texts:
Assume a 5-stage pipeline is used in each of two processors P1 and P2. 30% of all executed instructions are branches. 60% of all branches are taken. Branch outcomes are calculated during the Decode stage (stage 2). branch penalties are the only source of stalls. Both P1 and P2 run at the same clock frequency.
  Assume P1 uses static branch prediction (and assumes NOT TAKEN); while P2 uses dynamic branch prediction.

  What branch prediction accuracy must P2 have in order to perform as well as P1?
  If the branch prediction accuracy for P2 is 90%, what is the speedup of P2 over P1?

For (1) I know that the delay for P1 can be calculated as (.3)(.6)(1), does that mean P2 needs to have an accuracy of 40%?

For (2) I know that speedup = Tslow/Tfast, so would it be ((.3)(.6)(1))/((.3)(.1)(1))?


texts: Cleanest method for measuring the reported speed of multiple computer fans?

texts:
This question builds upon this previous one How to interpret output of 3-pin computer fan speed sensor? which was asking about the 'sense' wire output from computer fans.

I am designing a fan controller for PWM fans (spec) that needs to monitor the RPM of up to 5 fans concurrently. In the past I've used interrupts on a GPIO port to build a basic tachometer for a small motor, however my concern is that this approach will not scale given that:

Each fan runs at a maximum of 2000rpm
The linked question suggests that there will be 2 pulses per revolution
If an interrupt is generated for each pulse to increment a counter then that works out at a maximum of 333 interrupts per second (2000rpm *5 fans * 2 pulses)

I'd appreciate any suggestions for how to implement such a monitoring system. Incorporating additional chips, etc into the design is not an issue. I will be working with Cortex M3-class hardware, probably an LPC1768 (overkill for a fan controller, I know).

Edit: Indeed, my original calculation posted here neglected to convert from interrupts/min to interrupts/sec. Sorry for the confusion.


texts:
I have designed a synchronous buck converter to step down a 17.4V voltage source to 12V at the output. I have attached the schematic as shown.
Problem: The Buck is not operating as expected at all. Here are the measurements I was able to get from testing it:

PWM frequency: 62.5kHz
Vg of M1 = 8.5V
Vds = 0.03V
VL (Voltage drop across inductor) = 17.37V
Vload {Voltage at the load) = 0V

First off, I cannot understand why I am only getting 8.5V to the gate of M1. I am using a half bridge gate driver with bootstrap topology, but yet the voltage I am getting out of the HIGH pin of the driver is just the 8.5V. And not to mention the fact that I am even getting a significant voltage drop across the inductor. I can't understand why that is so at all. I am thinking that the buck may be operating in DCM which may explain it, but I'm not so sure. Could anyone help me make sense of what could be wrong here?

P.S.(I have attached a copy of the datasheet of the gate driver showing how I have hooked it up. See page 2)
DRV_HI pin feeds into the gate of M1, and DRV_LO pin feeds into M2. C4 and C3 are both 0.1uF ceramic capacitors. Vcc is 11V, and Vin from the microcontroller is roughly 5V

I apologize, here is the URL for the sheet: http://www.onsemi.com/pub_link/Collateral/NCP5111-D.PDF

simulate this circuit – Schematic created using CircuitLab


texts: Low power way to switch on MOSFET with ~100mV input singal?

texts:
Is there a low power (single digit uA's quiescent) technique to switch on a MOSFET when an input signal rises above ~100mV (too low for direct gate drive)?

You can buy ICs like the MCP6548 that functionally accomplish this, but I am looking to do it with discreets.

I am thinking there might be a way to bias a MOSFET gate so that the 100mV falls right in the transition region, and triggers positive feedback loop to throw it in to full active region, but I can't figure out how to do this.


texts:
I want to measure the amount of light striking a photodiode in a specific time window (about 1ms). In this window, we get \$10^6-10^7\$ photons, which get converted into electrons with about 80% efficiency.

The standard method of performing this measurement is to use a transimpedance amplifier to convert the current into a voltage which is then sampled rapidly throughout the time period and integrated. However, there are lots of places for noise to creep in. Each of the measurements is quite noisy, and this get integrated up.

I was wondering if there was a more accurate method of measuring the total charge produced in this window?

So far I have been considering something like an analog CCD:

A capacitor is used to store the charge.
When the time window is over a digital signal can isolate the capacitor from the photodiode
The charge on the capacitor is then measured, by some method I haven't thought of yet

If anyone has any advice I'd love to hear it. Essentially, I currently have a noisy measurement of the current over time, which I would like to trade for a more accurate measurement of the total charge produced.

Edit:
As some context, this question was brought up when I realised that a single-pixel CCD would actually do this job much better than a photodiode. They can have large quantum efficiencies and read noise in the 10s of electrons. Sadly, single-pixel CCD's don't appear to exist, as far as I can tell. (Also, the dark current is a little problematic, but you can always cool them down).

An avalanche photdiode (or photomultiplier) might also be better suited, but we're trying to avoid high voltage.


texts:
I'm designing a PWM output for a DC motor and I'm using
TL494CN chip.

It got two error amplifiers and one feedback. I can't understand why there
are error amplifiers and a feedback there? What does that error amplifier do
in there? I can't figure out.

And I have reviewed some motor driver circuits, like this one

I can't figure out why he connected reference voltage to error amplifier IN- pin?

Is that error amplifier gives a unity gain? Is that what it mean?


texts: What happens to the backup time when batteries are connected in series?

texts:
I have a backup power system consisting of a charger, a battery and an inverter. The inverter powers my load (a few mains appliances). Currently I am using a 12V 200 Ah battery which gives me a backup of say 2 hours for my load.

I am upgrading to an inverter that requires 24V, so I will need to use two batteries in series. To save on the cost of the batteries I am thinking of buying two smaller batteries so that it costs me the same as the larger battery I originally had.

My question is: If I use two 12V 100 Ah batteries in series, will I still have the same backup time (2 hours) for the same load?

I am confused about this because from what I remember connecting in series will only double the voltage and retain the rating at 100 Ah, however what is the benefit of 24V, should that not translate to the same backup time since at the end of the day the load consumes the same power?


texts: How do you use low-power mode on an MSP430G2553 using an Energia sketch?

texts:
I am using an energia sketch to program my MSP430G2553 controller. I need to know how to use low-power mode. Do I leave the loop section of the sketch empty and  set up an interrupt in the setup section? Or is there more to it than that? How do you turn low power mode on and off?

UPDATE:
I've discovered 2 things regarding low power mode:

sleep() puts you into LPM3
sleepSeconds puts you into LPM3
suspend() puts you into LPM4


texts: Can I use AA Duracell non-rechargeable in parallel?

texts:
I have never used non-rechargeable AA Duracell in parallel. I now have an application where I am forced to use batteries.

To increase battery capacity I am thinking of connecting AA Duracell in parallel for Arduino MCU Project.

I have seen rechargeable cells in parallel, but not conventional.

What happens if I connect non-rechargeable batteries in parallel?
Will those batteries charge each other?
Will they explode?


texts: Do I power a stepper motor with 24V and Arduino?

texts:
I am building a motorized barn door tracker using an Arduino UNO and a stepper motor I took from an old scanner (Mitsumi M35SP-7T). I have been unable to find the datasheet for this motor specifically, only that the motor has a 140 Ohm mark on it and that I assume it should be powered from 24V.

I was planning on running the system with the Adafruit Motor Shield which claims to power motors up to 25V, but I am having difficulty finding a power supply that can push 24V. Frankly I am also concerned that I shouldn't even be using a full 24V power source, but I'm not sure that feeling is justified.

Any recommendations on power configuration for this setup? If I should be using a 24V power source, what kind of source is recommended? This was the only datasheet I could find that came close to this stepper motor: http://vinvin.dyndns.org/projects/M35SP-7T.pdf

On a related note, on the Arduino forums, it looks like someone else was trying to use the exact same stepper motor with a 24V power source: http://arduino.cc/forum/index.php/topic,13711.0.html

Thanks.

UPDATE: It seems that the scanner itself ran on 12VDC 1A. Not sure how that might affect this situation. I just need to be able to run the motor with as much torque as possible.


texts: MIDI - clockless serial with TI MSP430 MCU software?

texts:
I'm planning to make a small MIDI transport box ( an encoder plus 6 buttons) but i don't have a lot of experience in serial communications( I have used shift registers but that's all) I would like to implement it in software because the device i'm using have no serial peripheral.
I tried to look at software examples on the net , but i didn't find anything that would make everything clear.  I'm planning to use a TI MSP430G2201.

Could someone help me understand how to transmit midi data? with something like pseudo code.

I know what i want to transmit, that part is clear, i understand how MIDI messages work, but i don't understand how to set up protocol for midi.


texts: Difference Between B330, B330A and B330B?

texts:
What is the difference between B330, B330A, and B330B?
I read the datasheets but I couldn't notice the difference.
I want to use it as a freewheeling diode for a DC-DC converter with 12V input, 5V/4A output.
For the selection of the Schottky diode  \$I_F\$  should be greater than 1.66A and the power dissipation equal to \$\mathrm{P_D=1.66A \cdot 0.5(V_{dropout})=880 mW}\$.
I didn't find the power rating for B330B (I intend to use it), B330A that why I am asking for the differences.


texts:
How can we calculate the breakdown voltage of a BJT in ADS?

Is it Possible or not in ADS?

Problem:- I have a ADS BJT model. I am using that to generate high voltage output. For that i need to bias the transistor as class C amplifier with biasing volatge 10 V to get the distortion less signal (In ADS, Collector output voltage without coupling capacitor is attached).

My input signal is Gaussian in nature with voltage swing 0V to 8V. I am getting my output in ADS environment but don't know whether it will work or not?

How can will I be sure that my design will work properly if realized?

Thanks


texts: Maintaining a constant current with varying loads

texts:
I've designed a constant current source using a current mirror, we need an output of about 50mA. The problem is that we build it and heat has become a problem.The transistors and the R_load are both heating up which decreases beta stabilization (our amperage through our load resistor increases constantly).

I think that by adding an emitter resistor we should be able to beta stabilize but I'm not sure if I'm doing it right.


texts: Is there a reason IC in the DIP package seem to have a very high propagation delay and so a very limited admitted frequency?

texts: I scrolled through Mouser and I noticed that when you search for ICs with very low propagation delays there are only IC avaible in packages quite hard to use for an hobbyst/noob like me with very limited tools.


texts:
I am building a device on the AVR platform. The device will need some timing information, so I was thinking of reimplementing Arduino millis-like functionality (though not exactly like this). However, after doing some back of the envelope calculations (partly based on this post), it started to appear to me that millis eats up at least 5% of the CPU time on a 20Mhz processor, and proportionally more than that on a 16Mhz one:

Each millisecond, the timer (timer0) overflows, triggers an interrupt, which increments millis
An ISR should take 26 clocks for pre/post ISR routine (5 PUSH + POP plus CLR, IN, and RETI
The ISR itself should take about 21 clocks (load 32-bit value, increment it, and store it back in SRAM)
This yields almost 50 clocks, or 50 microseconds each millisecond.
In fact, Arduino ISR function is slower than that (as revealed by this post) because it is really careful about keeping millis as accurate as possible, which takes more CPU cycles still

I don't need millis precision, so I am considering implementing centis or even decis to save processor cycles for other stuff. Is this unreasonable? Are my calculations wrong?  It would seem like an odd design choice, or am I missing something?


texts: How to apply high gain to filtered signal without shifting voltage level?

texts:
I have an op amp gain circuit at the output of a 2 stage filter. It seems like at high gain settings (x500), the steady state voltage shifts significantly. I am trying to keep it at ~1.7V and it shifts close to 3V after the amplification stage. In some circuit designs I see the amplification stage between stage 1 and 2 of the filter. Does that keep the voltage from shifting up? How can I keep the voltage consistent while also having high signal amplification?
Thank you!


texts: Are the non-metallic colored heat sinks of transistor packages electrically isolated/nonconductive?

texts:
When I look at transistor packages, I see two different heat sink types. One type is in metallic color, the other type is black plastic colored.

I read datasheets of some components, none of them mention about electrical connection of their heat sinks. Is there any standard about electrical connection of plastic-like black colored heat sinks? Can I place several transistors with that kind of heat sink on the same heat sink plate without any additional electrical isolation?

Example of TO-220 transistors with metallic and non-metallic heat sinks:


texts: I attached split the end of a USB  wire and attached a switch. When I press the switch, I measure 5V from the port, but am only measuring 33mA. Why am I getting only 33mA instead of 100mA?


texts: VHDL Error: Coudl not Implement register on this clock edge

texts:
I want to reset the variable v_count to 0 at the rising-edge of input
port i_pulse_run. But I get the following errors:

  Error: Could not Implement register on this clock edge.
  Error (10821): HDL error at PWM_Gen.vhd(85): can't infer register for
  "CTRL:v_count[15]" because its behavior does not match any supported
  register model.

How else can I reset the variable to 0. I want to reset it only at the
rising edge of signal i_pulse_run.

Any suggestions are welcomed.
Thanks

LIBRARY IEEE;
USE IEEE.numeric_std.all;
USE IEEE.std_logic_1164.all;
..
..
..
CTRL : PROCESS(i_Reset, i_Clock,i_pwm_pulse_run)

variable v_PWMout        : std_logic;
variable v_intPWMvalue    : integer range 0 to 8192;
variable  v_updatePWMvalue  : std_logic;
variable v_count : integer range 0 to 65535;

begin
if i_Reset = '0' then
  -- Asynchronous reset
  o_PWM        <= '0';
  s_PWMCounter     <= 0;
  v_updatePWMvalue  := '0';
elsif rising_edge(i_Clock) then
-- Increment the PWM counter

   if s_PWMCounter < i_PWM_Freq_Div - 1 then
      s_PWMCounter   <= s_PWMCounter + 1;
   else
      s_PWMCounter   <= 0;
      if rising_edge(i_pulse_run) then
          v_count := 0; -- Error
      end if;
      if i_pwm_pulse_en = '1' AND  v_count < i_pulse_count +1 then
         v_count := v_count + 1;
      end if;
end if;

..
..
end if;
end process CTRL;


texts: Why does the LLC converter have an Lm inductor? How does it interact with the LC circuit?

texts:
Task: to understand why the LLC converter has Lm inductance and how it interacts with the LC circuit.
What I learned:

LLC converter circuit:

The LLC converter is a DC to DC buck converter (transformer n >= 1).
Cr, Lr, Lp(Lp) - form a resonant tank.
Since the resistance of the inductor increases with frequency and the resistance of the capacitor decreases, at the resonant frequency the resistance Cr, Lr is 0.

I introduced the LLC converter as an equivalent controlled voltage divider (X1 - Cr, Lr and X2 - Lm, Rload). That is, there will be a total voltage drop at the resonant frequency at X2.

I checked this circuit in the simulator.

When I input a square wave 230..0VDC at the output, I get a sinusoid +115..-115VDC (at the resonant frequency).

By removing the Lm inductance, the signal has changed slightly (seen at the very beginning). The output is also about + -115VDC.

I learned that Lm is a magnetizing inductance and most likely it provides a higher current stability at the output of the converter.
Questions:

What role does Lm provide?
The resistance of Cr, Lr at the resonant frequency is 0Hz. Will Lm interfere with this behavior? Otherwise Cr-Lr = 0Ω, Lm has resistance.
Is Lm a separate inductor or is it usually already in the transformer design?
Additional question (if you can answer it)

The LLC receives 230VDC input.
Transformation ratio n = 2.
This means that at the resonant frequency the output of the transformer will be Vin/2 = 230/2 = 115V.
Will it be effective if this divider factor is changed by increasing the frequency?
That is, I will lower part of the output at the divider, and the rest at the transformer.


texts: Can I only use one 12V DC power supply for two solenoid valves? I got connect the solenoid valves with a 5V 4 channel relay module with arduino as my microcontroller. Each of the solenoid valve is 12V, 2A. The power supply i using is 12V 2A, and i also got connect each valve with 1N4001 Rectifier Diode.


texts:
Does anybody know how I would make a soft foam sword detect a hit on a vest? This is for a dueling game, sort of like fencing, with nerf weapons. I'm hoping to eventually create a system using an arduino.

These are some sensors I've looked into already but I haven't found enough similar projects to know for sure that they would be appropriate:

Membrane relay switches
this would require no hardware in the weapon. Can detect the intensity of a hit. but it could be detected by any kind of contact, even a crinkling vest.

Magnetic contact switches
Magnets inside of the sword would be detected when in close proximity to the vest. would make the weapon heavier, possible need for wiring between weapon and vest, difficulty getting the magnetism through a foam weapon.

Voltage Divider
foam sword needs a conductive material. Possible electrocution. Possible need for wiring between weapon and vest.

Frequency generator & microphones
Emit a supersonic frequency that is detected when in proximity of the vest. Difficulty getting the frequency through a foam weapon, possibility of water damage to microphones. Interference between many people using the same process.


texts: What might be the cause of high pitch sound coming from a switching regulator circuit?

texts:
We designed a switching regulator circuit using a 1.5MHz, internal-switch, switching regulator (semtech.com/images/datasheet/sc185.pdf). Vin is 5V, Vout is 3V3. We have an input capacitor (47uf), an output capacitor (47uf) and an inductor (1uH). The problem is that we hear a high pitch sound coming — presumably — from the inductor when we turn the system on. It appears that the sound is more noticeable when the circuit is drawing very small amounts of current. As the current demand increases, the sound usually becomes unnoticeable, but not always.
Any ideas what we might have done incorrectly? Is there any other information I can provide to be more specific? I've looked at the regulator output, just before the inductor, and I see some ringing, but I can't tell whether the ringing is normal or not.


texts: What to do with transistors I had desoldered from TV

texts:
I am a beginner in electronic design and want to learn about transistors.

I have an old TV and I decided to de-solder the following transistors.

Can you tell me what I can use them for, are they all the same, and if anyone has some literature where I can start, and some schematics if possible?

Here are the part numbers for the transistors I have de-soldered.


texts: Sending Voltage is higher than receiving voltage: Parallel Load Problem

texts:
I had a problem on an exam which reads as follows:

At the end of the day, I got that the sending end voltage is lower than the receiving end voltage, which I know isn't possible. I think I may have approached the problem the wrong way. But it is somewhat possible that the question just has incorrect/unworkable numbers. I know that in the original problem I have the sign of the third power angle wrong, but even when I change that the sending voltage is still lower than the receiving voltage. Here is my work:

Any help would be greatly appreciated.


texts:
I'm given a task to design a 4-bit register using D Flip-Flops (and MUXes) that operates according to the following selection inputs:

When..

S1S0 = 00, No Change;

S1S0 = 01, Register is Cleared to 0;

S1S0 = 10, Current State is Complemented;

S1S0 = 11, Parallel Data is Loaded.

Below is what I've made, but I'm not so sure if I've implemented it correctly.

Could you correct me if there's anything that's incorrect or that I should improve?


texts: DC Power supply, current and voltage are independent of each other?

texts:
This might be like a stupid question? But how come, in DC power supply, such as this one, you can set 5 mA, and 25V?

Shouldn't it be either just current or voltage? And then you only connect one wire to the circuit.

Say you connect this power supply to proto-board, and you simply have one resistor of 1k -> GND.

Does it mean there's gonna be 5 mA flowing in this simple circuit? or by ohm's law: \$ \frac{25V}{1K} = 25 mA \$

??

Am I missing something? But doesn't voltage in itself has the idea of current? Like if you have 25 Voltage you can't have no current through a resistor?

Yet you can set 25V and 0mA on the DC power supply linked above.

And also another related "stupid" question, in solar panel

  When the cells are exposed to sunlight, photons from the sun interact
  with electrons in the upper silicon layer, basically knocking them
  loose from their associated atoms. The loose electrons are attracted
  to atoms in the lower layer of silicon and travel through the wire to
  get there. This movement of electrons from one side of the cell to the
  other through the wire is electrical current.
  (c)

So the electrons never leave the solar panel, hence, no current can flow out from the solar panel! So solar panel only outputs voltage? But if you have a wire from the solar panel, and that wire is connected to some circuit, can't that circuit draw current from solar panel? I mean, if output of solar panel is some voltage, then by having a simple resistor the circuit can make the electrons flow towards the circuit and away from solar panel, no? Explain!


texts:
I have a probably obvious question about powering single phase loads from two legs of a 3 phase supply and how this impacts current draw calculations. This is something that is commonly done in my job (entertainment lighting) but in thinking about it today I have run into some confusion. The system I am working with is commonly 208v/120v 3 phase in Wye configuration.

208v * 200A * 1.732[sqrt(3)] gives me about 72,000 VA theoretical power output of the service. If I were to connect 200A of load on each leg to neutral (120v) I would be pulling 72,000 VA. 200A * 120v * 3 phases = 72,000. Firstly, is my thinking here correct? I understand not to think of this system as delivering 600A.

Now on to the real question. Say I am trying to figure out how many lights (dual voltage for 120v or 208v), that draw a resistive load of 1200w, I can power from the service. At 120v, this load is 10A. So therefore on this system I should be able to power 200A / 10A * 3 lights, or 60 lights. Now, the way I have been calculating and have been taught to calculate the load for 208v is by simply using ohm's law. At 208v, these should draw 5.77A. However, This only lets me power 200A / 5.77A lights, or 34.6 lights. If I instead calculate the current as 1200w / 208v / 1.732, I get 3.33A per light, which works out as 200A / 3.33A = 60 lights. Is it correct to apply the 1.732 figure for the difference in phase angle when using an unbalanced wye configuration and powering these effectively single phase loads from two phases?

Thank you in advance!


texts: Door lock relay needs higher amperage - what relay to use?

texts:
I have a door lock that requires 12VDC 750mA to get it to unlock, then it drops to 350mA to keep it open.  My door controller has a max load of 500mA, so it won't work connected directly to the door controller.  I have a power supply nearby that has the available load to unlock the door, but I am unsure what kind of relay to use so that when the door controller outputs it's 12VDC, the relay closes and supplies the power from the nearby power supply to the door lock?  I'm looking for something already mounted to a board with screw terminals for connecting it up.

Thanks!


texts: What's the difference between minimum feature size , transistor gate length and half pitch?

texts:
I've been looking into the limits that silicon based transistors. During this I've come across several terms describing the small size of a transistor, minimum feature size and transistor gate length are the most common, they seem to be used interchangeably.
Another term used is half-pitch, half of the distance between two identical components. So what is the exact difference between the three terms, and which one is the most descriptive of the size of a transistor?


texts:
I'm working on a samc21 and using the fat libraries provided in ASF.
I have a program that takes from serial information and has to write to an SD card. The amount of bytes its around 50KB.
I'm using the internal oscillator (48MHz).
The problem is that the write operation is extremely slow, like 5 seconds every 1KB of information.
Do I have to change the oscillator, or fat is always going to be that slow? I mean, when I write to the SD card from the computer it takes like a second.
Please help.
Where do I configure the SPI speed?


texts: Our GPS trackers on our dogs were broken over the weekend and upon analysis I found some pins that were removed from the chip.  It appears that there was some type of adhesive glue holding them onto place, but don't know what kind/type to purchase to attempt to repair.  I'm not even sure if these are the correct terminologies, so looking this up is a bit difficult.  Does anyone have any pointers as to what the adhesive was holding these onto place?  They weren't soldered.  It was like it was glue?


texts: When is the concurrent signal assignment executed?

texts:
Having the next code:

library IEEE;
use IEEE.std_l0gic_1l64.all;
—— entity
entity t_ff_s is
   port ( T,$,CLK : in std_logic;
          Q       : out std_log1c);
end t_ff_s;
—— entity

architecture my_t_ff_s of t_ff_s is
   signal t_tmp : std_logic;   —— intermediate signal declaration

begin
   tff: process (S,CLK)

   begin
      if (S I '0') then
         t_tmp <= '1';
      elsif (rising_edge(CLK)) then
         t_tmp <= T XOR t_tmp;   —— temp output assignment
      end if;
   end process tff;

   Q <= t_tmp;                   —— final output assignment
end my_t_ff_s;

I understand that the "process" and the "concurrent signal assignment" are executed concurrently and due that "Q" is an output port it can't be put at the right side of the "<=" and that's why the signal "t_tmp" it is being used to be able to do the XOR operation. My question is at what moment is the "Q<=t_tmp" executed? Is it done immediately after a value is assigned to the "t_tmp" signal at any point within the process statement? Or is it done at the end after all the lines in the process statement are executed?

In the answer of this post VHDL - How does a process run concurrent with other processes and components while it executes sequentially? I read that "it is said that the signals retain the last assignment is a process" so I think that the assignment is done at the end of the process regardless of how many times a different value is assigned to "t_tmp". Am I correct?


texts: Building a 2 bit comparator tips and tricks with truth table

texts:
Build a 2-bit comparator using either two 74151 8-to-1 MUXs or two 3 to 8 binary decoders. Additional gates such as AND, NAND, OR, NOR, inverters can be used.
So I got this question while coming across, and I would like to seek some advice/tips for these types of questions.

Assuming I want to try and build using MUXs, I will get the truth table of both a 2 bit comparator and MUXs.

In this case: For comparator:

And for MUX:

So from what I learned, MUX simply selects 1 input to be the output.
Are there any tips/tricks on how to start with this question by possibly comparing the outputs? How should I be thinking to tackle these types of use 'something else' to build 'something' questions?
Thanks


texts: LM311 Circuit only works when probe is attached

texts:
I'm trying to put together a circuit that takes a signal from a sensor, cuts out the negative side, compares it to a reference voltage and outputs a digital 1 when above the reference voltage.  That signal will get read by a microcontroller that does some timing manipulation (stays high for 5 seconds after last pulse received) and output to a relay.  My issue is with the comparator.

I can't figure out why my circuit only works when I have a probe attached.  I am putting a 6v peak to peak sine wave on my input jumpers.  I'm using a 2 channel oscilloscope, one channel attached between AC1 and AC2 and the other between ground and the output from the comparator (LM311).  The circuit works as expected when I have the probe attached to the output from the comparator (the ground disconnected doesn't affect it). But as soon as I detach it the output goes and stays high.

I've tried different values of resistors for the pull up (5k, 10k, 20k).  Other forums I've read about circuits only working when a probe is attached talk about the scope adding a little capacitance, so I tried adding a capacitor (0.1uf) between the output and ground which didn't do much.  I also tried adding a resistor in series between the rectifier and comparator and still no change.  Any help would be greatly appreciated!

Also my input signal is basically a +/- 12ac single cycle burst.  Not mains power.


texts: I need help understanding something from a RL circuit problem.

texts: In the below example, why is the voltage source shorted for t>0, and why does it say "the 6-ohm resistor is shorted" in the paragraph about t<0? Isnt it open circuit there?


texts:
I built an RGB LED strip controller with a Wemos D1 mini, using this schematic:

On the phone I have a color picker and just roll over it and the LED color changes accordingly, but sometimes I hear a whining noise (not from the 5V regulator, but from the power supply) and another strange thing is when I measure the voltage between red LED and 12V (I get something around 5.6V) but I should measure 12V, because this is what I measure on green and blue LEDs. I measure this value even if the code from arduino IDE is "analog write 255 -> RED LED, and for GREEN and BLUE is 0".


texts: How to determine capacitor values for common emitter amplifier?

texts:
Looking at this circuit:

I understand that the two capacitors are used to filter DC.

I don't understand how it is possible to know what values (in terms of farads) would be required for these.


texts: Power line communication by inducing a signal into a wire

texts:
I would like to make a small board with a simple MCU that just repeatedly sends a message via a modem on one end of a power line wire (14awg or so). On the other end will be a similar device for reading that message. The only requirement is not interfering with/cutting the wire or isolation in any way. There will not be access to a plug or any way to directly tap into the line like PLC home networks do. The device will be powered from an external source (3.3 or 5V).

I've done some reading on this topic and the ST7540 seems to be a good option, in my case I would not need to filter out the 50/60Hz because there would be no electricity on the line. I am mainly uncertain about the induction, possibly using some kind of coil around the power line. What I basically want is to use the power line wire as an antenna between two modules (approx 3m or 10ft apart). I can't use full wireless (315MHz for example) for various reasons.

What is the best way to inductively transmit data (only one direction is needed, tx to rx) over a power wire that has no voltage/current and what kind of parts would be required? Are there modems specifically made for something like this? I remember reading about something similar being used in under-water applications in the past.

Hypothetical example: There's a 2-lead mains wire permanently plugged into an outlet in my room. The wire leads to the next room and it powers a lamp with a switch (relay). I can't go into the next room. I want to induce a modulated signal into the mains line by means of a transceiver/MCU while the lamp is off (no voltage/current in the mains wire), the signal goes through the mains wire, which acts as an antenna. There's a receiver/MCU on the mains line in the other room, which reads the signal inductively and turns on the relay, lighting the lamp. I do not want to physically manipulate the mains wires in any way, but also can't use a regular RF link (I know this could easily be done wirelessly).


texts:
Regarding AC systems (like for homes and such), a circular path is called a parallel conductor. It's illegal (according to the NEC section 310) except under certain circumstances. But I have noticed that with DC circuits, circular conductors are also... taboo (for lack of a better word). See the picture below- just for example (there are probably better examples, so if another example is better for illustrating the problem or answer please, show and tell).

My question(s) is basically, what's wrong with a circular/parallel conductor?

Also, just for clarity, here's a picture of an illegal circuit (per NEC):

Edit- as a follow up to some of the comments below, I happen to have seen the LED circuit mentioned above. I currently have one similar PCB (sort of a poor example, pictured below, because the excuse for not connecting the rings could be that there is a conductor in the way) but I have seen another PCB without any excuse for not completing the ring, so I wondered why it was not connected.


texts:
Please Note by multiply I don't mean  11 * 11 = 11 But I mean 3*3=9 which is 1001 in binary
I am interested in knowing the following about multiplying numbers:
Let's say I have two 32-bit numbers like this:
A0 * 0B where A,B are 16 bits and 0 is 16 bit zero vector, then How can I perform multiply of these two numbers if I have only 16bit multiplier and 0/16/32 shifter?
For example let's say I have 10101010101010100000000000000000 * 00000000000000001111111101010111 How can I use 16bit multiplier here?

In case I have 0A * 0B then I use what I have to multiply A & B which gives 32 bit answer and I don't need to do anything about it.
In case I have A0 * B0 then I use what I have to multiply A & B which gives 32 bit answer that should appear at the most left so I use shift by 32 bit (the bits moved are filled with zeros)


texts: What software is generally used in industry to design cases for pcb boards?


texts: Is there a header pin connector with the pins in the same board plane?

texts:
Is there a standard pitch male header pin with pins in the same plane as PCB? My goal is shown on the figure in principle, with edge mounted pins. I would prefer a header connector, but accept single pins if that's the only solution available.
Seems like a simple requirement to me (it's saving space), but I haven't seen them.


texts: Can any MSP430 be programmed with a 4-wire JTAG?

texts: I am a senior in college and am designing a board based around the MSP430G2744IDA38. I have used an MSP430 launchpad but that was an easy USB connection to program. I notice that a JTAG can be used to program/debug chips so my question is really if all I have to do to program a chip is put a 4 pin pinheader on my board and connect VCC, GND, TEST, and RST pins? Or is it more involved than that and im just not seeing it?


texts:
I'm trying to use an RC oscillator on a PIC 16F84A-20 that I have on a breadboard. The code is supposed to (at this point) simply flip an output back and forth every so often.

I don't need it to run very fast, so I figured I'd try using the RC network on CLKIN instead of a crystal. My problem is that my code doesn't seem to be running consistently (I get some LED flashes for a few seconds, then nothing, then perhaps more flashes, etc).

I'm working on a plug-in breadboard. I've got +5 provided by a PIC dev board I had handy.
+5 is reading 4.94 volts via my DMM.
I used a 4.7K resistor from CLKIN to +5, and a 33pf cap to GND.

I put an o-scope on CLKIN, and I see a sawtooth-ish wave of about 2.5Mhz, but I also see some other, longer waveform in the background, if you will (it's far fainter than the sawtooth). it's a much wider, slowly decaying pulse. The sawtooth wave is, unfortunately, only about .2-.3 volt high, and centered between +5 and GND.

I put the scope on CLKOUT, and in the instances where I'm seeing my LEDs blink, I've got a nice squarewave on CLKOUT. Other times it's just flat.

My assumption is that I've made some basic error with the RC circuit that's causing it to not generate a sufficient waveform, and thus not work. I'd like pointers to what I should be checking next.


texts: Using li-ion battery in place of a lead acid one in a desk lamp

texts:
I have a rechargeable desk led lamp with USB power input. Although it's supposed to hold charge, it only works when plugged. I opened it and found that the problem is about included lead acid rechargeable battery.

I cut out the broken battery and connected a li-ion 3.7v in its place that I got from an old broken cellphone.

Lamp lights up just fine now but I'm afraid to connect the lamp to a power source since li ion and lead acid are different type of batteries. Am I creating a potential fire hazard or is it fine?


texts:
http://www.cheemi-tech.com/product-current-transformers-CMPT107.html

Voltage between B & C is 119V which is equal to 1.19mA but input current between A & B is 14mA. Why is it so?

Edit: In the common perforated board, unused parts are blurred

Edit 2: Let me assemble the circuit in another board and shall post the details. 05june18


texts: How to use the oscilloscope to show the average of the DC current?

texts:
Recently, I made a buck-boost converter.
The figure shown below is the input current.
The input is a DC current (I used the programmable DC power supplier).
The frenquecy of the buck-boost converter is 20kHZ.
As you can see, the input current is not stable as a straight line.
In fact, it increases and decrease in every period of 50us.
The Max and Min current is about 3.97A and 3.2A.

However, when I zoom out the waveform to 2.5s time scale, the waveform is shown as below, which is not what I want.
I think this waveform is exactly same as the waveform at the 50us time scale.
The waveform that I supposed should be a straight line at 3.7A, which is the average value of the input current.

The protype of the buck-boost is shown as below.
And you can also see the current probe.

The oscilloscope that I used is TDS2024C.

I think the way that I used the oscilloscope maybe wrong.
Therefore, my question is how to use the oscilloscope to show the average of the DC current.


texts: In FPGA world, what exactly are false path constraints for an HDL compiler? Why are they useful?


texts: What does an Impedance of a transformer mean?

texts:
If Impedance is given as following,

Center Frequency : 455KHz

Pri = 60KOhm

Sec = 600Ohm
Inductance = 680uH

Tuning Capacitane = 180pF + 5pF(ext.)

What do they mean?

Do they mean impedance at 455KHz?
Then, Shouldn't primary impedance depend on the inductance? which is 680uH which gives 2*pi*455KHz * 680uH = 2KOhm?

Datasheets for transformer


texts: What precisely thermal equilibrium implies in case of a semiconductor. One thing I know is that Fermi Level remains the same. But what other things does this implies, is there net current flow in case of a thermal equilibrium?


texts: Can I parallel charge with parallel batteries?

texts:
simulate this circuit – Schematic created using CircuitLab
My Ebike uses a 70 pack of batteries 18650, 10 in series to make 42 volts with 7 parallel batteries per series. One parallel row registers zero volts after a winter of not being charged, I also suspect that the motor control has a small drain even with the key on the off position.
And I'll be attempting to get that row to hold a charge again.
I've seen tutorials where you can take a dead 18650 battery and make it able to take a charge by jump starting it with a good 18650 battery by parallel charging.
Since the batteries are spot welded I will disconnect the BMS(battery management system) and try to parallel charge a parallel row with good 18650 batteries.
But I seen it done with a 1 good to 1 dead set up but can I do that with multiple parallel batteries? Or is that dangerous or even pointless?
If all goes well every row will have a charge to give the BMS the input it needs to charge the pack and see if it works.
[UPDATE] I tried this setup and the wires were getting (can't hold on to them) hot. The volt meter when charging reads .7 volts still not getting a reading after 4 * 10 second charges.
Batteries stay cool on both sides tho.
If all fails I will have to tear apart the row and figure how to safely solder them back together.


texts: Texas Instruments TPS57160 Enable Pin via P-Channel Open Drain Output

texts:
So I have a module that supposedly has a P-Channel Open Drain Output (INH on Infineon TLE6251-2G) and I am trying to interface that with the EN (Enable) pin of the Texas Instruments TPS57160-Q1 Step Down Converter.

The TPS57160-Q1 activates if the EN pin is at a voltage above 1.25V and has a "pullup current source" (whatever that means) in order for it to be activated when the EN pin is left floating.

Now the TLE6251-2G's INH active output (means the Step Down converter is to be activated) is VS=36V in my case. When the output is "disabled", the INH is left floating.

Now the question is: How can I interface the two pins? I only have the 36V rail and GND available and it should be ultra low power in the disabled state.

If I add a pulldown resistor at the INH pin and connect that to the EN pin of the TPS57160-Q1, I should have it properly disabled but I exceed the absolute maximum voltage rating of the EN pin by far. (36V vs. 5V)  To get around this, I thought of a simple voltage divider to get the voltage to a healthy range. Furthermore, I don't really know how the TPS57160-Q1's EN pin reacts to a pulldown resistor with its "pullup current source" (This is my main problem in creating a proper interface)

Thank you in advance!


texts: DDR3 skew matching for microstrip and striplines

texts:
I am designing DDR3 pcb first time so I started from guide about pcb design:
https://www.youtube.com/watch?v=ZNq_Ulm8cTk#t=32m
As I understand using only stripline highly recommended to avoid skew between signal passing top/bottom layer traces and inner layer traces, e.g. using only inner layers recommended to trace DDR3 signals.

But I have to use top and bottom layers to fit in 6 layer PCB. I am using Altium that can match traces length but without differentiation of used layers. So I don't clearly understand is time of flight of signal relative to impedance of trace? E.g. can I avoid worrying about used layers just by using different trace width  depending on a layer to keep required impedance so by achieving matching signal lengths I will match signal skews?


texts: Which way should this capacitor go on this circuit?

texts: Which way should this capacitor go on this AC Hysteresis Synchronous motor circuit? Which terminal is CCW and which is CW?


texts: Why does an audio DAC possess deemphasis hardware

texts:
The CS4334 data sheet states that the deemphasis hardware is enabled if external SCLK (used to latch I2S data) is not used and the pin is grounded.

I want to know, what is deemphasis in context of audio and why is it needed in an audio DAC. In other words, why would audio data be preemphasised to begin with and when?


texts: I have a question about SPI line. I have seen in several circuits that an RC filter (R in series and C is between the MISO line and ground). Does anyone know the usage of this filter in SPI MISO line? Many thanks for your time.


texts: Do Step-Down Transformers Increase Total Power Consumption?

texts:
Firstly I am not at all experienced in electrical matters so forgive any wrong terminology.

Here's the situation:
I recently moved out of US to a country that uses 220v. We have a single phase step-down transformer that provides 120v to the entire house. There are a few appliances that we would like to order with the option of either 110 or 220 versions. (220 versions are more expensive)

What I would like to know is, is there an increase in power consumption if I am to run an appliance through the step-down system vs the direct 220 sockets?

eg. 300w food dehydrator 110v version run through transformer vs 300w 220v version plugged into native wall socket

Another way to ask the question would be; Is the total power consumption of a 600w machine run through a step-down transformer 600w? Or is it more?

Thanks for any insight you can provide on this!


texts: Manual reset problem: CD4060 timer circuit

texts:
The following circuit shows a CD4060 in a timer circuit, intended to hold a relay (with a transistor driver) on for about an hour, then turn it off.  I want to have a reset switch so that at any time, I can push it to start the timing from an hour again.

orm.  It shows mostly the power and inputs.  For testing, the outputs are connected to a bank of LEDs with current-limiting resistors, showing every available state (Q4-Q10, Q12-14), but I did not show that in the diagram, for simplicity.  It counts correctly.  The relay is not in the circuit yet.

ONE output is shown, Q14 at pin 3, with a diode whose purpose is to latch the timer, to stop counting when it reaches Q14, or about one hour.  The latching effect works correctly.  Q14 is also connected to an LED as described above.

The 120K resistor and the 100nF capacitor are a power-on reset circuit, and that has been working every time I tried.  "Trying" means turning of the master power switch (before the power transformer in the power supply) and then turning it on again.

PROBLEM: the only thing that does not work correctly is the manual reset pushbutton across the 100nF capacitor.  As I understand it, the 4060 RESET (pin 12) can be connected HI to achieve a reset.  However, pushing the button, whether quickly or for a second or two, usually results in a non-zero state for the 4060 registers, typically with Q5-Q9 HI.

Why does the manual reset not clear all registers to zero, and how do I fix it?

UPDATE: in the original post, the resistor from pins 12 to 8 was said to be 1M, but it was 120K.  Per suggestions in comments and answer, I changed it to 10K.  Reset button works as long as I don't hold it down longer than say 1/2 second. When holding it down, releasing it leaves the registers in a non-zero state.


texts: Radio static caused by windscreen wipers

texts:
I was driving past a radio station transmitter of the radio station I was listening to. I turned on my windscreen wipers, which caused a noticeable static to be emitted through the speakers for the entirety I held the lever. The static intensified as I approached the transmitter and faded as I drove away. I have never witnessed this situation before and the radio within my car operates normally without issue.

How does the electrical signal that causes my windscreen wipers to operate cause a static to be played through the radio when passing by a radio transmitter? When trying a number of times, I pulled the windscreen wiper for a short period such that the wiper did not move and the sound was audible, making me think it has to do with electromagnetic interference. I am unsure how the power sent to the windscreen wipers would cause it considering that there are a number of other electrical signals transmitted throughout the vehicle and the signal would be weak.


texts:
Not sure if this is the correct place to post a programming based question so will have a go anyway.

Attached below is a piece of code and a table where I have to fill in the blanks. Just to clarify, the question essentially is, ("The table should contain both the address and value of each integer variable after the last line of code has been executed.")

The bottom table is my attempt and the boxes with a '?' are where I don't understand:

I do understand pointers but I am getting confused with the pointer to a pointer variables I think.

By the way this is based of a 32-bit micro-controller, hence the hex values.

Would be great if someone could explain the step by step logic I should be taking with this code to fill in the table.

Thanks


texts: Would a diode with a different forward voltage and response time cause this circuit to behave erratically?

texts:
I accidentally substituted diode RS1BB-13-F for S1BB-13-F.

RS1BB-13-F's forward voltage is 1.3V, while S1BB-13-F is 1.1V.

These substitutions were at D8 and D9 in the schematic (top right corner).

LEDs aren't behaving normally and ICs are overheating. Based on the circuit, could the incorrect diode be the culprit? Thanks for your help.


texts: How do PC sound cards cope with headsets of different impedance?

texts:
I recently got a PC motherboard that advertises a "smart" audio amplifier chip to manage headsets with different impedance:

However, I have never had a problem with headphones before.

Will I notice a big change in quality when I use the new motherboard? How did older motherboards without this capability deal with differences in impedance?


texts:
I have a board with a 7-segment display controlled by an AVR. I need to rotate the display's  characters in the firmware, so that the display is read correctly when physically rotated 180 degrees.

Currently, the display has an output defined by:

#define SEVEN_SEGMENT_PATTERN_0     0x7B
#define SEVEN_SEGMENT_PATTERN_1     0x09
#define SEVEN_SEGMENT_PATTERN_2     0xB3
#define SEVEN_SEGMENT_PATTERN_3     0x9B
#define SEVEN_SEGMENT_PATTERN_4     0xC9
#define SEVEN_SEGMENT_PATTERN_5     0xDA
#define SEVEN_SEGMENT_PATTERN_6     0xFa
#define SEVEN_SEGMENT_PATTERN_7     0x0B
#define SEVEN_SEGMENT_PATTERN_8     0xFB
#define SEVEN_SEGMENT_PATTERN_9     0xDB

#define SEVEN_SEGMENT_PATTERN_A     0xEB
#define SEVEN_SEGMENT_PATTERN_B     0xF8
#define SEVEN_SEGMENT_PATTERN_C     0x72
#define SEVEN_SEGMENT_PATTERN_D     0xB9
#define SEVEN_SEGMENT_PATTERN_E     0xF2
#define SEVEN_SEGMENT_PATTERN_F     0xE2

#define SEVEN_SEGMENT_PATTERN_G     0xdb
#define SEVEN_SEGMENT_PATTERN_H     0xE9
#define SEVEN_SEGMENT_PATTERN_I     0x09
#define SEVEN_SEGMENT_PATTERN_J     0x19
#define SEVEN_SEGMENT_PATTERN_L     0x70
#define SEVEN_SEGMENT_PATTERN_O     0x7b
#define SEVEN_SEGMENT_PATTERN_P     0xe3
#define SEVEN_SEGMENT_PATTERN_R     0xa0
#define SEVEN_SEGMENT_PATTERN_S     0xda
#define SEVEN_SEGMENT_PATTERN_U     0x79

#define SEVEN_SEGMENT_PATTERN_DOT   0x04

Of course, I could use this to extract the pinout of the display and manually figure out the new definitions for flipped characters. However, this would be time consuming and I'm thinking that there must be a smarter way.

Some would remain the same when flipped, such as SEVEN_SEGMENT_PATTERN_0. Some will be easy to flip if I knew the pinout, such as SEVEN_SEGMENT_PATTERN_1.

Is there some smart algorithm or whatever that can help me calculate the flipped values?


texts:
Modern SoC solutions (FPGA+ARM) can exist both as a PCIe board, but can also work disconnected (with a 19V PSU). So my question is - is there a solution which provides just a PCIe motherboard/bus, without the typical trappings of home PCs (such as CPU socket, RAM slots, SATA and all that)?

Basically, what I'm looking for is simply a general-purpose PCIe fabric that can connect to a power supply and provide power and communication capabilities to PCIe cards. In terms of the cards I'm interested, I'm talking mainly about SoC accelerators, GPUs and Xeon Phi.

P.S.: yes, I know this can be built on top of existing COTS motherboards, I'm wondering specifically if there are headless solution, and whether it is even feasible. Thanks!


texts: For the same JFET why are there two curves in a Transfer characteristics graph?

texts:
I am trying to learn about n-channel JFETs from David. A. Bell's book. In the transfer characteristics graph, there seem to be two curves as shown. Note that VGS(off) = Vp

As you can see, one curve is drawn for the minimum values of VGS(off) and IDSS and the other curve is drawn for the maximum values of VGS(off) and IDSS. The book shows an excerpt from a data sheet and says that the manufacturer has mentioned the values of minimum and maximum of VGS(off) and IDSS and uses this formula to draw the curves:

I can't understand how there can be maximum and minimum values for the cut-off voltage and the drain current. From the input characteristics graph, I understand that cut-off voltage is nothing but the Pinch-off voltage when there is no voltage applied between the gate and the source(ie) when VGS=0. Now, if there is a maximum and minimum cut off voltage then that means for VGS=0 there are two pinch-off voltages which doesn't make any sense. Also what does having a minimum "saturation" current even mean?


texts: 74hc165 inverting pins 15 and 2, does it work?

texts: I have a board that uses 74hc165 shift registers, when taking a look at schematic it appears that pins 2 (clk) and pin 15 (clk enable) are inverted, my first impression was that this is a mistake, but when verifying the board it turns out that this is not a mistake, so I had to take a look at the datasheet of the 74hc165, and I found out that those pins can be inverted, so I decided to do a simulation using Proteus unfortunately it didn't work, and I don't have this IC (74hc165) with me to do a hardware test so...Do you have guys any idea about this?? I'm so confused..


texts: To find the Fmax of a circuit designed using VHDL you need to have a register to register path. Because of this however, it takes 2 clock cycles to get the correct output after inputting some data. Is it correct to call this design a single cycle circuit then?


texts: My father is Bob Cook, an engineer that worked at TI with Jack Kilby in the 50’s/60’s. He has in his possession an SN 502 IC given to him by Jack Kilby. How rare is this chip?


texts: Bidirectional Monophasic 2 Motors Driver with ULN2803A and Relays

texts:
I am a hobbyist who is trying to build a DIY like car robot controlled via 2.4GHz radio and decided to use ULN2803A which was unused on my electronics equipment and has 8 outputs 4 for each motor and 2Ampers until 50Volts in DC if I'm not wrong. I'm good in programming so the problem is with electronics and understanding well the datasheets. I think ULNs are good for high voltages with DC and work with low current but they don't dissipate so much power (correct me if I'm wrong) so is a better option than L298N. The problem is that I can not change the polarity on monophasic motors (2-wire). Then I decided to use 4 relays to switch the poles of the motors with Arduino and digital pins. (LOW and HIGH, forward and backward).

The capacitor of the ULN2803A is an electrolytic one of 100 uF which I don't know if it's a problem. And the capacitor also electrolytic for the gyroscope is 1000 uF to prevent EMI of the motors. Also the motors have 100 nF ceramic capacitors 50V on each pole to the ground, to prevent EMI. (I read on Pololu's website).

I can draw the circuit for the relays but at the moment I'm showing you the circuit of the driver that is what I've drawn but it's easy to imagine what I've done with the relays (a typical board of 4 relays able for Arduino 3 holes with screws per relay): each wire of each motor is on the middle hole of the relay and as the relay switches between right and left connection the middle wire, in the left is positive and in the right negative. At first everything works fine until I start to switch, at first a motor stop to run and then after switching fast backward forward the ULN stop working completely.

So, the question is: Is possible to change polarities of the motors by this installation?

Sorry about my bad English and sorry about the complexity of the problem (I can imagine, I'm just a hobbyist).

Thanks in advance, I wish you a good day.


texts: Gate Drive Resistor size and/or Gate Driver IC

texts:
I am working on a design for a 16 channel LED driver design.
at the moment the basic design is based on three main components:

NCP781BMN050TAG Voltage regulator
PCA9685 I2C PWM Driver
CSD19534 MOSFET

the Circuit needs to initially drive a 110V led Light with 250mA LED strings but wants to be adjustable to driver sets of other LEDs e.g Ledengin LZ7

simulate this circuit – Schematic created using CircuitLab

without further components i think this design should work in principle
with M1 getting a RDS(on) of ~30 mOhm (other similar mosfets had larger RDS(on)). the RDS(on) can be reduced further if i can supply higher voltage (14.1 mOhm at 6V and 12.6 at 10V)

(this combination of R2, M1 Q1 R2 and  D1..n are repeated for each channel though R1 will be varied dependent on different D1..n on each channel)

the PCA9685 can supply limited current of 10mA per channel and if im reading it right 25mA total and can operate PWM at upto 1526 Hz

some simulation at 1526Hz PWM (assuming i did it right) shows if i have R2 with 10K resistor i get inrush current of 500uA which should be no issue

if i reduce r2 to 1k i get 5mA which is likely too large to operate more than 4 channels at once

and 100 gets 50mA which too large for a single channel and the PCA9685.

How do i determine the best value for R2?

Would the inefficiency of resulting from a large R2 make it worth putting in a gate driver e.g a MAX620EWN+ (would need 4) or a cheaper alternative?

or is there another, cost effective?, way to make this more efficient?

simulation model and output( the New macro are a PLW7070GA spice model)


texts: How exactly does a computer know what device is connected on the USB port?

texts:
I am working on a mini that uses USB.
This is probably something that I can get in the huge USB docs but if I can get a brief response I'll be happy. So since almost all devices interface with the computer via USB, how does the computer know what devices are connected? Do the devices some packets with info regarding device info (e.g memory, sound card, joystick)? If so, how exactly is the data packaged?


texts:
Im using a 5V OKI Murata DC-DC device to power an Arduino UNO R3 and a 4 channel 433MHz receiver. Ive got a 24V DC source which is a bench PSU at the moment. But ive noticed that every so often the RF module would fail as it heats up. Im not sure why but the regulator outputs a steady 4.95V.
The regulator is the 5V 1.5A OKI-78SR device which has a current draw of about 8-10mA applied to it with my components.

The only thing I can think of is that there might be oscillation or a voltage spike here or there that causes damage to the RF receiver. The data sheet available OKI Datasheet from here says that i dont really need external components.
I chose the OKI device as i didnt fancy the idea of reducing up to 24V down to 5V using a standard regualtor as it would likely heat up and go boom.
So far I have had two RF modules fail, im using the QIACHIP RF module available RF Datasheet from here
I have the wiring correct and I am only using D0 and D1 of the RF module and these are being read by the Arduino digital inputs directly.

Are there any external components i should use on the input or output of the DC-DC to prevent this odd issue? It got me confused at this point.
Im also driving a 2 channel relay board from the DC-DCs output.
The issue did occur when i didnt have it connected but it may be chance, initially i thought it may be floating voltages >5.5V (the maximum input of my RF device) due to the low current draw of <10mA. I may be wrong.

If anyone could help I would greatly appreciate it!
Thank you guys

UPDATE: ive added a schematic just to try and clear things up, if it helps
Ive also included a link to the relay board i am using for reference.


texts: 2-bit DAC from TTL logic using 2 MCU outputs

texts:
Basically I am trying to make a 2-bit DAC that can interface to an external device via one signal wire. I want to create a 3-step signal that can be ~0V, 2.5V, and ~5V.

For starters, I tried using two NPN transistors controlled by two 3.3V output pins from an MCU.

Here is the schematic I have simulated in LT Spice...

With this schematic, I can get my ~0V and ~2.5V fine, but I cannot get 5V. When I apply voltage only to Q5 (the top NPN), I only get 3.03V at the output.

Looking this up with google only yield results for a "tri-state buffer" that has the output possibilities of 0V, 5V, and high-z. I cannot find a shcematic or IC to accomplish what I am looking for exactly....but maybe my search terms are incorrect?

I need a suggested schematic mod or an IC to accomplish what I am looking for if anyone has any suggestions! Thanks!

UPDATE:

I found this Fig. in another post which will take care of reaching up to the 5V. I just need to add a second transistor switch and create a voltage divider which I already know how to do. The LED will replaced by an outbound signal.

Image source.


texts: Best And Cheapest Way To Isolate Multiple DC Power Sources

texts:
I need a way to create/simulate (by simulate I mean fool the circuit in to thinking they're isolated), at least 8 5v 1A power sources in the cheapest and easiest way possible.

I have a power source which is 5-5.5v and at least 8A (10A actually), but I need to split that source out to 8 other devices but that are completely isolated from the original source. If it's not isolated the units I'm supplying power to will short.

I've tried a schotkey rectifier but that does't seem to work. Any other ideas?

Example below:

simulate this circuit – Schematic created using CircuitLab


texts: Capacitor value for Mini PCI type III pins 97 & 101

texts:
On the motherboard of my old Fujitsu Siemens laptop A1650G, a capacitor (C316) burned out. It seems to be connecting pins 97 and 101 of Mini PCI type III connector, which are 5V and Ground respectively.

I would like to try and replace this capacitor, but have not found any reference as to what value this capacitor should be. It is small surface mount capacitor with no visible value markings.

P.S. - Tips on desoldering and resoldering small surface mount capacitors at home will also be appreciated.

It is a two sided board and connectors from capacitor come out on the other side near PCI slot as depicted in newly added third image. (The PCI pins shown are of odd numbers 1,3,5..127. Two dots can be seen near pins 97 and 101 which are exactly on the opposite side of the capacitor)

UPDATE2: I have desoldered the capacitor and the laptop now works, so the capacitator definately was the fault. I still have not determined what type and value the capacitor was. While looking at other capacitors it visually seems more like ceramic capacitor, but in that case I dont understand where did the black goo come from when it died (If I understand correctly ceramic capacitors fail by fractures and nothing melts or flows out of them)
Also wireless still works, but I am afraid that some powerspike will take it out if I dont replace the capacitor soon.

The black mess near burnt capacitor - came clean off with alcohol.

Offending capacitor in the middle, marked C316

Other side of the board. Mini PCI slot Type three, odd numbered pins with pin 127 on the right most side. Near pins 101 and 97 are the two leads from capacitor (small dots)


texts: Current Transducer with true RMS voltage output

texts:
Possible Duplicate:
  ICs that convert an AC signal into its true rms value

Can anybody please recommend me a current transducer which has the provision of true RMS voltage output and instantaneous voltage output. The measuring range is 0 to +-160A and has a supply voltage of +-15V.
Basically I am looking for a replacement for LTA 50PR/ LTA 100PR. (http://www.farnell.com/datasheets/96665.pdf) here
 These transducers are no more in production.


texts: Why is there no `nand` instruction in modern CPUs?

texts: Why did x86 designers (or other CPU architectures as well) decide not to include it? It is a logic gate that can be used to build other logic gates, thus it is fast as a single instruction.  Rather than chaining not and and instructions (both are created from nand), why no nand instruction?.


texts: When did LTI systems become part of the EE curriculum?

texts: When did universities start teaching the mathematics of LTI systems ("Signals and Systems") as part of the standard curriculum for electrical engineering majors?


texts:
I am trying to write code in assembly that detects an interrupt (pushbutton) on my PIC18F45K50 and upon detecting an interrupt, an LED turns on. For some reason the microcontroller is not detecting the interrupt. I am using an INT1 interrupt (thus B1 input) and the LED is at D1.

This is my asm code:

INCLUDE "p18f45k50.inc"

; Aim of program: input at B1 toggles the led at D1
; Assembly source line config statements

CONFIG  WDTEN = OFF
CONFIG LVP = OFF
CONFIG FOSC = INTOSCIO

begin       ORG 0
        BCF INTCON3, 0 ;clear flag INT1IF
        CLRF LATB ;clear latB
        goto prog

hinterrupt  ORG 0x08
        goto introutine

        ORG 0x22
prog    ;D1
        BCF ANSELD, 1 ;set D1 to digital
        BCF TRISD,1 ;configure PORTD.1 as output pin
        ;BSF PORTD, 1

        ;B1
        BCF ANSELB, 1 ;set B1 to digital
        BSF TRISB, 1 ;configure B1 as input pin

        ;INT1 hence B1 settings
        BSF INTCON3, 6 ;set INT1 to high priority
        BSF INTCON2, 5 ;+ve edge trigger for B1
        BSF INTCON3, 3 ;enable INT1
        BSF RCON, 7 ;set IPEN to HIGH thus enabling priorities on interrupts
        BSF INTCON, 7 ;set GIEH to high, enabling high priority interrupts

        goto prog

introutine  BCF INTCON3, 0 ;clear flag INT1IF
        BCF INTCON, 7 ;Disable all interrupts inside interrupt service routine (disable GIEH)
        MOVLW 0x01
        BSF PORTD, 1
        goto prog

END


texts: Steps for connecting femal-to-female sacrificial adaptor into a male connector in the RF measurement equipment

texts:
First of all, I am a newbie to the RF-mm-wave test equipments. I am trying to use this Agilent equipment shown in the image below where I want to connect a 1.85mm (F-to-F) sacrificial connector to the equipment's 2.4mm male connector. Could someone please guide me on how I should go about safely/properly make this connections? i.e. What steps I should take? For example, what part I should turn and what part I should be holding with the wrench OR hands?

Also, once I make the connection, please also let me know on steps to disconnect this connection.


texts:
I have a battery operated toothbrush that I want to generate notes with using PWM on the motor. The microcontroller used is an Arduino for testing and am able to get a bare motor to generate tones. I am using 3/4ths of an H-bridge so I can stall the motor, one terminal is positive and the other is both positive and negative.

The problem is when connected to the toothbrush, the brush head does not seem to stop fast enough to generate a tone. I am assuming that there is too much potential energy in the brush head to keep it from stopping through the PWM.

Has any one else tried something like this with any success? Does this seem like an impossible task?


texts: How do I turn on a magnetic lock with an Arduino?

texts:
I have a 12v magnetic lock, which is just an electromagnet. I want to turn it on with my Arduino.

I've been able to turn on/off a 5v motor with the Arduino. So I'm guessing the wiring is similar. The problem is I need 12v. I looked for a 5v to 12v DC convertor at Fry's and DigiKey, and couldn't find any. I can only find ones that go from 12v to 5v.

I found a this youtube video doing exactly what I want, but it's short on details. He only has a single electronic on his breadboard that he calls a "DC convertor". No transistor, no diode. How does that work?

Also, is the current from the Arduino enough to power a magnetic lock, or should I have an external power source?

I'm very new to electronics. Any help is appreciated.


texts: Will 0.16 amp rated fan replace a 0.3 amp fan?

texts:
I have a noisy PSU fan (400 watt Coolermaster PSU), It's 120mm and 12 volts. I have found an identical fan which is also 12v, but rated 0.16A, as opposed to the original 0.30A fan.

I'm aware PSU maintenance is dangerous, and have waited for the capacitors to discharge. The work is trivial, but I am cautious.
Now I notice the different specs and thought I might get an opinion here before I proceed.

The new one (top) is new, and even branded Coolermaster (found it in a bargain bin for $2).

Edit:

OK. Fan is installed and working. I'll keep an eye on it. But I think it's a win. Thanks for the help.


texts: Using WS2812b Addressable LEDs on Raspberry Pis

texts:
I am attempting to control WS2812b LEDs using a raspberry pi according to this guide: https://tutorials-raspberrypi.com/connect-control-raspberry-pi-ws2812-rgb-led-strips/

So far I executed the following lines in terminal without any issue:

git clone https://github.com/jgarff/rpi_ws281x
cd rpi_ws281x/
sudo scons
cd python

However when I try to execute the next couple of lines, I receive errors:

pi@raspberrypi:~/rpi_ws281x/python $ python setup.py build
Extracting in /tmp/tmpMzL9XM
Traceback (most recent call last):
  File "setup.py", line 4, in <module>
    use_setuptools()
  File "/home/pi/rpi_ws281x/python/ez_setup.py", line 161, in use_setuptools
    return _do_download(version, download_base, to_dir, download_delay)
  File "/home/pi/rpi_ws281x/python/ez_setup.py", line 120, in _do_download
    _build_egg(egg, archive, to_dir)
  File "/home/pi/rpi_ws281x/python/ez_setup.py", line 62, in _build_egg
    with archive_context(archive_filename):
  File "/usr/lib/python2.7/contextlib.py", line 17, in __enter__
    return self.gen.next()
  File "/home/pi/rpi_ws281x/python/ez_setup.py", line 100, in archive_context
    with ContextualZipFile(filename) as archive:
  File "/home/pi/rpi_ws281x/python/ez_setup.py", line 88, in __new__
    return zipfile.ZipFile(*args, **kwargs)
  File "/usr/lib/python2.7/zipfile.py", line 770, in __init__
    self._RealGetContents()
  File "/usr/lib/python2.7/zipfile.py", line 811, in _RealGetContents
    raise BadZipfile, "File is not a zip file"
zipfile.BadZipfile: File is not a zip file
pi@raspberrypi:~/rpi_ws281x/python $ python setup.py install
Extracting in /tmp/tmplrNAMs
Traceback (most recent call last):
  File "setup.py", line 4, in <module>
    use_setuptools()
  File "/home/pi/rpi_ws281x/python/ez_setup.py", line 161, in use_setuptools
    return _do_download(version, download_base, to_dir, download_delay)
  File "/home/pi/rpi_ws281x/python/ez_setup.py", line 120, in _do_download
    _build_egg(egg, archive, to_dir)
  File "/home/pi/rpi_ws281x/python/ez_setup.py", line 62, in _build_egg
    with archive_context(archive_filename):
  File "/usr/lib/python2.7/contextlib.py", line 17, in __enter__
    return self.gen.next()
  File "/home/pi/rpi_ws281x/python/ez_setup.py", line 100, in archive_context
    with ContextualZipFile(filename) as archive:
  File "/home/pi/rpi_ws281x/python/ez_setup.py", line 88, in __new__
    return zipfile.ZipFile(*args, **kwargs)
  File "/usr/lib/python2.7/zipfile.py", line 770, in __init__
    self._RealGetContents()
  File "/usr/lib/python2.7/zipfile.py", line 811, in _RealGetContents
    raise BadZipfile, "File is not a zip file"
zipfile.BadZipfile: File is not a zip file

Does anyone have any idea on what I should do?


texts: AC current measure using CT, 10-bit 200 ksps (mcp3008) or 12-bit 100 ksps (mcp3208), which is better?

texts:
First, sorry for my bad English

I try to build my own wifi energy metter using esp8266 and mcp3208. My electric knowledge is very simple, now my design use mcp3208 to measure AC current from CT, but I read from google that nowaday many households use switch power supply, so to measure more accurate, I need more sample rate. Mcp3008 is lower bit but double samples and lower price but not important than accurate measurement.
So which one is better?
Thanks


texts: What's the role of capacitors in this circuit?

texts:
This is a followup from a previous question: Analysing signal unbalancing stage which was quite broad as it encompassed couple of things, but answer there pointed me in the right directions so I'm able to pursuit further.
However, one particular thing is still a mystery to me:

The In+ and In- are voltages of the balanced audio line signal (https://en.m.wikipedia.org/wiki/Line_level) - meaning 600Ohms impedance and +4dBu level. What's the role of the capacitors? The answer to previous question suggests it is to block RF signal, so how do that work?
As far as my knowledge goes, those caps provide hi-impedance path to ground for the audio signal (the combined reactance for both input lines would be around 42pF, which, for the audio range would provide reactance of 190M to 190K), so only the negligible amount of signal would go that path (not sure what reactance the transformer coils provide, but probably small compared to the caps). If we take it that it's supposed to act as a shield against RF, then what would be the theoretical basis for that and how would that work? The reactance for RF frequencies would be much lower so they'd be shorted? But isn't the noise cancelled anyway because In+ and In- are inverted polarity, so noise inducted along the cable is cancelled (we sense the voltage difference between those).
The broader context:
I'm analysing a particular schematic, an audio compressor: https://www.soundskulptor.com/en/proddetail.php?prod=LA502
The schematic is here: https://www.soundskulptor.com/docs/la502-schematic-03.pdf


texts: What could be the issue with energy monitoring IC (HLW8012) and my non-isolated power supply?

texts:
This circuit works fine when I replace the 220v power supply with a cheap power supply(I assume they are isolated) from aliexpress. However, when I use my own power supply(schematic below), it causes the 0R resistor, fusible resistor, AMS1117 IC and HLW8012 IC to blow out with smoke.
my power supply circuit is also working fine under load when not connected to power monitoring circuit.
I think there is something wrong with my GND but I don't know how to solve it.
Chinese datasheet for HLW8012 can be found here and some english info about it here


texts: How to measure intensity (lumen) of a light source?

texts:
Let's say I have an x800 cree LED (which was supposed to be 4000lumen) and a cheap lux-meter (thinking of buying one like this).
My question is, which is the physical setup to measure the true intensity of the LED and covert it from lux to lumen?
The logic problem that I have is that not all the light of the LED will hit the sensor. Most will be "wasted" since the LED produces such a large circle of light, while the sensor is only a few centimeters in diameter.
How to I take into account this "wasted" light?
The formula is simple: 1 lx = 1 lm/m2, but that's obviously valid only when ALL the light from the LED hits the sensor.
There are calculators online but they ignore that most of the light is lost (does not hit the sensor). I guess they are fore measuring the light intensity on a surface, not the light intensity of the source.
Can that device be used to measure the intensity of the LED. I will gladly accept a 20% tolerance.
I never before measured brightness of a light source. As you can see, I have no clue what I talking about. So, I could be wrong in every possible way. I apologize for my newbie question.


texts: What is the advantage of a switching over a linear power supply?

texts:
I want to build my own switching power supply. I already know how to make a 10 Ampere Linear supply, and I'm wondering if I should bother.  What do I have to learn to do a switching supply? What makes a switching supply better if they both end up giving me DC?

What I don't get is the "inefficiency" argument. Maybe linear supplies get hot, yes, but so does every laptop switching power supply I have met. Looking at a schematic of a switching power supply shows that it has at least 3 times more components; that means 3 times more work and cost to build a power supply. Why would I feed a circuit using an expensive switching power supply that gets hot and that ends up being more expensive than a linear one?

Don't both just end up giving me plain regulated and filtered DC power? I should be able to use either for every application shouldn't I?

Also, if i wanted to make 10A one, how or which component can manage 10 Amps in a switching supply? (Darlington arrays are used in linears)


texts:
I want to use a transformer to convert AC voltage. Input is 220V AC at 50 Hz and output is, for example, 5V 30mA AC.

Many people told me, this transformer will be huge because the mains frequency is low. But, I still have no idea, how big it will be.  (BTW, 50Hz main Frequency is so low, I am not sure if the transformer could magnetize..., maybe need big Fe core...)

For my converting requirement, and take Piezo transformer or any other high-advanced transformer design (like pcb stack twisting transformer) for example (smaller, better). How large it will be? Suprise me.

(I have no idea about the transformer design, I mean, how thick the conventional coil wire, etc.  I just know the basic equations Vin x Iin = Vout x I out... some text book stuff, no experimental experience.)

How do I determine which core size is appropriate and how many windings of what type of wire I am supposed to use for primary and secondary?


texts: Thyristor/SCR \$i^2t\$ and \$i^2\sqrt{t}\$ Rating

texts:
I have commonly seen the \$i^2t\$ rating for fusing in a SCR datasheet. This is a helpful rating for assessing if pulses which exceed the surge current rating (Itsm) of the SCR will damage it.

However, I have also come across the \$i^2\sqrt{t}\$ rating. These are commonly found in Vishay datasheets. The \$i^2\sqrt{t}\$ rating in the datasheets is constant for pulse widths ranging from 0.1ms to 10ms. I am guessing that the \$\sqrt{t}\$ is the thermal response of the SCR junction.

Has anyone come across this rating before and is there any literature that explains this rating? Google is giving me a hard time.

My application is a pulse width of 100-200us at an interval of 1.0s. I am trying to justify if I can use a SCR where I exceed the Itsm rating.

Sample Vishay Datasheet = http://www.vishay.com/docs/94679/vs-25tts16spbf.pdf


texts: How can I measure the power output of RF Power amplifier

texts:
I have a power amp (50 Ohm) that is connected to a load of Z=55e(-0.77i), by standard coaxial cable with 50 ohm BNC connector.  The wiring is short, less than 1 metre.

The voltage reading from the RF PowerAmp is 40.1 V Amplitude (or 80.2 Vpp) with the load Z. How can I calculate the power output?

The reading I have is 10 W (from Power Amplifier integrated circuit) but I cannot calculate to anywhere close to that number


texts: How to implement X = ABC'+AD +A'CD'+A'E'F'

texts:
I'm working through my homework and there's one question that I absolutely cannot figure out.

I'm supposed to implement  X = ABC'+AD +A'CD'+A'E'F'  With the following constraints:

All gates must be 2-input
Each level of the circuit must alternate between AND and OR gates
The final level must be a single AND gate

For a previous question I had to implement this following the same constraints except that the last gate had to be an OR gate. For whatever reason, that was super easy. I manipulated the equation into X = A(BC'+D)+A'(C'D+E'F'), but I can't figure this out, my final gate is always an OR gate.

How do I approach this?


texts: How do I install UHF RFID readers in close proximity?

texts:
Greetings people of the internet, I need help...
I work for a company that installs and maintains security and access control equipment. Our latest project involved installing UHF tag readers in the entrance lanes to a residential estate and RFID tags (technical specs below) on the vehicles of the residents who live there so that the gates would open when they approach and they don't need to touch the biometrics scanners and such...
The system is operational and works around 90% of the time, the other 10% presents the issue where the vehicle tag is read by the wrong reader, causing the wrong entrance lane gate to open.
The tag readers we are using are the UHF5 series from ZKteco, the tags are Alien Technologies ALN-9654 mounted in the top left corner of the windshield of the vehicles.
The readers are mounted on the same wall 4.5 meters above the ground, approximately 4 meters apart, facing in the same direction in their respective entrance lanes, and angled to read tags approximately 5 meters from the gates (which are directly under the readers).
In normal operation, a car will approach one of the gates, that lane's reader will read the tag on the car and open the gate, no issue. The problem comes when a car approaches a gate and the reader in the other lane, 4 meters to the side, picks up the tag and opens the wrong gate, preventing the vehicle from entering the estate.
Is there any way to stop this from happening without changing the existing hardware on site?
Notes:
From observation and research, my best guess is that that one of the readers is energizing the tags, and the tag is broadcasting it's EPC which is being picked up by the wrong reader, I reckon the RF transmitter is directional but the receiver is not which is why the wrong reader picks up the EPC sometimes, I have no idea if this is even correct though or how to stop it, this is not my area of expertise.
I am aware of RSSI filtering but as far as I can tell, it is not something I can configure on the readers we are using.


texts: Input Voltage vs Output Voltage for a Shunt Positive Clipper with Bias Voltage

texts:
Assume voltage drop across diode is 0.7V in this case.

From what I understand

When V(input) is positive, but less than 0.7+V OR When V(input) is negative AKA When the diode is acting as open circuit:

V(output) will equal some fraction of V(input), depending on the value of R and the value of the Load Resistance. For example if R=RL, V(output) will equal 1/2 of V(input). And if R is very small compared to RL, V(output) will be approximately equal to V(input). This makes sense to me intuitively.

My confusion arises from the information I've read from varying sources, which all seem to indicate that V(output) will always be equal to V(input), when the diode is acting as an open circuit.

When V(input) is positive, and greater than 0.7+V AKA When the diode acts like a jumper wire

Vo is equal to 0.7+V. This makes sense because Vo is the voltage parallel to 0.7+V.

I tried simulating a circuit like this in falstad, and noticed that Vo will get clipped when Vo>(0.7+V), instead of when Vi>(0.7+V). I also noticed that Vo does not equal Vi when the diode is open circuit, Vo = 1/2Vi (I made the load resistance and the other resistor equal) But every source I've looked to says that Vo will always be equal to Vi AND that Vo will be clipped when Vi tries to go above 0.7+V.

My question is, what am I misunderstanding? Is Vo clipped when Vi is greater than 0.7+V or is Vo clipped when Vo is greater than 0.7+V. Is Vi always equal to Vo? The only situation in which I can think of Vi being equal to Vo for a circuit like this, is when R is small compared to RL, as  mentioned earlier.


texts: How to protect constant LED current from ripples & clamps?

texts:
I need to develope a constant current LED Driver. The product must be portable and as small as possible. So I can not use SMPS, I have use AC/DC adapter as source. This is the AC/DC adapters output:

50 Hz, double rectification = 100 Hz clamps are seen here.

and this is the LED driver, in a single form we want to use:

simulate this circuit – Schematic created using CircuitLab

In the system there are 3 LED driver like this so Max LED current is 3A. And here is the problem we have. Although, ripple level of the converter is just 40 mV over 12V DC, it causes to tremendous effect for us because in our specific application, we use this photodetector with 50 or 60 dB gain:

I do not know all the detail about the system(it is a medical solution) and I should not due to privacy policy, but I know that my driver will be used as DC comparison element so even with 60 dB gain, in oscilloscope, light absorbed from my LEDs should be ripple free. But, as I told, even smallest ripple in the electrical system(I can not even see the electrical effect of the ripple on the LEDs on oscilloscope) effects LEDs current like a few mA, an this extra power consumption detected by photodetector and amplified, and all system messed up afterwards.

So, here is what I have so far:

I have AD/DC adapter, Power lines are 50Hz in here, so 100 Hz ripples comes from double rectification.
The lab Team said any ripple or noise on above 100KHz is fine they can filter it out.


texts: LEDs keep dying in 12v circuit with powerful electromagnet

texts:
I have a circuit like this:
12V/2A DC input. A small blue LED with a 2.2k resistor in series. A powerful electromagnet with ~40ohm resistance in parallel. It is possible the electromagnet has more components on the inside.
When I turn the switch on the LED shines for a second or so and then turns off/dies. I don't see how that's possible with a series resistance this high.

What should I do to have the LED light up at the same time as the magnet is attractive without dying?


texts: Conditioning input signal range for sensor

texts:
I have piezo sensor which outputs around 1mV of signal. I am using an already build analog front end to measure the signal, with Vcc = 5V and Vss = 0V. To measure the signal, the front end has internal PGA and DAC and needs the input signals to be within range of 2.3V to 2.7V. I don't want to use any op-amps because I want to minimize the components and no additional PCBs.

I have thought something like this:

If R1 = R2, will the signal be centered to 2.5V? Are there any problems with this circuit? Or any other solutions?


texts:
I recently took apart a cheap ($7) LED light to use in a project.  It was attached to a heat-sink that I removed and discarded, thinking nothing of it.

Later when I turned on the light, I noticed that the circular piece of metal that had about 11 tiny LEDs on it was getting extremely hot!

If LEDs are suppose to be super energy-saving, why are they giving off so much heat?


texts: Using Unidirectional Electret Microphone as Static Pressure Sensor

texts:
Hi all posted question on reddit but giving it a shot here too, I've been working on a board that requires a pressure sensor to detect when there is a differential air pressure or not. The board needs to be quite small, and more importantly very cheap.
Even some of the cheapest pressure sensors are $5-$10 which is simply too much for the application. They also provide analog output dependent on the value of the differential pressure, whereas I only need it to detect when pressure is above a threshold.
I have seen something similar in e-cigarette/vape pens. They use what looks like a unidirectional (vented) electret mic as a static differential pressure sensor to detect when you are pulling. I was wondering if any of you have a better idea of how this works. From what I know, electret mics can only be used to measure dynamic differential pressure (sound) and will not work for static pressure.
My assumption is that to use the unidirectional mic as a pressure sensor they might instead measure the capacitance of the electret. I'm not sure how well this works considering that the ones I have seen have an internal JFET that wont allow for this measurement
Hoping some of you have some better answers as to how the e-cig companies use them for pressure sensors.


texts: I'm having problems contracting, in CADENCE for some modification that I can't use the layout, I normally did the INVERTER and AND ports, but when I get to the NAND port there are some errors, a message about the library (I'm using the correct library ), it does not look like the components even with the option GENERATE ALL FORM SOURCE and the metals are not in the list. See the image.


texts:
I have a transfer function like this:

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

I can separate the denominator into an expression of the type: \$(1+s/a)(1+s/b)\$ and then plot these two curves.

However, my textbook doesn't tell me how to plot the numerator: \$s^2+\frac{1}{LC}\$

It teaches how to draw curves for quadratic poles but they have a diferente form.

How do I manipulate it to make it look like one of these?

All these types of poles and zeros have \$j\omega\$ instead of \$\omega\$ which is what I would get if I separate in two terms: \$(1+\omega\sqrt{LC})(1-\omega\sqrt{LC})\$

Appreciate your attention.


texts: How to safely convert 120VAC from a lamp bulb socket to 12VDC

texts:
For the holidays, I'd like to make my chandelier light up with different colors.  There are all sorts of cheap RGB LED strips that, via remote, allow the user to program patterns of lights.

These strips can require 12VDC @ 6A, and I'm not sure how to get DC power at a remote location like a chandelier.

My idea was to replace one of the lights in my chandelier with something that magically converts the AC to 12VDC.  The only thing I was able to find were E27 to GU10 converters.  This is close, as I could simply wire a 12VDC converter into it.

But is it safe?

Are there any other safety-related things to consider when undertaking a project like this?  Since 72W (12V @ 6A) is below the maximum rating for the bulb, hopefully I am okay there.


texts: Can I use a point-of-load converter for providing USB power?

texts:
I'm designing a power supply that I would like to have a USB power output for charging/powering USB devices.

In an effort to reduce risk and design time, I'm looking at mounting a DC/DC converter on my PCB. I'd like to be able to supply >= 2A to support fast charging applications and for future-proofing.

The cheapest converters that fit the bill seem to be point-of-load modules (e.g. http://uk.rs-online.com/web/p/non-isolated-dc-dc-converters/6894703/).

I understand that these are meant for powering known loads (FPGAs, DSPs etc.) internal to the design.

Are these modules suitable for powering "unknown" loads down a cable?

You may assume that I have taken care of the other considerations with regard to meeting USB charging specs etc. I'm only concerned at this stage with the suitability of these modules for supplying power.


texts: How to identify specs of guitar pots and capacitors?

texts:
I have a 1986 Gibson Les Paul Custom. Looking into the control cavity, I see that all four potentiometers are stamped R1378511. The two tone pots also have the code 71-079 stamped on them. I cannot see the second stamp on the volume pots because these numbers are hidden underneath the solder connecting the various wires.

What resistance are these pots? Is it reasonable to assume that the volume and tone pots have the same resistance because they are all marked R1378511? Or is it possible that the volume pots have some other different code concealed under that solder? Any additional information about these pots and their codes would be appreciated.

Note: It did occur me to just put a multimeter across the pots, but they are wired together with the pickups, and I don't know the DC resistance of the pickups.

EDIT: I did managed to find a bit more information about the 71-079 code. This article also suggests that there is meaning in the R code. I might be overreaching a bit, but the code on mine might indicate they were manufactured in the 11th week of 1985.

I also want to identify the type + specs and any other details folks might have about the capacitors. I'm no expert but they appear to be ceramic or mica capacitors and are marked mp 203m 100v.


texts: designing a circuit to energize a 5hp motor when current is sensed to include a time delay (delay on release)

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I am designing a circuit that would energize a 5hp motor(dust collector) when any of several woodworking machines are energized and would include a time delay(delay on release).
I would like to use a current sensing device on one of the 230V legs of the feed line to a sub panel. This would then energize a contactor which would energize the dust collector. I would also like to have the collector run an additional 15s before de-energizing.
The dust collector(5HP) requires a 1 PH, 30amp circuit.
I have researched and found many options but none specific to my needs. Basically, what I want is that when I turn on one of several(8) machines in my wood shop, that a 5hp dust collector is energized and will continue to run 15s longer and then shut off. All the machines will be in the sub panel and the feed for the dust collector will be fed from a different panel (not subject to the current sensing device) I believe all the parts to do this are available, but can't seem to find them.
Any help, would be much appreciated.


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My new house flat is near an overhead power line. It's a steel structure so it's the higher energy lines. The line is about 1200 feet away at the closest point, I guess that is fairly far and you'll never know if you're ever under an electric cable. How safe is this?

The land the flat is on is 20 meters higher.

How safe is this?


texts: Select sampling frequency to closed loop control in a DC-DC converter

texts: For a DC-DC converter in current mode control the control variable is the inductor's current, which at steady state is periodic. which is the ratio between the switching frequency and the sampling frequency to use this type of control? By the Nyquist–Shannon theorem the sampling period should be at most half of the signal period, it is that enough?  but even them it will only apply for steady state, for the transient the sampling frequency should be even higher. Am I missing something?


texts: If one sends short bursts of electric current that abruptly turn on and off, why does the receiver receive a smoothed-out current?

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An Introduction to Information Theory: Symbols, Signals and Noise, by John R. Pierce, says the following:

The difficulty which Morse encountered with his underground wire remained an important problem. Different circuits which conduct a steady electric current equally well are not necessarily equally suited to electrical communication. If one sends dots and dashes too fast over an underground or undersea circuit, they are run together at the receiving end. As indicated in Figure II-1, when we send a short burst of current which turns abruptly on and off, we receive at the far end of the circuit a longer, smoothed-out rise and fall of current. This longer flow of current may overlap the current of another symbol sent, for instance, as an absence of current. Thus, as shown in Figure II-2, when a clear and distinct signal is transmitted it may be received as a vaguely wandering rise and fall of current which is difficult to interpret.

Of course, if we make our dots, spaces, and dashes long enough, the current at the far end will follow the current at the sending end better, but this slows the rate of transmission. It is clear that there is somehow associated with a given transmission circuit a limiting speed of transmission for dots and spaces. For submarine cables this speed is so slow as to trouble telegraphers; for wires on poles it is so fast as not to bother telegraphers. Early telegraphists were aware of this limitation, and it, too, lies at the heart of communication theory.

As someone who does not have an electrical engineering background, I find the described phenomenon perplexing. If one sends short bursts of electric current that abruptly turn on and off, why is it true that, depending on the type of circuit, the receiver may receive a smoothed-out current, rather than the discrete currents that were sent? One would expect, naively perhaps, that the signals received would be identical to the signals sent?
I would greatly appreciate it if people could please take the time to answer this using language that can be understood by someone without an electrical engineering background.


texts: Why do ICs interconnects have squared corners

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I was wondering, why do ICs interconnects have squared corners if they carry hi-frequency signals? (considering most transmission lines that handle high speed signals have chamfered/beveled corners for electromagnetic interference minimization).
Thanks in advance.


texts: RAM compression. Why hasn't it caught on?

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I was reading an journal on Hardware Compression of RAM and I was wondering why something like this hasn't become commonly used. Something like this would be really useful to servers or the kid at home who's rendering video for his Minecraft channel.

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.122.3232&rep=rep1&type=pdf