texts: In Analog to Analog conversion , why we multiply instead of adding?

texts: When we use AM i.e Amplitude Modulation , we multiply the source signal with the carrier , My Question is , why don't we add the signals ? it would be easier to modulate and demodulate I think.


texts: In a comment to this answer Kortuk asks what the ARM advantage is. I first added some arguments in my answer, but I think the question is interesting enough to be a question in itself, so that more answers are possible.


texts:
Today I learned about SystemC, a C++ library that make development on FPGA easier. (for people that know C++) Apparently, it is as efficient as VHDL (speaking of performance) and faster to learn and code.

Will VHDL disappear since they have the same performance with lower development time? What is the pros and cons of using one instead of the other?


texts:
I have this circuit here and need some help understanding it. The values for it is as follows:

VDD = 8 V
k'*W/2L=10mA/V^2
R=200 ohms
Laserdiod has U=2.2 volts

Now, I think the current through the diode and the current through the resistor should be the same, since no current goes in to the OP-AMp. Is this correct? Then the current through the diode I is given by I=Uin/R. I also want to know how to find the maximum current through the diode and calculate it.


texts: Host hopping mesh network over LOR or ZigBee

texts:
I am looking to do a proof of concept for a project where each node will broadcast a set of data (GPS Related) in predefined intervals, so every other node do some processing based on that data.

I am yet to finalise my exact list of core functionalities to focus on POC. Rough overall requirements are given below. I would decide based your feedback.

Network would be host hopping mesh network. Each node should be in coverage with at-least one other node to function. Network would be dynamic where there is a possibility of next node can go offline or off coverage.
Maximum 10 nodes will be in the network. Each node may broadcast every 10 Seconds.
ACK is a nice to have feature.
Expecting coverage around 2 to 3 Km in outback/bush-lands.
Prefer to be less than 50 USD.

I am based on Australia.

Based on my research, LORA OR ZigBee seems to be promising. Personally i am slightly inclined with LORA module because cost vs range over ZigBee.

RFM96 LORA 433Mhz Looks like good candidate. Check this product for LORA. Bundled with Atmel ATMega1284P microcontroller. This combo is resonalby priced and gives 16KB of ram to playaround.

I have found a good set of drivers and mesh network libraries for LORA RFM96.

Questions,

Anyone implemented mesh type network using LORA RFM96?
What would be practically achievable data rate using LORA RFM96? So i can decide what to leave/include in transmission.
What type of antenna gives more covarage and data rate for LORA RFM96?
I couldn't find a suitable ZigBee (Price and Range) Or Other modules in my case. Any recommendations if ZigBee or any other modules seems to be good candidate?

I believe this is not an opinion based question. I have given my research and finding and asking help to decide based on your past experience.


texts: Circuit for amplification and protection against input inductive spikes

texts:
I'm working on a permeability measurement project and my setup includes a primary as well as a secondary side of a coil. I need to measure the flux through the coil, hence on my secondary side I have an ARDUINO UNO card which I have programmed to integrate my secondary

simulate this circuit – Schematic created using CircuitLab

voltage. Now the problems I'm facing are

1> The ADC resolution for my arduino card is about 5mV and my signal on the secondary side is extremely weak, so I need to amplify it to increase my SNR
2> I also need to take into account inductive spikes on my secondary side, since going over 5V could damage my card altogether
3> In my toolbox I don't have a negative voltage rail, so I'm planning on using an op-amp to invert my positive rail into a negative and use it to rail other devices.

I have done my home work and come up with a circuit using ONLY my theoretical knowledge. I'm posting my circuit here, I would need certain clarifications about it.

Firstly, the way I intend my circuit to work is, I would use OA1 as a comparator, if the voltage spiked then it would bias the transistor and ground the secondary side and in the process I would also use my collector resistor to radiate away my stored energy. If my transistor is unbiased and the voltage is below a certain reference voltage, the transistor would be cut-off and the voltage would go through my OA3 as an amplifier and then through OA4 which is a voltage follower railed to certain limitations beyond which its output would saturate and hence it would provide finer protection to my U1 arduino card. Would the design work as expected? Or am I incorrect in some way?
My op-amps would be needing negative and positive rails, I don't have a negative rail, so I intended to create one using OA5. From a previously connected question, I was instructed to use a single supply rail to rail to be able to create a -Vref
Since my supply in OA1 could also peak beyond the rail limits due to inductive spikes, should I go for a single supply rail to rail there too? Any suggestions are welcome since I'm completely new to this
Can my power transistor handle outrageous Vcc limits like 50V or 100V or will my transistor break down? If my transistor breaks down, will it permanently short my collector and emitter or will it open it?
For my circuit since I don't have the experience or expertise as most people in this forum, any and all suggestions are welcome, changes in circuit design, railing supplies to any of the other op-amps etc. etc.

I'm in such a fix because my professor is currently on leave and will be for 2 months and I'm having to handle the project all alone with almost no practical experience prior to this whatsoever. Your help is extremely appreciated.


texts:
I'm hoping somebody can shine a light on this crazy scenario that I can not get passed right now.

I have a device that needs 3.6v to be powered on.

When I put a 3.6 battery straight to the device, it powers on as expected.

With my meter, I'm trying to measure the mA and uA usage of the device. The device's typical ON state current use is 100mA.

When I put the battery through the meter to test the current use, the device no longer powers on and the mA spikes I see on the meter reach 150mA.

However, when I use an adjustable power supply and set it to 3.6v and wire it exactly the same as I would the battery, the device powers on and I see almost exactly 100mA use.

I have replaced the batteries on my multimeter, replaced the croc leads from meter onto battery etc, but nothing makes a diff. What am I missing?

Why does the device power on when straight to battery, but not when wired through meter with battery. But meter works fine and device powers on when an adjustable power supply is connected?

Thanks in advance!!


texts: 12V lead acid charger with LM317 not charging

texts:
I have this circuit built and tested. I think this should work and charge the battery with 0.4A to about 13.5V.

The Problem: it doesn't charge and between U1 and U3 (Battery) is a current of about 0.03A, but why?

The LM2596 is a Buck converter Breakout board and that works flawlessly.
R1 is a 4W resistor so that won't be the problem

Why doesn't it charge?

simulate this circuit – Schematic created using CircuitLab


texts:
My design: Two cascade connected inverting amplifiers.

My problem: The output of second amplifier is saturated from -0.6 to -0.7V. The supply of OPAMPs is dual (+5-5V).

What is the problem? How can I fix it?

Note 1: Input is a 2V sinusoidal wave.
Note 2: Output of second OPAMP is connected Analog Multiplexer (ADG708).


texts: Our brushed DC motor is rated for 3-4 amps and can be overloaded for 8+ amps. We are currently changing the brushed motor for a brushless (BLDC) motor, rated at 3.5 amps. How much can I overload the BLDC motor? I think much less, than the brushed motor. Am I correct?


texts: Does the probability distribution of cosine transformation of uniformly distributed R.V. depend on phase shift of the cosine function?

texts:
Suppose, x is uniformly distributed over [0,2π], and y = cos(x + ∆), will the probability distribution function of y depend on ∆?

Is my solution to find out the Probability Distribution function of Y, correct?

Image of the solution: https://i.stack.imgur.com/ELoO0.jpg


texts: Turning on/off MOSFET using 4000 series CMOS

texts:
I intend to use 4000 series CMOS running at 12V to turn on some power MOSFETs (SUM55P06 and IRF2903) handling 8A at 12V.

However, the arrangement of logic gates I need to simplify the driving s/w will produce a race hazard when switching between states, of around 250ns. Can I ignore that? In other words, is the effective switching frequency of the MOSFETs driven from a 4000 much longer than that? I will be driving the MOSFETs around 1kHz

The relevant part of the circuit is shown below


texts: What am I doing wrong? Waveform generator and Oscilloscope test

texts:
In the circuit below, PS1 is a waveform generator. Originally, there will be the secondary of a current transformer. R36 is a MOV, D11 is a TVS diode and R29 a burden resistor. D12 sets the non inverting input of the opamp to Vcc/2. With the waveform generator I generate a sine wave 3V peak to peak, or 1.5V peak with no offset. When the input voltage is this high, x1 x2 (analog switch) close to reduce the opamp gain close to unity. But for now I'm not powering up the opamp, or the whole circuit. The issue is this: first I check with the oscilloscope the output waveform of the generator and it's OK. But when I connect the generator to the circuit and I measure it with the scope, then the signal disappears, i.e., it measures zero. Note I'm not energizing the circuit yet. My expectation is that when I connect the generator, I should see the same signal, but when I power up the circuit then the signal should swing around 1.65V.
What can cause this? What am I misunderstanding and doing wrongly?


texts: Where to connect Y capacitor with a low side switching element?

texts:
I was working on a power adapter, and we had a synchronous rectifier in the positive high side rail.
We have a Y capacitor between primary ground and secondary ground - between "A" and "B" in the diagram.

We are now looking to change the high side rectifier to a low side one - which side of the switching element does the Y capacitor go to - transformer side (B) or output side (C)?

Also, what are the benefits / advantages / disadvantages between having the switching element on the top or bottom side??


texts: Unable to change package footprint solder pad size in eagle

texts:
as the image shows, I want to change the BGA soldering dots from current size to something larger. Only size changes, or shall we say diameter changes, no shape or anything, but I couldn't.

I clicked change tool, entered the new diameter (and I'm sure it's different than the original) and then clicked the pads I wanted to change, nothing happens.

Can someone please help? Thank you.


texts:
One of my students are planning to make a simple musical keyboard with PIC microcontrolers, using MIDI output.

The main problem now is about the pressure/force sensor. I've found a good alternative in this question about flexiforce.

I'm wondering if there is a simpler sensor alternative, without ampops, to be used in AD input.

Thanks.


texts: Converting an SPI configuration for msp430 to msp432 IAR Workbench

texts:
I have a spi configuration code for a msp430 and DAC161S997 but i am trying to use the DAC with my msp-exp432p4111. One of the register has complately different use on msp432. So i couldnt figure it out. Here is my code

 EUSCI_B_CMSIS(EUSCI_B0_BASE)->BRW = 48000000 / 1000000;

and msp430 code

UCB0BR0 = 8;         // SMCLK/8 = SCLK (1MHz)
UCB0BR1 = 0;

Datasheet for DAC
msp432p411 datasheet


texts: Equivalent one-output of a SIMO converter

texts:
The single-inductor multiple-output (SIMO) converter below is a dc-dc converter with one input, one inductor and n outputs Vo1, Vo2,..., Von and load currents Io1, Io2,...,Ion.

Is there any theory, method to represent the SIMO by an equivalent single-inductor, single-input and single-output with equivalent output voltage and load current Voeq and Ioeq?

The image is taken from here.


texts: How measure the opening angle (integral rotation of a cone) in a emitter

texts:
I have an IR emitter (EMIRS200_AT01T_BR080_Series) with the datasheet showing the Optical output power versus the opening angle as below.

Now, I would like to understand how interpretation the opening angle (integral rotation of a cone). Does 90° mean the perpendicular direction from the emitter and lower angles until 0° that means to be parallel to the floor?

I'm using a Thin Film Pyroelectric Dual Channel Sensor as a receiver


texts:
Using Vivado 2017.4, I am trying to use a clock signal generated by the Clocking Wizard IP. I copied the instantiation and component code block from the Instantiation template, but I am getting some errors related to signal declaration. I have assigned the "count" signal under my architecture header, yet I keep getting an error saying " is not declared".

In addition to "count" I am also getting the same error with my "clk_wiz_0" variable even though I created the component. I also have some syntax warnings that could be contributing to the errors.

I have tried moving the library declarations to after the entity block but that didn't help. I don't think I'm missing any libraries either.

I am new to VHDL so maybe there are some type or syntax issues I am missing? --> signifies a "error <> not declared" error and * indicates syntax warnings. Thanks in advance!

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity mmcm is
    Port( clk_fpga : in STD_LOGIC;
          reset     : in STD_LOGIC;
          lock_led  : out STD_LOGIC;
          counter_led : out STD_LOGIC);

end mmcm;

architecture Behavioral of mmcm is
    signal clk_10M : std_logic;
    signal count   : std_logic_vector(3 downto 0);

 component clk_wiz_0
    port
     (-- Clock in ports
      -- Clock out ports
      clk_10M          : out    std_logic;
      -- Status and control signals
      reset             : in     std_logic;
      locked            : out    std_logic;
      clk_in1           : in     std_logic
      );
    end component;

   *mmcm_inst : clk_wiz_0*
       port map (
      -- Clock out ports
       clk_10M => clk_10M,
      -- Status and control signals
       reset => reset,
       locked => locked,
       -- Clock in ports
       clk_in1 => clk_in1
     );

  ATTRIBUTE SYN_BLACK_BOX : BOOLEAN;
  -->ATTRIBUTE SYN_BLACK_BOX OF clk_wiz_0 : COMPONENT IS TRUE;

  ATTRIBUTE BLACK_BOX_PAD_PIN : STRING;
-->ATTRIBUTE BLACK_BOX_PAD_PIN OF clk_wiz_0 : COMPONENT IS "clk_in1, clk_10M,
reset, locked";

    *process (clk_10M, reset)        --count from 0 to 9 at 10MHz*

begin

   if reset = '1' then
      -->count <= "0000";
   *elseif clk_10M'event and clk_10M = '1' then*
     if count = 9 then
         -->count <= "0000";
     *else*
         -->count <= count + 1;
     *end if;*
   end if;
end process;

counter_led <= '1' when count = 9 else '0';

end Behavioral;


texts: Understanding C20 value of lead battery for a low power circuit

texts:
I've developed a simple circuit using a Photon to send data to my database. It has to be a portable device and because of this I looked into lead batteries. My circuit runs on 5V and draws a maximum of 1A per day. I need it to run for about 2-3 weeks, continuously.

When looking at lead batteries, I see a lot about nominal capacity. For example: with this battery the nominal capacity at 1Ah at around 5.25V gives a C20 value of 20A.

Can this information give me any kind of indication about how long the battery will last if I draw only 1A per day? In an ideal situation, if I only draw 1A per 20 hours, this would mean I could run my circuit for 20 times 20 hours so a little over two weeks. But I doubt this is an ideal situation. What does this C20 tell me about a longer usage of the battery, if anything?

Based on the information of my circuit, what kind of battery can you recommend? I'm aware I need a buck converter as well, which power dissipation I have not taken into account for my calculations yet.

Thanks for any insights you can give me.


texts:
I'm trying to control 8 servos (tower pro sg90 micro servo) using a shift register (74hc595) . I planned on giving the pwm and ground pins common to all the motors and then controlling vcc via the shift register. The IC by itself cannot drive the motor so I need a make an additional drive circuit to power the motors via the output pins of the shift register. I was thinking of using a simple transistor switch. What transistor would be cheapest and best to drive the servo ?. Would it be better to just use a 5V relay controlled by the shift register ?. Will the shift register provide enough current to the coils of the relay ?

I only need to control one servo at a time. Also I only have very few pins left on the arduino.


texts: I am fitting a heating system to my boat and want to know which of these two systems will use less energy from my 12v batteries. System one is a heating unit which uses 190 watts at 240v through an inverter, and system two is a heating unit which uses 72 watts at 12v direct from the battery bank. Many thanks.


texts: Is using the wrong mA on a power supply dangerous?

texts:
I recently moved and didn't properly mark a couple of power supplies before I packed them up. I have a turntable and a pre-amplifier that both use 15v power supplies. One of the two power supplies outputs 15v 250mA and the other outputs 15v 550mA. The documentation for both devices just says "15v". I have done an exhaustive search online to see if I can find which adaptor belongs to which device, and have come up with nothing.

I'm at the point where I'm going to have to just guess. But both of these components are fairly expensive, so I'm concerned about using the wrong power supply and damaging the device. I'm not understanding exactly what the difference in mA means, and what is the risk of plugging the wrong one in.


texts: How to create a polygon with right angled corners in Eagle?

texts:
In the package editor how do I create a polygon pad with right angled corners?

The corners are rounded unless I set the width to zero, but then this causes DRC errors.  I have also read in forums that zero width polygons causes the Gerber files to become extremely large.

I would like my polygon corners to have nice right angles with no curves. How can I do this in Eagle?

Update:  The reason why I need right angled corners is that I am creating an antenna following a reference design, and it shows right angled corners.  The antenna is the BLE trace antenna, Cypress document AN91445.pdf.  See picture below.


texts:
I have a circuit, Arduino Leonardo clone, which I'm attempting to power with a buck regulator.  Specifically, I'm using a DSN MINI 360.  It's based on the MP2307 buck regulator.  If I power my board through the buck regulator, the board works fine.  However, if I disconnect the regulator from input power and then try to power my board with USB, the board seems to draw too much current until the PTC kicks in.  With the regulator connected to the +5v on my board, there isn't enough power supplied through the USB circuit to enable the circuit to run.

If I disconnect the regulator and power the board through USB, the circuit works normally.

I do not have a schematic for the regulator, but it seems to follow the typical application circuit described in the regulator's data sheet.

Below is the complete schematic for my custom circuit based on the ATMEGA32u4.  The circuit, as built, is complete, except U2 (SPX3819 Linear Regulator) has been removed. All other components are present on my circuit board.

My question is why does the buck regulator seem to be drawing so much power through its output, and is there any way to prevent this from happening without having to disconnect the buck regulator when using USB?  Would a diode be appropriate in this situation?


texts: Will current flow through my digital multimeter while it is powered off?

texts:
I've just got a cheapo < $20 digital multimeter here and was curious if anyone could tell me whether current might still flow through it after i turn the dial so that the power is off.

Some background: I have a wireless bluetooth mouse that always gave me problems charging because the contacts don't seem to line up properly. The mouse itself doesn't seem to give any indication whether it is charging or not but I am able to watch current start to flow on my multimeter when I move the mouse into just the right position within the cradle to make a proper connection. Now that it is seated correctly I'd like to just leave it charge for a while without disturbing it by disconnecting the leads and reconnecting the +5V wire.

I'll probably figure something out for this specific problem (just disconnect the leads from DMM and jumper them together for now) but I'm still kind of curious as to the original question of whether or not current flow is completely shut off when the DMM power is off.

It might vary by model but maybe somebody out there with 2 multimeters could test this for me?


texts:
Does Kirchoff's voltage law hold when we connect a single battery to a circuit that has no other components.

If it does hold, kindly let me know how.

If it doesn't, how do we reconcile with that?


texts: What is the reference pin on an instrumentation amplifier used for?

texts:
Happy new year all!

I'm wondering how to correctly use the reference pin on an INA128 Instrumentation Amplifier.  Is there a way to use this pin to eliminate negative voltages (i.e. do a voltage shift)?

Thanks again.


texts:
As far as I understand the flyback topology, it can be used in both buck and boost converters.

What I am not sure about is: Does it also work for the case where buck-boost is needed, i.e. \$V_{\text{in,min}} \leq V_{\text{out}} \leq V_{\text{in,max}}\$?

I think it should, but googling the topic immediately leads to the SEPIC converter. Also, I know that isolated SEPIC is possible, but I rarely see design examples.

Could you give me some idea on what topology to use for the specific case of:

\$9 < v_{\text{in}} < 24 \text{V}\$ for \$v_{\text{out}} = 12 \text{V}\$ at 1 A, galvanically isolated


texts:
I'm designing a board that consists of a dspic33F, responsible for running a noise reduction algorithm and compressing audio with a Speex library, and an audio codec connected to an electret microphone and amp + speaker.

The problem I'm having is while the dspic is running the compression algorithm noise is introduced to the microphone input. My best guess as to why this happens is that the current draw resulting from the computation heavy algorithm is causing sags on the power line and I've sort of confirmed this by reducing the time in between each encode and hearing the period of the noise change as well.

So far, I've tried eliminating the noise by splitting the digital components (the dspic) and the analog components (codec, amp, mic) onto different ground planes connected only where the main ground comes in. I also have each section on its own voltage regulator, again only connected where power enters the board. I have 0.1uF decoupling caps across the VDD/VSS pins of the codec and processor, 1uF decoupling caps across the voltage regulators, and a 100uF cap across the main power line. I added these in gradually, but none seem to have made a difference.

I'm fairly certain this is all due to the processor using too much power during this one algorithm ,but I'm totally at a loss on how to fix this. Any help would be greatly appreciated

Here's the schematic, I didn't realize stackexchange would shrink it when embedded, so full size url here.
http://i.stack.imgur.com/2Nxuy.png

And the layout, in case that's useful


texts:
As per standard DALI power supply should be 15 V at 250 mA. In the same time standard says that there can be up to 64 devices on the bus. So I can suppose that each DALI slave SHOULD cunsume 4 mA from the bus as the maximum.

Is this correct?

If so, is it OK to incorporate power supply in the controller with less current capabilities (let's say, 10 mA) for cases one controller - one luminare to avoid using of separate power supply?


texts:
Thought this was easy, but I can't find this information on how long / how many cycles a EEPROM read operation on an ATTINY84 takes.

Page 22 of the datasheet has a table with write and erase times:

Page 19 shows a code example where first the adress register EEAR is set, then the EERE bit is set and then the data is returned.

Besides that I could not find any information on the operation speed.

Am I correct in the assumption that the EEPROM read data are
instantly available in the EEDR register after EERE bit is set?
Does this mean that a EEPROM read is about same fast a storing the data in
SRAM?
How many cycles does a reap operation take?


texts: Designing a Arduino based circuit to power standard and RGB LEDs

texts:
I am very new to the world of circuit design and would greatly appreciate some feedback on this circuit I made. It is based on an Arduino Pro Mini and its purpose is to illuminate nine 2V, 20mA LEDs as well as twelve SK6812 RGB LEDs. At full brightness, they require 60mA. Since the circuit will be inserted inside a 3D printed scale model, I would like to make sure the components are well protected so they can last a long time.

Here is the schematic of the main circuit. The resistors values of 50Ω and 150Ω are there to limit the current inside the LEDs to 20mA which is the recommended limit per pin on the Arduino (see link above). Also, the 9 LEDs need a total of 180mA, just below the 200mA limit.

Each group named PIXEL_QUADx corresponds to a circuit that is very similar to the one at the end of the SK6812 datasheet. Their schematic is shown below. The 0.1µF capatitors, 470Ω resistor, and 1000µF capacitor (on the schematic above) are added because of the recommendations found on Adafruit's website.

My first question is: is this circuit correct? Other points I am not sure about are:

Should there be a 470Ω resistor on each PIXEL_QUAD group, or only on the first one?
Would it be possible to power everything from batteries? USB?
On the Arduino datasheet, it says the RAW input range is 5-16V, but recommended range is 6-12V. Should I use a 9V supply instead? How would this work?
180mA for the LEDs is close to the 200mA output limit of the Arduino. Would it be safer to power the white LEDs directly from the power supply? (This would mean no PWM brightness control)
Anything else that I missed that needs to be checked?


texts: I just fried a 555 timer IC and I'm trying to figure out how

texts:
I'm very new and just fried my first ic, trying to learn a lesson from it.

Here's what I was building:

(also here)

on the 6v in I used 6 AA batteries that were reading about 7.5v on my meter, was this my mistake?

I'm pretty sure I had all the components connected properly but the IC started to smoke and my speaker just clicked. Is 7.5v enough to fry a 555?


texts: How to calculate a cell constant of conductivity probe

texts:
I'm trying to design a 4 Pole probe to measure electrical conductivity and I having some doubts about the theoretical calculation of its cell constant.

I know the formula, K(cell constant)=L(Distance)/A(Sectional Area) and i how to calculate in a 2-Pole Probe, in which the L is the distance of the probes and the A is the sectional area of them.

My probe design is like the one in the figure in which the figure. The current sourcing electrodes are the external and are ring shaped and the voltage measurement poles are  metallic tips.

So for the cell constant calculation, in the distance part,  which distance should I consider, the distance between current electrodes or the voltage measurement poles?
And since the current poles are rings, what is cross sectional section, the section made by the voltage poles (rectangle) or the one made by rings (circle).

Thank you.


texts: Understanding memory requirements for an image file

texts:
I want to understand the memory requirements for image resource files to be displayed on a 240x400 resolution display.
The display has the following specs:

It supports upto 18 bits color depth and uses ILI9327 display driver.
Assuming that I need to display 50 different icons, each of size 10 mm X 10 mm, what is the storage space required?
Here are my calculations:
Pixels per mm = 400/61.2 = 6.536
Number of pixels in one image = 65.36 x 65.36 = 4272 pixels
Each pixel will require 18 bits X 3 (for R, G and B) = 54 bits
Total bits required = 4272 x 54 = 230688 bits = 28.16 kilobytes
For 50 images, I will require 1.375 megabytes of storage.
Is my calculation correct?


texts:
I have a device which uses 4.5 watts @ 18V (0.245A). The device can be powered by 12 volts, which I plan to do so.

I can I work out the current draw at 12 volts based off the above info?


texts: Can I modify a PC AT switching power supply to put out higher amps?

texts:
What I have is a 250W PC AT power supply.  It has 12V 8A, 5V 30A.  I don't need the 5V, so I was thinking maybe I can use a booster to kick the 5V up to 12V and add some amps to the 12V side.
So if my math is correct, 5V * 30A = 150W and 12V * 8A = 96W. If I can combine these into just 12V, I should get 20A and that's way more than I need, I only need about 12~15.
I see some DC->DC boost converter in that amp range want to start at 6V for the input, I'll only have the 5.
Q. is there a way to modify this old AT PS so that it outputs about 15A on 12V?  Maybe a boost converter, maybe there's a way to modify it internally, IDK.


texts: Does mutual capacitance increase for two positively charged plates when brought close?

texts:
My understanding is that any two charge carriers will exhibit what is known as mutual capacitance.  That is, there is an amount of charge that can be stored between any two objects, which is called mutual capacitance (typically just called capacitance).

As answered here, it seems very clear to me that this capacitance will increase when two objects of opposite charge come closer. (You generate a stronger electric field which draws more holes to the positively charged object and more electrons to the negatively charged object).

As I see it, mutual capacitance exists between any two positively (or negatively) charged objects.  According to the Wikipedia stub for Mutual Capactiance, no distinction is made about the charges, and it plainly says:

  All objects in the universe, conducting or non-conducting, that hold charge with respect to another exhibit capacitance. An object's capacitance increases when another object is brought closer to it.

The following diagram demonstrates what my question is about:

Since the right side has a larger (magnitude) charge than the left side, I'd expect the net field to go from right to left.  (If I threw a proton in the field, it would repel more from the right and end up on or close to the left).

But as I bring these two objects closer together I would expect that the capacitance would decrease because the right side would attract electrons from the left side, forcing out the holes in the left to some other part of the system.

Conversely, if the objects were moved further apart, I'd expect the field to diminish to the point where both objects have no effect on each other.  This would cause the capacitance to increase to its maximum.

So, what is true?  Does the mutual capacitance increase or decrease for these two objects as they come closer?  Is it even possible for these two objects to have a capacitance if they have like charges (both positive in this case)?

I may need to open up another question for this, but I'm trying to see how mutual capacitance is used for proximity/touch sensing.  As it seems right now, I can't tell how this mutual capacitance can be monitored if only one object is connected to the sensor system, while the target (a human hand for example) is not connected.


texts: How can you connect multiple monitors to one temperature sensor?

texts:
I have two monitors I want to connect to one temperature sensor. I tried connecting the sensor wires in parallel but it only outputs error. Sometimes the power doesn't even turn on. I'm guessing the signal can't be split in multiples. Anyone have an idea on how to read a single sensor to multiple monitors? What do I need? What do I have to purchase?
Temperature sensor using MF55 type of NTC thermistor, epoxy potting.
Operating voltage: 4.5-28V
Here is more info on the monitor.


texts: What maximum voltage will I need my ESC to be rated at?

texts:
I'm using a pair of drone motors in order to power a small vehicle. I have a 56V lawnmower battery, to which I will connect the two 22V motors in series. I need to be able to control the speed of the motors while in flight, bringing them down to 0 RPM or up to around 4,000 RPM.

I'm going to use an electric speed controller to do this. Does my ESC need to be rated to the 'remainder' voltage after the two motors, 12V? Or does it need to be rated to the voltage of the battery, 56V? I'm having significant trouble finding a 56V ESC.


texts:
I'm working on converting TTL S/PDIF to Coaxial level (0.5Vpp). I have implemented the following circuit using a Toshiba TC7W04, which is a 74HC04-type inverter:

But it does not appear to work in practice (I am working on getting access to a scope to look at the actual signal).

The source devices that I have tried are a Cirrus Logic WM8804 and a Sierra Wireless BC127 (CSR8675 Internally).

Interestingly enough, I did find a schematic (pictured below) from CSR on converting their TTL S/PDIF to Coax, but I'm not sure what kind of inverter is in use:

My questions are:

Is there anything inherently wrong with my implementation? I realize the output impedance is only 72 ohms, but that shouldn't matter too much, right?
Is there a way to tell what kind of inverter the CSR implementation is using?
Why does the CSR implementation make use of three parallel inverter gates?


texts: DIY attaching an EU power plug to an US charger?

texts:
I've received some Chinese walkie talkies today, which annoyingly enough had the charging adapters to the charging stations come with US plugs instead of EU plugs.

The adapters are marked with

INPUT: 100-240V ~ 50/60hz 0.3A
OUTPUT: 10V (DC symbol) 500mA

In my country (Norway) the outlets have cirka 230V AC at 50Hz (I'm 99.8% sure).

What would I need to be able to relatively safely be able to plug them into Norwegian mains?

Albeit, as temporarily less safe, (since I'm unable to get powerplug adapters at the moment), would something start to smoke if I were to carefully solder and heatshrink on some lamp plug-leads that I've got laying around the house, onto the power adapter's US pins?


texts: Ok to connect stranded wires with different strand counts?

texts:
I need to replace a damaged wire. The wire is UL1430 22AWG stranded with 17 strands. See here. I can find something very close, but it's not quite the same. It is UL1430 22AWG with 19 strands, instead of 17 strands. Listed here. Is that replacement wire ok or does the strand count matter that much?
I also need to replace a UL1010 18AWG stranded wire with 16 strands. See here. But I'm having trouble finding anything close. Is there an acceptable substitute that is widely available in the US?
The wire is for internal wiring of a ceiling fan on my screened-in porch. The wire will go from the fan housing, up the downrod, to the canopy.


texts: Multimeter not reading capacitance accurately?

texts:
I am trying to measure new electrolytic capacitors before they go into my guitar amp to make sure that they are up to spec.  I'm using a Morris #57044 multimeter, which has an autoranging capacitance measurement setting.

I've used it to test a couple of capacitors, all in the microfarad range (20 - 150 uF), and each time, the meter stays at 0 for a bit, shows a reading in nanofarads, then registers overload OL.  The meter is supposed to have a range from 10pF - 200uF.  EDIT: Looking more closely at the spec sheet, I see the meter has 40nF as its lowest range and 200uF as its highest range.  This should still read a 100uF cap fine though, if I understand correctly.

I am discharging my capacitors before measuring, making sure I am using the leads on the right sides of the cap, and using the relative REL button on the multimeter to zero out internal capacitance of the leads (though the problem persists even when I don't do this).

Is my meter not working properly?  Am I doing something wrong?

Product page:
https://www.morrisproducts.com/pc_product_detail.asp?key=B22E69AD80464A1584F58EF688EE7E38

Spec sheet:
https://www.morrisproducts.com/images/57044-specsheet.pdf

Thank you in advance for your help!


texts: Generating 19kHz and 38kHz phase-locked sine waves

texts:
As a personal project, I'm designing a stereo FM transmitter from scratch. Part of this entails design of a stereo multiplexer.

Using this description, I've worked out how I'm going to implement most of the stereo multiplexer in analog hardware. The only thing I'm having trouble with is figuring out how to generate 19kHz and 38kHz phase-locked sine waves. I'll need the 19kHz signal for the pilot tone and 38kHz signal for the DSBSC mixer. I'm pretty sure if they're too far out of phase, the receiver will choke up trying to demodulate the L-R channel.

As the square wave can be busted apart into sine waves with Fourier analysis, my current design feeds a 38k crystal oscillator into a TTL frequency divider to get in-phase 38k and 19k square waves, then uses Sallen-Key lowpass filters with a high Q-factor (Q=10) and the cutoff frequencies set to the fundamentals to pull out the fundamental frequenies and block the harmonics. Here's the circuit I was using to simulate that. The trouble is I can't easily guarantee the sine waves will be in-phase, as by setting the cutoff frequency close to the frequency of the sine wave I'm trying to get means that it's at the same spot as the steepest drop on the bode phase plot.

Ideas? I think PLL would help out here.


texts: Wiring a stereo TRS socket as a mono output

texts:
I'm designing a product that provides mono audio output via a 1/4" SN49B12B board-mounted socket.

This socket is actually a stereo socket, but I'm wondering if simply wiring the ring and sleeve pins together to ground will effectively make it a mono socket?

Are there any issues with this approach from a product design / durability / robustness perspective? One concern I had was that when plugging, the ring will connect the cable to ground earlier than if there was no ring present - would that create any extra plugging noise or anything like that?

The user will, of course, be using mono TS plugs.


texts: Reversed biased diode polarity in circuit

texts:
I have to find the operating interval of the diode in the following circuit..

NOTE: The DC source has its positive pole grounded.

My work so far is this..

\$V_i>-1.5 V\$: the diode does not conduct and we have open circuit which results in $$V_o=0$$.

\$V_i\le-1.5 V\$ the diode does conduct an it becomes short and we have voltage divider which results in $$V_{r2} = (V_i+E)*{R_2\over R_1+R_2}$$
and
$$V_{o} = V_{r2}-E =>V_o={3\over4}V_i-{3\over8}$$

So the sinewaves of input an output are the following:

Can somebody please tell me if I am right or if I am making some mistake I am missing??


texts: I bought a Stranger Things light panel from Spirit Halloween a few years ago. It was the floor model, not the merchandise at the store. It had weird wiring and I lost the cord that plugs into the wall. Anyone know the name of the piece that will connect this to the wall? I can share more images if needed. Thanks!


texts: Series protection resistors on I2C lines

texts:
In NXP's I2C specification and user manual Rev. 6, it states we can put series resistors on SDA and SCL lines for protection against high-voltage spikes:

And it gives a graph, to show the relation between Rs and Rp:

I wonder how NXP get this graph, if there is a closed form equation to show the relation between Rs and Rp?


texts: Do algorithms exist for tuning microwave filters?

texts:
I'm a systems engineering student and I have taken a summer job at a company that manufactures various microwave filters, my role is to "try" improve and standardise their processes in order to improve production reliability. As the company manufactures over 13,000 filters, it is common for an experienced tuner to show a less experienced tuner how to tune a filter that they have no experience with and thus diverting the more experienced tuners time from the more trickier tasks.

I have read a few papers that use vector fitting and aggressive space mapping (VF-ASM) to tune a general two-port cross-coupled network A FAST TUNING METHOD FOR MICROWAVE FILTER USING VF-ASM TECHNOLOGY, I believe this is concerned with reducing time taken by a human tuner and not something that I can use. However, I am wondering if algorithms exist to tune any filter that will enable me to create a process that can be followed to reduce the amount of time being diverted by the more experienced guys.

I have no experience with tuning filters so if my question seems crazy to some of you I apologise, I would appreciate any tips, advice or direction you can give me.


texts: I'm going to be working on my second major design where size is the number 1 goal. What are the theoretical issues going with 0201 or less for resistors/capacitors, besides soldering difficulties?


texts:
I've been doing USART on STM32 and got this at putty:

Actually I want to display :

printf("*  Thank you for using the board");

Do you have idea why ?


texts:
I don't understand how they got the mean free paths (ls) of each leg. I know that I should be calculating the longest + the shortest paths and divide them by two, but I don't know HOW I should be calculating these.

Thanks


texts: General purpose cpu as logic analyser better / worse than dedicated FPGA implementation

texts:
This question relates to building a cheap but capable logic analyzer. I had the idea of using an x86 cpu that was running a program that could fit in the fastest cache that would just read data from a group of pins as quickly as possible.  So the program would load from slow flash into cache and then just sample, perhaps into slower cache.

Given that a cpu that runs in the 3ghz range can be purchased for around $50, I wondered if performance might be better than an FPGA of similar cost

My question is: might it be possible to beat a dedicated fpga (or other design) for cost while equaling the sampling speed?


texts:
I've installed a 12V 80W solar panel plus controller and attached it to a 12V 105Ah leisure battery. At first it (appeared to?) work. The charge status on the solar charge controller was at max and it stayed that way even though I used power.

After a few months of no usage (but connected to the solar panel) I found the battery empty (the solar charge controller indicated overdischarge).

Recharging with an external charger brought the battery back up to 12.46 V, which I researched to be 85 % (I didn't measure before charging unfortunately), but the solar charge controller still only shows it at 25 % full (first LED lit as per image)

I can't figure out what this tells me - is the battery weak (it was new before the solar installation), did my solar set up damage it? Is the controller showing the wrong info?

UPDATE: Here's the manual and specs of the controller:


texts: Slide lock or flip lock for FPC connector?

texts:
I'm looking at different connectors for for an FPC cable, and I've narrowed it down to two nearly identical connectors, whose only difference in the lock. One uses a "slide lock":

While the other uses a "flip lock":

I get the conceptual difference between the two, but is there any advantage in using one over the other? For example, does one offer greater mechanical strength for the connection?


texts: CMSIS-RTOSv2 - Access out of bounds in RTX RTOS window

texts:
During migrating my project to RTOSv2 and RTXv5, I recognize that after a few minutes my program hangs and the messages appear at the RTX RTOS window:

Expression: 'QML[j + QCB[i].ml_idx].addr'
E303: Access out of bounds - <readlist 'QML[44]'> - actual index:=45

I find the source of the hard fault is the "memcpy" function.

CMSIS_5/CMSIS/RTOS2/RTX/Source/rtx_msgqueue.c

/// Put a Message into a Queue or timeout if Queue is full.
osStatus_t osMessageQueuePut (osMessageQueueId_t mq_id, const void *msg_ptr, uint8_t msg_prio, uint32_t timeout) {
  EvrRtxMessageQueuePut(mq_id, msg_ptr, msg_prio, timeout);
  if (IS_IRQ_MODE() || IS_IRQ_MASKED()) {
    return isrRtxMessageQueuePut(mq_id, msg_ptr, msg_prio, timeout);
  } else {
    return  __svcMessageQueuePut(mq_id, msg_ptr, msg_prio, timeout);
  }
}
...
/// Put a Message into a Queue or timeout if Queue is full.
/// \note API identical to osMessageQueuePut
__STATIC_INLINE
osStatus_t isrRtxMessageQueuePut (osMessageQueueId_t mq_id, const void *msg_ptr, uint8_t msg_prio, uint32_t timeout) {
  os_message_queue_t *mq = (os_message_queue_t *)mq_id;
  os_message_t       *msg;
  const void        **ptr;
  ...
  // Try to allocate memory
  msg = osRtxMemoryPoolAlloc(&mq->mp_info);
  if (msg != NULL) {
    // Copy Message
    memcpy((uint8_t *)msg + sizeof(os_message_t), msg_ptr, mq->msg_size);
    ...
  return osOK;
}

Does anyone have any ideas for this problem?
Thanks,...

Bacheh Karaji


texts:
I have an isr that is updating a display at a fixed frequency. I would like to tune my routine to minimize overhead and keep as much cpu time as possible open for other processing, but I don't have any good way to collect metrics to determine my cpu load.

I could look at the assembly and analyze the routine, but I don't have the patience or the ability to do that accurately. I don't feel like I need terribly fine grained results either, just a simple percentage of cpu time occupied by the isr.

I could set a pin high only when the isr is active and measure it externally. That has a minimum of overhead in the code, but I do not know what to measure it with. I don't have an oscilloscope or anything like that. Is there a simple ic or an easy way to use another micro to measure duty cycle? I have heard of dedicated frequency counter chips, but is there anything for duty cycle?


texts:
I'm using a non inverting opamp circuit with a LM741 opamp to make an output signal have twice the amplitude as the input signal.

The problem I am having is the output is twice the amplitude upto around 7kHz and after this point it begins to decrease with increasing frequency, anything I can do to stop this happening or a counter measure to fix it?


texts: How to reduce or remove noise when using an ADC to sample CAN bus

texts:
I'm working on a project to sample CAN messages based on a Xilinx Spartan-6 board. I want to get the timing information of CAN messages. The schematic of data acquisition module is shown below.
The module (including AD9226) is working under a clock of 50 MHz.

Subtracter:
Input from CANH minus input from CANL, to get the differential voltage.
Comparator:

If greater than the threshold value, then output dominant ‘0’.
If lower than the threshold value, then output recessive ‘1’.

The AD module which I choose is this one which can be directly connected to the FPGA board.
I linked the final output with one I/O pin of FPGA board so I can observe it by a logic analyzer. It looks good when using the logic analyzer.

But you can notice that there is noise which I don't want.
Here is the result I observed by ChipScope. The sample frequency is 50 MHz.

There are so many unwanted transitions.
The ADC module is well-designed and can be directly connected to the FPGA, so I don't expect so much noise from the input.
Is there a way I can remove the noise to improve the situation? Is there a design principle I can follow when using an ADC to sample a signal?


texts: How critical a resistor value for MSP430 spy-bi-wire on reset?

texts:
When setting up a circuit for the TI MSP430 - the reset line in all example circuits has a 47k Ohm resistor (R1 below) on it.  How critical is that specific value and why that value?

This is what I've currently been using to do this.

Can I use something else higher or lower? 47k isn't an SMD part I have on hand typically.


texts: Does input amperage matter in a DC-DC Booster?

texts:
I am planning to attach a 6V 100mA Solar Panel to a Step Up USB Charger you can see at this link, and yes I know it can only be charged during the day... that is OK.

Considering that most phone batteries today are at least 2000 mAh, would connecting two solar panels in parallel speed up the charging? In other words, does amperage of input into the booster have a direct correlation to the output amps, or would it be inefficient?

EDIT:

I updated the link to a different product that can give up to 2A of output current and takes up to 5.5V input. I plan to connect the two solar panels in parallel to the Step Up USB module. I will connect one end of a regular USB to the step up module and the other to the phone.

I realise that I am wasting power when I am not charging my phone. Perhaps I'll do that in my next DIY.


texts: NC JFET switch with only one voltage source

texts:
The below circuit functions as a NC switch. At Vgs = 0V current flows through the channel of J1 (the JFET). When S is closed J1 will open and
no current flows through the channel anymore. Right now the circuit has two voltage sources in it.

My question: Can we design a JFET switch circuit with only ONE voltage source?


texts: How does load affect an RC-filtered PWM DAC?

texts: When using a PWM as a DAC, how does load affect the output voltage & current? How do you know whether the design needs a buffer?


texts: How to plot a pole in the s-plane if it has a repeated root?

texts:
Let's suppose I have a transfer function H(s) with a repeated pole:

$$H(s) = \frac{1}{(s+2)^2}$$

What would that look like on a pole plot?

Do you just circle the -2 on the real number line twice?

(Just wanted to make sure that i'm not mixing it up with nth root of unity.)


texts:
My friend and I are repurposing an old rc car. We're trying to wire up the steering, but we've never seen the type of motor that it uses for steering. It has 7 wires. What is this component and how do we wire it (we are using an arduino)? Thanks.
Attached is a picture of the connection on the car's circuit board.


texts:
The input voltage of my system is ±15V. I need to generate the ±5V voltage. As I need it to power precise analog components (ADC, op amps), my plan is to use DC/DC converter for reducing it to, lets say ±7V, and than to use linear regulator (like LT3032) to get the required ±5V (as linear regulators in general have lower noise). As total current of my system is about 1A, I would avoid solution with only linear regulators because of substantial dissipation. However, I am not sure how to implement DC/DC conversion for negative rail. I know that there are options for supply inversion (make negative rail from positive), but it seems (maybe I am wrong) that those inversion rails circuits are usually for currents less than 1A. And those circuits only use positive rail, although I have also the negative one coming to the system.
I saw somewhere schematic with two (non-isolated) DC/DC converters, connected like in the following figure, but I am not sure if this is possible (at least work for higher currents)? Please suggest what would be the proper solution.

Thank you in advance.


texts: Trying to increase amperage of Arduino Uno digital pin (20mA) to control a cabinet lock that is rated at 12v / 2A

texts:
I am trying to use my Arduino Uno to send power from one of its digital pins to a cabinet lock, the cabinet lock is "fail-secure," so you send power to it to unlock it, and it is locked when in GND state. I purchased these, but being new to electronics, when I bought them, I failed to realize that I would need to increase amperage as well as voltage to make the lock function.

Alas, I had this lying around. I know it works with DC motors, but I was wondering if I could use it to increase the current for the lock. I'm trying to understand the specs - in some places I see that it can produce 600mA, in others I see 1.2A or 2A. If it can produce 1.2A from 5V, I think maybe that would open the lock (I don't know the minimum amperage that would open the lock). The specs seem to be for two models, I have the L293D.

So my overarching question is, can I connect the Arduino Uno digital pin to the L293D and then run the output from that to the DC boost module I got (amazon link above), and then run the output from the DC boost module to the lock...with enough amperage to open it?

Here are some pictures of what I have (I am still awaiting the DC boosters in the mail):

Cabinet lock:

L293D
[![enter image description here][4]][4]

Latch and power cord:

Thanks!

[4]: https://i.stack.imgur.com/fRqOA.jpg


texts: 8085 - binary equivalent of MOV and it's corresponding timing diagram

texts:
I've got two questions here:

#1

The MOV A,B is said to be a one byte instruction, where B = 000 and A = 111, then MOV should be equal to 00, but, The binary representation of the BC Rp is 00. So, I'm getting confused as to how it is a one byte instruction.

#2
The MVI instruction involves only registers and yet it required a memory read operation:

but, MOV instruction ALSO involves only registers and yet it doesn't require a memory read, WHY?


texts: What is the easiest way to stagger a signal chain on a stack of identical boards?

texts:
I am designing a stack of identical boards that each generate an analog signal. What I am trying to do is take the signal from the board above, mix it with the signal from this board, and then send it down to the next board.

The problem is that the board-to-board connectors need to be through-hole for mechanical support, which means that the output from one amplifier would be connected to the output of the next amplifier if they are all identical designs.

I need a way to alternate the connector pinout from one board to the next, but I would prefer not to design two versions of the board. Is there an elegant way to do that?


texts:
For this circuit, is the correct KVL:

+10V-V1-V0-V2-(-10V)=0 ?

V0 between the resistors is an open-circuit voltage.

What is the voltage across R1? Is it V1=10V-V0?

And is V2=10V or V2=V0-(-10V)?

simulate this circuit – Schematic created using CircuitLab

Thanks!


texts:
I’m trying to design a battery protection circuit for this 300mAh 3.7V LiPo battery.

I’m an EE student which is designing his first pcb. Please forgive questions with obvious answers.

My questions:

The seller specifies a battery protection circuit is already present. Should I trust it or I’d be better off providing my own?
The rating of the battery is 0.5C for average discharge current, 1C peak discharge current and 300 mAh. From what I understood, that is a really low rating for LiPO batteries and is not consistent with the 4 to 6 A current limiting protection which they state.
The IC which I would intend to use is TI BQ297x. The design suggested on its datasheet is typical, with 2 FETs to manage charging and discharging. The FETs should be chosen according to their rds. However, the overdischarge voltage threshold of the IC can vary from 90 mV to 200 mV in 5 mV steps and with a max current of 300 mA that would require 2rds = 300 mOhm, that is a quite high. Should I modify the suggested design to meet such a low current? Would it be a good idea to place a resistor between the 2k2 resistor and the FET to increase the voltage drop and avoid high rds FETs?

Edit

I understand that Chinese sellers are not a reliable source of information. However, I was not able to find any LiPO battery from online stores like Digikey, Mouser and so on. Where do you guys recommend to buy to be sure about the product listed?

150 mA would be more than enough for my application. I’ll try to find a better alternative to BQ297x. My final design needs to be as small as possibile because it has to be a smartwatch for health monitoring. I think a ready made protection circuit is not a good way to optimize space. Same holds for old Nokia batteries with integrated protection circuits, I fear.


texts:
On page 3 of this app note the following is said

  Pass Through—This I
  2C control enables communication with all the remote devices, whose device ID
  and corresponding device Alias fields is defined into the local device (Ser or Des), as discussed in
  Section 3.

What is the purpose and the concept behind "Pass through I2C" in the Electrical domain?


texts:
I am trying to understand how an H-Bridge circuit works.  The following is the diagram, from SparkFun's TB6612FNG product:

Specifically, what purpose do the C1, C2 and C3 capacitors serve? If they were not present in the circuit, what would happen?

(Disclaimer: Software engineer, lacking the deep fundamentals of electronics.)

EDIT:

Comments and one answer (so far) mention that capacitors need to be close to the IC.  Following is the image of the board; to my untrained eye, the capacitors seem to be located close to the IC.

However, the answer offered and comments seem to disagree.  One school of thought (by Maxim Ivanov) is that the capacitors provide protection against sagging voltage, while comments say they are for noise suppression.  Not sure how to proceed here.


texts: I have to come up with an architecture for a system where PC communicates to two identical(but independent) micro controllers(in-built usb controller) over 2 USB channels. I don't have experience in USB implementation. My question is How PC will identify these USB channels as different. I will be using third party USB library and device descriptors of which is accessible to edit. Is that enough for PC Application to identify these as separate channels. Or PC Application can handle this without even editing the descriptors??.


texts: Instrumentation (or diff) Amp saturating when measuring low voltage

texts:
I need to measure (amplify) a very low voltage, by low I mean in the order of 20 uV. Right now, using a lab multimeter, I am clearly and repeatably measuring the voltages so I thought that amplifying it to about 1V in order to measure it with a 10bit ADC would be easy. Of course I am having trouble with it.

After many tests with different resistance values and circuit config, I stepped back to a simple 2 stages differential amplifier, with a TL082 (2 op amps package, Input impedance of 10^12ohm). The voltage supply is of -15 to 15V so I have a quite good margin here.

simulate this circuit – Schematic created using CircuitLab

As you can see, I have a strain gauge circuit to the left. Since it was ripped from from a 10$ kitchen scale, the 2 gauges and the resistors are glued and unavailable. Still, being able to measure it with the multimeter made me confident that I could simply amplify the signal.

The problem is that my equivalent gain is (200k/1k)*(100k/1k) = 20000 (which I want). If I try to measure the voltage Vin, Vout goes to about half the positive rail voltage (here, around 7.5V), then bending the straing gauge assembly (varying Vin) shows a seemingly linear augmentation of Vout. According to my calculation an measurements, when Vin = 0.03mV, Vout should be of 0.03mV * 20000 = 0,6V. So, reading 7.5V at Vout is seemingly incorrect in the first place.

What is strange is that if I simply measure the voltage across a floating resistor of 1k, instead of reading ~0V (plus noise) I read a Vout of 7,5V. But if measure a floating resistor of 200k, damn I measure around 0,7V, which is exactly the kind of value I would expect of a noise being amplified 20000 times.

So, is anyone up with something on this? Oh, I should mention that:

First, we used a full instrumentation amplifier to provide the 20000 gain and the behaviour was similarly wrong, so we stepped back to this "simpler" circuit.
We have access to lab strain gauges and will probably try to use them instead of the ripped off bridge from the kitchen scale.
I am a TA, not a student with a homework ;) I want to use this a pedagogical tool for my student.

Thanks everyone!


texts: Power output in an Arduino using analogwrite()

texts:
I understand that using arduinowrite(anynumberoutput,0-255) will give me a average voltage output x/255 *5v to be outputted from Arduino.

Hence, when this question ask,

  An PWM is generated by the command analogWrite(pin,100). What is the power supplied thru 250ohms resistor.

I have assumed the answer to be (100/255*5)^2/250 but the answer is different. It is 39mW. Can someone explain this to me?


texts: Simple LED Circuit on audio jack not working

texts:
I am trying to connect a simple LED to the audio jack of my phone.
Finally i got the correct voltage with the right audio plug (headset 4pols), which is arround 2.7V on my phone. But the LED is not lighting up?
Does anyone have an explanation for that. It's an red LED which should normaly light up with 2.7V

simulate this circuit – Schematic created using CircuitLab


texts: Sensor & power wire length & connection inquiry

texts:
I'm an experienced SW engineer, but a noob when it comes to .NETMF & hardware. I've started working on my first project (garage controller that will monitor & control the open state of the garage doors & manage the sprinkler system) and thinking through the organization of where I want stuff.

Right now the sprinkler system controller is on the far end of the garage (about 40' from the door to the house where the garage door openers are). I'd like to put this single controller I'm building with a Netduino Plus 2 but had a concern/question about length of the wires. I wasn't planning to go wireless for cost reasons & because the distance seems a bit too far for Bluetooth reliability.

Thinking about the sensors I'm making to monitor the open state of the garage doors... the wires from the controller will be roughly 35-45' long & the wires to the sprinkler system valves will be even further... 50' or so. I understand I need to use a relay to power the 24V sprinkler valves and was planning to put that in the controller. Are either of these two wires (sensors for the garage door / sprinkler valves) too long or am I concerning myself with something I shouldn't worry about?

Another question about the connections to the controller box. I planned to create a serial connector for the garage door sensors on the exterior of the box to make the connections a bit cleaner, but I'm not sure if serial will work to power 4x 24V sprinkler valves (or if I can have 1x serial connection for each valve). Is that doable? If not, what other options would I have?


texts: How is digital data represented in analog waves?

texts:
This question is simply coming from an intrigued teenager, so if it has any flaws, I'm sorry for the inconvenience.
To my knowledge, when digital data is transmitted wirelessly, it is first encoded into analog, whether it is Bluetooth, Wifi, etc, it is built to represent that of 1's and 0's, but how? What specific changes are made to the analog wave (such as amplitude modulation or frequency modulation,) so that when it is decoded it (as in a computer receiving the data) distinctively knows where the ones and zeros are?
For example:
If I were to connect a Bluetooth keyboard to my computer, when I press the 'a' key, the ASCII binary code 01100001 will be sent to my computer via Bluetooth. But how does my computer decode that wave, and know where a 0 and 1 are?


texts:
I was given the task to evaluate existing boundary scan systems. At this moment, we are using a simple solution which allows us to define boundary scan vectors which we can check. This is fine for simple tests and is perfectly integrated into our ICT/Flying Probe/AOI chain.
For a new project we require testing of various high speed interfaces. We've been talking with Goepel about our requirements but I am not completely satisfied with the answers from their sales guys. I simply do not trust them (I think this is more my being than not believing the actual sales guys). When talking about more advanced microcontrollers (Cortex-A8/A9 core, ..) they said it was just a question of purchasing the appropriate model for the controller and an appropriate model for the DDR-RAM and it would be able to create the checks automatically. I believe that this holds true for interfaces which do not have the timing requirements and can be considered static (SRAM, various logic ICs, ...).
I asked about DDR-RAM (actually it's gonna be DDR2 or DDR3) functionality and they said it should work, but on the other side the demonstrated a "simple" SRAM.

Now for my question: Has anyone of you made an experience with such high speed circuits in conjunction with boundary scan? I just want to avoid telling our customer "Yes, we can do this" when it's just all wrong.
Furthermore: Using JTAG, we are definitely not able to achieve the timing requirements of DDR2/DDR3, this alone already seems like a problem to me.
How do you do testing of such high speed interfaces (GBit Eth, various SERDES, DDR)? We've been thinking about functional testing, would this be the way to go?

EDIT: Additional Information due to response from Dave Tweed:

I am in fact targeting manufacturing flaws. In no way I expect components to work out of specs or to differ between production runs, this is out of scope. Also, timing is no concern to me. Basically I would just like to rule out any shorts or unconnects which may happen during production (this is especially hard with BGAs which cannot be checked using AOI).

To have DDR-RAM work as expected, I need to stay within timing restrictions. Due to the speed of the JTAG interface (and its nature) it's just not possible to to stay within the specified timing. The main question is now: Is there something I might have left out or forgotten which makes testing (e.g. DDR-RAM) very easy or is this something which can only be done by performing a functional test at a later stage?

I'll give an example: I have a controller which supports Boundary Scan on its DDR lines. BUT the memory itself does NOT. Therefore I have the following options: 1) Do a functional test (a la memtest in Linux); 2) Build a "kind of" memory access sequence via Boundary Scan (which will be out of specs) to test memory access (address and data lines, write some data to RAM, read it back).


texts: I want to keep my circuit on after a push button is pressed and released. Trying to do this I stumbled upon soft latch circuits, but they are too complex and I don't need the turning off feature. What is the simplest possible way to keep my circuit on after a momentary trigger, like that of a push button?


texts:
How can I read the Beta value of a BJT for a specific circuit from the datasheet?
I tried to find currents first in order to find the Beta value but eventually I couldn't because I didn't had the Beta value. I couldn't make sense of the datasheet.


texts: Phase between two sinusoids and which one is leading

texts:
that's my first question here.
I'm studying fundamentals of electric ciruits
and I faced this question:

Determine which one leads and by how much:
$$v1(t) = 4*\cos(377t + 10)$$
$$v2(t) = -20*\cos (377t)$$

So I converted

$$v2 = -20*\cos (377t)$$ to
$$v2 = +20*\cos (377t+180)$$

and graphed the two sinusoids on the unit circuit but I'm confused about which one is leading the other and by how much

Thanks in advance!! =)

EDIT!!:


texts: Why isn't a 1 Farad capacitor equivalent to a wire in LTspice?

texts:
The following is a very basic driver circuit for one phase of a DC brushless motor. The input varies between -10V to 10V for a current between -2A to 2A.
The amplifier is a power opamp from PowerAmp.

Here are frequency sweep plots of the current in L1, respectively with and without 1F capacitor (no series or parallel C or R) in the feedback branch of the circuit:

Why the difference?

I wanted to get rid of the resonance at 10kHz which could be responsible for too much ripple due to noise being amplified, by trying out a few locations for a capacitor when I noticed this.


texts: What type of memory allows for most parallel read/write operations per clock cycle in an FPGA?

texts: If you imagine basic motion detection where you have two frames stored in memory: a previous 640x480 frame and the current 640x480 frame, what type of memory (SRAM, DRAM, SDRAM, DDR SDRAM, etc) would allow for the most parallel read/write operations per clock cycle? For example, the perfect solution would allow the simultaneous read of two frames, (307,200 x 2 pixels) in one clock cycle. What is the best memory for this, the SRAM built into the FPGA, or an external chip like DDR SDRAM? (In the bigger picture I'd be looking for the a FPGA dev board that has the smallest cost and size with the largest parallel read/write ability.)


texts: Can't update my schematic to PCB layout in Altium

texts: I have finished my schematic for an echo circuit using PT2399 IC as per the application circuit in datasheet. I have downloaded the part (including footprint) from snapeda.com and updated my Altium library. But I can't update the design to PCB. There's no option as 'Update PCB document' under the 'Design' tab to update the design to PCB. But it is showing for other projects I have done. I don't understand. Please help me, it's urgent.


texts: A question about a long-shunt compound DC generator

texts:
I am an engineering student and I encountered a tricky question while doing my assignment.
The question is as follows:

A long-shunt compound DC generator rated at 20 kW and 200 V has a total
armature circuit resistance of 0.3 ohms and a shunt field resistance of 50 ohms.
(a) Drawing an equivalent circuit for the generator with explanations for
each parameter in the circuit.
(b) Estimate the load, field and armature currents at full load.
(c) Estimate the generated voltage at full load at rated terminal voltage.
(d) Explain the difference between the terminal voltage and internal
generated voltage.

By now I already finished the part (a) and (b) of the question. The load, field and armature currents should be 100A, 4A and 104A if I recall correctly. But I get stuck while attempting part (c) of the question.
So as the question stated, we are required to find out the generated voltage at full load at rated terminal voltage of the dc generator. I tried to do so but I can't since I failed to find out the series field resistance of the generator, which I believe is needed to solve the part. So is the series field resistance necessary in solving this part? Or I am missing some governing equations? Could anyone provide me with some assistance?
Any help would be appreciated. Thank you!


texts: I have a generator that can produce 150 watts, i have a dc motor that takes in 100watts, why is it that my generator wont run the motor?

texts: I am trying to simplify this as much as possible as there are tons of variables that people could point out, but i made a small generator which then I rectify to produce DC straight out of the coils, I get 300V, and .5 amps so 150 watts when i spin this generator with a drill. I use a converter to turn the 300v into 24vDC at almost .6 amps, the exact numbers my generator says it needs to run, yet it barely runs without a load and with a load it still lags, why? it looks like its barely running at 20-30%


texts: What is the best way to identify unknown connectors?

texts:
I'm having trouble finding a replacement connector, it's the same as the one in this picture, the picture only calls it a "mini 2 way 2.54mm pitch female connector" - lots of these exist, so can someone please tell me the technical name of this particular one?:

This sort of thing happens all the time, does anyone know of a master document of connectors I can use to identify things with?


texts: Connecting a surround system without jacks

texts:
I have recently bought a house which has already the sound cables passing through the walls. These are raw cables without any jack connectors.

My question is, when you go to buy a 5.1 surround system (or any speakers for that matter), what do you ask for when you do not want speakers with wires already connected.

Basically, when you have an AV receiver, there are jack inputs and there are also 'pure wired' inputs (where the cables are exposed). I want speakers which also accept this 'pure wired' inputs. I wish to know what these 'pure wired' inputs are called.

Thanks in advance!


texts:
I successfully built an active DI box using this circuit (image posted below), everything went fine and I'm happy of the result.

Parts List

R1, R2 - 1k
R3, R5, R6, R7, R8, R11, R12 - 10k
R4 - 1M
R9 - Jumper
R10 - 100 ohms
R13 - 10k reverse log potentiometer
C2 - 1uF
C4 - 100pF
C1, C5, C6, C9 - 10uF
C7, C8 - 47uF
IC1 - NE5532

V+ is 9 Volts

Can anyone help me understand how this circuit arrangement provides differential signals and impedance balancing? Briefly, can anyone explain me how this circuit works in details?


texts:
I have a piezo harvester, capable of creating spikes of 50+Volts. My harvesting circuit which will be connected to the harvester output, has a maximum rating of 20Volts. Therefore I need some kind of overvoltage protection.
I considered adding 2 zener diodes rated at 20V as the below schematic indicates.

simulate this circuit – Schematic created using CircuitLab

If the piezo voltage is under 20V, it is my understanding that no current will flow through the diodes and all the power will be transferred to whatever is connected to Vout (battery, load, etc).
If however the voltage rises over 20V, then the diodes will start conducting, trying to keep a constant voltage of 20V across Vout. My question is, if I do not put a resistor, I believe that the diodes will be fried. If I however place a resistor in series with the piezo, I will be having power losses on the resistor, even during normal (Vpiezo<20V) operation.

Are the above correct? If so, what would be the easiest solution for overvoltage protection for my piezo harvester?


texts: JK-flip flop using gate level description in Verilog give me a timming error

texts:
I still playing in the lowest Verilog level (gate level).
I found this post:
Is it possible to create a working JK-flip flop using gate level description in Verilog
in that I could understand that shoud work the idea, and I could solve to have a Master-Slave JK Flip-Flop for use it as a frequency divider. I use Icestorm toolchain, Yosys is not complaining, but Next-PNR is giving me this error:
ERROR: timing analysis failed due to presence of combinatorial loops, incomplete specification of timing ports, etc.
This is my code:
module syncRX(clk, signal, detect);
    output wire [7:0] detect;
    input clk, signal;

    reg [6:0] det = 7'b1001010;

    assign detect = {det, jk5_out};

    jk_flip_flop_edge_triggered jk0(.Q(jk5_out), .Qn(Qn), .C(clk), .J(1), .K(1), .RESETn(0));

endmodule // top

module jk_flip_flop_edge_triggered(Q, Qn, C, J, K, RESETn);
   output Q;
   output Qn;
   input  C;
   input  J;
   input  K;
   input  RESETn;

   wire   Kn;   // The complement of the K input.
   wire   D;
   wire   D1;   // Data input to the D latch.
   wire   Cn;   // Control input to the D latch.
   wire   Cnn;  // Control input to the SR latch.
   wire   DQ;   // Output from the D latch, inputs to the gated SR latch (S).
   wire   DQn;  // Output from the D latch, inputs to the gated SR latch (R).

   assign D1 = !RESETn ? 0 : D;  // Upon reset force D1 = 0

   not(Kn, K);
   and(J1, J, Qn);
   and(K1, Kn, Q);
   or(D, J1, K1);
   not(Cn, C);
   not(Cnn, Cn);
   d_latch dl(DQ, DQn, Cn, D1);
   sr_latch_gated sr(Q, Qn, Cnn, DQ, DQn);
endmodule

module d_latch(Q, Qn, G, D);
   output Q;
   output Qn;
   input  G;
   input  D;

   wire   Dn;
   wire   D1;
   wire   Dn1;

   not(Dn, D);
   and(D1, G, D);
   and(Dn1, G, Dn);
   nor(Qn, D1, Q);
   nor(Q, Dn1, Qn);
endmodule

module sr_latch_gated(Q, Qn, G, S, R);
   output Q;
   output Qn;
   input  G;
   input  S;
   input  R;

   wire   S1;
   wire   R1;

   and(S1, G, S);
   and(R1, G, R);
   nor(Qn, S1, Q);
   nor(Q, R1, Qn);
endmodule

Well, I can imagine the answer if I ask what happends, I would like to know why and how make it works! Thanks to all!


texts: Project libraries don't show in Altium 14.1

texts:
I am having strange issue, because when I open my schematic document and try to add component, when I click on Libraries (it doesn't show my project libraries).
Libraries.
I try to edit in Preferences my paths and default locations but still can not resolve it.
My project has two libraries (schematic and pcb), I can see pcb (footprints and 3D models) but can not see components (schematic).
PCB libraries (footprints)

Can anyone help me?

EDIT:

Shouldn't Altium anyhow show libraries that are part of my project (in project tree) and are in same folder with project, not linked to the project but directly added?

EDIT:

I tried to set paths to the libraries, to be relative and absolute, neither one worked. Is it possible to be some kind of a bug in Altium? Because Altium 13 works fine with same preference setings.


texts: Would it damage a tile saw if I used a a dimmer switch on it?

texts:
It's a 10 inch Ridgid wet tile saw from home depot. I have a dimmer light switch, and I was hoping to use it to slow the saw down about half the regular speed.

Would doing this damage the motor or anything?


texts:
I designed and breadboarded a simple audio amplifier circuit and when I play audio through the speaker, it is pretty noisy and very quiet.
The +5V is being supplied from a USB port.

I'm still probing and testing different spots, so I'll try to update with some scope shots and real measurements besides "it sounds quiet and noisy", but in the meantime, does anyone see any design flaws?

I'm thinking that I may not being supplying enough current and I've noticed that the inverted signal on the output of the second op amp seems to have a clipped voltage swing, about 1V less than the voltage swing on the output of the first op amp.

And as I've been typing, I'm wondering if I should tie the output of my push-pull outputs back to the op amps.

Thanks


texts: So i was thinking, How do car trackers or long distance (over 100kms) remote control communicate to their central commands,? Do they use the cell phone network? what could one require to set up such a network?


texts: How to truncate the least significant bits in a Verilog assignment?

texts:
I have a register of around 120bits, where data is shifted in lsb first, at some point I want to assign it to smaller registers but instead of truncating the most significant bits, I'd like to truncate the least significant bits. In essence I want to keep the n most significant bits of a register.

The current way I'm doing it is for each register assign from MSB index of big register for a width of register width like:

rSmall1 <= rBig[BIG_REG_MSB_INDEX -: RSMALL1_WIDTH];
rSmall2 <= rBig[BIG_REG_MSB_INDEX -: RSMALL2_WIDTH];
[...]
rSmalln <= rBig[BIG_REG_MSB_INDEX -: RSMALLn_WIDTH];

While it works it clutters up pretty fast so, Is there a simpler way to do this same operation for any width of rSmalln?


texts: Is (BC + AD)<<16 equivalent to (BC << 16) + (AD <<16)?

texts:
Is the expression (BC + AD)<<16 equivalent to (BC << 16) + (AD <<16)?
From some examples which I tried it seems to be true but not sure at all


texts: Ethernet PHY and transformer turns ratio

texts:
I'm working on a PoE based system with the CS8900A as the Ethernet PHY. It is specified in the CS8900A datasheet that the isolation transformer required must be of 1CT: 1.414CT for 5V of supply.

Please let me know, on what basis is the above turns ratio chosen? What are the calculations involved?

Also, what happens if a transformer with a different turns ratio is chosen?


texts: MSP430F5529 USB communication drivers refuse to install correctly

texts:
I am learning how to do USB communication with the MSP430F5529 Launchpad and trying to upload the CDC 1 LEDonOff Example from the MSP430 USB Developers Package provided by TI.

I am also following this guide specifically section 2.5.3 but when I plug in my launchpad I see the MSP Application UART and MSP Debug Interface but the third (MSP430-USB Example) doesn't show up under Other Devices with the yellow "bang", instead it shows up as "Unknown Device" under the USB Controllers Tab of device manager.

I tried right  clicking it and manually installing the drivers by navigating to the USB_Config folder of the example I was on, but it doesn't install, instead windows says it already has installed the most up-to-date drivers.

This makes it impossible to use any USB communication examples because this occurs on every example I have tried.

How do I force the computer to install the right drivers and recolonize the device as the USB Example device?

EDIT: I discovered a strange symptom, the drivers install properly (manually) when I flash the device and try to run it outside of a debug session (just connected to the PC from USB) and the program runs as intended connected to my terminal program on my computer, but when I try to run it inside a debug session it will not install the device properly (even if I never set any breaks, just open debug session and hit run), it always shows up as "unknown device" in debug session, even now - after I have installed the drivers and windows remembers it outside debug session - it only works outside of debug session and shows up as "unknown device" inside a session.


texts: MCP555 manual, Yen symbol used in defining baud rate clock, what is it?

texts:
I am going through this manual for the Motorola MCP555 micro-controller and I found an odd notation/symbol that I cannot seem to figure out what it means. The symbol appears in section 14.7.5.2 "SCK Baud Rate selection" on page 14-34.

  SCK Baud Rate = SYS^f / 2 ¥ SPBR

I cannot get the formatting correct, the term SYS is "to the power of" f but the f is on the lefthand side of SYS in the manual. The rest appears verbosely.

I just would like to know what the ¥ symbol means in the equation.

EDIT: Screen cap of the equation


texts: I have a 24v DC circuit; I need a contact that breaks the positive line if the current in the negative line differs from the current in the positive line. So if the negative line has become broken or damaged and another earth is being found somewhere else in the system the power will be switched off.


texts:
Background of issue:
I have a LED lamp with 2 different modes and an on/off switch for each of these. There is a fan that's supposed to be cooling off the LEDs but is not functioning in 1 of the modes, so after taking the thing apart I found a small circuit board (illustrated in the attachment).

I have very limited knowledge in electronics but it's obvious the fan won't work for switch 1 since the wires are isolated and only the 2nd switch is connected to the fan wires through a bridge rectifier(MB10S).

Seems to me that the board was either set up wrong to start with or it's just wired incorrectly, and I'm trying to understand what's going on here.

What purpose does the bridge rectifier serve in this case ? Would it be an issue if I wired Switch1 directly to the fan wires ? Or is there a better way to make this work ?

**I have no idea what the L and N stand for, that's just how the board is labeled on the back.


texts: In what sense does the Laplace Transform give components of a signal in something called the 's-domain'?

texts:
Introduction.
This is a question raised not by me but some other engineer.  Unfortunately, by the time I got the question, there is already some answer.  Nevertheless, I take it as an opportunity to thoroughly review the roles of Laplace Transform play from basic analysis and synthesis to modern control Theory in terms of pole placement, pole zero plot, stability analysis.
Here is the original question from Math.SE by user Ryder Rude:

For example, I understand how this make sense for the Fourier transform. When we do the transform, we get 'how much of each frequency' in present in the signal. We get the value of the coefficients, such that when we multiply each coefficient with the corresponding constant frequency complex exponential and add those up, we get back our original signal. When engineers analyse the graph of amplitude squared in the frequency domain, they get the idea of how much of each frequency is present.
Is the same true for the Laplace transform as well? I know that Laplace transform is about getting "components" of a signal in terms of decaying complex exponentials, as opposed to unit magnitude complex exponentials in Fourier transform.
I haven't read much in detail about the inverse of Laplace transform. But its formula does not seem like we're summing up 'components times decaying exponential' over the entire s-plane. So what do we see when we look at, say, a colored graph in the 's-domain'? Is it really giving us the strength of the signal at each point in the s-plane? How is that true if we are not summing over the entire s-plane to get back our signal? Is this question clear?


texts: What is the theoretical minimum size of solar cells on wrist watches?

texts:
I was wondering what is the theoretical minimum amount of surface area in solar cells one would need to power an analog display wrist watch assuming the following scenario:

The watch's face has a diameter of 42mm.

The expected direct sunlight exposure is 3 hours daily.

The expected indoor light exposure is about 16 hours daily.

We can assume that the watch is an atomic watch, with classic rotating hour, minute, second hands to display the time.
There is a standard 5 year battery found on most wrist-watches.
 Edit: As far as power consumption goes, I couldn't find much. I was hoping someone might figure out the power consumption from the above info, but this is the best I could find on a google search:
"A typical watch battery has 30 mAh at 1.55 V, and lasts 5 years.

5 years = 43800 hours.

30 mAh / 43800 hours * 1.55 V = .001 mA V, or 0.000001 watts."

Not being an electrical engineer, I am ignorant of both electronic watch design, and the efficiency and specifics of solar cells. I have tried google, but did not find much on solar watch design.

I would really appreciate the answer in square mm, or better yet a percentage of the size of the face of the watch.


texts: How do I setup an SSH to remote into ARM using ethernet port

texts:
I am using the Xilinx Zynq 7000, on the TE0720-1 which is mounted on the TE0701-03 carrier board. I was wondering how do I set up an SSH to be able to remote into the ARM processor of the SoC to be able to transfer files and run commands.

I'm honestly not too familiar with SSH'ing just as a forewarning.


texts: What's the name of a connector usually used to connect a frontpanel to a PC mainboard?

texts:
Could someone tell me the technical name of this connector?

Visual description:

~2 mm thick (for one row)
6 ~ 8 mm long
~ 2 mm wide for each pin (e.g. 4 mm for 2 pins)
usually black housing

It may have 1, 2, 3 or more pins. Is there an upper limit?


texts: How I can solve this circuit with diodes?

texts: I tried to solve this circuit but without success.. Also is there any current flowing trough D3? and how this isn't short circuit?


texts: Are digital inputs of data acquisition devices differential or single ended?

texts:
I read that in almost all daq board datasheets the analog inputs are specified as single ended or differential inputs.

But the same daq have digital I/O ports. How can one understand whether the digital input is differential ended or single-ended. Or are the default one of them?

For example from a manual:

  16 single-ended (SE) or eight differential (DIFF) analog input
  channels

  Eight individually configurable digital I/O channels

As you see the differential or single input nature of the analog inputs are specified. But for digital inputs no information.

How is CM noise for a digital signal rejected ?

Which one of the opamp represents digital input?:

Edit:

The black is the pulse waveform below, and the red is the noise superimposed on it. So if the system were diff ended and inputs were diff ended the red CM noise would be rejected. But for digital inputs red will never be rejected since it is swinging between the thresholds?:


texts: Are there any design concerns that make an E12 switched socket infeasible?

texts:
Sorry if this comes across as a basic question, but this is the first place I thought to come and ask.

My wife and I have bedside lamps that have E12 40W sockets with inline switches. My wife hates the inline switch and we've been looking for an E12 switched socket online but cannot find anything at all to match this. It seems as if everyone selling an E12 socket expects the switch to be an inline wheel switch and I thought to ask if there is a particular design concern that makes an E12 switched socket infeasible or if we're just not Googling very well.


texts: Why do displays with auto-synchronization function get out of sync? (pixels blur)

texts:
I'd like to know why LCD displays that have the "Auto" button need it in the first place. Are they losing sync with the signal because of some special feature or all LCD displays really suffer from this (because I don't remember having that on CRT monitors)?

Or maybe the video card's signal changes?

My desktop PC has its monitor connected via D-Sub port and sometimes the screen gets blurry and I have to press "auto".

On my netbook, there is no "auto" button and the screen doesn't seem to ever blur pixels (I assume there is some kind of special connection between motherboard and display that doesn't have this problem).


texts: What Happens to Unit If We Divide Two Resistance

texts:
My question is very basic. I have a resistance circuit in which two resistances of 2 ohms are connected in parallel. I want to find the equivalent resistance. I know the equivalent resistanve will be

$$R_{eq} = \frac{R_1 \cdot R_2}{R_1 + R_2} = 1 \Omega$$

My doubts resides at the unit. My teacher says, the unit is ohm. But what we have done is a division. Since I perform division on same entity (in this case it is resistance), then it should become a unit-less quantity right ? But at the same time it is known as equivalent resistance. That means it is a resistance and hence it's unit should be ohm. This confuses me.

So my question is, what will be the unit if we divide same entity (say resistance) or it would be unitless ??

Note: Sorry for this basic doubts. But I really need an answer. If anyone can remove my doubt then that will be really a great help.


texts: What happens if more voltage hits your mobile phone charger?

texts: I am new here an i want to know that in the country i love AC voltage is 240 volts but sometimes it exceeds the limit. what happens if voltage like above 300 volts hits your mobile phone charger what would happen to it?


texts: confused about diode polarity vs circuit polarity

texts:
I know the anode has a + sign and cathode has negative sign. But are these signs reversed depending on how the diode is connected with the circuit?

In the above pic, in fig 4.2b, why isnt the - sign on the top and + sign on the bottom of the diode, since the cathode is on the top side? Also, what does -v indicate in fig 4.2b?


texts: What about water makes it destroy electronics?

texts:
From my understanding water shouldn't really damage electronics, but it does.
what about water actually causes damage, and why is water with impurities such as salt make it so much worse?


texts:
I'm trying to use the Xbee pro module underwater, more specifically the XBee3 PRO 2.4GHz.
I've been told that the GHz, and MHz frequency radio waves get absorbed by the ions underwater, and that I should use kHz waves. Is that true? If it is, then is there any other module I can use? Please note that I want the minimum possible latency, and the range to be at least 20-40 meters.
Also just out of curiosity, is there any module which can provide an underwater range of about 1-2 kilometers??
Edit: I want it to be in salt water at a depth of 60m... I am aware that it is highly conductive, and creates, a sort of faraday cage... But I've heard that low frequency RFs can permeate those cages... I meant to ask if there was any truth behind that statement.. and if so... Is there any module available in the commercial market for that kind of stuff? What will it's range be?


texts: Can a magnetic wire be used to extend/strengthen the signal coverage of a cellphone?

texts:
When i'm inside of our apartment, getting a cellphone signal is very hard, often times I wouldn't get any bar in my iPhone. My unit is in the ground floor and is surrounded by tall walls. My apartment has a small balcony (which is still surrounded by tall walls) where I can at least get a single or two bar signal from my iPhone.

This question was inspired by this video (https://youtu.be/pFx8tuSlCcQ) where a guy used some copper or magnetic wire to extend the range of it's mobile phone antenna. I'm aware that there are some repeater that are being sold but they're really expensive. I'm just looking for a cheap (below $10) solution that I can do or buy.

I'm planning to do a similar solution where I'll be extending some magnetic wire from the inside of my apartment to my balcony. But before I do that, I wanted to confirm if this idea would really work.

I also don't know where I will be connecting the end of the magnetic wire as iPhone doesn't have any external antenna port.


texts: estimate (measure) parasitic inductance of a lead frame of a chip package

texts:
UPDATE:
How to measure (/make a good approximation of) parasitic inductance of a lead frame of a chip package?

This parameter is very important at high frequencies (1GHz and more) because it affects power integrity. E.g. 10 mA current at 1 GHz flowing through 1 nH parasitic inductor causes voltage oscillation of 63 mV amplitude. Any additional 1 nH of parasitic inductance adds substantial power fluctuations (and it can't be bypassed by a capacitor, 'case inside the chip's package).

So, it would be nice to know how it can be estimated or measured.

I may simply rely on the manufacturer's figure (to be put into my simulator), but would be safer to double check it.

Addendum

Original title: how possible: inductance without specifying loop

Original question:

I came across multiple examples when inductance (usually parasitic) is reported without specifying a current loop.

Two examples:

MOSIS bond wire electrical parameters (URL, paragraph 14):
"Inductance of 1 mil gold wire of 2 mm length is 2 nH".
Formula for ESL (equivalent series inductance) of capacitors by Murata, URL:

.

In the both examples a loop was not specified.

How can they report inductance (ratio of magnetic flux though some contour to current) of something without specifying the loop (contour) first?

PS: Likely they assume some "typical" current return path but if so, it would require specifying additional parameters (e.g. for bond wire parasitic inductance  one needs to know PCB stackup heights, distance between chip's power and ground pins, etc. to draw the loop).


texts:
I'm having trouble diagnosing a faulty circuit. Here's the schematic, which is based on this instructables build. This is part of a bigger circuit, but I have tested it in isolation on a fresh board.

Link to the Eagle file (This is part of a bigger board, but hopefully this helps)

The purpose of the circuit is to drive 16 relays using I2C communication. I'm currently testing with an Arduino Mega. I'm using the MCP23017 for the 16 I/O pins, and two ULN2803ADWR darling transistor arrays to sink 5v on each G5Q-14 DC5 relay coil.

The circuit seems to be correct – I've gotten it to run a few times and the Arduino can successfully switch the relay. After less than a minute or so, pins 9 and 10 on the MCP (+5v and GND) start sparking and smoking. I've tested this on two PCBs meticulously testing for shorts between pins before turning it on - same issue. I also only encounter this issue once introducing the relay to the circuit.

I also find that pins 9 and 10 become connected after the sparking occurs. Not until I apply the soldering iron do they go back to being disconnected. Is it common that very close pins will bond when things get that hot?

I have no idea what's causing this short. Does it seem like a physical error or a circuit design error?

Note that:

In my circuit, the MCP is floating on A0 A1 A2 (address pins). Does this matter?
On my PCB, the MCP pin 9 (+5v) is connected after the relay coils (the trace goes from the +5v source, through each coil, then to the MCP). Could that be causing an issue?


texts:
I am using a LM395T transistor for an inductive load (a motor). The voltage limit is well within the 36V threshold. But current isn't limited. The specs of the transistor say that 1.5 A is maximum. Unfortunately the motor is big can drive up to 20 A of current.

Does the transistor have inherent current limiting ability? That will limit the input. Or will it get fried? Basically, do I need to change the circuit to limit current flowing through the transistor?

https://www.ti.com/lit/ds/symlink/lm395.pdf


texts: Would it be possible to construct a capacitor from clear tape and graphite?

texts: I read that graphene can be produced by attaching clear tape to graphite and then removing it.  This results in a layer of graphene on the tape.  If one were to take a very lone strip of clear tape, apply a layer of graphene, roll up the tape, and make suitable connections to wires, could a capacitor be produced?


texts: Non-clock signals routed into the clock tree


texts: Will switching a LED on and off at a said frequency reduce or increase heat loss?

texts:
In my case, a 50W 34V LED is being used to light a small box. To reduce heat generated by the LED, we are switching it on and off at 50Hz.

But I was wondering will this actually help? In the case of motors, transistors, and MOSFETS we have seen that it works the opposite way. Motors need an initial high current to start up. Transistors and MOSFETS operating at high frequencies heat up. So, does the same happen with LEDs?

Side question: What other components are affected by the switching the way motors and transistors are?

Thank you.


texts:
Hi friends i am trying step down converter using transistor.

Application:

Micro controller power-supply = 3.3 volt
Input battery supply range    = 10 - 13 volt
So i use BD139 for stepping down from 13 to 5v and the using 3.3v regulator.

Circuit works fine and i connected my controller. But the problem is BD139 is heating up-to "45-49 degree". My controller consume only 50ma current. But i don't whether this heating is normal or abnormal.