texts: Microcontroller not working as expected or crashes after a few days

texts:
I am using Atmel AVR ATmega8 in my monitoring project, which measures three phase voltage and sends data through a uart. It works great in 1 or 2 days. But after that amount of time, it is not working as expected, and no response comes from the uart and heartbeat led, which indicates uc is alive or not. And sometimes heartbeat led blinks and no response comes from uart. But after a hardware reset, it works again, then crashes again until hardware reset. I implemented a watchdog in it, but it seems not working. I reset the watchdog counter in 8 bit timer interrupt routine. Should I reset it in my main code, not in an interrupt routine?

I assume it is getting out of SRAM. ATmage8 SRAM is 1 kb, and my static data is using 71,2% of it. And I am not using any heap allocation. My question is: Is it possible to stack and static data collide?


texts: Does alcohol set off Liquid Contact Indicators?

texts:
I have a MacBook Pro PCB that has lots of yucky, gooey and sticky grime from a spill that thankfully didn't damage the board. I would like to clean thr PCB thoroughly, but I fear turning the liquid contact indicators red and raising eyebrows at AppleStore in case I take my machine in for paid repairs.

I've read about repair shops using ultrasonic cleaning using water mixed with Branson Ultrasonic Cleaning Solution to clean PCBs, but it is unclear wether it sets off the LCIs. Does it set them off?

I'm considering using a soft brush and denatured alcohol, which is around 90% ethyl with some methyl additives according to MSDS. Do I need to be extra careful to avoid having alcohol contact the LCIs?


texts: How to drive pin to open drain/collector?

texts:
I'm looking at a datasheet for a bit of hardware I am adding to a design. However, one of the pins on the chip is listed as:

ON/OFF - 1.8V must be driven to open drain/collector

It does not specify if it is an input or output.
I don't fully understand what open drain/collector means in this situation, however what I understand from my research is that it typically refers to an internal connection to a transistor. They usually seem to be used as outputs (as far as I understood).

However, what is confusing me is the use of "driven" in the pin description. This appears to imply that I should be powering the pin with an open drain/collector. Is this what I am supposed to be doing? How would I achieve this?


texts:
Im very stuck on where to go with this question.
The examples in class used complex numbers, where as this doesn't seem to need them.
Im aware that Zs = Zl, but does Zl=Cl+Rl?
Any help with how to approach this question would be great


texts: I'm trying to pick a stepper motor and motor driver. Are these compatible? (TMC2130 & ROB-13656)

texts:
I'm using stepper motor for an application that requires the motor to be extremely silent. (not 3D printing) So I found out that the TMC2130 driver (or TMC2100) does just that. In my research of specs between drivers and motors I've gotten pretty confused. I've come down to using the TMC2130 to drive a Sparkfun ROB-13656 stepper motor. Before I purchase I want to make sure the voltage and current ratings of both will work together.

The TMC2130 says it supports stepper motors up to 2.0A coil current (2.5A peak). The ROB-13656 says 2.0A/phase. Is that the same thing as coil current?

The TMC2130 says it has a voltage range of 4.75-46V DC. And the ROB-13656 says Voltage: 3.2V. I know these specs don't correlate since the driver is monitoring the current, but I still don't really understand how they relate to each other.


texts:
I'm trying to connect an old laptop webcam I bought for $0.93 on eBay to an Arduino Uno microcontroller.

Since I currently don't know what all the pins on the webcam are used for, I'm trying to connect it to a USB first. I don't have alligator clips, so I'm using jumper wires to connect the webcam and USB cable to a breadboard. I know this question has technically been asked and answered numerous times, however, the particular webcam that I have has 7 pins rather than 4 or 5. I assumed the blue and purple were the data pins because I noticed they were wrapped together before I cut off the connector, but I later realized that the green and yellow were also wrapped together. Then the red and orange, and then the grey was by itself. Whenever I perform a continuity test with my multimeter, it beeps when I touch both the green and yellow (I think that means they are ground).

My questions are:

How do I figure out what all the pins are for?
How do I connect the webcam if it has more pins than the USB?
If the yellow and green are ground do I just twist them together or leave it alone?
Does it even make sense to try to connect it to a USB first if I really want to connect it to an Arduino?

WebCam:

WebCamPins/Wires:

USB Pins/Wires:


texts: LAN8720A transmits without TXEN signal being asserted

texts:
I am trying to transmit some data with a LAN8720A (datasheet) ethernet chip and I've encountered some strange issues. I've broken up the chip on the prototype board and connect it to the Spartan 6 FPGA. From the FPGA I pass the data to the two data pins TXD0 and TXD1, a TXEN signal and a 50 MHz clock to the XTAL1/CLKIN pin on the chip. I also provide a reset signal from the FPGA with the length of 200us. The data and TXEN signal are synchronous with the clock and toggle on the falling edge (I only output to the TXD0 for simplicity). The clock is provided continuously. The simulated picture of the waveform:

My configuration is as follows:
Mode pins - 011 : 100Base-TX Full duplex, auto-negotiation disabled. CRS is active during Receive.
nINTSEL - HIGH. The 50 MHz clock as I said is provided to the XTAL1/CLKIN pin.
The issue is that the chip outputs data on the TXP/TXN pins continuously, without  any regard for TXEN, even though the data should be transmitted only when TXEN is high. Here's the snapshot of the signal on the pins (probe is set to 10X):

My initial thought was that it was some sort of auto-negotiation, but I have the feature disabled so I doubt it.
The pins are connected to the magnetics on the ethernet connector.
When I catch the actual moment when TXEN is asserted there is no difference in the signal.
When I set the config pins to use auto-negotiation there is a small delay after powering up until some sequence of bits is being transmitted (which I assume is auto-negotiation protocol). There is no such delay when the auto-negotiation is disabled, the stream starts immediately after power up/reset.
When I set the config pins to use 10Base-TX the bandwidth is reduced, so there are packets sent with a long time of silence in between, but again the data doesn't seem to be dependent on either what I pass to the data pins, or TXEN state.
When I loop back the transmitted signal to the RX pins, I don't get any output on the data pins.
I don't know what I'm missing here, any help would be much appreciated.


texts:
I need the smallest power source possible to get 5V to power ATTINY402 and one 100K pullup and turn ON a MOSFET with a 2K resistor for 5 seconds once a day (to switch ON 1W LEDs run by a dedicated LED driver like AL5890)

So the continuous power consumption will be around 0.5mA with peak of 3mA for 5 seconds.

The power supply does not needs to be an isolated one as it will be enclosed in a sealed container and requires no user interactions.

The power supply needs to be inductor less and should not require an EMI filtering cap.

Since the current consumption is so low the Power Factor and Efficiency should not matter that much right? So its OK if the they are low.

The preferred size is less then or equal to SOP8 package.
If there are no external components then that is preferable.

If this power supply requires a DC source like a bridge rectifier then it is already in our circuit so that should not be calculated in the size consideration.

simulate this circuit – Schematic created using CircuitLab

What I have considered so far:

Capacitor dropper circuit:
The reason I did not choose this is because the capacitor needs to mains rated and they are pretty big so I have discarded that thought.
Resistor dropper Circuit:
Placed as the last resort if nothing else is available.
SR086 Based power Supply:
Requires a lot of external components and pretty big 470uF electrolytic capacitor at the output.

Small Transformer:
I could not find a very small mains rated 60Hz transformer that could fulfill my requirements.

Suggestion:
 5. MP100L:
This looks promising but it requires an X capacitor at the mains to keep the EMI under Class B (Which is the requirements).

SMJR-N-1-24:
I used this LED driver in my previous circuit and it provides 5V for my ATTINY as it has an internal 5V auxilary supply inside. So I was thinking maybe there is a chip that has only the 5V power supply circuitry inside.

Ideally I need a small chip that can give me 5V 2.5mA power from 120VAC. With minimal external components.


texts: Should I use multiple voltage regulators?

texts:
I have five devices that need to be powered.  I would like to use one DC source to power the four devices.  Should I use voltage dividers, voltage regulators or a mixture of both?  Also, any recommendations/tips about the required parts and circuit design is greatly appreciated.

Here are the specs of the devices that need to be powered:

A) Temperature Probe, v: 5v,  current: 6uA
Temperature Probe - Datasheet

B) PH Sensor Circuit, v: 5v, current: 1.6mA
PH Circuit - Datasheet

C) EC Sensor, v: 5v stable, current: 4.2mA
Conductivity Circuit - Datasheet

D) Application Board, v: 4.5v - 9v, current: 500mA
MBED Application Board - Datasheet

E) Wifi Module, v: 3.3 stable, current: 180mA
RN-XV WiFly Module - Wire Antenna - Datasheet


texts:
i am looking for a datasheet, or ideally an eagle library, that has a female 6 pin pcie power plug, like this:

as easy as it seems, i cannot seem to find ANYTHING online.


texts: Other than an AC (Alternating Current) can a RF wave carry anything else ? How can the energy a RF wave carry be measured ? Would the frequency of the wave be related to the transmitted energy of the wave ?


texts: Understanding datasheet audio transformer

texts:
I am trying to understand the datasheet of this transformer: http://www.mouser.com/ds/2/449/XC-600133-202475.pdf

I have googled and found an answer about transformer datasheet (Understanding transformer datasheet), but it does not exactly fit the case I am looking at here.

My questions are (I quote parts of the datasheet in bold):

What do those two sentences mean?:

Isolation voltage(primary to secondary):  100VDC min. @ 10MΩ

Insulation:  >10MΩ @ 100VDC.

My understanding of the second quote would be that if there is a 100VDC component on the primary, then the leakage to the secondary is equivalent to a resistor of resistance at least 10MΩ. Is that right? What does the first quote means then?
About the table with Impedance and Resistance. I think I am really confused here.

First, I guess that the table data for Impedance are given at 1KHz because of the sentence Impedance variation: ±10% @ 1KHz. Am I right?
Then I guess resistance is simply the electrical resistance of the primary and secondary of the transformer, am I right?
Finally, what is the impedance that is given? Spontaneously, I would have guessed that since we are talking about transformers, that contain two coupled inductances, it would be \$Z = \Im(L j \omega)\$, where \$j^2 = -1\$, so that it would reflect the inductances of the primary and secondary. But this does not seem to be the case in Understanding transformer datasheet. If here also the given impedances refer to the case when loads are applied on the transformer, can I get the inductances from the datasheet? If not why are they not given? Is it irrelevant information in this context?

As a comment it feels like often, datasheets include data that are not really explicitly defined but which definitions are rather semi implicit, and dependent on the component considered... Not easy to understand then ;)


texts: why isn't Norton transform applicable on ideal sources?

texts:
An ideal voltage source has no resistance in series to it, so the it's transform the current source must have zero resistance in parallel to it.
This means that all the current passes through the short (zero resistance) and no current will pass through the load.

Why is this happening?


texts: Finding equivalent capacitance between P and Q

texts:
Figure below is the schematic diagram ,there  we need to find the equivalent capacitance

I know that this is a straight-forward question for most of them, because many of you are expert in the field,

Now lemme give you the things that I have tried

I reduce those capacitors step by step, you can clearly see what I have done by following  the images appeared in below,

Finally it is reduced to one in the below.

So finally the answer is $$(5/8)c$$

Now what I want to know is , does my method and the answer correct


texts: Using a Bluetooth receiver with 3.5mm jack headset

texts:
For the past 1/2 year I have been using a cordless Bluetooth headset (this one) connected with my motorcycle Garmin GPS device. While connected the device will not allow me to control the volume over it's own interface but only through it's own buttons (+/- buttons).

The thing is that while wearing all my motorcycle equipment such as leather jacket / gloves it is almost impossible to locate the button I want because it's resting somewhere under my jacket and has very small buttons. Also the size and shape of these earplugs is not quite big for my new tighter helmet and after a couple of hours it causes pain. Finally the headset's battery is quite small providing sound for 2-2.5 hours max.

Before that I have been using a plain 3.5 mm normal headset with stereo headphones, mic and button (this one) wearing them for 4+ hours without any pain issues.

Is there a way to connect this plain pair on a separate Bluetooth transceiver (listening only is ok but talking as well is preferred) with a small size factor that would be attached on a convenient place on my helmet so that I can control volume via it's buttons (preferably big ones) and at the same time being able to wear them for longer period?

How can I search for such a device?


texts: Are there any free simulators for SystemVerilog?

texts: Are there any free simulators available for a hardware design coded in SystemVerilog? In particular, I need SystemVerilog's dynamic arrays.


texts: How to tell if stripboard is plated or not?

texts:
It's my first time working with perfboards. My understanding is that if it is not plated, the copper layer is subject to corrosion and must be prepared before soldering anything on it.

I just got this perfboard, but I don't know if it's plated or not. How can I tell? And if unplated, what must one do to prepare it for soldering?


texts: changeover normally closed to normally open

texts:
I have a switch that is used for setting tool lengths on CNC Mill.  The switch operates normally closed, and breaks the signal when a tool touches it, which sets the length via a macro.
The control however, sees this the opposite way, and is looking for the signal to set the length.
When I run the macro it immediately sees the signal, and sets a tool length, even though the tool hasn't had time to move and is no where near the switch.

What I am looking for is a relay that will switch this NC to an NO, and ideally this trigger would happen instantly so these dozens of tools can be set at higher speeds.
Is that a thing?  What is it called?

Here are the specs for the switch:

Hopefully this is something that is readily available, bonus points available if you can help me find one for sale!
Thanks!


texts:
I am working on a boost PFC, and I'd like to calculate the boundaries between CCM and DCM, but I don't know exactly how, I tried choosing current ripple = 100% and find the inductance value that corresponds to it.

Is there any better method? and what are the parameters to calculate to find the boudary between DCM and CCM?

Thank you very much.


texts: I'm looking to build a simple test circuit, where I can get an LED to illuminate when it senses 20VDC or above, and to remain off if it is sensing any less.


texts: What options do I have when synthesising control registers?

texts:
When your design includes control registers that are set/read on a dedicated clock domain (SPI or I2C etc), how do you usually deal with those?

For instance:

Do you keep them on their own clock domain and false_path them to wherever they go, not worrying too much about metastability?
Or maybe take loads of care to make sure there are meta-stable flops on each domain crossing, pushing up area in the case of large reg-maps? And if they span out into multiple clock domains, well, you just hang multiple synchronisers off the control line?

Any other suggestions I'm missing?


texts: What do you call the kind of female header found on Arduinos and shields?

texts:
I'm trying to order a batch of headers, the same kind of female headers found on Arduinos and Arduino shields that take male jumper wires as inputs.

When I put in the physical characteristics of the header:

Female OR Socket
2.54mm pitch
Through Hole
Vertical OR Straight
[pin count]

...I still find myself with pages on pages of headers to scroll through, and the kind I'm looking for nowhere to be seen.


texts: Using an alternative specification of a capacitor

texts: I have a project that requires me to use an electrolytic-capacitor with this specification: 10 uF 16V. I want to know if its possible to use a 10 uF 50V capacitor instead. Thanks for your anticipated response guys.


texts: What is the purpose of a 1 Ω resistor to ground in the output filter of a voltage regulator?

texts:
This is the LDO regulator I am analyzing. While I was a referring to an existing design based on LP2951, it is noted there is an additional 1 Ω resistor at the output filter capacitor to ground.

What is the purpose of adding a 1 Ω resistor? How is this value selected?


texts: STM32 - Configure Output Compare Registers on the Fly

texts:
since this is my first, feel free to give newbie a feedback :)
I have a following setup with my STM32 Nucleo (simplified, ignore the HW behind):
a) one input signal acquisition (Square wave, consider it PWM)
b) one output signal (consider short pulses)
My goal is to read the signal a) and determine the frequency of the input PWM. Then on the rising edge of the signal a) I want to wait a calibratable amount of time (clock cycles) and then trigger short pulse with a calibratable width.
I have already done the first part (waiting for rising edge, estimating the frequency) by using Input Compare approach of TIM.
However I am a little bit stuck with a concept, how to manipulate Output Compare registers after specific time elapsed.
What would be most appropriate result? Triggering some kind of "update function" on every input rising edge, where this "update function" takes the current counter value of output compare register and "extend it" with predefined delay (mentioned above).
Would that be neat and clean approach?
Thank you for responses!
p.s. I have read about the "one pulse" option in STM32, but since the rising edges are occurring cyclically (with some jitter), I am thinking if I could use running counter with output compare runtime modification for my application.


texts: Would it be possible for an engineer (which I'm not) to produce a relatively accurate BOM from high resolution photos of a PCB?


texts: How does HFI (high frequency injection) work with BLDC motors

texts:
How does HFI work with BLDC motors.
In this video: VESC HFI: Sensorless position tracking at zero speed he explains how HFI works, however i don't get how it can work with motors that have trapezoid back-EMF such as the one he is using.

The code belongs to the author of the VESC project which is an open source firmware implementing FOC with HFI. I tried understanding the code, however i couldn't given the level of complexity.

Can someone explain how HFI is implemented and how it works with trapezoid back-EMF BLDC motors?

VESC github repo


texts:
I would like to know how to calculate battery life when using an LED strip.
The LED strip is powered by 8 AA batteries in series.
LED Current Draw = 260 mA.
LED power consumption: 3.1 W.
LED Operating Voltage range: 9-14.8 VDC.
Please see attached images for battery datasheet.

This is my calculation, but I'm not sure if it's correct:

  Battery Life = (Battery Capacity)/(Load Current) = 2000 mAh /260 mA = 7.7 Hours

This is for one battery, and the lights are powered by 8 batteries, so is the total battery life = (7.7)x(8) = 61.6 hours ?


texts: How does efficiency of transformer change with respect to primary voltage?

texts: Suppose we have a non-ideal transformer such that secondary load is fixed and we change the voltage applied to the primary side. How does efficiency change with respect to primary voltage? I know there is a relation for the change of efficiency with load but I don't know what is the answer for the primary voltage and when the efficiency is maximum? By efficiency I mean the ratio of powers in the secondary and primary circuit.


texts:
I have some questions about analyzing the bandwidth of an op amp circuit. In the attached circuit diagram, I understand that the low cutoff frequency is created by C1 and R3 and it's 1/(2*pi*RC), and it's about 22 Hz. This circuit is on a breakout board, which says on the product page that there is a  "-3dB roll off at 100Hz", so how do you get 100 Hz from this?

Another question: what is the purpose of C3? I read that the R4/C3 combination creates a 16 KHz high frequency low pass filter, which I understand based on 1/(2*pi*RC). Why not just remove C3? What's the point of having this "extra filter" of R4 and C3?

I know the high cutoff frequency is the Gain Bandwidth Product/Gain, and I understand it's 15 kHz.

For a similar circuit, I saw a calculation for the cutoff frequency of the bias voltage divider (1/(2*pi*5k*1uF)). What is the significance of this cutoff frequency? What is the purpose of C2?

If someone asked "what is the bandwidth of this amplifier?", is there a straightforward answer with single lower and single upper cutoff (-3 dB) frequencies?


texts: Questions about LM741 in an ECG Circuit Schematic

texts:
I'm doing an ECG circuit in which I want to use LM741 for active filters and the Right Leg Driver. Basically I will change the LT1007 in the schematic I used for simulations above with LM741 in real life.

1. Is the LM741 "good enough" for the task at hand?

Main reason I want to use the LM741 is because of budget. Any other similarly priced OP Amps suggestions are welcomed.

2. Will the LM741 have trouble with a voltage supply of +/- 9V from a battery if the signals I'm using are <1V

P.S.: I don't care for 99.999% accuracy, I just want a clear, filtered, bio-signal that I will read on an oscilloscope, this circuit is a personal project, NOT a real life ECG machine that will end in a clinic somewhere.


texts: How do I compute the required bandwidth for a given bitrate of digital TV signal?

texts:
In this Encyclopædia Britannica article, there is a paragraph which introduces why video compression was needed to switch from analog to digital television broadcasting. It gives the following example.

For example, the NTSC colour signal is based on 483 lines of 720 picture elements (pixels) each. With eight bits being used to encode the luminance information and another eight bits the chrominance information, an overall transmission rate of 162 million bits per second would be needed for the digitized television signal. This would require a bandwidth of about 80 megahertz—far more capacity than the six megahertz allocated for a channel in the NTSC system.

First, I am not sure how they compute "162 million bits per second" since
$$720 \times 483 \times 2 \times 8 \times 29.97 = 166,757,875 $$
and no other standard framerate matches their result. Am I missing something ?
However, my main question is : how do they compute the theoretical required bandwidth of 80MHz ?
Let's admit that their result of 162Mbit/s is correct.
If I considered the ideal case of a noiseless channel and computed Nyquist maximum channel capacity using 8 bit samples, I would get
$$ B = \frac{C}{2 \log_2(M)} = \frac{162 \times 10^6}{2 \log_2(2^8)} \approx 10.1 \text{MHz}$$
which is not their answer.
I have tried to reverse-engineer their result using Shannon-Hartley,
$$ C = B \log_2(1 + \frac{S}{N}) \implies \frac{S}{N} = 2^{\frac{C}{B}} - 1 = 2^{\frac{162 \times 10^6}{80 \times 10^6}} - 1 \approx 3.0$$
which leads me to think that they used a 5 dB signal-to-noise ratio. Where does it come from ? Did they eyeball it or is there a theoretical way to reproduce their result ?


texts: When to Use a Etched Prototyping PCB vs. Custom-Patterned PCB

texts:
I.e.  vs.

Would the reasons be similar to those answered here, but emphasized on unwanted capacitance, noise, and power issues?


texts: Why does the LSR (logical shift right) instruction only require a single clock cycle to execute?

texts:
A while ago, I was reading the book Some Assembly Required on programming assembly for the avr family of microcontrollers... Early on, it explained that the LSL ( logical shift left ) instruction was translated to an ADD instruction that essentially multiplied the register by 2. I understand why that would work, but what I don't understand is what I am reading about the LSR ( logical shift right ) instruction on Atmel's own documentation: http://www.atmel.com/webdoc/avrassembler/avrassembler.wb_LSR.html

The documentation displays the instructions opcode as, 1001 010d dddd 0110 and shows the cycle count as 1, meaning that the instruction is completed in a single clock cycle.

So, what exactly is happening here? I really can't tell.. Thanks!


texts: How to solder two USB-C female PCBs together?

texts:
I have two of these usb-c female sockets that I need to solder together to make a "gender changer"
https://www.amazon.com/gp/product/B00VJ944V2/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1
Would I just solder the same pads from each board to each other? ex. A11 -> A11, A12 -> A12, so on.


texts: Current source with op amp and transistor

texts:
I'm building current source with OP AMP LM358 and MOSFET transistor IRF5305. Here's schematic diagram of the circuit:

I have two questions about it:

1) Maximal gate-source voltage of IRF5305 is +/-20V. Since V+ is 24Vdc, is it a good idea to add 10V zener diode between source and gate to protect MOSFET?

2) Why they use voltage divider connected to non-inverting input and apply reference voltage to inverting input ? Here's an example of current sink schematic diagram with the same OP AMP. I'm assuming current sourcing can be done by "inverting" this circuit. Is it so ?

Thank you !


texts:
Using BLDC wheels is common on electric transport. A wheel is a multiphase motor, where each phase(coil) is separated from power source(battery) with some kind of transistor, driven by PWM-like signal. Almost like in the following illustration:

However, there also exists "recuperation". When you'll manage to press brakes - a motor should turn into a generator and charges battery again. But I've never seen any scheme or model of it.. You cannot simply push current in backwrd direction through fets.

How is this implemented? What approaches do you know (if there are many)?


texts: Computing the electric potential generated by a current density across media with different conductivities

texts:
Model: a right cylinder composed three layers of conductive media. The is a disk of unit charge density in the center of the cylinder. The disk radius is equal to the cylinder radius. The outer layers have effectively infinite length. I have numerically computed the electric potential at sampled distances from the disk, see below.

The solid blue trace represents my result for the model as described. The dashed red trace is my result if I set all three media conductivities to be equal to the central medium's conductivity. The dotted black lines show the boundaries between media.

Does this look correct?

My simple linear intuition is that the conductivities of the outer layers should not affect the potential in the inner layers due to a vague notion of causality, hence the red and blue traces are overlapping in that region.

However, my suspicion is that my intuition does not apply to electrostatics, and that the outer conductivities somehow "pull" on the inner layer rather than everything propagating outward.

If my suspicions are correct, how to I compute the potential correctly?

My methods are outlined here.

Thank you.

Edit:

Thank you so much @Janka. The intuition is that the model boils down to resistors in series. Becuase the effects of resistors in series sum linearly, the conductivity layers cannot affect each other, as this would yield non-linear summation, assuming a steady state.


texts:
Most of the Ethernet PHY chips (e.g. LAN8720) provide strapping option to control operation.

I am short of IO pins in my uC, and I do not need (AFAIK) to change anything more in the PHY operation.

(1) Can I just not use the MDIO interface (Just PU MDC/MDIO pins)?

(2) If not, What are the "required" operations I need to do with PHY?

Thanks.


texts: What voltage reference is the pwm signal using in the QUADRUPLE HALF-H DRIVER SN754410NE?

texts:
I have a QUADRUPLE HALF-H DRIVER SN754410NE, and i saw online that the 5V from the arduino goes to pin1, pin 9 and pine 16 and on pin 8 you attach a separate 5v supply that has at least or more than 2.2A.

The arduino 5v that comes out is really 4.73V in my case.

I want to know whether the pwm signal is being scaled or mapped on this 4.73 or the 5.3 V from my separate supply ?

From the spec sheet it states :
Pin 16 (VCC1) is provided for the logic input circuits to minimize device power dissipation.
Pin 8 (VCC2) is used for the output circuits.

I still don't understand what they meant by that statement in bold.

Datasheet


texts: I was reviewing for our class and I can't seem to understand how the book comes up with these answers.


texts:
I need to read the flash of an atmega8 chip. I program the chip with a working program, verification passes. Then I try to read the chip contents with the command below, and the read fails.

vorac@laptop:~/recorded$ sudo avrdude -p atmega8 -c usbasp -U flash:r:flash-image

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.00s

avrdude: Device signature = 0x1e9307
avrdude: reading flash memory:

Reading | ################################################## | 100% 2.32s

avrdude: writing output file "flash-mage"
avrdude: error opening flash-mage: No such file or directory
avrdude: output file flash-mage auto detected as invalid format
avrdude: invalid output file format: -1
avrdude: write to file 'flash-mage' failed

avrdude: safemode: Fuses OK (H:FF, E:DD, L:E4)

avrdude done.  Thank you.

vorac@laptop:~/recorded$ ll flash-image
-rw-r--r-- 1 root root 0 ное  5 10:29 flash-image

What is wrong? Something with permissions on my Ubuntu box? The file flash-image does not exist before running avrdude. I tried adding suffixes .bin and even .hex to flash-image, but the error is still there.

Also, no chip locking is programmed.

    # Default for the atmega8 is lfuse:E1, hfuse:D9
    # Low fuse for 8MHz clock: E4
    # High fuse with 512 bytes bootloader, start at application start: DD


texts: Where to ground digital and analog regulators when using separate planes?

texts: Below is a topology of my new project. I am noticed about importance of planes separation. But I'm in doubt how to ground power regulators and filters.


texts:
The circuit below is a resistance multiplier but I am having trouble deriving the effective input resistance, which should be a multiple of \$R_b\$.

The answer should be something like $$R_{\text{in}} = (1+R_3/R_1)R_b$$

Any thoughts on how to derive this?


texts: Ideal LC circuit decays over time in LTspice

texts:
I was trying to simulate a transformer without a load, and setting an initial condition to observe how the energy will flow from the primary to the secondary circuit.

I realized that the energy will decay and the waveforms I would get I was not able to interpret, thus I simplified my question to a simple LC circuit which I simulate with LTspice by setting an initial condition. Plotting the voltage of the circuit will correctly give me an oscillation of 18MHz but increasing the simulation time will show that the voltage will decay.

My question is why do I get this response? Since I have no resistive components the oscillation should not dampen. The only assumption I can make is that simulation has a finite time for numerical integration and this might affects the results (?). If so, what parameters could I change to see an ongoing oscillation? I also tried to change Gmin and Abstol but I did not see much of a difference.


texts:
I am builing a circuit, and i need to connect a few different IC's (obiosly). My circuit is based on 5V TTL logic and i found a part that is made only in AHC/AHCT variant.

So let's take it from the start:

HCT -> 5V TTL
HC  -> CMOS technology
AHCT -> advanced 5V TTL ?
AHC  -> advanced CMOS   ?

I have read, that i should not mix HC with HCT together, so can i use HCT <-> AHCT and HC <-> AHC? Does it work like that? What if i want to use a CMOS chip in my TTL design?

Tanks for any help.


texts: Charging current/voltage for lipo batteries

texts:
I have a 500mah 1S lipo battery.
I wanted to charge it with my lab bench power supply.

Easy, I thought:
I want to charge at 2C (which is 1A) so I simply set my power supply to 4.20V and 1A limit and done.

What actually happened is that the battery charged about 0.9C and it was slowing down the closer it got to 4.2V.
This means that to charge at a constant 2C current the whole way I have to use voltage much higher than 4.2V, but a fully charged lipo cell must not be over 4.2V or it does the FLAME ON thing.

So my question is, how do normal chargers do it? Do they simply bump up the charging voltage until they reach the desired current (so they work in constant current mode) and they every couple of seconds the stop charging and measure the battery voltage to find out if it is 4.2V and if it is, then they stop charging, and if it is not they jump back into constant current mode?

Thanks


texts:
How do I install the 12V equivalent of a radial/lighting circuit?

I am about to renovate a small 40m2 apartment.
I do not want to touch the existing 240VAC cabling at all.
I am looking to have approximately 20-30 small LED lights of varying sizes throughout the apartment. Eg. there will be some RGBW strip on the ceiling down to some small (1 or 2 LED) accent lights in cupboards.
I really don't want to have to install 20-30 LED drivers
as far as possible, I want each LED (or group in some cases) to be individually switchable, and ideally dimmable.

The mental picture I have is a large 12V PSU with its output running through 20-30 MOSFETs and controlled by an Arduino. I will then run 12V pair to each of the light positions.
In practice I'd probably have 2-3 PSUs rather than one, but the architecture (central PSU, 12V radial) is what is important. There is space in the consumer unit for an additional module so I'd put my 12V circuit on its own RCBO.
As a principle, is this the right way to go?


texts: Reduce clicks when switching over cd4066

texts: I make an audio switch on the chip cd4066 (I control using arduino), please tell me how to make a smoother switch without sharp clicks, I need the sound to appear with a small attack and just fade out, it should be minimal but help get rid of clicks , ideally it would be great if the duration of attack and damping could be adjusted. How to implement this schematically? I will be happy with any help.


texts: PCB layout: am I doing local power nets correctly?

texts:
I am working on a 4-layer board which integrates three 48 MHz ARM microcontrollers and a "Bluetooth module," along with some other features and supporting parts which are not so relevant to this question.

My stackup is as follows:

signals and most pads
GND
power
signals and a few pads

My GND plane is solid but I have split up the power plane to provide 3.3V local power nets for some of the ICs. Each of the 3 MCUs has its own Vdd area underneath, as well as an AVdd area fed from the local Vcc through a ferrite bead (as per the datasheet of the MCU). The BT module has its own digital Vdd. Differential stereo audio signals leave the BT module and are amplified into single-ended signals for output (to a car's audio system). This amplifier has its own local power pour underneath it.

Each of the local 3.3V nets is connected by a 10 uH inductor to the "main" 3.3V net, which contains a linear regulator. This is what the datasheet for the MCUs says to do, but I have applied it to the bluetooth module and the analog amplifier stuff as well. Each local net has a 47 uF bulk bypass cap, along with sufficiently many 100 nF bypass caps near the IC power pins. The datasheet for the MCU also calls for 10 uF caps, so I have included those as well. Would this application of the split power plane, inductor, and bulk cap be considered a best-practices approach to containing switching noise of the MCUs?

No traces cross the power plane gaps on the bottom layer, but many do cross on the top, the fastest of which carry signals which may switch at 2 MHz. My understanding is that the return current of traces running on the top will flow on the GND plane, which is solid. My conclusion is that crossing the power splits on the top is okay, but my knowledge of EMC is patchy, and so I am not 100% sure; there always seems to be something of which I am unaware. Am I correct in this regard?

Here's a screenshot of KiCAD showing part of the power plane:

Addendum:
Like I said in the original post, traces on the back layer, which is adjacent to the split power plane, never cross gaps in the power plane, but many traces on the front do, as shown below (power pours are colored pink, traces are colored red, and the GND plane is colored yellow):


texts: Energy harvesting circuit output inquiry

texts:
I am doing an energy harvesting circuit experiment (LTC3108 IC chip).
There was an example in the LTspice program.
I observed the current of Vout and it was 99nA as follows. The voltage was found to be about 5V.
Is this circuit a voltage-boosting circuit? Should the current increase in other ways?


texts: Lab supply schematic - negative rail and darlington transistor pair

texts:
While browsing the lab power supplies market and watching the price ranges, I've decided that I'd be better off with building my own, since I've got most of the needed parts anyways.

I've searched for schematics and stumbled across the one included below. It is self-explanatory in many ways, but there are two questions that keep bothering me.

The lower part of the schematic with the LM377L regulator handles the negative power rail for the TL082. I completely understand why is it needed when using the TL082 opamp, as it is not a rail-to-rail opamp.

The first question is: Why not just use a LM324 rail-to-rail opamp, for example? Will there be any drawbacks?
The second question is: Why is the BD139 transistor on the right part of the schematic needed at all? If it is there to increase the current gain - aren't there any high-power transistors with higher hFE that could be used instead of suggested 2N3055?


texts: Need help understanding simple FM transmitter

texts:
I made a simple FM transmitter following https://maker.pro/custom/tutorial/how-to-make-an-fm-transmitter and it worked!
Now I need some help to understand how.

My coil is made of 1 mm copper wire has 6 turns and 8 mm wire diameter.
According to this online calculator: https://www.eeweb.com/tools/coil-inductance
this means that:
L = 3.9e-7 H

I did not have any 5 pF trim capacitor so I used a 3 pF capacitor instead.

Am I correct in assuming that the frequency this will transmit on can be found by looking at the L1 C2 as a LC oscillator and using the frequency formulae:

fR = 1/(2*pi*sqrt(LC))

?

If so I should get fR = 147 MHz.
Which is strange since I received the signal on 91.5 MHz on my radio.

In a LC circuit I understand that the signal decays exponentially over time.
That is hopefully not happening here. Why? Because of C4 maybe?

Also what is the purpose of C1?

If I want to increase the range of this FM transmitter somewhat can I do this by simply replacing R2 with a 470 Ohm resistor?

Are there free simulator programs that let me see the resulting spectrum at the antenna?


texts:
I need to convert 5v to 3.3v, easy. I need an 2k resistor though so i looked if two 1k resistors could achieve the same effect. I found pretty contradictory information on the subject though, could someone help me out? (sry im kind of a newbie in electronics)  Source one: Are two (or N) resistors in series more precise than one big resistor?

Source two: https://www.eecs.tufts.edu/~dsculley/tutorial/voltageDividers/voltdiv2.html

EDIT: Yes, i am trying to power devices, an ESP8266-01 to be precise, the power will be coming from a Lithium battery.


texts: can I understand which way sound comes from?

texts:
Is it possible to understand which way sound source is located with using microphones? I was thinking using multiple mikes pointed out different ways and getting db differences to predict direction. Would it be accurate?

Edit: Lets say we have control of sound source. For example I can play a instant buzz at a specific frequency from source. Can I use time delays between microphones for getting direction. Is that process can be performed real-time. And if it can possible what kind of hardware should I use.


texts: Defining a nonlinear capacitor in Ngspice

texts:
I try to simulate an electronic circuit depicted in the  schematic below.

This circuit contains  two  nonlinear devices :
These two devices are depending on the charge density  and are defined as follows:

\$V_S = K \cdot Q^2 \$

\$I_d = k_{d1} \cdot exp(\frac{-Q^2}{k_{d2}})\$

where  \$I = \frac{d_Q}{dt}\$

Is it possible to use the Behavioral Source?
According to the ngspice manual 25 , the nonlinear Source are only depending on the node voltages and branch current.
In my case the nonlinear Source or device depends on the integration of the branch current.
Is it possible to  define a B-source which depends on the  integration of the branch current ?

\$ K ,\  K_{d1} \  \text{and}\    k_{d2}\$ are constant values!

\$ I_d\$ is the flowing current through the Diode-like device and is defined as follows:

\$ I_d = k_{d1} exp(\frac{-Q^2}{k_{d2}}) \$

\$ V_s\$ is the dropping voltage across the nonlinear condensator-like device and is described by the following term:

\$ V_s = k \cdot Q^2 \$


texts: Removing jumpers from an L298N Dual H-Bridge

texts:
I've got an L298N dual H-bridge which I'm using to control two DC motors with an arduino.  I want to be able to control the speed of the two motors using PWM.  My understanding is that I need to connect the two enabling pins ENA and ENB to PWM pins on the arduino (please correct me if I'm wrong).

If you notice closely at the picture of the dual H-bridge, you'll notice that the ENA and ENB pins are enclosed by jumpers connecting each of them to a 5V pin.  I believe that I need to remove the jumper in order to utilize the enabling pins directly (again, please correct me if I'm wrong).

If all the above is true, then this leads me to my primary question:  How do I remove these jumpers?

I've tried to remove them just by pulling on them with my bare fingers, but they don't seem to come out at all.  My fingertips are very large in comparison to the jumpers themselves and can't grasp them very easily.  I'm not sure if using pliers will damage the board in any way.

I'm a newbie at this, and I'm not sure how strongly attached the jumpers are to the board.  Is there any special trick to removing them?


texts:
I am trying to get a Multiplexer to work with the Arduino. Description at sparkfun Datasheet

I thought the wiring was pretty simple and as a basic test, I have AREF connected to C1(multiplexer) and a floating wire connected to C0. Everything on the interfacing side maps almost 1 to 1 with the arduino.

I am using this simple code for switching the multiplexer

void select_wire(char which){
    digitalWrite(S0,which&0x01);
    digitalWrite(S1,which&0x02);
    digitalWrite(S2,which&0x04);
    digitalWrite(S3,which&0x08);
    digitalWrite(EN,0);
    delay(1); //required?
}

and then I just read from the Analog pin at S on the multiplexer. My problem is that it is not switching! How do I fix this so that it will behave as intended and give a zero(or close) whenever I do select_wire(1) and read the analog pin?

Also, I am not using the Wiring "language" but I am using the Wiring library. I have also set all the appropriate pinModes  in the init


texts: Is the TC ("terminal count") output of a 4-bit sync counter (74163) reasonably assumed to be glitch-free?

texts: My gut tells me so, but the proof eludes me.  Effectively this output is the AND of all four bits.  These four bits go from 0 to 1 at very distinct times, assuming the counter is running at a reasonable clock rate.  From this, I assume that the TC output's transition from 0 to 1 is safe.  But what about the other way?  When the counter rolls over and all bits go from 1 to 0, may I assume that TC makes a glitch-free transition from 1 to 0 as well?  I sense that I'm missing some elementary rule of thumb here.


texts: How to calculate the size for differential amp

texts:
In the baker's book (CMOS. Circuit Design, Layout, and Simulation) ,it just teach us how to calculate the gain,but it does't teach us how to calculate the size for a amp,take the differential amp for example,if i want to let all mos be in the saturation region,how do i calculate it,because if the size is wrong,then the amp will not work.

I really want to know,because i just don't want to guess the size,and waste lots of time.Thanks all.


texts:
At first, I have to say, I'm not in Electrical Engineering, I'm studying for Computer Fundamental, and this question popped up, after a while considering, I decided to post it here.

I found some "quite similar" topics when posting this, but can't understand at all. Maybe because the OP and the answer providers are talking things like electrical engineers!

I can understand basic logic gates and basic flip-flop

This is the question:

  The figure shows an RS flip-flop using two NOR gates.   Which of the following is the  correct truth table for the flip-flop?  Here, “unchanged” shown in the table means the  outputs maintain a previous state, and “unstable” means the outputs are in an unstable  state.

This is the truth table I found on the internet, which indicates a is the right answer:

What I don't get here, is why Q = 0 and Q = 1 when S=0, R=1 and S=1, R=0 respectively, according to NOR gate truth table Q should be 0 and 0?

And how can we determine that Q will be "no change" or "unstable"? I believe there is a clear explanation for people like me can understand it, not only engineers!


texts:
how can I calculate the cut off frequency of the non inverting op amp circuit?
I calculated the one for the inverting op amp so far.

I calculated the unity gain bandwidth A0 = G1 + G2 / G2.

should I assume that s is wp?

thanks


texts: Arduino AC dimmer, with Wall switch control

texts: I'm building an AC dimmer with arduino, but I also want to have the ability to control the lamp from the wall switch (just on/off, with no dimming). What is the best way to achieve this? Do I also need to have a relay, so the two way from the circuit would be the relay's Normally Open (NO) and Normally Closed (NC) poles? Will the dimming circuit work with the relay, or will it cause any interference to it? Thanks!


texts: How to apply 180 degrees out of phase signal at inputs of differential amplifier in laboratory when only one function generator is provided in lab?

texts: In this differential operation experiment, two input AC signals have to be  applied to the bases such that they are 180 degrees out of phase with each other, but I am not sure how to invert an AC Signal. In DC,I had 2 power supplies and I just grounded the opposite polarity voltages together. What do I do here?


texts: Step Up DC DC [12 to 300] using MAX1771 Chip

texts:
I am trying to build my first circuit following the information posted here
12v to 300v Boost Converter - Ideal Inductor for 9kOhm load
I tried to answer there before opening this new topic,but I need at least 10 reputation....so,my goal is the same,obtaining 300 Vdc from a 12 Vdc source.

The layout is the following

All the datasheets of the components I used can be found here

Or here

The layout I used is pretty much similar to the one showed in the U1 datasheet,page 8 , fig. 2B.

I used a potentiometer instead of the R1 to obtain a variable voltage.

The input 12 Vdc is provided by a reliable and adjustable power source (set to 12 Volts and 1.5 Amp max. The source gives to the load the amount of power needed).

At first try the whole configuration worked,and I was able to obtain the desired output voltage. It was a little too much variable,from 280 to 320 approx, but I think that this is due to the high ESR of the output C4.

Then I was regulating the potentiometer a little randomly,and the configuration stopped working.

Now I am getting 28,7 Volt out,independently of the POT value.
Other Voltage values measured in the circuit:

V1(After Diode) 28,7

V1(Before Diode) 12

On chip U1

Vref 1,5

Vfb 0,2

V+ 12

Vext 0

Vcs 0

I tried to change one by one the following parts, U1 , Q1 , C4 , C1 with new ones.

I tried to elevate the value of C5 up to 330 pF.

I tried to remove C7 (which is not present in U1 datasheet).

The input voltage is fixed to 12 Volt,but the absorbed current is 0 Amps (the source as said can give up to 1,5 if requested by load).

Anyone has an idea of why the system is not working like in the beginning?
Thank you all in advance.

Datasheets:

U1 http://docs-europe.electrocomponents.com/webdocs/1253/0900766b81253c5c.pdf
Q1 http://docs-europe.electrocomponents.com/webdocs/10ea/0900766b810ea1ab.pdf
D1 http://docs-europe.electrocomponents.com/webdocs/11a6/0900766b811a65c3.pdf
L1 http://docs-europe.electrocomponents.com/webdocs/0fa5/0900766b80fa5686.pdf
C1 http://docs-europe.electrocomponents.com/webdocs/0027/0900766b800274c4.pdf
C3 http://docs-europe.electrocomponents.com/webdocs/1063/0900766b81063658.pdf
R1 http://docs-europe.electrocomponents.com/webdocs/0d81/0900766b80d81c44.pdf
POT http://docs-europe.electrocomponents.com/webdocs/0fa5/0900766b80fa58ed.pdf
R2 http://docs-europe.electrocomponents.com/webdocs/12cd/0900766b812cddf9.pdf
C5 http://docs-europe.electrocomponents.com/webdocs/002d/0900766b8002d512.pdf
C4 http://docs-europe.electrocomponents.com/webdocs/0ec9/0900766b80ec9186.pdf


texts: Converting single-phase 120 V or 240 V into three-phase 4-wire 120/208 V

texts:
I am needing to convert either 240 V or 120 V single-phase into 120/208 V three-phase 4-wire. The load needed is 30 A. My panel can supply up to 100 amps, so the amperage isn't an issue.

I've looked into static inverters, but then I'm going to need a step-down transformer which just adds to cost.

I'm considering a VFD rated for 120 V single-phase input, 208 V three-phase output. Yes, I know VFDs are used almost exclusively for motors. I will not be running a motor, there is already a VFD in my unit for a motor.

What is the best way to accomplish this? Can a VFD supply three-phase AC for something other than a motor?


texts: Difference between 74HC138N and 74AC138N

texts: What is the difference between 74HC138N and 74AC138, since the last one is way more expensive than the HC version? Can HC be used instead of AC version to drive TLC5490 Led Driver?


texts: Using noise to increase effective resolution of ADC

texts:
I managed to increase the effective resolution of a 10 bit ADC by several bits by repeatedly sampling a noisy input and taking an average over many samples.

I'm wondering what some techniques are for creating this sort of "noise" purposely to achieve the same effect. Obviously the simpler the circuit the better. There's probably a name for this technique that I'm not aware of?

I have some spare digital output pins on the microprocessor that I could some how use to generate the "noise". In case it matters, I'm using a 10 bit ADC with full scale 0-5v to measure the voltage across a thermistor (50k) in series with a 10k resistor, where the thermistor resistance will vary from about 7k to 160k.

Thanks!


texts: How does one use a transistor connected in either series or parallel with the load in a linear regulated power supply?

texts:
Let's say using a transformer and a rectifier to bring the voltage supply to roughly 18 DC (little voltage ripple which solved by using polarised capacitors) and I use a LM7812 regulator to bring down the capactior to 12V DC
How would I incoparted a high power transistor connected in either series/parallel with the load in a linear regulated power supply?
Edit: I want to be able to design a linear regulated power supply but with a bjt near the load, I'm on the basics of understanding electrical engineering and it's a requirement for my project however I'm not sure how to incorporate the transistor onto the linear regulated power supply. since the purpose of a transistor is to amplifer the current, would that impact the amount of voltage towards the end? My goal is to design a LRPS with a transistor. therefore I want to accomplish a goal to have such design to be able to supply electrical power to a load


texts: How to choose the right frequency when measuring coil inductance with LCR meter

texts:
I would like to drive a 12V DC hydraulic valve coil using a high side driver (VN7140AJ). The driver datasheet specifies the maximum demagnetization energy (page 24), and I would like to make sure that I can drive the coil without damaging the driver.
The datasheet for the valve does not specify its inductance and the manufacturer doesn't seem to know what I am talking about, so I decided to measure the coil inductance myself. I have a DE-5000 LCR meter, but depending on the frequency I select, the measured inductance changes:

100 kHz → 4.681 mH
10 kHz → 7.578 mH
1 kHz → 21.79 mH
120 Hz → 52.44 mH
100 Hz → 55.71 mH

Knowing that I'll be driving the coil at < 1 Hz, what frequency setting should I choose on the LCR meter, to obtain a value that can be checked against the demagnetization graph in the driver datasheet?


texts: When there is a potential difference between two points in an electric circuit current flows . Then why does not current flow through an open circuit?


texts:
Which board is better overall for .net mf development, the Tahoe 2 or the GHI EMX module?

Tahoe 2
GHI EMX

I'm looking at a general purpose board for plugging in different types of sensors (at once) and using functions like the NIC and SD file io.


texts: What is sine wave torque constant and voltage constant for electric motors

texts: I am wondering if anyone can explain to me what the sine wave torque constants and the voltage constants are and how to calculate them for a specific electric motor? Thanks!


texts:
I have an ARM926EJ MCU (datasheet) that I am learning how to program for a research project.  I have been researching, as well as reading a textbook on Professional Embedded ARM Development in order to learn how to program, and I have learned much about bare metal programming for my specific project.

However, I want to learn how to program with an operating system on my MCU.  I intend on running a simple program, and I would like for an operating system to do much of the low-level handling for me.  From my research, programming in the Linux environment will speed up my learning curve by much.

My question is two part:

How do I download an operating system onto my MCU?
How do I run a program on my MCU after installing an operating system on it?

If you are interested in the details of my project it is very simple: I will use the internal clock to detect the timing of 30 ns pulses received by a GPIO pin with a rough resolution; and I will upload these recorded clock values to another MCU via SPI connection.  So, I will have to simultaneously handle the GPIO pulse stream and the SPI upload connection.


texts: Altium won't let me move object to negative coordinates

texts:
I have imported a BRD document from Orcad to Altium. The origin is on the top left of the board and I can't move things or draw traces below or to the left of the origin, that is, negative coordinate levels, Altium just locks the mouse pointer and it doesn't move.
Is this a configuration inside Altium or is it a bug?


texts: Is it safe using more smaller ground wires instead of a bigger equivalent one?

texts:
I need to power up 4 resistive loads (at around 1A of current each, maximum), but the load provides only one returning ground capable of supporting 4A. I found that if I split this ground to 4 small wires, those can be put together with the other 4 supplies of each resistor, in one handy 8-pin connector.

In theory this split could work, since each of the 4 wires has more or less the same resistance, and so an average current of 1A can flow in each conductor.
But, is it safe in practice? Is there any lack of safety, or am I missing something else?

Thank you


texts:
I've been told that phase-locked loop (PLL) increases the bandwidth and therefore makes the time constant smaller.  (\$ \tau = 2Q/\omega_0 \$ and I understand \$Q \propto  1/ \delta\omega_0 \$)

I heard this in the context of the detection of forces with tuning fork sensors here  .

Could you given me an intuitive explanation as to why? The paper linked above explains it in terms of P and I constants but I wasn't able to understand it.

On page 22 (or page 30 of the pdf) here, it says the following "As explained in Refs. 54,56, a phase-locked loop (PLL) increases the bandwidth
and makes scanning probe microscopy with tuning-forks possible at reasonable scan speeds."

I went to the references and from reference 54, I was able to understand that in general, without a PLL loop, high Q means a tiny bandwidth and that it takes a long time to complete a measurement round.

Reference 56 seems to explain why using a PLL loop does solve the extremely long measurement time issue but it was this explanation that I wasn't able to understand


texts: How to overcome over-current in a circuit?

texts: I have a relay switch that operates at 10 A and 120 V connected to a DC motor that runs at 18 A and 36 V. Will the relay switch burn out? If so, how can I protect the relay switch?


texts: Do I need to use OpenSDA to program and debug MKL46Z256VLL4?

texts:
I am a novice to uC programming, though I have made simple circuits with the AVR ATMEGA series. For the AVRs, I used an ISP programming header along with the ATMEL-ICE. From what I am reading for the MKL46Z256VLL4 uC, it uses something called OpenSDA. I can see that the development board uses a PK20DX128VFM5 uC as the interface between the host computer and the target uC, the MKL46Z256VLL4.

Though if I am going to be implementing this into a product and need board space, do I need to use OpenSDA along with its circuitry? Is there something like the ATMEL-ICE for the MKL46Z256VLL4 uC that I can simply buy for ISP programming and debugging? My research shows that this would be the equivalent device but I am not quite sure:
https://www.digikey.com/products/en?mpart=U-MULTILINK&v=568

I am also not sue if it can be used with mcuxpresso.

PS: I am getting trained in embedded C in a few weeks and this is the uC we will be learning on along with using mcuxpresso. I am trying to get everything figured out for a development environment.


texts: Problem while simulating EMI Filter for power lines

texts:
I was designing an EMI Filter for the CE102 standard.
I was a bit confused on how to provide noise source to the circuit, since (as of my knowledge) EMI noise enters our system by parasitic capacitance or inductance coupled to power lines.
Also, I provided a noise source to the circuit as given below.
Please correct me if I am wrong.


texts: On/Off Transistor Switch by pulses of Voltage

texts:
So I have a remote switch to control a light bulb. The transmitter circuit basically consists of:

-transmitter IC ( RF 433M Hz)

-DC power supply

-Switch ( turn on/off by applying voltage, transistor maybe, or thyristor? )

-Mechanical Touch sensor that generates a pulse of 1.5-2.5 V within 0.5 s per press. The current generated here is almost negligible, around 20 nA.

(See the schematic)

All I need to do is to turn on the switch (transistor) when I press the mechanical sensor that is connected to the gate of the transistor to allow the DC power supply feed the "Data pin" and then transmit it through antenna.

The problem is, I don't know what type of transistor ( or any other electronic device) that can be used to detect such a small voltage/current pulse and turn ON.

Any suggestion? If you have totally different ideas to tranmist the data with that sensitive mechanical touch sensor you're most welcome to share with me and I'll appreciate it :)


texts:
I have been working a little bit on a hobby project of mine involving inductive power distribution. I have never done anything like this before and before I hook things together I would like to avoid blowing stuff up.

I plan on powering between 1 and 3 inductive loads (i.e. hand-wound coils about 4-6cm in diameter shaped like a ring with probably around 50-100 turns) in parallel from an H-Bridge. The coils will probably be wound with 28-30awg wire and my target is to transmit up to 2A between coils placed about 2-3mm apart. The 2A figure is the amount of current consumed by the "transmitting" coil and not the current induced in the "receiving" coil. Any of the coils being driven by the H-Bridge may or may not have a corrisponding coil lined up (in other words, some of them may have no "load" and others may have a load). This whole circuit may or may not be powered by an inductive method itself as well which further complicates matters of power.

I plan on running everything somewhere in the neighborhood of 100Khz, but that's really up for debate. I just know that it has to be a higher frequency since the coils are coupled inductively without any sort of core.

I understand that at the point of resonance for the inductor (which has to do with the capacitance between turns as I understand it), the inductor will stop being there in terms of impedance and the only limiting factor for current would be the resistance of the wire. I would imagine this would blow up my H-Bridge rather quickly unless I seriously oversized things, so I know I need to stay away from the resonant frequency of my inductor.

Here are my questions:

How does the inductor look from the viewpoint of the H-Bridge when nothing is inside its magnetic field other than itself? I imagine it looks just like an inductor
How does the inductor look from the viewpoint of the H-Bridge when another coil is placed in close proximity to it with a load attached?
What would happen if of 3 inductors in parallel, only one (or two) was coupled magnetically to a "receiving" coil?

Something I plan on trying out is the possibility of using the same coil for either sending or receiving power depending on sensor inputs (current and voltage on a coil, basically). What would happen if I were to drive an inductor which was inside the magnetic field of another inductor that was also being driven? What would I see from the perspective of either side in terms of impedance?

Thanks very much in advance for any insights.


texts: Basically i'm doing a small project where i'm using 2 dc motors on a bicycle as generators connected to a usb module to charge smart phones, is it possible to connect the motors together to generate the required voltage at a lower rpm.


texts: Why do higher frequency waves have better penetration?

texts:
In free space, lower frequency signals seems to go farther because the signal is either diffracted by the ground or reflected by the upper atmospheric layers, making it actually go farther.

In urban condition, where we need to penetrate walls, does 2.4GHz travel further than 433MHz radio?

In the electromagnetic spectrum, do Gamma rays and X-rays have good penetration because they have high frequency?


texts: AC signal gets unwanted DC offset when connected to circuit

texts:
Hi im a 4th year ELE student and I am creating a circuit which outputs 120khz square wave burst when it detects zero crossings from the input ac signal.
Here is the circuit diagram
Op amp 1 converts the ac signal coming from the transform to a square wave. The coupling capacitor changes the wave from +/- 5v into 10v to 0v. The lm7805 limits the voltage to 5v so it is a 5v to 0v square wave output. The atmega328p interprets the square wave rise and fall as the zero crossings of the original input sinewave. The second op-amp generates a 120khz square wave. The atmega328p toggles the transistor on/off to output this 120khz square wave when there are zero crossings. The circuit works as intended when using a power supply to input the 20v p-p sinewave.
The issue arises when I use a transformer to convert the VAC from the wall receptacle to input the sinewave instead. I am using a 1.1VA transformer it outputs approximately 13.2v p-p after the capacitor divider. The input wave looks like this after it goes through the capacitors (ignore channel 1):

Once it is plugged into op amp 1 a DC offset voltage appears which causes the square wave generated to not have a duty cycle of 50%:

here is what it looks like when I use a signal generator instead of the transformer:

here is what it looks like when i use an LM741 instead of a TL081 for op amp 1:

Lastly when i use an 9v 450mA ac-ac power supply instead of the transformer the issue is not present. Is it because the transformer is rated 1.1VA? is this not enough? What else could be the issue?


texts: Need to substitute a fusible resistor in an inrush limiter in a PSU

texts:
HP 6023A PSU again :) This time R1, which is a 20ohm 7W fusible. The relay pulls 1s after power is applied and I assume that the general idea is to take the egde of the rather substantial inrush into C2, C3, C4.

Since it is fusible it will blow in case something goes wrong at the input filter or later. Now the closest I can find is Yageo FKN7WSJR-91-22R from Digikey which is 22 ohms, but not stocked. OK, what I have there now are three 68ohm in parallell, but I want to stick to the original as far as possble. So what would be better? 22 ohm 7W or two 10ohm 3.5W of I can find such a beast?

Edit: When I compare to another HP unit (HP6038A), it says "0811-3667 res 20 5% 7W", no mention of fusible?

Edit:
I tried inrush limiting NTCs as per suggestions below in answers and comments. This is what the input current looks like with a fixed resistor of 22.6 ohms:

The first cycle is 20A or more. Unsure as we are outside the linear region of the transformer. With a 25 ohm NTC:

Two 80 ohm 1,6A (https://www.mouser.fi/ProductDetail/871-B57236S800M51) in series:

This was with the PSU set to output 100W into a resistive load. You can see the kick when the relay kicks in and then the load turns on. So, a 80-160ohm NTC?

It is rated for an Imax of 1.6A, but that is steady state, right. This NTC will only have any current through it for 1s (or if the relay fails). The label on the instrument says 850VA max and the mains fuse is 8A. 850VA at 230V is 3.7Amps. Should I select an NTC that is rated for 3.7amps? I guess not as there are not any large enough ones with that rating.

I feel more inclined to follow the table on page 3 of the datasheet where they discharge through the NTC. Or would the Ametherm MS22 12104 which is rated 120ohms 4A be a better choice?


texts: Voltage controlled current source question

texts: Need to find ratio Vs/Vo in terms of the 3 resistors and gm. I have expressed Vo/Vs as gmvgsR2/Vs but am unsure how to express Vgs in terms of the R1, R2 R3 and gm.


texts:
Wondering why you would choose to use smaller capacitors in parallel vs one bigger one.  Here's an example:

Multiple in Parallel

Page 4: One larger C

Is this a component size and track width choice?  Thanks!


texts: How to obtain current-voltage trace using a picoammeter?

texts: I am designing a probe where ions will finally impinge a metallic collector. The collector is connected to a picoammeter to measure the collected current. How can I finally obtain a current-voltage trace? Can I connect the picoammeter directly to an Oscilloscope which will store the signal and analyse it by a computer? Or can I directly connect the picoammeter to the computer using GPBI cable?


texts: Unstability condition for positive feedback network involving phase change

texts:
For positive feedback:
\$G=\frac{A}{1-AB}\$
According to Wikipedia, this system is unstable for AB>1.
This condition appears to be for the cases when 'A' and 'B' have real values. But in general, A and B are complex quantities. Is there a general form of this condition for complex AB (e.g. feedback network consisting of RC phase shifters)?
I considered the possibility of |AB|>1 being the general condition. But it seems wrong since it would imply that even for AB<-1 the system is always unstable, which is wrong since the system is in negative feedback for AB<-1.


texts: Multi-phase Buck Converter - Does the inductor breakdown during the startup transient?

texts:
In a multi-phase buck converter, when and how does the inductor breakdown?

Lets say the multi-phase buck converter has the following parameters:

V_in = 50V, V_out = 25V, P_in = 225W (so max amps = 225V/15V = 15A), R_load = 1 Ohm, Switching_frequency_per_phase = 62500Hz and the converter is 4 phases (lets call them phase A, B, C and D respectively)

Inductor wire is rated at 15A current and the saturation current rating is also rated at 15A.

When the phase A first turns on (phase B is off) the current going through the inductor will be (50V-25)/1Ohm = 25A. Will this current breakdown the inductor? Keep in mind that when the phase B turns on, the inductors on phase B will start drawing the rest of the current and so both inductors will have 25A/2 = 12.5A which the inductors can handle.


texts: Crystal or Crystal Oscillator for time sensitive device

texts:
A device that I'm working on is controlled by ATmega328P microcontroller.
This will be some sort of a watch, therefore I want it to be as precise as possible. For instance if left to run for a whole year I want the time deviation to be not more than absolute value of +/- 10 seconds by the end of the year. (I'm not saying the battery power will be enough for the whole year..)

Is crystal oscillator more precise than crystal with caps driven my micro? If so, are crystal oscillators more commonly used in time sensitive applications?

Or just a regular crystal will be sufficient and more suitable? (Especially when they will not consume power like oscillators) I don't need atomic precision of +/- 0.000001 sec/year.


texts:
I am doing a project, in which there are two dc source a) 48V_ DC b) 48V_Reg to power the board.
If either of two is present, that power source will power the board.
If two power source is also present then it should select 48V_DC
Please let me know any IC or circuit in where I can implement above features.


texts: Reading a Li-po battery's remaining charge

texts:
I want to read the remaining charge on a Li-po battery in a device I'm making but I'm confused as to exactly how to get an accurate reading.

I know that the voltages of the battery are different based on how much current you are pulling off of it and this will affect the reading. The problem is that the device I'm making pulls power off the battery in short bursts (not good for the battery but no way around it) so it seems to me to make sense to read the battery level while the device is idle (drawing mA as opposed to amps) and match that voltage against the unloaded voltage charts.

How long do i have to wait after a surge demand from the device before the battery voltage stabilizes again and I can take an accurate measurement of the remaining voltage of the battery? Or am I going about this the wrong way all together?

The batteries I'm using are in 4s2p configuration with individual cells rated at rated at 1500 mAh.


texts: Is it possible to create a reusable full subtractor in SystemVerilog?

texts:
I am trying to design a full subtractor in SystemVerilog.
I searched on Wikipedia and I found this https://en.wikibooks.org/w/index.php?title=Microprocessor_Design/Add_and_Subtract_Blocks
module full_adder(a, b, cin, cout, s);
   input a, b, cin;
   output cout, s;
   wire temp;
   temp = a ^ b;
   s = temp ^ cin;
   cout = (cin & temp) | (a & b);
endmodule

But this code seems quite lengthy, and works for only the 1-bit case. I am thinking of taking the 2's complement of the second operand to do subtraction, but that would work only for the 1-bit case. 2's complement is by applying the bitwise negation (~) operator and adding 1 to it.
But this won't be reusable since it works only for the 1-bit case. Is there a more reusable approach?


texts: Grounding and shielding between isolated devices

texts:
I have a battery operated micro controller with a hall sensor, mounted on a motorbike. The hall sensor has a shielded cable to counteract spark plug induced EMI. By default, the entire setup is isolated from the bike.

I am not sure what to do with battery negative / motorbike chassis / cable shield - please, give me advice regarding the following setup options:

option 1: cable shield connected to battery negative
option 2: cable shield connected to motorbike chassis
option 3: cable shield connected on both, the battery and the motorbike

...which further rises the following questions:

is connecting the battery negative to the motorbike chassis good or bad?
presumably, when the cable shield is connected to the battery negative, I do not need a separate negative carrying wire inside the cable as the shield can be used for that purpose - is it true?

Thanks!


texts: Please explain the following Verilog code of a D flip flop?

texts:
I am learning the Verilog language. Can someone explain the questions I ask in square brackets [] :

module d_ff(q,d,clk,reset);
     output q;
     input d,clk,reset;
     reg q;
     always @(posedge reset or negedge clk)  [what is this always @()]
     if (reset)
         q<= 1'b0; [what is 1'b0]
     else
         q<=d;
endmodule

For viewing output what is my next step? Does it mean I have to write a stimulus block after this code? What is the meaning of a stimulus block?


texts:
I have this circuit:

I was asked to measure the inrush current for this circuit section.
One floating output actually goes to a microcontroller input and the other goes to an op-amp input terminal. While performing the inrush current test, I have disconnected the connection to the microcontroller and the op-amp.
I am using an electronic load to sink the 5mA at the cathode side of the diode. Electronic Load
This is what I observed:

The maximum current through the diode is 6.80A for a time duration of around 10us.
I am unable to understand how there can be such a huge current through the diode D0001 even though it is for a small duration. Please check the input voltage rise time also.
What is the reason behind such high current through the diode D0001?


texts: Connecting breadboards with different batteries to a single switch

texts:
I have three different breadboards with ten LEDs & resistors connected in parallel.
All three are powered by a 9v battery.

I was wondering if there would be a way to wire all three batteries to a single switch so I could turn everything?

Here's the breadboard diagram:

Thanks!


texts: Will this circuit be able to power a 12V DC motor

texts:
The circuit below is designed to power a 12V DC motor, which has to operate in both directions with variable speeds, using the Arduino as control unit.

The center components (resistor, coil and capacitor) represent the motor (mainly for simulations.) The 4 transistors are power transistors (I'll probably use TIPs.)

The 2 sources at the bottom represent 2 PWM signals, given from an Arduino. The voltage divider in the center is there to measure the voltage and give it as feedback to the Arduino.

I already know that the voltage at the voltage divider can get as high as 6V, which will damage the Arduino without the Zener diode.

How can I solve this?

Will there be any other possible problems I need to investigate before buying the components and trying the circuit?


texts: In specifications for switches, what does "250 V / 20(4) A" mean?

texts: I've specifications of 250V switches here saying "250 V / 20(4) A" or "250 V / 10(4) A". What do these "20(4)" or "10(4)" exactly stand for? Does "250 V / 20(4) A" mean it is a 20 A switch or a 4 A switch?


texts: Using a x-speed transmission with a DC motor

texts:
I would like to ask whether there is any point in using a transmission with different gears (like the gearbox in a car) with a DC motor?

For instance in an RC car.  Are there any benefits to using a smaller gear ratio to decrease the rpm of the motor?


texts: Constant Current Driver with a Step-Up Regulator IC

texts:
First of all, although I couldn't find any similar question(s), excuse me if one has been asked before.

I want to make an LED driver for 2 different LED strips. One needs about 45 VDC and the other needs about 54 VDC. The manufacturer recommends using 150 mA constant-current driver.

So I'll make a single driver operating from 18-32 VDC for driving both. Note that only one of them will be driven at a time, not both at the same time.

Anyway, I have an LM2577 on hand and I want to use it as a constant current driver despite it is a voltage regulator. Of course there are many ICs on the market for this purpose, but I want to use this IC if possible. So here's my concept design:

simulate this circuit – Schematic created using CircuitLab

Since the IC will keep the FB pin at 1.23VDC, I think the strip will be driven with a constant current of 1.23V / 8R2 = 0.15A.

Will this work? Is there anything wrong with this? Any disadvantages or potential faults? Needs any improvements?


texts:
I need help creating a simple circuit. Essentially what I would like to accomplish is that by pushing a button to close a circuit, I would like to take that continuous signal and create multiple pulses, say 1 second apart. The pulses are only to keep going as long as the button is pressed and are stopped when the button is released.

Basically when I close the circuit by pushing a button, I want to turn it into multiple on-off pulses spaced 1 second apart for as long as the button is pushed. Keep in mind I have next to no knowledge of electronics, so if you could guide me in layman terms, it would be much appreciated. Thanks.


texts: 555 timer multivibrator charge and discharge

texts:
With this kind of connection I expect 555 to run as a multivibrator.

As far as I understand the discharge of the capacitor should be via R2, while charge of the capacitor via R3 and D1. => discharge slope should not depend on R3.

However,

I've got 3 different discharge slopes, for 3 different values of R3

Moreover, when R3 = 0, it seems as not a multivibrator anymore with constant voltage across the capacitor equals supply voltage.

Could anyone please explain, why discharge slope depend on R3, and why when R3 = 0, capacitor holds constant charge and does not discharge at all.


texts:
Whats the correct name for this button, it's 12mm high measured from the PCB with 6.5mm base. It is flexible in that it can move around in the switch base.

The button is used on an instrument panel on a motorcycle to adjust the clock. In the case of this switch it's stuck stopping me from changing the time.


texts: Device to power either a red LED or a green LED

texts:
I have a green LED and a red LED. I want a sort of switch to turn either the red LED or the green LED on.
For example:
Where if the switch is off, the red LED is on but if the switch is on, the green LED is on.


texts:
This is a gate driver circuit for a boost converter.
However, there is one part that I don't understand. Could you explain it or give me some links so I can read up about that?

Here is the part that is confusing:

The addition of several stages to the driver introduce a
propagation delay between the input and output signals. This
delay degrades the control loop phase margin and may lead
to instability. To counteracts this effect the drivers logic gates
connected in cascade should be progressively scaled.

I don't understand why delay degrade phase margin and why scale these gates like that will solve the problem.
Thank you very much for help.


texts:
I am a newbie in antennas generally, although I have a good grasp on electromagnetism and the physics involved around the topic.

What I want to do is to build a system that will be emitting a wave with frequency between 3 and 10 GHz (not defined yet) into a medium and it will be reading the reflected energy, in order to characterize some properties of the medium.

So I have several questions regarding this topic:

First of all is it possible to create 10 GHz wave on a PCB? Any clue on how to do something like, regarding the circuitry?

Do I need two separate antennas, one for transmitting and one for receiving, or one antenna is enough? How does one read the signal coming from an antenna?

How do I design the antenna? Does the shape of the printed antenna has any effect on the system's performance?


texts: Controlling a power supply with a MOSFET

texts:
I'm making a circuit that will have a main part (up to 5A load) in a back box, mostly unreachable, and a control panel at the front.
I want to have a kill switch at the front panel, so that I won't have to reach for the back part, but I don't want to bring the main load wires there, so I was thinking of having a MOSFET control the circuit, and then I would only need the wires to control the gate and a switch at the front.
Here's my idea:

Only SW2 would be at the front (SW1 would be a backup at the back), and the two wires to connect it, with everything else at the back. VCC and ground would then connect to the rest of the back circuit.
Does this even work?


texts:
I am trying to connect ICP CON i-7565 (USB <-> CAN interface) to a custom made device (supporting CAN 2.0B, proved to work with PCL-841 card). Although I think I have configured the Baud rate and acceptance code/mask correctly, I can't see any CAN messages coming from the device (ICP provides a tool that should allow me to send and receive CAN messages).

I-7565 might be wrong interface for me, I might have misconfigured it, or it is simply broken. Or I am just doing something wrong out of my ignorance. I don't think anyone can help me with my specific problem, so I am rather asking for general information on how are problems with CAN bus identified and analyzed. In TCP/IP for example, you would call ping, you'd recheck your IP address, gateway settings, etc.

Question is: How do you troubleshoot CAN bus communication?


texts: i2C : pull-up resistors "design pattern", Shielded cable and connector?

texts:
I'm designing an arduino based board which will uses I2C port a lot. I want to be able to connect several slave devices, and/or connect several mother boards together (at least 4 would be great). The I2C will run at 400kHz @ 3.3V. The flat cable between the boards can be up to 2 meter long.

Edit : When I say I plan to use 4 main boards at the same time, only 1 of them will be the master/host.

Pull up resistors

My problem is not really about choosing the right value of the pullup resistor (for that I found this interesting article). It's more about "design patern".

According the aforementioned article, I should use resistor between 4.7kR and 1.5kR. It's ok as long as I only have one main board with its pullups and slaves with no pullups, but if I connect several main boards together, the pullup resistor will be in parallel, and then too low.

Should I add some jumpers to enable/disable the pull-up resistors ? I don't like this solution at all, it takes space on the PCB and is not handy. And I want my board to be easy to use, just plug things together and everything works.

If I use 4.7kR resistors and hook up 4 main boards together, I will have a equivalent pullup of 1.2kR, which is pretty low, and then it will consume more current (my device is battery powered), the devices will have to sink all that current (I can't predict the sink capability of the slaves that will be connected to the I2C port).

Shielded cable

Should I use shielded cable between devices as it will be quite long (up to 2 meters) and the voltage quite low (3.3V)?

Connector

Finally, I didn't found any "regular" I2C connector. The most common seems to be 4 pin SIL connector with pins in that order : GND, VCC, DATA, CLOCK (on seeed's grove or tinkerkit for example). Sounds good to me, but any suggestion is welcome.

Naming

Bonus question : should I write "I2C" or "TWI" on my PCB ? According to wikipedia TWI seems to be an incomplete implementation of the I2C protocol. Tinkerkit uses "TWI", but "I2C" seems to be more common in electronics.


texts: How can I power a NodeMCU from a 12VAC building intercom?

texts:
Original situation
I live in an apartment with a 12VAC intercom/open button for the street door.

Current situation
I've wired a normally-open relay, linked to a NodeMCU, across the terminals for the open button. This works fine and I can now remotely open the street door. The NodeMCU is currently powered by a 9V battery and draws around 15mA.

Desired situation
I don't want to rely an a battery that I will exhaust, so I'm thinking of one of the following, and please feel free to recommend one or the other, or any other alternative approaches.

Option 1. Power the NodeMCU from the intercom. I understand I can use a bridge rectifier to produce a nominal 12VDC which I can pass through a small regulator to get a stable voltage to power the NodeMCU. But If I do this, won't I effectively be closing the switch circuit and thus permanently opening the door?

Option 2. Continue to power the NodeMCU by battery, but have it deep sleep, only to be awakened when the street doorbell is pressed. I understand I can do that by applying a voltage to RST. I'd appreciate any hints on how not to fry my NodeMCU by applying too much voltage with this approach.


texts: Adjusting Voltage regulator with PWMed optocoupler

texts:
I have LD1084V adjustable voltage regulator powering servo and want to control its output from MCU. Optocoupler should behave as variable resistor so my thinking was :

I am mainly concerned with gray rectangle area - other part works fine so far.
MCU is Attiny85.
I've measured current at RP2 when running servo at full speed (by voltmeter only) and it was 0.9 mA max.
Optocoupler should bypass RP2, when fully open.
R1 is for diode protection.
R3+C1 should smooth PWM to somehow-steady analog voltage.
I've used lot of internet to put it together, but I am still a noob ... so could as well missunderstood some parts all together.
I didn't tested it yet (I expertly killed my only opto at hand, so waiting for replacement).
I want to ask if my thinking is right and if this can be done with transistor-based opto (photodiode ones are a bit pricey)?
Thanks


texts: Use a single Voltage translator for multiple I2C with same voltage

texts:
Let's assume our Microcontroller is running on 3.3V and we have multiple I2c devices running on 3.3V and some on 5V. Can I use a single Voltage translator such as PCA9306 to run all 5V i2c devices, or do I need a voltage translator per each device which is not 3.3V? (All share same GND)
Image just for demonstration

simulate this circuit – Schematic created using CircuitLab


texts:
I recently got in my hand an old phone lcd display.
Display itself seems to be useful so I took apart it from the rest, and I begun to test its behaviour.
Display is named SHARP LM167511 and its control is made by the OKI MSM6262-01, of which I found the datasheet.
Display PCB has also two rows of buttons by its side, so the exported header by which telephone controlled it are buttons headers and OKI controller pins.
Referring on the datasheet names, pins are:
GND, VCC, V5, CS, R/W, E, A0, A1, D0~7
Based on my previous experiences, I assumed V5 to be the contrast of the device, so I connected to it a potentiometer, my hope was that changing V5 voltage I could see something, but it wasn't the case.
So I built an arduino based circuit trying changing signals on the control header. Until now I had no life signs.
I agree with everyone would say: consider it broken. but I also have a spare one which does the same.
My request is: does anybody have experience with this device, or other LCD who could give me any hint on how to proceed?


texts: LPC1110 confusion about default system clock and uart baud rate

texts:
I'm trying to get acquainted with ARMs on example of LPC1110 device. And there is some confusion about selecting baud rate for UART.

I suppose it is running at 12MHz after reset. The LPC111x manual (pdf) says that I should set UARTCLKDIV first (as I understand, it is pre-divisor for UART clock). I set it to 1. So I think UART_PCLK = 12MHz

Now I need to load divisor to 16-bit latch U0DLM:U0DLL. Manual says that

baud rate = UART_PCLK / (16 * divisor)

There is also fractional divisor adjuster, but I think I do not use it.

So the code looks like this:

int divisor = 12000000 / (16 * 9600);
UARTCLKDIV = 1;
U0LCR = 0x83; // enable divisor loading
U0DLM = divisor >> 8; // divisor high byte
U0DLL = divisor & 0xFF; // divisor low byte
U0LCR = 0x03; // disable divisor loading
U0FCR = 0x07;

And wonderfully this do not work, i.e. I see the mess in terminal. After some googling and experiments I've found that it will work all right if I change the first line to 48MHz:

int divisor = 48000000 / (16 * 9600);

So I supposed PLL could be enabled - but as I read the manual I came to conclusion it is not. After reset main clock should work directly from internal RC oscillator. And I use value 12000000 MHz when burning firmware with mxli tool.

What may I miss here?

P.S. Code example #3 from here do not use 16-bit divisor, instead loading 0x9B (155) to UARTCLKDIV. They say this gets 19200 baud rate which means they also run at about 47.6 MHz (as I understand).


texts: Raspberry Pi I2C with multiple slaves behaves erratically

texts:
I have a Raspberry Pi 3B+ that I'm using with two I2C devices on the same bus. The first device is a DAC from Adafruit (product here). The second device is an accelerometer, also from Adafruit (produce here).
The DAC is used to control a DC motor driver for a very large 24V motor. The accelerometer will measure vibrations caused by the motor.

When I use either device with the other disconnected, it works great. (I'm using the python libraries provided by Adafruit for both devices.) But when I try to use both devices at the same time (that is, both are powered on), I get interference. The accelerometer reports frequent spikes in acceleration (despite being perfectly still), and the DAC will occasionally change its output voltage. Also, the RPi frequently fails to read the accelerometer, throwing me an IOError. I don't understand what's going on.

More details

The DAC is powered by 5V. The accelerometer is powered by 3.3V. Both devices have built-in 10kOhm pullup resistors on their I2C lines going to their respective voltage sources. The RPi has built-in 1.8kOhm pullups.

Even though the DAC is on 5V, I measure 3.3V on the I2C lines as the resting high state. Also, the accelerometer is designed to work with 3.3V or 5V I2C voltage.

The DAC is connected to the Raspberry Pi by mere 4-inch wires, which are held apart from each other to minimize parasitic capacitance and EMI. The accelerometer is connected by 3 ft wires, which may seem long, but my o-scope shows clean I2C waveforms at the device end. At the RPi end, the waveforms are not quite as clean, but they seem good enough.

At the accelerometer, the I2C waveform is slightly rounded when the DAC is turned off (which is what you'd expect from high parasitic capacitance). When I turn the DAC on, those waveforms get crip and square. I would've expected the opposite to happen when I add a second device to the bus.

I took the RPi, DAC, accelerometer, and motor driver out of the machine for further testing. I disconnected the 24V power supply and 24V motor and left them in the machine. When I test the I2C devices now, I am unable to replicate any of the errors. It works flawlessly.

I considered that the problem might be EMI from the motor being picked up on my long accelerometer wires, but the motor did not have to be moving for my problems to appear. My 24V power supply is switch-mode, so perhaps it is what was producing EMI.

I considered faulty/damaged/shorted-while-troubleshooting components. I tried a new accelerometer and a new RPi and got the same results. I have not tried a new DAC. However, if any of these components are faulty, I would not expect them to work at all; and yet they work fine most of the time.

I tried changing the I2C frequency on the RPi between 100Hz to 100kHZ (the default) but I saw no effect.

I have verified all the wire connections.

As it is, I cannot put my electronics back in the machine without them behaving erratically.

Edit

Just for kicks, I put two knots in the accelerometer wire. The errors and spikes coming from the accelerometer were much reduced. However, I lost all communication with the DAC.


texts: Analog method for measuring distinct phase shifts

texts:
I have a signal that undergoes distinct 90 degree phase shifts but has an unpredictable frequency over a predefined range (anywhere from DC to 300MHz). From my limited knowledge on PFDs, they can only measure a phase difference between a reference frequency and another of the same frequency. Is there an analog way to detect those 90 degree phase shifts (like the ones that occur in BPSK modulation) and/or a method to measure the phase difference between two waves of different frequencies? Phase and frequency are linked hand-in-hand so I don't think the latter is possible.
I'd like to avoid having to use ADCs and digital signal processing if possible.


texts: 4 Wire Thermostat for Two Separate Heaters

texts:
Is there any reason why I cannot use a 4 wire thermostat (Honeywell T410B, DPST) to control two separate heaters (they are fairly close to each other)? The contacts are each(?) rated for 22 A and let's say hypothetically the heaters are going to draw 15 A each @ 240 VAC, so I cannot have both connected in the traditional sense. My plan is to have one heater on L1-T1 (thermostat contacts) and one heater on L2-T2 (N.O).

Below is the schematic of the typical system. Usually the L2-T2 contacts are used to break the neutral side of the heater (I'm assuming for extra safety). Since both the thermostat and N.O contacts operate simultaneously I can't see why this shouldn't be done. Both sets of contacts should be rated for 22 A since both will experience the same current when used in the traditional manner.

The real challenge is that I have one heater per wall receptacle (space heater) and I'd like both to turn off at the same time with one thermostat, rather than two separate thermostats.

I did contact Honeywell support, but I'm not confident in their responses.

UPDATE: I believe Eugene Sh and Charles Cowie are correct. The second set of contacts is only controlled via a adjustment knob. Ensures that when you switch the knob to OFF it remains off, regardless of the room temperature.


texts: LT Spice Automation and automatic Plot data extraction

texts: I am trying to automate LTspice from Matlab. I am running Lt spice netlist which is creating the .raw file. But I am unable to automatically extract the polt data after that. Any solution on how to extract the netlist output with Matlab or any other way except manually clicking export as .text?


texts: Raspberry Pi 2 to arduino RF Serial link with USB to Serial TTL Converter

texts:
This is my first question here.
I want to have a communication channel which will use a 433 MHz RF TX-RX pair. I want to use a Raspberry Pi 2 as a transmitter and an Arduino Mega as a receiver. Is it possible to replace the usb cable using the RF transmitter with a USB to Serial TTL Converter with the Raspberry Pi 2?
The communication would be like this :

Raspberry Pi 2 --> Serial (USB) port --> USB to Serial TTL Converter --> RF Transmitter --> Air --> RF Receiver --> Arduino

Now I dont want to program the arduino wirelessly or anything but only have the Raspberry Pi send small (extremely - about 100 bytes/sec) amounts of data from a python code to the arduino wirelessly.


texts: Converting headphone signals into MP3 using Arduino

texts:
For my project, I am looking for a way to take headphone audio signals (from TVs and other appliances), convert them into MP3 and send them over WiFi to a remote device (PC or other) using Arduino UNO and a Wifi Shield.

Any ideas as to a circuit design and required components that would achieve it?

Thanks!


texts: H-Bridge IC decay modes and MosFET conduction

texts:
TI's DRV8801 H-bridge has different decay modes, i.e. what happens when the switches are turned off - short the motor (slow decay) or reverse it until the current has decayed (fast decay).
They say that synchronous decay / rectification is more efficient than just using the freewheeling diodes for each FET (asynchronous decay / rectification).

However, the (overly simplified?) schematic figures in their application note SLVA321 (March 2009) all show N-channel FETs and thus a conflicting flow of current:

vs

I am omitting the figure of the intermediate phase of asynchronous rectification by means of body freewheeling diodes.

Are they using additional FETs or how does it work?