texts:
Ask: How to get (with a fixed range and offset) linearly proportional signal from a variable range on the input?
Conditions: There's a signal (to simplify, consider a sinusoid) with variable amplitude (min. 165mV to max. 1.65V) and variable offset so that the signal's lower value is above and close to 0.
I need a circuit to catch the signal no matter what amplitude and then get an output linearly proportional signal that goes from 0 to 3.3v, as shown bellow:

An AmpOp may be used in association with a digital potentiometer, to vary digitally it's gain. In this configuration, for the max. amplitude, gain should be 1. For the lower amplitude, the gain should be around 10.
P.S.: Said that, the actual signal is a trapezoidal signal that comes from a DC brushless motor phase, like bellow:

[EDIT - A test with a possibly solution]
Using the following circuit, it was possible to obtain a signal from the variable amplitude input signal:

Setting the input signal to a sinusoidal 0-to-6v, and the 50k potentiometer to 91%, we have both graphs bellow:

Setting the input signal to a sinusoidal 0-to-60v, and the 50k potentiometer to 51%, we have both graphs bellow:

Both situations were simulated to 1.0kHz signal on the input. I would like to know if you guys have any advice or any real question which simulation doesn't take into account. Thanks!


texts: I don't understand why this circuit works with MOSFET

texts: This circuit works, Vgs = 12V, when IN1 = 0V the circuit lets pass an external current that comes from A and goes out through OUT1, for them to happen the voltage between gate and source must be 12V, but the source is not at any voltage (it's actually floating), so why is there 12V between gate and source? to my understanding this circuit should not work but it works


texts:
Does any one know where to find buttons in EAGLE that look something like the one in this schematic?

I'm making a schematic and all I can find are complex looking buttons. If those are not available, then can someone help me find a normal switch, like this:

I can't seem to find this in the EAGLE libraries, either.


texts: Why would we use a Single Schmitt-Trigger Buffer?

texts:
The SN74LVC1G17 was used on a DIO circuit as a buffer on a FPGA. Is it used to have a higher current on the output ?
Here is the datasheet
https://www.ti.com/lit/ds/symlink/sn74lvc1g17.pdf?ts=1604252447419


texts:
I  recently fried my AVRISP MKII programmer, so I am looking for a new programmer. What is the best AVR programmer according to the following criteria:

Out of the box use
Works well with Ubuntu
Easy to use
Able to program common types of AVR uCs (such as ATmega328-PU or ATtiny85)

Any recommendations?


texts: Why does the electronics industry use the adjective "organic" when it adds no information?

texts:
This has been nagging me for a while. I'm an engineer, not a chemist, so I've probably misunderstood something.

The electronics industry uses the adjective "organic" a lot when describing materials.  According to Ye Olde Wikipedia, an "organic compound" is:

  An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon.

Here are three examples where the adjective seems to convey zero useful information:

Organic Solderability Preservate (surface finish)
Organic Substrate (for circuit boards or flip-chip assemblies)
Organic Acid (O*** flux types according to J-STD-0001, J-STD-0004)

The last one is particularly annoying, since Rosin flux is definitely organic in even the most restrictive sense (it comes from trees!) and contains many acids; Rosin fluxes are, in a literal sense, organic acid fluxes!

In the first two cases (OSP and "organic substrates"), well this could be just about anything including cookie dough.

Have I totally missed something here, or is it just understood that in the electronics industry the adjective "organic" means "super secret stuff we don't want to describe in any way so we will hide it behind this chemistry term that most EEs don't use on a daily basis"?

Here are more examples for the wall of incoherence

Organic Light Emitting Diode (OLED) (thanks @MarkU) although in this specific case I think "organic" has come to mean "individually tiny and therefore high resolution matrix at low cost".


texts: The most energy and space efficient source of 6 V DC for a trail camera

texts:
I use several low-end trail cameras for monitoring wildlife. All of them are powered with 4 x 1.5 V AA batteries. Replacing non-rechargeable cells in several trail cameras starts to generate more electro-waste than I like (and it also costs money). All cams have external 6 V DC input, so I am starting to think about options I have in order to get rechargeable source of 6 V. Regarding current, it only takes few mA (maybe les than 1 mA) in stand-by and this usually takes most of the battery life.

As first, I have asked a manufacturer of my recent trail camera (Suntek Mini300) about using 7.4 V (2S li-ion cells) as external power source. As I expected, they do not recommend it, because "the infra LED will not work" (no more details to this statement). So I will probably need source of 6 V. Below, I sum options I came with. There is a need to say, all of them will be really "external" - can not be fitted to 4xAA compartment in trail camera.

5xAA Ni-MH 1.2 V cells - probably the simplest solution, but re-charging 5 cells is really uncomfortable.
4xAA Ni-MH 1.2 V cells + step-up converter - I know very little about it, but stepping up 1.2 V might not be very efficient.
Li-ion 3.7 V cell / 2P cells + step-up converter - I have no experience with li-ion cells in outdoor conditions + uncertain efficiency. 1 cell might not have enough capacity, and connecting 2 cells in parallel may be dangerous.
Li-ion 2S cells @ 7.4 V + step-down converter - low voltage difference -> might not be very efficient (?)
Li-ion 3S cells @ 11.1 V + step-down converter - voltage difference is higher, so conversion might be more efficient(?)
Above mentioned with Li-po cells - no experience, aware of cold conditions
6V Pb cell - can have enough capacity, but is too bulky & heavy and especially not very eco-friendly.
Lion 2S @ 7.4 v directly :) - should I try it despite the fact it is not recommended? It is needed to assume 8.4 V when fully charged.
Other suggestions?

Personally, I mostly like first 2 options, but maybe I have not mentioned some obvious solution, that is why I am asking here. I will be very grateful for any suggestions or discussion of above stated options. thank you.


texts: Is it possible to daisy chain without hard-wired addresses?

texts: I wonder is it possible to use daisy-chaining, and instead of assigning each slave an address manually, they should be somehow be intelligent enough to communicate with each other?


texts: Is 2N9013 a good replacement for 2N3904?

texts:
I needed 2N3904 transistors, so I went to the few (poor) electronics shops we find in my country. They didn't have those, but they gave me 2N9013 and stated that those were equivalent NPN transistors. Both in TO-92 packages.

I've searched for a datasheet and found one from Promax-Johnton (who?) with "1W OUTPUT AMPLIFIER OF POTABLE RADIOS IN CLASS B PUSH-PULL OPERATION" which is worse than Chinese to me.

My questions are:

Is the 2N9013 a good replacement for my 2N3904?
What additional considerations I need to be aware?
Recommendations?


texts:
I'm trying to setup a low cost current injector for testing certain I/O modules.
I found a rather simple design for a current source using 7805.

simulate this circuit – Schematic created using CircuitLab

So I tried making that and changed the resistances to match my requirement.
I have a 24 Volt source on the test rack, which powers the I/O modules as well.
Since this is  a low cost project, I used the same power supply and ended up with this. -->

simulate this circuit

This circuit worked perfectly when I tested it with a multimeter. It gave 3.6mA to 20.1 mA.

However, while testing with the I/O module, the current through the load (I/O module's internal resistance) never went above 15.6 mA. The I/O module has a floating ground and therefore an isolated current measuring setup.
But when I touch the heat sink, the current rose to 20.7mA
Thinking this might be due to the capacitance effect from my body, I added a capacitor between the input and GND(what I could find lying around in the workshop was a 35v 100uF).
Now I see that the output is in the range of 3.6mA to 20.8mA.

I am not literate enough to calculate the correct capacitance required or evaluate whether this setup is reliable.Please advise.


texts: How does the DDR clock compensation capacitor improve signal quality?

texts:
I saw in some DDR3 designs that there is a capacitor between differential clock lines, for example the image below:

In the document this image comes from it says:

  On the DDR3 SDRAM DIMM, there is also a compensation capacitor, CCOMP of 2.2 pF, placed between the differential memory clocks to improve signal quality

My first thought was that it adds a pole at certain frequencies (problematic ones) that dampens high frequencies disturbance.

How does adding this capacitor help?  I've seen some graphs and the positive effect it has (smooths the signals) but what is the (simple?) theory behind it?


texts: USB trace impedance calculations, with termination resistors

texts:
I'm designing a PCB featuring a Renesas RZ-A1 microcontroller, and want to check that I'm doing my USB D+ and D- traces correctly.

This application note from Fairchild, which is one of the top Google results, says that D+ and D- trace single-ended impedance should be 45 ohms.

Using the EEWeb Microscrip Impedance Calculator, I find that with 1oz/ft^2 copper and a substrate height of 0.08mm, my trace width should be 0.17mm in order to achieve this 45 ohms.

The Fairchild application note also says that the differential characteristic impedance of the D+ and D- lines should be 90 ohms.

Using the EEWeb Edge Coupled Microstrip Impedance Calculator, I find that the spacing between my traces should be 0.098mm in order to achieve this.

Does that look right?

Next part of the question - I understand that series termination resistors are needed on D+ and D-. The Renesas RZ-A1 recommends 22 ohm ones. Does the presence of these resistors change anything in terms of the calculations above? E.g., because the resistors are already providing 22 ohms, should I in fact be aiming for 23 ohm single-ended impedance rather than 45, or something like that?


texts: What are the bare minimum parts needed to operate a magnetron?

texts:
I recently took apart a microwave, and I managed to get a magnetron out of it, as well as a transformer that appears to be the power source for the magnetron, but looks a little small for the advertised amount of power this magnetron can handle (~1 kW). Also, the magnetron does not have any leads for supplying the filament voltage, just for the HV. I would like to get that magnetron running, I plan to put on a waveguide and do a bit of experimentation with microwaves.

1) Does the magnetron have something built in to step down a fraction of the power recieved to the 3.3V required to heat the filament?

2) Is it possible to run the magnetron simply by powering the microwave transformer with mains and hooking up the hv output to the input of the magnetron, or do I need a microwave capacitor? I was not able to locate a capacitor in the microwave, I think that might be because it is an inverter-style microwave.


texts: Cheap method to drill neat holes in plastic casing?

texts:
A good deal of projects I see have their inputs and outputs neatly aligned in to plastic enclosures. I wish to do the same, however, I do not own a drill or anything similar.

What is a cheap but effective way to drill neat holes in my cases?


texts: If I plug in two separate strings of christmas lights into each other, is the voltage multipled by number of parallel circuits?

texts:
For example:

Say I plug in two 100-bulb strings in series - one into the other. Each is a series of 50 lights wired in parallel.

Would it then follow that now there are now four strings of 120v, even though only one source of 120v (the wall outlet)?

See this diagram picture I drew illustrating this:


texts:
I  found a  schematic from  an old  (80's) collection  which
shows a circuit to music reactive LEDs. The potentiometer is
supposed to control  the sensitivity and the  X Y connectors
are  supposed to  be  connected in  parallel  directly to  a
speaker.
These days  I don't  really have  direct access  to speakers
(unless I  dismantle my  "smart" speaker)  so I'm  trying to
connect this  directly to a  standard audio output.  I found
similar circuits which indicate that this idea could work.
In fact it works, however the variation in LED brightness is
minimal. On the extremes of P1 it is either completely on or
completely off. How  can I increase the  range of brightness
alteration in this circuit?
My first instinct  was to tweak R2, however  it hasn't shown
any effect. In fact since  I'm a complete beginner trying to
understand these calculations, any indication of material to
read on how this amplifying circuit math could be done is of
great help. Currently  the only resistor value  that I fully
comprehend R4. Nevertheless, I'm  not completely sure if the
change required is actually in any resistor at all.


texts: Understanding IR Protocol Checksum generation

texts:
To control my AC with an Arduino, I'm trying to emulate the IR Remote. Not with another IR LED, but directly connected to the IR Receivers Signal wire on the board.

Using the Arduino as a Logic Analyzer I was able to understand the Protocol to about 90%.

Problem is, that the last Byte seems to be some kind of checksum. To send my own commands I need to figure out how it is calculated. I have no Idea.

The following gist contains all the Information that I have about the Protocol. It's pretty long (112 Bit) By replaying the exact commands I can control the AC Unit.

https://gist.github.com/Hypfer/38b3b276e1a0fea92c30

Adding it directly to this page doesn't work very well, because the formatting gets completely messed up. The protocol is just way too long.

Important: The remote doesn't seem to work like a normal remote. It doesn't send keycodes, but whole state "objects".

Maybe someone here will see some kind of pattern in that data. :-)


texts: Is a crystal needed for burning firmware on AVR?

texts:
I want to program an AVR attiny2313 with my AVR ISP MKII

So I built a header that connects to a breadboard where I want to burn the firmware to the ATTiny via ISP,

so my question is,

I have a design that uses an external Crystal of 16MHz

but I don't have space on the actual protoboard for the ISP header,
so can i upload the firmware with out a Crystal [will configuration of fuses work?] and then use it the proper external Crystal ?


texts: Nyquist-Shannon sampling theorem and highest frequency

texts:
Nyquist-Shannon sampling theorem states that sufficient condition for sampling is sampling rate higher than twice the highest frequency.

By highest frequency, does this refer to the highest frequency content of the signal's Fourier transform?


texts: 40 GHz spectrum analyzer with N-type coax input?

texts:
We have an old Rohde & Schwarz FSEK 30 that is advertised as having a range from 20 Hz to 40 GHz, with an N-type input connector.  My conundrum is that a type-N connector with air dielectric should have a maximum frequency of approximately 19 GHz before the primary TEM-mode propagation is joined by the TE11-mode. From MIL-STD-348A the inner and outer coax diameters are 0.12 and 0.2759 inches, respectively.  According to Microwaves101 the cutoff wavelength for the TE11-mode in an air dielectric coax is $$\lambda_c = \pi\frac{D+d}{2}$$
where D is the outer diameter in meters and d in the inner diameter in meters.

This disconnect between the theoretical frequency limit of an N-type and the stated range of the instrument has me doubting the validity of measurements made above 19 GHz.  Can anyone shed light on this mystery?


texts:
It's rock solid, not like the cables glue.
What is it ?
What is it for ?
How do I remove it ?
How do I put it back ?


texts: How to clean/remove distortion/noise in my LM1458 Op-Amp?

texts:
I've made a LM1458 Op-Amp based on this video.

it amplifies the input music but it produces noise and has low volume.

How can I remove the noise and how to increase the volume?

when i parallel 2A333J Mylar Capacitor or 104 ceramic capacitor in the input sound it removes the noise but produces whistle sound.

Does adding gain and bypass on LM1458 or/and decoupling can remove the noise? but how to add?

In case anyone could help me how to remove noise, i want to add base and treble adjustment but how?

Schematic Diagram:

simulate this circuit – Schematic created using CircuitLab

Update:
I've made LM386 amplifier with gain and bass boost which is far better than LM1458 amplifier. Thanks for all the comments and suggestions.


texts: Amplitude Calibration for Pulse Amplitude Modulated (PAM) Infrared (IR) Link with Relative Motion Between Emitter and Receiver

texts:
I have a project on the drawing board that requires information from some sensors to be passed from a rotating platform via IR link.

This is basically going to be inside the generator next to the windings and I was worried about RF interference and the changing magnetic fields so I thought that going with IR would be better than RF.

The distance between emitter and receiver should be no more than 20 cm (it could be low as 10cm, depending on the mechanics of the generator, but I'm being conservative).

The bandwidth requirements (0.8 Mbps average rate per data channel, with possibly 3-4 data channels) necessitate some method of modulation that allow more bits per symbol.

I was considering PAM but it seems that one issue is how to calibrate for the change in brightness as the transmitter moves toward and away from the receiver. It doesn't seem I can use a reference calibration pulse at the beginning of the transmission since the distance between transmitter and receiver distance vary the entire transmission.

How is this normally handled? Is it just not possible with this PAM?


texts: Can I recharge batteries with a normal AC to DC transformer?

texts:
Possible Duplicate:
  Charging 3 AAs in series

My batteries charger is not working, but I have an AC to DC transformer that can output different voltages.

If I connect two 1.5v (rechargeable) batteries in series, and I send 3 volts through them using the AC to DC transformer...

Will they recharge?

The batteries are AA Nh 2000mAh

I know I should buy a new batteries charger, but it's weekend and I need some charged batteries today.


texts: Making voltmeter accepting bipolar input voltage, using a microcontroller

texts:
I want to build a very simple voltmeter using ATMEGA328 ADC. I can successfully measure up to 20v (using a voltage divider), but the problem is, I don't understand how to measure the voltage properly, if negative and positive terminals are switched.

Only way I could think of is adding another ADC input which is responsible for measuring the 'inverted voltage'. The join both ADC inputs, but add diodes in between, so one channel works with (+-) and the other channel works with (-+) and then 'merge' the input from both channels using code. Then I should be able to measure things like sin wave for example (where polarities switch).

Is the concept correct or is there a better way to do this? Thanks!


texts: Electronic Number Lock - Digital Electronic Systems

texts:
I've been set a Uni assignment to design an electronic number lock using a Keypad, an Electronic Control Unit and an Electromechanical Locking Actuator.  It's to be based on a 4-bit binary codeword.

Unfortunately Digital Electronics is by far my weakest subject and so I'm not particularly sure where to begin with this.  Any help will be massively appreciated.

Regards,

Connor


texts: Determine the impulse response of the following discrete system

texts:
I'm not sure how they got the answer (provided below) for the following discrete system

y[n] = x[n]- 2x[n-2]+ x[n-3]- 3x[n-4]

the answer is given as .... h[n] = [1 0 -2 1 -3]

why is this? any help would be greatly appreciated.

Thank you.


texts: 2 Layer power routing with mixed signals

texts:
I am working on a BLE Gamepad project using a module based on the Nordic NRF51822. This is the first project I have done that is more complicated then an arduino project so I am likely to make some big mistakes. I am getting close to finishing it, but I have this aching feeling like I am doing the power rails completely wrong.

I currently have one long +3V3 trace running under all the circuitry that powers two LED's, two analog thumbsticks, and the microcontroller module. In a four layer board I would have separate traces for AVDD and VDD, but I am already beginning to feel a little cramped in the areas where power traces are needed. I might be able to separate them if I route VDD under the module itself, but I am worried that it might cause noise in the module if I do this. Essentially, I would like to know what I should do for power routing in such an environment.

For specifics check out the github project with pics, gerbers, and the source for the KiCad project files.

If you see things that are wrong with the design and are not related to this question then feel free to post about them at this reddit post


texts: How individual LEDs in LED strips (or matrixes or cubes) are being powered when supplied with >=12V instead of 5V?

texts:
I've been wondering about LED strips and how its individual LEDs are being powered.
My knowledge about LEDs is very basic. I know they're diodes, I know they tend to draw more current than what's good for them, hence current needs to be limited. That happens e.g. via a constant current power supply or a resistor in front of every LED. Former one, as far as I get it, only makes sense if you know exactly how much current is to be drawn, which maps to the need of knowing the exact amount of LEDs to be driven, which is is not the case for LED strips which you can cut almost everywhere.
On top - at least that's what I'm assuming writing this post - individual LEDs need to be supplied with moderate voltages <= 5V, otherwise they might get damaged.
So, there's those WS28xx protocol driving LED strips, cubes, matrixes, .. where you're able to address single (groups of) LEDs individually.
And then there's those "5050" LEDs, which I understand as physical packages for (RGB(W)) LEDs having whatever control logic on top of it (e.g. implementing one of those WS28xx protocols).
There's those famous WS2812B LED strips with 5050 packages containing RGB LEDs where you can't only address every single RGB 5050 package, but also every single physical LED inside (=every color). Those strips can be cut after (almost) every 5050 package and are powered by 5V which makes sense to me, as you can "just" power each physical LED with those 5V (again, limiting current still necessary).
Then there's those WS28xx strips which can be powered by 12V where however only LEDs of groups of three can be individually addressed (which probably doesn't mean the three physical LEDs (=colours) in one 5050 package, but one physical LED (=colour) in three 5050 packages). Which also sounds sane to me, as 12V/3 = 4V which probably is also fine to drive individual LEDs.
Makes me wonder though, how to cut the strips then. According to my understanding I would also only be able to cut them into groups of three, as if the last part would be only a group of two or even one 5050 package, they would receive a too high voltage of 12V/2 = 6V or even 12V/1 = 12V. But at least the dumb (=non-WS28xx) 12V/24V RGB as well as white-only strips I have here I can apparently can cut after each 5050 package.
Then there's the relatively new WS2815 RGB LED strips, which are also powered by 12V, can be cut after each 5050 package, and where every physical LED (as in: every colour within each 5050 package) can be individually addressed without any grouping.
Question:
How do those >= 12V LED strips - which can be cut after each LED / 5050 package - manage to drive the individual (physical) LEDs at non-damaging voltages?
Half-knowledge: I doubt every package has a DC-DC step down converter in it - would be too big / costly. Also, I can't imagine the remaining energy (12V-5V = 8V) just being dispersed as heat (sounds like a horrible waste of energy and I'd also wonder if those strips could even handle the heat). When looking at some (admittedly rather dodgy) datasheets of the new WS2815 strips, I can see for some there's a mention of some 2kHz PWM control as part of the 5050 package. Are those individual physical LEDs maybe PWM'ed by >=12V in a way so they don't get damaged? If not that directly(because it's still >=12V) I could imagine the PWM curve being flattened so it boils down to some reasonable voltage? This only speculation based on half knowledge, though..


texts: Short-cut when using SN75441 h-bridge (with an Arduino)

texts:
I'm trying to control 6 bi-directional motors using an Arduino to feed an SN75441.

In order to minimise the number of wires between the two I'd like to tie the Motor Enable pins (1 & 9) to Vcc1 (c. 5v) and use Lo-Lo (or Hi-Hi) on the Motor Logic pins to disable the motor.

My concern is that the Enable pins must be there for a reason.

Is there any reason (other than dodgy Arduino code - I haven't programmed since the early Eighties!) why I shouldn't do this?

Funnily enough I woke up this morning pondering the problem and also came up with the idea of tying all the Enable pins together! I hadn't noticed the current draw implications in the datasheet, I'll go back for another look.


texts: How do I bias an AC signal for sampling?

texts:
I want to sample a 10Vp-p 50Hz sinusoidal signal.

My ADC can only sample between 0V and 5V, so I need to bias the voltage around 2.5V.

I only have a positive 5V power supply.

To do this, I was going to feed the AC signal to a resistor divider so that it will be 5Vp-p, then add a 2.5V DC offset with another resistor divider pair (AC coupling each stage).

However, I'm having trouble with the DC offset, and I'm not sure this is the best approach to do this.

As you can see, my voltage is still negative. How can I get a 5Vp-p signal offset around 2.5V?


texts: I have the following resistor network and I need to make a 7x7 matrix which would be the solution . I know the resistor values, but not the v1, v2, v3 or any of the current. I'm supposed to combine Kirchoff's Law with Ohm's Law to each resistor, but I'm not sure about how to actually create the matrix. If I have a 7x1 matrix of the unknowns, and rewrite them in terms on the resistor values, how do I then get to a 7x7 matrix?


texts:
I'm making a battery voltage meter with a Wemos D1 Mini. The Analog input has a Vref of 3.2v. The battery that i will measure is a Lithio one of 72v, minimal 68V to max 84V, the Analog Input of the Wemos give to me (3.2v / 1024) of precision and i need more precision because with a resistor divisor i have a range from 0-90v but i will not use 0-60v, so my question is if with a OpAmp (i have a LM324) and some resistors i can map 60v-90v to 0v-30v and then use resistor divisor to down to 0-3.2v and get more precision with the ADC. The resolution that i want get is aprox 3mV-5mV
Update
I was used the document "Designing Gain and Offset in Thirty Seconds" with this values:

And used proteus to simulate the circuit of positive m and negative b

Like you see Vref' not is same (even closed) to calc and Vout is outside 3.1v range of calc... what I'm doing wrong here?


texts: Differential Signal Measurement best practice

texts:
I have 4 differential signal pairs (LVDS Data lines and Clock) running between my Microcontroller and TFT. There are no test points over the lines.
Can someone tell me what is the best practice and how to measure the differential signal LVDS Lines (Measurement of Voltage levels and timings)?

Since there are no Test Points on the LVDS Lines, should I scratch the lines on the PCB vias and measure it on the PCB Vias?

Should I measure near the MCU or TFT?

Any resistor should I attach at the tips of the differential probe before measuring?

Apart from Voltage level measurement and timings (Setup and Hold time), are there any valid test I should do to check whether my LVDS Lines are fine?


texts: Modded speakers emit high frequency noise, how to filter it out?

texts:
I came up with an idea to convert my PC speakers into Bluetooth speakers. It's not really a serious project, rather a proof of concept, but I want to get it to work as well as possible.

Here's my idea: I wanted to use a Bluetooth audio receiver, connect its output to speaker's input and power it from speaker's power adapter.

So I got a cheap Bluetooth audio receiver. It's powered by an internal Li-Ion battery that you can charge via its microUSB socket. It obviously has a minijack audio output too.

Speakers are powered by a 10 V power adapter, so a tad too much for the Bluetooth module. I got a step-down adapter to get it down to 5 V. Here's how it's all connected:

simulate this circuit – Schematic created using CircuitLab

It more-or-less works, but I can hear a clearly audible high-pitched noise from the right speaker. I must note that all original circuits of the speakers are in the housing of right speaker and my additions are packed in there too. The left speaker is connected with a 1.5 m cable and it doesn't emit any high-pitched noise.

I tried to pinpoint the problem by powering the module from speakers' power adapter, but plugging in a set of headphones. No noise in that case, neither from speaker nor headphones.

Here's a screenshot of a sound analyzer app when the noise is audible:

As soon as I disable the BT module (just turn it off, without unplugging) the speakers work correctly again.

Is there anything I can do to filter out the noise?


texts: ESP32 I2C along with analogue read not working. How to fix it?

texts:
First of all I am new to electronics. I am using ESP32 dev kit and trying to communicate with an i2c sensor and an analogue sensor.
I am able to communicate both devices.
I am using freertos Task to gather output running on parallel threads on two cores of the ESP32.
I noticed that as the I2C communication begins the noise in the analogue signal increase to every high level. I am completely puzzled why this is happening. Could it be ghosting, or something that I don't know about?
I need your guidance on how to resolve this issue.
Please note if the I2C device is not running then the analogue values are read perfectly.


texts: Can you identify this battery connector?

texts: I am trying to identify this battery connector. The part on the battery has a 3.1mm height, and 2.34mm width. The pitch is around .8mm give or take .3mm. The mating connector is 3.83mm wide and 2.7mm tall. It has JST written on the receptacle.


texts: How does an "auto voltage setting" laptop charger work?

texts:
I recently came across a very interesting device for me, a laptop adapter that claims it adjusts its output voltage automatically:

https://www.trust.com/en/product/20194-plug-go-universal-90w-laptop-charger-black

The question is obvious: how can it possibly detect the voltage that the target laptop needs? I am planning to buy it but I have concerns over its safety.


texts: Butterworth filter with non arbitrary component

texts:
How do I design a filter with certain cutoff frequency and as flat pass-band as possible, given that:

one of the filter components is non arbitrary, and
that filter component does not match the corresponding Butterworth prototype (i.e., the impedance conditions and cutoff frequency)?

For this question, I understand that performance will be degraded compared to real Butterworth filter. Still, is there known analytical or numerical method for designing this to match the Butterworth filter as closely as possible?

As you see in the schematic below, I can arbitrarily choose values for \$L_{1}\$ and \$C_{2}\$. However, I cannot change the source or load impedances (since they do not change with frequency), nor can I change \$C_{fixed}\$.

simulate this circuit – Schematic created using CircuitLab


texts: How do you determine whether your product requires CE marking?

texts:
I haven't been able to come across definitive information regarding the procedure to find out whether an electronics product (PCB) requires CE marking or not.

Since it is difficult to ask hypothetical questions, let me ask by using specific examples. Let's take this RS485 IO card as a first example. Would this product require CE marking to be sold in Europe? (Maybe a similar question: would this product require any FCC approval/marking to be sold in the USA?)

Let's look at a second example. This is an A/D board. Would this product require any regulatory approvals/markings?

It would be a great help if someone with CE/FCC experience could give answers, explaining the reasoning behind those answers.


texts: Feedback on Crystal layout & signal routing for SPI /CAN

texts:
Crystal:NX5032GA 16Mhz
i havnt had the experience in laying out crystals, im personally using https://www.st.com/resource/en/application_note/cd00221665-oscillator-design-guide-for-stm8afals-stm32-mcus-and-mpus-stmicroelectronics.pdf as a reference and just want to double check if i've misunderstood something along the line.
main things i've taken away

a guard ring is required around the clock

seperate GND plane under the clock

Short distance from the MCU

With regards to the SPI line, its speed is at 4Mhz and i've set the MISO MOSI to be the same length.
is it important to have them all the same length ?
and with my CAN lines, i've used Saturn PCB toolkit to set the differential rules.

Updated board::


texts:
In AVR datasheets under the Electrical Characteristics section you will typically find a graph like this (this one is from the ATMega328):

I've seen designs that seem to "work" but operate outside the shaded envelope. Specifically, I've seen 3.3V (Arduino) designs that run the clock from an external 16MHz crystal. Clearly, this is out of spec. What are the practical negative consequences of running outside this envelope?


texts: Is the maximum current a resistance can draw limited by the maximum current available (current rating) in the power supply?

texts:
Let's say I have a single phase power supply at 100 V and 10 amps at my wall outlet. If I were to connect a very low resistance element (say 0.1 ohms), using Ohm's law I could say the resistance draws V/R = 100/0.1 = 1000 amps. This is what some people around me say happens. However, I think the current is limited to 10 amps and cannot go above that otherwise it violates the law of conservation of energy as follows.

The electrical power supply is 100V × 10 amps = 1000 W. If the resistance were to draw a current of 1000 amps, the heat dissipated would be I^2×R = 1000^2×0.1 = 100000 W = 100 kW, which is not quite possible. So the actual current drawn should be 10 amps, and the  heat dissipated by the resistance is 10^2×0.1 = 10 W. Therefore, the resistance is actually dissipating only a fraction of the power available.

Any explanations or clarifications will be appreciated.


texts: Impedance Matching: Minimum Reflection vs Maximum Power Transfer

texts:
The minimum reflection is achieved when the two "circuits" being connected have the same impedance. This makes sense because all the components of the wave can propagate without needing to be modified.
The maximum power transfer is achieved via complex conjugate matching. This is because the real parts of the source and load impedance must be equal in order to maximize the power transfer and reactances cancel out when complex conjugate impedances are used.

These two statements seem contradictory...

How is it that the maximum power is transfered into a system when the reflection is not minimized?


texts: Charging 18v Ni-CD battery pack with DROK voltage regulator

texts:
I have an 18v 2000mAh black and decker drill battery that I want to charge and use in the mean time while I wait for a proper charger to arrive.
I have a DROK Voltage Regulator/Buck converter (https://www.amazon.com/gp/product/B078Q1624B) that has a constant current mode and from what I understand should be sufficient in charging it but I wanted to confirm.
From what I've figured the charging voltage should be around 21v and the charging current should be Current/10 so 400mA constant charging current although the official charger states to output 500mA.
So with the Regulator set to output 21v and 400mA in constant current mode, this should charge the battery just fine without risk of overcharging or damaging the battery right?
If there is anything I'm misunderstanding or missing please let me know, thank you ;)


texts:
I have a cheap PSU of this sort, used for my 3d printer. It has a 110V input, and a 12V output with 20A maximum current. Unfortunately, it doesn't have detailed specs/data available beyond that.

Now, I would like to place a simple ON-OFF switch (like this) at a convenient physical position, and in series with the AC power line.

Of course, it's important that the switch I choose (for example a 3A-rated one) is safe enough for the input current of the PSU. By conservation of energy, can I assume that the input doesn't draw more than (12 * 20 / 110) = 2 to 3 A? Or will it be significantly more than that, since I'm underestimating losses in the form of heat?


texts:
I am trying to learn how to design PCBs, and for that purpose I am copying the simplest PCB I could found, a 4000W Dimmer:

The Squematic is this:

It has the next components:

1 TRIAC BTA416008 (STMicroelectronics, Series BTA41)
1 Capacitor 0.15 uF (Metallized Polypropylene Film, Grid  15.0 mm)
1 Capacitor 0.1 uF (630V 104J, Metallized Polypropylene Film, Grid 10.2 mm)
1 Resistor 2W 100Ω (Grid 15.0 mm)
1 Resistor 4.7 KΩ (Grid 7.5 mm)
1 DB3 DIAC (STMicroelectronics, Grid 7.5 mm)
1 Screw Terminal of Two Terminals (Grid: 8.0 mm)
1 Potentiometer 2W 500 KΩ (WTH118)

I am using EAGLE 9.1.3, to do the PCB Design the closest simmilar to the original I photocopied the PCB, and I obtained this:

and then I started to place the components on Eagle:

for some components I didn't have so much trouble, for example capacitors and resistors, but there are other ones that I don't know what should I do:

I am unable to find the BTA416008 TRIAC on Eagle Libraries, so I have to pick up another one, but I don't know if that is something correct to do.
I found a library for the DB3 DIAC on SnapEDA, but the grid does not correspond with the PCB Board and I don't know how to fix that.
There is no screw terminal with a grid of 8mm on Eagle Libraries, and I am unable to find a replacement
I am unable to find the potentiometer 2W 500 KΩ (WTH118) neither on Eagle Libraries or in SnapEDA

I am new on PCB Design, so I don't know how to fix that. Could you give me some recommendations?
Edit:
Electronic shops sell this circuit as a 4000W dimmer:


texts:
I tried several times but without success to get the trimmer changing the output voltage of the LM317T . I tired to link the Pin 1 and 2  then all goes to ADJ pin of the LM317T and pin 3 to ground or 2 and 3 to ADJ and pin 1 to ground or using only 2 pins as shown below but nothing worked . Nothing wokred means the voltage remains constant .

Note that the trimmer is working fine when it is not combined with the voltage regulator ( 1 to + , 2 to Vout, 3 to - )
Could you advise which pins numbers to use and how?

Last update :

The input voltage is 5V of an arduino uno . The output voltage required is 3.6 V


texts: Generating a delay on the order of microseconds (timer vs HAL_Delay())

texts:
So I am using an nRF24 radio module and I probably need a 10us delay after enabling chip select. But the thing is I can't use HAL_Delay() since the least it provides is 1ms delay (SCK/1000 is hardcoded in the HAL function).
I was suggested to not use SysTick timer for too small of a delay anyways and rather go for hardware timers. I read up on Timers and to me, it looks more like they're mainly used for tasks where you need to do a function at a specific interval i.e blinking LED every 4 seconds or something by changing the prescaler and counter period and I did try it out as well -- and it's nonblocking as opposed to a delay. So every time a counter hits the specific counter period, it generates an event/IRQ
Am I interpreting it incorrectly? Is there a way around it?
I'm using STM32F401RE.


texts: how to make a electric steam vapourizer at home

texts:
I want to make a durable electric steam vapourizer ( basically used to inhale steam to give comfort for nasal block and also facial steaming).
I have bought quite few from the market and i see it goes off within few months or max an year.
Some models i have (http://www.amazon.in/Facial-Sauna-Vaporiser-Steamer-Inhaler/dp/B00IWKKCQC)

I plan to make a durable/atleast maintainable one using the existing base(plastic) models i have. So want your help in getting the electrical & electronic components for the same.
So questions like what should be the type of heating metal( whats the best to use). what would the electrical circuit look like resistor/capacitor specification.

By the way i use AC 220V/50Hz power line. So please do suggest.


texts: Getting Incorrect Value of Current while Sensing Current Transfromer

texts:
I am working on AC Ammeter. To sense the current a current transformer is used which has 2500 Turns and sensing range up to 50A.

200 ohm Burden Resistor is used between the Ground and the Output Pin of Current Transformer.

I have previously worked on AC voltmeter and it worked fine and I used the same way to sense the current. As OUTPUT of current transformer is Sine wave, so I used RMS method to take out the value.

Here is what I have done :

#define ADC_BUFFER_LENGTH 40

     if(adc_data_index >= ADC_BUFFER_LENGTH )
          {
            adc_data_index = 0;

            // Time to Process and Display Data
            adc_buf_local = 0;
            adc_filter_val_current = 0.00;
            for(i=0; i<ADC_BUFFER_LENGTH; i++ )
            {
                adc_buf_local = adc_data[i];
                adc_filter_val_current += ((float)(adc_buf_local*(float)adc_buf_local ));
            }
            // 625*625 = 390625
            // 128*128 = 16384
            // 625^2 / 128^2 = 23.8414
            adc_filter_val_current = (unsigned long)((float)adc_filter_val_current * 23.84);
            adc_filter_val_current /= ADC_BUFFER_LENGTH;      // mean squared sum
            adc_filter_val_current *= 2; //To even Negative Pulse
            ac_value_current = (float)sqrt(adc_filter_val_current);// root mean square
            ac_value_current /= 1000;
            }

What am I missing?


texts:
I have a door sensor that works when the door open. I need to use it for other purpose so when the door open the circuit turned off.. While the door closed the circuit should goes on.

I want to link it to a on-lamp that should turned off when the door is open..


texts: NFC - design of inductor/"antenna" made of PCB traces

texts:
I did a layout of a NFC PCB inductor/"antenna"(I know it is not one exactly) drawn only on top side copper (nothing drawn on other layers at inductor area), and I wonder if there will be a considerable loss of working distance range on the opposite side due the PCB FR4 core itself is an obstacle... I need to read tags to both sides of the board at approximated distances.

I will share some screenshots.

Schematic of RF side, based on ST ST25R95, 230mW output power, QFN32:

Rant is 1.65 ohms and was calculated HERE

Lant is 1.09uH and came from ST's online tool eDesign Suite

This is my current drawing for the PCB coil/inductor. 10.5 x 26mm, 7 turns.

I wonder if I need (if it is suitable) to continue the "antenna" drawing on the bottom layer, and sum the inductances and resistances? (Or some other equation to calculate the inductance).

Also I wonder if I do that (antenna drawn on both sides) if I could reach more working distance (between the reader circuit and the tags) than doing coil only on top side.

If I need to continue the coil on bottom side also, do you have any recommendation about how to draw a good PCB inductor? So that I can reach the best distance range the chip can offer (it is 0.23W output power only, ST's ST25R95).

Regards.

EDIT 1

4 turns x 2 layer NFC coil.

TURN x mm:

1: 11.2 + 25.7 + 10.2 + 24.9 +

2: 9.4 + 24.1 + 8.6 + 23.3 +

3: 7.8 + 22.5 + 7 + 21.7 +

4: 6.2 + 20.9 + 5.4 + 20.1 + (2.7)

side = 251.7mm

total (x2) = 503mm

PARAMETERS of inductor traces:

witdh = 0.3mm
length = 503mm
copper tickness = 18um (1/2 oz final copper thickness)

According to HERE, Rant = 1.66 ohms

So Then I have new input values, Lant = 1.68uH and Rant = 1.66 ohms to input on the ST25R95 calculator spreadsheet. Now I can easily recalculate the NFC circuit, I mean the caps and indutors of matching and filter circuits.

I wonder if I should consider the capacitance created between the traces of spposite sides, they are on exact same place, they just are in opposite board sides. PCB is 1.6mm FR4. dk (dielectric constant) can consider as 4.5.

Single side inductance

new inductor drawing.

Rant value

Coil "pins"


texts: What options are available for measuring grounded thermocouples?

texts:
I'm using 4 MAX31855 ICs to measure 4 K-type thermocouples and realized that 2 of my thermocouples have grounded junctions; I simultaneously also realized the MAX31855 is stated to not support grounded thermocouples (returns a "nan" error). The 2 grounded TCs in my setup (of the 4 total) continuously give me errors, no matter which channel they're connected to - so clearly the issue is the grounded junction. Using non-grounded TCs for my specific application isn't a feasible solution since I need my device to be compatible with existing systems which use welded/grounded TCs. What options are there to read the grounded TCs in this kind of scenario? So far I've come up with the following:

- Modifying the circuit:
I looked into what I could do to change my IC circuit and/or the TC setup, but haven't been able to find anything yet that works as a solution. The grounded TCs are welded to earth-grounded components which are grounded to prevent operators from getting shocks when servicing the units. Un-grounding these components is not a good option, and so far tricks to make the IC work with the grounded TCs haven't provided any success. Isolating my TC-measuring device isn't very feasible since I need to permanently run off the target system's internal power supply and also connect via USB to a laptop - it may be possible to isolate but likely not practical.

- Replacing the grounded TCs with Un-grounded TCs:
This doesn't work as a solution because my TC-reading device needs to be able to work with existing system setups that already use welded grounded TCs which can't be swapped out without incurring large expenses.

- Alternative ICs:
While looking for ICs that can read grounded TCs my search results are much more meager than I hoped. I'm still combing through, but any specifically recommended ICs would be great. Writing new code for a different IC wouldn't be ideal but it's a potential solution.

My MAX31855 circuit is the following:

Below are examples of TC grounding configurations. I believe the thermocouple weld in my grounded TCs is like the middle configuration in this figure, though it's possible it may also be like the top option. My multimeter beeps during continuity check between ground and each side of the TC, implying a grounded junction weld, but I don't trust this as an "official" test since the resistance of each TC wire is rather low to begin with, so I suspect it may be possible it could be the top configuration in the figure:


texts: Apple power supply: thick AC cable, thin DC cable - why?

texts:
Apple power supply consists of a very thick, inflexible AC cable (wall outlet to converter) and a very thin, flexible DC cable (converter to computer):

Why? The currents through the cables should be comparable, right?

EDIT: the label on the converter says:

input: 110-240V ~ 1.5A 50-60Hz
output: 16.5V = 3.65A max

EDIT2: cf. ThinkPad power adaptor (typical cables, similar to hp/dell &c)

Which has a thicker (than Apple) DC part and thinner (than Apple) AC part and is rated

input: 100-240V ~1.5A 50/60Hz
output: 20V =3.25A

The characteristics seem to be similar - why are the cables so dissimilar in the ratio DC cable thickness / AC cable thickness?

EDIT3: cf. AC Adapter For System76 Pangolin (which has 3 wires - including earth - in the AC part)

It is rated similar to the above and has a thicker DC part and thinner AC part than the Apple cable.

EDIT4: Looks like Lenovo/ThinkPad cables are under-engineered, which explains the cable thickness discrepancy observed!


texts: If I connect the positive output of a LED driver to anode and cathode of LED is connected to power ground (Negative output of driver is remain unconnected), whether the LED Will work or not?


texts:
I hope I'm on the appropriate site.

Does anyone know what this thing is?

It has a mini mono plug.
The white square is slippery..but it is not covering double-sided tape.
A white LED did not light up when I plugged it into a mic input on my PC.
I thought there were little holes and it might be a mic but they are small indentations, not holes.

Thanks!


texts:
I've designed a simple PWM RGB LED slow fader to be used as a garden lighting effect. My circuit works great, but I under-estimated the amount of heat that is generated by the 7805 linear regulator.

It's mains powered, with a 6Vac transformer and a 5V 1A linear regulator. If all the LED's are at full brightness then it draws around 600mA.

I've mounted my circuit board in a plastic enclosure with a transparent lid, and it's rated at IP67 (and I want to keep it that way!).

I've put quite a small heatsink on the regulator, and it takes around 3 or 4 hours of continuous use to get to a temperature that is just about too hot to touch, I'm guessing around 70-80°C.

My plan is to give this to my Dad for him to use in his garden, but obviously I don't want it to melt or catch fire.

My questions are:

Is this an acceptable temperature for it to operate at?
Is it likely to get any hotter if left on for longer? I didn't want to test this as I didn't want to damage it, but the datasheet says the operating temp is max 125°C so I guess it would be ok.
What can I do to make it run cooler, given that I don't want to drill vents into the enclosure and ruin it's IP67 rating?
If it does happily operate at a high temperature, do I need to be worried about heat conduction through the PCB tracks into other components that may be damaged? Will it melt the solder?


texts:
Would you rather use LED with 30° or 140° viewing angle for Persistence of Vision display? I will have two columns (each column one color) of 16 LED, columns are very close to each other, cca. 0.1mm. Both LEDs have same mcd rating.

As I am restricted by current coming from the battery I could use only 2mA forward current LEDs, these LEDs have a typical 400mcd for green and 100mcd for red. Would you say that is enough bright? I really don't have any clue how do they look in reality based on mcd ratings.

Most importantly I would like to know how much is viewing angle important in this type of application ie. POV display.


texts: How to measure the current generated in permanent magnet dc motor/generaator?

texts:
A motor of dia 1cm and 3 cm height and 200gms of weight.
will it be able to generate 6 amperes of current?
Can it handle that much amount of current?
If not then how can I measure the current generated by this permanent magnet motor when I have Voltage generated?
Also how to measure the resistance of the motor?
Will it be current to use ohms law to find the current generated?


texts: What are these values on this capacitor?

texts:
As you can see from the images, this capacitor needs replacement, however I do not know what the top 2 values mean.
It doesn't state it's capacitance either...

I assume the first value is decijoule but I am not sure, the middle one just says 33, nothing else.

And the last one is 100 volts.

Also, if someone has any idea on how to replace this, I'd be very appreciated, as the capacitor doesn't seem to be soldered on the back of the board, it on some kind of plastic support, and it has 2 small soderings on the sides.
The board belongs to an LG monitor, an LG Flatron 22EA53VA to be precise.


texts: Weird Behaviour with Bootstrapping Circuit

texts:
I'm trying to make a 3 phase BLDC driver and picked up some FAN7888s since they're inexpensive gate drives with all 3 phases on one chip. I read the relevant datasheets and application notes and breadboarded the following circuit to test one of the phases:

This circuit mostly works -- if I alternate pressing SW1 and SW2 the LED turns firmly off and on as expected. However, if I leave the circuit untouched, the LED turns on brightly by itself and if I measure that node, it's 7.5V; Q1 has turned itself on despite the inputs being grounded.

Secondly, I never measure more than 12V at the gate of Q1 which means it's not actually bootstrapping. This is after I ground Q4 to let it charge.

I'm at a bit of a loss of what I'm doing wrong and how to fix it. I've read piles of material but this is the first time I've actually tried implementing one so I'm probably caught on some 'gotcha'. I've verified all the parts are working and that everything is wired correctly and in spec. Why is this not working?


texts: Why use complex numbers to represent amplitude and phase of AC

texts: Why is it that in AC circuits, sine waves are represented as a complex number in polar form? I don't logically understand from a physical perspective why there is an imaginary part at all. Is it purely from a mathematical point of view to make the analysis of circuits easier?


texts:
I am going to use a N channel JFET as a normally-ON switch. I am wondering if it would cause any problem in the long term reliability having the PN junction forward-biased. In other words, would it be considered a reliable design if I let the gate voltage be greater than the source voltage for some time (*)  during operation as long as the current flowing into the gate pin is limited much less than the absolute maximum of the forward gate current, Igf? Igf < 50mA is specified for MMBFJ201, the one I am trying to use.

(*: Roughly 2 seconds of Vgs>0 for every 30 minutes of operation)

Schematic of my circuit is:


texts: I need help with designing a specific circuit

texts:
Design an arithmetic unit. Let A and B be two 4-bit 2’s complement numbers. Design a circuit to compute:

Z = A + B         if k1k0=00

A + B + 1  if k1k0=01

A                if k1k0=10

A - B        if k1k0=11

Add logic to your above design that computes V, which is 1 when the output is a valid number and 0 when it is invalid. Assume signed numbers are always used.

I know the A+B and A-B can be done with a design like this

And I assume we'll need a MUX with k(1,0) being the select signal. But I'm stuck as to how to do the valid/invalid part.


texts: How can I use optocouplers with function generators?

texts:
I am using optocoupler PC817 to create optical isolation between my digital signal and arduino due and arduino mega 2560 . And I am using external pull-up resistor connected with 3.3 V (to pull up digital pins of arduino due and arduino mega 2560). And output pin of optocoupler is also attached with the above mentioned 3.3V.
When no digital signal is given to the input pin of optocoupler, its output pin( collector pin, as attached with the externally pulled up pin of arduino) gives 3.3V but when the optocoupler receives digital signal its output pin gives 0V and hence pulling down the input pin of arduino which is taken as input in arduino. It works fine when I give digital signal from external power supply.
But when I give digital signal from function generator(5V at 10Hz), the output of optocoupler does not get to '0' completely rather it gives around 2.5V.
I guess it's the function generator that is causing problem. It is not providing enough current to the LED in optocoupler to glow fully.  Could any one help me out how to make optocoupler work when signal is given from function generator?
The functiongenerator I am using is shown in the picture below... It is "erfi funktionsgenerator H 38. 030"
Its german function generator and its manual or guide line book is in German...


texts: Supply an Arduino via the magnetic energy created by a mains wire?

texts:
I'm a software developer trying out some electronics projects so this might be a stupid question but here it goes:

Is it possible to put a coil around the mains wire (220V/50Hz) that would be able to power a small Arduino circuit (5V/15mA) by induction only?

I've seen some power consumption monitoring devices that seem to be powered that way so I believe that such power supply is possible but I don't know what to search for in order to find eater schematics or complete circuit.


texts: Where can I find some basic information about ICT?

texts:
I'm trying to find some information about the basics of ICT (In Circuit Testing) but having trouble finding anything useful. From the few things I managed to find, I gather that an ICT tester is a machine that can inject power and signals, then read back voltages and currents. It looks like it usually does this through a bed of nails so that it can inject signals into any node it wants.

The part I'm having trouble with is finding answers to these questions:

I am guessing that there has to be some "code" written with which defines expected values, which test nodes to look at, sequence of signals, etc. What kind of language is this code written in? Is it a manufacturer specific language or some kind of industry standard?
In a typical workplace, whose responsibility is it to write this test code? Is this something that the design engineer would typically write, or something that an assembly house does.
Does ICT do functional testing or is it usually limited to low level things (like checking if the IC is actually an opamp, or making sure a resistor is within tolerance).
Is this typically used only for high volume boards, or is it used in low quantities as well? I'm guessing the bed of nails isn't cheap.
I couldn't expect that a bed of nails would work too well on modern, high-density PCAs. Do these kind of boards need to be designed with ICT in mind and have test pads placed all around?


texts: Make +6 and -6 and +3.6 and -3.6 volts from a 12 volt battery

texts:
We're working on a project that requires a stable +6 and -6 and +3.6 and -3.6 volts from a 12 volt battery. It has to be stable, even when the voltage of the source goes down. We came up with this:

But this doesn't work because the 6 volts aren't stable when the 12 volts drops. We can not use software in our project.


texts: How to Terminate DONE pin on TPL5110 when unused?

texts:
I'm using a TI TPL5110 in One_shot mode and do not need the DONE signal to shut down the timer.

I would leave it alone but static often makes it trigger,turning the timer off. Since the tpl5110 detect a rising edge, I tried grounding or pulling it up to VDD with no luck which confuses me further. It wont turn off or turn on automatically grounded or pulled up.

I don't know how to keep it from triggering, a capacitor perhaps?


texts: Structure of Larger Memory Modules by using different Size Blocks

texts:
I want to design a memory module that includes 2 types of memory cells. I know how to design the memory by using 1 type of memory cells  like shown in the picture.

But how about designing a memory with different size cells? I can't find any material on it.
Lets say in the above figure that i want to have also some cells of 256kx8bits. How will i proceed?
Probably i will have to make some arrangements on the address length of the smaller chips. Also what decoder will i use for the row selection if for example i have 9 rows of chips? Or should i keep the number of rows in the form of 2^k?


texts: Can anyone give me a brief overview or links to articles that might explain how different components might affect a sound signal?

texts:
I recently started experimenting with DIY guitar pedals and I have been wanting to try to modify some of the schematics I have found, and eventually, design some of my own.  I'm not an electrical engineer, but I have done a fair amount of circuit building/designing, however nothing having to do with an audio signal.  I've been looking all over to try to find some resources on how different components affect an audio signal.  Can anyone give me a run down, or know of any resources that might be helpful?

Thanks


texts: Is using Zener diode with a voltage divider sensible?

texts:
I need to convert a floating 12 V voltage to more or less stable 3.3V. So I bought the appropriate Zener diode. Now, since there's such a difference in voltage, I want to make Zener's life simpler and reduce the chance of it being blown up by using a 1:2.5 voltage divider. So I calculate the required Zener resistor value using 11 V - the lowest possible source voltage: (V/2.5 - 3.3)/Iz = (4.4 V-3.3 V)/0.005 A = 220 Ohm. And then I use this value to calculate the value of the other resistor required for the 2.5 ratio (147 Ohm).

simulate this circuit – Schematic created using CircuitLab

The question is: does this make any sense? Will this work, or will the R2 interfere with Zener's operation?
Is 4.4 V high enough source for 3.3 V Zener?


texts: command to identify struggling connection in eagle faster

texts:
I'm trying to auto-route a PCB which eagle determines there are 400 connections to. Sometimes I reach 100% and sometimes I reach 99.5 and 99.8% and as I watch the progress, sometimes eagle claims there's one track unroutable after trying to route it for several minutes straight.

I can stop the autorouter when it is struggling, but is there a way for eagle to identify just that ONE connection that it is struggling with? I was thinking something like "show struggled" but I'm looking for something official.

Any ideas?

and sorry if this question has already been asked but the autorouter is driving me and several other people nuts.


texts: What characteristics for 3D-printed capacitors made of interlacing conductive filament?

texts:
There are conductive filament for 3D printers which seem to have between 30 and 115 ohm/centimeter resistance depending on the axis. (Proto-Pasta conductive PLA)

They can be 3D printed as a capacitor of 2 cubicly-interlacing-but-not-touching matrices as follows, with one negative and one positive:

Does it have useful properties? I figure probably it could already be done, but here maybe it can be done at home simply and relatively cheaply, and so I wonder what that does, if someone can figure it out. I don't have yet the equipment to try. With a cheap printer I can't imagine doing more than 2x20x20x20 cubes, inside 20 * 20 * 20cm, with 1cm per side. I know that's surely not much compared to normal caps rolled onto themselves. I tried it with normal filament. The bridging is tricky, but it can be done, so I wonder about the theory.

Sorry, I only have a cheap smartphone, and cheap printer.

An interesting thing about 3D printers is that it can create shapes of things nested one into the other. But I don't understand capacitors and so it's possible the effect cancels out and that it's of no use as it is, or that the standard plate-against-plate is better.

Anyway, I'll be trying it eventually, or at the least, a standard configuration.


texts: Need help identifying this transformer in a tire balancer

texts: I have a tire balancer circuit board I'm trying to fix and am having trouble figuring out if I can get one of these (pic included). I believe it's a transformer but I'm not sure its ratings and such. I know I need a new capacitor also but I found those available online for 50 cents. The numbers on top read 71142 A and the side reads HI-POT OK.


texts: Is there a chart that translates old tube symbol to the new tube symbol

texts: Im looking for a chart that helps you translates the old tube symbol into the updated format.


texts: Two POE devices on One Ethernet Cable via a Y splitter

texts: Is it possible to run two PoE devices at the same time off of 1 ethernet cable from a PSE? Assuming that the ethernet cable is run through some sort of custom splitter  connector to both PoE Devices.


texts:
In many RF applications I have seen transistor circuit that looks something like this:

simulate this circuit – Schematic created using CircuitLab

Now, I understand the role of all the components, but one thing bothers me. The drain voltage is superposition of DC and AC voltages: \$V_{D} = V_{DC} + v_{AC}\$, where \$V_{DC}\$ is obviously 12 V and \$v_{AC}\$ is \$ G*v_{In}\$. Given the transistor gain G >> 1, the drain voltage swings about 12V, so its amplitude is definitely higher than 12V. But how can it be if the power source dictates the 12V limit??

With normal transistors and op amps, I would assume that this iduces a saturation. But it's not the case from what I have seen - RF transistors I used are highly linear and harmonic level is reasonably low so no effects of saturation have been observed.

So, how do I get drain voltage higher than power supply voltage?


texts:
I would like to know how many samples I have per second for the ADC and what is its maximum samples per second and can I achieve a sample per 1 µs?

Clock : 84 Mhz

The board is Nucleo F401RE

Here is the ADC configuration with DMA :

 void ConfigureDMA_ADC() {
 __DMA2_CLK_ENABLE()
;
g_DmaHandle.Instance = DMA2_Stream4;

g_DmaHandle.Init.Channel = DMA_CHANNEL_0;
g_DmaHandle.Init.Direction = DMA_PERIPH_TO_MEMORY;
g_DmaHandle.Init.PeriphInc = DMA_PINC_DISABLE;
g_DmaHandle.Init.MemInc = DMA_MINC_ENABLE;
g_DmaHandle.Init.PeriphDataAlignment = DMA_PDATAALIGN_WORD;
g_DmaHandle.Init.MemDataAlignment = DMA_MDATAALIGN_WORD;
g_DmaHandle.Init.Mode = DMA_CIRCULAR;
g_DmaHandle.Init.Priority = DMA_PRIORITY_HIGH;
g_DmaHandle.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
g_DmaHandle.Init.FIFOThreshold = DMA_FIFO_THRESHOLD_HALFFULL;
g_DmaHandle.Init.MemBurst = DMA_MBURST_SINGLE;
g_DmaHandle.Init.PeriphBurst = DMA_PBURST_SINGLE;

HAL_DMA_Init(&g_DmaHandle);

__HAL_LINKDMA(&g_AdcHandle, DMA_Handle, g_DmaHandle);

HAL_NVIC_SetPriority(DMA2_Stream4_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(DMA2_Stream4_IRQn);
}

void ConfigureADC() {
GPIO_InitTypeDef gpioInit;

__GPIOA_CLK_ENABLE()
;
__ADC1_CLK_ENABLE()
;

gpioInit.Pin = GPIO_PIN_1;
gpioInit.Mode = GPIO_MODE_ANALOG;
gpioInit.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOA, &gpioInit);

HAL_NVIC_SetPriority(ADC_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(ADC_IRQn);

ADC_ChannelConfTypeDef adcChannel;

g_AdcHandle.Instance = ADC1;

g_AdcHandle.Init.ClockPrescaler = ADC_CLOCKPRESCALER_PCLK_DIV2;
g_AdcHandle.Init.Resolution = ADC_RESOLUTION_12B;
g_AdcHandle.Init.ScanConvMode = DISABLE;
g_AdcHandle.Init.ContinuousConvMode = ENABLE;
g_AdcHandle.Init.DiscontinuousConvMode = DISABLE;
g_AdcHandle.Init.NbrOfDiscConversion = 0;
g_AdcHandle.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
g_AdcHandle.Init.ExternalTrigConv = ADC_EXTERNALTRIGCONV_T1_CC1;
g_AdcHandle.Init.DataAlign = ADC_DATAALIGN_RIGHT;
g_AdcHandle.Init.NbrOfConversion = 1;
g_AdcHandle.Init.DMAContinuousRequests = ENABLE;
g_AdcHandle.Init.EOCSelection = DISABLE;

HAL_ADC_Init(&g_AdcHandle);

adcChannel.Channel = ADC_CHANNEL_1;
adcChannel.Rank = 1;
adcChannel.SamplingTime = ADC_SAMPLETIME_144CYCLES;
adcChannel.Offset = 0;

if (HAL_ADC_ConfigChannel(&g_AdcHandle, &adcChannel) != HAL_OK) {
    asm("bkpt 255");
   }
}


texts: Connecting GSM SIM900A module with Ardunio

texts:
I have bought an SIM900A Mini V4 GSM module. Here is the module,

I want to configure with arduino to send and receive SMS.

Do I have to connect TXD of this module--Tx of Arduino & RXD of this module--Rx of Arduino or other way around?

There is no datasheet or documents on this new module.

When I search about RXD & TXD, I found this in enter link description here

  TxD means "Data to be transmitted over the comms link" - which will clearly be an input to the modem;
  Similarly, RxD means "Data that has been received from the comms link" - which will clearly be an output from the modem.

But I couldn't send or receive SMS using this configurations.

As I am new to this, It would be very helpful if anyone help on this.

Thank you in advance.


texts:
I cannot seem to wrap my head around this. I have read about using an instrumentation amplifier, however even then I am not sure how to use this in this scenario. Could someone explain to me how to:

Map a voltage range of 0.40-1.87(V) to 0-5V
Map a voltage range of X-Y(V) to 0-5V, where X is non-zero


texts: Simple Op-Amp setup for current sense has a strange working range

texts:
I am using a LM358D dual amplifier at the moment and my goal is to measure over-current on 2 motors. Before I'll be doing that, I made a test setup to test the equations and check the output signal of the op-amp. The gain is set to 100 with standard resistors.

simulate this circuit – Schematic created using CircuitLab

As you can see (don't mind the op-amp name, forgot to change), a voltage drop between the current sense resistor (something that I will implement later) is 0.02V (20mV). The op-amp amplifies it by 100 in an ideal situation so that I can read it with a STM32.

However, when I make this in reality, the Vout is around 0,7v and won't change until I decrease the 4.98 all the way down till 4.1v. When it reaches that point, the Vout changes dramatically when I decrease it slightly and reaches its max output of 3.9v (It's 3.9v because I connected the flexible source to v- and the VCC of the component) when the signal coming in the V- of the op-amp is 4v or lower.

My question is Why doesn't it amplify the difference between 5v(v+) and 4.98v (v-) but only starts the amplification at 5v(v+) and 4.10v(v-)?

I have checked the equations with an online calculator and used the circuitlab simulator and it should normally work. What am I doing wrong?

My ideal setup would be:

simulate this circuit

UPDATE 01/09/2018
I have increased the Vcc voltage for the op amp and thanks to you guys it displays now a somewhat normal behavior. However, I encountered another problem which is actually simple, but I can't seem to grasp it. To know how much current the load takes we use the Ohm's law. So I = U/R. Measuring the voltage drop while stopping the motor with my hand while supplying the motor with 7V, will have a drop of around 35mV(0,035V). When I use the equation, I= U/R = 0,035/1 = 0,035A. However, I don't think this is actually correct, since the motor is quite hard to hold with a hand. I have also a display in my self-built power supply and when I "load" the motor the current increases to around 2,2A. This might be the current that the resistor uses it up. Does it mean that I have to know the current first before I calculate it?

So, Volt per ampère = 0,035V/2,2A = 0,0159V = 15,9mV per ampère? I've looked it up and most doesn't fully explain it, just the principe of ohm's law.

simulate this circuit


texts: ESP - measure time between two inputs in high speed

texts:
I have a ESP32, and have 4 digital signals. At the beginning all 4 are low, and as soon as any one of those goes high, the other 3 follow up. I would need to measure the time between the first one and the other three.. The problem is that the time delta is very small. The other input should be high between 0.0003 ms and 0.023 ms. I am trying to measure the time sound takes to travel inside a 15 cm steel plate (about 3150m/s).
Is there any way (also with cheap external components) to measure such tiny intervals?


texts: Can I Connect Two Totally Different Transformers in Series?

texts:
I have 2 totally different toroidal transformers I want to put in series to make 75vac total. I have a decently large toroidal transformer in which I wound many, many turns of 10 gauge wire around. To give some perspective, the hole in the toroidal was about 3 inches wide(above the 120v primary), and there is only about half an inch left.  That gave me 40vac.  I have a smaller toroidal transformer that has about a 2 inch hole in the middle(also above the primary). The primary’s are likely different and the secondaries will be different. 40vac on one toroidal transformer and obviously 35 on another to achieve 75vac. I would use the same 10 gauge wire, but again, obviously, less turns on the second smaller toroidal transformer. Can I do this without an issue?

In short, can I connect 2 different transformers in series to get their combined voltage?


texts: Noise in Audio (DFPlayer) when adding LED strip

texts:
I'm having a problem with a weird audible noise in my sound player circuit.. It's due to an interference with a LED strip.

I've used this circuit (Arduino + DFplayer + Amplified Mini Speaker) many times  but since I decided to add a LED strip to the circuit, a very loud noise (which sounds like high frequency strings) appeared..

I've tried to use a 104 capacitor with 270ohm resistor to create a filter, but it didn't work.

Maybe a diode with a capacitor somewhere??

Could anyone give me some suggestions to fix this?

Many thanks in advance!
Ian

simulate this circuit – Schematic created using CircuitLab


texts: ATmega328P assembler inline text and assembelr ALIGN

texts:
I have a program in assembler like this:

        lots of code
        ......

.ORG $7000 ;;  (or somewhere)

atext:   .DB    "this is a test string 1"

         .ALIGN EVEN

Btext:   .DB    "this is a test string 2"

QUESTION :    Assuming the length of text 1 is ODD- Is it possible to ALIGN  Btext using some kínd of ALIGN command ( like above). The Atmel Assembler (studío 6.2) says NO - but I wonder....

(Problem easily solved by manually alignment like this:

atext:   .DB    "this is a test string 1",0,0
   //            01234567890123456789012  3 4

And adding zeroes where needed to align.

QUESTION :

I now want to write the text to my serial monitor.

So I do this;

      ldi zh,High (text1)
      ldi zl,LOW (text1)
      push ZH
      push ZL
      lsl ZL
      rol ZH  ;; to ensure LPM later

WRTE: lpm R16,Z+ ; get byte/data
      cpi R16,0
      breq wrte2
      call output
      rjmp wrte
wrte2:

      pop zl
      pop zh
      ret

Now I wonder:  If I use

      ......
WRTE: LD   R16,Z+      ; get byte/data /// BAD - DON'T

  .....

What will I get in R16?


texts: How to measure precision speed of bldc motor with encoder which has 1024 pulse per revolution

texts: I am trying to control bldc with SVPWM based FOC method.I have a bldc motor with 1024 pulse encoder. I calculate speed in encoder pulse interrupt. But i can't directly calculate d(encoder pulse)/dt. Because It cant measure precision speed. if I set constant iq referance value , it calculate speed like 5 - 8 - 3 rpm (open loop speed). Is it possible that measure precision speed especially low speed like 1 rpm.


texts: Using 2N2222 to generate noise - how would I make frequency lower / change frequency?

texts:
I've built the circuit shown in the snapshot below  :

The parts list is:

2 - 1 Meg Resistors
1 - 2.2K Resistor
1 - 2N2222 transistor
1 - 47nF  cap (Note: I actually used a 470nF cap in the one I built)
1 - ua741 op amp
1 - 3.5mm speaker output

I put the fritzing diagram together from watching the following youtube video:
https://youtu.be/dAIQHkicIoo

Built Real Circuit

I have actually built that circuit on a bread board and tested it and it works great.

Question: How might I lower the frequency?

Now, I am interested in how I might change the frequency of the sound so that it might emit a lower tone.

2N2222 Generates Sound (amplified by op amp)

I am an electronics novice so I know very little about how this works but I am fairly sure the 2N2222 is generating the sound which is amplified by the op amp.

I also see the emitter seems to generate the input (signal) to pin 2 of the op amp via the 2.2K ohm 470nF cap part of the circuit.  Is that the key to lowering the frequency that I hear?

If I increase resistance to that part of the circuit (lower input voltage to 741 input pin 2) would that cause the frequency to go lower?  Would that mean I have to drive the circuit with more voltage since I'm adding resistance?

That's all just guesses.

Can someone tell me how I should alter the circuit to lower the frequency I hear?

edit: Schematic from the YouTube page
YouTube Sound Sample of Circuit

Here's a very quick video I made so you can hear the sound? noise? that is created by the circuit.

https://youtu.be/cu29h9LWMTs

YouTube Video Example : Using .1uF Cap In Place of 470pF
I replaced the 470pF capacitor in my circuit with a .1uF cap (thanks to user to posted that answer) and now the noise is "lower" sounding to my ear.  Whatever that means.  :)  See what you think.

https://youtu.be/5D41GocraPE


texts: how do solaredge power optimizers work? Can I use them to charge battery pack directly?

texts:
When looking for some MPPT solutions for a solar car, one of the things I have considered were these wonderful small "Solar Optimizer" modules provided by SolarEdge. However, they are clearly intended to be connected to their SolarEdge household inverter, which is different from our application (to connect the MPPT's directly to a battery pack)

Is anyone aware how the Solaredge power optimizer system works? Is there some sort of AC data signal superimposed on the power rail for digital communication the power rail feeding the inverter? Or are these individual "power optimizer" modules simply dependent current sources which provide a constant-power output (current output drops as the output bus voltage increases) which feed a line of undefined voltage? (That is to say, the bus voltage will be defined by the inverter, which draws the current necessary to effectively shunt-regulate the bus voltage)

If it is the latter, and the solar optimizers can support an acceptable range of output bus voltages (from 96v to 135v for a 32S lithium battery pack) then I would imagine it would be possible to simply connect the optimizer directly to the battery pack. However these are big ifs, and I am not certain on exactly how their system works. Does anyone have insight on this or if there is some flaw in my reasoning?


texts:
While deriving equivalent T model of a MOSFET from its hybrid pi model,in the last step, how can we replace the portion of the circuit below node X into a resistance of value \$\frac{1}{g_m}\$ ?

Click to get the Source


texts: Can I use antennas as approximate proximity sensors?

texts: I want to use the concept of theremins for determining the presence and (approximate and not individual) distance of approaching people. The sensors should roughly cover radii of 2.5 meters. The measured distance does not have to be precise but it should be stable (noiseless) without being too delayed. Can I just take the same circuitry of a theremin and connect a bigger antenna to it in order to increase range? What kind of objects would affect the sensor readings apart from humans? It will be used in a very shielded environment, but there will a metal object (without any electricity though) and the data and power lines of the sensors nearby (please see figure).


texts: could any one give idea how to test 5Ghz antenna for connectivity, i.e. that interconnections between antenna parts, and feeders are ok. On of my ideas was to use some MCU with touch library, because antenna has its own capacity. Using MCU we can check if this capacity is in suitable  range, by charging and discharging it. However, I believe that such solution can damage circuit , because of received arbitrary signal. How do you think, what problems such solution can cause? Or do you have any other ideas?


texts: The desire for more light than what the led allows... or can that be used to light something else?

texts:
What would be a cheap and dirty way to use the illuminated led circuit that indicates which side of a chess timer is counting down to drive a better indicator? For example, a larger bank of leds or what have you.

I know that there is not a lot there to switch a relay and my brain is other projects that need more attention at the moment so I thought I'd ask the collective.


texts:
I'd like to simulate an LM384/ LM3886 in Protues. but I can't find any library for them. can you help me?

Is there any library for pspice or another simulation software?


texts: Multi-layer layout and return currents of high-speed signals

texts:
I am planning to use the following layer stackup for my 10-layer PCB:

Layer 1 - Components / Short traces / GND
Layer 2 - GND
Layer 3 - Signals (vertical)
Layer 4 - Signals (horizontal)
Layer 5 - PWR / GND
Layer 6 - PWR / GND
Layer 7 - Signals (horizontal)
Layer 8 - Signals (vertical)
Layer 9 - GND
Layer 10 - Components / Short traces / GND

The distances between the layers are not symmetrical and the thicknesses of 142.1 um and 124 um are alternated (this is given by the PCB manufacturer).

What has troubled me is what the reference planes for the return currents for high speed traces in layers 3, 4, 7 and 8 will be.

Let's take for example layers 3 and 4. They are between a GND plane on layer 2 and a Power plane on layer 5.

As it is well known, high speed signals will have their return currents on the trace's reference plane, following the route of the trace.

So in this particular case, will the return currents use layer 2 or 5 or both? Is the distance between the signal and the reference layers of any importance at all?

The background of the question is my concern regarding the power planes of layers 5 and 6. Since, naturally, there are many different power supplies, there is no such thing as continuous reference plane on these layers. So the question in the context of the return currents is, should I try to bridge the gaps with capacitors or I shouldn't care so much about it?


texts: 4 channel relay with Arduino issue, probably simple but need help

texts:
This is my equipment:
12V DC (10A) PSU powering Arduino Uno then 2 x Buck converters (3A) (one powers two solenoids, set at 9V, the other powers a 3.5V motor) connected to a 4-channel relay (active HIGH). One buck converter is set to 9V and is shared between two relay common points to switch two solenoids (0.1A each). The other buck converter is set to 3.5V and powers a 3.5V motor (0.12A startup, 0.6A free-run). The relay module is powered via the 5V pin and GND on the Arduino. I have a momentary switch that pulls a pin LOW and triggers relay 1 (solenoid1) to go LOW, then relay 2 (solenoid2) go HIGH, then the motor on relay 3 turns off and on until an LDR drops below a treshold) then the relays goes back to relay 1 on HIGH and the other two on LOW. There is some power supply issue I'm not understanding correctly because with it all connected, relay 1 just clicks off and on very quickly without completing the process after I press the momentary switch. When I disconnect one of the solenoids, the relay runs fine (relay 2 goes HIGH, relay 3 turns off and on). Also, when I drop the buck converter for the solenoids (relay 1 and 2 common) to < ~6.4 volts, it starts behaving correctly. I thought the switching, 5V side of the relay board is isolated from the output side that allows power to flow to the solenoids and motor. Why is the power coming from the buck converters affecting the 5V logic side of the relay module? I thought the coils were isolated from the things they are switching on/off. I've swapped the Arduino and tested the code on another 2-channel relay with the same behaviour occuring. How do the buck converters affect the 5V switching side of the circuit? The 4-channel module works fine with the USB plug connected to the Arduino (but nothing connected to the relays. How do I connect the 12V 10A PSU to the Arduino and the buck converters to get the relay module to switch correctly?


texts: Arduino water pump with relay not working

texts:
I'm trying to make a water pump work with arduino but I have a problem, it doesn't work and I don't know why. I'm a beginner with arduino so there are a lot of thing that I don't know.

I'm using a relay and a external energy suply, a battery, because I know that the arduino cannot do it by itself.

The conections in the relay are:
 INPUTS

DC+: positive power supply (VCC)
DC-: negative power supply (GND)
IN: Digital 9

 OUTPUTS

COM: Battery +
NC: Water pump

And finnaly I have the water pump connected to the Battery - and to the relay (NC).

Here is an image:

The code I'm using is this:

const int control = 9 ;

void setup()
    {
         pinMode(control,  OUTPUT) ;
    }
void loop()
    {
         digitalWrite(control, HIGH);
         delay(2000);
         digitalWrite(control, LOW);
         delay(1000);
    }

Can anybody help me please? I'm in a hurry and I don't know what else to do.
Thanks beforehand.


texts: Proving the formula for capacitance multiplier

texts:
I'm looking into the mathematical justification of how a capacitance multiplier works.
Here is the circuit.
I have to prove that resulted grounded (multiplied) capacitance is (R2 * C)/R1 here by means of mathematics.
It was checked in LTspice in that question:
Why does two-BJT transistor-based capacitance multiplier show bad performance
It turned out that a normal capacitor discharged over 0.22 sec whereas the equivalent of this circuit with R2 being 100k and R1 being 10 Ohms did so over 2200 sec

simulate this circuit – Schematic created using CircuitLab
So I do nodal and loop analysis for this circuit.
Nodal analysis based on Kirchhoff's current law for Node1:
\$
C\frac{d(V_{a}-0V)}{dt} + \frac{V_{a}-V_{b}}{R_{2}} + 0A = 0
\$
\$
C\frac{dV_{a}}{dt} + \frac{V_{a}}{R_{2}} - \frac{V_{b}}{R_{2}} = 0
\$
Nodal analysis based on Kirchhoff's current law for Node2:
\$
V_{o} = V_{a}
\$ (1)
This is because of op-amp "golden rules":
No current flows into the +/− inputs of the op amp. In a circuit with negative feedback, the output of the op amp will try to adjust its
output so that the voltage difference between the + and − inputs is zero (V+ = V−).
Loop analysis for pictured loop based on Kirchhoff's voltage law:
\$
V_{b} - R_{1}I_{1} - R_{2}I_{2} = 0
\$ (2)
Voltage drop on R2:
\$
V_{b} - V_{a} = R_{2}I_{2}
\$ (3)
\$
V_{b} - V_{a} - R_{2}I_{2} = 0
\$ (4)
\$
V_{b} - V_{o} - R_{2}I_{2} = 0
\$ (5)
From (2) and (4)
\$
V_{a} = R_{1}I_{1}
\$ (6)
Voltage drop on R1:
\$
V_{b} - V_{o} = R_{1}I_{1}
\$ (7)
From (1)
\$
V_{b} - V_{a} = R_{1}I_{1}
\$ (8)
From (3) and (8)
\$
R_{2}I_{2} = R_{1}I_{1}
\$ (9)
From (6) and (9)
\$
V_{a} = R_{2}I_{2}
\$ (10)
From (4) and (9)
\$
V_{b} - V_{a} - R_{1}I_{1} = 0
\$ (11)
\$
V_{b} = V_{a} + R_{1}I_{1}
\$ (12)
Getting back to capacitance:
\$
C\frac{dV_{a}}{dt} + \frac{V_{a}}{R_{2}} - \frac{V_{a} + R_{1}I_{1}}{R_{2}} = 0
\$
\$
C\frac{dV_{a}}{dt} = \frac{R_{1}I_{1}}{R_{2}}
\$
\$
\frac{dV_{a}}{dt} = \frac{R_{1}I_{1}}{CR_{2}}
\$
\$
I_{1} = \frac{q_{1}}{t}
\$
\$
C = \frac{q_{2}}{V_{a}}
\$
Now I'm stuck here.
What has to be done further?
Regards.


texts: Final Value Theorem yielding the wrong result?

texts:
C1 has an impedance of 1/0.1s Ohm in S-domain. Its impedance together with R1's is 100/(10s+10) Ohm

The transfer function is:
$$\frac{V_2}{V_1}=\frac{5}{\frac{100}{10s+10}+5}=\frac{50s+50}{50s+150}$$

Just looking at this transfer function, because the only pole is has a negative real part, in time domain, it's going to 0. But that is not correct according to the schematic. At time=infinity, C1 is open circuit, so \$V2=(1/3) * V1\$.

simulate this circuit – Schematic created using CircuitLab


texts: VHDL: Writing a character on a seven-segment display with VHDL

texts:
Normally when making a decoder from binary to hexadecimal, the only characters available are those in the hexadecimal system, which means A to F.

However, if I for instance want to show an H on a seven-segment display, how would I then be able to target the F, G, B, E and C parts of the seven-segment display below in VHDL code? Is ASCII available in VHDL?

EDIT:

The seven-segment display is on a FPGA board (Cyclone II), which I guess means that I can't directly change the individual pins of the seven-segment display from 0 to 1.


texts: Charging lead acid battery using boost/buck converter

texts:
I plan on permanently connecting a 12v lead acid battery to my home made wind turbine (dc). I already have a dc-dc buck/boost converter so I wonder if i can use that to charge the battery. Unfortunately the converter has no cc, constant curret function, only cv, constant voltage.

Will setting the output voltage of the converter to 13.5v be enough to charge the battery?

I know that the voltage difference between the "charger" and the battery can make the battery draw a lot of amps, Will that be a problem, (since i cannot limit the curret) even though my generator only supplies 0.1 amps at best?

Lastly, will I even be able to charge a battery of this size using my tiny generator?

By now you've probably noticed i'm no expert so please be gentle with me and keep it simple. Thanks!


texts: Atmega328 datasheet recommending against toggling pins in an interrupt

texts:
I'm making a motor driver that has too many PWM outputs to use hardware PWM, so my intent was to generate waveforms with a "tickless" timer scheme, as follows:
scheduled restack:
   for i in (pwm channels)
      stack in ascending order all pwm channels
   set OCR0A = lowest PWM channel

OC0A ISR:
   toggle GPIO of lowest PWM channel
   pop next PWM channel off stack
   set OCR0A = next lowest PWM channel
   if list is empty
       schedule a restack

This is, at most, 10 or so instructions in the ISR. At 16khz TCNT, this is worst case 16khz interrupts (255 PWM channels each spaced by one count), and usual case, probably around 500Hz, which I think this microcrontroller should have no issues handling. However, from the datasheet:

The output compare unit can be used to generate interrupts at some given time. Using the output compare to generate
waveforms in normal mode is not recommended, since this will occupy too much of the CPU time.

Is the proposed solution bad practice? From a purely CPU usage perspective, it seems totally within limits, despite what the datasheet says.


texts: Why is there a little nose on the PCIe connector?

texts:
PCI express cards have an edge connector with a little notch in it to prevent the card from moving if the socket is longer than the connector.  Additionally, the printed circuit board has a protrusion in front of the actual connector.  What is its purpose?

Depicted below is a PCIe card.  You can clearly see the protrusion I mean to the left of the edge connector.

Picture from Wikimedia Commons by Clemens PFEIFFER, Vienna.


texts:
i'm having trouble with making an AND gate on this circuit simulator website 123 circuits. This supposed to be AND-gate only responds to input from switch 1 on the dipswitch and 2 doesnt affect it at all. Am i doing something wrong or is this application bugged?

notice the led being lit while only 1 switch is toggled on


texts: What power in outlets forces electrons to flow back to anode in batteries?

texts:
title pretty much says it all...

I completely understand how battery works (because its simple right?).
But I´m little confused about recharging part... I understand that when you plug battery into the outlet you force electrons to flow back to anode.

But no matter how much I search and watch videos... Nobody describes more closely WHAT IS THIS POWER IN OUTLETS that forces those electrons to flow back?

What is this power that nobody describes? I assume it has to do something with AC/DC current in today outlets?

https://www.youtube.com/watch?v=3KX_KuS6FPI this is one of the examples of the videos where everything is explained briliantly but when it comes to recharging they describe it: POWER in an outlet forces electrons to force back...

But what is that POWER?

thank you so much for your answers and sorry for my noobie question (if it is)
but I really could find anything about this topic


texts: Circuit to indicate 1 to 10 based on pressed switch

texts:
I am looking for a circuit which can turn ON/OFF 10 LEDs based on the switch pressed (push to ON, release to OFF). It is like an LED graph.

My requirement is:

- Initially no LED is ON.
- If switch 1 is pressed then LED 1 turns ON LEDs 2 to 10 turns OFF
- If switch 2 is pressed then LEDs 1 to 2 turns ON and LEDs 3 to 10 turns OFF
- If switch 5 is pressed then LEDs 1 to 5 turns ON and LEDs 6 to 10 turns OFF
- If switch 4 is pressed then LEDs 1 to 4 turns ON and LEDs 5 to 10 turns OFF
- If switch 3 is pressed then LEDs 1 to 3 turns ON and LEDs 4 to 10 turns OFF
and so on...

The components can be ICs or transistors, doesn't matter as long as this can be achieved. But no Arduino please. Should be simple.

Thanks

Update 1:
Forgot to mention that the state of the LEDs should be maintained even after switch is released unless other switch is pressed. I hope this makes sense.


texts:
I've got a water cooler that has a centrifugal blower inside it. The blower fails to start most of the time, but I've verified that the motor works because it starts with a slight nudge. A slight torque assist gets the fan spinning, so has the capacitor gone bad?
If I nudge the blower in the wrong direction, it spins too.

I found a capacitor inside the cooler: CBB65 rated at 12uF.

This is probably a motor start and run capacitor from what little research I've done. The capacitor doesn't seem to be bulging or deformed in any way. Is there anyway for me to verify if the capacitor has gone bad, or any other test to diagnose the problem (if it's a motor issue)?


texts: What is the polarity of a car cigarette lighter adapter?

texts: There is a center pin, and two outside tabs.  Which are positive and negative?


texts: Wiring a switch to toggle both usb power and external power on Arduino

texts: I have a 5v Arduino Pro Micro. I am using it to run a series of motors. I am controlling it through the USB port. The USB power doesn't supply enough current to power the motors, so I am using a 9v external power supply and a series of transistors etc. I want an on/off switch for my project, but I need it to toggle the power for the 9v power supply and the USB connection at the same time. How could I do this?


texts: Understanding requirements for USB 2.0 high-speed

texts:
I am little bit confused about the requirements of USB 2.0 high-speed.

USB 2.0. high-speed maximum transfer rate is 480 Mbit/s. So from my understanding to fully utilize this data rate one should use IC(uC or FPGA) with frequency at least 480 MHz.

But for example STM32 F4 series microcontroller provide USB 2.0 high-speed support, though the maximum frequency they run on is 180 MHz.
Also Atmel SAM3U supports high-speed USB, despite absolute maximum frequency of 192 MHz.
How is that?

For Atmel I noticed they have additional clock of 480 MHz just for USB. This is even more confusing, since if microcontroller is capable only of 192 MHz -how it should communicate with internal USB periheral that runs on 480 MHz?

For STM32 it is also weird, in their CubeMX software it seems they run USB from 48 MHz clock. Searching datasheet, only mention I found was

  Bit 15 PHYLPCS:
  PHY Low-power clock select
  This bit selects either 480 MHz or 48 MHz (low-power) PHY mode. In FS and LS modes, the
  PHY can usually operate on a 48 MHz clock to save power.
  0: 480 MHz internal PLL clock
  1: 48 MHz external clock
  In 480 MHz mode, the UTMI interface operates at either 60 or 30 MHz, depending on whether the 8- or 16-bit data width is selected. In 48 MHz mode, the UTMI interface operates
  at 48 MHz in FS and LS modes.

So I suppose it uses 48 MHz clock to generate 480 MHz through PLL.
But again - if microcontroller itself can only go up to 180 MHz - what is the point of 480 MHz USB?

FPGAs are even more confusing(many run below 480 MHz), but I haven't done much research on FPGA yet, so I will not ask anything(but if you can give some advice/educate about FPGA - you are welcome, I am interested).

The question is - if we use 180 MHz microcontroller and want to transfer data with 480 MHz usb peripheral - how does it match the frequency? What is the process?


texts: DC step-up converter, slecting 2 different Vout with SPDT switch

texts:
I want to modify a DC-DC step-up converter that uses a single potentiometer that sets the voltage to use a single SPDT switch where I can select the output voltage during operation without turning the module off.
I think that I need a resistor in parallel to the switch so when there is switchover there is some resistance and not open circuit to not blow the chip up.
The main chip is SX1308/MT3608.
Vout to be set at 10.6V and 10.8V, because these values are so close I want to use poteniometers to set the voltage manually instead of trying to string resistors. My only limtation are the potentiometers, as I only have 10K and 100K on hand, the R1 and R2 are not a problem if these would be E12 standard values.
I've recreated the PCB (I think it's correct) of the module with my attempt at making what I want to achieve.
Edit: instead of trying to switch from one or the other resistor, have a switch in parallel to the resistor and switch it.

I'm not sure if the circuit is correct, as the original circuit has the 3 pins of potentiometer connected, it connects the wiper to the feedback pin.


texts: How can I tell Eagle to not export a 'part' to Bill of Materials?

texts:
I (as I believe many of you do too) have many parts that are not actually required for assembly but are on the schematic. (Some holes, logos, stamps, references, etc..).

Whenever I export a BOM I have to manually remove these parts from the list.

Is there a way to tell Eagle to always not export these parts to the BOM? On the package, device or symbol editor for example?