texts: Selecting good replacement resistors for SW-12's R87, R88, R89, and R90

texts:
Related questions I have posted here so far:

1.5 kΩ resistors vs. 750 Ω resistors

What should the minimum voltage rating of replacement power resistors be?

Thanks to those who answered or commented on the questions above, I'm ready to order replacement resistors for R87, R88, R89, and R90 highlighted below:

The main objective of replacing the current resistors with ones with different values is to help the amplifier run as cool as possible because the originals seem to get hot enough to make the amplifier unstable. (I wouldn't mind some reduction in the output power, etc.) So, with this objective in mind, what would be the best and the second best choices as.45 the replacement resistors, among the following? (They all fit in the originals' locations, and they're all available for immediate shipping in the US today.)

Choice 1:

5W 1.5K ohm (same foot print, volume, surface area as the original's)

Choice 2:

5W 1K ohm (same foot print, volume, surface area as the original's)

Choice 3:

7W 1k ohm (same foot print, but volume and surface area bigger than the original's)

Choice 4:

7W 750 ohm (same foot print, but volume and surface area bigger than the original's)


texts: I am looking for a way to connect my logic analyzer (an inexpensive Saleae which is intended for 1.8-5V targets) and a couple of other pieces of analysis equipment to a digital source with signals in the 12 V range. I see that there have been a couple questions on this Stack Exchange about connecting 12 V to 5V in a one-way capacity, but I'd like a solution like this transceiver chip that is used in the Logic Sniffer input buffer wing. Does a transceiver chip like this exist? If not, is there some way that I could go about building a circuit like this that would translate between high and low voltages?


texts: How do I energize a 12v relay coil using a 2N2222 bipolar transistor?

texts:
I'm relatively new to working with transistors, and I'm having some trouble getting this circuit to work.  I want to use an Arduino's I/O pins (5V out) to energize a 12V relay coil.  To do this, I'm powering the Arduino with 12 volts via the power port on the Arduino.  For my transistor circuit, I'm pulling from the Vin pin on the Arduinio, which is also 12V.

I cannot figure out how to make it so that flipping an i/o pin from 0v to 5v switches the transistor, this allowing 12v to go across the relay coil.

I know the equations for the operating regions and I'm assuming I'm trying to drive the transistor into active by having Vbe > 0.7V, but I don't really know how to set up the circuit to properly regulate this.


texts:
I need to acquire the temperature of a box thanks to a thermistor.
I am wondering how to do that with a really high precision. Here are the caracteristics of the thermistor:

T°            Thermistance

-55°C         500K

-30°C         135K

50°C          3.9K

And here are the wanted specification:

T°            Max error

-40°C         0.8°C

0°C           0.5°C

40°C          0.3°C

I already though about a divider entering an OPamp and then using an active filter but I think it will not be precise enough due to the other resistance error of the divider and of the error on the alimentation of the divider.

Does anyone have an idea to measure the thermistor with this precision?

Precision I need to convert the thermistor value into a 0-10V voltage.

Edit:
It will actually be directly read with a DAQ, then it is okay now I do not have to do the schema anymore. Thank you all


texts:
I am working with a PIC16F723A chip and I am trying to program it to toggle a pin (RA1) on and off. I am pretty sure I have the circuit setup correctly (below is what I have setup), but for some reason I get an error when trying to program it....

So, I am using MPLAB X IDE v1.70 on OS X version 10.8.2. The project configuration in MPLAB X is setup with the device of PIC16F723A, hardware tools of ICD 3, and compiler toolchain as XC8 (Location: /Applications/microchip/xc8/v1.12/bin). There is no supported plugin board. It is NOT setup to power the target circuit from the ICD 3.

The error I am getting is "Connection Failed.If the problem persists, please disconnect and reconnect the ICD 3 to the USB cable. If this does not fix the problem verify that the proper MPLAB X USB drivers have been installed."

The warning I am getting is "CAUTION: Check that the device selected in MPLAB IDE (PIC16F723A) is the same one that is physically attached to the debug tool. Selecting a 5V device when a 3.3V device is connected can result in damage to the device when the debugger checks the device ID. Do you wish to continue?"

Here is how I have the circuit setup...
PIC16F723A PIN 1 is connected to ICD3 MCLR
PIC16F723A PIN 28 is connected to ICD3 ICSPDAT
PIC16F723A PIN 27 is connected to ICD3 ICSPCLK
PIC16F723A PIN 1/ICD3 MCLR is connected to external VDD (+3.3V) through a 10K resistor (I have also tried a 4.7K)
PIC16F723A PIN 8 is connected to PIC16F723A PIN 19
PIC16F723A PIN 19 is connected to GND
PIC16F723A PIN 20 is connected to VDD (+3.3V)

I am checking the chip using a Tektronix Oscilloscope and when I continue from the warning message, I see data being transfered on the ICSPDAT pin, but nothing has changed for the RA1 pin.

Here is the code I am using:

#include <stdio.h>
#include <stdlib.h>
#include <pic16f723.h>

void main(void){
     int i = 0;
     TRISAbits.TRISA1 = 0; // RA1 to output
     ANSELAbits.ANSA1 = 0; // RA1 to Digital I/O

     while(1){
         PORTAbits.RA1 = 1;
         for(i = 0; i < 1000; i++);
         PORTAbits.RA1 = 0;
         for(i = 0; i < 1000; i++);
     }
}

I have checked the circuit design several times, I have checked to make sure the chip is correct (the silkscreen on it says PIC16F723A-I/SP 1142D3V). I have also tried programming it by supplying +3.3V from an external supply and a +5.0V from an external supply.

Here is the schematic:

Where I have attached an oscilloscope to SCOPE

I have tried the ICD3 test interface board and it came back saying everything is working correctly:

Test interface PGC clock line write succeeded.

Test interface PGD data line write succeeded.

Test interface PGC clock line read succeeded.

Test interface PGD data line read succeeded.

Test interface LVP control line test succeeded.

Test interface MCLR level test succeeded.

ICD3 is functioning properly. If you are still having problems with your target circuit  please check the Target Board Considerations section of the online help.

I have been able to successfully program a PIC16F1824 chip with this programmer and computer. I am using a PIC16F723A because I needed more I/O pins than the PIC16F1824 has. I have also used this computer to successfully program a Cerebot MX4cK. For some reason the PIC16F723A doesn't want to work. If I haven't mentioned it before, I have tried multiple chips.


texts:
I got these male connectors from a broken cable and some flat cables.

Can I make a short (10cm or less) male-male HDMI cable using this stuff without worries? If so, is there any kind of trick on wiring or can I just solder each pin from one connector to the same pin on the other side?


texts:
I am building a circuit that stops giving power to the load when the voltage drops below 3.08V. I am using MAX809T (3.08V version) and a SI2302 mosfet (\$R_{ds}\$ on 0.056Ω@2.5V)

When there is no load, the voltage at reset pin and mosfet's source is VCC unless the voltage is below 3.08V giving 0V at reset pin and mosfet's source. But when there is load, the reset pin is always 0V whatever voltage is at VCC.

What is wrong with my circuit?

There was a similar question supply-voltage supervision circuit (follow up) with no answers.

Update:

I 've updated the circuit based on your suggestions but the problem remains.

I 've used also pull up and pull down resistors at mosfet gate with same results.

I have this electronic load. When I start my power supply with 5V and the load adjusted to 0 mA, it works normally: Output is almost 5V (4.95V).

Then I adjust my load to 100mA and start decreasing the dc power to 3.0V. When voltage is about 3.1V output (load) is turned off (0V 0mA) as it should.

Then I start increasing the VCC voltage to 5V but the output (at load) is never recovered. It remains 0V. It recovers only if I adjust my load current to 0mA.

MAX809T reset pin remains grounded while increasing VCC. I can not understand why. When I test it without the mosfet if VCC<3.08 RESET = GND and if VCC>3.15 RESET = VCC.

I 've tried with AO3400 mosfet with same results.

Update 2:

After changing my load to a simple resistor of 22Ω my circuit works as expected. I don't know how my electronic load works but testing my circuit with it caused unexpected results. Thank you all for the help.

Update 3:

The circuit does not work with a real load.
I 've modified it like the following image, but still does not work.

When mosfet gate is not connected (floating) I can measure the voltage at transistor collector = VCC if reset is LOW and 0V if RESET = HIGH = VCC. But when I connect the mosfet gate to transistor collector, the voltage at collector is always equal to VCC.

I 've tried also a 2N7000 mosfet in place of the transistor with same results.


texts: How to transmit data over a long distance at a affordable price

texts:
Please do keep in mind that I have no background in electronic communication. The idea is to receive data from electronics at long distances.

The distance I will be looking at to read data from electronics is around 10 km (6 miles) and possibly at a later stage longer distances and I would like to keep cost as low as possible.

The route that seems to be low cost is getting a raspberry pi zero, connect the  electronic device to it and then transmit the data received from the device over radio.

The user will have a app on his or her phone/device which will receive these radio signals and then decode it into an app which the user in return can understand.

The problem, if I am not mistaken, with this route is security won't be that great as anybody with the same frequency will be able to receive the data and also, again if not mistaken, it is illegal the transmit radio signals over great distances.

The questions I have is

Is this theory even possible ?
Is there a better way of achieving
this goal ?
What topics do I have to research to understand how electronic
devices can communicate with a pie as well as sending and receiving
radio signals and decoding it ?

A simple example is that if a switch is flipped on or off the pi is notified the signal is broadcasted the user's phone receives it and then the user is notified through his or her phone.

EDITED
I see a lot of people mention GSM but this uses a cellular network, sadly this option won't suffice as there is no cellular network in the area the pi will be used.


texts: I am a mechanical engineer and I am developing a enclosure for one of the electrical setup. It has usb, ethernet and power supply ports. I am unaware how IP rated USB or any other USB port make sure that there is no water ingress inside the port.   Any suggestion would be great on how this can be achieved.


texts:
I have an Altera DE2 board and trying to draw sprites. I am having some trouble implementing a screen buffer.

I have a display entity that at a 25 MHZ rate outputs pixels for vga display.

I was hoping to implement a buffer in SDRAM. The original idea was to load pixels the next pixel at a rate of 25 MHZ from the SDRAM. This works, but I can't write pixels to the SDRAM at this rate nor can clear the screen fast enough for each new frame. It takes me 2 clocks to write data and my board operates at 50 MHZ so I have just enough time to do a complete read.

I would assume I'm doing something terribly, terribly wrong. How is such a drawing canvas normally implemented in VHDL?

I closest thing I could find is to use a 2-3-3 (R-G-B) color scheme to retrieve each pixel and write to the canvas ram during the "porch" (blanking) VGA time. This means that at each of the 25mhz clocks I can only update 15% of the screen and I somehow need my circuit the be aware of which 15% it is updating?

I can't figure out how to use double buffering because I can't figure out how to write data to the memory while reading. Is there a way to avoid bit-banging the protocol? How does this guy do it?


texts: How does area and intensity relate to perceptive brigthness of a light source?

texts:
I want to design tail-lights for onboard use in vehicles (mostly bicycles), but I wonder how should I configure the system so as to get the best visual perception from a distance.

Each lighting element of the system would be composed of a number of LEDs, and the design parameters would be:

Number of LEDs;
Brightness of each individual LED;
How far the LEDs are from each other (or alternatively, the area "covered" by each led array);

So if I had 3 Watts available, I wonder if it would be best to use a single, point-like high power led, versus using 3 x 1 W LED, and in the later case if they sould be as close as possible or a bit far from each other, or even yet to use a wider area with, say, ten or twelve 5mm "bright" leds similar to those used in traffic signs.

Is there well-established way to anticipate how perceptually bright any light source would be, as seen from a distance, regarding those three parameters in the context of LED lights?


texts: How can I use audio signal to actuate relay (or close dry contact)?

texts:
I have a time clock (prox reader) that has no contact or voltage output - other than a speaker chime.  I need to actuate a turnstile on valid time clock swipe (RFID card).  I'd hoped I could steal the speaker signal to actuate relay...but no luck so far.

Voltage before chime is roughly 200 mV; during chime: ~300 mV.

Is there a way to use/recognize/convert that signal to close a dry contact or generate adequate voltage to trigger relay?


texts: Can a wrong crystal oscilator capacitor burn the MCU?

texts:
Short story:

I am using an Atmel AT32UC3C2512C MCU and I selected a 20MHz crystal oscillator for it and two NP0 10pF capacitors. I was in doubt between 10pF, 15pF or 22pF, so I decided to start with the smaller one. Can this burn a MCU?

Long story:

The PCB is really a high density one and I use all of the 64 pins so I can't place the whole schematic and PCB in here. In the first time I turned the circuit on the LED connected to a GPIO turned on (which I think it wasn't supposed to do so, since usually the pins comes as inputs from the factory and the LED needed a HIGH output to turn on) and was very dimm...after some research in the immense datasheet it appears that I placed the LED in a pin that can't handle a LED (Murphy strikes again)...in my defense, the datasheet didn't provide enough information on pins current, the only hint I have for this is the drive strength of the pin and some examples, but no real data is provided.

I removed the LED and after playing a little in Atmel Studio the MCU burned...surprisingly it kept running! So I was able to code more and still with the MCU catching fire several times, it kept running. So after a while it just burned for good (usually reconnecting the power made it stop catching fire and operate as it should, but after a while, just by connecting the battery will make it light up and pop smoke).

So no surprises there, the LED pin couldn't handle too much current so I probably burned the port and the MCU became unstable. So I replaced the MCU for a new one....and in the first programming session it burned too! A brand new one! No LED connected to the wrong pin....all pins set as inputs with pull-ups...the fire (yellow glow light with smoke) started in the vicinity of the MCU's internal regulators pins, which are just on the side of the oscillator pins. I checked all voltages and the rails are clean and stable. I can program the MCU, and run it fine using the internal oscillator, but sometimes, randomly it catches fire, so I am afraid of turning it on every time! It's like "Russian roulette".

So my current guess is that maybe the crystal's capacitors made the MCU unstable, or the small burned pieces of flux from the previous MCU that I couldn't remove are acting as stray components and changing the behaviour of the MCU.

I checked all the pins before turning on for possible shorts with the next pin and all were clean. Have anyone else used this MCU and experienced something like it?

EDIT 1:

It's a wild guess but it could be it so I would like to hear opinions about it:
I have some pins connected to N-MOS Transistors pulled down by 10k resistor, so if the MCU came from the factory with all it's pin pulled up as inputs (and the datasheet states that the internal pull-up resistors can range from 2k to 16k) so the pin could be placed at 2.5V and since there is no buskeeper this could have destroied the port.

It's a wild guess because the fire didn't came from this pins but from the internal regulator pins and the Vcc connected to another port (the LED port, which makes sense for the first MCU but not for the second)...comments?


texts: How to Write ISR function for Hardware and Software Interrupt

texts:
Till now I used Vendor(Controller Vendor) ISR for handling the Interrupt. But I want to know how to write the ISR. I know about the Vector Table. Will take one simple example for GPIO Interrupt for Port 0. which is having the vector table P0INT_VECTOR(according to datasheet).

  Now can any one tell me, how to write a ISR function for this.

I have seen the vendor example,

 #pragma vector = P0INT_VECTOR
    __interrupt void p0_ISR(void)
      {
           /*Some statement*/
       }

why it is #pragma, and how the function defined as p0_ISR, can we change the function name. What will be the impact of changing the name

I am not used the Software Interrupt much, but I know some basic, it will be used via INT commands.

  How to write Software ISR.


texts:
Atmel recommends:

  "if the reprogram operations occur in a random fashion in which any number of pages is
  updated in a random order, then the system must ensure that each page of the Serial DataFlash memory array be updated/rewritten at least once within every 10,000 cumulative page reprogram operations" (http://www.piclist.com/techref/atmel/doc0842.pdf)

There is an algorithm proposed for rewriting pages, which use page adress pointer (or page reprogram counter).
My question is what is the right place for this pointer/counter? One of DataFlash pages?


texts: How to make the receiver send signal back to the transmitter with wireless RF 433MHz module

texts:
I want to buy a RF transmitter & receiver 433MHz on the internet for our research project which deals with radio frequency.

I badly need the concept of having the receiver notify the transmitter or giving the transmitter a signal so that the controller/owner of the device would be notified if the receiver is still receiving a signal or if it is out of range.

I'm wondering because all I know is that it only works with a transmitter sending signal to the receiver and decoding the signal.

I want to copy the idea from an alarm system for motorcycle when the alarm is triggered, the remote control also vibrates and lights on to notify the owner when his/her vehicle is being moved or stolen.


texts: Charging 2 cell LiPo battery with MCP73213

texts:
I'm using an MCP73213 to charge a two-cell 7.4v LiPo battery using this circuit, when I tried charging the battery it was fine when I did this steps:

Connect 12V power source
Connect LiPo Battery

But when I had the LiPo 1000 mAh Battery connected and then I plugged the 12V Power Source which is a wall adapter the MCP73213 started burning and it's no good right now, I'd like some help unraveling this mistery since I don't know why this happened.

I noticed the MCP73213 is heating a lot but this IC shouldn't be burned since it has thermal regulation which reduces the charging speed whenever the temperature goes beyond 85°C (Datasheet section 5.9)

Wall adapter
https://www.amazon.com/gp/product/B00KZ2ZQE8/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Battery
https://www.amazon.com/gp/product/B0072AEHIC/ref=oh_aui_detailpage_o07_s01?ie=UTF8&psc=1


texts: Amplify signal going to motor of kids electric car

texts:
I have a 6V electric kids car (similar to power wheels). I want to convert it to 12V. Since it has a lot of electronics that are dependent on 6V I was just thinking of keeping the electronics fed by 1 6V battery and using an extra 6V battery to amplify the power to the wheel motor. The motor is rated to take 12V. How would I do this? (I’m a CS major, not an EE major but would love to learn).
So I had the following ideas but I don’t know how to wire it:

Connect 2 6V batteries in a series and use a step down converter to convert to 6V for electronics and somehow amplify the signal to the motor to 12V
Connect a 6V battery just for electronics and then amplify the motor signal using another 12V battery (would rather not have 2 batteries). I don’t know how to amplify the signal.


texts: Residual flux conductivity on PCBs causing problems?

texts:
The question here is how much flux remains on boards under normal manufacturing conditions, how conductive is it, and does the conductivity change with humidity and temperature.

I know that for super sensitive electrometer amps the recommendations for the finished board include very extensive washing in multiple stages.


texts: Art Of Electronics Second Edition - Math Question - Complex Number Current Calculation

texts:
How does the author obtain the expression I is approximately equal to .059sin(wt)

In the beginning of the book, 30 pages back, the author stated that V was equal to Asin(wt) (if you ignore phase), why is V now equal to Acos(wt)?

More importantly though, How does I = V/Z bring in sin(wt) when V nor Z had sin in it?  Is sin(wt) equal to j where there is a 90 degree phase shift only?

Thanks for any help.  This is a real great site and hopefully I will get through Chapter 1 of this book.  Which should be downhill from there (I think).

I also don't calculate .059. I get .029 at best assuming w=2*3.14*f


texts: Why can't I find a 2.2ohm 0.25W 10% resistor

texts:
I am following the guide to create the Colour Maximite 2 computer (here: https://ufile.io/wv2xo4wg). It is asking for several resistors. Here are some of them:
Carbon Film 2.2Ω 0.25W 10% Resistor
Carbon Film 10Ω 0.25W 10% Resistor
Carbon Film 1KΩ 0.25W 10% Resistor

It is hard to find the exact resistors. Do I have to have the exact one?


texts: Share a magnetic door contact with a pool alarm and home alarm

texts:
I purchased this pool door alarm (289-4,) along with a reentry button (084-3).
My house came pre-wired with magnetic door and window contacts (normally closed I believe.)
I do not have a home alarm installed at this time. My plan is to pickup the wires from the reed switches I want monitored by the pool door alarm and run them back to the pool alarm.
I think I am good up until this point.
Next, If I ever want to install a home alarm in the future, could I share those reed switches between the pool door alarm and the home alarm?  I thought yes, but someone told me no recently. I figured the alarms are just checking for continuity. Can that not be done at the same time by two different alarm systems?


texts:
I am building a flashlight using a large(ish) 35W HID headlamp from a car, and I'm having troubles choosing a good battery technology.

The inverter draws about 3.5A - 4A at 12V, tested on a large power supply. The current range I have supplied is through a Pb battery's discharge curve, from 12.5V to 10.5V. I have looked at purchasing a small 4Ah 12V Pb battery, but I am hesitant, because I am unsure of what currents the battery may be able to supply. I know the battery is small, but I have a small budget (Got the HID bulbs for free off a friend), and I am OK with a 30 minute battery life, as that is the max time I will be using it.

Any suggestions on what kind of discharge rate I could get from such a small Pb battery?


texts: Is there a limit on the current carrying capacity of a wire?

texts:
Obviously, for continuous current there is - the melting point. If it is superconducting, the field strength at which it quenches. OTOH if we specify a pulse of arbitrarily short timescale in order to avoid melting we introduce high frequency components that create a skin effect, which in turn feeds back into any current limitation.

However - is there any other physical limit on the current carrying capacity? For example, at some point the field is going to liquify the metal due to sheer pressure. What else?


texts: Control a MOSFET using tactile switch with single power source connecting to gate and drain

texts:
simulate this circuit – Schematic created using CircuitLab

I'm trying to build a circuit with 2x NiMH batteries as power source that can output up to 2A when tact switch at mosfet gate is closed, and will stop at battery voltage is at or below 2.0V (to protect batteries from over discharging.)

To achieve this, I'm using a MOSFET with minimum Vgs of 2.0V.

The problem is, I can't find a way to do voltage protection and tact switch protection at the same time.
If I want to  prevent my tact switch from burning, I'll have to limit the current passing through by adding resistors. But doing this is of course impractical as it will make gate voltage too low to operate and work as over discharge protection....

I'm really curious if what I'm doing is actually feasible. I have no electrical engineering background so I have very limited knowledge on ways and parts to achieve desired function.

I do did some research and find some circuit called Soft Latching Power Switch, which uses single tact switch to control high current circuit.
It is very close to what I want to do, but I have no idea how to tweak the circuit to realize my thoughts...


texts:
I know that due to Early effect in a npn transistor the effective base width reduces.However I can't understand how this will lead to  an increase in emitter current.
Some sources say that the charge concentration gradient increases due to this Early effect and hence the increase in emitter current but how can the charge gradient increase since that is determined by doping.
. Can any one please explain it then.
Any help will be appreciated
Thank you.


texts: How to differentiate between Analog and Digital Pins in an STM32 MCU?

texts:
I am using an STM32F302C8 and while reading the datasheet I am unable to differentiate between analog and digital input pins I am on pages 34-42 of This datasheet.
I am porting over from Arduino Nano to STM32F302C8 and all I need are 3 Analog and 5 Digital Pins.


texts:
After recieving a couple of these boards to tinker with I have been searching online for some schematic. I have only found the following useful images:

Block Diagrams with several pinouts described such as the one that can be found on the github page from the forked graphics library FabGL by LilyGo:

Mechanical and other drawings found from the product page of Lilygo:

Block Diagrams from the Microcontroller TTGO Micro itself from a product page of the micro:

Other usefull resources I have found are:

Generic esp32 schematic from Fabgl Lib which the board is compatible with.
Multiple reverse-engineered schematics of other TTGO board such as this one from hackaday or bytebang

But none of the actual TTGO VGA32 Board.

I know that to use the board with the information provided, its enough but wanted to get more detail on the board.

So before I go and invest some time into reverse engineering my own schematic, which I probably will do eventualy I'm asking if anyone has done this already or knows where to find the schematic of the TTGO VGA32 V1.2 Board?

I also asked the question to have a placeholder to be able to find/share the Schematic of this board easier in the future.

Cheers


texts: Can you convert a headphone into a metal detector coil?

texts:
I was wondering if it's possible to convert a stereo headphone into a coil to be used as a signal transmitter and receiver for metal detecting?

The idea is to use a smartphone as a signal generator.


texts:
I built an infrared thermometer using the MLX90614 IR sensor and an Arduino Nano. I needed a little higher temperature reading so I changed to the OTI-301 sensor hoping that it would work with the same library as the MLX90614 in the Arduino IDE. Unfortunately the sensor does not work and there is very little documentation out there about the new sensor I'm using,OTI-301. if anyone could give me some guidance on how to make this sensor work with Arduino it would be much appreciated. Also, both the MLX90614 and TI-301 work with the I2c protocol so I am pretty sure I have the right connections since the MLX90614 sensor worked perfectly fine. Here is the link of new sensor

https://www.amazon.com/Non-Contact-Infrared-Temperature-Algorithms-interface/dp/B07V52M45H/ref=cm_cr_arp_d_product_top?ie=UTF8


texts: Understanding voltage drop on a transistor

texts:
I've been reading different answers online and am trying to get my head around calculating transistors.
I have a circuit like this:

(Imagine the base goes to a microcontroller and is connected properly.)
After the red LEDs, the voltage will drop to 3.2V.
Will the transistor (2N2222) drop any more voltage?
If this circuit goes to ground (remove the transistor) I've calculated about 15mA goes to each LED. If there was more voltage drop, would I need to reduce the resistance?


texts:
I am new to the logic analyzer mode of Bus Pirate, so to play with it i connected channel 3(MOSI) line to the output of an TSOP1708 IR decoder to see if the capture came through.

However when I complete the capture all i get is a flat line @ HIGH. and because of this, trigerring does not work obviously since the signal does not seem to change at all.

I know my setup is working with the TSOP1708 output connected to a LED, which flashes when I press the remote.

Any idea what i might be doing wrong ??


texts: Whats happening with my pond pump at reduced voltage?

texts: So, I wanted to slow down my pond pump, and I have a variac or variable transformer that I used to reduced the voltage going to pump. I guess I probably needed to vary the frequency, not the voltage to control the speed, but the pump does slow down as I turn the voltage down, maybe due to less torque? But, around 54% voltage or so, the motor spins down or dies off completely, but right as it would stop, something clicks and the motor boost, but begins to die again, beginning a perpetual cycle. I suppose a capacitor inside the motor is switching on and off as it begins to spin down. But, I want to know whats happening here, does the voltage reduction lower motor speed? Why can't I reduce the voltage past 54% without starting this cycling? Will running the motor at a reduced voltage shorten it's life?


texts:
What shielding techniques would be best suited for a digital sensor (3 wires - Pwr, Gnd, Sig) in a noisy environment (specifically fluorescent lighting)?

Twisted pair (trio in this case) works well for differential voltages, but I suspect it won't be effective here even though the current in the wires is balanced.

Does shielded wire require a separate ground wire, or is it acceptable to use the shielding as ground? Should the shielding be ground at both ends, or only at the PCB?

Edit: Sensor is connected to PCB via ~1m of cable.


texts: How to get fourier series of 8-bit character to be transmitted?

texts:
I have been reading this in a book, but can't understand how he used the 8-bit in fourier series equation to get the result below.

The transmission of the ASCII character ‘‘b’’ encoded in an 8-bit byte. The bit pattern that is to be transmitted is 01100010. The Fourier analysis of this signal yields the coefficients:

an =(1/πn)[cos(πn/4) − cos(3πn/4) + cos(6πn/4) − cos(7πn/4)]

bn = (1/πn)[sin(3πn/4) − sin(πn/4) + sin(7πn/4) − sin(6πn/4)]

c = 3/4

I mean if I want to transmit letter 'a' for example, in ASCII Code it's 97 and in 8-bit is 0110 0001. How can I get its Fourier equation? Any help would be appreciated!


texts: Debugging an RTD-to-ADC conditioning circuit

texts:
As a software developer, I got myself into a bit of a pickle trying to make a 3-wire Pt100 temperature probe readable by a 3.3v microcontroller's ADC pin.

I followed page 4 of this MCP document which describes how to do exactly what I'm trying to do, and breadboarded everything up. I adjusted the gain of the Sallen-Key filter by changing R_11 from 20kohms to 88kohms.

I've got the following problems: my multimeter is telling me the current source is putting out way less than 1mA (the needle barely budges), and the output voltage predicted by this simulator at the end of the Sallen-Key filter should be 2.954V, but I'm reading about 0.125V.

I tried swapping out the op-amp IC and the resistors, but I get the same result.

So here are my questions:

Is there something obviously wrong with my breadboard that I missed?
Why does the current source need two op-amps? Could that be why I might be having trouble?
Is there an easier way to do this?


texts: Programming Atmega8 with AVRISP mkII Error ispProgramMem

texts:
If I go to Tools > Device Programming in AVRStudio 6.0 to program the Atmega8 everything is working fine. I've set the ISP frequency to 1 MHz and checked the fuses as well.

But as I just hit F5, programming most of the times failes (sometimes it works for whatever reason) giving me an error message:

  Error: ispProgramMem: Error status received: Got 0x80, expected 0x00

but unfortunately no further information.

The build output does not report any errors:

------ Build started: Project: Blink, Configuration: Debug AVR ------
Build started.
Project "Blink.cproj" (default targets):
Target "PreBuildEvent" skipped, due to false condition; ('$(PreBuildEvent)'!='') was evaluated as (''!='').
Target "CoreBuild" in file "D:\Program Files (x86)\Atmel\Atmel Studio 6.0\Vs\Compiler.targets" from project "C:\Users\Stefan\Documents\Atmel Studio\Blink\Blink\Blink.cproj" (target "Build" depends on it):
    Task "RunCompilerTask"
        D:\Program Files (x86)\Atmel\Atmel Studio 6.0\make\make.exe all
        make: Nothing to be done for `all'.
    Done executing task "RunCompilerTask".
    Task "RunOutputFileVerifyTask"
                Program Memory Usage    :   128 bytes   1,6 % Full
                Data Memory Usage       :   0 bytes   0,0 % Full
    Done executing task "RunOutputFileVerifyTask".
Done building target "CoreBuild" in project "Blink.cproj".
Target "PostBuildEvent" skipped, due to false condition; ('$(PostBuildEvent)' != '') was evaluated as ('' != '').
Target "Build" in file "D:\Program Files (x86)\Atmel\Atmel Studio 6.0\Vs\Avr.common.targets" from project "C:\Users\Stefan\Documents\Atmel Studio\Blink\Blink\Blink.cproj" (entry point):
Done building target "Build" in project "Blink.cproj".
Done building project "Blink.cproj".

Build succeeded.
========== Build: 1 succeeded or up-to-date, 0 failed, 0 skipped ==========

Does anybody know what the problem might be?


texts: Feedback resistor value in op amp integrator

texts:
Without the feedback resistor,
\$\frac{v_{in}}{R}\$ current flows through the capacitor and charges it to \$v_{out}(t) = -\frac{1}{RC}\int\limits_0^tv_{in}\,dt \$

Good so far. My textbook says a feedback resistor must be added to prevent the output from saturating when no input signal is present. I get that the input offset current will saturate the output.

What I don't get is why the feedback resistor must be \$\ge 10R\$. Based on what the author came up with this factor? Why can't the feedback resistor be, for example, \$R\$ too ? Lower gain reduces the output offset voltage right?


texts: Advantages of consequent buck converters

texts:
Lets assume we have a 12V source (i.e. an external PSU). We need to go down to 1V8 to supply some load. Leaving the costs behind and using only synchronous buck converters, what are the advantages and disadvantages of the options a) and b)?
a) Cascaded solution with intermediate 3V3 converter

b) Direct solution with no intermediate converter

Of course we assume that input voltage is within the spec for every converter etc.
This is just an overall example, but I am trying to point out the differences. I would for instance say that solution a) is less effective, since each converter has a < 100% efficiency, so each additional converter in chain introduces more power losses. But for some reason I see this kind of solutions- this made me wonder whether there are some additional advantages here, or maybe disadvantages with option b)?


texts: Why is the following simulation not working?

texts:
The following is a multistage amplifier. It consists of 3 parts:

Waveform generator and inverting amplifier
A small signal amplifier with gain 20 and a small signal amplifier with gain 10
A power amplifier where efficiency = 0.6 * maximum efficiency

When I do not connect the power amplifier, the output waveform on the second small signal amplifier is as expected, that is, 10 V. But, when I connect the power amplifier to its output, the output waveform on the second small signal amplifier decreases to mV. Why is it so? How can I correct it?


texts: Simulation of Band-Pass Filter (RLC) in ngspice

texts:
*I think I've found the answer myself. Check out the question comments.*

Sorry for my bad English, I'm still learning it.

This week I started using ngspice. I've built some simple circuits to get used to its netlist syntax and CLI commands. One of those circuits I've tried is the band-pass filter circuit with the following netlist:

Band-Pass Filter

Vin 1 0 DC 0 AC 1
C1 1 2 0.0001m
L1 2 3 1
R1 3 0 100

.AC LIN 1000 0.1 1000

.end

The simulation runs without any errors, but there's something weird with the results:

In node #3 I get the correct result (Figure 1: Node 3: Voltage vs Frequency): peak of 1V RMS, the same magnitude of input AC source.

But there's something wrong with node #2: its voltage has a peak of 30V RMS, while my input AC source is limited to 1V RMS (Figure 2: Nodes 1, 2 and 3: Voltage vs Frequency).

Do you guys have any ideas of why this is happening? Do you see anything wrong with my netlist? I appreciate any ideas on the subject.


texts: Soldering a GPS antenna to a Samsung Tab 2

texts:
I want to solder a GPS antenna to a Samsung Tab 2 tablet.
I need it to increase its signal and because I have a bunch of them laying around. My question is, what should I connect where, and if I should use other electronic parts.

Samsung Tab 2 GPS antenna internal

http://www.fonejoy.com/media/catalog/product/cache/3/image/41a4ec2d52c38ed81ff0a55ea740edd5/f/i/filename5055866658617.jpg

Antenna that I have (similar):

http://image.dhgate.com/albu_253997659_00/1.0x0.jpg

The internal antenna have only one electrical isolated part, but the antenna have two.

I imagine that the internal antenna has no ground, but the external one has.

It would work if I only connect external non ground to internal electrical part?


texts: GaAs and GaN as low temperature carriers in transistor

texts:
I've been looking at HEMT to use at low temperatures.

GaAs and GaN seem to be discussed often in the context of low temperature amplification.

My questions are twofold.

To be suitable for low temperature operation, is it about having a small ionization energy value for electrons to break free?
For low temperature operation, I naturally care about the transistors' power dissipation.  I looked at the datasheet of ATF33143 (GaAs pHEMT) and it says its power dissipation is 600mW whereas the datasheet of CG2H40025 (GaN HEMT) does not seem to say anything about its power dissipation.  It does mention "Saturated Power Output" as 6W, which I think is different. How does one go about finding the power dissipation? Is it just Idss*Vds?   For ATF33143, Idss = 300mA, which was measured at Vds = 1.5V, which would give about 450mW, at least on the same order of magnitude as the power dissipation of 600mW given in the datasheet.


texts:
I am designing a motor system that has to run in a vacuum chamber (sub mbar). I am a little bit worried about the heat that would not dissipate at all in the vacuum. Therefore, I want the least amount of energy wasted to heat(high efficiency). Some people advised me to get a big motor that is much more capable so that it can withstand the heat generated under low load.

The rpm I need ranges from 30 rpm to 600 rpm. So I need PWM on top of gearbox+motor. PWM and speed input will be controlled using Arduino. Also I realised that there are brushless and brushed motors. I figured that brushless motors are a bit more efficient which means less wasted as heat.

So in conclusion, I want a setup that is, big brushless motor + gearbox + PWM. Am I thinking correct? I have never gotten a chance to do any electrical engineering so I might be missing obvious flaws. Please let me know if there are any better ways to achieve this.

Additional info) I chose dc motor because the important part is to run continuously and smoothly at a set constant speed without bumps or jittering.
One session of running time would be ~10 minutes. Torque is not so much of a problem, probably maximum of 1000gcm needed I guess.


texts: How does division occur in our computers?

texts:
How does division occur inside digital computers? What is the algorithm for it?

I have searched hard in google but haven't got satisfactory results. Please provide a very clear algorithm/flowchart for division algorithm with a sample illustration.


texts: How long will this battery power this LED strip?

texts:
I'm a novice when it comes to electronics and when researching this its blown my mind. I'm trying to figure out how long I can power 2 meters of this LED strip for using this battery?

Details:

LED Strip:

Voltage: 12V
Total wattage of 2 meters: 9.6W

Battery:

Voltage: 12V
Capacity: 4800mAh


texts: Do static electronic indicators, that does not need power, exist? (equivalent of epaper, eink)

texts:
Hello I am looking for some way to indicate an signal in long term, but with no power consumption (power needed just for state switching). Are there any lowcost indicators based on epaper or eink or just paper pixel flipping sides with different colors?
I would be glad for every hint.


texts:
I am writing a program to send data from one microcontroller and receive the data using on another PIC32 microcontroller and display the received data on LCD. I am using UART2 of both PIC32MX to send and receive data and I am using UART interrupt at receiver side. I am not getting any data on receiving side :( and the LCD display shows nothing. The code is as follows:

The buffer size is 20.

function to Initialise UART

void UARTinitialization(void)
{
    PPSUnLock;
    PPSOutput(2,RPC13,U2TX);   //Assign U2TX to pin RPC13
    PPSInput(1,U2RX, RPC14);  //Assign U2RX to pin RPC14
    PPSLock;
    TRISCbits.TRISC14 = 1;
    TRISCbits.TRISC13 = 0;
    U2MODE           = 0;

    // enable TX and RX
    U2STA            = 0x1400;
    U2BRG            = Baud2BRG(115200,pbclk);

    // enable UART2
    IFS1bits.U2RXIF       = 0;
    IPC9bits.U2IP         = 2;
    IPC9bits.U2IS         = 1;
    IEC1bits.U2RXIE       = 1;
    U2MODESET             = 0x8000;
    rxIndex               = 0;

    //RS485                 = READ;
}//END of UART Initialization

Function to display received char:

void Display(void)
{
    if(UART_Flag == 1)         //check whether the program enters into the ISR
    {
        int i;
        for (i=0; i<BUFFER_SIZE; i++)
        {
            LCDinitWriteChar(rxBuffer[i]);
            if (rxBuffer[i] == '\0')
                break;
        }
        UART_Flag = 0;
    }
}

Function to send the data (used at transmitter side):

void writeUART(char *string,size_t size)
{
    while(size > 0)
    {
        while(U2STAbits.UTXBF);

        // put data in to transmitt register
        U2TXREG = *string;
       string++;
       size--;
    }
    // wait for complete transmission of data
    while(!U2STAbits.TRMT);
}

ISR Code:

void __ISR(_UART_2_VECTOR, IPL6SRS) _U2Interrupt(void)
{
    //Receive Buffer Overrun Error Status bit.
    if(U2STAbits.OERR)
        U2STAbits.OERR = 0;
    else
        if(IFS1bits.U2RXIF)
        {
            rxBuffer[rxIndex]  = U2RXREG;
            // rxIndex++;
            if(rxBuffer[0]!='*')
            {
                rxIndex = 0;
            }
            else
            {
                rxIndex++;
            }
            UART_Flag = 1;
        }
        IFS1bits.U2RXIF = 0;
    }

main function at receiver side:

int main(int argc, char** argv) {
    pbclk = SYSTEMConfigPerformance(80000000);
    UARTinitialization();
    LCDInit();            // LCD Intialization
    clearScreen();
    while(1)
    {
       if (U2STAbits.OERR) U2STAbits.OERR = 0;
       if (U2STAbits.PERR) U2STAbits.PERR = 0;
       if (U2STAbits.FERR) U2STAbits.FERR = 0;
       Display();              //function to display received data
       LCDinitClear();
    }
    return (EXIT_SUCCESS);
}


texts: Proper (low power) use of a tri-state buffer when used as level shifter.

texts:
In my application, I have a 3.3v MCU driving a logic line based device at 4-5V where I need to be able to put the level shifter in a high impedance state. (This is particularly important to avoid current backflow with the badly designed chips I'm using.) Following advice from this answer, I sourced a NXP 74LVC2G125.

For the Tri-state buffer, I am driving VCC at 5 volts, but the OE and inputs using 3.3V logic. As I read the data sheet, these are acceptable ranges for logic input HIGH. However, I notice in practice that when the OE is pulled high (to 3.3V) to shut down the tri-state buffer, the chip continues to consume about 10mA. This suggests to me that despite the specifications, I am not saturating whatever transistor is driving the high impedance state. I am aiming for a low-power application.

I'm looking for a replacement chip that will serve the same purpose. What specification should I look for to be sure the 3.3V logic will completely shut down and fully activate the tri-state buffer? For instance, will this same chip SN74LVC2G125 from TI have the same problem? Or will a variation on the chip, such as SN74LVC2G241, address the issue?

I do not have any analog EE background.


texts:
In a transformer a sinusoidally varying voltage is applied to the primary coil of the transformer which give rise to a time varying flux which induce another sinusoidally varying EMF in the primary coil. The induced EMF has a 180° phase difference with the applied voltage and hence opposes it due to which the voltage across the coil should decrease leading to a decrease in the max value of the time varying flux. So the decrease in flux should then also decrease the max value of induced EMF.

How can the EMF across the primary then continue to be sinusoidal when the max value of sinusoidally varying out of phase induced EMF change with time? Shouldn't it be represented by a sinusoidal curve whose max value change with time?


texts: Why is battery C rating not a function of battery topology/voltage?

texts:
In a battery, there is a 'C' rating, which appears to be a function of its capacity. a 5 Ah battery charged or discharged at 1C charges or discharges at 5A.
However C capability is generally spoken of with respect to battery chemistry only.
If I have four cells, each 3 V, 0.8 Ah, then I can make a battery with three different topologies:

1S 4P: 3 V
2S 2P: 6 V
4S 1P: 12 V

Each variant has a 3.2 Ah capacity*, and 1C in each case suggests charging or discharging at 3.2 A. However in 1), each cell will experience 0.8 A of charge or discharge. In 2) each cell will see 1.6 A, and 3) each cell will see the full 3.2 A. Battery 3 at 3.2 A will charge 4x faster than battery 1, corresponding to four times the power input, totally changing how the chemistry might be expected to behave. C rating sure surely then include the topology, or else it would be a nonsensical metric. What is the reality?
*Incorrect. Amp hour rating varies as inverse of voltage from topology. Amp hour rating alone is insufficient to characterise energy capacity, voltage is required also leading to a common Watt hour capacity. Series topology is cancelled and the Amp hour rating of the battery is equal to the Amp hour rating of the smallest parallel arrangement of cells in the battery.


texts: Induction heater design - Current transformer windings ratio

texts:
I am currently building an induction heater and would like to verify my approach to this as I'm uncertain if it is correct. Below is the topology of the resonant tank circuit I have constructed. The tank circuit illustrated is coupled to a H bridge driver via a current transformer, with a resonant frequency of 12.841KHz.

simulate this circuit – Schematic created using CircuitLab

Each capacitor is rated at a peak current loading of 25A at 10KHz, achieving 50A in their current configuration. Therefore, considering peak current flow and factoring it against the ESR of the circuit (0.013 Ohms), the peak voltage of the secondary circuit must not exceed 0.65V assuming no impedance due to reactance is present. However, this would only be capable of producing 32.5W (0.65V x 50A) which is far below what I am aiming to achieve.

The primary side of the circuit supplies 48V (960VA) to the primary coil of the CT. The transformer ratio calculated gives: Vp/Vs = 48V/0.65V = 73.8 turns. This seems excessive and likely to result in a very high inductance/impedance on the primary side of the circuit, inhibiting current flow / overall power.

My questions are:

1) Is my approach to designing this circuit correct so far? If not, what mistakes am I making?

2) Does my power calculation reflect the total power of the circuit or just the power lost?


texts: How to get PN532 reader connected by SPI or UART getting detected by pcsc_scan?

texts: I have a PN532 board with SPI and UART connections both. I would like to get it integrated with PCSC so that it can be detected with pcsc_scan command. As PN532 is compatible with CCID as well. What is the process of configuring the driver by editing any conf files? Thank you.


texts:
Can cardboard be used as core of the transformer? I read that

  core of transformer do not conduct current, induction produces current in secondary coil.

So can cardboard be the core.
How do it affect the functioning and effectiveness of transformer?


texts: How can I calculate the sparks when I discharging a big capacitor?

texts:
Several years ago I've tried to find answer to this question but I couldn't find  the answers. I hope you help me.

Because my job I have  to discharging constantly "big"  capacitors ( 400 vdc, 300 vdc, and so on). Ok really they aren't so big but problem is sometimes when I shortcircuit the capacitors , they to make huge sparks.

I have to avoid sparks mostly because several time I've damages IC's very importants into the circuit, and second I'm afraid of the sparks every time I shortcircuit a "big" capacitor Jaja.

So my idea was to conect a parallel resistor to capacitors . Problem is How to calculate the resistor  to descharging quickly the capacitors but also avoiding  the sparks.

For example:

$$C=100uf -160vdc;
R=470 ohm$$

$$Vc = vo*e^{-t/T}$$

$$ vo=160 v$$
  $$ T=r*c$$
   $$T=100uF *470 ohm$$
   $$T=47mS$$

$$vc = 160*e^{-t/0.047}$$

Wao, this discharge very fast : five tao = 5*0.047 = 235mS to discharge the capacitor

This is result:

NO sparks

But I need more quickly so I try a 100 ohm resistor

$$C=100uf -160vdc;
R=100 ohm$$

$$Vc = vo*e^{-t/T}$$

$$ vo=160 v$$
  $$ T=r*c$$
   $$T=100uF *100 ohm$$
   $$T=0.01mS$$

$$vc = 160*e^{-t/0.01}$$

Wao, this discharge is faster : five tao = 5*0.01 = 50mS to discharge the capacitor

But this is problem : sparks

This is a litle spark. Problem is when I discharge bigger capacitors 300 vdc, 400 vdc, etc.

Are they some formule for trade-off quickly discharge and minimun sparks ?

Thank you.


texts:
Medium Wave AM in most countries is monophonic. AM stereo was never universally adopted. Given a monophonic signal, how can one create a stereo output?

I know there are some 'tricks' you can play on ears to make the original sound better. Is there something that could be done with phasing that could generate a stereo output? Would some scheme employing delays result in a stereo effect?

In practice, would a DSP solution be superior to an analog one?


texts:
I have my voltage rails coming off board and I have quite a number of ICs. Each has their own decoupling and for the really demanding ICs I have a bulk capacitor.

If I have some target impedance and it's said that to achieve that impedance I need 10 capacitors of various values and sizes, where do all these capacitors sit ?

Are they grouped together ?
Are they spread out over the board ?
Are they near the digital ICs ?
Are they placed where power enter the board ?


texts: DC motor is pulsing when connected to power supply

texts:
Apologies in advance if my terminology is not exact, as I'm a very amateur hobbyist just starting out.

I have a DC servo motor that I bought used, rated at 24V maximum, with variable RPM depending on how many volts I supply to it.  The motor works fine when I connect it to a 9V battery, but pulses and drains a connected power supply periodically (every second or so).

I bought a power supply so I could use the motor from an AC outlet (USA - 120V).

This is the power supply: https://www.amazon.com/gp/product/B01B1PRE42

Specifications:
Input Voltage: 110V/220V;
Output Voltage: 24V DC 2A Output
Current: 0~2A
Power: 48W
Shell Material: Metal case
Protection: Shortage Protection. Overload Protection. Over Voltage Protection
Safety Compliance: CCC/ FCC / CE
Working Temperature: 0~45 degree
Storage Temperature: -20~65 degree
Ambient Humidity: 0~96% Non-Condensation
Package Content : 1 x 24V 2A Switching Power Supply

The power supply has a small green LED above the variable output screw.  I tested the output with a multimeter when I connected it with 18/2 lamp wire to my outlet, and I verified (at least I think I did) that it is outputting between 9V minimum and 24V maximum, depending on the screw being fully counterclockwise or clockwise, respectively.

When the motor is connected, it spins for a brief moment (100 milliseconds or so) and the green led on the power supply goes out.  Then the green led turns on again (it takes about a second) and the motor again spins and the led goes out, and this cycle continues endlessly.

I have checked that all my positive and negative connections between the power supply and the motor are correct, and the neutral AC to power supply matches as well.

What am I doing wrong?

EDIT: photos of the motor...


texts: How to reduce rise/fall time while amplifying square pulses with op amp?

texts:
I'm trying to amplify a low signal with square pulses at 20 mV using op amps. According to simulation, rise and fall time of pulses increase too much after amplification, approximately 60 us. The component which will receive the signal accepts maximum 300 ns, the datasheet says so.

What kind of things can be done to reduce rise/fall time after amplification or to solve this problem? If I should choose another op amp, which is the best for this purpose?

I have another solution in my mind but I'm not sure. If I shift reference clock a little bit so that rising edges of clock don't meet the rising edges of signal(which are too long), will it work properly?

To see the details of application I'm working on it, visit the following question:
How to amplify a signal containing square pulses at milivolts to a couple volts


texts: Difference between Across the Line and Line to Earth

texts: I have to make a reverse engineering. I have two different type of capacitors. What do the Across-The-Line X2 and Line-To-Earth Y2 mean? And what are the differences between them. I searched it but i couldn't find a certain answer.


texts: A difference between Vdd and Vddio in datasheet of a sensor

texts: In many datasheets of various sensors I read that there are two ways to supply power - that is VDD and VDDIO. I would like to know why we need to supply power in these two different ways.


texts: Parallel and Series Circuits Question (Electron Flow)

texts:
So this is a pretty basic question, I understand the aspects of parallel and series circuits but don't understand why?

For instance:

How can the Battery be "drained" faster when say 3 LEDS are connected in Parallel.....How does the battery "know" I suppose? And why is this any different than a Series Circuit?
In a Series Circuit if we had an LED connected in between a 5v Battery such as +----LED----(Ground) We'd experience a voltage drop of 5v over the LED, however 2 leds would just be 2.5 voltage drop a piece.....I don't understand WHY that is? Shouldn't all the "Pressure" from the batterys voltage be used after the first LED? Furthermore how can equal pressure/voltage get distributed in a parallel circuit.....it just confuses me at "why".

I know this kinda stuff I don't "Need" to know the physics of it....I just "have" to know this stuff otherwise Im not satisfied with how it works haha.


texts:
Using the picture below as an example. What's the standard convention?

Link 0V of DC supply to chassis/mains earth
Have the 0V of the DC supply not connected to the chassis in any way

If it depends on the circumstances what's the better option in terms of reducing EMI and noise on the digital circuit


texts: Reverse biased capacitor on IC input pin

texts:
I am looking at the test circuits on the data sheet for the AN6884 VU meter IC, and I cannot understand the connection to pin 8 in the following diagram:

Pin 8 accepts a positive input voltage. The potentiometer is clear, but the 2.2uf capacitor is not. It appears to be reversed. If I "correct" the orientation, the circuit does not work at all. That's clear, because the input in my test circuit is DC.

This circuit will light the LEDs as the input voltage on pin 8 increases relative to pin 7. As displayed, the LEDs go from fully off to fully on over roughly the entire turn range of the potentiometer. If I remove the 2.2u capacitor, the circuit works, but the range of the potentiometer is greatly reduced. That is to say that the LEDs all come on at a much smaller turn of the potentiometer. Can someone explain what the reversed capacitor is doing here?


texts: Automatic Solar light far too dim, help with increasing brightness

texts:
simulate this circuit – Schematic created using CircuitLab

I've built a simple circuit that uses a transistor to switch from charging 2AA batteries during the day to discharging the batteries to power 3 white LEDs at night.

In order to fully power the 3 LEDs, I plan to add a third AA. (as shown in diagram above)
How would I change the components, specifically R1 and R2, to handle this increased voltage and fully illuminate the lights.
Also, are there any other pressing concerns that would effect the brightness that I should fix and how?

thanks for the help!


texts:
Before I begin, just to let you know that I'm new to electrical engineering, in case that my question sound weird to you, but here's my problem.

I bought few days ago ACS712 Low Current Sensor and hooked up everything on my Arduino board, but the values that I'm getting are weird.

From my understanding, the Vout from that sensor without any load should be 2.5v, right? And if there's any load, it should change.

However, I'm getting different values on Vout while I read them in my code (from 505 to 520) (as raw input without any analog to digital conversion). Is that normal? I thought I will get stable (constant) input value if there's no load?

How can I tweak that and how to convert it properly from that number into milliamps?


texts:
So, right, I'm trying to get 3A at 12V from a 4A 9V wall adapter. I'm trying to build a SMPS for that and I've got my eyes on the IC mentioned because it looks promising (let me know if it's not the best), and I can't find anything on how to do it, so any schematics and and how to calculate the values for them would be great, and yes, i looked in the datasheet
is this okay?

IC datasheet: https://pdf1.alldatasheet.com/datasheet-pdf/view/25562/STMICROELECTRONICS/UC3843.html
http://danyk.cz/univ_m_en.html


texts: High short circuit failure rate of aluminum electrolytic capacitors during the production processes

texts:
I have produced 1000 units of our new developed energy meter. Almost 20 aluminum electrolytic capacitors (2%) have failed short when we test them during the production processes. The Capacitor is a 470uF 35V (UPW1V471MPD) made by Nichicon.

The failure itself varies between total short circuit to small variable resistance. One of the caps spit out its electrolyte.

I have 3 other different aluminum electrolytic caps from the same manufacturer that didn’t fail. A year ago, I have produced 300 units (same design and part no.) and they running perfectly and didn’t find any failed capacitors.

My question has 3 parts:

How this occurred?

Is it normal to have an infant mortality of 2% with short circuit failure for aluminum electrolytic caps?

Or, may be the cap is counterfeited and the con manufacturer didn’t do enough quality testing. (I bought them through a PCB and components supplier in Shenzhen). If they are counterfeit, how to verify that?
What should I do with the rest of the batch?

If I release the batch, would I guarantee that there will be no more short circuit failure? If it didn’t die during the manufacturing, it will not die in the near future! (U shape/bathtub graph).

Or it is better to run my meters for a period of time (24 hours) if didn’t fail it will not fail in the future.

Or I should go the hard way and change them all?
How to avoid this in the future, because I will be going for large quantities > 100K.

I didn’t find very useful notes about electronics parts quality and reliability other than MIL-HDBK-978B. But it is out dated and didn’t have the electrolytic caps.

Added

Operation condition:

Voltage = 20V.
Inrush and ripple current =  the capacitor is used to store energy to supply a latch/rely only when operate. it operated about 5 times during production.  latch/relay impedance 60 ohm. it draw its voltage from a capacitive power supply capable of supplying a 17mA at maximum.
Temperature: about 30C.
there is a guarantee that no cap have been reversed biased.


texts: Connecting 36V LiIon packs in series to get ~120VDC to run lawn mower

texts:
I'm converting my electric plugin lawnmower to battery power.  I was able to get 3 used e-bike identical model 36V 5Ah packs (obviously not matched with respect to lifetime usage). Each pack has its own BMS (battery management system) built in.   I connected the packs in series to power the DC motor and measured 42V*3 = 126VDC when the packs are fully charged. The mower ran fine (4A idle current; 8A full-load) while cutting the grass last summer, except some times it would shut off (seemingly NOT dependent on motor load -- i.e. grass height). When shutting off, it would usually restart normally after waiting a minute or so.  I determined that if I partially charged the battery packs to about 40V instead of 42V (individual 36V chargers for each pack!), the shutdowns stopped happening.  But towards end of summer, one of the pack's BMS apparently went bad and that pack always measures 20V with my digital VOM (6V with my Simpson analogue meter).  The faulty pack does, however, draw the charger's rated 2A when connected to it, although the pack still never provides any current or voltage above 20V).
I presume I might have blown the BMS on the one pack? Its BMS might have shut that pack down due to undervoltage (3.0V/cell), but since the other 2 packs were still powering the mower, would the 80V or so appear across  the shutdown BMS and then permanently damage it?
I suppose I could design a relay circuit that would break the entire 3-pack series string when one pack shuts off via BMS.  But would the relay break the circuit fast enough to protect the BMS?   Alternatively, I could install analogue panel voltmeters on each pack to make sure all packs are well above cut-off voltage even under full motor load.   Thoughts/comments would be greatly appreciated.  Thanks!


texts:
I am working on a PIC project to connect it to a LCD in 4 bit mode.  My data lines for my LCD are connected to my PORTC (PORTC0-3), but I need 4 pins from PORTC to connect to a 4 switches also (PORTC4-7).  The PIC is a PIC16F886.  The code for my LCD.c is below.

/*
 *  LCD Interface Example
 *  This code will interface to a standard LCD controller
 *  like the Hitachi HD44780.  It uses it in 4 bit mode, with
 *  the hardware connected as follows (the standard 14 pin
 *  LCD connector is used):
 *
 *  PORTC bits 0-3 are connected to LCD Data Bits 4-7 (High Nibble)
 *  PORTA bit 2 is connected to the LCD RS input (Register Select)
 *  RW input (Read/Write) is connected to Ground
 *  PORTA bit 1 is connected to the LCD EN bit (Enable)
*/

#include    <htc.h>
#include    "lcd.h"

void pause (unsigned short usvalue);            //Establish pause routine function

#define LCD_RS          RA2
#define LCD_RW          RA4
#define LCD_EN          RA1
#define LCD_DATA        PORTC
#define LCD_STROBE()    ((LCD_EN = 1), (LCD_EN = 0))
#define  DelayS(T)              {unsigned char i; for (i = 0; i < T * 10; i++) __delay_ms(100);}    //Delay Macro
#define  _XTAL_FREQ             4000000

/*Write a byte to the LCD in 4 bit mode*/

void
lcd_write(unsigned char c)
{
    __delay_ms(1);
    LCD_DATA = ((c >> 4) & 0x0F);
    LCD_STROBE();
    LCD_DATA = (c & 0x0F);
    LCD_STROBE();
}

/*Clear and Home the LCD*/

void
lcd_clear(void)
{
    LCD_RS = 0;
    lcd_write(0x1);
    __delay_ms(2);
}

/*Write a string of characters to the LCD*/

void
lcd_puts(const char * s)
{
    LCD_RS = 1;                                 //Write Characters
    while(*s)
    {
        lcd_write(*s++);
    }
}

/*Write one character to the LCD*/

void
lcd_putch(char c)
{
    LCD_RS = 1;                                 //Write Characters
    lcd_write(c);
}

/*Go to the Specified Position*/

void
lcd_goto(unsigned char pos)
{
    LCD_RS = 0;
    lcd_write(0x80 + pos);
}

/*Initialize the LCD - put into 4 bit mode*/

void
lcd_init()
{
    char init_value;

    ANSEL = 0;                                  //Disable Analog Pins on PORTA

    init_value = 0x3;
    TRISA = 0;
    TRISC = 0;
    LCD_RS = 0;
    LCD_EN = 0;
    LCD_RW = 0;

    __delay_ms(15);                                 //Wait 15ms after Power applies)
    LCD_DATA = init_value;
    LCD_STROBE();
    __delay_ms(10);
    LCD_STROBE();
    __delay_ms(10);
    LCD_STROBE();
    __delay_ms(10);
    LCD_DATA = 2;                               //Four Bit Mode
    LCD_STROBE();

    lcd_write(0x28);                            //Set Interface Length
    lcd_write(0xF);                             //Display On, Cursor On, Cursor Blink
    lcd_clear();                                //Clear Screen
    lcd_write(0x6);                             //Set Entry Mode
}

Is there any way to "break" up PORTC so I can use it for both the LCD and the switches.

Thanks for any help provided.


texts: Why are OR gates using transistors different from OR gates using diodes?

texts:
There are two ways to make an OR gate:

 and:

But with diodes it is easier to make than with transistors, no? What are the advantages of the transistors version and drawbacks of the diodes version?


texts: How does one calculate the voltage ratio V+/Vo for this circuit?

texts:
I can understand the first case above, that seems simple as I can simply measure across the ground and V+, but I am getting very confused for the second case.

Is the capacitor and the resistor in parallel?


texts:
I am having some trouble understanding the behaviour of electrons inside an RC circuit. Let me explain:

One capacitor plate accumulates a lot of electrons, which pushes electrons away into the negative/ground from the other plate.
I disconnect the charged capacitor.
I insert it into the LC circuit.
Because of the attraction of the electrons on the one plate to the electron-deprived protons on the other plate, they start to "travel" in that direction through the wire.
The electrons hit the inductor, which creates a magnetic field due to the change in current, which pushes back against the electrons, but lets some pass through.
Now the discharge of the capacitor has completed and the magnetic field in the inductor collapses and causes electrons from the wire to be pushed towards the (previously) negative plate.
The plates have now switched and the same amount of electrons that were on the one plate before are now on the other.

Questions:

Regarding 4) Since there is a lack of electrons on the one plate, won't it simply attract free electrons from the wire (that is connected between the end of the inductor and the "negative" plate) to fill the "holes"?
Regarding 5) As I understand it, there is always some electrons passing through, it's just the number that changes?
Regarding 6) The plate that is being charged by the inductor (the initially "negtative" plate) should already have a slightly positive charge from the current that passed through the inductor while it was building the magnetic field. But this would only be true if my assumption about point 4) is true (the first question).

Could somebody try to clarify this, and tell me if my assumptions are correct?

EDIT:
My main question is how the overcharge from the one plate can create an overcharge on the other. Since the amount of positive charge on the one plate of the capacitor should match the amount of negative charge on the other, shouldn't they just cancel each other out once the discharge is complete? How does the inductor in between influence the current so that it ends up in a net positive charge? Are the electrons that were displaced by the charge still there to refill the space?


texts:
I have a magnetic core. I excite it with a current I, the magnetizing force is approximately equal to :
$$ H = {NI \over l_{c}} $$
Where N is the number of turn and l_c is the mean path length of the core.
And the flux density B is equal to :
$$ B = {µH} $$ where µ is the permeability of the core.
Whatever the section of the core, the flux density will always be the same...
If I take the approximate formula of the inductance, it can be shown that the flux density is equal from the previous equation :
$$ B = {L \Delta I \over NS} $$ where S is the section of the core and L is the inductance. L is proportional to S. So according to this formula, the flux density does not depends on the section
Finally, according to the electrical formula of an inductance :
$$ L \Delta I  = V \Delta T $$
Then B is equal to :
$$ B = {V \Delta T \over NS} $$
And it seems to depends on S ... But this is not what the first formula shows... Does the flux density depend on the section of the core or not ?
Have a nice day !


texts: Why are all my yellow 2V/20mA LEDs burning out with 330k Ohm resistor?

texts:
I have a very basic circuit on a breadboard using an Arduino's 5V+Gnd to power a few LEDs. All the LEDs are from Sparkfun and rated at 2V/20mA, coming in Red, Green, and Yellow. I'm using 330 Ohm resistors but I also have much higher resistors like 10k and 330k Ohm for testing this issue.

Only one LED is being connected at a time using the individual lanes. Nothing is connected to the power and ground rails on the breadboard. Red, green, and even my white LEDs work great, but so far 5 yellow LEDs in a row have immediately burned. I double-checked wiring, moved wires and LEDs, and went all the up to a 330,000 Ohm resistor, but no luck with the yellows. Is this likely a bad batch of yellow or am I missing a key component?

EDIT: Here is the full board (the wires are complex because this will be an electronics puzzle in a game):

And here is with the other wires removed to show what's actually connected:


texts: Learning by Making a USB data/power PCB - Will my design work?

texts:
Ever since I watched one of GreatScott!'s videos a while ago, I have wanted to make my own PCB. I now have an excuse to build one.(A school robotics project)

I am making a PCB to connect power from a battery bank (1A 5V), and data only USB for a Raspberry Pi. There would be a power output for the L298N and data and power and data from a USB port to a USB hub. (Yes, I know that there is a thing called an externally powered USB hub)

Easy EDA:

Usage:

My main question is: Would this work? I want to make sure before I buy 10 of these and wait 2 weeks.

Thank you for the help!


texts: Can I use 1 yellow 12V wire to power 2 12V pins?

texts: I'm trying to mod a C8220 Dell (mini 18-pin power) from an old ATX supply. I want to know if it's okay to use 1 yellow wire to supply 2 yellow sockets on the 18-pin. Thank you.


texts:
Overview

This project is my first with schematic/PCB design. The goal is to make a breakout board for the Fanstel BM833 module (built around the Nordic nRF52833 SoC).

Library

I first designed my own library for the BM833.

Footprint

I made the footprint based off of the specifications on page 11 of the BM833 datasheet.

Symbol

I only needed 16 of the 68 pins on the module, so my symbol looked like this:

Project

The project generally can be broken down into two sections:

Female connector pins for break away headers, and
Used pins for the integrated clock and LED

Schematic

Using the device from my new library, I designed this schematic. It's not pretty, and I would appreciate feedback especially on how to route the nets better. These are all the parts that I ended up using:

They make sense for this project, right? If I made some stupid mistake like wrong resistors/capacitors, please let me know!

Board

I was trying to minimize the size of the board, hence the crowding. Might it be dangerously crowded (such as prone to potential complications due to heat or charge)? Are there some changes in layout or general tips you would recommend? If you have any clever ways to reduce space even further, that would be awesome.

As a note, the BM833 lies off of the board as per the layout recommendations in the datasheet. That top part has the PCB antenna, so putting it off of the board minimizes interference and extra impedance or inductance I think.

Edit: new board. v1, v2, v3, v4, v5, v6.

So...

Please rip this apart! Few things are better for improvement than constructive criticism.


texts: Are there any advantages to either DC barrel connector polarity?

texts:
I was putting together a fairly basic LBB at the weekend to control a handful of DC devices which got me thinking. Why are both pin-positive and pin-negative DC barrel connectors used? Are there any concrete, electrical advantages to either design? Or is it just for manufacturer lock-in?

Pin-positive seems to me to be the obvious one to use from a safety point of view, but a quick audit of the supplies in my spares box revealed a not insignificant number of pin-negative supplies.


texts:
I have been developing a simulation of field oriented control of three phase induction motor. During this process I have encountered strange behavior of the Clarke transform. In case I have three phase voltage source consisting of three smooth sinewaves with 120° phase shifts between each other

the Clarke transform gives two sinewaves with 90° phase shift

That's what I have expected.
In case I have three phase voltage source consisting of three pulse width modulated signals
(fpwm = 1 kHz) produced by three phase voltage source inverter

the Clarke transform applied to those signals gives following outcomes

Those outcomes are strange for me because I have expected again two signals with the same shape
and with 90° phase shift as was the case for the smooth sinewaves. In both cases I have been using below given matrix multiplication for Clarke transformation
$$
\begin{bmatrix}
x_{\alpha} \\
x_{\beta}
\end{bmatrix}
=
\begin{bmatrix}
1 & 0 & 0 \\
0 & \frac{1}{\sqrt{3}} & -\frac{1}{\sqrt{3}}
\end{bmatrix}
\cdot
\begin{bmatrix}
x_{a} \\
x_{b} \\
x_{c}
\end{bmatrix}
$$
Can anybody tell me whether the outcomes of the Clarke transformation in the second case are correct or whether are caused by some mistake in my simulation? In case they are correct why are not in accordance with my expectation i.e. two signals with same shape and with 90 ° phase shift? Thanks in advance for explanation.
EDIT:
In case I use simple moving average filter with window width equal N samples before applying Clarke transform to the pwm signals I get

N = 8

N = 16

N = 32

N = 64


texts: Visual understanding of EM fields within a rectangular metal container

texts:
I have the following scenario setup inside a rectangular metal container. The container size is 12.03m by 2.39m by 1.84m (lxbxh). Additionally, inside the container I have placed 4 antennas equally spaced, this is shown using the green squares (ignore the red dots/balls). The frequency of these antennas is 915MHz. I would like to know how the EM field behaves inside the container, such as where there will exit destructive interference and constructive interference?

In terms of interference from the other antennas, this will not be an issue due to only one antenna will be on for a given period. Basically the antennas are switched on and off in a periodic manner.


texts: Production programming: is there a practical size limit to serialization length?

texts:
This is a follow on question from the answers of these two:

Is it practical for firmware to be uniquely identified in production
How to verify hardware is legitimate

I would like to be able to serialize hardware with an RSA key (1024 bit) and some unique information. This will come to a total of ~140 bytes. This doesn't seem to be a standard thing, so will this cause issues when it comes to production? Can production programmers serialize with any number of bytes, or like that image in the first question, are you limited to some standard number (4 bytes) etc.


texts: Drawing a bode plot of transfer function with unknown gain

texts:
I want to draw bode plot of this transfer function:

$$G(p) = {K \over p \space (1+0.1p) \space (1+0.05p)}$$

But I don't know what to do with that K (static gain) -- I've only drawn TF with known gain.


texts:
I'm trying to interface with an MCP40821 using SPI from an AVR. Using these pin maps:

#define SCK     PB7
#define MOSI    PB5
#define CS      PB4
#define LDAC    PC7

With these register settings:

void SetupSPI()
{
    DDRB  |= true << SCK | true << MOSI | true << CS;
    DDRC  |= true << LDAC;
    PORTC |= true << LDAC;
    PORTB |= true << CS;
    SPCR  |= true << SPIE | true << SPE | true << MSTR | true << CPOL | true << CPHA;
    SPSR  |= true << SPI2X;
}

I'm then transmitting the data using a buffer and an interrupt.

#define SHDN    12
void SendSPIData()
{
    if (SPIBytesTransferred < SPIPayloadBytes)
    {
        SPDR = SPITxBuffer[SPIBytesTransferred++];
    }
    else
    {
        DACReady = true;
    }
}

void SetDAC(uint16_t value)
{
    if (!DACReady) return;
    DACReady = false;
    value |= true << SHDN;

    SPIPayloadBytes = DAC_SPI_BYTES;
    SPIBytesTransferred = 0;
    SPITxBuffer[0] = value >> 8;
    SPITxBuffer[1] = value;

    SendSPIData(); //Kick-off transfer
}

ISR(SPI_STC_vect)
{
    SendSPIData(); //Send next byte
}

This all seems to look fine, using my logic analyser I can see the two byte commands go out successfully.

However, the DAC doesn't seem to respond and I'm not sure what else I need to do.


texts: Is the positive supply of Arduino USB port connected to 5V pin?

texts:
You can power the Arduino Uno/Nano using the following:

Barrel Jack (for UNO only), it is connected to the input to voltage regulator.
VIN pin, it is also connected to input of voltage regulator.
5V pin, it is connected to the output of the voltage regulator and directly of 5V of Atmega MCU.
Finally, the USB.

Is the positive supply of the USB port of an Arduino is connected to the 5V directly? I tried to use a connectivity test using multimeter but it is not connected.

Moreover, it is mentioned in the Arduino documentation around the internet that if you powered the Arduino via USB connection, the 5V pin will be limited to 500 mA only. What if I use an AC to DC adapter (2A output current) that is connected to the USB port of the Arduino, will I will still get only a max of 500 mA? Or if I use USB 3.0 that can supply 900 mA, will I still get 500 mA max for the 5V pin? I read that the polyfuse is the one that is limiting that current.

I have used Arduino Uno and Nano for a long time but I just became aware of this basic concepts when I made a project that should compute the overall power consumption of the device.


texts: Will this circuit damage my Raspberry Pi GPIO?

texts:
I'm making a circuit te be able to shutdown my Raspberry Pi after the shutdown sequence is complete to avoid sd card corruption. The circuit looks like this:

A little explanation:
The battery input which is variable from 2,5 to 3,6V and 3V average, is controlled by the switch named KEY1. When the switch is activated, the input feeds EN and the system powers up. Because the switch output is connected to a transistor, it controls the state of the GPIO that will trigger the shutdown script once the switch goes OFF. The TX pin will feed those 3V to the EN pin keeping the Raspberry Pi on while the shutdown sequence is going and the switch has already switched OFF.
As you can see, the circuit already has some protection resistors, but my concern is: could the battery input (VIN) damage the TX GPIO pin when the switch is ON by feeding voltage into the GPIO PIN directly?


texts: The purpose of a 10 uF cap for the MMC5883MA magnetic sensor

texts:
Datasheet: https://eu.mouser.com/datasheet/2/821/MMC5883MA-RevC-1219541.pdf
Here is their answer and my question:

Hello,
May I know whether or not I can do away without the 10 uF set/reset
coil's capacitor ?
The datasheet mentions something about a charge pump: In the device
status register, bit #3:
"Pump On        Indicates the charge pump status."
Does the 10 uF capacitor on the CAP pin have anything to do with this
charge pump ? If yes, what voltage swings are expected on the CAP pin
?
I do not intend to ever use the set/reset coil. Datasheet says:
"The SET/RESET function can be performed for each measurement,
periodically, or when the temperature changes by a predetermined
amount as the specific application requires. In addition, the
SET/RESET function clears the sensors of any residual magnetic
polarization resulting from exposure to strong external magnets."
I have no need for these functions above. So, will the MMC5883MA run
fine without that 10 uF cap ?
Thank you

Hi
10uF is a must for MMC5883MA, and no need to use the charge pump.
Please let us konw your application and company, then we can provide
better support. Thanks.

No further  answers from them.
I have tried taking out the 10 uf cap for testing; it seemed to work fine without it. Since they say I need it I shall leave it there. But I still wonder why it is needed...


texts: Thevenin equivalent circuit with external loop

texts:
I am tasked with the following exercise:

I am still finding Thevenin equivalent circuits challenging, and this example looks a bit daunting since it seems to have an external loop.

Hopefully, I made the correct assumption (though I could very much be wrong) that I only needed to find the equivalent circuit of the OPEN LOOP of this circuit. Namely, creating a thevenin equivalent circuit of this:

simulate this circuit – Schematic created using CircuitLab

Which led me to getting the following Thevenin Equivalent circuit:

simulate this circuit

Was my assumption correct? If not, how do I account for this? For example, this external circuit would make finding the open circuit voltage no different, I would think.


texts:
I’m curious to see if anyone has any experience on the accuracy differences in measuring 120V-277VAC in the following ohmic ways. In all cases, the voltage would be put through a voltage divider to provide a [-2.5V,2.5V] signal for an ADC:

Up shift the AC wave from +-2.5V to 0-5V, then read the 0-5V signal.
Rectify the signal to read 0-2.5V for the entire waveform.
Read the -2.5V to 2.5V signal directly.

I realize 3. is probably the most accurate, but curious to see how 1. and 2. impact the measurement.

Thanks for your help!


texts:
I started my project of interfacing MicroSD Card with PIC32MX795F512L. To start with this first I made a program to test SPI protocol in which I did loopback test by shorting the SDO & SDI line. It was working fine. Then I moved ahead and write a good program to interface card but I even failed to initialize the card. So I though of purchasing some tools like saleae logic and MicroSD Sniffer. As this is my first time using the analyzer, what my understanding is to when we start our program, at the same time we have to start capturing the data in analyzer.

With this understanding, I tested a UART:

while(1)
{
  putsUART1("Hello");
  DelayMs(500);
}

I captured this in analyzer and everything was fine. Now I thought of capturing the SPI loopback test program but I am seeing some random data in analyzer. Following is the code for it:

void initSPI(void)
{
SPI1BRG = 71;
SPI1CONbits.MSTEN = 1; //MasterEnable
SPI1CONbits.CKE = 1;  //CKE on. CKP OFF
SPI1CONbits.ON = 1;  //SPI Module ON
}

unsigned char writeSPI(unsigned int b)
{

    SPI1BUF=b; // write to buffer for TX
    while( !SPI1STATbits.SPIRBF); // wait transfer complete
    return(SPI1BUF);

}

and in main function, after calling initSPI, in while(1) I am sending data to SPI channel:

while(1)
{
 x = writeSPI(0x12);
}

I am sending 0x12. So in the analyzer MOSI(SDO) should show this value but its showing some random values. I have connected the pins correctly and SPI settings in the analyzer is according to my settings in the code. I am capturing the data for 1sec and speed at 24MS/s. Also I want to know that how can I check at what frequency SPI Protocol is running.? Any help.!

Here is the image of analyzer result

and analyzer settings for SPI


texts: Time Domain Analysis with Vector Network Analyzer

texts:
I have done some measurements with a VNA in time domain (by using the transform operation of the instrument). Precisely, I have selected the measurement of S11 (reflection coefficient at port 1 of the VNA) while leaving port 1 open, and I selected the Step Response Mode.

The result of my measurement is this one:

My question is: which is precisely the quantity on y axis? I think it is the reflected signal: in fact port 1 is open and so there is total reflection, and therefore we see exactly the voltage step that the instrument has sent to port 1. And if we look at the instrument display, we see that it is measured in Volt, so it is a voltage signal.

But I have set the measurement of S11: why do I get a measure in volt? I thought that it may be due to the fact that the reflected signal is proportional to S11 (Vreflected = S11 * Vincident), but I am not sure since S11 is function of frequency, so parts of the signal with different frequencies are multiplied by different coefficient.


texts:
I am still new to electronics and I am looking for a low noise and efficient way to provide 5V and 3.3V from AA batteries. My circuit requires 3.3V/200mA 10% of the time and less than 1mA the other 90%. 5V is 99% <1mA, 1% 50mA.

Here is how I am currently approching this problem :

I could use 4xAA and step-down converters but given my circuit
requirements the efficiency would be horrible. The noise would also be terrible.

I could use 4xAA and LDOs, but steping down to 3.3V from 6V doesn't sound like the good way to do it.

So I could use 3xAA (4.5V) with a LDO to provide 3.3V and a charge pump to provide 5V, but then :

the LDO will fail under 3.4V, wasting around 20% of the AA batteries. So maybe I should put the LDO after the 5V charge pump... or find a way to do that only when the LDO fails...
charge pump arn't exactly low noise. Maybe I should use an LDO after it to get rid of the noise...

I'm starting to have more questions than answers. What is the correct way to solve this beginner electronics engineering problem ?


texts: How do I know the value at which the Nyquist plot crosses -180 degrees from looking at the Phase plot from the Bode?


texts: Vivado: Reset signal flagged as primary clock by Timing Constraints Wizard?

texts:
I inherited an FPGA design (Avnet MicroZed PCB) that does not meet timing. I have found that many of the design constraints are missing, and I am in the process of trying to properly implement the missing constraints.

I found one strange thing: it appears that the main asynchronous reset line for the logic is being interpreted as an unconstrained primary clock by the Vivado timing constraints wizard:

For reference, rst_n is my active-low reset signal for my flip flops. Example:

always_ff @ (posedge clk or negedge rst_n)
   if(~rst_n) begin
      // do things on reset
   end
   else begin
      // do other things on rising clk edge
   end

I am not sure why this reset would pop up as a primary clock. Is this expected behavior?

If this is normal, how do I constrain this signal?
If this is not normal, what do I need to do to resolve the missing constraint?


texts: Is this soldering iron and power supply combo grounded and if so, how?

texts:
I'm interested in a TS100 soldering iron as a decent starter iron and a light one that doesn't take up too much space. It doesn't come with a power supply though, presumably to keep it flexible as it can take 12-24V input (max 65W usage). So I found this 24V power supply to go with it.

Here's the iron:

Here's the power supply purchased separately:

My question is whether this device is grounded and if so how, or if not, is it safe to use or does it risk shorting out into the user? I would think it is not grounded since most AC/DC adapter barrel connector power supplies I find are only 2-prong (is it necessarily only 2-prong). In that case, I'd hope the device is insulated - how would one check that?

The closest thing I could find to a spec sheet for this iron is here: https://imgmgr.banggood.com/images/upload/2015/11/TS100/TS100%20Soldering%20Iron%20Instruction%20Manual.pdf It mentions a ground screw and connecting a ground wire to that. Does that imply that for safe use of the device, I'd need to - in addition to the power supply - have a ground wire clipped under that screw and connected on the other end to a reliable ground like copper plumbing pipes?


texts: STM32F072 3.3V on UART with Wi-Fi ESP 8226

texts:
I do have STM32F072RB microcontroller which works on 5V but also have output power pins on 3.3V.

I do have Wi-Fi module (ESP 8226) that works on 3.3V. I can power it with STM easily but what about UART pins? Will they switch themselves to 3.3V and work properly? When not, how do I connect RX and TX busses so they can work properly?


texts:
I'd like to make a MUXer who switches between 2 signals let's say A and B. Signal A and B also generate both interrupts. The MUXer counts the interrupts and for example after n-interrupts of A, the output will become this of B.
If B generates m-interrupts, the output toggles back to A.

In underlying code I wait for 3 pulses of the A interrupt, during this the mux output is A. After that I wait for 5 pulses of the B interrupt while the mux out becomes B. The whole cycle is then repeated.

I'm implementing this with a 3 process FSM as explained here: http://www.csit-sun.pub.ro/courses/Masterat/Xilinx%20Synthesis%20Technology/toolbox.xilinx.com/docsan/xilinx4/data/docs/xst/hdlcode15.html

Can someone explain why it doesn't work properly? The vhdl code:

entity FSM_MUX is
    Port ( CLK : in STD_LOGIC;
           RST : in STD_LOGIC;
           A: in STD_LOGIC;
           A_INT : in STD_LOGIC;
           B: in STD_LOGIC;
           B_INT : in STD_LOGIC;
           START : in STD_LOGIC;
           MUX_OUT : out STD_LOGIC);
end FSM_MUX;

architecture Behavioral of FSM_MUX is

type state is (iddle,state_A,state_B) ;
signal old_state : state ;
signal new_state : state ;

begin
process(CLK)
    begin
        if (CLK' event and CLK = '1') then
            if RST = '0' or START = '0' then
                old_state <= iddle ;
            else
                old_state <= new_state;
            end if;
        end if;
end process;

process (old_state,A_INT,B_INT)
    variable counter : integer range 0 to ((2**16)-1):=0;
    begin
        case old_state is
            when iddle          =>          if  A_INT = '1' then
                                                new_state <= state_A;
                                            else
                                                new_state <= iddle;
                                            end if;

            when state_A       =>          if A_INT = '1' then
                                                if counter < 3  then
                                                    counter := counter + 1;
                                                    new_state <= state_A;
                                                else
                                                    counter := 0;
                                                    new_state <= state_B;
                                                end if;
                                            end if;

            when state_B       =>          if  B_INT = '1' then
                                                if counter < 5  then
                                                    counter := counter + 1;
                                                    new_state <= state_B;
                                                else
                                                    counter := 0;
                                                    new_state <= state_A;
                                                end if;
                                            end if;

        end case;
end process;

process(old_state)
begin
    case old_state is
        when iddle    =>        MUX <='0';
        when state_A =>         MUX <= A;
        when state_B =>         MUX <= B;
   end case;

end process;
end Behavioral;

Thanks in advance!


texts: Need help to stop power draining from relay switch when off?

texts:
thank you for your help.
I'm new to electronics, and learning as I go.  I need help on a circuit that otherwise works great.  This is a magnetic power on-off switch, I'm using a relay switch to supply LIPO BAT power to a regulator.  When turned on, the line to reg. measures full BAT power as expected, BUT when the switch is turned off the line to the reg. is still measuring around 0.76v, and slowly drains the battery over time.  Is anyone able to to help eliminate or reduce drain battery when off?
Answer - my mistake on this, I didn't show the full circuit, there was a resistor down the line causing a problem.


texts: Is a 9.6µs over-voltage transient long enough to fry my circuit (Details inside)?

texts:
I am designing a board for a 12V automotive environment, with a variety of input voltage transients including load dump and permanent 24V over-voltage. I am using a TVS at the input to clamp to around 60V followed by a TI LM5060, a power supply supervisor, which in case of an over-voltage above 18V (or overcurrent) will cut off the power to my circuit using an external 60V MOSFET. The LM5060 datasheet specifies a 9.6 microsecond delay from the onset of a over-voltage condition to the MOSFET gate turning off. On the other side of the LM5060 I have my bulk capacitor and number of linear regulators and other ICs which at their input can tolerate up to around 30V (or 45V depending on what parts I choose).

So my question is, during that 9.6µs it takes for LM5060 to kick in, how can I ensure that nothing on its down-side gets fried? Is a sufficiently large bulk capacitor (220uF?) enough to absorb that transient? Or would I be better off using a small zener? How would I choose a value for this zener/capacitor?

If anyone knows of a better/cheaper alternative to LM5060, please let me know. I only need it to provide over-voltage protection up to around 60V.


texts:
Could someone tell me if I breadboard this circuit correctly? I am very new to breadboarding.

  Note that

  Green = Resistor (take all to have same resistance)

  Red/Black = wires that hook up to battery

  Blue = just regular wires.

  I am trying to build the circuit below.

  With breadboard I got

  Did I do this right?

  Asked on 2012-08-17

edit 2012-08-21

Is the above breadboard the same as the schematic circuit? Also I can't find any function generators or oscilloscopes on Fritzing. Does Fritzing not have it?

Furthermore, these configurations seem kinda repetitive. Do they become very complicated if I include other devices?


texts: is it ok to use a lower wattage dc adaptor?

texts:
I have a Samsung TV, with the following specifications:
The AC/DC adapter broke and I need to buy a new one but I haven't found any adapter with 66W, the closest one was 65W. So I want to know:

1 - Is it ok to use a 65W dc once the TV says 66W?
2 - What does it means the "Typical power"?


texts: Problem with Vout of Honeywell ASDX Analog pressure sensor

texts:
Few months ago I decide to bought an absolute pressure measure system using a Honeywell ASDX differential analog pressure sensor (Model: ASDX ACX 030PAAA5). The datasheet of this type of sensor attached.

Base on datasheet, this sensor has 3 active pin, pin No.1 is for voltage supply, Pin No. 2 is Analog output and Pin No. 3 is GND. The manufacturer suggest to use a load resistace > 5K ohms (I used a 4.7K RL) and an external bypass capacitor is required across the supply voltage (Pins 1 and 3). I used  0.1 uF and 0.001 uF capacitors between Vsupply, Vout and GND respectively.

I design a circuit on a breadboard to mount the sensor. I use a 5Vdc power supply device for the circuit, now when I TURN ON the device and there is no applied pressure on sensor (just ambient pressure), the output voltage is almost 2.47 - 2.59 Volt (I checked Pin 1 voltage for the sensor an itś same 5Vdc). the problems are here:

Problems:
1. I expect when there is no applied pressure, the output voltage be 2.5V but as i mentioned above it is a little less, what is the reason?

This is the schematic.

I will be so appreciate if help me.