texts: A question about using stripboard/perfboard instead of PCB for long duration

texts:
I have made some analog interfaces by using perfboards or strip boards for a project which will run 6 months on a bridge but indoors and inside enclosures. The components were DIP package ICs and passive components. I also used conformal coating spray electrolube mostly at the solder sides.

I tested several times the circuits were working. But I am completely ignorant about life time or reliability of these boards. They will be powered and will process nonstop 6 months where I cannot have access.

Because of urgency, I didn't have time to spend drawing in a CAD program and obtain a PCB.

I'm not worried about not having ground plane and the circuits are working for low freq. applications.

I'm not expert in soldering and my biggest worry is that whether the solder joints would corrupt themselves after long time. But since the circuits were working I thought there is no cold solder.

Are there any problems using perfboard or strip board instead of PCB for such long durations? In other words is it a big risk or not to use stripboard or perfboard instead of PCB?


texts: Have I reached maximum current on my Arduino?

texts:
I'm wrapping my head around my electronics theory (it's been a long while).

I've read that the max current from the 5v VCC pin on the Arduino Uno is 200ma before any damage is done.

I'm using an Adafruit NeoPixel 24 LED ring. Based on this page, each LED draws up to 60mA at full brightness. If I max each LED out that's 1440ma of current required.

I (foolishly as I now know) have been running all pixels at white on full brightness directly from the Arduino. Measuring the current (serially) on the ground line, there was roughly 315mA flowing in the circuit.

My question is, is the Arduino managing to get the circuit up to 315mA but from that point cannot provide anymore current? Is this is then the absolute non documented maximum that my Arduino can provide?

Further to that, does that mean I've been damaging the Arduino?


texts: Write endurance: Is there a difference between eMMC and Micro SD Card?

texts:
I have seen several forum posts (link 1, link 2) debating whether eMMC offers an endurance advantage over SD cards for embedded applications.

My understanding was that the write endurance problem is an inherent feature of all Flash storage technology, and that there is only a nominal control interface difference between Micro SD cards and eMMC chips.

I am aware that there are differences in write endurance due to the structure of the Flash storage itself. As I understand it, this is essentially a trade-off between storage density and write endurance, where Triple Level Cells (TLC) have higher capacity than Single Level Cells (SLC), and Multi Level Cells (MLC) somewhere in the middle.

I can understand how write endurance is tied to this internal flash structure, but I don't think the write endurance has anything to do with whether there is an SD or eMMC interface on the front end.

Is this correct? Or am I missing something?


texts: Understanding "stereotyped" noise on MISO line

texts:
Just getting started with EE, so bear with me. I've got a bare-metal STM32G474RE communicating over SPI (~5MHz) with an LSM9DS1. I've got a probe hooked up and capturing the communication and it seems to be working well. I send 0x8F and get back 0x68 from the WHO_AM_I register:

CS/CLK/MOSI/MISO, respectively. What I'm trying to understand is the "stereotyped" noise in the signal. I understand that all signals will have some kind of a noise floor, but the MISO line is both noticeably noisier than the other lines (not clear to me why?), and the noise pattern appears to follow a consistent pattern frame-to-frame i.e. I can trigger a new recording and the signal looks almost identical.

Circled - I assume this dip that coincides with the first falling clock edge is due to the MOSI line dropping and affecting the VDD line (?).

Rect - The MISO line is super noisy compare to the MOSI. But it's not white-noise noisy; rather the ringing on the line is nearly identical each time I capture a new trigger. What might cause large-but-very-consistent noise like this?

Arrow - Not really noise-related, but I assume this gradual voltage rise back up to VDD is due to neither slave nor master driving the MISO line and there being an internal pull-up resistor + cap somewhere. Why would this happen only after CS goes high? Is it this "refactory period" what limits the SPI speed?

Edit: more detail

The micro is on the NUCLEO-G474RE board (pdf), and the LSM9DS1 is on the breakout board from Adafruit (link). SPI port is SPI2, with pins PB 12/13/14/15 for CS/CLK/MISO/MOSI, respectively. Connected with ~4" wires terminated with 1-pin female Dupont. Let me know if you need any more details!

Edit: Swapped probe

Swapped probes 3 and 4 on the PCB side. Noise does not follow the probe; it only appears on the MISO line.


texts: Photodiode and Arduino to measure the speed of a projectile

texts:
I am trying to build a chrono to measure the speed of a projectile.  I plan to use an Arduino and photodiode.  I would like the photodiode to change the state of the Arduino's digital pin when an object passes it.  I plan to have a reasonably powerful IR LED beaming upwards with the photodiode also looking in that direction - idea being that as a projectile passes overhead it will reflect some IR which will be detected by the diode.

I have the BPV10NF photodiode.  This looked like it had a fast response time and high radiant sensitivity which might be good for this project.  Reading various references on photodiodes I also procured a few MCP6002 OP-AMPs - my understanding being that the output of the photodiode is very small and must be amplified.

This is the circuit I have put together based on looking at different examples.  This only shows one PD but once I have it working as desired I would replicate a second time - a fixed distance from the first so that I can calculate the speed of the detected projectile.

simulate this circuit – Schematic created using CircuitLab

This doesn't seem to work as expected.  If I put a voltmeter across OA1 output and GND I get around 4.8v regardless of what level of light the PD is exposed to.  If I put a voltmeter across OA1+ and GND the voltage is around 4.8v and if I shine my iPhone torch on the PD it drops to ~3.3v.  I would imagine if I shine an IR LED on it then the voltage would go lower (given it's an IR PD).

Could somebody sanity check this circuit for me and explain where I have gone wrong?


texts: Bipolar Stepper Motor Negative Stator Voltage?

texts:
I have a tin can bipolar stepper motor.  It has two stators A & B.

When I disconnect the motor and measure the differential voltage across A, I get this:

It's actually strange as we are using a h-bridge configuration, so I would have expected a negative voltage as we are pulsing High, Low, nevertheless I am not too worried about this.

The issue that is causing major confusion to me is the next trace:

The sequence is correct but rather than go to zero, the voltage is only dropping to approximately half that of the high voltage.

The motor is actually stepping correctly and in the right direction.

Is the low voltage being high linked to the direction of movement?  I have been looking for an oscilloscope trace of a h-bridge online in order to compare what I have seen but found nothing .  Does anyone know if this is expected behaviour?


texts: Is it possible to make an op amp integrator that integrates a DC input?

texts: If the integral of a DC input is a ramp, can you make an op-amp circuit that integrates a DC input into a ramp, and then displays the ramp on an oscilloscope?


texts: I'm looking for an introductory book to CPU / microcontroller /microprocessor design. Any ideas? ARM or x86 are both great. I have a great assembler language book, but I'm looking for something more on the engineering level. Or maybe they're the same? Maybe it doesn't exist, or maybe I need to refine my question but anything would help. Thanks.


texts: Is the hfe of a transistor dependent on the resistance on the other parts of the circuit?

texts:
I have a circuit using a NPN transistor with a motor before it and a pwm into the base.

The motors draws a current of 600mA if I plug it directly into the power source, just under the maximum allowed by the transistor at 650mA.

The minimum gain of the transistor is listed at 100, with my multimeter reading about 200. The voltage is at 3.7V.

My question is, if I give a base current of lets say 20mA, even with the minimum gain, it is 2A, but will this current be limited by that the motor draws (600mA), or will it push 2A onto the motor?

I have blown 2 of these transistors already, but connecting the base directly to 3.7V. The transistor in question is 2N2222A in the metal case.

Another question is for a simple LED circuit switched by a transistor, is it Ok to depend on the hfe alone? For example, I only have a resistor connected to the base with the collector to HIGH and emitter to the LED?


texts: Designing an EMP Generator for school :^)

texts:
How would I go about calculating and designing a circuit that can produce an axial magnetic field greater than 20 Tesla for about 1.4 μs (full width at half maximum). The dimensions of the solenoid must meet the constraint of a cylinder with length=5mm and radius=0.5mm.  The risetime of the pulse must be less than or equal to 1μs.

This lab seems like a LOT to digest... Anyways, I figured it would make most sense to use a capacitive energy storage device. How would I go about beginning to develop a design for this, assuming that this needs to be buildable with real life components, and not just have a 2000A current source powering a solenoid with a little switch :^) Any pointers on what formulas to start looking at, terms to start googling would help. I tried to solve this as a physics problem, but I'm not getting much information from that. I assume this requires a more intricate usage of 1st and 2nd Order circuits.

Thanks in advance for the help! :P


texts: What is the transparent border around my Altium trace?

texts: I am routing my first ever PCB and half way through the routing process I've noticed my tracks now have this transparent border around it. Any idea what this is ? I must have clicked something? Not sure how to disable it nor what it actually represents.


texts: Pressure transducer being read using Labview

texts:
I understand this is not a typical question for this forum, and that NI Labview forum would be better (I posted there too), but I am hoping that someone who is proficient in Labview will see this.  I am merely an intern seeking help from the seasoned.

I am trying to measure pressure using a pitot tube hooked up to a MPX2010DP Pressure Transducer.  The pitot tube is taking the measurements from inside of a duct system.  Pressure is minimal, with PSI being around <1.

The transducer is rated for 25mV full range output, 10-16V input, and 0-1.45 PSI.  It has a 4 pin connection, 1=gnd, 2=V+out, 3=Vsupply, 4=V-out.  I have an exterior power supply connected to pin 1 and 3.

My problem is that I am unsure on how to exactly and correctly acquire the output voltage of this transducer.

My solution/attempt was to hook up pin 2 and 4 to the analog input of the NI 9215 module (AI2+ and AI2-) to read the output from the transducer.  However, I got meaningless values, with nothing corresponding to the pressure fluctuations.  I then tried module 9219 because it has signal conditioning which I need in order to accurately read the mV output.  This did not work either.

My question: What am I doing wrong exactly?  I thought this would be pretty straightforward but I was very wrong, or perhaps I am overlooking something simple such as calibrations.  I simply don't have enough experience at this time to effectively troubleshoot this issue.

Thanks!


texts: Relays: understanding "Rated carry current" and "Maximum contact current"

texts:
I'm trying to understand the limitations of connecting multiple relays, and how it relates to current.

Consider a relay with the following specs (rounded for easier math):

Rated current: 100mA
Rated voltage: 12V DC
Rated carry current: 3A
Maximum contact current: 3A

Let's also consider a power supply of 12V DC and 10A.

Is the following correct?

I could wire 100 (10A / 100mA) of these relays in parallel and be at the theoretical limit of my current.
I could wire 30 (3A / 100mA) of these relays in series and be at the theoretical limit of the relay themselves. At that point, the contacts would get too hot or the device would fail in some other way.
The power supply wouldn't really care how the relays are connected, as long as the total current draw is under its maximum. That is, "Rated current" * "Num Relays" <= "Power Supply Current"
I could mix and match parallel and series connections as long as stay under the limits in #1 and #2.

I'm new to hardware and I'm trying to not kill relays or burn down my house.


texts: oscilloscope time charging different from the math

texts:
For the above circuit, I calculate that the equivalent resistance of the charging circuit is 2.668 kΩ, and the equivalent capacitance is 2.055 µF. Therefore, the time constant would be 2.668*2.055 = 5.48 ms as the amount of time required to charge.
I simulated the circuit and got the following time constant:

It is almost twice as doubled, while it should be approximately the same. Can anyone explain to me the difference?
Thank you.


texts:
Both Wikipedia and other SO questions about VHDL vs Verilog mention digital when describing VHDL.

Can you use VHDL to design analog circuits?


texts:
I'm unable to get a proper response from my GSM modem300, sometimes it responds with nothing, sometimes it replies half of line of ONE message from full inbox, sometimes it just sends the command (AT+CMGR=1) I just sent, back many times.

Print screens:

sends my command back: http://imgur.com/Lyv8oui
responds with nothing: http://imgur.com/jHQOSxM
responds with half line of one message from FULL inbox!: http://imgur.com/zsmDcIc
responds with garbage: http://imgur.com/vTVSwyf

I'm using Arduino, directly connecting the Tx and Rx of board to Rx and Tx of arduino, and GND to Arduino GND.

CODE:

char incomingByte=0;
void setup()
 {
  Serial.begin(9600);
  delay(2000);
  Serial.println("AT+CMGF=1");
  delay(2000);
  Serial.println("AT+CMGR=1");
  delay(2000);
 }

 void loop()
 {
    while (Serial.available() > 0)
    {
       incomingByte = Serial.read();
       if(incomingByte!='\n'){ Serial.print(incomingByte); }
       if(incomingByte=='\n'){ Serial.print(incomingByte); }
    }
 }

It might be worth mentioning that, I can send messages properly, and make and receive calls with no problem.


texts:
I have a bit of a problem that in hoping someone can shed some light on.

I have a 4 wire fan (from a power mac g5) and I found that the pinout is positive, negative, PWM and rpm output. It's a bit strange in that the 12v must be connected constantly and the fan speed is actually controlled with either a variable voltage to the PWM pin or I'm guessing an actual PWM of 12v would be more likely. I have tested this with 12, 5 and 3v to the PWM input and it works.

I'm not trying to PWM the main 12v rail, most examples I've seen show this.

So what I am trying to do is control 4 of these fans with an arduino uno.

If I take a 12v wall wart and power the 12v rail on the fan, then use a mosfet to produce the 12v PWM signal using the arduino to drive the PWM input on the fan, is this the way to go? Can anyone show me an example of how to do this using 1 12v PSU?

My knowledge of transistors/mosfets is nil!

Thanks,


texts: How to determine voltage across LEDs in a circuit?

texts:
I simulated a basic circuit in Orcad but I don't know how it found voltages(6.08 V and 3.04 V) on the nodes? How do I calculate those voltages mathematically? I am attaching three image files of schematics and values.

NOTE: Current value in circuit is 23.92mA according to OrCAD calculations.

This is schematic diagram with values

These are LED values

These is the voltage across both LEDs

Please help me to understand this.


texts: where are constant variables stored in microcontroller?

texts:
As per the memory layout of C program ,constant variables are stored in the Initialized data segment  of the RAM. But as per some of the Microcontroller memory layout ,const variables are stored in FLASH Memory.
I have also seen that the size of BIN file of my code increases when I change
const variables to Macro definitions? Help me clear this ambiguity. I used Nuc2240 Cortex M0
.


texts: How does a solar garden LED work with just 1 AAA battery?

texts:
I am converting some solar LED garden lights to emit infrared light for a raspberry pi critter camera to see what kind of wildlife trifles through my garbage at night.

I just have one question.

These solar garden lights have a small 3v solar panel charging a AAA battery during the day.

How can a single AAA battery with just 1.2 volts power an LED?

When I take it out of the circuit board it fails to work.

There are no visible joule thief's or any other work arounds.

Ideas?


texts: Varying Speed of Brushless Motor Within The Same Cycle

texts:
Is it possible to vary the speed of rotation of brushless motor in its driver within the same cycle of rotation? I read that BLDC drivers use sinusoidal waves to drive the motor, would it be possible to change the shape of one sine peak thereby causing slowdown in one part of the cycle?

My goal is to be able to navigate a two rotor drone, if I could modify speed in one part of one rotor, that could cause a tilt.

The idea is based on this research,

https://www.modlabupenn.org/2014/10/23/underactuated-rotor/

They modify the tilt of the blade causing it to slow down in one part of the cycle. I was wondering if the same result could be achieved through the driver.


texts: Can you please help me identify this 2-pin, weatherproof DC connector?

texts:
I'm fixing an outdoor display item for a friend, and I need to replace the connector. I've pored over images from different Google searches, but I don't know if this type of connector has a special name. It is a 2-pin connector. The male pins have a D-shaped key to ensure proper polarity and are held in place by a plastic nut. I have several pictures of the connector, and I can provide dimensions if needed. If someone can point me in the direction of a vendor, that would also be helpful. I checked Jameco and McMaster-Carr, but I'm sure there are specialized suppliers that I don't know about.
Thanks in advance for your help.


texts:
We're using an LM393 Light sensor and a laser transmitter used for counting the fry that will enter into our machine. The machine counts properly when we use an object like a pen or a stick in front of the sensor.

Our problem is:
when water passes through the machine, it also counts the water and not only the fry.


texts: Why is the resistance of parallel circuits lower than either of the individual parts

texts:
I am watching this tutorial, and topic of parallel circuits came up. In the below image, the combined resistance is 60Ω, which is less than either of its parts (150Ω and 100Ω).
I understand how the combined resistance is calculated, with the 1/(1/150Ω + 1/100Ω) formula, but I still don't understand why the overall resistance is lower. Wouldn't it be impossible for anything to move through with less than 100Ω resistance?
My understand is that the electrons want to get from positive end of the voltage source to the negative end, and resistors reduce the speed that can happen. So, why does adding two resistors in parallel offer less resistance than if there were only one?


texts:
Could anyone advise me on how I would be able to solder on wires and use a relay to mimic a button press on the attached remote control?
I would not need to still be able to use the remote buttons when the relay is connected, I have a spare remote.


texts: How many watts does a 40 MHz radio frequency signal create?

texts:
I am new to the study of electromagnetic frequencies and electrical engineering as  a whole.

I am trying to understand how to convert a radio frequency into energy, or calculate the power density of a radio signal. i.e. ->

40 MHz = (x) Watts / meters^2 | Solve for x

Anyone have any idea?


texts: If I connected two outputs with a wire, one with the information A+B and the other with C+D what would these two combined signals make?

texts:
Lets suppose:

I connected the output of 2 different OR logic gates:

out 1: A+B
out 2: C+D

with a wire leading out such that these 2 outputs are connected.

what would these signals form to make?

If I was to somehow 'read' these what would it be?


texts: Switch a custom Arduino between wired and wireless connection

texts:
I have custom 5V 16MHz Arduino that runs grbl and I was hoping to use one of the HC-05 bluetooth modules to control it wirelessly. This Arduino can be connected to a USB port through a FTDI chip. I'd like this to work with either of them and not both of them. This works for the most part and here is the 'truth table' I've experienced:

USB  Bluetooth  Works over  Works over
ON   ON         USB?        Bluetooth?
---  ---------  ----------  ----------
Y    Y          N           Y
Y    N          Y           N
N    Y          N           Y

I'm guessing when both are ON the USB does not work because they both share the same RX and TX lines of the Arduino and it seems priority is being given to the bluetooth connection. Is there a way such that when the USB cable is plugged in to the host PC the bluetooth module cannot be used and priority is given to the wired connection?


texts:
I was testing a board of mine. I was testing the boards for any shorts. I have 3 Voltage planes 12V,5V and 3.3V.
I was using a multimeter in the connectivity/short mode to test if the Vcc and GND are shorted or not.
I have seen a strange behaviour. I connected the 2 probes of the multimeter to GNDs. So it has a long beeping noise which denotes a short(and is right).
Then I connected one of the probes to a non GND pin and it shows a short(1sec) beep and then silent.

What is this phenomenon. And what can be the causes of this pls.


texts:
I'm a newbie trying to figure out how to power a DIY project using USB-C PD.
I'm building a project using about 120 RGB LEDS (consuming 60mA at 5V) and a Raspberry Pi 4 (max 3A at 5V). So I would expect a max load of 7.2A for the LEDs + 3A = 10.2A.
I'd like to power both using the same USB-C port.
I have a 60W USB-C PD charger which would provide me with 3A at 20V and I had the intention to use this as an input for a step-down DC-DC converter (XW-12-5-50W) that would output 10A at 5V.
Is there a way I can get 20V 3A out of my charger via a USB-C PD module? I have a ZY12PDN USB-C PD module but I think the max output is 3A, so it might not be the right option.
Thanks


texts:
I have a very noisy 5V supply, the noise is in very low FQ around 1kHz.

From all the components In my project there is only one I have to provide with 10Hz - 2kHz clean 5V.

But because I need 5V and I only have 5V. I can not just use LDO.
So my current idea is to use low noise LDO with boost converter:

LT1109
LT1761

simulate this circuit – Schematic created using CircuitLab

I'm looking for integration solution and right now I have found only this one:

I found this one (http://cds.linear.com/docs/en/datasheet/3537fd.pdf) but Rejection Ration of this LDO is disporting + I would not have a way to hand solder it.

Any suggestion ?


texts: I have some solar panels, that I don't have any information about it. How can i measure how much current it is able to deliver? With my multimeter under the sunlight? Can I test it with a light bulb if there is no sunlight available at the moment?


texts:
I am confused about the I/V Conversion at the output of this DAC (PCM1798)

In the electrical characteristics section, a dc output current (called "Center Current") of -3.5 mA is given, for zero output.  In another DAC we have used(AD1955), this negative current specification is known to actually stand for current flowing into the device, so I am interpreting this specification also as current into the device.

The typical application circuit from the datasheet gives the following I/V conversion circuit for the output.

As far as I can see, the output voltage at I_OUTL- is 0V, which means that the "Center Current" of 3.5 mA would have to flow into the device with zero voltage drop, since the DAC is only supplied with 5V to GND.

There is an evaluation board for this particular DAC, and in that circuit a different configuration is used, where the voltage at I_OUTL- is roughly 0.7V, which would allow current flow into the DAC (the part number on the schematic is different, but the document states that it is valid also for the PCM1798)
The eval board is called "DEM-DSD1796/PCM1795/PCM1796/PCM1798" by the way.

Now the question:
How is it possible to use the I/V conversion shown in the typical application circuit? (image above)


texts: Altium : Place components in a square with one command

texts:
I remember I have seen someone in the past who could select component in the schematic in cross select mode and then later in the pcb layout to draw a square/rectangle surface, and then all the selected components in the schematic would place automatically in the drawn area in the pcb layout.

Does anyone know what is the procedure to perform this way ? I am a bit tired of dragging component one by one from romm to area where they should be located on the pab board.


texts: Connecting RaspberryPi & Leonardo-voltage divider needed?

texts:
According to this article when connecting a RPi to a Uno a voltage divider is needed because of the voltage difference.

Does the same apply to a RPi and Leonardo?


texts:
The first box is my modulating signal and the last box is my demodulated signal (filtered signal)

I used my signal to change the duty Cycle of a PWM modulator (fix PWM frequency and variable Duty cycle ).
MY PWM output frequency is 20KHz.
My input signal it will be from 0 to 100Hz.

My question is what is the best way to filter the signal to obtain the lowest distortion ?

I have two way, the simple one is to use an diode envelop detector:

The second which I just read about is Infinite Impedance Detector

What are your recommendations ?
Is it enough to use an diode envelop detector with third order low pass filer to eliminate the ripples ?


texts: Current-Voltage curve of Light emitting diode

texts: Under Real time Applications of LED, I am getting negative current in forward voltage(mili volts)...Please tell me what is the reason behind this and how can i avoid it from getting negative current.


texts: TIP120 transistor overheating with heatsink

texts: The transistor gets really hot even though I am using a heatsink. Have I connected something wrong?


texts:
I've used two-pronged LEDs and Diodes, but I've come across a three-pronged one:

What is this component called, and how would it work?


texts: I need some help understanding the schematics of DIY HS102 oscilloscope

texts:
I was looking on the schematics for the DIY HS102 oscilloscope by Martin Loren (http://hscope.martinloren.com/HS102-oscilloscope.html)
But I'm a bit confused about the role of the ASM1117 (LDO regulator ASM1117-1.2). it seems that the output is not used, so what's the point of having it?


texts: Using ATX PSU as stand-alone power supply: PSU doesn't stay on longer than ~1 second

texts:
as the title suggests I am trying to use an ATX power supply (Seasonic modular X-1050) as a stand-alone power supply. I have roughly followed guides available online, the best of which I have found to be this one on Instructables.

I have PS_ON (green) grounded to 0V (black). Once this is grounded, I switch on the PSU and the fan spins up and it briefly outputs +12V and +5V (I haven't checked other outputs) for  less than 1 second. I have also tried this with PS_OK connected to +5V. The PSU then turns off until I unground PS_ON and reground it.

I have also tried the above, with the addition of a load on the +5V rail, namely two USB devices I had lying around (iPod touch and AA battery charger) and 1 laptop HDD. I estimate the load to be ~1.2A or equivalent to a ~4.2Ohm resistance.

How do I get my power supply to stay on? Do I need additionally loads on +3.3V or +12V? Thanks


texts:
There's a Youtube video of a high speed ADC, using JESD204 high speed interface, interfacing with an FPGA via a fiber-optic transceiver:  http://youtu.be/vkrms2udeKI

Is there a commercial version of this? Are there any papers, Tech Notes, etc. discussing the problems [speed, distance, number of fibers etc] involved in creating such a link?

In the area I'm considering, the optic fiber runs would be up to 5 kilometres...


texts: STM32F0 EEPROM read problem with several variables

texts:
I use st eeprom library to save my variables. When I save a single variable, I do not have any problem. I can save it, refresh it and after disconnecting the power, I can read that variable. Now I want to save three different variables in three  different pages, when I want to read them, I see the latest value in all of them. With this code I save the variables:
HAL_FLASH_Unlock();
EE_Init();
EE_WriteVariable(VirtAddVarTab[0], 10);
EE_WriteVariable(VirtAddVarTab[1], 20);
EE_WriteVariable(VirtAddVarTab[2], 30);
HAL_Delay(10);
EE_ReadVariable(VirtAddVarTab[0], &VarDataTab[0]);
EE_ReadVariable(VirtAddVarTab[1], &VarDataTab[1]);
EE_ReadVariable(VirtAddVarTab[2], &VarDataTab[2]);
HAL_FLASH_Lock();

After programing this code, I program this one:
HAL_FLASH_Unlock();
EE_Init();
EE_ReadVariable(VirtAddVarTab[0], &VarDataTab[0]);
EE_ReadVariable(VirtAddVarTab[1], &VarDataTab[1]);
EE_ReadVariable(VirtAddVarTab[2], &VarDataTab[2]);
HAL_FLASH_Lock();

And I see "30" in all of the memory them instead of 10,20,30
What is my problem?
page addresses :
#define ADDR_FLASH_PAGE_0     ((uint32_t)0x08000800) /* Base @ of Page 0, 1 Kbytes *///0x08000000
#define ADDR_FLASH_PAGE_1     ((uint32_t)0x08001000) /* Base @ of Page 1, 1 Kbytes *///0x08000400
#define ADDR_FLASH_PAGE_2     ((uint32_t)0x08001800) /* Base @ of Page 2, 1 Kbytes *///0x08000800
#define ADDR_FLASH_PAGE_3     ((uint32_t)0x08002000) /* Base @ of Page 3, 1 Kbytes *///0x08000C00
#define ADDR_FLASH_PAGE_4     ((uint32_t)0x08002800) /* Base @ of Page 4, 1 Kbytes *///0x08001000
#define ADDR_FLASH_PAGE_5     ((uint32_t)0x08003000) /* Base @ of Page 5, 1 Kbytes *///0x08001400
#define ADDR_FLASH_PAGE_6     ((uint32_t)0x08003800) /* Base @ of Page 6, 1 Kbytes *///0x08001800
#define ADDR_FLASH_PAGE_7     ((uint32_t)0x08004000) /* Base @ of Page 7, 1 Kbytes *///0x08001C00
#define ADDR_FLASH_PAGE_8     ((uint32_t)0x08004800) /* Base @ of Page 8, 1 Kbytes *///0x08002000
#define ADDR_FLASH_PAGE_9     ((uint32_t)0x08005000) /* Base @ of Page 9, 1 Kbytes *///0x08002400
#define ADDR_FLASH_PAGE_10    ((uint32_t)0x08005800) /* Base @ of Page 10, 1 Kbytes *///0x08002800

And I have two IROM
IROM1 start address is 0x8000000 and its size is 0x400
IROM2 start address is 0x8000800 and its size is 0xF800
I define these in the beginning of the program :
uint16_t VirtAddVarTab[20];
uint16_t VarDataTab[20];

I did not initialize it. Do you mean I put for example 0 in the start and after that I use them?


texts: I have a 1960's Philips all transistor radio which I restored recently and replaced two of the AF11x PNP germanium transistors on the mixer/oscillator and IF amp stages. After these replacements, the set is picking up stations fine on all the SW 1/2/3 bands, but the sound is very low as if there is no amplification, but the audio stages can't be the culprit since the pick up is working fine. The second suspect appeared the antenna connections from the wave-changer but since I'm not having the circuit diagram of the radio I can't fiddle with them. What could be the reason for this almost inaudible sound?


texts: Correctling a sign in a simple circuit with parallel resistors

texts:
I've a simple circuit with two parallel resistors, but my derivation of the circuit equations gives a sign the opposite of what I know to occur, so I'm looking for help fixing the error as well as a general strategy for keeping the signs correct in the future.  Consider the circuit:

The voltage law on the left gives
$$v=v_1 \Longrightarrow v=i_1 R_1$$
and the circuit law at the top node gives
$$i = i_1 + i_2.$$
Now, I know that the voltage drop across the parallel resisitors should be the same and equal to v.  However, when I consider the voltages on the rightmost loop, I see
$$v_1 + v_2 = 0 \Longrightarrow i_1 R_1 + i_2 R_2=0$$
To me, if I have polarity labeled, even if it doesn't matter for resistors, I place positive flow into + as the left and positive flow into - on the right.  This is reversed for negative flow.  That said, this leads to the incorrect equation above.  If we do the outer loop, this gives the correct sign with
$$
v = v_2 \Longrightarrow v = i_2 R_2.
$$
which would imply, correctly, that
$$
i_1 R_1 = i_2 R_2.
$$
As such, what is the correct sign convention in this case in order to give the correct result?  What is a general strategy for determining the sign and maintaining consistency when the current is divided at a node?


texts: How to connect a photovoltaic to a heating element directly

texts:
I am trying to connect a photovoltaic panel directly to a heating element (coil) without using a battery or an inverter and switch it on or off by using a transistor or a thyristor.

I am well aware that the power won't be constant throughout the day and not have power at all in the night, so you don't have to warn me about that.

The panel supplies a max of 37V and a max current of 8.3A. First I was looking for a high current MOSFET and found quite a few. At home I had IRF3205 which are rated for currents up to 110A and 55V.

Just to be on the safe side, I connected two of them in parallel by following two schematics I found on stack overflow. You can see them in the pictures below:

And here's the link to the stack overflow post: Parallel MOSFETs

I placed the MOSFETS on a large heatsink and then I connected the photovoltaic panels. The MOSFETS have a diode between source and drain which got shorted in just a few seconds after I connected the power from the panels.

I also have a large diode connected to the heating element to prevent reverse current.

I never connected the +5V DC to the gate of the transistor which means it was always closed.

I have also tried using TIP35C which shorted out just like the IRF3502.

Can anyone suggest a solution to this problem with any kind of transistor, or maybe using thyristors and an optocoupler?

Just to clarify some things, the transistor or thyristor will be connected to a microcontroller which will control the switching of power from the photovoltaic panel to the heating element.


texts: How can I be sure my replacement SPI flash chip will work?

texts:
I am currently using the Cypress CX3 MIPI-USB bridge chip which needs an attached SPI FLASH chip. The datasheet recommends the W25Q32FW part, which is now obsolete.
I would like to choose a replacement device e.g. AT25SL321, but it must obviously be compatible.
What features of the SPI chips must be checked to ensure the replacement is compatible? Is it enough to go through the SPI protocol waveforms and check they all match, or is there anything in the layout of the memory which might be a gotcha? Or are they generally all compatible, and this is nothing to worry about?


texts: Smoothing out a switching DC power supply

texts:
I have an audio device that is powered by a dual switching DC power supply (+15V/-15V). I am hearing a hum on the audio device and I believe it is from the switching power supply. Can someone recommend a simple circuit to add to the power supply output to help smooth out the ripples?
An earlier thread suggested a 0.1uf capacitor and a 10uf cap in parallel over the outputs. But since this is a +/- power supply I'm not sure about the polarity of the electrolytics, or if there are other factors to consider.


texts:
One disadvantage of OFDM is apparantly the high instantaneous power variations (see Wikipedia).

What causes this? I assume this is a problem of forming orthogonal waveforms since regular frequency multiplexing (FDM) doesn't suffer from these high instantaneous power variations.


texts: Non-zero voltage between unloaded h-bridge output and input

texts:
I have an unloaded h-bridge, with the following layout:
U6 & U9 are totem-pole mosfet drivers--nothing particularly exciting there. When I have Q1 & Q7 on, I find that there's 70mV between OUT+ & 12V, as well as OUT- & 12V. This isn't a stray capacitance or anything like that--when I short it out with a 120ohm resistor, I still get a potential difference of about 1.75mV. When I remove the resistor, it jumps up to 70mV immediately.
Generally, this wouldn't be a problem. However, I'm also calculating the current through the internal resistance of the high-side mosfets, so this makes it impossible to get a good number, since the amplifiers are saturated. For reference, here's the amplifier portion of the circuit:

Any suggestions about what might be causing this stray voltage and how I can remove it?


texts:
Im new to PIC. Im working on PIC24FJ64GA002 PIC. Can any one pls explain how below code says "set RP10 to external interrupt"?

                   `RPINR0  =   0x0A00;`

I have gone through "PERIPHERAL PIN SELECT REGISTER MAP" from datasheet, RPINR0 register  didnt mention RP10. RPOR5 has mentioned RP10 only.

Thanks.


texts: Any potential issues with running traces on both sides to increase conductivity?

texts:
I have a few relays on my circuit board, they are classed as 10A 30VDC. The size and thickness of the traces I can create on my PCB is nowhere near that so I am thinking of running a parallel track on the other side of the PCB along with a few vias to increase the conductivity. Are there any concerns around this solution?
Thanks,
Marcus


texts: Interfacing OV7670 camera with STM32F4 (no FIFO)

texts:
I have to interface my STM32F401RE with an OV7670 camera module without external AL422. I followed some of the many tutorials for Arduino, and I was able to capture images using Arduino UNO. Unfortunately my requirements force me to use STM as board and to program it using the HAL library from ST.
So my aim is to be able to capture an image on request, so I tried to adapt the code structure used for Arduino to my board and library but the results are quite frustrating because all I could get are messy noisy images, like these

At the moment what my code does is taking an image and send it via UART where a Java application is listening the COM port and shows the image. Some more details:

I'm sure about the Java code correctness because if I send an image made of a single color it is perfectly shown;
I set the camera using QQVGA resolution and YUV color mode, the register values are the same that can be found surfing a bit on the net;
I tried both sending the image in stream, as in the first picture, and saving it in SRAM and then sending, second picture (there is a quite notable difference because the second case seems largely pure noise);
At the moment the camera is fed with a 8MHz clock form MCO pin that according many users seems to work even if the datasheets states 10MHz as minimum;
I played a bit with clock prescaling, but always striped messy images;
Sender and receiver baud rates are correct.

I am almost sure that there is some problem in reading signals correctly according the camera timing but I really cannot spot the problem. In my current settings PCLK does not toggle during horizontal blanking. The main function to capture the image is the following (almost the same that can be found surfing Arduino Forum):

    int camera_capture_image(uint8_t image_buffer[][2*COLS]) {
    uint16_t hg = 120, wg = 320, lg2;
    int num = 0;
    uint8_t buf[320];
    while(HAL_GPIO_ReadPin(VSYNC_PORT, VSYNC_PIN) == GPIO_PIN_RESET);
    while(HAL_GPIO_ReadPin(VSYNC_PORT, VSYNC_PIN) == GPIO_PIN_SET);
    while(hg--){
            uint8_t*b=buf,*b2=buf;
            lg2=wg/5;
            while(lg2--){
                while(HAL_GPIO_ReadPin(PCLK_PORT, PCLK_PIN) == GPIO_PIN_SET);
                *b++=(uint8_t)GPIOC->IDR;
                while(HAL_GPIO_ReadPin(PCLK_PORT, PCLK_PIN) == GPIO_PIN_RESET);//wait for high
                while(HAL_GPIO_ReadPin(PCLK_PORT, PCLK_PIN) == GPIO_PIN_SET);//wait for low
                *b++=(uint8_t)GPIOC->IDR;
                while(HAL_GPIO_ReadPin(PCLK_PORT, PCLK_PIN) == GPIO_PIN_RESET);//wait for high
                while(HAL_GPIO_ReadPin(PCLK_PORT, PCLK_PIN) == GPIO_PIN_SET);//wait for low
                *b++=(uint8_t)GPIOC->IDR;
                while(HAL_GPIO_ReadPin(PCLK_PORT, PCLK_PIN) == GPIO_PIN_RESET);//wait for high
                while(HAL_GPIO_ReadPin(PCLK_PORT, PCLK_PIN) == GPIO_PIN_SET);//wait for low
                *b++=(uint8_t)GPIOC->IDR;
                while(HAL_GPIO_ReadPin(PCLK_PORT, PCLK_PIN) == GPIO_PIN_RESET);//wait for high
                while(HAL_GPIO_ReadPin(PCLK_PORT, PCLK_PIN) == GPIO_PIN_SET);//wait for low
                *b++=(uint8_t)GPIOC->IDR;
                image_buffer[hg][lg2] = *b2++;
                num++;
                //HAL_UART_Transmit(&huart2, b2++, sizeof(b2), HAL_MAX_DELAY);
                while(HAL_GPIO_ReadPin(PCLK_PORT, PCLK_PIN) == GPIO_PIN_RESET);//wait for high
            }
            /* Finish sending the remainder during blanking */
            lg2=320-(wg/5);
            while(lg2--) {
                image_buffer[hg][lg2] = *b2++;
                num++;
                //HAL_UART_Transmit(&huart2, b2++, sizeof(b2), HAL_MAX_DELAY);
            }
        }
        return num;
}

If you need any other detail I am ready to provide it.


texts: Adapting a universal preamp to a piezo microphone

texts:
for a school project I'm trying to adapt a universal mic preamp to a piezo mic: obviusly with the original circuit i've obtained a low distortion.
The preamp is a Velleman k1803 mono preamp:

I've read in another topic that R1//R2 = 50k is the input impedance.
Generally piezo preamps have an input impedance of minimum 1Mohm/max 10Mohm so I'm asking myself: can I change R1 and R2 resistors and make it work like an high impedance input?
This preamp in particular has a peak of 40mV for the input and a piezo mic has clearly several volts when you play your instrument with an hard dynamic and generate distortions.
Hope my topic is clear and thanks in advance for your advices (:


texts: What are the best Electronics Soldering Techniques?

texts:
Is there a tutorial that shows different techniques and the dos/don't of soldering?

I was doing a kit last night that just said heat up both components for 5 seconds then put the solder close and let it oose into the join -> they all worked nicely....but as instructions go they are a bit basic,  and from past experience there are certain components that you shouldn't heat up too much.

I was doing Through-hole soldering but Surface Mount would also be great to learn about.


texts: How to correctly wire a SilentStepStick (TMC2130) to Arduino? (Noob question)

texts:
Ingredients:
1) Arduino Uno
2) SilentStepStick Stepper Driver (TMC2130)  (datasheet)
3) Fully Independent 24V and 5V power supplies
3) Driver code from: watterott
4) Board pinouts

I've wired up the TMC2130 driver board straight to an Arduino for bench testing.
+24V is connected to VM, and +5V connected to Vio.

Question: How to connect the ground's? Documentation seemed vague. There are two GND pins. Should the the -ve leads from each of the two power supplies be connected, one to each ground?  Or should only one ground, from one power supply be connected, to avoid any ground loops?

Sorry I know this will be a super easy question for someone. Thanks


texts: Brushless motor and voltage characteristics

texts:
In order to choose a small motor for a size constrained design, I have been looking at Faulhaber https://www.faulhaber.com/fr/produits/series/3216bxtr/ motors.

They always offer different models with different nominal voltages but the other characteristics remain more or less the same (dimensions, speed and torque), except for the current that is inversely proportional to the voltage (so the same power as well).

Since they are one of the only manufacturer found that offer such an option, I was wondering : How are they able to do so?

I assume that each model have different winding with a different number of turns and wire diameter (or that magnets are changed for each model) but it's just an hypothesis... If anybody could  satisfy my curiosity I would be delighted!

Thanks in advance!


texts: Electronic/electrical actuator that HOLDS its position if power is lost?

texts:
Is there any sort of electronic/electrical actuator that HOLDS its position if power is lost?

I am working on a project for a clutch actuator in an AWD system. One of the required tasks is to provide 3000N of force to a pressure plate which compresses a clutch pack.  This has to be accomplished by using the standard 12V or whatever you can get from an automobile.

The problem is, a design spec states that the clutch system needs to maintain its state if the vehicle has lost power.  This rules out the usage of an electromagnetic actuator, right?

The only thing I can think of doing is using some sort of mechanical lock after actuating with the electromagnetic actuator.

Would it make more sense to use a hydraulic actuator instead?

This actuation process needs to take no more than 200ms, so I'm not sure if something like a worm gear would be suitable (they tend to be slow, correct?)

Thanks in advance!

PS. If anyone has any recommendations of books about actuators in general, please mention them here!


texts: Controlling Proportional valve with NPN transistor (TIP 122) using PWM

texts:
We are working to control the proportional solenoid valve (9C, 2W) (VSO by parker, datasheet) by changing the voltage across it. For this we are using PWM from the controller, thus changing the average current across the valve.

The controller (i.MX RT1060 from NXP) is capable to give up-to +3.3V. We are using TIP 122 NPN Darlington transistor to switch the voltage to 9V. Whenever we are changing the duty cycle from 95% to 100%, then only the valve is getting ON. If we are giving duty cycle is below 90% the valve is completely OFF.

We are giving 5KHZ PWM frequency, with 16 bit PWM resolution. The experiment result is mentioned below.
Have a look at the sudden increase in the voltage from the duty cycle 95% onward.
We are getting controlled flow, in between 95% to 99% only. If the circuit should work, if should work for the whole range.

Initially we have used base resistor of 390 ohm. We thought at lower duty cycle the voltage from the controller to the base of the transistor should be less. We decreased the resistor value from 390 to 190 and then to 47 ohm. Still did not get significant change across solenoid voltage at lower duty cycle. The flow vs duty cycle graph is not matching the datasheet.


texts: General transfer function for a bandpass filter

texts: Is there a general form of transfer function (with peak frequency \$\omega_m\$ and quality factor \$Q\$) relevant for any type of bandpass filter ?


texts: Quartus Prime: Block synthesized away - why?

texts:
Doing my very first steps with FPGA. I successfully built an SPI slave (code found somewhere in the web) that receives something and turns an LED (via output SPI_DONE)  on my Altera Max10 evaluation board.
First I had simply the VHDL file, did the pin assignement, and it worked fine in simulation and on the real board.

Then I tried to create a "BDF" and replace the clk signal by the output of a PLL block.
With this approach, Quartus keeps warning me that the PLL block is "synthesized away" and that there are "No clocks defined in design".

I read some tutorial on integrating such a PLL block from the IP catalog, but I can't find what's wrong with my setup.
Any advice?

This is how my BDF looks like:

Here the code of spi_slave:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity spi_slave is
  port (
    RESET_in    : in  std_logic;
    CLK_in      : in  std_logic;
    SPI_CLK     : in std_logic;
    SPI_SS      : in std_logic;
    SPI_MOSI    : in  std_logic;
    SPI_MISO    : out std_logic;
    SPI_DONE    : out std_logic;
    DataToTx    : in std_logic_vector(7 downto 0);
    DataToTxLoad: in std_logic;
    DataRxd     : out std_logic_vector(7 downto 0)
    );
end spi_slave;

architecture Behavioral of spi_slave is

    signal SCLK_latched, SCLK_old : std_logic;
    signal SS_latched, SS_old : std_logic;
    signal MOSI_latched: std_logic;
    signal TxData : std_logic_vector(7 downto 0);
    signal index: natural range 0 to 7;
    signal RxdData : std_logic_vector(7 downto 0);
     signal comparison_value : integer;
begin

 --
 -- Sync process
 --

process(CLK_in, RESET_in)

    begin
        if (RESET_in = '1') then
            RxdData <= "00000000";
            index <= 7;
            TxData <= "00000000";
            SCLK_old <= '0';
            SCLK_latched <= '0';
            SS_old <= '0';
            SS_latched <= '0';
            SPI_DONE <= '0';
            MOSI_latched <= '0';
        elsif( rising_edge(CLK_in) ) then
            SCLK_latched <= SPI_CLK;
            SCLK_old <= SCLK_latched;
            SS_latched <= SPI_SS;
            SS_old <= SS_latched;
            -- SPI_done <= '0';
            MOSI_latched <= SPI_MOSI;

            if(DataToTxLoad = '1') then
                TxData <= DataToTx;
            end if;

            if (SS_old = '1' and SS_latched = '0') then
                index <= 7;
            end if;

            if( SS_latched = '0' ) then
                if(SCLK_old = '0' and SCLK_latched = '1') then
                    RxdData <= RxdData(6 downto 0) & MOSI_latched;
                    if(index = 0) then -- cycle ended
                        index <= 7;
                    else
                        index <= index-1;
                    end if;
                elsif(SCLK_old = '1' and SCLK_latched = '0') then
                    if( index = 7 ) then
                        if (to_integer(unsigned(RxdData)) = 160) then
                            SPI_DONE <= '1';
                        end if;
                    end if;
                    TxData <= TxData(6 downto 0) & '1';
                end if;
            end if;
        end if;
end process;

   --
   -- Combinational assignments
   --

   SPI_MISO <= TxData(7);
   DataRxd <= RxdData;

end Behavioral;

PIN_N5 is a clock input, and everything works fine without the pll block and N5 directly connected to CLK_in.


texts: Common Emitter Amplifier design problem - seeking quick solutions updated

texts:
Looking for a quick check of solutions to the below problem.

Design requirements:
AC gain of G = -10
Output impedance of R = 4.7 kΩ
T1 is 2N3904 npn transistor with β = 100 and
base-emitter voltage drop Vbe = 1.0 V

What are values of Rc and Re?
What is input impedance?
What value of Vcc should be chosen?
What values of R1 and R2 should be chosen to set the DC bias voltage at the base?

Update:
So here is "solution" - thought process and results
Re using the value for output impedance and gain: G = -Rc/Re; Rc = output impedance = 4.7k so Re = 0.47k
moving to finding the quiescent current of the collector again using gain and Re = 25/Ic gives Ic = (25*10)/470 = .053 mA so Vc = 0.053mA *4.7k = 0.235V
then calculating the input impedance: Zin = 25*β/Ic = 5 k
Using Vbe to get Vcc, assuming Vbe (given) = Vcc - Ve and Ie = Ic = Iq so Ve = Ie*Re = 0.053mA*0.47k = 0.0235V so Vcc = 1+0.0235 = 1.0235V but remembering to bias to middle of the load line so Vcc = 0.51V
Going through voltage divider to calculate R1 and R2:
Upper limit for R2 rule of thumb that it is less than or equal to one tenth of beta*Re so less than (100*0.47)/10 = 4.7k
Calculating Vb using given Vbe and Ve. (recalling transistor rules) Then calculating voltage across R1 and using ratio of Vr1 and Vr2 as same ratio for R1 and R2.


texts: Pass variable name as a string to task in verilog

texts:
I would like to create a task for debug purposes in which I can print the name of the variable and assign the value to that variable. I can think of these ways to do it with the following pseudo-code:

1) pass the variable by reference and the value, which seems to work fine and the variable gets assigned, but I can not figure out how to print its name.

reg myVarName;
debug_message1(myVarName, 1'b1);

// assigns myVarName=1'b1;
// Expected print output: "The variable name is myVarName and its value is 1"
task debug_message1(ref reg var, reg val);

  var = val;
  print("The variable name is %s and its value is %d", var.name, var);
endtask

2) pass variable name as a string, which makes it easy to print, but I don't know how to convert the string that contains the name of the variable to the actual variable, so I could assign to it.

reg myVarName;
debug_message2("myVarName", 1'b1);

// Need to somehow assign myVarName=1'b1;
// Printed output: "The variable name is myVarName and its value is 1"
task debug_message2;
  input string var;
  input    reg val;

  `var` = val; // need to make assignment here
  print("The variable name is %s and its value is %d", var, val);
endtask

3) Pass the variable, its name as a string, and the value, which does not like the second and the third arguments, because they are defined when calling the task, which gives the following error message:

Illegal connection to the ref port 'varname' of function/task 'debug_message3',formal argument should have same type as actual argument.

The same kind of error comes up for the 'val' argument.

reg myVarName;
debug_message3(myVarName, "myVarName", 1'b1);

// Assign myVarName=1'b1;
// Printed output: "The variable name is myVarName and its value is 1"
task debug_message3(ref reg var, string varname, reg val);

  var = val; // need to make assignment here
  print("The variable name is %s and its value is %d", varname, var);
endtask

Is there a way to implement any of the 1, 2 or 3 approaches?


texts: Beginner questions on some SMD components in phone motherboard

texts:
I'm trying to understand smartphone motherboard components and have a few questions that might be easy for some of you to answer. Please refer to the attached image for the question numbers:

Are these all capacitors?
What is that tiny component that was accidentally moved/damaged by repairmen I guess.
What are these black and silver components? Inductor coils?
What is this component? It's blackish in nature than how it appears in this photo.


texts: What are the tradeoffs for the various options coupling a LED to an optical fiber?

texts:
I'm trying to couple a white LED to a fiber bundle that's comprised of several 30 uM silica fibers.  The bundle outer diameter is on the order of .5 mm.  The NA of the fiber is .87 and the whole bundle is placed in a stainless steel ferrule that's .125" in diameter. I've read about different methods of coupling -- everything from a ball lens to gluing the fiber directly over the LED die.

I'm curious if anyone has experience doing something like this.  Can anyone delineate the advantages/disadvantages of the various methods?  Are the main tradeoffs cost vs transmission efficiency?  If so what methods are on which end of the spectrum?

It's worth stating that I'm not sold on any particular LED, but I have experimented with simply holding the ferrule over a LXML-PWC2 -- tons of light comes in (enough for my application) with iF ~400mA.  This would be a reasonable solution except that the efficiency of transfer is terrible (obviously) so I have to use more current than I'd like.  The result is a rather large heat sink, which I'd like to shrink or ditch all together.


texts: Burning out relays when supposed to be within ratings

texts:
I am using this Normally Closed Relay on a 24V circuit: DataSheet

The circuit is 24VDC source, which I measured the Amperage in series to be 29mA at the highest. I've breadboarded a lower voltage circuit (5V) fine with the relay. When I put the relay into the 24VDC circuit, I am able to open and close the circuit one time, but it burns out the relay: the relay can never be switched open again. I notice when switching it under the 24V load that when I close the switch again, it delays before completing the circuit.

For the switched circuit: I have 24VDC source connected to pin 1 of the Relay, and the rest of the circuit connected to pin 4 which is connected to a the magnetic door lock (and a push to exit button, which may use a capacitor to trigger the 30 second open circuit)

For the switching circuit: I have 5VDC from a Raspberry Pi connected to pin 2. On pin 3, I have it connected to the Collector side of an NPN relay, and the Emitter side is connected to a Ground pin on the Raspberry Pi. I have one of the GPIO pins connected to a 2kΩ resistor, which is then connected to the base of the relay

Reference circuit I used for my circuit is here


texts: hierarchy of op-amps choice for class use

texts:
I saw mentioned in another question that a 741 is one of the worst designs.  An LM324 is also pretty low-end.

Is there a better low-end operational amplifier for the money?
I would just appreciate knowing a hierarchy of people's favorites.
Obviously, if I can get LM324 for 0.18, it's not comparable to a higher end opamp costing $4.
I think the fact that the LM324 is a quad is very useful for class because we can use one chip to build a positive feedback amp, then a negative feedback with a source follower front end, and finally a differential amplifier, all with a single chip.  So all things being equal I guess I would tend to prefer quad packages over others for that reason.

So I'm looking for the best opamp/$ in 3 categories:

classroom use
low noise/higher speed (say, in the 10Mhz range rather than 1Mhz)
Power (10W or thereabouts)

In addition, after reading a question here about differential amplifiers I looked on Avnet to see what I could get in a single package.  I found some really nice ones, but only in surface mount packages.  Is there anyone selling differential amplifiers in PDIP format so they can be used in class?  They are pricier as well, of course.


texts: DIY Photobooth: LED puck lights potentiometer suggestions

texts:
I'm building a Raspberry Pi powered photobooth, and want to add some lighting.

I purchased this set of led puck lights, and would love to control their intensity from the Raspberry Pi, instead of the knob on the driver. The first row in this spec sheet describes the LED driver.

My goal is to replace the knob/potentiometer with a digital one and control through SPI, but I'm at the edge of my EE skills and not sure what the best digipot is for my application.

Any suggestions for a digipot?
Am I approaching this the best way?


texts: Connector datasheet is in chinese. Which part is which?

texts:
I have just a couple of questions...

Is the "male" side the one with the male contacts or the male contact shroud?
I'm also looking for the PNs for a 2 circuit configuration of the housing on the left side of the page.  I presume the number in parentheses is the PN for the contact and the left most table at bottom has the PN for the housing.


texts:
I've bought some cheap AC-DC converter online. The goal is to place it inside a roof lamp's base, and power an ESP8266 clone at 3,3 volts from mains (in Europe, so 220v/50Hz). The lamp connection (mains AC) runs through the roof and walls to the mains , and I can't know the length. I don't know the material or section either, nor if it's braided or solid.

So. The final goal is to power an ESP8266 which would activate either a relay or a dimming circuit. Of course, the same wires would be used to power the light through the relay or dimmer.

On the AC-DC converter, the places to connect N and L lines from mains seem quite small. And so I was wondering what section of wire I could use from the AC to the AC-DC converter, so it'd be a few centimeters (or inches).

The specifications for the AC-DC converter are the following:

Input characteristics:

  Input current:0.065 (AC110V) -0.032 (AC220V) A (at full load conditions)
  Input surge current:20A (full load)
  Input voltage:AC 85-265v 50/60HZ (at full load conditions)

Output Characteristics:

  Output voltage:DC3.3V (±0.2V)
  Output current:1A
  Output efficiency:85% (rated load)
  Output ripple:50Mv
  Power:3.5W
  Size:5.1*2.3*2.2(cm)
  Ambient temperature:-20 to 60 Centgrade
  Relative humidity:40 to 90% RH
  Switch overshoot:150%
  Output rise time:100MS


texts: can LM358 Output voltage be made equal to supply voltage?

texts:
I am using one op-amp of LM358 IC as a non inverting amplifier (Vcc-5V). Its input is from an IR proximity sensor. IR emitter used is SFH4350 and photodiode used is TEFT4300 also operating at 5V. I am pulsing my emitter at 15KHz using the second op-amp of LM358 IC as oscillator. Thus I also have to add a HPF (fc-11.5khz) at the input of amplifier part. I am feeding the output output of amplifier to an ADC which is reading values only up till 0 to 3.3V max. I am aware that LM358 is not a rail-to-rail op-amp, but I want my output voltage range to reach near 5V (+/- 0.5V). Is there some way out through which I could achieve the desired output voltage using the LM358 or some other IC but of the same price range?

Thank you all for your answers. I did a little research of my own and found the LMV358 which I think will do the job just fine.
LMV358 is a Dual Low-Voltage Rail-to-Rail Output Operational Amplifier available at even a lower price than LM358.


texts: What is the protective layer around microchips made out of?

texts:
I am just curious, what is the dark, almost black material that seems like all microchips are made out of? I did some searching on Google to try and find out, but I can only seem to find the material inside the chip, silicon, which I already knew. I am fairly certain the WHOLE chip isn't made out of silicon anyway.

Thanks!


texts: For this circuit, why won't ".param thing" resolve?

texts:
I have a voltage source V1 set to 5V, connected to a net named Vrser.
I then have ".param thing={V(Vrser)}", but "thing" won't resolve.
I have also tried ".param thing={V(V1)}".
What am I doing wrong?

LTspice XVII(x64) (17.0.21.0)


texts: What's the best way to integrate SPI and MSC buses?

texts:
I have two chips. The first chip has only an SPI interface. The second chip has only an MSC (microsecond channel) interface. What's the best way to integrate them? Do you know any IC manufacturer which has converters/adapters from SPI to MSC or vice versa? Should we create a custom SPI driver?

The first chip with SPI is SAK-XC2388E-136F128L.

I can't disclose information about the second chip, but is it very important? I think it's more important that it has an MSC interface and we need to integrate SPI with MSC.


texts:
I want to create a SPICE subcircuit file for an electronic component.
I have found the Verilog A code for the component, I want to know how to convert the Verilog A code to LTSPICE compatible subcircuit format.
If code conversion is not possible, where to learn programming of subcircuits for LTSPICE?


texts: Some help interpreting formula variables in Texas Instruments TPS565201 Buck regulator datasheet

texts:
I am working on a custom PCB for a robotics project, and so far it is going well. I already learned how to work with 3.3v/5v LDO voltage regulators, but now I need a high current 6V DC solution for the motors. I found the Texas Instruments TPS565201 as a solution, which would work great with 3S/4S LiPo batteries, and would give me the 6V/5A that I would need for my project.
I read the datasheet and used the typical application circuit to implement the IC on my PCB. The only step left is to choose the right coil. I used the formulas in the datasheet to calculate the values required for my project. Since I don't have much experience doing this, I did this in Excel to do the calculations more easily. I ran into some variables in the formula that I could not find a definition/explaination of (only an example value, but I want to understand what I am doing instead of just using that), could you guys maybe help me understand what these variables are?
The formula variables I need to calculate to proceed:

Lout
Cout
LO

These can be found on pages 13 and 14 of the TI datasheet
Unfortunately I could not find anything in the datasheet that explains what the variables should be/mean, which makes me assume that these variables should be common knowledge maybe? Could you guys guide me in the right direction?
Thanks in advance!


texts: Will a cheap RFID reader work behind a 2mm aluminium sheet?

texts:
I'm building a information contact panel that will serve as a point of communication between employees and their company. Part of this process involves putting an ID card to the panel, so it can be 'read' by an RFID reader inside the panel. I'm planning to use anodised aluminium for the front panel, with the rest of the enclosure made from treated wood and plastic.

From what I understand, Aluminium blocks radio frequencies (although this has been debated for certain specific situations). I'm using a cheap/standard RFID reader (RC522). Would cutting a small grill of 1mm or 2mm holes into the aluminium above the reader allow the RFID signal through to be read by the reader? Am also interested in other suggestions/thoughts too. Thanks in advance.


texts: Is it OK to route power traces underneath an MCU?

texts:
I am working on a 2 layer PCB: a STM32F405 break out board with I2C, SPI and UART. I am trying to minimize traces on the bottom ground plane and have arrived at a layout in which I have routed power traces underneath the MCU on the top layer.
Is it good practice to do that? Can the heating of the traces affect the MCU?
Attached is a snapshot of my layout. The highlighted traces are the power traces - 3.3V.

Thanks!


texts: Can I program or flash a microcontroller using UART? I previously thought UART is only for communication purposes.


texts: Shipping & Handling Electronics & Electro-mechanical parts

texts: What are common packaging(Shipping & Handling) guidelines (specs/stds) for Electronics & Electro-mechanical parts? Currently, working on adding onto our current generic guidelines for packaging aircraft parts. When it comes to electrical related components, we have some basic common sense packaging solutions. I think it's best to not re-invent the wheel in this scenario.


texts: Unknown electronic component. Does anyone recognize it?

texts:
A teacher gave me this electronic component.
In principle it looks like a resistor, but it has no value code.
I measured voltage, ohms, farads, etc.,  but it does not generate results.
Yes, when I hold it between my fingers it seems to give a high amount of resistance, but I don't know if it is because of my physical resistance or if it is with the heat I have a change.


texts: Can I use SCRs as the uppers in an H-bridge?

texts:
One might wish to switch DC through a transformer with an H-bridge. I'm leaving out antiparallel diodes and snubber caps, for simplicity.

simulate this circuit – Schematic created using CircuitLab

One issue with this approach is that the upper FETs need isolated gate drives, referenced to the windings of the transformer. This can increase the cost and complexity of the system substantially. It occurs to me that one might use SCRs in place of the upper transistors.

simulate this circuit

SCRs will have higher losses than FETs, and they consume more drive current, but they're substantially easier to drive and harder to kill, and cheaper at high voltages and currents. At high voltages and currents, one might use IGBTs instead of FETs, which would have losses more comparable to those of SCRs. SCRs would require separate antiparallel diodes.

Will this work? Is it done? Am I missing some critical flaw?


texts: Analog Sensor of 0 to 10 v connection to BeagleBone Black

texts:
I have an analog sensor(Thermocouple) which provides an output voltage range of 0 to 10 volt. I want to connect it with a Beagle Bone Black. BBB accepts 0 to 1.8 volt as analog input. I thought of using a normal OPAMP buffer circuit (for impedance matching) followed by a voltage divider circuit with 82 Kohm and 18 Kohm as the two resistors where voltage across 18 Kohm will be considered as for further processing by BBB.
Is it a good idea? My application is that of heating where depending on feedback of the thermocouple, heating will be controlled.


texts:
Using a fast ADC it is possible to sample motor currents multiple times per PWM period (instead of a single synchronous measurement) and to average the results. This technique (oversampling) can help to reduce the noise of the current measurement.
Question:
Are there any ADCs which have this functionality (i.e. oversampling) integrated?
E.g. I would like to trigger them once at the beginning of a PWM period, which starts the first of multiple equally spaced conversions. All conversion results are summed up inside the ADC and can be obtained as a single value (sum or scaled sum) via any interface afterwards.


texts:
My understanding problem is as follows : on figure 1 for the signal 2 (noted: S2) . If I understand correctly, the LED cannot reach S2 signal because polarity. Carrier Frequency is 38 KHz let 38 000 Hz (carrier freq) / 2 (channels L+R)) = 19 000 Hz / channel, then i can reach only 19 KHz ? But the understanding problem is my TV is successfully controled by this frequency, but why ? 19000Hz is far too far from the frequency carrier. 38 000 ~+20% or ~-20% from IR receiver general tolerance. I start in electronics it is possible that I miss or did not understand a certain part.If someone has an idea and time to grant me, thank you.

My 'problem' is why (not how) with only 1 LED and a stereo file i can control my TV ?


texts: Emulating Physical Switch Connecting Two Voltage Sources

texts: I'm currently working on a project that involves emulating cruise control key presses using a microcontroller, but I'm a little stuck on how to mimic the "on" key press. All of the other keys simply connect the speed control switch input wire and the speed control switch ground wire with different pull-down resistors, but the "on" key instead connects the speed control switch input with the horn relay control. I tested both wires in my car with my multimeter, and I found that the speed control input is about 8V on battery power and 10V on the alternator, while the horn relay control is about 12V on battery power and around 13.5 on the alternator. With the other switches I was planning on using a transistor array to simulate each key press. Is there any type of transistor or ic that can act as a switch between these two wires and be controlled by a microcontroller?


texts: Why is the LT3080 input voltage limited to 36V?

texts: The LT3080 is a current source based generator, that is, the reference voltage is set by the fixed 10uA flowing through the adjust pin and its external resistor. If so, I don't see (according to their schematic) why they say the input voltage is limited to 36V. Suppose for example I want to regulate a supply with 5V - 10V ripple at about 700V, and that I connect a 70MOhm resistor (approx.) to the adjust pin; how could the IC know that the input voltage is 700V since its reference is near the top voltage ?


texts:
This question is from my digital logic class but I don't understand it. Please help me understand what it is asking me.

A1 and A2 are octal shorthand for A1 = 572053777777 and A2 = 206556400000.  The question is:

  Perform the following 1's complement fixed-point integer arithmetic operations and note whether magnitude overflow has occurred in each case: (Hint: Use 7's complement arithmetic on the other octal shorthand).
  i) A3= A1+A2
  ii) A3= A1-A2

The full assignment can be found here, this is problem #1.

I thought you only take complements when you want to do subtraction. Can't I just do the subtraction in octal form? Can someone help me understand what the questions are asking?


texts: Altium - Impedance in Signal Integrity and DRU differ

texts:
I'm desinging a very simple 4 layer board with a USB connection. I defined an impedance of 90 Ohms (differential) in the layer stackup. This gave me a track width of 0.3 mm with a gap of 0.334 mm, which roughly agrees with my hand calculation. I used the differential pair routing option, matching the suggested measures as close as possible. I do need one pair of vias to get from a SMD connector to layer 3 where the routing is done, but apart from that the trace is a straight line.

However, the signal integrity calculates an impedance of 239 Ohms. This impedance doesn't change, no matter what I do. For test purposes, I changed the trace width, the dimension of the board, the thickness of the substrate and added a via fence around the differential pair traces. None of these measures caused any change to the impedance in Signal Integrity.

Am I doing something wrong? I mean I wouldn't expect the Signal Integrity impedance to be exactly the same, but this is off by a factor of more than 2.5... Has anyone experienced this problem before and found a solution to it? Any help would be highly appreciated.

Edit: I'm using Altium 19.1.8.


texts: Identify manufacturers of trimmer potentiometer and capacitor in photos

texts: Can somebody identify these manufacturers (marked in red rectangle)?


texts: Confusion about differential amplifier configuration

texts: As in the picture shows the signal applied at the base is say 1mv p-p, the circuit bias is not provided, then how this 1mv p-p able to forward bias the B-E junction?


texts:
I use an 7 GS/s ADC to acquire data with an frequency of 2 GHz. The input range of the device is between -0.35 and 0.35 volts. My signal is also between this range, but sometimes there is a short burst over 0.35 volts. So I have to protect the input of the ADC for signals with a higher level than 3.5 volts.

I don't think that it is a good idea to build my own small circuit with a diode protection circuit by signals with 2GHz.

How can I limit higher voltage? I tried to search for HF-Limiter, but most of the had an static attenuation.

I was searching on this site: http://www.minicircuits.com/


texts: How to set pointer to a specific signal in VHDL testbench by using access type?

texts:
Access type is basically a pointer in VHDL although perhaps it is not exactly the same thing as a pointer in C. I have found many examples online whereby we are using the VHDL access type to dynamically allocate memory to create a linked-list or some other type.
What I am looking for is, a way by which the VHDL access type can be made to point to a specific signal inside a tesbench so I can manipulate it but I might want to do the same for another variable also. This way a part of code will set the pointer to a specific signal and then I will change the value of this pointer to affect that specific signal. In this way, I don't need repeat of code that does the same thing to each of those signals.
VHDL does not have concept of returning an address of something which can be done in C language using the & operator.
Is this possible in VHDL-2008?


texts:
Got a project with the typical 5V and 3.3V power requirements. My initial prototype I used the LM3940 (datasheet). This worked pretty well but these regulators are damned expensive here in Australia ranging from $5.00 to $7.00 for one.

I have seen people use the LD1117V33 regulator for this as well. This one is considerably cheaper at +/- $2.00. This got me wondering a bit if I am really going down the right road with the design.

From my understanding the only differences are:

LM3940 only takes 5v in and deliver 3.3v out. While the LD1117V33
can take 15v and smaller and outputs 3.3v.
LM3940 is rated at 1A while LD1117V33 is rated for 800mA.
The LM3940 has limited packaging available (TO-220,TO-263,SOT-223) compared to the LD1117V33(DPAK,SO-8,SOT-223,TO-220).

My design is pretty modular so users can slot new modules/sensors into the board. Thus the current needed might vary from user to user depending on the configuration of the board/modules.

I feel that the LM3940 gives me  extra current compared to the LD1117V33 but 20% more current at nearly 4 times the price. I doubt the board will ever get close to 1A of power but I am pretty sure they can peak at about 900mA when some of these sensors/modules gets power hungry.

I noticed that the datasheet for the LD1117V33 says that the output current can range from 800mA to 1300mA. If my device generally stays under 800mA usage with occasional spikes up to 1A will the LD1117V33 not be a much cheaper and viable alternative?

Just to clarify I am not asking for a recommendation on the parts.

My concerns are as follows:

Can the LD1117V33 handle short peaks of up to 900mA? I see it can output in that range on the official datasheet? However I would rather go for stability than shaving off some cash.


texts:
I own a Rail track master and it needs two pull type continuous solenoids. The age of this machine is from the 1950's and both of the previous solenoids were unidentifiable. These solenoids operate the systems' sand boxes for dispersing sand on the track for the machine gain traction.

I need help with calculating/selecting the right type of solenoid. The specs that I have are:

12 volt system,
pull in solenoid,
1-3 inches stroke,
continuous cycle (energized by momentary electrical switch),
Cylindrical shape solenoid body,
watts needed unknown,
10-12 gauge wire will be used for install.


texts:
I have a question about designing a charge amplifier.

I am currently using this simple setup for my application. As input, I can use several commercial piezo-based accelerometers. I need a pretty wide bandwidth (up to 0.1Hz). Instead of a high valued resistor (which would be about 1000 GOhm) I use a T-network instead.
The amplification of the accelerometer signal works fine. However, the offset of the signal is rather undefined. It drifts all the time between the two rails of the OPA.
I understand that with a defined offset, I can perform a correction at the IN+ Input of the OPA. But as the offset is drifting there is no chance with this method.
I know, that with 20pF, the amplification is pretty high (I need it for the detection of seismic activity). But also if I replace the capacitor with 2.2nF, the problem remains.
At last, when I apply a high signal to the circuitry (for example harsh shaking of the accelerometer), the signal goes into the rails of the opa. It stays there for a certain time until it recovers.
After the recovery, the offset of the output has changed considerably. Not like a drift but a stepwise change.
I suppose the whole effect is due to a charging effect somewhere. But as I am not really a specialist in analog circuitry, I cannot see where.
Probably it is connected to the pretty high resistance in the feedback. But I really need this bandwidth. And I have seen in published papers that these high resistors are not unusual for detecting seismic activity.
I hope you guys can help me. Thanks in advance.
P.S. The JFET OPA I am using: https://www.ti.com/lit/ds/symlink/opa4140.pdf?ts=1609760897207&ref_url=https%253A%252F%252Fwww.ti.com%252Fstore%252Fti%252Fen%252Fp%252Fproduct%252F%253Fp%253DOPA4140AIPWR
Proposal from Bimpelrekkie:
Add a capacitor in series to R17 in order to lower the DC gain. Like this:

However, as Bimpelrekkie also mentioned, the capacity must be very high in order not to alter the cut-off frequency at low frequencies. LTSpice shows that with a 1mF capacitor this is guaranteed.
Unfortunately, I don't have this high valued capacitors in stock. So I cannot test it immediately.
Proposal from Andy aka:
Andy aka proposed to short out R17 and decrease C28 to roughly 3uF. Like this:

However, this not only drastically changes the transfer function of the charge amplifier, but also creates an unwanted resonance at low frequencies.
Proposal from Andy aka #2:
Andy aka proposed, in order to simulate my setup correctly, I have to put the capacitor, defining my accelerometer, parallel to a current source.
So up to now all simulations in LTSpice are performed like this (capacitor in series with voltage source):


texts: Communication between two Bluetooth devices

texts:
My supplier tells me that communication between 2 bluetooth devices requires authentication by an app. When reading online I believe it should be possible, but am not 100% sure.

One article from EDN gave me the impression that it should be possible, but I cannot oversee completely.

My application is a smart battery charger, which will allow the owner of an electric bicycle to charge the battery not full but e.g. 80% to save lifetime (like Tesla c.s. does - this roughly doubles the lifetime). A tester with Bluetooth at the e-bike dealer then (optionally) measures the exact capacity of the battery and marks the voltages at each 10% State of Charge.

I intend to do this BT communication without an app as that would be too complex. Here is the procedure:

The charger sends a data set (including device ID) and the tester receives. After measuring is completed the tester sends the updated dataset back to the charger. After verifying if the device ID is the charger's, the charger then updates the data set and is hence calibrated. Is this approach (working without App) feasible in your view?

It would help me best when I can copy an answer and pass this along to my supplier. They are a Chinese company and I prefer to work with them - even when they do not (yet) have hands-on experience. They are very experienced in EE.


texts: Solenoid circuit current draw doesn't match calculations

texts:
I have a circuit of 6 solenoids connected to Darlington Array (http://www.ti.com/lit/ds/symlink/uln2803a.pdf) and driven by 18V (2x9V batteries) as can be seen below:

From what I understand, each load should draw 200mA (18V/88Ohm) and when all of them are switched on at the same time, the total draw should be 1.2A. They are all in the active state for a brief moment (20ms).

I wanted to confirm my calculations by measuring the total current draw with a multimeter connecting it in series with the current source.

The measurements showed a maximum of 47mA draw instead of 1.2A.

What could be the reason why the actual measurement does not match the theoretical?


texts: Why do the TO-220 79xx series voltage regulators conduct the input voltage to their heat sink?

texts: I find it somewhat dangerous to connect a large heat sink on 79xx series voltage regulators. Because, they transfer all the negative input voltage to the heat sink. Why just they didn't make the 2nd pin of 79xx series GND, as it is done for the 78xx series? GND is safer in some sense compared to large negative voltage levels. Is there any reason for their pin configurations being different?


texts:
So we are having a discussion on if an Anti-Static ESD mat would conduct current across the leads of a battery leading to a short.

The overall consensus is that the battery would short out.


texts: Which microcontroller for audio synthesis/processing?

texts:
I want to get started designing my own hardware (digital) audio devices for signal generation and processing. The end goal is to design products which will be part of a modular synthesizer system.

I'm a bit of a beginner with hardware so I'm after some advice on an appropriate type of microcontroller to use. What features should I look for in a microcontroller to satisfy the needs.

I will need digital I/O for switches and audio in and out (presumably I will use discrete DACs/ADCs), analogue I/O for real-time control (pots/faders etc.) and sufficient computational power to do real-time DSP at reasonably high quality.

Through a bit of research and looking at the specs of existing hardware I was thinking that starting off with something general like an ARM Cortex M3 or M4. Would this microcontroller types be appropriate? I'd like if possible to program it in C.

The issue then is how I go about programming/prototyping with what I choose.
Should I get a development board? Will that include some kind of IDE? Can I get a bare chip and program it as is?

Any advice or redirection elsewhere is appreciated.


texts: Can I charge a 4S2P lithium battery pack with a 20V laptop power adapter?

texts:
I plan to build a 4S2P battery pack and have chosen to use a 30A BMS. My understanding is that the BMS will stop the individual cells from charging beyond 4.2V.

In such an environment, can I charge my battery pack using my 20V 4.5A laptop power adapter, or do I specifically need a 16.8V 1-2A charger?

The measured capacity of the cells are 1500 mAh or 3AH in the finished battery pack.

EDIT:

This is the BMS and charger I bought, respectively:

http://www.ebay.com/itm/192051343486

http://www.ebay.com/itm/332048841686

I am going to use two 4x18650 battery holders. I will connect the cells to the BMS as mentioned in the diagram and will connect the P+/P- to a 5.5x2.1mm female power jack.

I can then plug in my charger into that or plug in my motor or other electronics into that. Does this sound good?


texts: Can I overload resistors when they are in parallel?

texts:
I have 10 x 100 ohm, 1/4 watt resistors in parallel, to get a total resistance of 10 Ohms.

I do not have a datasheet for these, so I cannot look up the maximum ratings or anything like that, so I just need some general advice. I have tried searching, but this is for one resistor, not 10 in parallel.

I wanted to put a 10 watt load through all of them.

Is this safe for them?

If it is not, what is the maximum wattage I could put through all of them in total?

Is there anything that I can do to increase their wattage, like adding a heatsink?

Note, I have run out of other resistors, so I only have the 100 ohm ones.


texts: Using a low discharge accumulator to power a drone

texts:
I'm trying to figure out if there is a way to use a Lithium accumulator to power a drone.
Because of the maximum recommended continuous current of the battery, which is too low, I can't drive my motors and electronics.

Is there a way to hack this into working using a supercapacitor or an alternative like hooking up many lower capacity accumulators ?

I'm interested, as you have guessed, in low mass and high capacity.

The details of the accumulator are :

Nominal capacity : 19Ah
Voltage : 3.6V
Max. recommended continuous current : 230mA
Max. pulse current capability : 400mA
Weight : 98g
Volume : 51cm3

Link to the datasheet (page 6)

PS : I'm working on this. My version will incorporate a pinhole CMOS video camera and a wireless transmitter.


texts:
I need to control my PC with an IR remote control.

The piece of software I think I can use is WinLIRC. Or can someone can suggest something else?

Please can someone give me the simplest hardware design for an IR-Receiver?


texts:
I am building a large array of Light Switched relays, and due to the size of the array i want to keep the part count down.

Each 'Pixel module' has a 12V SPDT, bulb and an activate-on-dark circuit. There is a strong spotlight on the device and the viewers shadow is obscuring the light in their shadow so the swing is large.

I have seen the obvious LDR-and-Pot circuits with a junction out to a NPN Transistor, and the more stable comparator alternative

I was looking at "solar cell" types of Photodiodes (PiN Type), and I can't see why I cannot just lay one across a PNP transistor (Collector to Base?) or something so it applies a Base voltage when lit up.

Can someone briefly explain to me why I am wrong?
I figure it would be all over the net if it was that easy, and i cant find any examples!

Is this possibly the cheapest way to make a light switched 12V relay driver?

Note: I prefer solutions using discrete circuitry, as I have a thing for human readability, visual components etc :P


texts: If two resistors were connected in parallel and one was heated, would current flow due to johnson noise?

texts: Increasing the heat of one of the two resistors will increase the Johnson noise in that resistor. This will generate a noise voltage across the resistor, will this essentially convert the heat energy into electrical energy? If the heat and resistance was high enough, could the second resistor be replaced by a diode and capacitor so the noise could be rectified?


texts:
I'm working on a school group project which involves setting up a remote controlled car with a BeagleBone, webcam, WiFi module and a powered usb hub.

To handle the mechanical side, we bought a cheap car from Walmart and hacked it. It came with a battery compartment that holds 5 AA batteries that the motors run off of (at about 2 amps each. I think one measured 2.5). With Alkaline batteries, that gives us 7.5 volts at full charge. With rechargeable batteries (what we hope to use in the end), that is 6 volts. That's fine for the motors, but the issue I'm running into is the BeagleBone and hub. I'm using 7805s to provide power to each the BeagleBone (which requires one amp) and the hub (which should be about a half amp). The 7805s require at least 7v to function. So, I bought a 4AA battery holder to step up that voltage. Now, if I were to hook up that voltage to the motors, it would be way to much.

Final questions:

Could I safely run a wire from the middle of the battery pack to the motors?
Would that end up killing one set of batteries before the other?

If so, I've read that the less dead set will try to charge the other set. Would that matter if I'm using rechargeable batteries?

Is there a way to step down about 4-5 amps without too much cost or wasted energy (via heat)?


texts: Problem with a voltage follower transistor circuit

texts:
I'm trying to make a voltage-follower using an LM324 opamp and a BC547B transistor. Below is the schematics I use. Vcc is 12VDC and input is DC varying between 0-10V.

I then soldered this on a board as in the below photo:

C goes to Vcc, B goes to Vout, E goes to -input(pin2) and also goes to the load. I checked the connections many times.

The load is a resistor in series with an LED which indicates the output voltage.

When I vary input LED is always ON with same intensity. Even I remove the opamp LED still is ON.

What might be wrong here if the schematics is right?


texts: Using attenuators to damp reflections on transmission line?

texts:
I have a 3m long transmission line that transmits a 100ns bipolar square pulse every 200us. At the beginning of the coax cable is a pulsing circuit board, that generates the waveform, then it sends the pulse through a 50 ohm 3 m long coax line and at the other end of the coax line is connected to a load of 20 ohm.

I have noticed that by placing 6dB attenuators near at the output of the pulsing board then attaching the coax lines in series results in a greater power output from the load.

Is this due to the damping of reflections?

In addition would placing the attenuation close to the load result in a greater power transfer since the reflections are attenuated before travelling back a good portion of the cable?
I can not try this scenario yet as I do not have the correct connectors to attempt this.


texts: Help selecting rechargeable batteries for 3W 1A handheld lantern

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Salutes. I want to build a handheld lantern with a 3W 3V LED and the best I have is a 9V battery and I don't want to buy dozens of 1,5V, 9V batteries nor use a car battery (for a handheld lantern). Despite the LED asking for 3V which I could adjust for, the real problem is the 1A I should feed the LED with, which would blackout common batteries in seconds due to their Maximum Continuous Discharge Current property, according to this basic battery guide. I confirm that with a misconnection I once made and this site that once told me 9V batteries have a nominal current ourput around 12mA, although I know one of mine can stand stable providing 80mA.
According to that same second site, looks like I should use around 9 "D-batteries" to stay in a safe zone, but I wanted to know how many times I could force the reccommended current ("Corrente recomendada (mA)", in the referred website) while maintaining a basically stable discharge.
I'm new to bulk converters and I thought maybe I could lower a 9V battery voltage and increase the Maximum Continuous Discharge Current of the battery, but bulks also dissipate power and the idea seems awkward, it seems better to use lower voltage batteries instead (but expensive).
I could of course limit the current to 0,5 or 0,75A to ease the design, but I actually wanted to use two diodes instead of "half". So am I forced to opt for a wired power source?


texts: Diode-connected transistor, small-signal, Norton, Thevenin

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How do I calculate the equivalent Thevenin resistance of the small-signal model of a diode-connected transistor (base tied to collector)? Early-effect is neglected. The port of interest is between C and E.
In the figure, \$v_{\pi}\$ is the small-signal voltage between B and E.
I did the lower two circuits, so I'm not sure if the \$v_{\text{thev}}\$ and \$i_{\text{nor}}\$ are correct.
But if they are, then I get
$$Z_{\text{thev}} = \frac{v_{\text{thev}}}{i_{\text{nor}}} = -\frac{1}{g_m}$$
which isn't the same to the one I get when I apply a test voltage \$v_x\$ to the port, and set independent voltage source \$v_{\pi}\$ to zero. Then I just have a short circuit and can't calculate:
$$Z_{\text{thev}} = \frac{v_{x}}{i_{x}} $$


texts: BJT Common Emitter - Active Load Biasing

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I'm experimenting with/learning about the use of active-loads with a common emitter and I've hit a wall. When using a resistor in the collector it makes sense how the output voltage bias can be set to somewhere sensible such as half way between VCC and ground.
When using an active load however, how is this typically achieved so that you can retain the high gain that comes with an active load?
I've put together this quick circuit to play with and it shows that the Vout is biased down at 123mV. Can this be brought up to say 5V without losing all the gain?

Many Thanks


texts: Cluster Raspberry Pi power supply from an ATX PSU

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I've asked this question within the Raspberry Pi exchange but they stated that posting the question here might be more useful.

I built a Pi cluster with 6 nodes. This runs off a 90 watt astec atx-93 PSU.

Also attached to the PSU is a 12v fan and a 5v ethernet switch.

However it seems the 5v rail of the PSU is not supplying enough current to power everything.

Only 3 Pis boot properly, the others just keep rebooting. And with the Pi's that do boot, attaching any i/o devices to them send them in a spin.

There're four 5v outputs coming from the PSU. 2 Pi's to each output through the GPIO 5v pin with a fuse to protect incase of a power spike.

The 4th output is used to power the fan which is rated for 12v but I have it at a lower speed at 5v.

There is one 12v rail that has a 5v regulator attached. This is powering the ethernet switch.

If I put a multimeter over the Pi's the voltage is 5.12/5.20 v but the current seems to be around 0.9a to 1a max.

So my question is, is there anyway of getting more current to the devices without having to change to the PSU itself, or is it just that buying a more powerful PSU is the only way forward to get what is needed?


texts: Headphone audio amplifier - biasing problem

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Out of curiosity, I implemented the following headphone amp:

http://www.circuitstoday.com/few-transistor-amplifier-circuits#headphone

I used the exact same components (yes, even the 2N2222/2907 are the nice metal-can ones), checked all connections several times, but the amp just doesn't work. I'm using a bench power supply at 12V, as recommended, and I'm driving a 180 ohm headphones. The amplifier outputs something, but it is very quiet, the gain is less than 0.01. Practically unusable. Also I tried simulating the circuit in Falstad's online simulator, where it shows basically the same thing.
The same circuit is available in a few other sites, so it's probably drawn correctly.

One thing I noticed is that if I turn the supply voltage down, the gain actually increases, to the point that at 6 VDC it's almost unity gain, but with heavy distortion. There's almost no distortion at low levels (e.g., if I'm turning the pot to 1/10), but the distortion is unbearable at any usable gain levels.

After some tweaking in the simulator, I simply removed the biasing diodes D1 and D2 - and voilà - the amp works perfectly. It amplifies around 10x, and the distortion is gone.

Now, what I'm asking here is why are these diodes required, what kind of biasing is this? It is obvious that they do serve a purpose - without them, Q2 goes into saturation, and is basically bypassed - the amplification is done by Q3 alone. Without them, the current through Q2 and Q3 increases several times - at 12 V it is almost 100 mA and the transistors get quite hot (it's bearable at 9V though). The original circuit hints at 15 mA current. Is it possible that the original circuit designer made an error in the specification of the diodes? How can the circuit be "fixed" to adhere to its original idea?

I'm not very adept in analogue circuits, and biasing in particular, so some explanation of why the circuit was designed that way would help a lot.

EDIT: here's a link to the simulation. You can click the switch near the diodes to see what happens.


texts: What is the working power factor of induction generator? Is it leading or lagging ?