texts: Help with part and/or circuit 3-15V input, 5V output power supply - Boost, buck, SEPIC,?

texts:
My experience with power supplies so far is limited to linear regulators. I am looking to build a 5V charger capable of charging a smart-phone from a variety of battery sources. I'd like the allowable input voltage range to be ~3-15V, a maximum output current of >=1A, and a reasonable efficiency (i.e. not a critical requirement).  I'm having trouble finding a part including a reference design that will meet these requirements.  I have looked at several boost/buck converters with datasheets showing circuits for either boost or buck, but not both together.

Except, I did find a mention of this one part that seems to do what I want, but I'm not sure this is the best solution: http://www.ti.com/product/lm25118  I also have not been able to figure out how to search for similar parts- i.e. keywords / parameters to use.

I found this thread, How to adjust the voltage of this SMPS? which shows one method.  Someone in that thread pointed out that a SEPIC would be a better choice than using two regulators.  I found that Linear has a line of SEPICs.  This one looked promising http://www.linear.com/product/LT1935 but the datasheet seems to indicate that while the max switching current is 2A, in a SEPIC configuration it can only provide 5V at 550mA off of four AA batteries.

Anyway, I'm guessing this is a mostly solved problem and I was wondering if anyone could point me toward a part, app note, reference circuit, or some search terms that I might be able to work from.


texts: Should I buy a power supply for the input or nominal voltage of a DC device?

texts:
I'm looking to purchase a power supply/wall-wart for a small pump.  The pump is listed to operate at 12VDC input upto 3A.  I'd like a 12VDC/4A power supply so that I may power a second low-current device (mA order) from the supply, but then I noticed the nominal voltage rating of the pump: 9-14VDC.

The nominal voltage rating is confusing me and I'm no longer certain if the 12VDC supply will be sufficient for the general operation of the pump.  I think the nominal rating means that depending on the load, the voltage may fluctuate during operation.  In this case, a higher voltage demand may draw more current, which the power supply should provide.  Maybe -- I'm not sure anymore.

Is my concern warranted, or am I just thinking about this too hard?

Here is a picture of the "style" of the supply.  I'm not sure if it is regulated, but it looks like a typical supply that powers household electronics such as printers, speakers, and small form-factor computers.


texts: Difference between TLC272CP and TLC272CDR

texts:
I was using an operational amplifier in my project from Texas Instruments. The series is TLC272. There are many different models. Could someone tell me the significance or the meaning of CP or CDR in different types of TLC272?

Can you please explain which one is better and how does it make a difference? And also what is a reel?


texts: How to measure the accuracy of a digital multimeter when we don't have its datasheet?

texts: Is it possible to measure the accuracy of a measured value by a digital multimeter without referring to its datasheet?


texts: Voltage Regulated by Resistor in Generator Circuit

texts:
So I am tinkering with making a circuit that will allow a motor to generate power to charge a battery.  I have this, what I presumed to be an, AC induction motor I salvaged from an old Christmas decoration.

After removing the motor from its casing, I have learned it is a synchronous motor.

This one with the ratings of 120VAC 3.8W 4.2/5 RMP

It can output upwards of 200 Volts AC in short circuit (or DC using a rectifier bridge) at ~ 6.7mA.  I could only get the amperage reading from a short circuit through the rectifier.  Could be my $7 multimeter not doing well with AC or my ignorance on reading AC amperage.

Strangely enough (at least to me), no matter how I worked it: the amperage would stay at a consistent cap of ~ 6.7mA.  In my tinkerings I figured out there is, at least almost, a straight line which shows that the resistance given to the circuit will output a maximum voltage I can get from the motor itself.

The diagram posted is a test circuit to gather data points on this.

I'm wondering if there is anyone with an idea as to what is causing this phenomena?

Here is a chart and graph of the voltages across the entire circuit (from either end of the rectifier bridge), given the different values of R1.

Definitely some good answers.  Not sure which is the best answer.
I appreciate all of the input, and will select the best answer once I get back from work and have time to do some more testing, and take apart the motor to see what's really going on inside.

To clarify: the end game is to maximize on incoming voltage so I can reduce the voltage later in the circuit and bump up the amperage to charge a battery somewhat efficiently.  Also to understand why there seems to be this constant 6.5mA coming from this motor.

I may just go back to my research and choose a best answer for now.  If I run into anything interesting down the road, I'll make sure to post again.


texts: What kind of signals can a frequency synthesizer like this generate?

texts:
Take this chip as an example: http://www.maxim-ic.com/datasheet/index.mvp/id/3491.

It says that the frequency range is 8.1kHz to 133MHz on the main output and 8.2MHz to 133MHz on the reference output. But, to my untrained eye it doesn't say much else.

The datasheet left me with a few questions:

What kind of oscillator is it? Sine wave, triangle, saw tooth?
It says it only needs a single +5v supply, but what if I wanted the sine wave to oscillate between, for example, -2.5 volts and 2.5 volts?

I know I can build an oscillator with an op-amp, but this question doesn't relate to that. I'm merely curious about the nature of chips like the one I posted.


texts: Using FatFS on internal flash of STM32f303 microcontroller

texts:
I want to use FatFS library using STM32F303 internal flash memory. I created user_diskio.c file and described necessary functions USER_write, USER_read and USER_ioctl for reading and writing data to/from internal flash

  if (FATFS_LinkDriver(&USER_Driver, USER_Path) == 0)
  {
    result = f_mount(&FATFS_Obj,(TCHAR const*)USER_Path, 1);
    ...
  }

f_mount gets FR_NO_FILESYSTEM error. Using function f_mkfs((TCHAR const*)USER_Path, 0, 512); gets FR_NOT_ENABLED error. I don't understand, how should I format disk sector to use FatFS library.


texts: how to turn backlight on for BC1202A LCD

texts:
Hopefully this question isn't too novicelike:

I have an LCD (BC1202A) that I want to drive from a parallax propeller board.

Spec data:link1 and link2

After hours of mucking around (mis-wiring, contrast pin disconnected, wrong resistance on the contrast, trying to drive it with 3.3v instead of 5v, etc.) I finally got an LCD test program to work. Yay.

But I cannot for the life of me get the backlight to work.

Per the sheet this is supposed to be driven by pin 15, and from looking around that's apparently the normal way of doing it.  (Some LCDs seem to have a pin 16 which is the ground for the backlight, this LCD doesn't.)  It also talks about options to use pins 1 and 2 (which are already what are powering the regular LCD operation) and something about "A" and "K".

In any case, all of the examples I see when searching around are for the pin 15 mode.  Sounds good to me.  So then I look at page 13 of that second spec sheet above and it says:

 LED B/L drive from pin15 (LED+)

Okay, so I connect pin 15 to the + (5v). (I assume that's what that means) Tried that, does nothing.  Tried connecting to minus/ground - nothing.

It also has option b:

(Option) LED B/L drive from pin1 (Vss) pin2 (Vdd)
(1) Jump 1,2 Short
(2) Current Resistor required on RL
(3) Jump 15 open
(4)To be sure of enough current supply for both Vdd + LED B/L

I don't totally follow their shorthand here - but it seems to me that they are saying 1 and 2 are usual (ground and + respectively, with a resistor on 2?; tried 1kohm just for kicks, doesn't change anything), 15 is disconnected and make sure there's at least 42mA available (2 for the logic, 40 for the backlight - should not be a problem).

Specific questions:

In either option (a) or (b) is there something obvious that I'm not understanding about how they are saying to hook it up?
Maybe I fried the backlight by hooking it up wrong - is that possible/likely?
Any other ideas of where I might be going off here?

I'm either missing something obvious or this backlight really just doesn't work.

EDIT:

Here is what the thing looks like:


texts: Why is current (and not charge) an SI base unit?

texts:
Recently I've been wondering why the Ampere is an SI base unit and not the Coulomb (which is derived). I read this answer https://electronics.stackexchange.com/a/23456/16834 , but I'm not sure I'm understanding the discussion.

To me it seems like the Coulomb would be a base unit, especially because of the manner it is mentioned in the Wikipedia page, and because it is defined as the change of charge with respect to time; velocity, the change in displacement with respect to time is a derived unit.

Are there reasons that the Ampere is a better base unit than the Coulomb?


texts: Is it possible to implement a high-side current mirror with only NMOS FETs?

texts:
I need to implement a difference amplifier only using NMOS technology. I am struggling when trying to reference the voltage difference to ground. From my reading it looks like I need a high-side current mirror.

However, all of these are implemented using PMOS. Is there any way I can implement a high-side current mirror using NMOS?


texts: Switching two leds using transistor where one power feed still has small current present in off position

texts:
First time posting, totally new to electronics so please go easy on me.

I have a circuit made up of two smd leds with two seperate live feeds and grounds that switch from one to another using npn transistor. It all works perfect when tested on bench and 12v supply. But once connected in the car it seems that the second feed that when once on should kill the first led has constant small current running through it and immediately switching off the first led without being fully activated. I hope that makes sense?
Ive put a multimeter on it and it seems to read just below 0.8V in off position which possibly is enough to disable the first led instantly?
The first feed is illumination feed, second is interior light circuit connection.

Is there anything I can add to the circuit to have it working as I want it?

This is the schematic which works fine on bench with 12v supply

So red led gets power and is on. As soon as white led gets power it switches off the red one. Once the white led stops getting power the red one comes back on.

It’s all good when two 12v feeds are supplied on bench. But once connected in the vehicle as soon as the wire for white led is connected but not activated it knocks off the red one instantly.
The white led feed comes from interior light circuit from body control module so once the door opens etc it activates the led but somehow the feed isn’t 0v when it should be off hence the red led deactivation?

Thank you for any guidance and info on this.

Apologies for not making it very clear

Stanley


texts:
I'm putting together a circuit using an OP27. I was not sure if the the TRIM pins of the OpAmps are allowed to float if no triming is required.

Would allowing the pins to float adversely affect the OpAmps operation?


texts: Calculating true power of a predominantly inductive load?

texts:
I'm stuck at this problem, which doesn't seem to be so difficult, but, I guess there is some basic stuff that still confuses me.  So, if we have a load represented with complex impedance \$Z=30+j40 \ \Omega\$ powered with a sinusoidal signal generator of voltage \$U=200 \ V\$, how can we find a true power on that load?
What I did, knowing that true power is: \$P=U\cdot I\cdot \cos \phi\$, where \$\phi\$ is phase difference between voltage and current through the load and equals \$\phi=\cos\big(\arctan\frac{X}{R}\big)\$ \$\big(X\$ - reactance, \$R\$- resistance \$\big)\$, since I don't know the current, I expressed it as: \$I=\frac{U}{Z}\$ and then calculated true power as:
$$P=\frac{U^2}{Z}\cos\bigg(\arctan\frac{X}{R}\bigg)=742 \ W$$
but, I think I'm completely missing some parts regarding complex values of impedance and current.
Thank you for your time.


texts:
I am monitoring an external system which sends out a 5v pulse every 2 seconds when in normal mode. When the motor is working, it sends out a constant 5v designed to power a flashing light or LEDs as a warning system. When the pulse is not present, it is 0v. There is currently nothing connected to this, and I want to feed it into a micro so that I can monitor it (i.e., know when the device is active and send the appropriate signal to me).

There will be an optocoupler between the two circuits as these are powered independently (although now that I'm thinking about it, I certainly could integrate my micro into the existing framework, but that's not how it's currently setup).

I know I could programatically take out the pulse, by putting the input on an interrupt and waiting an appropriate amount of time before retesting, a kind of debounce. But I would like to know if I could do it by filtering out the pulse through circuitry.

My initial thought was to filter anything (for example) below 5Hz (since the pulse is at 1/2 Hz) and that I would need a high pass filter. But then someone pointed out to me I needed a LOW pass filter since the constant 5v I want to test for is actually at a lower frequency than the pulse.

As an additional point, the output of the filter will be driving a low impedence  opto with no other load. I have no idea how to take this into consideration.

Any help would be appreciated.


texts: Reading From a Large Array of Photoresistors

texts:
I'm an undergrad just starting to study Electrical Engineering. For the first hobby project I'm starting, I want to use a microcontroller to read analog voltage values from a very large array of photoresistors (18x24). From these values I will pinpoint the location of various light sources near the sensor array using some algorithm I haven't thought much about yet.

What is the "correct" way to structure the circuit so that I can access one resistor at a time from my microcontroller. I want to select one specific resistor using some sort of parallel output from the microcontroller that is set to the resistor's address. Once the resistor is selected I want a voltage corresponding to it's resistance to be put through a common analog-to-digital converter connected to the MCU. Then, I will read and analyze the value.


texts:
I'm a beginner to electronics. I just started to test transistors, but I've some doubts.

I've used this schematic to test a NPN 2N2222:

My questions:

1 - How much Voltage or Amps should the base and the collector receive to pass current to the emitter? I can't figure out the math.

2 - With this setup, the LED when I don't have the button pressed have 1V current. I'm wasting energy? I can tunning this schematic to not wast any voltage when the button is not pressed?

Please give me some clues.

Best Regards,


texts: Safe temperature range for 18650 battery - powerful flashlight

texts:
There are many powerful flashlights, some of them have just one 18650 li-ion cell, 10W LED and they are very small.

I have read few tests, I watched few video tests on YouTube and looks like some flashlights really work at 10W power for few minutes and some of them can operate 1 hour at 10W.

For example - there is Armytek Wizard ~1000lm flashlight prototype test here: link

Test results for maximum (about 1000lm) mode:

  5 minutes into the runtime test the headlamp is uncomfortable to hold. At the 15 minute mark it is unbearable to hold.
  At 56 minutes the headlamp flashed 3 times signaling that the voltage is in the “Warning Level”. This was followed by the ON and OFF
  switch indicator light flashing once every second in a green yellow
  orange combination. According to Armytek the “Warning Level” is
  triggered when the battery voltage is 3.1 V. At this point the light
  level has not dropped. There is also a “Critical Level”. According to
  Armytek the “Critical Level” is triggered when the battery voltage is
  2.9 V.
  At 1 hour and 8 minutes light output drops to firefly mode 2. At this point the runtime test was concluded.
  Immediately after the test was finished the battery was removed and checked for voltage and temperature. The voltage was 2.93 V and the
  temperature was 132°F (for the battery). After about a 60 minute rest
  the battery voltage was about 3.0 V.
  This headlamp has thermal protection built-in which is supposed to be
  triggered at 80°C or 176°F. When the thermal protection reaches what
  Armytek calls the “Critical Level” (80°C or 176°F ) the light output
  drops to 100 lm. During the whole runtime test the thermal protection
  did not activate.

132°F is about 55°C

I have tried to find that in Panasonic NCR-18650 datasheet, but there is nothing about temperature range exept that discharge characteristics for 60°C exists, so I guess 55°C is ok for discharging. But how high that temperature can be?

What is safe discharge temperature range for (high quality) Li-Ion 18650 battery?


texts: How does a wind farm prevent the fastest spinning turbine from driving the slowest one?

texts:
Just what the title says.

On a wind farm spread across several score hectares, I assume, the wind-speed wouldn't be uniform. The faster spinning turbines would probably induce more electricity than the slower ones ...

Assuming the output from the farm is ganged at some point, how is the output from the faster spinning turbines prevented from interfering with the slower ones? It wouldn't be just a matter of putting a diode, would it?


texts: Connect to Xilinx Zynq 7030 via JTAG connection?

texts:
Imagine you are trying to write Bare Metal applications on a Xilinx Zynq 7030 board.

Since burning sd cards all the time gets tiresome, you want to establish a JTAG connection. You get a JTAG HS3 programming cable, set up your lovely ARM DS-5, write a nice test "Hello world!" program.... and then what?

How would you establish a connection between your workstation and the Zynq board via JTAG? What are the next steps?


texts: How do i find the FNBW of a main lobe using a diagram?

texts:
Looking at the graph below, i can see that HPBW of the main lobe is around 45 degrees, but when it comes to identifying the FNBW i have trouble understanding it. Reading various articles online i've seen it mentioned that FNBW is around twice HPBW.
My approach was to look for a point in which the radiation power starts increasing after the main lobe and that would mean i've found a side lobe, thus having a null between main lobe and side lobe. For the diagram below, this would mean ~ -145 degrees and +120 degrees (power graph is on the right, amplitude is on the left) and obtain a FNBW of about 100 degrees that would coincide with about twice the width of the HPBW. Is this correct?
I am unsure whether this is correct as the power for those points is not 0. The only points with 0 power are at around +/- 25 degrees.


texts:
I'm working on a full bridge dc-dc converter, following the instructions on power supply cookbook.
It has a 350V output and 2kW total power, 30kHz switching frequency
I choose inductor current ripple as %5

Author says 30mV output voltage ripple is ok for forward-mode converters, but in my situation that means 2200uF output capacitor and it frightens me because it's so big and forces me to use aluminium capacitors. I'm so confused here, should I listen this 30mV rule in book or choose another ripple value?

I'm open to all advices


texts: How to find Equivalent resistance of solid regular bodies i-e solid sphere ,solid cube

texts: How we can find the equivalent resistance of solid regular shaped bodies e.g solid sphere, solid cube


texts: How to automatically assemble lithium polymer battery?

texts:
I'm redesigning a product for automatic assembly (DFA / DFX).  The current product includes a lithium polymer battery with solderable leads, very similar to this:

Right now the leads are hand-soldered.

How do I make this into something that can be assembled automatically?

I don't think there is any battery like this that can survive reflow, so it has to be added after the main pcb is assembled.  There are batteries with JST connectors (adds cost, and still wouldn't be easy to automatically plug in), and batteries with metal foil tabs (no protection circuit - it would have to be on the other pcb; and the tabs probably have to be hand soldered anyway).

I'm sure this is a very common problem in the manufacture of small wearable devices like mp3 players and bluetooth headsets, but how do people usually solve it?

P.S. It turns out everything else in the product can be assembled by (essentially) pick and place: picked up with a vacuum tip and dropped in from above.  The parts drop onto alignment pins in the bottom half of the case, then the top half of the case snaps on.. the battery is the one  headache.


texts: Ultracapacitors as a battery; how long will they last?

texts:
I would like a formula to be able to calculate how long it would take 6 2.7v 350f ultracapacitors connected in series to degrade from 14.4 volts to 11.5 volts given a parasitic draw of a specific load.

For example:
A bank of capacitors replacing the lead acid battery of an automobile, charged to 14.4 volts by the alternator. How long can the car sit with the engine off before the voltage dropped to 11.5 volts? 11.5v it's a minimum voltage before the starter will not turn over the engine.

6 2.7v 350f ultracapacitors at 16.2v 58.33f
Balancing board

Q. Do the balancing board resistors cause the capacitors to drain faster?
Q. How fast does a ultracapacitor drain on its own not connected to anything?

12v system
Parasitic current draw of 0.03Amps
58.33f
Starting voltage 14.4v
Minimum voltage 11.5


texts: I'm trying to design a PCB including DDR3 rams, I don't have much experience and knowledge working with DDR3. What are the most important guidelines to help ensure good signaling for the DDR3 chip? I found some information about it in forums, but maybe someone could tell more about DDR3 board design? What is the key aspects in order to design a working board?


texts:
Please be gentle, as I am a bit of a noob when it comes to these things.

I am attempting to use an IRS2186 to control 2x IRF3205s in a half bridge configuration (datasheets below). I am using a known good atmega168 to deliver 50% PWM at 32 kHz to the high side of the previous components. It is currently not turning on the high side.

On this application note, at the bottom of page 5, it says that in a standard PWM configuration, one need only use a bootstrap diode, and capacitor to make this setup work, so that is all I am using currently, everything else is in the configuration in the "typical configuration" section of the datasheet for the driver. My second question is is this true? The previously mentioned sheet is for a different driver IC, but they are very similar.

I have calculated using this page. That I need around a 500 nF cap as a bootstrap capacitor. My first question is am I correct here? I am unsure if this is the right calculation to use. I am also using a MBR160GS diode as a bootstrap diode, will this work?

My last question is does anyone have any idea what I'm doing wrong here? Any guess at all would help.


texts: Why doesn't PSE circuit maintain power to PD?

texts:
I am trying to make a PoE 802.3af solution. This are my schematics:

The problem is that the power does not maintain. It only provides 48V for about 300ms, then it drops. Also, the above statement is valid when I remove the DC converter input capacitor; I tried a 22uF, 47uF, 22uF, 100uF capacitor, but every time I connect the capacitor, the PSE (LTC4263) does not supply power, instead it indicates low signature resistance by flashing the LED with a specific pattern.

What is causing this behavior and how can it be resolved? What capacitor should I use?


texts: I have a battery pack of 8 Ni-MH 2400 mAh cells connected to a load that draws ~700 mAh (a Raspberry Pi Zero, display, WiFi dongle, USB hub, and a wireless keyboard dongle). I want to add a led that changes from green ( around full battery) to orange (around halfway) to red (nearly empty) depending on the battery voltage. What voltage are Ni-MH batteries at when full, halfway and nearly dead?


texts: How do I find the output voltage of a load?

texts:
I have a load powered by a 12V source. The load can draw up to ~2A:

The load has "on and off" modes, but it still draws ~40mA when in "off" mode.
I want to switch the load from an MCU to save power when the whole system is off, so I'm looking at adding a transistor:

I'm researching what transistor would be suitable. The TIP31 looks like a suitable candidate, but I believe I need to calculate the thermal requirements. I think I can probably follow this guide for the calculations, but I need to know what the voltage across the transistor (Vce) will be, and that's where I'm stumped.

How can I determine what the voltage will be at the transistor's collector? It seems so simple but my electronics knowledge is fairly basic. How can I calculate or measure this (before buying the transistors)?

Apologies if I've left off any necessary details. Just comment and I'll add them if I have.


texts: time it takes for the voltage to achieve 7 V

texts:
C1 = 56uF
C2 = 12uF
R = 12kohm
E = 13 V

I have this circuit and I want help to find out how long in takes for the voltage Uc2 to achieve the value 7 V?

I have calculated the time constant to 117 ms, and I tried to find the time through t = 0.117 * ln(13/13-7) but that doesn't seem to be right.
Could someone help me to go to the right direction?

Thank you!


texts: RE: Receiver Output Enable and DE: Driver Output Enable pins

texts:
Hello I am planning to use LT1785 UART-RS484 transceiver. I will use that chip in order to get RS485 data and convert it to UART signal. So I have read the datasheet but I couldn't be sure. It says

  A logic
  low on RE enables normal operation of the receiver output
  RO. A logic high level at RE places the receiver output pin
  RO into a high impedance state.

I shorted the RE/DE pins because I will only use this chip to receive RS-485 signal and convert it to UART. So my questions

Can I directly connect shorted RE/DE pin to the ground?
In the absolute maximum ratings Vcc is given 18V. Does that mean I can supply this chip with any voltage up to 18 V? In case of 5V supply voltage, will this chip work?

I also added the image that shows connection of the pins.


texts: Alternative to V divider for high currents

texts:
I am looking for suggestions as to how to supply power to a gate drive optocoupler i am using.

The supply being used is a 25V (rms) ac supply and intend to supply 10V DC at around 500mA+ from my supply.
When i have reduced the voltage, i will maintain it with some caps.

I was looking for an alternative to a high power resistor divider. I thought about a zener diode and i am aware of high power zeners, though this would still need a high power resistor to limit the current.

Any input is greatly appreciated.


texts:
I have developed an application by using STM32F4-Discovery development kit. Now code is mature and I need to build a custom circuit.

I started building the bare circuit first:

I soldered the chip on the pcb via a standard 30 Watts soldering iron with a technique like in this video: http://www.youtube.com/watch?v=6YU3v_w7x7o

Since I didn't get the point of connecting 1uF//100nF capacitors between every VDD-VSS pin, I only connected a 4.7uF capacitor to the entry point of power lines.

My pin connection is as follows:

VDD <- 11,19,28,50,75,100,21,22,6
GND <- 20,10,27,74,99
2.2 uF cap is between 49 and GND
2.2 uF cap is between 73 and GND
10 K resistor is between 94 and GND
MCU.72 is connected to STM32F4-Discovery.SWD_connector.4
MCU.76 is connected to STM32F4-Discovery.SWD_connector.2
MCU.VDD is connected to STM32F4-Discovery.3V
MCU.GND is connected to STM32F4-Discovery.GND

Question:

I'm expecting to connect the MCU via STM32F4-Discovery's ST-Link/V2, but ST-Link utility is not being connected. I'm not able to get a heartbeat with the MCU.

What is the point I am possibly missing?

Edit:

(moved to the answer)


texts: What innovation made WiFi amenable to mobile devices without prematurely depleting them of power?

texts:
In June 2004, the Economist, in reference to the nascent WiFi standard stated that "It is currently too power-hungry for mobile devices"
So how did WiFi go from being extremely power-hungry to being suitable to mobile device usage?


texts:
I'm trying to use the Alinx board to get images from industrial cameras, process those images, and determine the size of the object showing in the image.
I'll read the image using USB (from the PS part), buffer the image, and send it using DMA to PL where it will be filtered and returned to memory. Then I'll detect the size of the object and transmit it via Ethernet.
I started with HLS code, where the image filtration will be done, I created the bloc design using DMA on Vivado. Now I need to put the environment together to detect the size of the object. I am working under windows10, and I have a working SD card from the manufacturer with Debian installed.
Now my questions are:

How can I configure the PL part with my own PL configuration generated from Vivado? (I have the BOOT.bin and the image.ub I generated in petalinux using the .hdl file from my vivado project)

Is it possible to clone the board's SD card to get the Linux filesystem, then use this clone on my own SD card with the substitute BOOT.bin and image.ub I’ve generated?

Can SDK and JTAG do this?

I'm short on time. What's the fastest way to do this?


texts:
Is there a way to buffer a large DC signal accurately?

I would like to measure a voltage that can go from 0 to 50VDC, with 16 bit accuracy (so down to the mV level at the highest voltage, and µV levels at the lowest).  Since this is a 10ppm measurement, I need to be very careful about not affecting the voltage that I am trying to measure.

The typical way to do this (I believe) is to use a unity gain buffer at the voltage, with something like a FET op amp.

The problem is that there aren't that many op amps that can have 50VDC inputs.  Of those that can, there are fewer that can have 50VDC outputs.  And finally, of those, there really aren't that many that would be very accurate at low voltage measurements.  Typical offset voltages in the mV are common I believe.  Finally, I'm not aware of any that can measure down to the lower rail.

Anyone have any idea how to buffer something like this?  Noise is less of a concern due to the DC nature of the voltage that is being measured, but accuracy is important.


texts: Driving high power LED using WS2811 or WS2801

texts:
I want to use either WS2811 or WS2801 to drive high power LEDs with spacing between LEDs up to 15 meters. These are going to be used outdoors or in a water feature. As you know WS2811 output is constant current but WS2801 output can be constant voltage, I've come up with the following circuit to drive power LEDs constantly at about 350mA (R_load).

simulate this circuit – Schematic created using CircuitLab

I'm no EE, is the circuit ok? any suggestions to make it better?

Considering the distance between LED's will it work if I use 74hc125 buffer IC to "power up" the data signals of WS2811 (or WS2801) ICs?

WS2801 uses SPI but WS2811 uses I2C, which one is better for my case?


texts: (Altium) Multi-Channel Design - Net-Names don't change and how to use Harness?

texts:
I have a circuit which I want to use 3 times in my project. So, I thought it would be nice to try multi-channel design function in AD. I read the oline documentation and it seems to work (I used the repeat function) but I have 2 problems:

My component designators get the right naming (R11_1, R11_2. R11_3) but my net names are still all same. In the online documentation the net-names also change. My question is how I can fix this problem?
My 2nd problem is, how I can use multi-channel design with harness?  I couldn't find any information in the online documentation. Maybe I need to use multiple sheet-symbols, so I have 3 harness-ports but again the naming of the would not change.

i will attach 2 pictures:


texts: How to tent a via without changing DRC file in EAGLE

texts: For tent vias I setup Mask Limit in DRC file, this will tent all vias allowing me to set single vias to not tent. But if I want to tent only some vias, in a large board with a lot of vias this way is impraticable. So, there is a way allowing me to direcly tent some via that I select?


texts: Charging battery through relais and arduino

texts:
I'm designing a charger system for my lawn mower robot.

The idea that I had is based on a relay. As soon as the robot reaches the charging station, with "Volt Sense" pin it detects a charging voltage, so enables the "enable charge" output.
In this way the the relay coil is turned on and so the battery switches from the normal circuitery to the charging one. I didn't put the charging part of the system, but that one is quite easy, since I have a lead acid battery.

The enable charge pin is there also to control the charging of the battery. When it's fully charged, the pin is switched off, so the battery can go back to normal functioning mode.

I will add a current measurement IC, so when the current drop to very low values, the battery is considered charged.

I'm not sure if the following schematic is ok, could you please tell me your opinion?
Thanks

EDIT: I added the charge measurement pin.

simulate this circuit – Schematic created using CircuitLab


texts: How a decoded picture is stored in a memory?

texts:
If we decode an image (any format) we will get matrix of pixels.
For example consider a picture with resolution 10x10 and colour depth of 16777216. Therefore pixel is represented by 24 (888 RGB) bit 10x10 matrix data.

My doubt is how this data is stored in a Random Access Memory?

One option:

0x00 : first pixel(24 bit)
0x03 : second pixel (24 bit)
...

option two:

0x00 : red part of first pixel (8 bit)
0x01 : red part of second pixel (8 bit)
...

0x64 : green part of first pixel (8 bit)
0x65 : green part of second pixel (8 bit)
...

Which method is common? Or is there is any third method?


texts: Fiber Optics as a video source and a switch?

texts:
Is it possible to put a fiber optic bundle together and play video thru the colors of the tips (if they were all flush next to each other
Is it possible to touch the end of fiber optics with hand or any object and receive the signal on the other end?

For example, if i had a grid of 50 x 50 fiber optic cables and I was looking at the flat ends side-by-side I would like to be able to display a graphic that can recognize touch.


texts: Significant Oscillation/Instability at Output of AD783JQ Sample and Hold

texts:
I am currently working with an AD783JQ sample and hold chip and am trying to characterize its functionality and familiarize myself with its operation before applying it to my project. I believed that I understood its behavior, in theory, but the results I am obtaining are wildly far from expectation.
To give you some info into my setup, I am powering the S&H using a +/- 5V signal from a Global Specialties 1310 power supply. I have placed a +5V signal in Vcc (pin 1) of the S&H and it's ground at the common (pin 3) of the S&H. I have placed the other +5V signal at the common (pin 3) of the S&H and its ground at Vee (pin 5) of the S&H. I believe this should be all good and well. I am supplying a 1 kHz 2Vpp signal with no offset from a BK Precision 4055B function generator to the input (pin 2) of the S&H and connecting its ground to the common (pin 3). I am using the same function generator to apply a 1 kHz digital pulse signal with high level 2.5V, low level 0V, pulse width 200 us, and rising edge 16.8 ns to the S/H toggle (pin 7) of the S&H. I am measuring these two inputs as well as the output (pin 8) using a Teledyne T3DSO1204 200MHz oscilloscope. This setup is all performed in a solderless breadboard, so there may be considerable capacitive leaking between the high frequency signals.
When the S/H toggle is high, the output of the S&H tracks the input sine wave as expected. However, when the toggle goes low, the output becomes extremely unstable:

I zoomed in on the instability and was able to ascertain some of it's characteristics. Unfortunately, the oscilloscope is seemingly unable to export data with time intervals less than about 100ns, so I was unable to get a nice MATLAB plot, but here is a PNG of the oscilloscope's screen:

I have been told it is a sin to include such a screenshot, but it is unfortunately the best I can do. The color codes from the above plots match with the signals on the oscilloscopes. The scope is set to 20ns/div. The output seems to have a dominant frequency of about 11.6 MHz and typical amplitude of 1 Vpp, but varied from test to test. Interestingly, there is noise in the trigger signal of the same frequency, but 180 degrees out of phase, which I suspect aligns with some effective filter/pole in the system. This noise is also present in the input signal, but does not dominate. Instead there is also an ~93 MHz noise signal that dominates the input, which leaks somewhat into the trigger, but is significantly attenuated in the output signal. The amplitude of the noise in the input is about 33 mV, while the amplitude of the noise on the trigger is about 55 mV.
UPDATE: I added two 47 nF bypass capacitors, one from Vcc to Ground and one from Vee to ground. It cleared the problem up for the most part, but there is still some noise and some discontinuity at the output:

UPDATE 2: I added a 10k resistor from output to ground and a 1k resistor in series with the scope:

Also here is a picture of the setup:

I implemented the same setup with a trapezoidal pulse rather than a square pulse. (Rise and Fall times 20 us):

Any guidance on how to reduce this instability would be greatly appreciated. Thanks!


texts:
I am using MPU6050 breakout board IMU along with ATtiny2313 microcontroller to get the accelerometer and gyroscope values from the IMU.
Here's the question :
I want to know what values are computer by the DMP inside the MPU6050 and how can i read the values using I2C (i.e. what are the register numbers in which the DMP values are stored ?)

I am not using any libraries since i have written all the code myself. I just need to know what is the data that the DMP provides and how to read it.
Please Help !


texts: What is the function of this circuit? (Included an op-amp, capacitors and resistors)

texts:
What is the function of this circuit?
What is the role of the C2 in Op-amp's input?
This is probably a filter circuit but I am not sure.


texts: I would like an explanation of the importance of window utilization in transformer design. I understand that it is the ratio of area occupied by windings to total area available for windings on the core. Specifically, I want to know typical values one would find across applications & sizes of transformers. Also, What is the effect of higher vs lower window utilization.


texts: Is static negative resistance practically available?

texts:
I learned that negative resistance (NR) could be simulated by involving active devices like op-amps and others. I'm interested in the static/absolute NR rather than the differential NR.
My question is whether it is really practically feasible to be used when making an AC circuit network with about a hundred RLC components and nodes grounded through NR. The purpose is to cancel some effect of R, but not all (otherwise I would go completely without R). Is it just a routine thing or out of the reach of current techs? And any possible reasons.

People are asking why I need such a thing. It’s not for a particular engineering purpose. It’s more of a construction to show some mathematics of a certain circuit with only RLC and NR. The original problem is just outside what EE usually concerns and distracting to show here. We're interested only in the linear equations of ideal circuits and want to build a real working example.


texts:
So I understand that high current through a conductor generates heat, and too high heat can melt things or cause components to fail. Short circuits are frequent causes of overcurrent, no?

Overvoltage is bad because it can cause overcurrent, or in the case of capacitors, trigger a breakdown voltage.

From what I understand, some components 'blow' (or inflate, explode, otherwise fail aside from direct melting) from dielectric breakdown - other components like diodes can fail for the same reason.

But is it actually the voltage that's causing these things to expand and pop like they do, or is it actually the rapid transit of electrons as a result of the excess voltage triggering an overheat and igniting something? I'm not sure my understanding of all this is correct.


texts: How the transistor works in this 555 circuit?

texts:
555 Is not able to provide long timing due to its leakage current.
The following circuit is very useful to build a long time timer such as 1 hour or more.
The accuracy of the time is not important for me. I don't care if the 1 hour become 50 min or 70 min.

I know how monostable operation works but I don't understand how the transistor works and What the principle of operation is. How can it prevent the leakage current of 555 and provide long timer? and how is the capacitor charged and discharged?
Thank you,


texts: Does the signal to the NFC antenna require shielding?

texts:
My design requires a NFC antenna to be located on a different board and due to space limitations, a uFL connector can't be placed for a mini coax connection. A flex cable solves many of the design issues. However, since a coax is shielded, will the flex cable need to be shielded too?
I am using the TRF7970A transceiver IC and the matching network will be placed on the flex cable, close to the antenna. The entire length of the flex would be 1.5". TI recommends matching the TX_OUT net to 50 Ohm Single Ended. So my intention was to breakout the 50 ohm trace to a FPC connector and then run a 50 ohm trace (referenced to a ground plane) on the FPC. The NFC antenna is a discrete component and will be mounted on a stiffener. Specifically, my question is as follows:
Since the coax is shielded, will the signal on the flex need to be shielded too? i.e. sandwiched between 2 ground planes? If so, adding a 2nd copper layer will significantly reduce flexibility and I might opt for a mesh plane, though from what I gathered, that might not work well for controlled impedance.

Most NFC antennas I searched do have a mini coax. But I also bumped into a couple FPC NFC antennas, including one from Laird shown below (part number: 0600-00061), which don't have any shielding. So that made me think it's ok to just have a 2 layer FPC.


texts: Determining Absolute Maximums for IC Output Current and Power

texts:
I'm having a small gap in understanding with a project I'm working on.  The project is reliability related and requires looking at the absolute maximum values for some 54ALS family logic (Max Vcc, junction temp, Output Current, Power Dissipation) and doing some derating calculations on those values.

Just as a basic test to see if I can accurately find these values, I pulled up the datasheet for the 54ALS08 from TI.  The only real absolute max I was able to pull from this was Max Vcc is 7V.

Digging a little deeper, TI's website referenced a standard military datasheet for the component: 5962-86842.  That one helped a little more giving me:

Max power dissipation, per device: 22mW
Junction Temp: 175C.

Cool!  I'm getting close.  How the heck do I determine the maximum output current though?  I know for logic-low I don't want to be going over 4mA it's going to impact the logic function of other gates down the line.  But, I'm more interested in the current source/sink that's going to damage the IC.  Searching around I found a similar post asking about this that referenced 74HC08 (HC logic family version of this).  That datasheet seemed more straight forward.  Icc under Table 4 (absolute maximum values) is 50mA.

Last things, "max power dissipation, per device".  I'm assuming this means that for this particular IC (quad gate) I shouldn't exceed 88mW for the entire chip in addition to 22mW from each individual gate?


texts: I have set up a circuit similar to the one here. I was wondering instead of the 10 uf 50V capacitor, would A 100 uf 16 V or a 47 uf 6.3V capacitor work? I am asking because I don't know how much kickback into the hbridge there is. I know there can be enough to damage it, but how much is that? Also, how would I determine the amount of current used by a 4v motor?


texts: How to connect an Arduino to a STM32F4 evaluation board?

texts:
I have a few Arduino and sensors on Arduino shields. I also have a STM32F4 Discovery evaluation board. For a hobby project, I have a feature on an Arduino (Ethernet port on my EtherMega) that I would like to use from the STM32. The STM32 can generate VGA signal, but needs a connection to my local network.

How can I transfer information between these two boards, and what additional components are required ?


texts: How to connect a home to the government electrical network

texts: I want to connect my home to the government electrical network, I used twisted cable, my home is 200m meters from the nearest electric pole. How do I calculate the twisted cable section?


texts: Replacing an analog pot with a digi pot in a flying drone controller

texts: I'm working on a project at the moment and I'm supposed to change the analog pot on the controller with a digi one. My question is does installing the digi pot changes anything in the controller circuit that requires to fix the interface between the digi pot and the controller or the controller and the drone. Thanks!!


texts:
Can a trim-pot wiper or contact point gets oxidized over time? For example when a potential (high) current is flowing and the contact point of the wiper on the resistive element heats up a little. I don't mean hot, just a little warm because of resistance. The effect takes years before it will be noticable.

For example this trim-pot, it is connected to a laser (CD-player).

After years of working properly, most of the time when the wiper is moved, just a fraction, the laser will work again. Maybe it works again because more current is flowing and boost the laser diode (above limits), however could it be possible that previous position was oxidized (by heat and vaporization of something - maybe resistive element, carbon, vaporised by heat), the resistance increased (a thin film is formed on contact point) and because of this the laser is reduced in power. So the laser is not in bad shape, the pot is in bad shape and caused the problem.

A couple of months ago I have taken apart some equipment and on the lid I discovered some black dust/dirt (?) positioned above elements that heating up when operating. I don't know where the black dust came from or what it is however it is caused by components that produces heat.

So I wonder if this is possible inside a trim-pot when it produces some heat, does the contamination (vaporization of something) cause malfunction/changes the value of the pot. Is this possible?

This is all curiosity, it is nice to know.


texts: What does "CL" stand for in this processor architecture block diagram?

texts:
I'm learning about pipelining but can't understand this abbreviation: "CL". You can see it in processors' schemes.

It is shown with with and without a line above it; what is the line for?

Diagram taken from here http://lgjohn.ecen.ceat.okstate.edu/4243/lectures/unpiped.pdf - page 3.


texts: Why does each device have two SMBus addresses?

texts:
I am working on PMM240 (a power management board for RRC battery) with RRC2054-2 battery.

First when I only connect PMM240, the manual has address 0x20, but when I scan the port, I have two addresses, 0x20 and 0x21.
If I connect the battery, in addition to 0x20 and 0x21 for PMM240, I also find 0x16 and 0x17 for the RRC battery.

When I do transmit or receive command, shall I stick to one address? By default the first address?


texts: The relay controller circuit in a pre-amp stopped working properly

texts: I have a pre-amp with a controller circuit which controls input signal micro-relays and a power supply relay. While the input signal micro-relays work normally, all of a sudden the 30 second delay for the power supply relay stopped working, in other words, the power supply relay connects as soon as I hit the power switch, without any delay. The unit worked perfectly for a long time. It was recently re-capped and worked normally for a while. Attached is the circuit schematic. Any help would be more than appreciated.


texts:
This part with a "B1" on it is in series between a FET and it's load, I'm trying to figure out what it is.  This is on a e-bike display that should get up to 85V.
While I don't know if it is normal (this unit has failed), these components measure 0 ohms.


texts: Can you reduce audio noise by decreasing input impedance with a resistive load?

texts:
First asked this over at sound stackexchange but they pointed me over here as a better place for it.

A general question but inspired by a specific example so framed as such.

I have powered studio monitors attached to a computer's unbalanced headphone port, and there is some amount of underlying noise, either from the computer's DAC or induced along the unbalanced cable or some combination. Overall not particularly surprising. With headphones plugged in instead, I don't hear the same noise at all.

My thought is that the likely cause of this difference is that the headphones, being a relatively low impedance load (64 ohm in this case) act to short out the noise so it's not heard. Basically the noise, wherever it's coming from, isn't strong enough to drive the headphones' drivers enough to be audible.

When the powered speakers are plugged in instead, they have a very high input impedance that then goes into their amplifiers (10k ohm). Now the same noise can drive the input easily, and is then amplified and played through the speaker.

So, the question is, if I were to put a resistor in parallel with the speaker input, or even plug the headphones in in parallel for that matter, would this decrease or eliminate the noise? Am I thinking about some part of this wrong?

thanks!


texts: Is it possible to use multiple LTM8049 in parallel?

texts: Is it possible to use multiple LTM8049 Dual SEPIC or Inverting μModule DC/DC Converters in parallel in order to further reduce noise, increase output current, and spread heat on the PCB? It is possible for more conventional regulators like the LT3045, but I could not find any such reference for a μModule.


texts:
I'm trying to get a CPS03631BR 3 digit 7 segments LEDs to work. I've wired it to my Arduino UNO like this:

And I'm using this code, which should light all the LEDs digit-by-digit, then light everything:

// Diagram: http://search.alkon.net/cgi-bin/pdf.pl?pdfname=13600.pdf
const int digit[] = { 9, 10, 11 };
const int led[]   = { 2, 3, 4, 5, 6, 7, 8, 12 };
                  //  a  b  c  d  e  f  g  dp

void setup() {
  for (int i = 0; i < 3; i++) {
    pinMode(digit[i], OUTPUT);
  }

  for (int i = 0; i < 8; i++) {
    pinMode(led[i], OUTPUT);
  }
}

void lights_off() {
  for (int i = 0; i < 3; i++) {
    digitalWrite(digit[i], LOW);
  }

  for (int j = 0; j < 8; j++) {
    digitalWrite(led[j], HIGH);
  }
}

void light_digit(int number) {
  switch (number) {
    case 0:
      digitalWrite(digit[0], HIGH);
      digitalWrite(digit[1], LOW);
      digitalWrite(digit[2], LOW);
      break;
    case 1:
      digitalWrite(digit[0], LOW);
      digitalWrite(digit[1], HIGH);
      digitalWrite(digit[2], LOW);
      break;
    case 2:
      digitalWrite(digit[0], LOW);
      digitalWrite(digit[1], LOW);
      digitalWrite(digit[2], HIGH);
      break;
  }
}

void light_num(int number) {
  switch (number) {
    case 0:
      digitalWrite(led[0], LOW);
      digitalWrite(led[1], LOW);
      digitalWrite(led[2], LOW);
      digitalWrite(led[3], LOW);
      digitalWrite(led[4], LOW);
      digitalWrite(led[5], LOW);
      digitalWrite(led[6], HIGH);
      digitalWrite(led[7], HIGH);
      break;
    case 1:
      digitalWrite(led[0], HIGH);
      digitalWrite(led[1], LOW);
      digitalWrite(led[2], LOW);
      digitalWrite(led[3], HIGH);
      digitalWrite(led[4], HIGH);
      digitalWrite(led[5], HIGH);
      digitalWrite(led[6], HIGH);
      digitalWrite(led[7], HIGH);
      break;
    case 2:
      digitalWrite(led[0], HIGH);
      digitalWrite(led[1], HIGH);
      digitalWrite(led[2], HIGH);
      digitalWrite(led[3], HIGH);
      digitalWrite(led[4], HIGH);
      digitalWrite(led[5], HIGH);
      digitalWrite(led[6], HIGH);
      digitalWrite(led[7], HIGH);
      break;
  }
}

void loop() {
  digitalWrite(led[0], LOW);
  digitalWrite(led[1], LOW);
  digitalWrite(led[2], LOW);
  digitalWrite(led[3], LOW);
  digitalWrite(led[4], LOW);
  digitalWrite(led[5], LOW);
  digitalWrite(led[6], LOW);
  digitalWrite(led[7], LOW);

  digitalWrite(digit[0], HIGH);
  digitalWrite(digit[1], LOW);
  digitalWrite(digit[2], LOW);
  delay(500);
  digitalWrite(digit[0], LOW);
  digitalWrite(digit[1], HIGH);
  digitalWrite(digit[2], LOW);
  delay(500);
  digitalWrite(digit[0], LOW);
  digitalWrite(digit[1], LOW);
  digitalWrite(digit[2], HIGH);
  delay(500);
  digitalWrite(digit[0], HIGH);
  digitalWrite(digit[1], HIGH);
  digitalWrite(digit[2], HIGH);
  delay(500);
}

But instead what I'm getting is this:

http://www.youtube.com/watch?v=cOB-JGoO-fg

When it should be lighting all the digit it's doing a 9 with a dot. When it reaches the third digit nothing happens. When all the LEDs should be ON it's displaying 33 and the third digit is completely OFF. I've tested each LED individually and they all work.

Any ideas?


texts: Excitation current calculation for alternator

texts:
I have an old brush alternator where field excitation happens in the stator. Unfortunately no information is given about the required field excitation current.

The alternator is rated 3 Phase, 400V, 11.5A. The field winding has a resistance of 8 Ohm.

Given these specifications, please help to find a suitable automatic voltage regulator. What maximum current should an AVR be capable to deliver?


texts:
I've been reading about a USB style true random number generator called BitBabbler.  The following screen shot is from a section (linked above) explaining how the device works.  It's been designed by a group of engineers.  It apparently uses 11.5 billion electrons to produce a random 3.3V signal.  There's even a 'scope piccy of it working.  Strangely there is no schematic though.  Hmm.

Does anyone have the faintest idea of what an analogue shift register is or how they work?  I suspect that this might be waste from a Bos taurus. Thing is, they sell these...


texts: I2S Connections - MEMS Digital Microphone, CODEC, and Raspberry Pi Zero W

texts:
I have a MEMS Digital Microphone with PDM output. I am planning to use this:

http://www.st.com/content/ccc/resource/technical/document/datasheet/57/af/88/31/7b/59/4f/77/DM00111225.pdf/files/DM00111225.pdf/jcr:content/translations/en.DM00111225.pdf

Based on my research, PDM output signals have high-frequency ranges; usually in MHz. To be further processed, it must be filtered/decimated with the use of CODEC. I am planning to use the WM8731:

http://www.cs.columbia.edu/~sedwards/classes/2008/4840/Wolfson-WM8731-audio-CODEC.pdf

Based on the datasheet of the digital microphone, typical connection is as follows:

However, I do not exactly know as to what exact pins on the WM8731 CODEC do the Digital output of the mic to be connected, and also the clock signal. Can anyone help me out with this?

Also, I understand that the Raspberry Pi Zero W can communicate with the CODEC via I2S. And to do so, I must utilize the SPI pins of the Rpi. However, still same questions arise as to what exact pins on the WM8731 CODEC should I connect the SPI signals to.

Thanks.


texts:
So I'm just getting my feet wet with CPLDs, in fact I programmed a chip successfully for the first time last night (success being programming it with the correct program, not the one recovered from it which is what I think I did the day before), and I got an output pin set to high meaning I can light an LED (with appropriate resistor).

Then I wanted to make it flash, and set about using the internal oscillator. I'm using Quartus Prime, and found the oscillator and tied it to an input pin that I left unassigned for the OSCENA, thinking that would default high. I fed that as the clock into a 74xx counter and used the high bit to drive the LED, but no joy.

how do I ensure a wire is high in the schematic builder?

From research this seems to be quite easy using Verilog or VHDL and found examples, but I am a software developer so doing so holds less interest for me as for such a simple use case it boils down to something akin to a for loop.

This is what I've cooked up so far, using the guide available here to make the oscillator available:

The guide says "make a wire, give it a logic value of 1" and that doesn't seem possible here, though I checked the Verilog provided and it seems they're basically hooking up a switch, so I did the same.

From what I understand the 7457 is 1:60 frequency divider, and I know that even dividing this oscillator's clock by 60 isn't going to help on the human scale, I thought I'd see something when running a simulation, but that seems to not be the case.

Simulation setup:

And the result, showing the clock output as "unknown" (too fast?!) and the LED as logic low.

So, any pointers on what I'm doing wrong?


texts:
I take the function \$ \sin(2 \cdot \pi \cdot f \cdot t) \$.

with \$ f = 1 \$

And plot it in excel with sampling frequency fd = 4,10

Why there is a low frequency?


texts:
I'm using a MOSFET to switch a 24V, 15A load, with the gate input being a 500Hz PWM signal. However, this is causing the MOSFET to overheat and blow. Any suggestions would be appreciated.

R1 = 100 Ohm

R2 = 1000 Ohm

Q1 = IRL3103PbF (Vdss = 30V, Id = 64A)


texts: How do I calculate the voltage needed to heat up a wire to a certain temperature?

texts: The wire I am using is standard temp. nitinol wire which needs to be heated up to 45 degrees Celsius in order to be effective (move). What voltage do I need to achieve this?


texts: Ways to thermally manage a small enclosure?

texts:
hopefully this is an okay place to ask this question, but anyway, I'm working on a project to measure efficiency of a mono-crystalline solar cell based off temperature in the enclosure. The solar cell is 150x130mm and the enclosure will match that size and be a bit taller so I can introduce a light source. My first plan for increasing the temperature beyond ambient temperature was to use either a heat-gun or a hair-dryer. I have a thermal sensor to see the temperature inside as it increases, but I'm wondering what other options I have to more effectively control the temperature in this small enclosure. I would like to increase the temperature to at least ~50 degrees Celsius, and on the other end possibly 0 degrees celsius, which would likely require a different tool. I've also thought of using a small Thermoelectric Cooler in order to cool down the environment, as well as heat up, but that requires a bit of setup so I'm not sure what other options I have.

TL;DR: What can I use to heat (and / or) cool a small insulated box?


texts: What is the resistive humidity sensor working principle in DC vs AC?

texts:
I have to make a weather station project using the PIC16F887 uC, powered with 5V DC, and it is mandatory to have an analog humidity sensor conditioned with a circuit using opamps (up to 3). I was thinking to use a resistive type, like the HR202 (datasheet), in a voltage divider with an upper resistor, and a non-inverting amplifier between the sensor voltage drop and the analogic pin of the uC. Or I have the option to use a transducer bridge with a differential amplification.

I have several questions. In what case do I need to amplify the voltage and how to choose the upper resistance value? I ve seen that the impedance starts from 10M down to a few k-ohms, on 1 kHz and 1 V sine AC.
Also, if I use this sensor in DC (in datasheet says 100% AC), but theoretic, what if I will supply it with DC? The 'impedance' curve will still be available or it will change due to polarization? How much it will be the measurement error? There was no specification on what should I use AC or DC.

On the other hand, how can I make an AC signal using the uC to measure correctly from the sensor? The PWM signal will do the job?

Thank you!


texts:
I am having a slight problem with the above circuit.  I am driving the "set" side of a latching relay with either the input of pin D5 from an ESP8266-12E or from a data pin from a HT12D attached to a RF receiver.
When I activate the D5 pin using Blynk the Transistor (2N222) "sets" the relay turning off that ESP and turning on another ESP which does its thing and then activates its D5 pin "resetting" the relay turning it off and turning back on the original ESP.
This works great every time.
However when I "set" the relay using the HT12D sometimes the ESP "resets" the relay and sometimes it doesn't and gets stuck continuously looping through its code.  The strange thing is that usually it works fine when the transmitter and receiver are in close range of each other (5 yards) but at longer distances (15 yards) the ESP does rarely "resets" the relay.  I have tried replacing R2 with a 100K resistor and a 4.7K resistor.  Neither helped, in fact with the 100K it never "reset" even with the Blynk ESP.
Should I try using a different R1 resistor for each input before D1 and D2 or is there a value for R2 that would work as it is set up now.
I don't think it is the code as it does resetting.
Does anyone have any suggestions?  I am not an electrical engineer, just putting thing together from what I can learn from places like this. So any and all help would be appreciated as well as an explanation (keep it simple for me please)
Thanks.

would this be how I would wire in the second 2n2222 for the ESP 8266-12E.  This shouldn't cause any problems?


texts: Alternative to AM and FM transmitting for data transmission?

texts:
So, I need to communicate wirelessly between a micro-controller and my computer. I'm building a radio receiver circuit, and a radio transmitter circuit that works on FM transmission. However, I had an idea.

I'm just transmitting binary. The receiver will go into the micro-controller's UART lane. If I'm transmitting serial data, wouldn't it be easier to simply transmit a specific un-modulated frequency that represents a one, then design the circuit to accept no radio transmission as a zero?

Then the micro-controller program could simply seek out combinations of one's and zeros that it recognized as bytes?

Is there a downside to this that I'm not thinking about? Is there already a name for this kind of rf data transmission?


texts: On the LM386 opamp Module, why I am getting an output without giving input

texts:
I am using an LM386 opamp Module from Amazon. I am powering it with a 5V input (just to power it, not intending to amplify anything at this point). Nevertheless a multimeter measures an amplified output of around 1v-2v.
When I put an actual input that I want to amplify nothing really changes. Why I am getting an output without giving input?


texts: Arduino Pro Micro clone: connect USB and RAW power at the same time?

texts:
I have fried two Pro Micro clone boards that are the same as the ones discussed in this post: Are these two Arduino Pro Micros jumpered correctly?

They are 5V/16MHz models which came with SJ1 open so I naively shorted out the SJ1 jumper with a solder bridge to match what the SparkFun open hardware schematic notes state - that SJ1 should be closed for 5V and open for 3.3V.

They worked fine on USB power but when I connected +12VDC to RAW while leaving USB connected, the USB host computer shut down the USB port and the Pro Micro boards no longer work: when connecting just USB, the green power LED turns on for a few seconds then fades out (since the polyfuse is in overcurrent mode and shuts down). One reads 4.4 ohms from VCC to GND and the other 6.6 ohms so it seems that the Atmel chip is blown.

This doesn't make sense to me. There is a protection diode between RAW and UVCC which prevents over-voltage going out the USB. Why are the boards damaged now? Even with SJ1 bridged, the worst case is feeding back the 5V from the regulator output through the polyfuse into the USB power pin which shouldn't damage either the USB port nor the Pro Micro which is still isolated from RAW by the diode.

Ultimately it needs to run on external power alone without USB connected at all. During code development I would like to connect and disconnect USB as required, leaving external RAW power connected otherwise I won't be able to debug with the IDE's serial port monitor over USB. RAW external 12VDC is used to power the Arduino as well as other peripherals using the Arduino's onboard regulator. RAW power is DC and not AC since it's a wall-wart style PSU. Polarity was correct since RAW was already used to power peripheral and just the + jumpered to the RAW pin.

Since these are the 16MHz version, they need at least 4.5V for guaranteed operation. Therefore, logically, the regulator is a MIC5219-5.0V to generate 5VDC. It needs about 5.5V on input to work, plus diode drop of 0.2V (Schottky). I don't see how it would work on USB power alone. I measured 5.1V on UVCC and 4.9V on the other side of the diode as expected. Since I had solder-bridged SJ1, UVCC was bypassing the regulator and powering the whole circuit.

On one board I get 0.22V across D2 using diode mode on my DMM and 0.97V in the reverse. On the other board I also get 0.22V forward drop on D2 but 1.2V in the reverse. I unsoldered the bridges across SJ1 on both boards.

It seems the regulators may be blown as I get nothing on VCC with 12VDC applied to RAW input.

I've got a few more on order and don't want to fry them all as well. Plan of attack for new ones is to NOT solder-bridge SJ1 and try with just USB. I suspect they won't work as the regulator will not have enough to work with. Then I'll try with 12VDC on RAW and see if one of them survives. Maybe having SJ1 bridged caused the problem.

Additionally, reading the datasheet for the MIC5219 reveals that these are lightweight power handlers. In fact, I don't think they can handle 12VDC input at all as the power dissipation requirement goes beyond what the SOT-23-5 (M5) package is rated for. Most of the calculations on the datasheet show a paltry 6V input for >150mA operation! I think I should reconsider my design approach and feed the whimpy Arduino Pro Micro with an external regulated 5V VCC directly.

What have I missed? Any other thoughts?


texts: Current limiting for at the input side of the transimpedance amplifier ( photodiode protection)

texts:
So I've used the standard trans-impedance amplifier to sense the current of a photodiode. The photodiode is unbiased.

https://en.wikipedia.org/wiki/File:TIA_simple.svg#/media/File:TIA_simple.svg

I went through the Spice simulations to calculate the stability and the value of the compensating capacitors I need and then I did the analog testing and then I made the pcb and it all works as designed.

However I encountered a possible failure mode that results in blowing the photodiode ( I did blow a test one) and I can't afford for that to happen ( there are 25 embeded photodidoes in a part that I can't replace easily and can't afford to).

I'm using a power supply (+-15V and ground) and if for whatever reason one of the power supply rails fails (simplest example is the +15 gets unplugged by mistake but originally I had a faulty power supply that resulted in this) the photodiode sees across it's terminals either + or - 15 V depending on which rail was unplugged (possibly 30 V ? if the ground cable is the disconnected ones?).

Either one of these ( 15V of forward or reverse bias) kills my photodiodes.  As I said I have made my pcb so I don't have much space to implement some sort of current limiting. I considered fuses but I think they might be too slow or if I rate them low and the current peaks when the photodiode is illuminated by a particularly large source and it blows it would create the same failure mode as if I were to unplug one of the rails.

Anyone has any experience with this sort of problem ? The possible ideas I'd found so far are:

use a voltage regulators with a resistor to limit the current ( essentially becoming a current source)
www.ti.com/lit/an/sbva011/sbva011.pdf

use some sort of current limiting circuit after the power supply.
www.radio-electronics.com/info/circuits/transistor_current_limiter/transistor_current_limiter.php

Obviously I'd need two on both + and - side, but I'm not entirely sure how they would behave.

Any suggestions or advice is more than welcome.

P.s. links are not links since I don't have the rep to post links ...


texts: Few days ago I got sample of toroidal core from my friend. I don't know any technical details of core just know OD-10cm, ID-6cm, height- 5cm and wet about 1.845 kg(M4 grade CRGO). I want to make toroidal transformer using this core but how to calculate core area and maximum VA capacity of core.I take some photos and attach.


texts:
I'm trying to wire up the LM324 using only op amp 1 to amplify a 0-5v input to 0-12v scale. I found I need to use a 7/5 ratio for the resistors on my negative feedback loop. I get the theory, I even built the circuit on a simulator and works fine, but I can't seem to hook it up right on my bread board.
Here's the LM324 Pin Diagram:

Here's how I've hooked it up right now,

VCC -> +16V.
GND -> 0v.
Input 1 +  -> 5v.
Input 1 - -> 33K-ohm Ressistor -> GND
Input 1 - (again) -> 47K-ohm Resistor -> Output 1
then Finally, Output 1 -> LED Strip (Expecting 12 Volts here, but getting nothing).

simulate this circuit – Schematic created using CircuitLab


texts: How to wire LEDs and CR2032 battery to make it work

texts:
I've got a problem and it seems that there is an issue with understanding electronic's fundamentals.
I've got inspired by Jiri Praus video
I am trying to make this Rabbit-shape circuit to work.

What I have:

0.8mm brass wire,(black lines on a picture)
1206 SMD LEDs, (tried to draw them in Photoshop, to show where exactly they are placed on a pic)
coin cell battery CR2032 (grey round thing which is held in place with a wire that should touch opposite pole of a battery)

What I do:

I use multimeter to make sure that LED working (it lights up)
Solder two wires to each LED's pads and check it with multimeter again (it works)
Solder Led with two wires into the whole "circuit" - NOT working
Solder a wire to the circut in a way that it would keep battery from both sides - NOT working

So I have an issue with step 3 and 4. I believe it's because I don't know how electricity flows.
Troubleshooting steps that I've already tried:

I've bought flux to make connection more solid
I tried all these steps with a wire that is used in USB cable
I tried to not to solder one of wires that goes to soldering pad - when one end is not soldered to circuit - it works. Once soldered - stops working.

What I would like to ask you for:

Please advise what to read in order to have a better understanding in terms of electrictiy
Please advise on how to fix the issue that I have faced (should all LEDs be pointing by the same pole toward the battery?)
Any comments would be highly appreciated.


texts: Is diode reverse recovery time related to diode capacitance?

texts: The title. Is there some relationship between the two parameters? For example, fast diode recovery time indicates low capacitance, or even farther, can one be calculated from the other? Thank you in advance.


texts:
I had a look to other posts about Triac and I am pretty sure my problem was not in there.

The goal of my system is to realized a controlled switch for home appliance. Then I designed a power supply system (non isolated) that supply energy to my microcontroler (STM32F030C8T6). It is all working fine.

I would like to controlled a triac (NXP BTA316-800E) with one of the logical output of the STM, then I realized this circuit:

NOTE: The earth symbol is a mistake, it is a 0V point of the circuit.

As I would like to control every types of appliance I add a snubber circuit for inductive load.

To turn on the applicance I set the STM32 output (logic 1 : 3.3V), and I clear this output to turn off the appliance (logic 0; 0V). This ouptput is a push pull type.

My problem is : The appliance is always ON. I can see that logic levels are well applied (at the output of the STM32), however, here is what I get at the Triac gate, when output is 0:

I guess the short 1.8V spikes keep the triac on, but I don't know why these spikes are present.

Anyway, I tried to remove R2 and tied T1 gate to ground in order to be sure that no current is flowing through but the appliance is still on.

Do you have any idea?

Thank you very much.

IMPORTANT: This circuit is dangerous (deadly) as you deal directly with main power. All care has to be taken to experiment.


texts: These things called binding posts came with my breadboard. How am I supposed to use them? Should I screw them into the back plate?


texts: Dynamically dimming individual LEDs in a lighting system

texts:
I'm planning to build an aquarium lightning system with individually controllable LED's, I don't have much experience with electronics except from the irregular tinkering, but I'm a programmer and I think I'll be able to put something decent together.

The system will consist of about 30 * 3W LEDs, I already have those as well as heat-sinks, lenses, thermal glue and a couple of PWM-boards similar to this. My initial plan was to build some kind of simple transistor switch between each individual LED and the power supply, a switch that I could control with the PWM-board, which in itself is controlled by an arduinio/raspberry pi.

Then I read on and discovered that LEDs are supposed to be current regulated, not voltage regulated. So now I'm not sure about how to move on.

I've considered just buying a bunch of individual constant current drivers like these, but I don't see how I'd be able to pwm those properly. (I realized that most of my LEDs aqually are in the 700mA range instead of the 300mA that I first thought, now it's starting to get unreasonable expensive to buy one of these for each single LED, in an otherwise quite cheap system...)

What I really would need is some kind of variable current driver, from between 0(?)-800mA (I've understood that very dimmed LEDs draws very little current, so I need a big range there), that I can control with pwm, but that does not seem to be a thing I can buy like the regular constant current circuits.

Any ideas? I've considered to buy a current sensor for each LED and to use this data to properly modulate the individual LED's myself. But I'm not sure I can find some that reliably can measure the low currents that I need. Or does the spec sheet for that MAX471-chip really say that it has a resolution of 0.5 mA per A (Current-Sense Ratio)?

Clarification on functional needs

I need a lot of light in order for the plants in the aquarium to thrive. I need as much white light as I can get from each watt.
I want to be able to control the light in aspect of intensity as well as tone/temperature (I have different temperature LED's).
I want to be able to control exactly what parts of the tank are lit and how those parts are lit. E.g., I want to able to simulate similar dynamics as to clouds passing by or lightning, or just to selectively light certain parts of the landscape.
Not critical but valuable: Scalability. The ability to easily to add or remove LEDs.


texts: M2P DMA transfer with trigger from a different peripheral

texts:
The microcontroller on my board is STM32F429IGT6 and I want to use a timer as a trigger of a DMA -e.g. HTIM_SOUND_SAMPLER- and transfer my data from an array to CCP of another timer -e.g. HTIM_SOUND_DC_MAKER-.

HAL_DMA_Start(HTIM_SOUND_SAMPLER.hdma[TIM_DMA_ID_UPDATE], (uint32_t)dual_sine_12bit, (uint32_t)&HTIM_SOUND_DC_MAKER.Instance->CCR1, 32);

/* Enable the TIM Update DMA request */
__HAL_TIM_ENABLE_DMA(&HTIM_SOUND_SAMPLER, TIM_DMA_UPDATE);

Consider htim2 as HTIM_SOUND_DC_MAKER.

When I define htim8 as HTIM_SOUND_SAMPLER there will be no problem.
But when I change HTIM_SOUND_SAMPLER to htim3 it doesn't work as I expect.
The reason I do this is that I want to use DMA1 so I have to use htim3 instead of htim8.

Is there anything I missed? why does it happen?
Is it possible to use one peripheral as the trigger and another one as the destination or source? If not, then why when I use htim8, it is possible?


texts: Is the voltage from peak to peak my thevenin in voltage?

texts: I used a function generator and set it to 1kHz. And used an oscilloscope to measure the time constant of an rl and rc circuit. my question was that what would I consider as Vth or voltage thevenin , is it the Vpeak-peak or Vpeak?


texts:
I'm designing a small system that uses an ATMEGA328P and a LoRa module that runs on 3.3V using a AAA 1.5V battery. The battery is connected to a Boost Converter which steps up the 1.5V to 3.3V to power the entire system. So obviously the whole system needs to have a low power consumption to save battery power. I want to attach a push button in the circuit that displays the battery level when pressed through LEDs.

The LED indicators are as follows.

Green LED  - V_Bat > 1.4V
Yellow LED - 0.9V < V_Bat < 1.4V
Red LED    - V_Bat < 0.9V

Here is the design of my circuit using the following components

Voltage Regulator - TPS61221DCKT
SCHOTTKY Diode - STPS1L30A
Analog Comparator - TSX393IYDT
XOR Logic Gates   - 74AC86SC
Green LED - KP-2012LSGC
Orange LED - KPT-2012LVSECK-J4-PRV
Red LED - KPT-2012LVSECK-J3-PRV

simulate this circuit – Schematic created using CircuitLab

Here are my questions.

Will the circuit work?
Will the components I picked out worked? (I picked components that are all low power)
Are there any necessary resistors or passive components needed in the circuit to limit current anywhere?
In my voltage divider, how high can I set the resistors to reduce power consumption before it starts giving problem?
Any suggestions to improve the circuit?

Thanks for the help in advance and sorry for the many questions


texts:
I got this problem:
A transmission system is composed by an amplifier and the antenna. The transmit amplifier has an available power of 2mW and a resistive impedance of 10Ω. The antenna (in series with the amplifier) has input impedance given by a series of a resistance R=10 and an inductance L=31.8nH. Evaluate the power on the antenna assuming the impedance content over the bandwidth of the signal. Signal has f=100Mhz

simulate this circuit – Schematic created using CircuitLab

This is the schematic. The signal input is a QPSK modulated signal.

Now, in this case, we are not in the maximum transfer of the power on the load because, clearly, the impedances are different.
The exercise says the answer is 1mW but, if I apply the formula \$P_{L}=P_{in}\tfrac{\left | Z_{L} \right |^{2}}{\left | Z_{L}+Z_{in} \right |^{2}}\$ the result is different.

How should I proceed?


texts: Varying performance of mbed, depending on Power Supply

texts:
I've written a very basic program (without the mbed library) to turn on all LEDs on an mbed board (https://os.mbed.com/platforms/mbed-LPC1768/):

#include "lpc17xx.h"

int main (void)
{
    SystemInit();

    LPC_GPIO1->FIODIR = 0xffffffff;         // P1.29 = Outputs
    LPC_GPIO1->FIOCLR = 0xffffffff;         // Turn-OFF LED

    //Loop LED Test
    while(1)
    {
        LPC_GPIO1->FIOSET = 0xffffffff;     // Turn-ON LED

    }
}

I initially ran the program on the mbed using the standard USB connection, and it worked perfectly, with all LEDs lighting up.

Conversely, when I powered the mbed using a 5v supply (http://www.hobbyandyou.com/adraxx-33v-and-5v-power-supply-module-for-mb102-bread-board), the LEDs light at a lower brightness, and flicker, occasionally switching off briefly.

Naturally, I suspected there was a problem with the 5v supply, but I tried re-writing the program to use the mbed library, and it worked perfectly with the 5v supply (identical brightness, no flicker, etc):

#include "mbed.h"

DigitalOut myled(LED1);
DigitalOut myled1(LED2);
DigitalOut myled2(LED3);
DigitalOut myled3(LED4);

int main() {
    while(1) {
        myled = 1;
        myled1 = 1;
        myled2 = 1;
        myled3 = 1;

    }
}

Based on this, I can only suspect that the original code is somehow not playing nicely with the external supply. Can anyone explain what's happening? I'm completely stumped.

Note, the original program was compiled with MCUXpresso.


texts: where did laws like distributivity and DeMorgan's come from?

texts:
I am asking about the laws of logic gates.
so for example,
if we have an input A, and input B, like this:

A'&B' + A'B

with the law of Distributivity, an equivalent circuit would be:
A'&(B'+B)

which is true, but how did they figure that one out?  Did they just keep experimenting and found the property by accident?


texts: STM32 - Clock signal generator using a timer - STM32CubeMX generated code

texts:
I am trying to generate a clock of 1.4 MHz using the STM32F103C8Tx using STM32CubeMX.

First of all, in my code I have pin PB13 as output and in main I toggle it every two seconds. This works.

Now the more important part. Things I have set up in CubeMX:

I have set up the base clock of the device to 28 MHz.
TIM3 Channel2: Output compare CH2 PWM Generation CH2
Internal Clock
Timer3:

I have compiled the generated code in the IDE from OpenSTM32 and uploaded it. The LED is blinking at the set interval, but I have no output on the pin B5 A7 (Timer3 channel 2). This is verified on the oscilloscope.

Code(main):

int main(void)
{
  HAL_Init();

  SystemClock_Config();

  MX_GPIO_Init();
  MX_TIM3_Init();

  //These two lines were manually added
  HAL_TIM_Base_Start(&htim3);
  HAL_TIM_PWM_Start(&htim3, TIM_CHANNEL_2);

  while (1)
  {
        HAL_GPIO_TogglePin(GPIOC, GPIO_PIN_13);
        HAL_Delay(5000);
  }
}

The rest can be found here.


texts: Determining resistor values for common source amplifier

texts:
I want to design a Common Source Amplifier. I will be using an lnd_150 datasheet.

I need to get the most gain out of the mosfet, as it will be used with a potentiometer before to adjust the gain.

The lnd has ID.min=1mA ID.max=3mA, I will set it to 2mA (I follow this formula [Idq= (Idmin + Id max)/2]). Then I understood this :

Rd=320V/2mA=160K

I have read (Allow 1/3VCC across Rd, Vds and R2):

VDD=320V/3=106.7V

Since I use 2mA : Rd=106.7V/2mA=53.4K

R1=160K*66%=106K
R2=160K*33%=54K

Then I am lost because now it seem I have to make Rs 160k, to have amplification.
On another link here I have read you need to determine Vd and Vs before Rd and Rs. Now I am really lost, I someone could explain me step by step how to do it, I will be grateful. Thank you.

simulate this circuit – Schematic created using CircuitLab


texts: Too low voltage on digital input on attiny45

texts:
I'm using one of my attiny's pins as digital input. I am using a 2k2 pulldown resistor on the input. I am applying a simple square wave generated by a separate waveform generator. The high state for square wave is 5V, low is 0V.

However, when I look at the voltage on the digital input, voltage of high state is below 2V, while low state is 0V. My arduino doesnt detect high state as "1".

Does anyone has any idea why is it so?


texts: Is there any limitation in how quickly/often I can change a 6V DC motor direction of rotation?

texts:
I have a 6V DC motor, which needs to change rotation direction every 5 seconds or so.
The motor is powered and controlled by an Arduino. Arduino is providing approx. 8.5V and I'm using PWM control to lower the average voltage to approx. 2.5V, which is giving me the motor RPM I need. Motor is similar to this one (micro gear motor) and I discussed the suitability of PWM in this thread.
This motor was previously running for a long time on a bench DC power supply. But when I started it using Arduino it stopped working after less than two days. When I connected it again to DC supply it started working normally, across a range of voltages. So I don't think there is a mechanical failure.
I'm now troubleshooting what went wrong. While I'm checking my Arduino control code, I also wanted to ask if you can think of anything electr-mechanical that could go wrong with this setup (I'm not an electrical guy). The control sequence is very simple - a loop that will issue direction change command at set interval. So I'm thinking about windings, impendance, current, or whatever. By all means, you're free to have a laugh at my silliness but please bear with me. I's appreciate any advice.
Thanks!


texts: PIC18F44K22: Can't use MCLR/RE3 pin as input. MCU resets when RE3 is held down

texts:
I'm trying  to use the 4-bit wide PORTE on a PIC18F44K22 MCU. This port contains the RE3/MCLR pin which can be configured as a reset pin or as an input pin by setting/clearing the MCLRE bit on CONFIG3H.

No matter what value is set on the MCLRE bit, if the RE3/MCLR pin is held LOW, the MCU refuses to execute any instruction. Setting the RB3/MCLR pin up and the MCU works as expected (with one less onput pin).

This has been tested using a pickit 2 programmer and a multimeter, powering the MCU with the programmer itself. power pins on the MCU are decoupled using 1pF capacitors and an aditional 22uF capacitor on the board power input.

BOR is disabled and the program loaded is as simple as it can posibly be (set RB3 UP). Tested using both 5V and 3.2V

I have read of ESD ocasionally triggering resets but in this case is a low value keeping the device on reset.

Solution:
For MCLRE to have any effect, LVP bit must be disabled. In gpasm:

    CONFIG MCLRE  = INTMCLR
    CONFIG LVP    = OFF


texts:
For the code, which I am referring following is syntax:

Write_Parameter(0x00);

In above line, what does "x" stands for and what is data size for x?  My assumption is its dec format.

So, What other format, we can use?

Thank you.


texts: What is simpliest possible guitar active preamp design

texts:
I want to build guitar active preamp inside my bass guitar. It has 2 humbacker pickups (3.4kOhm DC resistance each) for 2 lower and for 2 upper strings, and i want to preamplify each with a separate preamp, so i choose TL072. Let's look at just one pickup.

I draw following schematics, using non-inverting op-amp design:

I have no oscilloscope and i cannot answer how much voltage does produce the coil, but what i want to get is +4dBu (1.737V) line output. So i cannot even estimate required gain. I just suppose it is around 10db, from the external sources. As it also stated in that document, upper scheme has gain of 20*log(1+R2/R1). But there are infinitely many combinations of R1 and R2 which would give me gain of 10dB. You could calculate one if you know the nominal of another.

My question is - how to estimate nominal of R2? I could not find the good basic explanation for that.

Also, being a novice, i appreciate any comment if my schematics is wrong or i miss something, or maybe improve. More passive components introduce more noise and attenuation. And input is well-known. Could we go with a simplier design, soldering the coil directly to the op-amp inputs, since we want just to ampify the difference between coil ends?


texts: RC time constant in astable multivibrators

texts:
I'm having trouble figuring out why exactly \$T=0.693 R C\$ is used for astable multivibrators (and why \$T=1.1 R C\$ for monostable).
At first I assumed this was only used for 555 timers but the same formula is also used with astable multivibrators made with transistors.

Since \$\tau=R C\$, we're basically finding the time it takes to get to 69% of \$\tau\$. The only thing I have figured out is that we are finding the \$T_{1/2}\$ value but I don't understand why. Why is this value used for astable multivibrators?


texts:
Can anyone help my 13 year-old with an assignment? I have little knowledge about electricity and I need to teach her about circuits. We have a question from her seventh grade science book that has us stumped. The chapter is titled "Electric Charges and Currents" and the section from which it comes is titled "Series and Parallel Circuits". The section gives a basic definition for a series circuit and a parallel circuit followed by several questions. The one we are stumped on is written exactly like this:

  Can a circuit be a combination of series connections and parallel connections? Explain your answer.

Any examples would be appreciated.


texts: Modelling grounding reactor as transformer

texts:
First: This is not a question about electronics, it's about large (three-phase) power systems where the components have ratings in kV and MVA. I'm mainly interested in symmetrical components, and how the zero-sequence network is modeled. Although the terminology and simulation tools might differ, the physics should be pretty much the same for small and large components.

I have a three-winding transformer connected YNynd, where the primary side is solidly grounded, the secondary is resistance grounded, and the tertiary winding is delta connected.

In the simulation tool I'm using (PSS/E), three-winding transformers can be modeled, but not transformer with the parameters described aboce. I'm wondering if the following will be a physically correct way to model the system.

Disregard this paragraph (I'll let it be, as this was the original proposal:

If I'm modelling this as a YNdd transformer with solid ground on the primary side, and delta windings with angle 30 deg on the secondary and tertiary sides. Between the secondary winding and the bus on the primary side, I insert a zero-impedance 1:1 two-winding transformer with vector group Dyn where the secondary side is resistance grounded, and the angle reverses the 30 degrees from the three-winding transformer.

New proposal (after Lewis' comments):

Model the three-winding transformer as YNynd1, transformer, with both primary and secondary solidly grounded. Then, I add a 1:1 transformer with the primary side solidly grounded, and the secondary resistance grounded, as shown in the last figure. I'm not sure if the intermediate windings (secondary of three-winding and primary on two-winding should be grounded or not). I can't wrap my head around the zero-sequence equivalent of this (a few years since my university days).

I'm mainly interested in simulating line-ground faults on the secondary side of the transformer, but I obviously want the model to be correct for all other cases. I'm not interested in internal faults in the transformer.

Real system:

Suggested model:


texts: Why there is 625 lines [ PAL ] in T.V. scanning or odd lines?

texts:
I can't get why there are 625 lines in a PAL scanning system.  I read R.R.Gulatti's standard book.  In that there is a reason like:

"Suppose there are x lines in 1 field.  Then for two field its 2x.For 1 field there are 292.5 scanning lines, so for 2 fields there are 2x=292.5*2=585 & 40 other lines ( because of merging effect and all).So 585+40=625."

I searched this on net but I could not find a proper reason for this.  Also in Wikipedia there is no satisfactory answer.

I can't understand why there are 625 lines or odd lines in T.V. scanning.  There is a sentence that mentions that "Scanning lines are always odd" but there is no reason given.

I got this solution is it right?

If you had an even number of lines then all lines must start at the beginning of the frame. If you have an odd number of lines then you will achieve the same resolution on the screen but the half line (the odd line), split in half with half at the start of the second frame and half at the end of the second frame allows for an extra line period in order to flyback vertically.

This "appears" to the human eye to be a better picture. If you think about the lines, they are all sloping so if you use full lines then for a full line scan the area at the top right and bottom left have no data in for a wider area than with half line second frame scan. The missing data area remains the same but is now split into two parts, immediately before the half line starts and at the end of the first half line.


texts: AVR assembly: Most fastest way to increment two combined bytes

texts:
What could be the fastest way to increment two combined bytes in assembler (assuming I'm working on a 8-bit CPU)? Currently I'm doing this:

OVF1_handler: ; TIMER1 overflow ISR

lds r21, timerhl ; load low byte into working register; 2 cycles
add r21, counter_inc ; add 1 to working register (value of counter_inc is 1); 1 cycle

brbs 0, OVF1_handler_carry ; branch if bit 0 (carry flag bit) of SREG is set; 1 cycle if false . 2 cycles if true
sts timerhl, r21 ; otherwise write value back to variable; 2 cycles
reti ; we're done

OVF1_handler_carry: ; in case of carry bit is set
    sts timerhl, r21 ; write value of low byte back to variable; 2 cycles

    lds r21, timerhh ; load high byte into working register; 2 cycles
    inc r21 ; increment it by 1 (no carry check needed here); 1 cycle
    sts timerhh, r21 ; write value of high byte back to variable; 2 cycles

reti ; we're done

So in sum there are

255 * (2+1+1+2) + (2+1+2+2+2+1+2) = 1542 cycles

to count from 0 to 256 (255 times (2+1+1+2) because no overflow plus 1 time (2+1+2+2+2+1+2) when overflow occurs).

Is my calculation correct and is there a faster way?


texts: VHDL: How to double read a register bank?

texts:
We have been tasked with creating a register bank that can dual read, but only single write. At the moment I've got it all working apart from the dual read. Could someone point me in the right direction?

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
use IEEE.NUMERIC_STD.ALL;

entity RegisterBank is
     Generic(N : integer := 16;
     M: integer := 16);
    Port ( CLK : in  STD_LOGIC;
           Din : in  STD_LOGIC_VECTOR(N downto 0);
              ReadNum : in STD_LOGIC_VECTOR(M downto 0);
              WriteNum : in STD_LOGIC_VECTOR(M downto 0);
              ReadEnable : in STD_LOGIC;
              WriteEnable : in STD_LOGIC;
           Dout : out  STD_LOGIC_VECTOR(N downto 0));
end RegisterBank;

architecture Behavioral of RegisterBank is
    Component RegisterN port(
        D: in STD_LOGIC_VECTOR(N downto 0);
        Q: in STD_LOGIC_VECTOR(N downto 0);
        Load, CLK: in STD_LOGIC);
    end Component;
    Type RegisterArray is Array(N downto 0) of STD_LOGIC_VECTOR(N downto 0);
    Signal RegisterSignal: RegisterArray;
    Signal W: STD_LOGIC_VECTOR(N downto 0);
begin
    Reg0: RegisterN port map(Din, RegisterSignal(0), W(0), CLK);
    Gen: for i in N downto 1 generate
        RegN: RegisterN port map(Din, RegisterSignal(i), W(i), CLK);
    end generate Gen;
    RegisterSignal(0) <= STD_LOGIC_VECTOR(TO_UNSIGNED(0, M));
    process(CLK) begin
        if RISING_EDGE(CLK) then
            if WriteEnable='1' then
                RegisterSignal(TO_INTEGER(UNSIGNED(WriteNum))) <= Din;
            end if;
            if ReadEnable='1' then
                Dout <= RegisterSignal(TO_INTEGER(UNSIGNED(ReadNum)));
            else
                Dout <= (others => 'Z');
            end if;
        end if;
    end process;

end Behavioral;


texts: How to setup PCB to correct for signal integrity issues after boards are made?

texts:
I have a board layed like the in the image below. I have a microcontroller that generated clk1, which feeds into U1. After 8 clock cycles, the clock passes through to U2 and does this 30 times. It's a shift register.

The microcontroller generates clk2, which is running in parallel across 30 some components.

I've included a place holder for possible termination resistor at the source pins itself (R1 and R2) so I can maybe experiment with different values to get my signals looking correct, however I do not know if this will work.

So my question is, if adding those place holder resistors is not enough to correct for SI issues, what can I add to the board that can help me correct it after ?

simulate this circuit – Schematic created using CircuitLab


texts: Low speed electric motor (from a blender)

texts:
I'm trying to build a Van der Graaf generator with my little brother for a school project. The thing is we get a electric motor from and old blender and want to use that for power our generator, but the motor is too fast and make vibrate everything around.

I was wondering if there is a simple (and safe way) to reduce the speed, I read that the speed in this induction motors is regulated by the frequency, so the question is: is there a simple (and safe) circuit to lower the 60 Hz ( and 110 V) of the electric network, to say the half of that frequency? Or a third?

Thanks for your answers.


texts: astable multivibrator: capacitor polarization

texts:
Looking at this circuit, I'm wondering if the capacitor polarization "+" is correctly draw. Assuming T2 is in cut, T1 is on, left capacitor will have a 0.7v in its right side (connected to T1 emitter) and Vcc(without load) in its left side (connect to T2 collector).

Looking for this circuit in internet, all kind of draws appears.

Please, could someone help me to analyze the issue?

In fact, I'm wondering if polar capacitor can be used in this kind of circuits.


texts: Crystal's ESR or Frequency Stability/Tolerance, which is more of a priority?

texts: I'll be using a 12MHz crystal, CL=20pF on an NXP chip. Currently choosing between lower ESR (60ohms vs 100ohms) or lower stability (50ppm vs 10ppm). Which spec is more important? Should I choose a lower ESR @50ppm or higher ESR @10ppm?