentine pad is connected to the input an the other to GND. The finger act as a bridge.

I tried several button design. I wish to improve the pad patterns to reach better on/off performance as a real button NO-switch.

I was thinking to use this formula https://www.allaboutcircuits.com/tools/resistance-calculator to find the  resistivity of a component (in this case my finger).

I have some questions:

Is not clear to me if L is the length of my skin between the ground and input PAD on my PCB button or how much am I tall.
what represent the Area (the rectangle of skin between the pads or the area of my body)
how can I know the resistance of my skin in ohm-m (Ω-m) (assuming dry skin worst case scenario)
if I print only two big pads with 1 mm distance between them instead of a serpentine I can obtain a better on/off switch.

Thanks very much for help :)


texts: Getting garbage output in serial monitor while communicating with OBD using CAN interface (MCP2515) and nodemcu

texts:
I am doing a project which involves getting vehicle speed from a car's OBD port and storing it in my database using nodemcu.

I am programming nodemcu using the Arduino IDE and using this library for working with CAN.

Here is a simple example program which I am trying to test, but I am getting garbage output on the serial monitor:

#include <SPI.h>
#include "mcp_can.h"

INT32U canId = 0x000;
unsigned char buf[8];
char str[20];
MCP_CAN CAN0(10);

void setup()
{
    Serial.begin(38400);
START_INIT:

    if(CAN_OK == CAN0.begin(MCP_ANY, CAN_125KBPS, MCP_80MHZ))
    {
        Serial.println("Initialized successfully");
    }
    else
    {
        Serial.println("Initializing is failed");
        Serial.println("Reloading...");
        delay(100);
        goto START_INIT;
    }
}

void loop()
{
    INT8U len=8;
    if(CAN_MSGAVAIL == CAN0.checkReceive())
    {
        CAN0.readMsgBuf(&canId,&len, buf);
        Serial.print("<");Serial.print(canId);Serial.print(",");
        for(int i = 0; i<len; i++)
        {
            Serial.print(buf[i]);Serial.print(",");
        }
        Serial.print(">");
        Serial.println();
    }
}

My speculations:

A CAN ID can differ from car to car. If so how do I know CAN ID of my car? (It is Maruti Suzuki Ertiga)
The baudrate which I am using maybe wrong
The frequency or the kbps I am using in the function call CAN0.begin(MCP_ANY, CAN_125KBPS, MCP_80MHZ) maybe wrong.

If any of the above mentioned points are wrong, then how do I know/what are the correct values?


texts: Negative peak detector hits "minimum" value

texts:
I am using LTSpice simulation to average value of a function. To do that I detect positive and negative peaks and average them together. My function, however, starts at ~-3.3V. And the circuit I am using is unable to register any negative peak values lower than ~-1.7V. It results in this:

What changes should I make to my circuit for it to be able to detect lower values of negative peaks?

Vdd=5V; Vee=-5V;


texts: Understanding parts of this BLDC driver schematic

texts:
I have a couple of question on ST's STSPIN32F0A 3-phase BLDC driver and I was hoping someone can help me figure out some parts of the schematic. The schematic shows the STSPIN32F0A (pg. 1) connected to the onboard ST-LINK debugger via the SWD pins (SWD_IO and SWD_CLK, pins PA13 and PA14 respectively) and also via the UART lines (pins PB6 and PB7).

The SWD lines are for programming the STSPIN32F0A correct? What role is the UART playing here? THere doesn't seem to be any specific firmware for the onboard ST-LINK on the product page. Does this mean it has some custom firmware that isn't public?


texts: How can i create a button with a clock that is connected to a LED that the LED turns on when the button is pressed but even if you keep holding it it will turn off


texts:
I have a little piece of code, that applies again and again, in different places. The places are too irregular, the code is too small, and the input and varies too much to be able to use an entity.

Is there anything macro like in VHDL?

for example:

macro do_something(input_a, output_b);
  counter_1 <= counter_1 + 1;
  output_b <= input_a & other_input;
  other_output <= input_a;
end macro;
-- note: since this uses other_output, it can obviously only be used in one process!

process(clock) begin
  if some_condition then
    do_something(local_signal_p,local_signal_q);
  elsif some_other_condition then
    do_something(local_r,local_s);
  end if;
end process

The idea would be that the "do_something" would be replaced by the individual instructions.

Is there such a thing?


texts:
The transformer of the picture is connected to a transmission line of 230kV.

As you can see the transformer is delta-star connected. Its turns ratio is a=1:10. I had a go at the solution but when checking the solution manual I found something wrong.

In my solution for the right side of the transformer and for single phases the voltage is  $$E_{ph}=\frac{E_l}{\sqrt 3}=230/\sqrt 3=132.8kV$$

The solution manual does the same but when it comes to drawing the equivalent circuit of the single phase the following is drawn
Note that Va'n' is the E_{ph} of my calculations. As you can see in the transformer 'box' appart from the 30 degree shift and the ratio 1/10 the voltage is also divided by the square root of 3.

Why is that? The left side is delta connected and we've already converted the voltage.

Idea: Could the voltage ratio be for the whole system? Meaning that this is not true $$a=\frac{Van}{Va'n'}$$ but this is instead $$a=\frac{Van}{\sqrt 3 Va'n'}$$


texts: Replace mains 12v power-supply with 12v battery

texts:
A Yamaha digital piano is powered by a mains power-supply.  The power-supply states the following input/output values:
INPUT 100-240V~50/60Hz 0.5A
OUTPUT 12V === 1.5A
(Where I have written === there is actually a solid line over a dotted line).
He is keen to go busking with this piano. I am therefore looking to substitute the mains adapter with a 12V battery which I have to hand.
I don't want to risk damaging his piano. Should I place some sort of circuit (voltage regulator?) around the battery to protect the piano.  Can anyone assist in telling me exactly what the circuit diagram should be?