texts: Would you explain the output waveform of this FM transmitter circuit?

texts:
I build this circuit and it works. I wanted to look at the output waveform by my soundcard oscilloscope software. I would expect something like the following picture:

But the output waveform was this:

The input of the circuit was a song played from my computer. The output of the circuit (the antenna) was connected to  the input of the virtual oscilloscope. The other input of the virtual oscilloscope was connected to ground.

My questions are:

1- Why is the output waveform different from standard (or normal) FM waveform?

2- Why is the frequency 100.1 Hz only? I received the signal at 88 Mhz.

Thank you very much,


texts: AC adaptor needed to power multiple devices

texts: Basically working on a project, still in the conceptualizing stage, where I need to output power to 3 devices, 12v 2A, 12v 2A and 5v 2A, ideally off one ac adapter. I was thinking of using a dc to dc step down converter for the 5v 2A device, that way I could power everything off of one ac adaptor. What size voltage/amp ac adaptor would I need to pull this off? I'm not sure exactly what it should be taking into account the input of the dc to dc step down converter. Thanks


texts: Why does voltage regulator heat up and starts to switch the supply when it is used for driving a high power LED?

texts:
The regulator is LM2596HVS (max supply voltage: 63V) and it is connected to a Cree high power LED. The regulator is part of a off-the-shelf buck converter. It makes silly noise when circuit is closed and heats up quite a lot (i.e. only when connected to the power LED). After a few seconds, the LED starts to blink. The LED can take 6-12V however, it starts to blink even below 5V.

simulate this circuit – Schematic created using CircuitLab


texts: Multiple buck converters from same source?

texts:
I'm trying to build a 18 servomotor hexapod robot (6 legs), running from a 11.1 V Li-Po battery supply. I needed to step down the voltage to 5 V for the servos to operate, but the current requirements are very high (approx 10-14 A). I can't build my own high current buck converter right now because the TI chip I was considering for my use is surface mount.

The only buck converter I can get from my area are cheap 5A ones. Can I wire three separate 5A buck converters for a pair of legs each, and connect them to the same battery? If not, is there any other possible solution (different battery source, etc) I could use to power up the servos?


texts: VHDL design went from occupying a few percent of logic elements to 90%

texts:
I had a design in VHDL which I compiled and it used just a few percent of the total number of logical elements on the FPGA. When I made som minor changes (removed the current controller which controlled the input signals) and added one 3x1 multiplexer and one 1x3 demultiplexer the design took 2,5 hours to compile compared to 20 min for the previous model and it took up 90% of the total number of logic elements.

Why is there such a big difference in resource usage? How do I optimize the hardware utilization?


texts: Current/power requirements for electric fence?

texts:
We just ordered some new electric fence chargers for our farm. The new chargers are designed to work off mains or battery. Due to the location, we are considering running off battery with a solar recharger (25w or larger panel) instead of permanently running wire to the nearest fenceline. That would also give us the option to more easily move the charger around and energize different pastures.

I'm hoping someone here could help me understand - I looked for a smaller/lighter battery pack (lithium ion, maybe a small bank of 18650 cells?), but the only batteries I'm finding for electric fences are the larger/heavier lead batteries. Assuming everything was weatherproof, is there something fundamental about current draw or 'rechargability' that would make 18650s undesirable in this type of application? I get they might be a little more expensive, but the trade off for easy portability seems worth it.

I appreciate any insights you can provide!


texts:
I'm working with 6 LEDs in series, which are rated at:

3V Typical / 3.2V Maximum
20mA.

My power supply is:

19V
3A Maximum

According to my calculations:

I'd need a 50 ohm resistor at 3V
I'd be in the negative at 3.2V.

Because my target resistance with the LEDs alone would be below the maximum LED voltage specification, do I need any sort of resistor at all?

Is this the appropriate use case for a 0 ohm resistor?

I plugged in the array last night for around 20 seconds or so, and the wiring seemed to get rather hot which is a bit worrisome... The LEDs however, didn't appear to be brighter than when connecting one at the appropriate resistance.


texts: How to prevent voltage until a specific voltage is met?

texts:
I have a question that I have not been able to answer through hours of searching (or at least I don't believe I have found the answer.)
I'm trying to get a DC relay to trigger at a certain voltage but not before that threshold is met.
Here is the scenario:
The vehicle has an electronic throttle body and gas pedal. From just idling to full throttle, the throttle pedal reads 0.800v +- 0.050 (idle)  to 4.4V +- 0.050 (full throttle).
If I connect the relay to the throttle wire it will trigger it almost immediately once the car is on. I don't want to have the relay trigger to get voltage until around 3V to 3.5V.  How do I achieve blocking the voltage until that specific range?


texts:
I designed the following PCB, where after testing a faced a severe (EMC related?) problem.

This board houses an STM32F103 developing board.

On the right of the PCB, there are 6 thermistors connected to measure various temperatures, which during all testing where connected directly to the PCB, without any long cabling. On the bottom of the PCB there are 7 relays, SANYOU SRD-S-112D, which are driven from the ULN2003A above them. The diode of the ULN2003A is properly connected, and there is no problem with the back-EMF of the relays. No other connections where done during testing.

While I was testing the board with nothing connected to the relays, everything performs as expected.

Then I connected a mains (220V) relay to the on-board one. The connection thus is ULN2003A=>on-board relay =>mains relay. And here the problems begun. Every time the 220V relay changes state I get excessive noise spikes on the PCB. I2C data are corrupt, data of the shift register controlling the ULN2003A are also corrupt etc. The problem is more severe when the relay is being deenergized.

The PSU, the PCB and all used instruments are properly grounded. The PSU is isolated, with the DC ground connected to earth. The on-board relays are tested, and my DMM reports OL between the contact and the coil for all. Apart from ground nothing else connects electrically the mains relay and the PCB under test.

I hooked up my oscilloscope and I got the following trace. Channel 2 is the +12V supply of the PCB. These spikes are observed 6ms after the ULN2003A output changes, so I believe this is the time the on-board relay needs to change state, and the coil of the 220V relay to start/stop operating.

These spikes can be observed to any point on the PCB, on any trace and voltage level.

What exactly is causing this? How can I combat it? How can I determine whether these spikes get to my circuit through the PSU, or through the air, and in each case which is the solution?

As I have manufactured a small batch of these boards, I am interested in solutions both to make them work and not throw them away, and solutions to implement to the next revision.

More tests can be performed, please ask in comments.

EDIT:

As per recommendation in the answer, I installed a 1.5KE400CA TVS on the on-board relay's contact. I can say that it helped a bit, but definitely the problem persists.

Here is the output of the 5V regulator before the TVS:

And here it is after:

EDIT 2:

As you see on the schematic, there is a serial output, for daisy chaining more shift registers, and relays. I connected such a board on this output. It is made on a strip-board, so I do not have any schematics at hand, but it is a simple 74HC595 connected to a ULN2003A. Just the same circuit as in the main board. When doing the same test (mains relay connected, to the contact of the expansion board relay), the spikes are much more severe, and the system becomes completely unresponsive, with data on all buses (I2C, and SPI) totally corrupt.

I tried adding TVS diodes on everything (relay coil, relay contact, mains relay coil, mains relay contact), but did absolutely nothing.


texts: Use the BMS from laptop battery for single cell

texts:
I have just disassembled a battery pack from a Lenovo laptop (Series: 45N1005 with six cells, Specs: 10.8V, 5.2Ah, 57Wh) and I would like to use the BMS for controlling a single 18650 cell (2.8Ah) which should power an Arduino board. I would like to have the overvoltage and undervoltage protection (see also my previous post).

I have tried to do some testing and see if I can read the voltage of a single battery through the BMS terminals, but the voltage is 0, so I'm wondering why.

Please see below how the board looks. Unfortunately, I couldn't find any information about its parameters or components and therefore I would like to ask if any of you can help me to figure out:

If this BMS can be used to control the charging/discharging of a single cell instead of 6;
How to test the BMS so that I can figure out the parameters. Which methods should I use?

Basically, I'm more interested in the overdischarge protection. That is, a cut-off voltage of 2.7 V.

Here is the unknown BMS with the sketched battery connection.

Top view:

Top view close-up:

Back view:

The only searchable keyword that looked relevant was "94v-0", but the results were totally different than what I have.


texts: linear model of a power load at the end of a transmission line

texts:
I am working on a controller that will regulate the voltage at the end of a transmission line into a variable load. I am able to ignore the inductive effects of the line at the frequencies of interst, so I can model the line as a simple RC filter. I have a variable voltage power supply at the input of the transmission line, and the goal of the controller is hold the output voltage constant (zero ss error) by varying the input voltage with measured output current.

For the simple case of a fixed load, I can model the load as a resistor, and then the transfer function of the transmission line/load system is just
G(s) = (1/(RtCt))/(s + (Rt + Rl)/(RtRlCt)), where Rt is the total resistance of the transmission line, Ct is the capacitance of the line, and Rl is the load resistance. This is good for simple analysis, but it's trivial because if the load were constant I wouldn't need the controller and variable power supply in the first place!

However, Rl isn't really a resistor, it is just a stand-in for the power load at the end of the line. That is, it is a voltage and current pair, the product of which is what is actually varying. If I could hold Vl fixed, Rl decreases with the inverse of the load current flow. Of course, due to lag I know that the load voltage will not be constant during transients, so that isn't an assumption that I would like to make!

Is there a good model that I could use in place of Rl that would let me derive a set of linear system equations for analysis and controller design? I know that it will require a linear approximation, but the good news is that as the power into Rl increases, Rl decreases, pushing the single pole of the line/load's transfer function towards negative infinity, meaning that the system becomes more stable, not less. Furthermore, as power into Rl approaches zero, the pole approaches -1/(RtCt), which is safely in the LHP for any transmission line that I will be dealing with for this project.

TL;DR: looking for a decent model of a power load (PF=1) at the end of a transmission line that I can use for linear analysis.

EDIT: Based on Ben's comment below, I have remodeled this system by replacing the load resistor simply with an output current. Then I analyzed the system in two parts: 1: assume the output current to the load is zero and derive the transmission line transfer function Vc/Vs. Then, to include the effect of load current on the capacitor voltage, I simply divide the load Ct and integrate and subtract this from Vc. This gives me the block diagram below. Does this make sense? I'm less sure about how I have included the effect of output current, but if this is correct that means that I have a block diagram that I can use as the basis of my controller design.


texts: Looking for general advice on ESD protection on board inputs that are carrying small signals, for example, tens of millivolts at very low current. I suspect that hanging diodes off it might compromise signal integrity due to diode leakage. Advice?


texts:
What is the best way to break out a Flat Flexible Cable (FFC)? Specifically I've got a sensor which uses the 0.5mm pitch FFC that I would like to break out onto a breadboard. As you might already know these cables are extremely small and thin and soldering wires directly to them is almost impossible.

Note I DO NOT have access to the inside of the sensor so solder/connecting to the board directly is not an option.


texts: How can fully charge a capacitor without having it prematurely discharge?

texts:
I am looking to power a circuit using a 5.5V, 5F supercapacitor. I want to charge it to approx. 5V but I don't want it to discharge into my circuit until it has charged to 5V. I can do this by simply using a switch or disconnecting/connecting the appropriate wires of the switch, but I want to control this automatically. Is there any way to do this?
Thank you for your help!

Edit 12/8/18:
I built the following circuit, kindly suggested by user Transistor. For my SCR, I am using a NTE5402 and for the Zener diode I am using a 4.7V 1N4732A. The resister is 1k ohm and the circuit is a simple buck booster (Adafruit Powerboost 1000) connected to an Arduino.


texts:
I want to generate 20mV Vref using Op amp, like this:

When simulate with TINA using model from TI, instead of 20mV at output (Vref port), i see that it is 27.95mV.

My question is:

Why I can't get 20mV at Vref
How to improve this circuit to have accurate 20mV (+/- 5%)
Any recommendation for me (other way) to have 20mV Vref?

Update:

The full schematic here:

Current max is 0.4A, Shunt is 10mOhm. AC voltage is 220V 50Hz. R14/R15~ 100 Ohm

3.3VDC is generate from AC/DC Power supply (using LNK306 - I've have prototype)

I don't want to add negative Power supply because of cost and space of board.

Thanks


texts: How would you all implement a simple delay of a signal?

texts:
I am a console game developer by profession, and has no formal education on electronics / electrical engineering. In gaming lingo, a 'noob' if you will, at it. And yet I have a new found passion for fiddling with this wonderful craft.
At the moment, I am trying to learn and have fun while make a 'scrolling LED' toy for my daughter. My idea for it is quite simple, I have a shift register (SN74HC595), and 8 LEDs taking input from it. There will be two buttons. When button A is pressed, it 'inserts' a 1 into the register, and when B is pressed, it pushes a 0 into the register. With this you can 'program your LED pattern'. And then with the flick of another toggle, the shift register will get clocked (using a simple RC astable multi vibrator) (looping QH' to QA). Making the pattern to scroll. Simple enough.
But, my problem comes at the part which does the 'inserting' of data into the register. Let's say, to insert a 1 to the register when button A is pressed and released, I first have to pull the 'SER' (data) line of the register high, then after a brief period of time (setup time, 25ns for the register's datasheet) pull the SRCLK (Shift register clock) high. And that's it. However..
My switch buttons are debounced. I learned about debouncing from  this wonderful article : Debouncing. I didn't had any parts that would help me with hysterisis so I had to just ignore it. But using the methods specified there, I was able to calculate the exact values of my resistors and cap, to keep the voltage just right while my switch clank and knock with itself. The switch bounces for 10ms ( got  myself a cheap O-scope, china one. But does the job ), so am keeping it steady for about 20ms. My calculations and the results of simulating it using Multisim.com matched. So my button debouncing works as expected.
Except, when I try to use that 'signal'. I have to do two things with this signal. First, route it to SER line of the register. And then after a brief delay (25ns - a few ms?) route it to SRCLK line to clock it. In other words, first pull SER high, then pull SRCLK high. And to introduce this 'delay' I turned to the only delay mechanism I know - RC network. So once I get the debounced output, I charge a cap through a resistor, and that charged output is what I use to drive SRCLK.
The moment this new capacitor and resistor gets added to my 'debounce circuit',my calculations for the parts value doesn't hold true anymore because the new 'delay' capacitor and resistor is now in parallel or serial (I don't even know anymore) with my good and previously well behaving 'debounce' capacitor.
All this predicament makes me wonder if even using an RC delay timer is even the right thing to do. How do I connect input from a debounced switch to a node that already has a capacitor, without messing up all my calculations.,or to rephrase it, How would you all implement a simple delay of a signal without using all fancy micro controller etc..?
Here is the schematic of the denounce and delay. Note that this is only addressing the single button (not both A and B). SW2 in the first image is just for debugging.

simulate this circuit – Schematic created using CircuitLab


texts: STM32L073xx Internal Bootloader - Disabling Read Protection bricks device

texts:
I would like to continue what I started here about internal bootloader. Now I would like to add read protection to my uC.

Connect uC via UART2 to PC
Trigger jumping to internal bootloader by pressing some key
Send erase page by page commands (got ACKs)
Send new flash content to micro (got ACKs)
Send turn on read protection comnand (got ACK and uC resets, needs power on reset - it's ok)

So far so good, till this moment everything works as intended.
After reset when read protection is turned on (I can check it via ST-Link utility). Now I want to send another SW to uC:

Triggers internal bootloader
Send Extended Erase Memory command (0x44 0xBB) and get...0x1F.
This is actually ok and works as shown on Figure 17 in AN3155 Rev5, page 26. I have RDP active and get NACK.
I want to turn it off, I send Readout Unprotect command (0x92 0x6D) and get double ACK (it's fine). Micro makes Mass Erase due to disabling RDP and makes reset.

From that point, flash is empty, BOOT0 pin is connected to GND (boot from user flash memory) and it's impossible to come back to bootloader to continue programming flash with new SW.

Is there any way to boot from system memory after such reset? It looks like only way to use internal bootloader is to have access to BOOT0 pin which in my case is not possible because whole device will be flooded in resin. Am I missing something from Boot configuration?


texts: Need a way to limit DC voltage of MAF sensor output

texts:
Hi I have an output voltage ranging from 0-5v that increase linearly.

The ECU reading the voltage puts the vehicle in a limp mode when the voltage increases over 4.6v. The modifications completed to the vehicle cause the sensor the read voltages slightly over that amount momentarily.

Is there a way the cap the output voltage to 4.6v without altering the linear increase in voltage the sensor reads up until the 4.6v

I thought a zenor diode would work but I am not sure

Cheers Luke


texts:
I have an ADC input that may be connected to an external sensor (based on how the user configures it).  If I leave the input floating, I get a wide range of ADC values.

Is there a way to weakly ground this input to get a stable reading if nothing is connected?


texts: What do you call a cable that has string along with its conductors?

texts:
I'm trying to replace the cable that connects the magic wand in a VTech Magic Wand toy laptop. It's an interesting beast. Inside its outer insulator is a bunch of strands of string plus the two conductors. Each of the two conductors is a braided bundle of enameled wires around a string core.

It's clear to me that this was designed this way so that it wouldn't break under tension or repeated flexing as a kid uses the magic wand to point-to-select things on the toy's LCD screen.

But what do you call such a bundle? I'd like to replace it with something similar to the original cable, but I'm having trouble naming the product that I'm searching for.


texts:
I am new to number systems and binary.

Can someone tell me why is X>=11 and Y>=6 in this problem?
Can someone also explain how the values X=12 and Y=16 are obtained from the conditions shown in the answer?


texts:
I was looking at using the OPA860 for a voltage controlled load. Reading in the OPA860 datasheet it says:

  The OPA860 combines a high-performance buffer with a transconductance
  section. This transconductance section is discussed in the OTA The
  buffer section of the OPA860 is an 1600MHz, (Operational
  Transconductance Amplifier) section of 4000V/μs closed-loop buffer
  that can be used as a this data sheet. Over the years and depending on
  the building block for AGC amplifiers, LED driver circuit, writer, the
  OTA section of an op amp has been integrator for fast pulse, fast
  control loop amplifiers, referred to as a Diamond Transistor, and
  control amplifiers for capacitive sensors and Voltage-Controlled
  Current source, Transconductor, active filters.

Are they achieving the transconductance with regular boring silicon tech (which is probably the case) or something else?

My main reason for asking the question is because its a cool part (low noise and transconductance), and because even though I suspect there is no secret sauce maybe there is, it also says ±1.2V differential input which I thought was interesting.


texts:
Sorry if this question has been asked before, I've tried looking through google and Stack Exchange and I can't seem to find the answer.

Resistors on the gate (R3 on the picture) are usually in the K ohms with good reason.
The part I don't understand is the voltage drop that to my knowledge should occur to that resistor due to it being in series. Considering the other side of the resistor after the mosfet is connected to the ground, wouldn't applying let's say 5V to the left side of R3, where the OUT pin on the picture is, make all the current go through the resistor and nothing left for the mosfet ?

I'm guessing my assumption is wrong and the other side of the gate is not connected to the ground, or I simply don't understand how a PMOS works well enough, but basically I don't get how Vgs(th) could ever get enabled considering there is a high resistance resistor in front of the gate.

Sorry for the stupid question, I don't exactly know what to ask on google and I've been at it for a couple hours looking and can't find a good answer.

Thank you !

Image is taken from this Stack Exchange link


texts:
I am using a PIC18f25K80 and an XC8 compiler. I have included the files from the MDD library. However, after compiling I get the following in the "FSIO.c" file:

make -f nbproject/Makefile-default.mk SUBPROJECTS= .build-conf
make[1]: Entering directory 'H:/SPATIAL/SPATIAL.X/SPATIAL.X'
make  -f nbproject/Makefile-default.mk dist/default/production/SPATIAL.X.production.hex
make[2]: Entering directory 'H:/SPATIAL/SPATIAL.X/SPATIAL.X'
"C:\Program Files (x86)\Microchip\xc8\v1.32\bin\xc8.exe" --pass1  --chip=18F25K80 -Q -G  --double=24 --float=24 --emi=wordwrite --opt=default,+asm,+asmfile,-speed,+space,-debug --addrqual=ignore --mode=free -P -N255 --warn=0 --asmlist --summary=default,-psect,-class,+mem,-hex,-file --output=default,-inhx032 --runtime=default,+clear,+init,-keep,-no_startup,-download,+config,+clib,+plib --output=-mcof,+elf:multilocs --stack=compiled:auto:auto:auto "--errformat=%f:%l: error: (%n) %s" "--warnformat=%f:%l: warning: (%n) %s" "--msgformat=%f:%l: advisory: (%n) %s"    -obuild/default/production/main.p1  main.c
main.c:217: warning: (350) unused variable definition "pointer2" (from line 200)
main.c:217: warning: (350) unused variable definition "pointer" (from line 197)
"C:\Program Files (x86)\Microchip\xc8\v1.32\bin\xc8.exe" --pass1  --chip=18F25K80 -Q -G  --double=24 --float=24 --emi=wordwrite --opt=default,+asm,+asmfile,-speed,+space,-debug --addrqual=ignore --mode=free -P -N255 --warn=0 --asmlist --summary=default,-psect,-class,+mem,-hex,-file --output=default,-inhx032 --runtime=default,+clear,+init,-keep,-no_startup,-download,+config,+clib,+plib --output=-mcof,+elf:multilocs --stack=compiled:auto:auto:auto "--errformat=%f:%l: error: (%n) %s" "--warnformat=%f:%l: warning: (%n) %s" "--msgformat=%f:%l: advisory: (%n) %s"    -obuild/default/production/FSIO.p1  FSIO.c
FSIO.c:197: warning: (335) unknown pragma "udata"
FSIO.c:199: warning: (335) unknown pragma "udata"
FSIO.c:201: warning: (335) unknown pragma "udata"
FSIO.c:7120: warning: (345) unreachable code
FSIO.c:7983: error: (195) expression syntax
FSIO.c:8081: error: (195) expression syntax
FSIO.c:8132: error: (195) expression syntax
FSIO.c:8690: warning: (359) illegal conversion between pointer types
pointer to const unsigned char -> pointer to unsigned char
FSIO.c:9359: warning: (343) implicit return at end of non-void function
FSIO.c:9359: warning: (350) unused variable definition "utf16path2" (from line 8691)
FSIO.c:10311: warning: (359) illegal conversion between pointer types
pointer to const unsigned char -> pointer to unsigned char
FSIO.c:10566: warning: (359) illegal conversion between pointer types
pointer to const unsigned char -> pointer to unsigned char
FSIO.c:11104: warning: (343) implicit return at end of non-void function
(908) exit status = 1
make[2]: *** [build/default/production/FSIO.p1] Error 1
make[1]: *** [.build-conf] Error 2
make: *** [.build-impl] Error 2
nbproject/Makefile-default.mk:163: recipe for target 'build/default/production/FSIO.p1' failed
make[2]: Leaving directory 'H:/SPATIAL/SPATIAL.X/SPATIAL.X'
nbproject/Makefile-default.mk:75: recipe for target '.build-conf' failed
make[1]: Leaving directory 'H:/SPATIAL/SPATIAL.X/SPATIAL.X'
nbproject/Makefile-impl.mk:39: recipe for target '.build-impl' failed

BUILD FAILED (exit value 2, total time: 5s)

For some reason it doesn't like the following

_asm TBLRDPOSTINC _endasm


texts:
I'm trying to power a board through both usb & a 9V battery (with the usb taking precedence) with a P channel MOSFET, a schottky diode & a pull down resistor. I'm confident this will work with just a battery, since the gate of the PMOS is pulled down and so the MOSFET will be on.

What I'm concerned about is when a USB cable is connected. Primarily because the battery is 9V and runs through a DC/DC converter which is disabled once the USB is connected. So the +5Vbat will actually be low when the MOSFET is off (gate & source will be at ~ +5V). I know having a floating source or gate can be bad/damaging; should I be concerned about any current leakage when the drain is ambiguous?


texts: Why do sidebands appear after Amplitude Modulation?

texts: In amplitude modulation, the amplitude of the carrier wave is changed according to the variations in the message signal, and that's what we draw inside the two envelops of the message signal, that's totally fine, but what is confusing to me, that we never changed the frequency of the carrier wave, then why do those two sidebands appear in the frequency response of the AM wave, I know that the mathematics works out to be like that, but how on the earth they appear in first place, when we never tried to mess with the frequency of the carrier?


texts:
Can someone show me how to calculate voltage drops and current on this circuit?

simulate this circuit – Schematic created using CircuitLab

I have 9 V source and 100 Ohm resistor.

So for the resistor on its own, the current would be 9 / 100 = 0.09 A across the whole circuit.

But I don't know what to look up to determine the voltage on the diode, or what the current will be on the circuit, now that it is added.


texts: Is it possible to use buck boost converter at the same time?

texts:
I have a input source from 50mV to 4V and I want a fixed/regulated voltage of 3V. Input voltage is varying every time so in order to achieve the 3V I have to implement Buck as well as Boost converter with respect to the input voltage.

I couldn't find any chip/IC which operates at such a low voltage 50mV, So what could be the solution for this?  Do I need to detect the input voltage before using Buck/Boost converter?


texts:
Given that there are many differences in the way data is written to EEPROM and Flash, how exactly is EEPROM emulation done with internal flash?

Also, flash needs to be erased in large blocks before data can be written over. In that case, if we want to write only a small amount of data in emulated EEPROM without disturbing the other contents, how is it achieved? What are the software techniques for this?


texts: Read voltage of the battery that feeds ATmega328p

texts:
I am designing a system focused on the uC ATmega328p and I am feeding it directly with a 3.7V LiPo battery.
I also have a 3.3V LDO feeding several sensors in the system.

My question is the next,
If I want to read the battery voltage [full charge = 4V, discharged = 3V (approx.)]
How should I configure the Vcc, AVcc and AREF pins of ATmega in order to achieve that result?

At the moment I feed the ATmega328p (with internal crystal 8MHz) to the battery voltage and I was thinking of connecting Vcc with AVCC and with the 3.3V that the LDO gives me to connect them to AREF and put the voltage of the battery with a voltage divider to an analog arduino input.

What do you think?
Any better solution?

PS: I would not like to add any extra components to the system.

Thank you.


texts: Subtractor op-amp configuration to find the diference of 2 signals

texts: How can a differential op-amp be configured in a way that it doesn't amplify but only takes the difference between the signals at the inverting and non inverting input?


texts: With LED brightness and different resistors, do I talk about the current or the voltage?

texts:
I'm building a parallel circuit that uses a red LED and a green LED and a 3v power supply. I know that I use a higher Ohm resistor (using 130 Ohm) on the red LED because it has a lower forward voltage than the green LED (using 75 Ohm on that one). I also know that if I used the same 75 Ohm resistor on both, the red LED will glow brighter than the green LED.

How do I talk about what the resistor is doing? Do I say that the red LED needs less current than the green LED to glow as brightly, so it has a stronger resistor to reduce the current? Or do I say that the red LED needs less voltage than the green LED to glow as brightly, and the resistor soaks up voltage because of V=IR? It seems like resistors are always talked about with current, but LEDs are always talked about with voltage. Not sure if there's even really a difference between these two ways of phrasing.


texts:
I am designing time critical application where I need time resolution in order of 100 picoseconds.

I am considering to make an ring oscillator of 20 GHz and clock from ring oscillator.

Is there IC's for it or can I implement it using CoolRunner II CPLD or other FPGA?

I looked at its datasheet, and the maximum frequency for system clock is about 256 MHz and external clock is 145 MHz.Datasheet

Should I look for faster device or is there any other way to build it?


texts: Using ADC of PIC18F4520 to convert full-wave rectified analog signal to digital

texts: I am building a AC voltage and current (50 Hz) data logger and I have built and tested the measuring circuit and it works fine. I used an ideal full-wave rectifier to reflect the negative voltages to positive and my challenge now is converting the rectified signal to digital using the built-in modules of the PIC18F4520 (Microchip claims that the ADC this MCU can do  100K samples per second) so that I save the measured signal to the SD card. I am aware of the Nyquist theorem. What are the steps I should follow?


texts: Why does adding an emitter resistor to a common emitter amp reduce its gain?

texts: According to the Wikipedia page for common emitter amplifiers,  the addition of an emitter resistor decreased the gain of the circuit. However, to me it appears that if the resistor was omitted, then V_out would be approximately equal to the ground mode (when the transistor is conducting). But when the resistor is present, V_out would be equal to the drop across the resistor. Why then does the resistor reduce the gain? Please note I am very new to transistor circuits, and to electronics in general.


texts: Thyratrons: How they work, what they are used for, and how to read their datasheets

texts:
I recently ran into an interesting device called a thyratron. I have a basic understanding of thyratrons as gas filled vacuum tubes. I understand that they can switch large amounts of currents and voltages over short time spans very accurately. However, I come across a lot of thyratrons that have more than 4 pins (sometimes 6 or 7.) When I look at the datasheet (such as
this one) The pins labeling seems quite different from their scr couterparts.

I am trying to understand how these pins interact--so if the device were a black box, what relationships would I observe between current and voltages between the different pins?


texts: What is the effect of addition of a compensator(either Lead or Lag) to a system?in terms of addition of poles and zeros?

texts:
When we add a compensator(either Lead or Lag) to a plant in series, what is the effect in terms of addition of poles and zeros?
A pole-zero pair is added(meaning one pole and one zero)?
or
a pair of closed loop poles is added?(meaning two poles)


texts: Returning Current on power planes? (High frequencies)

texts:
For a 4-Layered design (Signal-Ground-Power-Signal):

I wonder that, I need both bottom signal layer and top signal layer for high frequency signals. I will use both of them for my high frequency signals. So do i have to carry about for my Signal-Ground-Power-Signal design. Do i need to change it as Signal-Ground-(Power+Signal)-Ground because of RF s.

if i use bottom layer for high frequency(100 mhz) signals too, is there any benefits of power plane for returning current or it must be exactly the ground plane for returning currents.


texts: Most series capacitors needs balancing resistors to keep the same voltage across them, but in my case, I'm using with three capacitors of 45uF in parallel that are working very close to its maximum RMS current rating. I'd like to know, is it necessary to put any resistor or inductor to balance the current of the capacitors? If so, could you please guide me on how to do that.


texts: I would like to use my arduino pins to control a 12 V light that has its own power supply. So what I need is something that can be used as a switch (here is in pink color) but I don't know much about electronics so I don't know what part to put there. I don't want to use transistors as they require to use the same ground potential.


texts:
From reading the book titled "Advanced Chip Design practical examples by verilog", I faced some questions about when the Ethernet packet is read from the FIFO and how the rollback works for the Ethernet packet FIFO.

The chaper 8.3.4 of the book explains the reason why rollback is necessary in the FIFO in the aspects of reading a packet and processing its CRC; when the CRC calculated from the receiver doesn't match with the pre-calculated CRC attached together with the packet, it needs to rollback the current FIFO write pointer to the rollback write pointer (rollback_wrptr). Here, rollback_wrptr is the write pointer of the FIFO saved right before it starts to receive the packet.

And the book says...

  At the end of the packet, when we find CRC does not match, we assert one-clock wide signal, rollback_wrptr that reloads the snapshot value to the main wrptr of the FIFO.

I am wondering why the book only mentioned about the write_ptr but read_ptr and read_ptr_rollback. To calculate the CRC, it seems that the packets should be read from the queue; it will consume some elements from the FIFO, which moves the read_ptr of the FIFO. Does the hardware logic prevent the receiver from fetching the data from the FIFO until the CRC calculation done in usual?

It seems that it should rewind the not only the write_ptr but also the read_ptr. If available, could I get some code implementing the FIFO with the rollback in verilog or VHDL?


texts: Computer PCIE slot power in parallel with external power supply?

texts:
I have an output card for my computer it is in the PCIe slot of the PC.  From there it goes to a break out box.  Where Pins 1 and 50 are power (5v) and 49 and 99 are ground.  If i turn on alot of the pins on the card at once, there is not enough amps to power everything.

Can i take an outside 5v power supply and can connect it in parallel with the 5vs coming out of the break out box/output card?


texts: Wheel speed from Shimano dyamo hub using arduino

texts: I'm trying to figure out a way to extrapolate wheel speed from the Dynamo hub I just purchased. I outputs 6V 3W AC, and I would like to potentially measure it using an arduino if possible, I' assuming I would have to measure the sinewave somehow. Any ideas?


texts: Boot sequence Harvard arch. Vs Von neumenn arch.

texts:
From https://electronics.stackexchange.com/a/224160/150597 is it necessory that the code and data should be loaded in RAM before execution for Von neumenn architecture. While in harward arch. the code can be executed from ROM and data can be loaded from RAM??

What if only busses are based on harvard archi. (ARM) and the address space is still unified (similar to von neumenn except busses)? In von neumenn cant we execute code from ROM space?


texts: To charge a 14AH battery in the cold with 2-4 weeks of no use with solar panels

texts:
I want to know if I can do this.  I have 2 panels, 1.5 watt ea that put out a max of 110 milliamps.  I bought a new AGM 14AH battery because my lead acid died early.

I plan to run both panels that fit in my small southern facing window, from the inside.  I want to plug the panels’ 12v plugs into a splitter to run a single 12v extension cord to my ATV accessory plug to charge the battery. I don’t want to over charge, but I doubt these little panels would do it.  I would lose some voltage with 16’ of cord I would imagine.  I could check the battery with a meter on sunny days to see what the battery is measuring, but wondered if you all could run numbers and tell a novice.  The panels are the small 1.5 watt at Northerntool.  https://www.northerntool.com/shop/tools/product_200660262_200660262


texts:
For an energy havesting application I needed a power management circuit so that it can power a wireless sensor module. The sensor module requires roughly 25mA current in active mode and 100uA in sleep mode. I used the LT3012B which is a low power linear regulator for this. It is given in datasheet that this IC can give 250mA output current but it is not happening in simulation. I want capacitor C4 to discharge through the transistor when it crosses 6V and power the IC . Why is output voltage different from a constant dc voltage?

asc code

    Version 4
SHEET 1 3448 680
WIRE 976 -32 656 -32
WIRE 976 32 976 -32
WIRE 976 144 976 96
WIRE 976 144 896 144
WIRE 1152 144 976 144
WIRE 1168 144 1152 144
WIRE 1328 144 1232 144
WIRE 1536 144 1328 144
WIRE 896 160 896 144
WIRE 976 160 976 144
WIRE 656 176 656 -32
WIRE 1152 176 1152 144
WIRE 1536 176 1536 144
WIRE 1328 208 1328 144
WIRE 1760 224 1600 224
WIRE 896 288 896 224
WIRE 976 288 976 224
WIRE 656 304 656 256
WIRE 1152 304 1152 240
WIRE 1232 304 1152 304
WIRE 1328 304 1328 272
WIRE 1328 304 1232 304
WIRE 1536 320 1536 272
WIRE 1696 320 1536 320
WIRE 1856 320 1696 320
WIRE 2320 320 2144 320
WIRE 2560 320 2320 320
WIRE 1232 336 1232 304
WIRE 2560 336 2560 320
WIRE 1696 400 1696 384
WIRE 2560 400 2560 384
WIRE 2320 416 2320 400
WIRE 2320 416 2144 416
WIRE 2320 480 2320 416
WIRE 2000 528 2000 480
WIRE 2320 624 2320 560
FLAG 656 304 0
FLAG 976 288 0
FLAG 896 288 0
FLAG 2000 528 0
FLAG 2320 624 0
FLAG 2560 400 0
FLAG 1232 336 0
FLAG 1760 288 0
FLAG 1696 400 0
SYMBOL voltage 656 160 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 124 Left 2
SYMATTR SpiceLine Rser=100
SYMATTR InstName V2
SYMATTR Value SINE(0 311 60)
SYMBOL cap 960 32 R0
SYMATTR InstName C1
SYMATTR Value 30pF
SYMATTR SpiceLine Rser=0.1
SYMBOL cap 880 160 R0
SYMATTR InstName C2
SYMATTR Value 30pF
SYMATTR SpiceLine Rser=0.1
SYMBOL cap 960 160 R0
SYMATTR InstName C3
SYMATTR Value 30pF
SYMATTR SpiceLine Rser=0.1
SYMBOL diode 1168 160 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D2
SYMBOL diode 1168 240 R180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName D3
SYMBOL cap 1312 208 R0
SYMATTR InstName C4
SYMATTR Value 100n
SYMATTR SpiceLine Rser=2
SYMBOL PowerProducts\\LT3012B 2000 352 R0
SYMATTR InstName U1
SYMBOL res 2304 304 R0
SYMATTR InstName R1
SYMATTR Value 750K
SYMBOL res 2304 464 R0
SYMATTR InstName R2
SYMATTR Value 249K
SYMBOL cap 2544 320 R0
SYMATTR InstName C6
SYMATTR Value 3.3µ
SYMBOL pnp 1600 272 R180
SYMATTR InstName Q1
SYMATTR Value 2N3906
SYMBOL zener 1776 288 R180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName D1
SYMATTR Value EDZV6_2B
SYMBOL cap 1680 320 R0
SYMATTR InstName C5
SYMATTR Value 1µ
TEXT 624 328 Left 2 !.tran 0 1 0 uic
TEXT 1016 424 Left 2 !.model d d ron=1 roff=1g vfwd=0.45 vrev=1k


texts:
I am designing a block that performs addition and subtraction with the IC74283. In short, it receives three inputs: \$A\$, \$B\$ and \$subtract\$. When \$subtract\$ is 1, the block performs \$A - B\$ (in 2's complement), otherwise, it will just do \$A + B\$. The outputs are the result of the operation, \$R\$, and \$C_{out}\$.

But I'm still struggling to understand the meaning of \$C_{out}\$ in this context, I can't found a pattern to identify when \$C_{out}\$ is 0 or 1 and what information it gives about the operation/result. Is it just an overflow indication, or does it give me a hint about the sign of the result?


texts: Latency concerns for a wireless audio mixer?

texts:
I want to design an audio mixer that works wirelessly and has a web interface. Here's what I'm generally thinking:

One component is a 1/4 inch plug with an amplifying circuit and a WiFi module which communicates via UDP over the local network to a Raspberry Pi.

Several of these units are connected to guitars, keyboard, microphones, etc.

On the Pi, I have a simple interface running locally in the browser for mixing signals from different instruments and outputting to a single set of speakers from the Pi.

I'm really just looking for some general thoughts from someone who has experience with audio electronics (I have none).

Would Bluetooth be a better choice than UDP? Or maybe even Zigbee?


texts:
I am on a learning curve to gain updated knowledge of 1.5 kV MOSFETs and IGBTs and their drivers, flyback transformers and the many ways of generating and switching high voltages.

My question is what kind of general purpose loads should I be building for my experimentation?

Do I buy a bag of 1 and 10 ohm wire wound high wattage resistors, to lash up into a suitable frame to test my 1.5 kV 60 A IGBT. Do I have to build a snubber for these loads?

And how does one load a flyback transformer as they normally plug into a CRT which is a capacitor from the circuit's point of view.


texts: How does this voltage detector IC work in a circuit? What does open drain vs. CMOS output mean?

texts:
I'm evaluating the Rohm BD48/BD49 series voltage detector.  I'm having trouble understanding the data sheet.

I want to generate a high signal when the input voltage is above a desired threshold (3.0 volts, so the BD4xx30x), and low when it's below that.  This chip comes in two varieties, one of which is an "open drain" and the other is "CMOS".  The data sheet says:

  For both the open drain type ... and the CMOS output type ... When the voltage applied to the VDD pins reaches the appropriate threshold voltage, the VOUT terminal
  voltage switches from either “High” to “Low” or from “Low” to “High”.

I think that means high-to-low, or low-to-high respectively?  I.E. A) the open drain type when input voltage is below the threshold generates a high signal on the output pin (but as mentioned elsewhere, only via an external pullup), which goes low when input voltage exceeds the threshold, while B) the CMOS type generates a low signal when the input voltage is below the threshold, which switches high when the input voltage exceeds the threshold.

So I think that I want the BD49 CMOS series, with its Vout hooked straight to the control pin (active high) of the chip I want to pair it with.  Is that right?  I'm guessing based mostly on some assumptions of the accompanying figures.


texts: How to localize cause of short circuit in proto board design?

texts:
I'm working on a basic application with a microcontroller controlling several components including a:

12V DC pump (Darlington array)
12V PWM fan (Darlington array)
humidity sensor (I2C)
and LED controllers (SPI)

Online circuit can be found here.

I've setup and tested each component individually to ensure they work given my circuit.  From there, I transitioned from breadboard stage to a more intermediate stage using a protoboard along with various wires soldered in the right place.

After placing everything into a small housing, I recently went to connect everything only to end up frying the microcontroller and the UBEC.  Since all the components were previously working, I'm not certain exactly what caused it except for perhaps a short caused by my mess of wires on the protoboard.

I know general questions like this are generally not within guidelines, but I'm just looking for insight into whether I'm completely off the mark somewhere.

Update

Per the comments I added:

diode to protect the PWM pin on the fan (although I'm not certain I actually need this - I figured the circuit built into the fan would already have this type of protection; unfortunately their datasheets don't share the circuit)
fuse on the +5V & +12V rail
power description on fan & pump
added link to schematic


texts: How does electricity move when slowed down?

texts:
Everything I know about the basics of how electricity works assumes that everything happens instantly, which obviously can't be true since it would violate causality.

So say you have a battery and a switch hooked up close enough to be considered 'instantaneous', and then have a 1000 mile-long cable (assume near-zero resistance so things don't get ridiculous) running to a light, and back. The light cannot turn on until at least 5 miliseconds later, and likely longer since electrical field changes propagate at 60%-90% the speed of light according to this answer. But then what would this light look light? Would it go from no light to full instantly, or would it slowly turn on? And what about how much current the lightbulb draws? That information has to somehow be sent back, hence taking another 5ms, since some sources of power provide less voltage if more current is pulled. Is there some back & forth in such a system, where it takes some time for things to even out?

When does the light turn on?


texts: SD Card (Sandisk SDHC) not responding for CMD9 with 0x00 in SPI mode and it responds with time out error 0xFF

texts: I am trying to interface Sandisk SDHC micro sd card of 8GB size with MSP430FR5969. I am able to initialize the SD card correctly in SPI mode. But When I try to read CSD with CMD9 it responds with 0xFF time out error. It is not responding with 0x00 (R1 response in SPI mode). Please help.


texts: Why will HAL_SPI_Receive() not read the L3GD20H gyro on my STM32F303 Discovery board?

texts:
I have an STM32F303 discovery board for which the mems gyro L3GD20H is connected to the SPI1 peripheral by default, that is the Sclk, MISO and MOSI are connected to pins PA5, PA6 and PA7 respectively. The chip enable is connected to PE3. I need to understand the high level functions from the HAL library for the STM32F3 microcontroller. Hence, for experimentation, I try to communicate with the gyro using HAL_SPI_Transmit() and HAL_SPI_Receive().

I use CubeMX to initialize all peripherals. Settings for the SPI1 is shown below

Since CubeMX takes care of initialization code, I will only show the additional code that enables the control register ctrlReg1 with 0x0f (see figure)

I do not care about settings, I just wish to get some data in polling mode.
The XDataOut_L register (0x28) is the one that I try to read

I use CubeMX and AC6, that is System Workbench (Eclipse-based), to build/compile and run/debug the project. The user-defined code is as follows

uint8_t data_ctrl1, address_ctrl1;
uint8_t data_out1, address_out1;

HAL_GPIO_WritePin(GPIOE,GPIO_PIN_3, GPIO_PIN_RESET);
address_ctrl1 = 0x20;
data_ctrl1 = 0x0f;
HAL_SPI_Transmit(&hspi1, &address_ctrl1, 1, 50);
HAL_SPI_Transmit(&hspi1, &data_ctrl1, 1, 50);
HAL_GPIO_WritePin(GPIOE,GPIO_PIN_3, GPIO_PIN_SET);

while(1)
{
    HAL_GPIO_WritePin(GPIOE, GPIO_PIN_3, GPIO_PIN_RESET);
    address_out1 = 0x28 | 0x80;  // MSB bit = 1 to read
    HAL_SPI_Transmit(&hspi1, &address_out1, 1, 50);
    HAL_SPI_Receive(&hspi1, &data_out1, 1, 50);
    HAL_GPIO_WritePin(GPIOE, GPIO_PIN_3, GPIO_PIN_SET);
    HAL_Delay(100);
 }

The code is based on an example on YouTube (MohamedYaqoobSTM) where Mohamed successfully reads his LIS302DL on his STM32F4 Discovery board.

My question is why will not the SPI_HAL_Receive() work as intended?
I always get result 255 on the data_out1 buffer...


texts:
I attempted to build an 8-bit adder in Logisim by carefully chaining together a half-adder and 7 full adders, all made from basic logic gates. Unfortunately, it produced erroneous results; for example, 00000011 + 00000011 = 000000100 ! I found that the problem seems to occur around the half-adder and the least significant bit, so I tried to pinpoint it with a smaller, 2-bit adder:

As you can see (unless I am going crazy), this one is off, too; s1 should also be lit! I can see why it's not lit; a0 and b0 produce a carry bit, which, along with a1 and b1 (or even if it DIDN'T carry), makes the XOR gate for s1 false. But from the book I am using, this should be the way to hook them up? What am I missing here?


texts:
I am trying to build a robotic arm and for the base I need a servo with a lot of torque. After browsing through hobbyking's servo selections I noticed that winch servos offer a higher torque for generally a lower price, however, I do not have any experience using them.

Before I commit to spending a lot of money on potentially incorrect servos for my project does someone know whether there would be a problem using winch servo for the base that would only need to rotate around 90 degrees?

I have read that winch servos are not as precise, but as long as the servo is within 1-3 degrees of what it should be that is fine with me.

Also can you still tell the servo to turn to 0 degrees or 35 or 87 degrees like a normal servo or is it like a continuous rotation servo where it keeps turning until it hits the end of its rotation and writing 100 vs 180 simply controls the speed?

Thanks for your help.


texts: lpc1768 keil USB host component missing?

texts:
I'm trying to run an lpc1768 as a USB host and connect to a device through a VirtualCOM but there doesn't seem to be a USB host component available in my project:

Why is there no USB host component in the components menu on keil?
When opening a sample project (USB Host Keyboard), the components menu looks like:

There is a USB host component.


texts: What is this white stuff on the solder of this PCB?

texts:
These photos were taken from a new-in-box 16kB memory expander for a Timex Sinclair 1000 computer. As far as I'm aware, it was never used.

The box was made of thin cardboard with a two part styrofoam insert. There are plenty of large air gaps for atmosphere to penetrate behind the plastic housing to the PCB.

It doesn't seem to be centered in any one area and instead clings to any of the open solder connections. At first it looked like battery corrosion but there is no battery inside. Inspecting it with my microscope makes it look less like something you might see from a battery and more like a viscous white substance. Maybe something from a flux residue?

I have several other ram packs and none of them display this type of substance on the surface.

I'll probably just wash the PCB in the sink with some soap and an anti-static brush, and that has done well for me when cleaning flux residue in the past.

Has anyone ever seen anything like this or know what caused it?

Sorry for the poor microscope pictures. I have to hold my camera up to he lens and it's almost impossible to get a clear shot.


texts:
Have been considering rebuilding the transformer in an older 200A Schumacher (auto) battery charger/starter. Some time ago, the transformer itself began making an unsettling buzzing noise, then the burning and smoke started...

It clearly has at least 3 windings in it, the largest of which appears to be the one overheating and burned. Unit was sold by Sears as a H963; a common (repackaged Schumacher SE-6242-A) item with 2/40/200 Amp output.

What advice would you give on rebuilding this on a hobbyist basis - meaning, have done quite a bit of electrical work/soldering/other - and would be interested in this as a learning project. Clearly, it's not a time-or-cost-effective approach.

Have added a few photos. Emboldened by comments here, I've ground off the top of this bad boy; clearly there's a welder in my future(!)

Discoloration/damage to windings will be clear; some questions?

There are 2 gauges of wire on the bobbbin; including coating, these measure out to 0.92mm and 1.22mm diameters. Hoping these are 19G and 17G...

Before I unwind it, is there any way to estimate (weigh?) the quantity of wire I'd need to re-wrap this thing? Would prefer to order all needed before beginning the rebuild.

Having burned the transformer, is it likely the thyristors are also damaged? Plate is based on 8x ST BTW69-200NS thyristors. Without disassembling the entire rectifier plate, I'm not sure I can reliably test these.

There is also a components embedded with the windings - a capacitor?

Is there any downside to painting this thing, now that I've got it apart?

Finally, how practicable is it to re-coat the wire and re-use it? Can anybody point to specific materials/practices/techniques? Is it OK to splice wire together, as long as it remains insulated from other strands?

Interested in your insights.


texts:
I am using lithium polymer batteries without much internal protection, as is common in RC planes and such (weight constraints). I have noticed that some of the older ones feel like they built up some slight pressure or like they have a bit of gas or liquid inside.
If one presses rather gently (on the flat side) with a finger, they yield about 1mm (0.04 inches), then one can feel solid material again. The voltage seems fine (cells balanced) and there is at least no noticable loss of capacity (I haven't measured that though).

Is this dangerous? What is the cause for it (aging, abuse, …)? What is the cause from a chemical/physical perspective?


texts:
I'm trying to use the ROM bootloader on the SAMG55 as described in AT09002. The application note describes using a tool 'hex2fw.py'. Where can I get that and the config files it uses?

I found this thread - https://community.atmel.com/forum/entering-bootloader-atmel-samg55-xplained-pro - which has a modified version of the script, but no config files that it needs.


texts:
I am currently trying to work out whether a particular PCB is faulty. The board consists of a low capacitance a.c filter in parallel across the line and neutral. The circuit also consists of potentiometer and transistor and few other smaller components which im not sure what they are for. The function of the board is to increase and decrease the power for a motor (A.C). The power goes into the PCB then out and down to spade connectors which connect to the motor.

I measure roughly 50 Mega ohms of resistance across the PCB which is why firstly i assumed it may be faulty, but then when I measured voltage at the spade connectors by the motor I was getting 240 volts. Surely with 50 mega ohms I would have a large voltage drop and not read the full 240v.

So if the PCB is fine and functioning correctly is it perhaps due to the transistor acting as a switch which is why i'm reading such a high resistance while it is not energised.

Thanks if anyone can share any light on the situation.


texts: We are using USB keyboard it is working with PC. We are using Same keyboard with our microcontroller kit with USB to PS2 convertor also it is working. I wanted to know that, whether USB signals D+ and D- are similar to PS2 signals Clock and Data??


texts: How do I analyze a sequential asynchronous circuit? The yellow part is the one I don't get (I know how it works, but don't know how to write it when I do the analysis)


texts: how to convert bytes into ASCII in C language

texts:
I am receiving bytes from my UART as uint8. How do I convert these bytes into ASCII? I am using Atmel 6.0 and my microcontroller is ATMega16L.

EDIT

I am using an android phone to send and receive information to a Wifi module (RN-131) from Roving networks. The wifi module connects to the microcontroller (atmega16L) through UART. Whatever the wifi module receives from the phone is transmitted out its UART. Similarly, whatever is written to its UART is transmitted out through wifi.

Now, what I'm trying to do is send a string from the phone which gets converted into bytes. The code is shown below:

PrintWriter out = new PrintWriter(new BufferedWriter(new outputStreamWriter(socket.getOutputStream())), true);
out.println("Eclipse");

here, the 'BufferedWriter' - Constructs a new BufferedWriter, providing out with a buffer of 8192 bytes. and 'PrintWriter' - Constructs a new PrintWriter with out as its target writer. The parameter autoFlush determines if the print writer automatically flushes its contents to the target writer when a newline is encountered.

now to program the microcontroller, I'm using AVR studio 6.0

uint8_t data;
char arr[32];
data = UDR;
length = strlen(data);
itoa(data, arr, 10);

But what I receive is "50, 53, 52" even when I'm sending "Eclipse".

EDIT 20th June 2012

Here is my code till now. Note: the code is written in AVR Studio 6.0 so it looks a bit different to other codes written in AVR Studio 4.18.

/**************************************************
 *  Includes
 */
#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include <stdlib.h>
#include <stdbool.h>
#include <stdio.h>
#include "../../../../../../Program Files (x86)/Atmel/Atmel Studio 6.0/extensions/Atmel/AVRGCC/3.4.0.65/AVRToolchain/avr/include/avr/iom16.h"

/**************************************************
 *  Global Variables
 */
int trigger=0, length=0;
int i=0, n=0;
uint8_t data;
char arr[8];

/**************************************************
 *  Defines
 */
#define LED_PORT PORTA
#define RED_ON (PORTA | 0x01)
#define RED_OFF (PORTA & ~0x01)
#define YELLOW_ON (PORTA | 0x02)
#define YELLOW_OFF (PORTA & ~0x02)
#define GREEN_ON (PORTA | 0x04)
#define GREEN_OFF (PORTA & ~0x04)

/**************************************************
 *  Function Prototypes
 */
void initialize(void);
void time_display(void);

int main(void){
    initialize();

    while(1){
        //TODO:: Please write your application code

    }
}

void initialize(void){

    DDRA = 0x07; //PORTA pins 0,1,2 set as outputs
//  DDRD = 0x02; //PORTD pin 1 is output (TX) and pin 0 is input (RX)

    //Timer SETUP
    TCCR1A = 0x80; //OCR1A enable in CTC mode
    TCCR1B = 0x0C; //CTC mode, 256 prescale
    TIMSK = 0x10; //CTC on OCR1A enabled, overflow disabled
    OCR1A = 2000; //OCR value set to get an interrupt every 1 second (15624)

    //USART SETUP
    UCSRA = 0x00; //no Frame Error, no parity error, no Data OverRun
    UCSRB = 0xE0; //receiver enable, transmitter enable (0x18)
    UCSRC = 0x8E; //Asynchronous USART mode, no parity, 1 stop bit, 8-bit character size, Data transmitted on rising edge and received on falling edge of the clock
    UBRRL = 51; //Baud rate of 9600bps
    UBRRH = 0;

    sei(); //Global interrupt enable
}

//timer capture interrupt
ISR(TIMER1_COMPA_vect){

}

ISR(USART_RXC_vect){
    LED_PORT = RED_ON;
    _delay_ms(100);

    for(int x=0; x<5; x++){
        arr[x] = UDR;
    }

    LED_PORT = RED_OFF;
    _delay_ms(100);

    trigger = 1;
}

ISR(USART_UDRE_vect){
    if(trigger >= 1){
        LED_PORT = GREEN_ON;
        _delay_ms(200);
        LED_PORT = GREEN_OFF;
        _delay_ms(200);

        UDR = data; //transmit the data
        trigger = 0;
    }
}


texts: Clip on connector to program board (so no extra weight when not programming)

texts:
I am designing a circuit with an Attiny85 microcontroller and a temperature sensor, eventually I want everything including the battery to weigh less than 5g (preferably<3g).  I want to be able to reprogram the Attiny while it is soldered to the board, so I need some way to connect the programmer to the attiny85.

I am drawing the PCB using Fritzing (pcb design program), eventually I hope it will only be 1cm by 1cm using surface mount components, though might be twice that if I put the battery on the board.  I know I could just add some rows of pins next to the attiny and use the pins to connect to the programmer, but putting more pins on the board would add weight and also stop it being a nice flat design.  I know I could solder and desolder the pins whenever I want to program but I think there must be a better way.

I was thinking maybe there is some way to draw tracks to the side of the board and then get some type of clip on connector which connects to the tracks?

Could anyone suggest something, that doesn't add extra weight to the board, or very very lightweight (e.g. maybe 0.2g).

Thanks in advance.  Sorry if I'm missing something obvious!


texts:
I am designing a simple circuit that will light a LED when a given resistance is between 0 and about 1K.  At about 1k the LED would not be lit at all.  The test circuit should not have more than .5ma go though the tested resistor.  The supply voltage is coming from a car battery so it will vary between 12.5 to about 11 volts.

What I have worked out so far with limited success is to setup a voltage divider between the supply and ground using a 39k resistor (on the positive  side) and the unknown test resistor to ground.  At their junction I have put a 1k resistor in series with a red LED.  The anode of the LED goes to the supply.

The above circuit will test down to about 22k before the LED will begin to glow somewhat. when testing 0 ohms, the LED will glow about half full brightness. The current though the LED is about .48 ma.  I can get by with the that amount of brightness but I would like to be able to test down to a lower level.


texts: Microchip MTCH6102 - 2 touch surfaces (3x3) on one chip

texts:
building a project that utilizes Microchip's gesture recognition on their MTCH6102 chip - the device has two touch surfaces (circles, diameter 20mm each, 3x3 conductive mesh outline).

The documentation does not talk about splitting the capacitive mesh to x-number of areas. Do I need two chips, for each touch surface, or there is a way to connect two touch surfaces to one chip AND utilize the on-chip gesture recognition of MTCH6102? It is important to tell which touchsurface recognised the gesture.

Thank you in advance


texts: How do different kinds of motors behave electrically under operation?

texts:
This is sort of a follow-up to this topic: Overclocking my toothbrush

I have since measured some numbers with my DMM. Remember this is a tiny brushed DC motor in a $5 toothbrush that I am driving with a 3.7V Lithium-Manganese cell.

A worn-out motor measures 4.1 Ohms with the DMM.
A motor which has only been used to deplete an alkaline cell measures 3.8 Ohms.

Both motors draw over 500mA when driven directly with the 3.7V cell. This kind of makes sense since based on the resistance I measured previously I could expect about 1A if it does not change while the motor runs. I don't really want to wear out this motor by seeing how many actual amps it draws but I should probably do it in the name of science.

Still, it leads to the question of what factors determine the effective resistance of a motor while it runs. Will it stay the same? increase? decrease?

BTW I am going to connect a 4.7Ohm resistor in series inside the toothbrush to regulate the current to about 300mA. This should dissipate about .42W and the resistor is rated for .5W... We'll see if running the motor at "only" 300mA extends its life or not.

Edit: This is gonna have to wait till tomorrow because i need to break out the dremel in order to make a cavity for the resistor to fit.


texts: Help identifying a varistor (on a shredder PCB)?

texts:
I am trying to identify what I think is a varistor. The markings are : "9 / MVG" and "10K431".
I think "10" is the diameter, "K" is the tolerance and "431" is voltage. Am I correct?
What does "9 / MVG" mean?
In reference to the the following sample part, how do I find out the "Clamping voltage", "Amperage" and "Capacitance" for the varistor I need to replace?
A sample part from RS:

Vishay VDRS - E Series Metal Oxide Varistor
140pF 10A, Clamping 710V, Varistor 430V RS Stock No.178-071 Mfr. Part
No.VDRS07H275BSE

The PCB I am trying to fix comes from a Fellowes 225i shredder.


texts:
I'm looking for the smallest circuit to make some noise. This sound has to be constant and annoying, it's intended for the alarm on a timing device. Any ideas?

The circuit will be triggered with a high line from a microcontroller. Supply voltage can be 5V or 9V.


texts:
I'm trying to analyze this RF circuit:

This circuit is designed for about 915 MHz operation. I'd be happy in fact understanding this smaller section of the circuit:

I have been trying to find the transfer function of this section. I bet it's some kind of filter, and while I did take classes on electronics, I unfortunately never paid attention in them. What analysis method could I use to determine the transfer function of this section? I tried figuring out Vout/Vin via impedances but I couldn't figure out anything meaningful. The grounded connection is confusing me. How is the grounded L304-C303 impedance modeled as a transfer function with respect to the rest of the circuit?
For the schematic as a whole, I'm trying to figure out if the connection into the antenna (off the right of C304) is matched to 50Ω, since I'm going to use a different antenna system from what is in the schematic. It probably is, but I would rather make sure, if that's possible. What analysis approach could I use to figure this out?

CC430 datasheet.


texts:
I've recently run into this error where openocd wont flash the binary to my discovery board. I'm using the same linker script that i've been using all along.

arm-none-eabi-objdump gives the following output:

src/stm32_uavcan/stm32test:     file format elf32-littlearm

Disassembly of section .init:

00008000 <_init>:
    8000: b5f8        push  {r3, r4, r5, r6, r7, lr}
    8002: bf00        nop
    8004: bcf8        pop {r3, r4, r5, r6, r7}
    8006: bc08        pop {r3}
    8008: 469e        mov lr, r3
    800a: 4770        bx  lr

Disassembly of section .text:

00008040 <exit>:
    8040: b508        push  {r3, lr}
    8042: 2100        movs  r1, #0
    8044: 4604        mov r4, r0
    8046: f002 fe91   bl  ad6c <__call_exitprocs>
    804a: 4b04        ldr r3, [pc, #16] ; (805c <exit+0x1c>)
    804c: 6818        ldr r0, [r3, #0]
    804e: 6bc3        ldr r3, [r0, #60] ; 0x3c
    8050: b103        cbz r3, 8054 <exit+0x14>
    8052: 4798        blx r3
    8054: 4620        mov r0, r4
    8056: f000 ff03   bl  8e60 <_exit>
    805a: bf00        nop
    805c: 0000eec8  .word 0x0000eec8

The flash addresses are completely off.

From what i know this is the correct address "0x08000000". And is defined as such in my linker script. Below is the copy of the relevant part of the linker script

MEMORY
{
  RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 192K
  CCMRAM (xrw) : ORIGIN = 0x10000000, LENGTH = 64K
  FLASH (rx) : ORIGIN = 0x08000000, LENGTH = 1024K
  FLASHB1 (rx) : ORIGIN = 0x00000000, LENGTH = 0
  EXTMEMB0 (rx) : ORIGIN = 0x00000000, LENGTH = 0
  EXTMEMB1 (rx) : ORIGIN = 0x00000000, LENGTH = 0
  EXTMEMB2 (rx) : ORIGIN = 0x00000000, LENGTH = 0
  EXTMEMB3 (rx) : ORIGIN = 0x00000000, LENGTH = 0
  MEMORY_ARRAY (xrw)  : ORIGIN = 0x20002000, LENGTH = 32
}

I'm using CMake. The project uses other third-party libraries as well, uavcan, chibios and stm32plus. I dont think that should be an issue. Below is the CMakeLists for this project.

cmake_minimum_required(VERSION 3.2)
project(stm32_uavcan)

list(APPEND CMAKE_PREFIX_PATH /usr/local/arm-none-eabi /usr/arm-none-eabi CACHE STRING "Library Search Paths")
set(MCU_FAMILY f429)

if((CMAKE_BUILD_TYPE MATCHES RelWithDebInfo))
  set(STM32PLUS_CONFIGURATION fast-${MCU_FAMILY}-8000000)
endif((CMAKE_BUILD_TYPE MATCHES RelWithDebInfo))

if((CMAKE_BUILD_TYPE MATCHES MinSizeRelease))
  set(STM32PLUS_CONFIGURATION small-${MCU_FAMILY}-8000000)
endif((CMAKE_BUILD_TYPE MATCHES MinSizeRelease))

if((CMAKE_BUILD_TYPE MATCHES Debug))
  set(STM32PLUS_CONFIGURATION debug-${MCU_FAMILY}-8000000)
endif((CMAKE_BUILD_TYPE MATCHES Debug))

set(CMAKE_SHARED_LIBRARY_LINK_C_FLAGS "")
set(CMAKE_SHARED_LIBRARY_LINK_CXX_FLAGS "")

find_package(stm32plus REQUIRED)

add_executable(stm32test
        src/AX2550.cpp
        src/main.cpp
        src/LibraryHacks.cpp
        src/ringbuf.c
        src/system_stm32f4xx.c
        )
target_sources(stm32test
        PRIVATE
        ${CHIBIOS_SOURCES}
        )

target_include_directories(stm32test
        PUBLIC
            include
            ${PROJECT_CONF_DIR}
            ${CHIBIOS_INCLUDE_DIRS}
            ${STM32PLUS_INCLUDE_DIRS}
            ${STM32PLUS_FWLIB_DIR}
            ${STM32PLUS_DEVINC})

target_link_libraries(stm32test ${STM32PLUS_LIBS})

set_target_properties(stm32test PROPERTIES
    CXX_STANDARD 14
    CXX_STANDARD_REQUIRED YES
    CXX_EXTENSIONS NO
)

I dont know how to solve this. Any advice or suggestions could really help me out.

Regards.


texts: Should a mechanical power switch float or ground main power when the system is off?

texts:
Whenever I've put a mechanical switch on a design to allow a battery to be connected / disconnected, I've always just floated system power whenever the switch is open, like this:

However, a colleague asked during a design review whether it makes more sense to ground system power when the device is off:

From a basic functionality perspective, I believe that either should work. However, I was curious if there is a particular reason to choose to float or ground the main supply in the "off" state?

Edit: Several (very helpful!) initial answers and comments discuss potential harms or considerations if we do choose to ground the input. Are there any extra risks or considerations for leaving the input floating (the first design)?


texts: Philips 9 W luminaire quotes 7 A for 300 ms inrush!

texts:
In his answer to Will repeatedly turning a light bulb on and off damage it? @Bradicul stated,

  An example of inrush current is an LED downlight fitting with 9 W (0.0375 A at 240 V) will have any average inrush current of 7 A for 300 ms.

Figure 1. The 220 - 240 V, 9 W Philips downlighter has an overall diameter of 84 mm.

I thought he was mistaken but he linked to the Philips DN135B LED6S/830 PSR-E II WH datasheet and it states that the inrush for this 9 W lamp is 7 A for up to 300 ms.

Can anyone think of a reason the PSU in these luminaires could draw 1.75 kVA for up to 300 ms when the lamp is only 9 W with a 0.9 power factor? Where is the juice going?


texts: Design a Photodiode TIA for a certain bandwidth?

texts:
I am working on my master thesis these days, and I am having a serious problem. I am using FDS100 photodiode with LT6268-10 Amp to design a circuit. The required bandwidth for me is 10MHz, and I am using photodiode circuit design wizard to help me with my design. My problem is that when I use the equations to calculate the feedback resistance and capacitance then use these numbers in the design I get a frequency response around 23MHz, which is higher than the bandwidth required.
Let's say I have a current around 30uA from the photodiode, and I want the peak voltage value to be 1V, so

  1V/30u=33.4KOhm.

Then

  Cf=1/(2piRfBW)=0.48pF!!

which is really low, and I am not sure if we can even manage to get it in real life.
I am not sure if my methods to calculate these values are correct, but there is a lot of them and they all should give the same results in the end.
How do I calculate the equations correctly?


texts: Suggestions for tuning slow response pid - fire box control

texts:
I have developed a computer controlled BBQ smoker, using a raspberry pi and car throttle valve damper, driven by a stepper motor, the temperature pick up is a thermocouple.

I have a python PID class to control the system and am struggling to tune it.  When the set point temperature is reached (rising temp) the damper closes as expected, then re-opens once the temperature passes the set point (falling) but by this point the charcoal fire has gone out.  I have tried different kP values to get a steady oscillation about the set point but I am plagued with it fully undershooting, ie going out.  I need the damper to start re-opening as soon as the temperature starts falling, not once the system is in falling overshoot.  I feel it is something to do with kI and kD.  Please can I have some advice before spanking another kilo of charcoal!  Many thanks people.


texts: Is it acceptable to leave a capacitor across batteries even when turned off?

texts:
Is it acceptable to leave a capacitor across batteries when the circuit is powered off?

The capacitor will be either an aluminum or ceramic. My concern is double sided. Making sure that the switch does not have reduced life from arcing do to the capacitor inrush every time the capacitor is switched in. Or reduced battery life do to capacitor leakage current if the capacitor is left in the circuit all the time.

simulate this circuit – Schematic created using CircuitLab


texts:
I am developing a data logger for use in high schools like ( http://www.pasco.com ). The main difference is that mine is primary supposed to be used with an iPad. I have a connection between a micro controller and an iPad up and running, but I have a question regarding the communication between sensors and the 'hub' which is the part that makes it possible to connect up to 3 sensors to the iPad.

On the prototype level my hub consists of an Atmega328 (arduino) and the sensors are just connected directly to the A/D converter pins.

But because this system is supposed to support a variety of sensors this solution is not generic enough (i.e.. if a distance sensors should be connected, it would not work on the anlog pin, because it would be the difference between 2 timestamps). So I am thinking of adding a micro controller in every sensor and let that microcontroller communicate with the micro controller of the hub, which then will transmit the data to the iPad.

Which protocols should be used to communicate between these micro controllers? And is at all the way to go?

The length of the wire would be maximum 2m.
The maximum amount of wires is 4 and it should include +5 and GND to
the sensor.
The readings should in some cases be fast 20hz or preferably even
more.
It should be possible to send some sort of identification along to
the hub, so the hub knows which kind of sensors is attached.

It is possible to see a video of the prototype here.


texts: Why do we use two parallel capacitors in a voltage regulator circuit?

texts:
C1 and C2 are parallel capacitors and their total capacitance is 1000.1 uF. I think C1 is large enough and I can remove C2 from the circuit. The result will be an open circuit.

Let's assume that I can buy one capacitor that has the value of 1000.1 uF. I know I can't do it in the real world because a 1000.1uf capacitor does not exist in the shops but the question will help me understand the circuit well.

Can I replace C1 and C2 with the 1000.1 uF cap?
Does this 0.1 uF really matter? Is it important?


texts: Quarter Wavelength Matching : Missing Reflections?

texts:
With regards to the quarter wavelength impedance matcher, I understand it is used to correct a mismatch and looks as follows where \$ Z_T \$ is the matching line:

I understand that we have set up the problem such that the input impedance of the combined matching line and the load is the same as \$ Z_0 \$ meaning that we have no reflections here at all. We find that \$ Z_T \$ must be the geometric mean of \$ Z_0 \$ and \$ Z_L \$ through this condition.

However, surely the matching line and the load itself aren't matched and hence we should have some reflections at this point itself?


texts: How exactly does a matrix converter work? Is this even a question that could be answered without months of study?

texts:
I learned a while ago about the matrix converter, a type of power electronic device that, I'm told, does direct AC-to-AC conversion without an intermediate DC step. I'm told it can convert input AC voltage at any frequency to any other frequency (presumably there's an implied "within reason" there) without an intermediate DC stage.

I'm having difficulty wrapping my head around how exactly this works, and would appreciate someone elucidating it for me. In particular, control algorithms for this type of device seem like they'd be incredibly complex. (perhaps they are, and that's why I haven't seen one used in practice?)

...as an aside, I'm also curious to know where the name "matrix converter" comes from, if anyone can answer that as well.


texts: Switch placement on electronic circuits on the positive wire

texts:
Why are main on/off switches in electronic circuits/appliances (any small, low power electronics) always placed on the positive wire (in case of DC circuits) between the power supply (batteries, adapters, etc.) and the circuit regardless of the low operating voltage?

Does it affect the efficiency and makes any difference in power consumption when it's turned off?

Wouldn't placing the switch on the negative wire between the power supply and the circuit just work the same?


texts:
The LM2575 is a simple switcher regulator for smaller currents/voltages. There is some fixed voltage versions (5,6,12V) and a variable.

The most flexibe stock could obvious be the variable version, but if You have a stock of, say 6 volt and want to use the same trick as seen with the L7805 where a set of voltage-divider resistors on the regulator pin makes it possible to get higher output voltages than the fixed 5V (the trick is that the L7805 seeks 5V on it's reg. pin).

Similar there is a direct feed-back pin on the L2575 (and a 2xR voltage divider on the variable to the feed-back pin).

I could test it myself, but if anyone has more knowledge and allready tested, then I will see..


texts:
I have recently took MCU board and testing continuity across button.

When board is not powered i.e; not executing code, continuity on button is as expected (i.e; diagonally opposite pins are not showing connected). However, while MCU board is executing code and I try to check connectivity across switch pins it shows shorting.

Am I doing something wrong?
Is there any rule that continuity should be checked only when Board is powered off?
Does it means, that board has some fault?

For the reference, I have added snapshot of swich I am using.


texts: Capacitor as a ripple filter in the rectifier circuit - difference in charging and discharging time

texts: Most of the times attached picture is used to depict the use of Capacitor as filter in the rectifier circuit. I guess, i understand the broad concept but I am struggling with the fact that charging happens for a very little time (as per the picture) and discharging happens for alomost one half cycle. The time constant for charging and discharging is same. How can charging for a small amount allows it to discharge for such a long time.?


texts:
I started to write a program for an ATXMega. This program should read a command via USART, and then execute this command (i.e. either sending data via SPI or sending data back via USART). But the µC should execute one command after another, i.e. if there is a current command running (for example sending bits via SPI), the received command should be put back into a waiting loop until the µC has finished doing this task. Now I was wondering how I should design this waiting loop. When writing a program for the same task on my pc, I simply created two threads, and one thread filled a buffer, and the second one emptied it and executed the command. But as far as I know multithreading is not possible on a µC.
What is the best way to approach the described behaviour without multithreading on a µC? Is my current approach (use a buffer with fixed length, fill it up via Interrupts, and let the µC check the buffer every 100 ms for new stuff) the best way to do that? Or is there a better way?


texts: Software UART of 2 PICs with diffrerent clock frequency

texts: Is it possible to communicate the 2 PICs with different clock frequency via software UART? By the way I'm using 2 PIC16f877a. One is connected to PC use 16mhz oscillator and the other one is using 4 mhz oscillator. Im using mikroC compiler for this. Thank you.


texts:
I've been playing with these through hole reed switches: MDSR-4-12-23. It has been my experience so far that you have to be very careful in handling them, including when bending the leads to 90 degree angles for PCB insertion. It doesn't take much applied force to chip or crack the hermetically sealed capsule.

So my questions are two:

Is there any advice for handling and lead-forming that I should instruct a PCB assembler about as part of my design package?
Is the principle function of the reed switch as a magnetic switch compromised if the capsule seal is  compromised?


texts: What is the best way to heat sink a chip when soldering it on?

texts:
I generally like to solder sockets to my boards, rather than the chip directly, but am now forced to solder the chips directly. I have several DIP and SMD components that this needs to be done with.

I am concerned that the heat from soldering them might damage the chips so was wondering how I could heat sink them? Is this even necessary?

It doesn't apply to me right now, but how is this done with other packages?


texts: Measurement of the beta of a BJT with a multimeter

texts:
When we measure the beta of a BJT transistor with a multimeter, which beta is giving us, the maximum, the average or the minimum beta and under what conditions of Ic and Vce?
Thanks


texts: Calculating electrical limits of a DC motor?

texts:
I have a small DC motor left over from a crappy toy car, that I want to reuse for a small project.

How can I find out the voltage/current requirements/limits if all I have is the motor in hand without a specs sheet?


texts:
I was wondering if anybody is aware of any up and coming circuit simulators for mac? I have a little bit of experience with National Instruments Multisim and I quite like its layout and functionality.

I know that I could purchase a virtual machine environment (Parallels) with the Windows OS and run Multisim, but I was curious whether or not a fully featured software would be arriving for Mac. I've used iCircuit a bit and it is fun to play around with, it lacks the robust circuit library of a  Multisim.

I'm amazed by the lack of EE software available for the Mac in 2015.


texts: Can I connect Battery positive terminal directly to MCU ADC input Pin?

texts:
MCU is powered directly from 3 V battery and I am using ADC input of MCU to monitor the battery voltage to detect low battery situation. I have got good inputs on this site(I need to monitor the battery voltage very rarely and this is a battery powered board and designed for long life) to use a NFET, PFET and a resistive divider circuit to connect the signal MCU. Why shouldn’t I directly connect the battery voltage to ADC Pin? Perhaps with a series resistor.

EDIT:
MCU has internal 1.45 V standard reference for ADC. The 1.45 V can be one of possible ADC input and also can be used as Reference voltage for ADC.
From the safety aspects, can I connect battery directly to MCU ADC input Pin?


texts: LTspice - Extracting magnitude of signal from AC analysis using .meas and the phase

texts: I want to be able to produce a measure function such that the output of that function would give me the magnitude of a signal when its phase is -360deg. I tried using .meas AC name FIND mag(V(out)) WHEN ph(V(out)) = 360deg but it seems that ph(V(out)) returns a plot of the imaginary component of the signal (b if the signal was represented as a+jb) so that didn't work. I cant only use the cursor to find the corresponding magnitude to the phase, since I will be measuring multiple tests at once and outputting the output of the .meas function to a .txt file. Does anyone have any suggestions on what I may be able to do to get this right? I would greatly appreciate the help!


texts: gray code clock domain crossing FIFO fast to slow

texts:
I'm trying to understand how clock crossing FIFOs are implemented, and the usual answer I see to convert the read/write address pointers to gray code and then pass through synchronizer circuits into each others clock domain to determine if there's data in contained in the FIFO. The idea of using gray code is so the other clock domain can detect metastability on the other end by the fact that only one bit should change per address increment...and it can safely ignore the address pointer until it looks valid.

What about the scenario where the write clock domain is much faster than the slow clock domain? If the write address pointer can increment many times per read clock cycle, at some point there will be more than 1 bit flipped in the gray code value, and that wouldn't necessarily be a mistake. How is this situation usually handled?

I know there's a similar question on SE, but the answer seems to show an example of the write clock being only 2x faster than the read clock, so maybe this situation is never experienced.


texts: A few questions about the application of ethernet controller and PHY chip and SFP module

texts:
I have a question about the connection/application between the ethernet controller and PHY/SFP modules.
Actually, there're so many scenarios for building up a NIC card, which makes me confused.
For example, we can use an ethernet controller with the following connections:

controller ==> PHY chip ==> RJ45 connector ==> copper cable

controller ==> PHY chip ==> SFP module ==> fiber cable

controller ==> SFP module without PHY ==> fiber cable

controller ==> SFP module with PHY ==>copper cable
....

And the controller is the same, with the same serdes lanes.
I don't quite understand why there are so many combinations to built up an ethernet link.
Can someone give me some hints about the history of these setups?
I can get the idea that the controller is working as MAC layer and PHY chip as physical layer, but the SFP thing really confuses me.
Another question is that, if the controller's serdes directly connected to SFP module (without PHY on the module),
which protocol/interface will be used between controller and SFP module?
If the SFP module only does the electrical-optical conversion, what data format is transmitted out?
Since there is no PHY chip to deal with the physical layer stuff, can this communication be considered as data link layer communication?
About the controller, since it has the ability to directly interact with the SFP module, why the PHY chip vendor still need to implement the function to interface with SFP module?


texts: Issue with bipolar to unipolar opamp circuit

texts:
i want to measure ac voltage.For that i need to shift an ac differential voltage (+1.23/-1.23 across R20) to 0v - 2.5v range for a unipolar adc.The R1,R21,R22 divides the voltage and gives +/-1.23v across R20. The second part of
the circuit (opamp summing) is to shift this to 0-2.5v range. The V5 is an external voltage reference.The simulation shows that this external voltage reference (for opamp circuit) is effecting the voltage drop at R20, which is now between -0.47v to 1.23v.So the opamp output is also wrong, 0.77v to 2.5v (instead of 0-2.5v).How can i solve this? You can assume an ideal opamp.

PS: I am a software engineer, don't have deep understanding in electronics/circuits.


texts: Why can certain resistors not be the starting point when finding R Thevenin

texts:
I'm currently learning about Norton and Thevenin equivalents and it all makes sense for the most part except when it comes to finding RTh (the Thevenin equivalent resister in instances with no dependent sources. The best way to explain this I guess is to use the example from my book.

My question is related to figure (a) below and how they solved for RN or RTh. They said the 5 must be in parallel with the rest of the resistors in series. My question is why could it not be the 8 or 4 Ohm resistors in parallel with the other resistors in series? When solving so, they clearly give different results so I'm wondering why the 5 Ohm resistor must be the one in parallel with the others?


texts: IAR EWARM gives error on everything in startup_stm32

texts:
I'm trying to compile a project for school, which all my fellow classmates have no trouble compiling. This assignment is nothing more than dragging already written source code and compiling an, already proven to be a working, program.
I have added the file startup_stm32f30x.s from ST Microelectronics website, as per instructions in my school assignment, and i have not modified it at all. When i hit Rebuild all IAR gives errors on basically everything assembler.

For example:

AREA, SPACE, PROC and ENDP gives Error[40] Bad Instruction.

EXPORT  Reset_Handler [WEAK] gives Error[0] Invalid syntax

ALIGN gives a rather verbose error called
Error[413]: 'ALIGN' is illegal. Use directive ALIGNROM or ALIGNRAM (the first parameter is raised to the power of 2, the second is a 32-bit fill value).

I am right at the start of the course, and i am not supposed to yet be able to handle, and/or find solutions beyond your ye olde "Gosh! I forgot to plug the cable in".

Does anyone have an idea of where to continue now? I will happily supply whatever more information is needed to understand my problem, but please be patient with me being a noob on these things!


texts: Can I use PWM to control the speeds of more than two motors separately in ATmega32A?

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Can I use PWM to control the speeds of  more than two motors  separately in ATmega32A ?

The latest thing I could do is controlling The speeds of two mototrs using fast PWM  mode in counter 1 with two compare values OCR1A & OCR1B.


texts: 5A connector that fits through 1/4" hole?

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I'm powering a load that draws 5A at 18V from a brick power supply. The power supply and load are separated by a thin metal wall that has 1/4" (6.35mm) holes in it. So I'm trying to find connectors that can fit through 0.25" diameter holes.

The best I've found is small JST plugs, but they're more like 0.29" so we'd have to file them down to fit through the holes.

I'd appreciate any suggestions, either for a 2-circuit connector or two 1-circuit connectors.


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Do all memory devices use shift registers for writing data to memory?
For example
USB, EEPROM, RAM

Serial in and parallel out into memory devices data in lines?
Or
Parallel in parallel out into memory devices data lines?


texts: Not accurate readings when connecting OpAmp AD822 to ADC MCP3008

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for my project, I am using a photodiode, that I connected to the AD822 OpAmp. This OpAmp should then be connected to the MCP3008 ADC. I am reading the data from the MCP3008 with a RaspberryPi. I am however getting weird readings from the ADC. I guess that this is because there is some sort of fluctuations in the voltage coming out of the OpAmp. Below there is a diagram of my wiring as it currently is (I am using the negative side of the 9V battery as ground):

I use single supply voltage for the OpAmp, as I do not have the possibility of dual supply.
If I try to measure the Voltage across the 10kOhm resistor with an multimeter, I get a value of 0V. However, according to my ADC the Voltage input Voltage fluctuates between 0 and 1.7V.
Now, if I disconnect the ADC and remove the 10µF capacitor and connect the 10kOhm resistor directly to ground, I get readings with my multimeter of 0.04V with ambient light and about 05.V if I put my flashlight over the Photodiode. So it seems to be working like that
Am I wiring something wrong? Are my capacitors or resistors wrong / at the wrong place?
Here are the datasheets:
Datasheet Op Amp; Datasheet ADC
Thank you in advance!
EDIT after jusaca response:

EDIT with Solution:
Jusaca, thank you for the decoupling advice and the relation between Rf and Cf.
I have worked on it more and finally realised what the last error was:
I had to connect the negative side of the 9V battery to the ground of the MCP3008 and to the ground of the RaspberryPi. So connecting the entire "ground" side (the bottom line in my diagram) to both the negative side of the battery and the ground of the RaspberryPi and both grounds of the MCP3008! :)


texts:
This is somewhat a duplicate.

I'm looking for a way to limit the inrush current of a small supercapacitor circuit. Input is regulated 5V (USB), output feeds a 3.3V regulator. Goal is a 10s runtime at 100mA, so the supercap is 5V, around 500mF if my math are correct.

The simplest inrush limiter is well presented in the question above, but I'd like to find something that charges the supercap faster, without loosing the ability to charge it to (almost) the supply voltage. Something like constant current, around 300mA.

The other typical answer to this question is the LTC4425, or another supercap charger from Linear. From what I read, those are

expensive and
designed to handle and equalize two 2.5/2.7V supercap, which isn't warranted given the large availability of 5V supercaps.

What's the intermediate solution?
The system isn't battery powered, so efficiency is not a major consideration.


texts: LT1010 (Unitay Gain Buffer) - Voltage output depends on load? (LTSpice simulation)

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I need to drive a TTL signal into a 50ohm load (connected to a 5V supply, not to the ground) from a DAQ card that can only output 5mA.
I therefore looked around and found Linear Technology has LT1010, which is a buffer with 150mA current capability.

It should be very simple to use, but when trying to simulate it using LTspice, I get very weird results.
I've attached a picture of my schematic (sorry it's ugly, was supposed to be a quick and dirty simulation):

When I set the input to 5V, everything is OK. But when I set it to 0V, The output is reaching 1.2V.

The bias 20ohm resistor can be changed to any value from 0 (no resistor) to 1k and it doesn't change anything, I've also tried adding a negative supply to the V-, but it doesn't change much.

According to the LT1010 spec, it should be able to drive a 150mA load, doesn't it means that the output should follow the input (up to a small offset) up to 150mA?


texts: Applying FFT on I/Q signal to get range and velocity

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I managed to get correct I/Q signal from an FMCW radar.

From my last questions I understand that I have to do FFT on the root of I^2+Q^2
so I will have an array of I^2+Q^2 then do FFT on it.

My questions are
1. How would I get the velocity ? my guess I have to do another FFT on the result ?
2. If the values of I/Q comes from an ADC which the values are from 0 to 2^16, is there a conversion that should be taken care ?


texts: I2c between beaglebone black and STM32F4-discovery

texts: I'm planning to connect my beaglebone black to stm32f4-discovery. The purpose is to test i2c library of beaglebone black written in c. But I'd like to check if I'd fry my boards. Would it be okay to connect i2c pins of two boards? Or can you connect 'gpio out' pin of stm32f4 directly to 'gpio in' pin of beaglebone?


texts: Why is using a potentimeter as a rheostat treated different way than a resistor?

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This might sound a bit weird question but I’m having some confusion regarding some fundamentals on potentiometers used as rheostats.

Here I will try to explain by using the simple circuit below:

I simulated it so we can see the currents passing through each wire. R1, R2 values are 470 ohm and 10 ohm. Similarly R3 is 470 ohm and 10k Pot is set to 10 ohm.

So far so good, and we can see that the same amount of current passes through each component which is around 20mA.

R2 and Pot values are the same. Common sense says we can replace them safely since they are identical.

Let’s also assume their rated wattage is also the same i.e. 0.5 Watt.
Now Iet’s examine if R2 can handle this circuit. The way to do that is to measure its power which is P = I^2*R. So for R2, P = 20mA*20ma*10 = 4mW roughly. Now the question to be asked here:

Does R2 have enough wattage? Since R2 is rated 0.5W which is 500mW, and since R2 in the circuit dissipates only 4mW we can say that the R2 is safe.
Until recently I would use the same logic for the 10k Pot in the circuit which is set to 10 Ohm. So I would say it is safe.

But my previous question (A question on using potentiometer as a variable resistor) revealed the fact that when it is a potentiometer we examine the situation by the current passing through the pot not by the wattage.

Some explained it is done in the following way:

Wattage of the pot is given for its max resistance so in this case the max current of poti at 10k is I = sqrt(P/R). So I = sqrt(0.5W/10k) which is around 7mA. And this 7mA should never be exceeded whatever the pot value is set to. And since the current in my example circuit is 20mA, the pot is not safe since it exceeds 7mA limit.

So R2 is safe but not the pot?

My questions are:

Is the above logic is true? Why?