texts: 5V 5A rail controlled by 3.3v microcontroller - dual switching or power mosfet?

texts:
I think this is a common situation so hopefully an answer helps more than just me. I have a 3.3v low power MCU which will be controlling a 5v 5A run of LEDs.  When the LEDs are off the system will go to low power sleep mode, however the LEDs have a relatively high quiescent current which I’ll need to cut off. I’ve narrowed my power management setup down to two options with different tradeoffs that I’ve list below but I’d love some feedback on which would be better, if I’m mistaken about something or if I’m missing some other solution.

Everything will be powered from a 9.6v-12v supply.

Option 1) 3.3v rail is its own switching regulator and the 5v rail is also its own dedicated switching regulator rated to above the required 5A.  Both lines will be powered directly from the 12v supply and the MCU on the 3.3v line will control the enable pin of the 5V regulator giving it the ability to turn of the 5v line and cut the LED quiescent current.

Pros - Most efficient on both 5v and 3.3v and I only have to worry about the heat dissipation on the 5v reg.
Cons - Most complex option with the most components, which means most likely the most expensive and with two switching regulators should I ever need EMC certs it could be tricky. Also at the low loads of sleep mode on the 3.3v rail my switching reg is not at peak efficiency.

Option 2) 5v line is still a 5A rated switching regulator but now the 3.3v line is just an LDO downstream from the 5v rail.  The MCU on the 3.3v rail now would not be able to switch off the enable pin on the 5v rail so I would have to use a power mosfet between the 5v regulator and my 5A led strip to kill the quiescent current.

Pros - Simpler design and slightly cheaper replacing the 3.3v switching with the LDO, plus I get back some space on the PCB
Cons - I’ve been researching the power mosfets and I’m worried about heat dissipation if I’m actually driving near 5v 5A.  I’m also not sure what having the LDO off the 5v switching regulator will do for my overall power efficiency vs. a 5v and 3.3v dedicate switching reg in option 1, could be this option lets me switch off the quiescent current but then I give that power savings right back by sending power to the micro from a 5v reg to a 3.3v LDO.

As I see it I have a tradeoff between complexity and cost vs. simplicity and possible heat issues.  On top of that I have to consider PCB space and possible EMC issues with two switching regulators.

Thanks for any input.


texts: Will a PSU with Active PFC Work with Normal UPS

texts: Im getting a Seasonic SII 620 with Active PFC.The problem is that i have a pseudo sine wave ups or just a normal UPS.Will this PSU work with the back up power offered by the UPS?


texts:
So I have a problem with The UC382x Family of chips from TI.
Here is the datasheet that I'm working off UC382x, I had some confusion already with datasheets seems there's a few floating around but TI themselves have confirmed that this is the data sheet I'm working off with the chips I'm using.
Now from that datasheet I made a circuit based off the UC3825ADW. I now want to get a 95% duty cycle output, so my understand is that I should just be able to pop a UC3823ADW down on the PCB instead and it should just work ¬¬.
Below is the circuit I'm using, trimmed down for this, the values are the ones I'm using the pots are both 10kΩ. 1 to set the frequency and 1 to set the error ref voltage. I have it set to a frequency of 15kHz and I can see the ramp and the clock. for me this is enough to say the chip is working. The other trimmer is set to have the full 5.1V from Vref going to NI and at the moment the feedback circuit is actually removed from the board so it's not needed here. The main thing is that EA out is at 5.1V which is going to drive maximum duty cycle out of Out A. I also know they should be schottkys, they are but the drawing is normal diodes, please forgive me.
Now I put a UC3825 down on the board I see the Ramp and I see the clock and I see the PWM switching the MOSFET gate at a good 12V with a 45% duty cycle. I put down a UC3823 on the same board. I see the ramp, I see the clock but Pin 11 Out A is a flat 800mV as is pin 14 Out B
I've been over the datasheet many times, I've been on to TI a few times and I'm stumped. Last ditch is to ask here to see if anyone might be able to offer a pair of fresh eyes or see something I'm missing. But from what I can see these 2 chips should be more or less interchangeable. I'd appreciate it if those fresh eye can confirm for me if they are interchangeable?
also the confirmation of using the right datasheets is coming from the ADW suffix there are UC3835 and UC3823 which are the same but different. as a double confirmation I've shorted pin 11 to pin 10 and probed pin 14 and still the same.


texts: Solve Resistance per unit in simple problem

texts:
I'm just learning basic electronic. I don't understand this simple problem.

A 400 ohm resistor carries a current of 60 Ampers.

resistance is R per unit (pu) = 400ohm/32ohm = 12.5

how can I obtain this 32 ohm? I have no idea where it come from.

EDIT: This is a resolved problem with resolved exercices, the thing is that I don't understand how to get some values, the process I mean.


texts:
So I want to find h(t) for a convolution integral for a series RL circuit with an input of Vi(t)
I know that the impulse response is h(t) and hence: $$i(t) = \frac{K}{L}e^{\frac{-t}{\tau}}, t\geq 0$$
Now in the 3rd part of the question, they say 'interchange the resistor and inductor'. Obviously I know now that V0 is across inductor the output will be different.
However I cannot see how I am meant to set up the convolution integral differently since h(t) doesn't change (from my perspective) despite the question asking me to re-derive the equation for the impulse response?


texts: Can anyone help me identify this component from an old rechargeable battery pack?

texts:
I was given an old, maybe 10 years, battery drill, it had seen almost no use, but, unsurprisingly, the battery pack would not charge.  I took the pack apart and several of the cells were obviously completely shot.

It is quite a heavy duty drill an I thought it would be worth swapping out the cells for some new ones like I have done with other power tools.

However, when I came to fully disassemble the battery pack, a wire that I had thought was simply a connecting wire turned out to be 2 x 50mm lengths of bare wire with this in the middle all encased in a length of insulation.

The wires were completely corroded and fell to bits as soon as I touched them so I cannot even tell which way round it was, but it was connected from the -ive side of the battery pack to a third connector that mated with the charger.

The internet tells me that this could be any one of dozens of things, but I suspect it maybe some sort of diode that tells the charger when the cells are fully charged.  This would appear to have been common in rechargeable batteries ten years ago.

So, the question I am asking is, what is it? and how do I size a replacement?
The drill is not really worth much, but I had already bought the new cells and it seems a shame to bin it for the sake of this.

The original battery pack was rated at 24V and 1.7Ah, and the charger at 24V and 2amps, but putting a meter across the terminals says it outputs about 35V.  The new cells are a bit bigger at 2.8Ah

The component is about 3.5mm long and 1.75mm diameter, with absolutely no markings on it.


texts: How thin is the base region are compared to collector or emmiter in a BJT?

texts: I have never seen how does a BJT look like inside the plastic container. I know base region is pretty thin as compared to collector and emitter. I am curious regarding the ratio of thickness of base region and other regions.


texts: How do we know \$R_x=\frac{R_2R_3}{R_1}\$,and \$L_x=C_1R_2R_3\$ in the maxwell bridge

texts:
There is a maxwell bridge below

The book said when

$$(R_1//\frac{1}{jwC_1})(R_x+jwL_x)=R_2R_3$$

We can find that \$R_x=\frac{R_2R_3}{R_1}\$, and \$L_x=C_1R_2R_3\$

I want to ask how can we mathematically manipulate this:

$$(R_1//\frac{1}{jwC_1})(R_x+jwL_x)=R_2R_3$$

To prove that:

$$R_x=\frac{R_2R_3}{R_1}$$

And:

$$L_x=C_1R_2R_3$$

Because i think we can't because of the imaginary number \$j\$.


texts:
I was wondering if there is a difference between the following switch circuits:

I simulated these here and here and they both seem to have the same behavior. The one with two FETs was suggested in BQ25505 datasheet here as a switch to disconnect the load from the power management IC.

Is there any difference between their switching speed or power dissipation?

PS: I'd appreciate any suggestions regarding the choice of the FETs in terms of low power dissipation and fast speed. The source voltage is maximum 6V (max 500mA) and the gate voltage is minimum 3V.


texts: What is a better way to prevent over-discharge in this low current circuit?

texts:
I made a nightlight and was very happy with the dim yet usable output and runtime (months), but my assumptions about battery safety were wrong. I expected the LDO 3.3 V regulator to stop output when the source voltage dipped below 3.3 V, and that it would not draw much current in that case. I must have been wrong, since the 18650 lithium ion cell was irredeemably dead after a couple months. The circuit is below.

(Note: the output would be more efficient with two LEDs and a changed resistance to reduce the current as needed. At tiny currents like this, even a white LED does not have the expected large voltage drop.)

How could I better protect the battery from over-discharge? Could I use an additional regulator (3 V), a comparator, and a MOSFET so the comparator switches off the MOSFET if the battery's output voltage becomes less than 3 V? Even if it works, finding low power versions of these chips might be hard (or expensive). Is there a better way to cause the circuit to turn off instead of draining the battery? I assume a dedicated battery protection IC would be best, but most seem to come in a package that I won't be able to solder at home.


texts:
I have 2 questions:

1 - The Brushed DC motor variety has a type when one turns the shaft manually it free runs with no friction or resistance at all, and then another type which feels like a mild step friction/resistance as though magnets inside causing some type of resistance when the shaft passes them? Which type are these and what is the difference.

2 - The type causing a mild friction does not allow the motor shaft to return to it's original starting position. If say you have a string attached to the motor with the other end of the string attached to like an elastic yarn that the motor extends it to it's stall point and when the current is cut off.

I need it to free flow to the original starting point the the elastic band helps it do that but because of the stepping like friction of the shaft it does not quite unwind and return to the original position because the motor resistance.

I am thinking is it possible to use the EMF energy to give the motor a kick in the opposite direction?

thanks


texts: Low pass sallen key filter using single supply for audio transmission

texts:
I have used TI filter tool design to make sallen key low pass filter, their are four op-amps stages. But filter tools has not calculated AC coupling capacitor that has to be included after every stage. We are amplifying audio signal hence both positive and negative cycle needs amplification. Otherwise the DC voltage that is being generated after every stage will make the amplification unsymmetrical.  (Schematic is attached below)

Do we have to manually insert AC coupling capacitor or their is provision in the filter design software which I am unaware of.

Regards,

Edit: After reading the comments, I have done changes in the circuit. Then I performed simulation in the Multisim. I am simulating only first stage of the circuit. And it is working according to the design. Can anyone please explain adding 100K ohm resistor between inverting and non inverting terminal is solving the problem. In my previous design I have made inverting amplifier using single supply, but V/2 (DC bias) was only given to non-inverting terminal of the op-amp. I was applying same logic for salley key configuration


texts: Li Ion CC-CV Charger needed for standard protection board?

texts:
I am currently designign a 4S2P Li-Ion battery pack. The cells I use are unprotected, so I want to use one of those BMS/Protection/Balance boards like this:

https://www.ebay.de/itm/4S-40A-16-8V-40A-18650-Li-ion-Battery-Batterie-BMS-Protection-Board-mit-Balance/264137388088?hash=item3d7fd0b038:g:EcMAAOSw5e5cd1Qe

I want to include the charging in my project and all these boards talk about being "charging boards" and specifying a "charging voltage".

Do I assume correctly, that those boards do not implement proper CC/CV charging procedures?

If I want balanced charging, and my protection board provides balancing, would I be able to charge the pack by using a CC/CV circuit to apply a charging voltage to the entire pack?

I'm also thinking about not using balancing, since I have new identical cells.


texts:
I'm using an STM32 for AC dimming, for which I use a GPIO output (or timer channel out) to drive a triac, whenever I get a zero crossing detection (rising edge). Is there a way to solve this only using timers architecture and without firmware overhead?i.e not using interrupt handlers.

Toff -> configurable.
Tonn -> remains the same.


texts: Does the emf source live forever with a purely capacitive load?

texts:
Pardon me, but this question has been troubling me for several days. I've searched a lot but couldn't find any convincing explanation.

In a purely resistive circuit, instantaneous power is given by \$P = V_m\sin(\omega t) \times I_m\sin(\omega t)\$. This power heats up the resistor and is always positive, the energy is flowing from emf source to the resistor; so the emf source will die after transferring all its energy to the resistor.

In a purely capacitive circuit, \$P = V_m\sin(\omega t) \times I_m\sin(\omega t+90) = \frac12 V_mI_m\sin(2\omega t)\$. Average value of this is \$0\$. This means energy goes back and forth between capacitor and the emf source.

Does the emf source live forever? If the emf source were ac mains, would I get any bill? Since I didn't use any energy, what was working on charging and discharging the capacitor? Charging and discharging requires work and needs energy right?


texts: How does this simple FM slope detector work?

texts: I understand what happens from the diode onwards, it's a rectifying amp and a low pass filter that filters any unwanted frequencies from the carrier, but what is going on in terms of voltage between the first capacitor and the primary coil of the transformer, and between the secondary coil of the transformer and the second capacitor, that allows the FM signal to vary in amplitude according to the frequency input?


texts: Are there more (mains) electrical safety incidents in the United States compared to the UK?

texts:
Forgive me if this question isn't exactly "on topic" for this site -- it's a bit meta.

I am an academic in the UK, and I occasionally design electrical devices that plug into "the mains" in one guise or another. Some of these are (novel) medical devices. We have an internal blinded peer-review process for this, wherein designs that I produce are reviewed informally, and then formally, for electrical safety prior to manufacturing taking place. I find this invaluable: it isn't my job to know a lot about the wiring regulations and can focus on the science I am interested in (which inevitably isn't at 230 VAC).

It is an internal requirement that anything I use on a patient is designed as if it were for sale in the EU, and we meet appropriate standards accordingly. Note that this is pretty common: there are strict limitations on what work one can do on your house without being a qualified electrician, for example, and it's generally a legal requirement that a 'competent person' sign off on anything involving electricity.

Many of the rules I have been asked to follow surprise me in their depth of thought. For example, above a certain current limit, ventilation hole sizes are further reduced on a device to prevent a dropped-in screwdriver welding contacts together. The order of washers and contacts (star, then spring, then contact, then spring, then nut) is specified for binding protective earthing bolts to metal casework panels. Fuses are specified on the incoming live side only, and not neutral (and, in fact The Electricity Safety, Quality and Continuity Regulations state that, as of 31st January 2013, fused neutrals shall not be retained. There is an HSE requirement for fused neutrals cut-outs to be removed within 28 days of being identified.). I could go on.

Occasionally, we will buy something from elsewhere in the world (e.g. the US, China) sold for an international audience, and this committee will declare it electrically substandard, and mandate remedies. Typically these faults relate either to earthing resistance, conductor-to-earth insulation (i.e. it fails a meggar test) or power supply leakage currents. Often our internal standards seem to go beyond those required internationally -- e.g. IEC 60601 vs BS60601.

However, I've noticed that this level of "paranoia" seems to not be the case elsewhere. In particular, DIY stackexchange has examples of wiring that I would naïvely consider to be almost criminal, often with commentators agreeing. What I call RCDs (common on every socket in the country) are only required to be used in the US in "high risk" areas -- e.g. in the bathroom (where no UK house has a conventional 13 A socket at all). I haven't even mentioned how the Type G plug is wonderfully over-engineered, and the average device has two fuses (typically one lower, slow-blow, one higher current and faster one), not one.

[Edit: Some quick examples of what I'm talking about would be:

A child sticking scissors into a socket (not possible with a type G plug -- and they didn't trigger an appropriate CB quickly enough)
An unbonded neutral without other fault (not possible with multiple PEN house wiring, specifically designed against otherwise)
A fault with current conducing to ground through plumbing, also likely to stopped with an RCD/GFCI]

My question is this: is the UK's paranoia justified? Do we have anything to show for it? Is the rate at which electrical safety incidents occur higher in the United States compared to the UK? Or does the magic difference between 110 VRMS and 230 VRMS obliterate any potential safety gain that this vast amount of work would achieve?


texts: Best Battery pack solution for raspberry pi and lcd

texts:
I'm trying to create a portable raspberry pi with an lcd screen.

My lcd screen requires 12v and 4A to work properly and i already tried to follow guides like the following: http://www.makeuseof.com/tag/pi-go-x-ways-powering-raspberry-pi-portable-projects/ (the battery pack diy solution)

I'm thinking about using a battery pack of 6 AA (12V)

From what I understand so far, i need to wire the battery to a regulator like this sparkfun.com/products/107 to force 5v on output to the pi board to make it work. Then again from the battery to the lcd controller. Am I missing something?

I would like to make it portable, but not to change batteries every single time. Using the rechargeable ones, is it possibile to charge them? (with a usb, micro usb charger for ex.). Do I need a particular adapter?

Edit:

Thanks for the answers, i will try the several solutions you proposed. As you asked this is the model of my lcd screen: LQ121S1LH03
As i get it from a really old laptop i bought online a controller for that specific lcd, and on the requirements page was clearly written 12V and 4A. I tried to power it up with a charger i had at home (the charger is 12V and 1.2A) and i got a white screen as result. After googling i discovered it was a lack of current, that's why i thought about 4V.

The controller i used is the following one: http://www.ebay.it/itm/M-NT68676-2A-HDMI-DVI-VGA-Audio-LCD-Controller-Board-DIY-Kit-Power-Adapter-/121059321784?hash=item1c2fb2a7b8:g:4AUAAOxyjNlRym3z (the power adapter was not included)


texts: Is a Real-Time Clock (RTC) necessary for real-time systems?

texts:
Assuming that we are working on a real-time Linux system and hardware which consists of high resolution timers, does having an RTC affect the real-timeliness of the system?

Here it says that it reduces CPU and memory usage, but is there a way to compare the difference somehow?


texts: Can an ESC-rectifier combination be used as a replacement for a buck converter?

texts:
I am working on a project that involves a DC-DC power step-down. The details are as follows :

Input : 48V , 15A
Output : 18V ( around 700W ; due to losses)

However, I could not get any buck converter directly for such high output current. My question is - Could I use a 48V (4S-5S) ESC (of proper rated current) along with a 3-phase full wave rectifier to get the desired DC output? Could the exact voltage that I need could be set with a PWM signal to the ESC?

I am posting this question because I tried this concept with a 4S ESC and a 160V MDS40 3-phase bridge rectifier, and it did not work. I currently do not have an oscilloscope, hence couldn't determine what exactly was happening. Also, I am operating the ESC at 50Hz.

Could anyone please point out what the problem is?

Update: 16th Oct,2019

I connected the ESC to my pc-oscilloscope and I am getting mostly zero voltage reading but there are funny little pulses (see video here) that are occurring in the waveform.


texts: Active Antenna with Off The Shelf GPS Module

texts:
I'm trying to use an active antenna with the GY-GPSV3-NEO-M8N GPS module.
In the hardware manual for NEO-M8N it is said that I need a DC bias circuit like shown in the picture below.

As shown I need RLC components connected to RF_IN and VCC_RF. I'm not embedding the GPS chip to my PCB so I need to change the components on the blue module itself. But I'm not certain which of the components is connected to which pin.

The antenna I'm trying to use has the specs shown in the picture below:

I was told I need to be aware of the bias circuit to use any active antenna as well as the max gain of the GPS module.
Question #1: There are 2 components near the RF_IN pin in the blue module. (The ones inside the yellow box on the picture above.) The white component is for sure connected to RF_IN (I'm also not sure whether this is an inductor or not) and the resistor on the left. But I'm not sure where the resistor is connected. The bias circuit schematic from the datasheet says that the resistor next to the inductor needs to be connected to VCC_RF but this resistor seems to be connected to the pin next to VCC_RF, so RESET_N
Question #2: Should I seek a GPS antenna with lower gain? Max gain for this chip is said to be 30dB in the datasheet. The antenna that I picked has 28+-2dB gain. Is it better to go for 22dB? ,
Any help is very much appreciated thank you for reading.


texts: Changing voltage levels from 5V to 3.3 V

texts:
I am asking some basic questions here. I have a sensor whose voltage specs are 0-5V and I have to interface this with my TI MSP430's ADC, whose voltage Vcc is 3.3V . For this I have to convert the level of the output of the sensor.

1) Can I accomplish this using a simple potential divider, that is, I use two appropriate resistors in series, and then tap the drop across one of them and feed that to the ADC?

2)If yes, then are there some additional things that I should look into?

3)If no, can someone suggest a suitable alternative?


texts: How often should I tin my soldering iron?  It doesn't seem to pick up the solder quickly any more; I have to hold it there for 10 seconds before it melts.


texts: I would like to connect two GPS receivers to a single active antenna letting the DC voltage form only one receiver to reach the antenna. In this blog post the guy made his own RF part by putting a capacitor into a male to male SMA adapter which is a very low-cost solution. I wonder whether there are similarly working low-cost parts readily available off the shelf so that I do not have to build it myself. The cheapest GPS antenna splitter I could find is a Tallysman TW150 for $85 while the solution with a custom capacitor must cost much less.


texts: Running an electric motor beyond its ratings

texts:
I ordered a 36V 500W brushed DC motor but unfortunately a 24V one came. I'm faced with the dilemma of returning it and waiting for a month before getting a refund, then ordering a new one and waiting about a month again for it to arrive, totaling 3 months of waiting (with the current one), OR run it beyond its ratings.

I understand that increasing the voltage will increase the rotation speed proportionally. It is currently rated at 2700 rpm @ 24V and ~27A drawn. If I increase the voltage to 36V then rpm will rise to about 4000 and to maintain the 500W power output I will need to supply ~14A.

Questions that arise are:

Are my assumptions correct in the first place?
Is it possible for construction damage to occur when running a motor beyound its rated rotation speed?
Is efficiency compromised in such setup.


texts:
I've got a system here where I get 12V DC from a laptop charger which is connected to the wall. That 12V gets stepped down to 5V using the TPS56221 buck converter (running this at 500 kHz, with an occasional load step of 12A and more frequently 1.5A). The max current that the 5V converter will be outputting is 16A. I also have MII ethernet on the board that will be running at 10/100 Mbits/s. Furthermore I also have UART, SPI, and I2C but all will be running less than the GHz range.

simulate this circuit – Schematic created using CircuitLab

I want to put a common mode choke between 12V coming onto the board and the input of the buck converter. I've chosen this common mode choke because it seems to provide a decent amount of impedance all throughout the range of frequencies I am dealing with. What are your guys thoughts/recommendations ?


texts: Is my phone battery better / more capacitative than my laptop battery?

texts:
When we go out and look for phones, the first thing I do I always look at the battery capacity, usually 2000 mAh, 3000, up to 10000 mAh for a (external?) battery.

Looking at laptop batteries, they are much much larger and have only afraction of what the most massive batteries for phones have.

My laptop battery has, for example, 5000 mAh, probably not much higher than 15-20V,

if I get four 10,000 mAh phone batteries I get the same voltage range in serial connection and still those 10,000 mAh, or not? (or maybe 40,000 mAh). Yet I will save space.

Is it a wise choice to construct such a battery for my laptop?

Is my logic correct?


texts: Driving an LED from an 1.8V GPIO pin that defaults to "IN"

texts:
I have an EspressoBIN board, which has 1.8V GPIO pins with a max current of 8mA.

I'm attempting to drive some status LEDs from them, and a 5V fan, so I'm using 2N2222s with 220 Ohm base resistors connected to the GPIO pins, emitters on ground, and between 0 and a few hundred ohms connecting collectors, load and +5V. (220 Ohm so I'm not losing much voltage to drive the fan)

This works fine, except during boot. Turns out the EspressoBIN, by default, sets the GPIO pins to "IN". In that state they are at 1.8V with about 10kOhm internal impedance. This is enough to turn on the transistors so the LEDs and the fan come on (on half speed).

I can only turn the GPIOs to "OUT" once the board has fully booted (about 60 seconds later).

What's the simplest-possible circuit you can think of that keeps my loads off during boot, and lets me have them switch 5V on/off once the GPIO is set to "OUT"? Note that per vendor, 8mA is the max current I may draw.


texts: Send analog audio through the rs232 port of a data transmitter

texts:
I would like to convert an analog audio signal into an rs232 datafeed to send it through a data transmitter and receive it at the other end.
I already have the data transmitter and receiver.
Thanks for your answer.

I would like to create a camera communication between the OB van and the wireless camera we have.
The problem is, I could do it via a normal radio like Motorola but I have some parts left from my last project.
The transmitter and receiver that I have can only communicate with each other via RS232. This was used as a data transmitter to controll the camera.
Now I want to use this as this is a narrow band transmitter and it's easier to get a license for this kind of communication.

It is a Line level signal that has to be converted and transmitted.
If possible the circuit should be as small as possible.

The transmitter is a link L1128.


texts: Have I placed too much on this PCB layout?

texts:
I am doing my first PCB layout (using Altium) and have finally gotten past the auto-router stage. The result is a mess and there are some missing nets and design rule violations. Have I packed too much on this board or do I just need to re-think my component placement?

The board is two layers.

I am stuck with a very specific enclosure and won't be able to make the board bigger in the x-y axis.

This is a hobby board, but I have a full SMD soldering setup at home (nice scope and all). The connector placement is part of the enclosure (otherwise those would be the first things to move). It's a drop-in replacement for an older engine monitoring system. It takes measurements mostly from thermocouples and thermistors. The large chip in the center is an ATmega2560 running at 16 MHz.

UPDATE:

Thanks for all of the input. I rearranged the board and moved to 4-layers. Then I routed it all by hand. It looks much better now!


texts: wiring 555 to disconnect itself from electricity

texts:
i had idea for a circuit with 555 and here is the IDEA:

circuit is stationary somewhere, it is in "passive state" meaning its drawing no current from battery and pin 3 is set low, then someone comes by, presses the button and LED turns on, after 15 seconds LED turns off and circuit continues to draw no current and remains in this "passive state" untill next button press

QUESTION: this circuit doesn't work, and im wondering where did I make a mistake?

LINK:
http://prntscr.com/5u1be2

PS: imagine LED connected to pin 3


texts: 0R resistor performance in RF Pi Network

texts:
I have a prototype board for Sigfox and LoRaWAN (915MHz) with spaces to install components for a Pi network on the antenna.

We're using a 0R 0603 SMD resistor in place of the inductor, and no capacitors at the moment. I.e. we have bypassed the Pi network.

I was wondering, is a standard 0603 0R resistor ok for the link or do we need special RF rated resistors even though it's 0R?


texts:
I'm trying to use timer2 in STM32L475 but it doesn't start firing the interrupt at all.

I would like to configure the timer for a minute.

void InitializeTimer()
{
    TIM_SlaveConfigTypeDef sSlaveConfig;
  TIM_MasterConfigTypeDef sMasterConfig;

  htim2.Instance = TIM2;
  htim2.Init.Prescaler = 10000;
  htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim2.Init.Period = 500;
  htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  if (HAL_TIM_Base_Init(&htim2) != HAL_OK)
  {
          _Error_Handler(__FILE__, __LINE__);
  }

  sSlaveConfig.SlaveMode = TIM_SLAVEMODE_RESET;
  sSlaveConfig.InputTrigger = TIM_TS_ITR0;
  if (HAL_TIM_SlaveConfigSynchronization(&htim2, &sSlaveConfig) != HAL_OK)
  {
          _Error_Handler(__FILE__, __LINE__);
  }

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

if(HAL_TIM_Base_Start_IT(&htim2) != HAL_OK)
{
  _Error_Handler(__FILE__, __LINE__);
}

}

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
    if (htim->Instance == TIM2) {
          start_processing = true;

    }
}

void TIM2_IRQHandler()
{
    /* Clear interrupt flag first. It cannot be the last instruction in an interrupt handler. */
     __HAL_TIM_CLEAR_FLAG(&htim2, TIM_FLAG_UPDATE);            //clear interrupt flag
    start_processing = true;
}

before main loop:

 MX_I2C3_Init();
  InitializeTimer();
  //MX_SPI3_Init();
  HAL_NVIC_SetPriority(TIM2_IRQn, 0, 1);
  HAL_NVIC_EnableIRQ(TIM2_IRQn);// Enable interrupt from TIM3 (NVIC level)


texts:
I'm using a Attiny45 microcontroller and USBtinyISP as my programer, and this is the first time I need to hook stuff up (in this case just LEDs, but eventually I'll want to conect a raspberry pi) to the programing pins (SCK, MISO, MOSI). As I want the microcontroller to be re-programmable when it's all soldered up. I first breadboarded the circuit to make sure it works. This is what I found:

If I have a LED and resistor in series between SCK or MOSI, avrdude throws this error at me:

  avrdude: initialization failed, rc=-1

unplugging the LED gets rid of the error, but isn't ISP ment to allow this?(Arduino's have a LED connected to pin 13 SCK)

However on MISO this never happens and I'm free to upload the program with the LED attached. Why is this? Is there a way to obtain this behaviour on the SCK and MOSI? How is this issue going to be affected if I replace the LEDs with raspberry pi GPIO thru a logic level converter?


texts: What does Pin type I mean on the ESP32 datasheet

texts:
On page 3 of the esp32-wroom datasheet (PDF) it shows a series of pins with type "I".

What does pin type I mean? Are these different to the pin type I/O pins? If so, how?


texts: Photodiode amplification works with LM258N but doesn't with LF356N

texts:
The circuit is as follows

I'm powering the op-amp from a 9V battery.

It gives me constant 3.6V at the output and it doesn't change with changing the illumination of the diode.

I tried replacing the 1M resistor with 10K and 10R, but it doesn't change anything.

I've double checked the pinout and it appears to be correct based on the datasheets that I can find.

The offset pins are floating in my circuit if this is of importance in this case.

When I swap LF356N with LM258N or CA3140 it works as expected with the output reacting to changes in the illumination.

What am I doing wrong?


texts: FSM modeling when outputs are not simple functions of input and current states

texts:
All the two/three process block modeling style(the recommended style) examples for FSM  have logic for nextstate that is a function of current state and inputs. The outputs in these examples also take specific values depending on current state and optionally inputs.

Ex :

always_ff@(posedge clk) begin
   if(rst) currentState<=IDLE;
   else    currentState<=nextState;
end

always_comb begin
     nextState = 'x;
     case(currentState)
           IDLE  : if(in1)           nextState = CALC1;
                   else              nextState = IDLE;
           CALC1 : if(in1)           nextState = CALC2;
                   else if(in2)      nextState = IDLE;
                   else              nextState = CALC1;
           ......

     endcase

end

always_comb begin
    out1 = '0;
    out2 = '0;
    case(currentState)
        CALC1 : out1 = 1'b1;
        CALC2 : out2 = 1'b1;
    endcase
end

Consider an example for an FSM for a memory BIST. I want my FSM to be in state1 while my address is less than 1000, change to state2 when it reaches the value of 1000. I want the address to keep incrementing from 0 to 1000 while in state1 and start decrementing when in state2. Furthermore I want my FSM to be in state0 for 500 cycles just after reset.

always_comb begin
    nextState = 'x;
    case(currentState)
         state0 : if(resetCount<500)  nextState = state1;
                  else                nextState = state0;
         state1 : if(addr<1000)       nextState = state2;
                  else                nextState = state1;
         state2 : if(addr>0)          nextState = state3;
                  else                nextState = state2;
         ....
    endcase
end

always_ff@(posedge clk) begin
      ...
      case(currentState)
           state0 : addr<='0;
           state1 : addr<=add+'d1;
           state2 : addr<=add-'d1;
           ...
      endcase
end

always_ff@(posedge clk) begin
    ...
    if(currentState=='0) resetCount<=restCount+'d1;
    else                 resetCount<='0;
end

The next state and output calculation is not straight forward. If I keep adding signals like data/control signals, these dependencies will increase.

For a case such as this, is it still recommended that we follow 2/3 process block FSM and remove all the extraneous logic(Ex : the reset counter) from the module where FSM is coded? I can move the reset counter  outside of the FSM module and have a signal indicate to the FSM when counter reaches 500, and generate a signal from FSM that indicates to the  counter outside the FSM to count or not depending on state.

But isn't it extra effort just to keep it in 2 processes?


texts:
Here is a problem to which the obvious answer is "use a switch," but that is not permitted in the design. ;)

I am writing software for a USB audio application that is supposed to be able to play audio from iP{od,ad,hone}s, Android devices, and also Samsung Audio from Samsung devices.

(quick note: USB Device with capital D = USB Peripheral = device with B-Connector)

I wouldn't have to ask this question if all these devices played nice and were just USB Devices. iPxx and Android devices are USB Devcies, but Samsung devices playing Samsung Audio act as USB Hosts (but they can also be USB Devices not playing Samsung Audio but as regular Android devices).

All devices have to connect to a single Type Standard-A connector on our embedded system running on a PIC32. Yeah, I know that's not USB-legal, but that's what the requirements are.

Since both USB Hosts and Devices have to connect to our embedded device, I need a way to detect when a device is plugged-in if it is a USB Host or a USB Device, so that my USB system shuts/brings itself up with the correct role depending on the attached device.

I have read the On-The-Go and Embedded Host Supplement to the USB Revision 2.0 Spec. The closest thing I got was Attach Detection Protocol. That helps with the general detection of attached devices but doesn't help detect the role of the device (Host or Device). Our hardware design is not final yet, so I am able to consider any hardware solutions that help that aren't... well... a switch. ;)

Look forward to the community's insight.


texts: Magnetic material demagnetization through Curie temperature

texts:
It is known that some materials lose their permanent magnetic properties when they are heated above certain temperature known as Curie temperature or Curie point. As those materials are cooled down to lower temperatures they will contain no residual magnetic field.

After some given material with magnetic properties that has never been magnetized before is magnetized from H=0 & B=0 state, the quiescent point follows initial magnetization curve all the way up to saturation. After it is saturated, the quiescent point follows hysteresis loop curve. And after external magnetic field is removed, given material stays magnetized to some degree, known as remanence or retentivity of material. Now, if this same material is heated beyond Curie temperature and cooled down then this material is demagnetized and put into H=0 & B=0 state, right? And from there, the quiescent point follows initial magnetization curve as external magnetic field is applied to magnetize the given material, right?


texts: Problem with PIC18F46J50 family USB enumeration

texts:
I am having an issue with getting my PIC18F46J50 device enumerated. I think this is the problem because when I plug in my device, I get the "USB device not recognized error". Also, PID and VID are both 0000 even though in FW I have set them to be otherwise. I was under the impression that the USB SIE takes care of config and enumeration stuffs.

Not sure what other info to give you guys to be more useful, but if you need any other info let me know and I will happily post it.

EDIT 1:

In response to Chris Stratton. It is a custom board. Using FW that can be obtained for PIC18F14K50, but modified for PIC18F46J50. I have verified that the PIC is being programmed via some stuff that I am asking the board to do (I am adding USB functionality last to the board and there is alot of other stuff that can be run and is working). I have configured pullups, reciever correctly (UCON register = 0x16).

I'm not sure if the chip is getting a reset when powered. How would I check that?


texts: Op-Amps in custom current limiter acting strangely

texts:
I'm building a small current limiter (~20 mA). It's important that there is little drop over the current limiter and that the load receives almost the full supply voltage when it's pulling less than max current, so I chose not to use a pure BJT solution that would require at least .5 volts of drop (to make the BE junction conduct). So, I've developed this schematic:

simulate this circuit – Schematic created using CircuitLab

I thought this circuit would limit current to about 5mA. When the current reaches 5mA, the drop over the sense resistor R3 should be about 10mV. OA2 should amplify this to 1V. This will go to the comparator OA3, which will go low and deactivate Q1, decreasing the current to the load. However, it's not working, either in the circuitlab simulation or in real life. In the simulation, circuitlab says the non-inverting input on OA2 is about 200mV while the inverting input is almost grounded, yet the output is still grounded. So, it doesn't activate OA3 and current is unlimited (nearly 100mA). In real life, it seems to fail for a different reason. OA2's inputs are equal and it amplifies as expected, but OA3 isn't comparating as it should be; the output still stays at a 1-1.5 volt that's enough to drive Q1 after the inverting input has gone higher than the non-inverting one. That being said, the real life version still decreases the current to some extent -- but it doesn't have a hard cutoff point like I want it to.

When I replace the op-amps in the simulator with ideal op-amps, the circuit works as expected, limiting current to just under 5mA as soon as the load gets too small. What is it about a real LM324 op-amp that is causing this circuit to fail? The LM324 datasheet indicates that it can handle common-mode inputs all the way down to ground.

EDIT: I think something was wrong with the 734 unit I was using. After replacing it, the current is successfully limited to the maximum design value. However, OA3 still isn't behaving as I would expect -- when the current drops below 5mA, I would expect it to drive the output as high as it can, fully saturating Q1. However, even when the inverting input is 20mV lower than the non-inverting input, the output stays at 1.5V or so, partially limiting the current and keeping Q1 in the active region.


texts: Number of cycles for AGM battery with an inverter

texts:
I have an AC system which has a continuous load of 7 amps at 120 volts. To run this system, I need a set of AGM battery and an Inverter system (power factor- 0.8). The inverter is 24 volts and rated for 2 Kva. I have a few 12 volt, 200 AH batteries.
Now, how do I calculate the run time of my battery at full load mentioned above for the following situations ?

a.) Two 24V, 200 AH batteries.
b.) Two 24V, 400 AH batteries.

Also, from the battery manufacturer, I know that the cycles available for the battery are 1200-1300 for 30% DOD and around 600 for 50% DOD for each 12volt, 200AH battery. Now, will I get more cycles if I connect two 12V, 200ah batteries in series/parallel (More than 1200-1300 or 600 cycles ?) for the entire battery system, or even more cycles if I connect four 12V, 200AH batteries in series/parallel or a combination of series and parallel for the entire battery system?


texts: Unknown schematic symbol in BQ27750EVM schematic by texas instruments

texts:
My sincerest apologies if this is a duplicate question. Disclaimer: I did my best to crawl through the forums to see if I could find the answer and after an hour, I am lost. With that out of the way, below is my issue:

I am looking to determine what the below symbols are for a battery protection design using ti's BQ27750EVM board. The picture of the symbols (circled in red) in the schematic is below:

And below is a picture of where, on the development board, the E2 and E3 components are:

These pictures can be found at the following link: https://www.ti.com/tool/BQ27750EVM-837

Any help on this issue would be greatly appreciated.

Cheers!


texts: The effect of rust on a transformer core

texts:
I want to make a transformer with a core of laminated electrical steel sheets. I have some EI core sheets, 0.5mm thick. My design is for a gapped core transformer, and the shape of the gap is unusual, so I need to cut the sheets to get the gap I want. I am considering using water jet cutting as the way to cut the sheets. The water jet cutting shop has told me that the process will make the steel sheets a little rusty.

I will stack the sheets first and bond them with a non water soluble adhesive, so the rust will not be on every sheet, but on the surface of the stack of sheets. How much of a problem would rust on the surface of the sheets be? What effect would it have on the efficiency/core loss of the transformer?

Water jet cutting involves no heat from friction so there is no danger of the heat affecting the magnetic properties of the steel. Conventional cutting does involve some heat from friction, but whether this is enough to affect the steel, I am not sure. It seems to be a case of No Heat but Rust VS No Rust, but Friction/Heat. Any thoughts on which is the best option?

PS. The summary of the study at the link below says “The experimental results show that the iron loss of the specimen by water jet cutting is the lowest, but the magnetic induction under the low magnetic field is the highest”
https://link.springer.com/article/10.1007/s11595-014-1076-3

However, this study says ”As a result of the test measurements, losses occurred in electrical steels cut with abrasive water jet are found to be higher than the other cutting methods.
http://journals.sagepub.com/doi/abs/10.1177/0954405416666899

Hard to know which to follow, so for now I am just trying to think about the rust!


texts: Frequency ranges that causes a hazard to humans

texts: I hope many people might feel little awkward to see this question. But I feel this is important. Because in my place where I am living I can get a radio (Audio Receiver) very cheaply. I don't know till what extent they allow the audio frequency ranges. I guess they use  ICs for Frequency Demodulators, Frequency Clippers, etc. If the Frequency demodulator doesn't work properly and allows all the frequencies that comes through air then its going to be a big problem to the humans. Can somebody answer which are all the frequency ranges that are available and which causes human hazards?


texts: Is there an I²C device out there for reading a set of PWM inputs?

texts:
I'm thinking about getting a bunch of Maxbotix Ultrasonic rangefinders. I'd like to use as few pins on my controller as possible. Since I don't think you can have multiple devices on an RS232 serial connection, I'd quite like to interface their PWM output with the controller using I²C.

Is there some I²C device I can buy that accepts around 8 PWM inputs, and stores a representation of \$\frac{\text{pulse width}}{\text{period}}\$ in its registers?


texts: In order to prolong a battery lifespan, can a mobile phone (or a laptop) be programmed to charge up to a maximum level of less than 100%?


texts: How many relays can I control arduino/raspi at the same time?

texts:
I'm thinking about a project using arduino or raspberry pi (I don't mind working with one or another). The thing is that in my project, I have to control at least.. 50 leds/relays and there will be activated at least 10 of them at the same time.

The easy way is using gpio directly with the leds/relays, but of course, neither arduino nor raspi have so many gpio outputs.

I was thinking on using some demultiplexers, but if I use them, then I may loose the ability to activate at least 10 at the same time..

For example: My project has 50+ leds/relays, and now I want to activate [1, 7, 12, 17, 21, 26, 32, 41, 44, 48] at the same time. One second after, I want to activate [6, 12, 15, 27, 29, 31, 35, 44, 47, 50] and all others will remain disabled.

Thanks in advance!


texts: Two identical bits of kit with different voltage... trying to cannibalise parts

texts:
My 250V UV ballast box blew its control board.  I bought a identical model on ebay from the US and when it arrived the plate on the back stated 90-130VAC.  I was hopping the US item was dual voltage so I could just start using it.  If it was not, my plan was to swap in the power supply from my dud 250V box.

Opened the US box and saw that the internal components were identical to my 250V box.  I have attached a photo of the components with a close up of the power supply and circuit breaker from the US box.  The labels are IDENTICAL on the US and UK boxes.  I therefore thought that there should be no problem running the new US box off the UK 250V supply.  When I turned it on it worked but after a minute there was a smell of burning.  I discovered this was coming from the fan, which on close inspection has a 115V label on it.

My question is about the power supply unit.  Can someone please interpret the circuit diagram on the label for me.  Is it possible that this unit puts out 115 or 250V depending on the input?  I find this hard to believe.  However, it would explain why the US box has a 115V fan that is burning up with the 250 V input.  One last piece of info is that all the brown wires that I can get the meter on are showing 250VAC when I connect the UK mains.

Thanks for your help.

[![enter image description here][2]][2]

Here is a photo of the board.  It does not look like would be easy to convert it to run on 250V.  I therefore think it would be best to add a chassis transformer after the emi.  What do you guys think?


texts: Power Sources for outdoor electronics/electrical projects

texts:
Very new to Electronics Fields but compelled by my obsession.
I would like to start with small projects which is very necessary at my house. I will explain some of my project ideas here.
First stage

I would like to design a DIY project using Light Dependent Resistor which controls the light (very small light- 1 Watt cool white LED) on my backyards and/ or frontwards controlled by PIR sensors. That means turn the light ON when the sensors feels something/somebody otherwise leave as it is.

Second stage

I would like to design a mobile app for a Bluetooth module that I would like to combine with Ardruino /PIC microcontroller to control the light.
Since this is outdoor project, I am very much limited with Power Source.

Now, where I am bit hesitant about:
What should I use as a Power Source for my project?
I can use Batteries ( different Volts , 1.5, 9V etc) but what types of circuit I should be using so that the circuits make the battery last long or controls the battery voltage only when needed.
There are many components to think about like Bluetooth module, microcontroller, light etc.
Being a beginner, I am trying to avoid High Voltage if possible. I would like to mainly concentrate on DC sides at the moment.
I would be interested on elaborating my projects idea more and more but I am stuck with Power Source planning.


texts: If a Li-Ion cell has 3000mAh capacity shouldn't I be able to pull 3A from it for 1 hour?

texts:
I have these brand new Li-Ion cells that are rated for 3000mAh and I'm trying to get their actual capacity. I have a discharger and its max current it can draw is 2A. However when I set that and run the discharging process it typically never exceeds the range of 1.6 to 1.8A.
In one example I measured on average 1.7A draw for 46 minutes. This was set to stop at 3V. In the first 30 seconds at 1.6A the voltage drops from 4.2V to 3.7V.
This seems terrible for the 3Ah rating. If I'm pulling 1.7A that means in theory it should last 1.8 hours right?
Just trying to confirm if I'm thinking about this correctly. The charger/discharger is an iMax B6AC.
edit:
The full product "name" is:

EBL 3.7V Li-ion Rechargeable Batteries 3000mAh 18J Lithium Battery

Although I can't seem to find much about it.
I will do some lower current draw samples eg. 0.5A 1.0A and see how it goes. I guess this battery is made for toys/torches(flash light) not sure what kind of operating current is normal there.


texts: How to control multiple servo motors using two timers?

texts:
How can I control several servo motors using 2 timers in an ATmega16?
I have searched for "servo bit banging" but no coherent post explains it fully. I found some code but I don't thoroughly understand it.

    #include<avr/io.h>
    #include <avr/io.h>
    #include <avr/interrupt.h>
    #include "util.h"
    #include "std_typed.h"

    volatile u8 X, lowCount, highCount, arrCount = 0;
    u8 array[180]={0};

void main( void)
{
    DDRD = 0xff;
    PORTD = 0b11111111;
    //DDRA = 0xff;
    // Set no prescaler for both t- and t2
    TCCR0 = (0<<CS02) |(0<<CS01) | (1<<CS00) ;
    TCCR2 = (0<<CS22) |(0<<CS21) | (1<<CS20) ;

    // for the first time only let the interrupts start
    TCNT0 = 0xd4;
    TCNT2 = 0xf4;

    SET_BIT(TIMSK, TOIE0);
    SET_BIT(TIMSK, TOIE2);

    // Enable Global Interrrupt
    sei();

    while(1)
    {

    }
}

ISR( TIMER2_OVF_vect)
{
    TCNT2 = 0xd4;

    if(highCount<45)
    {
        X = 0xff;
        highCount++;
    }
    else if( arrCount<180)
    {
        X = array[arrCount];
        arrCount++;
    }
    else if(lowCount< 1591)
    {
        X = 0;
        lowCount++;
    }
    else
    {
        X, lowCount, highCount, arrCount = 0;
    }
    //PORTA ^=0b10000000;

}

ISR( TIMER0_OVF_vect)
{
    TCNT0 = 0xd4;
    PORTD = X;
    //PORTA ^=0b00000001;
}

Any link or explanation would be great.


texts: Do I need to include overhead when picking a power supply?

texts:
I need to power 40 Raspberry Pis, each requiring a 5V input and have a maximum current draw is 2.5A.
This would mean:
5 x 2.5 = 12.5W
12.5W x 40 = 500W

That I need a 500W PSU. I was planning on getting a 504W Meanwell SMPS, which outputs 12V, and step it down with a buck converter (LM2596) (one converter per Pi) to 5V which each Pi would be connected to.
However I am unfamiliar if there's a known 'overhead' you should include when choosing power supplies.
Am I safe to choose a 504W PSU knowing my maximum power draw would be 500W, or should I be adding for example a 10% overhead.


texts: Measure Lab DC Power Supply with oscilloscope

texts:
As I am exploring instruments and played with them, in order to understand them better.

I have digital oscilloscope and Lab DC Power supply.

With DC Lab Power supply set to 5V and tip to positive terminal and clip to ground terminal, to my surprise, the mean reading is 430mV while RMS reading is 75.5V.

Using the clip on ground pane of any DC circuit board is akin to ground terminal of the Lab Dc Power Supply.  The question is how are they different?

What can I do do with ground terminal of power supply, besides rail to rail DC output? Can I use this ground terminal to connect to any ground pane of the circuit board under test with +/- or + power supplied?

Thanks in advance


texts:
I have to provide an isolated voltage that spans between 0V and 3V. Accuracy and space are more important than cost.

The only solution I see (without go to digital) is to use something like ISO122/124. The drawbacks are:

they require a dual supply, so I need two DCDCs to provide rails for both sides
space: the package is quite big and also the two DCDCs are bulky

I've already two isolated 5V voltage on both sides, and I would like to use them.

I found many cheap isolation amplifier but with only few hundreds mV of input range (they are for shunt resistor). Another way is to scale down and then up my signal to fit these constraints but I'm afraid about the accuracy when I'm close to 0V.

EDIT

I add some more information about my scenario:

the signal is pretty close to DC, say 1 Hz bandwidth
on the second side there is a 16-bit ADC, the accuracy needed is about 1-2 LSB


texts: What are my options if I need to deal with relatively large amounts of data on an embedded processor? I've found storage around ~2-4GB with an SPI controller, but I'm thinking about something in the 10s to 100s of GB.


texts:
Does anyone know any links, books, tutorials etc. that will help me better understand how transistors are used to design gates/functions?

Here is a link that does a good job of explaining the basics.
Looking for more complex examples that are similar to the link above


texts:
I have an NTC Temperature Sensor thermistor connected to a PID Temperature Controller. The main use of this controller is to control the temperature of chemicals in a reactor.

Due to the environment of the chemicals in the reactor (low and high pH, acids, vacuum etc.) I want to insulate the probe of the thermistor.

Does anybody know a way to perform such an insulation?


texts: Can enough motors generate the current to turn a separate one?

texts: I'm trying to keep a battery on an aircraft charged, but an alternator won't do the job. Can a lot of DC motors keep a battery in a state of sufficient charge to run two others? And, even more importantly, can a DC motor generate the same level of current and voltage output as is required for an input on that motor? For example, can a motor with a 12V 2A input create 12V 2A of output?


texts: Soil Humidity sensor value rising over time

texts:
So I have this soil humidity sensor placed in a pot. It's about half way in soil, cause that's how deep the pot is.

I'm trying to get a pump to trigger once the soil dries out below 20%, but something strange is happening. I can see the soil physically drying out, but the sensor value is constantly rising.

Any ideas what could be causing this?


texts: What motor type is better suited for instant torque supply

texts:
I am working in a robotics project and I am looking way to make my robot "dash" as soon as possible. Therefore I need to have a quite high acceleration for a brief time.

To be more specific, I am trying to have my robot (~0.5-0.7kg, dimensions are ~ 0.3mx0.2m) to move ~0.3m as fast as possible (best is like 0.1sec). (I am free to choose wheel diameter freely.)

I tried to estimate it roughly as follows:
0.5 * a *0.01 = 0.3
a = 60m/s^2
F = 0.5*60 (if the robot is 0.5kg) = 30N
torque = F*x = 30*0.3 = 9*Nm

Therefore I am looking for a light motor which can supply an instant torque of ~9-10 Nm. I might try using 2-4 motors together if I need to. I looked for the stepper motors but as far as I saw, this is unlikely to happen with them.

Is this possible, or is it impossible to find any small motor type that can achieve this?

Edit: I would prefer ~20$ but can go up to ~40$ if it will improve everything significantly.


texts: I'm given this 555 timer based monostable saw-tooth generator. This is a known arrangement for this part. The difference from other circuits I've seen is that the bias network of the external transistor is composed from a Zener + regular (small signal) diode. Why is the Zener diode been used? What advantage does it have over a simple resistor and why is the other diode needed?


texts: BJT amplifier with differential input and negative feedback - Open loop analysis

texts:
I am analysing the amplifier circuit drawn in the Art of Electronics 3rd edition (p. 121) and, while I follow the analysis presented and understand all the calculations in the text, I encountered an issue related to opening the feedback path. In particular, I don't seem to be able to wrap my head around what happens DCwise when I ground the right side of R6 (see circuit attached) as indicated for the open loop gain and impedance analysis in the text. This appears to reduce by a factor of 10 the current through the collector load of Q3, as a consequence of a tenfold drop in base current for Q3 (from ≈ 70μA to ≈ 7μA). It follows that the voltages in the output section are all negative (base of Q4 and Q5 of about -11.1V and -13.1V respectively). All appears to be caused by a 0.5μA increase of base current for Q2; current across R2 does not change having the feeback path open or closed. I do not understand how opening the feedback path results in such a significant move away from 0V DC quiesent voltage output, and I can't seem to figure out how to derive mathematically the values that I measure in my simulation.
Can anyone please point me in the right direction?
I purposefully used output transistors with very similar hFE for pnp and npn to exclude that as a reason of asymmetry. A resistor value for R6 of 140kΩ appears to bring both output transistor bases where they are when feedback is present(+/-1V; a 230Ω Q2 collector resistor to match the parallel resistance of R3 and the base impedance of Q3 at 10mA reduces even further the DC offset at the output).


texts: What could be the reason for 50Hz noise with isolated input signals?

texts:
A PCI data-acquisition board has 16 referenced single-ended channels. Here is the board:
http://www.mccdaq.com/pdfs/manuals/PCI-DAS6034-35-36.pdf

I'm using all 16 channels with BNC cables. The two channels are used as output and the rest 14 channels as inputs.  When I make single-ended measurements with all channels plugged, I get 50Hz noise and its harmonic in the signals. For low signals this causes a problem for data analysis.

Problem is: when all the 16 channels are plugged, the data from channel 1 has 50Hz noise, similarly other channels as well. But if I only plug channel 1 and plug off all the other channels there is no 50Hz noise.

All the input channels have isolated power supplies. I couldn't figure our where the noise can come from?


texts: Does appliance wattage differ by country, since the voltage does?

texts:
As an example, I have an AC-DC "wall wart" that specifies an input voltage of 100-230 volts and an input current of 0.3 amps. Since my mains supply is 230v:

Does that mean that it uses 230*0.3=69 watts?
If I were to use it in a 110v country, would it use 110*0.3=33 watts instead?


texts: What is the source of noise in this current measurement?

texts:
I'm measuring the current through a 100W motor with a 50A current sensor and I'm getting reasonably good data but there's also a fair amount of noise:

This is the current sensor I'm using. It measures current on the high side of the motor coming from a 3s1p lithium ion battery pack. To collect the data, I'm using the 10-bit ADC on an Arduino nano and saving it to an SD card the sampling rate is about 30ms.

There is no PWM controlling the motor, only a switch.

Is this normal for motor current data? If I used the 30A current sensor (instead of 50A) would the data be less noisy? Where is this noise coming from?

Thanks in advance.


texts: How to compute the effective voltage across a DC motor driven by a pulse train?

texts:
I'm driving a DC motor with a pulse train and effectively reducing the battery voltage to control the speed by adjusting the duty cycle.  Pretty standard.  What I'm unclear on is whether to use V_rms or V_avg for the effective voltage across the motor.
According to this article, the average power across a resistor subjected to a pulse train is defined with the V_rms (P_avg = V_rms^2 / R).
TLDR;
V_motor(D) = V_bat * D

OR
V_motor(D) = V_rms * sqrt(D)

where
V_motor = effective voltage seen by the motor terminals, [V]
D = duty cycle, [%]
V_rms = RMS voltage of a pulse train, [V]
V_avg = average voltage of a pulse train, [V]


texts:
I have a circuit with IGBTs which charges and discharges two different capacitor lines as a function of the voltage. i.e. when a voltage is detected below 160V, Q1 charges C1 and when a voltage over 160V and below 500V is detected, Q2 charges C2, and all voltages over 500V and up to 1000V are charged with Q3 and C2 and C3 in series.
After charging, the capacitors are discharged by R1 and R3 depending on which circuit was used.
All IGBTs are driven with a UCC21520 driver by means of a microcontroller. Isolated power supplies are obtained from an NMK1515SC DCDC converter with 3000Vrms isolation during 1 second.

simulate this circuit – Schematic created using CircuitLab
The problem is that charging at high voltages (over 800V typically,) Q1 is failing, going into short-circuit and therefore C1 gets exposed to 800V and ends up exploding.
Sometimes it also happens in Q2, although less frequently. I suspect various things could be happening but not 100% in any of them and not even sure if it could be some other thing:

When Q3 is closed V_CE of Q1 changes from 850 to 0V and then slowly back to 850V with the charging of C2 and C3. This without Q1 beign activated and could be the cause of the failue of Q1.
Right now not using a resistor betwenn the IGBT driver and the IGBT gate which could cause voltage overshoot and cause the IGBT to fail. But this should occur on the IGBT beign triggered and not another one.
Maybe IGBT model is not the most appropiate.

Any other ideas would be very much appreciated.
IGBT datasheet.
IGBT driver circuit:


texts: Circuit mesh analysis with 2 voltage sources

texts:
I'm pretty stuck trying to solve the below circuit. I need to find the node voltages and branch currents. I've tried it using mesh, nodal and superposition analyses, but I just can't get the right answer. I'm really not sure where I'm going wrong.
Using the mesh analysis, I took the clockwise left-hand loop as x and the clockwise right-hand loop as y.
Then:
$$10V=10I_x+30(I_x-I_y)$$
$$10V=40I_x-30I_y$$
And:
$$6V=40I_y+30(I_y-I_x)+20I_y$$
$$6V=90I_y-30I_x$$
Solving these gives $$I_x=0.4A, I_y=0.2A$$
But I've been told that $$I_x=0.267A, I_y=-0.022A$$
I know my solution is wrong anyway, because I end up with a resistor supplying power to the circuit.
Where am I going wrong?


texts: Is there a way to download extra components for LT spice on a MacOS?

texts: I am new to LT spice and I have been using it on MacOS (not recommended) I am struggling to find advice on how to download Spice models and add them to my components library. Following the same steps given to windows users doesn't seem to work. Anyone know how I can do this?


texts: Flyback power supply - 132 kHz radiated magnetic field issue

texts:
I request your expertise on a radiated magnetic field around 132 kHz (low frequency) on a Flyback power supply.
I'm using the LNK3694 driver with a switching frequency around 66 kHz. Using a circular antenna placed at 0 cm from the power supply, I have radiated emissions around 10 dBμA/m at 66 kHz, and also second fourth... harmonic.
I want to lower this level to -2 dBμA/m. I tried with copper strip shielding, Fe (ferromagnetic) shielding around the transformer without good results.
Is this radiation coming from the driver or the transformer?
Should I shield the driver instead of the transformer?
As the switching frequency cannot be changed, what shield or small modification do you suggest to lower this emissions at those frequencies?


texts:
I am confused with the I/O clock input mentioned in this datasheet: http://www.ti.com/lit/ds/symlink/tlc1543.pdf

Do I need to output clock from this adc to 8051 or do I need to use an external crystal for both the TLC1543CN and 8051 together?


texts: What surge/lightning protection is needed for an elevated off-grid solar security system?

texts:
I have a semi-urban hunting location that I would like to monitor remotely. I have an elevated (~20ft) box blind I am installing off-grid solar system (specs below) in. The purpose is to power a small consumer-grade 4 camera NVR security system using a cell hotspot for connection to the world (and instant notifications of intruders!).
I have all of the above squared away for the most part, but I am concerned that I might want to add fuses and or extra lightning rod type feature to the setup to protect it properly. Prior to this, I've had a game camera and small solar panel combo mounted on a 2x4 post at the top of this blind for 2 years without any sort of surge-related issues. There are lots of tall trees around. Here's a pic:

The new solar setup I've installed is a 180 watt panel and 2 deep cycle 12 volt batteries and renogy controller and inverter. The panel is mounted to 2x4 frame which is ratchet strapped to the blind (didn't want to put a bunch of fastener holes into the blind itself.
Specific questions:

Would adding fuses in line with the power supply for the nvr provide any lightning protection?
Would adding a lightning rod to the blind be prudent?
Should I consider myself lucky that my previous game camera setup survived unscathed for 2 seasons?


texts: What is the difference between capacity and throughput in context of wireless/cellular communication?

texts:
From what I understand:

Throughput tells you how much data was actually transferred from a source at any given time
Bandwidth tells you how much data could theoretically be transferred from a source at any given point
Capacity is the maximum information transmitted per unit time

I'm not able to perfectly capture the differences between throughput and capacity. Any help would be much appreciated.


texts: How to properly scale, time-reverse and shift a signal?

texts:
I'm not sure if this one is on-topic here, but I'll give it a shot anyway.

I know that if I have some sort of signal, like for example \$y(t)=x(t)\$, and I want a signal with twice the frequency, I can write that as \$z(t)=x(2t)\$.

I also know that if I have signal \$y(t)=x(t)\$ and I want to shift it to right, I can write the shifted signal as \$z(t)=x(t-1)\$.

I also know that if I have signal \$y(t)=x(t)\$ and I want to time-reverse it, I can write the time-reversed signal as \$z(t)=x(-t)\$.

What confuses me is if I have a signal which has already been shifted, time-reversed or scaled and I need to shift it or scale it again.

For example I have a signal which is \$y(t)=x(2t-1)\$ and I need a signal which has been time-reversed, should that be \$z(t)=x(-2t-1)\$ or \$z(t)=x(-2t+1)\$?  Same thing for scaling: If I have \$y(t)=x(2t-1)\$ and want to scale it by a factor of 2, should the result be \$z(t)=x(4t-1)\$ or \$z(t)=x(4t-2)\$?

Note that this is a homework question, so I'm looking for an answer which will explain the principle behind the transformations.


texts: Initial Conditions and current for an RLC circuit

texts:
It is required to find \$i_L\$ and \$v_c\$. It is quite easy to find \$v_c\$ from \$i_L\$ using simple integration. So, for now finding \$i_L\$ will be the concern of the question. Prior to closing the switch or at \$0^{-}\$, the current in \$i_L\$ is 2A because it is a short circuit and the capacitor is a open circuit assuming that its been in this state for a while. My concern is at \$0^{+}\$ what is the voltage across the inductor-\$\frac{di(0^{+})}{dt}=\frac{v_L}{L}\$. So, once the switch is closed the short circuit and the current source can be ignored. What is the voltage across the inductor? Its one of two: either \$0 V \ \text{or}  \ 10 V\$

I am finding the voltage across the inductor in order to find the initial conditions later on. There is another way to find the other initial condition using the voltage across the capacitor at \$t=0^{+}\$ but I only use that to evaluate my other method. Following the capicitor method, the voltage 0V across the inductor provides the same answer. This leads me to believe that the voltage across the inductor is in fact zero.

Can someone please explain to me what the voltage across the inductor is at \$t=0^{+}\$? Why it is or isn't zero?


texts: Why don't we use wireless electricity today?

texts:
I was reading about Nikola Tesla today (via the Oatmeal) and read about the Wardenclyffe Tower which (among other things) was intended to transmit electricity wirelessly. Forgive the naivety of the question, but if technology that could transmit electrical current wirelessly was invented over 100 years ago, why don't we use wireless electricity in our day to day lives today? In other words, why do we have to physically plug in our electrical devices (phones/computer, etc) if there exist such a thing as wireless electricity? If its an issue of efficiency/cost then I would imagine that some rich people still wouldn't mind paying extra, in light of the waste, for the added convenience.

Please explain in layman's terms (though a simple answer would suffice).


texts: Multiplying numbers with number 12 on Logisim

texts:
I need a bit help/tips about solving my exercises.
So I got the excerise as follow: Im gonna multiply all 4-bit numbers (0-15) with the decimal number 12.
Now, 12 is 1100.

Input is going to be 4 bit, and output should give us 8 bit, because 12*15 is the highest output number.

Now the exercise requires us that if we eg. need to use adder, we have got to implement the adder by basic gates.

As now I've made a table on my notebook with all inputs and outputs such that:
If innput is 0000, then output is 00000000 etc..

So to multiply binary numbers it should be eg.:

$$1100 :(m_0=1,m_1=1,m_2=0,m_3=0)$$

and we use the number two in this case:
$$ 0010: (n_0=0,n_1=0,n_2=1,n_3=0)$$

So we got to use AND-gate for each 'n' and 'm' combination, which gives us 8  AND-gates.

But on that part im stuck, and I really dont know if im doing the right steps...

Tips are highly appreciated.


texts: What are AC and DC transients, rather do we even classify transients that way?

texts:
We are provided a syllabus in our university stating "Unit III - Transient responses of RL,RC,RLC circuits, DC and AC sinusoidal input".

As far as I can see, "transients" are the response a circuit gives when you switch it on abruptly.

I really can't understand transients, I just follow the procedure, form a differential equation, take the Laplace transform find I(s), take inverse Laplace. What does this effectively do. In-class the professor taught us about step and impulse input, and their responses and we got a bunch of waveform corresponding to different cases,

What does the Impulse and step input have to do with transients?
What are AC and DC transients?
How is transient analysis different from AC and DC analysis?
Suppose I'm given a RLC. Assuming zero initial conditions, I switch it on with a DC input, I formulate a differential equation. Take Laplace transform, find I(s) and then take inverse Laplace, to find i(t), what is this i(t), is this the transient response ?


texts:
I have a goofy idea: a user is given a PCB and a pack of surface mount metal film resistors. To configure the board's settings, the user places various combinations of resistors into several 'sockets' or little clips on the board which surface mount resistors fit in in the same fashion as batteries in a battery holder.

Are there any current components that could make such a 'socket'? If not, how could this effect be achieved? I have thought about soldering two small spongy-like conductive blocks with grooves in them to the board and inserting the resistor between them and using tin foil or even a solid block and an oval wheel that rotates and locks the resistor in place but all seem a little complicated compared to two memory-metal contacts.


texts: Interpretation of mathematicial and corresponding physical meaning of gain and phase margin

texts:
In my textbook these are the definition of gain and phase margin:

  The gain margin is defined as the change in open-loop gain required to
  make the system unstable.

  The phase margin is defined as the change in open-loop phase shift
  required to make a closed-loop system unstable.

Sure, some quick plug and chug into MATLAB allow me to acquire these two values, the more gain margin and phase margin the merrier. But what does this all mean?

For example given the following plot

If I were to increase the open loop gain K, then the observed effect on the Bode plot would be a vertical translation upward. I can't see exactly a simple shift upward in the Bode plot implies instability of the system.

Further more, how can I understand these two parameters physically? Here is my simplistic understanding (if I were to pretend to be doing some analog design). The open loop gain K is induced by the amplifier which can exceed the maximum power handling capability of the amplifier hence causing the system to blow up. On phase margin, since the phase implies a delay in the system, then this could potentially cause some scheduling issue in a real time controller.

But none of the above interpretation is satisfactory for me and I can't find any satisfactory explanation why changing the gain and the phase of the system will induce instability. Say I had some circuit, then I plug in a device that induces a phase delay (an inductor for example)...I can't see the cause and effect that would imply the system could go unstable.  Can someone quickly comment on the physical interpretation of these two parameters.


texts: What is the use of a RLC circuit placed before a full bridge rectifier?

texts:
While analysing a PCB, I realised that a RLC circuit was placed before the full bridge rectifier. I am wondering, what functional use does it have?

simulate this circuit – Schematic created using CircuitLab

The primary of the transformer, the capacitor near the side and the SMD resistor seem to form a RLC circuit.
I think it should have something to do with filtering. There is a toroidal transformer there with a 1:1 ratio which seems to output whatever voltage and current runs through the primary.


texts:
We have two circuits in the figure.
For each find I and V.
The answers are

3 mA, 3V
4mA +1 V

This isn't homework,before you tell me to add this to the homework.I just found this and I want to know how to solve this.They look similar to the logic gates,the first one to OR gate and the second to AND gate,but where do I go from there?


texts: What values of resistor and capacitor to use for AVR reset pin isolation?

texts:
Background...

I'm a newbie to AVR applications. I recently built two ATTINY13-based circuits (glorified LED blinkers) which worked correctly (independently) on the breadboard. When I combined them on a solder perfboard with a shared power supply, things went haywire. After much investigation, it appeared they were constantly resetting.

I had left pin 1 (reset) of each micro un-connected. I researched proper ways of handling the reset pin and from this implemented the following:

Added a 100uF electrolytic capacitor in parallel with the power supply to help with any potential current draw the power supply would be too "slow" to deal with.
Added a 4.7K resistor from VCC to RESET
Added a 0.1uF ceramic capacitor from GND to RESET

These steps solved the problem completely.

The question:

The page I linked above is providing advice when doing ISP (in-system programming) which I am not doing (yet). (I'm programming the micros separately with no other components connected to them.)

I've seen several different values of capacitor (10nF, 0.1uF, etc.) and resistor (4.7K, 10K, etc.) and am not sure what factors alter these values. Can anyone shed some light on how reset pin isolation works, and how to calculate component values to use? Can you explain what values to use if there is no in-system programming header?


texts:
I found it easy to workout the open loop input impedance and the open loop output impedance of a buck converter. But when it comes to the closed loop output impedance, it is hard to me. In some books it is given as follows: Zoc=Zoo/(1+T) where
Zoc: is the closed loop output impedance.
Zoo= is the open loop output impedance.
T: is the loop gain.

Could anyone explain to me how to workout this formula? or propose to me any book that deals with deriving this formula?


texts: SystemVerilog Enumerated Multi-Domain Array -> how to declare/define?

texts:
Here is an example how to define the 2*N array of enum types of {S0,S1,S2,S3}:

typedef enum logic [N-1:0][1:0]{S0,S1,S2,S3} state_t;  (*)

So, each element of the above 2*N array could be either S0 or S1 or S2 or S3.

Let's say the {S0,S1,S2,S3} are defined as a separate enum type:

typedef enum {S0,S1,S2,S3} st_t;

So how now could I rewrite the first statement (*)?

Could it be re-written as the following:

typedef enum st_t [N-1:0][1:0] state_t;

Thank you!


texts: How to measure Inductor maximum current?

texts:
I have an inductor and seller claims that inductor supports a maximum of 5A current and he asked me to test it myself. Can someone help how to test that how much this inductor can support/ draw maximum current?

I have the following components.

24VDC power supply which supports 5A current.
I have multimeter
Breadboard.
120ohm resistor.

Please tell me the procedure for testing the maximum inductor current and what all the supporting components required?

P.S. I am not an electrical student. Please support me in the practical experiment.


texts:
I got a screw terminal with the following pin configuration:

X1
+-------------+
| (X) (X) (X) |       1 = 24V    2 = SIGNAL    3 = 0V
|  |   |   |  |
+--|---|---|--+
   1   2   3

My "requirements":

Convert 24V SIGNAL to 12V logic
Add bypass capacitor for supply

At the moment my schematic looks like this:

I need the design as compact as possible but I don't want to confuse myself in future.

What do you think: is the above schematic easy understandable or is it already too complex?
And what is commonly more important in a schematic: simplicity or sheet "space"?


texts: Attached a 9vdc motor to an LED to simulate a simple "generator" and I can get it to illuminate by swiftly spinning the motor in quick bursts, but if I connect a drill to the motor so there's a constant spin, the LED doesn't illuminate at all. Why is that?


texts: MicroSD card stuck after CMD8, responding 0x5 before next CMD is issued

texts:
I have a problem for which I can't find the solution in previous topics.

I'm using a microcontroller to read data from a Kodak 2GB Micro SD Card. I want to write a minimal driver in SPI mode, no need to do writing or formatting operations, just read some files.

I can see those signals on a 4 channel scope: CS, MOSI, MISO, CLK.

I do the following:

I send 100 bytes at 100KHz, with MOSI and CS high.
I send CMD 1, no argument, response type R1 returns 0x1, correct.
I send CMD 8, arg=0x1AA, response type R7 returns 0x1+ arg 0x1AA, correct.
At this point every command returns 0x5 at the 4th byte of the command. In other words, before the 6 bytes command is completely issued.

Any explanation for that?


texts: Inductors for local power supply filtering

texts:
Lets say I have a circuit which involves an OpAmp and a comparator. They're both single supply running from a noisy USB power supply.

Each component has local bypass capacitors, a big and a small one (10µF and 0.1µF, here simplified as one capacitor).

The comparator drives a load of +20mA and during switching I see the signal feeding back into the OpAmp over the power supply line. This cause my signal to degrade quite a bit and I need more hysteresis that I would like to.

I thought about adding some kind of noise isolation between the two components by placing inductors between them like this:

Inductors are in the range of 10µH and have series resistance around 2Ohm.

Simulation shows that the interaction over the shared power supply is almost non existent afterwards. Also the improved filtering reduces the noise from the USB supply a lot. This is to be expected because it is a CLC or Pi-filter.

The question: Is this a good or bad idea? I'm specifically asking because I've never seen this done in commercial circuits so far.


texts: electronic switch, understanding on-resistance measurements

texts:
I'm trying to understand from the datasheet, how much on-resistance I will get from this electronic switch:

DG411

datasheet: https://datasheets.maximintegrated.com/en/ds/DG411-DG413.pdf

given this conditions:

bipolar power supply +/-10V
logic 1 = +10V, logic 0 = 0V
signal to be switched: AC signal up to +/-7.5V, so quite close to rail voltage.

I'm asking since, as far as I know, on those switches the on-resistance should raise as the voltage to be switched get close to the rail voltage.

I'm not an engineer, and try to read the datasheet, this is what I may have understood:

"guaranteed on-resistance flatness over the signal range (Δ4Ω max)"

does this mean that even if the signal raise up, the on-resistance will not vary more than 4Ω?

"Low RDS(ON) (35Ω max)"

does this mean the in the worst case, 35Ω will be the maximum on-resistance?

The, watching some graphs at page 5, I'm a bit confused.
I think the most important graph for my doubts is the first one, "ON-RESISTANCE vs. VD AND POWER-SUPPLY VOLTAGE"

I guess I should check the B line (+/-10V), and it looks like the on-resistance in my situation will be something in the range of 27Ω to 33Ω (not considering temperature)

but what is VD?

by the way, I don't need low Ω or precise on-resistance measurement, I'm just trying to understand how to read the datasheet.


texts: How to tell if a repaired laptop power cord adapter is safe?

texts:
I bought my mom, who lives in India, a Panasonic toughbook CF-W8 a couple of years back. A few days back, due to some voltage fluctuations, her adapter/power cord blew out (along with a whole bunch or other stuff in the house).

Her laptop is fine and she has used it a bit with whatever power it has remaining. I have bought a new adapter for her over eBay and it should reach her in 3-4 weeks. In the mean time my dad asked a friend of a friend to fix the adapter and now some random person has "fixed" the adapter.

Now I am a bit nervous about the state of the adaptor and have asked my mom not to use it since i don't want her to damage her laptop.

I was wondering if there is any way to test if the "fixed" adapter is safe for use? and also, I just want to confirm that it is indeed dangerous to actually try the adapter on the laptop since I have no idea if the person who fixed it knew what he was doing.


texts:
I am trying to implement an algorithm on audio signals. The algo operates on the signal on a frame-by-frame basis. One of the intermediate stages requires addition of the signal to the previous frames. The output frame is saturated at the end of this stage.

Clarification: The output frame of the addition operation is in double, though the final output frame HAS to be in short. Thus the problem with saturation.

I have tried the following for prevention of saturation:
1. hard-limiting: Limit any sample to a pre-defined max_val.
2. Normaliation: Compute the max. of the frame and then scale every sample in the frame appropriately.

None of these approaches have worked since I have to work on a frame by frame basis.

Any help on preventing saturation of signals is most welcome.


texts: These are two examples from the book. Why in the first one it's neglecting \$i_{2}\$ ,shouldn't the diode's current be found with Kirchhoff's first law like in the second example? How can I know when to consider the second current and when not? I know that the diode's current get's very large for forward voltage but why the current isn't neglected in every parallel circuit like in these two.


texts: Inductive wireless mobile charger circuit

texts: In wireless mobile charging circuit, is there any formula of spacing which varifies that by increasing diameter and turns, spacing (range) can be increased?


texts: How are very long component lifetime claims ascertained/evaluated?

texts:
Its a common specification for household devices such as lightbulbs. However, I can't figure out how you'd truly evaluate/prove such a claim without running the device for the specified amount of time.

Consider a lightbulb that is said to have a lifetime of 9000 hours. If I were to test this, the only way I can think of truly measuring this is to let the lightbulb run for 9000 hours, which is approximately a year!

If a year is not long enough, consider certain LED bulbs rated at 50,000 hours!

Clearly its not feasible to run a test for this long. So I guess I'm asking; on what basis are these claims made?

Perhaps one way to test it is to stress the component at higher than normal operating conditions, so that it burns out faster, and then somehow create a prediction based on measurements. Or perhaps run the component for some (short) time and measure the deterioration/ageing and use that to create a prediction.


texts: PCB Trace Width : Common (LINE) Trace for 2 Relays

texts:
I am designing a simple switch controlled relay board. On board I have two 5Vdc 10Amp Sugar Cube Relays which will receive 230Vac from Terminal block connector and will be controlled with 5Vdc input via SPST Switch.
Operating current : 10 Amps
Terminal Block : Pitch 2.54mm
According to trace width calculation trace width required for 10 Amps is 4.2mm
PCB Copper Thickness : 60 micron
PCB Schematic and Layout are attached,

Will 230Vac LINE trace from terminal block (Pin 1) to both relays(via Relay K1) needs to be 4.2mm or 8.4mm(i.e. double) or different as single trace is coming from terminal block and going to both relays?


texts:
I need to switch 8 IRF9540 (P-Channel Mosfets) with about 32kHz (so 1 MOSFET about 4kHz) so that only one is On at one time. I thought about using the decade counter 4017 for this, and the 555 Timer for driving the 4017. Because of the low output current of the 4017 the Mosfet would take a long time to switch completly or am I thinking wrong? Is this a possible layout for a simple Mosfet driver for switching the mosfet faster than without the npn transistor?

EDIT: Maybe it's helping I have to switch 4A at maximum. It should switch with about 32kHz (so 1 MOSFET about 4kHz)

simulate this circuit – Schematic created using CircuitLab

respectively what is the differnce between these two schematics in switching speeds?

simulate this circuit


texts:
I want to use the full output resolution of DACs (12bit) in the range of 0-1 Volt (and not in the range 0-3.3 Volt). I see there is a pin VDD in this board (STM32F429ZI), please help me to understand how use it or other pins (what is the correct connection to be used) to correctly set the desired maximum voltage of DAC.
In addition, if I change the reference voltage for DAC, do ADCs consequently use this voltage or can I set different reference voltage for them?


texts: common-mode noise in single-ended parallel wire

texts:
As we all know that common-mode voltage is the average of voltages in two lines Vcm = (V1+V2)/2. So as shown in the figure below, a transmission line composed of two parallel wires above a ground plane, there will be common-mode noise of 8V coupled into ground.

Everything is clear to me by now, however, when I am thinking another case, as shown in the picture below, where the voltage on second line is 0V (GND, same as the ground plane), based on the same equation, the common-mode noise will be 5V. However, to me it is no longer a differential pair, it is actually a single ended transmission line, can single ended transmission line have common-mode noise (coupled into the ground plan in this case)? This is where I confuse about. Thanks for your answers!


texts: FM Quadrature detector - is it the best choice

texts:
My input is an FM carrier of 80.00MHz. It is FM modulated with 625kbpsec data. The deviation from carrier is about +/-700kHz. The data never spends more than about 38us in a low state or high state i.e. it is scrambled. Carrier is frequency locked using a PIC and a PLL (ADF4111 from memory but this isn't too important other than to say the varactor that "centres" the frequency is fed from a much slower signal than even the lowest data might produce). Please ask if I've forgotten anything relevant.

The above are all givens.

I'm considering using FM quadrature detection - is this the best choice given that I can't alter the transmitter design (well maybe not this month anyway!!).

EDIT - March 21st - the answer below about counting the cycles stirred thoughts and it provoked me to consider using a high-speed Exclusive or gate as an alternative to the conventional mixer circuit within the heart of the quadrature detector. It would still require a resonant 90º phase shift circuit and simple amplitude limiting so, is this a better choice? Options

Conventional Quadrature Detector
Quad detector using an exclusive or gate
Cycle counting techniques
A PLL (I've added this but i can't see a decent way of doing it though somebody may)

If one of the above is the best technique, an answer that adequately justifies it gets the nod from me!


texts: Sending and getting commands through the Internet

texts:
I have a little chopper (adult toy to be exact) that can be controlled by the controller within 30 metres. What I have in my mind whether I can send commands to this toy chopper though the Internet, a website (maybe fetches the HTML or php code) or whatever--the chopper will use the Internet just like we use the Internet on our cellphones. Briefly, Instead of pushing "turn right" button on the controller, I want to send that command through the Internet so that it will have a very large range, or unlimited, to be contolled.

I am an engineering student so I want to build something touchable right now:) The problem is that I dont know where to start. I would google it but I don't even know keywords to search for. So even little push would be great. Which devices should I use, which language should I know, exactly, what is next I should do now?

I hope I am not asking this question in wrong place.


texts: Wireless power transfer choosing of mosfets

texts:
I'm an ee student and for the group project we have chosen to make a Wireless power transfer. Our goal is to charge a laptop. As for the result we have to demonstrate charging a laptop, so considering modern laptops I think we need at least 60-80 watts of power to be transferred to the receiving coil.

So for the first step we need to create the driver for the primary coil which will creates an alternating current using DC voltage, for the purpose we intend to use a H-bridge and a mosfet driver and an arduino.
The purpose of using an arduino is to be able to vary the switching frequency.
Also we intend to use resonant mode instead of inductive mode because the resonant mode can transfer energy more than inductive.

As our syllabus doesn't cover any of this wireless power transfer, we are gathering information and learning of it.

Is the use of h-bridge is suitable for this purpose?
Input voltage of transferring is 12volts, on which factors we should choose the mosfets on the current rating.

We are also in a tight situation as we only have about 2 months to complete this.

Note:- the distance between two coils can be just few centimetres and the receiving coil won't be built to the laptop. For the demonstration purpose we will just use the secondary coil and laptop apart from each other.

Any help would be appreciated.
Regards


texts: Can I fix the Weller PES51 soldering pencil?

texts:
I have a Weller WES51 soldering station with the PES51 pencil. It's about 10 years old however I have kept it very well. I've changed the tip a few days ago and noticed that the tip does not get hot enough to melt the solder. I've turned the temp. dial to max. and tried again and still it would not melt the solder.
After the pencil cooled down I took it apart and noticed that the heating element (or at least the part of it that comes in contact with the tip) is heavily corroded, so much that most of it is black. Is this something I can replace or does this mean the entire pencil has to go?

Update - I've spent some time online and it seems that the heating element is something that one can buy online for $40+ which makes it a bad solution as a new pencil is about $50 shipped. Another problem could be the the temp. sensing which might or might not be cheaper to fix but I don't have anyway to measure the tip temp. at this point.


texts:
I have a problem with uploading my EasyEDA project to EAGLE.
Is there a way to open project from EasyEDA in EAGLE, I'm unable to find anything about it.
EasyEDA exports files in .json format.


texts: Something is wrong with my understanding of this D-Flip flop design

texts:
I am a little rusty with flip-flops.

Consider this diagram:

This is a 4 channel stereo digital switcher. I am trying to understand the flip flop and the OR parts.

Because this is a 4 channel switcher, my feeling says that the flip-flops and the OR gates will be providing 4 different outputs and I am trying to understand how it works.

Lets talk about FF1 and FF2.

When the circuit is first powered, C15 is an "short circuit" and will let 5 volts reach R17, making FF1 clock be 1 for a brief period of time and then charge and "cut" the current to R17, making it 0 volts. So, we see clock going from 1 to 0, during startup.

Because this D-Flip-flop CD4013 will not do anything on 1 to 0 clock transition, I think FF1 will be with the following states after startup: (Q = 1), (Q' = 0), (D = 1).

Because of the wiring between FF1 and FF2, after startup FF2 clock will be 1, (Q = 0), (Q' = 1) and (D = 1).

At this point the OR ports will be with these states (from top down):

N1 (0, 0).... output 0
N2 (1, 0).... output 1
N3 (0, 1).... output 1
N4 (1, 1).... output 1

Then I press S1. We have a transition from 0 to 1 on FF1 clock.

FF1 changes to the following states: (Q = 1), (Q' = 0 = D)

Nothing happens on FF2.

The OR ports are now

N1 (1, 0).... output 1
N2 (0, 0).... output 0
N3 (1, 1).... output 1
N4 (1, 0).... output 1

I press S1 again. We have a transition from 0 to 1 on FF1 clock.

FF1 changes to the following states: (Q = 0), (Q' = 1 = D)

Now the clock of FF2 changes from 0 to 1

So, FF2 changes to: (Q = 1), (Q' = 0 = D)

The OR ports are now

N1 (0, 1).... output 1
N2 (1, 1).... output 1
N3 (0, 0).... output 0
N4 (0, 1).... output 1

I press S1 again. We have a transition from 0 to 1 on FF1 clock.

FF1 changes to the following states: (Q = 1), (Q' = 0 = D)

Nothing happens on FF2.

The OR ports are now

N1 (1, 1).... output 1
N2 (0, 1).... output 1
N3 (1, 0).... output 1
N4 (0, 0).... output 0

So, in sequence, the OR ports will produce, from top down:

0111
1011
1101
1110

But here is the problem, 4066 is a switch. Looking at my numbers I see a zero changing position. But in that case, I would expect the inverse of that, I mean

1000
0100
0010
0001

or a 1 changing position, so this 1 could select one of the four channels of IC3 and IC4 as stated by the 4066 data sheet.

Where is my error?