texts: How to match two impedances which both have an imaginary component?

texts:
I am designing a matching network for an inverted F antenna, the source RF pin impedance is 30 Ω + j10 Ω (source IC is an ESP32-D0WDQ6, datasheet here, RF pin impedance in section 2.5 on page 7). I will be designing the antenna using the openEMS simulator software. The datasheet calls for a pi-network close to the IC and a 50 ohm transmission line (datasheet in section 3.1.5 on page 16) the antenna will be as close to 50 ohms as possible, frequency is 2.4 GHz. The PCB layout is very similar to what is shown in the image below, I have the output capacitor of the pi-filter connected directly to the antenna input with no transmission line, and the transmission line coming from the IC is only 1 mm in length.

I asked a similar previous question to which someone offered a solution on how to match the source impedance to 50 ohms using this method:

If your antenna is 50 Ω and your source is 30 Ω + j10 Ω then, add a
series capacitor of -j10 Ω to cancel out the +j10 Ω effect of the
inductor.
This now means you are trying to match 30 Ω resistive to an antenna of
50 Ω resistive.
Then use an L-pad calculator like this: -

You can double check the formula derivation on that site.
Series inductance needs to be about 1.6 nH Parallel capacitance needs
to be about 1.1 pF Then, if you went back to the start of the problem
and analysed what value of inductance is needed to produce the j10 Ω
in your driver output impedance, you'd calculate it to be 0.663 nH at
2.4 GHz.
This means that you can actually dispense with the added series
capacitor of -j10 Ω (as originally proposed) because you need 1.624 nH
from the above calculator. The upshot of this is that 1.624 nH might
as well be 1.663 nH so, the external series inductor you need to add
is 1 nH.

But an antenna is rarely ever purely 50 ohms resistive once it is on the board, and will involve some imaginary component. My question is, how will I match the source impedance to the antenna impedance if the antenna impedance also has an imaginary component, say it ends up being 55 Ω + j 15 Ω.
HERE IS MY 2 PART QUESTION:

How would I match 30 Ω + j 10 Ω to 55 Ω + j 15 Ω using a pi-filter? Or any other filter topology if another would be any advantage?

The datasheet says the pi-filter should be placed close to the IC and the output transmission line should be 50 ohms to the 50 ohm antenna, but I essentially do not have a transmission line, only the 1 mm trace leading to the pi-filter. Since the source is not 50 ohms, would there be a more ideal impedance to set the transmission line at which leads to the pi-filter from the IC? Such as 30 or 40 ohms?

Here is an image of the layout they use on the ESP32 module:


texts: Determine voltage of PWM signal with only a multimeter

texts:
For my new project, I'm trying to convert an old LED computer monitor (the Dell SE2717H) into a cool lamp by stripping everything but the LED panel.
The LED panel is currently driven by a big power circuit board which I would like to replace by a simple power supply. My problem is, I can't seem to figure out the voltage at which the LED are powered. When I put my multimeter on one of the 6 wires going to the LED panel, it reads 0.5v. I'm assuming this is because the LEDs are driven using PWM.
My question is, therefore, is there any way to figure out the nominal voltage of these LEDs using only a multimeter ?
Cheers!
The picture of the board. The wires going to the panel are 6 pins at the very top of the board


texts: Comparison between AC and DC power flow analyses

texts:
Consider a power flow problem. Injected real and reactive power at a bus are functions of voltage magnitudes and voltage angles and are given by
\begin{align*}
P_i = \sum_{k=1}^N|V_i||V_k|(G_{ik}\cos(\theta_{i}-\theta_k) + B_{ik}\sin(\theta_i-\theta_k)\\
Q_i = \sum_{k=1}^N|V_i||V_k|(G_{ik}\sin(\theta_{i}-\theta_k) - B_{ik}\cos(\theta_i-\theta_k)
\end{align*}
The above are termed the AC power flow equations. To simplify analysis, one often considers only real power via the DC approximation which allows one to write the vector of power injections as a linear function of the vector of voltage angles (all voltage magnitudes are set to 1 p.u.)
\begin{align*}
{\bf P}_{DC} = {\bf B}\theta_{DC}
\end{align*}
where the above is termed the DC power flow equation.

Say for a given system we solve for both the voltage magnitudes and angles of the AC power flow equations (via Newton Raphson) as well as the voltage angles of the DC power flow equations (by matrix inversion).

Now my question is as follows: what are the resulting injections in each case? For the AC solution, it's clear, just substitute the AC voltage magnitudes and angles back into the equations to get the resulting injections. I'm a little confused as to what the DC injections are though; the actual power injected at a bus is given by the AC power flow equations, so should I take my DC angles and the unity voltage magnitudes and substitute them into the AC power flow equations for real power to determine the resulting real power injections under the DC approximation?

If this is the case, then one can also substitute the DC voltage angles and unity voltages into the expression for reactive power and obtain an answer; this is the source of my confusion, I thought the DC approximation did not consider reactive power? Is this substitution meaningless?


texts: self-heating effect of dual PT100 temperature probe in a moving mass of water

texts:
I'm trying to know how much self-heating should I expect in these conditions:

Temperature range: 0-45 C
Using a 1050Ohm pullup resistor to feed each PT100 (2-wire configuration) with 5 volt excitation and 5 volt reference.
Temperature probe with two PT100 inside
Temperature probe will be inserted in a pipe with a moving mass of water using a thermowhell.

According with what I've read in several sites, including this texas instruments reference the self-heating coefficient should be 0.01-0.02 C/mW for a moving mass of water.

with a 5V excitation, 1050 Ohm resistor and max value of 117.47Ohm of the PT100 at 45C I get 2.1546mW so the temperature would raise the negligible amount of 0.043 mK using 0.02 C/mW coefficient. Am I right in my calculations? Also, since both PT100 are fitted in the same probe, may they affect each other in terms of heat in a significant way?

EDIT: Andy  corrected my calculation error and introduced the water SH as a variable but Spehro answered my second cuestion and provided more practical info./tips :

Increased thermal resistance from poor thermowell coupling.
Self heating coefficient being variable depending on material,construction.


texts: Preventing integrated circuits from receiving/causing EMI

texts:
I have two almost-identical circuits:

Before continuing, I want to point out that I used three sets of jumpers for making logic selections to some of the pins. I know the better approach would be to use a pull-down or pull up resistor with a key, but my question isn't focused on those inputs.

I'm sharing the same power source with other circuits and if I don't use any EMI protection, then one IC in one connected circuit could screw up all other circuits relying on the same power source.

What I want to know is:

Which of these two circuits is recommended for best protection against EMI?
and if the answer is the first one, will I need to replace the wire located at the bottom-right of the big X with another RC filter?

Also, do the resistors that form the EMI protection network (resistors connected to +ve) need to be higher than 1/4 watt? I intend to make the values low enough (in ohms) so current can flow through but I don't want too low of values or I'll feel I'll make the EMI protection circuit useless.

Additional question

The reason why I considered resistors is because then each subcircuit can draw less power from the main battery, that way, there won't be any chance of components fighting for power.

Based on the answers, it is claimed that using any resistor for R1 and R3 increases EMI. I think there are two issues with shorting out those resistors. For one, I still want some sort of noise filtering, and also, It makes PCB routing more difficult.

Perhaps I should just hit ebay and buy axial ferrite beads. But wouldn't inductors in the uH be better to filter out bad frequencies? After all, they are very low resistance as well.


texts: Li-ion battery pack from non- identical batteries

texts:
I'm building a battery pack for my portable speaker, and I'm using a random collection of second hand Li-ion cells.
I'm going to have cell phone batteries with differing capacities and also 18650 cells.
The 200W amplifier accepts between 12V and 24V, so at 24V it needs about 8.7A. I also have some low power stuff there, so 200W should be sufficient any way (yeah, I know it's overkill.)

Problem
The phone cell's discharge is close to 2A, 18650's discharge can be more than 10A.
However BMSs from china are mostly for lipo batteries and their enormous discharge rates of 10A and are too high for these cells.
So:
I'm planning to use per-cell protection of overdischarge (2A or 3A)
I could use one 18650 and one phone cell on parallel, and put those "combinations"
I know, that this will cause uneven SOC, but if each cell has its own protection, this does no harm. only shortens battery pack's "life".
Is there a way to limit discharge current of balancing BMS?
And how do I charge such a pack?
Would it be better to make, say, 3 3s packs instead of 1 9s, so I could charge it with lower voltages?
I have played with Li-ions before, but there are too many question marks for me at this moment, so I had to ask :D
Thanks in advance.
EDIT:
Okay, i hear you. I have good amount of those batteries, so i can form packs of identical batteries. so that is settled.
I plan to use overcharge and overdischarge protection per cell (2A or 3A overdischarge limit), so if the cell would be subjected to too much, the protection will kick in, and shut down the pack.
Even though it may not sound like it, i'm doing this with safety in mind, and all the packs i'm creating will be put on fireproof bags.
I may have given an image, that i know less about this subject than i actually do, sorry about that.
So to clarify, questions revised;
-do li-ion packs need a certain charger in addition to excisting BMS? (my lipo battery pack needs, as it doesn't have any electronics in it)
-can i limit the overdischarge/overcharge current of BMS?


texts:
I have designed a simple battery voltage monitoring circuit to monitor a 3.7V Li-Po battery. My microcontroller (ESP32) uses a 3.3V supply.

simulate this circuit – Schematic created using CircuitLab

The MOSFET M1 is an attempt to save power when I'm not measuring the battery level.

Is this circuit suitable to measure voltage across the ADC pin of my MCU? Please review the circuit and provide me with inputs if I'm doing something wrong, or if it could improved in any way.

Thanks.


texts: Alitum issues: Placed via/pads on PCB which is not in the schematic

texts:
I have a big problem with Altium. To immune my board I want to place special VIA/Pads with hole on all the board (at the corner). I know this is possible with the tools "via stitching", but the tools doesn't work on my design (Altium PCB design: Vias stitching problem).

The idea is to place special EMC via on the board, but every time I update my PCB, all of my VIA are delete. Is there a possibility to tick an option for this component ? (I tried to change the type in "net tie " or "mechanical" but that doesn't work)

I don't want to place 50 specials via or emc schematic...

EDIT: A screen to show what I need to do: Three vias in triangle that will deacrese the impedance connection with the ground. On the screen I placed every signle VIA but it is very long and impossible to align with others..

Thanks for reading


texts:
Im trying to understand how pull up/down circuits works . Let's consider this schematic :

I understand that there are two possible current flows :

When the button is not pressed, the current flows from VCC through the input pin .
When the button is pressed , the current flows from Vcc through the button , to the GND .

I cant understand the second flow . Why the the current goes directlly through the button ? After the R1 resistor there is a "crossroad" . So , why the current flow is not divided to both paths (left to the button , and right to the input) ? How it knows to flow only to the left path i.e.  to the button, and not right to the input ?

Thanks


texts: Would a device with different power rails become one if both rails are shorted to ground

texts:
I'm trying to repair a nintendo switch that seems to have multiply shorts to ground.
The shorts to ground are on the 3v3 rail and on the 1v8 rail.

I seem to be getting continuity between the two different rails so if i was to inject power into one rail would the other rail become powered aswell.

What I'm asking is would the separate rails become joined if both are shorted?


texts: Boost operation in inverting Buck-Boost converter

texts: Regarding the inverting BUCK-BOOST shown in figure, I understand how it works as Buck. Please explain how it can act as a BOOST. Because during the off time there is no connection with input supply so i think it cant act as boost. Then why its name as "BUCK-BOOST"


texts:
This is what I have, but I not sure if it's right.  Can someone please help me.  Thanks in advance

Q A B | Q(t+1)

0 0 0 | 1

0 0 1 | 0

0 1 0 | 0

0 1 1 | 1

1 0 0 | 0

1 0 1 | 1

1 1 0 | 1

1 1 1 | 0


texts: High voltage, low current, power supply for night vision gen. 1+ tube - single AA cell or 3V

texts:
I would like to build a new power supply for a gen. 1+ night vision intensifier tube, the current supply is robust but big and heavy plus the input is 9 to 24V.
The tube it self requires approximately 16-18kV and 20 microamperes.
I came across a circuit for such a project but unfortunately it is only for 9V battery, 13,5kV output, plus I cant find out what king of transformer is used. Attached the circuit:

Would be nice if someone could help me with a circuit build commonly available parts, thanks.


texts: Program multiple arduinos simultaneously

texts: I have a 10 port USB extender hub and connected to it are 10 arduinos. Is there a way by which I can send the same program to all of them at one go and not program them one by one?


texts: For an operational amplifier, is the path from input to operational amplifier to output considered a feed forward path?

texts:
I actually don't have much knowledge about control systems or anything so based on what I have searched, people use both the terminologies feedforward path and forward path for the path which starts at the input, goes to the operational amplifier and ends at the output. This is to contrast it with the feedback path when a resistor is connected between the input and output terminals.
I just wonder if the term feedforward is appropriate because based on what I have read, the feedforward and feedback concepts are suppose to be like interventions to a certain process. The operational amplifier performs the process that we are talking about and it does go in the forward direction or input to output.
I am aware that feedforward is a term that is almost never used. I just want to get a better idea on what it is so I have something to compare with the concept of feedback.


texts: Strange stepper motor behavior- moves too far

texts:
I have 3 CD drive stepper motors on a 9V 2A power supply, and they are being driven with EasyDrivers. I am using an Arduino with grbl to control the drivers. The current for the motors is at the lowest point possible (because the voltage at TP1 on the EasyDriver is at the lowest point possible), but the motors are still very hot (painful to touch) for some reason.

I have been testing out the motors with commands like X10 Y10 with an acceleration of 10 mm/s^2 to get the motors to move. However, the motors will still be very hot. Is this part of the problem?

But the strangest part is the the motors will move for way more distance than they should- they will just "roll" as if they are not torqued at all after they move the assigned 10 mm. But when they are stopped, there is definitely torque on the motor.

How do I fix this behavior? I can't change the voltage, so should I change the acceleration, or the current supplied to the motors, or something else?


texts:
I am trying to make a copper pipe which is placed in a natural park capacitive. It is placed in the soil meaning that it is already grounded. I am using a basic arduino and their capacitive sensing library to quickly experiment with, but the issue I am having is that the arduino itself needs to be grounded in order to have a decent value output. But grounding the arduino to the copper pipe (or anywhere) doesn't work. Because than the ground and the capacitive sensor are directly connected.

tl;dr: How can I make a grounded object capacitive?


texts: Are there any Wifi/Networked Lights available to purchase?

texts:
Summary
I'm trying to find a light that can be connected straight into a network via WIFI or LAN Cable (cat5, etc..).
Details
We have a server which handles automated builds and deployment for our website development. If the automated build (aka our continuous integration) failed, we would like to be told.
So - traditionally, people have been using lights or monitors to visually display the status of their builds.
green - last build worked 100% fine.
yellow - in progress
red - last build failed.
So, I was hoping to find a light (bulb/lava lamp/whatever) that can be connected to the network and I can hack up a program to then tell that light to display as red/yellow/green, depending on the state of the build.
So - are there any lights that can be connected to a network, preferably via WIFI but via cable is fine. I'm assuming they will also need a power plug to get power .. unless maybe the lan cable can supply power, if the light doesn't require too much?


texts: Suitable low-power ~10" graphical display options

texts:
I am looking for suitable display options for a battery-powered device, kind of like an e-book reader/tablet/mid device.

size - 10" or so.
resolution - preferably a high DPI
colour - mono/gray
static - low refresh rate/static is
fine
power - low enough to last 12 hours
on a ~1000 mAH battery assuming 80%
static usage.
Brightness - readable in-doors, mainly.

I know of the existence of E-ink, Pixel-Qi and even ChLCD displays. I am wondering if there are any other display options available?


texts: Why should I use 2 resistor to drop a voltage?

texts:
I have a voltage of 12v and I would like to get it down to around 8v. I know how voltage divider works and I already used it lots of times. But I ask you this: why cant I use only one resistor to drop the voltage in series with my circuit?

For example, suppose I have a motor with resistance 10ohm and I want to drop the voltage to 8v, why can I do this below?

(12V) -> RESISTOR -> MOTOR -> GND

I could easily calculate the voltage drop around the resistor so the remaining would be with the motor. Right?


texts: Altium Designer - Net has only one pin | Pin out of grid | Floating Label | Diferential Pair

texts:
I would like to ask a few questions about designing PCB boards on Altium Designer.
I am currently designing a STM32 board, but having a few issues with the schematic design.
Upon reading some post about the following errors:

Net has only one pin, and
Pin out of grid

I understood that 1 occurs when the NetLabel in schematics is not used anywhere else therefore the connection does not exists and there is an error.
There is an instance in this project which I don't understand: Pin 9 & 10 PA 11, 12 on J1 aren't used anywhere in both sheets but PA 11 & 12 on the IC is actually used for D_P and D_N for the USB. Does anyone has an idea as to why it would be used in this way?
And for 2 it happens when the pins of components don't align with the grid. Some posts suggested to redraw all components to make it fit the grid. I solved quite a few of the instances by just repositioning the components using the metric grid.
Am I correct?
Now for the floating label is it that the label is not attached to any wires?
Also I tried creating a Differential Pair for a USB Connector on the board, but not success when trying to use the rule wizard for the differential pairs editor as it is not stated in the list.
I have attached a picture for rules settings of the created pair.
All the pictures are attached in this post.


texts: Wake up circuit - keep the circuit off when not in use

texts:
Goal: As the power supply is a battery, I want to shut down the circuit when it is not in use.

Circuit description: Basic 555 timer circuit. By pressing the switch, the light turns on.

What I have done:

With a diode, I have tried to put the ground directly to the switch. To connect the circuit to the ground when the switch is pressed. After that, I've have planned to connect a transistor to the 555 output to maintain the ground connection during the session. But it doesn't work as the the led is on when the ground is not connected.
As it's working manually, I tried to do the same but with the 5 volts. With a 2NO in one switch but I failed (I couldn't find a good switch): I want to keep only one switch and as small as I can.

There is my current switch.

What is the best way to make a wake up circuit without using all my battery? I'm a hobbyist, can someone help me?


texts: Find the capacitance of this rectangular slab of two films of metal virtually 0 thickness and 2 sheets of plastic. Then it is rolled into a cylinder

texts:
this question may be pretty simple for some people on this forum.
Here's a basic image to go with the question.

 (also here)

Two films of metal, virtually 0 thickness and 2 sheets of plastic. Find the capacitance.
The assembly is then rolled into a cylinder, estimate its radius.
Why does the capacitance approximatly double?

Ok, first of all this is whats i've got so far.
I've just used the Er of plastic as 2.

C=(A*E0*Er)/h so (1*0.02*(8.85*10-12)*2)/10-4 =  3.54*10-9F

But would you multiply that by 2 since there are two plastic sheets and two metal parts?
Or would you add them in capacitance of them both in series?
Also if the metal sheets were thicker and had a realative permitivity how would you find the capacitance in this assembly? Could you multiply the Er of the metal with the Er of the plastic and E0. But what about the new thickness? Essentially this just two dielectrics correct?

now for 2. this where I'm even more confused. the volume of a cylinder \$ \pi r^2 d\$ we could get d. oh, i'm not sure to be honest.

Any help would be greatly appreciated.

Edit. Hang on, there is just one dielectric, the plastic and the metal is just used as a conductor between them. Sorry. Would be interesting to know how to calculate two dielectrics in the capacitor though. I'm thinking you would just need to know whether they were in series or parallel.


texts: How much 12V DC current can I safely draw from an AC 230V 13A socket and why?

texts:
In my cabin I have a sollar cell and a 12V battery that I use to power my electronics. However I'm dissatisfied with the standard CL sockets used in cars (apparently I'm not the only one) and I decided to reuse a foreign AC socket instead, specifically the United Kingdom's “13 amp socket” (BS 1363).

I chose the UK socket because it's well designed and it's very rare that anyone has UK plugs in my country. I will take actions to ensure no-one will thoughtlessly plug an UK electronic device to these sockets!

The socket is designed for 230 V and up to 13 A of alternating current. That means it can supply up to ~3 kW of power. However with the 12 V I'll be using, thirteen amps can barely reach 150 W. Since some popular water pumps need ~700 W, this seems like a serious limitation.

In a different question here on Electrical Engineering SE, someone asked whether they can use a 10A@250V-rated socket to draw 13A@230v and the most popular answer says that “the only important parameter is the current rating, [...] 10 amps through the socket will heat it up just as much at 1 volt as it will at 5,000 volts.” Sadly, they don't provide an explanation why. Does this apply to my case and why / why not?

Another thing that concerns me is I'll be using DC instead of AC. There are several things that work differently with direct and alternating current. Is it safe to use the socket this way?

EDIT: There is a question about the current rating of fuses where they explain why fuses blow at a certain current, not power. However I failed to understand the reasoning in the answers, so I can't tell whether it also extends to my case, or not.


texts: How to show that voltages on diagram are 120° apart?

texts:
So i'm doing a matlab simulation of delta wye transformer and would need to show the phase shift between voltages. Here is a picture of input voltages so how would I show on this graph mathematically or graphically that these voltages are 120 degrees apart?

I tought of doing it like on this picture, to find degrees or radians and compare them, but on the graph from simulink above numbers are small so I don't know how.


texts: How set the baud rate for serial communication in ATmega32u4

texts:
I have a teensy 2.0 board and am trying to use it to control this LCD through serial TTL.

I got it to work fine with my Arduino uno and some sample Arduino code, but I want to do it with the teensy and the C language.

The teensy uses the ATmega32u4 and here is the datasheet for that chip.

In the datasheet, starting on page 186, is the section on USART.  On page 192 is some sample C language code on how to initialize the USART.  I am confused on a couple of lines and could use some help.

void USART_Init( unsigned int baud )
{
  /* Set baud rate */
  UBRRHn = (unsigned char)(baud>>8);
  UBRRLn = (unsigned char)baud;

  /*rest of code here*/
}

First, I am not clear on what the baud rate number should be.  My LCD is calling for 9600 baud with 1 start bit, 1 stop bit, no parity bit, and 8 bits of data.  On page 189 of the ATmega32u4's datasheet I did the calculation on what the baud rate should be which in the case of the teensy and LCD combination should be 103 because the chip frequency is 16mhz and the baud rate is 9600.  This also matches the number in the chart on page 213 of the ATmega32u4's datasheet.  So, is this the correct number that would be passed into the USART_Init function for the variable baud?

I am also confused on the two lines that set the baud rate.  I understand that, as per page 209 of the ATmega32u4's datasheet the baud rate registers are broken into a low and high register but only bits 8:10 on the high register are used making it a combined 12-bit register.  So, going back to the code, I don't understand some things:

Why is it being typecast to an unsigned char because I am assuming that UBRRHn should be in binary notation.
I also do not understand the (baud>>8) part because if you fill in 103 for baud then you get (103>>8) and that ain't right.  Can someone explain this line for me?  Thanks.

UBRRHn = (unsigned char)(baud>>8);<br/>
UBRRLn = (unsigned char)baud;

Should baud be the 12 bit binary version of 103 which is 00001100111?  If so, then how would the code be written?

Also, I found some sample code(http://www.pjrc.com/teensy/uart.html) on the teensy website that sets up the UART and it sets up the baud rate like this:

void uart_init(uint32_t baud)
{
    cli();
    UBRR1 = (F_CPU / 4 / baud - 1) / 2;

    /*rest of code here*/
}

If I plug in the numbers it would look like this:

UBRR1 = (16000000 / 4 / 9600 - 1) / 2; /* Which would equal 208 */

The number 208 is different than 103 so I don't understand where they are getting the equation to calculate it.
UBRRn is only mentioned in ATmega32u4's datasheet on pages 188 and 189.  It looks like that holds the value of both UBRRHn and UBRRLn.  The above code seems to be trying to set both at the same time but as an int.  I am so confused, doesn't that need to be in binary notation?

Well, I am looking forward to getting over this hump and moving on to making my LCD dance.  :)


texts: How to increase an output of opamp in this noise generator?

texts: I'm working on a noise generator for my analog synthesizer and have problems with current design I built. As a noise source I use NPN-transistor in avalanche mode with only base and emitter connected. I tried different but stopped on BC548, which give 10mV peak to peak in current configuration. All signals in synth are normalized to [-2.5,2.5]V range, so I need to multiply this signal with a factor of 500. I tried to use a multistage transistor amplifier, built one stage with amp of 50 and dropped this idea. Now I sketched and build this circuit on a breadboard, with 1/2 of TL072 (don't have other on hand) but measuring it with my scope gives same amplitude on output as on input, only reduced in bandwidth. I tried to use a pot as R3, and rotating it left and right don't affect an output. Can you help me to trace a problem or advice better design for this circuit?


texts: I am trying to design a step-down power supply. I was searching and browsing from Texas Instruments products and found one that might be the best for my use. I want to step down from 24V to 5V, output current of 1A. I looked into the datasheet and found an example schematic. I know how to select the components around the IC, but I don't know what is Vdd applied do PGOOD pin and what voltage it should be. Thanks for help.


texts: I need a toroidal inductor for my ZVS flyback driver. The value should be between 47uH to 200uH. It should be able to handle 6A. Where can I salvage them from?


texts:
I'm putting together a high current (200A+), low voltage (<5v) rectifier circuit.

I have sufficient bridge rectifiers, but to smooth out the waveform I need a strong enough capacitor bank. Besides opting for capacitors rated at a voltage of 10vdc (double the 5v just to be safe), what other stats or capacitor specs should I be looking for? Just get three one with the highest max operating temperature? The AC wave will be 50hz.


texts: Can someone explain how frequency and inductance affects this pair of coupled inductors?

texts:
I am simulating this simple circuit on PSIM; a single-phase AC voltage source connected to the primary of a pair of coupled inductors, with a 12 Ohms load on the secondary side. I want to increase the voltage across the load. The PSIM manual mentioned the following formula for the voltage across these two coupled inductors:

$$V_{1}= L_{11}\tfrac{d_{i1}}{dt} + L_{12}\tfrac{d_{i2}}{dt}$$
$$V_{2}= L_{12}\tfrac{d_{i1}}{dt} + L_{22}\tfrac{d_{i2}}{dt}$$

Where
V1 is the voltage across the primary inductor (righthand side) in volts.
V2 is the voltage across the secondary inductor (lefthand side) in volts.
L11 is the self-inductance of the primary inductor in Henry.
L22 is the self-inductance of the secondary inductor in Henry.
L12 is the mutual inductance between the two inductors in Henry.

So, as per the formula, I tried increasing the frequency to increase the rate of change of current, and, consequently, increase V2. Raising the frequency from 10 Hz to 40 Hz did increase the V2, but any frequency of 41 Hz and higher resulted in a decrease in the output voltage.

I also tried increasing the self-inductance of the coils (and consequently the mutual inductance at a coupling factor of 0.9) but the V2 still decreased, regardless of the frequency range...

I don't understand why my output voltage does not match this formula...What am I doing wrong?

Edit: One of the answers suggested that the voltage drops due to the leakage inductance of the coils. However, when I want to assign the inductance parameters for two coupled coils, PSIM clearly refers to them as self-inductance, and not leakage inductance, as shown in the image below. And PSIM clearly differentiates between leakage inductance and self-inductance because if one were to use a single phase transformer (not ideal), there will be a parameter for leakage inductance as shown in the lowermost image. I assume that this coupled pair of inductors has (ideally) zero leakage reactance...


texts:
So I asked this question previously in the control theory section and got no responses. Ill try it here. Basically I need to find the ranges of k and \$\beta\$ such that the steady state error will be less than 10% for unit step input.

I'm currently at the point where I know that the steady state error is given by:

$$ 9 < \beta k$$

Now I'm using the closed loop characteristic equation:

$$2s^4 +2s^3+ (2 + \beta)s^2 + (\beta - 10 + 2k)s + 1 +\beta k = 0$$

$$
        \begin{matrix}
        s^4 & 2 & (2+\beta) & (1+\beta k) \\
        s^3 & 2 & \beta-10+2k \\
        s^2 &12-2k & 1+\beta k \\
        s^1 & \frac{(12-2k)(\beta-10+2k)-(2)(1+\beta k)}{12-2k} \\
        s^0 & 1+\beta k
        \end{matrix}
$$

So at this point I'm not sure how to find the ranges for k and \$\beta\$ and apply it to the steady state error? Can I say that:

$$ 12 - 2k > 0$$
$$ - 2k > -12$$
$$ 2k < 12$$
$$ k < 6$$

I'm just stuck as this point. Any thoughts? Thanks.


texts: Correct PWM approach for best brightness

texts:
I have a red laser that I like to make it as bright as possible. (Given eye safety regulations) Currently I am pumping Dc current but due to several concerns I like to make the driver pulse width modulated (Pwm).

I suspect (but not really sure) there must be a sweet spot where our eyes cannot identify there is a reduction in total power even though there is. For example if you Pwm the laser with 10khz with 25% duty cycle this is as good as dc to our eyes as we cannot see the on off cycle.  Again I suspect we probably perceive this as bright as the dc laser. (Not sure though like to find out).

I am basically looking for the magic numbers derived from potential research done on the subject or direct experience. I think this is probably well researched area due to power savings.


texts:
I'm making a small autonomous vehicle, it is about 300x300mm in size.
I need to get a heading for the robot.
I currently have a CMPS03 compass but am finding that it is highly sensitive to soft iron interference.
I would like to know if the LSM303 or CHR-6dm would provide a greater resistance to these environmental distortions?


texts: Electret microphone preamp is buzzing , weird noise and cannot find a solution

texts:
I'm building an electret microphone pre-amp following this application note, the output of the preamp is connected to an LM386 and then to some headphones.
So my pre-amp circuit looks like this, where VCC is 3V, all other components are the same:

and the LM386 part:

And it works, I hear the sound being amplified but, it's buzzing quite a lot.
So here there are some details about the implementation and things that I've done to try reduce/identify the noise:

The preamp stage was implemented using a different op amp, the one that I had available, an OPA313 which doesn't seem to be the reason because it's a relatively low noise op amp, and most of it's characteristics are very similar to the one used in the AN.

My first guess was the LM386 circuit, so I grounded the input to check if the noise was still there, and it wasn't, so it's quite clear that the noise is coming from the preamp stage. Which makes sense because that stage has the highest gain.

The board was initially powered using a USB (with an RC filter at the input 100 ohms + 330uF). So to remove the possible 'unfiltered' noise I powered the board with a 9V battery and a 7805 and the buzzing was still there.

The wire that connects the microphone to the pre-amp is as short as it could get, to eliminate any induced noise there, so I basically connected the C3 cap pin to the op amp pin.

Since I don't have the electret capsule datasheet I used the component values from the AN, except for R1, because the pre-amp stage is powered from a 3V regulator.

The noise it's not at 50 Hz, it's a higher frequency, around 3 KHz.

I have tried with different electret capsules but the noise is still there. Am I missing something? The capsules I found are the generic ones, anyway I don't think that the amount of noise I'm hearing is due to that. I've been struggling with this for many days now and looks like the solution is really simple but I can't see it.


texts:
The recommended way to mount a TO-220 package is to use a spring clip or bar pressing on the body of device.  But the package was designed to be mounted using a bolt through the hole in the heatsink, and the manufacturers provide mounting instructions for doing so.

The mounting instructions frequently (Phillips, Alpha&Omega, Vishay, IR, Infineon, TI, ON semi etc) contain the suggestion that a rectangular washer be used, particularly when trying to mount fullpack (insulated) packages. For example, infineon, Mounting considerations for TO220 Full PAK.

... but the recomendation is as old as the package, and the same diagram seems to have been copied down from some ancient original source.

The main purpose of the washer is to protect the package: a secondary purpose is load spreading. This is not the insulated washer used for isolation beneath a standard TO-220 package.

Does anyone still use rectangular washers on TO220 packages? Does anyone supply TO-220 rectangular washers as a standard part? Have you ever seen a rectangular washer on the tab of a TO-220? If so, when?


texts: Difference between in-band and out-band 3rd order intercept points?

texts:
I am reading the datasheet of this IC. The specification has listed in-band and out-band 3rd order intercept point (Page 11). I have read about intercept points and learned that intercept point of nth order gives the relative magnitude of gain and nth inter-modulation products. However, I am confused between in-band and out-band terms. What are they?

I can make a guess and my instinct says in-band 3rd order intercept point is related to 3rd-order inter-modulation product which is closet to input signal frequency and out-band refers to the relative magnitude of gain (first-order) and amplitude of inter-modulation products which are far away from input signal frequency.

Am I right?

If yes, then I should be concerned with in-band IIP3 only? I think I can filter out out-band frequencies components using a cheap filter. Am I correct?


texts:
I want my design to use as many common footprints as possible (eg. 0805/0603 for capacitors and resistors, powerSO8 for big switching MOSFETs, etc) so that I am less restricted by manufacturers and suppliers, and so that people in other countries etc. can build the design easier.

It appears that HC-49 is a very common footprint for crystals across a wide frequency range. I am also aware of a (less common) SMD version where it sits on a little plastic base and the leads are bent flat.

Are there any more compact SMD packages for crystals that have the broad support across many frequencies and suppliers? When I look on DigiKey it seems that all the smaller devices are in unique/manufacturer-specific packages with fairly narrow ranges of frequencies.

Am I just missing something? Is there a "go-to" package for small SMD crystals, like there is for resistors? Or perhaps a few different "go-to" packages for different frequency ranges (since lower frequency xtals probably need to be physically larger)?

(To clarify, I have no issues with reflow-only packages)


texts: Ground plane under power inductor in DC to DC converters

texts:
Is it a good idea to put ground plane (fill the area with copper) under the power inductor in DC to DC converters?

I was looking for answers about step down regulators but I would like to know about step up regulators as well.


texts: How can there be a zero sequence current in a single line to ground fault with an ungrounded neutral

texts:
The circuit that describes a single line to ground fault in a system with an ungrounded neutral is:

I neglect capacitance between phases and only look at capacitance to ground.
The definition of zero sequence current is
$$I^{(0)} = \frac{1}{3}(I_1 + I_2 + I_3)$$
But if apllied to the circuit above, Kirchoff current law should state that:$$(I_1 + I_2 + I_3) = 0$$
So how can there be a zero sequence current in this circuit? What am I missing here?


texts: Arduino/RPI module to control LED fairy lights with reverse polarity

texts:
I cant find any module to control my garland of lights by any embedded device. This module should be powered by DC12V input (but also possible to use Step Up/Step Down DC-DC voltage converter). The garland is controlled by two wires. Controller should rapidly change voltage polarity (tens times per sec) to control odd and even LEDs. It should change voltage in -35V..+35V range. Total power of the garland is less than 1A.
Does this task is too specific that needs soldering of custom board or there is a module to implement it? I suppose it is question about H-bridge module?
Thank you.


texts: How to use 3.3V and 5V outputting sensors with Arduino?

texts:
To get full resolution from Arduino ADC when using 3.3V sensors you must do two things.

Connect 3.3V power supply to AREF pin.
Call analogReference(EXTERNAL) in the code.

But what about if I must mix 3.3V and 5V outputting sensors. What are my options?


texts: How do I control a 12V relay with a 1.8V microchip?

texts:
Background
I have a 12V power supply that is connected to a switching regulator to get a 1.8V power signal. I have a microchip running at 1.8V and want to control a 12V relay via GPIO. The relay is used to open and close a lock that only functions on 12V.
Help in
1:Must-operate voltage
2:Must  release voltage
3:Coil voltage
4:Switching voltage
5:Current rating
What I have
I think I need operating voltage at 1.8V because the chip sends 1.8V GPIO signals. A release at 12V because that's the power needed for the lock. A coil at 12V with switching at 12V because of the lock. And current at 2A because the lock runs at 2A.
References for the lock

I need help figuring out the right relay to use and how to hook up the relay to the microchip and lock.


texts: How does television EHT Transformer (that connected to anode) operates in DC?

texts:
A step-up transformer takes AC input and gives AC output. Then, how does the E.H.T (Extra high-tension transformer) create 18 KiloVolt or more, DC-output on the CRT (enough to shot the electrons on screen) from the 12V rectified DC output from main power-transformer?

If I assume, the television EHT is just an  ordinary step-up transformer, then how does so-many kilovolts output are rectified to DC? with any special-type of diodes?


texts: Spectrum Analyzer Sweep Times Sub 1-ms vs. EMI Test Receivers?

texts:
I've got a Rigol DSA 832 and I have a client design that sends out a 1ms  message every 100ms.

The original protocol was a 1ms message every 6 seconds, which was darn near impossible to capture on our spectrum analyzer.

We had them change the packet structure to make some EMC measurements, but it's still like finding a needle in a haystack because the message duration is just 1 millisecond.

On my Rigol, once you change the span & resolution bandwidths it does not indicate sweep speeds lower then 1ms on the GUI.

Does anyone know if Rigol supports sweep speeds lower then 1 ms, even though the GUI doesn't indicate it?

But my main question: if you get into a formal test chamber with an EMI receiver does anyone know from-hands-on experience how quickly they can sweep say a 1MHz zone?

I feel like I would like a 100us type scan speed over a 1MHz to capture these stupid messages at this point.


texts: Basic 12v LC Filter for Video noise reduction

texts:
I'm very new to electronics and I want to build a basic LC Filter with a 12v regulator and below is my basic schematic. Now i'm sure its incorrect but I want to know why and what i'm missing so I can learn.

I'm planning on using the following components:

C1: http://uk.farnell.com/panasonic-electronic-components/eeefc1e471ap/cap-alu-elec-470uf-25v-smd/dp/1244366
L1: http://uk.farnell.com/coiltronics/dr73-101-r/inductor-shielded-100uh-790ma/dp/2369131?ost=2369131

The power would be provided by either 12.6v or 16.8v from a high capacity lip battery

EDIT:

Change of design:


texts: Convert 10.5V to 15V into 0 - 3.3V range for adc input

texts:
I need to measure a voltage range of 10.5-15V to 0.025mv accuracy. This is a resolution of 180,000 - which is huge i know. The reason for this is because I will be measuring the voltage drop across a shunt (0.25mohm) to 0.1A accuracy. The battery voltage (deep cycle) will vary from 10.5 to 15V.

I know how to scale the voltage down from 15V to 5V with a voltage divider, but this puts 10.5 in the middle of the ADC's range.

I saw this post:

How can I measure voltage in range -15 V to 50 V with an ADC in a microcontroller in a single circuit arrangement for scaling?

and this one:

ADC for measuring 0-5V but connected to 3.3V device

which suggest that this can be done with 3 resistors, but I can't work it out. What is the name of this little network?


texts:
I am struggling with CAN bus reverse-engineering. It might be a silly question, but it irritates me.

These are traffics that arise from pressing buttons A and B which is lifting up the 1. Axis of the robot at the end.

Pressing down button A changes the value "09" in 181h node and
button B changes the value "C8" in 281h.

If I am not wrong, I have to feed RPDOs to replicate the lifting up action instead of sending the messages "0A 00 09 00 00 00 00 FF" to 181h and "00 00 00 C8 6F BD 00 FF" to 281h. So basically I resent the messages from RPDOs back to RPDOs.

Is there anything wrong until now? (It must be...otherwise it would have worked.)

As you can see from the above screenshot I manullay sent the messages by pressing each line with the space bar. And it seems like that between my Tx messages lots of Rx messages show up. Is this maybe the reason why the robot shows no reaction?

UPDATE:

The TPDO message "0A 00 09 00 00 00 00 FF" that arises from the pressing down button A gets ignored because whenever I write a TPDO message 0A 00 09 00 00 00 00 FF, it gets overwritten with its default value 0A 00 0A 00 00 00 00 FF so fast that my message is like "not arrived" at all.

The transmission type of TPDO is currently asynchronous with event timer of 50 ms. This leads that my TPDO somehow overwritten with default value 0A 00 0A every 50 ms. How do I handle this problem? I thought this asynchronous transmission type with 50 ms means that the TPDO has to be checked every 50 ms and if there was a change -> transmission. But where does this 0A 00 0A 00 00 00 00 FF default value come from then?

Another question: I thought the whole time that I have to write the RPDOs value back to RPDO to replicate the action. But it seems like that only from pressing down the button A the RPDOs does not change at all. Then how can I replicate the pressing button A action at all?

UPDATE 2: The bit rate is 125 kbit/s. I am using CANopen so that I can control the robot with my computer, instead of using the remote controller. The robot that I am using is Brokk 170. Below you can find an Excel file where the recorded CAN messages are. Those CAN messages arose when I powered up the robot using the robot controller.

I transmitted the messages until the message with number 107, since the value 0A 00 0A 00 00 00 00 FF indicates that the robot is now powered up. But somehow the transmitted sequence does not power up the robot. Now I am trying to find a way to block the messages from the remote controller.

https://drive.google.com/open?id=1Du4J27KykzrTtCquFt29uMa_qhpZP4Ov


texts: How can this circuit be solved with the node method?

texts:
I tried to solve this using the node method and it yields 0 on Mathematica, which I believe isn't correct. I'm trying to solve I1 first.

simulate this circuit – Schematic created using CircuitLab

These are my equations:

Thanks!


texts: How exactly does activating CLEAR cause an asynchronous modulus 12 counter to reset?

texts:
I'm confused about how Clear manages to reset the counter. The trigger is falling edge.
Starting from where the counter is in the image (I'll refer to each JK flip-flop as F1 etc.):

At first, we have F1 Q = 1, F2 Q = 1, F3 Q = 0, F4 Q = 1.

For a split second, after falling edge trigger: F1 Q = 0, F2 Q = 0, F3 Q = 1, F4 Q = 1.

Because F3 and F4 both emit 1, Clear is activated by a HIGH input - the thing is, F1 Q is already 0 (so there is no falling edge trigger effect) and I don't understand how Clear affects F3 and F4.

How is it possible that F3 Q and F4 Q become 0, and therefore we end up with the counter restarting at F1 Q = 0, F2 Q = 0, F3 Q = 0, F4 Q = 0?


texts:
I have a pcb design in Eagle. I would like to see all distances and sizes at once, such as :corner radius size, exact connectors locations and sizes, etc .

Is there a way to see it all at once in front of me ? if not, how you measure a distance?
How do I get an STL or other 3D file from the Gerbers or from Eagle ?

Thank you.


texts: Troubleshooting: Soldering new headphone plug

texts:
I have Sony MDR-7506 headphones. The isolation of the cable near the original plug embrittled over time and fell off. Therefore, I cut off the cable at that spot to replace the original plug with a new one.

There are 3 small wires inside: 2 rose ones and 1 black one. I connected the black wire to the Ground and the rose ones to the left and right connection of the plug, respectively.

Now, when listening to stereo signals, I've made the following observations: The right audio appears on the right ear (correct). The left audio, however, appears to be centered, whereas the centered sounds seem left.

Honestly, I have no explanations for these observations because I thought that centered sounds are produced by left and right sounds with the same amplitude and the only errors I could observe are either left and right sounds are swapped or no sound at all on either or both sides.

Can you please give me a clue about what could happened. What happens if I swap one of the directional wires (of the left or right earphone) with Ground?


texts:
The last page of this DAC datasheet gives dimensions of the chip:

Some of these dimensions come is 3-tuples (such as the pin width: 0.30 | 0.37 | 0.45). What does each of the numbers mean? Is it min, mean and max?


texts: I need circuit to choice between two voltages. So, circuit has two input terminals 12V,24V and one output terminal. If there is no 12V on input (floating)  - output is connected to 24V, and if there is 12V - output connected to 12V. Is it possible to design such circuit without comparators? I think there should be P- channel mosfet on 24V.


texts:
I need to find the output at the amplifier in the first column. The row with the grey arrow indicates that we have switched to ground, from what was initially Vref. I thought I could treat it as a voltage divider with R_c and the row resistor as the terms.

It's a circuit from a research paper, but the equation is not provided.

So what is the single sensor reading? Which is essentially the voltage from the amplifier in column one and the second to last row... I'm really just trying to derive an equation wherein I can solve for the variable row resistor.


texts:
I am attempting to repair my multimeter which hasn't worked since I tried to take an AC reading of an electrical item that blew a fuse and caused a loud pop on the source. Since this even the lcd displays incomplete characters and won't take readings. I opened it up and it looks as if the glass component(bottom of photo) may have blown.

Would replacing this fix the unit? I know this items are cheap enough to throwaway but I'm curious to attempt a fix.


texts: Multisim (2008) - How do I provide a reset stimulus using a controlled one shot pulse, in order to properly initialize my design under simulation?

texts:
Apologies for the captured image quality but I have a circuit from a communications textbook Fundamentals of Electronic Communication Systems 3rd Edition, by Louis E. Frenzel Jr.
The image below consist of a Commutating SCF (Switching Capacitive Filter) for which I do not understand how it works on conditioning an input signal, like an arbitrary sine wave.

To help resolve my gap in understanding,  I created a circuit in a 2008 Student Edition of National Instruments Multisim 10.1.

Except for output, all discrete components, voltage sources, ground points, are placed, connected, with all relevant points of measurement hooked into the three devices all in my software environment

Agilent Function Generator (50 Hz = 1/4 of the divided input clock output of 200 Hz)

Tektronix Oscilloscope (Time Scaled at 10 ms / division)

Decoder Out 0
Decoder Out 1
Decoder Out 2
Decoder Out 3

4 Channel Oscilloscope (Time scaled at 10ms / division)

Channel A - Clock (400Hz)
Channel B - Reset
Channel C - Decoder Input A
Channel D - Decoder Input B

Problem:  All non clock signals are displaying flat lines on both oscilloscope measurement channels
Questions:

How do I set up the controlled one shot for reset functionality, and properly wire the left three pins above the rectangular blocks along side the diamond voltage source.
Would the present resistor value of 2.21kΩ and 4 capacitor values of 6.2μF produce any sort of reasonable result?


texts: (Arduino) When turning TIP120 on again, sometimes the slave flashes trigger without being told to. Why?

texts:
I have two mini slave flashes, that have no stand-by modes by themselves. So, even when charged and ready to flash, current keep flowing from the two AAA batteries each, and, if I forget to turn them off, their batteries run out of charge.

So I assembled this circuit a year ago maybe, with an arduino Micro (Leonardo) that has a raw pin to accept a wider voltage and I use one NP-F550 lipo battery (8.4V) to power the arduino and the flashes. In each flash, in the space where the batteries would be inserted, I soldered a small voltage regulator breakout board to make the 8.4V to 3.0V.  And I used a TIP120 to turn off the flashes with an arduino, after some time it was on. So I created a standy-by code in the arduino for the flashes. And only one battery to replace instead of four.

What happens one time or another, it's not frequent, is that, when the flashes are fully charged and I turn off the unit (I put a on-off lever switch also on the battery wire) and later I turn it on again, as they are then fully charged, sometimes they both trigger without being told too.

These flashes are slave ones, so they need another flash to trigger them. But in these conditions they trigger just because I turned on the switch. And it happens one time or another. I can't replicate this when I want to.

It never happens when leaving stand-by mode (with the arduino "energized). It only happens when I cut power from the battery with the flashes fully energized and ready to be triggered. And one time or another. It never happens also when I turn off the switch with the flashes not fully energized (there's a little led in each unit that tells you if they're charged or not)

Is I made this circuit a while ago, I remember that each flash when charging drew close to 0,8A. So both together don't draw more current than 1.6A, for maybe 5 seconds (time to fully charge). So I didn't use any heatsink on the TIP120.

So, why does this happen? Is there any way to prevent this sudden trigger to happen? Should I use a different circuit to turn on and off them?

Thanks for reading!

I’ll add a link I’ve just found for a hack someone did on this flash this year. Shows the disassembly of the unit. The flashes I used are two of these Vivitar DF120 units

One thing to mention is that, the OFF position of the flash sliding lateral switch is also a “firing test” position. So it has a OFF/ Test position, and three slave modes to choose from. That fires on the first, second or third flashes, from diverse camera types.

https://youtu.be/2NnHCSXMVfM

Second Edit:

I managed  to measure the current of this flash (DF-120):

At 3V, it charges in close to 10 seconds by drawing 0.84A. At 12 seconds current drops to 0.3A. At 25 seconds current drops to 0.13A. At 30 seconds, after firing and re-charging it stabilizes at 0.12A and stays forever at 0.12A, until next firing. So it's stand-by current is 0.12A, after 30 seconds of have fired.

When they are fully charged, and arduino enters stand-by, as soon it leaves stand-by the flashes are already at 100% charge. They don't slow re-charge. The green led, goes from dead (stand-by) to full green instantaneously.

The same effect happens when I turn the battery switch off, that powers both the arduino and the flashes. If I then turn again the switch on, they are instantaneously at 100% power ready to flash. So, as I never turn off their own switch (that is a Off/test switch), they hold their charge.

And today I tried and tried and never managed to make them fire when switching on and off the battery....


texts: How to read RPM data from car with micro-controller?

texts:
I am building a Vehicle diagnostic tracker device. I want to read all the data from different sensor interfaces in the car. The problem I am facing is with reading the RPM data. The data I could get regarding the RPM is :-

How can I read it with my micro-controller. I need to step down the voltage level is one thing. What else I need?


texts:
I have a solenoid operating pneumatic cylinder which is controlled by a timer. timer is fixed on a certain value (25s working followed by 60s rest) and as it starts to count stoke opens fully for 25s then retreats back. I want my cylinder to stop half way through its stroke so added a limit switch to cut the power of solenoid valve when triggered. The problem is that as soon as limit switch is released to normal position solenoid push the stroke to hit LS again till 25s is over. I need a circuit that breaks as soon as LS is triggered and remains that way until the timer restarts its counting again.
Timing diagram for OP to edit.
                     <-- 25 s-->
                      _________                    ________
Solenoid        _____|         |__________________|        |_________
                      _                            _
switch(desired) _____| |__________________________| |________


texts: PID Control Loops with large and unpredictable anomalies

texts:
Short Question
Is there a common way to handle very large anomalies (order of magnitude) within an otherwise uniform control region?

Background
I am working on a control algorithm that drives a motor across a generally uniform control region.  With no / minimal loading the PID control works great (fast response, little to no overshoot).  The issue I'm running into is there will usually be at least one high load location.  The position is determined by the user during installation, so there is no reasonable way for me to know when / where to expect it.

When I tune the PID to handle the high load location, it causes large over shoots on the non-loaded areas (which I fully expected).  While it is OK to overshoot mid travel, there are no mechanical hard stops on the enclosure.  The lack of hardstops means that any significant overshoot can / does cause the control arm to be disconnected from the motor (yielding a dead unit).

Things I'm Prototyping

Nested PIDs (very agressive when far away from target, conservative when close by)
Fixed gain when far away, PID when close
Conservative PID (works with no load) + an external control that looks for the PID to stall and apply additional energy until either: the target is achieved or rapid rate of change is detected (ie leaving the high load area)

Limitations

Full travel defined
Hardstops cannot be added (at this point in time)
Error will likely never zero out
The high load could have be obtained from a less than 10% travel (meaning no "running start")


texts:
I would like to be able control if the live wire of an electric fence is hot or not using a microcontroller.

Turning the energizer on and of is not an option because it is powering the whole premier fence. The system I am trying to build will be used to switch the electric fence on or off for specific segments.

I have not found anything that can handle the 12kv pulse, I tried a relay but the pulse arched between the contacts.

How do I build a circuit that can switch the 12kv generated by an energizer?


texts:
I am trying to estimate the worst case absolute error for a DAC (the example I'm taking is MAXIM MX7524). I'm getting familiar with the concepts of INL, DNL,... But how would you estimate the worst case error? What errors need to be accounted in a cumulative manner?

Additional info:

After some further research I have found this website. I tried to compute the error for this DAC and for me it would go like:
$$TUE = \pm \sqrt{(0.5)^2 + (3.5)^2 + 1^2} \approx \pm 3.7 LSB$$
Where the maximal values used are: relative accuracy = 1/2 LSB, Diff non lin = 1 LSB, gain error = 3.5 LSB
Am I doing it in the right way?

Is it in general a large error or I can find better DAC?


texts:
I have a task to find a number of poles and rated slip of induction motor if frequency is 50 HZ and full load speed is 2950 rpm.
However synchronous speed is not given. Is it correct to put full load speed value into
P = f x 120 / n, where P is poles number and just round the result?


texts:
In transformers, we prove that the induced voltage per turn is the same in both primary and the secondary coils of the transformers, i:e (Ep/Np)=(Es/Ns). But when it comes to currents, we show that (Ip/Np= - Is/Ns), which should yeld to (Ep x Ip= - Es x Is). This equation should yeld to say that Power in is opposite to power out, or Pin=-Pout.
Beside this we say that Power supplied to the primary coil is equal to the power supplied to the second coil.
What did I miss from this concept of power transfer in transformers ? how do I should understand or explain the existence of the minus sign in the currents and the equality of the power In and Out


texts: voltage divider driving PMOS with slow turn-off time

texts:
I have a voltage divider that is driving the gate of a high side PMOS switch. The voltage divider turns the PMOS on once the NMOS is turned on by a 5v logic controller. The PMOS turns on instantaneously, but it takes 9 milliseconds for it to turn back off(9ms for Vout to reach 0v again). At first I thought it must be my resistor values so I changed them to R2=47 Ohms and R1=470 Ohms, but it was still taking 9 milliseconds for the PMOS to turn off.

I think my issue might be similar to this question:
Slow PNP turn-off time, how to optimize it

But my R2 should be acting as a pull-up resistor already, so I'm not sure how to decrease the turn-off time of the PMOS.


texts: Why are functions for the frequency domain expressed in terms of a whole complex number rather than just omega?

texts:
I don't understand why some formulas used in electrical engineering, especially why using fourier analysis, include static numbers in function inputs, rather than just the changing variable.

For example, the formula for the Fourier Transform of $$x(t)=\cos\omega_0t$$ is $$X(j\omega)=\pi\delta(\omega-\omega_0)+\pi\delta(\omega+\omega_0)$$
Why is this in terms of \$j\omega\$ rather than just \$\omega\$, because \$j\$ never changes. I've seen other formulas use complex numbers as the function input, such as
$$X(e^{j\Omega})=1$$
Again, if \$e\$ and \$j\$ are not changing, why include them as a function input?


texts: How can a phone transmit the signal back to tower?

texts:
If cellphones have such a low power transmitter (around 200mW for LTE) and also doesn't have directionality then how can they talk back to the tower even though they are so powerful and built specifically with aim for better direction.
And how sensitive are the tower receivers?


texts: Bjt Amplifier Design - Clarification on Specs

texts:
Hi,

Just having trouble unpacking the question attached. I know that Vcc = 12, Zout of Voltage/Pre amp = 600 ohms, f = 20Hz to 20kHz, Zin = 47k ohms. However, I'm having a but of trouble understanding what my output is. Is it 2mV or 2V Rms (2.83V peak)? And could you clarify any information above that I may have misinterpreted?

Thanks.


texts:
I am using the IRF540N. Its gate to source threshold voltage is 2v - 4V (VGS = VDS, ID = 250µA.)

Does "gate to source threshold" mean I need to apply voltage above 4V to the gate?

How is Id = 250uA related to the threshold voltage?

There is one more drain current in datasheet given a 33A.  In what situation do we need to use this?


texts: Does an ac servo motor experience high "inrush current" every time it moves after initial power up

texts:
we are currently building a motion platform for an airplane simulator and the linear motion actuators will be driven by 6 servo motors of type: Syntron 3KW AC 380V 130HMB-30100.

The datasheet says that the inrush current is 22.1A compared to 7A nominal current, and since the motors will be starting and stopping all the time we wondered if this could cause problems with our supply (63A 3 phase 400V).

Hence I wonder if ac servo motors will draw a significant high current each time they start after stopping, or if the motor only draws high current during the initial power up.

Eventually if anyone knows whether the motor driver (HS0300A-P22S) will help eliminate this in some way.


texts: Characteristics of a transformer question

texts:
I'm trying to solve some problems and I'm confusing one thing . We have , let's say a 30MVA, 24.5/345 KV  3-phase transformer connected in wye-delta.
I try to use one-phase analysis and want to find the voltage ratio and make use of the following equation: $$S=\sqrt 3VI$$.

The values V and I are phase or line voltage/current? And when I find the voltage ratio which of the following is right? $$a=\frac{24.5}{345}$$ $$a=\frac{\frac{24.5}{\sqrt3}}{345}$$

I divide by the root of 3 because of the Y connection.


texts:
Quick concept related question, I have a system with 5 generation units and I have to find the maximum demand that the system can support and still be N-1 secure.

their max outputs are:

Unit A= 155, Unit B = 195, Unit C = 165, Unit D = 305 and Unit E = 280

Considering the reserve constrain their max outputs are:

Unit A= 155, Unit B = 195, Unit C = 165, Unit D = 175 and Unit E = 205

The approach I took was to create a matrix and Tripp one unit per time and sum their max outputs like as follows:

                                                    Max demand supported
**Unit A Tripping**         Unit B  Unit C  Unit D  Unit E  740
**Unit B Tripping** Unit A          Unit C  Unit D  Unit E  700
**Unit C Tripping** Unit A  Unit B          Unit D  Unit E  730
**Unit D Tripping** Unit A  Unit B  Unit C          Unit E  720
**Unit E Tripping** Unit A  Unit B  Unit C  Unit D          690

However discussing with two other friends, each one has a different approach, one of them summed all the max outputs of each unit regardless any constraint, the second summed all the max outputs regarding the reserve constrain finding 895MW

I wonder, who got it right, and what is it meant by N-1 then.

Thanks


texts: How to assign a hexadecimal value to integer type in VHDL?

texts:
ModelSim is unable to compile this in VHDL:

constant mem_size_bytes: integer := x"FFFFFFFF";

It says:

Bit string literal found where non-array type std.STANDARD.INTEGER was expected.

Similarly for;

if address< x"3FFFFF" then

it says

Operator "<" is ambiguous

I keep running into this problem. How in the world am I supposed to use hexadecimal numbers in VHDL with integer types like integer, natural and positive? Its just that specifying something hexadecimal is more convinient at times than having to use the calculator to determine what something is in radix-10. I had hoped that the tool will automatically know what the literal means since it is preceded by x which marks it as hexadecimal numeric quantity!!!

So, when assigning literals to constants or when using literals in comparison operator how does one qualify the literal? In other word for a literal constant value like "1010", how do explicitly tell the compiler if this is a string or std_logic_vector or unsigned or signed?


texts: What would constitute a good selection of medium power and gain transistors that are modern equivalents of discontinued parts?

texts:
TLDR: I need to build a collection of NPN and PNP transistors(mostly medium powered complementary audio amplifier transistors) in order to avoid constantly ordering specific parts and waiting for them to arrive. Packaging and pin configuration is not important; what I am more concerned about are common combinations of Vce, hFE, Ic, Ipc, and Veb.  What would be decent selection of five to ten sets of modern complementary pair replacements I might order to cover most of my needs?

Background: I am an engineer that recently got a fantastic job that is very laid back(I can work whenever I like) repairing vintage electronics, mostly amplifiers.  The company had previously been buying old electronics from garage sales, flea markets, etc, and repairing any very simple problems they found(such as frayed power cords, replacing belts in cassette decks, or cosmetic issues) that didn't include any sort of electronic diagnosis.  Any units they couldn't repair themselves, they started storing in the back warehouse several years ago, so there is now a huge backlog of items in need of repair.  Since they had no technician previously, they had no replacement parts on hand, and had been discarding any non-working electronics that weren't worth any money non-working.  Upon my arrival, I immediately put a halt to the disposal of non-working items in order to be able to later salvage parts, and in the last few months have sourced at least a hundred parts from the broken items we have since collected.  I also built up a large stock of new capacitors, resistors, linear regulators, and low power transistors in order to facilitate my repairs in a timely manner.  High powered output transistors are expensive, and will still need to be ordered on an as-needed basis, but I would like to order a selection of modern medium powered transistors that would be common replacements for older discontinued transistors.  As an example, I once ordered many extra modern BD139/BD140 transistors when I needed one of each for a specific repair, and I have since used the extras to successfully replace several other older discontinued transistors of various part numbers.  I would like to know if anyone with extensive repair experience would know the part numbers of the most commonly used modern replacements transistors, like the BD139/140s I have been frequently using.


texts: How do you find the peak-to-peak ripple voltage of a full wave bridge rectifier?

texts:
The 32VRMS secondary of a transformer feeds a full wave rectifier and capacitor filter as shown in
the circuit
The peak-to-peak ripple of the output voltage of this circuit needs to be less than 1V when it delivers
a current of 3A. A filter capacitor of about 30 000 uF is required. I need to find the frequency.
I am unsure of the formula for finding peak-to-peak ripple voltage of a full wave bridge rectifier.
Is this correct:
V(p-p) = I/(2fC),
Therefore, f = 50 Hz.
I am unsure because I have seen the equation :
V(p-p) = Vm/(2f R*C) used.
Which equation is correct?


texts: Recommendations for analog tri-state buffer?

texts:
I'm currently working on a project that requires interfacing to a clock and data line at a configurable voltage between 0V-5V with nonstandard logic levels, this voltage is generated elsewhere. To be able to receive data the lines needs to be able to go into a high impedance state.

I'm currently playing around with a 4066, I have two lines of two pairs hooked together, one channel of the 4066 is hooked to the voltage and the other to ground and I simply drive them inverted. To get a high impedance state I drive both switches low. This being said it doesn't work real well since I'm having trouble hitting the ground rail.

All the buffers I found with tri-state outputs are for digital logic levels, could anyone recommend a analog one or another approach?

(For anyone interested I'm investigating the lowest voltages that I can use to interface to various IC's)

I eventually found this bug, I replaced the the 4066 with one from another manufacturer and it worked...


texts: Gate with 2 inputs, one being "select". If select is high, output is always low regardless of other input

texts:
I am tring to figure out how I can have some sort of module that can create the following scenario:

The module has two inputs and one output. One of the inputs is "select". If select is high, then the output of the module is always low. If select is low, then the output of the module will equal the state of the other input.

Here is the truth table for my desired module:

Here is the circuit I am trying to achieve this outcome with:

Subtract is the "select" input and each of the "overflow" inputs are the 2nd inputs. Therefore I need 3 of my desired modules where each of the XOR gates are. The XOR gates achieve what I want when "overflow" is high, but not when it is low.

I'm sure this is relatively easy to achieve but I just can't seem to think straight at the moment. I think that some type of flip-flop would be my best bet.


texts: How do SOCs transmit at a higher speed than the internal clock?

texts:
E.g. ESP 32 has an internal clock of 240MHz, but can transmit at 2.4GHz (following 802.11 standard).
How is this accomplished? Does it really generates a wave at 2.4GHz frequency? Is it not limited by the internal clock?
I know it's digital modulation and I'm still learning about RF so any recomended literature would also be appreciated.


texts: How to shield for electromagnetic interference (DIY level)?

texts:
I am building an optical rotation encoder for my "autonomous robot" (a LED pointing to a photodiode that gets interrupted as the axis rotates).

My issue is that at the voltage that I am using the motors (~9v) they generate too much electromagnetic interference so the microcontroller (arduino) triggers a "falling" without any physical move (it makes a ~5v value oscillate below ~2.2v)

I believe that's what is happening. See my image for my testing setting.

I have my circuit connected to the computer and I have a completely independent dc motor connected to isolated batteries. When I turn the motor ON, the microcontroller starts triggering like crazy (even 50 times per second, at about 20cm of distance).

I think that the only possible cause is electromagnetic interference. I realize my circuit is exposed (I am using LEDs, resistors, etc., without covering).

So, as a test I covered my "rotation encoder" (the red protoboard in the image) in aluminium foil. It helped a lot (but it didn't fix the issue completely in the static testing setting - the issue is even worse if the axis is actually moving).  I also covered the DC motor in aluminium foil with no improvement (I believe that it actually made it worse).

I didn't cover the resistences and LEDs with plastic isolation (thermoshrinkable) because this is the prototype in the protoboard (want to avoid investing all the time it takes because I am breaking it apart the minute it works to mount it in the real robot). I can do that if I find indications it would help.

So the question is: for a DIY/hobby level project, what approach should I take to isolate the circuit from the interference that seems to be coming from the DC motor?.

Thanks.

Note: per request added encoder circuit.


texts: Generate magnetic field from card stripe wav or text data

texts:
Internet has a couple of answers about reading and decoding card magnetic stripe. I have another question -- how can I create magnetic field from stored stripe data?

I want to take the data that I've read from a magnetic stripe card and use it to generate the equivalent sequence of magnetic fields in another place.


texts:
I have a signal that is 3mV range, I like to use a bandpass filter for this signal at 800Khz to eliminate unwanted signals (i.e. noise etc) I have the following questions:

Since the amplitude of my signal is small, shall I amplify first? (Just pass through a high speed opamp) and than filter it?
I have looked at TI's filter design software and I see that I can use an opamp based filter, is this better compared to RLC filters?
If I use the opamp filter, I can amplify the signal, can I directly feed the 3mV signal to the filter and get 300mV type signal and filter at the same time? (100x gain and filter, sounds ambitious to me)
Do I need to take care of the impedance of my signal? (I have no idea about the impedance of the source of this signal, is it important for designing the filter)


texts: Is there an IC like the ULN2003A but for high side switching?

texts:
I'm looking for an IC to switch multiple ground-connected loads but having trouble finding a suitable chip. Is there anything kind of like a reverse ULN2003A but with a common collector and multiple emitters? Or just a bunch of MOSFETs with a common drain?

I need to switch 24V with 3.3V controller output.


texts:
simulate this circuit – Schematic created using CircuitLab
I have here a voltage regulator circuit using a Zener diode.
We were tasked to find the maximum allowable \$i_L\$ given the varying voltage input so the the load voltage will remain at 8 V.
The way I understood the problem, we are asked to looked for \$I_{z(max)}\$ since past that, the Zener diode would no longer be able to maintain the voltage at 8 V. But then, I thought \$I_{z(max)}\$ is supposed to be given in a Zener diode's data sheet and also depends on the power rating of the diode (which was not given,) so I am unsure how to proceed with this problem.


texts: What is the file extension of the file that is loaded in a Xilinx FPGA?

texts:
I wonder what is the file extension that described the functionality of my design and is the file that is loaded in a Virtex 4 FPGA to get the behavior of my VHDL design.
Thank you.


texts: I want to measure 50 miliamps by multimeter which range i should select?

texts:
I have a multi meter I want to measure DC 1-50 milliamps which range I should select by the knob?

Also where I need to plug in 20A or mA?


texts:
The code snippet below shows a two-step variable manipulation:

1) Convert an integer to an unsigned number

2) Cast an unsigned number to a std_logic_vector and extract a certain number of uppermost bits.

Could these two steps be consolidated into a single one?  That is, is this just typecasting (wire connections) or is some sort of clocked circuitry involved that could potentially result in a problem?

signal integrator_inter_uns :  unsigned(20 downto 0):= (others => '0');

...
...

counter : process(CLK)
begin
 if clk'event and clk = '1' then

   -- oveflow
    if pwm_counter = N then
        pwm_counter <= 0;

    -- 1
    elsif pwm_counter = 1 then
        pwm_counter <= pwm_counter + 1;

        integrator_inter_uns <= to_unsigned(integrator, integrator_inter_uns'length); -- 20 bit unsigned

    -- 2
    elsif pwm_counter = 2 then
        pwm_counter <= pwm_counter + 1;

        data <= std_logic_vector(integrator_inter_uns(15 downto 0));
    -- 3
    elsif pwm_counter = 3 then
        pwm_counter <= pwm_counter + 1;

        dac_input <= data;

else
    pwm_counter  <= pwm_counter   + 1;

 end if;

end if;
end process;


texts:
What is the significance of the forward recovery time of a diode, does it have a significant impact on the switching frequency of a diode?

For instance I have a diode with reverse recovery time (trr) = 65 ns where as the forward recovery time (tfr) = 500 ns.

I have read that to find the max frequency a diode is capable of switching at one should use the trr value so using that I get 1/65 ns around 15 MHz, is this correct?

However from the data sheet, I found that the forward recovery time is significantly higher than the reverse recovery time.

Upto what frequencies can I safely use this diode?

Your comments would be highly appreciated.


texts: I need some help to adjust the volume of the amplifier. It is a 2.5 W amplifier and it has to be connected to a 2 W speaker. I want to reduce the gain of the amplifier in order to avoid damage to the speaker. How can I do it? Or can I just connect the amplifier to the speaker without anything between them?


texts: Is there an internal resistivity in buzzers?

texts:
I would like to know if there is an internal resistance in buzzers, and if yes, what could be the internal resistance for a cheap buzzer that can go up to 12V.
Thank you


texts: Why does not my opamp-latch work as I expect?

texts:
See schematic:

Opamp is OPA2132. (I forgot to draw a resistor in schematic: just at the V is an 8k2)

U is fixed 5V, making in+ about 4.4V reference.
V is square wave, either 5V or 1V.

If V=5, X~=5
If V=1, X~=1

No problems there.

The purpose of the BJT-feedback is that if V=1, X goes high, BJT (BC547) gets saturated and pulls in- down. Emitter-resistor is 1k.

In- is in the voltage divider of 8k2/1k.

In theory, and in my simulations, this latch should work: as soon as the BJT is saturated, in- is kept low and will not ever make the opamp go low again.

But, on my breadboard, as soon as the BJT-feedback is connected, the opamp-output is always high, no matter what V is. I started with V=5 and never switched it, but the feedback is somehow triggering.

If I break the feedback (either pull BJT, diode or resistor), the opamp behaves as expected (except for the latch ofcourse). Same goes if the BJT stays but doesn't get any base current.

So, something here makes the base conduct and make the BJT latch immediately, but I cannot find out what, since exactly this circuit works in my simulator.

Have I done some obvious error?


texts: Connect motor control board's 4 terminals to brushed motor

texts:
Although I have a degree in engineering, it's mechanical engineering. In addition, I have been developing software since I graduated, so please excuse my obvious ignorance about electronics hardware.
I need to connect the control board to the small circular board and/or connectors on top of the motor, or, perhaps, the motor casing?! I'd like to avoid another 3 month wait like the one which resulted from previously having shorted them out :-).  If anyone could help by explaining what the various thing are, I would be very grateful!
The motor is from a sea scooter, which is powered by a 24V lead-acid battery.  So, 24V DC into the board and 24V out. There are a couple of magnetic relays on the board, which control the following: one controls stop/go, while the other takes it from half to full speed. That's about as much as I can give :-(
Many thanks in advance, even if it's just a link to a page where I can inform myself.


texts:
I am curious about how to determine the turn ratio to get the minimum power loss. Assuming n=Np/Ns Vin=380, Vo=40, different turn ratios can get the same output because Vo =VinD/(n(1-D)).

When the n is small ids increase, Vd decrease, ids decrease, Vds increase.
When the n is large ids decrease, Vd increase, ids increase, Vds decrease.

Above these two situation, how do I choose the MOSFET and diode to get the minimum total loss?


texts: netduino SPI stops clock after write on WriteRead()

texts:
I am having an issue where the SPI bus on my netduino stops the SCK clock generator after the write has completed on a WriteRead() method. Because of this, the device (a Microchips 25LC320 EEPROM doesn't send any data.) Any help as to why this is happening would be greatly appreciated.

Source code:

SPI.Configuration config = new SPI.Configuration(Pins.GPIO_PIN_D10, false, 1, 1, false, false, 1000, SPI.SPI_module.SPI1);
SPI bus = new SPI(config);

byte[] write = new byte[] { 5 };
byte[] read = new byte[1];

spi.WriteRead(write, read);

Schematic:

simulate this circuit – Schematic created using CircuitLab

Saleae capture:


texts:
i need help to identify the following capacitors

This seems to be a 33µF at 100V but iam not sure.

I cant identify this one. What does the small letter at the end(maybe a F) mean?


texts: Stuck with demonstrating effect of output impedance from EMI in SPICE simulation

texts:
The sources Vs1 and Vs2 are both measured by an ideal scope or ADC which has input impedance of 100Meg:

The only difference between two sources are their output impedances 50 Ohm and 10k Ohm.
My aim is to simplify and demonstrate that high output impedance source picks up more noise than the lower. For simplicity, I first made the source outputs 0V.
Now where I am stuck at is:
How can I diagrammatically couple electric field or magnetic filed noise to both of these circuits above so that the simulation shows us the higher output impedance circuit results more interface pick up?
I am stuck how to use a current or voltage source to mimic such interference in the circuits. A modified schematics of mine would be great help.


texts: I'm trying to connect a BNO080(IMU) to my microcontroller on a PCB. There are capacitors at the voltage input to the IC and I don't properly understand what these capacitors are doing or how their values are determined to be 0.1uF. Any help?


texts:
In this exercise I need to find I using source-transformation. This task should be easy because s-t I a simple concept.
The problem for me here is that I have some voltage sources in parallel with the resistors and a current source in series with a resistor.
How should I proceed with source transformation? Could you tell which transformations should I do here?
Thanks,
Claudio Carbone


texts: Compatibility of devices with different voltage thresholds/noise margins/static disciplines

texts:
tl;dr included at the bottom.

Suppose we have two logical buffers from different logic families, where buffer A drives buffer B. Buffer A has the following voltage thresholds: \$V_{OH}=8\ V\$, \$V_{IH}=6\ V\$, \$V_{IL}=4\ V\$, \$V_{OL}=2\ V\$; thus buffer A interprets all received voltages up to 4 V as a logical 0 and all received voltages above 6 B as a logical 1.

Suppose that the thresholds for buffer B are the same as that of A with the exception that B's \$V_{IL}=4.5\ V\$. This means that for all received voltages which A would interpret as valid logical 0, B also interprets as logical 0. According to my textbook (Foundations of Analog and Digital Circuits by Agarwal and Lang) this means that devices from B's logic family can be used with devices from A's logic family, since B guarantees that whenever A sends a valid signal, B will send a valid output; and that B will interpret as valid all the signals which A would interpret as valid.

So then there is this range of voltages \$ 4 < V_{received} < 4.5 \$ which is interpreted as valid logical 0 by B but would be considered invalid by A. I can see that since B's noise margin  for logical 0s is bigger than A's, that B is in this respect an improvement over A, since if A sends a 0 which is received as 4.25 volts, B will still be able to interpret it as 0 whereas an A receiver would consider it invalid.

But it also seems that B's higher \$V_{IL}\$ means it could make more mistakes of the kind where A sends a logical 1 which through (a lot of) noise is received as 4.25 volts. An A receiver would consider this invalid but B will consider it a valid logical 0, when really it was a valid logical 1, so B propagates an incorrect bit.

So the bottom line is, do we just have to accept that fact that some types of errors will be more common when mixing logic families as long as valid signals will be handled correctly, or am I misinterpreting something?


texts: This Potentiometer Keeps Catching Fire And I Can't Locate The Short

texts:
Device: KADA 852 Hotair rework station (not 852D)

VR9 keeps catching on fire and R42 is half toasted but still keeping its resistance, I removed and checked CA12 and CA13 and they are not shorted. Tested T11 & diodes D17 to D24 in place and they seemed okay. I'm not sure what else could be shorting out causing so much current to run into these resistors.

VR9 has a dial and sets the pump speed/power, R42 sets the minimum pump speed, VR11 and R47 trim VR9 and R42.

Test condition: to narrow down the cause, this issue is present when I connector labeled "RED" has BRN connected briefly to BLU so C9 charges and then returned to connect "BRN" to "WHT". This way the left part of the circuit is not powered, just the relay connecting AC to the right side and AC running to D17. The circuit runs until the delay set by C9 runs out and the relay disconnects.

In this schematic, the missing part on the left is unconnected, 220 VAC enters on the right "BLU labeled connector", a switch at connector labeled "RED" on the left connects either BRN to WHT or BRN to BLU, at connector labeled "BLU" there is a diaphragm pump connected.

PS: R44 & R45 = 30K each instead of 300.


texts:
I am using a PIC18F25k80 microprocessor, which is communicating by using I2C protocol with peripheral ICs. After collecting the data from the ICs I want to store them in an SD card. However for the SD card I need to transfer the data by using an SPI protocol, since it cannot operate with a low data transfer protocol. For that reason I put an I2c-to-SPI bridge (SC18IS602BIPW) on the bus. By writing the address of the interface bridge, followed by a 0 (control bit / write), on the I2C bus you can communicate with it. After the address a predefined function needs to follow (the functions are explained inside the datasheet) and then a series of data, which can be 0-200 bytes long. The data is stored in a buffer inside the interface bridge chip and then are automatically sent over SPI to a device. The predefined function determined the chip select bit and thus, the device with which the bridge is communicating.

I want to initialise a file system on the SD card, so that I can create files where my data is going to be stored. How can I use the function inside the FSIO.h in order to do that. Do I need to send the functions over the bus to the SD card and if yes how can I do that?

Interface Bridge datasheet:
http://www.nxp.com/documents/data_sheet/SC18IS602B.pdf


texts:
Previously I have switched line level audio using a Zettler AZ850P2 relay (Bistable Latching DPDT 5V 2-Coil, 1A). Currently, I am planning a somewhat more complex soulution allowing switching audio/mic between two computers, as well as switching the output between speakers and headphones.
I realize the diagram below might be completely misunderstood, but if not completely, is this somwhat viable? It seems like the AZ850P2 is somewhat difficult to find online (at least at a reasonable price), so I am wondering if there are any good alternatives for this kind of application - maybe even a 3(4?)PDT latching relay to switch both mic/audio between A/B?
(Planning on doing the switching itself using an Arduino or similar.)


texts: Choosing crystal, strangely narrow requirements in MCU datasheet?

texts:
I am making a prototype using the Atmel ATSAM4S2B microcontroller, but I am having trouble choosing a crystal. I need a 12MHz crystal to use the integrated USB module.

The problem is, in the datasheet of the MCU, it says "allowed crystal capacitance load" must be between 12.5 pF and 17.5 pF.

https://i.gyazo.com/e617a28de6322e6060544194aefc8751.png

This is a problem, such a crystal seems to be quite rare. I tried looking up those specs in digikey, and when filtering out out-of-stock items, I am left with only three products, all of which are quite expensive (two of them VERY expensive I think) and all of them also having a no-lead DFN footprint which is unfortunate as small-run manufacturing will be expensive or hard.

http://www.digikey.com/product-search/en/crystals-and-oscillators/crystals/852333?k=&FV=fff4000d%2Cfff8016d%2C8c0001%2C8c0004%2C8c0005%2C8c0009%2C8c000c%2C8c001f%2C8c0020%2C8c0032%2C8c0033%2C22c019d&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

My question is, am I misunderstanding something here? It just seems so strange that a crystal that fits the required spec is so rare. What happens if I choose a crystal with a load capacitance of for example 12 or 18 pF, both of which are much more common?


texts: What are these connectors called (home applicances)?

texts: I see these connectors inside a microwave oven and other home appliances. They are installed on the ends of wires and have round edges, while the middle section is flat. What are they called and do splitters exist that split one such connection into two? Thanks


texts:
I am currently struggling with the following homework problem:

It asks to find the voltage across the points a and b.

I first redesigned the circuit to make it look for straightforward and I figured that no current goes through 1000 Ohm resistor since point a is not attached to anything, thus, the potential difference there should be zero. Also, according to KVL, voltage within a loop should be zero, thus, only 4V and 500 Ohm resistor matter in this problem. However, it is still unclear to me how to finalize it and I am not sure whether my claims above are correct. Any help will be highly appreciated!

P.S: the answer to the task is -3V


texts:
My stepper motor have 4 wire is VEXTA motor 2 phase 1.8"/Step, DC 1.96V, 2.8A.
when i measure the resistance wire 1 & 2 is 0.8 ohms, 3 & 4 is 0.9ohms.
Is it the correct way to measure the resistance?


texts: "Switch mode" and "switching" - are they the same?

texts:
I live in the UK and have purchased an american FPGA (circuit board) that comes with a US plug.  I have found a US-to-UK power adapter; one of the comments about it says
"...only use it with US items that are switch mode (things like laptop computers and phone chargers). You must not just plug in a US item that needs 110V - 120V for that you would need a Voltage Transformer as this adapter will not convert Voltage."
Now, on the plug for my FPGA is written
LTE Switching AC/DC power adapter
I/P: AC 100-240V 50/60H
O/P: DC 7.5V 0.2A
Will the adapter I linked to work safely with this FPGA plug?
PS I'm sorry if I have asked this in the wrong area, but I felt this area would be frequented by people who are most likely to be able to help.
PPS I know the plug says "switching" but I'm not sure if this is the same as "switch mode", and would rather hear the facts from someone on here.
PPS I have done lots of google research prior to asking this but cannot find anything that suggests "switch mode" means "switching", so please be gentle :)


texts: Advice on generating a negative supply rail (-5V) in an embedded, mixed signal design

texts:
I'm designing a board that can take an input DC supply of between +8 and +36V DC (+12V nominally) and needs rails of +5V, +3.3V, +2.5V and +1.8V. My current design uses a step-down regulator (LMR23625) to generate the +5V and I use LDOs to generate the rest. This all works fine. This block diagram illustrates it:

The problem is that I also have an analog section to the board (8x INA141 instrumentation amplifiers and an 8 channel ADC). The INA141s need a negative supply rail of -5V. What is the best way for me to generate the -5V? I was thinking about daisy-chaining the TPS63700 off the LMR23635, e.g.:

Is this a good idea or should I consider something like a dual-supply/split-rail regulator in place of the LMR23625?

I'm not constrained for PCB space. The board is 200x60 mm (4 layer, double sided) and I can dedicate a good 3rd of that to power supplies. The overall system current is maximum 2.5A (nominally lower).

The worst case current requirement of the -5V rail 80 mA, maybe 100 mA to be safe (10mA per INA141 x 8 + some head-room). Nominal value is about 3 mA each.


texts: How do I replace an existing servo with a geared DC motor?

texts:
I am a complete beginner, just getting into the world of electronics, in particular robotics. I have found a really nice open source set up that I want to build on and change for my own ends.

The existing bot has several servos attached to a custom Arduino shield putting out PWM signals and the 6V required to run them. Most of these motors are "joints" in the bot but not all of them are required.

I want to repurpose two or four of these servos to run either wheels or tracks, so the bot would now have increased range and speed. Several friends mentioned continuous servos but these would not run very fast or wouldn't produce much torque (educated guess, please correct me if I'm wrong). Another group suggested stepper motors, but again, unsure to how these would perform.

Am I going along the right lines with geared motors? If so, how can I control these from standard 3 wire servo motor connections and Arduino programming?

I was assuming I would have to "run" them for a period of time in programming to achieve a set distance or introduce a range sensor. I really hope I can repurpose the existing connections and board as it would save a lot of hassle in assembling my initial components.

Any help or links to hidden knowledge would be amazing.


texts: How does a dot matrix led driver know the voltage of an led?

texts:
I wanted to make a 7x10 led dot matrix using two 5x7 led dot matrix from lite-on (LTP757KR). I first thought of using shift registers, then I found a 12 x 8 dot matrix led driver with a bunch of additional functions. I checked the datasheet for schematics on how to use the driver and found that the leds are connected without a resistor on them.

It got me thinking how the voltage on the leds were controlled. The datasheet specifies how the current per led can be controlled by PWM register value and the GCC(global current control) Value.

Does this mean that I can control the leds with only the current, not caring about the voltage? How does the driver know what voltage V the led would be at some amount of current I? Or am I doing something wrong?


texts:
As shown in the graph, I'm trying to use mcu-controlled switches to turn a segment of rs-485 bus on or off (so that only one segment is on at a time). I was considering analog switches but I'm not confident how to take care of the negative voltage.

My question is:

Is an analog switch the best choice in this situation?(cost is an important consideration)

If so, what kind of analog switches should I use to switch the negative voltage line? or is there a better general method to do it? (a few specific recommendations would be even better!)

Thanks!