texts: ADC eliminating noise for improved accuracy

texts:
I am working on a 24 bit ADC and would like to eliminate noise as much as possible in order to maximize the performance of the 24 bit ADC.

There are two main areas where I am concerned where noise can come from:

Internal noise where the noise from the circuit itself.
External noises where noise from the environment can affect the reading.

I have a general idea of how to protect from these noises but I lack specifics if my counter measures are enough.

Internal Noise

Internal noise from traces and power supply can affect the reading so I have used digital isolator to isolate the ADCs both power, ground, and data lines from the rest of the system. The power supply can either come from a power over rthernet module or a simple 5V USB cable.

Taking an advice from an answer to a previous question, the power supply is filtered by a series of low - pass RC filters. Should I place low pass filters on the AVDD of the ADC, too?

Parts used that is involved in Power Rails: ISOW7481 ISO7731

Another solution I found is using a multi-layered PCB with the signal traces be like this.  According to an article I read, it helps reduce noise. With the top and bottom layers are either GND or Vcc.

External Noise

This can be a bit tricky since the device will be in close proximity (less than 1 meter) of 50Hz AC mains lines.  Those lines carry a maximum 50-75A of AC current (beyond this master breaker would trip.) My first idea is to use some of this shielding material which can be tediously cut and soldered to the board. Just like one of those wifi/bluetooth modules that has a metal covering the IC. Would that be sufficient? Also does shielding need to be connected to the ground of the circuit? If so which ground (digital or analog?)

If that is not enough I might go as far as placing the whole module into a solid metal container with holes just enough for the wires to go through. This should block those low frequency noises. Does it block the high frequency noise too? If so then the shielding above may be redundunt, but how thick would that need to be for it to be effective? What metal should it be?

Since its metal near power lines, I assumed this solid metal should be connected to earth. Should this metal also be connected to the circuit's ground? Would that affect the reading?

Conclusion

Although I may not need this many bits, I may as well go all out. Even modern oscilloscopes do not need this much of bit accuracy. Noise can still be induced by the probing. But since this project allows me to go a bit further I might as well go ahead and learn as much as I can.


texts: How to connect a spare mobile phone camera to a display and power?

texts:
I have an Apple iPhone front and rear cameras along with its A4 motherboard (yep, I disassembled it)
is it possible that I can get a live feed from these camera(s) to a display and connected to a power source? or maybe storing the recorded thing on a memory drive?
I could not find the exact terms so the searches were not relevant.
(images for reference attached)


texts: How do the different kind of lamp dimmers work

texts:
Hooked up the scope to a dimmer expecting to see how it altered the waveform, and didn't see it do much of any difference from all the way down to all the way up.

I bought an LED bulb and was told it needs a "special" CL dimmer.  How do the different kind of dimmers work, and how do I manage to see what they do with my scope?


texts: Im hoping to get some suggestions and ideas on how to read in 200+ phototransistors voltages (0-5) into an ADC?   I only need to look at 1 by 1 rather than all at once.


texts:
I am building a coilgun and I have constructed a coil with several thousand turns, an ohm meter measures its resistance at 300 ohms, so I am having trouble powering it, I ran 240v through it and got nothing, it barely moved a paper clip. According to my calculations, I need to run 1000 volts at the minimum through the coil in order for it to work. From my research there are three ways to do that:

1)A really big transformer (such as a microwave transformer)

2)A Marx Generator

3)or with a Voltage Multiplier.

A Marx generator seems like it would be perfect for a coilgun, as it releases an extremely high voltage, high current pulse in a small amount of time, but it seems like a rather dangerous build.
You are supposed to connect the voltage multiplier to the Marx Generator, but wouldn't it be easier to just to make more multiplier stages and remove the Marx Generator entirely? I've seen voltage multipliers go up to 15kv, which is more than enough.


texts: my question is regarding galvanic isolation between three photovoltaic modules

texts: actually i am working on partially shading effect on photovoltaic (PV) module, in a PV array many nodule are connected in series, and voltage of every module are sum up with the next module, i want to find the shaded and unshadded module by measuring the each module voltage.so i need galvanic isolation between every module so that i could measure the every module voltage, any one help is it possible or not if possible how it can be designed.


texts:
I'm fairly new to VHDL and was wondering if anyone could have a look at the code I constructed for a DFF. I haven't added the reset or preset on as of yet. Just the basic function. Also don't have the software at home to test it on so I'm going by your guys experience that its fine!

LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.std_logic_arith.all;

ENTITY dff IS
    PORT(
        D:  IN  std_logic;  --data in
        CLK:    IN  std_logic;  --clock in
        Q:  OUT std_logic   --data out
    );

END dff;

ARCHITECTURE rtl OF dff IS
BEGIN
    process(CLK)
        BEGIN
            if (rising_edge(CLK)) then
                Q <= D;
            end if;
    END process;
END rtl;


texts: Performing switching time test with NMOS (5LN01SP)

texts:
I am about to feed my switching time test circuit with input signal from signal generator. In a 5LN01SP's specification input test signal is marked as:
PW = 10us
D.C. <= 1%
(see the picture)

It is clear pulse high level state is 10us (4V). I am not sure whether D.C. there stands for duty cycle or DC (direct current)
and if it's latter:
I would like to confirm it's 20 us long pulse with duty cycle of 50% (thus 10us high level state). What about D.C. ?
if it's the first:
I would like to confirm it's 1000us long pulse with duty cycle of 1% (thus again 10us high level).


texts:
I've been following this tutorial on Arduinos, for the ones that are interested it's this one.

Yesterday I was struggling to get a servo moving. Sometimes it made small twitchy kind of movements, other times it wouldn't move at all. So I did some research on what the reason for this could have been.

The most common answer was: Don't use a 9V battery for a motor.

I ended up buying 6xAA batteries, which do very well in moving the servo.

But in the tutorial he IS using a 9V battery, so what are the differences that matter here? (Quality, more mAh, alkaline vs non-alkaline, ...?)

My knowledge regarding batteries is still very poor, so I've put three images at the bottom that I would like to compare if possible.

What's the difference with my 9V battery and his 9V battery?
Why are 6xAA batteries (1.5V) recommended over a 9V battery?

Images:

My 9V Battery
His 9V Battery (I believe it says 'Radioshack Enercell 9v Alkaline Battery')
My 1.5V batteries


texts:
I have a circuit of switches like this. The switches are a long way from the supply and a long way from each other.

                 S1     S2     S3     S4     S5
[24VDC+]----->>-o=o----o=o----o=o----o=o----o=o--+
                                                 |
[input ]-----<<----------------------------------+

[24VDC-]--|

Assuming the power supply is not accessible at all — it must always be on, and you cannot get access to 24VDC reference, is there a simple way to test at each switch with a multimeter to determine between which switches there is a break in the line?

If you test with a multimeter, voltage across a closed switch is 0. Voltage across an open switch is also 0 as the input is high impedance.

Any ideas?


texts: Connect a 12v 200a deep cycle battery to a 12v 3.5a motor

texts: What would be the correct connection to avoid damaging my motor? Should there be a resistor set between the source and load?


texts: Need help in selection of FET for transfer gate

texts: I was studying the variable potentiometer X9C10x series. They are using a series of fixed resistors and some FETs to select points in this series branch. I need one variable point in my circuit. Can anyone tell me which type of FET I can use here?


texts: Simulating absolute value circuit in TINA-TI

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I am looking to build an absolute value circuit using a pair of op-amps, hopefully using a single supply and would like to simulate my design using TINA-TI.

The ultimate aim is to measure the voltage difference between an input and a reference voltage that is not necessarily ground. The modified LT1001 circuit in the answer to this question would be okay, but it is dual supply.

TI provide a useful application bulletin with various designs for absolute value circuits. Figure 5 in the application bulletin offers a nice single supply variant. I have reproduced it here in case of a stale link later.

I have entered the design into TINA-TI - I think without errors, but the simulation is not working with the output swinging immediately to mid-supply.

Why aren't I seeing the waveform as shown in the application bulletin?

Also at the bottom of the clip (below Figure 5.1) it contains the sentence "Notice that the input range of the circuit is 4V below the power supply rail.".
What does this mean - the diagram shows the input to be -4V to +4V and the output 0 to 4V for a 5V supply?


texts:
I have just started using KiCAD (with no other experience e.g. in Eagle). I was basically able to put together a schematic and layout a board but I am struggling with some footprints. How would I search for, e.g., a footprint for these?
Can I expect footprints somewhere in the library for most components or is creating my own a common task?


texts: How to add an RC filter between a header pin and a ribbon cable

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I'm a software engineer diving head-first into the world of embedded systems design and development.  This question is basically about "plumbing" -- what's the best way to physically wire up a particular circuit. So:

I have a small microcontroller evaluation module, the CC11EMK, with a 2x5 header debug port.

I also have an evaluation board (the CC1110-CC1111DK) to program the evaluation module, also with a 2x5 header. (The dongle is in the lower left) below:

The two are connected with a 10-wire ribbon cable.

My problem is that the microcontroller reset pin is sensitive to noise, causing random resets. Not fun. The datasheet for the CC111 has this to say in section 6.11.1:

  The RESET_N pin is sensitive to noise and can cause unintended reset of the chip. For a long reset line add an external RC filter with values 1 nF and 2.7 kOhm close to the RESET_N pin.

I also have some sensors and an SPI bus setup on a breadboard.

What's a relatively simple way to insert the resister and the capacitor into the circuit?  I thought I might be able to stick a pair of 2x5 headers onto the breadboard, use two ribbon cables, and wire corresponding pins together with the exception of the reset line, which I'd pass through the RC filter.  But I don't think that can work on a breadboard -- the header won't fit over the gutter, so no matter how I do it, I'd be shorting together pairs of pins.

Any suggestions?


texts: maximum possible common mode voltage for npn

texts:
First I would like to thank everybody here for providing the help. This great resource allows me to understand things beyond what my textbook only offers.
I have the question below:

Here is the figure they are referring to in the question:

(Source of images: "Microelectronic Circuits" book by Sedra/Smith, 7th edition, chapter 9)

HERE YOU FORGET TO INSERT AN IMPORTANT ASSUMPTION

AND IT EXPLAINS WHY YOU ARE MISSING 0.4 V taken from sedra-smith

So using the small signal analysis model, which am not going make you bored from it, I was able to find the value to Rc = 5k ohms which totally agrees with the text book's answer. Now my struggle is to find the maximum Vcm.
Here is my analysis

\begin{equation}
V_{cm,max}=V_{BE}+V_C=0.4+V_{CC}-\frac{I}{2}R_C=0.4+5-\left(0.5mA\right)\left(5k\Omega \right)=2.9V
\end{equation}

But my book says that:

\begin{equation}
V_{cm,max}=1.6V
\end{equation}

Can somebody please tell me how that came about?? Am really confused! Thank you for your help in advance.

UPDATE 1:
Here is an LTspice simulation of the problem. Please let me know if my model is correct or not because am a beginner with LTSpice. You can see from the simulation results that change in collector voltages and currents don't happen till around vb=2.9V


texts: Using 2 postive regulators with 2 prong power supplies for bipolor power supply

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My nephew and I have been working on a circuit that uses +/- 4.5V.  Up until now we have been using 2 3-AAA battery holders to supply each leg and now wish to move to mains power.

My question is, discounting the more unusual topographies(auto transformers, cap dividers), is it safe to assume that 2 2-prong 5V(12V) power supplies are isolated from each, and therefore I can use 2 positive regulators to regulate the output.  As noted in some of the comments, I have metered inside/outside of the barrel to each prong, with all of them showing open.

I know I can use 2 separate taps from a transformer for this.

In the past I've used 2 supplies like this in a audio application(sans regulators), and it worked fine.

If it comes down to it, I can dig out a multi-tap transformer(not a center-tap) and use that, but that's a lot of work, and the result is much heavier, hotter and less efficient compared to using 2 wall-warts.

And as far as I know, using an inverted buck DC/DC still requires a negative regulator.


texts: Weird value of track width with calculator

texts:
I am currently working on a design where the power input will be connected to battery of car. I have a series of LDo and DC-Dc but the entry point is 9-36v and I am unsure what the current can be . I read here and there on the internet that car batteries can deliver until 40A.
Considering this I have checked with track width calculator but the result looks conpletely wrong (I find 111mm around).
What's wrong there ? What I am missing ? What should the be track width for car battery ?


texts: What is the best way to short adjacent SMD pads?

texts:
Which of the three ways shown above would be the best way to short two adjacent SMD pads together, and why?  These are TSSOP pads and the assembly process will be lead-free reflow, if that matters.  If there are better ways that I have not pictured, feel free to show them too.

I can imagine that in terms of impedance, C is best and A is worst.  But I'm not sure if C or even B could somehow complicate the assembly process.


texts: Protecting Solid State Relays from Short Circuits

texts:
I have 4 SSRs on my board with a steady state current rating of 2A and a peak current rating of 9A (Relays are CPC1976). This product is meant to be a commercial one and the relays will be powering bulbs (CFLs, Incandescent etc) upto 100W @ 240VAC

My main concern is short-circuits. A lot of CFLs that I've used in my house short circuit for a small time when they fuse. The short circuit is serious enough that the circuit breaker trips. This will obviously fry my relays.

I can easily include a fast-acting fuse but that will be have to be replaced everytime the lights fuse! I could consider a resettable fuse but most of them seem to be too slow to act to save a semiconductor device.

What are my options here to have a resettable solution yet save my relays from damage?

One idea I had was to do away with the relays and use opto-coupler + triacs instead. Triacs are cheap and I can easily find some that can handle large amounts of current (obviously a short circuit will be more than they can handle). These may survive such short circuits with the addition of a resettable fuse?


texts: Blind vias pitfalls when hand soldering parts

texts:
I'm going to use blind and buried vias in an upcoming project for the first time.

As with all boards, there is a high chance of hand soldering for the first revision, and since the vias will be much smaller then the ones we've used previously, I wanted to know what are the pitfalls when doing hand soldering near there vias?

Are they more susceptible to collapse? Should we use lower temperature on the solder iron, different flux/solder paste?
Basically any advice will be welcome :)


texts: Fatal Error Audio equalization simulation LTSpice

texts:
I'm doing a 3s audio.wav simulation on LTSpice with the following circuit (3 band pass filters and amplifiers):

In this example it's boosting the bass and attenuating the highs.
It loads the first second really fast and then it start to take a longer time:

When done amplifying the highs it gets stuck in 2s of the simulation.
The error I get is Fatal Error: Analysis: Time step too small; time = xxxxx,timestep=1.25e-15: trouble with u3:qx-instance q:u3:1.
Or sometimes it's U6 that fails.
How can I solve this?
Thanks in advance!


texts:
So laptops with thunderbolt 3 are pretty common, docks are common, every other kind of USB seems to be able to be used with a hub. I know thunderbolt 3 can be daisy chained, theoretically eliminating the need for a hub. That's not the point, the point is that I have never seen a simple hub that allows you to plug in a thunderbolt 3 laptop with 1 cable and expand it to connect multiple thunderbolt 3 devices directly to 1 hub through several USB C ports. Why is that?
I get the sense that the answer is something along the lines of "Because Thunderbolt 3 is much more complex than USB and can hardly be called USB" or "It has something to do with network topology because the way it connects multiple devices makes it a network" or maybe even something to do with CPU PCIe lanes. Unfortunately I can't find a straightforward but in depth and technical answer anywhere.


texts:
I'm constructing a custom(cheap) power supply, with digital current meters and such.
I'm using 2 ATX power supplies to build it.  I'm using 1 for the standard -12, -5, +3.3, +5, +12 outputs. I've modded the other to output ~0 - ~24V(off of the 12V line).
I've tested both of them separately, and they work great.

My concern is if I have 2 separate GNDs. If I change the voltage on the one power supply, would it affect the other power supply?

added explanation

I had the 1 atx power supply stay to same because it is easy to use the standard ATX powers supplied.

I wanted something that I could change as well.  So I did a little research on the circuit inside the ATX power supply.  There is a voltage divider that controls the output voltage on the power supply. It is on pin 1 of the TL494 chip (guessing on actual chip).  You also have to change the Over voltage protection on (I think) pin 4.  I placed a small circuit turn pot on the Pin 1 with a resistor.  I tested it, and I was able to get 0 - 24V on the 12V line.
I estimate that I would be able to get 5amps out of this variable control.

I also added some Amp meters and 1 voltage meter.
Here is an image my ideal design.

Thanks


texts: Relationship between switching frequency and controller's crossover frequency in buck SMPS

texts:
Context: tuning the control loop of a buck SMPS. I specicifally have a TI TPS40200-based circuit in mind, but I think this applies to SMPS design in general.
Quoting from Type 2 compensation network:

Mr. Maniktala suggests that the loop gain transfer function of the
switcher intersect the 0 dB point at approximately 1/6th the switching
frequency, with a slope of -1.

I have heard this before from another engineer, but did not get a chance to ask why. What is the reason the crossover frequency of the control network should be a fraction of the switching frequency? Why specifically around 1/5th or 1/6th?
Are there any other desirable traits when designing a compensation network for an SMPS controller other than the most basic criterion of >45 degree phase margin for system stability?


texts: Using Microphone preamplifier IC Max4468

texts:
I am designing microphone preamplifier using MAX4468 (datasheet), but the reference diagram shows output from microphone (microphone input) going to both inverting and non-inverting terminals of the device. (picture attached below). Non-inverting terminal should be connected to ground or both non-inverting and inverting terminal should be given microphone input.

The datasheet describes a point:
The MAX4466/MAX4468 are decompensated for a minimum stable gain of +5V/V.

Does it means that opamp will provide inherent gain of 5, irrespective of feedback resistors.(Page 1 of datasheet)


texts: Substitute power supply for batteries in motor controller

texts:
I'm rigging up a demo stand that will use a (large) model RC car. We can't use its batteries since we can't get to the unit to recharge, so we're using a power supply instead. The requirement is for about 10V at about 20A.

One obvious issue is that these cars use regenerative braking, great for batteries but not so much for a power supply. I plan to put a large capacitor bank on the DC leads to soak up the back EMF -- should I take any other measures?

Would a common open-frame switching supply be OK here, or is there a better type of supply for this purpose?


texts: Is it safe to send 12V to the Arduino Pin/USB Ground?

texts:
am wondering if it's safe to send 12V to the Ground Pin on the arduino which I think is connected somehow to the usb port. Am afraid that it might burn something up. I found this sketch online ->

Am a total newbie is this circuit safe?


texts:
I'm working on a project to build usb car charger for my phone.  The goal is to do it using only off the shelf parts (radio shack) and as cheap as possible.  The size is also a bit of an issue but I'll deal with that later.  I expect the phone to draw about 500mA and my car puts out a pretty steady 14.1V from the cigarette lighter.

I came up with the design below but I though of one big problem.  IC1 is a 7805 5V regulator (sorry forgot to label it).  It will give off somewhere around 4W, which is way too much and right on the edge of what it's rated for.

I set it up on the bread board and confirmed that it's very hot.  Then I put the diode in to try and help distribute some of the heat but still way too hot.  Any ideas?  It seems like this will work as long as I can take care of the heat.  There's not enough room in the case for a heat-sink either.


texts: How can a light bulb run on different voltages (USA and EU)?

texts:
There is a concept in EE I don't understand.

In Europe we have a 230 V supply voltage and in the USA e.g. 120 V.
Now the thing I don't understand, how can I use my charger( or a light bulb) in different voltage supply regions, wouldn't the current not be way smaller in North America (as I = V / R). So if the voltage is smaller, so should be the charging current or am I wrong?


texts:
Why are there no isolated AC/DC buck converters around?  For applications < 10W (say 5V/1A output) and mains input (85 - 264VC), is it feasible to use a standard buck circuit but add a 1:1 isolation transformer at the input?

This way you could enjoy the benefits of a buck topology while also having the benefit of isolation.


texts: SD card both photo/video recording and data logging

texts:
How can I capture photos and videos (JPEG and MPEG4 respectively) taken from an NTSC camera to an SD card and also log text data to it?

I am working on a project in which I need to log analog data from sensors in the form of a csv or txt file to an SD card continuously (I would say every second or so).   I also need to record video or photos to the SD card every so often (when the appropriate signal is given to the microcontroller by the user).   I know many digital cameras, consumer drones, and other devices can save photos/videos to an SD card and also access settings and save other data to the SD card, so it must be possible.

I know that NTSC video can be saved to an SD card in MPEG4 format, as this circuit does exactly that.   One of the chips on this board is an NTSC to BT.656 decoder.   The other IC on the board is sharpied out, however, and I'm not sure how they compress the BT.656 video to MPEG4 and save it to an SD card.   I assume they use a microcontroller fast enough to compress the raw BT.656 video output from the first IC to MPEG4 and then save it to the SD via SPI.

Could a possible solution to my problem be to use this decoder and then program an ARM or other powerful microcontroller to compress the BT.656 video to MPEG4 and then save it to the SD card?   Or for photos just take a frame of the raw video and convert that to JPEG to save to SD?   While the microcontroller is dealing with video or photos the sensor data could be logged to EEPROM by the aforementioned sensory/user input microcontroller, and then when the video/photo processing microcontroller isn't saving photos or videos it could catch up on logging the sensor data it missed to the csv/txt file.   If this could work I would have to do more research on how video codecs are programmed so that I could compress the BT.656 in code.   Hopefully someone has some insight as to whether I should go down this path.

Note: please don't offer solutions that involve not designing such a circuit.   I know there are solutions that I could buy to do this job, however I am looking to create my own design that I can tailor to the capabilities that I need.   Furthermore, a question asking for recommendations on products to buy does not comply with this site's rules, and this is not what this question is asking for.   I would greatly appreciate an answer that gave insight into the conventions for saving video/photos to SD cards and that detailed whether or not my proposed plan could work.   Thank you in advance to anyone willing to share their knowledge on this subject.

I have edited this question to remove confusing background information and to make the question more specific and less broad.   In researching this problem I have found few online resources with relevant information so I hope this question will be reopened to allow for the chance for useful information pertaining to this question to be made available to users of this site and to internet users in general.

Finally, if this question would be more appropriate on signal processing stack exchange please let me know and I will move the question there.


texts:
I've been trying to design precise distance measurements similar to the digital caliper or dial micrometer for my CNC project by capacitance sensing between prob and base metal. I can connect base metal to ground and prob to 5-12 DC volt for capacitance measurement OR connect base metal to AC for impedance measurement THEN feed to 1 or multi-stage OPAMP for amplitude signals
My QUESTION is which one is more ACCURATE and more immune to NOISE


texts: Switch or gate that activates when not grounded

texts:
I have a audio jack with a build in switch that when an nothing is plunged in the switch lead is grounded but when you plug something in its no longer grounded. I want to use this audio jack as a power switch so when you plug in something an arduino gets power and turns on.

I am not running power through the jacks, I am using them for audio in my project. I am making a small box with no visible switches that when you plug in some ear phones it turns on and plays music. I just need some kind of switch or relay that will turn on the device when the switch leg if of the audio jack is no longer connected to ground.

I am not sure how to make this circuit, maybe there is some kind of transistor or relay that works this way but i just don't know about it.

Please help.


texts:
I am examining a schematic which concerns the TPS61030 boost converter IC and I have a question regarding the logic behind pulling the enable pin (EN). The schematic is from Adafruit and can be found here: https://learn.adafruit.com/adafruit-powerboost-1000-basic/downloads#schematics

General information:
The TPS61030 boost converter (datasheet) utilizes a signal on its EN pin to turn the converter on or off. If the EN pin is set to 0VDC, the converter is put into shutdown mode which effectively isolates the load from the input. When the EN pin receives an input >= 1VDC (but less than the 7VDC maximum), the device is put into operation mode and starts to function.

The circuit is designed for a 3.7VDC (nominal) LiPo battery. Under ideal conditions, the circuit boosts the 3.7VDC from the battery to ~5.2VDC required by many devices. I believe the +0.2VDC is meant to compensate for low-grade wires.

In their diagram, Adafruit pulls the EN pin high and uses a switch to GND to turn the device off. The schematic resembles the following:

simulate this circuit – Schematic created using CircuitLab

When the switch is open, the converter will enter operate mode. When the switch is closed, the device converter will enter shutdown mode; however, the circuit will become a parasitic drain on the battery. It seems odd to me that the circuit was designed to draw current when the converter, and by extension the device being powered, is meant to be off. I know it will only be ~0.02mA but I do not understand why they wouldn't pull the pin low and use a high side switch instead such as in the following schematic:

simulate this circuit

The above circuit will form a voltage divider which will output ~2.4VDC to the EN pin which is more than enough to enable the device. When the switch is open, the EN pin will be pulled to GND and the converter will enter shutdown mode. This would eliminate the parasitic drain when the converter is in shutdown mode.

Questions
Why they are pulling the pin high instead of low to eliminate the parasitic drain? I am a novice in electronics so I assume Adafruit has a good reason for doing so and I'm just too inexperienced to understand why. Any input would be greatly appreciated!


texts: Why does the current in MOSFET have a quadratic function (explain logically without using the integration method)?

texts: The current equation relating Vds ,Vgs and Vt is already known to us ,but if there is any way we can find out how it varies quadratically without using the formulae?


texts:
I am new to USB. I am studying the USB in a Nutshell Guide and the relevant parts of the USB2.0 spec.

As per what I have read, a max of 127 devices can be connected to a single bus. As only one host can be connected to a bus (save the on-the-go spec), I take it that 127 devices can be connected to a host.

However, on reading the WikiPedia page for USB Hub, it is written that a hub can extend the USB network to a max of 127 ports.

Does this mean that I can then have 127 x 127 devices attached to a single USB bus (read host)?


texts: Microphone on Arduino for Sound Detection

texts:
I'm working on a design to have a microphone on Arduino board for sound detection (clapping sound etc). I see there are lot of circuits floating on internet but almost everyone has an output to ADC pin on Arduino. On my design, all the ADC pins are exhausted (using 6 PIR sensors), so i'm left with digital pins.

How can i use an analog microphone on digital pin, can it be done through peak detection circuit? Can anyone share a reference schematic?

Also, an audio amplifier is required or can i get this done through a rail to rail opamp with good slew rate?


texts: adding secondary sub-board to pin-out header

texts:
Possibly a very basic question, but I am trying to add a secondary sub-board (receiver) to a micro controller for roller shutter door.

The control board already has a right angle 6-way pinout with 2.54mm pitch. This connects directly into the existing sub-board (receiver).

What I would like to do is to somehow passthrough the pinout to another receiver with the same pinout using simple wires.

The image below shows the current state with the purple existing board connected directly to the right angle pin-out from the control board. The new board is in blue, however they can be swapped around. The order doesn't matter.

My question is: how can I connect a secondary board (shown in blue) to the existing pins? I can't access the pins directly as there are plugged in. I'm guessing I would need some kind of pass-through device or splitter.

EDIT: Would the below configuration work on a stripboard?


texts: Describe qualitatively the amount of current passing through resistor if the source oscillated at low frequency?

texts:
I am stuck on lab question 3. I do not know how to determine the current crossing the resistor for oscillating current at varying frequencies.

Help is greatly appreciated


texts: Lower Power Inductive Heating Circuit Design Questions

texts: I'm trying to design a very low power (<=10W) inductive heating circuit that will heat the work material to 40-50degC. I've seen plenty of Royer Oscillator circuits online (see here: http://www.rmcybernetics.com/images/induction-heater-schematic.jpg) but how can the temperature output be configured in the circuit? Also, I want to make the power draw as low as possible. What are some parameters I can play with to achieve these design constraints?


texts: Getting no response from MCP2515 using SPI

texts:
I have a board with a working SPI interface. I can read one slave via the SPI interface successfully.

When I try to read data or get a status on a secondary slave, the MCP2515 IC, I'm not getting any response. I have verified the connections by using a voltmeter continuity test, I have verified the ground and voltage connections to the IC. I understand that the MCP2515 is unique in how it initializes at start-up per the datasheet. I have tried numerous initialization sequences with no success. I am beginning to think I have a bad IC, but I would like to be able to test it and prove that theory.

The only other issue I can think of is a possible clocking issue. I have a 16 MHz crystal on the MCU and a 16 MHz crystal on the MCP2515 per the datasheet. Both have 22 pF capacitors. If the clocking is off, I think I would at least get garbage. Can someone look at the code and validate it looks good and that I do in fact have a clocking or hardware issue?

bool mcp2515_init(void)
{
    char str[80];
    unsigned int test_value;

    SET(MCP2515_CS);
    SET_OUTPUT(MCP2515_CS);

    SET(USB_CS);
    //SET_OUTPUT(USB_CS);

    SET(SD_CS);
    //SET_OUTPUT(SD_CS);

    RESET(P_SCK);
    RESET(P_MOSI);
    RESET(P_MISO);

    SET_OUTPUT(P_SCK);
    SET_OUTPUT(P_MOSI);
    SET_INPUT(P_MISO);

    SET_INPUT(MCP2515_INT);
    SET(MCP2515_INT);

    // Active SPI master interface
    SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0);
    SPSR = 0;

    // Reset MCP2515 by software reset.
    // After this it is in configuration mode.
    RESET(MCP2515_CS);
    spi_putc(SPI_RESET);
    SET(MCP2515_CS);

    // Wait a little bit until the MCP2515 has restarted
    _delay_us(15);

    // Load CNF1..3 Register
    RESET(MCP2515_CS);

    spi_putc(SPI_WRITE);
    spi_putc(CNF3);

    spi_putc((1<<PHSEG21));  // Bitrate 125 kbps at 16 MHz
    spi_putc((1<<BTLMODE)|(1<<PHSEG11));
    spi_putc((1<<BRP2)|(1<<BRP1)|(1<<BRP0));

    // Activate interrupts
    spi_putc((1<<RX1IE)|(1<<RX0IE));
    SET(MCP2515_CS);

    test_value = mcp2515_read_register(CANCTRL);
    sprintf(str, "test value is [%d]\n\n",test_value);
    UART1_TxString(str);

    // Test if we could read back the value => is the chip accessible?
    if (mcp2515_read_register(CNF1) != ((1<<BRP2)|(1<<BRP1)|(1<<BRP0))) {

        return false;
    }

    // Deactivate the RXnBF pins (high impedance state)
    mcp2515_write_register(BFPCTRL, 0);

    // Set TXnRTS as inputs
    mcp2515_write_register(TXRTSCTRL, 0);

    // Turn off filters => receive any message
    mcp2515_write_register(RXB0CTRL, (1<<RXM1)|(1<<RXM0));
    mcp2515_write_register(RXB1CTRL, (1<<RXM1)|(1<<RXM0));

    // Reset device to normal mode
    mcp2515_write_register(CANCTRL, 0);

    return true;
}


texts: 12 VDC battery supply with automatic 12 VDC adapter override

texts:
I am designing a 12 V circuit to provide 12 V DC (500 mA). I would like to have 12 V battery but also be able to plug in 12 V adapter to automatically override the battery without a switch and without removing the battery.

I saw a 12 VDC with 9 V battery circuit on this site with two diodes but I’m afraid this may not work for me as the voltage will be the same for both diodes so it won’t override? Thanks for your help.


texts: How to calculate Op Amp's gain using Arduino's ADC

texts:
Hi, I'm feeding a 500 Hz PWM signal to the Op Amp's V_IN using Arduino DUE.

The Op Amp, which is ADA4000-2 from Analog device, is connected to +12V, -12V using an external power supply.

The power supply's GND is also connected to Arduino's GND.

The R1 part is replaced with a potentiometer to adjust the gain and R2 = 10k Ohms.

The signals from Vout were amplified as I expected.

However, I wanted to read the gain using my Arduino, maybe using the ADC, and print that out using the serial UART.

What methods or circuits should be used to get the Op Amp's gain?

I'm curious this both works for inverting/non-inverting case.

Thanks for your help!


texts:
My LED panel broke (it is a ceiling lamp).
I disassembled it, and it looks like this:

It has a series of LED strips (the last one is missing in the image), connected in series. There are connectors like the one on the left in the picture between strips; the last connector is just a closed loop of wire, and the first strip is attached to the transformer:

By testing individual strips, I discovered that one of them is broken (some of its LEDs look damaged, with a black dot in the center). With all the strips, the panel doesn't work when attached to AC.
I'd like to repair it, I'd be fine with one less strip (since I can't find a replacement online).
Questions:

If I remove the broken strip, should I expect the others to break? I'm confused by what I read on the transformer label, it says "Output: 30-39V". Why is there a delta? Is the transformer/driver able to regulate the voltage/current depending on what is connected to it?

If the answer to 1 is "yes", is there something I can do to avoid it?

Bonus question: as you may see in the first image, there are arrows on the strips, reading "+/-" on the right, and "+/+" on the left. They were mounted like this:

→
←  this one failed
←
←
←
TRANSFORMER
I this it doesn't make sense, I would have expected either all the same direction, or alternating ones. Does it make a difference?
I apologize for my scarce knowledge of electronics if the question is trivial, my local repair shop did not even want to see the LEDs and I wanted to try some DIY.
Thank you.


texts: Looking at the pins of USB 3.0 receptacles, I can see that there are separate transmission and reception pairs, however for USB 2.0 there is only one "data" pin pair. How does USB 2.0 ensure that the devices aren't communicating simultaneously?


texts:
I am quite lost when it comes to grouping >4 variable k-maps. Can someone enlighten me on the matter?

For example ... sorry for the mess ... is the below grouping correct ... but I dont suppose so ... esp the inverse one


texts: Range error during Modelsim simulation of a VHDL user-defined resolved data type

texts:
When running a simulation of a testbench involving a user-defined resolved data-type, I get an error report of the form:

"** Fatal: (vsim-3734) Index value 1 is out of range 0 to 1"

, followed by simulated time and location in testbench source code. The offending data type is a custom resolved type, used to represent the equivalent of STD_Logic for Real variables. The type is employed for simulating things like open-collector drivers, pull-up resistors, etc. driving a variable carrying a real value that represents voltage on a wire. I am pretty sure that the fatal error occurs within the type's resolution function, but cannot figure out the error mechanism. Has anyone come across something similar? The custom data type is as follows:

LIBRARY IEEE;
USE IEEE.std_logic_1164.all;

USE IEEE.std_logic_ARITH.all;

USE IEEE.std_logic_UNSIGNED.all;

PACKAGE Tbench_pkg IS

--=====================================================================
--  Definitions for a resolved REAL data type, to be used strictly
--  for behavioral simulations of analog networks.
--=====================================================================
--
TYPE R_Strength_t IS    (RU, RS, RW, RZ, RX);
--
TYPE U_Real IS RECORD
    rval        : REAL;
    strength    : R_Strength_t;
END RECORD;
--
TYPE U_Real_Vector IS ARRAY(NATURAL RANGE <>) OF U_Real;
TYPE Strngth_Tbl_t IS ARRAY(R_Strength_t, R_Strength_t) OF R_Strength_t;
SUBTYPE ix_t IS NATURAL RANGE 0 TO 2;
TYPE VSel_Tbl_t IS ARRAY(R_Strength_t, R_Strength_t) OF ix_t;
-- Resolution Truth Table                RU  RS  RW  RZ  RX
CONSTANT RR_Table   : Strngth_Tbl_t := ((RU, RX, RX, RU, RX),   -- RU
                                        (RX, RX, RS, RS, RX),   -- RS
                                        (RX, RS, RX, RW, RX),   -- RW
                                        (RU, RS, RW, RZ, RX),   -- RZ
                                        (RX, RX, RX, RX, RX));  -- RX
-- Real Value Selection Table           RU RS RW RZ RX
CONSTANT VS_Table   : VSel_Tbl_t    := ((0, 0, 1, 1, 0),    -- RU
                                        (0, 0, 1, 1, 0),    -- RS
                                        (2, 2, 0, 1, 2),    -- RW
                                        (2, 2, 2, 0, 2),    -- RZ
                                        (0, 0, 1, 1, 0));   -- RX
FUNCTION rresolved(r : U_Real_Vector) RETURN U_Real;
--
SUBTYPE R_Real IS rresolved U_Real;
TYPE R_Real_Vector IS ARRAY (NATURAL RANGE <>) OF R_Real;
--

END Tbench_pkg;

PACKAGE BODY Tbench_pkg IS

FUNCTION rresolved(r : U_Real_Vector) RETURN U_Real IS
--
VARIABLE rtv    : U_Real    := (0.0, RZ);
VARIABLE raux   : REAL      := 0.0;
VARIABLE ix     : ix_t      := 0;
--
BEGIN
    IF (r'LENGTH = 1) THEN
        RETURN r(r'LOW);
    ELSE
        FOR i IN r'RANGE LOOP
            ix := VS_Table(rtv.strength, r(i).strength);
            CASE ix IS
                WHEN 0 =>
                    raux := (rtv.rval + r(i).rval)*0.5;
                WHEN 1 =>
                    raux := rtv.rval;
                WHEN 2 =>
                    raux := r(i).rval;
            END CASE;
            rtv.rval     := raux;
            rtv.strength := RR_Table(rtv.strength, r(i).strength);
        END LOOP;
        RETURN rtv;
    END IF;
END FUNCTION rresolved;

END Tbench_pkg;


texts: Ground-referenced current mirror with low voltage drop

texts:
The following circuit produces a voltage v2 that is the logarithm of I[dut].  I've modeled it with I1 ranging from 1uA to 100mA and it does essentially what I want, but it could stand some improvement:

the theory

Q2,Q3 work as a current mirror so the emitter current on Q1 matches the current of the DUT.  And since Q1 is a diode-connected BJT, v2 is essentially log(I[dut]).  So far, so good.

the problem

For many applications, the voltage drop from Q2's Vbe (aka Vcc-v1) is not an issue: most DUT's we'll be working with have their own voltage regulator and are not sensitive to changes in voltage.

But to make this a more generally useful tool, I'd like to "stiffen" the voltage at v1, i.e. make it so changes in I1 have minimal effect on (Vcc-v1).

the ask

Is there an equivalent ground-referenced current mirror -- perhaps using an op-amp -- that replaces Q2 and Q3 and decreases changes in (Vcc-V1) as I1 changes?  One constraint: Vcc is the only voltage source available.


texts: How to figure out if a 25V capacitor can replace 50V in this circuit

texts:
I'm following this video Astable 555 timer - 8-bit computer clock - part 1 where he builds this circuit:

simulate this circuit – Schematic created using CircuitLab

I just realized that the 1000uF capacitor I have is 25V and not 50V as the one he uses in the video. I suspect that 25V will do but I don't know for sure.

I've tested the voltage where the capacitor would have been in the circuit on my multimeter and that reads 55.3mV which is much less that 25V but maybe the 555 timer can change that?

Is this a valid way to figure out the maximum voltage the circuit will apply to the capacitor?


texts: Does powering a module with 5v instead of 3.3v affect it's logic level?

texts: I bought a NEO-6 u-blox 6 GPS Module (datasheet, pages 9 and 14), which has a standard serial connection. I have a USB to serial converter, which is 5v logic. This board says it can be supplied 3v-5v, and I have seen people say that it is 3.3v logic, but these people always say to power the board from 3.3v. My question is: If I power the module with 5v, will the logic become 5v tolerant?


texts: How does this BJT circuit produce 0V at output for any input dc voltage?

texts:
I've been trying to understand how the dc bias is removed at the ouput inside an op amp. Below circuit seems to work

Some explanation is given below by the author

  To shift the output dc level to zero, level translator circuits are
  used. An emitter follower with voltage divider is the simplest form of
  level translator as shown in fig. 2.

  Thus a dc voltage at the base of Q produces 0V dc at the output. It is
  decided by R1 and R2.

But I don't quite get how R1 and R2 manage to maintain 0V at the output no matter what dc value we put at the Input. As the Input changes, \$V_{CE}\$ of the transistor \$Q\$ varies on the load line, so I don't see how the o/p can stay at 0V. Appreciate any help.


texts:
After typing C, microcontroller responds with #
Next, I type k, microcontroller responds with #INFO: TWI master enabled
Next, I type !, microcontroller responds with C

after typing in the next command "EG", the screen gives that error. i have tried screen package on linux and it has the same issue.

switch (command){
        case 'E': //Experiment options
            experiment_handler(getchar());
            break;

        case 'S': //Settings options
            settings_handler(getchar());
            break;

        case 'T': ;
            uint16_t tcs_data[] = {0,0,0,0};
            if (settings.settings.tcs_enabled == 0){
                printf("T-1.-1.-1.-1\n");
            }
            else {
                tcs_readvalues(tcs_data);
                printf("#INFO: TCS—%u %u %u %u\n", tcs_data[0], tcs_data[1], tcs_data[2], tcs_data[3]);
                printf("T%u.%u.%u.%u\n", tcs_data[0], tcs_data[1], tcs_data[2], tcs_data[3]);
            }
            break;

        case 'V': //check version
            #define STRING2(x) #x
            #define STRING(x) STRING2(x)
            #pragma message "GIT_COMMIT = " STRING(GIT_COMMIT)
            printf("V%u.%u.%u-%s\n", BOARD_VER_MAJOR, BOARD_VER_MINOR, BOARD_VER_MICRO, GIT_COMMIT);
            break;

        default:
            printf("#ERR: Command %c not recognized\n", command);
            return;
    }
    printf("no\n");
    return;
}

int main(void){

    board_init();
    pot_init();
    pmic_init();

    irq_initialize_vectors();
    cpu_irq_enable();
    sleepmgr_init();
    sysclk_init(); //Disables ALL peripheral clocks D:
    rtc_init();
    sysclk_enable_module(SYSCLK_PORT_GEN, SYSCLK_EVSYS);

    pmic_set_scheduling(PMIC_SCH_ROUND_ROBIN);

    delay_ms(500);

    stdio_usb_init();
    stdio_usb_enable();

    ads1255_init_pins();
    ads1255_init_module();

    PORTD.INT0MASK = PIN5_bm;
    PORTD.INT1MASK = PIN5_bm;
    PORTD.INTCTRL = PORT_INT0LVL_OFF_gc | PORT_INT1LVL_OFF_gc;

    max5443_init_pins();
    max5443_init_module();

    ads1255_wakeup();
    ads1255_rdatac();
    ads1255_standby();

    ads1255_setup(ADS_BUFF_ON,ADS_DR_60,ADS_PGA_2);

    autogain_enable = 0;
    g_gain = POT_GAIN_30k;
    pot_set_gain();

    settings_read_eeprom();

    wdt_set_timeout_period(WDT_TIMEOUT_PERIOD_8KCLK); // 8 secs

    //  Wait for application connection - Get 'c', reply '#', get 'k'
    while(1){
        while(getchar() != 'c');
        putchar('#');
        while(getchar() != 'k');
        printf("\n\r");
        break;
    }

    tcs_init();
    wdt_enable();

    program_loop:
        while(getchar() != '!');
        printf ("C\n");
        command_handler(getchar());
        wdt_reset();
    goto program_loop;
}


texts: Pin order differs in reality for my chip

texts:
I bought a DS3232MZ+, and I noticed that in the datasheet, the pins schematic looks like this:

However, when I received my chip, I noticed that in reality it looks like this:

Usually I tell which side is which by the name positioning, but as you can see the name is rotated so I'm confused. Moreover, in the the datasheet there can be found a "typical circuit" which looks like this:

which is even more confusing, as it differs from the pin order schematic, where two pins have switched sides.

I'm a newbie in electronics, can anyone help me understand this schematic and help me figure out which pin is which for my second picture?


texts: Controlling LED strip with Wemos D1 mini

texts:
I have a 12v led strip and have tested the current draw at ~500mA per colour.

I want to drive this via my Wemos GPIOs which are 3.3V @ 12mA max.

For testing I have been using 2N2222 transistors with 330Ω resistors and it seems to work well, in that the current draw is similar as via 12V directly. Ideally I should aim for 12mA base current right, so 220Ω resistor?

Although measuring the base current only gives 4mA which is less than I would have expected given (3.3 - 0.7)/330 = ~8mA, any explanation for this?

Also with a transistor gain of 500/8 = 62.5 (or 500/4 = 125?) I think the transistor is not fully switched on, and it does start to get hot quite quickly so this is probably true.

I suspect that gain is too high so I need to cascade 2 transistors to increase the gain in two steps. Like 5mA -> 50mA -> 500mA. So it would be something like GPIO 3.3V via 510Ω to give (3.3 - 0.7)/510 = 5mA, then 12V via 220Ω to give (12 - 0.7)/220 = 51mA

I also have some IRL540N mosfets which I tried but these don't fully switch on at 3.3v so would need a transistor to switch these anyway.

edit: Looking back at my original order for these transistors and these are what I bought https://www.aliexpress.com/item/2N2222A-Free-shipping-100pcs-in-line-triode-transistor-NPN-switching-transistors-TO-92-0-6A-30V/32816748799.html they say 2N2222A on the packaging but are not the old style metal case ones, so not entirely sure what they are now MSP2222 maybe?

This is what I had in mind for the circuit


texts: How can I increase the output current to make it sufficient for relay module?

texts:
I am using the following circuit as an industrial warning and control system.
According to input signals, LEDs and other outputs are HIGH or LOW. So, 24V in input is not always connected actually. System works quite well. Now I should add also relay outputs.
The outputs on J4 should control the relays. I am using this relay module.
My problem is that the relay module doesn't receive enough input current so it doesn't work.
I am thinking about reducing input resistor (24V input) and using a ULN2803A to drive the relay. However I think it will still not sufficient input current for relays. How can I solve this problem or what else can you recommend?
(I know the circuit is too newbie, therefore I would be glad to receive recommendations and advice instead of humiliation and non-useful critism.)


texts:
I tried to build a very simple servomotor tester.

I am using astable mode with a potentiometer and resistor on a NE555 to generate a 20 ms period. It has a correct frequency on the output between 50.5 Hz and 49.97 Hz and around 0.7 V so I think this part is OK.

oh C3 has bad value on schematic but it is a 0.1mF in real.

To drive a servomotor I tried the following circuit but nothing moved:

What I've tried:

Changing transistors (2N2222/BC547/2N3904)
Changing resistors (but no values)
Changing resistors values to 1K
Changed 555 (tried 3 different ones)
Changed servomotors (6 ones)

I had here a toy-like oscilloscope capture at servosignal point

original

but its voltage measurement is bad (compared to the multimeter(s))


texts: Circuit to select from 2 inputs 4-20mA and 0-10V

texts:
I want to select one from the 2 inputs.
if (BSP pressed) then
output=0-10V
else output=4-20mA.
I used an and gate based on PNP and NPN mosfet but it didn't work.
any suggestion plZ.


texts: Building a 555 timer's SR Flip Flop using Op Amps

texts:
How can I build a SR flip flop using op amps? (for a hand made 555 timer) Transistors may be used. I was thinking of using a hysteric op-amp and putting a schmitt trigger on the input of comparator 2. However, my solution fails in simulation. Here's my current circuit.

It works with the LTSpice model of a SR Flip-Flop so I know everything else is working as desired.


texts: Open collector outputs with logic gates causing infinite loop scenario

texts:
About my project:

I am working on a project that involves controlling several LEDs with two Intel Edison microcontrollers and a comparator circuit. There are five LEDs total controlled by four relays. Three LEDs are connected to the N.O. pin on each relay while the fault/ status LEDs are connected to the N.O. and N.C. pins on the same relay. Please see schematic below.

The first Edison chip is installed on a Mini-Breakout board which controls when the LEDs are turned on through relays triggered by GPIO pins. The second Edison is mounted on the Arduino breakout board which measures the voltage across the LEDs using analog inputs.

Using the LM2903 as a window comparator, and some voltage dividers as inputs, the circuit is designed to turn on a fault LED (relay 4 is N.C.) when the voltage across the three main LEDs falls outside of the recommended min and max values from the LED datasheet.

I am using the 7400LS series logic gates along with a bi-directional level shifter from Sparkfun (BOB-12009). The level shifter is used to step up the voltage from the Mini-Breakout board which uses 1.8V logic.

The problem:

The main idea is to indicate a fault in the system by disabling all three LEDs unless certain conditions are met, i.e., the 4th relay can only be turned on if both Edisons and the comparator circuit's output is high. However, when the comparator output (open collector) is triggered (pulled low) the relay is turned off which then turns off the relays to the three LEDS causing the output of the comparator to return to a high state, because, when the comparator chip is off its output state is high due to either a floating input to the AND gate or a 10k pull-up resistor. So, when the comparator returns high the relays are enabled again and the whole process repeats.

I am beginning to think that the only way this circuit can work is by allowing the fault LED to come on once and requiring the user to reset the circuit to re-enable the LEDs. I am able to turn the fault LED on by directly connecting the comparator output to the gate of the p-channel MOSFET (IRDF9210) at the N.C. pin of relay 4 but then both the status LED (indicating no problems) and the fault LED can be on at the same time.

My questions:

If possible, how can I disable the LEDs when there is a fault and automatically restore functionality to them when the problem is fixed?
Is it possible to incorporate a transistor that will serve as a switch between the input of the AND gate and the output of the comparator?
Are there other more suitable comparator chips for this particular application?

simulate this circuit – Schematic created using CircuitLab


texts:
I am looking for some information on how to measure the current output of a power supply that I took out of an old DVD player. On the PCB there are multiple outputs from 3.3V to 24V, but it doesn't mention anything about the current rating/output.

Basically I need to drive four 12V motors each with a current rating of 400mA, so presumably I need no less than 1.6A output?

Anyone know how to measure the current capabilities of this PSU?

Thanks
D


texts:
This question on physics.stackexchange has an answer, which has a piece of information which is new to me:

  Now, you could say "OK, let's increase the chip size instead". It turns out that it's also limited. Again, cost aside (pure silicon isn't cheap), the signals must be transmitted across the chip in less than a clock cycle, so that the chip stays in sync. The information isn't travelling any faster than the speed of light, but what is the size of a chip that gets its information in less than 1/2 clock cycle at, say, 5GHz? That's 30mm. And that's assuming electric potential travels in silicon at speed of light in vacuum (it doesn't), and that's assuming it's OK to have signals 180° phase-shifted (it isn't).

Seeing as I'm doing a project on Moore's law and its limits, I found this interesting, but I don't quite understand what "the signals must be transmitted across the chip in less than a clock cycle, so that the chip stays in sync". What exactly is a "clock cycle" and what does it mean for a chip to be "in sync"? Also, does this have to do with frenquency ("5 GHz")


texts: Why are JJ Electronic R.F. preamp tubes preferred over A.F. tubes in guitar amps?

texts:
JJ Electronic has both R.F. (radio-frequency) and A.F. (audio frequency) versions of some of their tubes.
Yet in far the most tubeshops for guitar amps they only sell the R.F. versions (ECC83 S - 12AX7, ECC803 S etc.)

Why is the R.F. version preferred over the corresponding A.F. version?

(when speaking of power tubes, EL34, 6L6 etc the A.F. version seem to be preferred)

All spec sheets can be found here, click the "more" links.


texts: Strange opamp's output impedance in spice

texts:
I'm simulating this circuit in Micro-Cap, which is the clipping stage of a guitar effect. The opamp model is the "NE-5532"

I want to measure the input and the output impedance. I expected an output impedance closer to zero Ohm, and an input impedance of about 10kOhm, with an "infinite" impedance at 0Hz due to the decoupling capacitor at the input.

Here it is the analysis in Micro-Cap.

As you can see the input impedance (the blue graph) is close to what i expected, but the red graph, which is the output impedance, it's really strange. It's almost 10kOhm, with a peak of almost 1MegOhm, and i can't really explain why.
If i switch the model to a "LF-155" i get a more "reasonable" results, with an output impedance of 1.680E-68 Ohm, which is also strange.

Can you help me? This thing is driving me crazy.


texts: Feasibility Question and Advice on CAD software

texts:
For a hobby project I have bread boarded, I am considering using a pair detectors that operate as a single use physical barrier. When hit by a projectile, a trace is broken allowing +5VDC to to trigger a flipflop that is part of my gate logic for a counter-timer.

I have envisioned this  detector  as a thin adhesive sticker with a thin copper trace embedded in it that forms a simple pattern to cover the area, zigzaging across the surface. Similar to the passive RF sticker tags used by retail stores for antitheft.

My questions are:
1) Will it be practical to have a manufacturer print a batch of these things for me?
2) I've never used CAD software before, is there a suggestion for a free CAD program, that doesn't have a huge learning curve for this type of project  (I'm a linux guy but thinkning W7 is more likely here ) ?

EDIT: Photo diodes are a great idea, and I will likely try them and ask questions in a separate thread. The break-able trace allows for more configurations and keeps slew rates ( and other rates ) small. I plan to use a very small distance to track the velocity of said projectile, like 1 or 2 cm.I have a 10 Mhz clock for my timer.

EDIT2: I should have added a current limiting resistor to the diagram so as not to start a fire with the trace...but I think you get the idea from this diagram.


texts: Why do some microchips have a mirror-like surface?

texts: I have a few development boards I was working on and I noticed that a few of the microchips have a completely mirror-like surface on top of the chip. The chips tend to be very small, just a few millimeters wide and deep. What is on the surface of these chips and why?


texts:
I'm using an MCP73833 (link to the datasheet) as the charging chip in one of my projects. We use its STAT1 pin (which is an open drain that goes to GND when a battery is being charged and floats if the battery is fully charged, or no battery is connected) to interface with a microcontroller to play an LED effect when the charge is underway and another one when it's completed. The pin is pulled high with a 10k resistor, and the GPIO pin of the microcontroller is also pulled high internally. Our current design follows the recommended design on the datasheet with some changes to accommodate our needs (nothing critical, things like max current, etc.)

So far, everything worked as expected, but we wanted to also add an LED to the same pin to use as a second indication (for a very particular reason. I know it's redundant, it's a long story). When we added the LED, the LED turns on when a battery is being charged, as expected, but we noticed that the microcontroller would rarely detect a battery charging. After measuring the voltage at the pin, we noticed that the voltage was ~0.8V, and not 0V, well above the logic level for 0. If I cut the trace that goes to the microcontroller, then the LED works and the voltage at the pin goes to GND.  I drew a small schematic, hope it helps.

So to sum up, we follow the recommended design of the charging chip and want to use STAT1 to know the status of the charge cycle. If we interface with a microcontroller, or we use an LED as an indication, the pin goes to GND, as expected. If we use both, then the pin shows ~0.8V, and only the LED turns on, but the voltage is too high for the μC to see a low level, and I just can't think why. I know that the current drawn by the LED is a tad above the typ sinking current of the STAT1 pin, but it's well within spec. I could also see that an internal pull down in the GPIO pin in the μC could cause a voltage rise if some of that current leaked into it, but that's not the case.


texts: Load and store CPU registers in application context

texts:
I just recently started working with a bare STM32F103C8T6 (an ARM Cortex M3) and ran into some difficulties.

I have set up a SysTick_Handler to switch the current context of the application. The handler invokes a PendSV_Handler in which I want to save the registers of the CPU to a datastructure. This is the simplified code:

typedef struct Registers {
    int r0, r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12;
    int sp, lr, pc, xPSR;
} Registers;

void PendSV_Handler()
{
    Registers reg;

    register int r0 asm("r0");
    reg.r0 = r0;
    /* and so on with all other registers */
}

However while testing the inline asm I ran across an issue. I adapted my handler like this:

void PendSV_Handler()
{
    asm volatile(
      "movw r0 100"  // This should store the integer 100 in register r0
    );

    register int temp asm("r0");  // This should store the value in
                                  // register r0 into temp

    toggleLED();     // Toggles an LED to visualise the behavior
    delay_ms(temp);  // Delays the execution by [temp] ms, known to work
    toggleLED();
}

Now the problem is that the LED to be toggled only switches on once and then stays stuck. Also in the SysTick_Handler another LED is toggled with SysTick-frequency, which also stops toggling after the first PendSV call. I know that they have the same priority, which is why I conclude, that the Tick-LED is stuck, because the delay is way too long and this lets me conclude, that the value from the register is not stored correctly. Did I miss out on how to store data from CPU registers or is there another flaw in my conclusions?


texts: Convert digital 12V/7V inputs to 3V3 levels

texts:
I'd like to read the digital inputs of my alarm sensor into a microcontroller (mainly PIR and Reed switches). The alarm system and the sensors operate at 12V (actually a tad higher) and the MCU uses 3.3V. I also noticed that the PIRs provide an idle signal of ~7V (no motion) and an alarm signal of ~13V.
My question is, how would I go about safely reading the sensor values into the microcontroller. I found a few voltage divider examples, but they don't take into account the idle voltage (i.e. they scale 12V/0V to 3.3V/0V). The idle signal can also vary between PIRs, so I might need an adjustable (potentiometer?) solution. Any help would be appreciated.


texts: How to plot state space variables against time on unit step input?

texts:
I have a system defined in state space model with the following matrices

A =

$$
        \begin{matrix}
        0 & 1 & 0 & 0 \\
        0 & 0 & 1 & 0 \\
       -1280  & -254  &  -26 &  3400 \\
        -1    &  0    &  0   &   0 \\
        \end{matrix}
$$

B =

$$
        \begin{matrix}
        0 \\
        0 \\
        1 \\
        0 \\
        \end{matrix}
$$

C =
$$
        \begin{matrix}
        1 &  0 &  0 &  0 \\
        \end{matrix}
$$

D= 0

As you see I have 4 state variables , I want to plot them against time with step input in matlab.


texts: Problems with Atari Punk Console circuit

texts:
I am trying to build an APC using the following schematic:

(source: instructables.com)
And the output is having some issues.
Sound only comes out when the rightmost potentiometer is at 0 resistance, and in that position the rightmost 555 heats up rapidly. In any other spot, the speaker simply makes clicking noises.
One possible difference is that I am using TLC555 chips instead of LM555 as suggested in the diagram. Would that make a difference?


texts: Bulk current injection - Resonant frequency of ESD protection diode CAN bus

texts:
Link to the application note that I'm referring to below.

I was going through an application note by On Semi, System Level Surge
Suppression Solutions for the CAN Bus -AND8253/D, where it says that the TVS diode's resonant frequency can be a design issue for high frequency EMI tests like BCI and that adding 5pF capacitors in parallel with the TVS diodes is the solution.
I'm not sure I understand this very well, could someone please elaborate. My general doubt is that the resonant frequency of ESD diodes is usually not specified in the datasheets and also the impedance versus frequency curve is not available, so how do I determine the resonant frequency.
ALso how is the resonant frequency a design issue for high frequency BCI , is it because at the resonant frequency the impedance is minimum ?

One other doubt is that in the screenshot that I have attached below, it says that the total capacitance of choke filter and TVS devices has to be less than or equal to 30pF for 1Mhz signal, but in the next paragraph it says that adding 5pF capacitors help in the design issue caused by resonant frequency of TVS diode for BCI, but wouldn't this 5pF add up to the existing capacitance of choke filter and capacitance of TVS diode and further increase the capacitance and maybe go above 30pF ?


texts: Calculating charge time of a large capacitor from a boost with a limited power source

texts:
I am trying to work out the math of what is the highest cap voltage or capacity I can have to charge from a boost topology in a given time from a source of 5V, 500mA. Here is a rough sketch of what I am describing.

simulate this circuit – Schematic created using CircuitLab

SW1 will be on for 90mS to charge the cap, then will close, then SW2 will open for 10mS to dumb current to a load. So 10Hz duty cycle.

I started to see if I have enough power: (Please correct me if I did this wrong)

PART 1

I am going to look at this from joules side first.

My source has a 2.5W which is 2.5 joules/s. There for for my duty cycle of 90mS I have 2.5 joules/s * .09 = 0.225 joules/ 90ms.

A cap of 30V 300uF with has energy of 1/2*C*V^2 = 135m joules.

So from energy point of view knowing switching loses and what not, that I have enough energy to charge my capacitor. Is this correct?

PART 2

This is where it all falls a part when I try to calculate it using constant current capacitor charging equations. The numbers don't add up.

My source is 2.5W, lets assume switching losses of 0.5W to make the math easy.

So I have 2W at the cap. Using P=VI with V=30 and P=2W, I will be 66mA.

Using the equation of charge of the capacitor V = It/C assuming I is constant and solving for t=dVC/I (Note: dv=25V since my 2V buck converter will most likely not work below 5V on the cap. I know this will make the math a bit different but I don't think it should change by that much)

So we solve for t = 25V * 300 / 66mA = 113mS. So it will take me 113mS to charge the cap even though I have almost double the amount of energy needed? Perhaps I am looking at this all wrong and just want someone to point out why my numbers are not adding up and that I am just mixing up two different thing together.

Thanks

EDIT: The load is a laser of 10A for 6mS 10Hz


texts:
I'm in the process of designing an 8 layer PCB with a stackup of:

Signal, GND plane, Signal, Power plane, Power plane, Signal, GND plane, Signal.

For calculating the trace widths necessary for 50ohm traces I'll be using either https://www.eeweb.com/toolbox/microstrip-impedance/ or http://wcalc.sourceforge.net/cgi-wcalc.html

I assume it's correct to use the microstrip model for the top and bottom signal layers but what would be the correct model for the inner two layers from these websites.

Thanks!


texts:
I have already configured an I2C protocol between a master device (PIC) and two slave devices (sensor ICs). After obtaining the measurements from the sensors I want to store them on an SD card. For that I need to configure an SPI protocol instead. Would it be possible to use the same bus for both protocols. Open I2C, get the data, close I2C and then configure the SPI. Is that possible?

Thank you

EDIT:
I2C uses the SDA and SCL pins on the chip. Can I use the same two lines for the SPI and connect the chip select and the data-in lines straight to the PIC?


texts:
I am designing a PCB and would like to have a white board with clear text in the middle like this:
I have looked up altium text options online and I believe this is the "boarder option", however altium only gives me the following options:

If you could guide me in the right direction in how to enable this option or tell me how to get this text, that would be much appreciated.
Thanks,


texts: Difficulty in understanding the paragraph concerning h- parameters

texts: This is a paragraph from "Engineering circuit analysis" by W H Hayt. I really don't understand the statement "it is difficult to open circuit the open terminals...." What does he mean in the paragraph? I also don't understand if we are able to open circuit for measurement of Z parameters why is it difficult here?


texts: Sending power to passive subwoofer via RCA connections

texts:
I have a home theater receiver with a powered subwoofer output and a matching passive subwoofer. I've always connected these two items using speaker wire.

Recently I moved into a place that has passive in-wall speakers. There is a faceplate with speaker connections. The in-wall speakers do not include a subwoofer.

There is a single RCA port on the speaker input faceplate and an RCA connection in another part of the room for the subwoofer. This would be perfect if I were using a powered subwoofer, but I'm not - and I would prefer to not have to purchase a new subwoofer and new receiver.

My preference, if possible, is to run from the receivers red/white connectors to the RCA port and then from the other end of the RCA port back to the red/white connectors on the subwoofer.

Is this possible? How would I got from speaker wire to an RCA connector?

Yes, I could just use the subwoofer as I have previously but then I'll lose the benefit of being able to easily hide it away in a corner. This is what I will do if I can't use existing wire run.


texts: Identify processor type from raw binary code?

texts:
Not really related to chips, but hopefully I'll get some directions to follow from here.

I got a chunk of code, but I don't know what processor it intended for.
Are there tools available that can help me identify the code type?
What statistic methods can help? Byte distribution? Pairs distribution, etc?
Markov chains maybe?


texts: SCPI message exchange control implementation

texts:
This is more of a software question but I figured more would be known about SCPI (IEEE 488.2) here.

I am implementing a full serial (using IEEE 1174) SCPI parser on an IC device but am wondering about the best way to implement this (in C). Currently I have used a large case switch but it is not ideal and am thinking of moving to a table approach. Does anyone have experience or suggestions on this?


texts: What should be the potential drop across the Oscillator? I am facing a problem that a simple flashing program also does not work. I checked Oscillator pin and found out that the potential drop across these pins is 2.17 VDC. The Microcontroller has 5VDC. What does this 2.17VDC indicate? Does it mean Oscillator is not working?


texts: How to create unique label on macro definition on AVR GNU assembler?

texts:
On AVR GNU assembler I'm trying to create a label inside a macro definition.

I would like to create a macro, which has a private lable, or unique label inside - just to be able to jump inside macro definition and use multiple instances of this macro.

Below is example of what I'm trying to do.

.macro SetFlag par0
    brid  local_noInt

    cli
    lds   RTMP,FLAGS_M
    sbr   RTMP,(1<<\par0)
    sts   FLAGS_M,RTMP
    sei

    rjmp  local_end
    local_noInt:

    lds   RTMP,FLAGS_M
    sbr   RTMP,(1<<\par0)
    sts   FLAGS_M,RTMP

    local_end:
.endm


texts: Is this a possible design of Triggered Spark Gap?

texts:
I am trying to make a triggered spark gap for discharging capacitors (around 470uF, charged to 300-400V), for entertainment purpose. I have searched for triggered spark gap designs, but I am not sure whether this one works.

I suppose that the gap between two round heads (possibly from carriage bolts, separated by 1-2mm) will sustain the voltage. Then a voltage pulse from piezo igniter will create an arc in the gap, and hopefully the ionized air inside the gap will conduct current and discharge the capacitor (and create some huge flash and noise). Alternatively, if this is not practical, is it possible with the igniter replaced by something powerful like Mazilli ZVS oscillator + CRT flyback transformer?

I have almost no idea about how electrical arcs behave, so I am not sure whether this design will work.


texts:
Schematic 1 shows a discrete operational amplifier which is used as a gain block to make up to 450V out of 12V. Q3 and Q4 are used to generate a current which is used by the current mirror. This is basically a simple op amp with a impedance transformation at the end (Q11 and Q1). The gain is set with R1 and R2. The other resistors are just for current measurement in ngspice which is use to simulate.

The dc transfer characteristic is shwon in figure 2. The source V3 is used as the dc control input.

Do you guys have any ideas how to make the output more linear starting from near zero and get rid of the plateau at the end?


texts:
I've seen a number of posts out there concerning adding/removing DC biases, and I can't seem to find one that has been directly applicable to my problem.

Question: How do I remove the 1.5V DC step that occurs when the MCP4921 outputs audio?

Problem: When I play sound, there is a clicking noise that occurs at the start and end of the audio sample.  I am sure that I have removed any transients in my original samples by adding fade in/fade out, and the hex files that I have generated from these samples do not contain any transients at the beginning or end, either, as they begin and end with 0x00's.  Other background information, such as my audio driver code, can be found here: Audio Noise: ATMEGA328P, MCP4921, and LM386

I have tried the following two possible solutions from different posts, with no change in the output characteristic:

Adding a 1.5V DC Bias to the MCP4921 output, using the topology of the first answer from this post: DC biasing audio signal
Adding two diodes between the output (after the AC coupling cap) and 5V power supply, to get an equivalent diode voltage drop to the step I am seeing

See attached for screenshot of the oscilloscope, with the probe being on the MCP4921 output (after the AC coupling cap).  Also attached is the schematic.  The schematic does not show the two possible solutions which I mentioned above.  The purpose of the V_REF Resistors is to make a voltage divider that will give 0.25V at the V_Ref of the MCP4921.  This was done so that the default gain of the amplifier, 20, will produce a 5Vp-p signal at the speaker.

Thank You,


texts: Recording sensory nerve action potentials at the skin surface without electrical stimulus

texts:
I studied many nerve conduction studies. In these studies, there is one stimulator that excites the nerve and there are electrodes placed at the skin surface on the path of the nerves to record the nerve action potentials. There are a few questions, of which I am unable to find the answers. Please guide me as I am finding a way to record nerve action potentials for mechanical stimuli like vibration. Your answers will help me proceeding towards the goal.

The machine used to study Nerve conduction will be able to pick the action potential only when the stimulator excites the nerve. We know that the action potential of any nerve fiber is constant and cannot go beyond the maximum value. So external stimulus like touch can also generate an action potential. So, why are these machines not able to pick action potential against external stimulus?
The frequency of nerve impulses depends on the stimulus intensity. Is there any study that I can refer to, which shows that these impulses change some parameters like skin conductance, etc.?

Please pardon if I did not provide enough information.


texts: Calculating max peak current at different conditions

texts:
I have an IR LED (IR383), and I want to power it with 5v@38KHz. I'm actually calculating the resistor so I need the LED's maximum current. In the datasheet, it says that it accepts 100mA continuous and 1A peak, this being at Pulse Width <= 100uS and 1% duty. How can I calculate, using this information, the peak maximum current with my 38KHz (50% duty)?

(1/38KHz = 26.3157895uS)


texts: Two stage amplifier, low gain at high frequencies

texts:
When I simulate one stage amplifier it is capable of amplifying to a much higher frequency than a two stage amplifier.
I added a 100 ohm resistor to reduce the gain of the two stage amplifier so both the gain curves could fit in one graph, but you get my point. The two stage amplifier is dying much earlier than the single stage.
Why is that?
Can I prevent this?


texts: How to cut of the DC supply from a high power motor control?

texts:
For my project I built a BLDC motor controller.

Now I have to cut of the controller from the battery.
A relay is not    easy because common  my application needs >200Amps

The highside switches I found is the Voltage rating too low.
The max Voltage I found was 60V.

Battery voltage is 60V and the max current about 200A.

Also I am afraid of using semiconductors because they like to shoot trough after burning...


texts: Arduino shows voltage drop, voltmeter doesn't

texts:
I'm totally lost with the behavior of this simple schematics.
issue http://img72.imageshack.us/img72/9421/issueh.png

Once the charging process starts, Arduino's voltage reading becomes very different (should I say wrong) from the one voltmeter shows, as if there was some invisible 10 Ohm resistor in place of the switch, resulting in huge voltage drop due to some 0.5 A current.
How can Atmega's A1 & A2, both being connected to the same wire, indicate different voltages?

Are here some internal Atmega's clamping diodes kicking-in or else?
As for the internal resistance of the batteries, I presume voltmeter correctly indicates 0.2V drop.

ps: yes, I know, the schematics is incomplete. It has no protection resistors on Analogue input pins, also, the high-side MOSFET should replace the switch.


texts: Battery charger with reversible polarity

texts:
I am building a charger for NiCD batteries and wondered if it was possible to accept the battery in either orientation and rather then protecting the battery detect the battery's polarity and switch the charging current polarity so it can be charged either way around?
Thanks in advance!

Thanks for your responses! The idea is to do it for a single NiCD AA battery. It seems that most charging chips do check the polarity as a safety measure. Is there any reason they don't use the result to change the charging polarity rather than cutting the charge altogether. I guess its not really any more difficult?

Thanks again guys. I have been told by the person doing the electronics that it's going to need 2 power relays and a fair bit of additional feedback circuitry which makes it work. this pretty much rules it out. Does anybody have any smart solutions?


texts: Does anyone have experience with the recom rpx-1.0 or similar that could explain a few things to me?

texts:
I'm looking to have 4 dc-dc converters each with different outputs but one voltage input value. Vout of 9V 12V 15V and 18V.
Would this chip be able to do that?

Here is a bit from the data sheet and I believe that to change Vout all I have to do is change R4, is that correct?
Also I'm unsure of what PG, AGND and PGND are in the below picture. Could someone clarify?
I know DC-DC converters separate gnd from two circuits so can AGND not connect to PGND?
Below is also a link to the data sheet if that would help to answer my question.
https://www.mouser.com/datasheet/2/468/RPX_1_0-1903909.pdf


texts: Is bandwidth of cmos comparator important?

texts: The concept of bandwidth is developed based on small-signal analysis. However, comparator works usually under large-signal conditions, and transistors are not in saturation region, since comparator works in open loop. So why do we care about bandwidth of comparator? Isn't slew rate the right thing to look at for characterizing comparator's speed?


texts: Triggering Raspberry Pi GPIO with 127V AC

texts:
I'm building a home automation system with raspberry pi and would like to trigger it with a regular pulse switch, connected to my home's 127V AC power network. I'm doing this so I don't need to rewire my power outlets.
I came up with a circuit like this. Do you guys think it would work?

Thanks!
Edit 1: Here's what I'm trying to achieve:

The switch is far away from the raspberry and the wiring is already in place, that's why I would like to use 127V.
Edit 2: deleted
Edit 3: new diagram:


texts: Arduino analog only reading 40 when grounded

texts:
As the title suggests, I am trying to work out why my Arduino won't go lower than around 40 on the analog pin scale when that pin is simply grounded.

Could it be interference (it's part of a breadboard circuit)?

I've tried both analog pins 0 and 1 with same result, printing to serial.


texts: I2C at 2.4 MHz with five microcontrollers over 2 meters

texts:
I have five Teensy 3.1 and I would like to interface them with I2C running at 2.4 MHz.

The maximum Line Length will be around 2 meters.

Will it work?

What's the best way I can wire this up?

update on Aug 25:

Regarding the manual saying 100kbit at page 1169;  that's a generic note about I2C.  If you go down a couple of pages, there is a table with the divider values needed to set the Clock speed of the bus.  And the maximum is 240  (2.4 mhz).

Apart from this; I  done a couple of test between two teensy 3.1 and the bus works flawlessy at 2.4 Mhz.   Its still slower since (According to wikipedia)  some devices can support up to 5Mhz Clock speed

I just want to link 5 Teensy 3.1 and not any other devices.

My problem is that I Don't have a scope and i cannot afford one at the moment; so I'm going by guess.

If 2 meters is too much; I could perhaps reduce the link length to 40 cm by using the second I2C port on each Teensy 3.1 to link to the next.

Should I use Cat5 cable?
twisted pair?


texts: DALI Command's reply to the meaning of representatives

texts:
I have some control gears which already have short addresses, are connected on DALI lines.
I tried to send Query Short Address (command 269)& verification Short Address (command 268), but I didn't get any response.Is this right?

If above is right, I tried to send command 153, I got response 06 and when I tried to send command 144 I got response 04.

What is the meaning of these responses?


texts: Calculating Op-amp supply bypass caps values

texts: Either I suck at searching or there is not a lot information about calculating values of bypass caps for opamps(I found a bunch on the topic in general). The question is, what it says in the title, say I have an audio range circuit with variable gain with an op amp run off of +/- 4.5V ( voltage divider on a 9V cell ) output current is probably under 50mA, now how would I go about calculating the values for the supply bypass caps?


texts: Using a SMPS converter IC as a controller

texts: I'm building an LED driver using the LM3410. The internal switch supports a current of about 2A which should be adequate for my needs, but if I need more, can I use an external MOSFET to act as a switch instead? I was thinking a pFET with the gate connected to the switching pin, since in a boost converter the inductor is connected to ground during the charging phase.


texts: Verilog proper use of high impedance value?

texts:
In verilog, what are some examples of when one should opt to use the high impedance value Z?

Thanks


texts: Possible to determine a device's power requirements based on the batteries it takes?

texts:
I have a magnifying glass LED lamp that I lost the power adapter to. There are no power requirement markings anywhere on the device, nor do I have the box/manual.

Short of trying to find the device's specs online (easily doable), I'm wondering if it's possible to determine what power rating of an adapter it would use based off the type and number of batteries it takes? The battery compartment takes 3x AA batteries.

Would that simply mean I need an adapter of 4.5 volts? Or is the rating between the two power supplies not as simple of a correlation as that?

I understand that amperage is "pulled", but would I also just add the amperage ratings of AA's together?

And finally, what about polarity? Is it possible to determine what adapter would have the correct polarity (short of looking it up)?


texts: Control the lights both with wall switch and arduino

texts:
I am starting to build new house and want to add some home automation features, for now, turning lights and sockets on and off.
i bought arduino mega, ethernet shield, current sensors to see if the light is on, and relays. Can you tell me what is the best practice to get this working, and other thing, i want lights to be turned on and off from the wall switches and in the same time from the arduino. if the arduino is not working or off, lights should still work from the wall switches,
thanks a lot


texts:
I'm pretty new to circuits and I only know basic rule from Ohm's law that U=I*R. I quite don't understand how was following formula for Ui created:

Why are there only two resistances in numerator? And why is the whole fraction multiplied by original voltage? Sorry for my dumb question, but I'm trying to figure out how does this work. I'm not sure how to take a right look at this example.


texts:
I am wondering whether there is a solid standard on how to give components an unique identifier. In Altium it is called a Design Item ID, and in our company we used it as a unique identifier on the ERP and our whole workflow (design, purchasing, manufacturing, testing, servicing etc.) used that ID in order to distinguish components. It is packaging ignorant, so same for tube, tray, tape.

It is a de-facto standard which is homebrew. (for example, IPC doesn't have one AFAIK.) In my old company, it would be something like this:

IND205101029 - An common mode choke from Würth, hence IND for inductor.
ICTJF1051T31 - A CAN Transciever from NXP , TJF1051

and so on. Many times this code incorporates some key parameters like values like resistance, inductance, or would have modifiers for AEC qualification for automotive parts, industrial temperature range or flexible terminations.

I am wondering whether I have to devise my N+1 th standard that fits me now but will probably wear out in a decade? (Obligatory XKCD?)

Right now I am wondering whether I can just use someone else's code which needs to put so much more time in this that I can just rely on them? I was thinking I could use the Digikey order number for this unique identifier. I know that it is incomprehensible, but it is at least a solution for a problem.

My question might sound like a poll (I hope that I was able to express that this is a design standardization question, I am sure that there is an industry best practice out there that I don't know.), but I really feel the need to hear the best standards in this.


texts: Why is it necessary to halt program execution for the breakpoint to be effective?

texts:
When I'm following this procedure, program execution is successfully stopped when the payload program is run:

Setting breakpoint to beginning of program which is gets loaded by the bootloader afterwards. The breakpoint gets set with the GDB command break *0x2000001c. As OpenOCD tells me that the CPU has 6 harware breakpoints when connecting, I suppose one of those is used.
Resetting Mikrocontroller with GDB command monitor reset run
Loading programm by bootloader into the SRAM region.
Halting and then continuing execution by GDB commands monitor halt and continue.
Instructing bootloader to run loaded program.

However, when I'm exchanging step 3. and 4, program execution is not stopped when hitting the breakpoint.

Can anyone tell me why? It seems to my, that the core "looses" the breakpoint when the register the breakpoint is set to gets overwritten.

This is the equipment I'm using:

STM32F4 mikrocontroller
ST-Link
OpenOCD
GDB


texts: Why is it desirable to inject reactive power into a transmission system?

texts:
This website explains the basics of FACTS technologies and how they can be used to exchange active and reactive power with the transmission system, namely:

SSSCs - can exchange active and reactive power
STATCOM - can exchange reactive power only

But why is this desirable? Why do we want to add or remove reactive power onto the transmission system?


texts: What kind of component would I need to put a break in a RS-485 bus?

texts:
I'd like to have some kind of electronically controlled switch (transistor, relay, solid-state relay, etc) that acts as a break in a RS-485 bus. The effect I would like is to optionally split the bus into two halves, isolating one half from the other. Obviously RS-485 signals would need to be transmitted clearly (even high-speed 2Mbps+ signals) when the switch is in the 'on' state and no signal should get through when the signal is in the 'off' state.

What kind of component should I be using, and how should I wire it up?

P.S. I'm looking for a component that is as physically small as possible, and I'd like the switching voltage to be 5V or lower.

P.P.S. The RS-485 bus cables in my application will be short enough that signal reflection won't be a problem, so I'm not going to worry about any termination at the moment. Nevertheless, bonus kudos is available for a solution that could optionally incorporate switching in a termination resistor on each side of the break - as I'm sure that would be useful to someone in the future.


texts: STM32F103 Debug Error - Cannot Access Target

texts:
Im having problem at debugging, tried to load basic led toggle program for test purpose and its work fine but when i tried to debug it, im getting " Cannot Access Target, Shutting Down Debug Session ". My other concern is this device has 256 KBytes Flash Memory though at keil there is only 512 KBytes option. Hoping to get some information from you about this problem. Thanks for your time.
MCU = STM32F103CVT6
IDE= Keil 5.34.0.0


texts: Photoresistor audio switch on battery power

texts:
I'm trying to build a light-driven chime silencer for a wall clock. The schematic from https://electronics.stackexchange.com/a/177401/18259 seem like a very good starting design for this:

It, however, requires a control voltage of 10V. Testing this in LTspice confirms that 3V won't drive this. I'd like to run this ideally on a single 1.5V battery, or at most two. (This would work on a 9V battery, but it feels like overkill for the problem.)
I'm also uncertain where would be best to add the photoresistor (1k-10k) that won't excessively drain the battery.
The chime signal seems to be about 250mV, and I'd like to squelch it when there is low light on the photoresistor.
(Unfortunately, while I took several electronics classes in college, it's been too many decades to remember how to actually design these things.)
Responding to the helpful comment from @dandavis: I believe just using a photoresistor in series going to make it much quieter when I want it on (the resistance range is 1-10kHz), and then make the sound very proportional to the light. I want it to be off (or extremely quiet) when there's little light and full volume when there is a lot of light, with a fairly sharp transition that I can tune.


texts: Controlling current through low value inductor

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I have an inductor on the order of 1uH whose current I want to regulate using a PWM signal using a circuit like this:

simulate this circuit – Schematic created using CircuitLab

Where I have a microcontroller generating the 1MHz square wave, which would normally be a PWM signal.

According to my understanding, the PWM duty cycle should be maybe 1/10th or less of the L / R time constant (in this case, the L / R time constant is 10 microseconds).  Even though my circuit satisfies this requirement, the current going through the inductor in this simulation is very jagged, like this:

If I increase the PWM frequency to 10MHz, the signal is still jagged (which is what I would expect), but the amplitude of the current over time is much smaller, which is what I want.

question
Aside from having a faster PWM signal (not really an option... my MCU is only so fast) or having a lower ESR inductor (also kinda tough), what are my options for achieving this?

Do programmable current source IC's exist that would do the job for me?  Could I use a DAC + Op-amp and rely on the ESR of the inductor?

Edit:

Using a 47uF capacitor with Dmitry Grigoryev's solution gives me a current output that is way closer to what I want.  The current won't need to be modulated very quickly, so using a higher value capacitor works well for me, and it lets me lower my pwm frequency to 180kHz, which is what my MCU can produce.

This is a current graph generated with 180kHz and 47uF capacitor

Still wondering if some sort of op-amp + BJT solution would be completely daft or not.


texts:
I have an RFID module I want to mount in the driver's window of a car. It connects to a box that will probably be in the footwell. It uses 5v RS-232. Given that RS-232 isn't balanced, is there any advantage in using UTP cable to connect the two? If so, what would the wiring look like? At a minimum, I'd need power, ground, and a simplex data line, but if I could control a couple of LEDs over that too, that'd be great (presumably they could share a pair, as they're constant voltages).

If there's no advantage, is there a disadvantage to doing so? It's just for a prototype, and I happen to have plenty of Cat5.


texts: How to connect clean power to multiple pins

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I’m more inclined with software than hardware, so there may be a simple answer I’ve missed somewhere.

Most of the ICs I’ve been looking at require multiple VCC and VSS pairs such as cortex processors. I have read many posts elsewhere aging that these pins need to be connected and that they need clean power. What I don’t know is how to properly do it. I’m not asking for exact part numbers or the like, I just want a template that I can adjust for as many or few power pins as I need. I’ve been warned against placing multiple voltage regulators in parallel to accomplish this.

Constraint; I want to supply power to the circuit board with a single pair of wires from an appropriate battery pack and then split that power cleanly to the multiple VCC/VSS pins.

Assume required power will be either 3v or 5v

Any equations I will required to determine the correct parts would be nice, but I really need a diagram with indicated repeatable sections.


texts:
I am trying to place components in Altium designer using the Manufacturer part search but the "Place" option is inactive.
.


texts: PSU drops both current and voltage when connecting to an LED

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I'm connecting a DC PSU to a high power LED. I'm setting the maximal current, and a voltage. For the first few seconds, I'm in the c.c mode (voltage drops from its initial value to a lower one). But after a few seconds, probably since the LED heats up, something strange happens: both the current, and the voltage drop to very low values.

If the heating causes the resistance to increase, I would expect the voltage to increase.

A few more details:
It's an unbranded 100W LED I got from ebay (link)
Unfortunately, there is no spec.

I'm setting the voltage to 30V, and maximum current to 2.7A.
The LED heats up, there's a fan attached to it, that does its best to keep it cool.

Thank you.


texts: I have Eagle schematics, which contains ISA connector. Is it possible to mark this part in schematic as "hidden", so it is ignored in PCB editor - not shown and neither routes are not shown for this connector? I do not want to delete this connector in schematic.


texts: Hardware for Generating Low Frequency Vibrations

texts: I am interested in having a small device generate low frequency vibrations in the range of 1Hz - 10Hz which can be adjustable. Doing my research, I came across small coin shaped motors which are ideal in size, but have a high RPM 12000-15000 which would translate to a high frequency. Are there any devices that can generate low frequency vibrations? I am open to motors or other hardware that can easily be purchased.