texts: Dropping 24V to 12V simply and efficiently

texts:
I have a 24V solar system, and I want to get only 12V from the DC output.
Currently I am taking a wire from only 1 battery, but this causes unbalance in the batteries and I have to check it a lot and switch the wires to balance, also the wire is a bit long and I get a drop and when it is near or below 12V my devices stop functioning.
I thought if I can get the 24V down to 12V at the end of the wire I'd be sure to get constant voltage for the devices, and would not have to worry about the balance of the batteries and it woyld be safe since the charge controller has a deep discharge safety.
The problem is I can't use resistors or transistors (voltage regulator) due to excess heat and a transformer is not an option (nor DC to DC converters - can't get any here,) I am looking for nearly 5A of current.
So I am kind of stuck here.
How can I do this?
--EDIT--
Would making a stairs of voltage regulators be ok to use? (24V-19V-15V-12V) or would it be better if I put multiple 12V regulators from 24V?
Efficiency isn't a problem, but I don't have large heat sinks. Or is there a way to drop enough voltage so I can feed it to the 12V voltage regulator? Using a resistor will limit the current and I want to avoid that.


texts: Why do microcontrollers have so many functionalities at once?

texts:
Being fairly new in the field of electronics, and being a computer scientist, it strikes me as a bit odd that almost every single microcontroller that I've come across thus far is fitted with:

Multiple timers, with multiple trigger modes
Multi-channel PWM
Multi-channel ADC
Multiple hardware supported communication protocols
Multiple external interrupt pins
EEPROM
Sometimes DAC and analog comparators

It seems, at least to me, a bit wasteful to jam all of this specialized (even through commonly used) equipment inside the microcontroller, if I'm only using 1/50 of it. Even if I wanted to, I'd only be able to use, say, 1/10th of it, as pins are often mapped to many of these features at once.

Why are they jammed up, i.e. what's the argument of not just using external chips or even just software implementations?
Are there any ATMega-like processing chips, i.e. chips with a lot of processing power instead of PWM, ADC etc.?


texts:
I have a question about the problem below. I have attached my work, but the answer I am getting a different answer than the given answer. Please explain.

Thank you so much!


texts:
I was just creating some vias in Eagle and was playing with the drill diameter, and for some reason Eagle seems to put differing notations around the hole when the size changes, is there any reason for this, or is it purely cosmetic?

For example, here's a crosshair looking thing

And, when I decrease the drill size just a bit, it changes to a concentric circle with a diagonal line:

Furthering my confusion, some differing stuff happens when creating regular holes with the drill tool, here is a crosshair at 45 degrees:

I also got the concentric circle with a diagonal line, but also this weird fish-looking thing?

Is there any sense to be made of this? Or is it just something eagle does when the pad/hole size changes so that the marking is clear that it's a hole?

Thanks!

(this is eagle 7.6.0 if that matters)


texts: Smoothing the on/off transition of mains LED lamps

texts:
A project with which I've been involved is an interactive portrait gallery, with seventy mains LED lamps, turned on and off using VO2223A optocoupler/phototriacs, driven by a microcontroller.  The lamps draw only 20mA each, which was one of the reasons they were chosen (negligible heat generation in the display).

All works fine, except that the clients would like the lamps to turn on and off slowly (over a half second, say) rather than simply jolting on and off, as the optocouplers switch the mains.

Below is a small schematic of the lamp circuit, showing the arrangement described above, and (on the right) what I'd like to be able to do. (Note that I've left out lots of components (such as the current-limiting resistors on the PIC outputs), to keep the diagram simple.) lamp circuit http://www.scifun.ed.ac.uk/downloads/atiyah/LED-lamp-switching.gif

Is there a circuit or component that could be installed inline with the mains supply to all of the lamps (via the optocouplers) as shown, such that there would be graceful rises and falls in current, rather than step changes?

As you can imagine, I'd rather that I didn't have to consider some individual circuitry on every lamp input, seeing as how there are seventy of them...


texts: MOSFET and Driver. Gate current questions

texts:
I am designing a three phase bridge inverter and I have some questions about the MOSFET driver. My MOSFET has a total gate charge (Qg) of 200 nC and a internal gate resistance of 2 ohm. I want it to switch in 200 ns (the PWM frequency will be 50 kHz, I think 1/100th is okay for turn on time isn't it?)

According to this formula, Ig = Q/t. I need 1 A. If I feed my driver with 15 V, I need a 13 ohm  resistor between its output pin and MOSFET gate. (15 V / (13 ohm + 2 ohm) = 1 A).

Is it correct? Am I doing something wrong?

Also A last question. I am powering the drivers by using a LDO

http://www.ti.com/lit/ds/symlink/lm317hv.pdf

Page 4. Current limit plot.

I'll have an input output differential of 15-20 V so 1.5 A of output current. Is it maximum peak current? or average. How can I know if it can provide a peak current high and fast enough as my driver needs?

Thank you.


texts:
I have been using 10 mil trace with 10 mil spacing.  The PCB vendors quote that they like traces down to 7 mil.  But then I ran across a PDF showing how to fan out a QFP to get all the signals accessible.  They use millimeters because the QFPs are packaged with 0.4mm or 0.6mm pitches.

They also make an argument that using a 0.05mm grid approximates mils, but mm allows you to route buses in between the vias and pads.

Should I be using mil or mm when I am routing a PCB?


texts:
I edited circuit like this:

I tried representing currents like:
$$
\begin{aligned}
&I_{R1}=100_{B1}+I_{B2}\\
&I_{R2}=101 I_{B2}-I_{B1}\\
&I_{i}=101 I_{B2}+100 I_{B1}
\end{aligned}
$$

Also I get:
$$
U_{BC1}=U_{BE1}-U_{CE1}=4,3(V)
$$

Then setting up equations from second Kirchoff law:

$$
I: U_{CB1}-U_{BE2}+I_{E 2} \cdot 1 k+I_{B 1} \cdot R=0
$$
$$
II:-I_{R 1} \cdot 18 k+I_{C 2} \cdot 7 k-U_{C B 2}=0
$$
$$
III:-25-I_{R 2} \cdot 2 k-I_{E 2} \cdot 1 k+U_{C E 2}-I_{C 2} \cdot 7 k=0
$$
$$
IV:-I_{E_{1}} \cdot 2 k+U_{CE1}-U_{BE2}+I_{E2} \cdot 1 k+I_{R 2} \cdot 2 k=0
$$

After solving system of equations I get wrong numbers so where is problem in this my method?

I'm safer with Symbolab so these are wrong results which I get: $$x=I_{B1}, y=I_{B2}, z=U_{CE}, q=R $$

$$x=I_{B1}=-\left(\frac{13.61731 \ldots}{2040000}\right), y=I_{B2}=-0.0000186856, z=U_{CE}=6.271711, q=R=1.503483 \cdot 10^{8}$$

https://www.symbolab.com/solver/system-of-equations-calculator/3.6%2B101%5Ccdot%20y%2B1000%2Bx%5Ccdot%20q%3D0%2C-18000%5Ccdot%5Cleft(100x%2By%5Cright)%2B7000%5Ccdot100%5Ccdot%20y-%5Cleft(-07%2Bz%5Cright)%3D0%2C-25-%5Cleft(101y-x%5Cright)%5Ccdot2000-101y%5Ccdot1000%2Bz-100y%5Ccdot7000%3D0%2C-101x%5Ccdot2000%2B4.3%2B101y%5Ccdot1000%2B%5Cleft(101y-x%5Cright)%5Ccdot2000%3D0


texts: Use of internal PCB ground plane as ESD baseplate/EMC reference plane of product in plastic enclosure

texts:
I am designing an electronic product which will be housed in a plastic (non-conductive) enclosure. There are a number of, mostly shielded, I/O cables (Copper 10/100/1000Mb/s Ethernet, USB 2.0, RS232, low/audio-frequency analogue inputs). The product will be installed inside a metal cabinet in an industrial (noisy) environment, and I am concerned about ESD and EMC issues.

At schematic level, there are a number of TVS diodes, ESD current limiting resistors, filter capacitors on the I/O lines. Now it is time to do PCB layout and routing and I am wondering how best to implement the ground system.

I have turned to (the guru) Henry Ott's Electromagnetic Compatibility Engineering, and have found two figures in particular and the corresponding text, very useful:

For ESD reasons: Fig 15-17 (image below) shows how the use of a metal plate in the enclosure is used to divert ESD currents away from the PCB, via its stray capacitance, to (earth) ground. The key is to make a low impedance connection between I/O cables/screens and metal plate.
This is intuitive to me and is also suggested as a solution to ESD in this electronics.stackexchange answer.

For EMC reasons: Fig D-13 (image below) shows how the use of a metal plate in the enclosure is used to create an intentional reference plane with the cable so as to form a monopole antenna which can be controlled, so as not to radiate, by bonding the cable and plate together. Again, the key is to make a low impedance connection between cable/screen and metal plate.
.

My question is: can the ESD ground plate/reference plane be implemented, instead of using a metal plate, by using an internal PCB copper layer? And if so what are the benefits/drawbacks?
It would make the implementation far simpler (no mechanical design, easier to make low impedance connections between plane and IO cable/shield) and more cost effective. I cannot find anything in Ott (or elsewhere) that explicitly states this is not a good idea, but I cannot recall ever seeing an entire plane being used this way; sometimes chassis GND or IO planes are used, but normally these are in regions near the IO area not an entire plane (I would still do an IO GND plane in addition to the reference plane).

Follow up  question: for the EMC case when an intentional/controlled monopole antenna is formed with the reference plane; whether using a metal plate or PCB plane, what stops the IO cable (now bonded to the plate/plane) from forming an antenna with other power/signal GND layers on the PCB?


texts: Does N-type or P-type semi-conductor show electrical effect?

texts:
I am reading the book Electrical Engineering 101. It's a book of basics for not-so-newbie.

It contains below description in Chapter 3:

  A diode is made of two types of semiconductors pushed together. They
  are known as type P and type N. They are created by a process called
  doping...Some dopants will create a type N structure in which there
  are some extra electrons simply hanging out with nowhere to go. Other
  dopants will create a type P structure in which there are missing
  electrons, also called holes.

So, if I have a piece of P-type or N-type semiconductor in my hand, does it show any electrical effect? Say, electrostatic field?

And a similar question:

How is a semiconductor electrically neutral?


texts: Intel CPU and Surface Mounted Capacitors (located directly on top)

texts: I would like to know what is the purpose of the surface mounted capacitors found directly on the top of a CPU such as the Intel i3 2120 or the one depicted in the photo ? Does this type capacitor directly feed the internal circuitry of the CPU with a charge ? Directly to a specific layer on die of this Intel CPU ? If yes does a SMC and its charge ie voltage somehow follow a trace directly to a location a particular layer on die ?


texts: Add board names to custom components eagle

texts:
I have created two custom components for use in eagle 9.5.2 premium. When I insert the components to a project there are no visible names in neither the schematic or the PCB design.

I just want visible names in my PCB design just like the default components have, R1, C4 etc.

I looked into 3 component making tutorials but I still have not figured it out.

How do I make the names of custom components visible in the PCB design?


texts:
When debugging or accessing hardware firmware, JTAG and SWD can be really helpful to the developer, engineer or reverse engineer.

When looking at an unknown board/device tools such as JTAGEnum or JTAGulator are really helpful in identifying JTAG pinouts or pads.

What techniques exist for enumerating or identifying SWD pinouts?


texts: Will shorting secondary winding of transformer cause damage?

texts:
The transformer in question is a step up transformer, which converts 240 VAC @ 3.75 Amps to about 2100 VAC @ 0.4-0.5 Amps. (50 Hz)

I want to test whether it works, it is salvaged anyways. If the secondary coil is shorted, would that cause any problems? I know that the impendance of the primary coil is enough to keep it from being shorted, since it's AC.

But what about the secondary coil, would it be damaged? Would it just output 0.4-0.5 Amps as it is designed in a short circuit, or would it spike (like in DC)?

(I've also heard that it is common to short the secondary, as leaving it open would be dangerous, I would like to know if the secondary would be damaged)

For lower voltage transformers, I've seen videos like this, however I'm not sure whether it would be wise to do that on a 2200 V transformer: https://youtu.be/mE_K7sG_wEQ (2:22)


texts:
I have a simple circuit:

(Note: RN4 is currently 180 ohms. The label got left off the image.)

When the 339 is setting an output low, the output is only dropping to about 2.3v, and not 0. Not low enough for the 74LS240 to recognize it as low. If I short the cathode of an LED to GND, then the 74LS240 works as intended, obviously.

At first, I realized that my pull-up resistors (RN5) may not even BE needed, thanks to the LEDs. However, removing it from the circuit drops the output to about 1.5v.

The LEDs have a forward voltage of 2v, and use 20mA. (Part: https://www.digikey.com/product-detail/en/kingbright/APT1608SYCK/754-1124-1-ND/1747841 )

Am I trying to overdrive the LEDs? Would increasing the resistance of RN4 help? And is RN5 even necessary?


texts: The right vocabulary for everything related to booting a µC and loading a program

texts:
The more I learn about all the steps required for bringing a µC to the phase of finally executing the program, the more I get the impression that there is no "golden path". It seems to me that the exact steps required are different from project to project.

In general, following steps are required for execution of a normal bare-metal C program on a common 32bit µC like the ARM Cortex-M3:

Clock must be configured. (Internal, external clock, prescalers and so on)
Stack pointer must be initialized.
.data region must be initialized with the right values.
.bss region must be zeroed.
Code to be executed must be in the memory range it was linked into.

My question: Which of the steps above are done by the loader? Which are done by a boot-loader such as U-Boot? What's the difference of a boot loader to a normal loader?

When I use U-Boot, it can copy the program (.text and .data) from ROM or even network to RAM and execute it from there. Does that mean that U-Boot is loading my program? What about .bss, it still has to be set up. If my program zeroes-out .bss myself, does that mean that my project is partly loaded by U-Boot and partly self-loading?

There might also be projects which can run from ROM and don't have any global variables. (Hence, no .bss and .data) Is the wording correct, that such a program dosn't require any loading?


texts: How can be calculated the open circuit power test on this transformer?

texts:
I'm given that after a short circuit test a one phase transformer rated at \$2500\$ kVA, \$50000/10000\$ at \$50\$ Hz yields the values of voltage, current and power as follows:

$$720V, 225A,37947W$$.
The transformer has a open circuit current of \$3\$ \$\%\$ of the nominal and the efficiency with nominal charge and power factor \$1\$ is \$97.66\$ \$\%\$

It asked for many things, but where I'm stuck is how can calculate the power of open circuit test?

I'm assuming from the data that the voltage of open circuit is the nominal one (\$50kV\$), the current its the \$3\%\$ of \$I_{1N}\$

$$3\%I_{1N}=0.03\frac{2500kVA}{50kV}=1.5A  $$

and the \$P_{0}\$ could be calculated from the \$\eta\$ data, since the power factor is 1 and the charge is \$C=1\$

$$\eta=\frac{2500kVA}{2500kVA+P_{0}+37.947kW}100=97.66\%$$

doing the math this would be \$P_{0}=21.954kW\$
but the reference says this value should be \$13.054kW\$.
Then how should be calculated?


texts: How to set NACK right after current byte in TWI (ATMega8)

texts:
I have some experience with I²C (TWI) as I used it before, but it seems I can't solve this particular problem. I intend to communicate two CPUs via I²C. One is always the master and the other is the slave. I'm defining the communication protocol myself, so it's somewhat flexible, but I intend it to be as efficient as possible (i.e. the fewer bytes, the better).

I want the slave to set NACK for certain values; for instance:

MASTER = START + sends SLAVE ADDRESS
SLAVE = sets ACK
MASTER = sends any one "byte" command
SLAVE = sets ACK or NACK depending if "byte" was a valid command or not.

The last statement is the problem, because apparently I -as the slave- have to decide for ACK or NACK before receiving the one "byte" command; i.e., in response to TWSR = 0x60 (SLA+W received). The problem is, I don't know in advance if the command will be valid or not! Apparently setting or clearing the TWEA bit is only effective for the next byte to be received.

As much as I digged into the docs, I cannot find a way to respond with NACK "on the fly" because the ATMega sets the interrupt AFTER sending the ACK (or NACK). TWSR will be either 0x80 or 0x88, which means "byte received, ACK sent" and "byte received, NACK sent" respectively.

Aside from adding padding bytes or implementing a bit-banging I²C library, is there some way to solve this?

The master controller is an NXP LPC2148, while the slave controller is an ATMega1284P.

Thank you.


texts: How to interpret the PMBus response delay time value?

texts:
EDIT: I should make it clear that I am asking in terms of creating the PMBus firmware for the device rather than attempting to program the device using PMBus commands.

In section 10 The PMBus specification (>= rev 1) states that the fault response parameter is a byte made up of several values, one of which is the 3-bit Delay Time value described as

  The number of delay time units, which vary depending on the type of fault. This delay time is used for either the amount of time a unit is to continue operating after a fault is detected or for the amount of time between attempts to restart.

The latter part seems ambiguous: "the amount of time between attempts to restart". Is this the amount of time from the start of one restart to the start of the next (fig 1), or from the end of one restart to the start of the next (fig 2)

If the first meaning (fig 1) is correct then well and good.

However, if the second meaning (fig 2) is intended then how can one know whether a subsequent fault is part of the previous fault response and should constitute one of the allowed number of retries, or an entirely new fault that should start a response anew?

EDIT: I realised there is a third possible interpretation where the former meaning is taken but the delay time is enforced by stopping any further retry occurring until the delay time for the first retry has expired (fig 3)


texts: Impedance matching - amplifier and surface acoustic wave (SAW) filter

texts: How would I properly do impedance matching for the amplifier and saw filter at the output of the circuit?


texts: Designing isolated flyback with multiple outputs

texts:
UPDATE: as suggested, I split this question into separate parts (links below). I left the last one here. It is so silly I am rather proud of it ;)

UPDATE 2: it seems that breaking one post into multiple questions only annoyed people, which wasn't my intention. Please, accept my apologies for the spam.

Over past few weeks I've been reading LT datasheets and application notes and everything I googled on the web. While I think I am getting the basics right, some rather unexpected questions popped up and I could not find definite answer to them. I'd appreciate any help or even a point to the reading material I could use, something like "flyback for dummies" would be the best :)

Switch voltage drop

Isolated secondary coils

Calculating minimum primary turns - Answered

Wire selection - Answered

DZ snubber - Answered

Final question, if the load draws pulsed power and output caps are sufficiently big can I use average load current for the purpose of DC-DC calculations?
For example if output is modulated at 50% duty, can I use 1/2 of its current as secondary coil current?


texts: Microcontroller with both ethernet and radio onboard?

texts:
Does anyone know of any (reasonably low-cost) SoC which combines all of:

Microcontroller (any architecture, at least 4KB RAM/8KB flash)
Radio transceiver (433MHz - 915MHz or 2.4GHz)
Ethernet MAC + PHY

(For a wireless sensor application - connecting to low power sensor nodes)

I can find examples of micros with either peripheral, but not both:

Eg.

Micro + ethernet:

LM3S9B9x = ARM Cortex-M3 + Ethernet MAC and PHY

PIC18F66J6x = PIC18 + Ethernet MAC and PHY

Micro + radio:

CC430 = MSP430 + Sub-1GHz radio

EM250 = XAP2b + 802.15.4/ZigBee

Please only answer this question if you can name a chip.


texts: Why isn't this Elenco circuit working in Falstad's simulator?

texts:
I'm learning electronics engineering with the Elenco 130-in-1 kit, and I'm trying to get better at visualizing how these circuits are working by making them in the Falstad simulator, but the first one I'm trying isn't working.  Any ideas why not?

Here's a link to the Falstad circuit.

The purpose of the circuit: It's described as an "Electronic Grandfather Clock", which gives a click every second.  I couldn't find a speaker in the Falstad simulator so I used a diode instead.


texts:
How is it possible that the Signal Output will have the same frequencies as the Reference Signal?\$f_1\$, Frequency of the Reference Signal;\$f_2\$, Frequency of the VCO.

Let's assume that \$f_1>f_2\$, so the phase detector will create a positive voltage \$V_1\$
At this point \$V_1\$ will ensure that the VCO will increase his frequency  of oscillation.
At this point \$f_1=f_2\$, and this will make \$V_1=0\$, but if \$V_1=0\$, then \$f_2\$ will drop.
If \$f_2\$ drops, \$f_1\$ will become again \$>f_2\$, and \$V_1\$ will be positive.

In according to this reasoning this circuit will create an oscillation, where am I wrong, (Since this circuit will create a very stable Signal Output with the same frequency of the Reference)?

Why this circuit need an error in the phase for create a lock and so Phase1 must be not equal to Phase2?
What will happen if \$f_2>f_1\$, will the Phase Detector create a Negative Voltage?


texts:
I need to create a high pass filter to attenuate frequencies below 50KHz, I intend to use an RC circuit with an operational amplifier.

My question is: How do I set my cutoff frequency? I know that if I set a cutoff frequency of exactly 50K Hz I will get losses in my signal, how do I find the ideal cutoff frequency? Do I Use the Bode Diagram? If so, how does it apply in this situation?

Thanks!!


texts:
I found the following picture of the connectors of a monitor.

The serial connector looks like a phone connector. But I know only the D-sub and RJ connectors for serial ports. Can anybody tell me the name of the specification for this cabling?


texts:
I have a batch of Sanguino 1.3a RepRap boards, with the following "bug" listed:

  The USB 5V VBUS is connected to the output of the 5V regulator. This is bad for the regulator and bad for the PC. Some users report the regulator getting very hot (because it is trying to power the PC), other users report the PC giving USB over current errors. Nophead recommends cutting the 5V track to the USB connector. The only downside is the board needs the 12V supply before it will do anything.

We've seen this in several cases, the LED in the schematic will drop in brightness when USB is plugged in, and the voltage regulator gets really hot really fast.  However, this behavior is intermittent, and I'm curious as to the cause, behavior, and how USB is expecting the +5V to behave.

You can see in the schematic below in the FTDI/USB2TTL panel that USB 5V connects to the board's 5V bus, and the "Power from screw terminals and vreg" puts 5V straight onto the 5V bus without any kind of diodes.  So, I can see where this is happening.  Are most USB devices either powered exclusively by USB's +5V power, or they just reference ground and let 5V float?

Full size schematic


texts: Is using same ground and VDD for MCU and motor driver module safe?

texts: I'm trying to design an MCU prototyping board. I have two voltage regulators (3.3 and 5V) and motor driver on my board. All grounds are common, VDD of MCU comes from 3.3V reg and power supply for motor driver module from 5V reg. The current flow from 5V reg can reach up to 2 A (most consumption from motors on driver). Plus servos and other devices can be attached to my board as required. The question is if its wrong or dangerous and what kind of security tactics do I have to take?


texts:
I'm building a circuit that uses a really low voltage and current. I thought that instead of using a standard battery it would be nice if I could use a rechargeable battery and charge it with  electromagntic waves (2100MHz or 850MHz). I may use a LC circuit and set it to the right resonant frequency. If I set it to 2100MHz I will need:

1pF and 0.0057438 MicroHenrys

That may work, but how will it be possible? If I used 100MHz
it might work but I don't know how efficient it will be and what will be most efficient? I would like to achieve 3V at 1-2mA at a distance of 20-30km.


texts: How many i2c slaves can a i2c master support?

texts: Is there a maximum number of i2c slaves that a i2c master can drive? What are the physical limiting factors?


texts: The current of M5 and M7 of two stage OTA

texts:
Let direct current = 100μ,i know the drain current of M3=M4=M6=M1=M2=100μ

My question :

Is the  drain current of M8=50μ ? Oμ ? i think drain current will flow to the gate of M8 dircectly

Is the  drain current of M5=M1+M2=100μ or M5=M8?

Is the  drain current of M7=M5? or M7=M6?


texts:
Ok so I've been working on this problem for a while now. I've been given

mux(\$p_{11}, p_{10}, p_{01}, p_{00}, x_1, x_0) = p_{x_1x_0}.\$

I found the boolean formula to be:

\$(!(x_1x_0))p_{11} + ((!x_1)x_0)P_{10} + (x_1(!x_0))p_{01} + (x_1x_0)p_{00}. \$

My question is what would the circuit that computes mux look like using only and, or, and not gates.

Thanks in advance!


texts: Solve \$n \times n\$ rectangular grid of resistors for mesh currents

texts:
I am modeling a mechanical process by using an electrical analogue. I need to calculate the loop (mesh) currents, then I can see if any mesh current is greater than a predetermined value \$\lambda\$. There are voltage bars connected to the top, and the bottom is connected to GND. Initially the voltage, \$_{VCC}\$ is 10V. Each edge is a \$ 1 \Omega \$ ideal resistor.

The way I thought to do it was use Kirchoff's voltage law for each loop

\$\sum^N_{k=0} V_k = 0\$.

then solve the system of equations using: I = np.linalg.solve(Z,V)

where Z is my impedance matrix and V is my voltage matrix.

So if you look a the picture above there should be four loops, but networkx, a graph theory based library for python3, returns using nx.cycle_basis(G):

[(1, 1), (1, 2), (0, 2), (0, 1)]
[(1, 1), (2, 1), (2, 2), (1, 2)]
[(0, 0), (1, 0), (2, 0), (2, 1), (2, 2), (1, 2), (0, 2), (0, 1)]
[(1, 1), (1, 0), (2, 0), (2, 1)]

which is WRONG.

[(0, 0), (1, 0), (2, 0), (2, 1), (2, 2), (1, 2), (0, 2), (0, 1)]

should be:

[(1,1), (0,1), (0,0), (1,0)]

to get the mesh in the bottom left corner.

I know how to calculate the resistance between two points by using the Kronecker product in numpy, but I don't see what use that would be to me because I need the current and to solve Ohm's law I need the voltage between the nodes.

So yes my question is how can I efficiently calculate the branch currents of a massive resistor network?


texts:
I am bit confused between these two terms. I understand SINR is signal to interference+ noise ratio and SNR is signal to noise but isn't interference noise too? Then why have he segregated these two terms?

Further I also encountered signal dependent and signal independent interference. I couldn't find much about it except the research paper where people have worked on increasing SNR or SINR.


texts:
Most ATX motherboards have those same pins for 'interfacing' with the computer case... depending on the manufacturer they vary on position (hence loose wires at the case end) but never function. So i guess there is a standard somewhere.

they usually looks like this:

and you connect wires like these:

I looked on the ATX standard but there only seems to be board sizing and the power connector.

I'd love to have the specs for everything on that bundle... but if not, to unblock my work i'd just need to know now the LED (power_led, or p_led) specs. Do I need a resistor? or just a led? which leds are compatible? 5V? 3V?


texts:
I'm trying to build a robot that requires 5 micro servos and 4 standard servos. The micro controller board I am using is a 'DFRobot Bluno' (compatible with Arduino software). The board gets power from a 7.4v Li-Po battery, which is enough to power the servos (and so the robot) for a good 10-15 minutes before needing to recharge it.
The original robot that i'm basing this on is a BQZum Core. The BQZum Core board has these 'triple pins' (see image) with ground, 5v, and signal that the servos can be easily plugged into. Having so many 5v and ground pins, this board has no issue in running all of the servos. Unfortunately I could not get my hands on one of these boards nor have I found one that matches my requirements (has to be <8x8cm and integrated bluetooth) and also has these 'triple pin rows'.
Since my Bluno board doesn't have the same 'triple pin rows' I am worried about the setup (see diagram) because all of the power to the servos comes from the 5v pin. Would this result in servo performance issues? And is it damaging to the board? If so, what's the best course of action? Using an external supply for the servos? Using a different micro controller board?
I am working in a really tight space and so I might not be able to fit in a separate power supply in the robot for the servos. Could it be an option to split the power supply? Part to the board and part to the servos?
Any help is greatly appreciated.
Setup diagram
[1]: https://i.stack.imgur.com/aihJp.png
BQZumCore board
[2]: https://i.stack.imgur.com/UNWBi.jpg


texts: Help to build a circuit to trigger event only after input signal changes from "1" to "0"

texts:
I'd like to build a kind of logic as shown in the picture ,but I can't do it and I really appreciate if someone can help on that.
Basically what I'd like to achieve is that when the input signal changes from 1 to 0 it must trigger a switch at last 2-3 seconds and after everything released.
The input signal is not synchronous which means that it might last undefined time.
Thanks !

Thanks to comments and based on the link HandyHowie provided at paragraph "8. More about triggering" as shown in the picture above it looks it might be the right solution ,but I'm not 100% sure. Please let me know if this might do the job.


texts: From where I can find definition of this function PWM1_Set_Duty actually I am trying to customize this function for some reasons. I want to access his code, from where I can ?


texts: Controlling Mosfet with ATTiny85 and IR Reflective Sensor

texts:
My plan is to start a motor, then stop the motor when the gear teeth gets to 15 (out of 16) I will be able to tell at what position the gear is by placing an IR reflective sensor under the teeth. The sensor is a VCNT2020. I am controlling the motor with three MOSFETs in the schematic here (Leaving out M1):

And using the VCNT2020 Sensor in the schematic here:

And finally using an ATtiny85 as the microcontroller. I was originally going to use an arduino, but there is not that much IO so I thought it wouldn't be worth it.

My question is, will the motor be able to stop in time, should I begin to stop it on an earlier gear or will I need to do some kind of braking where I use a fourth FET to short the motor terminals. Also, I would like you to take a look at my unfinished code and ask if you could suggest anything. The reading of the sensor pin and the digital writing to the Mosfet need to be very fast otherwise the motor could do another few rotations and the gear go another tooth, going past the 15th one. I don't mind if it is exactly 15, but it needs to be 16 or below, and 13 or above.

Here is the motor, I couldn't find the datasheet but it runs on a maximum of 30 amps and 12.6v 3s lipo. The maximum rpm is 34,000

Code:

    int gearcounter = 0;

    int noiseAllowance = 10 // Ill change this when I 'calibrate' the design on a breadboard.

    void setup() {
      Serial.begin(9600);
      pinMode(A1, INPUT); // Ir sensor pin
      pinMode(5, OUTPUT); // Mosfet gate pin

    }

    void loop() {
      gear10us = analogRead(A1);
      delayMicroseconds(10)
      gearNow = analogRead(A1);
      if ((gearNow < gear10us - noiseAllowance) || (gear10us + noiseAllowance < gearNow)) {
      gearcounter += 1;
      }
        }

        if (gearcounter == 16) {//Maximum gear is 16, I just want to stop it one before the maximum
        gearcounter = 1;
        }

        while(gearcounter < 15){
          digitalWrite(5, HIGH);
        }

    }

Thanks

EDIT: My current schematic -


texts: FOC current control autotuning PI Controller for BLDC Motors

texts:
I try to understand, how the guys from odrive tuned the current control PI parameters for Field Oriented Control:

https://github.com/madcowswe/ODrive/blob/master/Firmware/MotorControl/low_level.c

In the Function "motor_calibration", K_i and K_p are choosen as:

// Calculate current control gains
    float current_control_bandwidth = 1000.0f;  // [rad/s]
    motor->current_control.p_gain = current_control_bandwidth * motor->phase_inductance;
    float plant_pole = motor->phase_resistance / motor->phase_inductance;
    motor->current_control.i_gain = plant_pole * motor->current_control.p_gain;

How they came up with this dependecies of K_i and K_p from L and R? They somehow must place the poles the right way with this, but I don't see how they guarantee to shift the poles to the negative half plane.

The State Space Model of a BLDC motor looks like this, but from here we cannot simply assume, that the input u is F*x, such that we come up with a closed loop system, because the back EMF voltages we cannot control directly:

Edit: Is it possible, that the following simple model was used?
So the closed loop system has the transfer function:

$$
G(s)= \frac{K_p s + K_i}{s^2 L + s(R+K_p) + K_i}
$$


texts:
Dividing a clock down in Verilog is a basic exercise, and there are loads of answers online about how to do it.  What I want to know is whether it is OK to use a clock that has been divided down using verilog on a real FPGA to clock flip flops.

I'm asking because common knowledge dictates that we should never put combinational logic on a clock line and then use the resulting signal to drive a flip flop's clock.

Sure, a clock divider isn't what we would call combinational logic, but at the end of the day, I would still be putting logic gates between a (presumably) complex clock network and the clock signal of a flip-flop.

It's worth noting that I've certainly done this in some hardware projects and it has worked, but it was on a low performance FPGA.  I'm wondering if this would work consistently and reliably on most FPGAs, or if I just got lucky with the chip I was using.


texts: Reading isolated multichannel input with voltage drop on all channels

texts:
I am building a circuit to read atleast 22 input channels (24 vdc) using an Arduino board which essentially works on 3.3 vdc or 5 vdc.
My current setup makes use of 22 PC817 optocoupler. I am sharing the most basic circuit diagram below with only one channel reading capability to keep it simple to understand.

To drop the voltage and keep the optocoupler safe, I've used a voltage divider with a 68K and 1.5K Resistance (±5%/±10% tolerance) that would drop the voltage to around 3.3 vdc, that I think would be safe for PC817 (please correct if I'm wrong).
Now since there are 22 channels to read, using 22 x PC817, 22 x 68K and 22 x 1.5K resistance adds a lot of complexity to the circuit, I wanted to know if there's a better way to do it.
I read about 8 channels Digital Isolators like Si838x, and have following questions:

From what I understand I can feed 24 vdc directly to this IC and will be able to handle?
If not, is there any other alternative to this digital isolator were I can handle preferably more channels on one IC?
If it is a no for both 1 and 2 above, what are the best options I have for a multi-channel Opto-coupler?
Any other suggestions to keep the final circuit small?


texts:
My arduino UNO can provide max 40mA and 5V and what i need to control is 2.2V 60mA. I will use 4 shift registers (74hc595) connected to arduino and each shift register output will have a transistor attached, which will control 3 LEDs (2.2v, 20mA each) in parallel. The power source will be of 3V (two AA batteries in series)
Will this (http://www.taydaelectronics.com/2n3904-npn-general-propose-transistor.html) work? If yes, what resistor should I use with the transistor?
Moreover, will this configuration work?


texts: How can I calculate the charging time for a battery from photovoltaic panels?

texts:
I'm trying to develop a spreadsheet that will work out a power budget for a photovoltaic solar powered installation. There are 2 panels which I think output 35 Watts. There are 2 x 200 Ah lead acid batteries.

I know roughly how much current my installation will draw and how long it will draw it for per day.

I need a formula for the time it will take to recharge the batteries given the current drawn. Alternatively, I'd like to be able to work out (given the panel output), what's the maximum time per day (on average) that I can run my installation without depleting batteries.

I don't know much about battery chemistry or charging so I don't really know how to work this out. Can someone help?


texts: SignalTap II: OR trigger conditions, instead of AND

texts:
I'm using the Altera SignalTap II that comes with Quartus II. As far as I understand, each pin can be assigned a trigger condition. It seems that acquisition only stops when all the trigger conditions are satisfied.

How can I tell SignalTap II to stop acquiring when any of the pin trigger conditions I have set occurs?


texts: How to set SD card clock frequency between 100 kHz - 400 kHz

texts:
I am interfacing a 32 GB microSD card with PIC32MX795F512L. I am following the examples provided in Lucio de Jasio's book.

As the author has described that to set a 250 kHz, they are driving their peripheral clock frequency by 144. Which means 36 MHz when divided by 144 gives 250 kHz. But then why are they setting the SPI1BRG = 71;? (SPI1BRG = SPI baudrate register.)

I am using 44 MHz as a peripheral clock frequency. What value should I use?

I am really confused in setting the clock frequency for the SD card.


texts: ATtiny85 to control a relay, which will turn on and off a motor

texts:
I am trying trying to control a 5V relay (SRD-05VDC-SL-C) with the ATtiny85. I have a simple sketch uploaded (Blink without Delay example):

const int ledPin =  0;      // the number of the LED pin
int ledState = LOW;             // ledState used to set the LED
unsigned long previousMillis = 0;        // will store last time LED was updated
const long interval = 1000;           // interval at which to blink (milliseconds)

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop()
{
  unsigned long currentMillis = millis();

  if(currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;

    if (ledState == LOW)
      ledState = HIGH;
    else
      ledState = LOW;

    digitalWrite(ledPin, ledState);
  }
}

The whole thing is being powered by an 18650 Li-Ion battery (3.7V-4.2V) and the measured input is averaging 3.88V. Here is a quick sketch of how the circuit looks like:

Some issues comes up WITHOUT the motor connected:

If I connect the battery and relay directly, you can hear it click, despite it being rated at 5V input.
If I try to trigger the relay from Pin0, the oscilloscope will show the voltage of Pin0 to be about 2.72V, when the relay looks to be switching. If I replaced the relay with an LED, the voltage of Pin0 is about 3.88V. What causes the drop in voltage? I believe the current should be enough since it's an Li-Ion battery.
What sort of protection do I need to implement in this circuit?
Will the Li-Ion battery be enough to power this circuit? If I connect just battery, relay, and motor, it runs fine. The issue comes with the addition of the ATtiny85.


texts: Undestanding the SOA of MOSFET from the datasheet?

texts:
I was checking my MOSFET for the selected power class. Could somebody explain the decoding of SOA of the MOSFET from the datasheet specs. I want to know which regions are considered during the different phases of MOSFET for example during
1. DC operation
2. Switching
3.Linear etc...
 Reference SOA can be considered from the below image:


texts: Balance charging connection for 2 cell li-ion

texts:
I am designing a circuit powered using two 18650 li ion cells in series, I will wish to charge it with an imax b6 charger with balance output. Is it enough to connect the 3 terminals of the charger to the batteries directly (one at -ve of bat1, one between the series connection and one at +ve of bat2)? Or any additional circuit is needed? Is it okay to charge while the circuit is powered?
Thanks.


texts: How can calculate the turn-off time of an LDO?

texts:
This is the datasheet of TPS7A8101 LDO I am analyzing. In the datasheet, start-up time of the LDO is given as 80 ms for given conditions.

My question is, how can I calculate the turn-off time of the LDO. I was doing a shut-down timing sequence diagram for my circuit and came across this LDO. I believe LTSpice simulation can get an idea of turn-off time. But not sure about that.

How can I find the turn off time of an LDO?


texts:
The RTC MCP7940N is used in the system. The microcontroller and RTC MCP7940N are connected through the I2C interface.

I would to know what is the better design to read the timer value from the RTC.

Method #1:
Upon receiving the request from other high level modules, the I2C frames are prapared and sent it. The I2C data receive interrupt is used to read the I2C data and compute the time value. An event mechanism is used to inform the required modules about the availability of the new timer value

Method #2:
Cyclic task is used to send the I2C frames every 5ms and the received I2C data is polled by the cyclic task to calculate the timer value. The high level modules can read the time value synchonously but the timer value will have the accuracy error of 5ms due to the fact that the RTC timer value is read every 5ms.

Please provide your views on this and the better approach to read the timer value without loading CPU much.


texts: resistor values of a 4th order bessel high pass filter

texts: I have a question about cascading the 2nd order bessel high pass filter to form a 4th order bessel high pass filter, I have an equation to solve for R1 and R2, will the same equation be used to solve for R3 and R4 of the cascaded 2nd order bessel high pass filter?


texts:
Can a intrinsic semiconductor, when it is biased, have diffusion current?

diffusion current exists when there is change in concentration of charges w.r.t distance. But when it is biased the voltage changes through out the semi conductor resulting in drift current. so how diffusion current comes into picture?


texts: How to model a DC motor in LTSpice if only its nominal voltage and max. current is known?

texts:
Is there a simple way to model a DC motor in LTSpice when controlling it with a PWM signal? Lets say the motor is 9V/2A.

I was thinking the safest way to measure the stall current and use the nominal voltage but I think there is more to handle this.

edit: Or should I say, can we model a DC motor as a resistance if we know at a particular rpm and voltage it draws known amount of current?


texts:
I was trying to get my EEPROM read/write working on my PIC.

I first programmed a write cycle, and then reprogrammed it to read it out. (To avoid writing every time I start the program/pic)

But I luckily found out that re-programming your PIC causes EEPROM to get... changed?
I found a way to fix this, by using the setting "Preserve EEPROM".

My questions on this are:

Does "Preserve EEPROM" write the EEPROM everytime you program your chip? (So re-programming a million times will break EEPROM theoretically)
What value is EEPROM after it's programmed... (val != 0xFF) returns true Can I say it's corrupted after programming, or does it get a default value I could check on?

Using: (though it's more theoretical)

MPLAB X IDE
PICKIT3
PIC18F66K22


texts: Is the bracket of a graphics card grounded?

texts:
I would guess so, but I want to make sure.
Edit: After measuring with a multimeter, I suspect that brackets (of most graphics cards) are grounded to the graphics card's ground-plane.
I measured 0 ohm between the traces around the motherboard screw holes and the bracket of a (old) 75W graphics card. (All power from the PCIe x16 slot. No power cable needed. So, graphics card's ground-plane == motherboard's ground-plane.)
The motherboard was outside the case, on a wooden table.
On some newer graphics card, a screw (which fastens the bracket to the board) is clearly visible on the back side, suggesting direct contact between the bracket and the graphics card's ground. (This construction also counteracts sagging. A little bit.)


texts: STM32F4 ADC: Dual interleaved + Independent

texts:
Some STM32F4 microcontrollers have 3 ADCs on board, they can be configured in various modes.
I wonder is it possible to configure ADC1 and ADC2 in "Dual interleaved" mode, but have ADC3 configured as independent channel?

When generating project in CubeMX, if I turn on all 3 ADCs, and select for example "Dual interleaved mode only" in ADC1 - all other ADC default to this mode without possibility to change it. This is quite weird, since CubeMX basically says that all 3 ADCs are configured in dual interleaved mode, which is illogical (3 ADCs working in Dual...). There is no way to change ADC3 to any other mode, even though having it as "Independent" seems to be the only logical solution.

On page 402 here under bullet 2 it says "In the Dual ADC mode, the ADC3 slave part is not present.", I am not sure what is meant by that: is ADC3 as a whole is not working in dual mode or simply ADC3 is not SLAVE anymore?
I'm afraid it is the only reference to ADC3 in dual mode in official reference manual.

On page 78 here it says "ADC1 master and ADC2 slave, ADC3 is independently.", which kinda suggests that ADC3 can be configured as independent, but this pdf doesn't describe it any further.

I also found this application note, but it is only for microcontrollers with 2 ADCs inside. If there is the same note but taking into account ADC3 - please share, I haven't found it.

So the following questions arise:

Is CubeMX bugged? I mean, clearly there is no sense to configure 3 ADCs in dual configuration. It either has to set ADC3 to independent mode or show error message "You can't use ADC3 anymore, lol".
Can I configure it manually in code or this is not supposed to work like that at all?

I could of course try to make it work by building a project in such config and see if it works, but if it is not supposed to work like that at all that would be just a waste of many hours. There is no documentation about it, even if it will somewhat work it will be a hell of a mess to try to make it work with DMA I presume.

So if anybody has done something similar or knows for a fact that it is not supposed to work would be nice to hear.

Oh and if somebody wonder why do it in a first place:
it would be nice to have "one channel" that utilizes dual mode to get 4.8 MSPS and the other just regular (from ADC3) with 2.4 MSPS. As opposed to having two simple channels at 2.4 MSPS.


texts: Self charging wood-gas camping stove using thermoelectric module/modules

texts: Is it better to string 3 teg thermoelectric generator modules in series to charge 8 NiMH batteries at a current of around 700 mA Delta T of ~80 deg. C or should I use 1 module and try a voltage tripler to get 12-14 Volts and drop the Amperes accordingly? The application is a wood-gas (Little Wolf Energetics) camping stove, harvesting the waste heat from the bottom of the burner unit. I have laid out three modules radially mounted on 5x5" aluminum 1/8" plates above the fan which supplies air to for primary and secondary combustion. This stove may be going to Ethiopia for cooking and charging electronics. Thanks.


texts: Hobbyist: Is this a reasonable design for an audio amplifier? (very sketchy design)

texts:
I have always wanted to design and build my own audio amplifier. Is the following a reasonable design?

The input stage takes in line level signals (say, up to +/-3 V, but typically more like 0.3 - 0.8 V).
TI OPA 134 "audio op amp", in buffer configuration, to impedance match for...
Low pass filter (ideally one I can turn on and off, so I can put the amp in "subwoofer mode")
TI OPA 134 in non-inverting amplifier configuration, aiming for gain of 5-20
A push-pull BJT amplifier stage, with enough gain to push 100 W through 8 ohms of impedance.

All of this powered by a, say, a 150 W power supply with high voltage rails.

I originally wrote +/- 15 here. I had op amps on the brain, since I am actively working on designing the line level circuit and want to figure out what gain factor I'll eventually need.

Obviously, there are a lot of details/features I'm not including or even designing at the moment. The BJT part is especially sketchy at the moment.  I'll get to that, but I want to know if it's even "plausible" and reasonable.

Questions:

Is this a reasonable first attempt at sketching out design?(This is actually version 0.0.4 of my design). Any additions/advice for a beginner?
Given that I'll have a low pass filter, is the buffer op amp necessary or does modern audio equipment typically have a high enough output impedance at line level? Does it make sense to use an audio op amp in the buffer configuration?
I'm guessing it makes more sense to do the low pass filtering on a line level signal as opposed to after the BJT amplifier stage, but that's just a guess. Is it right?
How do I calculate the voltage I need across my 8 ohm load? If I do a DC approximation, it comes to about a 28 V difference (i.e., +/- 14 V). (Did I flub this math? P = I^2 R = 100 W / 8o = 12.5 A^2, so I is about 3.5 A, which means the voltage difference must be about 28 V give or take.) But presumably, AC imparts less power at +/- 14 V than DC at +/- 14 V. (But then again -- perhaps as a naive guess? -- a square wave swinging between +14v and -14v "should" intuitively push out as much power as +/- 14 V DC...) So what output voltage do I really need to get 100 "real" watts out of my speaker? What assumptions should I make about the input signal and it's spectrum? Square waves?  White noise?

Or am I overthinking this, and should just aim for some rule of thumb?

Despite some of the comments, I am going to do this. Even if it takes me 50 practice circuits and and auditing a course on EE. I am not trying to kill myself or start a fire. I am trying to plan out a long term project -- to figure out how much time to invest in learning the line-level components and to figure out what kind of transistor technology and amplifier layout to learn about next, in order to accomplish my goal. Assuming this sketch of a design (barring the power supply issues mentioned) is even plausible.  Which is why I asked in the first place. I am working on a roadmap, not trying to sit down and solder random parts together.

I'm totally green when it comes to building circuits, though I did learn a lot as a kid (Mims III) and vaguely remember some circuit design/analysis from college (passive components, Ohm's law, DC analysis, RCL analysis (though I don't remember the formulas right now and would have to look them up to solve for capacitances, etc.), transistor basics, and op amps, Fourier analysis for signals and in real analysis. I also have a math degree and took a bunch of physics classes.


texts: Colpitts / Clapp oscillator crystal drive level

texts:
simulate this circuit – Schematic created using CircuitLab

As I understand this circuit has some initial gain at startup, then as the oscillation builds up gain goes to unity at some moment. How to modify such circuit to change crystal power dissipation from lets say 1mw to 100uw, but still keep initial gain same for reliable startup? I mean, how to control transition point where it goes to unity gain? Also, what could be possible consequencies of adding series resistor to a crystal to lower drive level? Say 5 to 10 Ohms?


texts: Layer Type Detection Bug in Altium Designer

texts:
When I open the "Layer Types Detection Template" by going to "Tables" -> "Layer Type Detection..." I see a list of "Layer Type" and next to that, the "Layer Type String Template". The strings that are used to try and detect the layers are incorrect.

Basically, what happens is this. If I install a fresh copy of Altium, and I try to make gerber files for a pcb, I can detect the layer types using that layer type detection template. The first time I do this, it will work fine. If I made a mistake or had to do another board, the file extensions in each row appear to shift up one row, and merge with the items in the row above. The attached picture shows how the bottom row shifted the file extensions up one row. If I used this tool again, the cells in the second column would shift up yet again.

You can look at the extensions and see how they are obviously not associated with the correct label in the left column.

I have had this bug in a version of Altium 18, 19 and 20. I must not be the only one having this issue and it is adding a TON of time to me getting boards created. Has anyone else had this issue and found a work around?


texts: How to do DC Analysis for a Common Source Biasing Circuit using NMOS

texts:
I am having a lot of trouble with this specific problem. I want to find Vg, Vd, Vs, and Id for this specific common source biasing circuit that has an NMOS.
I have these values given: Vdd = 9V, k/2 = 2.9, Vt 1.55 V

So far I have these equations (assuming active/saturation mode)

Vg = 9V * (10k/(10k+10k)) = 4.5 V (I used voltage divider here)

Then using the equation for active/saturation mode:

Id = k/2(Vgs - Vt)^2 = 2.9(Vgs - 1.55)^2

Last I tried using KVL for these equations:

GS loop: 9V - Vgs - 1k*Id = 0

DS loop: 9V - 2kId - Vds - 1kId = 0

When I try solving equations with these loop equations, I get very stuck. I get incorrect/differing answers depending on what variable I substitute. Can anyone help me solve this problem?


texts:
I have problem with the model of given power limiter (below are the images). Problem is in the red rounded resistor on the last image - that resistor overheats for some reason (I've put 3 ohm one instead of 2.2 ohm).

What should I do?


texts:
I'm trying to create a simple state-diagram for a JK flip-flop, and this is what I've come up with.

I've seen other variants of this diagram, but to me this seems like a correct one if you look at the state table:

Is this correct?


texts: Transistors choice for buck boost converter using LM34936

texts:
I've been using TI's Webench online design tool for buck boost design purposes that uses LM34936.
The simplified schematic in LM324936's datasheet looks:

Webench design tool generated 4 different MOS transistors (CSD series):
M1 CSD16321Q5;
M2 CSD18511Q5A;
M3 CSD17303Q5;
M4 CSD17573Q5B;

My question is, could I use one just type of transistors instead of 4 different?
The output I'm trying to get is 12V, so what is the maximum Vds that could occur on MOS' drains?


texts: Cable wires - confirmation of live and ground

texts:
I bought a generic DC power extension cable and I'm trying to wire it to a connector with a cable attached. The connectors cable clearly has two wires - a red and black/+ and -. This is what I'm used to, coming from the world of breakout boards and tiny wires. The generic wire, once stripped, however has outer bare wire strands surrounding a sheathed tiny wire:

(I've attached a photo. I've twisted up the outer wire so I could test it with my multimeter). My logical assumption is that the inner sheathed wire is + and the outer is -. Is this correct? I've hooked it up to my solar panel and tested it on my multimeter. It shows 7v when I've got the red wired touching the inner sheathed wire and the black wire touching the outer, and -7v the other way round. I just don't want to connect it up and fry my solar charger board. It's be great if someone could give me a 'yes! you're right!' confirmation please?


texts:
I have to measure the up-time of devices such as refrigerators and geysers and store that data in the database. What is the easiest way to measure this up-time? I read that timing circuits could be used for the same. But there was no clarity on this application. As a mechanical engineer with absolutely zero knowledge about circuits, the simplest solution that comes to my mind would be to add a sensor that responds to electric current and then connect it to a timer who's reading would then be read by my micro-controller. Could someone tell me how I could implement the above solution? or could someone suggest a more efficient and cleaner solution?

EDIT: As requested, I will edit the question and clarify what exactly I want to do. The question as to why a refrigerator would be switched off, well power cuts? Now my main aim is to determine the time period for which the device is 'actively' consuming energy!


texts: Basic question related to relay operation

texts:
Electromechanical relays are generally based on the principle that electromagnets(due to supply current ) attracts armature of relay which is made up of ferromagnetic material (because ferromagnetic materials are attracted towards high magnetic field density region) and close or open the switch depending on design.
My question is -
Can we make a slight change in the principle  of operation of relay by using a low resistance non ferromagnetic conductor as armature of relay and due to low resistance a high  current induced (Eddy current) in the armature when we turn on or off the supply and a transient high repulsive force(lenz law) acts on the armature and hence we can open or close the switch ?
Or
there is any practical problem in this operation ?


texts: Can I power ICs directly from a wall adapter?

texts:
I am designing an audio circuit that operates at 5 volts. Is it reasonable to buy a wall adapter that outputs 5V, or should I buy a wall adapter that outputs a higher voltage and step the voltage down at the PCB with a linear or switching regulator?

The audio circuit operates at 5V to achieve a volume level. The audio signal source will come from a microcontroller regulated at 3.3V.

The wall adapter I am considering is medical grade; part # MDS-030AAC05 AB.


texts: Is it feasible to have a Touchscreen with 2 (mirrored) USB outputs?

texts:
Background:
I'm investigating an AV project that requires large touchscreen panels driven by a media PC. The design calls for a redundant PC that can be switched to in the event of the primary failing. This is achievable in the sense that the screens input can switch from one source to another (e.g HDMI1 to HDMI2) however I am hitting a roadblock when it comes to how to switch the touchscreen (HID) output from PC1 to PC2.

Other Investigations:
I've exhausted a number of avenues looking into "mirroring" the USB signal between both machines and found this inst feasible. A possible alternative would be a USB / KVM switch however this is impractical and adds another possible point of failure into the design.

Potential Solution:
What id like to know is, is it possible to create a touch screen panel with two identical USB outputs (literally two USB cables sending the exact same signal to two independent PCs). My knowledge on the topic is sketchy but to my mind it would work something like this> Analog input from user touching screen > touch screen controller converts signal to digital > controller "splits" signal > controller serializes data > controller sends 2 separate USB outputs (one to each PC)

The touch panel overlays are being custom build so hardware isn't an issue I'm just trying to find out if I'm some how breaking some basic fundamental law of physics here or if I'm on the right track. All help / feedback / suggestions greatly appreciated!


texts: IoT device Power using 2.7V Super Capacitors Solar Charger Dc-DC

texts:
I have an NB-IOT Transmitter which sleeps most of the time, but one a day wakes up and transmits a file over FTP to my web server. My device runs on 3.7V and needs at least 1A for very short bursts during tranmissions.

I wish to use the following power supply:

5.5V, 200mA Solar Panel
2.7V 100F - 500F Super Capacitor, which will be charged via the above solar panel
2.7V to 3.7V DC-DC Up Converter, which will be connected to the Super Capacitor
A non-Rechargable 3.7V Battery

I wish my IoT device to use the power from the Super Capacitor, unless its depleted, in which case it will use power from the non-rechargable battery.

The building blocks seems to be

Current Limiting Super Cap Charger, between solar panel and the super capacitor
DC-DC convertor to take the 2.7V from the Super Cap to the required 3.7V
Some kind of switch to decide if power comes from 6) or from the non-rechargable battery.

The device is a remote monitoring sensor.

I have searched everywhere to find a circuit that comes close to what I want to do, but can't find it, so am hoping to get some pointers here. How can I do what I want to?


texts: Will sticking plastic (PLA) in a usb port cause a short?

texts:
The problem: I want to mount a webcam to the top of my monitor (monitor is in portrait orientation). The webcam I have on hand has an awkward clamping mechanism, and I'm struggling to get it to mount sturdily. I don't want it pressing against my screen, as it blocks the view of the top of my screen and could potentially damage the screen.
The solution: Taking advantage of the 2 usb ports along the top edge of the monitor, 3D print a simple webcam holder using PLA that slots into the 2 USB ports. This would provide a place to mount the webcam and also elevate the webcam so that the screen is not blocked.
Potential problems?:

Short out the monitor - based on what I'm reading, PLA has a high resistance, so this is unlikely. I can use a multimeter to test my specific filaments resistance
Get broken plastic stuck in the usb port - annoying but I could fish it out with the monitor off/unplugged.
Waste of 2 USB ports - not a problem for me.

I acknowledge that this is not the most elegant solution, but it is something I could do right away to solve my problem. Would this work?


texts: I'm trying to hook up the load cells from a Wii fit balance board to an esp8266 using the HX711 ADC. Ideally, a way using only one HX711 but, a hookup guide for two HX711 with two load cells apiece would be helpful as well.


texts: Readily available or commonly used transparent conductors?

texts: Are they any transparent conductors (inks paints or otherwise) that are readily available to hobbyists? (i.e. cost effective and purchasable online)?


texts: Questions about automotive electronics PCB layout

texts:
I am a student of vehicle engineering and I love automotive electronics very much. Right now, I have an ESP sensor cluster to study, and I am lucky to have a look at the PCB inside. I have some questions about it.
First, why don't they use teardrops at the trace/via junction?

Second, why do they use only one trace to connect the resistor to the ground?

I am new here and my English is not so good.


texts: What is the theory behind these current equations? (for Z paramaters)

texts:
In the photo below is shown the method for deriving z-parameters of the circuit. Apologies for my badly drawn values for resistors as they weren't shown in the original image. Basically I'm struggling to see where the parts in red circles are coming from. I understand each of the Z equations but I don't know the actual theory behind those identities for Io and Io'.

The Io identity applies when I2 is 0. I can't tell if the 1/2 in the identity is actually a half, or if its the resistor values(there is a 1 and a 2 ohm resistor in the circuit). The reason this confuses me is because I'm doing this with a similar circuit which doesn't have that 1ohm resistor, but does have the other 3, so I need to know if the identity would be different for my circuit.

The Io' identity applies when I1 is 0. It seems like it is 2/(2+4+6) but again I'm not sure why.

So can anyone tell me whats the name of the rule that would provide an explanation for the circled identities, and help me understand why they apply when I1 and I2 equal 0.

Sorry if I haven't explained this well I'm having difficulty putting it into words, so if you're confused I'll happily clear up anything you need!


texts:
I have the question "Using the waveform given, draw a phasor for the following point"

So here is the waveform:

Here is the answer to the question, however I am not sure how this is achieved. I have tried to learn about drawing phasors but I still don't understand how this answer is achieved.


texts: Power supply output voltage drift with temperature

texts:
The PSU that I've built, output voltage is drifting when it's turned off;

First set values:

Turned it back on again after 10 hours:

The values being read using a 16 bit ADC and is spot on.

The constant current values didn't change but voltage value increased by ~8 mV and started to drop as it's warming up. as I'm writing this, voltage dropped to 3.003.

When it's warmed up voltage stays steady (tested it for 4 hours), so the drift only happens when it's cool down.

Same op amp controlling the voltage is controlling the current too so the drift with temperature is not caused by the op amp because the current value stays steady. also current and voltage each have it's own voltage reference and both are TL431.

The only suspects I can think of is the voltage regulator itself (infamous LM317) and maybe the 10 turn on-board potentiometer.

Problem like this seems common, for example a power supply from Keysight in it's datasheet notes:

Is this amount of drift considered ok? Is there a way to compensate for it in hardware or software?

Yesterday I asked this question but had to delete it because I haven't had the long run test result and extra info.


texts: I am designing and building a power supply with TPS54531 switching regulators from TI.  I am double LC filtering the output.  The 5 volt PH output pin feeds a 9.2uH inductor, then to a 47uF ceramic capacitor then through a 0.47uH inductor and finally to a 15uF ceramic capacitor at the output.  My question is where should the V_sense resistors connect, before or after the secondary LC filter?


texts: I have a power window motor which is powering a rock tumbler and baffled!

texts:
I have two AC / DC adaptors.

Model SY-002-5-12
Output 12V_...2A
       5V_...2A
and

Model LX1205
Output 12V_...5A

Only the 12V _2A will run the motor.

What am I missing?
I thought the 12V_5A would be the better choice as a power window motor usually runs around 12V_5A.

Help please.


texts: Determine the currents in the following circuit

texts:
Here I have such a problem. I'm asked to determine the values of currents in this circuit(the circuit is in permanent sinusoidal regim). The double-sided arrow in the image represents the magnetic coupling:

Where: E = 140 V, L1 = 4mH, L2 = 20mH,
       R1 = 1 Ohm, L3 = 6 mH, C2 = \$ 500 * 10^{-6} F\$
       ,\$Z_s = 1 - 2j\$, \$ w = 1000 \frac{rad}{s} \$.

\$ 1mH = 1 * 10^{-3} H \$

C1,C2, C3 = capacitors

\$R_k  \$ = resistors

\$L_k  \$ = inductors

E = voltage source

The problem is I do not know how to deal with impedance \$ Z_s\$ while  composing the system using Theorem Joubert and Kirchhoff in complex.

I hope I was understandable. Thank you in advance.


texts: AP22802 Load Switch Sometimes Burning Unexpectedly!

texts:
I have been using AP22802 high-side load switch on many projects for non-inductive loads without any problem until now.
But sometimes it was burning even it has light loads (5V/10~150mA).
If input capacitance is lower than output/load capacitance it burns because of unkown effect.
but it works any problem most of times.

Any idea about why it is burning sometimes even on light loads?

The list of people who have similar issues with AP22802:
https://www.gitmemory.com/issue/newaetech/phywhispererusb/5/578445400
https://forums.parallax.com/discussion/comment/1479361
https://www.eevblog.com/forum/projects/weird-load-switch-problem-ap22802-with-bluetooth-hc-05-module/
[http://e2e.ti.com/support/power-management/f/196/p/744690/2780431#2780431?jktype=e2e]
[6]

[6]: http://e2e.ti.com/support/power-management/f/196/p/744690/2780431#2780431?jktype=e2e## Heading ##


texts: Inverse Laplace via Decomposition Theorem

texts:
The original query is to find x(t) with a Laplace transform of X(s) = 4(s+1) / s(s+2)^2. The poles are s_1 = 0 and s_2 = -2 (with a multiplicity of 2).

Because the second pole is not simple, its x(t) should be solved via the Decomposition Theorem, correct?

I.e. lim(s->s_{2}) = d/ds [ X(s) (s-s_{2})^2 e^st ]

Continuing to solve, I reach the following and am unsure of how to continue:

$$
lim_{(s->s_{2})} \frac{d}{ds} \left(\frac{4(s+1)}{s}\right) * e^st
$$

Because x(t) for the first pole is x(t) = 1, and x(t) for the second (non-simple pole) is x(t) = (2t-1)*e^(-2t), the final solution is the sum of the two:

$$
x(t) = 1 + (2t-1)*e^(-2t)
$$

How is this reached (i.e. how is the solution for the second pole reached, from the point where I left off)?


texts: Synchronous Buck High Side Driver - Why is the Fall Time of High-Side Gate Drive so Slow?

texts:
Below is the picture of my gate drive signals. The blue trace is the low side gate signal and the yellow trace is the high side gate signal. Both signals are measured across the gate and source of the high and low side mosfets.

As you can see the high-side gate signal (yellow trace) is falling very slowly. Why is this the case? I am using an NCP5181 as my gate driver.

Below is my circuit.

For completeness, below is the block diagram of my gate driver IC. In the block diagram of the datasheet it shows that the high side is driven low by a push-pull MOSFET configuration so I would think that the gate signal should go low quickly.

For reference here are the scope signals when they are both measured with reference to the ground of the circuit.


texts: Inductor Polarity Reversal - Flyback Voltage

texts:
I have a question about how to intuitively think about the polarity reversal (flyback voltage) that occurs in an inductor when removed from a supply.
Here is my understanding:
When the switch is closed, current flows through the inductor to ground, with a positive voltage across the inductor.

Then, when the switch is opened, I understand that the polarity reverses, but I'm trying to make sense of this fact.
I know that the average value of the voltage across an inductor must be 0. From this perspective, it makes sense that the polarity switches, it was previously positive, and now must be negative to have an average value of 0. However, when thinking about it in terms of maintaining current direction, I can't wrap my head around it.
I know that the inductor will try to resist the change in current flow. So when the switch is closed, it is storing up a magnetic field with the original positive polarity. Then, when the switch opens, the inductor should act in a way to keep the current flowing in the same direction as when the switch was closed. Knowing that current flows from high potential to low potential, it would make sense that the inductor would force a positive voltage across it, to keep the current flowing in the same direction. However, what actually happens is it forces a negative voltage across itself.

Wouldn't flipping the polarity mean that current goes in the opposite direction as before, since it must go from high potential to low potential?
Can someone help clear the confusion for me?


texts: The op amp error based Power Supply, Driving the load.....?

texts:
My question is based on the MOSFET circuit shown in a question by uMinded..
"High Voltage Series Pass Transistor - Low Voltage Control" here

This circuit is a little unique in that it is not using a follower type load driver.. if you Google power supplies, 99% use an source- or emitter-follower based design driving the load..

My question is: yes a follower MOSFET or BJT has high current gain with no voltage gain and is simple, but adding a varying value of load capacitance and the error op-amp circuit becomes very unstable as the op-amp see's this capacitance on its output. So, why is the load, NOT Usually driven as it is in the circuit mentioned above (from the Drain or Collector) more isolating the op-amp from load capacitance... after all the op-amp has lots of gain.

I have simulated the circuit mentioned above with appropriate changes, and even when varying the load capacitance from 1 µF to 10000 µF it showed no sign of instability.


texts: Controlling a mechanical shutter with an electromagnet

texts:
I'd like to drive a pair of mechanical shutter / apertures with an electromagnet. For those curious, we're using a shutter from Edmond optical. For the particular application, I'd like to design a compact actuator to drive it. (I had considered just hacking a camera lens with a shutter, but couldn't find one that was large enough for my needs).

So at present I am thinking about attaching a neodymium magnet to the lever of the shutter and then using a series of electromagnets to push it between open and closed. Which all leads to my first question: how can build compact electromagnet?

It seems like the steps involved are to find a solenoid and then to drive it with a decent voltage difference. I wonder if anyone could recommend a good small solenoid for such purposes. Does it make more sense to roll my own with an iron core and insulated wire?

My second question is more open-ended: can you think of a better way to drive such a shutter? How would you design the shutter motor?

UPDATE: in response to comments:

@tyblu the shutter needs to be open or closed in about 500 microseconds (but exactness is not important).

@bt2 a solenoid is interesting, are you thinking of hitting the lever and letting momentum carry it across to the close position?


texts: Can I replace Arduino with Raspberry Pi and still use the same circuit board?

texts:
I have an Arduino project that consists of a motor and a solenoid valve, but I want to use a Raspberry Pi because it seems to be easier to make it communicate with my computer because it has built in wifi.
I want to be able to control the microcontroller/raspbi with a code in my computer.
I've never connected my Raspberry Pi to a circuit board.
Is it possible to use the same circuitry while slightly adjusting the input/output lines? Or will that damage everything?


texts: Why is that the gate current cannot be negative for SCR?

texts: Why is that the gate current cannot be negative for SCR ? If the gate current is negative it should only increase the breakover voltage , why is that the SCR does not work ?


texts:
This is a homework assignment problem and I tried to solve this all last night but I am still a newbie in Assembly language.

Dont give me the full solution, just give me a hint.

  Design an ARM Assembly Language program that will examine a 32-bit
  value stored in R1 and count the number of contiguous sequences of 1s.
  For example, the value: 01110001000111101100011100011111 contains six
  sequences of 1s.

  Write the final value in register, R2.

Now, the algorithm I think is to read each character one by one, and increase i by 1 everytime it faces 2 continuous 1s. But how to do it in Assembly Language?


texts: how would inductor react if I inject current impulse into parallel LC tank?

texts:
What would happen if I inject current impulse into parallel LC tank?
How would current flowing through inductor look like over time?

If we look at the delta function in the S-domain (laplace transform), energy is uniformly distributed over s-domain. This means, delta function cannot be just treated as high frequency signal.

This means, some of current impulse will flow through capacitor, and some will flow through inductor.

Since they are LC tanks (let's assume they are ideal LC tanks), then oscillation will occur. This case, which will react to this oscillation first: inductor? or capacitor?
would inductor start dumping current into capacitor first? or would capacitor start dumping current to inductor first?

I want to know what you guys think about this problem

Thanks,


texts:
How to make sure you have "adequate" ground in a self-enclosed portable circuit?  I read that a good ground ensures steady signals.  But, if you run a circuit from a battery it is not connected to anything else.

What do you use for "adequate" ground that is able to handle your circuit?  Do you add more ground metal like metal sheet, larger PCB traces, an elaborate PCB ground-plane?  How do you determine/calculate what is adequate?


texts: Why does tracking different plant states result in totally different observer estimates?

texts:
I am trying to design a Luenberger observer (or a full state feedback observer) such that with one sensor available I can estimate all the states. A good tutorial is shown here.

My system is 4th order:

num = [-0.00198 2];
den = [1 0.1201 12.22 0.4201 2];
sys = tf(num,den);
[A, B, C, D] = tf2ss(num,den);

First I have a row vector of poles to get my desired response:

poles = [-2.6 + 1i*2.39, -2.6 - 1i*2.39, -100, -120];
K = acker(A,B,poles)
rank(obsv(A,C));  % =4
Mo = rank([C;C*A;C*A^2;C*A^3]) % =4

I then proceed to calculate the plant poles and thus the poles I want for my observer should be around 3x faster.

plant = (A-B*K);
poles_cl = eig(plant)

poles = 3*poles_cl  % THIS IS WRONG
des_poles = (min(real(poles_cl))*3)-(1:4); %This is better

des_poles =

 -361.0000 -362.0000 -363.0000 -364.0000

I then proceed to use Ackermann's formula for pole placement using the new poles:

% design observer by placing poles of A-LC at des_poles
L=acker(A',C',poles_des)'
eig_obs = eig(A-L*C)

L =

   1.0e+09 *

    8.6121
    0.1037
    0.0005
    0.0000

eig_obs =

 -361.0000
 -362.0000
 -363.0000
 -364.0000

And finally plot. For the observer (software) to give us all the states as output we need to set C = eye(4):

C = eye(4);
mysys=ss(A-L*C,[B L],C,0); %Not sure if this is correct
tf(mysys)
step(mysys)

Four outputs can be seen:

Following this model for a full state feedback observer:

I am then trying to verify the results on Simulink and am having issue with the block diagram. As can be  seen I have two state space models, one for the real plant and one for the observer.

In the below diagram I am comparing state 1, which results in the second graph depicted below.

I am using the base workspace generated by the code above:

Upon running I get an output from the observer which does not track or follow the plant as expected:

Actual and Observer states when comparing state 4 through summing block:

Actual and Observer states when comparing state 1 through summing block:

Any suggestions on why the state I choose to compare via the summing block is effecting the observer estimations would be appreciated.

Observer Parameters:

Plant Parameters:

Why does the state which I am comparing, effect the observer response?


texts: What can I waterproof a car remote central locking fob circuit board with?

texts:
Apologies if this isn't on topic; let me know and I'll remove it.

Having keyless fobs is quite wonderful, but it does seem easier to accidentally put the key through the laundry cycle because it never comes out of my pocket and I thus forget it's there

Having fully washed and dried the current car's fob for this, third, time (the previous two times I've had a moment's realization and stopped the cycle before too much water got into the fob) I cracked it open to find a few of the solder joints looking a bit furry and corroded, battery was ruined (never seen rust around the edge of the -ve of a CR2032 before), but scrubbing with distilled water, rinsing and blowing off with the air compressor and replacing the battery seems to have produced a working fob.

I'm not sure how many time I'm likely to be able to repeat the stunt so I'm looking for a way to protect the board from the laundry. The rubber seal on the housing itself is intact, but seems poorly designed (ford fob) compared to my previous (volvo) fob that went through the wash many times and was always bone dry inside

I'm hence looking to find out of the board itself can be coated with something protective. I'm not too bothered if this coating cannot protect the mechanical switches as they can be replaced if they get ruined - I'm more thinking the antenna coil, ICs etc. I'd also have to scratch it off for the battery terminals, so i guess I'm looking for something that adheres to the board, and cannot be cleaned off by up to 60 degree water but I also need the coating to be thin because there isn't a lot of space inside the fob. I read some sugggestions here but epoxy/urethane don't seem thin enough, "acrylic conformal coating" is a bit vague and I've a doubt marine grease would survive the wash temperatures without causing issues for clothing

I'm not averse to dipping the entire fob external housing in plastidip, but the result would be a bit ugly; I'm keen to know if a PCB based solve would be more workable


texts: *Very* high precision, *very* stable current source

texts:
My background: experimental physics. Not an electrical engineer, but I have some experience putting together basic electronic circuits for physics experiments. So please be kind and explain as if I'm a noob. Thank you!

What I'm trying to do: A very accurate (<10 ppm accuracy, 5ppm ideal) measurement of charge passing through a load over a period of time of hundreds of hours. The currents are typically between 50 mA and 500 mA.

Typically, this is done using an off-the-shelf programmable high precision <10 ppm precision current source to drive the load, and measuring the current separately on the low-side using a calibrated precision resistor and a high accuracy multimeter. The measurements from the multimeter are then integrated to estimate coulombs. The calibrated resistor and multimeter are temperature stabilized in an incubator to minimize thermal drift.

Now my problem is that these precision current sources are expensive and I need to build several of these setups for relatively cheap.

So I need to build a <10ppm precision, 50-500 mA current source & sink that will be stable and low-noise for hundreds of hours. Set-point accuracy is not very important, since I will be measuring the current separately anyway. But the current does need to be very stable and precise, so that I don't have to take too many samples to get high accuracy on the integrated coulombs. (Remember that the measurement will go on over hundreds of hours, so it is practical to take a sample once every ten or twenty seconds at most, otherwise there will be too much data to process). The current source does not need to be programmable, as long as I can change a scaling resistor or two to change the set point for the particular experiment. (scaling resistor and the source in general can be temperature stabilized in an incubator)

Now all the technical notes and forums I read are for 0.01% (100 ppm) or .005% (50 ppm) precision at most. I need something that is much better than that, and I haven't found strategies for doing that online. Any ideas on how this can be done?

Thanks in advance for your help!


texts: Switch from one battery to another when one is discharged/disconnected?

texts:
I'm trying to figure out how to switch source power from one battery to another when one is dead or disconnected. the circuit needs to be able detect the loss of power on the jettisoned battery and switch to main battery. and have a fast switching time or a capacitor for powering the device during the switch.

What its for: I want to be able to carry external batteries on my RC plane and use these batteries first. When they are discharged I want to drop them (when it is safe and yes it is legal to drop things from RC craft when proper safety is ensured. i plan on dropping them near me with small parachutes so they can be recovered and reused) the  switch need to be fast so not to reset the flight controller or Electronic Speed Controller (ESC) and so not to lose GPS signal.

lowest voltage at the battery(droppable) would be 12.2V and the ESC and flight controller can opperate down to 7v
The system with the motor at 0% throttle draws about 700mA(being generous OSD shows 600mA)

update:  In response ton the answer by @DonJoe.  Would the circuit look something like this?


texts: Why put a resistor in series with signal line?

texts: A lot of times in circuits I see a resistor placed in series in a signal line and sometimes even in series with an MCU's VDD line. Is the intention of this to smooth out noise in the line? How is this different from using a small cap, like a .1µF to do the same thing?


texts: Can somebody explain what IQ (quadrature) means in terms of SDR?

texts:
This is a bit of a basic question, but I am having trouble understanding why a signal needs to be broken up into I and Q components to be useful for software-defined radio (SDR).

I understand that the I and Q components are the same signal, just 90 degrees out of phase, but I don't understand why this is important.  Why can't you just digitise one signal?  Why do you need an apparently identical signal that's out of phase by 90 degrees?  And if you do need this second signal, why can't you create it yourself (e.g. in software) by just delaying the first signal?

All I can make out is that it's needed for some reason to do FM-style demodulation in software, but I can't find anything anywhere to explain what the need is, and why this demodulation is not possible without both I and Q components.

Is anyone able to shed some light on this?  Wikipedia isn't particularly helpful, with each page having a link in lieu of an explanation, and each link pointing to the next in an endless loop.


texts: Feedback resistance condition (Rf > 29R) in Phase-shift oscillators

texts:
In an equal resistance , equal capacitance CR   phase-shift oscillator, the feedback resistor has to be slightly larger than 29*R

When     I  am    attempting to simulate the circuit at 29*R, there's an oscillating transient response but it is not unstable, hence the circuit will reach a steady-state, however once I increase the feedback resistance slightly above 29R, the response is unstable and the phase-shift oscillator is functioning properly. why is that? shouldnt a feedback resistance of 29R be theoretically sufficient for an unstable response?


texts: CRC polynomial and Parity Error detection

texts:
My question is about the CRC generator polynomial.

If I have a generator of level 5, say:

$$X^5+X^4+X^2+1$$

How can I know if it can or cannot detect a parity error?

Also how can I know the error patterns that can pass without being detected?


texts: .step and .list param function for real components in LTSpice

texts:
I know that LTSpice can compute simulation in .step and .list param functions. However, those lists are ideal (not real).
Is there a means to use the .step and .list param function for real components (components in the library)?.


texts:
I was reading about capacitor based DACs for a SAR ADC in an Analog Devices pdf(https://www.analog.com/media/en/training-seminars/tutorials/MT-021.pdf) and I saw this

About the highlighted part, I understand charge redistribution takes place, but how do we know that it will be exactly Vref/2 added on?


texts: D-Flip-Flop Hold and Setup Timing Requirements

texts:
Update: The answer is 28ns for sure
Giving the following circuit and timing table:

Question: It's known that the time between positive-edge and negative-edge of the clock (which comes after) is required to be 13ns or bigger. and that the input X gets updated when the clock reaches negative-edge. what's the minimal value of clock cycle time so that the circuit works with no problems?
Note: Clock cycle isn't symmetric (For example it could be 80% up and 20% down).
Final Answer: 28ns

I tried to solve this one using a similar technique to what Mitu Raj suggested here: D-Flip-Flop Hold and Setup Timing
In order to make sure that the circuit works with no problems I need to make sure that Both Hold and Setup requirements are met, So I made the following check:
T_hold:
T_cd(FF1)+T_cd(OR) >= T_hold(FF2)
T_cd(FF1)+2 >= 2? Always True
T_setup:
T_in+T_pd(OR)+T_setup(FF2) <= T_clc (T_in=time where clock is up)
T_up+5+7 <= T_up+T_down
12 <= T_down
So we have one requirement 12 <= T_down which is already given (We know that 13 <= T_down)
Where did I make a mistake, and how to solve this one?


texts: Can someone review my first Arduino schematic please?

texts:
Can someone review my first Arduino schematic please ? Basically it is Atmega328 + RFM-12B + RGB LEDs. It works fine on breadboard.
I was mainly inspired by JeeNode and Arduino.

Original schematic is here

My main concerns are :

Power

board will be powered by 3.7V Li-Po battery without any power regulator because all used components can work with input voltage 3-3.7V supplied by the battery. Is some easy way how can I implement some charging circuit which can charge the battery ? Sometime is not possible disconnect battery for charging.

Transistors

I want use BC850, each for powering single channel on LEDs. Transistor is powered through 1k resistor, which should be fine.

Capacitors

I don’t know if I really need decoupling capacitors, but Arduino use it as well and according to this it can be quite useful.
For smoothing input I want to use this capacitor.

LEDs

only red channel needs a resistor, blue and green has forward voltage high enough to be powered directly.

RFM-12B

radio is connected to same pins as ISP header used for bootstrap, I’m slightly worried if it can cause some interference, but JeeNode has it same.

Atmega328

On schema is Atmega168 only because I can’t find 328 in Eagle :) It will use its internal 8Mhz oscillator because external oscillator is another thing is another thing which can go wrong, I don’t need extra performance and power consumption.

edit: earlier related thread


texts: How to configure an AVR32 as a USB CDC Device?

texts:
I am trying to configure an AVR32(UC3B0512) microcontroller so that it can appear as a Virtual COM Port to the PC. I followed the instructions in this application note, but could not get it working. I get the error : Unknown USB Device (Device Descriptor Request Failed), when I connect it to the PC.

Source Code :

main.c

#include <asf.h>

int main (void)
{
    sysclk_init();
    irq_initialize_vectors();
    cpu_irq_enable();
    board_init();

    udc_start();

    delay_init(sysclk_get_cpu_hz());

    AVR32_GPIO.port[1].gpers = 0b111;
    AVR32_GPIO.port[1].oders = 0b111;

    while (1)
    {
        AVR32_GPIO.port[1].ovr = 0b111;
        delay_ms(250);

        AVR32_GPIO.port[1].ovr = 0b000;
        delay_ms(250);
    }

    return 0;
}

conf_usb.h

#ifndef _CONF_USB_H_
#define _CONF_USB_H_

#include "compiler.h"

#define  USB_DEVICE_VENDOR_ID             USB_VID_ATMEL
#define  USB_DEVICE_PRODUCT_ID            USB_PID_ATMEL_ASF_CDC
#define  USB_DEVICE_MAJOR_VERSION         1
#define  USB_DEVICE_MINOR_VERSION         0
#define  USB_DEVICE_POWER                 100 // Consumption on Vbus line (mA)
#define  USB_DEVICE_ATTR                  (USB_CONFIG_ATTR_BUS_POWERED)

#define  USB_DEVICE_MANUFACTURE_NAME      "ATMEL"
#define  USB_DEVICE_PRODUCT_NAME          "UC3B0512"
#define  USB_DEVICE_SERIAL_NAME           "12...EF"

#define USB_DEVICE_LOW_SPEED

//! Number of communication port used (1 to 3)
#define  UDI_CDC_PORT_NB 1

//! Interface callback definition
#define  UDI_CDC_ENABLE_EXT(port)          true
#define  UDI_CDC_DISABLE_EXT(port)
#define  UDI_CDC_RX_NOTIFY(port)
#define  UDI_CDC_TX_EMPTY_NOTIFY(port)
#define  UDI_CDC_SET_CODING_EXT(port,cfg)
#define  UDI_CDC_SET_DTR_EXT(port,set)
#define  UDI_CDC_SET_RTS_EXT(port,set)

//! Define it when the transfer CDC Device to Host is a low rate (<512000 bauds)
//! to reduce CDC buffers size
#define  UDI_CDC_LOW_RATE

//! Default configuration of communication port
#define  UDI_CDC_DEFAULT_RATE             115200
#define  UDI_CDC_DEFAULT_STOPBITS         CDC_STOP_BITS_1
#define  UDI_CDC_DEFAULT_PARITY           CDC_PAR_NONE
#define  UDI_CDC_DEFAULT_DATABITS         8

//! The includes of classes and other headers must be done at the end of this file to avoid compile error
#include "udi_cdc_conf.h"

#endif // _CONF_USB_H_

conf_clock.h

#ifndef CONF_CLOCK_H_INCLUDED
#define CONF_CLOCK_H_INCLUDED

#define CONFIG_SYSCLK_SOURCE        SYSCLK_SRC_OSC0

/* Fbus = Fsys / (2 ^ BUS_div) */
#define CONFIG_SYSCLK_CPU_DIV         0
#define CONFIG_SYSCLK_PBA_DIV         0
#define CONFIG_SYSCLK_PBB_DIV         0

#define CONFIG_USBCLK_SOURCE          USBCLK_SRC_PLL1

/* Fusb = Fsys / USB_div */
#define CONFIG_USBCLK_DIV             1 /* Fusb = Fsys/(2 ^ USB_div) */

#define   CONFIG_PLL1_SOURCE          PLL_SRC_OSC0

/* Fpll1 = (Fclk * PLL_mul) / PLL_div */
#define CONFIG_PLL1_MUL               (48000000UL / BOARD_OSC0_HZ)
#define CONFIG_PLL1_DIV               2

#endif /* CONF_CLOCK_H_INCLUDED */

conf_board.h

#ifndef CONF_BOARD_H
#define CONF_BOARD_H

#define BOARD_OSC0_HZ 12000000UL
#define BOARD_OSC0_STARTUP_US OSC_STARTUP_4096
#define BOARD_OSC0_IS_XTAL true

#endif // CONF_BOARD_H


texts: What is the reason behind different pot resistance in such instruments?

texts:
Is there any advantage of using 10k vane to 1k or vice versa?
An example of such instruments:
https://www.windspeed.co.uk/ws/index.php?option=displaypage&Itemid=59&op=page&SubMenu=


texts: Radio direction finding - dependence on source signal type

texts:
I want to make a robot that can track the direction of the transmitter that is controlling it, for example to aim a camera at the transmitter. The robot vehicle will be controlled by a 2.4ghz NRF24L01+ link from within about 40 meters away.

I found this page which uses antenna switching to accomplish something quite similar: http://www.robowarner.com/robot/rdfbotarduino
However, as he points out "This project requires a transmitter that outputs a clean, unmodulated waveform."

Thankfully, I can mostly grasp the concept of how that particular example works, but what I don't understand is how this same type of RDF was used in wartime to locate signal sources that not only were not outputting clean waveforms, they were doing their best to remain hidden.

So there must be another variant on this method that does not rely on the source signal being of a certain type, right? It would be great if I could just do antenna switching with my receiving NRF24L01+ and do the same kind of phase comparison, but I guess that ain't gonna work (would it also screw up the communication?).

Any ideas about a good way to proceed? I suppose I could transmit a second, clean waveform, from the transmitter as well, but it would be nice if there was some way to avoid doing that.

(Bonus marks if you can tell me why that guy is switching the antennas four times before taking a reading... is once not enough?)


texts:
I am looking for a temperature sensor which is in for of DIP suitable for breadboards and serial communication that is usable for Arduino.

I am not after a resistive or an analogue sensor.
I am not after anything that contains a PCB board in it either. I am after pure chip. Because, in future, I may decide putting it on a PCB neatly.

I tried a lot searching and found no result. How can I send serial data from a DIP chip to Arduino?

PS. This question should not be on hold. To remove excuse, I changed the wording.


texts: Writing bootloader for STM32 by C language in Keil

texts:
I want to write a bootloader for my MCU. It's an STM32F103RET6. I searched for information about writing a bootloader for it, but I couldn't find anything. Now I have these questions:

Where can I find any information (website, book etc.) about writing a bootloader?
Can I write a bootloader for my MCU just using C language and the Keil compiler?


texts:
I'm building a light organ for a school project.

I've got a crossover to separate the frequencies, now I need to make an LED grid.

The input will be an constantly changing analog signal (whose voltage ranges I don't actually know yet, but I can adjust that as needed later).

First, I need to rectify the signal (as I understand LEDs tend to burn out when a negative voltage is applied across them?), then I'd like to light up a different number of LEDs based on the value of the rectified signal.

If it's low voltage (but higher than zero), then I'll want 4 (or maybe 6 or 8 or whatever) of some color LED to light up (say blue).
At a slightly higher voltage, I'll want the 4 blue LEDs to light up, but also 4 more LEDs (say green) to light as well.
At a slightly higher voltage, I'll have the 4 blues and 4 greens plus 4 yellows light up.

I'd like to have at least 4 different stages (each stage being 4 more LEDs light up), and this needs to be voltage regulated (I don't want to blow the blues, when I have a high enough voltage to turn on the yellows).

The input voltages will be changing pretty fast, so ideally this needs to be pretty responsive.

NOTE: Because this is a school project, I need to be able to build as much of this as possible with just basic components (R's, L's, C's, transistors, op-amps, diodes, etc) as opposed to just buying ICs which do everything for me.

I figure I can rectify it with 4 diodes made into a diamond (I forget what that's called) at the front, and I think I should be able to use switches with varying resistors to turn on each new set of LEDs (will that work?), but how do I regulate the voltage so that I don't blow the first stage (blue) LEDs when I turn on later stage (yellow) LEDs?