texts: Smallest possible solution to boost DC voltage

texts:
I need to take unregulated li-ion voltage (3.3-4.2 V) and convert it to regulated DC around 6-12 V. The load is a 555 timer driving a component that needs 3V very-low-current AC.

The application is insanely space-constrained. At the most, there is room for a SOT-23 and two bypass capacitors, and that's it.

All of the boost regulators that I've seen require an inductor, three resistors, a capacitor, and a diode, not even including the bypass caps. There simply is not room for all of these external components.

Is there some circuit I can make, no matter how many corners need to be cut, that will let a boost regulator do its job "good enough" to drive a 555, without all these external components?

I'm guessing I don't really need the load-side bypass cap, so ditching that should make room for one other component.


texts: Soldered wires don't last very long on PCB

texts:
I am having a very bad experience with soldering wires on my boards. The problem is I have tried wires from various manufactures and suppliers but when I solder them initially they appear good but overtime (within couple of days) the insulation near the solder point on PCB starts cracking or in some case the conductor itself starts breaking.

My soldering technique is

Strip the wire end.
Tin the wire with solder end and make sure no split ends.
Solder the wire on the PCB and then cut the bits that might be sticking out.

Any ideas or wire makes that can solve this problem and make the solder last?


texts: Solving for adding a voltage to eliminate the non-ideality of the op-amp

texts:
The circuit as shown above.

Conditions known:

The op-amp is nonideal.
Both inputs have current flow, lets say 0.7 \$\mu\$A.
Only \$R_F\$ is known, which is 450 \$k\Omega\$.
Open-loop gain is high.
Close-loop gain needs to be around 13.
Initial \$V_{in}\$ and \$V_{out}\$ is unknown.

Question: How much voltage should be added to \$V_{in}\$ to eliminate the impact from the non-ideal op-amp to the circuit? (So that \$V_{in}\$ will be equal to \$V_{in}+V_x\$ after the modification, and solve for \$V_x\$).

I used the formula, \${V_{out}/V_{in}=1+R_F/R_2}\$ to find \$R_2\$, then I stuck.... I have no idea how to apply the current to solve this problem.


texts:
For my birthday I got a small NSOP-A Microcontroller in a kit and I was wondering if I could use it to convert analog signals to 8-bit digital signals for My raspberry pi. Anyway, that isn't the question.
I was looking to see how to program it and I could not find any documentation on what sort of architecture it used.
The Microcontroller I'm using is the HT46f47e(made by holtek).

What type of chip is it?
And how would I program it?


texts: Why do dual-rank DIMMs have twice the bandwidth of quad-rank DIMMs?

texts:
I'm looking at the RAM compatibility table for my motherboard:

and it shows that dual-rank (DRx4) memory modules can operate at twice the speed of quad-rank (QRx4) memory modules (1600 MT/s vs 800 MT/s with 2 DIMMs per Channel).

Does this mean DRx4 DIMMs' connection to the CPU has twice the bandwidth of QRx4 DIMMs, or are the higher MT/s numbers offset by each transfer being twice smaller?

If the bandwidth is actually lower for QRx4 DIMMs, then why?

As I understand it, at least with registered RAM, the CPU is not directly connected to the RAM chips, so any additional load inside the DIMM should be a separate issue.


texts: How to convert output from a split phase inverter to single phase with only 1 hot?

texts:
Here in USA, we use split phase 240VAC 60Hz.  In Philippines, they use single phase 220VAC also 60Hz.  How do I make an inverter designed for 240VAC split phase output work properly over there in Philippines for their appliances expecting 220VAC single phase?  I believe they use one hot and one neutral but I am not sure.  Is there some special way to connect it and/or do I need some special adapter or wiring harness?  The outlets there look similar to the NEMA 5-15R used here in USA, except many of them (I think) are tipped sideways and have 3 receptacles instead of the typical 2 vertical ones in USA.  They use a combination of both 2 prong (type A) and 3 prong (type B) plugs (even in the same house).  Type C plugs are also used but I am not so concerned with those.

Also, a friend of mine who is good with technical stuff told me their stuff will run even better with 240VAC so I might not even have to worry about the 20 "extra" volts.  All the appliances might "like" it (run more efficiently).  Does anyone have experience with this?


texts: Confused about Full-Subtractor truth table

texts:
I'm a little confused about the 011 condition in the Full-Subtractor truth table.

I don't get how the output can be D = 0, B = 1.  Since D = A - B - C, that gives D = 0 - 1 - 1 = -2

How does a difference of 0, and borrow of 1 represent a -2?  Makes no sense at all.


texts: Example of Electrical Apparatus that draw leading VARS and Electrical Apparatus that draw lagging VARS

texts: I understand that an AC inductive circuit will draw lagging vars while a capacitive AC circuit will draw leading vars (ELI the ICE man), but what are some examples of real-life electrical apparatus that draw these types of Reactive Power.


texts: ATMega32u4 output power to input without external resistor?

texts: I am new to electronics and have a SparkFun Pro Micro clone with an ATMEGA microcontroller. I wanted to know if I could set one pin to be an output that sends power to another pin that I have set as an input without using an external resistor. Will this cause any issues, such as frying the chip?


texts:
I have a system that's sampling two 50Hz sine waves at 1kHz.  What's the best way to estimate the phase shift between the two?

The measurements are somewhat noisy and the sampling period is not very even.  I know the sample times to a high resolution but can't control them to be evenly spaced.  The phase shift needs to be estimated on chunks of data covering approximately one second.

The measurement noise makes the zero-crossing method unreliable; if the noise causes a measured signal to cross zero twice at one "real" zero-crossing then the algorithm breaks down somewhat.

At present I'm doing something like this (python code):

t, v, a = [NumPY arrays of samples]
p_inst = v * a
s = numpy.sign(p_inst)
s_avg = numpy.trapz(s, x=t) / (t[-1] - t[0])
shift_fraction = s_avg / 2 + 0.5
shift_angle = (1 - shift_fraction) * numpy.pi

Here s is the sign of the product of the two sine waves.  Finding the average of this using numpy.trapz gives a value representing how often the two signals have the same sign, with 1 meaning "all of the time", -1 meaning "none of the time" and zero meaning "half of the time".  This is converted to a fraction of the time the signals have the same sign (shift_fraction) and this is converted to a phase-shift angle.

The biggest problem with this is that it doesn't tell you whether the phase difference is leading or lagging.

Does anyone have a better method?

Edit For those suggesting finding the correlation peak, am I right in thinking that, with 20 samples per cycle, that method will necessarily limit the resolution of the estimate to 18 degrees?  What would you think of instead calculating numpy.correlate(v, -a), finding the first zero crossing and then interpolating to estimate the actual zero point?  I think that, for sinusoidal signals, the correlation should also be sinusoidal, and so the small angle approximation should make the interpolation reasonably good.

Can anyone compare the correlation and demodulation methods?

Further edit And, for those giving the demodulation method, am I right in thinking that if I don't care about the actual phase difference, just the power factor, then I can do this:

s = sin(t * 2 * pi * f)
c = sin(t * 2 * pi * f)
a_s_d = s * a
v_s_d = s * v
a_c_d = c * a
v_c_d = c * v
s_a = numpy.trapz(a_s_d, t)
c_a = numpy.trapz(a_c_d, t)
s_v = numpy.trapz(v_s_d, t)
c_v = numpy.trapz(v_c_d, t)
# cos ( a - b ) = cos a * cos b + sin a * sin b
power_factor = c_a * c_v + s_a * s_v

Or can I not rely on 0 < s_a, c_a, s_v, c_v < 1?


texts:
I have this driver. It has two MOSFETs and two complementary signals to drive them:

The load (a bunch of LEDs) sees 5 V or 0 V and, in average, they take a maximum of 100 mA.
However, the top MOSFET needs a driver signal that is not referenced to ground, which makes things a bit complicated.

I am looking for a similar driver that:

is simple (it does not have many components).
does not need floating signals (and ideally only one control signal).
does not have any big resistors in the 100 mA path to avoid losses (in voltage or in power)
is an all or nothing driver (5 V or 0 V), so the LEDs light up properly when they are ON.

I am open to any suggestions (with BJTs, with extra components to create the floating driver signal from the pins of the microcontroller, etc.).

Thank you for your help!


texts:
Calculating The  complex power of the 120 supply.
$$ S = V_{rms} \times I_{rms}^* $$
should I consider I negative since it's entering the negative terrminal?
I am really confused here!
so assuming $$i^* = 10 j \ \    S_{120} = - V \times i^* = - 120 (-j) \times 10 j = -1200 VA \angle 0 $$


texts: Flaky GPIO on ESP8266, how do I solve it?

texts:
I have an ESP8266 where I took one of the GPIO pins, configured the pullup on the input, then connected it to one lead of a 15m cable and the other lead to the ESP8266 ground.

The problem I have is that the input is flaky all the times, high/low. If I remove the leads to the cable, it's stable high. I measured the cable and with the leads connected together to one another, there's is a resistance of a 1.03 ohm. If the leads are not connected as they are 99.9% of the time, there is no resistance on the cable.

What am I doing wrong? How can I fix this issue?


texts: Asynchronous FIFO design with PULSE synchronizer

texts:
I'm trying to understand various implementations of asynchronous FIFO from the following link
https://inst.eecs.berkeley.edu/~cs150/sp10/Collections/Discussion/Honors/Honors14_1PP.pdf
In the slide 7 there's a proposal where pulse synchronizers are used for read and write signals which are the. This design doesn't work because if the reads and writes are high in successive cycles(burst transfer), pulse synchronizer output will only output one pulse in destination clock domain. Am I correct?
Suppose if I have a case where writes and reads are not continuous  but are separated by fixed 2-3 cycles will this design work? Will it have any further issues?


texts: Regarding PCB IFA microstrip antenna mirror image on ground plane hole areas

texts:
This is regarding the adjacent mirror image formed over the ground plane by a PCB antenna during operation. Take the first image of the IFA with the ground plane highlighted in yellow on layer 2, the top signal layer is hidden in the image. Say I have some through-hole components or vias to other layers which would punch holes in the second layer ground plane as shown.

Now take the second photo of the antenna image mirrored over the ground plane as it would be during operation. Do these holes in the ground plane where the mirror image is forming have any effect on the function or effectiveness of the antenna, or degrade the performance at all?


texts: What is derivative of FFT outputs with respect to time?

texts:
I am quite new Digital Signal Processing.I am trying to implement anti-cogging algortihm for my permanent magnet synchronous motor (=PMSM) control algortihm. I follow this documentation
I collected velocity data according to the rotation angle. I have 1024 bytes long sampling buffer. Each sample is stored when my rotation encoder gave a pulse, so each index actually means mechanical rotation angle. Each stored value is the velocity at related angle.
I transformed the collected samples to frequency domain with FFT. It's not clear to me what is my Fs (=sampling frequency). When I examined the frequency spectrum, dominant harmonics are related multiplies of 14 - 27 index numbers which is number of slot(27) and number of pp(14).
But the last step of the suggested method, Acceleration Based Waveform Analysis, need calculated derivative of FFT outputs with respect to time. Outputs are in frequency domain, so how could I calculate derivative of FFT outputs with respect to time and why does the method need this calculation?


texts:
I'm thinking of making a simple PCB with RJ45 connector delivering both data to the control MCU and power to the whole PCB using the PoE technology. I'd like to use a LM5071 as a power source and i.e. W5100 as a TCP/IP stack.
In all of the application notes and example projects for the LM5071, I can see all 4 wire pairs connected through diode rectifiers into the IC as a PoE+ and PoE-. I assume that this connection is there in order to support power distribution over both data and spare pairs.
Can I also connect all 8 wires to the W5100, even though I know that at least 4 of the wires will be used as a power source and will have high voltages? Or do I have to design the PCB for a fixed PoE switch configuration, i.e. data pairs will always contain data and will be connected to the W5100 and spare pair will always contain power and will be connected to the LM5071?
Also, how can I make this PCB 1Gb Ethernet ready (data and power sharing the same wires)? Will I need to use different IC for TCP/IP stack?
Thanks!


texts:
The L6203 states that it typically has and Rds(on) of about 0.3 ohm. After implementing the circuit below, I'm measuring a significant voltage drop across the transistors when the motor is stalled (or with increased current). The results correspond to a Rds(on) between 1.5 and 2 ohm. I'm using a supply voltage of 17 V.

This is much greater than the value indicated on the front page of the datasheet of 0.3 ohm. Furthermore, the device is labelled on the datasheet as being "High Efficiency". The only conclusion that I can make is that I may be missing something important. My problem/results are very similar to a previous post which was never fully resolved. I'm hoping someone could offer some new insight?

Edit

Here is some more data. The circuit is as shown above with a 1uF capacitor between Vs and gnd.

Load is a 5 ohm motor at stall
Supply voltage (after series multimeter measuring supply current) = 15.8V
EN = high
V_IN1 = 5V PWM at 80% duty
V_IN2 = gnd
Total current draw from supply = 1.6A
V_OUT1 = 1.8V
V_OUT2 = 9.6V
The chip is at room temperature for these measurements

If the load is removed then output waveform swings to the rails as expected. These results seem to indicate a much larger Rds(on) than 0.3 ohm as stated by the datasheet.


texts: How to get a Lipo to discharge at 3volts continuously

texts: So let me start off by saying I'm brand new at this, but I'd like to learn. I have a 3v Motor that I need to run. I want to create a way to use a rechargeable Lipo to run the motor. How can I keep a lipo battery discharging at 3volts continuously? If I am being to Vague let me know. I'll answer any questions you have. I'm also connecting the motor to a momentary switch. I want everything to be as safe as possible. Thank you again.


texts: Project development: control of a DC motor

texts:
Is it feasible to control a DC motor as it is described in the following picture?

What would be a possible application of this circuit? It is kind of tricky because the operational amplifier's current is feeding this machine, so I will either need a high power OpAmp or a low power DC motor, but I can't see a real life application of the latter.


texts: STM32 Digital Inputs allowed voltage range

texts:
I have an application where my STM32F0 is operating at 3.3V, I have some pins connected to a module which tries to talk to the STM32 first at 1.8V, then at 3.3V. I have configured all of the pins bar 1 as digital inputs, when I see that the pin I have configured as an analog input shows me that the bus voltage is 3.3V, I know I can now communicate with the module.
I have a colleague who is convinced that it is a bad idea to have 1.8V on the digital inputs, but I am not trying to read digital levels until the voltage on the interface is high enough.
Do you see any problems with having 1.8V on a digital 3.3V input? My colleague is convinced that the digital inputs can sync large current when the input is at this level, what is your opinion? I see no problem with the current setup


texts:
I have done some development with the ATMega and I'm looking to broaden my horizons.  I have a couple Cortex M4 series chips and would like make an ARM equivalent to the Breadboarduino

I plan to either etch my own board or use a breakout board for the ARM and breadboard the rest.  A reference or schematic of the minimum components would be greatly appreciated.

Are there any good resources for determining the minimum required components to operate, and ideally program, an ARM chip?

UPDATE:

I'm open to alternative hardware suggestions.  Below is the chip that I'm currently trying to work with:

STM32F407ZGT6
Datasheet


texts: How to remove the DC offset from the output of my op-amp integrator?

texts:
I am trying to simulate a active integrator for Rogowski coil based current sensing application. Following is  my circuit.
The current to be sensed is passed through the inductance L2 which is mutually coupled with the Rogowski Coil with coupling co-efficient 0.0192, which is passed through an active integrator circuit.
Following is the input and output.. As seen from the images, the input vary from 0-40A,but the output varies from -30mV to 20mV,I want it to vary from 0 to 50mV. How can that be done? What is the reason of this -30mv DC shift?
EDIT 1:- I have added the waveform of the input to the integrator for clarity.I(L1) is the current but which gets differentiated and scaled. So that (V(integin)) is an AC signal i.e it has an average value of 0V or no DC component
EDIT 2:- If I input a sinusoid, to the same integrator, I don't have a DC shift.Why is that happening?


texts: Implementing Integer Division in hardware

texts:
I am trying to figure out how to create an efficient way to divide 5 bit numbers in hardware (using registers, Shift Registers, Comparators, Muxes, basic logic
gates, bit shifters, bit extenders, and Subtractors).

I know i can just iteratively subtract the divisor from the dividend until the result is less than the dividend but that takes an unknown number of clock ticks. I am looking for a way to have the entire division done in 6 clock ticks (assuming the above circuits all do their job on a single tick).

I am having trouble getting started because the only methods i come up with use a looping method.

Any advice on how to approach this problem is greatly appreciated.


texts: Two active-low switches, delay between the two

texts:
I have two active low outputs, each with a 12V potential when opened.  I'd like to create a circuit where, after the a switch to the first input is grounded, there is a small delay (>= 500ms) and then the second output is grounded.
I feel like this should be possible with an RC circuit and a transistor, but my design skills are severely limited.  I have already tried such a circuit, wired as shown:


texts: Li-po Charging circuit question (switching between battery and power supply)

texts:
I'm building a circuit containing a Li-Po battery and a battery charging chip. I do understand the working of the chip, but don't really get how to switch the system load to a normal power supply while the battery is charging.

The datasheet provides the following diagram which I assumes works:

  (source: Microchip reference design DS51746A section 1.1)

The only thing is that I don't really know why it should work. I'd love to understand why it works. I guess that as soon as Vin is high it shuts the gate (Q1) from the Li-ion cell to the system load. And current goes to the system load from Vin directly via D1. But I don't really understand why it would shut Q1. It would be great if someone could give a brief explanation what happens with Q1, Rpull and D1 when Vin is High and Low.

The MCP73833 works as follows: When Vin is high, Vbat will be high and charge the Li-ion cell. (Vbat will be a bit lower than Vin). As soon as Vin will be low, Vbat (9,10) will be low and stop charging.


texts: STM32F4 How are Preemption Priorities and Sub-Priorities used?

texts:
I have started working with ARM-based microcontrollers.

I not understand subpriority and preeemptionpriority. For example:

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x00;
NVIC_InitStructure.NVIC_IRQChannelSubPriority        = 0x01;

Why would we use these?


texts: Mount SMD component raised 45 degree from board

texts:
My challenge is, how can mount a SMD component in a 45 degree angle raised from the PCB.

I am doing a temperature sensing device, which is intended to be mounted on a wall, hence the PCB will be parallel to the wall, but is going to measure the temeprature on the surface of the floor. The temperature sensor for this device is an IR sensor TMP007 from TI.

So what I need is a genius way on how can I mount the sensor, so it points towards the floor, with an angle between 45 and 60 degrees in relation to the PCB (0 degree will be mounted on the PCB) so it is pointing towards the floor.

The mounting method should preferably be suitable for mass production, so not something to labor intensive.

Hope some one have some good ideas or solutions.


texts: KiCad - Using a generic LQFP64 component in schematic to design an adapter

texts:
I want to make an LQFP64 adapter PCB so I can solder a microcontroller with through hole connectors. This is mainly for STM32 ARM Microcontrollers and I plan to use different versions of the same 32bit family (Cortex M0, M3, M4 etc).

However, it looks like there isn't a generic component in KiCad that I can use. I want all the pins on the component arranged sequentially, but that's not the case if I use a specific microcontroller component. The pins are arranged all over the place and it makes wiring sequentially rather difficult.

I'm hoping I don't have to create a generic component myself, it's a bit of a pain having to define and create 64 pins. Is there any other way to do this?

EDIT: Per DiBosco's suggestion, I ended up making a symbol from scratch in KiCad. Took me an hour to make it.


texts: How does one pass signals through instances in VHDL using hierarchical names possibly

texts:
I have some VHDL code written for synthesis with three instances in the top level and the three subs so I can pass inputs and outputs. Call them top, sub1, sub2, sub3. I now want to add a signal and use it as a flag across the top and all subs. For example.

signal  flag: std_logic_vector(3 downto 0):= "0000";

On each sub and the top page, I want to read/write to this signal so I can trouble shoot and start one subroutine after one sub is complete or other variations using the flag values. I can assign "flag" as a port and give it direction but it seems cumbersome. I then saw "hierarchical names" and I tried the following inside of top in my list of signals.

alias flag is
<< signal sub1 : std_logic_vector(3 downto 0)>>;

In sub1, sub2, sub3, I would have the following, from my understanding:

   signal  flag: std_logic_vector(3 downto 0);

I then get a syntax error near  "<" and ">". How do I get this to work? I am using VHDL-2008.


texts:
So I know the theory behind a bootstrap current source in power audio amplifier and understand its operating principle but some things remain uncertain to me.
First - how to divide the collector resistance in voltage amplification stage? I did run some simulations and it's clear, that $$ \frac{R_1}{R_2} $$ ratio actually matters.
When \$R_1>R_2\$:

Gain drops
Crossover distortion becomes apparent (despite the biasing)
voltage across \$R_2\$ is not stable so current from current source does not maintain its value very well (unstable current source)

When \$R_2>R_1\$:

Gain raises
Less distortion
Curernt source very stable

I don't understand why it happens. From the theoretical point of view, it should not matter which resistance is bigger.
Second - how to calculate the open loop gain after applying a bootstrap? Or perhaps I should ask - what's the actual value of collector resistance then? I need this to choose the correct value of \$R_{\text{in}}\$.
Here's the circuit: LINK

Quiescent current - \$3\text{mA}\$
Desired max power - \$5\text{W}\$
Input - \$1\text{V}_{\text{pp}}\$
Total collector resistance - \$3.6\text{k}\Omega\$


texts:
I'm attempting to build a system to help my Father-in-law monitor the power to his house.  Here's the details of his problem: He lives in the woods where power is somewhat unreliable so he has a whole house generator.  He travels frequently and he'd like a system to let him know when he's A) lost external power to the house B) lost external power and is on generator power and C) lost generator power.

My current solution which detects B and C: an arduino Uno with a Adafruit PowerBoost 1000 and a Adafruit Fona 808.  The PowerBoost is connected to an outlet with on Generator power, so I can monitor whether my device has AC power and whether it's on battery power.  I use the Fona for notification via SMS.

My initial configuration to detect A was to put a simple 5VDC A/C Adapter into an outlet that wasn't on the Generator circuit and have that power a relay.  If the relay contact is closed, I have external AC power.  I'm concerned about the reliability of a relay being closed for several days/months/years at a time... is my concern valid?  Is there a simple/more elegant solution to this part?


texts:
Common sense says that you don't wave solder batteries, because the wave would short them for seconds. Yet in this appnote I read

  Primary lithium cells may be wave soldered as long as the cell temperature does not exceed +85°C. Cells may be placed in a holder or hand soldered after reflow (tabbed cells).

The first sentence seems to suggest that it's OK to wave solder batteries. Do I read this correctly, and doesn't the battery suffer from the shorting?


texts: What's a good substitute for the TD62783AFNG?

texts:
According to its datasheet, the TD62783AFNG is an 8-channel high-voltage high source-current driver. It is a Darlington arrangement that can source (not sink) up to half an amp through a pin. What similar chips are available?

http://www.semicon.toshiba.co.jp/docs/datasheet/en/LinearIC/TD62783AFNG_en_datasheet_091116.pdf


texts: Thermal impedance too high for proper use

texts:
I'm not sure to correctly understand the datasheet of Traco THN24 family.
I read this:

  Thermal impedance – Natural convection 17.6°C/W

but the DCDC is rated for 20W without de-rating (100% output power) at ambient temperature of 60 °C with natural convection and without heatsink.

This makes no sense for me, because the temperature should rise up to 20W * 17.6 °C/W = 352 °C!

Of course I'm wrong, otherwise the product cannot be used at the specified power.
Where is my mistake?


texts: Change selected lines between layers in kicad

texts:
I have a very complex board profile in DXF format that I was able to import into pcbnew version 5. Now I have every line loaded on a single layer dwgs.User, I can move all of them to edge.Cuts by using Edit -> Move and swap layer, but how can I move only selected lines to margin layer for example? I know I can edit line by line and select its new layer, but as I've said it's a very complex profile with many line to be moved to margin, f.cu, b.cu and f.fab, so moving selected groups would be much easier since I have up to 5 variations of this board (in DXF), to convert to a kicad's template.

Will be happy with any tip!


texts:
I want to detect when a car horn is pressed. The only way I can detect it currently is using the voltage on its line.
When the car is turned on, there is always 12V being supplied to the horn through the battery i.e. When the horn is NOT being used the voltage to it is 12V.

When the horn is being used the line voltage drops between 2V-1V due to the consumption by the horn.
I was thinking of using the High/Low voltage detect module of the pic 18f4520 to detect this voltage drop when the horn is pressed. But the module seems to be more for detecting a drop in operational voltage. Is there a downside to using the HLDV in such a manner, also is there a better/other way to do this? Any code snippets to HLVD or other methods are greatly appreciated.

Thank you for your time and have a great day.


texts: Can conformal coating help against high-temperature environments if the chips heat up as well?

texts:
I have seen many claims of conformal coating helping for protection against, amongst many other things, extreme temperature.
One such claim in here would be: Question regarding PCB coating

My understanding is that such coatings act as a relatively good thermal insulator; is that right?
What I do not understand, however, is how they can be effective when the components themselves need to dissipate heat?

We use heat sinks with good thermal conductivity and large surface area to ensure heat can dissipate quickly, so long as the environment's temperature is lower. And if the environment is warm, then I can see how coatings could help insulate the board from the environment.

I'm probably missing something obvious, but how about conditions where we expect the environment and electronic component to warm up beyond its specified operating temperature limits?

In my specific scenario, I'm looking at PIC32MZ, probably the extended temperature range (-40 to 125 deg C), and thinking of having a system-level operation range that gets to about 110 deg C, and want a good tolerance margin. I could also do with using the industrial version of PCB components if I can get away with it.


texts: In Fig 1 of Simple CMOS Analog Square-Rooting and Squaring Circuits , Why would the lower transistor Q1 guaranteed to be in triode operating region ?


texts: Need to have two volume levels for a magnetic transducer buzzer

texts:
I am using an ATMEGA328PB TQFP and the  Arduino IDE to activate a magnetic transducer buzzer (CUI CSS-14B20-SMT-TR).  I'm using the Arduino Tone Library to produce 3 short beeps and then a 1 second pause, then repeats.  I need the volume of these beeps to increase to, and remain at, a second volume level after approximately  10 seconds.

I only have one pin available, so cannot activate a second circuit with a second pin.  Using ATMEGA328PB pin 25 (Arduino pin 16/A2).

Is there a circuit I could add to connect to a lower resistance path after a designated time or number of Tone commands, thereby increasing volume?  Looking around, could it be a resistor, capacitor, transistor circuit?  Or a 555 timer?  Not sure if these would work considering the beep signal is not a steady "on" signal that could charge a cap, or trigger a 555 (or could it), but square waves that turn on and off.
Is there a way to control volume in software using Duty Cycle and the Tone command?

Here is the schematic:

Here is the Arduino Code, which works for 1 volume.

int Speaker = 16;
unsigned long beep_previousMillis = 0;
unsigned long currentMillis=0;
int BuzzerState = LOW;
int Short_beep_count = 0;

void setup() {

pinMode(Speaker, OUTPUT);
}

void loop() {

  beep();   // call beep function
  }

void beep()
{
  const long LongInterval = 800;
  const long ShortInterval = 75;
  int Time;

//Short Delay
currentMillis = millis();
  if ((currentMillis - beep_previousMillis >= ShortInterval) && Short_beep_count <4)
 {
     if ((BuzzerState == HIGH) && (Short_beep_count < 4))
      {
        BuzzerState = LOW;
        noTone(Speaker);
        currentMillis = millis();
        beep_previousMillis = currentMillis;
        Short_beep_count = Short_beep_count +1; //counting LOWs
      }

    else {
          BuzzerState = HIGH;
          tone(Speaker,2730);
          currentMillis = millis();
          beep_previousMillis = currentMillis;
          }
 }

//Long Delay
if ((currentMillis - beep_previousMillis >= LongInterval) &&  Short_beep_count >=4)
 {
        if(Short_beep_count >= 4)
         { Short_beep_count = 0;
         }
        BuzzerState = HIGH;
        tone(Speaker,2730);
        currentMillis = millis();
        beep_previousMillis = currentMillis;
  }
}


texts: How to tell if an electronic component is counterfeit?

texts: I've been looking into sites (like Alibaba, etc...) for components, but they are usually at the price of the rain. How can someone know if a company or factory is not a scam and that those components really belong to said factory?


texts:
I am making an electric 4x4 car, will it make a difference in overall speed if:
Case1: all 4 motors are high torque and relatively low rpm
Case2: 2 high torque relatively low rpm and 2 high rpm relatively low torque

if Case2 will provide better speed, how much? (no numbers, i mean to what extent? (what will it depend on?))
i know high enough torque and high rpm will be faster, but i can't afford it


texts:
I am new to making circuits. What I am trying to do is get +-20V to be readable by an arduino. I found this circuit:

and got it to work. It scales +-6V to 0V - 5V. The problem I am having is changing the range from +-6V to +-20V. It seems like all I would have to do is change the resistor values, but I don't know how to approach finding them. Also I don't want to just know the values, but I want to learn how to find the values in other cases and for other circuits.

Thanks


texts:
I am trying to implement a non-inverting operational amplifier circuit; essentially, to double the potential difference of a shunt using the differential amplifying effects of the op-amp, so that I may be able to measure current through it without blowing an ammeter.  The schematic I am referencing is:

The following is my attempt at its implementation on the breadboard:

As can be seen on the multimeter, the circuit does not function correctly.  Can someone help?


texts:
I have read that ramp means slope
but what is the meaning of "ramp time" ?

For example,if we have a saw-tooth wave,what will be its ramp time?

Please kindly explain with figure/graphics


texts: VDDA / VSSA - how do LC filters isolate the input pins to minimize error and noise

texts:
I am trying to design a PCB with LPC4088 microcontroller which needs digital power supply VDD/VSS and analog power supply VDDA/VSSA. I had no problem with understanding how to connect digital power supply pins to a regulator and add some decoupling capacitors which work like RC filters that increase stability (I discussed this in my other thread). But understanding how to connect the analog power supply pins is on a new level.

In the LPC4088 datasheet I found descriptions for analog power pins:

What I understand here is that:

VDDA needs to have same voltage as VDD
VSSA needs to have same voltage as VSS

But what I don't understand is:

How can we isolate the VDDA from VDD and VSSA from VSS if they need to have same voltage? Doesn't this mean they are connected? The only thing that came to my mind was to use two identical regulators to supply digital and analog pins separately. But according to this thread it turns out this might not be the best solution because:

  Separate regulators aren't a good idea. They won't have the exact same
  start-up and shut-down characteristics, so during those times, there
  will be a significant voltage difference between the analogue and
  digital supplies on the chip. Depending on how the chip is designed,
  these differences might cause substantial current to flow through the
  die, which in turn can destroy the chip.

I don't understand how exactly noise and error is minimised. I saw that engineers solve this by connecting VDDA to VDD and VSSA to VSS through LC circuits or they sometimes use ferrite beads in place of inductors. This is one of the cases:

And another one:

I learned that LC circuits work like a resonator which resonates at certain frequencies. It looks like they don't even work like filters which remove noise and error but they even magnify it. Why would we do this? I am sure this is not what we are doing here... Could anyone explain to me what is being done here and how we need to choose LC circuit parameters in order to suppress noise and error?


texts:
This op amp circuit is used to offset stepped-down AC voltage by 2.5V(approx), so that the RMS of the voltage can be calculated. I can not change the configuration of the circuit, so that is ruled out.

This looks like a differential configuration, but i have not been able to understand certain decisions:

Why the 2.5V DC offset is fed into using a 10Kohm resistor and why there is a 1Kohm following it.
Why the + and - input of the op am p has this 1Kohm across it.
Why go to the trouble of adding the resistor network consisting of 4.7K and 100K when the AC is stepped down to 5V RMS.
Whether the AC source must be connected to ground or not. (Connecting and disconnecting gives different results).

UPDATE: I noticed something fishy today. When i ramp up the frequency to 50Hz, the mains frequency in India, i see that the Voltage at both the points are equal in magnitude and in DIRECTION! Isn't that 0V across the VSINE then? This happens only when the op amp is connected with the DC offset. When i remove the op amp and DC offset, the voltages are equal in magnitude and opposite in polarity. Is this because of the negative feedback; removing the negative feedback also gives similar results but lower magnitude voltages. See picture.

I confirmed that the resistor network before the op amp was only to bring the voltage down. See picture.


texts:
I am initializing my differential pairs in my schematic.
I have a RMII port and i can't find information on which signals are differential pairs.

Maybe IND*, OUTD*, NON?

Here are my signals :

Thank you for your help


texts: What does "point mode" and "track mode" mean for a closed loop stepper motor

texts:
I have this closed loop stepper motor and driver bundle:
https://www.omc-stepperonline.com/closed-loop-stepper-kit/ye-series-1-axis-closed-loop-stepper-cnc-kit-2-0-nm-283-28oz-in-nema-23-motor-and-driver.html
Driver Data sheet (Not very descriptive):
https://www.omc-stepperonline.com/download/Y-serie-closed-loop-driver.pdf
Q1: The driver has an option of "point mode" vs "track mode", what do these mean? The datasheet doesn't mention these anywhere.
Q2: Also, for bonus points, which one is better?
Q3: For extra bonus points, is step/direction mode or CW/CCW mode better in general?
I'd be very grateful for any help.
Edit:
I failed to find anything online explaining this. My initial guess was that "point mode" corrected missing steps at the end of the commanded movement and "track mode" corrected missing steps throughout the movement.
Edit 2:
From testing the device it and listening to the noise it makes when moving I've found that I think it meets my guess, 'track mode' produces intermittent louder steps throughout the commanded move which I assume is it trying to correct the steps as they happen. 'Point mode' moves quietly to the destination and then has some louder steps at the end of the commanded move which I assume is it compensating for lost steps. I will post this and other info as an answer below.
Edit 3: Cropped driver picture


texts:
I am installing a Ring door bell.  At the old intercom I have 50VAC currently (NO other source).  According to the manufacturer I need between 8VAC and 24VAC.  My question is what resistance (resisters) would I need to reduce the voltage?

The input is 50vac, I can NOT get a source of 120vac. Could I go with a regulator that has a steady 12vac output instead?  Just not sure it can take the 50VAC input. I am located in California.

Thanks!!!


texts:
I've recently got myself a bus pirate to read an EEPROM which is labelled fm24c32a since that's the only thing I could recognize on the board (the IC was covered by a blob). I managed to identify a little more than half the pins on the IC (LCD, Antenna, EEPROM, CLOCK, VCC, GND) out of the 100 pins but I don't know if there is a way to find the IC back with this information only.

So as I was stuck with this I moved to another circuit which uses RFID and has a chip on board (yay...) and two other components : One unlabeled (no text on it, 8 pins, 6 pins soldered) and another (8 pins) one with this text:

emsfic
814100A
2G

This labeled module is linked to the RFID antenna but I can't find any datasheet.

So my question is how do you go about identifying an unknown component or one with label on it (I didn't manage to find anything about the emsfic component on the Internet).

And specifically what is this emsfic component above and how do you go about identifying component because I can't seem to find anything useful.

Thanks in advance and sorry for the noob question...

Edit : Turns out after unsoldering the unlabeled 8 pins chip, it is labeled on the bottom side of the chip as follow :

DT1502
1?081 (? could be a 1 or T)
FC05061 0E

Also from a PDF i read on the internet this is most likely an SPI Flash chip since its layed out this way :

    ---- VCC
    -  -
    -  -
GND ----

I've tried doing an I2C scan but no address was found. Under the unsoldered chip was written P15.

But once again i couldn't find anything with this info so idk what im doing wrong :/

Here is a picture of the second board :


texts: when does the neutral wire in a 3 phase system carry voltage?

texts:
I am curious, and I've found a bit of information online, but maybe its not clicking in my head... when does the neutral line in a 3 phase system carry voltage.

i do understand the answer is quite simple (When the legs are unbalanced) but for whatever reason, its not making sense to me.

why is it important that the loads are balanced on all legs?


texts: Can a potato battery charge a capacitor?

texts:
If it can, what kind would I get?  Two potatoes if that helps.  I know you have to have a fair amount of potatoes to power an LED, so outside of having eight potatoes wired up, I thought maybe two could charge a capacitor.

I thought if I could charge a capacitor with a potato or two, then I could let the capacitor charge up and light the LED, since a continuous flow from a couple of potatoes isn't enough to power the LED alone (I have to have a bunch of taters for that.)


texts: How to reach ultra low power on STM32Lxx?

texts:
I'm having some problem reaching the said ultra-low power available for the STM32Lxx series. With no active register, the UC should consume around 10 uA, but I can't get it down from 1 mA. The datasheet says to first reduce the frequency, then the core voltage then enter the ultra low power mode as one can no longer program it.

The lines I use to enter the lower power mode are :

RCC_MSICmd(ENABLE); % Activate the Multi-speed internal clock
RCC_MSIRangeConfig(RCC_MSIRange_0); % Reduce to 32 kHz the Multi-speed internal clock
RCC_SYSCLKConfig(RCC_SYSCLKSource_MSI); % The system clock that will be used is the MSI clock.
RCC_HCLKConfig(RCC_SYSCLK_Div512);  % Reduce furthermore the clock frequency
RCC_PCLK1Config(RCC_HCLK_Div16); % Reduce furthermore the clock frequency
PWR_VoltageScalingConfig(PWR_CR_VOS); % Reduce the core voltage
PWR_EnterLowPowerRunMode(ENABLE); % Enter the low power run mode

I'd be very grateful if someone could point me the mistake I am doing.


texts: Why doesn't my latch work (schematic attached)?

texts:
I tried to make a simple latch with a PNP transistor and a MOSFET.  The idea is that initially it is off, when you press the button it turns on and stays on.

But it doesn't stay on.

Here is the circuit:

I've tried it with both 12v and 5v, it doesn't work.

I also tried increasing the pullup and pulldown resistors R1 and R4 to 4.7K, in which case the LED is initially on.  (Not sure why!)

I attached a picture of the actual implementation, I don't know how much you can make out from it but here it is:


texts:
I am using an L293DD Dual H-Bridge IC to power my DC motors. I have realized I am using inadequate heatsinks, and 1,5 times the nominal maximum current(1,8A instead of 1,2A), but the circuit is working.

The datasheet says, that this IC has overtemperature protection, but doesn't mention exact data.

My question is, can I rely on its overtemperature protection? I don't mind if the IC shuts down, when I overdrive it, but when it cools down, it should start working again.

Note: This is a prototype, I know its horrible practice, Still I want to know what can I expect, perhaps understand what is going on in more depth.


texts: Small signal equivalent circuit - MOSFET

texts:
Let's consider the following amplifier circuit:

Now, if we would analyze small signal operation, we could represent the circuit with small signal equivalent:

The part that bothers me is the PMOS representation in my workbook. Shouldn't the voltage controlled current source of the PMOS transistor (index 2 in the drawing) be rotated so that the current goes from its source to drain?


texts: ZigBee vs WiFi for wireless communication

texts:
I've been working on a product using WiFi. The reason I picked WiFi, is cause I essentially have 20-30 nodes communicating to a main node via a router. This all works very well, and its easy as its simple TCP/IP requests.

However,the nodes sometimes get submerged in water and when they do, the node quickly loses connection, and takes a long time to connect back to the network (5-10). Additionally, the devices communicate via HTTP requests, and the latency of the communication isn't the greatest.

I've recently started exploring Zigbee as an alternative. However, I can't find any information around node reconnect times, power usage, and communication latency. Does anybody have any information they would like to share? Also, does it automatically work in a star network?

I'm not particularly married to Zigbee either. If there are other modules/protocols/frequencies I should consider - I'd love to hear them. I essentially want something with which I'd be able to replace my WiFi communications stack quickly, and isn't a huge power hog.

If its any help, I'm using the Atmega1284P as my microcontroller.


texts: Error in simulating bdf with Waveform.vwf.vht, but bdf compiles successfully

texts:
I am trying to design an instruction register and controller for an ALU that I designed previously.  I made the register with 2 muxes and 2 D flip-flops, and I made the controller with a T flip-flop and a part I programmed in VHDL.  Both the BDF and the VHDL file compile successfully; however, when I try to run a simulation with Quartus's University Program VWF, I always get errors that prevent the simulation.  I've run a lot of simulations for other projects, and I've never had this issue before.  Any help would be appreciated.  Here's my VHDL code:

    library ieee; use ieee.std_logic_1164.all;
    entity Controller is port(
        S: in std_logic;
        IR: in std_logic_vector (1 downto 0);
        IR_LD: out std_logic;
        MSA: out std_logic_vector (1 downto 0);
        MSB: out std_logic_vector (1 downto 0);
        MSC: out std_logic_vector (2 downto 0)
    );
    end Controller;
    architecture behavior of Controller is
    begin
        IR_LD <=
                (NOT S);
        MSC(2) <=
                (S AND IR(1));
        MSC(1) <=
                (S AND IR(1) AND IR(0));
        MSC(0) <=
                (S AND IR(1));
        MSB(1) <=
                ((NOT S) OR IR(1) OR IR(0));
        MSB(0) <=
                (S AND (NOT IR(1)) AND (NOT IR(0)));
        MSA(1) <=
                (S AND IR(1));
        MSA(0) <=
                ((NOT S) OR IR(1) OR (NOT IR(0)));
    end behavior;

Here are screenshots of my BDF:

Here's a screenshot of the vwf file:

And here's a screenshot of the part of the Simulation Flow Progress report where the errors occur:

The errors read as follows:

  ** Error: Waveform.vwf.vht(39): near "In": (vcom-1576) expecting IDENTIFIER.

  ** Error: Waveform.vwf.vht(41): near "Out": (vcom-1576) expecting IDENTIFIER.

  ** Error: Waveform.vwf.vht(63): near "In": syntax error

  ** Error: Waveform.vwf.vht(71): Statement cannot be labeled.

  ** Error: Waveform.vwf.vht(89): near "t_prcs_": Identifier may not end with >an underline.

  ** Error: Waveform.vwf.vht(89): near "\In\": (vcom-1576) expecting == or '+' >or '-' or '&'.

  ** Error: Waveform.vwf.vht(89): near "3:": (vcom-111) No digits found in >mantissa part of based literal.

  ** Error: Waveform.vwf.vht(89): near "3: ": (vcom-113) Mantissa part of based >integer literal terminates with ' '; should be ':'.

  ** Error: Waveform.vwf.vht(92): Illegal concurrent statement.

  ** Error: Waveform.vwf.vht(93): near "In": syntax error

  ** Error: Waveform.vwf.vht(94): Illegal concurrent statement.

  ** Error: Waveform.vwf.vht(95): near "In": syntax error

  ** Error: Waveform.vwf.vht(96): Illegal concurrent statement.

  ** Error: Waveform.vwf.vht(97): near "PROCESS": (vcom-1576) expecting ';'.

  End time: 19:21:31 on Jul 23,2019, Elapsed time: 0:00:00

  Errors: 14, Warnings: 0

  ** Error: c:/intelfpga_lite/18.1/modelsim_ase/win32aloem/vcom failed.

  Executing ONERROR command at macro ./LAB6_Part1.do line 4


texts: Need help interfacing an ADC with a pressure transducer

texts:
I am trying to connect a pressure transducer which gives a 4- 20mA current output to an ADC which I believe can only take voltage inputs. How will I be able to read a current output from the ADC? Do I need to change the way it is connected or do I need to purchase a new ADC or a sensor? Any advice would be appreciated.

Link to ADC used: https://www.analog.com/media/en/technical-documentation/data-sheets/AD7606B.pdf

Link to pressure sensor used: https://www.pmc1.com/Customer-Content/www/Products/Files/ATM.1st.T.705a.pdf


texts: Rubber insides and circuit transparent sheets of USB keyboard don't work outside of plastic case

texts:
I have very little knowledge of electronics and circuits, so I apologize in advance if the question is dumb. I couldn't find answer anywhere.

I am trying to remove plastic part of my keyboard and have it be only that white rubber part on the inside with those transparent circuit sheets.  Reasons are I can't see which letter is where, so I wanted to challenge myself in a weird way and second was that it feels nicer.

I disassembled my keyboard and I saw those pins on microcontroller, and found a datasheet for it. I thought that the microcontroller (on one side green on other brownish board) sends current through that transparrent circuit sheet and checks if there is a pressed key. With that in mind I put the sheets with rubber keys over it on my wooden desk and placed microcontroller over the pins the exact same way as it was in the keyboard. Problem is, it does not work, numlock led diode is still lit on, but it won't change when I press the numlock key.

EDIT
My phone camera died few days ago, so I found few photos online that could better explain it:

I wanted to have these parts inside of keyboard without black plastic around them sitting on my desk.

Questions:

Is it possible for current to go through those circuits if I change black plastic for wooden table?
Do the little pins (on picture bottom left on keyboard) that connect to microcontroller have to be on certain surface or is wood fine for them too?

Desk:


texts: Difference between and meaning of VSS & VDDS

texts:
I am working on a small project that involves BGA's. It has a section of VSS and VDDS pins. The device is an AM437x Sitara.

My assumption is, VSS is + and VDDS is ground; would I be correct in thinking so?


texts:
I think I know how to solve this, but I'm not sure about passive sign convention. Let me run though my reasoning.

We are told that the capacitor has no initial energy, so I can assume
that V0 in the capacitor voltage equation is 0.
Since the terminal voltage=0, V(capacitor)=Vd,    where V(capacitor) = (1/C) [integral][i(t)] + 0
By inspection, i(t) = 1/125k = 8E-8 amps
From all of this, I calculate that the initial voltage at t=>infinity
is 8v.
I can reuse the capacitor voltage equation, integrating from 0 to t
and subbing in the dc biases (+20v, -10v) for V(capacitor) to find a
t where the op amp is about to saturate.

I think that's how I solve the circuit(correct me if I'm wrong).

My question is, between the 2 time intervals (before and after the switch moves), I think passive sign convention necessitates a negative sign in the capacitor voltage equation in the second half, and no negative in the first half, because of the new voltage source. Is that right? Or am I forgetting something?

Like this:

t=20ms-: V(cap)= + (1/C) [integral][i(t)] +V0
Versus
t=20ms+: V(cap)= - (1/C) [integral][i(t)] +V0

If my guess is right and there is a negative sign in the second half, I find that t= -.03, .0045s. So that would mean that the Op amp never saturates. Would that be right?


texts: Using MCU to supply SPI signals to amplifier chip

texts:
I'm working with an amplifier chip (slave mode) that is currently receiving the SPI commands through an SPI cable connected to an FPGA board (master mode). I'm looking into making the chip operate on a wireless platform and being independent of the FPGA, and also have power and size/weight limitations so am trying to make the device as small as possible. Essentially what I'm looking for is an MCU that could be used to substitute for the FPGA board and supply the required SPI signals (CS+, SCLK+, MOSI+) to make the chip continously run and put data out through MISO+ (which doesn't need to be processed by the MCU as it would be processed elsewhere) The chip carries out 16 bit ADC, with the min SCLK period being 40.8 ns (24 MHz) depending on the sampling rate. The chip samples MOSI+ on the rising edge of SCLK.

Since I'm relatively new to microelectronics I was wondering what the most efficient way of doing this would be, and what would be the best MCU (or a small low power FPGA?) to carry out this task?

So far the two MCUs that I have been thinking about are:

CC2650 SimpleLink™ Multistandard Wireless
nRF52832 Advanced performance Bluetooth5/ANT/2.4GHz proprietary
SoC

EDIT:

I was hoping the MCU could be programmed to send the commands down the MOSI+ line, which would include: setting 18 16-bit registers of the chip at power-up, send a 16 bit command to calibrate the chip, and send the convert command to start carrying out the ADC (continue cycling through the channels of the chip as long as it is powered). The wireless capabilities of the MCU would only really be used to turn on/off the slave chip.   Since the chip carries out 16 bit ADC, and reads 16 bit commands SCLK is pulsed 16 times when CS is pulled low. MISO+ from the slave chip is sent elsewhere to be sent off-board (to a device that only requires the raw bit stream coming out from MISO+), so the MCU wouldn't have to process it.

Since the chip requires 16-bit words to operate, wouldn't it need at least a 16-bit uC to control it?

Noticed that just cause an uC runs at a certain frequency doesn't mean it can provide SPI signals at that same frequency. For example from what I gathered about the TI CC2650 if it is set as an SPI master, the max SPI bitstream is 12 Mhz even though the MCU itself runs at 48 Mhz. Is there normally a correlation between how the base clock of the MCU relates to what SPI frequencies it can provide?

Thank you in advance,


texts: Designing lookup table(LUT) for half adder in FPGA

texts:
I want to implement half adder using FPGA. For this I need to design CLB, more specifically LUT for half adder. I know LUT gives only one output. But, for half adder we get two output. One for sum and other for carry.
How can I design CLB for half adder?
How can I get two output from LUT? What I am doing wrong?

From study what I understood about FPGA is, This image represent building block of FPGA which is CLB. CLB consists of LUT, D-Flipflop and MUX.
LUT is used to configure any type of logic gates. AND, OR, NOT or any other complex logic gate. By using program we store output of truth table for say AND gate in LUT. And while we give input to FPGA it goes through LUT via address bar and access specific memory address in LUT. And then output of LUT goes through two paths. Here, we need to choose whether we want our output through combinational circuit or sequential circuit. We use MUX for this selecting purpose. 0 for combinational circuit and 1 for sequential circuit.
Am I correct What I understood so far?
When we need to choose sequential circuit and combinational circuit?


texts:
I managed to make variable voltage and current for dummy load using IGBT with PWM control from Arduino, I plan to use the output as a variable power supply. The output from IGBT is a square wave so I plan to use lLC low pass filter from IGBT output to make it pure DC.

How to determine/calculate the spec of inductor and capacitor for up to 100A usage? I tried to simulate with Multisim and tried different values and get 10mH and 4700uF. Is there any issue to apply this?

I found a shop that can make custom inductors, I just need to enter the value of inductance and current and it lists several types with different turns and resistances but same inductance and ampere. I'm not sure with the physical size, it states really small, is the spec legit?


texts:
I'm trying to make a display out of 2811 LEDs from China (15 meters long x 7 LED strips). Each strip consumes 18W@5V(3.6A) per meter and I plan to use 7 strips, each 15m long. My calculations show we'll need a 5V power supply capable of producing ~460A...

(15 meters * 18 watts per meter * 7 strands of LEDs / 0.8 power supply efficiency) ~= 2300W @5V ~>460A.

I was planning on purchasing a 600A 5V power supply, running a power bus behind the LEDs and tack it to the strips every 2 meters to ensure even power distribution, but when I tried to calculate necessary wire gauge online, all the calculators say values "out of Bounds" suggesting that the cable needed would be too large. Would I really need to have a separate power bus for each strip?

How do we make this work? :-/ We're installing the LEDs between two elevators so it's not like we can hide power supplies in the middle. It would have to be at either end of the 15m runs...

Any crazy suggestions would be appreciated.


texts:
I am pulsing the VDD with 50% duty cycle at a frequency of 188 Hz (PWM).
I get some weird spikes on my output TP3. Am I missing something about phototransistors?

Here is the picture of the IR circuit and the output from TP3:

Here is the circuit of the PWM output and how it looks:


texts: Impedance matching audio transformer windings

texts:
I want to create an isolation, impedance matching, balancing transformer for a DI box.
I want it to work on Audio frequency and use a toroidal ferrite core.

The input is an electric guitar, so it needs 1M Ohm input impedance.
The output is a line-in so it needs about 2k Ohm impedance.

I attempted to calculate the required turns using this, but I am baffled as it seems that only the ratio matters.

If it indeed is so, how many turns should I use? What determines the frequency range of the transformer?

If I am wrong(probably I am), then please explain how exactly.


texts: Good compact antenna for FM audio transmitter module?

texts:
I've been looking at building a short range FM transmitter using this module, the idea is to create a small module that I can integrate into other projects. I'd prefer having the antenna on the same PCB using a trace or chip antenna, would this be reliable considering the low power output of the unit? (I'm hoping to get at least a 20m range)

If so I'd appreciate any suggestions for this antenna.


texts:
I want to design amplifier in 20kHz - 200 kHz range. I have designed following circuit using  BC547 transistor.

I have set VCE voltage to 6v and set  Q point to the middle of the load line. But when I supply  20 kHz    200mv peak to peak sinusoidal signal, the output signal shape in two half cycles are not identical.

How can I solve this problem?


texts: Transistors basic question, Voltage is confusing me

texts:
you can't go sticking a voltage across the base-emitter terminals,
  because an enormous current will flow if the base is more positive
  than the emitter by more than about 0.6 to 0.8 volt.

Base being more positive, is it saying that base has more holes ? And what does it mean that base is 0.6 volt more positive ? It also says: Vb= Ve+Vbe, the concept of voltage is really bothering me here, is this equation saying the voltage needed across base for current to flow throught it is equal to voltage across emitter plus the voltage drop from base to emitter ? What does this even mean ? These are probably very dumb questions but I'm really frustrated because anything I have read for the past 10 hours won't explain it in a more basic way.


texts:
10x bidirectional diodes 1.5KE400CA in series, balanced, then the chain in parallel for DC line protection. Breakdown voltage 400V per diode. Still got 10kV+ voltage spikes (picture below, x100000 attenuation). Why?

Edit:

Pulse shape and duration varies greatly (another example pictured below).
Rise time for the first oscillation: 10-20 ns.
Estimated inductance: ~20 uH.

The negative peak is timed at 8 us, way over the clamping voltage (7kV peak and 4kV clamping voltage) and TVS diodes still not conducting.

Edit 2:
Equivalent circuit pictured below. D3 undergoes catastrophic failure on higher voltages. (Scope readings shown here ~ 300V; real working conditions ~3kV)

Edit 3:
Equivalent circuit, measurements by precision shunt.

Edit 4:
Hardware set-up. Power electronics module.


texts: What is a good circuit model for an AC generator?

texts:
A very simple electrical AC generator can be made by spinning magnets around a fixed stator coil. The changing magnetic field induces current in the stator winding.
It would seem that at a fixed frequency, this system is best modeled as a current source with some series resistance and inductance. Is this a good model?
If so, it would suggest that the behavior of the system in an open-circuit scenario would be to generate a very high voltage at the output pins with zero current flow. Conversely, in a short circuit scenario, it would run a fixed amount of current through the loop which would be dissipated as heat in the series resistance (stator wires).


texts: Carrying out multiple synchronous tasks with a micrcontroller

texts:
I am making a robot which has several mechanisms on board. To keep things simple, let us say it has 2 DC motors, and 2 servos. Most of the time, the servos are not doing anything, and the 2 DC motors are moving in the same direction (using an L239D motor driver). This is using an AVR MCU by the way (likely an ATmega 328). The motors use PWM signals.

So suppose I send a command to turn one motor CW, the other CCW, and actuate the two servos. I need this to all happen at the same time. So how does this work?

If something like threading exists, I would create one thread for the motors, one thread for one servo, and another for the second servo so that they all go off and do their thing at the same time. But I don't think threading exists, or is common at least.

So how would I run multiple commands at the same time?


texts:
I have a problem while trying to do a Delay on a PIC16LF1823. My program tries to toggle some bits on PORTC for 30ms. I did a simple Delay based on the decrement of a variable; however, each time the PIC execute the Delay it gets stuck on the Delay subroutine forever. I have tried everything and I traced the problem to the DECFSZ instruction (If it is removed the bits toggle without the delay and the program executes normally). Is this a known issue? Or, Am I doing something wrong?
My configuration: 31kHz Internal Oscillator. Using MPLAB X and MPASM v5.46.
I hope anyone can point me in the right direction; I have been trying to fix this for a week now.
Thanks,
Here's my code:

    INCLUDE "P16F1823.inc"

; CONFIG1
__CONFIG _CONFIG1, _FOSC_INTOSC & _WDTE_NSLEEP & _PWRTE_OFF & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_OFF & _FCMEN_OFF
; CONFIG2
__CONFIG _CONFIG2, _WRT_OFF & _PLLEN_OFF & _STVREN_ON & _BORV_LO & _LVP_ON

org 0x00
GOTO Start
org 0x04
GOTO Interrupt

#Define LCK 0x01
#Define LTC 0x04
#Define RLS 0x05

IOA EQU B'00000011'
IOC EQU B'00000000'
IOP EQU B'00000011'
ION EQU B'00000010'
INT EQU B'10001000'
OSC EQU B'00000000'
OPT EQU B'11010000'

CBLOCK
d1
ENDC

;;;;;;;;;;;;;;;;;;
;;INITIALIZATION;;
;;;;;;;;;;;;;;;;;;
Start
BANKSEL PORTA
CLRF PORTA
BANKSEL LATA
CLRF LATA
BANKSEL ANSELA
CLRF ANSELA
BANKSEL TRISA
MOVLW IOA
MOVWF TRISA

BANKSEL PORTC
CLRF PORTC
BANKSEL LATC
CLRF LATC
BANKSEL ANSELC
CLRF ANSELC
BANKSEL TRISC
MOVLW IOC
MOVWF TRISC

BANKSEL OSCCON
MOVLW OSC
MOVWF OSCCON

BANKSEL OPTION_REG
MOVLW OPT
MOVWF OPTION_REG

BANKSEL INTCON
MOVLW INT
MOVWF INTCON
BANKSEL IOCAP
MOVLW IOP
MOVWF IOCAP
BANKSEL IOCAN
MOVLW ION
MOVWF IOCAN

CLRF BSR
;;;;;;;;;;;;;;;;;;
;; MAIN PROGRAM ;;
;;;;;;;;;;;;;;;;;;
Loop
CALL Toggle
GOTO  Loop
;;;;;;;;;;;;;;;;;;
;;  INTERRUPTS  ;;
;;;;;;;;;;;;;;;;;;

;;;;;;;;;;;;;;;;;;
;; SUBROUTINES  ;;
;;;;;;;;;;;;;;;;;;
Toggle
   ;; LATCH ;;
CLRWDT
BSF  PORTC,LTC
CALL Delay30ms
BCF  PORTC,LTC
   ;; WAIT ;;
CALL Delay30ms
   ;;RELEASE;;
BSF  PORTC,RLS
CALL Delay30ms
BCF  PORTC,RLS
   ;; EXIT ;;
RETURN

Delay30ms
MOVLW   0x4C
MOVWF   d1
D30Loop
CLRWDT
DECFSZ  d1, f
GOTO D30Loop
RETURN
;;;;;;;;;;;;;;;;;;
;;END OF PROGRAM;;
;;;;;;;;;;;;;;;;;;
END


texts: At which point and how to connect VNA on the PCB for antenna tuning?

texts:
I am working on a 2.45 GHz(Bluetooth) project. I have used a ceramic chip antenna with 50 Ω impedance for this board.

I've placed a Pi network close to the antenna and also I have used an integrated low-pass filter (F1) close to the RF chip for matching the RF chip to the feed line.

I intend to tune the antenna impedance using the Pi network using VNA.

I also have a footprint for a UF-L connector which overlaps the output pin of F1.

At which point exactly on the feedline should I connect the VNA probes?
My understanding for the first question is that it would be right to connect connect the VNA at the output of the low pass filter(F1) instead right close to the matching network because if we connect the VNA close to the matching network we will be ignoring the electrical delay caused by the feedline trace between F1 output and the matching network.
Which option would be better soldering the coaxial cable to the PCB directly vs using the UF-L connector for this purpose?
Also I understand I will have to do a port extension for the extra length of adapter cable used here is there anything I should aware of while doing this?

Edit: I've added the image of the schematic and layout for the antenna circuit.


texts: Is this STM32F based CAN bus circuit ok?

texts:
So this is my first time moving away from Arduino based projects and I am now planning a project using the STM32F105RBT6.

It is a simple CAN bus analyser with some leds. I may add some extra i/o in the future.

As for the power supply, I plan to have it powered from a 8-30v input or the USB port. I think the attached power supply circuit should work.

I have used parts of example schematics and the schematics from development and evaluation boards I have found online.

Will the attached circuit work? I am mainly concerned about the STM32 circuit along with the power and usb.


texts: How to mathematically simulate a zener diode

texts: I would like to simulate a circuit with a resistor and zener diode for various voltages in an excel spread sheet and need a way to model it.


texts: I have what it looks to me as a stepped motor, power at 24DC, but it has no name or mark, and i can't find any documentation about the wiring, here are some pictures of the plug and the motor, I'll be so thankful


texts: Full Bridge Rectifier - Voltage Drop Under Load

texts:
I am trying to get 5v DC by rectifying  the output of a microwave transformer i rewound (the transformer gets approx 4.2V AC on the secondary winding).

I managed to get approx 5V open circuit voltage on the DC side of the rectifier but as soon as i connect a small load (tiny 6v test light which can be seen on the photos) the voltage drops from 5v to approx 4.3 volt; the AC voltage on the secondary winding of the transformer barely changes when connecting/disconnecting the light bulb). Also the voltage drop over each diode is approx 1.5v (which confuses me since  i thought it should always be 0.7volt). The measurements can be seen on the photos. I have also tested with a different load (18650 charge controller ic) which gives approximately the same results. I have tried using 10A10M10 diodes bit that also gave the same results.

I am using IN4004 DC Diodes. I am using a 25v 2200uF capacitor for smoothing out the dc output (I also tried with a 4700uF cap). The capacitor is in parallel with the load as can be seen in the schematic.

Is this sort of voltage drop normal? Is there anything i can do to prevent it? Have i made a mistake somewhere in terms of circuitry or component choice?

Any input is greatly appreciated. Thank you very much!


texts: Output Current Derating for Buck converter for powering RF sampling data converters

texts:
I am new to the use of DC-DC converters.

I am designing power supply for powering DAC from TI whose part number is DAC38RF80.

DAC38RF80 is  high speed RF sampling DAC with sampling rate as high as 9 GSPS and it supports JESD204B.

There will be three DAC38RF80 on the single PCB.

There are four voltage levels required to power-up this DAC and these are:

•   1v Digital

•   1v Analog

•   1.8v

•   -1.8v

Now the current consumption for all the four voltage rails varies with the different operating modes given in the datasheet.

Maximum current consumption of 1v Digital supply is 2.29A for 1No. of DAC. So for three DAC38RF80 current consumption for 1v Digital supply is 6.87A.

I am planning to power 1v digital supply of all three DACs from single buck converter.

I have chosen TI's TPSM84824 power module which has maximum output current rating of 8A.

So my question is :

Will TPSM84824 module with 8A of output current be able to power up all three DAC's 1v @ 6.87A digital supply without any issue or will there be any issue like shut down of regulator due to exceeding the max current limit of regulator because of inrush at start-up?

How much derating of the current needs to be done while selecting DC-DC converter?

Also it will be very helpful to know what parameters does experienced EEs look for in datasheet of DC-DC converter for powering high speed RF sampling converters, so that performance of data converters can be improved?

Thanks.


texts: How big current I can commutate using D-sub connectors?

texts:
The question

Did someone knows what are the current capabilities of the standard D-sub (aka Cannon) connector. I want to use it for power source connection together with the signal.

I need pretty high currents - something like 10A or even higher and also, I can use several pins for this task. Even more pin connector (15 or 25 instead of 9) is acceptable.

Special modifications (special power D-sub connectors) are not acceptable. I want to keep the element base very standard and cheap.

Did someone has personal experience with such D-sub use?

The experiment

After some not very informative search, I decided to make some experiment. I connected all the pins in a pair of D-sub 15 pin connectors in series and then connected it to a 3A current source. This way, through the whole connector, 45A of current is flowing (15pins x 3A each). The total voltage drop on all pins is 0.12V and the power is 0.36W total. Now I will leave it for a while in order to see how it will degrade with the time.

Experimental results 1

After 1 hour of work on 3A per pin (45A total) the temperature of the external metal body of the connectors raised to 39 deg. Celsius (27 deg ambient temperature). The average contact resistance is 3mOhms per pin. I leaved it to work for a night and tomorrow will try to couple/decouple them several hundred times and to check what will happen.

Experimental results 2

After a night of work nothing changed. The body temperature is stable, 12°C above the ambient temperature. After several tents of times coupling/decoupling under voltage, the contact resistance has been increased from 2.4mΩ to 2.7mΩ per pin.


texts: how to determine resistor value calculation for common anode 7-segment display multiplexed

texts:
Resistor is required to limit the current flow through the LED since otherwise so much current will pass through that power dissipation shall destroy the LED in less than a second.

For nonmultiplexed display it is quite simple to determine the value of this resistor since... the LED has 1 diode drop when it is turned on, the rest shall be across the resistor. This enables use of simple Ohm's law.

The situation gets complicated for a multiplexed display, now there is voltage drop across the PNP (for common anode) emitter collector junction and the base of this transistor also needs a resistor.

(1) Is the resistor on the base used to limit base current?

(2) How does one determine how much current shall be flowing through the transistor i.e collector current? I don't think the transistor action equations can be used since the transistor is likely in saturation mode. Using beta value will not help. Besides, the base current value is also unknown.

(3) How does one determine the value of the base resistor and the display resistors in this case? The collector-emitter voltage drop is unknown which is creating the complication.


texts:
I followed a simple tutorial on setting up an RGB LED. The LED uses pins 11, 12 and 13. Via the serial interface I can issue commands such as the following:

  r5g7b9

The letters activate the color, and the number immediately after the letter specifies the brightness of the color.

That worked just fine. I then decided to find a way of controling my RGB project from a web interface.
To make the connection to the internet, I mounted my Ethernet shield on my Arduino Uno, included a MAC and server IP address etc.

In my setup function, when I call ethernet.begin(), I get very strange combined effects.

The red aspect of my LED is permanently on
My sketch no longer responds to my input

Can anyone offer any ideas why a call to ethernet.begin() would have such negative effects, please ?


texts: Why footprint dimensions are to edges and not centers

texts:
Whenever I'm looking at electronic components, I regularly see footprints with this kind of thing:

Dimension E seems to me to be somewhat unhelpful; rather than simply reading the centre distance (even something closer to C would be helpful, since it references the pad origin), I have to take E, then find X and subtract half of it. This isn't even close to the worst example; sometimes almost nothing references the origin and I have to chain 3 or 4 measurements together to figure out where to place something.

Why are pad layouts often given like this? My first thought is it could be for manufacturers rather than designers; knowing where the edge is makes more sense than knowing where the center is if one wishes to route out a shape.


texts: Is it safe to boost output voltage to the maximum limit?

texts:
I'm going to be using the MCP1640 for boosting one AA battery to 5.5V. However, its max output voltage is 5.5V. Will it be safe to boost the output to the maximum limit and not cause damage to the chip?

Thanks


texts: Measuring the resonant frequency of an RLC circuit

texts:
I have a simple RLC circuit (100 ohm resistor, 10mH inductor and 1uf capacitor in series) and I need to measure the circuit's resonant/natural frequency and damping coefficient. The input to the circuit is a 2% duty cycle, 1khz 1V square wave (like the unit impulse).

My understanding is that when the circuit resonates, the combined impedance of the inductor and capacitor is zero, so the circuit's impedance is at a minimum. If I measure the voltage across the resistor, this should be at a maximum (since the current is at a maximum).

I calculate the resonant frequency for this circuit to be ~1.6KHz however I don't measure any maximum or minimum voltage around this point. The voltage just keeps decreasing as the frequency increases.

This seems to have something to do with using an impulse input because if I use a sine wave instead it is easy to see this effect. Why does it not resonate in this case?

I also calculated the damping coefficient to be 0.5. This should mean the system is underdamped and should oscillate. I haven't been able to work out how to measure this yet. Any suggestions?


texts: How to change date format in Altium schematic title block?

texts: This is the default title block. As you can see it already has a date filled in. But being european I don't like the mm-dd-yyy order. Is there a way to change that?


texts: What's the largest practical stable gain possible?

texts:
I have a feedback application to set the voltage of a node in which there is considerable loss in the loop. Simulations tell me that a differential voltage gain of 10000, 80dB (roughly about what you normally get from a single open-loop opamp) is not adequate and I would need on the order of 140dB to make the application feasible.

Note that noise is not really an issue in this application (within reason), but a bandwidth of ~1MHz is desirable, which sets a somewhat insane GBW product of \$~10^{13}\$. In addition I need very low input bias current (<1µA.)

A multi-stage amplifier does not seem viable, as this would increase the order of the system and would tend to make it unstable under feedback conditions. Before I even start considering discrete designs and optimizations (or building my own ICs for this application), or simply scratch the whole idea and go back to the drawing board, I would like to know how viable this would be:

What is the largest single-stage/single-pole wide-bandwidth gain/GBW attainable (I seem to recall that a gain of ~200 is about the limit of discrete electronics).
What is the largest dual-stage gain/GBW attainable (most op amps would fall into this category).
Could a multi-stage (>3) amplifier be compensated in such a way to make this possible?
What is the largest gain/GBW op amp currently available in the market?
Would a different topology (e.g., Norton or Transconductance amplifier) provide a way around these limitations?

I am currently designing around a somewhat hard to get LTC6269IDD-10. A non-unity gain compensated 4GHz GBW op amp. But even this is proving to be a challenge.

Conceptual schematic
(note that most parameters cannot be modified and are somewhat random in nature, that includes the resistors, capacitors, and signal source):

simulate this circuit – Schematic created using CircuitLab

Related questions:

What's special about "unity-gain stable"?

What is the largest gain configurable with an opamp?


texts: Strange behaviour in PCB when solenoid turns off

texts:
Hi all,

I designed a PCB for a lock control. You can see the PCB on the image. Some explanation on the abbreviations:

Ext: exterior 12V power source
Batt: 12V battery
1702: 12V to 5V power converter
Keypad: here comes a classic 4 by 3 keypad
MCU: Atmel Atmega 328P
IRL520N: transistor to drive the solenoid of the lock

Other components are not relevant for the discussion I think.

The program is as follows: you enter a code. When the code is correct, the transistor is activated, thus the lock opens. This for two seconds. Then locks turns off.

Everything works fine, except for... When the locks turns off again, circuit is starting to act strangely. Sometimes it blocks, sometimes the chip reboots.

I post the drawing of the PCB and not of the circuit, because I think the problem lies in the way the PCB is laid out.

Thank you very much for your help!

So, given all your answers, I redrew the circuit a bit (a lot):

Use of SMD components
Crystal is a lot closer to the MCU
Use of decoupling capacitor (C5)
Use of ground fill (pink area on bottom of PCB)

Could you please tell me if this PCB would have the good performance wone would require? Or am I still getting it wrong?

Thanks a lot


texts:
Is it practical to connect the output of a ferrite-core 1:40 transformer in series with the input of a 1:6 ferrite-core transformer as a means of acquiring 240 V?What would the pitfalls be of this method compared to using a ferrite-core 1:240 transformer?

Assume that in each case the ferrite-core is made of two E-shaped cores placed together with the primary and secondary leads wrapped around the long side of the gap.


texts: How does the DMA know "when to send" the next byte?

texts: I'm transferring data from memory to a peripherial's register in an STM32 uC. For example take 20 bytes. I understand that after sending all the 20 bytes, the "Transfer Complete" interrupt will occur. My question is: between individual bytes (e.g. 4th and 5th) how does the DMA know when it is time to send the next byte? How does it adjust its   speed?


texts: What are the effects of connecting an external battery pack to a laptop's power jack?

texts:
I want to make a very simple external battery pack for a laptop, connecting to its 19V DC power jack. I plan to use a series of four lithium batteries that should provide between 11V and 16.8V of power.

The internal battery pack consists of 3 Li-Polymer cells, which I assume provides the laptop with approximately 8.1V to 12.6V of power.

When I connect the 4-cell external battery pack to the 19V DC input, what are the effects? Does it make sense to assume that the laptop is fine with voltages below 19V? Will it take whatever voltage it needs to run, which should be related to what the internal battery provides, i.e ~8.1+V, and direct only excess voltage to recharge the internal batteries? Are there any terrible inefficiencies going on? Does this even make sense at all?


texts: Voltage spikes on Arduino Input affecting digital and analog readings

texts:
I am working on an Arduino project where I have a few inputs both analog and digital into the Arduino from remote buttons and sensors.

I have installed a prototype in our building, but when other loads, external to my project, in the building like air-conditioning and extraction fans get turned ON and OFF, the readings on the inputs are affected on the Arduino. For example, when an extraction fan is turned off, the Arduino reads a change in state on the digital inputs, and the readings on the analogue inputs are affected.

How would I go about dealing with this in my circuit design? I'm assuming some kind of power smoothing or filtering on my power input? But I'm just not sure where to start, and I couldn't find much on the topic.

Any help/advice would be appreciated.

Cheers

EDIT: For a bit of additional context, the project is an access control system, specifically the inputs affected are push to exit buttons and door sensors. When the aforementioned loads in the building get switched on and off, my Arduino seems to think the PTE button is being pressed and the door sensors are changing states.


texts: Can i wire a pump with 2 Voltages like this?

texts:
so i wanted to reduce the speed of my water pump but i feared that the 7-8V might be to low to start it up. So i thought starting it at 12V and then switching it to 7-8V should do the trick. Main question will this wiring work? I am a complete novice and rarely solder or wire things.

My main concern is that once i fire it up at 12V the 0V going to the Step Down controller might damage or even fry it somehow. Also will a regular pc power supply be okay with this.

I deliberatly picked a step down controller because i did not want to use a PWM as i hear all bad thing about using with my pump.
I also thought if there was a way to maybe switch automaticaly after 5-10 secounds have passed but i could not find any lead to how to do that.

If anyone has better ideas i am open to change everything about it.

Step down converter is rated for 75W. The chip seems to be a xl4015e.
The pump is rated for 18 Watts at 12V but heard that at the start-up it can be more (30W?).

Thanks in advance!


texts: Why does this parallel->series rewrite change my AC simulation results a little?

texts:
Here are two circuits I've simulated. Both have a current source of \$\sin(\omega t)\$ mA with \$\omega=1000\$. They should be equivalent but give different simulation results.

Here are the simulated currents across R1:

I(R1):   mag:  0.0672338 phase:   -137.752°  device_current
I(R1):   mag:  0.0673282 phase:   -137.783°  device_current

Here is how I calculated the new R2 and L1: The total complex impedance of R2 and L1 in parallel is \$1/( 1/R_2 + 1/(j\omega L_1)) = 1/(1+1/j) = 0.5 + 0.5j\$ which can be written as the series resistance and inductance \$0.5+j\omega \times 0.5\times10^{-3}\$.

So my question is: where did this calculation go wrong? Are the circuits not equivalent or have I missed something in the simulation?

I don't think this is a numerical error since the current is wrong in the third significant digit whereas the model should be accurate to the floating-point precision.


texts: Circuit safety -> Preventing smoke through accidental connection of battery voltages

texts:
I'm building a circuit whereby users are able to connect their battery to the pcb which will then be sampled by a micrcontroller. Voltage divider circuitry is all good so please don't focus you attention on this.

The battery is a LIPO battery and I was planning on getting the user to connect the JST-XH balance lead to the PCB.  Now for those familiar with LIPO batteries the connector is different based on the number of cells the battery has.

See this website for more on balance leads if you need to:
https://sites.google.com/site/tjinguytech/charging-how-tos/balance-connectors/

So I was thinking of having various JST-XH female connectors on the PCB so if the user had, for example, a 3-cell battery they'd connect the balance lead of the battery to the 3-cell female connector on the PCB. If they had a 4-cell battery they'd connect the 4 pin female balance connector to the pcb, 5-cell battery to 5 pin connector to pcb, etc....

The problem here I guess is if a user accidentally connected 2 batteries say a 3 cell and 4 cell battery at the same time: the circuitry is not only dangerous but things might start smoking (as at the moment I have the + and - ends of the pcb female connectors on the same net.

Does anyone have any suggestions as to how this can be achieved (without diodes, I don't want the voltage drop, plus I believe the diode cannot be connected in parallel due to the fact that the battery will be discharging large amounts of current through a parallel connection to the motor).

I have thought about just havine one two-pin female connecotor on the pcb then issuing a converter which suitable for the different types of batteries, to prevent any mishaps, but would like to see other alternatives/solutions.

In particular the possibility of having some form of dip switch on the board so that when the dip switch is at a particular position it will pass either the three, four or five cell battery voltage through to the adc circuitry (but only one) or any other solution you can think of.


texts:
I'm trying to find the current across all the components but am having trouble doing so because I don't know how to deal with the extra battery in this case.

I've found that without the battery V(out)should be 4V, so is this cancelled by the battery? How does the battery add to current in this case?


texts: Why do LF RFID tags use near field and why is reading distance longer with UHF RFID?

texts:
Why do LF/HF RFID tags use the near field (magnetic coupling) and not the far field?
Well, I guess it's easier. The two antennas can just be modeled as a "transformer" and power transfer is straight forward.

But would it be possible to use the far field as well (assuming we antenna size is not the issue)? How would the energy transfer change?

Why are "long distance" RFID tags UHF tags?

According to Frii's transmission equation, the received power is indirectly proportional to frequency. So a lower frequency would mean more power at the tag.

Is the reason just the large required antenna or something else?


texts:
I'm using an alternator to charge a 300Ah lead-acid battery bank. The cable has a 60A fuse, yet measuring a shunt suggest that the current is about 70-90A for the first 10-20 seconds, and after a few minutes it is down to about 30-35A.

The alternator provides 14.0V at the car battery, and cable losses further reduce the voltage to about 13.8V at the battery bank.

I'm trying to introduce an automatic switch using a P-channel mosfet.

The problem I'm facing is that the voltage drop over the MOSFET should be minimal, since a lower voltage will significantly reduce the charge current.
A better alternative would be a boost circuit to 14.4V, but at 30-50A, they get very expensive.

The P-channel MOSFETs tend to have higher on-resistance that N-channel.
But I've found this: AP6681GMT

The package is undesirable, and heatsinking is only possible through the PCB.

I built a circuit, but when I tried it, black smoke came out of it, and it failed open.

I'm wondering what I did wrong, and what my alternatives are. I understand a relay has a high on-resistance?

Would it make sense to buy a starter relay for a car? The specification is typically not provided and perhaps the on-resistance will be too much.

simulate this circuit – Schematic created using CircuitLab

For testing the circuit, I connected the drain-side to a blower motor, and switched the gate-signal on/off every 1000ms. The circuit worked correctly, even with peak currents of 20A and sustained current of 7A.

I then connected the drain-side to the battery bank.
When I turned on the alternator, it jumped to 14.0V on the source side.
Is it possible that the 1k resistor didn't raise the Vgs fast enough, such that it continued to conduct without pulling-up? e.g. a runaway scenario.

UPDATE: Using an N-channel MOSFET instead?

N-channel MOSFET: IRFB4410Z (100V, 97A, 9mOhm/10V)

or AP99T03GP (30V, 200A, 2.5mOhm/10V 4mOhm/4V)

simulate this circuit

This would allow me to use a heat sink, to have lower on-resistance, bigger package. But with the inconvenience of a boost-circuit.


texts: Designing a Fast Powerup Bandpass Filter

texts:
I'm trying to design a simple bandpass filter with fast settling time after powerup.  I have tried several methods and in every case am finding limitation between requirements of HPF frequency, gain, and powerup settling time.  I am hoping to learn if my limitation is due to my requirements or if there might be a circuit topology I haven't considered.
At a high level the application of this circuit is to be a rudimentary sound level meter for specific frequency range.  The plan is to take a signal from MEMs microphone, amplify/filter it, and then read the output via a fast ADC built into my MCU. The accuracy requirements are very low and the design is working well, but requires a 35ms delay before signal settles which is too long for this application.  The MEMs mic I am using is Knowles SPU0410LR5H-QB, which biases the signal at ~0.7V.  The output is stable after approximately 0.5ms.
The approximate specifications I'm designing towards are:

Passband: 85Hz-500Hz
Gain: 37 V/V
Powerup Settling Time: <10ms

Here is the circuit that is currently working, but requires a 35ms settling time:

Note that here the powerup settling time is dependent upon both HPF and gain settings.  I'm a little confused here because I believe that the delay is due to charging C1 through R1+R2, however that would be a time constant of 71ms (e.g. 213ms to being mostly settled), while I'm finding the signal settles within ~35ms.  Irregardless, I find that reduction of C1-R1-R2 does reduce my settling time, however to get time under 10ms I need to cut gain in half and double HPF which is quite significant of a deviation from my desired spec.
My leading option right now is to use a non-inverting amp and let it cut out half of the signal.  The issue with passing the full signal is adding a resistor bias increases the delay and this design does not have room for a dual-supply rail.  Note that I've doubled the gain here to account for having only half the signal.  The other consideration is that the LPF will distort the half-wave signal, but I believe this is fine as long as I only track the peak voltage.  The powerup settling time is independent of gain and although it is dependent upon HPF frequency, at 85Hz it is just under 10ms.

I don't want to make my description too long, but here is a brief overview of some of the other options I've considered:

With mentioned inverting amp circuit, I have tried adding a FET between IN- and IN+ controlled by the MCU at powerup.  After optimizing the length of the control signal I find it still takes ~20ms before signal settles.  Although the signal is never large enough to overcome the FET's body diode, I'm not a big fan of this approach of having a FET linked to the signal path.
I have tried an IGMF filter with F0=250Hz, Q=0.707, and G=37.  Although simulation showed a 6ms step response settling time, I find ~20ms settling after powerup when I breadboarded the circuit.
I have tried a 2-stage approach with filtering in first stage and gain in second stage, however the second stage requires AC coupling capacitor and bias resistors which create an additional HPF stage and additional delay.

I'm happy to provide circuits on any of these if anyone would find it beneficial.
I think the non-inverting circuit will be okay, but thought it would be wise to reach out to this forum to see if I can gain a better understanding of the limitation and see if there might be an approach I haven't considered.  Hopefully I'll learn something here and others will find the topic useful as well.  I appreciate any insight I might receive.
EDIT: Here is the schematic and Scope captures of the IGMF Filter I tried:

Here are scope captures of the response with
CH1 (yellow): Power rail
CH2 (blue): Input signal
CH3 (pink): Output
This is powerup with the mic:

This is a step response from my function generator:


texts: Directional/menu selector component name

texts:
I'm new to eletronics and I don't know some component names I need to use to find some. Example, I'm looking for a 'kit' or a button set like this to use on a dashboard panel project I'm working on:

Is there a proper name for this component?


texts:
I have an APC UPS and one of the caps - an SIEMENS EPCOS 20uF 150V Capacitor - started making a buzzing noise.

This seems to be a AC, non-electrolytic capacitor and most local stores have it priced at ~$20 + tax.

They look like this:

I also realized that caps of similar rating (20uF 250V) are present in the cheap pedestal fans they sell at Walmart!

Those look like this:

Most importantly, these ones are also available on eBay for ~$5 and are worth a shot, but I had a few questions:

Is the buzzing because of the capacitor is bad or that a different component could be failing and having a secondary, audible effect on the capacitor?

I thought the AC capacitors didn't have electrolytes in them and hence can't understand why they would be buzzing loudly when they did not previously
Should not both these caps be interchangeable in this application?
I am thinking of plugging out the 20uF 250V pedestal fan capacitor and putting this capacitor into such a fan instead, to confirm if the cap itself is causing the noise - sounds like a good idea?

I am not sure why the fans use 250V caps but my assumption is that these Chinese makers just stock up on one variety of the caps since most of the world are at or below 250V.

Hence, for this experiment, using a 150V cap instead of the 250V one for the fan  (in the US) should not damage either fan or cap?
If it's confirmed that the cap's at fault, could I put in the 20uF 250V pedestal fan capacitor on the APC UPS board and expect it to have no detrimental effect on the UPS?

My understanding is that this is a power cap and as long as the capacitance and voltage rating is good, other cap chars like ESR don't matter?

Here are pictures of the board:

It seems the noise is from the yellow cap, although there is a slight chance it could be from components around it (or because of malfunction of a component that's leading to the noise in the cap?).


texts: STM32 USB device - device descriptor request failed

texts:
I'm using STM32F7-45 on my own board, and I am trying to program USB device (I tried virtual COM and HID, separately).

But after plugging into PC it is detected (after a while) with "Unknown device (device descriptor request failed)" error.

Electrically (PCB):
I think that PCB is not an error here - I just have D+ and D- short tracks from the connector to the uC and that's all.
I have a pull-up 1.5k (I tried with and without it), but it is not even needed in STM32.
I have check connection and a cable and I'm certain it connects.

Code:
I'm using HAL and STM32CubeMx generated code merged with my project. Generally programs freezes.

1) After executing line (from library code) USBx->GAHBCFG |= USB_OTG_GAHBCFG_GINT;. I know that, as I tried printing before and after that line and only first printf() prints. I don't understand how the program can stuck there.
Anyway, if I disable VBUS sensing then the program doesn't get stuck there and the whole MX_USB_DEVICE_Init finishes.

2) But then, program executes few cycles (for example, it will print "done" and lit the LED) and after that it freezes. Completely. This LED should blink in an infinite loop, but it doesn't. I have other LED to be enabled in all error handlers (like hard fault etc.) and it seems that the the program doesn't go there (as the LED is off), so I don't understand where it get stuck.

After virtual COM, I tried HID but to no avail. It gives me the same behavior.
If I power the board from the charger (not PC) then the program doesn't get stuck.


texts: What additional factors need to be considered when calculating voltage drop?

texts:
Considering the following formulas for voltage drop, what additional factors need to be included and how can resistance be derived to thoroughly calculate theoretical voltage drop for multiple scenarios?

For example, cables run in steel conduit will need to be treated differently than cables run in 'free space' (this falls under resistance but is additional to cable resistance). The National Electric Code contains resistance & impedance data but only for specific scenarios and cable ratings.

How can one cover all necessary factors in the absence of raw data in order to produce an accurate result? Or, how can one obtain the data if it exists?

DC:
Vd = \$2IRL\$
Single phase:
Vd = \$2IZL\$
Three phase:
Vd = \$\sqrt{3}ZL\$