texts:
I am trying to determine all possible failure cases for a heating application with a peltier. Most sources I find on the internet are looking at peltiers as a way of cooling CPUs, so I have heard already that of course they act as an insulator when dead, but I am trying to find out more of the worse-case-scenario of heating effects.

It is unclear from my research whether a failed peltier or an improperly managed peltier ends up effectively being a resistive heater, and if so, is it at the wattage level of the original peltier?

I regularly have used peltiers in heating box applications currently and am trying to design a safer heat box, out of concern that a failed 100W peltier would act as a 100W heater which might create an isolated hotspot (say if the fan also failed) capable of igniting something. But my experience has not validated this theory. In my experience a failed peltier generates less/no heat compared to when it was functioning, not more. But perhaps there are multiple types of failure.

So can anyone give me a straight answer on the possible temperature/error states of a peltier? I am guessing it is something like.

Working Peltier: maximum surface temperature on hot-side is a fixed differential over the ambient room temperature on the cold side defined by the heat pump capacity and helped along by a small amount of resistance.
Shorted Peltier: becomes a typical resistor, at a wattage dependent on where the short occurred inside? Is this common, possible?
Broken Connection Peltier: does nothing if the connection is broken somewhere inside.


texts:
I want to design a circuit using ws2811 on page 5 of the datasheet It says "To prevent the reflection and hot-swap protection, we suggest to connect a 33ohm resistor at the data input or output port for impedance."

But on modules and boards on the market I don't see these 33ohm resistors, How important is it to add these? In what situations may it be neccessary?


texts:
For the circuit shown below:

It's obvious that $$\mathbf{i_1= 4 A}$$
So, is it acceptable to apply KVL to the left loop as follows:
$$\mathbf{3i_1+5i_1-3i_2-5i_3= 0}$$
$$ \mathbf{8i_1-3i_2-5i_3= 0}$$
substituting for $$\mathbf{i_1= 4 A}$$
$$ \mathbf{8*(4)-3i_2-5i_3= 0}$$
$$ \mathbf{3i_2+5i_3= 32\qquad\qquad \fbox1}$$
Is equation 1 above accurate or not?
Source:
FUNDAMENTALS OF ELECTRIC CIRCUITS, SIXTH EDITION By Charles K. Alexander, ISBN 978-0-07-802822-9


texts: How does a thermoelectric generator generates electricity?

texts: I want to know how a thermoelectric generator generates electricity. I know that it converts 'heat flow' to electricity.But some people say it consumes heat and converts it into electricity.The rest of the heat is dissipated  through the other side. Which is true?


texts:
I am working with AT90USB1287 controller with USB communication to PC. I am sending some commands from PC to controller using USB communication to activate some controlled switch. I am able to change the states of switch by sending commands(ON and OFF, voltage controlled switch).

My problem is when switch is ON and unfortunately user forgot to send OFF command from PC and he shutdown the PC but still controller is running or suppose if i lost PC connection via usb,  At that times it is causing problems.

I want to check the in ATUSB1287 controller code itself if usb connection loosed then swicth t command should be zero.

Can any one help me how to know usb connection is lost or not? this is my approach like is it possible to check in the main loop that usb connection is lost? if lost then switch off.

Any other way to switch off? after losing connection to PC or PC shutdown.

I am new to this type of thing, if anything wrong in this question please excuse me.


texts: Variable Current Lead Acide Battery Charger

texts:
Digitally controlling charge voltage with some regulator like Lm317 is a matter of using some resistor and transistor as stated in lm317 datasheet to select from multiple pre defined voltage.
But what about choosing output current ? How it can be adjust with digital signals from microcontroller ?
Normally what i found on the web and lm317 datasheet is using a fixed high wattage resistor to limit charge current.
I am trying to build a smart charger as a part of smart ups and i want to use a range of battery with different voltage and current and it must be selectable from software.
So what is your suggestion for digitally selecting charge current ?


texts: how to write output of the monitor to a file

texts:
I have a testbench and a verilog modules. I want to write ouput of the testbench to a file anmed as output.txt. While doing this job, I want to use $monitor.

Is it possible ? If yes, can you give me pseudo code of that segment ?


texts: NPN transistor switch with load at emitter pin

texts:
I found a schematic with a 55 timer driving two transistors, each of which switches an LED (see below).
When the 555 output is low, LED1 is OFF and LED2 is ON.
When the 555 output is high, LED1 is ON and LED2 is OFF.
I have the query why it uses the Box 1 circuit, which looks like a common collector circuit, instead of the Box 2 wiring, which is more common.
Does the Box 1 circuit have some advantages over the Box 2 circuit?
Also, I think capacitor C2 is to stop oscillations but I can't completely understand what oscillations it is for. And would so small a capacitance value have any impact?


texts:
I am designing a circuit to protect a load from over-voltage. The voltage at the load must be around 380VDC and the current consumption will be around 2A. In normal operation the Power Supply must increase the voltage as the load pulls more current so that the voltage drop across the cable is compensated.
However, if by any reason the power supply shoots the voltage to 800VDC, the circuit on the load must be opened, avoiding the load to see such a high voltage. The power supply is capable of delivering 8A.

I tried the circuit in the picture, it works pretty well as it opens at 400VDC (triggered by the two zeners in series). But at 500VDC the zeners blow up even with a 150k resistor.

Would a crowbar work in this situation ? I really don't want to use glass fuses to avoid opening the enclosure where the load is installed.

Any ideas?


texts: When do I have to use rectifier-inverter, and when is "dimmer circuit" sufficient in driving AC motor?

texts:
I'm trying to design a device that is to use a variable speed 1-phase AC motor. I still haven't decided upon power and other parameters of the motor. I have a few models to choose from, with "bigger is better" metric, but complexity of the device is a significant factor, so I'd prefer to avoid the need to use an amplifier-rectifier circuit.

Is there some rule-of-thumb or guide, how far can one go using a circuit with a triac chopping pieces of phase off the AC supply voltage, and when that solution is inadequate and I need a variable-frequency rectifier instead?


texts: Where does j come from in the reactance of L and C components?

texts:
So the reactance of the inductor is jωL while that of capacitor is 1/jωC. My question is that starting from the differential equations that describe the dynamic behavior of these circuit components, how in the world did a person actually realize that Oh! lets put a j which represents an imaginary number?

Why is it merely j and not -j or some other j value? And why is j not in numerator of both the reactances?


texts: Is it safe to use my multimeter to test UK wall outlet voltage?

texts:
From the question it should be clear I'm no expert. Just want to learn.

I have a digital multimeter.

If I connect the multimeter to hot+ground & hot+neutral on the 240v 50hz (max ~30A) AC wall outlet to get an AC voltage reading, is it safe to do so on the input fused for 250mA? The 10A input doesn't allow voltage readings.

And if I connect the 10A input will it be safe to measure the amperage of the wall outlet? I've already used the 10A input to successfully measure DC current of a 12V 1.25A power adapter, and the 250mA input to measure the voltage of the same device.

Current, in amps, is basically provided based on demand right? So I'm thinking the multimeter won't demand much to measure voltage (microamps) so it won't blow the 250mA fuse? Then when I switch to Amp Mode connected to 10A input it won't demand more than 10A to give a reading, correct?

Please excuse me if I've said anything totally incorrect. I'm an electronics novice just trying to learn the fundamentals.

Thanks!


texts: Is FCC certification needed for receiver device?

texts:
Is FCC certification needed for product acting as receiver but having transceiver chip inside? or there should specifically be a receiver only chip inside in order to bypass complicated certification process?

The document by TI "ISM-Band and Short Range Device Regulatory Compliance
Overview" here states that "Receivers do not need a certification, but the vendor has to state in a Declaration of Conformity (DOC) that each device complies with the spurious emission requirements of unintentional radiators according to section 15.209."

The frequency of operation for this device is 902–928 MHz ISM band.


texts: --Electric Bike-- How to measure left percent of battery?

texts:
I intend to make a module to measure battery of the electric bike instead of using the bike's indicator.

Measured battery (VRLA) is 48V, 12Ah. As I know, the specifications of an battery are voltage(V), current(A) and capacity(Ah.)

I want to find out the basic knowledge about battery help to measure the quality, the left electric percent.


texts:
I've got OV5642 camera module initialize issue.
I put 3.3V and 24Mhz XCLK into the camera. I've double checked it.
But it does not make a initial work.
there is no PCLK output
there is no HREF, VSYNC outputs
there is no D[9:0] output
Can you help me please the initialize that camera?
Should I have to do something else to get those signal at the power up?

update


texts: Can Vds ever becomes negative in mosfet?

texts:
Due to the symmetry in mosfet, source and drain are interchangeable. So we define the source of nmos is the terminal with the lower voltage. So if we force Vds to become negative the drain and source should flip. So Vds becomes positive again.

If that is true then the following is true?

If the overdrive voltage of an nmos is 0.2, for example, and I forced Vds to -0.3 will the mosfet operate in sat with source and drain flipped?

Here is a circuit from CMOS analog design book by Razavi showing flipping of the drain and source.


texts:
I'm searching for camera modules using CMOS image sensor. But I found something interesting. Some vendors specified operation humidity between 20~80%. But does it make sense that low humidity affect to camera? Could anyone please explain what happens when you put camera in such environment?

Here are examples

http://astronomy-imaging-camera.com/products/usb-3-0/asi224mc/#comment-4142
https://www.leopardimaging.com/uploads/LI-USB30-M021X_datasheet.pdf


texts: Why is the inductor crossed by null current in this simple circuit problem?

texts:
I'm new to EE. While doing some exercises, I encountered a problem where I have the following sine wave circuit, where:

e(t)=10cos(1000t)[V], a(t)=4sqrt(2)cos(1000t+pi/4)[A], C=1[mF], L=2[mH]

The problem asks me to find the Thevenin equivalent in the endpoints AB.

First of all, I found the impedance of the capacitor and inductor, then I found the voltage between the endpoints AB. Now, the textbook's solution says that in this condition, the inductor is crossed by null current. Can someone explain why is it that?


texts: Why is the notation for gain to be \$g_m\$?

texts: I have been unable to find the origin of the notation for gain, \$g_m\$.  I'm specifically curious about transconductance.  I have a book from 1931 by van der Bijl (who surprisingly has a wikipedia page) on the topic of vacuum tubes that uses \$g_m\$ as the notation for transconductance, which would suggest that it is very old indeed.  Assuming English origin, perhaps that the "g" is shorthand for "gain", what would the origin of the subscript "m" be?  I feel that the answer lies somewhere in German due to age of the term.  Does anyone know the origin of the term, \$g_m\$?


texts: LTspice DC-blocking capacitor not working

texts: I have been busy with a frequency shift keying modulation circuit in LTspice. The modulator works but I have this horrible DC-offset! I have tried high-pass filters and DC-blocking capacitors but I cannot get it to work correctly. Can someone point out my mistake? I a screenshot of the circuit below. As you see the signal is not oscillating around 0V but instead on top of 0V. My filter or DC-blocking cap work fine when I use a spice signal generator with offset just not on this signal and I don't understand it. Any help would be appreciated.


texts: I'm starting to learn AVR microcontrollers. I used some books,  and the hardware I use is the ATMega328P. I would just like to ask if both SPI and I2C can operate at the same time. Thanks for the awesome replies!


texts: Why is average voltage across an ideal inductor zero?

texts:
In some texts it mentions that the average voltage across an ideal inductor is always zero.

How can we derive this conclusion by using: V = L (dI/dt)

Why is average voltage across an ideal inductor is always zero in steady state? Can you give an example when the source voltage is a PWM signal and a sinusoidal signal?

edit: They sometimes give buck converters as example. But how can they assume the current will be constant before making this assumption?


texts:
Below is my schematic design and below that is my layout.
My overall project is that same schematic but repeated five times.
The same Vin but 5 different and isolated vouts.
I'd prefer to not re-do the layout by hand four more times is there any way to copy the branch five times?


texts: What is the advantage of kWh based tariff?

texts:
Electricity consumers are divided into domestic, commercial, industrial , etc based on the power factor. Domestic loads are mainly resistive. But not 100% resistive always. The industrial meters shows the power factor. The tariff changes if the power factor drops below a specific range.
Won't it be better if all meters measured power consumption in KVA and all consumers have to pay for total KVA consumption?
Or there is more advantage in the KWh tariff?


texts:
I am trying to build something that will require relays and I can't figure out if this one requires 12V DC to trigger or it won't burn at 12V DC.

Absolute RLS125 12-VCD Automotive Relay SPDT 30/40A


texts: How to configure STM32F4s TIM1 and 8 for PWM

texts:
I have configured timer 4 for PWM with following code and connected LED to the configured pin. It is working.

TIM_TimeBaseInitTypeDef TIM_BaseStruct;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);    // Enable bus clock

TIM_BaseStruct.TIM_Prescaler = 0;   // Set prescaler (frequency divider)
TIM_BaseStruct.TIM_CounterMode = TIM_CounterMode_CenterAligned1;    // Set counting mode (up, down, center-aligned) to center aligned for better motor control
TIM_BaseStruct.TIM_Period = 4000; // Set timer period (timer reset/change direction value)
TIM_BaseStruct.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_BaseStruct.TIM_RepetitionCounter = 0;
TIM_TimeBaseInit(TIM4, &TIM_BaseStruct);    // Initialize timer with chosen settings
TIM_Cmd(TIM4, ENABLE);  // Start timer

GPIO_InitTypeDef GPIO_InitStruct;

/* Clock for GPIOD */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);

/* Alternating functions for pins */
GPIO_PinAFConfig(GPIOD, GPIO_PinSource12, GPIO_AF_TIM4);

/* Set pins */
GPIO_InitStruct.GPIO_Pin = GPIO_Pin_12;

GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_Init(GPIOD, &GPIO_InitStruct);

TIM_OCInitTypeDef TIM_OCStruct;

TIM_OCStruct.TIM_OCMode = TIM_OCMode_PWM2;
TIM_OCStruct.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCStruct.TIM_OCIdleState = TIM_OCIdleState_Reset;

TIM_OCStruct.TIM_OCPolarity = TIM_OCPolarity_Low;
TIM_OCStruct.TIM_Pulse = 1999;
TIM_OC1Init(TIM4, &TIM_OCStruct);
TIM_OC1PreloadConfig(TIM4, TIM_OCPreload_Enable);

but when I configured TIM 1 and connected LED to its pin, nothing happened (I tested pin separately by toggling it as output to make sure I connected LED to the right pin and it lit up)

TIM_TimeBaseInitTypeDef TIM_BaseStruct;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);    // Enable bus clock

TIM_BaseStruct.TIM_Prescaler = 1;   // Set prescaler (frequency divider)
TIM_BaseStruct.TIM_CounterMode = TIM_CounterMode_CenterAligned1;    // Set counting mode (up, down, center-aligned) to center aligned for better motor control
TIM_BaseStruct.TIM_Period = 4000; // Set timer period (timer reset/change direction value)
TIM_BaseStruct.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_BaseStruct.TIM_RepetitionCounter = 0;
TIM_TimeBaseInit(TIM1, &TIM_BaseStruct);    // Initialize timer with chosen settings
TIM_Cmd(TIM1, ENABLE);  // Start timer

GPIO_InitTypeDef GPIO_InitStruct;

/* Clock for GPIOE */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE);

/* Alternating functions for pins */
GPIO_PinAFConfig(GPIOE, GPIO_PinSource9, GPIO_AF_TIM1);

/* Set pins */
GPIO_InitStruct.GPIO_Pin = GPIO_Pin_9;
GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_Init(GPIOE, &GPIO_InitStruct);

TIM_OCInitTypeDef TIM_OCStruct;

TIM_OCStruct.TIM_OCMode = TIM_OCMode_PWM2;
TIM_OCStruct.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCStruct.TIM_OCIdleState = TIM_OCIdleState_Reset;

TIM_OCStruct.TIM_OCPolarity = TIM_OCPolarity_Low;
TIM_OCStruct.TIM_Pulse = 1999;
TIM_OC1Init(TIM1, &TIM_OCStruct);
TIM_OC1PreloadConfig(TIM1, TIM_OCPreload_Enable);

Is there something different I have to do about advanced timers to make them work with pwm? I also achieved success with TIM3 and TIM12 (which are general purpose timers), but not with TIM8 (which is also an advanced timer).


texts:
I am fairly new to half bridge drivers and understand the concept of a full bridge.  I was looking at building a basic full bridge using 2 half bridge drivers, the driver IC's I was going to use were the international rectifier IRS2004 (datasheet can be found here http://www.irf.com/product-info/datasheets/data/irs2004pbf.pdf).

However the college will have issues ordering them due to USA stock so extra carriage, so I have been looking at the IRS2003 (datasheet can be found here http://www.irf.com/product-info/datasheets/data/irs2003pbf.pdf)

This seems like it will do the task, but I am struggling to understand the timing diagram and the benefit of having the LIN input out of phase by what looks like 180 degrees.

The datasheet states:

My understanding is that if I want to use the irs2003 in a similar fashion to the irs2004 (minus the ShutDown input) , I Feed the same PWM signal into both the HIN and LIN pins?


texts:
The 5VSB rail puts out voltages that are way out of the nomial range.
It sweeps from 2.5 to 7.3 V or better said, jumps values randomly.
All other rails are ok. The PSU turns on fine, but sometimes the PC doesn't boot. Just the fans and lights turn on. The graphics card is not powered from the PSU directly, so there is also no signal to display when that happens.
I replaced the PSU with a new one and the PC works fine now, so the 5VSB rail has to be the problem.
I opened it up and there is no sign of fried components or bulges on electrolytic caps. What should i do next to determine why the 5VSB output is not within tolerance?


texts:
There is a task in Pong chu's fpga prototyping book which is to basically generate a random number from 0 to 15_000 millisecond. I saw someone's code  who used LFSR. (ctto owner)
The author used a free-running counter and when the "start" button is pressed, the value of the counter at that moment will be used as the seed to the LFSR(linear feedback shift register). But I don't understand the need of the LFSR if the number of times that LFSR will be shifted is fixed (shift_count_next = 6'd14 @line69) ,meaning a specific counter value will HAVE A FIXED LFSR value which I believe is a round-about way of generating a random number. So I thought, why not just use the value of the free-running counter itself as the random number?
But am I missing something? Why use LFSR on this context if the number of times it will be shifted is fixed?


texts: AC-mains capable SSR (Solid State Relay) with very low leakage current?

texts:
Requirements:

Can switch 230VAC
Can switch at least 0.5A (i.e. ol' good 100W incandescent lamp)
Wastes no more than 3mW in off state
Low-on resistance is always good too

The stated power usage translates to under 15uA of leakage current.

Unfortunately, I was able to find stated leakage current only in low-current (Io.max < 200mA) devices, e.g. HSF2 (10uA), HSSR-8400 (<1uA). Whenever Io.max is stated at ~2A, leakage current is 10+mA. Do higher-current, yet still modest leakage current SSR exist? Alternatively, can someone point to "raw" thyristor/triac with similar specs?


texts:
The Arduino bootloader has a wait-time to facilitate "sketch" (code) uploading; this causes a delay of a couple of seconds before the start of the main code.

I would like to modify the bootloader file (specifically for the Arduino Mega) so as to reduce this time to less than 1000 milliseconds at most.

I am unsure how to get started on this -- Could someone point me in the correct direction?

(Note: I am aware that I can instead directly upload only the hex file corresponding to my firmware, but in this case, I would like to maintain the bootloader.)


texts: adjustable window and adjustable reset delay watchdog Timer

texts: I am using watchdog timer which have adjustable window BUT ITS RESET delay is fixed.This reset pin  is active high during normal operation and during fault condition its gives 200ms low pulse. So how can I drive  power supply using this reset pulse?


texts:
This question is slightly related to: What's radiating on my PCB?

These are Beckhoff's EtherCAT industrial IO modules. Each module is connected to its neighbours by 100mbps LVDS. Each module contains an ET1200 ASIC which handles all of the communications on the bus.

I recently opened some to see what EMI filtering they use.

They seem to use a lot of filtering components that are not mentioned anywhere in the datasheet for the ET1200 IC (or in any document on LVDS I can find). Specifically, the LVDS lines are decorated with much more than the single 100R termination resistor that is suggested.

I'm fairly sure that the components labelled in green are:

Capacitor
Ferrite beads
Common mode choke

Here is what I believe is the schematic for the LVDS components:

Clearly they have had to add all of these components in order to pass EMC testing. I'm quite surprised about the ferrite beads. I've often seen capacitors used in those locations to achieve AC coupling. I would never have thought of putting ferrites in there.

I am designing hardware which implements EtherCAT using the ET1200 ASIC.  I would like to pass EMC too, and so I guess it would be wise of me to use the same components.

Questions: What likely values of capacitor and ferrite bead would I need to use? Are there any documents which discuss such EMI filtering techniques for LVDS?


texts: How can I control the position of this sled motor

texts:
I got this sled from an old 1999 Toshiba CDROM Drive.
I was expecting a stepper motor controllingthe sled.  But it uses a DC motor with two wires.
It seems to me that the positioning of the sled is controlled by two sensors disposed below the first gear.  Can anybody give me a hint how the motor control is performed?
Thanks.


texts: Theory: Creating "LPS" transmitter for GPS receivers

texts:
As I understand it, GPS works by having transmitters with known locations send a timestamp, and calculating the time it took to receive it, so that you can triangulate your own position, (essentially an intersect of three or more circles with known centers).

I am interested in whether it is possible to create a "local" gps sender and using it with an unmodified gps receiver.

Sci-Fi Example to clarify

Let's assume that "suddenly" a country finds itself transported 100 years back in time, and all GPSs are rendered useless. Would they be able to (for example) establish GPS transmitter towers without having to reconfigure the GPSes, or would each GPS unit have to be programmed with information (eg. the coordinates) about the new transmitters?


texts: NJM2072D Application Questions for Audio Detection Circuit

texts:
I am building an audio switch with channel priorities.

I will use this in car events where we communicate car-to-car on FRS radios. A few of us also use 2 meter amateur radios for longer range communication. The intent will be that, when no radio signal is being picked up by either radio, the audio from my media player will be on. If a signal is detected on the 2 meter radio, the switch will mute the media channel and play the 2 meter audio. If a signal is detected on the FRS channel, no matter what other signals are present, it will be selected.

I have found a signal detection ship I intend to use as part of the circuit: (NJM2072D - "Datasheet")

The above image is extracted from the datasheet for reference.

There appears to be a capacitor symbol above the "INPUT" label connected to pin 1 but there is no associated value. I find no indication in the datasheet about how to select a value. Is this just a DC blocking cap? What would be an appropriate value?
Pin 2 is labeled "GAIN" but there is no description of what component to attach to vary gain. Does the internal schematic suggest anything?
Pin 5 shows what appears to be a 10uF capacitor but the schematic symbol is confusing. This cap is used to adjust recovery time. Does the symbol indicate I should attach this pin to ground if no cap is used?
The example enter code here application circuit shows the audio signal being sampled after an microphone amp. My intention is to sample the audio at speaker output signal levels. Does this appear to be a problem and, if so, what signal conditioning would I have to apply?


texts:
I power the peltier on 12v with a heatsink on the hot side

The hot side gets lightly warm and they cold side gets nice and cold except one part, The very top right corner on the cold side is hot, the rest of all the corners (and middle) is cold......is it broke in the right corner or do they just do that?


texts: NPN Transistor Data Sheet, Source vs. Sink Current

texts: Even though I'm an EE with 30+ years experience, a simple question asked by a junior colleague really stumped me. Namely, on a data sheet (e.g., for a 2N2222), that transistor can only SINK conventional current so why does the Ic or Ib not have a minus sign on the specs and curves? Same thing for a PNP.


texts: what kind (brand) of LCD display is this? it has no pins

texts:
I just gutted working new kitchen scale, and I have never seen a LCD display like this before. There are no pins just a black strip that goes on to the PCB.
What brand of LCD is this?


texts: Updating and connecting to server using esp8266

texts: I have been experimenting waking up computers on my LAN by sending them a 'magic packet' using an ESP8266 and this library. I've got it working internally but now need a way to connect to the ESP8266 from outside the network(Internet). I am behind a firewall in my office and no real feasible way to enable port forwarding so I thought I could get the ESP to connect to a server which can be updated with whether to wake up a computer or not. My question is, could anyone suggest a simple implementation of this scenario? Forgive me if this is in the wrong place. thanks.


texts:
I'm using a PIC18F452 in my project, and L293d for driving motors. I'm using two completely separate power supplies for driving motors and driving the PIC. completely separate two power packs. a 12 v 1A one for driving motors. the circuit diagram is as below:

My problem is when motors work the PIC get reset. when motors are disconnected it works fine and when the motors input voltage is reduced to about 6v also it works fine but with less speed. I have three questions.

When the motor supple is separate how can that voltage affect the MCU to reset?
if I use only one supply (12v battery), and 7805 to regulate and supply 5v to PIC how should I modify the circuit to work properly without resiting? (I used separate supply because this method was unsuccessful first, but my second option also was unsuccessful.)
I want to know whether L293D reduse the current flow and how to prevent it? the motors are enough powerful when I directly power it. but when it is driven from L293 and same power pack they are very poor. (I use 12v motors and when they are directly powered and with load it draws about 460mA )

please help me regarding this issue, I can't solve it myself...


texts: How can you evaluate if a component is going to have a long life (manufacturing)?

texts:
Before I pick a component for a PCB, I am trying to make sure it would not become obsolete in the near future because it's a mess and it happened to us a few times.

How would you check if a chip is going to have at least a few years of life?


texts: How to implement an analog PI controller using op amps

texts:
I'm working on an analogue PI controller as a hobby project and I would like to have some advice on practical implementation and some feedback on the critical points of the circuit. I have 4 questions asked below.

The objective is to design a controller that takes an input voltage (ideally through a potentiometer) as a set_point and should be able to follow the input signal (steps, square waves, triangular and sine waves) within reason, i.e.:

A rise time in the step of some 30ms is more than acceptable.
Signals should be in the 0-10 Hz range (0 being the step)
Overshoot would be interesting to see just for fun, but preferably it should be avoided.
Delay is not really an issue
Supply voltage should be in the 10V range for the op-amp

The output voltage can then be buffered and used in another part of the circuit.

As a first step, I decided to use an integrator op amp circuit as follows (click here to download the ltspice file)

This circuit seems to satisfy most of my requirements:

No overshoot
Rise time of about 30ms (pole at 1/(R6C1))
Unity gain at low frequencies
Follows mentioned signals reasonably well

Using Matlab I simulated the transfer function and double checked the frequency response, poles and closed loop behaviour. Everything looks fine.

However, I'm a bit worried when it comes to implementing the circuit, my questions are the following:

Is the op-amp LT1007 a good choice or is there a better one? What should I look for in a "PID op amp"? I have no experience with other than the LM741 which works horribly in LTspice in my experience, that's why I chose this one for the simulation.
The integrator at low frequencies is basically an inverting amplifier, with gain given by the classical formula. Is it really performing integration of the error? My answer is yes, it still performs integration (the LTspice traces seem to support this) however, for theoretical purposes (read: in class) at low frequency it can be approximated as a simple inverting amplifier.
Is the differential amplifier block good enough for this application or should I be using a different configuration? (For instance, instrumental differential amplifier)
Things seems to go HORRIBLY wrong (output saturate even with very small signals and low closed loop gains) as soon as I add a derivative and/or a proportional block and a summating block. Why is this happening? Matlab seems to disagree in this case, still showing a stable closed loop but with complex roots and therefore overshoot with oscillations, I wonder if this has to do with the op-amp in the sum block, see the example below of such implementation (click here for the ltspice file)

By the way, the final amplifier with a 2x gain is just for inverting the sign of the PID output.

Thanks

EDIT:
In my short lab experience, derivative block with LM741 seems to be a pain in the *** due to noise from other circuits, so I'm not really thinking of using it, aside from the fact that it is theoretically not needed. But I still wonder what went wrong in the spice simulation and would like to know.


texts: Ratio of colors to produce white in color television

texts: If you consult pretty much any book on the theory of color television, it says that because the human eye is more sensitive to green than red or blue, the reference white for color television has been chosen as a mixture of 30% red, 59% green and 11% blue. Surely, though, if the eye is most sensitive to green, it is the proportion of red and blue that should be boosted, not green?


texts: Voltage calculation with the nodal analysis

texts:
I'm having problems with the calulation of \$v\$ in this circuit.

simulate this circuit – Schematic created using CircuitLab

With the nodal analysis (K.C.L. at the node 1) I got:

$$\frac{e_1-v_e}{R_1}+\frac{e_1}{R_2}+\frac{e_1-v}{R_3}=0$$

Now: $$e_1=v_e+\frac{e_1-v_e}{R_1}\implies e_1\left(1-\frac{1}{R_1}\right)=v_e\left(1-\frac{1}{R_1}\right)\implies e_1=v_e$$

Then the previous equation becomes:

$$\frac{v_e-v_e}{R_1}+\frac{v_e}{R_2}+\frac{v_e-v}{R_3}=0\implies\frac{v_e}{R_2}+\frac{v_e}{R_3}=\frac{v}{R_3}=>v=v_e\frac{R_3}{R_2}+v_e$$

Now, since the (given) quantities are: \$v_e=30\text{V}\$,\$R_2=2\text{k}\Omega\$ and \$R_3=0.8\text{k}\Omega\$ I get \$v=30\frac{0.8}{2}+30=30\frac{8}{10}\frac{1}{2}+30=12+30=42\$V, which is wrong because the solution reports it as \$v=10\$V.

Could anybody kindly tell me where am I wrong?


texts: Dipole antenna length calculation -- why so much variation?

texts:
Was checking few online calculators for dipole antenna length computation, and found that each tool, gave a different length. Is dipole construction based purely on heuristics, or is there some sound mathematical model to determine the dipole lengths ?

The two calculators, for instance, whose answers do not match -

Calculator #1
Calculator #2

Any one of the two, which I could consider authoritative ?


texts: Is the DC-Link capacitor (C1,C2) necessary in cascaded H-bridge to achieve more balance and reduce stress on switches?

texts:
What is the purpose of the dc-link capacitor?
(Cascaded H-Bridge topology is free from voltage balancing problem because it does not contain DC link capacitors. but Many papers discussed this issue in cascaded h-bridge).


texts:
I spend a lot of time trying to find these connectors in many different eagle libs, but without any success.

https://caltestelectronics.com/ctitem/91-jacks-banana-jacks/CT3151SP

http://www.newark.com/cliff-electronic-components/fcr7350l/banana-jack-4mm-r-a-24a-pcb-blue/dp/20T2057

Can you recommend any?


texts:
My goal is to build a battery powered RF transmitter that will reach its accompanied receiver through trees, tall grass, brush, and some outside terrain at a reasonable distance (up to a couple miles would be great).

The main thing I want to focus on is the transmitter for now but for completeness, think of the receiver as a handheld device. The transmitter needs to be small and run on a small battery. The antenna can be probably a foot long. Basically think of those GPS dog collars that emit their GPS location via RF, as this is essentially what I'm hoping to make.

I am expecting that I will want/need to use a transmitter in the 900MHz range as that seems to be what would work best for this application based on what my research has shown. Unfortunately I'm having a difficult time figuring out what a good chip or module would be to use in this case. I will likely need to pair it with a GPS chip and a simple microcontroller(?).

I expect the data rate needs for this will be as follows:

6 bytes for a fairly precise GPS coordinates
Between 4 and 32 bytes for a unique identifier
Some packet overhead
I think transmitting this message once per minute would be plenty sufficient and it would still be usable at higher periods (5 minutes?)

I'm not sure what the packet rate limitations are at the 900MHz range or the max power output (2 Watts maybe)? Are companies like Garmin able to achieve this by via licensing? If I used license hardware would that make a difference?

I have a good amount of software experience and some assembly/C/C++/C# for the programming aspect of the microcontroller but hardly any RF or signal processing experience.

Can anyone recommend some components that would be useful for this application? Explanations for why these components would work best would also be helpful.


texts:
I have ordered a set of transceiver with NRF24L01 from various vendors. (with and without external antenna)

http://www.ebay.com/itm/NRF24L01-PA-LNA-SMA-Antenna-Wireless-Transceiver-communication-module-2-4G-1100m-/310651702557?pt=LH_DefaultDomain_0&hash=item485448cd1d

http://www.ebay.com/itm/K1BO-4pcs-NRF24L01-2-4GHz-Antenna-Wireless-Transceiver-Module-for-Arduino-New-/271336954345?pt=LH_DefaultDomain_2&hash=item3f2cf159e9

Are they all compatible?

It tells that it supports 1 to 6 communication? But will transmitters from different vendors work with each other?


texts: graphic LCD with the greatest ease_of_use:cost ratio

texts:
I'm looking for a (graphic) LCD to get started with. It doesn't need to be color. It doesn't need to be serial (but it should at least be multiplexed so I don't have to connect wires to each individual row/column). I don't care about the resolution as long as it's greater than about 40 pixels in both dimensions. Size should be > 1".

It must be straightforward to use, have plenty of documentation (preferably even example code, but not necessary), and be easy to connect to (with <30 I/O lines. <18 would be great). And of course, I'd prefer something inexpensive ($20 max) ;-)

Feel free to list more than one LCD per post. Try to include resolution, size, I/O lines and approximate cost. Bonus points if you provide a link to a supplier ;-)


texts: What is Sensitivity in an ultrasonic transducer Specification?

texts:
So far I understand that Sensitivity of the transducer is defined as the ratio of its electrical output to mechanical input.

While going through ultrasonic transducer specs, they have a rated sensitivity e.g. -25db/V/uBar

Can someone please explain the rated sensitivity in simple terms ?
How is this used in calculating amplitude of a receiving transducer (mV), when it receives lets say 10dB ?


texts: Can I charge 4 12v batteries with a single12v charger?

texts:
I bought a motomaster eliminator smart charger, it has reverse polarity and all that jazz, it says it's a 12 volt charger.

I am trying to charge 4 12 volt batteries for my electric bike. They are all wired together. they are soldered and I can't undo them because I don't have a solder gun. The charger didn't seem to work so I reversed the wires a few times to make sure my positive and negative were correct (black, and white wire).

The charger blew shortly after I plugged it into the wall. Is it the charger, or me. I can exchange it and get a new one, but what's the point if im going to just blow up another one?

Is this charger just not powerful enough to do what I want it to do?

Is it the charger? Or am I doing something wrong?


texts:
I was wondering what advantage is gained by modeling a power plug after the lower design. These are American power plugs, and they both exist.

Perhaps the only consumer-based effect gained by using the upper plug is that the plug can be put in upside down, which is helpful when using big, bulky wall warts.

I know that electricity-wise, the orientation really doesn't matter, and that the options below don't matter if there is a ground pin. The ground pin will limit the orientation to the upright position.

However, I can't really think of a solid advantage gained by the lower option.

Also, why are there sometimes holes in the end of the plug? I think that they may exist to save metal.

As always, thanks for your input.


texts: Do the bremsstrahlung radiation size depends on the size of the accelerator?

texts: According to https://apps.dtic.mil/dtic/tr/fulltext/u2/a351472.pdf HERMES III, a 16 terawatt pulsed power accelerator at Sandia National Labs, which fired electron beams with peak energy at 22 MeV and 730 ka current that later converted into Bremsstrahlung radiation is used to irradiate very large area and very large test objects such as military tanks to simulate nuclear explosion gamma ray radiation effects on whole weapon systems and large armoured vehicles. What determined the size of the Bremsstrahlung radiation fields? Is it simply the size of the accelerator or the voltage and current regardless the size of the accelerator?


texts: How to read serial data from the Neurosky chips

texts:
I recently bought a Star Wars Force Trainer II with the intention of using it to read the attention and meditation values.
I looked at the Arduino Brain library but that didn't work.
I started reading the serial data at a 9600 baud rate and got this data (https://pastebin.com/2SH1yarQ). Can anyone help me figure out how to use this data to find the attention and meditation values or how to get the Arduino Brain library to start working?


texts:
I have a inductor made up of ~5cm of 20AWG wire. Switching frequency of the inductor is 500kHz. And the duty cycle is somewhere between 10-30%. Maximum current through the inductor is 8A at around 13.5V.

I am wondering can this "relatively small" wire, take this amount of current? How could I calculate it out?

If it cant, will simply tying together more wires work? How many would I have to tie together?

EDIT:

Since it isn't possible, I am thinking of buying one. Would this be suitable? Its supposebly high-frequency rated for 9A.


texts: DC-DC boost converter not working as it should

texts:
I have been experimenting with DC-DC boost converter design. After I made some calculations in order to obtain a certain output based on certain parameters, I tested the SMPS and saw that it's not working as I designed it to.

simulate this circuit – Schematic created using CircuitLab

Parameters:
\$V_{in}\$=2.4V
\$V_{out}\$=5.1V
\$I_{out(min)}\$=1A
\$I_{out(max)}\$=1.5A
D=0.629 or 62.9%
L=94 uH
C=1517 uF
f=6239.54 Hz

The batteries are rechargeable (2 X 1.2V) NiMH 800 mAh. I checked them after I used the converter last time and they were almost fully charged (2.3V). The PWM part (the 555 and resistors + capacitor) are powered by a 9V battery.

I used this site for most of the variables, and this site only for C1. There are two supply rails in the schematic (one for PWM and the other for the actual boost converter) and only one ground.

By checking the boost converter with a multimeter, I found that the output was 20V and 80mA, which is far from what I wanted. I noticed that once I connect the probes it takes some time (but it's still short) before the output reaches 20V.

It sounds like I traded voltage for current without knowing. The diode I used is not great, but I would not consider it to be the cause. According to the second site, output current is influenced by IC current and this can be a possible cause, but I'm not sure of it. Reducing the value of the inductor doesn't seem to help in increasing the current.

What do I have to change in my circuit, in order to get the desired results? How do I increase output current?


texts: Reasoning behind "neutral pin nearest the edge" rule of thumb?

texts:
I've been told that there's a design rule of thumb that whenever you have a "bus" providing power and ground (for example, in an array of PWM outputs) that the ground connection is placed nearest the edge.

What is the reasoning behind this?


texts: Understanding Ohm's law(?) for transmission lines

texts:
I have this easy schematic

Next to this is stated that:

$$Vb = \frac{Z_{in1}e_{b}}{R_{B}+Z_{in1}}$$

non Latex-version of the formula: Vb = (eb*Zin1)/(Rb+Zin1)

I would like to know from where this formula comes and what it actually calculates. Is it based on Ohm's law? If yes, how do you eventually modify ohm's law in order to obtain this?
It is also stated that Vb can be a complex number. Under which conditions would this be true?


texts:
I am trying to hook up the  Waveshare USB3300 to a stm32f429 discovery board. I have been having an issue getting it to work. It has two pins that specify 5V and two pins that specify 3V. I am not sure if both are needed or just one.

When i try to hookup the 3V (with or without the 5v connected) the stm32f429 dicovery board shuts down. When i connect just the 5v stm32f429 board stays on. Usb3300 ground pins terminated to stm32f429 ground. I would like to connect usb3300 via usb mini to pc for serial transfer. The logic pins are pretty easy, but the power requirements for the board have me a little confused. Does anybody have experience using this USB3300 waveshare board. Are both 3v and 5v required? Or just one or the other?

Thanks


texts:
First, a little background -
I'm working on replacing an old (late 1970's) output driver board. The old equipment this came off of has a very dirty and poorly-regulated 5V system. Since I'm using newer pieces and replacing some address decoders with a FPGA, I need to have a more stable 5V on the board.

The 5V coming in can range from 4.75V to 5.5V (or more, if the other boards have bad caps, thermal wear, etc). I was looking at using a 1117 to at least keep the voltage close to 5V when/if possible - to avoid a bad power board destroying the new board.

I haven't used 1117's before (2705's usually in the past), and noticed on the datasheet it says:

  Vin: This pin must always be 1.3V higher than Vout in order for the device to regulate properly.

Am I correct in assuming that means that in a case like this, if the inpute voltage was between 4.75V and 6.3V, my FPGA and buffers would get the same as the incoming voltage, and then if say the power board blew up and fed 8V in, it would prevent the 8V from frying everything?


texts:
what does this term mean? "the grid in the evening is capacitive"?
I work at a company and we are working on integrating a battery storage system on a utility scale for peak shaving of solar. When we asked a consultant, the reply was: "it does not matter because the grid is capacitive"

Any clue on where to start looking even?


texts: ARM microcontrollers in DIP packages that can be fitted to a breadboard

texts:
Are there any MCUs from ARM that can be fitted to a breadboard?
As far as I have found, they are all in non-DIP packages that are incompatible with breadboards.
If not, what are the alternatives? Is the only option just buying a development board? Do you have any good recommendations on that front?


texts: Analyzing sniffed data from pins of LCD 2*16 using Atmega32

texts:
I sniffed DB4..7 of an 2*16 LCD using the below circuit : (Atmega32.PORTA1..3 is connected to GND)

As you see above I connected En pin of LCD to INT0 of Atmega32 (That is configured for Falling Edge firing).

In the interrupt routine I wrote this below codes:

interrupt [EXT_INT0] void ext_int0_isr(void)
    {
    printf("%c",'#');
    printf("%02x", PINA);
    }

In the other hand, in my computer I wrote this code :

import serial
ser=serial.Serial('COM3')

while(1):
    if (ser.read(1)=='#'):
        print '#'
        print ser.read(2)
    else:
        print 'Oops'

And when I powered on my circuit, This below output appears in python :

#
00
#
30
#
30
#
80
#
c0
#
10
#
10
#
00
#
11
#
41
#
61
#
00
#
91
#
a1
#
b1
#
b1
#
b1
#
b1
#
b1
#
b1
#
b1
#
b1
#
10
#
10
#
00
#
d1
#
a1
#
00
#
91
#
91
#
91
#
91
#
91
#
91
#
91
#
91
#
00
#
30
#
30
#
80
#
c0
#
10
#
10
#
00
#
11
#
41
#
61
#
01
#
e1
#
a1
#
b1
#
b1
#
b1
#
b1
#
b1
#
b1
#
b1
#
b1
#
10
#
10
#
00
#
d1
#
a1
#
00
#
91
#
91
#
91
#
91
#
91
#
91
#
81
#
81
#
00
#
30
#
30
#
80
#
c0
#
10
#
10
#
00
#
11
#
41
#
61
#
01
#
e1
#
a1
#
b1
#
b1
#
b1
#
b1
#
b1
#
b1
#
b1
#
b1
#
10
#
10
#
00
#
d1
#
a1
#
00
#
91
#
91
#
91
#
91
#
91
#
91
#
71
#
71

Now I want to analyze this output! But I don't have any idea what is the meaning of it. I appreciate if translate some part of it.


texts:
Recently I've been working on a project and have encountered a problem. The gadget I'm working on has a kind of knob that rotates and acts as a potentiometer.

The problem is I can't use a normal potentiometer because of design difficulties (I can't put anything under the knob).

What I've been thinking about is if I could make a sort of potentiometer strip that I could flex around the knob and then attach a tap to the knob. Of course I can wind a NiChrome wire and make such a strip myself, but if I'm going to increase the scale of production I'd rather use something already existing for that.

What could I use for this application?

I thought about force sensitive resistors that work kinda like a potentiometer, but they are quite expensive. The resistance value I'm talking about is around 100 kΩ. Thanks in advance.


texts: How to design a PI controller for fourth-order transfer-function?

texts: Fourth-order systems may render very complex characteristic equation that are difficult for tuning. Is there any method to tune controllers for these systems easily?


texts:
This program is in Verilog and simulating on Modelsim. I am trying to transfer 48 bits data from 192 bits latch to Parallel in Parallel Out (Register) in 4 slots.

I am not getting output at PIPO. Data is not getting transferred at output of PIPO. For sake for simplicity i have used to transfer 96 bits. Data should come on every 48 sclk and sclk is counted by cnt(counter). The size of PIPO is 48 bits and size of Latch is 192 bits.

/*LATCH FOR 192 BITS */

Parameter  N= 192;

  always@(xlat,dcsel,sipo_out_gs,rst)

    begin
   if(rst)
 gs_latch <= gs_latch;
   else
 if(xlat == 1)
   gs_latch <= sipo_out_gs;
 else
   gs_latch <= gs_latch;
end
/* 48 BITS DATA FROM LATCH TO PIPO*/

 always@(posedge sclk,posedge rst,cnt)

     begin

     if(rst)
   pipo_lat <= pipo_lat;
 else
   if(cnt >= 47 & cnt <= 94)
   pipo_lat <= gs_latch[47:0];
 end

 always@(posedge sclk,posedge rst,cnt)
    begin
       if(rst)
         pipo_lat <= pipo_lat;
     else
        if(cnt >= 95 && cnt <=142)
          pipo_lat  <= gs_latch[95:48];
     else
       pipo_lat  <= gs_latch[95:48];

   end

 /* counter for grayscale to count upto 192 bits  */

   always@(posedge sclk,posedge rst)
 begin
if(rst)
  cnt <= 0;
else
  if(cnt != N)
    cnt <= cnt + 1;
  else
    cnt <= 0;
 end


texts: Altium Pad Net names vertically mirrored

texts:
I'm trying to make a printout of a PCB design, showing the net names each component pad is connected to. I'm running into a problem though -- after I enable the option to show these net names, the displayed names are all mirrored vertically:

I've tried setting the printout to be mirrored, but that just mirrors everything horizontally (not vertically), so the problem remains. Does anybody know how to correct this?


texts: Some power across a relay even when open?

texts:
I'm working on making a switch that can be turned on with a microcontroller.
I have it mostly wired on a protoboard, and it kind of works, except that even when the relay coil isn't energized and the relay is open, there is a little bit of current still flowing.
The relay I'm using is a PCJ-112D3M.
I hooked the black multimeter wire to the neutral AC wire, and the red multimeter wire to the hot AC wire after it goes through the relay. When the coil is energized the meter reads 120VAC as expected.
But when the coil power is turned off, the meter reads 40VAC.
I'm not sure if it's just a bad relay, or if this is somehow expected behavior, but it doesn't seem right.
I just wanted to double check before I desolder the relay and replace it with a different one.


texts: MSP430 printf function executes too slow

texts:
I try to use Sky mote (MSP430 F1611 + CC2420) to read the data from I2C sensor with 100Hz sampling frequency and write the data to serial port (USB). I tried a couple of tests and realized that the total output data have a sampling frequency of 78Hz. I used rtimer to profile my sampling and printing code and found the print function slows down the entire process. Here are some profiling outputs:

start 50628
15490,f074,20,3b8c,ffab,49,ffcf,fb70
end 51189
start 51293
15491,f0a8,fff4,3ba4,ffc6,24,ffd8,fb90
end 51880
start 51984
15492,f094,20,3b30,ffa7,5b,fff3,fb70
end 52544
start 52647
15493,f118,bc,3ce0,ffab,70,fffc,fb90
end 53207
start 53311
15494,f030,1b0,3b44,ffa9,1f7,1f,fb80
end 53871

The rtimer has 4098*8 ticks for one second. Here we can clearly see that the printing takes about 560 ticks (17ms). If the sampling frequency is 100Hz, the printing function should be completed within 10ms (327 ticks).

The embedded system I am using is Contiki OS and the baud rate is 115200 (maximum baud rate). The sensor sample contains 112-bits signed int.

Here is my code:

mpu_data_union samples;
int m=mpu_sample_all(&samples);
printf("start %u\n",RTIMER_NOW());
printf("%lu,%x,%x,%x,%x,%x,%x,%x\n",
  counterxx,samples.data.accel_x,samples.data.accel_y,
  samples.data.accel_z,samples.data.gyro_x,
  samples.data.gyro_y,samples.data.gyro_z,
  samples.data.temperature);
printf("end %u\n",RTIMER_NOW());

I hope some people with previous experience on optimizing printf or UART in general could provide some suggestions.


texts: which is the best book or any resource to study about the fundamentals of RF transmitter and receiver?

texts: want to know from where should I study the fundamentals of RF transmitter and receivers ?


texts:
I'd like to make an analog SPDT switch along the same lines as FSA2259UMX or similar chips, but out of simple discrete components.  This is partly for learning, and partly because I'm redesigning a circuit that has a whole bunch of these, and wondering if something like a simple dual MOSFET (DMG1029 etc) would do the same job without using a tiny/hard to assemble/expensive part.  A bit later on I'd like to know how to build my own N:1 multiplexers for fairly large N values (100's) which might be just a cascade of SPDTs.

Some of the nice specs that purpose-built switch ICs give are: break-before-make; controlled slew rate; flat resistance over different voltages; and flat attenuation up to pretty high frequencies.  I don't especially care about any of these in my simple circuit; I'd like the off state to have reasonably low leakage, but that's about it.  The circuit can be make-before-break, it can be slow to switch, and it can have fairly high (and variable) resistance.  Making this out of a small number of common components is the trick.

I'm looking at signals around 0-3V and a logic level (3V) control input.  On-state resistance can be around 1-10 ohm (and may vary); off state leakage a few uA; and switching time in the 1us range.


texts:
For my university project I'm trying to flatten out my bass frequencies while keeping the other frequencies intact. (The idea is to first amplify a part of the input signal and input this signal into the system.) This is because of the bass lacking 11 dB from 20 Hz to 32 Hz, after that a -40dB/decade rolloff is needed till 75 Hz. So this means a second order low-pass filter was needed (since our system cuts off all frequencies below 20 Hz and above 40kHz). Also the rest of the frequencies must remain and therefore a summing amp was needed to amplify the low frequncy signal and keep the rest of the signal. So this is the design I came up with:

However, there is this weird dip which I can't really explain. (I was thinking of feedback from one of the op-amps, but not really sure about that)

The green line is the total response and the blue line is the filter, which seems to act normal. So how can I either fix my design or can someone help me with a new design which meets the requirements?

So, here is a graph which shows our frequency response:

The lower blue line is our response, the upper blue one can be ignored but the orange one is the transfer we thought was needed to compensate our lacking bass. However later we heard from our instructor that the peak could be a result of the measuring program we used and thus a simple second order LPF would be needed.

Edit:
Thanks to everyone for the help! I decided to stick to an second order filter, but I added an all pass filter to the design, as seen below:

However, during testing the design didn't work as simulated. At 20khz it gave (not really sure if this was the exact value because we were short on time) approximately 0.1V RMS on the output with 0.5V as input. At 20Hz however it gave 0.35V. So it looks like it's amplifying, but not as expected. I was thinking of maybe a dead (or two) opamp(s), is there anything else I could check? (Solder joints are triple checked and the opamps (Lm741 and lm742) are recommended for 15v but we decided to use 10.4 V with a voltage division since our psu can deliver 21V unloaded but loaded 19V)


texts:
I am learning to use a RTOS, CMSIS RTOS in this case, so my question is basic. I want to know what is the best way to share information between two tasks.

What I am trying to do is basically a controller with some external communication. This system has two tasks.

Task 1. Controller task:

It is executed at fixed intervals, each X ms, as fast as possible
It has a setpoint
It reads several sensors
It calculates and sets several outputs

Task 2. Communication task:

It’s a slave in a master/slave communication (Modbus). So, it only communicates when it receives a request from master
It must be able to set the setpoint
It must be able to read the value/status of sensors and outputs

How should these two tasks communicate? If I was not using an RTOS I will use private global variables, wrapped with some public get/set functions. But as far as I understand that is not the way to do it in a RTOS.

Should I use a queue where the communication task writes a request message, that the controller task will check every iteration? The problem I see with this solution is that the controller task must execute as fast as possible, so either the controller task only replies to one request each iteration making the communication task less responsive or, it responses to all the request making its execution time longer.


texts: Signal Flow Diagram for a biquadratic section

texts:
I'm doing a theoretical preparation for an Electronics laboratory. This laboratory is about Tow-Thomas biquadratic section which can be represented by the following circuit:

The first thing that is asked on the guide is to do a signal flow diagram of this circuit without analising it(just using logic). My teacher didn't teach me how to do it. He just show me the solution in one of his apresentation slides:

I know that the first sub-circuit is a summing-inverter amplifier (if we consider the equivalent impedance of \$Z_{C_1}\$ and \$R_6\$), the second a integrator-inverter amplifier and the third a multiplicator-inverter amplifier. So, I know how he obtained at least the coefficients in the two last boxes (but only if \$R_5=R_2\$ which is given by the guide). My problem is about  the term on the first box and where do \$\frac{1}{Q}\$ and \$K\$ came from?

I think we can't immediately associate \$\frac{1}{Q}\$ to an element of the circuit, or just saying that is there a \$K\$ which corresponds to the \$DC\$ gain for second an third sub-circuts ( I just figure it out the significance of \$K\$ after some extense circuit analysis ).

So, I think this is about usual logic. If this is a circuit of a usual and well known group circuits (which I didn't know in the first place), then there's some way to do the signal flow diagram immediately. One thing that I noticed is that if we change, for example the value of one resistance then the diagram could be a little bit different. So, to do immediately this  diagram we need to assume that the values for those resistances and capacitances aren't random.

Can you advise me some interesting links about signal flow diagrams, or explain how would you do to get immedately the diagram of this circuit?


texts: simplify A'B'C'+A'B'C+A'BC'+A'BC+ABC into minimal 1st canonical form

texts:
Is there anyone who can advise me?
I cannot seem to simplify this function into minimal 1st canonical form using boolean algebra.

With my first attempt I obtained:

With my second attempt I obtained:

I used the K-Map loop technique and I got:

The correct answer I obtained from the online Logic circuit simplification solver also gave the answer:

Can someone please point out the mistakes I have made in my 1st and 2nd attempts using Boolean algebra method?

Also can you please let me know the reason why I did not obtain the minimal 1st canonical form directly from the K-Map loops and needed to further simplify the expression?


texts: What is causing a loud static POP when PTT mic is keyed?

texts:
Hi folks! I have been investigating this static POP noise problem for a while now, including talking to the sound shop I bought the amp from and consulting with the manufacturer of the amp.

I am using an Astatic 611 dymamic PTT mic designed for paging/cb systems with an XLR male plug into the female XLR on the Traynor TVM10 amp (left side of diagram). There are only two wires from the mic and one ground connected to the XLR.

Always on the first keying of the mic, there is a very loud static-like POP from the amp. This POP noise reduces significantly with each successive keying of the mic, until the POP sound is at a more normal level - a slight click sound - that you would expect to hear when keying a PTT mic. If the mic sits idle for a few minutes, the dreaded loud POP returns and fades out as mentioned above.

On the advice of the manufacturer, I have tried many different grounding combinations on the XLR male end on the PTT mic with no effect on the POP noise.

It really seems like there is a static build up that dissipates thru the PTT switch when it closes - but where is the static coming from and how to ground it out? A standard dynamic singing/speech mic with an ON/OFF switch does not make this static POP noise at all when plugged into the amp and turned ON.

The amp is portable and powered by an internal 12V/7.2A rechargeable battery. The charger is removed from the battery charging port before using the amp.


texts: I2C communication with MCP4728 and ATSAMD20J18 using HAL libraries

texts:
I'm trying to communicate MCP4728 with ATSAMD20J18 controller using HAL libraries.
But the commands are returning NACK.
Below are the commands.
i2c_m_sync_set_slaveaddr(&I2C_0,0x64,I2C_M_SEVEN);
i2c_m_sync_cmd_write(&I2C_0, DAC_mcp4728_VREFWRITE, TxFrame, 0x01);

Basically, the address of DAC is 0XC8, which is 8bit. But, the command above support either 7 bit address or 10 bit.
Here I'm not getting acknowledgement bit.
The same code and DAC are working perfectly fine with STM32.
Can anyone help me out with Atmel Studio?


texts: Why are more powerful tools using higher voltage?

texts:
AFAIK each of the world leading cordless power tools manufacturers produces several "product lines" of cordless power tools with different voltages. For example, Bosch currently produces tools with Li-Ion batteries with 10,7V, 14,4V, 18V and 36V output and the higher the voltage the more powerful a tool is.

Now those tools are powered by batteries that are assembled from cells with lower voltage (something like 3,7 volts for Li-Ion cells I guess) and cells are connected in sequence until the target voltage is reached.

They could instead connect cells in parallel. They would have the same voltage, but higher current and that would again yield higher power.

Why do they choose higher voltage over same voltage and higher current to get higher power in electric tools?


texts:
I am trying to learning about the Watch Dog Timer peripheral of MSP430FR6989 (link to MSP430).

It's Watch Dog Timer peripheral WDT_A have a 16 bit control register (WDTCTL), in order to perform a write operation, we need to load 0x5A in it's upper byte.

If we want to perform read operation we would read 0x69 to the upper byte.

(User Guide page 635)

  write accesses must include the write password 05Ah in the upper byte.
  A write to WDTCTL with any value other than 05Ah in the upper byte is
  a password violation and causes a PUC system reset, regardless of
  timer mode. Any read of WDTCTL reads 069h in the upper byte.

This is my code:

#include <msp430.h>

int main(void)
{
    WDTCTL = 0x5A80;
    PM5CTL0 = 0xFFFE;//Line A

    //rest of the code

    while(1);

    return 0;
}

When, I build it and debug it, and the debugger reaches line A, I expected WDTCTL = 0x5A80, not WDTCTL = 0x6980 (image below).

I understand, if I have a statement like if(WDTCTL == number), we would find WDTCTL = 0x69XX, but why do I see 0x6980 at the Register Watch Window, when I just assigned 0x5A80 to it.


texts: Building a voltage switcher for an h-bridge using bipolar transistors

texts:
I'm trying to build an h-bridge with bipolar transistors and I'm having a real hard time figuring out how to put together the input logic. I'm using an intel galileo to handle pwm control. The circuit is working with fixed inputs, but the real trouble here is switching between two voltages (27V and 0V) based on the digital output from the galileo (5V/0V). Here's the sketch:
The right side of the bridge is fixed at 27V and I'm trying to set 0V as the voltage on the other side with that transistor. I've tried a lot of different ways to wire this and had no luck so far.


texts: It's the 6-pin SOIC in the middle with what looks like "67T" or "T76" on the top.  I can't find any info on this I'm hoping someone here has come across this.  The top left pin is possibly a digital I/O pin but that's all the info I have.  Any ideas on how to trace this?


texts: Can a magnet cause a microwave oven to unsafely radiate energy?

texts:
I've already successfully warped the colors on a large old CRT Television by setting unshielded speakers on top of it. If I understand correctly, this was due to the deviation of the electro-magnetic (EM) radiation beam from its intended target, as influenced by the speakers' magnets.
If I further understand correctly, the magnetron of a microwave to produces a beam of EM energy which is directed at a reflector or scatterer, and then into the cooking cavity which attenuates the energy through notch-filtering and corner-wave traps.  (I'm probably using slightly incorrect terms, feel free to correct my terminology.)

Is the magnetron contained within the cavity/[farraday ]cage, and if not, can the beam of EM be deflected such that it could escape or deviate enough to emit radiation into the surrounding space? (If the magnetron should be situated within the containment structure, are there regulations stipulating this?)

This situation is more practical than hypothetical: We have a neat kitchen gadget with a strong (rare-earth, I think) magnet on its    base, designed to hold itself to an oven door with substantial    certainty. Attaching it to the oven isn't an option, so it's    currently on the over-range microwave oven. In a moment of analysis,    I realized this may be a poor choice...

If my consideration of risk due to magnetic deviation is unfounded, is there another concern, short of magnetically affecting the safety switches (which shouldn't be possible without intentional compromising) to having a stronger, rare-earth magnet attached to a microwave?


texts: How the Depletion Region of PN Junction changes under Bias

texts:
There are several other questions on PN Junctions out there, but I don't think this one has been asked specifically.

I am having a severe misunderstanding of how the depletion region width varies under bias. I know that what I am thinking is incorrect somehow, but I am unsure wear.

I will reference this picture from a textbook I like:

The depletion region is created due to a balance of diffusion and drift current. Diffusion pressure causes holes to travel from the P-side and electrons to travel to the N-side and combine with one another around the junction. This combination leaves behind positive charge on the N-side and negative charge on the P-side. This charge creates an electric field that opposes the diffusion current with a drift current. The width of the depletion region is determined by whatever amount of charge transfer balances the drift and diffusion pressures.

Now, if you have a higher concentration of dopants, you end up with more diffusion pressure which means the electric field must be bigger in order to oppose it, meaning that the depletion/space charge region must be wider. However, what I just said is incorrect, but i don't understand where my reasoning is wrong.

Now again, if you have a higher electric field applied you should get proportionally less diffusion current meaning that the width of the depletion region can be smaller and still fully oppose the diffusion current. This is also incorrect reasoning, but where did i go wrong?

The natural follow up is under forward and reverse bias. During a reverse bias I know that the depletion region grows, and under forward bias it shrinks. I can use Kirchoff's voltage laws and Fermi Levels and tons of other ways to reason out why that MUST be true. But what I CAN'T do is explain what physical motion of holes and electrons and recombination in the system under bias results in the the depletion region shrinking and growing under forward and reverse bias respectively.

Essentially, during the application of a bias, what are the holes and electrons phsyically doing during the transient under this new electric field applied to them? How does the depletion region physically change size?

Feel free to get as technical as needed, but I understand all of this in terms of just using math, but I am looking for a more intuitive understanding. Thanks.


texts:
I want to control the FP6293 ICs enable pin with the Atmega 328p pin PD5 (configured as digital out). The EN pin (active high) on the IC is rated at max 6V with a minimum HIGH voltage of 0.96V. As the microcontrollers IO will be setup as an output, when the output is high current will flow to the FP6293 right?

Do I have to use some sort of series resistor between the IO and the EN pin?

Or is it ok to just connect the two pin together and have a pull-down resistor?

link to FP6293 datasheet: https://datasheet.lcsc.com/szlcsc/Feeling-Tech-FP6293XR-G1_C83576.pdf


texts: I'm designing a power section for my guitar pedal circuit that will supply power to my pedal using either a 9V power supply or a 9V battery. I'm using a switched barrel jack but I'm not sure if I have it wired up correctly, I do know that the center pin should be negative. Before I build it to test I was hoping that I might get confirmation if I've got things arranged correctly? Thanks!


texts:
Background:
I am designing a "smart charger" for my personal Android phone.
I would like it to be able to adjust the amount of (or turn off) power going to the phone.
Planned Implementation:
The "smart" features would be implemented on the phone, and all communications handled by a device such as the MAX3421E (Ie. Android ADK).
Here's a block diagram:

Question:
What is the proper way to communicate with the phone so that the phone's charge circuitry takes as much power as possible (Is this even possible with the Maxim chip)?


texts: How to connect 15kΩ NTC thermistor sensor to thermostat which requires 10kΩ NTC thermistor

texts:
I have a electric floor heating in my house. Old DEVI thermostat broke down few day ago. Problem is that DEVI thermostats are expensive and a little bit dump (not smart). I want to replace thermostat to with new one with smart functions. But every other model requires 10kΩ NTC. So i thinking what if i add 30kΩ resistor parallel to 15kΩ NTC thermistor = 10kΩ. The thermistor is firmly built into the wall, so it cannot be pulled out.
Temperature interval is about 15 °C to 35 °C.
Can anyone judge me this solution, please?


texts: using a MOSFET to switch a voltage lower than the gate

texts:
I'm using a p-channel mosfet to switch a 3.5V load, using a gate voltage that's ~5V. The gate goes from 5V to 0V, but the mosfet doesn't start conducting. Did I just fry the mosfet by having the gate be above the source, or is something else happening?

Edit: here's the MOSFET in question


texts:
This question is actually from one of my previous discussions, which I still don't understand how to implement. The goal is to use abstraction to design a circuit, which  converts two-digit ASCII decimal numbers into 2’s complement representation.

"Recall that characters in ASCII are represented with seven bits and that the decimal digits are 0x30 (the digit 0) through 0x39 (the digit 9)."

In addition to the comparator and adder, one or more zero extention units, one or more muxes, and gates and wires are to be used.

Basically, what are the key steps and concepts which I must know to arrive at a solution to this design problem? I'm sort of aware of how an adder works, as I've done some bit-slice problems with control units to implement different functions, but I don't know how to put all of this together.


texts:
i want to build induction furnace

i parallel 16 power mosfet(irfp460) 8 fet for high side and 8 fet for low side for half bridge

i use ir2104s and bd139 and bd140 totem pole for drive mosfet.

like this

According to irfp460 datasheet, Total Gate Charge=210 nc and td(on)=18 and tr=59

td(on)+tr=77ns then 210/77=2.7 amp. V=IR then R=6.6 and i use 6.8 ohm resistor for each gate and use 10 ohm for bd139 and bd140 bias.

i see the output of totem pole with oscop and its nice and clean square wave without any noise or ringing. like this

but when i connect output of totem pole to high side mosfet the output is ringing and have Too much noise with 12 volt switching power supply without any load for test.

like this

freq is 20khz

why this is happen?

how to reduce or Eliminate this ringing and noise?

thank you


texts: Large signal with DC offset matching to ADC with input centered around 0V

texts:
I'm new to this forum, so plear bear with me.

I have a 0 to 23v signal coming from a transimpedance amplifier that I need to squeeze into -2.5v to 2.5v input for an ADC. The signal is first put into a buffer amplifier for a high input impedance.
I've used a resistor divider to get the signal to 0 - 2V which goes to a non inverting op-amp with a gain of approximately 2 with some offset voltage applied through the feedback. (R1) this however messes a bit with the gain of the opamp which is not preferable as it lead to more tuning.

I' haven't tested this in real life, but it seems to work in simulation. Would this be any good? Are there more elegant solutions to have this functionality? No AC coupling is allowed as the signal changes very slowly. Maximum frequency is about 0.017Hz.

thanks,

Jona


texts: Why convolution in time domain is multiplication in frequency domain?

texts:
I am trying to understand intuitively why convolution is multiplication in frequency domain. I started at the mathematical derivation of this, but didn't understand what is happening intuitively. This question may seem very easy for someone or very vague for someone else, so i would also like to put my efforts here in understanding the same.

I would be glad if someone is able to understand what i understand as of now and give answer in similar way, but any other thought-process is also fine. Also, i would prefer more wordy explanation rather than seeing math derivation. If anyone explain derivation of this theorem, by showing the steps in derivation and explaining each step, that is also fine.

  Current Understanding:

I know fourier transform is a process of wrapping a signal x(t) around a circle which is nothing but obtained by $$x(t)\cdot e^{-j\omega t}$$ where w is frequency with which we are wrapping x(t) around circle. Now for a given frequency w, we will get some 2D shape in complex plane. If i integrate this over dt, i will get $$\int{x(t)\cdot e^{-j\omega t}dt}$$, which can be though as if i am calculating location of "center of mass" of that shape in 2D complex plane. So i will get some complex number. All this we did is for a single value of w (winding frequency). If i repeat same procedure for all w, i will get frequency plot.

Now, let's say if i want to convolve 2 same signals, meaning of this in frequency domain turns out to be X(w) times X(w) as stated by convolution theorem. Now, in time domain its equivalent will be y-axis showing the value of convolution integral and x-axis showing the value of shift between 2 signal, which in this case are same signals.

Now in frequency domain, for a given value of w, if i multiply X(w) with itself, it means multiplication of 2 complex numbers. Although 2 complex numbers here are same, generally thinking, multiplying 2 complex numbers results in addition of phases and multiplication of amplitudes. Also, each complex number here represents the "center of mass" of the shape we got when we wrapped up the whole signal around a circle.

After this, i am not able to think!!!


texts: Learning the principles of op-amps - Why are there so many?

texts:
I started learning the theory of opamps, I want to try to do a small circuit, but the problem is that there are so many.
Is there something special about each opamp, or it just the brand? Do they work differently?


texts: Would it work if I have a lithium ion battery that's connected to a voltage regulator that's connect to a Raspberry PI then another voltage regulator to a display?


texts: Charging a 18650 battery using a 5V charger

texts:
I built a power bank which had Seven 18650, savage some from laptop batteries and others from an old power bank... I recently just noticed that the power bank circuit won't charge the batteries  though the output process is good to go... It came to my knowledge that charging the batteries directly from the charger would severely damaged the batteries.. So I dropped the voltage using two diodes connected in series,  it gave me 4.0V, I don't need an ammeter to know that the diodes also took down the current,  because it took an hour and half to charge a 18650 from 2.8V to 3.2V meanwhile I'm using a 5V 1A charger... So any help on how to increase the current or any alternative to charge a 3.7V 18650 using a 5V 1A charger. Thank you in advance for your anticipation on getting me a solution..
Forgive my English,  its crappy.


texts:
If the reactive power that is induced by an inductor that is connected to a resistor (a lamp) is corrected by a capacitor, does that mean that I get more light out of a lamp?

The way I see it is that, in this case the real power stays unchanged and the power factor goes to zero then the apparent power gets equal to the real power.


texts: Fix a vintage computer (IBM PS/2 55SX) without a DS1287 Real Time Clock

texts:
I want to reanimate an a old vintage computer, the IBM PS/2 55SX.
The dead component is the DS1287 Real Time Clock (in particular, the battery inside).
Is it possible to simulate with a BASIC Stamp micro-controller the behavior
of a DS1287 so that I can boot my old IBM PS/2 55SX?
The DS1287 pin are damaged (I mean current can not flow between the broken DS1287 and its socket) so I can't modify it, to use another battery.


texts: Maximum length of high-speed LVDS cable in automotive environment versus using SerDes

texts:
I would like to connect a small TFT display that uses LVDS, 4 channels for data and 1 channel for clock. Data rate is maximum 200 Mbps per lane. Very strict EMC requirements are applicable, namely automotive.

What would be the maximum length of a typical LVDS cable that would still work in this environment? Length could be up to 1 meter. I would use twisted pairs in any case. Shielding would preferably be avoided but could be applied if needed. Common mode chokes can be implemented on the PCB; clamps on the cable should be avoided if possible.

I am wondering from what length onwards I should use something like an FPD Link III SerDes (e.g. TI DS90UB927)? Or would that be overkill? BOM cost is important.

Theory like this suggests that I am still well within the regime for LVDS, but it does not quantify the EMC aspects, which are crucial in this application.


texts: OpAmp with high output current and capacitive load

texts:
I am trying to solve the following problem which - until today - I thought to be a trivial one: I have multiple reference voltages (from different sources) that I need to buffer and/or invert, filter with a large cap (10uF) and needing to supply around 100mA to the load:

simulate this circuit – Schematic created using CircuitLab

The input references range from 0V to 4V and the supplies should be either single supply +5V (for the buffers) and +/-3.3V dual supply (for the inverting ones). Furthermore, it should be two opamps per chip.

The canonical solution to the problem is using an op-amp in (a) unity gain configuration (b) inverting amplifier:

simulate this circuit

I wasted my whole day finding the right opamp. There are many that can drive arbitrary caps (I do not want to deal too much with compensation networks) and there are many that can supply >100mA. But the intersection is zero.

For example, the AD8655 provides +/-220mA but drive max. 500pF (and that rings already).
The ADA4807 is stable for CL>100nF without compensation but the output current is limited to about 50mA.
Many op amps are explicitely built to be stable for all capacitive loads, like the AD826 but again, current too low.

Am I missing something?


texts: Are one side signals affected by other side signals on multilayer PCBs?

texts:
Designing a 4 layer board I've found that if I place some power lines running on top layer I can easly keep them wide and route them without headaches. But this lines are very noisy becouse they powers a group of PWM leds(at 5V/1.5A) and one brushed motor(at 5V/1A). Since this is not a professional board, maybe I can ignore this, but this made me think about how much this will affect signals and components on the other side of PCB.
I've studied that metal covers acts like a Faraday's cage creating an "immunity" on circuits that are inside and having the ground connected to the cover.

My generic question:
Since one layer of the PCB is a solid ground plane and it's like a wall between signal/components and power lines, this assumption it's still true?
If yes, this is used in professional boards?

My specific question: In my case, can EMI from this lines disrupt my 3.3v logic circuits or will they be so little to even affect an ADC read? (it's just a small general board with with an STM32 L0, lines are impedence matched, no longer than 2cm signals)


texts: How to predict which machine will act as motor or generator in Hopkinson's test?

texts:
Is there any way to predict which machine will act as a motor and which acts as a generator before applying the supply voltage?

I cannot find a way to predict what will be the behaviour(motor or generator ) of both machines after applying the external voltage source.
To me both machines in this test seems very symmetrical and we already know that for Hopkinson's test both machines should be identical.  That is why I cannot find a way to predict the behaviour after applying the voltage source.
Are there  any factors prior (or after) to applying voltage source which makes one of them behave as a motor and other as a generator?
Or is there not a way predict their behaviour behaviour before applying the voltage source?


texts: Where should hardcoded variables typically be stored in FLASH on a microcontroller?

texts:
I want to store calibration data on a microcontroller (namely the STM32 line) however with a large amount of flash memory available to ustilise, I wondered if there is a standard area of memory that is typicaly cordoned off  for such hardcoded user constants.

My initial thought is to put the data in the last page of the flash memory. This is the furthest from the programming code which starts in the first page and thus unlikely to corrupt the programming code.

Is there a generic rule of thumb for location of writing such constants into flash? (like in the last pages of Flash)


texts:
Perhaps I don't fully understand extern. With the XC8 C compiler, it seems like I can get away without using it.

In the file keypad.c I have a function signed char keypadGetPressedKeyLabel(void). In the header file keypad.h I have:

signed char keypadGetPressedKeyLabel(void);

I thought I would have to use extern, ie:

extern signed char keypadGetPressedKeyLabel(void);

The project builds without extern. And it works. Might this due to the fact that keypad.c and keypad.h are all part of the project? I'm using MPLABX.


texts:
I'm using KiCAD version 5, and I have an issue with it. Previously, I've been using OrCAD up until the point to where I needed multiple layers for my board. So, I redesigned my components, but I'm having an issue with my SOT-23 footprint.

Previously, in OrCAD, there were no problems. I managed to design my part, and in the layout, the ground plane managed to fill in the gaps between the pads as shown in the image below. You can see my pad here, and my soldermask clearances are 0.1 mm for all sides. It passed the DFM checks with no issues.

However, when working in KiCAD, I can't seem to get my copper plane to go in between the gaps. The pads are the same size, but I can't view the soldermask, so my rough workaround is to change the net pad clearance to be 0.1 all around, so it fits with my old part from OrCAD. However, it still doesn't solve the issue of the planes going in between the pads. How can I resolve this issue without affecting the other components of my board (is it possible to do this on a part-by-part basis)? Also, is there a way to view the soldermask layer? I see the mask layer as an option, but it doesn't show on the component. Perhaps being able to see the soldermask on my components might be helpful for this issue.


texts: Problems with STM32F746G-Discovery using another display

texts:
I encountered a problem during the configuration of a STM32F746G-DISCO Board for the use with another display.
Initial situation:
I unsoldered the connection between the STM32F7 Board and the default display. After that I soldered a connection onto the other display.
I successfully put the default screen and another display (Display 1) in operation. No problem whatsoever.
I use TouchGFX to show a bright red screen. No fancy pictures, graphs or something like that.
But when I connect yet another display (Display 2) with a STM32F746G-DISCO board --> just a dark screen that slowly gets white. Like it gets false or no information at all and the background gets slowly brighter and brighter.
Configuration (Display 2):
Settings CubeMX

Datasheet

For me it seems to be right. The basic project is the same as the two other (working) examples.
It would be great if someone could tell me if I have a fault in the configuration. So I can check if I've got a fault in the wiring between the board and the display. At the moment its like finding the needle in the haystack.


texts:
The basic understanding of this that I have is that:
Assume clock low is 0V, clock high is 3V and Vin is at a fixed 3V. Ignore diode drops

Initially Clock is low (0V) and Vin is at 3V (always). Voltage at the first capacitor node is thus 3V (ignoring diode drop). The left capacitor has got positive charges on it's top plate and attracts an equal number of negative charges on it's bottom plate thus giving 3V across it.
Clock goes high (3V). Now since we already had 3V across the first capacitor with respect to ground, it somehow doubles to 6V now? Can someone explain to me with charge carries what happens to the first capacitor? How does it magically become 6V (I realise the reference node has changed, but surely charges on that capacitor must change too).


texts: What idea/field in electronics is revolutionary nowadays

texts:
i realize that back then in the 30's-40's Von Neumann architecture was revolutionary, parallel at MIT, information and communication theory, and vacuum tubes were revolutionary fields, in the 70's solid state, VLSI, microelectronics, was revolutionary, 80's and 90's with networks, digital communications hardware, internet, massive programming languages, and computer architecture, were revolutionary. Now days, what are the leading areas in electronics, if you know at least one, what researcher institutes or universities are leading those advances. This question is with the purpose of a get an original idea for a research that can expand electronics.

I must concrete myself, i am looking for theoretical stuff, not practical stuff

Thank you very much


texts:
I am currently involved in a university project to implementing a processor of an existing instruction set. The idea is that by the end of the project I should be able to synthesise this design and run it in an FPGA. Everything is going well so far, I started implementing the design in Verilog HDL a few days ago and got a very simple version working. Now the problem: I got in touch with some people that have been involved in hardware design for years and they suggested that before I go any further I should shift to using SystemC for the implementation. Now, made me very very confused because this was my thought:
Verilog -> As an HDL language specifically targets hardware design. Has some levels of abstraction like structural and behavioural Verilog, but it is a very neat form of specifying the RTL of a design. You can definitely synthesize it using a bunch of tools depending on the FPGA you choose (in my case I am using Xilinx Vivado 2014 and Zynq boards). On the down side plain Verilog does not offer enough abstraction for verification and that is why you have stuff like System Verilog.
SystemC -> This is a C++ class library that effectively introduces the concept of time in C++ and allows you to do an event driven simulation. Clearly it is a lot more high-level than any HDL and things here can be implemented much quicker. This makes it a very good tool for stuff like verification and even implementation of simulators so that people can start designing drivers and things for a chip before the thing is actually manufactured. Apparently, there is also a subset of SystemC that is synthesizable (I think even Xilinx Vivado can do this) and in some cases it enables SystemC to be used to design very large systems where a higher level of abstraction is handy.
So, my questions are:

Are these notions of SystemC and Verilog (or other HDL languages) correct?
When should I use SystemC and when Verilog?
I am told that even in Verilog, using a lot of behavioral code can be a bit problematic in critical sections of the implementation because you are basically giving a lot less constraints to the synthesis tool on how to synthesise it. With a higher level of abstraction wouldn't this be a problem? i.e. If I use SystemC I might end up with a very slow, power hungry, large design...
The person that suggested SystemC mentioned that it looks like I am doing "architectural exploration" and that is why he would prefer Verilog. What exactly does that mean? I was under the impression that the architecture typically refers to the instruction set and the microarchitecture to an implementation of an instruction set (so the microarchitecture is the actual rtl that executes the instructions). So does architectural exploration mean that he thinks I am implementing a processor to see how feasible an instruction set is?
He said that an argument for using SystemC is that it is a lot easier because it is at a higher level of abstraction than an HDL. He also claimed that it was easier to get the timing of the design right. To what extent is this true?

Help would be greatly appreciated, I am a bit confused and finding it difficult to get clear information about this online. Thanks!


texts: Connecting SDI and SDO to a single DATA pin

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On the MMA7455 accelerometer, there is only one DATA pin which is used for both input and output. On the manual, it tells me to connect this pin to SDI and SDO. Now that's all fine, but on my chip, these are two separate pins.

If I connect SDI and SDO pins to the DATA pin, won't the data that flows out of SDO go into the SDI pin as well? Wouldn't this cause any problems?

Is there are any buffering that would potentially store the data the comes in through SDI? (So maybe after sending something out of SDO, I can clear the buffer at SDI to avoid reading what I just sent).


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I am using a magnetic rotary encoder(AS5048B) to detect the rotation angle of a motor shaft. This is fed to a pid loop to calculate the PWM value for motor position control.
The encoder has a 14Bit output. It gives an output of 0 - 16383 which is then right shifted by 4 to get a range of 0 - 1023.

When we give values closer to 1023 the sensor value goes back to 0 after a complete rotation and the pid error goes to huge values resulting in unstable motor movements. Suppose my current position is 10 and setpoint is 1023. The error is 1023 - 10 = 1013 and the motor starts to move towards 1023 to decrease error. When it reaches 1023 sometimes it overshoots and goes back to a value of 0 which gives us a wrong PWM value of 1023(1023 - 0). Is there any workaround for this issue?

Implementation details:- The experimentation setup consists of a 60RPM geared DC motor, an H bridge(VNH5019) and a magnetic rotary encoder(AS5048B). The H bridge has a PWM input for speed control and 2 other pins for direction control. It is an absolute encoder which gives a 14Bit output corresponding to 0 - 360-degree rotation of the motor shaft and the same act as a feedback signal for the plant. PID update function is written as a periodic timer interrupts with 10KHz frequency. Inside the ISR I read the setpoint from a rotary encoder and the feedback signal from the magnetic encoder. An error is then calculated, corresponding PWM values are generated and sent to the H bridge IC for changing the motor shaft position for that error. Because of the nature of the PID loops the motor starts rotating and when the error approaches zero the PWM value also approaches 0, thus stopping the motor at the set-point. My plan is to make this motor as a 0 - 359-degree position servo for normal applications (and 0 - 180-degree servo for hobby servo applications in the future).

I tried with a P only controller. It works fine at all the positions except the overflow point. Since the error is calculated as the difference between setpoint and input, an overflow makes the error value extremely high. The motor thinks that it needs to apply that much of PWM(which decreases as the error approaches 0) to reach that position. The net result is a motor which goes from 0 - 359 degrees (when the setpoint is a value corresponding to 359 degrees), overflows by 1 degree and goes back to 359, thus repeating the process infinite times.


texts: How to design a circuit which provides a range of voltages to test an ADC?

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I designed a circuit to read analog signal, in range of -10V to +10V with resolution of 1mV. I need to validate my design by testing it in different input voltages. So I soldered a voltage divider circuit using a potentiometer. But I think it is not a good way due to the fact that it affects actual voltage by drawing current. Other way is to use an op-amp as a voltage buffer to eliminate effect of voltage divider circuit. I want to know: how to make a circuit to provide different input voltages for ADC with negligible effect on ADC? Thanks in advance.

EDIT1: Link suggested by Roger Rowland is about validating procedure, but my question is about the circuit which provides different input voltages for ADC with negligible effect.

EDIT2: I measure the voltage test by Fluk8846A. When I connect it, voltage changes and oscillates 4mV peak to peak. How Can I remove the noise induced by Fluk?


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I want to design a 4-way lighting system using LEDs. This is what I have so far.
LED driver: https://www.ledsupply.com/led-drivers/buckblock-dc-led-driver
LED: https://www.ledsupply.com/leds/cree-xlamp-xp-l-high-density-led-star
one way will have, one series line (9 LED's) with one LED driver.
Constant current = 2100mA
Total forward voltage = 9 * 3.1V = 28V
Flux at 2100mA =~ 800 lm for cool white.
Total flux/side = 9 * 800 lm = 7200 lm
Total flux = 4 * 7200lm = 28800 lm
My questions:
So with 4 LED drivers, 4 of 9 series LED strips, 1 battery pack of 36V, I should be able to power this system right?
Also, could somebody confirm my lumen calculations. It's my first time dealing with multiple LEDs.
Is there another efficient way to implement this? This is the highest current output driver I could find. If the is one that can output 9A, one driver can power all these 9 strip led's in parallel by itself.


texts: Arduino esp01 UART connected server with driver

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I have a project of WiFi oven driver and I would like to know if I don't overcomplicate any aspects. Or are there any existing tools for what I'm trying to do.
I decided, to connect mentioned devices - Arduino as a driver, so I could use ADC and esp 01, only able to set demanded temperature, so no matter what only thing I can f up is burning my roast, not entire house.
The procedure would be as follows:
I click STH on my UI, it freezes, esp sends settings, Arduino changes settings and sends back confirmation, UI defreezes.
I will write a function, that will read chars from a line until space occurs, then it finds a function pointer, that fits to that word and passes rest of a line as an argument.
Pseudo code:
void (*func)(string)[];
string fname[];
for (int i = 0; uartline[i] != ' ';i++)
 currentfunction.append(uartline[i]);
 uartline.delete (i)
int i;
for (i = 0; currentfunction != fname(i); i++);
func[i](uartline);

and I will make a library, that does it.


texts: Would LEDs on Tx and Rx lines cause too much voltage drop?

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So I keep seeing that people use LEDs and a limiting resistor in series on tx and rx lines to create status leds.

My question is, wouldn't this cause a voltage drop on the expected input voltage into the chip?  If I'm feeding a 3v3 logic line and throw a resistor and an LED in front of it, wouldn't the voltage to the chip be too low to drive it high?  But I keep seeing this solution everywhere.  Am I misunderstanding something?  My knowledge of electronics is iffy at best.


texts:
I have the following circuit

I am having some trouble determining the relationships between Iac, Io and Iacpk.  I'm not quite seeing how the final equation for Iac was determined, specifically the factor of (2/π) and Iacpk.

Thanks.


texts:
Say you were wanting to measure a signal with a higher voltage than the ADC could handle. Is there some best practice or commonly used circuitry that goes beyond a simple voltage divider to protect the ADC?

Or is it common for professional designs to simply rely on a voltage divider?