texts: PCB Technique for Disconnecting Decoupling Capacitors

texts:
I'm working on a PCB design for an FPGA chip where I want to do power analysis and voltage fault injection. Because of that I want to minimize the decoupling capacitance of this chip, but of course it should still work. I don't know the exact amount of capacitance required and would like to easily experiment with different values and capacitors.
What would be a good way to quickly connect/disconnect (different) decoupling capacitors from a chip? I'd like a quick and easy solution without soldering again and again. I've thought about jumpers or SMD dip switches but was afraid that the inductance would be too high or the current capability too low for the capacitor to still be effective. Sockets for SMD capacitors would probably be perfect, but I've never seen something like that.


texts:
Today I saw the schematic of a lenovo G480-la-7981p (download or download). On page 6 you can see this part:

In the green box you can see a buffered Reset line. My questions are:

Why they've used a buffer? To filter noise?
If so, then why a buffer? why not a simple capacitor?(e.g. 100nf) or an LC filter?
What's the usage of resistors R32 and R34?
I'm still diging whole of the schematic but don't get what is the difference between this resistor symbol  and this one  ?

Edit: datasheet of SN74LVC1G07DCKR


texts: Need help with break beam sensors for an art installation

texts:
I've been commissioned to create a piece of public art that fuses technology, light, and sound.
The final piece must have six beams that can be broken and trigger musical notes. My first idea was to use break beams sensors and an Arduino or several Arduinos if needed.
I have, however, no background in this type of thing although I am a lighting engineer so have some grasp of basic coding and electronics.
My issue is the gap between the break beam sensor and emitter is around 2 meters. With there being 6 of them next to each other (side by side) I clearly would need an industrial sensor that is super directional.
Is this a silly solution and if so I'm open to suggestions on alternatives? If this is possible then I have no idea what the best components are and could use some advice.


texts: How to connect a frame buffer to an LCD monitor through DisplayPort or DVI in an integrated system

texts:
I would first like to state that I am primarily a software engineer. While I have spent 14ish hours researching this so far, I apologize in advance if I miss a core concept or use incorrect terminology. Feel free to correct me if I do!

I am currently working on an electrical generator that is run by an integrated main micro controller. Right now I am displaying the user interface with a simple display module over a serial connection, but it will eventually need to be able to connect to a commercial LCD monitor.

Most modern monitors have HDMI, DVI, and DisplayPort inputs. HDMI requires a royalty for it's use in a commercial project, so it's not an option.

Going forward I am working under a 4 component model.

Main micro ---> Frame Buffer ---> Display Controller ---> Monitor

I will have a main micro that writes 24bit RGB values to a frame buffer. The display controller will then pull a frame of those values, process them, and send them to the display.

Writing the values from the micro to the buffer will be no problem. It's from that point I am not sure how to proceed. When googling for display controllers online, I can find none that will output to DisplayPort or DVI on their own. Most of them have 24 outputs for each color bit as well as a few other important things for an LCD screen such as horizontal and vertical sync and a clock output. Page 731 on (http://ww1.microchip.com/downloads/en/DeviceDoc/DS60001476B.pdf) is a good example.

No where on the internet have I been able to find a way to put that sort of output on a DisplayPort or DVI wire so that it can connect to a normal display. I've found such little information that I fear I might be missing something very fundamental about one of these concepts.

Is there something I am missing, is this just not possible for some reason, or am I simply not searching the right terms?

At the end of the day, I really just need to get a frame of RGB values from a chunk of RAM onto a normal 720p monitor, so if anyone knows a better way to go about this then I would be happy to hear those suggestions as well.


texts:
How do I start with this question?

There are 2 transistors which are more complicated and I have no clue on how to start working on it.

  The transistors shown in the figure below operate in the active region and have \$ \beta=100\$ and \$V_{BE}=0.7\$ V. Determine \$I_C\$ and \$V_{CE}\$ for each transistor.

simulate this circuit – Schematic created using CircuitLab


texts: Using 27MHz car with 49MHz remote control

texts: I managed to do something like this guy here, but after I connected the Arduino to the 49MHz remote control, I figured out that I have another car which works on 27MHz, so I would like to ask is there any way with which I can control the 27MHz car with 49MHz controller?


texts: How is an incandescent light bulb used for gain stabilisation?

texts:
If a circuit like the Wien bridge oscillator below uses an incandescent bulb for automatic gain control, how does this actually vary the gain?

I know that the resistance of the bulb increases as the filament heats up, but I've been told that it can be used as a variable gain element for gain stabilisation. What I don't understand is how it varies.

As far as I can tell, the bulb in this circuit is being used in place of another resistor that forms a voltage divider with R3 which outputs to the op-amp's inverting terminal. If the bulb was replaced with a resistor, R4, I could understand how selecting values for the resistors would allow the user to control the gain, but I don't understand how the lamp does it.

Maybe I'm misunderstanding, but from what I could tell, the lamp was able to control gain automatically, instead of needing to be a chosen value of a resistor. Is it because incandescent bulbs heat up so much that the resistance is constantly increasing? And if this is the reason, how is this property related to the gain of the circuit?

I'm also wondering what is the actual advantage of using these lamps instead of other gain stabilisation methods like JFET or diodes. With most incandescent bulbs not being used any more due to their inefficiency, is there any particular advantage that would mean someone might prefer to use it in their circuit?


texts: What to look in a desktop/small DC Power Supply?

texts:
I'm looking for the most adequate power supply that can go between ~0-30v and ~0-5A. These are going to be used for software development for automotive infotainment systems and the operation specs for the current one that we are developing goes from 7-18v at 1.4 A but could vary slightly in the future.

Beyond those specs, what other specs are good comparison points to tell how good is a power supply? (i.e. stable & clean power). Do brands matter?, if so, why and how?.


texts: Will this H-Bridge and it's driver work?

texts:
I am creating a half bridge, I though about it a bit and came up with this idea
First for the controlling side we have a typical 555 timer wired up like this

(But the resistors are variable resistors to adjust output frequency)
It's output is then fed into a mosfet driver (Which i don't know how to quite use yet)( It is an IR 2112) in this way

and then the mosfet driver's output is connected to the two mosfets in my Half bridge, Is skipping a gate drive transformer safe for this?
Also,Is all the wiring correct?


texts: Will a 3HP motor ever use less electricity (power) than a 1.5HP

texts:
You have two motors, one being 1.5HP and the other being 3HP. All other ratings are the same (e.g. motor efficiency ratings).

You attach a load to each motor. The load on each motor is identical at any given point in time. This load will range from no load to some stall load (obviously the stall load would be greater with the 3HP motor).

So for example, no load on each, take reading (how much power draw), add load, take reading of power draw, add more load, take reading of power draw...all the way to stall load...take power reading.

My question is, up until the smaller motor stalls, will the larger motor ever consume less power? Same goes for say a 2HP vs a 1.5HP. Can someone point me to the formula for doing this type of calculation?


texts:
I need a way to transfer small amount of data (4 8bit integers + checksum) over wireless.

I'm struggling to find any information dealing with sending serial transmissions over some sort of radio link. Sending is quite simple, but I have no idea how would the receiving end work, as it needs a clock, which can't be provided over radio.

The second thing is I don't really know which technology to choose for the radio. I'm hoping to build something really really simple and cheap. Range wise i'd be happy with a few meters, say 10, in unobstructed space. Transmission speeds of about 10kbit per second would be sufficient, I think at that speed the bandwidth falls within voice range.

I've built a small FM transmitter before but I have no idea how to make both transmitter and the receiver with a fixed tuning that won't drift when the circuit heats up or the antenna changes shape.

Also I realise that this question is a bit vague, and i'm not looking for finished solution, just some pointers on how to address these problems

Thank you

EDIT: I haven't made up my mind yet. The proposed modules are either more expensive or require more work to set up in the configuration that I want.
What I think i'm going to do in meantime is build a small FM transmitter with two signal generators, each frequency associated with 0 or 1. I can generate the frequency directly from the MCU on the transmitter end. On the receiver I will do a simple freq filter, that should give me 0 or 1 output, I still have to figure out how to clock it though. In the end total parts will definitely be under £1. i'll try to find some material on data transmissions, maybe there is a better way of doing it.

Thanks for the answer Anindo, I will accept if my attempt ends up futile.


texts: how to remote control LED matrix within nearby sealed environment

texts:
I want to display text on an LED matrix that is located within a sealed environment.  I want to change the text by remote control, by using my iPhone.
Power is available in the environment for electronics.
Environment allows RF.
iPhone would be about 10 feet away.

WiFi or Bluetooth sounds good.
I want to do as little hardware development as possible.
What low power microcontroller will work?  I can program it myself.

How can I do this?


texts: Why does the bias decreases in this clamper circuit?

texts:
I'm trying to do a positive clamper circuit in easyeda.com to bias a triangular signal of 200mV pk-to-pk at 1kHz centered around 0V. Here's the circuit:

The bias seems to work only during the first cycle:

But as you can see, the bias exponentially decreases slowly and after ~1s, it's almost at the same DC as the original signal. What I want is a circuit that bias the signal for half of the pk-to-pk so that it always stays like the orange signal in the 2nd picture.

The triangular signal's frequency could be from 1Hz up to 1kHz. Why does the bias decreases in time? Would you suggest another circuit to bias this signal without the decay that would work for the frequency range I want? Does it has to do with the values of R and C?


texts: What is the difference between a USB Hub and an the I/O device?

texts:
I am learning about the USB interface. My current understanding is the following:

The Host Computer contains an I/O interface, called root hub. This root hub is connected with either other hubs or I/O devices.

Now my question is. What is exactly the difference between hubs and I/O devices? There is a diagram in the textbook I am reading that shows the two as clearly being difference from each other:


texts: What are the series inductors used for in this filter?

texts:
Regarding the below filter, are the series toroid inductors at the very right end of the filter used for CM or differential mode filtering?:

I think R and Cx are for differential filtering. And the CM choke in the middle and the Cy caps are for CM filtering.

But how about the series inductors at the very end of the filter lines L' and N'?


texts:
How many LEDs can I supply from my home power supply.
If I make AC to DC the voltage drops too low.I read this article but dont tell the output DC voltage http://www.wikihow.com/Convert-AC-to-DC .


texts: Why do we sometime use Pins instead of explicit Power Sources in Cadence?

texts:
Is it something technical? I read the manual and few tutorials, yet I could not find the reason of switching to pins (especially in digital design).

For example:


texts: SN74HC138 demultiplexer. How do I implement a switch?

texts: I have this demultiplexer and I need to configure it in such a way that I can control 8 transistors using its outputs. They NEED to be NPN transistors, so when I select an output using the addresses, it must give me logic level 1, not 0. The problem is, in the data sheet of this multiplexer there is a logic table and according to it there doesn't seem to be any possibility of getting a HIGH logic level at the selected output, and only LOW logic levels at the other, not selected, outputs. Is there a way I can do that using this demux?


texts: What is the exact name of this type of transformer?

texts:
I know, it is a (1:1) isolation transformer [wrong, see answer], found in some power supplies. However, when I search on this I get all kind of transformers except these. I have searched with the numbers on the components without any result.

Especially the middle one is very useful as ground loop isolator for analog audio (test results - great frequency response) and compact, however, got only one of these (two channels need two 'copies'). I know, there are audio transformers available and the reviews are mixed especially for the cheap ones, so I want to find a diversity of these transformers to be able to pick up two (at least) of these because I know it can be useful.

What is the exact name of these kind of transformers?

Two photos of the three I have:

update 18-march-2018:

The answer points out those are common mode filters/inductors/chokes. Played with many of these with great results. You can use these as a (1:1) isolation transformer however, you need a resistor in serie with the device for each channel on the input side to avoid pre-amp clipping on high gain/volume of the pre-amp on the input. These coil devices have a very low resistance, almost zero or just a few ohms. I figure out that it must at least 300 ohms, after adding a resistor of 300 ohms the clipping is gone.


texts: Why my buck converter is not performing well?

texts:
I have designed this buck converter which was supposed to lower the input voltage range 13V - 15V to the 5V and should be capable of delivering 1.5A at 5V. It actually works okay with not load, I measure 5.17V, also works with small load. But when I connected actual load, which would draw current of 1.5A - something just happened, inductor started to make noise and the chip burned(although the white smoke did not left the chip).

Is it possible that this load has peak currents which are too big for the output capacitor? I wasn't able to power it from benchtop adjustable power supply which should be capable to supply 2A - although it works for few seconds on it and then restarts(it is Raspberry Pi with external LCD).

The component pick is coming directly from the TI WEBENCH tool. You can see them in schematics. The actual chip used is TPS563219. *9 is Bourns SDR0805-3R3ML inductor. C20 is C3216JB1A476M. C21 & C22 are GRM31CR61E106KA12L.

This is my schematics and board layout(2-layer, 1oz copper, made in Altium Designer). Beneath whole design there is clear copper pour connected to GND, with no other traces. (S1 is here for different reasons, not connected to the switcher design)

What might be wrong? Is it in peak currents that my load draws? Is the layout wrong at some part? Am I using the wrong chip?
(I haven't tried connecting output to osciloscope before burning it).


texts: How significant is 16bit in 16bit PWM resolution?

texts:
Is there any significance other than the granularity of duty cycle levels?. I'm working on an led driver where the light output levels should be very smooth while dimming. There will be 254 levels of brightness. if it is just about brightness levels a 10bit PMW is enough, isn't it?. Is there something to do with PWM frequency and resolution considering the flickering of led.
Any help would be very much appreciated.

Thanks


texts: I'm trying to estimate the direction of arrival of sound using a microphone array. This requires me to find the delay of the sound signal upon arriving the different microphones. For  convenience, I was hoping to use 4 USB mini microphones and connect them all to a USB hub to create a 4 mic array. Is this possible?


texts:
Please refer to this reference design for AC701 (snippet below).

The schematics, specifically the current sensing sections in pages 34-36, show this:

I want to understand why, for the REF output of INA333, there is a pull-up of 0.05V?


texts: Identifying 60's vintage PE Ebner amp components: are those capacitors or resistors in the picture?

texts:
In the picture there are:
1) 2 brown ones with (silver, black, yellow) bands
2) 2 beige ones with (silver, red, red, red)
3) 2 beige ones with (silver, red, red, orange)
4) 1 beige one with (silver, yellow, red, brown)
5) 2 black ones with (silver, yellow, purple, yellow)
6) 2 small silvery ones with 10?? (and also 25V that cant be seen on the picture) written on them (connected to the triple red silver ones).
7) two yellow caps with 47000pF 10%

What are the 1) - 6) ones? Are they caps? Resistors?


texts: I have a circuit with both logic-level control ICs (5v) and power electronics (FETs, relays etc @ 60v). I am powering the logic level supply from a USB power bank and the power side from my lab bench power supply. Depending on where I connect the ground clip of my DSO, the measured voltage of any signal changes. There is also a huge level of high frequency noise on my measurement lines from the DSO’s perspective, no matter where I connect the ground clip. I recognize that by wiring my two ground lines together I am creating multiple paths to ground, which is a bad idea and creates noise in my circuit. What should I do for my circuit to eliminate noise induced by having two supplies?


texts: Will this servo stall detection circuit damage an Arduino?

texts:
I am part of a group building a project for school that involves a servo. We made a circuit for our Arduino to detect when the servo is under heavy load / stalling. The circuit we built detects stalls quite well, but we aren't sure about circuit damage.

We know there are other "stall detection" circuits on the web. However, we wanted a generic form of detection that can be accomplished with a method that:

Uses common components we would have lying around (resistors, caps, diodes)
Needs no heavy-power-rated "shunt" resistors
Needs no ICs
Doesn't reduce the output of the servo

Here is what we have:

The servo PS (V1) has it's + line going through a 75KΩ resistor, and then to an analog input pin on the Arduino (A0), with a 0.1μF ceramic cap going to ground, and a Schottky diode from ground to A0.

When the servo is moving without additional load, the current was measured at about 100mA. Under heavy load, it draws about 300mA. A complete stall is about 500mA.

When the servo is under low load, the analog pin reads 1023 out of 1023, with a small amount of bounce down to around 900. If the servo is under a heavy load, the bouncing is strong. Under a complete stall, the analog reading stays around 850 with little bounce. Obviously those readings weren't difficult to use for stall detection.

As for protecting the components, I am not very familiar with flyback or EMF. I was not able to find anything about them in relation to servos, only regular motors, almost as if people aren't worried about servos. It appears some people believe the internal circuitry of servos protects from flyback/EMF...?
The diode was added for flyback protection, but I don't know if it really helps in that setup.

We are also not sure how a servo is supposed to act in relation to resistance and voltage drop under load. The stall detection was put "before" the servo in the circuit so as to avoid reducing the power of the servo by having a resistor in series with it, and to avoid having to order a heavy-power-rated shunt resistor. I can't personally say why this detection works, but it does.

Regardless, can we continue using this circuit as-is, or do we run a large risk of damaging the Arduino? If the circuit needs modification for safety, what would be a minimal way of doing so with common components?


texts:
De Morgan

$$y=\overline{a+\overline{b(\overline{c+d})}}+\bar{b}$$
$$y=\bar{a}(\overline{\overline{b(\overline{c+d})}})+\bar{b}$$
$$y=\bar{a}(b(\overline{c+d}))+\bar{b}$$
$$y=\bar{a}(b\overline{cd})+\bar{b}$$
$$y=\bar{a}b\overline{cd}+\bar{b}$$

This is as far as I've got on my simplification:

$$x+\bar{x}y=1+0\cdot1~or~0+1\cdot1$$

So it might be

$$1+0~or~0+1=1$$

But

$$\bar{a}b\overline{cd}+\bar{b}=\overline{acd}(b+\bar{b})=\overline{acd}\cdot 1=\overline{ac}d$$

I can't understand why it's will be \$y=\overline{acd}+b\$, so how I must to minimize this \$b\$?

Maybe I solved it!
a'bc'd'+b'=
(a+b'+c+d)'+b'=
((a+b'+c+d)b)'=
(ab+b'b+cb+db)'=
(ab+1+cb+db)'=
((a+c+d)b)'=
(a+c+d)'+b'=
=a'c'd'+b' Is it correct?


texts: How to calculate equivalent capacitance to a battery?

texts:
I have a 1.25V 2Ah battery and I'm trying to calculate a equivalent capacitance with rated voltage of 2.7V for each of those batteries. This is what I did:

Work of Battery = \$1.25V \cdot 2A \cdot 3600s = 9000J\$

From the capacitor work equation:

$$W = 0.5 \cdot C \cdot V^2$$

$$9000J = 0.5 \cdot C \cdot 2.7V^2$$

$$C=2469.1358F$$

Is this correct?


texts: Any examples of an SPI based protocol with a checksum?

texts:
I have an application in mind in which I need to communicate via SPI with an FPGA. Both the FPGA and microcontroller are in our control, and so I have the flexibility to define the protocol as I see fit. However, I was wondering if there are any good example uses out there that work well.

Here is what I was thinking. (byte oriented)

Master: <REG><WR+LEN><MSTR_DATA><CHK>
Slave : < 0 ><  0   ><SLAV_DATA><CHK>

REG : register within FPGA to read or write
WR  : read / write bit
LEN : 7 bit payload length (not including REG,WR+LEN or CHK)
MSTR: master data if write mode.
SLAV: slave data if read mode.
MCHK: 8 bit checksum of MSTR_DATA (by master), (CRC8, XOR, mod 256 etc)
SCHK: 8 bit checksum of SLAV_DATA (by slave ), (CRC8, XOR, mod 256 etc)

Is this workable? Are there any better examples out there?

EDIT1:
Some clarification on requirements:

The microcontroller is to read and
write small blocks of data to/from
the FPGA.
The FPGA will support
read/write operations to registers.
The registers can be many bytes deep
(like a fifo) or autoincrementing
(next read or write byte comes from
the next register).
I would like the
operation including the checksum /
ack to occur in a single
transmission.
I would like this have a low overhead, some operations will be fetching or posting 5-10 bytes. The largest could be 127 or 64.


texts: Simple single-supply op amp virtual ground questions

texts:
I found this circuit online and made it and it works.

It uses an LM358 op amp to amplify an oscillation from a 555 in astable mode.

simulate this circuit – Schematic created using CircuitLab

How were the values of R2 and R3 arrived at? I know they should be equal but why 100k?
What function does the capacitor serve? And how was its value arrived at? Is there a formula for these things or just trial and error?


texts: Downside to use a higher current Solid State Relay?

texts:
I need to buy a solid state relay and I found that the price difference between a 10A one and a 40A one is really small, sometimes even 0. So I'm wondering, what are the downsides of buying the bigger ones which is probably more robust if it's only a few cents more ?
I looked at the datasheet and from what I understand, the control circuit is the same, and the output voltage drop is also the same. So I'm wondering, with a price difference that small, the company making them would probably have benefited from only having one reference to build and sell, so if they're still making the small ones, there should be a reason, right ?


texts: What are the noteworthy differences between an inverting and non-inverting op amps?

texts: It seems like they both have the same ideal rules except that non-inverting op-amps are used more often. So what are the important differences between them?


texts: how to connect PIR sensor to arduino using RS485

texts:
I have to connect PIR sensor HC-SR01 to Arduino using RS485 such that PIR sensor's TTL signal gets converted to RS485 while transfer and gets converted back to TTL while receiving on Arduino side.
Since my circuit is not working as expected I replaced Arduino with a LED for testing. Can any let me know what is wrong with below circuit? my LED gets on for few seconds as soon as I give power and goes off after that indefinitely. Ideally it should be on and off when there is a motion in front of PIR sensor.

simulate this circuit – Schematic created using CircuitLab
the data sheet for pir sensor is    https://www.mpja.com/download/31227sc.pdf
my objective is
----> TTL ----> RS485 transmitter ---------> Long Cable-------> RS485 Receiver -----> Arduino
Thanks


texts: Running a 7v shift register from arduino 3.3v

texts:
Im trying to learn some electronics, so im not that confident with some of these systems,

I recently bought a load of the alphanumeric displays from Sparkfun  but foolishly read the data sheet for the red, then bought the blue. The difference is the operating voltage is 7v instead of 5v which is making things difficult.

I have also some shift registers, eg 74HC595 but they are rated only up to 6v, I have found other shift registers that take a higher voltage, such as the cd4006b, but they look like the clock and latch pins etc. also need to be at the higher voltage, so driving them from an Arduino is proving difficult.

Can someone give a simple solution or suggestion that im missing for keeping this simple?


texts: what is the good antena length for 433Mhz modules used for low distance domestic usage?

texts:
I want to use a low cost 433Mhz module  for low distance domestic usage, but I need to solder an antenna , (there is a place for that on the reception module),  to get a better signal across my walls. how to choose its length ?

I guess a simple wire of X% of wave length ??  or another calculation ?
or is this more complex & I need something more like an old radio antenna ?


texts: Electric circuit diagram proof check - simple

texts:
I'm completely new in this field (electronics, I began today) and therefore I am quite the newcomer and would like to know if I understood the purpose of the transistors and capacitors and the diagram in a whole.

This diagram is made for a remote controlled electronic electromagnetic toy crane.

LOAD 5 is the part where the electromagnet is supposed to be.

The crane is made out of primary scrap parts and therefore I do not know the voltage of the battery yet.

Diagram:

simulate this circuit – Schematic created using CircuitLab

My current understanding of the transistors and capacitors:

A NPN transistor can work like a switch. If at the base is applied a current it will allow the current from the collector to be emitted out through the emitter.

A PNP transistor can also work like a switch, if at the base there isn't applied a current it will allow the current from the collector to flow out of the emitter.

A capacitor can be used to stabilise the current and work as a backup source if the voltage drops aka it will try to make the current stay constant.

So to sum it up:

Would this work?
Did I use the transistors correctly?
Did I use the capacitors correctly?


texts: Collector currents of different BJT Models and Ebers-Moll

texts:
Per Horowitz&Hill book, the Ebers-Moll equation for the collector current in a BJT is:

Ic = Is (e ^ (Vbe/Vt) - 1)
where Ic is the collector current and Is is the saturation current.

Now, I am sure different BJTs (say, 2N2222, 2N3904, BC548,...) produce different amounts of collector current for the same value of base-emitter voltage Vbe.

(Q1) Would it be fairly correct to model those differences just by taking different values for Is?

In some books, the equation includes an ideality factor in the exponent. So, the equation gets written as Ic = Is (e ^ (Vbe/(n*Vt)) - 1) where n is the ideality factor. With that, the differences in collector current values for different BJTs can be accounted for by selecting different ideality factors while taking Is to be the same. That leads to my second question:
(Q2) Is it more accurate to model the differences in collector currents by taking different values for Is or by taking different values for the ideality factor?

Thanks!
P.S. My context: I am writing a simple simulator for BJTs.


texts: What's the purpose of components in these mosfet driver

texts:
I see these double ended transformer drivers on many places, I know the working principles of these gate drive transformers but still don't have an idea about external components that I've marked with red.

What's the purpose of capacitor connected series in primary, how the pnp bjt is working here, what's the purpose of these diodes and why two of them?

Thak you.


texts:
I was reading a specification sheet for a flash memory controller and came across a diagram for a particular command:

I was wondering what the "X" lines on the SI line actually mean?
Does it mean the line could be in any state, before CE# goes low, and we don't care about it at that point?


texts: Dependency of leakage on the gate oxide thickness

texts:
This is a follow-up question to this one.

I would like to investigate the effect of the gate oxide thickness Tox on the leakage current. To this end, I ran a set of SPICE simulations and plotted the obtained data:

Now, I am trying to find an explanation to this curve. As far as I know, leakage should increase exponential as Tox decreases; this can be seen on the left-hand side of the plot. However, a similar behavior can be seen also on the other side. So, the question is: What is going on on the right-hand side? Thank you.

UPDATE 1: The observed behavior seems to be what is described in the first paragraph of this section.

UPDATE 2: Using the notation introduced here, the following pictures displays the currents flowing through each of the four voltage sources (divided by two as there are two inverters in the circuit):

UPDATE 3 (by Vasiliy): Using the model file provided by Ivan I simulated the circuit and measured currents at all terminals of all the transistors separately.

Few clarifications:

Negative current means that the current is flowing out of the respective terminal.
Purple curve - Gate current
Navy curve - Source current
Cherry curve - Drain current
Green curve - Bulk current
Drain and Source currents overlap on the last graph (NMOS of the second inverter). Seems very strange as the polarity of these currents must be opposite. I double checked the Spice code, but it seems fine. Still, treat the last graph with care.

UPDATE 4: Please right-click on the graphs and choose "Open Image in New Window/Tab" to see them in full size.


texts:
I am doing a PWM with the PIC18f4550 and it managed to do it.
But only activate an output by varying the value of CCP1CON.
What I want to achieve is to have three PWM outputs and then be able to offset them to control a BLDC motor.

I attach the part of the code where I initialize the PWM:

public override PWM_Initialize ()
{
   PR2 = ("% # x", (_XTAL_FREQ / (PWM_freq * 4 * TMR2PRESCALE)) - 1);
   CCPR1L = 0x1F;
   TRISCbits.RC1 = 0;
   TRISCbits.RC2 = 0;
   TRISDbits.RD5 = 0;
   TRISDbits.RD6 = 0;
   TRISDbits.RD7 = 0;
   T2CON = 0x03;

   //CCP1CON = 0b01001100;
   CCP1CON = 0b11001100;

   TMR2 = 0;
   T2CONbits.TMR2ON = 1;
}

Attached image of the idea I have of the driver for the BLDC


texts:
I plan to build 2 high-side switch, following this circuit :

The two switchs will be controlled by a ESP32 output : 3.3V, 40mA max.
The first one should power on/off a device with 5V / 500mA max
The second one should power on/off a device with 5V / 5A max

The first device is made of and I2C chip, some leds and some sensors.
The second device is made of 5 servo motors.

All the logic to control I2C, sensors, leds, motors is working fine.
Now I just want to switch power of these devices.

Since I'm aware of programming and "logical" components but a total newbie to all power management questions :

could you tell me how to choose the right parts for R1/Q1 and R2/Q2, for each device ?
What parameters should I compute ?
Where do I found the relevant informations in the transistors/mosfets datasheets ?

Note : I know there's some decoupling/flyback diodes issues, this is not the point here.

Thanks.


texts: Magnetic Field Strength Measurement at Extreme Temperatures

texts: Hi I have just been given a project at work and we are magnetically stress testing DUTs at extreme temperatures going from -40 Degrees Celsius to 200 Degrees Celsius, I need to come up with a way that we can read the magnetic field strength while we are testing. I have tried looking into a hall sensor but i would need it in die form and cant find it anywhere especially in the temperature range given. Do ye have any suggestions, I only started as a Co-Op student and am drawing blanks as don't have much experience in this field.


texts: How to determine number of pixels required to interface any vga display

texts:
I have a guide that tells me that for interfacing 640x480 screen you need 800 pixels in a row and 521 lines along with all of that front and back porch stuff
I wanna know how do they determine that number?
If i have a screen of different resolution how do i determine the pixels and lines?
also the non displayable  area i.e porches and retrace time , how are they determined


texts: Using zero crossing detector for brightness control of several loads

texts: Zero cross detector(IC H11AA1) generates a pulse exactly at zero crossing of AC wave. I am trying to control the brightness of several bulbs(nearly 48 loads). I have 5 different states for them. At state 5 triacs will fire instantly. At state 4 triacs will fire after 1960 micro seconds. Same way for all other states with the delay of 1960 micro seconds. The problem is I need different logic instead of delayMicroseconds() method in arduino to avoid the unwanted delay. I need to generate four interrupts with time interval of 1960 microseconds after zero crossing detector interrupt for every half cycle of AC wave. Is there any software or hardware implementation?


texts: Calculating Rout of a bjt while using correct RL

texts:
I'm studying the notes of my professor of electronics, and I'm noticing an inconsistency of \$R_{L}\:\$  compared to what I've seen around in books and on the web. Here's what is considered \$R_{L}\:\$ in those notes:

As you see, it's taking \$R_{L}\$ to be \$R_{3}\$ and \$R_{7}\$ in parallel. In my book, \$R_{L}\$ is meant to be what in this image specifically is \$R_{7}\$

My main issue rises when I try to calculate \$R_{out}\$, which is supposed to be calculated with

\$u_{in}=0\:\$, and

\$R_{L}=\infty\:\$, meaning \$R_{L}\$ is to be removed from the circuit to calculate \$R_{out}\$

Coming to this, I'm confused as to which \$R_{L}\$ I'm supposed to be using, or which one is the correct one to begin with.

For example, in the professor's notes \$R_{out}=r_{o}(1+g_{m}(r_{π}//R_{th}))\$, while in my book, a common base bjt has \$R_{out}=R_{C}=R_{3}\$.

Topologies table:

Which one of the two ways is the correct one?


texts: How to detect potentially poor antenna placement from GPS data?

texts:
Below is data from a 6.5 hour run collecting NMEA sentences from a u-BLOX NEO-6 GPS module (datasheet, protocol spec) with an active external antenna via Raspberry Pi.

This is my first analysis to see if there is any way to detect poor antenna placement from the data, and flag a user if so. Here the antenna was placed very poorly, almost a worst-case situation with narrow sky view and strong reflections from between a pair of metal walls.

Every 30 seconds I collected 3 seconds of serial data, parsed $GNGGA sentences for lat, lon, alt, HDOP, and n_sats, and $GPGSV for C/No (dBHz) and alt/az of satellites used for solutions (alt/az not analyzed yet). If I understand correctly the presence of an SNR value for a given satellite in a given sentence (rather than a blank) indicates the satellite was used for a recent solution.

For GPS coordinates, each dot in the first plot represents results from one sentence, since multiple sentence appeared in the 3 second sample window, I've just plotted all of them as a first-pass analysis.

Question: What strategies might I try myself for a "poor reception" scheme? Examples might be:

too many HDOP's greater than X in a Y-minute interval
too many low C/No (dBHz) satellites used in solutions Sect. 7.4 (just asked What exactly does C/No (dBHz) mean in u-Blox GPS data?)
too many satellites with high altitudes (elevations) are not being used in solutions

If it's necessary, I can calculate the positions of the satellites independently, but it seems that should simply agree with the ephemeris data in the module and $GPGSV sentences.

note 1: I'm not asking about reporting an accuracy, that's addressed in the following question.

Inaccuracy in the GPS data
How to calculate gps accuracy in meters from nmea sentence information
How can I convert Horizontal dilution of position to a radius of 68% confidence?
How correct is the “Accuracy” value given by GPS devices?
Calculating absolute precision confidence number from Dilution of Precision indicators from GPS receiver

note 2: E-W and N-S coordinates are relative to median value of all data, Alt is absolute.


texts: How to achieve an interrupt frequency of 100 kHz on SAM E70?

texts:
Setup: ATMEL Studio 7, ASF3.47.0, SAME70 XPlained eval board.

In the minimum working example shown below, I use the onboard LED for visualizing if the timer and interrupt enabling have executed. PIO_PD20 is used to check if the interrupt is working. For that I simply connected my oscilloscope probe to MISO on the six-pin header near the center of the board. The code below works as expected up to frequencies of 2287 Hz. Once I choose frequencies higher than that, the interrupt doesn't seem to get triggered. What am I doing wrong? I need this to clock at 100 kHz.

I've also used the debugger to step through the individual lines of code. A breakpoint in the TC0 handler gets trigger at frequencies at or below 2287 Hz. Higher frequencies do not trigger the breakpoint, reconfirming that the interrupt routine doesn't fire.

#include <asf.h>

void TC0_Handler(void) {
    volatile uint32_t ul_dummy;

    pio_set_output(PIOD, PIO_PD20, HIGH, DISABLE, DISABLE);

    ul_dummy=TC0->TC_CHANNEL[0].TC_SR;  // read status register to clear interrupt flag.
    UNUSED(ul_dummy);

    pio_set_output(PIOD, PIO_PD20, LOW, DISABLE, DISABLE);
}

int main (void) {
    static uint32_t ul_sysclk, ul_div, ul_tcclks;
    uint32_t interrupt_frequency=2287; // in Hz

    sysclk_init();
    board_init();
    pmc_enable_periph_clk(ID_PIOC);
    pmc_enable_periph_clk(ID_PIOD);

    // Turn onboard LED off
    pio_set_output(PIOC, PIO_PC8, HIGH, DISABLE, DISABLE);

    // Timer and interrupt configuration
    ul_sysclk=sysclk_get_cpu_hz();
    pmc_enable_periph_clk(ID_TC0);
    tc_find_mck_divisor(interrupt_frequency, ul_sysclk, &ul_div, &ul_tcclks, ul_sysclk);
    tc_init(TC0, 0, ul_tcclks | TC_CMR_CPCTRG);
    tc_write_rc(TC0, 0, (ul_sysclk/ul_div)/interrupt_frequency);
    NVIC_EnableIRQ((IRQn_Type) ID_TC0);
    tc_enable_interrupt(TC0, 0, TC_IER_CPCS);
    tc_start(TC0, 0);

    // Turn onboard LED on
    pio_set_output(PIOC, PIO_PC8, LOW, DISABLE, DISABLE);

    while(true){};
}


texts: Very Long Range Beam Break Trigger Sensor

texts:
I am having trouble locating solutions for a long range trigger sensor. Want to detect an approaching vehicle 300 feet or more down the road from a pole mounted device. My first thought was a laser or IR beam break sensor, but the only ones I have seen need a reflector at the target point and the unit registers the absence of the reflected beam when obstructed. I cannot put a reflector in the middle of the road.

Only device I have ever seen that works similar to what I need are laser range finders but I would have no idea how to reverse engineer one. This sensor would supplement a PIR dome lens sensor in a security application. Can't give too many specifics but the PIR works great for pedestrians. However there is an inherent delay within my system between trigger time and when the system becomes active, meaning that fast moving vehicles are long gone before the system activates.


texts: What does a double arrow mean on a schematic?

texts:
In this schematic, what might the double arrows at M5 and M4 represent?

This is in the power supply for a 1980's CRT monitor, if that narrows it down any.


texts: How to generate highest voltage possible without sparking?

texts:
I need to precisely control high voltage in order to maximize the corona discharge zone while preventing arcing for a physics apparatus. The actual voltage when the corona breaks down will vary depending on environmental factors such as humidity, pressure, and contaminants in the air so the circuit would need to gradually ramp up the voltage until the point of arcing (indicated by sudden resistance drop / current spike) and then depending on the reaction time of the circuit either back off slightly on the voltage to arrest the spark formation - or else cut the voltage all the way back to zero, wait for the ionized path to dissipate and then ramp up to just below the established breakdown voltage.

This is exactly like keeping a capacitor teetering on the edge of its breakdown voltage - except if it does breakdown we get to try again instead of having to replace the cap!

Is anyone familiar with any tried and tested circuits that would fit this application, Or else just some suggestions for keeping down the component count? - The apparatus will be using multiple units either running independently, or managed by a separate control board.

The spacing between electrodes would be around 10 mm  to 20 mm which I'm guessing could take up to 30 kV before the corona broke down.


texts:
I'm currently working on the resonant tank design for an LLC converter.
When investigating different resonant tank designs, the allowed voltage stress on the resonant capacitor is a limiting quantity. Depending on the design, the peak voltage \$v_{c,max}\$ can be between 200 V and 500 V. The switching frequency will be between 150 kHz and 300 kHz depending on the operating point of the converter.
Most of the time when looking at ceramic capacitor datasheets, only a DC voltage-rating is provided. This specification from TDK suggests limiting the peak-to-peak voltage in AC applications to the DC voltage-rating of the capacitor:

The only datasheet I could find with some information on the AC voltage rating is this one from KEMET, providing this plot for example:

As you can see, for frequencies lower than about 150 kHz the plotted voltage rating is in accordance with the TDK specification. For higher frequencies, the voltage rating is decreasing. Can I infer a similar behaviour for similar ceramic capacitors that do not provide an AC rating? At 300 kHz, would a derating to 50% of the DC voltage-rating be reasonable even for other ceramic capacitors?


texts: No output reading from Op Amp on Oscilloscope

texts:
So I have an inverting op amp (gain = -1) wired up, and it works with a DC signal. I checked the DC signal by measuring the input and output voltages with a multimeter which were 5V and -5V, respectively.

Now I hooked up a function generator to the input signal. The input is now 5V peak-to-peak at 1kHz. The input shows up fine on the oscilloscope, but that is because it is practically connected to the source of the generator. When I measure the output, nothing shows up on the oscilloscope (just a little bit of noise). I tried connecting the output to the virtual ground and then measure the output with the oscilloscope, but that didn't do anything.

The op amp I am using is TL051CP.

How am I not measuring it correctly?

Solution

So I guess the problem was my signal was grounded and that messed up the output. I just removed the ground from the circuit, and it is working fine. I don't know why it works when the signal is not grounded.

I believe I was shorting the circuit with the oscilloscope, which caused this to happen.


texts: Trying to match Frequency-Gain chart in paper and not succeeding

texts:
I am trying to reproduce the chart on page 3 of this paper for the transfer function:

H(s) = 1/(1+jw/s0)
where s0=-3x10^9
or 1/s0=3.33e-10

I have tried in a spreadsheet as the paper suggests and had to fudge things to make them a close match.
I used s0=2e-9 to get to -40dB at 5x10^10 Hz. It seems somewhat reasonable compared to my next attempt (s0 only differs by a magnitude and some change).)
My next attempt was in python:
from scipy import signal
import numpy as np

S1=signal.ZerosPolesGain([],[0.000000002],1)

win=np.arange(0,6e10,10000000)
w,mag,phase=signal.bode(S1,win)
mag[0] # produces 173.97940009
mag[-1] # produces -215.56157724 <- I assume these are in dB

The values in mag seem even more off to me. Does anyone have any suggestions of what I can try to get the same results as the author?


texts: How is this circuit for interfacing 20V signal with 3v3 microcontroller

texts:
I have designed the following circuit to interface a 12-20V signal to a microcontroller running on 3.3 volts.
The signal is either 20V or open circuit.

I want the circuit to be as resilient as possible. It should be able to handle EMI and ESD.

R1 is to limit the current and bias the transistor.
C1 is to implement a low pass filter.
R2 is used to pull down the transistor base and discharge the
capacitor C1, the 20V input is either 20V or open circuit.
D1 is used to protect the transistor from negative voltage at the
base.
R3 is to pull up microcontroller pin.

Any comments and improvements upon this circuit are welcomed.

Side question: Whats the maximum positive voltage this transistor can tolerate. The datasheet states peak base current to be 100mA. If base is maintained at 0.7 volts, then input can be as much as 1000 volts (10k ohm * 100mA). But if input is 1000 Volts the potential divider makes voltage the base at 500 volts. And the maximum Vcb according to datasheet is 60volts.


texts: Making an 8-bit register using an 74LS377

texts:
I am trying to build a an 8-bit register using 74LS377 IC (It's from Motorola and the complete part name is 74LS377NDS but I haven't been able to find out what the extra letters mean, here is a datasheet I found: datasheet).

From what I understand, the IC's behaviour should be the following: if the enable input is low (it's an inverted input, active low) then the 8 D flip-flops should store the data at the input pins (inputs D0 through D7) at the next rising clock edge. Once the enable input goes high, it should retain the previous value. However, in the circuit I have constructed once the enable was set to LOW, the outputs mirrored the inputs (Q0-Q7) and when the enable was set to HIGH all of the outputs were turned off. I tried replacing the "clock" with a SPDT switch which would connect the pin to ground or Vcc alternatively and it seems as if the outputs turn on and off regardless of the clock. Furthermore, I observed the same behaviour yet again (enable goes low, outputs reflect inputs, enable goes high, all outputs turn off).

I am using a 555 timer in astable mode to generate the clock signal, and the connections for all the other 7 flip-flops of the 74LS377 are identical to the ones specified for D0 and Q0.

The data input pins are connected with SPST switches to Vcc and with pull-down resistors to ground (so that the inputs don't float).

I really don't know what is causing this behaviour and how can I make work like I want to (when enable goes high, the IC retains the outputs -- acting like a register)?


texts: Is an Arduino Uno capable of running 24/7?

texts:
I'm curious as to the reliability and durability of the Arduino Uno.

Does anybody have experience in "killing" one due to excessive use?

If so, how long did it take for the board to fail?


texts: What limits the lower bound of DRAM CAS latency

texts:
When a dram module receives a read/write command (while a row is active) it needs to:

decode the command along with bank and column.
multiplex the bank and send command along.
(when reading) move the data from the column's latches to the send buffer ready to shift out after the CL expires, barrel shifting along the way according to the column address.

(when writing) associate the relevant places in the receive buffer to he correct bank and barrel shift.

All this together seems to take a consistent 10 ns on modern DDRx dram modules while there is a clock that goes 10 times faster.

What is the biggest bottleneck in this sequence and could it be improved significantly or is there something else I'm missing here?


texts: Yet another constant current LED driver design, almost

texts:
I am about to design a constant current LED driver, with the following requirements:

The LED string is fed with 24 V
The FPGA interface is 3.3 V
The system consist of 8 LEDs in a row, with corresponding 8 sensors.
The LED current should be defined in 256 steps (in this case with a digital potentiometer => current is defined in 3.3 V / 256 steps)
There is a PWM signal that controls whether the LED should be on (when the sensors are measuring) or the LEDs should be off (the PWM is NOT used to determinate the LED intensity, only when to measure)
The PWM signal can either be always off, always on, or between 10-40 kHz with 50% duty cycle.
The forward voltage of the LED is 1.4 V
The max constant current (PWM is always on) is 100 mA and if a pulsed PWM is used the max current is 200 mA.

Any buck/boost solution is not applicable due to the ripple in LED current, which introduces ripple in the emitted light. This is the reason to use a constant current driver, unless someone has an example of a very good buck/boost driver, with less than 1% ripple.

Does anyone have a suggestion of an "out of the box" LED constant current driver chip, that will do the job?
Because the LEDs have forward voltage of 1.6 V and there are 8 in a row, the voltage drop is 12.8 V, the constant current driver must burn away the rest of the energy and with 0.2 A it means 2.24 W.

Is it a good idea to insert like a 2 ohm, 1 W resistor in series with the LEDs, to take away some heat from the transistor?
One attractive idea is use op-amp->transistor where the op-amp is fed with the voltage setting the current and the voltage from a shunt resistor below the transistor. The op-amp needs to be fast, to avoid problems with a MOSFET gate.

Is it better to use a MOSFET or BJT (they are more linear)? They have to work in their linear area.


texts:
Along with my z80 development board I found a 16166 16*1 display.

I have found datasheets for the electronics, it have 8 data (but can be run in 4 bit also) and 3 control, but I have failed to find any actual programming manual.

Can anybody help?


texts:
I have three OSRAM Quicktronic DIM T8 1x 18W in the same room. One is near the wall outlet, the other two are each about 10 m away. Each one is very close to the respective T8 tube.

While the first one has been grounded, given the proximity of the earth wire in the wall, now I have to connect the other two. I already have several metres of 2 wire electrical cable and maybe I could use that one, instead of buying some additional cable. Besides not having to buy more cables, the 2 wire is also quite more flexible and easy to route.

The ECG devices will be also used in dimmed mode and I plan to locate, just next to the ECG itself in a plastic enclosure, an Arduino or equivalent to add WiFi remote control to the 1-10V dimming.

What are the potential issues resulting from the lack of grounding?


texts: What is SEMTECH's "secret sauce" that makes LoRa Picocells viable?

texts:
tl;dr: "Standard" LoRa and specifically LoRaWAN are not designed to support many densely packed independently operated networks like WiFi does (for example). And yet SEMTECH has announced they will support LoRa Picocells for home LoRa networks. How do they overcome LoRaWAN's limitations?

I have news in several places that SEMTECH is now distributing the SX1308 LoRa Picocell gateway chip. In most places I read the same press-release material, but in EDN-Europe the title of the item LoRa Picocell Gateway reference design extends LoRaWAN coverage has the additional term reference design. I haven't been able to find this gateway reference design yet, perhaps it's available only to LoRa Alliance members at this point?

I would like to know how SEMTECH plans for the LoRa Picocells - at a density of say one per household - manage to avoid the collisions, blocking each other or otherwise interfering with each other that can happen if two radios (nodes or gateways) transmit on the same combination of frequency and spreading function (SF) at times close enough that they effectively overlap.

LoRa has primarily been optimized for low power, low data rate, low update rate, and long distance applications. Currently the best way to avoid these limitations is for multiple independent users to work with one or a few gateway providing services.

A home-by-home gateway implementation with from kilometer to tens of kilometer range would certainly lead to some problems, and since power is often available in homes, if there are any externally powered nodes they would not have the practical constraint of infrequent transmission to conserve battery life.

This answer to my previous question contains a hint about one potential method, and I can imagine others, including limits on transmitted power, but I would like to know how SEMTECH's plan for Picocell implementation actually does this, and at least roughly how it is specified, or how the LoRa chips must be configured for LoRa Picocell operation.

Some reference material can be found in:

Low Power Wide Area Networks: An Overview (2017)
Understanding the limits of LoRaWAN (2016)

NOTE: About the bounty: I can't edit the comment in the bounty, but recognizing that there really isn't anything official out there, at this point I will gladly consider careful, reasoned speculation.


texts: to lt spice users, how do you include a MOSFET into your ltspice circuit? if it helps the mosfet I'm trying to include is IRLZ44N


texts:
I am attempting to get an ESP8266 to read temp from an analog temp sensor (TMP36). The ESP is on the Adafruit HUZZAH ESP8266 breakout. The board has a single analog pin that I believe will allow me to do this. The description of the board says the analog input has a 1.8v max voltage. I will be supplying the TMP36 with 3.3v.

Do I need to divide the output of the TMP36 to get a proper reading? How should this division be done? Once it is done, do I also then multiply the reading from the TMP36 by they same amount it was divided?


texts:
I am trying to design a convertor from analog to PWM with very good THD as in this http://www.ti.com/lit/ug/slau508/slau508.pdf

The triangle generator  (fig 2) (I am trying for 750Khz to 1Mhz) is a very important aspect and any malformations or jitter will directly impact the THD

I have a second circuit that can make triangle waveform (you can see it http://www.circuitstoday.com/triangular-wave-generator from cmos input)

Anyone has any experience with those , what design should I concentrate on ?


texts: Replaced 4x AA battery with 6V 3A DC adapter, but device won't work

texts:
I'm hoping you smart folks can help me. I'm puzzled by what I thought would be a simple DC battery to DC adapter swap.

The device I'm trying to mod is a a microchip activated pet door (SureFlap Microchip Pet Door on Amazon for about $150).

It normally takes 4x Alkaline AA batteries. The manual does NOT recommend using rechargeable batteries because they may trigger a battery replacement warning due to their lower voltage.

I thought, I could take a 6V 3A adapter (actual 6.3V on DMM) and splice on some alligator clips, clip them onto the battery springs and not have to worry about my cats being locked in/out due to a dead battery. I was WRONG.

This mod resulted in a powered device, but no longer would the door trigger to my pet's microchips. Switching back to the batteries eliminates the issue completely. therefore, I know the device is not broken.

I have confirmed power is being provided to the device, by taking my DMM probe to the springs on the device, and by pushing the "Learn" button on the device, which puts the door into the learn mode (unlocks the latch mechanism to allow a pet to pass through and register, it's supposed to re-latch to confirm a learned chip).

Issues while on DC adapter power:

Putting the door into "Learn Mode" initiates the unlock mechanism for the pet to pass through, but does not complete the learn process (re-locking) no matter how many times I try. It just hangs perpetually unlocked in this mode until it is canceled. Again, going back on battery only mode I can learn a chip easily.
The device has a memory function so microchips do not need to be re-learned after a battery swap. However, previously learned chips no longer trigger the door to open. I can no longer get the door to trigger for my cats. Again, going back on battery only mode I can learn a chip easily.

I thought initially I had an under-powered adapter, as I had a 6V 1A (6.0V on DMM) lying around. I bought a 3A adapter mentioned above and the problem persists. I am absolutely puzzled.

Is there something I am missing about the characteristic differences of DC batteries and power supplies? I've had success in the past doing the exact same mod with toy motors and the like, but I'm wondering if the issues is due to the device being a more complex electrical device.

4x Alkaline batteries are 6.3V on my DMM, so I don't think over-voltage is an issue. Also, my 6V 1A power supply is dead on 6V.


texts:
I have an internship coming up working with comparators and amplifiers, so I wanted to take on a side project involving both of those components. Designing a D-Class amplifier seemed like a great way to get some experience making a more involved pcb layout, but before that, I wanted to verify that my schematic is ok. Below is the circuit I came up with.

LTspice Schematic

Link to LTspice schematic (google drive)

Inputs are a 1Vp-max audio signal from an audio jack and a 200kHz triangle wave.
For the triangle wave I am planning on using a SN54LS624 VCO. Audio inputs are offset ~.1V in in order to cause dead time for minimization of shoot through current of the amplifier FETs.

For my PWM I'm using a pair of LT1819s, chosen for high slew rate and ability to handle 200kHz without issue.

For the gate drivers I'm using LTC4440-5, chosen for its voltage output range. I've never worked or learned about a gate driver prior to this, so it's possible that I'm grossly misusing it. High side driver ranges from -20 to 42V, while low side ranges from -20V to 4V. Is there a way to change this? I don't think it's necessary to bia my NMOS at 42/-20V, and doing so might damage them at worst or slow them down at best. Is this something I'm missing or is my design valid thus far? I know that dual high side and low side drivers exist, and can have built in dead time, should I consider using one of those instead?

Power MOSFETs are IPB136N08N3, chosen for Vds max of 80V, and Vgs max of +-20V. My high side gate driver biases with a Vgs max of 22V, yet another reason I think I'm messing that bit up.

Filter is a 3rd order low pass with a cutoff of 23kHz and attenuation of -45dB at 200kHz. Initially I had a 2nd order but was noticing a low signal to noise ratio at the lower input voltages (Input = 0.5Vp).

Project is planned to use two 20V 3.25A DC power supplies, using diodes for 5V and ~1V (1V for offset and potentially for tri-gen). I've never had any experience with power supplies, so this is another shaky area for me.

Other concerns are current spikes in the push-pull NMOS show below. I don't think it's a big deal as each spike is ~25-50ns long, so maybe that's just the simulation being really precise and wouldn't happen in reality but I'm not sure.

^Power dissipation on high side NMOS

^Zoomed into spike, lasts approx 50ns


texts: Multiple dc-dc Converters mid-tap on batteries connected in series

texts:
I want to design a 48v system for an RV with multiple Lithium batteries connected in series (either four 12v or two 24v lithium batteries).

I like the idea of a 48v system to reduce the size of the wires needed for the high output inverter.

I would need 12 volts to run some of the systems on the RV (Fridge, lights, etc).

My question is: Would it be possible to connect two DC-DC converters across each of the 24v battery (or battery sets) instead of using a single 48V-12V converter?  I'm thinking this would make the lower voltage converters more efficient, but I can't figure out what the impact would be on the output end and the balancing load of the batteries.


texts: Minimal start-up current of a PV inverter

texts: In the datasheet of PV inverters, typically (only) a minimal start-up input voltage is given, e.g. for an SMA Sunny Boy the datasheet indicates 100V/125V. However, why isn't there a minimal start-up current specified as well? Assuming early in the morning: even if the PV modules have a total open circuit voltage of around 100V, the current that they generate can still be very low due to the low irradiance, for example 0.1 A. I assume that there needs to be also a minimal input current for the inverter to work properly. If the MPP stage of the inverter is for example a boost converter and designed to work in continuous conduction mode, the minimal input current should be related to the used inductance. I can't seem to find a lot of details on this topic, so any input is welcome. On Google Patents, there is this 'Inverter Setup Algorithm' (https://patents.google.com/patent/US7433215B2/en) where they indeed verify if the power level is sufficiently high but it dates back from 2006 so I suppose better methods exist now but I don't find any.


texts: Advice on selecting a replacement transistor for a high voltage transformer

texts:
We can replace a resistor or capacitor with somewhat similar characteristics if same not available. Similarly I want to know if we can replace a transistor with some other and is there any golden rule for this?
As in my case I want to replace BD679 with BD540 or BD711 as both are available to me.

I'm using it with a 555 timer.

BD711 datasheet

Material of transistor: Si
Polarity: NPN
Maximum collector power dissipation (Pc), W: 75
Maximum collector-base voltage |Ucb|, V: 100
Maximum collector-emitter voltage |Uce|, V: 100
Maximum emitter-base voltage |Ueb|, V: 5
Maximum collector current |Ic max|, A: 12
Maksimalna temperatura (Tj), °C: 150
Transition frequency (ft), MHz: 3
Collector capacitance (Cc), pF:
Forward current transfer ratio (hFE), min: 15
Noise Figure, dB: -
Package of BD711 transistor: TO220

BD679 datasheet

Type Designator: BD679
Material of transistor: Si
Polarity: NPN
Maximum collector power dissipation (Pc), W: 40
Maximum collector-base voltage |Ucb|, V: 80
Maximum collector-emitter voltage |Uce|, V: 80
Maximum emitter-base voltage |Ueb|, V: 5
Maximum collector current |Ic max|, A: 4
Maksimalna temperatura (Tj), °C: 150
Transition frequency (ft), MHz: 1
Collector capacitance (Cc), pF:
Forward current transfer ratio (hFE), min: 750
Noise Figure, dB: -
Package of BD679 transistor: TO126


texts: How can I keep this MOSFET in cut-off when Vcc > 5.5V?

texts:
This is a follow up-question for this question where I had troubles with a latch occuring at start-up. While solving the earlier issue I found another one which I had not been able to anticipate since this is the first time I'm playing with a P-channel MOSFET.

Have a look at this schematic, where I have stripped away everything that's not relevant to the actual problem:

Circuit explanation

The circuit is a part of a voltage monitor. Nominal input is Vcc = 5V, and if the voltage goes higher than 5.5V (feel free to read the above mentioned question for further details) the outgoing supply line (Vcc_OUT) is cut-off to prevent damage.

The opamp is configured as a comparator. It's unfortunately not rail-to-rail, so "high" is ~4.5V, "low" ~0.5V.

When the opamp output is "low", it means that the voltage tripping has not occured. The PNP (Q2) is therefore saturated and pulls the Gate to ground, making the MOSFET go wide open and Vcc_OUT is around Vcc. This is expected, and also works as expected.

When the opamp output is "high", it means that the voltage tripping has occured. The PNP is cut-off, and Gate is tied to Vcc effectively closing the MOSFET and cutting off the supply to Vcc_OUT. This also works as expected.

Background info about Vcc

Vcc comes from a linear regulated power supply. A 9V-transformer is rectified, fed and filtered into a 7805. Their design are beyond my reach. Sometimes error can occur and the Vcc gets raised slightly, and that's where my voltage monitor comes in.

Absolute worst case disaster scenario would be if the rectifier diodes and the 7805 all gets shorted, meaning Vcc will be 9VAC (RMS), around 13VAC. This will instantaneously kill everything.

The problem

The opamp controls the MOSFET as I expect, but when I played around earlier with my lab supply I increased Vcc to the level of the worst case scenario described above; 13V. At this voltage, the MOSFET conducted (or whatever the word, it was not "cut-off")! It should definately not conduct at this Vcc-level! My test-LED that's connected to Drain was very, very lit.

I turned my lab supply back to 5V, and the LED went dark. Increased to 6V, still dark. 7V, still dark. 8V: a tiny, tiny light can be seen in the LED. Increasing to about 10.5V made the Drain / Vcc_OUT have ~5V, and increasing to the disaster level 13V, Vcc_OUT was around 7V.

The guess

As stated earlier, this is my first try with a MOSFET so I'm unable to pin-point the error. My only hypothesis is that because Vcc is floating, and GND is not, the Vgs level is somehow affected at Vcc > 8V, making the MOSFET conduct (which it shouldn't).

The question

Using this setup, is there any way to keep the MOSFET cut-off at all times whenever opamp is "high", no matter what level Vcc has?

Datasheets: FDD6637, OPA2132


texts: Big voltage drop across MOSFET with LED strip load

texts:
I'm trying to power up a Giderwell RGBCCT LED strip using ESP32 (a 3.3V microcontroller) with the help of an IRL540N MOSFET.

My circuit looks like this:

(sorry for the amateurish/nonstandard diagram, I'm not educated in EE)

R1 is a simple pull-down resistor to ensure the gate is low while the chip is powered off/booting.
I actually have 5 MOSFETs driving 5 channels of an RGBCCT strip, but everything is the same if only one channel is powered.

My problem: When the gate is high and there is no load, I measure 12V across the drain and source terminals of the MOSFET (as expected). However, when the LED strip is connected, this voltage drops significantly, to 6-8V, depending on the MOSFET and channel I'm measuring. The LEDs are also much darker than when connected to +12V and GND directly.

This is a small segment of an LED strip containing 6 LEDs per channel, and by spec should peak at 300mA for the whole segment, so approx. 60mA per channel.

What could be causing this? I'm using a perfboard - is my soldering to blame? (It's pretty atrocious, this is my first soldering project.) Maybe I cooked the MOSFETs while soldering, causing them to not be able to deliver the current? Is the 3.3V logic level too low to fully activate the MOSFET? The datasheet suggests a max 2.0V threshold and ~10A of continuous current at 3.0V gate-to-source, which should be plenty. I might be missing another parameter though.

I measured the resistance from GND to the source pin on the MOSFET, and from the drain pin of the MOSFET to the cathode pad at the end of the strip, and it's around 0.3 ohm. If it matters, I used AWG 20 wire (0.5mm²) to connect everything, joined by soldering on the perfboard.

Update: I measured the drain-source resistance on the MOSFETs while their gates were high. Most of them have around ~20 ohms, give or take, while one has 3.9 ohms, but even across that one the voltage is ~9V, a 3V drop. For one with 25 ohms, the drop is 6V. I'm even more confused now as the resistances are different and the drops are not proportional to the resistance...


texts:
I have a coin cell battery operated device that I'd like to detect a weak pulse.
The device will be able to operate down to approx. 2.5 volt, so my Vref will be in the range 2.5 to 3V.

The pulse frequency is 30-300 Hz and measured with my oscilloscope it generates a signal as in the image below. I assume the signal is very weak (low current), but I've got more a less the same result when I set my probe on low impedance (X10).

I'd like to convert this pulse into a digital signal, and make sure that it's not fooled by the "bouncing" nature. I also need to bias the trigger and +-20mV might be a good delta value.

I've looked at using a single OpAmp or an instrumental amplifier, but I'm not sure what the most effective solution is. Actually I think I need a combination of the two, where the instrumental amplifier will just amplify the signal difference, and then I will compare the output with an OpAmp in comparator mode, where the negative input is my bias.

Anyway, I'm not sure whether this will work, or if there's an even better alternative.

UPDATE!

Well, I think I actually misunderstood WhatRoughBeast's answer, and reworked the pickup circuit to ground both the connecting wire and the pickup wire. I also wrapped the pickup wire around the connecting wire. Here's a drawing:

With this new wiring, I went out and measured two engines this morning, and the difference in signal amplitude is significant, so it's not a "weak" signal anymore.

Engine A:

Engine B:

Engine B is consistently producing a small unwanted spike in between the expected pulses

I'm glad that the pulses are much stronger now, but sorry that the premises of the original question are "slightly" changed. Anyway, I still need a trigger on this, and filter out the unwanted spikes from Engine B. I've got a lot of inspiration, and I see that you agree on a using a comparator for the job, so I will try to look into that.


texts: What kind of amplifier do I need for differential to single-ended audio conversion?

texts:
This is a follow up to my previous question: For my Amazon Echo related project, I realized that the speakers in the Echo are being driven from a differential amplifier, and not a single ended one.
What I'm trying to do is sample audio from the tweeter and subwoofer speakers into the ESP32 microcontroller for a music reactive LED project. The reason why I believe I need to convert the signal to a single ended one is because the signal needs to be referenced to GND so the ADC on the ESP32 will be able to read the signal properly.
Any help or additional info would be great.


texts: LED Polarity: Why does this LED have the anode as the short pin?

texts:
Typically the guidance seen is that on LEDs the long pin is the anode and the short pin is the cathode. Often it's also said that if you look inside the LED, the large plate is the cathode while the small plate is the anode.

However, this Lite-On LED has the anode on the short pin according to the datasheet. The short pin is still connected to the large plate, however.

I've confirmed that you must wire the short pin to the positive terminal of the battery for the LED to light up. What gives? First of all, is there a reason the convention is broken? Also, how come the plates are also seemingly reversed? Is there any particular reason for this or is it just manufacturer discretion?


texts: Inrush current and number of devices per MCB

texts:
I'm looking at some LED drivers meant to be powered by the regular mains voltage (230V). The datasheet specifies how many drivers can be connected to a single Miniature Circuit Breaker (MCB) on account of the inrush current and specifies the basic outline of the inrush current itself.

So, three values are always given on these driver-types' datasheets:

The peak value of the inrush current (A).
The duration of the inrush current measured at 50% of the peak level (µs).
The amount of drivers allowed on a type-B 16A MCB.

For most applications the amount of drivers per MCB is enough information - but i'm wondering (mostly for curiosity's sake)  if it is possible to calculate the amount of drivers per MCB GIVEN the information about the inrush current (peak and duration)? Or if more information about the inrush current is needed?

Also, is it possible to "combine" the inrush current of two different types of drivers?


texts: Stumped on a new mystery cord I found in my drawer

texts:
enter image

I am sure this will be easy for most of you. I found this new (to me) cord in a drawer and can’t figure out what it might go to. There is nothing written on it aside from a “B” at one end. Since my significant other is not claiming it I am all the more curious!  Thank you.


texts: Signal invertor for power switch using 3.5mm audio jack switch

texts:
I have a 3.5mm audio jack with a switch build in. When you plug a jack in the switch opens. I would love to use this build in switch as a power on switch for a small device so when i plug in a head phone jack it closes a circuit and powers on the device. I don't know how to use the open circuit of the audio jack to close a power circuit.

Can anyone help me figure this out?


texts: How does a computer signal via VGA for the monitor to sleep

texts:
Could somebody please explain how a "modern" monitor is told to sleep.  I need to know this for a VGA with blue connector, i.e. it has DDC.  I've heard that the sync stops.  If true, which sync?

Reason for asking: I'm trying to connect to an industrial single-board computer that has a 2 x 5 pin VGA header.  I've made a cable that matches the documented pinout, but the company doesn't output the +5V that should be on pin 9.  And the monitor stays asleep.


texts: Is "transient detection" exclusive to Freescale?

texts:
I'd like to detect the dynamic component of acceleration, i.e. the change in acceleration, and generate an interrupt when such change is detected. I see that MMA8451/2/3 calls this "Transient Detection".

However, I can't seem to find any other manufacturer supporting "transient detection". I've tried Analog, Kionix, STM, etc. Is it something exclusive to Freescale accelerometers or is it coined up by their marketing department?

I'm not certain of the mechanics, but "Transient Detection" seems to involve a HPF. Does that mean any accelerometer that has a HPF onboard will likely be equivalent to "Transient Detection"?

UPDATE

I believe the MMA8451 is a digital device since it supports I2C.


texts: Is there a convention for lines separating areas in circuit diagrams?

texts:
I often see boxes of various styles to separate areas and increase clarity in circuit diagrams. I'm wondering if there is a line style convention in circuit diagrams for illustrating:

A set of parts located in a particular part of the board? (Such as a high-voltage area)
An optional sub-circuit that may (or may not) be installed.

such as short dash, long dash, long-short dash etc....

If there is none, I guess I should just choose something clear and stick to it consistently. In engineering/ technical drawings they are quite exact about this kind of thing, but I haven't come across anything in electronics.


texts:
Is parameters(Z parameter,  Y parameter etc.) of two port networks are constants? I try to figure out this and found that if  network contain some active elements or independent source then these parameters might  become  variables, but
I don't know whether my conclusion is right or wrong,
Anyone, correct me if there is something wrong in my conclusion.
2.and why  for these parameters, there is a special mention(ex-book I'm reading
i.e author Franklin F kuo)
of reciprocity condition in each parameters? , are reciprocal networks have some special relation with these parameters other than just a mathematical relation?


texts: 4 channel software PWM using Atmega16 for controlling 4 ESCs for brushless DC motors

texts:
I am trying to implement software implemented PWM for controlling 4 ESCs using an atmega 16 microcontroller.

To achieve that I am sequentially generating the pulses for each ESC one by one in every period of the signal.

Here's the code -

#define TOTAL_ESC 4
int ESC_pulse[TOTAL_ESC];
int ESC_pins[TOTAL_ESC];
int currentESC;

int main(void)
{
    initESCs();
    initUSART();

    sei();
    while (1)
    {
    }
}

void initESCs()
{
    ESC_pulse[0] = ESC_pulse[1] = ESC_pulse[2] = ESC_pulse[3] = 2000;
    ESC_pins[0] = PIND4;
    ESC_pins[1] = PIND5;
    ESC_pins[2] = PIND6;
    ESC_pins[3] = PIND7;
    currentESC = TOTAL_ESC - 1;

    ICR1 = 39999;   //50Hz signal @ 16MHz clock
    OCR1A = 1000;

    DDRD |= 1<<ESC_pins[0] | 1<<ESC_pins[1] | 1<<ESC_pins[2] | 1<<ESC_pins[3];
    PORTD &= ~(1<<ESC_pins[0] | 1<<ESC_pins[1] | 1<<ESC_pins[2] | 1<<ESC_pins[3]);

    TIMSK |= 1<<OCIE1A;
    TCCR1A |= 1<<WGM11;
    TCCR1B |= 1<<WGM13 | 1<<WGM12 | 1<<CS11;
}

ISR(TIMER1_COMPA_vect)
{
    PORTD &= ~(1<<ESC_pins[currentESC]);    //End prev ESC pulse

    if(currentESC == TOTAL_ESC - 1 && OCR1A != 1000)
    {
        OCR1A = 1000;
        return;
    }

    currentESC = (currentESC + 1) % TOTAL_ESC;

    PORTD |= 1<<ESC_pins[currentESC];   //Start next ESC pulse
    OCR1A += ESC_pulse[currentESC];
}

So, I am trying to generate 50Hz signals with 1ms - 2ms pulses. My CPU Clock is 16MHz and the timer clock is prescaled to 2MHz.

I have an array ESC_pulse for storing the width of the pulses for each ESC. The values in it will range from 2000 to 4000 for the 1ms to 2ms pulses that the ESCs require. The logic I am applying is that everytime the timer compare interrupt occurs I clear the last ESC's output pin and set the next one's and update the OCR1A value with current OCR1A value + current ESC's pulse width as stored in ESC_pulse.

With the hardware generated PWM using the timer my ESC is able to run the brushless DC motor. However, the software generated technique doesn't work. I don't have any equipment to actually see what the generated PWM signals are actually. All that happens is that the ESC generates beep sounds signifying no signal.

I am not sure what I am doing wrong here.


texts: Is there such a thing as a pulse relay? So that I do not have to supply constant power for it to remain open, instead just pulse it?


texts: How to implement derivative, and create a delay of dozens of clock cycles?

texts:
I have uart entity which have the following signals (I write only the relevant - for tx)

-- The output data: 8 bit - this is the UART receiver
-- Data is only valid during the time the STB is high
-- Acknowledge the data with a pulse on ACK, which is confirmed by
-- revoking STB.
-- When the following start bit is received the data becomes
-- invalid and the STB is revoked. So take care about fetching the
-- data early enough, or install your own FIFO buffer
DATA_STREAM_OUT     : out std_logic_vector(7 downto 0);
DATA_STREAM_OUT_STB : out std_logic;
DATA_STREAM_OUT_ACK : in  std_logic;
TX                  : out std_logic;

I have another block which its enable input should changed to high for only one clock when there is a change of the DATA_STREAM_OUT_ACK (high to low) plus delay of 50 clk cycles.

I guess I should derive DATA_STREAM_OUT_ACK, but I'm not sure hot to implement this, and also the delay (may be with counter).


texts: How can I know if I'm safe from burning out my robot with more voltage?

texts:
I have a Wowwee animatronic robot that I've been tinkering with, with the goal of hooking my arduino up to it so that I can control it from my computer.

The problem is, using a multimeter, I've tested that the voltage on the robot's control lines/pins is 3.3v; but the arduino outputs 5v through its pins.

Will hooking up the arduino and using its 5v pins damage the robot? And, realizing this is likely subjective to the robot's specific electronics, is there a way I can test/see/analyze if it would be ok to use 5v digital signal on its lines?

If not, I've been researching the feasibility of just putting a resistor on each of the arduino's output pins to bring the voltage back down to around 3.3v (although I'm not sure if I might need a more in-depth solution, as that would "corrupt" the digital signal?).


texts: UVC Lamp causes Atmega 328P to malfunction

texts:
I have got an Atmega328p which connected to a TFT LCD 1.3 inch using SPI. The Atmega 328P is powered through a 5V adaptor. The problem is most of the time when I switched on the UVC Lamp the LCD will stop working and sometimes the Atmega328p also stops working. Even when I connect the UVC lamp directly to the power line, and did not connect it at all to the Atmega328p it still causes malfunction. I have tried adding 680uF capacitor to Atmega 5V and GND but it seems to not solve the problem either. Does anyone know why this happens? And what steps should I take to solve this?
Here is my Schematics:

I connect the UVC lamp separately and directly to the power lines.
This is the UVC Lamp that I use, I can't seem to find any datasheet for this:

Yamano UVC Lamp Germicidal


texts: Im helping with ele homework and and can't seem to come to a conclusion. Here is the circuit. Is this a valid interconnection of ideal sources? Why or why not? I know the two voltage sources by themselves would make it invalid because the voltage sources are not the same magnitude. Does this still apply with a current source?


texts: Finding the optimal voltage for a sealed transformer

texts:
I stumbled across a sealed transformer (step-up) which i believe came out of a neon power supply. Its completely covered in epoxy like goop and the internals cannot be seen.
However,on the tin it indicates a output voltage of 10kv but i have huge doubts if it takes 230V in the primary.

I have taken some readings of both the primary and the secondary using a LCR but not really sure if i can get a good voltage ratio.

I'm just willing to know what's the best way to drive this..
(P.S no feedback coil either)

The right hand side was the input for 230vac.
Left side is the output. And the soldered points is the primary winding.
I have NO idea what happens in the right side all is assumed.
I also do not have a lot knowledge in transformers. (learnt physics up until 12th grade)
Thanks,


texts: Depletion-mode P-channel MOSFET availability?

texts:
I need a P-channel depletion-mode MOSFET for a circuit I'm building. However, there is no model available in LTspice that I have found, nor is there any available that I have found to buy online.

How can I simulate this kind of MOSFET in LTspice, and where can I get one?


texts:
I have a 0.3W (RMS), .8ohm speaker coil + cone that I want to test using various music. However, the 8ohm impedance is lower than typical earbuds (24ohm), and also I can't find headphone jack power specs for my computer (Macbook Air 2010) or phone (Nexus S), so I'm worried I'll blow out my speaker sample.

I found this amplifier that's for 8ohm speakers, but it outputs up to 20W! I could turn it to its lowest setting but I'm worried that in tweaking the volume I'd accidentally exceed the speaker's rating just by the error of my hand's motor control abilities. Could I use that amp plus a current limiter, or will its digital electronics become under-currented?

Alternatively, if I can find a "powered / active speaker" product such as for desktop computers which happens to have a 0.3W, 8ohm coil internally, I could just swap out the coil. Know any?

Last resort would be to breadboard an amplifier circuit myself based on an 8ohm-load, 0.3W amplifier IC like the LM4864MM, but that's extra work just for a throwaway test circuit.

What is the laziest way to safely accomplish this test?


texts:
What are these white connectors called?  I'm assuming they have a common name, with different numbers of pins.

Update:  better pictures, showing "BM Z" on the board connector.  The board is identified by the vendor as a "600TVL Sony Super CCD" camera.

Update:  the pins are 1.25mm center-to-center.  It seems they are part of the Molex Picoblade family.

Sad observation: the connectors are quite cheap (.07 USD in small quantities) but requires a crimping tool that retails for about 200 USD.


texts: Would this minimal NPN-based metal-detector circuit work?

texts:
I found various circuits online (1, 2), but they seem rather complicated.

Would this work..?


texts: The maximum input voltage of a MSP430 is Vcc+0.3V. What is the result of the ADC if I provide Vcc+0.3V as input? Is the digital output of the ADC just the maximal value?


texts: automatic plant watering system using microcontroller

texts:
I am trying to build an automatic plant watering system using ATmega16. We are using moisture sensor YL69 for our project. The following is the image of the moisture sensor we have used.

The circuit diagram of the project is as follows:

The following is the code fragment we used:

#include<avr/io.h>
int adc(void);
void pump(void);
int adc_value;
int main(void)
 {
  DDRC=0x01;                          //Defining PC0 as output
  ADCSRA=0x87;                    //Setting the mode of operation
  ADMUX=0x00;                     //Selection of channel and bit alignment
  while(1)
   {
     adc_value=adc();                //reading moisture level
     pump();                               //Pump activator routine
   }
   return 0;
 }

int adc(void)
{
   int lower_bits,higher_bits,result;
   ADCSRA |= (1 << ADSC)|(1 << ADIF);  //Turn on conversion and clear flag
   while(ADCSRA & (1 << ADIF) == 0);  //wait for flag
   lower_bits=ADCL;
   higher_bits=ADCH;
   result=lower_bits|(higher_bits<<8);         //Accessing converted value by shifting
   return result;
 }

void pump(void)
 {
  if(adc_value>=700)                                //Pump ON trigger point
   {
     PORTC|=(1<<0);
   }
  else if(adc_value<=600)                        //Pump Off trigger point
   {
     PORTC&=~(1<<0);
   }
 }

Is there anything wrong in the code? Because after burning it, i am getting  low voltage(0.15) for wet soil and high voltage(4.84) for dry soil from the analog sensor input which is ok … but the problem is, I am always getting voltage like 0.7 (and sometimes like  0.15) at PC0  in both cases(I am using multimeter for measuring this). There in no change in the values for dry and wet soil at PC0.. in such case where is the actual problem? Is there anything wrong in the circuit design or in the code? And one more thing, can anyone please tell me the proper way of measuring the output value I am getting from PC0 which in turn is switching on/off the pump?

Another question is, I am using AVR programmer for 5V DC supply. In the above circuit design I have not made any connection  at pin MOSI,MISO,RESET and SCK (of ATmega 16) with AVR programmer. Will I have to make this?


texts: How do I log UART ASCI data at high speed (above 921600 baud)

texts:
I am transmitting data from a microcontroller via UART and this is going to the USB port of a laptop.
The data comes formatted as ASCII, and I am viewing in real time and logging in a PC using TeraTerm. The problem is TeraTerm can only go up to 921600 baud, whereas the microcontroller could transmit at up to 3Mbaud.
Is there any software or device which I could use to view and log this data at higher than 921600 baud?
921600 is enough for now, but I would actually like to increase my sample rate for the data so I need to go higher.


texts: H-Bridge shoot through at high voltage problem - Don't know the cause

texts:
I have this H-bridge circuit

The circuit is for driving a 180VDC motor, it is built to taking in the High Bus voltage from 169VDC to 340VDC. it works with no problem up to 310VDC. However, at 340VDC, the High and Low side FETs (depends on which side I energize first) will shoot through and short the whole circuit. I have calculated every component value to work with the MOSFETs rating and so I am lost at figuring out where is the problem to fix the circuit.

I use this FET and this gate driver

Here is the waveform I captured at the HO, LO and the PWM input of the gate driver.

As you can see, the PWM switch off, then a short delay layer, the HO tried to switch off but for some reason, it cannot sink it to ground and stay floating for eternity later. With this characteristic, I thought it would not work at all but it is working fine up to 310VDC.

If you have an experiment with such a case, can you please give me some guidance.

Thank you for your time


texts: Compiler / Assembler (Toolchain) for PIC micro's using Ubuntu 11.04

texts:
I used to use Hi-Tide from Hi-Tech before they were purchased by MPLab. In my opinion it was great. I wrote the C code, selected the processor and out popped a hex file.
I've now migrated to Ubuntu 11.04 and need to be able to compile/assemble C code for Pic micros. I've been trying to bend SDCC to my will for some time with little success, and apparently their support of PIC is still in development (according to the man).
I tried using Hi-Tide 3 for Linux, but had no success even launching the IDE.
I am not looking for an IDE or anything like that. Just need a solid, sane, relatively easy toolchain that doesnt need to be poked and prodded at every step to produce a functioning hex file for PIC's.
Does anyone have any suggestions?
I'm near the points where I might as well just start writting my own hex files.


texts: Is passive RFID range limited by the activation signal or the reflected signal?

texts:
In other words, at the end of a tag's read range, does the read fail because the tag isn't activated or because the tag is activated but the return signal can't be decoded by the reader? I'm concerned mostly with passive UHF tags.

Also, what is the typical difference between the activation range and the read range?


texts:
In my application, I am using LPC2138 controller and TI's TLV320DAC3100 DAC with built in amplifier to interface audio data.

To implement I2S interface using SPI, some extra hardware circuitry needed which I found from below link:

http://www.ti.com/lit/an/slaa449a/slaa449a.pdf

From above application note, I am able to get following hardware for SPI - I2S interface.

And 5 bit counter is implemented as follows:

My question is above note is specifically for MSP430F Texas controller and I need to interface with NXP LPC2138 controller.

In that case,Is this design logically correct for interfacing I2S on SPI bus? Or LPC associated hardware will differ for such implementation.

Thank you.


texts: Isolation transformer and AC potential between grounds

texts:
Wisely (I think) after connecting my DUT (Tektronix 2710 Spectrum Analyzer) to an isolation transformer, I measured AC voltage between the DUT chassis ground and my scope (Tektronix 2440) ground lead.  I see around 19VAC as measured by a fluke multimeter.  Therefore, I did NOT try to attach the scope ground to the DUT.

The 2710's service manual says to use an isolation transformer as its PSU is switched mode (and apparently not isolated), which can be a big problem during service.

It should be noted that the DUT GND connection in relation to the isolation transformer is floating.  There's no "ground" on the isolation transformer and therefore none to the DUT.  As I understand the concept, connecting an otherwise isolated device to mains (earth) GND would defeat the purpose of the isolation.

My question is: where is this 19V coming from?  Would a leakage path be possible through the scope's input EMI filter?  Would connecting the grounds together draw a huge amount of current?  Or, is this perfectly normal?

Never been here or done this... and never discovered it either as I've happily connected scope GND to instruments (not on an isolation transformer, however), with no issues in the past.


texts:
What is meant by reactive power in AC circuits?
Power is joules per second.
Real power is the energy dissipated in the resistor per second.
What is meant by the reactive power? Does this mean the energy being stored in capacitor and inductor per second, or does it mean the stored energy supplied per second by the inductor or capacitor.
If we have a voltage source connect with  an RLC network and after some time the inductor and capacitor are suddenly detached from the network and then they are supplied to another resistor with diffent value without voltage source then of course they will supply the energy at a new rate to the new resistance depending upon value the resistance. Will this not make the value of stored energy per second different from the value of energy supplied per second? Doesn't that give two different values of reactive power? Doesn't this mean that the reactive power is now changed for the same capacitor and inductor?


texts: Questions regarding BJT saturation for a circuit

texts:
I have the following circuit which converts weak sine signal to pulses:

I have tried it on breadboard and it seems it works fine. In my application freq. is between 1Hz to 30Hz or max 100Hz. And the input signal Vpp will be from 200mV to 2Vpp.

Below is the collector and base currents:

And here below graph zoomed to show Vce which is 50mV during saturation:

Here are my questions:

1) I'm not sure if R2 and R3 is set correct/optimum for using this circuit for switching action even though in practice it works(I set R2 and R3 empirically). Am I oversaturating this transistor? In my second plot above Ic/Ib<10 but in its data sheet at saturation Ic/Ib should be around 10. It is a bit confusing.

Briefly I want to learn how can we calculate R2 and R3 for good saturation and what should be their rough value?

2) All the texts I have seen says Vce is around 0.2 during BJT's saturation but in my simulation(3rd plot) it is only 50mV. Why is that so?


texts: What's the reason for wiring a relay this way?

texts:
I came across the following automotive wiring diagram:

One thing I don't quite understand is the way they wired the relay. I've got two main questions.

It appears to me that they used the exact same wire from terminal 87 to provide power to terminal 86. I don't think that there is anything wrong with this approach, but I haven't seen it before. The exact same wire gauge is used although one would expect that the load (the radiator fan) draws more current than the relay coil, right? Why did they do it this way?
Why did they connect battery positive (30) to terminal 87 on the relay? Why didn't they use terminal 30 on the relay? It makes no sense to me, but I guess there must be a good reason.


texts: Current feedback and voltage feedback at the same time?

texts: Can I use current negative feedback and voltage negative feedback together to set the operating point of an amplifier?


texts: Connect Ring.co doorbell to Loxone controller

texts:
I've a ring.com doorbell which can be connected as shown in the diagram on the right.

My goal would be to replace the chime in that diagram by something that can replace the push button in the left diagram.

What would that "something" be?

I hope the above makes some sense, I've only a basic electronics knowledge.


texts: How lenient can I be about motor stall current?

texts:
I'm thinking of using two of these motors with this motor driver. However, one thing concerns me: the stall current of the motor is 3.3A, and the motor driver has a peak current output of 3A.
The motor would be used in a robotics situation involving rapid changes of direction, and potential stalling.
Could this cause an issue, and do I need to get a lower power motor / better driver, or will it still work?
EDIT:
What will happen if I DO exceed that thing's current rating, given that it has temperature protection? Will it blow the microcontroller, the motor chip, or the motors?


texts:
I'm fascinated by zero voltage switching (ZVS) drivers.  So I've been playing with simulations of them in Falstad.

Two things I don't understand:

How is the oscillation initiated in an actual ZVS?  If you follow the linked simulation you will see it's oscillating consistently.  But if you reset it then it will not oscillate: Voltage will simply flow through the top MOSFET while the bottom one stays off.
How does one size the inductor to keep it balanced (i.e., roughly equal time running through both MOSFETs)?  I imagine there's some equation for this, but I can't find it.


texts:
simulate this circuit – Schematic created using CircuitLab
An old bicycle headlamp + battery pack. The batteries were 3.7V li-ion but broke down. I don't know how were they connected in the pack thus assume serial connection (output voltage 3.7V nominal).
I connected the light to a wall brick (old, there's a bulky transformer) of specification
Output:
3.7V 355mA

The torch has several modes of shining. When is shines, there's noise coming from the light (not the wall brick) with volume proportional to the brightness. There's a blinking mode which makes is obvious the light emitting circuit generates the noise.
Assuming power ripples, I inserted a filter in the power loop (2.2mF electrolytic, a tiny ceramic in parallel and two inductors of 680uH +-10%). Noise being present even at the lowest brightness setting should have tipped me off that it's not this.
No change. Any ideas how to power the torch in a home environment? It shines bright and I would hate to toss it.