texts: What challenges restrict the resolution of spacefaring digital cameras?

texts:
I've been reading up about NASA's Juno mission, and came across the Wikipedia article about JunoCam, which is Juno's onboard visible-light camera.

In the article, it's mentioned that the resolution of the sensor is 1200x1600 pixels, which comes out to just under 2MP.

Obviously, sending any camera into deep space and establishing a stable orbit around Jupiter is no small feat -- but seeing as Juno launched in 2011, why is JunoCam's sensor's resolution so low?

I'm assuming - maybe too optimistically - that design changes like sensor selection would be finalized 4-5 years before launch. In 2006-2007, entry-level consumer DLSRs often sported 10MP sensors.

Basically;

Is it more difficult to harden a higher-resolution sensor against hazards in space?
If not, what reasons could NASA have to avoid using higher-resolution sensors?


texts: Solenoid's field intensity calculation dependency on width/diameter of coil?

texts:
Textbook formula for field intensity in solenoid coil is

H = (N * I) / l

H magnetic field intensity in ampere-turns

NI ampere-turns

l is length between the coil poles (along the axis of the field flux)

This formula does not take into consideration the width (or diameter) of the coil. Apparently it is based on assumption that diameter is smaller than the length and hence does not significantly impact this calculation.

I am considering a single electromagnet as a model for a BLDC motor' stator coil. Those are often more wider coil diameter and of short coil length.
Wider coil surely weakens the intensity of the field inside the coil. Imagine the flux lines getting thinner as the coil loops get wider. How to reflect this fact in the calculation of the field?
How to adjust that formula to include the width/diameter of the coil?

Also, a bit aside from the main question, please give me a hint How to calculate the attracting force developed in such a wide solenoid in Newtons, knowing field intensity and, say, attracting an iron cylinder of known mass and permeability ?
 Note: for the sake of simplicity assume air core in solenoid.

Edit: if my second question seems to spill into larger area of expertise please disregard it and simply suggest the answer to the main question as it is important for finding if the range of the field stays below the saturation point.


texts: What is the meaning of "400 kHz when other system delays permit?"

texts:
I am going through the datasheet of the P82B715 I2C extender.

The datasheet says "400 kHz when other system delays permit."

What does this mean? (In the Texas Instruments datasheet they do not mention anything like that.)

Will it affect my application?

My application:

I need a multidrop configuration with 400kHz.
cable cat 5 (50pF per meter)
15 sensor drops, from sensor to sensor 2 feet cat 5 cable
total bus capacitance buffered = 15x(2/3)x50 = 500pF
total 16 of P82B715 chips (including MCU board), one P82B715 for each sensor drop
sensor data are sequentially continuously collected from an MCU at 400KHz

The reason to select this IC is its 2 wire communication. I need a low number of wires for the communication bus.

Updated

one sensor drop is one sensor node
sensor node = sensor IC + P82B715 IC

Mcu P82B715 IC--> 2ft cable --> 1st sensor node-> 2ft cable -->2nd sensor node-> 2ft cable --> 3rd sensor node -> 2ft cable -->... --> 15th  sensor node

so the 15th sensor node is 30ft away from the MCU board

from data sheet

as shown above, other nodes will be connected buffered bus, same as I2C 3, in a  parallel way


texts: Unbalanced three phase system - Neutral fails/opens/disconnects - consequence?

texts:
I have a very basic question about three phase system. I am not an electrical engineer hence I might not have a good understanding of the subject. So, please be bit lenient in answering and asking clarifications.

My home receives a 220v (between one phase and neutral) 3 phase connection from grid. From the post comes 4 wires to our home. Each phase is connected to various loads in my house and since not all loads will be switched on, the three phase circuit will be unbalanced.

So, if I draw a very crude schematic diagram with text:

R--------L1---+
              |
Y-----L2---+  |
           |  |
B---L3--+  |  |
        |  |  |
N-------+--+--+

R, Y, B are the three phases, N is the neutral and L1, L2 and L3 are the loads (unequal resistive and inductive combined).

What happens when the connection to neutral fails as shown by the following diagram?

R--------L1---+
              |
Y-----L2---+  |
           |  |
B---L3--+  |  |
        |  |  |
N--  ---+--+--+
    ^
    |
    +------- Neutral disconnection

Some say that the loads L1, L2 and L3 experience high voltages as they will be connected between phases rather than between phase and neutral.

While some say that the entire circuit will self adjust and achieve a balance.

Either way I am not clear. Could you just let me know which version is correct?

Thanks.

I had searched for this Google and could not come up with any suitable answer. Also this question also didn't help.


texts: Resistor ladder with digital (interrupt) and analog (analogRead) output

texts:
I want to create a resistor ladder with 3 switches with the following properties:

if no switch is pressed, no current must be flowing
when any of the switches is pressed, a line is set "high" to the input voltage (3.3v)
when switch 1 is pressed, I want voltage a, switch 2 = voltage b, switch 3 = voltage c, while the exact voltages are not important as long as they are at least 0.1v apart from eachother

I am an electronics noob and read myself into it, and created the following drawing. I think it's not correct, and any hints on how to achieve the above would be awesome.
Thanks
Raphi


texts: I have this circuit of class C amplifier and want to set up its conduction angle at 45 degree. Could any one help me to what should I do?


texts: Question about current output of a DC-DC stepdown converter

texts: If we have a solar panel of 5V and we want to keep voltage on the output to 3V, what current we are getting on the output? The same as in the input? Or a different one?


texts: How do usb-c connectors carry 100W at 20V without melting?

texts:
USB-c connectors are tiny. How is it possible for them to carry 100W at 20V without melting? I understand that power = VA and with V=20V then A only needs to be 5. But 5A through most tiny wires makes them melt. So how does USB-c pull off this trick?

Wikipedia has several articles on USB-c power delivery, including https://en.wikipedia.org/wiki/USB_hardware#PD, but I still don’t understand how the standard avoids this problem. It’s not like the cable is made from room temperature super-conductors...


texts:
I have a battery that's designed to power a MacBook Pro (it's not an internal battery, it's an external battery meant to act in place of a charger, so it's got all the monitoring electronics internally).

Now, I wish to use this battery to power an iPhone dock. This dock has internal batteries itself, but they run out fast (only 3.6V, 1.8Ah), whilst this MacBook battery can provide 60Wh - which would increase the duration of the playback by many times, and stop the voltage dropping etc.

The only issue is that the iPhone dock DC in wants a 12V, 2A supply, whilst the Macbook battery will supply between 14.5 and 18.5V (4.5A max). I don't wish to play with fire by putting in too high a voltage (there could be no damage, I might have to buy a new dock), so I was hoping to regulate the voltage of the MacBook battery so that it could safely power the iPod dock.

I've been reading 'A designer's guide to the L200C voltage regulator' and it seems to ideal for this purpose, but some aspects seem a bit strange. Can I get someone to answer the questions I have with this circuit? The ST datasheet is here.

Firstly, I'm not sure what the black rectangle at the bottom is. It seems like one plate of a capacitor, but that can't be right... Can that be explained?

Secondly, am I to attach the positive lead of the battery to the top left line and the negative lead to the bottom left line? Is it the same for the output? (top right for positive, bottom right for negative?

Finally, I'm not really sure what Vref means in all of the equations in the datasheet. The values for R1 and R2 given in the documentation for a 12V output are 1 kilo-Ohm for R1, and 3.3kW for R2 (I assume that's a typo, and they mean kilo-Ohm). Do these values seem reasonable, and should I have R2 as a potentiometer (If so, what sort of potentiometer?)

I'm sorry to sound really needy - I wish to get this working, and I also have barely any knowledge of electronics!


texts:
I have to redo a schematic for a PCB. I have a paper version of the schematic, the Gerber file of the PCB and the PCB in a CADSTAR project but not the schematic. I'm using Altium and wanted to know if there was an easy way to redo the schematic or do I have to do it all by hand?

Ps. the PCB has ~720 component and thats why I'm asking

EDIT

I found a diagram of the PCB made in Zuken's E3.schematic, if it can help me not to do it by hand, let me know.


texts: easy to construct FM low-pass or band-pass filter

texts: Suppose I wanted to filter a Raspberry Pi's (or other similar) GPIO digital output (running pifm or rpitx or similar) to be clean enough to not splatter RF harmonics outside of FCC Part 15 (or equivalent for other countries) unlicensed RF broadcast allowances.  What might be some suitable FM broadcast band low-pass filter or band-pass filter designs that could be constructed out of the easiest-to-procure and manipulate components and materials (e.g. something suitable for a kid's student project, nothing tiny surface mount, etc.)  Is this possible?


texts: Opamp comparator output interfacing with digital circuit

texts:
I want to use Op amp as a comparator to shape the 50Hz sine wave to square wave, then route it to the PLL reference signal input, the PLL chip is 74HC4046. And i use AC coupled method. Because the supply of the Op amp is +/-15V, but the output signal amplitude need to be within +/-5V range. I have two solution to convert it:

Use diode to clamp the output to +/-0.7V or so.

Use transistor as below:

I want to know which one is better. Such as rising/falling time, delay, etc. I want the frequency is as stable as more.


texts: Why aren't there any 3-phase domestic power-outlets, or any interest in 3-phase for household (mains) power or anything relatively low-power?

texts:
Since I discovered what 3-phase electrical power is on Wikipedia, I have noticed that it's associated with very high-power applications.  I have not been able to find anything on the subject of 3-phase power for anything but very high-power applications, and it appears that the only 3-phase power outlets in existence are meant for ultra-high-power industrial equipment.  I find this strange because I imagine (lower voltage) 3-phase would be better than single-phase for household power outlets.

The main reason that I think 3-phase would be better, is that it could be rectified into cleaner DC power. 3-phase consistently provides power while single-phase repeatedly goes down to 0 volts before rising back up. 3-phase would naturally make less power-supply noise, so we could have cleaner power with smaller capacitors.
I make guitar pedals as a hobby, and power supply noise is quite a nuisance.

It might possibly be safer, as the AC voltage could be lower (in case if two wires are shorted together by a person), but it could still have a higher DC output power with a 3-phase rectifier, and possibly other things.

So why is it that home power outlets aren't 3-phase anywhere in the world, or even interest in it?


texts: Confusion over wire\array notatin in verilog

texts: What's the meaning of wire [a:b] c? Is it different from wire [b:a] c? or verilog considers them equal? Is there any syntax to convert different arrays to each other?


texts: DC supply voltage in op amps and instrumentation amplifiers

texts:
My question is very simple, i dont have much experience with electronics, and i am developing a project where i will use some operational amplifiers (TL081) and 1 instrumentation amplifier (INA118).

I'll need the TL081 to build voltage followers, and a Voltage-Controlled Current Source (Mirrored Modified Howland):

Source: http://iopscience.iop.org/article/10.1088/1742-6596/407/1/012030/pdf

The INA118 amplifies the input voltage from the two electrodes placed on the body. Similar to this project.

In these cases, do I need to use a DC supply voltage in my ICs TL081 and INA118?
I was looking at projects that use applications similar to mine, and I did not see any comments about it.

Thanks!


texts: How is this transfer function generated using this LTIC circuit diagram?

texts:
I am studying for my signals and systems final in 3 hours and cannot seem to wrap my head around one of the homework/practice problems. We are given the following figure:

For each figures (1, 2, and 3) we are asked to prove that the 3 dB bandwidth of the system is:

Wc
10Wc
Wc/10

I understand how to go about doing the first system. I first calculate |H(w)| and then get |H(0)| and |H(Wc)| and then run the results through 20log(|H(Wc)|/|H(0)|) (which comes out to -3 dB).

However I cannot figure out how to calculate the transfer function for the next two systems. The solutions provide me with this formula:

Which for the second system ends up being

However I would love to understand how they got to that point. I guess I do not understand how to translate the circuit diagram into a new equation.

Can anyone provide some hints in this regard? Thanks!


texts:
I'm thinking of choosing and creating step-up convertor for spark-gap demo. Currently I'm thinking of a kind of pulse transformer to raise the voltage to 10-30 kV.

For now I have plenty of time so I'm interesting in trying to create the thing myself. I have no problem creating pulse voltage of 300 V at 50-100 kHz (rectifying it and slicing with ne555 controlled transistor). But then I need to make calculations about the transformer itself.

I understand I need to fetch wire and ferrite core from the local shop. But how to choose minimum core section area and minimum amount of turns, depending on frequency and desired output power? Internet is bloating on "transformer calculation" query, but it is mostly about simple ratio of turns. So could you please help me with some links/instructions?

Is the idea viable, by the way? I understand that unless I take some precautions, I can get breakdown of isolation between turns due to high voltage in the secondary coil...


texts: Generator to Main changeover issue RCCB not moving up

texts:
RCCB not moving to up position while DG to EB ( generator to mains) changeover.

I live in a community where we have almost 1200 apartments in India which will serve power through generators when the main supply goes OFF. (230v)

The following diagram shows my wiring in my distribution board.

My four-room apartment has 4 MCB for each room for lighting circuits and one MCB for heating circuits.

Whenever a change over happens from the generator to main, RCCB won't automatically move the knob from down position to up position, there is no issue while, main to the generator changeover, in this case, RCCB will automatically move the knob from up position to the down position.

So I have to manually go and move the knob in RCCB towards the above position, bring the power back from mains.

How to solve the problem, looks like the wiring problem. Let me know what more information required, I can post info and pictures based on requests to solve this.

I need to go and move RCCB switch to manually up in the middle of my sleep at night, so many sleepless nights, no expert electricians still can't solve it.


texts:
I'm trying to calculate the forced response for a current in the above problem. I'm having trouble getting the right answer, and I was hoping someone could take a look
and point me in the right direction

Here is my attempt to solve it. With forced response problems, I calculate the desired voltage or current, usually from either a voltage or current divider, and then use that to calculate the new amplitude and phase angle. But I'm not sure that's correct, and I'm not sure how to make the final jump Here is my work:

Can anyone point me in the right direction? Sorry if this is the wrong place.


texts: Can I use a variable resistor to control the heating of a heating element?

texts: I want to make something that heats up , can I use a variable resistor to control the temperature of the heating element since it is based on current.


texts: How to interpret derating charts for resistors

texts:
A data sheet for a 750 ohm 5W 5% resistor:

http://www.parts-express.com/pedocs/specs/xicon-cement-power-resistors-spec-sheet-specifications.pdf

What does this resistor's derating chart say about what happens above 150 degrees C? Undefined or just not guaranteed (but likely to follow its linear descent to 0% load at 275 degrees C)? Or something else?

[Edit: Corrected "F" to "C"]


texts: Can 220v touch shock an insulated person?

texts: In one-phase system, voltage is distributed over one phase while the other is called "neutral" and should be grounded, AFAIK. But, I think that I have experienced shock when touched one phase in 3-phase system, which does not even have a common ground. Is it charging-recharging of the the body capasistance? Is it less adverse than plugging a person between the phase and ground/neutral? If that is the case then why does the phase gives you the shock but ground does not? I see that birds are fine sitting on the power transmission lines, the high voltage one, I suppose.


texts: Lowering the voltage of a motorcycle regulator

texts:
I've recently replaced the voltage regulator on my TW125 and it seems the voltage is a bit high for the AGM 12V battery that's inside.

At the moment, I have north of 15V unloaded with just the full battery connected and 14,6-7V with the headlights on.

I suspect this is just due to production tolerances (it's probably a chinese-built regulator copy) but I'd like to keep my (new!) battery working and not gas it prematurely.

So I thought of putting a big power diode in the regulator to battery line but I'm afraid of frying it... Please note I didn't say I was putting a diode between the battery and the starter.
The common wisdom is to never run a motorcycle without the battery : is it to keep a load on the regulator? smooth the output? not completely clear depending on where you ask... But in any case, I'm afraid of a regulator malfunction because of that.

Am I in the clear or is there something I'm missing?


texts:
I've made a couple of PCBs which need the odd few 10 mil tracks, but are mostly 20/30 mil. Unfortunately the etching process isn't fantastic and there are numerous breaks in the traces, most of them small.

I've managed to convince solder lumps to go over the top of the smaller gaps, and have used components legs to bridge some of the larger ones. The solder lumps don't feel particularly reliable though, and there are some gaps which are too small and awkward to get a piece of wire across but too big to be bridged with just the iron.

Are there any standard ways to reliably fix up broken traces?

Update: Thanks for the suggestions everyone!

I found and tried out a silver conductive pen. As a first time user I found it difficult to dispense, and obviously I didn't use enough of it or mix it properly because it didn't even end up being conductive.

It seems like the main problem was that I was trying to use pieces of wire which are too short. I found some small gauge tinned wire and used longer lengths, running it over significant lengths of good track on either side of the fault. That makes it much easier to position, and you can tack them down one end at a time.


texts: Is there a non recursive formula for mixed resistors?

texts:
In equivalent resistors in multiple parallel resistors, like this

simulate this circuit – Schematic created using CircuitLab

I need a formula for the equivalent resistance for the whole circuit, but in a way that, this formula can be generalized for more than 5 nets.

I've done this:

2E is the equivalent resistor for the last net, because they're in serie. Then, the next is in parallel: 2ED/(2E+D) and so on... but it looks really awful when finally get to the first net.

Every time this expression keeps growing and growing, I would like a simple formula for this:

By using some power of 2 instead of the R's, I get those simplifications:

But, nothing simple to make a generalization for further terms.
NOTE: \$Req(i)\$ represents a circuit with \$i\$ nets on it.


texts: Impedance matching: L-network or micro strips?

texts:
I'm trying to embed a u-blox neo6m gps module to an stm32 controlled board. I'm planning to connect the module to an SMA connector and use a 50ohm antenna.

The datasheet of the neo6m states that the impedance of the connection between the module and the antenna must be 50ohm. The datasheet only contains info about the microstrip impedance matching method. However, all the schematics I found online implement LR networks to match the impedance. An example is below,

My questions are: Can I use any of the two methods to match the 50ohm impedance?

Also, if I used the L-network method, would there be anything specific(trace dimensions, planes under the network etc.) I'd need to do when routing the network to the antenna and the module?

Finally, does any of the two methods have advantages over the other? If so, what are they?


texts: What would be the best, cheapest, smallest way to power a Bluetooth bone conduction headset project?

texts:
Please, be forewarned, I'm an idiot when it comes to electronic builds. The last thing I soldered was a pick-up in a guitar kit I built, and the thing still isn't grounded right.
I'm trying to build a Bluetooth bone conduction headset, on the cheap, that will fit into a baseball hat discreetly, so the smaller the better.
The "headphones" will be two 20mm piezo transducers connected to a Bluetooth module.  This is what I was thinking.

I've seen a similar project (but with a regular, non-Bluetooth headphone connection) work at 5W, so that's my goal.
My initial idea was to power all of it using two CR2032 coin batteries and putting a linear regulator between them and the BT module, but am being told that's going to be underpowered.
Is there a power solution strong and small enough and if so, what would that be?
Also, would it need a voltage regulator, and if so, what kind?
If you could offer any help on components and such, that would be amazing too.


texts:
I have heard anecdotally that a square HF RFID antenna performs worse than a circular one, but I am struggling to find any articles on why this is the case.

I assume there is a charge concentration at a sharp corner, as electric charges accumulate at sharp points. Is the result similar to the Skin effect, in that it artificially increases resistance, making the antenna more lossy? If so, is there a way to calculate the impact of this? I can calculate the increase in resistance due to the skin effect (which can be significant in RFID antenna design), so it seems like it should be possible to calculate the effect of this too, but none of the papers I have read on the topic of HF antennas cover this.

There seem to be a lot of RFID tags which are rectangular, with the corners being rounded with a fairly small bend radius (i.e. not far from a right angle).


texts:
If we have for example 3x16bit shift registers connected in series, can we clock 48 bits of data through one shift register at once and then latch all of them to output data registers, LATCH CLK and OE pins are shared.

If my thinking is not right, please explain how data clock works when shift registers are in series.


texts: What is a good low cost antenna design for a low cost 433 MHz transceiver?

texts:
I am designing a low-cost ($5) transceiver based remote system, that uses a CC110L or rfm22b type transceiver (i.e. low cost).  What are some cost-effective, yet high performance antenna options?  My goal here is to maximize range (minimize antenna losses), and range is more important than bit-rate.

Goals:

Antenna efficiency of >70%, larger is better
Omnidirectional (as much as possible)
Space constraints: must fit within 25cm x 150cm area

The options I'm considering are:

A simple wire seems to be the easiest, but performance might not be good.
An off-the-shelf PCB-mount antenna (SMD chip, helix, etc)
PCB trace antenna

a. whip design

b. helix

c. dipole

d. others?

The preferred option here is PCB trace antenna due to cost reasons...so kind of focusing on that.

Using a standard FR-4 2-layer standard-spec PCB, is it possible to design a high-performing PCB trace antenna?

What type of PCB trace antennas would be the best and why?  Helical?  Whip?  Others?  Are there any good reference designs or guidelines to design this type of 433MHz PCB trace antenna?


texts: Buzzing, quality loss. Relay control system

texts:
I have been working on a home project and got a bit disappointed now..
It seems that the sound control I have been working on looses quality or something else is affecting the sound quality with a very annoying buzz.

The buzz seems to be influenced by the colours on the screen on my main machine, ex: when gaming, if I turn and look up in the sky the screen gets brighter therefore the buzz intensifies, if I turn to a dark wall or so the buzz diminishes.

This is a home made control system, here are some of the details:

The audio output of my main machine (Jack) goes into the first - Relay (the cable is stripped and the wires are connected directly into the relay's contacts); as I have knowledge and experience working in electricity I made sure each wire makes proper contact with each contact from the Relay
From the Relay1 the Normally Closed contact (out) goes to Relay2 common contact (in)
and from Relay2 the NC contact (out) goes to Relay3 common contact (in)
The Relay3's NC contact (out) is the main and most used output, which is where the main Audio System is connected
All Grounds are connected together
Each cable is no longer than 2m
The Audio output panel is actually the end of each Jack cable (female) (as in the image)
Each Relay deals with only one cable (ex: R - right) then it goes to the next one
Longest distance between cables is 2m + 2m + ~0.5m = max ~5m

The buzz is notable in the Audio System as it is in the Headphones (in the Headphones seems to be a bit more intense).

On low volume the buzz is almost not present.

(I CAN'T POST MORE THAN 2 LINKS)

Please search on Amazon these product codes:

cables: B007OH6QLY
relay module: B0148BMACW

I do not have knowledge in audio performance or issues, just basics.

Any help, ideas or links are much appreciated.

Would this amplifier solve my problem? (I intend to use only: input (from main machine) -> amplify -> output to the Relay)

amplifier: B000KIPT30

Devices:

Relay diagram:


texts: PCB stackup for capacitive buttons, LEDs and other components

texts:
The design I am working on has about 30 capacitive buttons, LEDs for back-lighting, about 8-10 ICs (capsense controllers, LED drivers, MCU, etc), many passive components and coin cell batteries.
I am using Cypress MBR3 Capsense controllers for this application. Board size is such that the whole top layer is covered with capacitive buttons. Buttons pitch is 20mm.

I have two questions:

PCB stackup
I asked this question on Cypress forums as well and got this recommendation.

  4-Layer PCB:

  Place the sensors on the top layer of the PCB.
  Route the sensor traces in the layer-2.
  Place a hatch fill of 7-mil trace and 70-mil spacing and connect it to ground in layer-3.
  Place components in the bottom layer, The unoccupied areas can be filled with a hatch copper fill of 7-mil trace and 70-mil spacing and should be connected to ground.

The problem with this stackup is that I only get one layer for components and digital traces but I need at least two layers for digital signals.

So should I choose a six layer stackup?  If yes, what should be the copper, prepreg and core configuration?

Can I make layer-3 and layer-4 Power planes in a six layer stackup? For normal six-layer PCBs, usually layer-2 and layer-5 are power planes but here I need sensor traces on layer-2. One other requirement for capacitive sensor PCBs is that the spacing between sensor traces (layer-2) and ground plane (layer-3) should be larger to minimize parasitic capacitance.

SMD LEDs on top layer
Most common recommendation for back-lighting in such applications is to drill a hole at the center of button electrode and place back-firing LEDs at the bottom. But since I have a lot of components to place, I can't have a 2-3mm hole every 20mm.

So can I place surface mount LEDs (say, 0603) on top layer at the centers of electrodes?
I have never seen such example in manufacturers' layout guidelines.

Edit:

Can I go with this odd 5-layer stack-up? It satisfies the CapSense recommendations and gives me two layers for digital signals :)


texts: In the datasheet for the LM336-5.0 5V reference it uses a 5k resistor fed by 10V. Am I correct in saying that I can give it 12V and it wouldn't matter as long as the current is limited to less than 10mA? It's absolute maximum forward current is 10mA. It's easier for me to feed it 12V because of how I laid out my board.


texts: Do DeWalt charging safety features reside in a dewalt charger or a dewalt battery?

texts:
This is a cordless battery of the the type I mean, a DeWalt flexvolt:
https://images.app.goo.gl/zKHBsvBnT4ViMJL56

This is the kind of charger I'm talking about:
https://images.app.goo.gl/FvzAZAF2X31BXwEA6

I'm aware that there are safeguards to stop the battery overcharging and catching fire, but I don't know what they are. Other than the fan, how does it work? Does the battery refuse further charging once it's full, or does the charger detect when the battery is full and cut off power?

I'm asking because I want to charge the battery with a Turnigy or similar charger like this one here, but I don't want to die in a fire.


texts: Using pulsed power source and capacitors for driving solenoids

texts:
I'm converting a reed organ to be MIDI controlled, and I'm using solenoids to pull down on the keys. There's 88 solenoids total, and I'm going to be powering it with 2x 40A 12V power supplies.

The solenoid control circuit I'm using is this:

My problem is that each solenoid draws around 1.3A @ 12V. This results in very hot solenoids after less than a minute of being held down.

There are clever solenoid driver circuits that use a capacitor to give the solenoid the full power at first, then once the capacitor is charged (therefore no longer conducting DC power), power flows through a resistor that limits the current. However, this system needs time for the capacitor to discharge before being triggered again, and the capacitor has to be of a large value which would not work in this application well (my solenoid driver board design is dense enough at the moment... I want my component count to stay as low as possible). There are more complex circuits that get around the capacitor discharge problem using transistors and even more components (how they work is besides the point here) but again, I don't want many more components since every component gets multiplied by 88 circuits.

However, I think I have an idea for a solution, but I don't know if it would work. My idea is to PWM the raw power going into (all of) the existing circuits and then adding a single capacitor in parallel with my solenoid, like this:

Thus, when the MOSFET was triggered, this capacitor would get charged to 12V before discharging into the solenoid, making it fire. Now that the solenoid is down, the PWM power (lets say its 50% duty cycle, therefore equal to 6V) can keep it held down.

Is this idea completely flawed? If it is, any ideas? Thanks.


texts: Is there a capacitance between the Earth and the Moon, and if there was enough potential difference, could a discharge strike occur?


texts: Will this circuit work ? 100 Leds project

texts:
I am new to electronics. I have been given 100 Leds project by my teacher at college . Can anyone here validate this circuit.
Thanks in advance.


texts:
So, I was trying to create an FSM for my module which supposed to control five sensors. I thought I did it, but when I synthesized it, I saw that the code is synthesized as bunch of buffers and nothing else.

I think I do not understand what FSM can or can't do but I really couldn't find the problem.

 module RX_to_TX(
    input logic i_clk, i_reset,
    input logic[7:0] i_from_Rx ,
    input logic[7:0] i_Dev1 , i_distance_Dev1,
    input logic[7:0] i_Dev2 , i_distance_Dev2,
    input logic[7:0] i_Dev3 , i_distance_Dev3,
    input logic[7:0] i_Dev4 , i_distance_Dev4,
    input logic[7:0] i_Dev5 , i_distance_Dev5,
    output logic[7:0] o_Tx ,
    output logic o_Tx_DV
    );
    logic[7:0] next_Tx;
    logic[1:0] curState , next_State , DistanceState , StopState;
    always_ff @(posedge i_clk )
        begin
            if ( i_reset == 1'b1)
                begin
                    o_Tx <= 0;
                    curState <= DistanceState;
                end
            else
                begin
                    o_Tx <= next_Tx;
                    curState <= next_State;
                end

        end

     always_comb
        begin
             next_Tx = o_Tx;
             case(curState)
                DistanceState:
                    begin
                           if( i_Dev1 == i_from_Rx )
                                o_Tx = i_distance_Dev1;
                           if( i_Dev2 == i_from_Rx )
                                o_Tx = i_distance_Dev2;
                            if( i_Dev3 == i_from_Rx)
                                o_Tx = i_distance_Dev3;
                            if( i_Dev4 == i_from_Rx )
                                o_Tx = i_distance_Dev4;
                            if (i_Dev5 == i_from_Rx)
                                o_Tx = i_distance_Dev5;
                        next_State = StopState;
                        o_Tx_DV = 1'b1;
                    end
              StopState:
                begin
                    o_Tx = 8'b11111111;
                    o_Tx_DV = 1'b0;
                end
              endcase

        end
endmodule


texts: Optoisolate two ICs sharing same power supply

texts:
I have two ICs. The former acts like an ADC, measuring the voltage in a power outlet and transmitting the result to the last. Both ICs requires 5 Volts to work.

I want to opto-isolate the channel between the two ICs to protect the last IC against peaks in the grid that the former IC is measuring.

Below there is a VERY simplified version of the circuit:

The power supply is the classic one (voltage transformer, regulator, capacitors, etc) and the input voltage is the same as the power line: 220 Volts RMS. The power line has a transformer too (not shown).

Is safe to both ICs share the same power supply? It is possible that in presence of a very large noise, the first IC affects  the second in that common point?

If it is wrong... how to accomplish the isolation?

EDIT
IC1's datasheet

IC1 is a specific purpose IC to measure voltage (and current) from the power grid. The IC's datasheet has a example circuit that I pretend to use.

IC2 is a microcontroller that will receive the information from IC1.

The example circuit

Although the circuit does not use a transformer and voltage regulator, I intend to use them to power the IC.

The datasheet recommends to isolate the channel between ICs.

My focus right now is discover if it is possible to use the same supply for both ICs and yet opto-isolate this channel between them.


texts: How can one determine the pulse width of a servo motor?

texts:
I have recently started to fiddle with an Arduino UNO R3 kit I bought some time ago, and I got so hyped that I have decided to build a robotic arm.
This robotic arm which I found on Thingiverse requires to use 4 servo motors. I got some cheap SG90 motors off amazon. Since these servos require a rather large current to run, I am going to use an external power supply to power them at the same time, and a PCA9685 16-channels servo controller.
Now... I have come to the understanding that the position of a servo motor horn can be chosen using pulse width modulation (PWM) at 50Hz, with 1ms pulse widths corresponding to 0° and 2ms to 180°, according to the data sheet of my SG90 servo.
However, I have seen that since my motor is rather cheap, it could be that the the servo positions could correspond to a slightly different pulse widths from the data sheet.
How can I determine for certain which pulse width corresponds to 0° and 180° using Arduino?
Also, if I were to send a pulse width that's lower than the one corresponding to 0° to the servo, would it damage the motor?
Thank you very much!


texts:
I'm thinking about selling a small batch of a simple gadget that would have some electronics inside.

If I want to use an online shop and sell it worldwide, what are the certifications and licenses to be aware of?

If I qualify something for the UE, can it be sold to the USA?


texts: Verilog: Conditionally setting single bits to high-Z in vector

texts:
I have written a single-pin GPIO module for my project, and it is working fine. A simplified version looks like this:

module gpio_port(
    input clk,
    input reset,
    ...
    inout gpio_pin
);

reg read_data;
reg write_data;
reg pin_direction;  // 1: Write, 0: Read

// This line is problematic.
assign gpio_pin = pin_direction == 1'b1 ? write_data : 1'bZ;

always @(posedge clk or negedge reset) begin
    // ...
    read_data <= gpio_pin;
    write_data <= ...
end

I now want to extend this concept to a full 16-bit GPIO-port. So when I tried extending it, I came across a problem: In the version with only a single pin, the direction bit is used to determine whether the write bit should be put onto the inout wire, or if it should be driven high-Z.
But I can't figure out, in the 16-bit wide example, how to selectively set the single bits in the inout pin vector to high-Z or the the bit in the write register.

module gpio_port(
    input clk,
    input reset,
    ...
    inout [15:0] gpio_pin
);

reg [15:0] read_data;
reg [15:0] write_data;
reg [15:0] pin_direction;   // 1: Write, 0: Read

// This line is problematic.
assign gpio_pin = ???

My problem is that I am pretty new to Verilog, so I don't even know what to google for here, so I am sorry if this question is super trivial. I understand that I could just use a single direction flag, but I would like the pins to be individually definable as either input or output.

What I have tried:

I am currently using the following solution, which is super hacky:

assign gpio_pins[0] = (pin_direction[0] == 1'b1) ? write_data[0] : 1'bZ;
assign gpio_pins[1] = (pin_direction[1] == 1'b1) ? write_data[1] : 1'bZ;
assign gpio_pins[2] = (pin_direction[2] == 1'b1) ? write_data[2] : 1'bZ;
// ... and on and on ..


texts:
I have been looking at ceiling LEDs for a while; I am owner-building a house ATM, and "wondered" how I can control the ceiling LEDs -- most 9-12W, probably 30-ish of them; in 3-4 different zones.
Smaller rooms (3 x 3 m2) may have two zones and 4-6 LED lights.
Ideally say if a square room has 4, each should be able to be controlled individually (always on|off, dim).

The "wondering" part is the approach, given these constraints:

while I like DIY wherever possible; using Arduinos to do all
sorts of tasks; integrated with openHAB, I am conscious that 230V
needs to be wired by a licensed electrician (law in Australia; DIY =
illegal). This implies to me (I could be wrong) that I should use
standard LED bulb + driver + plug combinations; dimmable. Reasoning:
because the LEDs have a plug, the whole set can be replaced in case
of a fault (or desire to change any LED parameter, colour, wattage,
angle, etc.) by a layman.
If I were to control the LED bulbs directly (on|off, dim), I
would need a driver to supply the right V and constant A these LEDs
are running on. They are presumably different for each wattage LED?!
If the bulb has to be replaced, and say, the Wattage no longer
exists, the driver would either need to be changed too or
reconfigured to suit the new LED.
would it then be best to wire each LED to a central location,
which gives me the benefit of grouping the lights as I need them;
planning and real world might change, hence, the need to be able to
reconfigure easily.
Assuming I install standard sets (LED, driver, plug) would it be
best to build triac circuitry to control each LED fixture?
(Ultimately controlled by some sort of micro-controller, e.g Arduino.
If so, which is the best way to do this?

With the constraints stated above, is it the best approach to use a multi-channel triac set-up to dim each standard LED fixture?

I looked at say 9W LEDs, they come with a driver; I could build my own driver to control this LED, but then I assume I need different drivers for a different wattage LED?!
The solution should be also cost-effective.

Any hints, thoughts, questions and feedback would be much appreciated.


texts: Calculating H-Bridge without motor specifications

texts:
I am currently calculating elements for an H-Bridge for brushed dc motor and PWM speed control that operates on 6V and maximum current of 2A. However I want it to work with different 6V brushed DC motors, depending on its use and here comes my issue:

How do I calculate decoupling capacitors, motor terminal capacitors and working frequency when I have no specific Lm and Rm of the motor itself?


texts:
I am building an electrified "fence" of sorts to keep slugs out of my raised garden beds. The "fence" consists of two 18ga galvanized steel wires, stapled to wood and connected to a 9V battery. The circuit is open until the slug touches both wires, at which point he completes the circuit and gets a little shock. This works great in small scale tests, but my garden bed as a circumference of 30' (9.1 meters) and I'm concerned that a little 9V battery will have a hard time working at full power over that distance of wire.

Because I don't really know how resistance works (I just know how to get my volt meter to measure resistance so that I can make sure my solders are done well) I'm not sure how to do the math to see what kind of a drop in voltage I'm going to get.

If someone can answer this question directly, great. But I'd also love a website that I can use to help learn about this stuff.

How can I find out the resistance of this wire? (Doesn't resistance change with voltage/amperage?)
How does that resistance compound over distance?
Are there simple parts (transistors, resistors, whatever) that I can go get at Radio Shack or the like that will help get over this resistance or should I just wire a second 9V battery into the system?

Bonus question: While 9V is a very light charge, if you imagine I'm building a much more powerful electric fence, what would I have to do to protect the battery if the circuit were completed for an extended period of time? (A slug dies on the line or something.) I wouldn't want some grass completing the circuit and having my battery explode.


texts:
I know this is an easy question but for some reason I'm not getting the correct answer.
The question is:

The current through a \$100 \mu\text{F}\$ capacitor is $$i(t)=50\sin(120\pi t)\text{ mA}$$

Calculate the voltage across it at \$t=1\text{ ms}\$ and \$t=5\text{ ms}\$.

Assume \$v(0)=0\$.

So, $$v(t)=1/C \int i(t)dt + V(t_0)$$

Isn't the integral of \$i(t)\$ in this case equal to \$50(-\cos120\pi \times t/120\pi)\$?

I've been stuck on this question for like 20 minutes. I could use some help. Thanks.

The answers are \$V(1\text{ ms})= -93.14\text{ V}\$ and \$V(5\text{ ms})= -1.74\text{ V}\$


texts: How do I calculate voltage using the complete diode method?

texts:
Doing extra examples for a electronics class, came across a section uses the Complete Diode Model (We haven't covered it in class in much detail, only the definition).

The question is: Determine the voltage across the diode using the complete diode model with r'd (forward dynamic resistance) = 10 ohms and r'R (internal reverse resistance) = 100 Mega-ohms.

simulate this circuit – Schematic created using CircuitLab

I know I need to determine the equivalent resistance circuit, and that the voltage splits 50/50 after the R2 into R3 and R4 according to the voltage division principle.

I saw from another question that one can use the Superposition Principle, but that example has 2 DC sources. I cannot see how this method is applicable to an example with only one DC source. Could someone maybe explain to me how to approach this question? I want to understand, not merely copy what someone else has done.

Here is the link to the other question: Diode in Parallel with Two DC Sources


texts: Why do the Wh and mAh ratings of a USB battery pack appear to be inconsistent?

texts:
I received a battery pack that I had ordered today, one of those ones that provide 5 volts using a USB connector, and plug into a USB socket to charge.

I noticed that on the box, it said it was rated for 6000 mAh.
The battery itself said 22.2 Wh, and that the output voltage was 5V DC.
Converting that back to mAh was: (22.2 / 5) x 1000 = 4,400 mAh.  About 75% of the 6,000 mAh printed on the box!

Feeling shortchanged, I picked up another (Li-Polimer) battery pack from a different manufacturer I had lying around and saw it's capacity was: 15 Wh, 4,000 mAh.  The voltage again being 5 volts.
Converting the Wh reading to mAh was: (15.0 / 5) * 1000 = 3,000 mAh (about 75% of the mAh reading).

My guess is that as the batteries deplete, like the lead-acid batteries of old, the voltage decreases.  So if the voltage dropped to 3 volts, it would still deliver the milliamps for the mAh reading, but the Wh for the watt hour reading would be reduced.

I suppose this means that the useful capacity of the battery (the period of time where it actually delivers 5 volts) is even less... perhaps only just half of the mAh rating?


texts: Can electric circuit simulation software simulate capacitor charging process

texts:
I would like to simulate process of capacitor charging. Basically I would like to see current drop as capacitor gets charged. I used multisim.com. Here is me circuit.

Unfortunately, it only shows constant current of 12 pA. Is 12pA initial charging current or average?
Is this normal or am I am missing something?


texts: Automatic Capacitor Charge/Discharge Circuit

texts:
I am still somewhat of a beginner in electronics, so please go easy on me, but here is a situation I have encountered, and hopefully some of you have as well.

I have a voltage source of 5volts, but extremely low current. This power source is connected to a large capacitor (in my case 3F 5.5V). After a period of time, the capacitor does eventually charge up to 5V as expected, this is all fine and dandy, but now I need to use this energy. The capacitor's load is a small, 500ma DC-DC boost converter, to utilize most of the capacitors charge, but it only works down to a minimum of 0.7 Volts.

So here is what I am looking to do, build a circuit that allows the capacitor to discharge only once it's reached 5V (or 4.5V to leave some wiggle room), and stops discharging once it drops below 1V or so. Only to start discharging again once the cap reaches its 5V threshold.

It should also be said that efficiency is very important here, as power is extremely limited for this circuit. The power source is a nuclear device capable of producing small amounts of power, unfortunately I am unable to provide exact specifications, other that that it is capable of powering the circuit enough to slowly recharge the storage capacitors.

I apologize if I am not being clear, feel free to ask for more details. :)

EDIT:
Here is a schematic of my circuit, built only by memory so lets hope its accurate xD

MAX756 Datasheet

simulate this circuit – Schematic created using CircuitLab


texts: Headphones with dual jack, reduced volume

texts:
I recently built a pair of headphones and added an audio jack input to both the cans, for convenience of connecting.

That would also serve another purpose of letting my girlfriend hear the same music without me having to take off the headphone.

But the problem I noticed is that the volume gets reduced. Now this is primarily because its getting connected in parallel, so is there any way to subdue the problem.

Thanks.


texts: Electronic Circuit with Opamp and Transistor to pull down a reference voltage via a diode. (Voltage Limiting)

texts:
I have a circuit which I have designed to pull down a voltage via sinking current into the opamp output. When the source signal is of higher output impedance this works fine, but when the source signal impedance is lower the minimum voltage which this signal can be pulled down to is affected by the opamp output impedance. This source signal is supplied at max 20mA.

In the circuit the opamp will pull the input voltage (VF3) down via the diode to the voltage set on VG2, but can not push the voltage above the input voltage due the diode being reversed biased.

Does someone maybe have a suggestion as to how this could be improved via adding a transistor on the opamp output? E.g have the transistor base connected to the opamp output and the collector connected to the diode negative? I hope to be able to pull this voltage down to a much lower value, ideally rail to rail.

Thanks in advance!


texts: How to power a high current / low voltage circuit through wall outlets?

texts:
I'm trying to wrap my head around this basic problem but I'm stuck here: I'm using 4 of these LED strips and I'm not sure how to safely power them.

They are rated at 18W/M, so 4 strips * 5m * 18W = 360W with an input voltage of 5VDC, meaning they would draw 72A if they all were lit at the same time. Let's say I only turn on 75% of them at once, the circuit would then draw 54A.

My understanding of wall outlets is probably wrong, but I read that they are rated at 15 or 20A. Does that mean that I cannot use the same outlet to power this circuit? If not, can I use  outlets on the same circuit or will I have to use separate lines from the circuit breaker? Or any other solution that I'm not aware of?

Optional question: Power converters that can output that much current are usually big, so I'm considering setting up 4 power converters in parallel all coming from the same power supply, is there any other potential issue I should be aware of if I choose this route?


texts: How to calculate 4 MHz crystal trace width on PCB?

texts: I have no idea about how to draw crystal trace on pcb. I have stm32f0 chip and 4 MHz external crystal and 15 pF capacitor. Can you help me that how to get suitable trace for crystal trace? Should I use gnd trace around them?


texts: How to design a crystal radio receiver on a bread board?

texts:
Is it possible to design this circuit of crystal radio reciever on bread board?
After tuning the LC tank circuit to the required frequency the output voltage from the parallel LC circuit will be fed to the diode and ear phones.
Can this circuit be made as it is on the bread board so that the output voltage is enough to drive the diode and earphones?
It will also be appreciated if one likes to share the steps it takes to design that type of radio on the bread board.


texts: Battery directly connected to input of unpowered opamp. Will the input current drain the battery?

texts:
Is it possible to hardwire battery to opamp input, considering that most of the time normal power on opamp will be off ?
Battery positive wire is connected to non-inverting input of opamp workiing as a buffer (inverting input is connected to output). In opamp specs the input current is in picoampere range, but is it true for the unpowered state ?

Thank you


texts: Why is the order of these serial components changing the current flowing? (Keithley 236)

texts:
I have an electronics setup I'm using for research purposes. I'm having some strange behavior so I've tried to boil it down to the simplest working example. Most basically, a voltage is being applied to a device under test (DUT), which in this case is a 10kOhm resistor.

More specifically, I have two Source Measure Units (SMUs), both Keithley 236s. They're both in voltage source/current measure mode, but one of them (SMU1) actually sources a bias and the other (SMU2) just measures the current going through the circuit serially. I do this (rather than just recording the current SMU1 is supplying) because for my real-use case, the DC bias from SMU1 is going to be mixed with another signal by an op-amp, so the current SMU1 is supplying would not actually be the current going through the sample. SMU2 is set up as described on page 1-4 of the manual linked above, in "Measure (current) only" mode. It should basically function exactly as a simple ammeter you can stick serially into the circuit somewhere.

This is fine, but I'm finding a strange problem. If I test two configurations of this circuit at SMU1=0V:

C1:

SMU1---DUT---SMU2---GND

and C2:

SMU1---SMU2---DUT---GND

I get slightly different behavior from the current read by SMU2. C1 gives a fluctuation of +-0.05 microamps, while C2 gives a steady current of ~0.03 uA, with smaller fluctuations around it, but definitely a steady 0.03 uA baseline current.

I'm not exactly worried that I'm not getting perfectly 0 current, because the manual says that in the voltage source range (11V) for the 236 I'm using, it has a 1mV resolution, so if it's a full 1mV across the 10kOhm resistor, that gives us fluctuations/an offset as large as 0.1 uA.

However, what I'm unsure of is, why are the two configurations giving different currents? (one a reasonable fluctuation, the other a strange systemic offset


texts:
I am trying to make a capacitor out of a CNT ink as a touch pad.  I dye two strips of fabric which each have an end resistance of ~0.5-1kohm.  I have tried various dielectrics and separation distances.  When the separations distance is very close (using paper or thin plastic as a dielectric), the fabric conducts and acts as a resistor (I can tell because when measuring voltage, the voltage deceases and does not recover when touched).  Yet when the separation distance is increased, no voltage change is detected when the capacitor is pressed down.

Any idea why this is happening? Why doesn't this act as a capacitor?

I should also mention that no capacitance readings appear in either case.  I am just confused because this should work in theory.


texts: Why does a resistor not affect Charge on capacitor

texts:
simulate this circuit – Schematic created using CircuitLab

For a circuit like the above - why is the charge on the Capacitor right after the battery is added Capacitance * Voltage of the battery and not Capacitance * (Voltage of Battery - Voltage Drop due to Resistor)?

Isn't the potential difference on the Capacitor the Battery voltage - the voltage drop due to R1?

I'm doing book problems and it has a circuit set up this way and solutions state that the charge on the upper plate of this capacitor after contact with the battery is 1uF * 9V = 9uC.

Thanks for your time.


texts: How to determine transistor specification range for voltage and current (in relation to design requirements)

texts:
Attached is my current circuit for using a 5V logic output device to control 24V  going to a load with max current draw of 14mA.  (Ignore the name for transistor Q1, that is just a random NPN BJT).

The max current draw of the logic source is 300mA (a Velocio e-1450 PLC).

I am new to transistor design and selection, and I would like to know what you consider when choosing a transistor - what range of values do you allow for a given circuit?  Should the base voltage be exactly what you expect it to be? (5V rating for 5V logic control, etc.)

Also, are the resistor values relatively ok for the desired output?  For R1, I took (24V - 0.3V) / 14mA ~= 1.69 kOhm.

Thanks for your input.

EDIT

To sum it all up, is this the right design to use 5V logic to power a solenoid (J1) with 24V?  Forgetting the resistors and transistor values.

1)  The 5V logic output (V1) from the Velocio e-1450 can provide up to 300mA

2)  The solenoid (J1) draws max 14mA.


texts: Using wxMaxima to obtain a transfer function from T-twin filter & op amp

texts:
I'm trying to get the transfer function from this circuit using wxMaxima

So first using the ideal op amp model I know Vx = Vy and I can know Vy from that voltage divider from Vo

Now I solve this system

From here I'm not pretty sure what should I do next.

I've tried some solutions without success. Like this

Anyone can give me a hint about what to do next? I'm not pretty familiar with Maxima nor op amps but I guess I have the right idea about this.

Thanks in advance for any suggestion and your time reading this.


texts: Why are all my motors and transformers failing at this specific location?

texts:
At my job there is a vacuum oven.

There is a 50 hp, enclosed cooling fan. that circulates N2 gas upon quench, the design of the unit runs 480 volts through a reduction transformer to 230 volts. This runs the 50 hp motor at 230 volts (when it burned out).

The motor was replaced with a good motor, the transformer has been tested to be good also.

The 480 volt building power is running many motors without issue. However when the transformer is hooked up to the 480 power to run the motor at 230 volts the motor free spins at 470 amps per leg. 200 volt draw down.

The 480 volts input power goes to 457 volts and the amps per leg is 244 amps on two legs and 222 on the third. the motor and transformer has been tested run at a different location to run at less the 10 amps free spin per leg..normal.

On that motor. if the motor is not hooked up to the transformer it has a normal 235 volt output. three pole output no draw as normal.

if any 3 ph. motor is hooked up. has the same issue very high amp draw for no reason.

(2) transformers were put to the same test both did the same high amp draw on any motor hooked up.

What would cause this issue?

From the input building power from the street is 600 amp at 3ph wye, three pole transformers.

If a motor is hooked up without running through a reduction transformer it runs fine. Running through a transformer it goes to hell. Only in this location!?

I have never seen this before 480 building power seem fine if it goes through a 3 ph transformer to run a motor there is a very high draw on the motor a free run 5 hp. ran at 109 amps. (very loud buss noise). hook up without a transformer run at 3 amps. fine. is it magic 3ph in should be 3 ph out on a transformer from street power. not so at this location.

This is very abnormal. I have no answer.

EDIT: 7/8/19
Project has been put on hold, no longer working on it. No answer though, still something unique and strange about this situation. Thank you all for contributing this will always be stuck in my head as time goes on, but i cant do anything about it now.


texts: How can I reduce parasitic inductance in flyback diode?

texts:
I have built a simple RL circuit with a MOSFET switch and a flyback diode, as shown, which behaves perfectly in a Spice model, but which exhibits what appears to be a fairly large parasitic inductance in parallel with the main circuit (seemingly in the diode) which causes large voltage oscillations at the MOSFET drain and in the (less than ideal) voltage source (most images are for V3 = 1, with inductance closer to 1.5m and resistance closer to .3 in the test circuit).

The voltage spikes at the drain look like this. I have included some images of the physical circuit as well. At 1V V3, the spikes can reach 60 or 70V at the drain, and they pull the power supply voltage up and down with them. The power leads from the supply to the circuit are quite large, but from my Spice simulation, I do not think that can be responsible for the observed behavior, which seems to be in the diode. If I model the circuit with a small (20uH) inductor in series with the diode, I get behavior which looks extremely similar (although not exact, but that may just depend on the exact inductance value).

The MOSFET in question is an IXFB210N30P3 and the diode is a STPS200170TV1 Schottky diode. Because I depend on the exact current values, I cannot afford to add a large snubber across the FET that could "short" some of the current, and anything smaller seems to either have very little effect or to dissipate too much power. I just don't understand where this inductance is coming from, and how I can address it in practice.


texts:
I have a 3-phase motor h-bridge.  The inputs to the motor require 3 different phases, +, -, and 0.  I've got the circuit below that I'm using:

The problem is that there are three states required:

Q1 = Q2 = Low for 0
Q1 = High and Q2 = Low for +
Q1 = Low  and Q2 = High for -

And typical logic is binary.  However, I would expect a High-Z state (meaning no current would be flowing), to be equivalent to "off" for both Q1 and Q2, since these are BJTs.  Is this something that can be depended on?


texts:
I have a problem using ESP8266-01 with a relay. I would like to control a 110 V light using a 5 V relay.
Here is the circuit I made:

I am sure that the code is correct, because when the relay's pins are not connected to 110 V, everything works just fine. I know that because I can hear relay's contacts "click".

The problem comes when I connect 110 V lines to the relay. It works fine until I get a boot message. In general, a boot(3,6) message, and everything is restarted.

I think the problem is that I use GPIO 0 to control the system. I guess some current flows into the GPIO 0 pin and makes the ESP8266-01 go on boot mode (that is why I put D2), but I am not sure.

I really want to use GPIO 0 pin because it is smaller than node MCU.

Any ideas?


texts: Why is the capacitance of a short infinite?

texts: The voltage across a short is 0. It also does not store any charge. So the capacitance of a short is 0/0. However, I am told the capacitance of a short is infinite. How can this be?


texts: Zero-crossing in AC with DC offset signal

texts:
Introduction

I have a project about measuring the voltage, current and power factor of an electrical system. I had designed a system that allows the microcontroller to measure the peak of an AC with DC offset signal. The whole system relies on making an ADC conversion right on the middle of the half positive cycle of the signal. I have two AC with DC offset signals, one that comes from a current transformer and other from a voltage transformer. When I finally got both ADC measurements I can calculate how much is the actual voltage, current flowing through the system, and the power factor between signals.

This is my circuit schematic. It’s a bit large so you might want to expand it:

Explanation of the circuit:

It has a sort of “Load selector” because since the current transformer is a current supply I can change the voltage range by changing the load resistor. (I’m using a 120 ohm for measuring >15 A and 1 kohm for measuring <1 A)

I’ve simulated the whole circuit on VSM Proteus and the results were flawless. I can correctly measure voltage, current and power factor with my microcontroller.

The problem

The problem comes with the real circuit. I had designed and built the PCB for the shown circuit. The resulting output signals were expected. The zero-crossing signal from the current and voltage transformers had a 10 ms HIGH and 10 ms LOW logic levels, this means a 20 ms period signal, thus 50 Hz signal; seems PERFECT! But, when I tried to measure the middle of the positive half cycle the results were not as expected, on the other hand the results on the simulated circuit were ideal, steady output numbers. On the real circuit the ADC measurements were “oscillating”, this might imply that the middle of the zero-crossing signal doesn’t point to the peak of the original signal.

Simulated results:

2.869-1.696-2.874-2.874-2.874-2.874-2.874-2.874-2.874-2.874-1.701-2.879-2.879-2.879-2.879-2.879-2.874-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-1.701-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-1.706-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879-2.879

Real results:

2.801-1.740-2.400-3.182-2.278-1.686-2.776-3.089-1.940-2.053-3.079-2.581-1.730- 2.527-3.196-2.136-1.706-2.933-2.898-2.019-2.248-3.177-2.351-1.691-2.674-3.167-2.297-1.887-  3.065-2.708-1.716-2.444-3.148-2.239-1.696-2.835-3.040-1.926-2.414-3.099-2.522-1.691-2.615- 3.187-2.107-1.730-2.957-2.889-1.799-2.283-3.148-2.341-1.691-2.698-3.143-2.058-1.916-3.030-  2.796-1.711-2.468-3.177-2.239-1.716-2.845-3.025-1.916-2.107-3.104-2.498-1.691-2.576-3.172

Thanks for reading, any hint on this would help me! If you need more information just ask. P.S: I'm not a native speaker so feel free to correct any grammar errors.


texts: Thermocouple + Instrumentation amplifier. Does it make sense to have one input grounded?

texts:
I am trying to read a thermocouple (of an existing assembly) and half way into the project I noticed that one pin is grounded (protective earth). Makes no sense to use an inamp this way, does it? Instead I could use a very low pA bias current single op-amp in negative feedback configuration ...

Or are there any problems with that? I could also try to create a floating ground for the inamp or isolate the heater assembly from PE ...


texts: Tests to verify complete functionality of a PCB

texts:
What tests can be carried out on a power supply PCB to verify its complete functionality?

For example:-

I have designed a custom board using the JCM3012S3V. It takes 12V input and produces 3.3V.

What tests does this particular board need other than basic power on and verifying the output voltage with respect to input voltage?

The designed board may be working fine, I don't want this board to impact the working of other boards.

I am talking about tests like:

Measuring the noise generated from the board

What other tests does a board need to pass?


texts: May I ask about feasibility of the following circuit?

texts: Generally, I learned about one diode rectifier and bridge diode (4 diodes) rectifier for making DC signal. Both outputs' maximal value is maximal positive value of input source (using ideal diode). However, if I construct the following circuit, we can get doubled maximal positive DC voltage. May the following circuit operate well?


texts: How to utilize HDMI port on FPGA (basic)

texts:
Two questions.

I have a Xilinx Spartan 6 FPGA which only has HDMI ins and outs. Is there some sort of guide or pre-written code that I can use to start sending images to the screen? I have no idea how to begin and I have not been able to find resources.

Second, the reason I'm doing this is because I want to use and modify Atari 2600 code a guy implemented on a Spartan 3E with VGA. Is it even possible to easily adapt the video aspect of my project?

Any help, resources, or advice would be greatly appreciated!


texts: Fitting USB Data in Cat5 Cable with External Power

texts:
I have a camera system at home with a DVR, which connects to a VGA monitor and mouse with which you can read and edit its settings (the cameras can be accessed over the Internet). I've been trying to move the monitor out of the closet it was in before (that's where the DVR is) to a more convenient spot, on a desk in my room. As it turns out there is a Cat5 cable that leads to the closet from my room, and I was able to splice together a VGA cable to both ends of the Cat5 wire, which allows me to see the video feed from the DVR. The VGA setup I have uses 6 of the 8 wires in the Cat5 cable, leaving 2 behind. I wanted to also connect a USB mouse to the DVR from my room using the Cat5 cable, however you'd normally need 4 wires in Cat5 cable in order to do that. Despite this, I tried to run the USB mouse's Data+ and Data- through the Cat5 cable's remaining pair of wires, and I connected the VCC and Ground wires to a power supply. The mouse was powered (ie it lit up) but it did not appear to be controlling the DVR from my room despite the data cables being connected. Is there any way to run only the USB data through Cat5 and not VCC and Ground? This would allow me to run VGA video and USB through the same Cat5 cable, which I am hoping to do.

Here's the current setup, where the mouse is powered but not "connected:"

                         To   <----VCC------+ (loose)
                        DVR's <----GND------+ (loose)
                         USB  <----------+         To DVR's VGA out
                         in   <--------+ |  D-      ^ ^ ^ ^ ^ ^
                                       | +--------+ | | | | | |
                                       +--------+ | | | | | | |
             External USB Power Supply      D+  | | | | | | | |
               (an iPhone wall USB              | | | | | | | |
                 charger adapter)          (cable goes through walls)
                        ^   ^                   | | | | | | | |
                    VCC |   | GND               | | | | | | | |
                        |   |            +------+ | | | | | | |
                        |   |         D+ | +------+ | | | | | |
                        |   |            | | D-     | | | | | |
                        |   +----------+ | |        V V V V V V
                        +------------+ | | |       All VGA video,
                                     | | | |         to monitor
                                     V V V V
                                     To Mouse


texts:
I'm making a VU meter with an LM3915 and I would like to be able to plug my computers audio output into the LM3915 directly and get it to register. I've been  searching the internet for a design but can seem to get any to work without a preamp. Anyone know of a schematic that would work without a pre amp?

Data Sheets

LM3915: http://www.national.com/ds/LM/LM3915.pdf


texts: What can I use to replace an SV-04F bias diode?

texts:
I had a nice Wega V3840-2 audio amplifier, but sadly, it broke. During my attempts to test what was wrong, a diode, attached to the heat sink, failed with a nice whiff of magic smoke. According to the Kundendienstanleituing (user service manual), this particular diode is a SV04F. I cannot check the markings on diode itself, since it's embedded in epoxy in a little clamp that attaches it to the heat sink. I cannot find this particular diode at my local stores, so my question is, what can I use to replace it?
For your convencience, I also added part of the schematic. The top rail is +32V (also the leftmost connection coming from above), the bottom rail -32V. The connection center left is the actual audio signal, the output on the right goes to the speakers.
The failed diode is D201, that's attached to the heat sink of T210 (which is in turn attached to the main heat sink of all four final stage transistors).

Note about the circumstances it broke under for those interested: I replaced T210 and T211 with a BD2430 and BD244C in an earlier attempt to fix the amplifier (see first link of this post). I now realise that the trafo is set for 220V even though we have 230V these days, perhaps I'll set it for 240V. Other than that, I still don't know how or why my amp is no longer working...


texts:
So a while ago, i was stumbled upon a post what will happen to the dc circuit when we supply ac to it. Lets assume the ac has the same voltage as the dc. We know that ac switches direcions so there will come a tome it is positive, zero and negative.

If the ac is in its positive voltage, the dc circuit will work fine. By the time it approaches zero voltage, no current will flow and so thr circuit is not functioning. Now what bothers me is the negative voltage applied. What really happens on the inside? Technically speaking. Lets say the dc circuit can be jus any device like a piano, laptop, etc

Thanks


texts: What is the DC analysis of shorting both ends of a diode?

texts:
I was studying diodes. I understand the depletion region.
I am wondering if I tie together the P and N end of the diode, there will be a depletion region around the junction. But there should also be a depletion region around the wire connection due to majority carriers combining by flowing around the wire, and the depletion region should be opposite to the depletion region around the junction, thereby cancelling out the built-in voltage. This must be the case so measuring exactly the negative of the built-in voltage. Can someone comment on my thoughts?
Another way to express my question is if I connect a P type semiconductor with an N type semiconductor together using wires, will there be a PN juncton?
clarification n is tied to the ground..


texts: "Sniffing" into a Boiler's LED panel (Central Heating)

texts:
I've built an esp8266 based web thermostat to control my heating system. Everything seems to be working fine for the moment  :)

What I want to accomplish is "sniff" or intercept the boiler´s status from the front panel's status LEDs, to see if this heater is actually turned on, on a MQTT Dashboard.

A very nasty way would be to connect some wires from the boiler's LEDs to some GPIO pins. But I'm not quite sure about that approach. I believe I would have to use some type of buffer, optoisolator, etc.
(I could also place a LDR, o phototransistor in from of the boiler's LED, but I dont want to physically block the visual feedback)

How could I accomplish this?
Any ideas?

Appreciate your help,
Cheers!
Marc

PD: This exact same question has been asked in the Arduino Forum almost a month ago, but haven´t received any replies yet. Sorry for the double post.


texts: What operating system manages resources in ARM cortex M4 based development board?

texts:
Is there any operating system written in board which manages its resources.

My development board is STM32F407


texts: Where to start when designing a custom PCB as per requirements?

texts:
Before I ask this question let me tell you that I am an IT professional with little knowledge of electronics.

Here is my problem:

> I want to design such a device which will stream video to my mobile upon press of a button. [the button will be on the device].
> The device will have a camera and mic. [so the micro-controller used will need to have video streaming capabilities]
> This device will be connected to WiFi.

The mobile app development part of this device can be easily done.

But what do I need to read to create a design of the PCB for the requirements I just mentioned?

I am aware that I can buy CCTV for my purpose, but this is something I want to try out by myself as a DIY project.


texts: Do I need a galvanically isolated step-down DC-DC converter to power my digital electronic from a battery pack that powers also the electrical motor?

texts:
I have a battery pack with lithium ion cells. The battery pack has a maximal voltage of 84V (it goes from 84V to ~50V -> depending about the current state of charge).

I use this battery pack to power all sort of things (lights, horns, MCU(BMS), inverter - that then gives power to the eletrical motor...). The inverter draws about 60A of current continuously from a battery pack when the motor is rotating.

For my concept to work I must have different DC voltages on a single PCB:

12 VDC (for lights and horns)
5 VDC (for some sensors...)
3.3 VDC (for MCU, operational amplifiers...)

The idea is to use some sort of step-down converters on the PCB to convert from 84V to 12VDC and to convert from 84V to 5VDC. And then to use a LDO to give me 3.3V from 5V.

The 12VDC must have a power of ~40W, and the 5VDC must have a power of ~10W.

The question is regarding if the step-down converter should have galvanic isolation (like a flyback) so that I can have different grounds for high voltage and low voltage? Or is OK to use a "normal" buck regulator?

I think that for 12VDC that supplies the horns and lights is not so necessary to have different grounds as for 5VDC that supplies most of the electronic ?

Any suggestion?


texts: Schematic Confusion: How to connect the Ground Terminal?

texts:
GND means ground. How am I supposed to connect this GND ? Does it means that I have to simply hook up a wire and leave it floating? What is it's significance in the circuit?
I am designing a PCB and I want to know how to connect this GND in a PCB???


texts: Measuring mains voltage and powering a raspberry pi from the same adapter

texts:
I'm looking to measure AC voltage (just the voltage, not the phase etc.) and power a raspberry pi 3 with a lora concentrator (so there would be a power draw up to 2A @ 5V) from the same ac-ac adaptor, like in the schematic:

The main reason I don't want to use a separate power supply and sense adapter is installation inconvenience.

Would this work, if I chose a beefed up enough wall wart? I'm thinking that a 12V 24VA should be more than sufficient. And since it's using a transformer, the voltage at the adc divider should be linearly proportional to the mains.

The required resolution is 1V, so using a 10bit should be sufficient.
1V @ 240V translates to 12.5mV @ 3V and the ADC has a resolution of 3.2mV @ 3.3VRef

Edit: The 5V regulator before the raspi would most probably be a switching one


texts:
I'm trying to improve the range on my 433 MHz radios and came across http://www.att.com/edo/en_US/pdf/AntennaFundamentals.pdf. (Geez, there's so much RF information in many bits and pieces, if only there were a more complete source somewhere)

Section 3.2 talks about antenna efficiency and defines it to be the amount of power that is radiated by the antenna (excluding the reflections to the signal source and the power absorbed by nearby objects).

Is this the reason why most PCB designs put the antenna at a corner of the board? So that less of the power will be absorbed by the board? The reason why I ask this is that our current board does something like this:

My initial thought is that the power absorbed by the board is directional. Or in other words, the size optimization that we did by putting the antenna directly behind the board should not affect the antenna efficiency in the directions away from the board. Does this theory make sense? If so, why does everyone isolate their antenna? Is it just for a more omnidirectional radiation pattern?


texts: Need a circuit to detect if something has gone from off-on or on-off

texts:
I'm new to circuit design but I'm trying to design a circuit for a power antenna that will send a 5 second pulse whenever it detects a a wire has gone from off-on or on-off.

So far I have designed the circuit below. 12V is is always on and 'T' is the 12V trigger from the radio that is on whenever the radio is. It uses the relay on the left to detect the trigger wire from the radio changing state, the brief moment when the relay switches over and is not making contact with anything, it will make the NOT gate pulse on which will be extended to ~5 seconds or whatever by the time delay relay circuit at the bottom which will run the motor relay.

As you can see I'm more familiar with electromechanical and relay logic and was wondering if anybody can provide a more elegant solution preferably using solid state?


texts:
What I mean by one way relay is manually reset it to run again.
What I need it for:
I want a pump to run when a relay is on(manually turned on), when there is no power the relay trips and stays like that in off position. Because even if the power comes back on I don't want the pump on. Until I reset the relay.
I keep saying a relay, but it doesn't have to be. Anything that could handle 240V.
Is there anything I could use for this?


texts: Powering buck converter using charged capacitor

texts: Is it possible to design a buck converter using a charged capacitor to get regulated voltage output? When the capacitor voltage falls below some threshold value the inductor should be able to provide output across the load resistance(during this time the source capacitor will be charged).


texts: Arduino: What is the best way to send and receive data with I2C?

texts:
I am using I2C to send and receive int values from a RaspberryPi to an Arduino then echoed back to the Pi.

The primary problem I am having is with int values larger than 255.

A secondary problem is when trying to stream values constantly. My goal is to send MouseX,Y coordinates constantly from the Pi to an Arduino. here is my test code showing basic ability to send int values 0-255 from a RPi to an Arduino.

My first question is, should I keep values as ints or convert everything to String BEFORE sending over serial?

My second question is, if keeping as int, what modifications should I make to the following so that values larger than 255 will work?

RPi Python code first.

import smbus
import time
# for RPI version 1, use "bus = smbus.SMBus(0)"
bus = smbus.SMBus(1)

# This is the address we setup in the Arduino Program
address = 0x04

def writeNumber(value):
    bus.write_byte(address, value)
    # bus.write_byte_data(address, 0, value)
    return -1

def readNumber():
    number = bus.read_byte(address)
    # number = bus.read_byte_data(address, 1)
    return number

while True:
    try:
        var = int(raw_input("Enter 1 - 9: "))
    except ValueError:
        print "Could you at least give me an actual number?"
        continue

    writeNumber(var)
    print "RPI: Hi Arduino, I sent you ", var
    # sleep one second
    #time.sleep(1)

    number = readNumber()
    print "Arduino: Hey RPI, I received a digit ", number
    print

Arduino code

#include <Wire.h>

#define SLAVE_ADDRESS 0x04
int number = 0;
int state = 0;

void setup() {
    pinMode(13, OUTPUT);
    Serial.begin(9600);         // start serial for output
    // initialize i2c as slave
    Wire.begin(SLAVE_ADDRESS);

    // define callbacks for i2c communication
    Wire.onReceive(receiveData);
    Wire.onRequest(sendData);

    Serial.println("Ready!");
}

void loop() {
    delay(100);
}

// callback for received data
void receiveData(int byteCount){

    while(Wire.available()) {
        number = Wire.read();
        if (Wire.available() > 1)  // at least 2 bytes
        {
          number = Wire.read() * 256 + Wire.read();
        }
        Serial.print("data received: ");
        Serial.println(number);
        //sendData();
        if (number == 1){

            if (state == 0){
                digitalWrite(13, HIGH); // set the LED on
                state = 1;
            }
            else{
                digitalWrite(13, LOW); // set the LED off
                state = 0;
            }
         }
     }
}

// callback for sending data
void sendData(){
    Wire.write(number);
}


texts:
I made some measurements near few cell towers and i have noticed that i get 2 values that is changing every few seconds.
For example i get a reading of 20uW/cm2 for few seconds and after that the value spikes to 60uW/cm2 for some seconds and again it go down to 20uW/cm2 and so on.
What is the reason for this phenomenon?
Thanks.


texts: what's wrong with my codec's op amp output?

texts:
There's some thing wrong with my audio codec. Unlike the modern codec, its input gain is configured externally with op amp's resistor. However with unity gain, I see strange wave form on the input amplifier's output(AO pin), like below(My input signal is a DTMF signal):

And looks like this when enlarged, is a 10MHz sine wave.

I was thinking that the probe capacitance is causing this, because firstly I use passive probe which has about 19pF input capacitance. However, after I changed to an active probe(Cin in less than 1pF), which measured the above picture, the problem is still there.

I occasionally switch the passive probe to 1x with 90pF Cin, then there's no problem on output signal. And it is also OK when I add an 82pF output capacitor for op amp output terminal.

So why my input op amp's output is not stable without the adequate capacitance?
Thank you.

Here's my schematic:

The input op amp is configured like this:

And here's the codec's datasheet.


texts: How to protect a buck DC-DC being backfed from the load (e.g. a battery as a load)?

texts:
Background

I want to design a DC-DC adapter that is foolproof and has some protections in place so that it doesn't accidentally damage the somewhat expensive equipment downstream.

Here's what I have right now:

simulate this circuit – Schematic created using CircuitLab

The input is variable, and doesn't need protection by itself. I've protected the LTC3637 against a few fault conditions. My biggest fear being that if it fails, and shorts the input to the output in the process, this might fry the equipment downstream. So far:

I've protected the input of the LTC3637 against overvoltage;
I have a TVS on the output just in case (this might also become a real crowbar circuit);
I've made it impossible to backfeed the DCDC - if there's no input (SW1 open), and somebody connects a battery at the output, nothing happens;
If somebody connects the same battery with reverse polarity, this would close the circuit around F1 and the TVS, tripping the polyfuse.

The load to the regulator is usually just the aforementioned equipment, but users might try to connect a battery as well, as this was required in the previous instantiation of this adapter and they may be unaware it is no longer needed. This prompted the scenarios in the last two bullet points, however I think the circuit would cope with them even without the D4 and the TVS, because of the buck topology itself, namely:

positive backfeeding: If there were a wire instead of D4, the voltage from the battery would connect via the body diode of the power PMOS inside U2 to the input, so the regulator would be powered (Vin one diode drop below Vout). So it would be a strange condition, but not dangerous or damaging (and U1 doesn't care about backfeeding either);
negative backfeeding: the battery would close around F1, L1 and D2, tripping F1 as before.

Question

Are my worries about backfeeding well-founded, or is the buck topology is inherently protected against it (as suggested)?

Additional tips on how to make the circuit more resilient to faults and dumb users are very welcome.


texts: Send a Single pulse "On"; Channel remains on until device's power is cut. Prefer op-amp solution

texts:
I would like to activate a portion of my circuit electronically. A single pulse should activate a portion of the circuit, and this portion should remain on until the device is disconnected from its source. A transistor wouldn't work because I would need the circuit to remain ON even when the initial pulse has faded.

I know using a 555 timer, it's possible to do this. A single "trigger" input will leave the 555 timer in its ON state until power is cut. However the 555 timer is sort of a noob tool? I'm wondering if there's a similar alternative using an op-amp or other cheaper device that could be used.

Alternatively, is a relay switch the cheapest, smallest, and best option here? What if the initial current is extremely small, like 1 mA?

Additionally... are there such things as relay switches that shut off after a certain amount of time without an activating pulse?

Kind of a long question but thanks


texts: Protecting External Connector Ground Pin from ESD

texts:
I have some TRS (stereo phone) connectors on my protable USB device (no earth ground), and I'm wondering what to do about ESD events that enter the device via the sleeve (ground) of the connector.
Currently I have the TRS ground connected directly to the ground plane of the PCB, and I've noticed that an ESD event can cause my device to reset and very occasionally completely hang.
As a test, I added a 0.1uF capacitor between the TRS connector ground pin and VCC such the the TSR is still connected directly to ground, but also has a capacitor to VCC. This has seemed to stopped the device from resetting.  I've been googling my brains out, but I can't seem to get much indication as to whether this is a good practice, or indeed if there is something else I should be doing instead.
I'm particularly worried that the capacitor will have an adverse affect on analog measurements of the piezos plugged into the TRS connectors.  The signal from the piezo goes off to an opamp buffer and I just want to make sure that the capacitor used in the situation will not affect my signal integrity.
I might have also seen that a ferrite bead in series with the TRS connector ground pin before it goes to the ground plane might also be effective.
I would love to hear any advise and wisdom you can share.  Thank-you for taking the time to read this post.


texts:
I am trying to help my dad with a project of his where were trying to build a lighthouse powered by solar panel in which it spins a motor at night and charges battery during the day. This is a DC application. We have the front end, being charging the battery all figured out. However, the backend, being controlling motor and having motor only turn at night, is the hard part. We have a controller for controlling the speed of the motor working with no issues. It is the last part that we need help with, which is the photocell sensor light switch. We figured that we need to place the photocell between the battery and the speed controller. The photo sensor switch says it works for AC and DC application and says AC/DC on the device we received. The directions that came with it state this for working with DC application, "black line connect to input power (-) negative. White line connect to input power (+) positive and load device (+) positive. Red line connect to load device (-) negative." So I believe line is meaning wire and load device will be the speed controller with power being my battery. I have tried it using the directions and doesn't work. I looked on  comments on the amazon page where we brought the products (got 2 of them) and the comment said that black wire is hot wire with red wire goes to load and then white wire is ground. That didn't work either. I have waited at least a minute with light shining directly at the sensor and it doesn't turn off the motor to simulate day. Here is a link to my diagram with both directions based and amazon comment based that I tried: https://imgur.com/a/Kc7ejfG

Here is a link to the sensor on amazon: https://www.amazon.com/gp/product/B01M1O3C1V/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Here is a link to the speed controller on amazon:
https://www.amazon.com/gp/product/B00F839VNQ/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

here is a link to the motor: https://www.amazon.com/gp/product/B07FKKWSFJ/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

The battery is a car battery rated for 12 volts and 23 amp max. The speed controller is rated for 6v-90v at a max of 15 amp. The sensor is rated for 12 volts at 10 amp max. We need the speed controller to slow the speed of the motor as it is way to fast for those of you wondering. The motor is rated for 12 volts at 150 watts max. I do not know if I have fried the sensor or not, but I do not think so because I do not smell any smoke or anything and it is NOT black to indicate frying it. I do have the second one I can use, but I prefer not to use it until I know for sure what I did wrong in case my current one is damaged, if it is.

So my question is what is wrong with my diagram or why isn't it working? Thanks in advance.


texts: Using AA(A) batteries to power a 3.3V SoC

texts:
I have a 3.3V SoC that could draw up to around 250mA - 300mA. Is it a good idea to power it using 2x AA(A) batteries? Is it supposed to be an unstable setup without decoupling capacitors?

Thanks


texts:
I have the below circuit:

Forward diode D0002 - Datasheet SIJ series for reverse protection and C0001-C0004 capacitors for ESD protection.
Zener diode - Datasheet - 36V reverse breakdown.
Question :
BATT1 is the Vcc supply for certain ICs in my design whose absolute maximum ratings is 40V.
I have provided the Zener diode circuitry to clamp if the battery voltage goes above 36V (during transient ISO7637 pulses namely pulses 2a,3b and 5a.)
I have performed simulations in Simetrix with the proper models for each part, but the Zener diode circuitry is not clamping the voltage to 36V during these ISO7637 positive pulses. Why is it so?  Is the Zener diode slow to respond or react to the input transient pulses 2a, 3b and 5a?
Please let me know like if there is something like Zener response time which makes it unable to do this clamping. Or what might be the reason?


texts: CMOS Gate and Coupling Noise from Loose Wires

texts:
I am currently working on this small circuit which as you can see, has to level shift a 3.3v 1Hz PPS signal into a 5v pulse.

Everything is marvelous when I measure the level shifted pulse with the CRO leads with ground springs (rather than leads) right off the CMOS gate.

However, this design is going to carry the output pulse from my PCB to the destination using some loose wires (Not a shielded cable which doesn't get effected).

simulate this circuit – Schematic created using CircuitLab

And these loose wires introduce the following coupling effect to my design.

How I know this? In my 3D electronics version, I have added a bunch of zip tied loose wires to my signal, ground and Vcc wires (exactly how the final product is going to be) and measured the signal at the end of loose wires with the perfect CRO leads with spring grounds.

Wanna make it harder for you? I cannot use heavy filtering on the input or output pulse as this device is used for a time measurement and correction purposes with a 300ns rise time limit, so we wouldn't want to slow down the rising time.

How can I prevent this coupling from happening while using loose wires to carry the signal?


texts:
I have a PICKit 3, but I understand these aren't for production.

What does a production workflow look like?  PC -> Programmer -> Chip.

Do people usually verify that the chip copied properly, or is that not necessary (fail rate?)


texts:
I would like to know please why is it that I can't start an .ac LTSpice simulation at f= 0Hz. I would like to know the DC impedance (or the equivalent resistance of my circuit that also contains inductors and capacitors) of my system. Any workarounds?
Thanks in advance :-)


texts: Confused about higher potential at junction in real(practical) diode

texts:
My text book (Microelectronics by Sedra and Smith 7th edition) states:

  Hence a potential difference results across the depletion region, with the n side at a positive voltage relative to the p side, as shown in Fig. 3.9(b).

page 150

But again solving circuits with real diodes,
concept from below image works well.Since the junction potential opposes applied electric field during forward bias, it is quite logical to put "p" side at higher potential. But, my text book states that "n" side is at higher potential.

Which side ("p" or "n") is at higher potential?

According to theory, it's the n side. According to the simple concept of overcoming barrier potential when a p-n junction is forward biased, it's the p side. For example, E1 has greater potential than E2 (assumed), and E1 has to overcome the electric field applied by E2.

So I am confused.

While this question seems to be asked before, I made it more simple than before (editing previous question would hamper answers in them).


texts:
So I have PWM signal controlling an N-FET switch at around 20kHz.

While it works in theory, in reality it takes longer to switch the MOSFET off. I assume it is because of output capacity parameter?

And then there's the fact that it starts shutting off from negative voltage. Why is that?

Real world example uses BS170.

Blue trace - Vgs, Green trace - Vd:

Yellow trace - Vgs, Red trace - Vd:


texts:
I am designing my own solar charge controller using the MPTT algorithm, having a variable solar panel voltage.

I have decided to design a buck converter that will match and convert the input resistance (from the solar panel \$ \Large \frac{V_{mpp}}{I_{mpp}} \$ ) into output resistance (\$ \Large \frac{V_{out}}{I_{out}(D2)} \$) by a change in duty ratio.

On the the other hand I want to track the MPPT of solar which uses the switch to change the duty ratio to track the MPP (maximum power point).

My problem is that though, I have designed my buck converter to have a stable 12 V output, that is not the case when I simulate it. The output voltage changes abruptly with a change in duty ratio, that results to an unstable output voltage. I realized that when the system is tracking the maximum power point by changing the duty ratio, the output voltage also changes.

I was asking is there something I am missing or doing wrong with concept I just explained? Or any idea which I should consider when doing such a design?


texts: Assigning numbers to the new components in Altium designer?

texts:
I am drawing a schematics in Altium designer. I have several schematics (sheets) in my current project. Some of the components have already a designator numbers like R5, C20, L13 ... etc.

But some new components does not have yet, and it is like R?, C?, L? ...etc.

My question: How to make numbers to these new components ? Can one assign numbers to all these components at once ?


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TI recommends their low-data rate transceivers to cope with long stub lengths for RS485 networks -- eg Page 3 of http://www.ti.com/lit/an/slla272c/slla272c.pdf

I want to use an isolated interface, so I was thinking about using the il3085 chip, but it has fast rise/fall times for high speeds (I'm using 115kbaud at most, so this is unwanted overkill).

Can I add some series resistance to the il3085 and be OK (how do you calculate that?), or should I switch to the sn65hvd1780 and give up on isolation?


texts: how to solder MEMS microphone to PCB at home?

texts:
I would like to experiment with audio applications using MEMS microphone.
The problem is i cannot think of a way to solder these microphones on a pcb as PCB prototype manufacturers that i know won't do re-flow soldering for a single board.


texts:
I am designing a pen-type barcode scanner (1D) which is operated by user, which means that the speed at which the scanner moves is random. Even worse is that it gets stuck sometimes, so the signal gets stretched or even goes back sometimes.

Well, all is not so bad as it sounds since I ran some tests and it seems that this distortion always happens at the 4th pulse. As it can be seen from picture, this pulse has a very long fall time. So here is the question:

What signal processing techniques can you recommend to make this right? I mean just to mark this pulse as a 1 without making the micro controller crazy? (The output of the photodiode of the scanner is fed to the ADC of a MSP430)