texts: DH-11 Sensor on a Raspberry Pi & Arduino

texts:
I am trying to make my DH-11 sensor work on my raspberry pi but I have not succeeded after several attempts. I followed the following tutorial from Adafruit:

https://learn.adafruit.com/dht-humidity-sensing-on-raspberry-pi-with-gdocs-logging

My attempts were unsuccessful. I just do not get any feedback whatsoever from the sensor. I know that both my DH11/DH22 sensors do work because I do read data from them if I do the same circuit using my arduinos and run a script. I also don't think my raspberry's GPIOs are damaged in any way since I tried with like 5 and I didn't get any data.

I am not trying to log stuff to a google doc like the tutorial does, I am just trying to read data from the sensor using the raspberry.. I have plans to log the data in a server an access it remotely... But for that I have to get readings from the sensor first.

Now, has anyone achieved this? Reading data from a DH11/DH22 in the raspberry pi? If so, could you tell me which tutorial you followed? I've been looking for some out there but it seems that Adafruit's is by far the most popular one.

Thanks for your help!

Cheers!


texts:
A signal is defined as :
logic [width_x-1:0] x;

I want to assign x a value where the second bit from the top is '1' and all other bits are '0'.
For example, if width_x is 4 then I want x to be "0100". In VHDL, it can be done as follows:
x<=(x'length-1=>'1',others=>'0');

What will be the closest Verilog/SV equivalent ?


texts: Unbalanced pi- attenuator - Problem with simulation

texts:
I've been trying to simulate the asymmetric  pi-attenuator example on this page with different source and load impedances: http://www.electronics-tutorials.ws/attenuators/pi-pad-attenuator.html

I simulated it with an input voltage of 1V.
http://postimg.org/image/a25pao46z/

The output I get, however, is 0.41V which corresponds to an attenuation of 7.75dB. Why does this happen?

I also tried simulation the 10dB balanced pi attenuator shown in the page and get near perfect result from it. Would appreciate it if anyone could explain the discrepancy to me.


texts: Does a dry human body in contact between 230 volt mains voltage and ground has any form of capacitance ? Shouldn't there be some, or else is it just resistance ? I was thinking whether the Xc component plays any part when a person gets electrocuted


texts: AC signal and ground plane with another trace passing between - is this bad?

texts:
In learning about reducing a circuit's EMI emissions, I've learned the importance of a ground plane, in that it allows the current-return for an AC signal in an adjacent layer to flow directly under that signal's trace, due to that return-path having the lowest inductance due to the smallest loop area, which also consequently reduces EMI.

What I'm now wondering is, what if something gets in between the two layers in question? Particularly, what if I have a power plane or power traces in between my signal trace and the ground plane which allows its current-return?

I've learned that the return current may in fact (confusingly) hop between ground and power planes by any decoupling capacitors along the way. See here. This doesn't sound quite ideal, so I'm considering not having a power plane at all, and instead simply running power traces where I need them. However, I'm wondering whether anything bad will happen if I run a power trace on a layer between an AC signal and its return path. Consider this example, crudely depicted:

Firstly, will the presence of the (yellow) power line disrupt the depicted current return path?

And secondly, perhaps more worryingly, the yellow power trace is travelling directly through the "loop" formed between my trace (red) and its current return path on the GND layer, presumably then being subjected to the resulting field (electro-magnetic?) that occurs within this loop. Will that field then induce extra AC currents in the power trace?

Or is there a better way to route power - should I route it on the surface layers only, and have the inner layers as GND only?


texts:
In the U.S. where I am from, my company's field techs are required to measure AC wall current of our products frequently. To to this, they either make their own harness with a Hot (Line) wire to clamp on to or they opt to use a commercial line splitter like this:

The problem is that field techs in the UK are adamant that they are not comfortable using a homemade version and I can't find any commercially available. Does anyone know where to buy one of these using 230 VAC UK style plugs? Sorry for such a silly question, but I'm really stumped.


texts:
What's the minimum number of NOR gate needed to build a 3-input XOR gate using only NOR gate?
Information I know:
https://en.wikipedia.org/wiki/NOR_logic
A XOR B = [ ( A NOR A ) NOR ( B NOR B ) ] NOR ( A NOR B )
A XOR B XOR C = ( A XOR B ) XOR C
Using the above formulas, I can implement 3-input XOR with 20 NOR gates.
What I don't know:
What's the minimum number of NOR gate? Is there a simpler way to implement 3-input XOR gate?


texts: I2C and SPI ,if they share same connection , is there confilict or not

texts:
We have a product which uses PIC18F4520, and we used some devices like LCD driver and so on, that all use I2C bus to comunicate with the micro. But now we want to add a couple of AD5504, which is a DAC with a SPI interface. We now have a question as to whether they could share the same connection with the I2C bus or not.

Do you have a good suggestion about it?


texts: Dual Supply Voltages in Op-Amp Circuit & Op-Amp parameters

texts:
I have few questions about Op-Amp circuits that i could not found the right answer with my research. These are;

Why do we need dual supply voltages in Op-Amp circuits ?

Which parameter of Op-amp causes to make a square signal's shifting between 0-1,1-0 slower?

Sorry for grammar mistakes.


texts: How would you make a 3-bit binary adder that adds two instead of 1?

texts:
I am trying to make an asynchronous adder that holds three bits and adds two to the number. Can someone help? A Google search shows nothing and I'm having a hard time visualizing how to make the circuit.
Edit: This circuit is part of a larger circuit I have to make for a problem. The circuit needs to add two to either an even three-bit number or an odd three-bit number. I have the rest of the problem done except for the adding two part.
(If anyone wonders, the problem says the circuit is supposed to act like a normal down-counter when an input w = 0, then switch to adding two if w = 1.)
Edit 2: I know this is a late edit (and might be illegal), but here is my attempt at the circuit using four flip-flops (I am required to use d flip-flops). IT IS VERY UGLY AND CONVOLUTED, I apologize. :(
The first four count down when w = 0 while the fourth d flip-flop stores the value of the least-bit (0 = even, 1 = odd). When w = 1, the clock to the fourth becomes zero and therefor stores the value of the least bit indefinitely. Ev/odd becomes Q_0, Y_0 then becomes Q_1 and Y_1 becomes Q_2, "adding" one to the two's place and, to my understanding, simulating the addition of two to the number.

I feel this is the simplest way to do it, but I feel I am using more gates than are necessary or that I am miscalculating the clock timing.


texts: Does Neopixel require a continuous signal to keep the LEDs lit?

texts:
I want to use Neopixels in a project which lights up some Neopixels, does a lot of computation and then changes some other Neopixels. Now since the program is synchronous I do not want to lose the present lit Neopixels.
I want to know whether the Neopixels remember their state or do we need to provide continuous pulses to control the Neopixels?
Thanks in advance!


texts: Not use current limiting resistor for switching device on off using TIP122 possible?

texts:
I wanting to control MP3 player and amplifier box through PIC board.

My project is doing announcement when person standing in near PIC board with proximity sensor.

When proximity sensor detecting people, sending signal that processing by PIC board.

Now from PIC I want turn on (person present) or off (person not present) the MP3 player and also the amplifier box connected to MP3 player output and speaker.

I thinking using cheap 5A BJT like TIP122 to turn on and off the MP3 player and also the amplifier box?

Now amplifier box requiring 30V @ 2.5A, so if I need put current limiting resistor for switching TIP122, then that resistor rating calculating as:

R = (30 - 1)V/ 2.5A = 11 Ohm
Wattage = (I**2) * R = (2.5**2) * 11 = 68.75W

This very big resistor impossible for purchasing!

I thinking if possible to completely not use current limiting resistor for switching TIP122 at all?

If this possible, then base of TIP122 connect to PIC pin and TIP122 in series with amplifier box power supply path sink.

Is this workable and reliable design (not want burn TIP122)?


texts:
Below is the output of an accelerometer when it is standing still:

The zoomed 0.5 seconds of time series voltage data above is from a 4 seconds of measurement with a data acquisition board at 30kHz sampling rate. I also observed the same waveform with a scope.

And here below is the FFT of the signal:

As you at the FFT plot there are peaks at 100Hz, 200Hz, 300Hz, 400Hz, 500Hz, 600hz so forth and so on.

I have been told that the shield of the cable(CAT6) is either floating or wired to mains earth or wired to the DC ground of the SMPS power supply inside the enclosure. I dont know which one is set now.

But before I go and examine it, I'm wonderin what can be said about nature of such noise.

If it was 50Hz noise I thought I would see only 50Hz dominating. But now both even and odd harmonics of 50Hz appears at FFT. Can this be related to 50Hz coupling or SMPS switching noise?


texts: Does the 74LS09 have an adequate internal input pullup?

texts:
I want to feed an output of the 74LS05 open collector inverter into one of the inputs of the 74LS09 AND gate. The internal schematics in the datasheet shows that there is an internal resistor and 2 diodes between VCC and inputs:

Can I treat the AND gate as having an internal pullup and thus avoid an extra pullup resistor for the 74LS05 or do I still need an external pullup resistor?


texts: Why is USB cable maximum length is shorter than in RS232?

texts:
Why do we need to buffer USB signal if the cable is longer than 5m?
Is that because a signal voltage drop?
Is that because it drives currents?


texts: Karnaugh Veitch diagram and ordering of the variables

texts:
I have a little problem understanding the ordering of the variables at the axis.

For example, at the lecture we did 4 variable Karnaugh Veitch diagram as a

    A
  0 1 1 0
C 1     0
  1     1 D
  0 0 1 1
      B

On this site I found it like this(page 5)
http://sus.ziti.uni-heidelberg.de/Lehre/DSTVorlesung1213/DST_Fischer_05_KMAPs.pdf

      A
  0 0 1 1
D 1     0
  1     1 c
  0 1 1 1
     B

And examples here are also different.
http://de.wikibooks.org/wiki/Karnaugh-Veitch-Diagramm:_Theorie_des_KV-Diagramms

0 represents logical not, 1 represents normal

Can somebody explain or refer me to a website/book where I can find out, how to put variables on the right place at the axis.

Thank you very much!!!


texts:
Is it possible to construct an adjustable output switching power supply based on the MC34063? I read over the On Semi datasheet and app notes but didn't see any examples of an adjustable output application.

Is it just a matter of replacing the "R1" and "R2" resistors with a potentiometer and then calculating the other components values based on a Vout in the middle of the the target Vout range (i.e. so for a Vout of 5-12V, you'd base calculations on 8.5V)?


texts: I have made a very simple battery backup for my garage door. 2 x 12v batteries in series and hooked into the battery terminals of my opener.  This charges the battery and switches to backup on power failure. My question is before I build a second backup for my other door can I simply wire both doors into this one backup.  I am concerned with having 2 door openers charging the batteries at the same time. I was considering having an DPDT switch so the one backup can open both doors but I have to manually switch between them.  But if there are no issues wiring them together it would be best option.


texts: What happens inside a battery connected in parallel to a load and MPPT solar charger?

texts:
This seems like a common configuration: connecting solar panels + MPPT charger to lead-acid batteries which are also connected in parallel to an inverter.

Assume that, momentarily, the battery has been charged fully (as per the charger's logic), the solar panels are supplying their peak power, and the inverter is drawing current. I would like to know what is happening inside the battery in the following cases:

Both the battery and solar panel are capable of supplying the power requirement.
The solar panel is not able to satisfy the power requirement, so the battery has to provide it.

Does the battery undergo chemical changes which count towards cycles of the battery? How to count these cycles which I assume are not complete cycles?


texts: How to measure a clock signal from a positioning module with an oscilloscope

texts:
I am trying to measure the clock Signal of a positioning module in SSI mode using an oscilloscope. The Problem is that with a high Transfer frequency let say 1Mhz there is some missing pulse in the clock Signal I have been able to see it with my Simulation. How can I measure that with an oscilloscope? Is there someone who has an idea how I can do that?

many thanks


texts:
Hey i dont know how to solve this. Can somebody help me?

In the two-plate arrangement shown in the sketch, there is homogeneous electrical field strength
$$\vec{E_0} = -\vec{e}_y * 10\frac{kV}{cm}$$

Calculate the work done by the field when the charge Q = 1 μC from
Point P 1 (l, a, 0) is moved to point P 2 (0, 0, 0). Integrate once over for practice
the direct, sloping path and once over the square path along the
Coordinate axes.

This my try to solve this task ... But i dont know if it is right
$$ r = (-l\vec{e}_x -a\vec{e}_y) * t $$
$$ 0 <= t <= 1$$
$$ dr = (-l\vec{e}_x -a\vec{e}_y) * dt $$

$$ W = Q * \int_{0}^{1}\vec{E} dr$$

UPDATE1

$$ W = Q* E_0 * \int_{0}^{1} -\vec{e}_y* (-l\vec{e}_x - a\vec{e}_y)dt$$
$$ W = Q* E_0 * -\vec{e}y* (-l\vec{e}_x - a\vec{e}_y)$$
$$ W = Q* E_0 * a$$

Thanks to the answers. I think this is the solution.


texts: 50 (or more) channels picoscope/oscilloscope

texts: I need to debug communication protocol over 50 digital channels cable and 2MS/s sample rate. What kind of tool would be best suited to do that task? What other aspects should I consider?


texts:
I have a project where I am using two clocks at the same frequency, with one having a -90 degree phase shift. The FPGA board I am using is an Nexys A7-100T configured with Vivado in VHDL.
I have used in internal clock on the board with a constraints file which is pin E3 at 100MHz. I have then created a component with the clock wizard on Vivado that takes the input 100MHz clock and should output two 5MHz clocks; Clock1 and Clock2 with Clock2 having the phase shift.
Now when testing my design it did not work so I decided to test the two clock signals by running through clock divider counters bringing them out on an separate LED on the FPGA board.
When I run the design there is no phase shift on the clocks as both LED's blink at the same time, explaining why my design won't work.
My question is has anyone came across a problem like this before? What is the only information I have to enter in the images below to do such a simple clock setup?
I don't have access to Vivado currently to provide images of my clock wizard setup, but I will show a Google image of the wizard and I have entered all the above information correctly.
Thanks for any help, I am unsure what to do.
EDIT
Here are screenshots of my clock wizard settings:

Here is my screenshot of the oscilloscope measurements below. The clocks show the 90 degree phase shift but I am unsure why they appear 'rounded'. Is this an issue with my measurements on the oscilloscope?


texts: How to make bipolar supply -2.5v to +2.5v from unipolar supply?

texts: I need a regulated bipolar supply for precision adc. It should have two fixed outputs: +2.5v and -2.5v. How to build such supply using unipolar supply with voltage 5v or higher?


texts: Replace a power adapter 12V/1A DC with 15V/0.8A

texts:
I have a battery-charger that has an input of 12V/1A as specified in the specs.

Can I replace the adapter with a 15V/0.8A adapter ? I also have a 9V/0.85A

Will both work ? Which is more suitable and safer to replace with, or should I buy a 12V/1A ?

I was told 15V/0.8A and 12V/1A are practically the save since the have the same Power result in watts of 12W = 12*1 = 15*0.8 ? Is this correct ?


texts:
As I am trying to create a program that addresses the various luminaires, I wanted to know better theoretically not the commands to give, but why I am giving that specific command.
I've searched for a long time to find also examples about Dali2 addressing light commands.
Then I found an article that told me that I had to enter some kind of command twice, for Dali to understand them.
This is what I've read:

According to IEC 60929, a DALI Master has to repeat several commands within 100ms, so that DALI-Slaves will execute them.

My questions for you are these:

What commands do I need to repeat in my program to be effective?
Which order of commands should I respect?
Would it be better if I used the state automaton process type or buffering?
Why should I repeat the commands?

I am using the Stm32 microprocessor so my code must be the most
light and efficient as possible.


texts: Should I check battery current by ammeter?

texts:
I had the concept that in order to check the maximum current a battery can supply, it is fine to connect an ammeter in series with battery because ammeter has low resistance in series and this will yield the maximum current a battery can supply.
Many people have said it is wrong, but I can't understand why.


texts: Relationship between time constant and frequency

texts:
I have seen the relationship that the RC time constant (\$\tau\$) is equal to the inverse of the -3dB angular frequency (\$\omega\$). The time constant is in units of seconds, while the angular frequency is in units of radians per second.

My question is why the time constant (in seconds) isn't equal to the inverse of frequency (in 1/seconds) rather than the inverse of angular frequency (in radians per second)?


texts: Are decoupling capacitors needed with battery power?

texts: Currently I run all my gadgets from batteries and don't use decoupling capacitors.  Are they generally needed/useful when drawing energy from a battery?


texts:
I am designing an hardware including MCU's, camera , RF components etc. Shematic looks fine and my question is actually about powering part. I have put some battery powered applications based LDO. It can handle 2.2V to 5.5V.
I want power my system when I plug USB too.

But If USB power lines is connected before Battery , then battery will go under tension with 5V. There must be a way to block battery when USB is on. how can I block battery without exceeding BOM file too much?


texts: VHDL/FPGA Should I block down an array into arrays of dimensions with powers of 2?

texts:
I'm building a VGA display with a Xilinx FPGA. I'm not exactly sure what's the best way to store VGA frames. The resolution is 640x480. Should I just use a 640x480 2D array or block 640x480 into following:

[ 256x512 256x128 ]
[ 128x512 128x128 ]
[ 64x512  64x128  ]
[ 32x512  32x128  ]

each 2^N X K block represents a Block RAM with N-bit address, and K bit word.

In reality, each color is 8 bits, so word widths will end up 8 times higher.

Or better yet, what are better ways to build this memory?


texts: How many routers can the Powerbank power and how long?

texts:
I have a power bank,
Capacity: 27000mAh/99.9WH
Input: 19V/1.6A
AC output: 220V/50Hz 100w Max

Router (MR600)
Input: 100-240v 50/60hz 0.6A
output 12v 1.5A


texts:
Suppose I need to make transformer at home, but I am unable to wind 100k turns obviously, then can I just connect a resistor in series with a winding to achieve desired impedance? Will it have serious problems like bad frequency response? I understand that resistor would not behave like an inductive load, so I also thought maybe it is possible to connect inductor in series for impedance matching?
Or is there any other way to make high-impedance(~10kOhm) transformer winding at home? It would obviously require insane amount of hand-winding even to get to 1kOhm :(

UPD: See the comments, apparently I got the concept wrong.


texts: NPN Darlington circuit for 12V Diesel Glowplug

texts:
I'm trying to build a very simple circuit to drive a glowplug. I am using a TIP122 NPN.

simulate this circuit – Schematic created using CircuitLab

I wanted 0.017A going through the 12V plug. I estimated no more than 0.204W. I also assumed my NPN's HFE was 1000.

To find power dissipation \$12V \times 0.017A = 0.204 W\$.

Calculated base current with

$$Ib = \dfrac{0.017}{1000} = 0.000017A$$

$$R1 = \dfrac{4V-1.4V}{0.000017A} = 152941 \Omega$$

I hooked all this up, and the NPN got pretty hot. The glowplug started to get a little hot, probably around 100F by the time the NPN was around 200F and climbing fast.

I'm very new and have been more or less dealing with NPN saturation on simple devices like LED and Fans with no issues. I have done this exact circuit with a 12V relay I pulled from a car, but I was really just experimenting here trying to learn the limitations of an NPN.


texts: How ignition coil in automobile works..?? what are the winding count for ignition coil..?

texts: I just want to make ignition coil on my own. can you please help to done primary and secondary winding for same..? 40KV output required from 12v input supply.


texts: Use rotary switch potentiometer from amplifier as main power switch

texts:
I am working on a battery powered audio project that uses a cheap amplifier (PAM8403 5V Mini 2*3W D Class Digital Amplifier Board).
The volume can be changed using a rotary switch potentiometer.

Now I would like to use the switch of the potentiometer to be the main switch for my project.
The ultimate goal is to drive the enable pin of the Adafruit PowerBoost Charger by the switch of the potentiometer. The BowerPoost Charger is OFF when the enable pin is connected to ground (the switch is closed - reverse logic). I measured 5V between the pins of the switch when it's turned off, and 0V (switch is closed) when it's turned on.

So how do I have to connect the potentiometer to the charger board?


texts: How can I apply process corners (TT, SS, FF) to my simulation in HSPICE?


texts: PCA9456A i2c switch channel 1 not showing up

texts:
I am using an PCA9456A i2c switch to help me toggle between i2c devices with the same address, but i am having problems opening channel 1 (second channel out of 4) and i ran out of ideas what is causing it

Here are the code and schematics, I am using the busio and board library in python

import busio
import board

i2c = busio.I2C(board.SCL, board.SDA, frequency=100000)

i2c.writeto(0x70, bytes([0x0F]), stop=True) # 0x0F = b00001111 which turns all channels on

With this code i am able to toggle between the other 3 channels (be it only 1 channel is enabled or any combination of the 3)

I am planning of using it on a raspberry pi 4.

what i have tried checking:

I have tried double checking all connections and if they are
connected to the correct pins EDIT: This turns out to be false
I have tried changing the pull up resistors' value (decreasing and increasing it)
I have tried creating another circuit using another PCA chip and a different i2c device than what i am supposed to be using. It is always channel one that i cannot enable

here a picture for the i2c scan, you may notice that there is a gap between the addresses, 0x49. That is the device connected to channel 1.


texts: Connecting PWM computer fan to transistor and adjustable resistor

texts:
Edit: Please do not change the circuit after the circuit has been discussed and answered. Thank-you. --MathKeepsMeBusy

simulate this circuit – Schematic created using CircuitLab
I'm making a jet car, and I'm making the electronics for it. Is it safe to control the speed of the PWM fan by controlling the voltage across the positive and negative leads with a transistor connected to an adjustable resistor? The adjustable resistor is the throttle lever in my car.


texts: Step Down Regulator - Output voltage unstable/voltage drop with load

texts:
I'm currently trying to build a USB charger device for my mobile phone using an old 12V car battery as power source. I purchased different step down modules (see below) to regulate the voltage from approx. 12V down to 5V.

My problem is, that as soon as I connect my mobile phone to the output of the step down regulator, the previously adjusted output voltage (via potentiometer) drops for about 0.7V causing the mobile phone to not charge properly. Example: I configured the step down module to provide 5.2V at the output. Without load, there is no problem. With my mobile phone attached the output of the step down regulator, the voltage drops to approx. 4.5V.

I checked the input voltage of the regulator from the battery.
Without Load: 12.85V, with mobile phone connected: 12.74V.

Is the "unstable" input voltage responsible for the massive voltage drop on the step down output? Or is there anything I can do to improve output voltage stability under load? Because I don't want to set the regulator to 5.9V only that it will really deliver 5V when connected to my phone - I think that's not very comftable for the mobile phone?!

Thank you!

I tried the following "ready-to-use" modules:

MP1584EN
LM2596


texts: What does 600R@100M mean from RDA5807M datasheet?

texts:
I’m trying to assemble a bare radio module using RDA5807M IC. The most popular diagram I can find is this:

What the filter is used on vcc input?
That inductor sign, 600R@100M, what does it mean?

EDIT:
as this marked duplicate, i want explain i need just a component which can be placed there, if its an inductor, inductors are specified by microhenry, where, how can i find some thing place able in there


texts: Why does impedance decrease in an MLCC as frequency increases?

texts:
I understand that the impedance of any capacitor decreases as frequency reaches the resonance frequency, following the formula Xc = 1 / ( 2 pi f C ), but why does the impedance of an MLCC such a better frequency response than other capacitor types like electrolytic and tantalum?
 Additionally I read somewhere that "this equation is not ( in math terms ) "rigorously correct", it is actually a crude "rule of thumb", which has some built-in assumptions that are NEVER identified, anywhere." on one of the answers [here][1] Is this true? And why are the assumption never identified anywhere?


texts: Need a Loud Electrical Component for Magnetic Lock

texts:
On our main front door at the Stack Exchange offices we have a glass door with a magnetic lock installed.  As is common at offices, visitors can ring a doorbell and then our receptionist will press an RTE button to release the door lock and allow them to open it.

The problem we have is that the maglock does not make the typical loud clicking noise from any of it's internal components activating - which is how most people know to open the door.  Instead, the door unlocks silently and they just stand there not realizing they can open it.

SO - here's the question:
I'm looking for a simple circuit I can build and install in the maglock that will make some sort of recognizable noise whenever the door is unlocked.  The lock is normally powered with a 24V feed from a power supply, so the simplest way would probably be something that just connects inline and then activates whenever the power drops out on that 24V line.

The problem is that I don't know exactly what to use to do that.  I'd imagine a relay might do just the trick (since there's normally a noise from the internal switch activating), but looking for some guidance/confirmation on that.


texts: SENT protocol output unit is LSB. What does this mean?

texts:
I have read couple of datasheet of devices which uses SENT protocol. They define the output between 193 and 3896. The unit is LSB. I think that this does not mean least significant bit?

Example:
https://www.infineon.com/dgdl/Infineon-KP275-PB-v01_00-EN.pdf?fileId=5546d4625b10283a015b34276c891ce0


texts: The thermal reliefs of my ground polygon to one of the pads of my footprint are just simply weird! I dont know what causes it? It seems to me that the lines leading up from the polygon to the pads are just too thick and are out of proportion to the pad.


texts: 12v dual battery setup - wiring, grounding and busbars

texts:
I am installing a 2nd 12v battery into my van to run eletronic devices. The 2nd battery is a bank of 2x LiFePO4 12v 120Ah connected in parallel.
My three questions are surrounding the circuit diagram pictured below:

Is running a ground from the negative pole of Lithium 2 to the negative pole of the starter battery sufficient to earth the system?
Is the green Inverter ground wire earthed if I connect to the negative BusBar (going to negative of battery bank), and what should the rating of the negative BusBar be?
What should the amp rating of the positive BusBar be?

I understand cable needs to thick enough to carry the amps in that circuit, e.g. the circuit with fuse block needs to include wire rated for 100A. What about the interconnecting batteries? Should this be rated for the largest circuit, i.e. the 550A from one of the positive BusBars?.


texts: Algorithm for mixing 2 axis analog input to control a differential motor drive

texts:
I am looking for information about how to implement proper mixing of 2 analog joystick signals (X an Y axis) to control a dual differential motor drive ("tank like" drive) using a uC (ATMega328p in my case, but same should apply to any uC with ADC inputs and PWM outputs):

I have a analog stick, that gives 2 analog values:

(direction)X: 0 to 1023
(throttle)Y: 0 to 1023

Rest position is (direction and throttle neutral) 512,512
Throttle forward/direction left is 0,0
Full forward-full right is 1023,0
etc.

The motors are controlled by 2 H-bridge drivers, 2 PWM pins for each (Forward, backward), like so:
Left Motor: -255 to 255
Right Motor: -255 to 255
(positive values enable forward PWM pin, negative enable reverse PWM pin, 0 disables both)

The goal is to mix joystick analog signals to achive following response :

a)Throttle forward, direction neutral = vehicle moving forward
b)Throttle forward, direction left    = vehicle moving forward and turning left
c)Throttle neutral, direction left    = vehicle turning left IN PLACE that is right motor   full forward, left motor full reverse

...and similarly for other combinations. Of course, the output should be "analog" that is, it should allow gradual transition from for example from option a) to b) to c).

The concept is:


texts: (How) does blocking a (servo/DC) motor break it?

texts:
I don't know why, where or how I picked this up, but I believe that if you power an electric motor while blocking it, and thus stopping it from moving, you'll damage it. I'm thinking of the following type of motor, and possibly servo motors:

Is it indeed true that holding the shaft in place while powering it will damage it? And if so, why? And could this be prevented by simple measures? (Like putting a resistor in front of it.)

Is the "damaging process" any different in servos, or do they get damaged in the same way?


texts: I want to have a contact open/closed when a USB port is powered on or off. When monitoring the USB port with a multimeter it takes >1 minute for the voltage to drop from 5v to zero. What is a simple circuit (or single component) that will close and open (in <1 second) a contact when the USB port is outputting 5v and draw minimal current while operating?


texts: Buck boost converter + LDO or 2 Buck boost converter

texts:
I am currently designing a circuit where we have a lipo battery powering two rails:

Rail 1: some RGB LED with 5V power supply
Rail 2: a bluetooth chip with 3.3V power supply

Option 1: use 2 buck boost converter to go up from [3V-4.2V] to 5V one side and to 3.3V on the other side
Option 2: use 1 buck boost converter to go up to 5V creating rail 1, then use rail 1 + a LDO or DC-DC to go from 5V to 3.3V to create rail 2

What is it better to do and why?


texts: Low voltage drop regulators and switches for battery powered device

texts:
I am building a battery backup system for a DC appliance that runs on 6V.

I have a 6V sealed lead acid battery to serve as the backup source.

However I read that a lead acid battery at full charge has slightly more voltage than its rated at. E.g. a full charge lead acid 6V battery would rest at 7.15V

At this voltage it would be damaging for the appliance so a voltage regulator is desirable.

However many voltage regulators like LM317 give a drop of about 1.5V. So, at full charge the battery's 7.15V would get regulated to 5.65V which is lower than the required 6V. Not to mention it would drop more as the battery discharges.

I'd also wish to put a transistor switch between the battery and the appliance to turn it off when battery is discharged to prevent a deep discharge. Again that would lead to some voltage drop.

What is the best regulator and switch to use in this scenario? A Zener diode?


texts:
Need to repair a legacy system that has been discontinued and am confused by the PNP based circuit below.

The input signal (max. freq = 20Khz) is applied at IN and is active low. It's TTL level.
It is actually the output of TSOP1738.

The output is tapped from OUT and 3.3V is applied to this point through a weak pullup.
The output signal (OUT) goes to a 3V3 microprocessor

Given this information, is the circuit effectively a 3.3V level convertor?
Can I replace this with a diode based circuit below for an equally effective 3.3V level convertor?
(Please disregard that short. It does not exist and was drawn in error)

Why would a company prefer the PNP based circuit over the diode based circuit?


texts: Really occasional malfunction of the Schmitt-trigger input

texts:
I'm using some Schmitt-trigger inputs for debouncing the interrupt problems.

Referring to above circuit, the circuit has a RC circuit and the output of the RC circuit goes to the Schmitt-trigger IC(74HC14).
Also, I soldered like this circuit and the look is like as below picture.

Well, the picture is not good I apologize for the view. (18k : R1, 2k : R2, 0.1u : C1)

Anyway, I'm convinced of the equality of the circuit picture and the real one.
However there is a very small issue.

The output of the Schmitt-trigger IC is connected to the MCU interrupt pin. So, if the Schmitt-trigger output goes to low(I use falling-edge-triggered interrupt), the MCU will run some ISR. Suppose I "bring(NOT push the button)" my hand to control the device on my own. At most, the device not malfunction. However, very occasionally the device goes to interrupt mode(ISR).

The schmitt-trigger goes to MCU(ATmega2560, STM32F411RE, and so forth) and the MCU has some attached interrupts that can respond for the some schmitt-trigger inputs. And if the problem occurs, MCU just execute some ISRs. I thought the problem is occurred by the ESD so I used some TVSs and collected all the GNDs as near as the SMPS input, but the issue is not entirely solved. The problem hardly happens(probably just one time of a day) so this wouldn't be important one, but what could be the cause of this situation? Could I get some intuitions for the issue and the solutions?


texts: Spot beam (Coverage area) and beam width

texts:
Spot beam is simply a manifestation of my simulation model.  It says that given a certain azimuth angle and an elevation angle, then what is the area of circle in space at a distance R away from the origin.  For this I have to  assume a conical geometry, and so the further you move away from the apex of a cone, the larger the circular area of the base of the cone.  This marks the spot beam and it is the area of interest in space.

Beamwidth does not grow with distance (else you're assuming that its gaining power from somewhere).  It stays constant, and with my assumption that its circular, it marks the area within the spot beam where there is relevant energy, either transmitted (incident) or gain (observant). And therefore, for a given spot beam (an area of interest in the 3 dimensional space) I'm first trying to see if that area is greater than the beam width

So my question is: What is the relationship between a spot beam and beam width? If I assume a cone, will the angle, theta be equal to the beamwidth? or what angle should I take so that the area of circle in space at a distance R away from the origin can be calculate?


texts:
I am working on a project and I use several PIC18F26K83's for this project. For communication between PIC's I use UART. Now I also need to send data with RS232 to the user. As I have understood the main difference between UART and RS-232 is voltage levels. And with PIC I cannot supply proper voltage level that is required for RS232. Because of that UART to RS232 converter's look like a must. (i.e. MAX232) I have two questions.

Using UART to RS232 chips is the only option in this case? Are there any alternative ways?
I am planning to send UART data directly to the UART to RS232 converter chip. I do not know how they work, code wise do I need to change anything? Can I directly put UART tx data to the receive pin of these chips? Thanks beforehand.


texts: Electricity needed to maintain power for camera

texts:
I am not an electrical engineer by any means and do not even know the terms I should use to ask this question but basically I am trying to determine which solar panel I can use to power my camera.

I am not looking to charge it insomuch as the camera will be in operation while the solar is hooked up to it.
Let's assume the solar power is perfectly consistent and no loss in transit. (I know it is not but I will just double the final numbers to give some flexibility).
The Camera is rated at 1030mAH, 3.8V, 3.23Wh (it's a gopro 4 session)

My understanding (limited) is that to charge a battery, I need to basically match the amperage and voltage (assuming a perfect connection) but how does this work if the battery to charge is also being drained simultaneously? Is there a formula specific to this?

My maths suggests that I need at minimum a 1030mA and a 3.8volt solar charger... To scale this up (to account for solar charging fluctuations) do I simply increases the amps but not the voltage or is both ok to increase?

Also, what is the wiggle room on voltage? I found a charger for 3.7 volts but not 3.8 and am wondering if that is ok.


texts:
I am dealing with synthesis of verilog sources using Vivado Design Suite 2013.3 tool for the first time.
The behavior of my design is correct as verified by the pre-synthesis simulation.
My problem is that once I perform the synthesis, the resulting netlist is empty and this is confirmed by the utilization report which shows that anything has been utilized on the board I previously chose.
The only thing I can see from the scheme are the ports of the top module of my architecture:

This is the utilization:

I have been told that, since my data source is from outside of my device, I have to set the IOB option in the synthesis settings, but neither the official Xilinx guides are helping me on this.


texts: Help with specific simple Schematic design

texts:
This is for a tactile combination scroll wheel & pushbutton assembly.  TSW Switch  This switch includes a quadrature encoder for rotary as well as several buttons for up, down, left, right as well as a center Enter button.

I am making a pcb for the above schematic. S1,A,B go to COM A and S2,S3,S4,S5 go to COM B but all 7 each are going to have different functionalities when they are clicked but they are grouped in a set of 3 and a set of 4. As a thru hole pcb do I have 7 hole for each or just 2; one for COM A and one for COM B. having 2 seems to be what the schematic is showing.

My question is though, if I only have holes for COM A and COM B, how will it differentiate that S2,S3,S4,or S5 was clicked in COM B or S1,A,or B was click in COM A

But if there are thru holes for all seven then I can easily tell which one of the seven was clicked but that doesn't seem to follow the schematic.

Any insight is much appreciated. I'm am very new to electrical engineering and am a hobbyist so let me know if I didn't explain something correctly or if more information is needed to answer my question. Thanks - Jeff


texts: Storing a possibly damaged Li-Ion battery

texts:
I replaced the battery of my mobile phone earlier this day. Because of adhesive, narrow spaces etc it happened that I slightly bent the old battery during removal (see sketch below).

    top view     v---contacts                            side view
----------------[]-                                              _________
|                 |                              _______________/  _______| "bottom"
|                 |    contacts on this side >   |________________/
|                 |
|                 |                                             |<--1cm-->|
|                 |
|                 |
-------------------
      "bottom"

Sorry for the bad sketches, I stored the battery away to (probable) safety and didn't take any pictures beforehand. The bend starts about 1cm away from "bottom" and at the very bottom the battery is not more than 1mm elevated. There is no visible damage of the hull.

I cannot dispose the battery before friday and hearing of all the troubles regarding Li-Ion and LiPo batteries I am a bit worried now.

It is a 2300 mA Li-Ion mobile phone battery and at the time of removal it was probably around 20-25 % charged.

I have limited options for storage, no garden available. I thought about burying it in a glass jar filled with sand (would be available) in order to make it impossible for a fire to start (least possible amount of air available) - but the tightly closed lid would make it impossible for fumes to escape and the jar might explode from pressure?

I could also wrap the battery (or jar) in some fireproof blanket (like they are available for kitchen fires) and just hope for the best.

Do I have to worry at all? I know that LiPo-batteries like they are used for racing cars or model planes can be dangerous when damaged, but what about phone batteries? How should I store it in order to be safe until friday?

How fast would I notice any possible danger, if the battery would have been damaged? I watched it for about 3 hours before storing it away (it's in the jar of sand at the moment, with the lid open) and nothing happened. Does that mean that there will not happen anything anymore?


texts: I'm currently documenting a wireless, microcontroller-based system that I've built and I would like to use the standard industry terminology to help anyone who comes behind me comprehend it easier.  It seems like the OSI Model for describing communications systems in terms of abstraction is the standard model.  I would like to understand the layers a little deeper, but all the examples I can find use the Internet Protocol Suite (TCP/IP) as their example case.  Depending on who you read, the TCP/IP only uses a subset (anywhere between 3-7 layers) which makes it somewhat harder to understand due to the lack of implementation of layers & differences in classification of layers between sources.  I don't just want to read the OSI spec as that seems too detailed, and the usual Wikipedia research doesn't seem to clear it up completely for me either.  Can anyone explain, in general, what parts of communications system are included in each abstraction layer?  Do these layers build on one another, or are some of them completely parallel?


texts: How to find the best way to fade in/out?

texts:
I have a bunch of these PAR lights below. They work with DMX and have per LED PAR 3 red, 3 green, 3 blue and 3 white LEDs.

I can set the value for the red, green, blue and white lights independently (so four values, where 0 = off, 255 = max intensity).

When fading I had the idea to let the values from all colors go up from 0 to 255 and back. However, there are some issues:

Some colors do not turn on unless having a minimum value (e.g. red at 8, blue at 2 etc).
Some colors do not seem to have the same intensity curve as others (meaning value 10 for red has the same intensity as 2 for green)
Some curves are far from linear (meaning the intensity brightness from 2 to 10, is much bigger than 100 to 200).

So I have the idea to 'measure' the values per intensity and make my own intensity curves.

But I wonder what is the best way to do this?  Probably by using a LDR but maybe there are better ways?


texts:
I traced the below circuit from one of the WiFi based LED downlight available in the market. This circuit works at 17V (Regulated Supply) and takes 450mA max. current if fully bright. Now I am going to replace the white LEDs with the one I will purchase from the market, but the problem is with every lot the forward voltage will change with their voltage group.

Schematic :-

Specs of LEDs which I will be using :-

If (Forward Current) : 60mA(Typical) and 90mA (Max)

Forward Voltage Group :-

Graph :-

LED PCB :-

Questions :-

What can be the thermal issues with New LEDs I will be using?
Also How to deal with different voltage groups LEDs in the circuit?
Because it's difficult to change the circuit every time for every
lot.
The forward voltage decreases with increase in temperature, so will
hog more current? How to deal with that?
Do I need any kind of limiting resistor with the LEDs string?


texts: how to choose components for boost converter

texts:
I'm relatively new to electronics and I'm trying to make a boost converter for a nixie tube watch that runs off of 3v.

I'm pretty sure that the most current that will be drawn is about 70mA. I'm not sure how to choose what components I need for it.

simulate this circuit – Schematic created using CircuitLab

The duty cycle will be provided by an atmega328p. If there's any other information that you need please let me know, any help would be appreciated.


texts: How do I determine the requirements of a switching FET?

texts:
A part we're using in a half-bridge LLC soft-switching DC-DC converter is getting hard to find (STW20NM60, 600 V, 20 A, 0.25 Ω, 192 W), and I need to find a replacement.  What parameters do I need to care about?

The first thing to check is the voltage rating.  The voltage supplying the converter is nominally 400 V, but can temporarily rise to 460 V or so.  600 V parts should be plenty, right?

According to Selection of MOSFETs in Switch Mode DC-DC Converters, it's probably dissipating around 10 W, so the >140 W power ratings of every TO-247 component I've found seem perfectly adequate.

So how about the current rating?  I'm not sure how to calculate this.  The AN2492 example circuit is for a 400 W supply, and they use a 14 A FET.  I think the actual peak current through them is more like 3 A, though.  Why such a big margin?

What other parameters are important?  I think a "fast diode" version would be best for reliability and efficiency:

  This
  revolutionary Power MOSFET associates a new
  vertical structure to the company's strip layout
  and associates all advantages of reduced on-resistance
  and fast switching with an intrinsic fast-recovery
  body diode. It is therefore strongly
  recommended for bridge topologies, in ZVS
  phase-shift converters.


texts: What is the noise figure of a signal generator?

texts: I'm wondering what's the noise figure or the overall noise contribution of typical signal generators? For example, if there is a test system with a signal generator that outputs 3 dBm signal (50 ohms), an amplifier with 3 dB noise figure and 10 dB gain and a spectrum analyzer with lets say -140 dBm noise floor with 100 Hz RBW. How much does the signal generator raise the noise level and how much is the noise floor when the generator and amp are connected to the analyzer?


texts: What is considered low or high frequency?

texts:
I've been reading some guides and papers on data acquisition and often times on the subject of measuring frequency they will simply say

  For low-frequency signals, it is sufficient to use one counter, or
  timebase. The rising edge of the input signal triggers the number of
  timebase ticks to be counted

They fail to define what constitutes a high frequency, what is the threshold? My online research often takes me into the realm of radio frequency and Rf at which point I wonder if the same applies to electronics in general.

So if I'm looking to measure the frequency of a 4,100Hz signal - is that considered LOW or HIGH frequency?


texts: How to assign a pull-up/down resistor in Verilog for inputs?

texts:
As a newbie in FPGA world, I realized that it is possible to set pull-up/down resistors in Verilog but I don't know how.

I have written my code that works just fine but when I connect my XC3S400 to AVR micro-controller, At the start-up time it does weird things. I thought to add pull down resistors to input ports but the code for pull-up/down is a kind of assignment that rejects inputs.For example in the Verilog (under Xilinx ISE Webpack 14.7) , when I write:

input   in1;
pulldown  i0( in1 );

I receive this error: " Unsupported gate instantiation. "

Is it possible to add pullup/downs to "Inputs"?


texts: 2 wire rtd pt100 in a wheatstone bridge using ad620

texts: can i use ad620 with rtdp pt100??i already made a schematics in Proteus but it  give me constant voltage 3.7 v.increasing or decreasing temperature didn't effect output voltage at ad620 ..i place a 100 ohm resistor for gain...vs=+5 and -vs=-5 for ad620


texts:
is there an electrical component that exists that would act similar to a potentiometer, but could be turned either clockwise or counterclockwise past a middle point, and would either release positive or negative voltage depending on which direction past that point?

So for example, you would turn it left to release a negative voltage, and turn it back to the right to release a positive voltage.

If this doesn't exist, is there a simple circuit I could create to emulate this ability?

Thanks


texts: Arduino beacon for IR Seeker v2 (Mindstorms NXT Sensor) - Pulse IR at 38Khz Carrier and 1200 Frequency

texts:
I hate to ask a question like this, that is kinda just like "give me the code" but seriously. I've tried reading up on it everywhere, and I just don't seem to get a thing of having both a carrier signal AND a frequency.

I have the IR Seeker V2 ( http://www.hitechnic.com/cgi-bin/commerce.cgi?preadd=action&key=NSK1042 ) for my Mindstorms NXT, and I want to make a base that it can home in on to recharge. I've seen a couple of 555 Timer designs floating around the internet, but my stockpile of 555 timers are out and we don't have any "part shops" in DK, so I will literally have to wait WEEKS for them to arrive. So I thought: "The Arduino can control a TV at 38KHz, so why not do this?"

Can someone point me in the right direction, or maybe just provide me some code (yeah I know, but I'm seriously LOST!), for how to do this?

I need to flash the IR LED at 1200Hz on a 38KHz carrier signal, to get the sensor to read it clearly!
Actually it can be anything from 600Hz to 1200Hz, but 1200Hz is the prefered as far as I can see.


texts: Type of capacitor to bridge X10 signals in household power

texts:
X10 is a protocol for communication among electronic devices used for home automation where the signals involve brief radio frequency (RF) bursts over a home's A/C power lines.

Household wiring often has two different power circuits; each of the two 220V offers a single phase circuit to neutral.  This means if the X10 controller is on one of those 110V circuits, the signals are not passed to the other of those circuits.

The solution to this is to bridge the two 110V circuits so the RF signals may pass between them.  This question is about what the specs for the capacitor should be if we wanted it to be very reliable over time.

I bought and installed a capacitor like this (for a dollar) and it worked for probably five or more years:

But then it failed, and looked like this when I found it:

Capacitors, when operating properly, do not conduct [significant] current across their leads, but this season (putting up Christmas lights), the signals were not passing to all outlets, and when I looked in the breaker box, the capacitor had dropped away and fallen to the bottom.  The leads were gone (apparently melted).  So the dielectric apparently broke down over time and the capacitor failed.

This got me to thinking, would there be a higher quality / higher spec capacitor that would be less likely to fail?  If it meant I could count on it when I needed it, for decades to come, it would be worth spending more on it.  But I don't know what to buy.  I suppose I could install more than one, then if one failed, I'd have another.  But I'm not going to be pulling the cover off of the breaker box to see if one or the other blew.  Obviously not a critical problem, but just curious if there's a solution where a little more investment would mean no problems in the future.

Follow-up Appended Edit:

I ordered another one from the same place as I got the one the that had earlier failed:


texts: STM32F103ZET6 ADC with DMA whilst sleeping and interrupt every 0.5s

texts:
I am currently trying to get my STM32F1 MCU to ADC 500 samples and DMA these into memory whilst asleep and wakeup after 0.5 seconds, i.e. have a sample from every 0.01s and then wake up after 0.5 seconds to process. I am currently getting a wakeup every 2 seconds. I am unclear of where I am incorrectly seting up my DMA, or less likely the ADC.

I know that my processor is definitely entering into deepsleep as the board goes from 50mA to 30mA, the interrupt i've setup does trigger in debug mode and in my interrupt I have input a delay so I can see it in the scope. Any suggestions on what settings I am missing?

// Local Variables
ADC_InitTypeDef     ADC_InitStructure;
DMA_InitTypeDef     DMA_InitStructure;
NVIC_InitTypeDef    NVIC_InitStructure;

// Code
RCC_ADCCLKConfig(RCC_PCLK2_Div6);               // PCLK2 is the APB2 clock ADCCLK = PCLK2/2 = 24/2 = 12MHz
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);      // Enable DMA1 clock so that we can talk to it
RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);        // Enable ADC1 clock so that we can talk to it
ADC_DeInit(ADC1);                   // Put everything back to power-on defaults

// DMA1 channel1 configuration
DMA_DeInit(DMA1_Channel1);
DMA_InitStructure.DMA_PeripheralBaseAddr    =  ((uint32_t)0x4001244C);
DMA_InitStructure.DMA_MemoryBaseAddr        =  (uint32_t)&ADC_output;
DMA_InitStructure.DMA_DIR           =  DMA_DIR_PeripheralSRC;
DMA_InitStructure.DMA_BufferSize        =  1000;        // Number of samples in buffer
DMA_InitStructure.DMA_PeripheralInc     =  DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc         =  DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize    =  DMA_PeripheralDataSize_HalfWord;
DMA_InitStructure.DMA_MemoryDataSize        =  DMA_MemoryDataSize_HalfWord;     // 0x400 = 1024
DMA_InitStructure.DMA_Mode          =  DMA_Mode_Circular;
DMA_InitStructure.DMA_Priority          =  DMA_Priority_High;

DMA_InitStructure.DMA_M2M           =  DMA_M2M_Disable;
DMA_Init(DMA1_Channel1, &DMA_InitStructure);
DMA_ITConfig(DMA1_Channel1, DMA_IT_HT, ENABLE);

// DMA1 NVIC configuration
NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel1_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

/* Enable DMA1 NVIC channel1 */
NVIC_Init(&NVIC_InitStructure);

/* Enable DMA1 channel1 */
DMA_Cmd(DMA1_Channel1, ENABLE);

/* ADC1 Configuration */
ADC_InitStructure.ADC_Mode          = ADC_Mode_Independent;
ADC_InitStructure.ADC_ScanConvMode      = ENABLE;
ADC_InitStructure.ADC_ContinuousConvMode    = DISABLE;
ADC_InitStructure.ADC_ExternalTrigConv      = ADC_ExternalTrigConv_T2_CC2;      // Timer 1 ADC_ExternalTrigConv_T1_CC1 / Timer 2 ADC_ExternalTrigConv_T2_CC2
ADC_InitStructure.ADC_DataAlign         = ADC_DataAlign_Right;
ADC_InitStructure.ADC_NbrOfChannel      = 1;                    // Number of ADC channels
ADC_Init(ADC1, &ADC_InitStructure);

ADC_DMACmd(ADC1, ENABLE);

ADC_Cmd(ADC1, ENABLE);

ADC_ResetCalibration(ADC1);
while(ADC_GetResetCalibrationStatus(ADC1));
ADC_StartCalibration(ADC1);
while(ADC_GetCalibrationStatus(ADC1));

// ADC1 regular channels configuration                      // Configure ADC channels to be sampled
ADC_RegularChannelConfig(ADC1, ADC_Channel_2,   1, ADC_SampleTime_55Cycles5);

ADC_ExternalTrigConvCmd(ADC1, ENABLE);

// TIM1 counter enable
// Change if using a different timer trigger
TIM_Cmd(TIM2, ENABLE);

// TIM1 main Output Enable                                                      // Change if using a different timer trigger
TIM_CtrlPWMOutputs(TIM2, ENABLE);


texts: Seeing feedback voltage only on a regulator instead of 2.5V. Any ideas?

texts:
I'm trying to debug a hardware issue where I am only seeing the feedback voltage on the output of a regulator that is part of a PMIC. The voltage divider that goes into the feedback pin have the correct resistor values. The inductor is properly placed onto the board and the switching frequency looks comparable to the datasheet. I'm thinking that the PMIC isn't properly placed on the board (it's a 48 pin QFN), but the switching pin and feedback pin on the part look like they're properly soldered. Should I use a heat gun and try to reflow the QFN part? Any other ideas? What about replacing the feedback resistors even though they're the appropriate values? I would hope that the issue would be something easy that is going over my head.

Any help is appreciated.

Part I'm referring to is the ADP5052ACPZ-R7, Regulator #4


texts: How do multiple transmitters and single reciever work?

texts: I have multiple digital transmitters sending packets to an receiver, and packets from different transmitters may arrive at the same time, how can the receiver differentiate multiple packets at the same time given each packet carries an ID of the transmitter? Must each transmitter use a different channel in order for the receiver to differentiate them?


texts: Simple on and off switch to toggle between two circuit (headlight high or low)

texts:
to start off, honestly I just know simple circuits that's why I went on asking in this forum,
So basically I have a driving light that has two modes, high and low. It consists 3 wires. A black (gnd), red (low light), yellow (high light) wires. So this can be toggled if I used a 3 way switch. But I wanted to use a simple on and off switch to toggle between high and low beam. Is there a readily made circuit that I could use? Or can anybody point me to the right keywords on what to search?
So basically it goes like this:

Off switch : Off lights
On switch: High light
Off switch: Off light
On switch: Low light
Off switch : Off lights
On switch: High light
Off switch: Off light
On switch: Low light


texts: how to reduce the current without changing voltage for charging a 9 v battery

texts:
I have some rechargeable ni-mh 9v batteries  (all 200mah) laying around and a 9v adapter with current output of 210ma... I know that 9 v batteries require 1/10th of its capacity to be charged (ie 20ma)...So ,is there a way to reduce the current output without reducing the voltage (maybe with some kind of resistors in series) so that i can charge these batteries safely??

thanks in advance

edit:
i have found some circuits online ..will this work??

1.

2.


texts:
I'm new to electronic circuit, I'm solving some problems in the book and come across this one, but I cannot calculate the value of Rs and Rp according to the info provided. Can someone help me with this, I solved equations using Thevenin but there is no solution for the value of those two resistors
(sorry for my bad English, I'm Vietnamese )


texts: How to wire up a 3-wire load cell/strain gauge and an amplifier?

texts:
I have a 3-wire load sensor that looks like this:

I'm trying to wire it up to my Arduino to detect changes in weight. From what I understand, the changes in voltage are so small that the Arduino can't detect the changes without amplifying the voltage. So I bought an 8-pin LM741CN Op-Amp at Radio Shack that looks something this:

I found this video that shows how to wire everything up. However, I can't figure out the schematic and why they are using two load sensors instead of just one. They also mention resistors but I'm not sure why they are using them (and why the sizes they chose), or where in the circuit to put them.

Can someone please help me figure out how to wire this thing up to detect changes in voltage? Also, is there a way to do this by using only one of these sensors? This is what I've done so far:

The amp also has some pins that I don't understand: Offset null, NC. What are these pins for? Should I be using them?

Update: Now I am working with an Instrumentation Amplifier (AD623). I also now have a 4-wire load sensor that I am playing with. Still can't get it to work, but I thought I would try to understand that before moving to the 3-wire load sensor.


texts: Converting an ATX power supply to bench power supply.

texts:
I'm planning to convert an ATX power supply to a bench powersupply. It came to my knowledge that the DC ground is actually connected to earth. As I understand, this might become a major issue if I were to connect an oscilloscope to a device with a earth ground.

So I opened the case of my power supply and I see that the ground is directly connected to the case. It seems the board has the DC ground connected through the screws to the case then from the case to earth.

Is there a particular reason why I should not isolate the DC ground from earth?

Some solution would be to use non conductive screws. Use a file to remove conductive material around the holes and use some non conductive washer to add some space between the board and the case.


texts:
I would like to attempt to assemble an outrunner BLDC motor from scratch. Its working principle seems ridiculously simple and I'm up for the challenge. There is one thing that I would like to clear up for myself as of now, which is not related to BLDC but rather any electric motor.

Might be a stupid question but I really need to clear this up in my mind, because it's quite foggy at this point. If I provide current to any coil as shown in the schematic above, isn't that going to short it since there is no resistance anywhere?


texts: Is there a common message protocol for sensor data on top of MQTT-SN?

texts:
I want to communicate various sensor data in a network of sensors.

I found MQTT and MQTT-SN as suitable protocols for that. The latter being better suited for sensor networks with support for sleeping devices, predefined communication, alternatives to TCP, etc. (https://stackoverflow.com/a/29083422)

However, both are payload agnostic. The message sent can be of arbitrary format and content. Is there a common format specifically for sensor data with small footprint?

I'd like to communicate a measurement value of a specified unit and dimensionality. Maybe with a specified tolerance/expected error.
I could come up with a custom format and just shove it into the payload, but I do not want to reinvent the wheel and rather use existing formats if any exist. That would also ensure compatibility to other networks that use this format.

I found

an experimental proposal for an extension to XMPP which supports things like Unit or Timestamp. However, the overhead of the format being XML based makes it undesirable for my application.

<message from='device@example.org'
         to='client@example.org/amr'>
   <fields xmlns='urn:xmpp:iot:sensordata' seqnr='1' done='true'>
      <node nodeId='Device01'>
         <timestamp value='2013-03-07T16:24:30'>
            <numeric name='Temperature' momentary='true' automaticReadout='true' value='23.4' unit='°C'/>
         </timestamp>
      </node>
   </fields>
</message>

Home Assistant, which specifies a format that also has unit_of_measurement and value_template. But this is more about extracting data from arbitrary MQTT messages into a format of the platform instead of specifying a format for the MQTT message itself. In fact, people write extensions to use JSON in the MQTT message

Is there simply no such thing as a standard (or at least common) lightweight message format for sensor data?


texts:
I want to connect an ATMEGA328P to a mobile phone, a Samsung Galaxy S3 to interface some data.

I need to use the microSD port behind the battery cover for this purpose, so here is the question, Is it possible to use SPI to emulate an SDIO card, or even an MMC card if I hook up the ATMEGA328P via SPI to the microSD slot on the back of the Samsung Galaxy S3? If so, how can I wire it up and which modes are suitable? What is the difference between MMC, SD, SDIO. Can all of them be used without some kind of license? What voltage can I expect? Will the ATMEGA328P be runnable on both 1.8v and 3.3v?

EDIT:
This question is really about MMC/SDIO and not looking for different solution. There are companies manufacturing MicroSDIO cards with NFC functionality and ZigBee functionalities and I have read multiple users who had no problem getting these to work on Android, so my guess is that they either emulate a memory card and read/write to files or if there is actually a possibility to develop user land drivers, or they have rooted their device and made changes in the system. But since there are companies advertising these products i am doubtful they require root access. From what I read SDIO should be supported in the kernel since Android 2.2 but the online information on this I have found is very limited. If SDIO is supported I would still expect there to be support for user land drivers. If it is the case that SDIO mode on Android need drivers in the system image I would appreciate a reference on this and how to accomplish it.

I would have no problem making this work using Android open accessory protocol, USB OTG, Bluetooth LE (Smart) or WiFi, with all these I can write user land "drivers". I have no experience in SDIO and that is why I am asking the question here I realize that my original question was not clear enough on this point.

I am interested if someone have real experience in this and suggestions of other solutions will unfortunately not help me at this point. Thanks for your understanding


texts: Can I quickly charge supercapacitors with a power adapter?

texts: I am trying to make a super capacitor bank that I can charge is a couple minutes and it will output a 5v USB charge (aka a power bank). My materials: a 15v 8a power adapter, 2 Maxwell 2.7v 3000F Supercapacitors, a high power buck converter and small circuit boards to produce the 5v USB. I was wondering if it was safe to connect 15v to the buck converter, step it down to close to 5.2v and connect the buck converter directly to the capacitor. I DID do some experiments with the power adapter and it seems that it has a short circuit protection as when I short the leads, it cuts off, then a couple seconds later it comes back on which repeats again and again. What will happen if I connect the capacitors? Any ideas of what I can do with it?


texts:
I can see that most of the gadgets that use proprietary protocols use 433MHz, 915MHz, or 2.45GHz, but I don't understand why. 433MHz is highly regulated in the US and 915MHz can not be used in Europe. Why is that noone uses other frequencies?

What unlicensed frequencies can (or should) be used for proprietary wireless communication? Can you please help me finding a whole list of frequencies that can be used for an unlicensed wireless communication? And maybe some issues that has to ba taken into account when you select a frequency?

Thanks in advance!


texts: 125 mW resistor subjected to 600 mW dissipation in professional safety system

texts:
The schematic below is the input circuit of a signalling PCB, which we buy from one of our suppliers of fire detection systems. Said PCB has to be built into a so called geographic evacuation panel which allows firemen to see in which zone of a building a fire has started, and as such is part of a safety system.

simulate this circuit – Schematic created using CircuitLab

The LED shown is actually the IR LED of an optocoupler (needed for reasons of common mode rejection).
Each fire detection zone has such an input. The optocoupler's outputs are fed into an Atmel MCU where they are processed in order to light certain LEDs on a floor plan of the building. In the absence of any input signals, the MCU will reset all LEDs on the panel.

The 820 ohm resistor is an SMD type, and from its dimensions I estimate it to be package 0805 and as such it is rated for 125mW. Documentation from our supplier claims the input voltage range is from 2.2 up to 24V. This is by design, in order to support many brands of fire detection computer. Not all, but a number of systems do actually output 24V. By my own calculations the resistor dissipates about 600mW at 24V input, assuming a total forward voltage of 1.9V for both diode and LED. Actually applying 24V at the input for as short as 5 seconds makes the resistor heat up so much that you can't touch it. At this point the input current is about 26 mA. As I am not very experienced with SMD components, being out of electronics for many years, I need to know if there is any risk that the resistor will burn out, and the panel will not do what is is designed for, potentially resulting in the loss of human life.

The moment the fire service can eyeball the panel is on average first detection + 15 minutes. This means that the resistors in the activated inputs will be subjected to those conditions for at least 15 minutes, in densely populated areas. In rural areas with less firefighting personnel this can be even longer.

Authoritative answers, or links to them, are highly appreciated.

Picture of a geographic panel:

Picture of board with input circuit:

There are eight identical input circuits. I added the text "820 ohm" below one of the resistors. To the left of this resistor is the diode, above and to the left is the opto-isolator. It is a 4 pin device with SMD code 824.

Very close-up view of the resistor in question:


texts: How do appliances prefer to use my solar power from a grid-tie inverter over the power from the grid?

texts:
I have a grid-connected solar inverter. In the swtich board the incoming wire from the street, the incoming wire from the inverter and the outgoing wire to the loads in my house are all connected together (wired in parallel).
It appears that the loads in the house will consume all available solar power (if needed) before drawing power from the grid.
How does this work? Why doesn't the load draw power equally from the solar inverter and from the grid?
I suspect that the inverter monitors the grid voltage and produces an output voltage that is just a few volts higher. Is that all that is needed for the loads in the house to use all the solar power before using grid power?


texts: How do you store A or B in a RAM of a CPU datapath?

texts:
I have an assignment to make a CPU, but am confused with how f_left and f_right are going to be used. I think they are to store the input from f(ALU) as "a" or "b", whereby I would have to connect them implement it. I can't get it, I need help with how to use them?

I am also further confused because the register schematic doesn't seem like it has space for two bits, it looks like it's one bit in the second picture.

I am basically stuck on this whole RAM register.

(Original)

(Original)


texts: Best pattern for WFI (wait-for-interrupt) on Cortex (ARM) microcontrolers

texts:
I'm looking into developing battery-powered software using the EFM Gekko controllers (http://energymicro.com/) and would like the controller to be asleep whenever there's nothing useful for it to be doing.  The WFI (Wait For Interrupt) instruction is used for this purpose; it will put the processor to sleep until an interrupt occurs.

If sleep were engaged by storing something someplace, one could use load-exclusive/store-exclusive operations to do something like:

  // dont_sleep gets loaded with 2 any time something happens that
  // should force the main loop to cycle at least once.  If an interrupt
  // occurs that causes it to be reset to 2 during the following statement,
  // behavior will be as though the interrupt happened after it.

  store_exclusive(load_exclusive(dont_sleep) >> 1);

  while(!dont_sleep)
  {
    // If interrupt occurs between next statement and store_exclusive, don't sleep
    load_exclusive(SLEEP_TRIGGER);
    if (!dont_sleep)
      store_exclusive(SLEEP_TRIGGER);
  }

If an interrupt were to occur between the load_exclusive and store_exclusive operations,
the effect would be to skip the store_exclusive, thus causing the system to run through the loop one more time (to see if the interrupt had set dont_sleep).  Unfortunately, the Gekko uses a WFI instruction rather than a write address to trigger sleep mode; writing code like

  if (!dont_sleep)
    WFI();

would run the risk that an interrupt could occur between the 'if' and the 'wfi' and set dont_sleep, but the wfi would go ahead and execute anyway.  What's the best pattern to prevent that?  Set PRIMASK to 1 to prevent interrupts from interrupting the processor just before executing the WFI, and clear it immediately after?  Or is there some better trick?

EDIT

I'm wondering about the Event bit.  By the general description, it woulds like it's intended for multi-processor support, but was wondering whether something like the following might work:

  if (dont_sleep)
    SEV();  /* Will make following WFE clear event flag but not sleep */
  WFE();

Every interrupt that sets don't_sleep should also execute an SEV instruction, so if the interrupt happens after the "if" test, the WFE would clear the event flag but not go to sleep.  Does that sound like a good paradigm?


texts: Finding some variables in a second-order circuit?

texts:
Can any one please help me solving these questions .. I always get a wrong answers :/
The first order circuit is much easier than this one !!

This is my answer :

for the first time i thought it will not be easy .. but after understanding the concept .. it become much easier ; how ever .. I solved all of them but i need one to check the answers .. Specially (c) :

a) 12/7 * 5 = 60/7 =v(0-)=v(0+)

b) 12/7 =i(0-)=i(0+)

Now for (c) i added the inductors in the formula .. but i'm not sure if it is right :

(c)  i(t)=12/7 e^(-t/(3*(0.1m+0.3))) !

and for the final

(d) Vc(inf.)=12 V !


texts:
I am utilizing a development board that has an expansion header. The header brings out a 2.5 VDC power rail that is sourced from a buck converter SMPS. I need to use this 2.5 VDC, run it through a boost converter, and generate 3.3 VDC, where I will run a light load (about 50 milliamperes).

Are there any issues with attaching the output of a buck converter to the input of a boost converter?


texts: Why does my shaded pole motor barely rotate when driven at 1/2 its rated voltage?

texts:
Hello electronics community!

I'm attempting to service a shaded pole motor (pictured below) that is used for rotating a cylindrical fan from an electrical heater.  The fan stopped rotating and so I thought I'd take it apart to see if I could figure out what's wrong with it.

After cleaning the unit and lubricating the bearings with dielectric silicone grease, I ran the motor from the mains at 120V (I don't have a safe test rig to run at 240V).  I expected it to run at half a reasonable RPM as the motor generally operates at 240V when in the heater assembly.  Unfortunately it barely rotates (maybe 60 RPM at best), and with the weight of the fan, I doubt it would move at all.

Is this expected when operating one of these motors at a lower-rated voltage?  What other test can I perform to verify the integrity of the motor?

Incidentally, the bushings that attach to the rotor don't easily rotate; they do pivot easily though.  I believe is intentional since they are supposed to stabilize the rotor's axis of rotation, and not grip the axle and rotate with it.  Several videos and articles suggest saturating the bushing with a lubricant, which I've done, so that doesn't appear to be the problem.

Finally, I tested for continuity on the primary coil and read a resistance of about 150Ω, which is about right as the label on the coil gives a current rating of 1.3A (240V/150Ω = 1.8A).

Any thoughts or suggestions on how to proceed testing are appreciated!


texts:
I have three Nitecore NL147 14500 Li-ion Rechargeable Batteries 750mAh 3.7V 2.8Wh in a 11.1 volt pack.

Am I correct to say that my battery pack is 750mAh and 8.325Wh ?

Thanks.


texts: Can 3 phase AC current be applied to a BLDC and vise versa?

texts: I am just wondering because the designs of a synchronous motor and BLDC are the same. Could you please explain the downsides of not using the designated current?


texts:
I am designing a board that has 2 DB9 plugs/connectors. They are used to supply power(Vcc and GND) and data signals respectively. Now, I wont be using all the pins in the DB9. Some will be left floating.

I will then be trying to get FCC/CE certifications for the board. Now, I know, at least in MCUs and such ICs, pins are not left floating. They are eithey pulled up to Vcc or down to GND. Do, I need to do any such thing to some of the unconnected DB9 pins ? If so, what are the criteria or design changes I need to make to them ?


texts: Boost Converter Efficiency goes down as Duty Cycle goes up?

texts:
simulate this circuit – Schematic created using CircuitLab

I have tested a boost converter under different duty cycles. I know the voltage is related to the input voltage by V = Vin/(1-D) where D is the duty cycle. But for some reason, as I increase this duty cycle with my input voltage kept constant, the power efficiency of the converter goes down.

I am using a function generator to make the MOSFET switching, and a DC voltage supply for input. (something like this: http://shop.rabtron.co.za/catalog/bench-power-supply-c-46_374.html)

Can someone tell me why the power efficiency of a boost converter reduces as the duty cycle is increased?

EDIT: I put a circuit to make the question more clear. I actually did not bother to check the type of diode or MOSFET, and it seems like that would've been important...


texts: How to safely switch a big inductive load with a Triac using a capacitor snubber?

texts:
I am building a Spot Welder with a big powerful transformer.
I have to switch a big inductive load of 70mH (input of a transformer)
The switching will be done with an SSR (Opto Triac Zero crossing SSR-90DA).

When the transformer is under load the input impedance is almost resistive.
My problem is this transformer is also open circuit output sometime.
This is equivalent to switching a 120VAC into a 70mH inductance.
The zero crossing feature is great but with at purely inductive load it become a problem.
Switching ON is OK. Switching OFF is not OK because the inductive load will
shoot a big reverse pulse much higher than the MAX voltage of the SSR.
I want to put an bipolar AC capacitor in parallel with the inductor,
reducing the pulse to acceptable voltage.
I am missing math involved necessary to calculate the Cap value.
What is the energy stored in the coil at Switch OFF ?
What voltage this energy will charge the capacitor at Switch OFF ?

The Questions:
How can I calculate the pulse voltage .vs. Capacitor value (at switch OFF time) ?
How can I calculate the necessary value of this capacitor ?


texts:
I’ve seen people ask how to discharge a lead-acid battery, which is easy enough.

I have a lead-acid battery that I must have connected to my on-board boat charger backwards. It must have been very dead, because it reversed the polarity. I know to reverse it back, I’ll need to discharge the battery pretty completely.

My question is how much damage is this going to do to the battery? Is there any other way to reverse this polarity without discharging completely?


texts: Why does a resistor in my Neopixel data line work at all?

texts:
Adafruit's best practices for their Neopixel LED strings say, "Place a 300 to 500 Ohm resistor between the Arduino data output pin and the input to the first NeoPixel."

Someone asked about the purpose of that resistor here and I'm reading about parasitic diodes and termination resistors to understand that more, but in a nutshell, why doesn't adding this resistor also drop voltage? In other words, if I had a 5V logic signal touching my Neopixel data line, won't adding this resistor in series make that signal fewer volts?

For example, if the Neopixel data circuit doesn't have any resistance then now I would expect 5V on one side of the resistor and 0V on the other... right? And if I have 0V going to the Neopixel data in, then how does signaling work at all? I'm super new to electronics but it just seems like this is the definition of a voltage divider circuit.

Also, if you didn't know about the 300-500 Ohm resistor, how would you choose that value? Is that based on an equation or just looking at something under a scope until it seems stable?

Thanks for helping, this is really puzzling me =)


texts: Is there a commonly used name for a "local ground" or "local common"?

texts:
Suppose we have a circuit that measures some external voltage like so:

simulate this circuit – Schematic created using CircuitLab
We will assume that the circuit is powered by batteries, and the circuit is well insulated and isolated from coupling to other circuits except through the \$V_{in+}\$ and \$V_{in-}\$ nodes. The "ground" in this circuit is just a common reference point in this circuit, and is not connected to any external "ground". Because this measuring circuit is isolated in this way, it can be used to measure potential differences (differential voltages) that themselves are at a potential difference from an earth ground. (Think of a battery powered volt-meter).
Note that \$V_{in-}\$ is tied to the "ground" (or common) for this circuit.
Now let us suppose that the above circuit is used to test a voltage in another circuit which has it's own ground, let's say a ground connected to the earth. However, the ground in the circuit under test is not where \$V_{in-}\$ is connected. Like so:

simulate this circuit
My question is whether there is an accepted terminology to explain this situation. I am tempted to call the "ground" in my testing circuit a "local ground" or a "local common" or a "floating common". But I would like to use terminology that others might readily understand as referring to a situation like that described.


texts: Can I drive several LEDs using a Li-Ion charging chip

texts: I have several IR LEDs (1.2-1.8v) and I would like to run them in a semi protected environment. I can run them off of an 18650 3.7v battery with the diodes in series however if a fault occurs in just 1 of them it will easily burn out the others. I have a TP4056 chip for charging Li-ion batteries I would like to use. It varies voltage based on the charge of the battery its connected to. If it is used to drive LEDs and one faults would it in theory drop the output accordingly therein saving the other diodes?


texts:
I would like to accurately design and model a current transformer in FEMM. I'm hoping this will enable me to accurately estimate the secondary current in a current transformer, including it's phase relative to the primary current.  The model will also help to size the core.
I've used the FEMM software previously to design magnetic concentrators for hall effect sensors.  The problem I'm running into is that I cannot induce a current in the secondary winding in FEMM, it seems I have to guess and specify the secondary current.
I've followed David Meeker's example on transformer design, but I cannot follow it exactly because I'm not designing a voltage transformer, i.e. the secondary current is never zero.
These are the 2 equations I'm trying to solve for Is (secondary current):
(source: gsu.edu)
:
I know (or can choose) the following:

Ip - Current in the primary
Rb - Burden resistance
w - Natural frequency of the primary
Vp - Voltage in the primary, reflected burden resistance (from FEMM)
All relevant material properties
All relevant physical properties

this leaves me with 4 unknowns, specifically:

Rp+jwLp - primary coil impedance
jwM - mutual impedance
Rs+Rb+jwLs - secondary coil impedance + burden resistance
Is - current in secondary winding

Currently considering trying the following:

Use super position to independently determine Rp+jwLp and Rs+Rb+jwLs (i.e. remove the each coil and separately calculate these as constants)
Independently calculate values for R, L, M based on idealized equations.

Both of these would be followed by regression to get Is, I'm not certain how to formulate this yet either.
Any help would be greatly appreciated, thanks!


texts:
I have read multiple posts on here regarding voltage/watt loss but I wanted to see how it would apply in this situation that I can not seem to solve using available resources. Maybe I just do not understand too well.

If I have a surge protector 10ft that has 15a 125v 1875w that is plugged into another surge protector that’s specifications are 15A 6ft and that’s all I could find. Lastly this second surge protector has an extension cord 13a, 10ft 125v and 1625watts. That the end is the units power cord about 8ft that needs 110 watts at max power consumption .

Note: that the I am not going over the rated amount of watts this circuit can handle.

Using the specifications above if I have an appliance at the end of the surge protector + surge protector + extension cord + units power cable that max power consumption is 110 watts do I risk under powering it? Does the voltage/ watt loss for that much cable length affect the amount of power this tv will receive that it will not be able to have the required power it needs?

Thank you for helping me understand.


texts:
Most of you will know how three-phase rectification works and how cool it is.

My idea is: replacing the diodes in a three-phase full-wave diode bridge with MOSFETs, as in active rectification, and switching the MOSFETs depending on the rotation angle of the generator. Say, using a Hall-effect sensor to trigger switching.

It sounds feasible in my head - but then a lot of things do ... so I thought I'd run this idea by the pros first.


texts: How to measure output voltage of this Li-Ion battery circuit?

texts:
I've designed an AtTiny85 based Lithium-Ion battery protection/boost circuit that monitors the battery voltage and cuts the battery power to the external powered circuit when the battery dips below a predetermined voltage.  The battery monitor part of the circuit is working well but I also want to monitor and display (on an optionally attached I2C LCD) the output voltage of the DC/DC boost converter.  To monitor the output voltage I am using the voltage divider (R1 and R2).

I'm using an internal measurement of the ATtiny85 to monitor the battery voltage (measuring the 1.1v bandgap voltage using Vcc as a reference) which works well and is fairly accurate.  The problem is with measuring the Boost Converter output voltage.  Through much head scratching and hair pulling I discovered that the reason I can't accurately measure the Boot Converter output voltage is because the Boost ground is not the same as the battery ground.  (i.e.  MOSFET drain verses MOSFET source).  Depending on the battery voltage there is anywhere between 180mV to 250mV difference between the drain and source side of the MOSFET pins (when the gate is on).  Since the AtTiny85 is grounded on the source side of the MOSFET, the ADC measurment on PB3 is biased by the drain side of the MOSFET in a non-linear fashion.  If I move the ground side of R2 over to battery ground I can accurately measure the boost output voltage but with a couple of undesired results.  One being the voltage divider will continuously drain ~500uA of current, even after the MOSFET is switched off.  The second undesirable effect is that for some reason, the boost output voltage will drop to about 3V when the battery voltage approaches around 3.2V.
When R2 is grounded to the MOSFET drain (as in the schematic) these issues do not occur but the boost voltage measurement is off by ~0.5 to 1.2V.
So, my question is how to accurately measure the boost output voltage without the negative effects described above?
Additionally, what is the a voltage difference between the MOSFET drain and source when the MOSFET is switched ON?  I don't see anything in the datasheet (that I understand) which accounts for this drop.
For reference the load on the boost converter in my test setup is the LCD (with backlight) and an ~100mA LED laser.


texts: Running Application on SIM808 GNSS module beside it's internal firmware

texts:
I'm trying to load my written program to SIM808 and the module will be responsible for running my program and also its internal firmware.
SIMCOM has a document about doing this in SIM800 module but there are not any equivalent for SIM808. Does SIM808 support this ability?


texts: How do I design a cascade network of 1-bit comparators to determine if two n-bit numbers are equal?

texts:
I'm reading through the "Logic Design" chapter in Givone's Digitial Principles and Design and this is one of the problems at the end of the chapter. I read the section on comparators thoroughly, but still do not understand how to do this problem.

Essentially, the end goal is to design a 1-bit comparator that can be cascaded into a larger network in order to determine if 2 n-bit numbers are equal.

How do I even approach this problem?

What's primarily tripping me up is the "n-bit number" restriction. Does this mean my network should be able to handle two numbers of infinite length? or does it mean that the 1-bit comparator I design should be able to function if it's put into a cascaded network containing n of them?

Any pointers would be greatly appreciated.


texts: Interfacing switched resistors to an ADC input of a microcontroller

texts:
I am tying to interface switched resistors to a micro controller (TI CC3220 - http://www.ti.com/lit/ds/symlink/cc3220.pdf) which uses 3.3VDC for its operation and has an ADC input range of 1.4VDC.

My requirements are

ADC input should not exceed 1.4 VDC
The switch has total 6 steps i.e 0 to 5, where in each step different resistor values are used to connect to Vcc and for 0 there wont be any connection to Vcc.
When the switch resistor module (3 wires to the module) is removed, ADC should always read high.

With my limited knowledge and experience, I have created a schematic as shown below. Would be great if someone can validate it or suggest other solutions to solve my use case.

Note : I do have constraints on additional components and cost, hence a cheaper and optimal solution is preferred. The ADC input impedance as per datasheet is 2.12K

Proposed Schematic (updated on 15-June-2018)

simulate this circuit – Schematic created using CircuitLab

ADC Calculations


texts:
I wish to view 3 phase waveforms from an alternator (DUT) through isolation transformers via a digital oscilloscope. A 4 channel oscilloscope is obviously ideal for this as I can view the waveforms as they occur 'simultaneously' and the frequency is very low, but can this be done any way on a 2 channel scope?
I think the only way is to save each waveform them view them on at once.

Thanks


texts: How do I reverse this following circuit, i.e. when the laser is off then it should stop buzzing?

texts: All the necessary symbols are given in the circuit itself. When the laser is shooted to photoresistor, then buzzer stops. I want to stop the buzzer as soon as laser gets off.


texts: Constant Current LED Driver Output Control using PWM

texts:
I want to control the brightness of a led which is powered by a constant current driver.

On utilizing a MOSFET and pwm signal from an arduino uno the led starts to fade in as the duty cycle increases. But the problem is that the led "blinks" at lower duty cycle and stabilizes only at about the full brightness. (The constant current driver that came with led is used here).

Please suggest me a new circuit in which I am able to avoid the blinking issue while utilizing the driver that came with the led.

Also, take a look at this : how to control constant current led driver output with pwm?

simulate this circuit – Schematic created using CircuitLab


texts:
The circuit I have attached is basically LED arrays with some transistor and N channel Field-Effect Transistor. It requires 17v, 400mA to work. I will only glow either white led or RGB. They won't glow at same time, due to less current.
.
The N channel Field-Effect Transistor (XORB48) has

IDS: 5.8A
VGS: ±12V
VDS: 30V
CISS: 623
VGS(th) = 1.05V

It has low gate charger and operation gate voltages as low as 2.5V.

Each white led is of 0.2W (2835) and RGB is of 1W (5050) each.

I will control and dim the LEDs using Arduino PWM, for that individual GPIOs are connected, mentioned in circuit.

I want to know what kind of supply is needed for this? Constant current? Constant voltage? Does it require High power factor? How about ST's Viper22a or power integration's LNK IC?

Schematic :-


texts: CSxCC stage, series-shunt feedback, identify sign of feedback

texts:
MY ANALISIS
The stage is inverting x non inverting = non inverting.
Shunt sampling since it perturbs the output current, Series mixing.
Thus if a positive input voltage is applied, the output is negative.
Thus the voltage applied on the source by the feedback network is negative and it increases Vgs

Thus feedback is positive.

Is my analysis correct?


texts: What does this rail-splitter-like circuit do?

texts:
I'm repairing an audio amplifier for a car. It has a switching supply that generates +/- 50V rails from the ~12V battery. In the output section of the amplifier, I found this small circuit with obviously damaged components. When I found it, the base and collector of Q2 were bridged with solder in what I assume was an error made by a previous attempt at a repair by someone else.
R1 is scorched badly enough that I can't identify it, though it tests as 23.2 kohms. R2 has color bands indicating it's supposed to be 33.2 ohms, though it actually tests as 3.32 kohms. R3 appears to be labelled as 200 ohms, but the 3rd band could be a faded yellow or gold. R3 tests as open circuit. D1 used to be a 1N4735A zener but it doesn't zeen anymore and instead tests as a 5 Mohm resistor in both directions.
I'd like to replace all the parts in this circuit with known good parts, but I'm having difficultly understanding what this circuit is supposed to do so that I can select appropriate resistor values. It looks like a rail-splitter, but it has no inputs or outputs other than the two rails. The circuit doesn't produce a virtual ground, but there's also no need for one here because the battery negative terminal serves as a ground.
I've removed this circuit from the board entirely and everything seems to work fine without it, though I haven't tested the amplifier at full load.

simulate this circuit – Schematic created using CircuitLab
What is this circuit supposed to do? What would appropriate values for R1, R2, and R3 be?


texts: When to use P-Type current source(using pMOS) and when to use N-type current Source(nMOS)?

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I am referring to Prof. Behzad Razavi Lecture https://www.youtube.com/watch?v=GAvZLyii3aw&list=PLiDoPUX9nLkIw9EnIv_3K19wlcyJ6msYd&index=2  (Minutes 19-26)

Prof. says to use nMOS when we draw a current from a node and supply to ground and to use pMOS when we draw current from Vdd(supply voltage) and supply to another node. But why is it done like this? Why can't we use nMOS as current source to draw current from Vdd to another node?


texts: Is there a definitive way to determine the positive and negative leads of a laser diode?

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I am trying to use a laser diode that I pulled out of a laser printer, but the circuit board doesn't have the ground and power leads of the diode labeled. I can't find any diagrams of the circuitry or of the specific diode online. Is there a way to find the positive and negative leads without risking breaking anything?

If there is any other information needed I will try and supply it upon request.


texts: Looking to identify an old National 8-pin DIP (M8440)

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I have a rail of these 8-pin DIP's that I'm guessing was bought 15 - 20 years ago.  My guess is that they could be op-amps or comparators.  There are 3 printed lines on these chips:

N M8440
28930
35-00

Where "N" is the double-wave National symbol.  Any idea what they are?


texts: I apologize in advance, if this isn't the right place to ask this. I want to find out, what kind of electronic device this is. The tape recorder is just on top of it, but I am talking about the device beneath it. It is integrated into a metal suitcase, it is manufactured by Siemens, and the keyboard doesn't have letters on it, but instead has weird combinations of letters on it, like OMN, OA etc.


texts: How can I create a controllable solenoid array?

texts:
So to briefly summarize my situation, I am trying to create a programmable solenoid array that will be used to raise and lower pins for a braille display. Considering that each braille character has 6 dots and that I want to be able to output 5 characters, I will need to control at least 30 solenoids.
I've attached an idea that I had on how to tackle this problem, however, I am unsure how feasible it is or if there are some other things that I should consider. The design would work so that one character would be updated at a time. Any advice or feedback would be greatly appreciated. Thanks.


texts: What advantages do the absolute encoders gain by employing Gray code transmission instead of binary code?

texts:
I have read about the Gray code, but in practice I don't get what is the advantage of it over the binary code.

Some absolute encoder manufacturers offer both types so one has to decide before buying one. I for example need to measure the rotation angle for a very slowly rotating rod and many tomes fixed. In what circumstances or applications gray code output has advantage?