texts: Why are V and I out of phase for a resistor in parallel with an inductor for the resistor?

texts: Vth is the voltage across RL so the current through the load should be in phase with Vth. But the current through the load is 1.8A with phase angle of 100.43 degrees and the voltage across it is 72.76V with phase angle of 134 degrees. I am not able to figure out why they are different.


texts: Switching a 20mA LED with 4mA output of same voltage

texts:
I have a USB controller card with output pins of 3.3V and a maximum current draw of 4mA per pin, and I'm trying to use it to control 3.3V 20mA LED's.

I figured I'd need to use probably an NPN transistor and have seen that they generally seem to look like this:

simulate this circuit – Schematic created using CircuitLab

However there's many things I'm unsure about

Will this need resistors R1/R2/R3? If so, what values?
The output card's dedicated +3.3V pin will likely not be able to supply the required current either. Can the collector be connected to an external power source or could this cause problems as the pin is powered by a computer's USB port?

Thanks in advance


texts: Why do we need a voltage divider when we get the same voltage at the output as the input?

texts:
I am using a voltage divider circuit of 100 Ω and 10 kΩ resistors, and using their output for the (IRF740) transistor's input.

I'm trying to figure out why do the resistors have those specific values. It makes sense that if I use voltage divider, I get 0.99x as a result with 100 Ω and 10 kΩ, resulting in the same output voltage as the output.

But if that's true, then why do I need those resistors in the first place, if I get the same voltage as input. Can't I achieve the same without them?


texts: Will capacitor in high pass filter pass high frequencies while it is blocking low frequencies?

texts:
I thought that capacitors will only act as a conductor while is is being charged and once fully charged it will not conduct any more. I know that current does not actually pass through the capacitor due to the plate between the insulator between the two plates but I use the word 'conduct' here for simplicity.
At low frequencies and DC currents the capacitor gets fully charged very early at the beginning of the cycle and acting afterward as an open circuit until the voltage drops in the second half cycle below the capacitor voltage when the capacitor starts to discharge. As a result the capacitor in the HP filter will will block low frequencies.
Also at high frequencies there is less electricity in the cycle so the capacitor does not get fully charged and it is always either charging and conducting or discharging so the current is not blocked at all and the capacitor is acting as a short circuit. As a result in HP filter high frequencies will pass.
Now if the capacitor receives two signals at the same time, the first has very low frequency and the other has very high frequency, the first will cause the capacitor to be fully charged so not allowing any more current to pass.
How the high frequency signal will pass now?
Will it actually pass?


texts:
I have a project that will run 20,000volts and 2amps.
The electricity should not arc to my skin, but just in case I'd like to have the proper protection. Will it need to be good electrical gloves or can it be regular thick gloves with layers of electrical tape?


texts: How to know the kind of filter from the transfer function

texts:
I got that system \$x_n \to x_n-x_{n-1}\$, so \$h_n=[.....,0,1,-1,0,...]\$, with \$h_0=1\$ and \$h_1=-1\$, so the transfer function given by:

$$H(\omega)=\sum_{i=-\infty}^{\infty} h_ne^{-jwn} = h_0e^{-jw(0)}+h_1e^{-jw(1)}=1-e^{-jw}$$. How to knwo the type of filter, if it is high pass filter, low pass filter, etc.

I appreciate your help.


texts: Weird resistor with dots around it on the schematic

texts:
I was looking through the LTC4041 datasheet and saw this:

The 10mOhm resistor with the two nodes really close to it - is that a "special" resistor or something? Why have they drawn it like that?


texts: How much battery power will my Arduino need?

texts:
So I am designing an arduino project that uses multiple devices.

GPS, NFC, IFR Temp gauge, and bluetooth trans.

The trick is though that it needs to be battery powered. I am a great programmer but I am just learning about circuitry and I have no clue how to determine how much power I will need.

Is there an easy way I can calculate which battery I will need?

Please use laymen s terms.


texts: How to calculate the tolerance of this constant current circuit?

texts:
I am using the circuit below to provide constant current to th LEDs. I request your suggestion on how to calculate the tolerance of current (minimum and maximum variation of set current) due to temperature alone.

How to consider changes in Vbe to calculate the current?


texts: Node voltage analysis on circuit with a dependant voltage source

texts:
I am carrying out node voltage analysis on a circuit that has 2 voltage sources.

One source is independent
The other is dependent on a current through a resistor in the circuit

After i carry out my analysis i have equations for the unknown node voltages however one equation contains the dependent source as per KCL.

  Question

  In essence i need to know what i am missing in my analysis,

  should the current be found first through superposition?

  all help is greatly appreciated.


texts: Is this an optocoupler ans how do I identify the pins?

texts: I bought an Arduino starter kit with some basic components, and I know among them is an optocoupler. I need one for my project, and the only thing resembling it is a chip marked 'L1513 LTV4N35.' How can I find out?


texts: Why would one mount components above the PCB?

texts: Inside of an automotive ECU I noticed that all three crystals are mounted about 1/4" above the PCB.  What is the advantage of doing this versus mounting the case flush with the board?  This seems like it could lead to vibration cracking the solder joints over time.  Is there a thermal issue - crystals don't really dissipate much heat?  Manufacturing constraint?  Some of the capacitors are mounted in a similar way, although this looks more normal to me.


texts: How to BJT NPN switch 12v using 5v with common ground?

texts:
I want to build the AVR High-Voltage programmer, it requires the RESET pin to source 12 volts while the rest of the AVR is powered by 5 volts. The ground for 12 volts and 5 volts is common.

I know how to switch a led/motor/whatever with a BJT like the 2N2222, but it does not connect in such a way that it can have the same ground as the 5 volts across Vbe.

How to switch 12 volts using the same GND as the 5 volts doing the Vbe switching?

Context - From page 167 (19.7.1) of the datasheet:
http://ww1.microchip.com/downloads/en/DeviceDoc/doc8006.pdf

Enter High-voltage Serial Programming Mode

Set ... RESET pin and VCC to 0V.
Apply 4.5 - 5.5V between VCC and GND. Ensure that VCC reaches at least 1.8V within the next 20 µs.
Wait 20 - 60 µs, and apply 11.5 - 12.5V to RESET.
...
Exit Programming mode by power the device down or by bringing RESET pin to 0V.


texts: Understanding USB Inrush Current Requirements

texts:
In relation to a previous question, I'm trying to understand the USB 2.0 requirements for inrush current.  I understand the basic idea, but a few details are still unclear to me.  The specification states, in part, that:

  The maximum load (CRPB) that can be placed at the downstream end of a cable is 10 μF in
  parallel with 44 Ω. The 10 μF capacitance represents any bypass capacitor directly
  connected across the VBUS lines in
  the function plus any capacitive effects visible through the regulator in the device.
  The  44 Ω resistance represents one unit load of current drawn by the device during
  connect.

  If more bypass capacitance is required in the device, then the device must incorporate
  some form of VBUS surge current limiting, such that it matches the characteristics of the
  above load.

The USB-IF also provides a description of an inrush current test:

  Inrush current is measured for a minimum of 100 milliseconds after attach.  Attach is
  defined at the moment the VBus and ground pins of the plug mate with the receptacle.
  Any current exceeding 100 mA during the 100 ms interval is considered part of the inrush
  current event.  The inrush current is divided into regions.  A region is an interval
  where the current exceeds 100 mA until the time the current falls below 100 mA for at
  least 100 µs.  There can be multiple inrush regions during the 100 ms period. Pass/fail
  is determined by the region having the highest charge.

That is explicit as far as it goes, but it only gives a minimum measurement time, and it doesn't spell out what algorithm is applied to the inrush regions to come up with a pass/fail decision. I think the idea is that during the regions when the current exceeds 100 mA, the current is integrated to get the total charge transferred during this window, and the total charge must not be greater than what you would get with the 10 uF // 44 Ω load. According to one source, this would be 5V * 10 µF = 50 µC.  That is where my understanding gets a little shaky.

To help me understand, I analyzed the following circuit:

[The R1 resistance is not part of any specification, but I need it to do the math, and I can let it go to zero as needed.] The current starts at \$V_1/R_1\$ and decays exponentially to \$V_1/(R_1 + R_2)\$ with time constant \$(1/R_1 + 1/R_2)^{-1} C_1\$.

The total charge transferred at time \$t\$ will be

$$ Q(t) = \frac{V_1}{R_1 + R_2}t + \frac{V_1 R_2^2 C}{(R_1 + R_2)^2}\{1 - \exp(\frac{-t}{C_1}(\frac{1}{R_1} + \frac{1}{R_2})  )\} $$

In the limit as \$R_1\$ goes to zero, this simplifies to

$$ Q(t) = \frac{V_1}{R_2} t + V_1 C$$

One part I don't understand is that with 5 volts from the USB bus and the prescribed 44 Ω load, there will always be a 5V/44 Ω = 114 mA current, which is more than the 100 mA limit described in the quoted USB-IF test, and also more than the maximum one unit (i.e. 100 mA) load allowed for a low-power USB function (USB 2.0 spec. section 7.2.1). In the R1 = 0 limiting case, this current will draw as much charge as the capacitor (i.e. 50 µC) in R2*C1 = 440 µs.

So the question, if you're still reading, is what does it mean, precisely, to "[match] the characteristics of the above load" (i.e. 44 Ω parallel with 10 µF), and how does the described USB-IF inrush current test decide how much current is too much?

Thanks.


texts:
Most microcontrollers (e.g. AVRs,MSP430s, PICs, etc) support a number of different sleep modes. The "deepest" sleep mode is the one that purports the lowest power draw (e.g. "Power Down", "Shut Down"), but all the clock systems are typically halted in these modes and it seems to me that the only way to "wake up" from them is via external stimulus (e.g. pin change interrupts, chip reset). Am I missing something? Are there awesomely low power methods of generating a periodic wakeup signal for an MCU?

Assuming my goal is to minimize power consumption (i.e. sleep deeply for as long as possible, stay awake as briefly as possible), while periodically waking up to execute a function, what's the common way to achieve this type of behavior? To further simplify matters, lets assume that my function is stateless (I don't have to remember anything from the past to perform it).

I've had some success using the WDT on the MSP430 to get this effect. I just made my main routine be my function, with the last line enabling the watchdog timer to expire after a certain period and going into LPM4.5 or whatever the "deep sleep" mode is called. The net result is the function is performed, the MCU sleeps, the WDT expires, and the chip resets, ad nauseum. Seems to work, just wondering if there is a "better" or "more elegant" or "more power efficient" way of getting this type of behavior?

I haven't tried this approach with an AVR yet, but I think the WDT is more "power hungry" in the AVRs than on the MSP430 so it may be less attractive for low power work. Perhaps there is not a "universal" approach to low power, and you have to use the tools afforded by a given product line? I know the new picoPower line has lots of whiz-bang features like the Event System and Sleep Walking that in some cases hardly require the CPU to be awake at all if you can make your application fit into that structure...

OK enough of my wandering, lets here what ya'll have to say :)

Edit
Concrete examples illustrating techniques would also be cool!


texts: What are "sense" pins in 8-pin PCI Express power plug?

texts:
I have an ATX PSU that has two 6pin connectors for PCI Express power. Both have Gnd on the lock bar side, and +12V on the opposite side. I lost modular cables that came with the PSU, and it made me to start to dig.

According to this answer on our sister site, in 6-pin configuration pin 5 is Sense A. In 8-pin, pin 6 is sense A (same position as Sense A in 6-pin config) and pin 4 is Sense B.

But what are these pins supposed to do? I know that most people just connects Gnd there and calls it a day, and I could too, but I wanted to ask about the meaning behind it. It's called "Sense" for a reason, I suppose. So, what is that reason?


texts: How do I attach a bridge rectifier to a PCB or breadboard?

texts:
Newbie question here...I need to know the proper terminology so I know what I'm looking for. I have a bridge rectifier that has four flat blades on the bottom.

I want to throw it on a breadboard to test my circuit, and will eventally want to get it onto a pcb. Right now, I've got it connected to jumpers on my breadboard via four alligator clip cables, but there's GOT to be a better way.

Searching for "bridge rectifier socket" led me to some proprietary socket datasheets for a very specific rectifier that didn't fit. But not even a Mouser or DigiKey page in the top 50 or so results.

What am I looking for so I can get better search results?


texts: Is a battery management system necessary for wearables?

texts:
My team and I are working on developing a wearable device (like a heart rate monitor with IP68 dust/waterproofing) and we're utilising wireless charging for our 3.7V 350mAh non-removable battery.

We'll be using TI's BQ51050B IC and whilst it performs the roles of wireless receiver and battery charger in one IC, I noted that it does not perform the full suite of voltage, current and temperature protections that a good battery management system (like the BQ77905) does.

I have reviewed a few different safety standards including IEC, UL and CE and they all discuss the potential hazards however don't give a definitive verdict as to whether the BMS would be advisable for small wearables specifically.

Given the experience on this forum, would these extra protections be necessary/advisable in an internationally distributed small wearable product or would they be unnecessary? In other words, is a BMS necessary with a 3.7V battery or are they are primarily designed and aimed at things like cordless drills which are usually 18V+?

Kind Regards,
Andy


texts: 3 LEDs / 1 POT - fade each LED in turn as POT is changed in value ?

texts:
I'm looking for a simple (hopefully !) circuit which would allow a variable resistor to control the brightness of three different coloured LED's. As the variable resesistance is changed in value first one, then the second, then third LED would fade out in brightness.

It doesn't matter if there's a bit of crossover so that LED2 starts fading before LED1 is completely out.

I thought at first this was simply a case of wiring the LEDs in parallel at a point after the power had been through the variable resistor but I read that wiring up LED's in parallel had difficulties so I thought I would ask.


texts: What components work better when they warm up? (apart from vacuum tubes)

texts:
Conventional wisdom is that heat is bad for electronics. Metals and most doped semiconductors conduct more poorly, and everything ages faster.

But in my experience, some faulty appliances don't work when I first turn them on, but start working after a while, presumably due to warming up. I don't mean ancient amplifiers with vacuum tubes in them, but a modern PC and flatscreen TV. Both had some bad electrolytic capacitors in them and replacing two of those fixed the TV (I didn't bother with the PC - too old), but that doesn't necessarily mean the caps were benefiting from warmth - some other component might have been working better when it warmed up and compensating for the bad caps.

So my question is, what are the components (either perfect or degraded with age) that work better when they warm up? (I already know about vacuum tubes AKA valves)


texts: I'm very new to circuits and was confused about HFE affecting collector current in a BJT. How does the base current affect collector current? Shouldn't it just amplifies the current at the emitter and not change the current drawn through the collector (what I mean to say is that shouldn't the current gain only affect output at the emitter and not the input at the collector)


texts: PIC program LED on off with same push button

texts:
I have written a small PIC program in mikroC for turning on and off an led with same push button. That is pressing the switch will turn on the led and if the same switch is  pressed again the led will turn off. Here is the program that I wrote

void main()
{
TRISB=0X00;
TRISC=OXFF;
PORTB=0X00;
PORTC=0XFF;

while(1)
{
if (portc.f3==0) /*checking if the switch is pressed*/
portb = ~portb; /*if the switch is pressed, the led will go off if it is already          on or  the  led will go on if the it is already off*/
portc = 0xff;
}
}
}

another version of the same program that I have written is

void main()
{
int flag=0;
TRISB=0X00;
TRISC=OXFF;
PORTB=0X00;
PORTC=0XFF;

while(1)
{
if (portc.f3==0 && flag==0)
{
portb = 0xff;
flag=1;
portc=0xff
}
if (portc.f3==0 && flag==1)
{
porb=0x00;
flag=0;
portc=0xff;

}
}
}

in both cases it doesn't works as expected. when i press switch the led turns
on but after some time it turns off itself (without pressing the switch again).

please help me and make me know whats wrong with my programs if any.


texts: How should I detach those kinds of components on my motherboard?

texts:
How should I detach both components linked by white, blue and red wires from the computer motherboard on the attached picture?

Just pulling them?

Indeed, I don't want to damage them.


texts: Can you feed in a voltage higher than your supply to the input of an opamp?

texts:
I have a 28V digital signal. 28V being logic 1 and 0V being logic 0.

Can I feed the 28V into an opamp (Vcc @5V) to level shift it ? Or will I  have to create a voltage divider to bring the 28V < Vcc ?


texts:
Sir's/ madam,
Is it possible to make a parallel comnection of 110V DC battery bank which are about 4 kms apart from each others. How to calculate the voltage drop and size of cable in between. Thanks. Pls. help.


texts: Bluetooth based Sensors to the Cloud, processor choice?

texts:
This is a pretty broad question, but I'm curious to hear how people would go about this and what parts they would use to do the heavy lifting.

Imagine you had a bluetooth module, it works fine and can be reprogrammed to act as a central device without too much fuss. You want to bridge data from your bluetooth peripheral devices to a wifi network. How would you go about this? would you pick a wifi MCU like a TI CC3200 or Freescale (NXP) KW series and just connect it directly to the bluetooth module? Or would you want an intermediate microcontroller like a PIC32 to do some of the heavy lifting and have a separate module for the WiFi too? What would your reason for either be?

Edit:
To be more transparent, I've noticed a few IoT systems which have a bluetooth-wifi bridge component, which usually have a wifi and bluetooth module, then an additional microcontroller in between. WunderBar is a good example of this. Why would you bother with an additional microcontroller if you were using something as capable as a CC3200?


texts: What are the considerations using two DC-DC converts in serial or sharing a common input?

texts:
In my design I need two power sources. They are 3.3V and 5V.
I am using two DC/DC converters for this.

Please bear with me as I am fairly new in designing circuits.

What if I feed R-78E3.3-0.5 from R-78E5.0-0.5, will there be any important different?  (For a minute, forget about extra current stress on the 5V converter.)

I appreciate for your inputs from now.


texts: Best way to allocate boot loader memory space in the micro controller

texts:
I'm confused about how to allocate boot loader memory space in the pic18 micro controller and spend sometime researching on it and landed up here .

I'll put my question :

I have a controller whose linker script looks like this and it defines the memory sections of the controller (which includes the SFR,GPR and other memory starting and ending locations).

My question is how does the boot loader should be placed in micro controllers, should they be kept on the starting of program memory?
I'm having this doubt because one one example this guy advocates keeping the boot loader on program memory locations 0x000-0xfff

USB-HID bootloader link

Should all bootloaders replace the starting address of programming memory if we want to  use boot loaders?
Is there any thing we need to be careful while allocating space for bootloaders?

/

Original linker fileof pic18

/ File: 18f47j53_g.lkr
// Generic linker script for the PIC18F47J53 processor

#DEFINE _CODEEND _DEBUGCODESTART - 1
#DEFINE _CEND _CODEEND + _DEBUGCODELEN
#DEFINE _DATAEND _DEBUGDATASTART - 1
#DEFINE _DEND _DATAEND + _DEBUGDATALEN

LIBPATH .

#IFDEF _CRUNTIME
  #IFDEF _EXTENDEDMODE
    FILES c018i_e.o
    FILES clib_e.lib
    FILES p18f47j53_e.lib

  #ELSE
    FILES c018i.o
    FILES clib.lib
    FILES p18f47j53.lib
  #FI

#FI

#IFDEF _DEBUGCODESTART
  CODEPAGE   NAME=page       START=0x0               END=_CODEEND
  CODEPAGE   NAME=debug      START=_DEBUGCODESTART   END=_CEND        PROTECTED
#ELSE
  CODEPAGE   NAME=page       START=0x0               END=0x1FFF7
#FI

CODEPAGE   NAME=config     START=0x1FFF8           END=0x1FFFF        PROTECTED
CODEPAGE   NAME=devid      START=0x3FFFFE          END=0x3FFFFF       PROTECTED

#IFDEF _EXTENDEDMODE
  DATABANK   NAME=gpre       START=0x0               END=0x5F
#ELSE
  ACCESSBANK NAME=accessram  START=0x0               END=0x5F
#FI

DATABANK   NAME=gpr0       START=0x60              END=0xFF
DATABANK   NAME=gpr1       START=0x100             END=0x1FF
DATABANK   NAME=gpr2       START=0x200             END=0x2FF
DATABANK   NAME=gpr3       START=0x300             END=0x3FF
DATABANK   NAME=gpr4       START=0x400             END=0x4FF
DATABANK   NAME=gpr5       START=0x500             END=0x5FF
DATABANK   NAME=gpr6       START=0x600             END=0x6FF
DATABANK   NAME=gpr7       START=0x700             END=0x7FF
DATABANK   NAME=gpr8       START=0x800             END=0x8FF
DATABANK   NAME=gpr9       START=0x900             END=0x9FF
DATABANK   NAME=gpr10      START=0xA00             END=0xAFF
DATABANK   NAME=gpr11      START=0xB00             END=0xBFF

#IFDEF _DEBUGDATASTART
  DATABANK   NAME=gpr12      START=0xC00             END=_DATAEND
  DATABANK   NAME=dbgspr     START=_DEBUGDATASTART   END=_DEND           PROTECTED
#ELSE //no debug
  DATABANK   NAME=gpr12      START=0xC00             END=0xCFF
#FI

DATABANK   NAME=gpr13      START=0xD00             END=0xDFF
DATABANK   NAME=gpr14      START=0xE00             END=0xEAF
DATABANK   NAME=sfr14      START=0xEB0             END=0xEFF          PROTECTED
DATABANK   NAME=sfr15      START=0xF00             END=0xF5F          PROTECTED
ACCESSBANK NAME=accesssfr  START=0xF60             END=0xFFF          PROTECTED

#IFDEF _CRUNTIME
  SECTION    NAME=CONFIG     ROM=config
  #IFDEF _DEBUGDATASTART
    STACK SIZE=0x100 RAM=gpr11
  #ELSE
    STACK SIZE=0x100 RAM=gpr12
  #FI
#FI


texts:
How do I use feedback function in MATLAB when I have sys1 and sys1 as impulse responses (and not transfer functions, as required)? The syntax for using feedback is as follows:
sys = feedback(sys1, sys2);


texts: How to figure out the maximum throughput on a capacitor?

texts:
How can I figure out what the maximum throughput of a capacitor is?

(I have a 20V DC power source that is very unstable. When you start drawing from it, the voltage briefly drops. I'm using some circuitry that can't handle this drop. This is why I need to smooth it out using a capacitor, and need a capacitor that can handle a continuous throughput of 30A at 20V.)


texts:
For a current project, I have to read the state of an LED in another circuit with a Raspberry Pi.

My current schematic is this:

simulate this circuit – Schematic created using CircuitLab

Everything inside the dashed box is not physically accessible to me in the final version of the project so I can only attach the wires next to the button. (The LED is still visible)

Now when I start my code for reading the state of Pin 12 with the internal pull-down resistor I only get 0s as Output.

Code for reading the Pin (with pull-down) :

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)
GPIO.setup(12, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)

for i in range (5):
    print GPIO.input(12)
    time.sleep(.01)
GPIO.clear

Output (pull-down) :

0
0
0
0
0

My idea here is that the current might go through the resistor and not the pin but I am not sure on that one.

So if I eliminate the pull-down and try the same thing again I'll get an alternating pattern of 1s and 0s.

Code for reading the Pin (without pull-down):

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)
GPIO.setup(12, GPIO.IN)

for i in range (10):
    print GPIO.input(12)
    time.sleep(0.01)
GPIO.clear

Output (no pull-down) :

0
1
0
1
0
1
0
1

From my understanding this comes due to missing pull-down resistor since the current has nowhere to go so it is creating this interference.

Now I wanted to ask how it would be possible for me to get the current state of the LED with circumstances given and where this alternating pattern is coming from? (Maybe it's a misunderstanding of pull-down resistors).

Solution:

Thank you @Transistor

  the Pi needs a return path for the sensing current.

The final schematic is this:

simulate this circuit

Now the Output is:

LED off : 1
LED on  : 0


texts: 12v battery reading 10.7v not supplying 5v load

texts:
I have a solar charge controller connected to a solar panel (30w), also connected to the charge controller are a 12v battery (4.5Ah) and a raspberry pi Zero (5v, draws approx. 200mA).

This evening the charge controller is showing the battery voltage as 10.7v.

I turn on the load switch to supply power to the Raspberry Pi but as soon as it draws current the controller switches power off again.

So my question is, should my 12v battery be able to supply enough power to the raspberry pi (5v & 200mA ) when it is only charged to 10.7v?

If not, why not?
I would have thought 10.7v being far higher than 5v so it should be well capable.

Battery details:

12volt/4.5Ah
Constant voltage charge(25C)
cycle use: 14.5 - 14.9V
Standby use: 13.6 -13.8V
Initial current: 1.35A

Charge controller details:

Anself: https://www.amazon.com/Anself-Controller-Regulator-Overload-Protection/dp/B01A0D18MU?SubscriptionId=AKIAILSHYYTFIVPWUY6Q&tag=duckduckgo-ffab-20&linkCode=xm2&camp=2025&creative=165953&creativeASIN=B01A0D18MU

Schema:

30w solar panel----charge_controller/Battery(USB interface)---raspberry pi


texts: How to connect a Sparkfun LiPoly Charger to an Arduino Nano?

texts:
I was able to upload the Adafruit SSD 1306 OLED Library to an OLED Display using an Arduino Nano.
Now I want to power the Arduino Nano via a Lipo Battery but the battery must be rechargeable and I already have a Sparkfun LiPoly Charger. The Sparkfun Lipoly Charger can use the System Out Header to power a 3.3v Arduino Pro.

Where do I connect the System Out Header on the Sparkfun LiPoly Charger to power the Arduino Nano with a 3.7v LiPo Battery?


texts:
I have some trouble about the design of my homemade double sided pcb shield. I'm not an electronic engineering, i'm just an hobbyist.
In my shield i have a 9V power input and from that, using two separate circuits (with two voltage regulator), i split the 9V input power in two power line, respectively in 5V and 3.3V for supplies three IC components present on my shield.
I have designed my shield using the bottom side for the ground plane and the top side for routing all track, splitting the top side into three separate areas where i placed three separate power plane. One power plane is for the input voltage and the two voltage regulator circuits. The other two areas are for the 5V circuit and for the 3.3V circuit.
Is correct to design the top plane into three separate power plane as I did?
I attach two images to better explain what i did.

Update

this is my new layout, is not definitive, but is a good start! ;)


texts: What is the right way to wire a power inlet to a switch to a dual-primary transformer?

texts:
I have a fused power inlet with a voltage selector (Schaffner FN1394-10-05-11). I want to connect it through a separate DPDT switch to a transformer with dual 115V primary windings, and make everything work on either 110-120V or 220-240V grids.

Here is the wiring diagram for the inlet and voltage selector:

Schaffner voltage selector diagram http://schaffner.com/uploads/pics/FN390_Typical_electrical_schematic.png

Top position on the voltage selector is parallel wiring for the four outputs (for 110-120V), and bottom position is series wiring (for 220-240V). The four outputs on the inlet are numbered 2-4-3-1 from the top down in the diagram.

The DPDT switch is pretty simple, it just has two sets of terminals, each consisting of an open-closed-common triple. When the switch is open, both open terminals short to common, and when it's closed, both closed terminals short to common. (Two separate common terminals.)

The transformer is also simple: two 115V windings, four wires.

What is the correct way to wire the inlet to the switch to the transformer, assuming P is the mains hot wire?

PS: I know that the inlet has a built-in switch. I want a separate switch because it has a nice LED on-off display and will be on the front panel of the device, rather than its back.

PPS: When connecting mains wires to the primary windings, does polarity matter?

(I think that wires 1 and 4 should run to the two closed terminals on the switch, and the common terminals on the switch should run to matching wires on the transformer. Wires 2 and 3 should go directly to the transformer. That way, when the switch is open, the hot wires terminate at the switch, no matter what the voltage selector switch is set to.)


texts: Protecting low voltage high C capacitor with high voltage low C capacitor

texts:
With regards to "catching" very high voltage transients on a DC power supply, is it possible to use a small, high voltage capacitor with a current limiting resistor to catch the transient in order to protect a much lower voltage, larger capacitor in parallel? Or will the transient destroy the lower voltage capacitor regardless? I assume that the high voltage capacitor and current-limiting resistor will have to be sized appropriately to be able to absorb the total energy of the transient.

Example circuit:


texts: How are manually and electromechanically actuatable switches called?

texts:
I'm looking for (the name of) a part that is basically a bistable relay that has a mechanical interface as well, but I don't know how to look for it. I have seen a simpler but similar part in a printer that has a predefinable idle timeout - after which it switches itself off by manipulating its main AC switch that, from the user side, apart from this, looks and behaves exactly like a usual rocker switch. I'm unfortunately not at liberty to take that apart.

Thanks!


texts: Current when two batteries (voltage sources) of different potentials are in a circuit

texts: What will happen when I connect two batteries of different potential in a circuit like below? And if there will be a current will it be the same in the whole circuit? How is it possible since electrons can't travel through batteries (electrolyte) and cathode is depleted of electrons?


texts: Does bbc micro bit support bluetooth 2.0

texts:
I have a bbc micro bit. It has a ARM Cortex M0 chip that supports BLE.

I want to be able to send messages via Bluetooth to this usb dongle (with only Bluetooth 2.0 support).
Will I be able to send messages back and forth to the bbc micro bit with this usb dongle. Or is it the case that the bbc micro only supports BLE?


texts: I/O Board accepts "5V TTL, open/closed circuit" - So it will accept the closing of a circuit with no voltage?

texts:
A digital I/O board has the following pins:

Digital In Pin 1

Digital In Pin 2

Signal Ground

Digital Out Pin 1

Digital Out Pin 2

I am interested on how inputs into this board can be made. Its spec sheet says that it accepts "5V TTL, open/closed circuit". The spec sheet can be found here: Link. There is no additional information.
I understand the 5V TTL part, if I have a sensor with a logical Output Pin, I could connect it to the I/O board this way:

Sensor Output Pin <---> Board Digital In Pin 1
Sensor Ground <---> Board Signal Ground

I do not understand the "open/closed circuit" part. Does this means that if I connect the Digitial In Pin 1 to the signal ground, it will read a 1? It would look like this:

Board Digital In Pin 1 <--> Board Signal Ground

If so, how does the board monitor both cases? The voltage can be monitored by an internal voltimeter. The Open/closed by a resistance measurement circuit? And when the circuit is closed, resistance should be very low?


texts: What kind of circuit is it (negative voltage generating)?

texts: What is the name/type of this negative voltage-generating circuit?


texts: What is the "maximum power" of an antenna?

texts: I was reading the datasheet of an antenna and I came across the parameter "Max. Power (total)", measured in Watts. What does this stand for? Can it be measured to check that the datasheet is right?


texts:
This query is for a college project.
The Source can give 0.3 V to 0.8 V.
Need to boost the voltage to 12 V, so 6 x NiCd batteries can be charged through LM317 CC charger.
The converters available are from Pololu.

Can the boost converter be used in series as shown?
If not can somebody suggest an alternative?

thanks

Hi ,

Sorry for the confusion I have created. First time I have used the forum, and it is learning time.
Now I will put the project in details and you people help me out to take it to the logical end.

The Energy source for the TEG is pure sunlight, and there are eight TEG’s in series. This TEG Hot Side are mounted on to an Aluminum Plate 3mm thick (300mm x 140mm). The Cold side is also fixed to an aluminum sheet (120mm x 85mm x 3mm) and also two heat sinks are used to help in the cooling. I have used Thermal paste in between all mating points.
There are no other energy source and the idea is to harvest the sun energy and charge 6 * Ni –Cd Batteries (1.2v, 2500mAH), which in turn drives an Arduino and two servo Motor.
Also The Hot side plate is enclosed in an Acrylic (plexi) Box, to enhance the temperature of the plate. (Green House Idea). The sides of the box are fixed with reflectors. (Will attach photos for clarity)
The cold side is outside the box. (At ambient temperature)

The Setup sits on a dual axis tracker, so that the hot side plate is always perpendicular to the sun.

I have not measured the temperature on the heat sinks as of now (no access to the measuring instrument). I am planning to fix the Dallas DS18B20 on both the hot side and cold side to take reading using Arduino.

The voltage I am getting is approx 800mV from the series connected 8 no’s TEG. (Also I have a same setup where I have used TEC 12706, 8 no’s in series and I am getting approx 700mV).

The specification of the TEG & TEC is way higher from what I am getting. The temperature difference I am assuming might be around 15 – 20 C. will check ASAP and update.
Can you people guide me, if I am doing something wrong?


texts:
My book says the following:

  As noted previously, every method of circuit analysis must satisfy KVL, KCL, and the device i–v relationships. In developing the node-voltage equations in Eqs. (3–4), it may appear that we have not used KVL. However, KVL is satisfied because the equations \$v_1 = v_1\$, \$v_2=v_A-v_B\$, and \$v_3=v_B\$ were used to write the right side of the element equations in Eqs. (3–3). The KVL constraints do not appear explicitly in the formulation of node equations, but they are implicitly included when the fundamental property of node analysis is used to write the element voltages in terms of the node voltages.

I don't see why this is part of the above excerpt is true:

  The KVL constraints do not appear explicitly in the formulation of node equations, but they are implicitly included when the fundamental property of node analysis is used to write the element voltages in terms of the node voltages.

How is KVL used to write the element voltages in terms of the node voltages? Note that I'm not asking how to write the element voltages in terms of the node voltages. I'm asking why the author claims KVL plays a role in this.


texts:
would like to get a feedback on a zero cross circuit as it does not work.

Circuit is based on this.

240V AC, 50 Hz

Expect that C2 is 50V.
R1,R2, R4 are SMD.

After connecting to mains and measuring voltage across R1, the track between J1(Ac+) and R1 exploded. R1 is alive.

Voltage on C2, R6 and U1 is 100 V

Is this circuit valid ?


texts: Mesh Current method for solving a variable resistor?

texts:
I have a circuit with a variable resistor R which I need to find the value of. I am told that the power dissipated in the resistor is 250W.

The circuit:

I used the mesh current method naming the loops from left to right as Ia, Ib, and Ic.

These are my equations thus far:

25Ia + 100(Ia - Ib) - 200V = 0

10Ib + 20(Ib - Ic) + 30ix + 100(Ib - Ia) = 0

RIc - 30ix + 20(Ic-Ib) = 0

At this point I realized I needed a restraint equation for both ix and R.
My ix restraint equation is:

ix - Ib = 0

For R's restraint equation, I related it to the power dissipated by the resistor which is 250W. I know that p = i^2 * R, so I can say that

250W = Ic^2 * R

However, when setting up my matrix I run into the problem of what to do with Ic^2. How would I set up the matrix to solve the system of equations using these equations? Or are my equations incorrect?

P.S. I cannot use any Thevenin stuff.

EDIT: The answer key I am looking at states that the two values or R should be 2.5 Ohms and 22.5 Ohms. I am just confused at how to arrive at those values.


texts: CD4050 Voltage leaks, what can I be doing wrong?

texts:
As often as I see the CD4050 used as a logic level converter, I'm surprised that I haven't heard much about how it seems to leak voltage from the inputs into Vdd.  I hope this isn't a case where the chips I purchased are simply not working correctly.

The version I'm using was bought off eBay, and the top says "13YR26D / CD4050BE".

I was using this chip to try and work with a Nokia 3310 LCD, and I first noticed things were weird when the screen was dim.  When I disconnected power to my breadboard, the LCD lit up!  Where was this power coming from??

Turns out, it was coming from the 4050.  The 5V coming from the Arduino outputs were actually powering the chip, and providing power to my breadboard rails.

OK, so I thought "I must be doing something wrong" (I still think that!) and I came up with a simple circuit to test the chip.

Vdd (pin 1) to 3.3V
Vss (pin 8) to GND
1A (pin 2) to 5V
1Y (pin 3) to an LED/1k, then to GND

The other input/output pins I tied to GND.  I don't show that in this diagram:

I am measuring the voltage between Vdd and GND.  When I plug 1A into GND, I measure 3.3V as expected.  When I plug it into the 5V rail, I measure 4.13V at Vdd.  The voltage at 1Y is only 3.4V though.  So my question is: is it expected for the voltage at Vdd to change?  To me this is not just unexpected, but a problem, because I'm powering the LCD from this output.

My workaround right now is to use one of the buffers to power my LCD.  The output is closer to 3.3V, and so this seems to work.  But I wish I understood this better.


texts: How should I power these components at different voltages?

texts:
I'll be using a 12V power source, as this is an automotive application.

I have the following components:

ATmega2560, 1.8V-5.5V, 200mA (actually an Arduino Mega 2560, as I couldn't find a through-hole AVR with four UARTs)
GPS module, 3.3V-5V with 5V-safe inputs, 20mA
GSM module, 3.4V-4.5V (4.0V is recommended), 3.3V logic, 2A peak
MCP2515 CAN controller, 2.7V-5.5V, 5mA
MCP2551 CAN tranceiver, 4.5V-5.5V, 75mA

Everything would be a nice, easy 5V if it weren't for the GSM module, which wants around 4V. So should I use two regulators (a 5V one and an adjustable one set to 4V)? Or if I already have a 5V regulator, is it possible to just use a voltage divider after that for the 4V?

I plan to use a 4050 for level conversion from the MCU to the GSM module (the MCU at 5V reads 3.3V as high).

Would I also require a heatsink? The Arduino's regulator doesn't have one, but it gets hot given a 12V supply.


texts: Is MPPT of PV array possible if only converters are used and the connected load is a battery?

texts: I am currently working on a project to harvest energy from solar PV panels. There are some difficulties that i am facing. I was able to achieve mppt using a constant resistive load with a converter. Implemented system is shown in the figure (Scenario 1). Now i want to extend this system by adding another converter (for current regulation) with a battery (as the only load in my whole system). The intended system is shown as Scenario 2. But i am unable to achieve mppt as well as current regulation. Is there any flaw in my system or approach? kindly guide me.


texts: I've been trying to simplify a combinational circuit and wanted to know whether there was any simpler way of solving such questions. Do we have to find all the outputs and such or we can use a simpler method ?


texts:
Following on from this question. Can I place the capacitor anywhere in the circuit before the IR Distance Sensor? In my project I have 2 PCBs: A power circuit and a Processing Circuit. In the Diagram below you see the two PCBs Power Board and Processing as well as the Sharp distance sensor. Following the diagram, can I place the capacitor on the power board or will it be ineffective by the time it reaches the sensor? I don't want to damage my expensive sensors.

---------------         12V             ------------------
|             |-------------------------|                |
| Power board |          5V             |  Processing    |
|             |-------------------------|     Board      |
|             |         GND             |                |
|_____________|-------------------------|________________|
                                          |       |     |
                                          |       |     |
                                      GND |   Out |  5V |
                                          |       |     |
                                        ------------------
                                        |    Sensor      |
                                        ------------------


texts: Using 3PDT Relay To Switch Grid and Inverter Output

texts:
I have a battery backup setup for my aquarium that I'm trying to make more robust. I'll go ahead and ask my question first, then you can decide if you want to read all the background info.

Is it safe to use a 3PDT relay to switch between grid power and the output of an inverter? My plan would be to attach the load to COM, the inverter output to NC and the grid to NO. Under normal operation the coil would be powered and the relay would be open, supplying grid power to COM. On grid failure, the relay would close, supplying inverter power from NC to COM. I would plan on using a 3PDT relay so I could switch ground, hot and neutral to minimize the chance of grid power backfeeding into the inverter. If all three are switched at once, my thoughts are that it's either all inverter or all grid going to COM, never both.

Also, sort of an aside, are mechanical relays designed to be used in this manner? The load on COM with different inputs feeding NC and NO? I don't see why it wouldn't work, but I'm not an electrician and I've never done this before, so I don't know!

Now for the background. The basic idea is that an inverter powers the critical life support equipment on my aquarium. The inverter is powered by a 12V power supply when the grid is on. On power failure, a relay switches the inverter's DC source to a battery. When the power comes back on, the relay switches back to the 12V supply, the battery is recharged by a battery maintainer, and all is well.

My problem with this design is there are several weak points. First, the inverter which powers the critical life support equipment could fail. This renders the entire system inoperable. Whether the grid is on or the batteries are charged, it doesn't matter, because the inverter failed. The second problem is the switching relay. If the relay fails on NC, then the system runs the batteries flat and fails. If the relay fails on NO and the grid goes out, the system fails. The third source of failure is the 12V power supply that powers the system when the grid is up. If this fails, the system will switch to battery (detecting this as an outage) and drain the batteries, at which point the system fails.

Switching the AC outputs of the inverter and the AC from the grid directly would solve a lot of the headaches mentioned above. The only question would be if it's safe to do so.


texts:
I acquired two large bipolar stepper motors a couple of years ago. One, I briefly dismantled and then put back together. Now, when I come to use them, the one I took apart doesn't work, and when I rotate the shaft manually, I can't 'feel' the steps. It's just really smooth.

I know that the driver works as it works with it's identical twin which I didn't take apart. A brief glance inside both motors seems that no bits have gone missing...

Any Ideas what part of the stepper I may not have put back right or is it an electrical problem?


texts: I am working on a project that uses infrared LEDs to send signals at certain intervals. The arduino I was planning to use would've been sending data @ 9600 mbps, and sent a signal, such as "hi" every ten seconds. Then, the arduino on the other side would send back "hello".The only problem is do I have to use the RX and TX pins or can I use any pin on the Board?


texts: Best way to read 18kHz PWM signal with wide V_pk-pk (5.5-18V)

texts:
I am trying to design a circuit for level-shifting a PWM signal coming from a sensor and reading it with a 5V micro controller in an automotive environment. I will run my design by an EE at the end but I am trying to give it a good go myself. Here are the specs:

PWM signal has a frequency of 18kHz and operational peak to peak voltage of min 5.5V and max 15.5V. There are are conducted transients on the input line as well as possibility of ESD but I am using a TVS diode to clamp to a safe voltage (if possible to around 45V but I can clamp lower at a cost penalty). During transients/ESD, signal integrity is not important.
Since I am measuring the positive duty cycle (minimum 6.4us) I would like to keep the rising/falling edges of the signal sharp. Current rise time of the signal is 50ns and it can probably be degraded up to 200ns before accuracy becomes a concern
Maximum allowable current drawn from the PWM source is 1 mA (preferably less).
Cost should be kept as low as possible while satisfying the above constraints.

I can think of a few alternatives:

PWM > series resistor > N-channel MOSFET in common-source configuration.
PWM > series resistor > NPN BJT in common-emmitter configuration.
PWM > series resistor > schottky diodes clamping to 5V and GND (cheap, but the current draw at 15.5V with 2.2K series resistor is 4mA which is too much. Any more than 2.2K and the signal is degraded too much)

What one of these alternatives (or others) do you guys recommend?


texts: Cascode current mirror: current to voltage

texts:
This is a cascode current mirror. Assuming that all transistors are idential so that Iin equals Iout.

With the current, the gate to source voltage of all transistor are equal and it is Vgs.

Now I am confused about how Vgs of transistor Q4 is established by Iin or Iout.

For transitors Q1, Q3, they are diode connected transistors (feedback between input and output), so the current Iin is converted to the gate source voltage Vgs.

This is easy to understand. The diode connnected transistor is something like current to voltage converter here.

However, how the voltage Vgs of Q4 is established by the current In or Iout?

I don't see any kind of feedback here so that the output current Iin or Iout can be converted to its input voltage Vgs.

Could anyone explain what is happening here? How Q4 converts its current into the gate source voltage Vgs?

Thank you.


texts: Hi friends iam new to PIC programming , I'm coding my pic in mikroC pro , please help me out.. iam attaching my file with this!the code i want is message from transceiver should receiver and check whether the message is ON or OFF then pic should function on my output accordingly!


texts: How to change Designator text size by script in Altium 17 or newer

texts:
For the assembly drawing I have to move all the designators to a prefefined layer, rotate them as needed and set the text size. I know this is possible via "find similar objects" but I would like to do it via a script. I found a Vb script which is able to set the layer and rotation but the VB API does seems to not supporting a change of the text size. CompDes.Name.Height=0.5 does not work. Our default text font is "TrueType".

This VB script will rotate the designators in one of two ways, center them on the component and move it to the desired layer.

Please help me to set the Text size via script.
(Conversion of the script to Delphi is also an option)

Sub RotateDesignators
Dim Board
Dim Component
Dim CompDes
Dim I

Set Board = PCBServer.GetCurrentPCBBoard
If Board is Nothing Then Exit Sub

Iterator = Board.BoardIterator_Create

Iterator.AddFilter_ObjectSet(MkSet(eComponentObject))
Iterator.AddFilter_LayerSet(AllLayers)
Iterator.AddFilter_Method(eProcessAll)

Set CompDes = Iterator.FirstPCBObject
PCBServer.PreProcess
I = 0

'Mech Layer 1 Layer Idx = 57
MechL1 = 57
TopDesignator = MechL1 + 12
BotDesignator = MechL1 + 13

While Not (CompDes Is Nothing)

Call PCBServer.SendMessageToRobots(CompDes.Name.I_ObjectAddress, c_Broadcast, PCBM_BeginModify, c_NoEventData)
I = I + 1

    If CompDes.Layer = eTopLayer then           'Component is on the top

       Select Case CompDes.Rotation
           Case 0, 180, 360
                CompDes.Name.Rotation  = 0
           Case 90, 270
                CompDes.Name.Rotation  = 90
       End Select
       CompDes.Name.Layer = TopDesignator

    else                                     'Component is on the bottom

       Select Case CompDes.Rotation
           Case 0, 180, 360
                CompDes.Name.Rotation  = 0
           Case 90, 270
                CompDes.Name.Rotation  = 270
       End Select
       CompDes.Name.Layer = BotDesignator
    End If
    Call PCBServer.SendMessageToRobots(CompDes.Name.I_ObjectAddress, c_Broadcast, PCBM_EndModify , c_NoEventData)

    Call PCBServer.SendMessageToRobots(CompDes.Name.I_ObjectAddress, c_Broadcast, PCBM_BeginModify, c_NoEventData)
    CompDes.ChangeNameAutoposition = eAutoPos_CenterCenter
    Call PCBServer.SendMessageToRobots(CompDes.Name.I_ObjectAddress, c_Broadcast, PCBM_EndModify , c_NoEventData)

       Set CompDes = Iterator.NextPCBObject
Wend

'ShowMessage(I & " were found") 'Uncomment this line if you want a message after it has finished.
Board.BoardIterator_Destroy(Iterator)

Pcbserver.PostProcess
Call AddStringParameter("Action", "Redraw")
RunProcess("PCB:Zoom")
End Sub


texts: Significance of -1 slope in CMOS inverter transfer characteristics

texts: In the CMOS inverter transfer characteristics what is the significance of slope of \$-1\$ at the points where \$V_{IH}\$ and \$V_{IL}\$ have been shown? And how is this the occurrence of the values, \$V_{IL}\$ and \$V_{IH}\$ related to the point where the slope is \$-1\$?


texts: Roland ACH power supply connector identification

texts:
Can anyone please identify this connector, as used for the output of the ±10 VDC "ACH" series power supply for a Roland R-8 drum machine from the late '80s?

The male socket into which this fits has internal measurements of about 18.0mm x 9.5mm.

Annoyingly the female pins are larger than the "standard" 0.093" Molex connector pins that you'd find in e.g. a hard drive power connector.

(I don't have this plug, this is a photo found online)


texts: Upload Mp3/Database files from PEN DRIVE to SD CARD problem with speed

texts:
I am using a PIC32MZ2048EFH144 micro controller in my project with Microchip harmony. I am using USB for the pen-drive and SPI protocol for the SD card. Everything was working properly when I uploaded the pen-drive's data to SD card. When I upload above 2000 mp3 files, though, it takes 20 to 25 minutes. How can I boost transfer speed and upload all the files in 5 to 10 minutes? The SPI is running at 40MHZ and the USB at full speed.

If the file size is under 10kb then 500 files are uploaded in less then 2 minutes. Can anyone please give me suggestions on how I can boost transfer speed.


texts: How can I get my atmega328 to run for a year on batteries?

texts:
Scenario
I have created a nice electronic door lock for my dorm room. It is currently an Arduino Diecimila with a servo [un]locking the door. It has a numerical keypad with 3x4 buttons and 5 LED's (2 serie pairs and one single LED). It also currently runs on a cellphone charger.
I have now redesigned it to run on a standalone Arduino (ATmega328), but would really like to have it run on AA batteries or even a 9V battery.
For the software part, I figured I could put sleep calls for certain times inside the loop method to keep the ATmega power consumption as low as possible. And let the LED's "flash" with as long as possible time off.
Question 1
When a button is pressed during the few milliseconds which the board sleeps, will it be "remembered"/"held" until it comes out of sleep and then be picked up as a button press?
What would be the best way to handle this button press on sleep? Can I code it to wake up upon button activity, or must I just let it sleep for e.g. 10m.s. in every loop?
Question 2
How would I approach the math of calculating how many AA batteries are needed to run this device for 10 months?
Also, I don't know how to measure the average power usage per minute or so, since it alternates quickly etc.
The Device


texts: Before I build: will this circuit work, or have I overlooked something?

texts:
I'm an engineering student (ChemE), just starting to get in to electronics and electrical engineering.  Next semester I'm planning on adding an electrical engineering minor, but I wanted to get some hands-on experience first, so I'm about to build a bluetooth speaker, as shown below (sorry if anything about that diagram is unconventional):

Before I start soldering, I'd like to know if I've made any egregious/obvious errors.  I have all of the components for this build already, but I'm fine buying new components if I've messed things up.

On the bottom left I've shown a battery and charging port, and I just sort of connected them on the diagram, but this is all one piece in reality and already wired, and as I've charged it up and it hasn't burned my house down I assume it works fine.   Then I've got a step down (12V to 5V) to power the bluetooth card and some indicator LEDs.  There's a toggle switch right before the volume potentiometer to switch between that and a headphone port as input.  Then I've got a ground-loop isolator, followed by my amp, and then the crossover circuit and the speakers.

I think I made sure that all of my parts are rated correctly for the current/voltage they'll need to handle.

If there are problems somewhere I don't know where, so instead of listing the specs for every part in here, if anyone wants to know the specs for a specific part just comment and I'll edit them in.

Thanks much for any help you all can give!

Requested information:

I can't find any technical specs for the bluetooth card, as I'm
ripping it out of this USB receiver
The potentiometer I bought (here) has a resistance of 10k Ohms
This is the ground loop isolator I'm using.  Again, unfortunately I can't find any technical specs, as this product is intended for consumer end-use in audio systems.
Here is the full spec sheet for the amplifier I'm using
Both LEDs have the same specs, here is the data sheet, it lists Vf as 3.2V when If = 20mA

Sorry I couldn't find some of the information you wanted, I'll let you know if I can get my hands on it.


texts: Measuring the rotation of a bicycle steering wheel

texts:
I would like to mount a bracket onto the head tube of a bike frame to measure the degree of rotation the bike's handlebars have been turned. Ideally, this would be a contactless solution to increase the chance of the bracket fitting correctly.

Two of the options I have researched are:

A Hall Effect sensor on the fixed head tube and a magnet on the rotating bike fork
Optical sensor on the fixed head tube and encoded object on the rotating bike fork

Before I delve too deep into creating a Hall Effect prototype, does anyone have a better suggestion than the above options or any tips on how to best design this sensor?

Thanks in advance!

EDIT:

@TelaClavo @RocketMagnet Thankyou both of you guys for the detailed answers. I think due to the requirement of mounting the sensor(s)/magnet on the perimeter of the head tube I am more favoured towards TelaClavo's solution. The sensor would be located in a bracket fitting on the front of the head tube, just above the moving ring between the head tube and fork. The magnets attached around the ring.

The assumption I am making now, is that in order to accommodate head tubes of different diameters, a universal bracket can be manufactured to house the PCB components and sensors to fit flush to the head tube in both the sensor and magnets.


texts: Is it possible to use 7805 regulator without capacitors at its input and output pins?

texts:
I have to drive a magnetic buzzer whose current is 50mA and max. voltage is 6V. I will use 7805 regulator to drive it as my supply voltage is variable 9V to 24V DC. There will be another small load connected on this 7805 whose current will be 100mA. So total current drawn from 7805 will be less than 200mA.

As the current is small so is it ok to use 7805 without the capacitors at its input and output pins? I want to avoid capacitors to reduce the component count to minimum.

If instead of the two capacitors I only use 1 capacitor then which one to use.. input or output capacitor? and what would be its sufficient value for a current of less than 200mA?


texts: Reading an IR signal and running one of 5 motors

texts:
Before you judge me, I'm fairly new  to electronics besides the very basics, so be gentle. However, I'm quite proficient with computers at a high level; I'm decent at writing code, and have experience with Java, C#, and JavaScript.

Basically what I want to is send an IR signal from a computer to an IR receiver in a box about 2-3 feet away. (yes, it has to be IR.) Once the receiver gets the signal, it needs to turn on one of five small motors for, oh, 500msec, (each of which take in ~1.5-3v) depending on which of 5 signals is sent to it.

Now there are several parts to this:

1. Sending the IR signal

This transmitter must send data at least 2 feet, up to 5. (Shouldn't be an issue, I think). I'll need to control it via USB. I've found two:

http://adafruit.com/products/387 - a cheap ($.75) IR LED. However, I'm not sure if one of these can send multiple signals.

I can't post more than 2 links, so search Amazon for Syba SD-U1IRDA-NM USB Fast Infra-Red Adapter - a more expensive ($12) IR adapter. One of the pros of this is that it already has a USB port.

2. Receiving the IR signal

The receiver must be fairly small (maybe up to a max of 2 cubic cm). So far I've found one:

http://www.adafruit.com/products/157 - only $1.95. It's small, seems like it'd work, is cheap, etc. If there are any problems with using it, I'd love to know.

3. Processing the IR signal & doing stuff

Now, something needs to move the motors. I'm guessing a PIC (not sure which one, please suggest one) since they're cheap, popular, and a relative gave me a PIC programmer, circa 2006 (I assume this doesn't matter), for last xmas (she had no clue what it was - but someone told her it was a good present for a programmer)

This is the area I'm most fuzzy on. I guess that I'd somehow connect power to two legs of the sensor, connect the third leg to part of the PIC, have the PIC run some simple code to figure out which of the 5 signals it received, and then turn on power for one the 5 motors, turning it off ~500msec (in no way has to be precise) later.

tl;dr: Which, if any, PIC should I buy? Which IR transmitter works? Does this IR receiver work? How do I program the PIC and how should I wire it to control the motors?


texts: Device Cannot Start on AVRISP mkII + AVR Studio 4.19 730 Parallels 7 + Windows 7 64

texts:
I'm looking for guidance on establishing a connection to an AVRISP mkII programmer via OS X.

Parallels Desktop 7 for Mac Build 7.0 14920
Windows 7 64-bit
AVR Studio 4.19 730

After AVR Studio is installed I plug in the USB for the AVRISP mkII, it appears to detect the driver, then I attempt to connect from AVR Studio:
Tools -> Program AVR -> Connect...

Then In the Select AVR Programmer dialog:
Platform: AVRISP mkII
Port: USB

After a few seconds I get a "Connect failed - Select AVR Programmer" message in that dialog.

When I check the Device Manager, under Jungo I see only AVRISP mkII (expected is to see both this and WinDriver).  The AVRISP mkII shows an error like:
This device cannot start. (Code 10)

I also tried an XP install via BootCamp - both the Win driver and AVRISP mkII drivers appeared in the device manager, and there was no Code 10 error, but I still received the "Connect failed" message on connect attempts from AVR Studio.


texts: Connect Arduino to ESC with BEC (without using its power)

texts:
I am using the Arduino Servo library to control two servo's on a RC-car. One of the servo's (for steering) is without ESC (as it should be), so easy to connect and power.

However, the motor that provides the speed uses a ESC with BEC. Which means that the 3 wires coming out of the ESC (red, black and white, which I need to send pulses to) are providing me with current. This would be fine, I could use BEC to power my Arduino, but I like battery life and I have a totally different plan..

So now my actual question; how do I connect the ESC so that I would not have to use the BEC's power supply. I can not imagine only connecting the ground and signal wires, so I need a little help :-)


texts: How do you connect 3 x 12V globes together with a buzzer. The 3 globes must work separately with its own switch, but each globe must work together with only one buzzer, eg if I switch on globe 1, the buzzer must also sound (without the other globes working) ,the same if I switch on globe 2, the buzzer must sound....,


texts:
when we say that in a wire there is a parasitic inductance, what is its cause? Is it the skin effect of the wire, the magnetic flux (generated by the current) through the surface of the total circuit in which the wire is inserted, or others?

I was told it is the skin effect of the conductor, but I was thinking that the dependence of the impedance is not linear so it should be wrong to consider this phenomenon as an inductance.


texts: Which float switch to use for my A/C unit?

texts:
This is my A/C unit in the attic.

These are the two switches I've found.  But the specs don't really match up with that document.

Switch 1

I can't post 3 links due to lack of reputation but here are the specs for the other switch:

72-Inch lead wires
48 VAC/DC
5 Amps Auxiliary safety switch

How do I know what will work?


texts: What is the difference between a tank circuit in an oscillator and a resonance circuit?

texts:
I understand that if a charged capacitor is placed with an inductor (and then remove the power supply,) the capacitor and inductor will exchange energy back and forth, it will basically oscillate and then slowly die out. Similarly, a resonance circuit (as I know RLC circuit with AC source) oscillates.

Then, what's the difference between these two circuits? Am I right thinking a resonance circuit sustains oscillation and a tank circuit oscillation dies out?


texts:
I have a simple 8 digit calculator and want to use it in a way that instead of pushing the keys on keypad, connecting the keypad wire to an Arduino to control the calculator.

In general I know how the Arduino can read the matrix keypad, but it seems this calculator keypad is not using the scan technique that makes a column wire to 1
and then reading the row wire to detect the digit pressed.

There are 11 wires from MCU to the keypad and there are 24 keys on the calculator keypad.

I checked all 11 wires with an oscilloscope: 5 of them have 1.58 volts and 6 of them are 0 volts. There is no pulse on any of them.

The calculator works with a 1.5 volt coin battery. In my test, I connected an AAA battery and at that time battery voltage was 1.62 volts.

I found that the calculator MCU will convert 1.5 volts to 3 volts for internal use.

My question is what technique is used in this calculator to read keypad?


texts: Can I hard wire an IR remote directly into the receiver?

texts: I have a IR remote control and a clock (which it is designed to control.) I would like to remove the IR LED from the remote and the sensor from the clock, and run a wire between the two (so the clock can be controlled from another room.)  I thought this would be easy, but there are a few issues (like the LED having 2 leads and the sensor having 3.)  Is there a way to do this?


texts: Unstable boost converter with short bursts of current draw

texts:
I'm designing a boost converter that boosts a 9V battery to about 10.5V. The objective is to maintain 10.5V despite the V_in reduction due to battery dissipation, e.g. boost 6V to 10.5V. This boost converter works great under steady loads such as when I hook a resistor from V_out to GND. The problem arises when I hook it up to the desired load which is a cellular modem. This modem draws somewhere around 100mA for normal operation but when transmitting it jumps to about 1.2A for 500ms at a time. This causes a massive ripple (really a dip) in my output voltage to as low as V_in. The minimum input to the modem is 8V before it shuts down so these ripples often cause the modem to restart.

Below is my schematic and board design using the LM2731 boost converter IC.

I've tried various inductances (10uH, 22uH, and 33uH) and they all yield the same result. I've also increased the ceramic output capacitors with only a marginal increase in stability. For fun I tried a 1000uF electrolitic between V_out and GND and that helped keep the modem on but still yielded ripples on the order of 1 to 2V which I'd like to reduce to the several hundred mV range.

Does anyone have any insight into how to reduce ripples with short bursts of draw?


texts: Solved: How to Sweep NMOS4 Device Parameters in LTspice IV?

texts:
EDIT: Solved. I misinterpreted Linear's use of the period character prior to the measurements and LTspice was reading these values on the hundred's of nm scale, which is too small for this transistor technology.

I am currently attempting to simulate an NMOS enhancement load inverter to retrieve it's Voltage Transfer Curve for various gains by sweeping the parameter W of the switching transistor (M1 in my circuit below). From Linear's website, I found an explanation of the .step Spice directive where it matches the following formula:

.step param [variable] list [val1] [val2] ... [valn]

Their example (Parameter Sweep Solution - Linear) involves sweeping the capacitance of a capacitor.

I am running into errors while trying to sweep regarding the width being less than or equal to 0. Is there a different format for the directive when sweeping a device's parameters?

My circuit is below:


texts:
I have a transistor, driving a normally open reed relay (protecting transistor with flyback diode), driving a solenoid.  The solenoid is actuating at about 3 Hz.

The relay is good for a few million actuations.  And then, it mysteriously stops working.  Replacing the relay works, for another few million actuations.  I conclude that the problem is not the transistor or the solenoid.

The nature of the failure is somewhat peculiar.  At first, it appears to be a stuck closed failure; the relay will not open when the transistor is not driven.  When power is removed from the relay, it then opens.  When power is re-applied, the relay stays open, until the transistor drives it, at which point it becomes stuck closed again.

I tested one of the "dead" relays.  The coil exhibits the correct resistance, 250 ohm.  The reed switch is also open.

I would have expected this to be a failure where the contacts are welded together, but the fact that a "dead" relay is open and that it only sticks after it has first been energized lead me to believe there is something else going on.  Does anyone have an explanation for this failure?

EDIT: Addressing some comments

Using the reed relay because that's what we have already, this is a small one-off project.  The relay is a Radio Shack relay, SPST 5VDC 20 mA nominal, rated for 500 mA 125 VAC/60VDC.  I believe the equivalent relay (OMR-106H) can be found on digikey here http://www.digikey.com/product-detail/en/OMR-106H,V000/PB886-ND/1095211.  The DC power supply for the solenoid (12V) shows about 400 mA peak current.  The datasheet lists 5 million "operations" at 24V 400 mA.  Two relays have now died around 3 million at 12V.

The diode is across the coil, not the switch.  The literature I have read indicates that the diode is usually for the protection of whatever drives the reed relay's coil.


texts: Mesh Analysis on CCT with Voltage and Current Source

texts:
I'm not sure where to apply the supermesh on this problem, would it be over the top mesh and the one containing the current source? I have only tried doing the problem without a supermesh but am not able to get an answer. Without using a supermesh I used KVL in each mesh and got an answer, however this is clearly wrong since I did not take the 6mA current source into account. The trouble I am having is identifying whether or not I need to just set the mesh current in the bottom left mesh to 6mA or to create a supermesh.

Assuming that the mesh with the current source has a mesh current of 6mA resulted in an answer of 3V on for V0


texts: Sampling DC and AC components of capacitive sensor

texts:
I'm using a MEMS capacitive pressure sensor SCB10H. As I understand it, I can wire it up in one of two ways. Either I can measure the absolute capacitance using a chip like the TI FDC1004. In this case, my sample rate is limited to what the chip offers.

Or I can wire it up like a microphone, amplify the signal and sample it as fast as I like using an ADC.

In my application, I am interested in measuring both the absolute pressure with a sample rate of 1kHz, and the arrival time of small pressure pulses to within about 1 micro second or so.

Am I right in thinking that the two measurement techniques are incompatible? If so, how can I measure the absolute pressure, and also sample the AC component at high speed?


texts: How many times can you split the 3.5mm audio line cable signal from a music player

texts: How will the volume of the sound decay as you iterate the splitting of a 3.5mm audio line cable signal from a music player?


texts: Measuring the angle to an object using IR sensors?

texts:
I would like to be able to use IR emitter/receivers to measure the ANGLE to an object. As far as I am aware this is how the Sharp IR distance sensors work, by using triangulation to measure the angle of a reflected IR light source to work out the distance to the object.

I just need to work out the angle an object is from the emitter/receiver pair and by using more than one pair I could then work out (using triangulation) the distance to the object as well its position in 2D space.

However, researching this has proved fruitless so far. I believe the receiving end of a Sharp distance sensor is a pin photodiode (correct me if I am wrong?). If it is not a pin photodiode then what is it? What measures the angle of the IR beam?

If anyone could help with this it would be appreciated.

Thanks,

Mike


texts: What happens when I connect the GND of a LDO in a Diode to the real GND?

texts:
A friend of mine told me to put a diode between the LDO's GND pin and the circuit's GND. He said the LDO will regulate it's fixed voltage plus the diode drop. Is it true? How does it work?
I am using the MCP1703 regulating 5V, but I wanted it to regulate 5.2V~5.3V (a Schottky drop), so doing so with a Shottky will work?

How does this affects the thermal dissipation calculations? Ot it's just a matter of changing the Vout in the formula?


texts: "Current is pulled not pushed" they say. Doesn't the transistor working the other way around?

texts: The emitter current is defined by hfe and the base current not the load. The load does not "define" Iemitter.


texts:
I have several old microcontrollers, I am sure I bought them over 10 years ago.  It is my assumption that the numbers on these would still be categorized, but I cannot find a way to search the internet by the number to find out what I can use these microcontrollers are for.  When I do a search for the number I generally either find a data sheet about a similar number or nothing at all.  I have 14 so I won't list all the numbers here, but here are a few examples.

GAL16V8D 15LP C914D16
74LS 138 661
T74LS74B1 98640A

Is there a site that I can enter these numbers in to find out what the purpose of these microcontrollers can do?


texts:
I just bought STM32F429-DISC1 a few weeks ago.
I did the following:

Turned it ON by connecting to my laptop.
installed the drivers.
and updated the firmware

Everything worked perfectly fine.

Then I put it in a box safely because I was busy with other things. Today, after a week or so I connected it again and observed the following things::

COM and PWR LEDs are RED (static).
The LCD Screen is stuck and completely white.
(Image Attached)

WHAT I CHECKED/Resolved ::

My device is still being detected by the PC as a Flash drive.
I then Compiled and Loaded a LED Toggle program to check and it's running without any error.
I tried using a different Cable and PC , but the problem persists.
I tried to connect external 5V and 3V Sources,but the problem persists.
My firmware and drivers are up to date.

So , I draw the conclusion that the only problem is with the LCD screen.
Can someone guide me with any solution (As soon as possible) ?
Any help shall be appreciated.


texts:
I bought this micro usb part:

I need to solder it to a PCB that I designed, but I'm having a ton of trouble figuring out how to do so because the tabs are very close together and hard to reach. Is there a technique to do this / are there extraneous parts on the connector that I can remove to make it easier to solder?


texts: Do I need zero-crossing detection for controlling a heater?

texts:
I need to control a heater element (about 500W) using arduino. For switching part I would go with zero-crossing SSR or zero-crossing optoisolator and triac (the second seems to be cheaper).

The question is do I still need a zero-crossing detection for the arduino. The time the load is switched on clearly depends on phase between arduino control pulses and line voltage.

In the first picture the load is switched on about half a cycle. And in the second it's switched on the whole time. But the only difference between these two cases is the phase of signals.

For controlling the heater I probably can make period of the pulses much longer which somewhat solves the problem.

But if I would like to use the same circuit to dimm a light bulb then I need to do zero-crossing detection in the micro controller to keep pulses in phase with AC line? And do I need zero-crossing SSR/optoisolator then?

Does this mean zero-crossing SSRs are suitable only in cases where switching period is long enough that the phase of control signal is not a problem?


texts: How to use a Polyswitch Self Resetting Fuse and light up led when fuse has been disconnected

texts: I'm designing a circuit that will be connected to usb of a pc. How can I isolate the supply when a short has been detected on any part of the circuit. An led should light up indicating there's a short somewhere in the circuit.


texts:
While researching how to debounce a switch for digital applications, I often come around this diagram :

simulate this circuit – Schematic created using CircuitLab

Or other similar diagrams, with modified resistance / capacitance values.
I understand that R1 is a pull-up, and R2 is here to limit the discharge rate of C1 and to augment the value of the time constant and to avoid short circuit when discharging, but why is there a Schmitt trigger ?

When the button is open

The current is flowing through R1 and R2, and is sourcing current for whatever circuitry there is at the Schmitt trigger / output of the sub-circuit.

When the button is closed

The capacitor C1 discharges through R2 to the common ground, following the equation of the discharge of a capacitor. But, at the junction between R2 and Schmitt trigger / output, the voltage should drop instantly, given that the resistance R2 is lower than the one of a Schmitt trigger IC, or any transistor base pin for the matter. So the Shmitt trigger shouldn't be required, given that we don't need any hysteresis  ?

There is obviously a flaw in my reasoning, but I don't find it. Any transistor base pin or Schmitt trigger should have an impedance high enough so almost no current would come in, and the voltage would be too low for the threshold of the transistor, so , not only the Schmitt trigger would not be required, but fail the sub-system ? It's obvious there's a mistake I'm making, but again, I don't find it. Sorry if i'm stupid.


texts: How to calculate Vce and Ic from transistor gain

texts:
How would I calculate Vce and Ic from a given DC transistor gain?
Thanks.


texts: Using TP4056 module to charge battery while load remains connected

texts:
I need a circuit that utilizes the tp4056 breakout board to power a NodeMCU ESP like so:

tp4056 USB port connected: 18650 battery charging and NodeMCU running of USB
tp4056 USB port not connected: NodeMCU running of 18650 battery

The problem is that the load of the tp4056 should be disconnected while charging, otherwise it can mess with the overcharge protection of the tp4056 (see here).

I have designed the following circuit hoping it will achieve my goal. My reasoning is that when no USB is connected the relay will let the boost module run off the battery and when USB is connected the relay will close and power the boost module over USB while letting the battery charge as usual.

Does the circuit achieve my goal? Are there any other issues with the setup?

Please note that there will be more components connected to the NodeMCU, so the exact current draw remains unknown (<500ma though).


texts: Rigid-Flex PCB Fabrication: Window opening vs slot opening

texts:
We had issue with one of the rigid-flex design cracking at the joint of Rigid and flex intersection.
It is important to note that this is second batch of same PCB and PCB was not cracking in first batch.
So we reached out to manufacturer and asked for root cause.
They said reason incorrect laser parameters of their machine and also said that they will change the PP design from window opening to Slot opening which will eliminate need of laser all together.

My question is what exactly is changing? What does Window or slot opening actually achieve?


texts:
I have been soldering for a lot of years, but all I had was a single 30W temp iron and no desolder gun.

Is it ok to use the wire brush on my bench grinder brush to clean my tips ?


texts: Power wire-to-board connector identification

texts: I am laying out my PCB and I would like to include this power connector in the layout. I am unable to identify the connector based on the its locking ability and layout. It could even be a common one and I am just missing something.


texts: Parallel of transformers. Is R/X condition necessary?

texts:
Let say I've got two transformer T1 and T2 with both the same voltage ratio. Each transformer has an internal impedance Z1=R1+jX1 and Z2=R2+jX2 respectivley. Also each transformer has a power capacity S1 and S2 [kVA]. Then I connect both them in parallel (parallel windings to the same supply line, and secondaries to the same load)

simulate this circuit – Schematic created using CircuitLab

What conditions should Z1 and Z2 meet in order to achive an evenly distribution of load betwen the two transformers?

I'm pretty much sure that the only condition that should be met is that:
$$
|Z_1|\cdot|I_1| = |Z_2|\cdot|I_2|
$$
where I1, and I2 are the nominal currents of each transformer.

Also, I have read about the condition:
$$
\frac{R_1}{X_1}=\frac{R_2}{X_2}
$$
I've been thinking about this relation and I think it's only necessary to achive the same current phase in both transformers, but it is not necesary to accomplish an evenly distribution of load betwen the two transformers.

Can you provide any evidence that the last relation is useful in any way other than the one alredy explained (3.b. is the one explained useful)?
Is it really necessary to met the last reltion to connect two transformers in parallel?

...this issue is treated in most textbooks. Though, I found that some sources state that the ratio R/X is a necessary condition, and I don't think so.


texts: Using a LS248 7-segment driver, but segments are dim. Can't figure out why

texts:
I'm building a project where I want to use two double-digit 7-segment-LED displays (green, common cathode). From what I've read, a shift register wouldn't be able to source enough current, so I decided upon using a SN74LS248N IC (datasheet). This IC takes Binary Coded Decimals (BCD) as input and has 7 outputs to drive the segment LEDs, minus the decimal point LED. As I understand the *248 ICs are for common cathode displays, so pins connected to active segments are HIGH.

My problem: I can't get the LED segments to light up properly using this IC. It's visible in the image below, but worse in real life. Check the photo album I've made for comparison with a circuit where the segment is driven directly. This album also includes a circuit diagram, to help illustrate the problem.

When I connect using the driver IC, the segments light up only weakly . My bench power supply indicates the circuit is using 9 mA.

Now, I've tested the display using only power leads and a 150Ω resistor. That works beautifully, using up more than three times the power: 30 mA according to my bench power supply.

Does anyone here have any clues or tips?


texts: This may be a lame question but, Speed controllers on big RC cars can they be controlled from Arduino? If yes, do they have a standart? do I control them using PWM values? What should i look for if I am going to buy one?


texts:
I know from the equation of Id that

K = Id / ( Vgs - Vth ) ^ 2

but what Id if I don't have the value of Id? Should I use the value of Id on from the datasheet?

And I have another question : why are there two equations for Id one is

Id = k     ( Vgs - Vth ) ^ 2

and one is

Id = k / 2 ( Vgs - Vth ) ^ 2


texts: How to kill an Arduino when (dis)connecting 12V to Vin?

texts:
I have (had?) an Arduino Nano. I had it connected to the USB port and was working a charm.

I also had it connected a 12V battery pack to VIN and GND. I had done this several times without any problems, in fact, it had been running practically all day like this. I read that there's a diode on the board which selects the highest voltage in.

At one point I disconnected the pack and then reconnected. Not too sure what happened next (if LEDs went on or off, etc) since I was not expecting much to happen!

Point is, now the board wont start. Pin 13 LED permanently lights up while connected to USB, reset button does nothing and board appears to be generally dead! When the board is connected to 12V external power only the power LED lights and nothing else seems to work. IDE can see the Arduino in the port but when uploading gives "avrdude: stk500_recv(): programmer is not responding"

I did not change anything in my wiring, just disconnected and then reconnected the 12V external power source. So the 64k question: what happened?

I have ordered a couple more boards since I'm quite certain I fried this unit, but would love to understand what I may have done!


texts:
I am new to designing PCB on eagle, schematic is simple. But making a PCB board is where it gets interesting.

Here's my question to you guys:

I have realized that daisy chaining power supply from one IC to another cannot be good. And in a simple double sided PCB board layout (free eagle version), multiple power planes are out of the question and increases unnecessary complications.

So, I have decided to run a couple of power line (thick lines) along the entire length of my board.

Is that a good idea?
Has anyone done that before, and if so, any general guidelines to handle power buses in PCB?
Any rules pertaining to handling the capacitors on the supply lines to the ICs (op-amps ) lines?
Am I an idiot? and is there a better way


texts: How to precisely measure low currents if the voltage is high? Shoestring Budget

texts:
I have a circuit that will be using an ignition coil from a car to produce voltages in the range of 20kV to 30kV.

These will be arced across a gap and I'd like to measure the current across the spark gap.

Can I use a normal multimeter for this if the current is low?
If not is there a cheap (<£15 including p&p) way to measure this current non-destructively?

PS I am in the UK at college and we need to keep our project under budget, and this is already proving difficult but we are very interested in the results of the experiment so we would rather not have to do something else.


texts: How can I explain the unexpected negative voltage in the output signal obtained from half wave rectifier?

texts:
I observed the output signal of half-wave rectifier sending sine wave and square wave for an experiment. The rectifier was built with a 1N 4001 diode and a 100 ohm resistor. The output signal across the resistor was observed.
In both of the output signals displayed by the oscilloscope, negative voltage was observed. While the negative voltage in output sine signal was minor, the negative voltage observed in output square signal was much more obvious, in fact it goes beyond the maximum positive voltage.
In the output signal there is also a minor increase in the negative voltage when frequency increases, which I can't explain either.


texts: Correct AMPS & volts for DC motor controller

texts:
I'm definitely an amateur hobbyist, but I need to fix something for a friend.

I have a existing DC motor and the controller is shot. The motor is rated at 0-90 VDC (5Amps)

I wanted to see if this controller would work.

http://www.batteryspace.com/dc-motor-controller-electronic-speed-controller-kit-for-90v-dc-motor.aspx

It is rated at 6 amps (Max). Will this cause any problems with the motors? They will mostly be running quite slowly.

I eventually want to replace the pot with an Arduino.

EDIT Here is the motor. Its old. Can't find any specs other than what is printed on the label.
http://www.lakecityelectric.net/show.php?motorid=20813


texts:
I am having trouble choosing a flyback diode for my 5v relay. The switching current of the relay for 83Ohm is ~60mA.
Goind through the parameter list of the RS catalog I selected:

Maximum Continous forward current > 100mA
Peak reverse voltage >30V
Power dissipation >500mW
SMD

One of the first entries were 1N4148WSF and BAT54WS. The BTA54WS is a Schottky diode, but still in the parameter range.

Does it matter which diode I use as long they are in my parameter range? Do I need more parameters to choose the correct diode?

EDIT: follow up question


texts: What decides the response time parameter requirement for zener diode

texts: Assuming that a zener diode is being used to prevent over voltage condition from destroying an electronic component; how does the designer know what range of response time is required when choosing the zener?


texts: How to implement a "circuit breaker" for an air cylinder

texts: Basically I have a machine connected to the end of an air cylinder, a paint mixer to be specific. I want to implement some kind of device that won't allow the mixer to be turned on until the air cylinder is fully extended, I was thinking maybe a tripping mechanism that closes the circuit when it reaches full length. I'm not an electrical engineer so I'm sure circuit breaker is probably the wrong term but I was hoping for guidance on what to look for and where to find it! Thanks!


texts: 1.8V to 5V, still not comfortable with transistors

texts:
I have a H-bridge IC L293DNE that needs 5V input signals to operate, however my available outputs are only 1.8V from a Gumstix Overo GPIO pin. I have a power supply that supplies me with +5V 1A.
I've searched around for information about "Level Shifters" and "Logic Level Translation", but have been unable to find any good basic information.

I have a few 2N2222 transistors laying around, and I need to convert four 1.8V outputs to 5V, but I have no idea how the circuit should work. Will the 2N2222 do? Do I need resistors, and if so, where do I put them and how do I calculate the resistance needed?


texts: Making a synchronized, rising edge reset signal to a decade counter

texts: I made a decade counter as in the picture above, but i still would like to build a signal/button that would make the counter reset to 0 after the clocks rising edge when the signal is at 1, and to do nothing at value of 0. The simplest way i tried to achieve this was to just take the AND-gate and connect the clock and a simple 0/1-pin to it, which would reset the counter to zero during the rising edge. But this makes the counter run up to 15, which is not what i'm aiming for. How could i build the command properly?


texts: How to control High Voltage Power Supply (HVPS) voltage output?

texts: I am trying to explore good options that allow me to control the voltage output of an HVPS from 1KV to 10KV DC voltage. I have very little experience dealing with voltage range above 1KV. I understand that you need to be extremely cautious when you work with HVPS. Any thoughts on control mechanisms on the output voltage and any safety precautions will be more than welcome! Thanks!


texts: Two identical stepper motors behaving differently at higher (but below their rated) speeds

texts:
Note:

My question might be short on specifics here when it comes to the motor-parameters, but I have been trying to understand a situation for the last 2~3 Weeks, and I still don't have an explanation for it, and was just hoping that someone with more experience might be able to throw some insight.

Background:

I had to use 2 stepper motors for a specific project. Both the motors are from the same supplier and of the same type with exactly the same parameters.

Unfortunately, the two motors seem to behave differently and this is where it gets curious. After already going through checking all the motor parameters, and any electrical connection issues, we have come down to localizing the problem to the motors (or their encoders).

What is observed:

Both motors, behave similarly at low speeds (low but above their lower limit).
Upon increasing speed, one of the motor keeps working, while the other starts reporting "position control" errors, meaning the commanded-position and the position reported by the encoder have diverged from each other beyond our tolerance limit. (Remember the motors are identical.)
At first we thought the encoder has a problem, because the problematic motor itself when driven in an open-loop at different speeds seems to run smoothly. We could push it up all the way to its rated maximum speed without any noticeable issues.
But after checking the encoder signals, (it is a rotary encoder), it seems the encoder signal has no problem. We don't see any skips or other phenomenon. If the motor is rotated with constant speed, we see equidistant square wave encoder signals with same amplitude.
Then we thought that the motor itself has probably problems only when running in a closed-loop. So if the encoder is ok, then what else could be a problem? Probably the current drawn by the motor? So we measured the current drawn by the motors. And here it gets interesting. And this is what I want to understand.

Question:

For the same voltage, same commanded movement and same speed, the two motors exhibit two completely different graphs.

The "good" motor has a smooth sinusoidal graph for the absolute RMS current, that varies between 0.1 to 0.4 Amperes.
The "bad" motor has a very irregularly formed curve from the drawn current, even though the commanded movement, the speed and the voltage is exactly the same. Also the current varies between 0.1 to 0.8 Amperes.

We checked the resistance of both the coils of both the motors. They are about the same 2.7 Ohm +/- 0.4Ohm.

So why do the motors exhibit different behavior? Anyone has any ideas, guesses? Because I have no more ideas left now on what to try.

Followup test:

As a further check, I doubled the voltage on both the stepper motors. Now both the motors run smoothly with pretty smooth and nearly identical current curves.

So, at higher voltage the problem disappears.

What is however curious, is that for the "good" motor a doubling of the voltage lead to an almost doubling of the absolute RMS current.

For the "bad" motor, a doubling of the voltage still showed a graph for the absolute RMS current that swings between 0.1A and 0.8A. Is this to be expected?

Further followup Test:

To isolate the case that the Controller and not the motor is the issue, I exchanged the two controllers between the good motor and the bad motor. Switching the controllers had no effect. The bad side stayed bad while the good side remained good. So it can't be the controller.

Note:

The motors are being tested well below their rated current limit (30% of the max) and rated speed limit (about 40%~50% of the max), even when doubling the voltage. This is not a case of me, testing the motor beyond its rated capacity. Also, there are no mechanical obstacles or weights. I am testing the two motors without any load.

What else could I be missing?

p.s. is it even significant that the absolute RMS current graphs are different for the two motors?

Any feedback is greatly appreciated.


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