texts: Bluetooth receiver combining differential outputs to single ended (LR, N) to one (main) secondary amplifier

texts:
Hello I am new to this forum recently purchased a CSR8645 Bluetooth Module

I have a Sony MHC GX Music system  with AUX/MD Video Audio input (Left Right Ground).

But in my CSR8645

SPK L P1
SPK L N1

SPK R P1
SPK R N1

How to combine these to power the music system.

Connected LP1, RP1, battery - to music system but getting low volumes, also tried connecting both LN1+RN1 to ground input to music system getting a lot of distortion.

TPA6120A2

powered with battery

very high distortion

.

Sorry for my bad English.

Thanks in advance :)


texts:
I was capturing waveform of SPI signal using scope , signal is in 8-10Khz range, scope is 100Mhz bandwidth.

What I see both high and low level of signal at same time on scope ( see above pics with red marks) , Scope running in auto mode and normal triggering mode both. But i do single trigger or stop the capture then this become OK, look to me any setting or refresh rate of scope.

Did any one see this type of thing with DSO.


texts: So I understand that the capacitor charges up to the peak voltage and remains there since it cannot discharge due to the diode. But when I reduce the voltage on the input, the capacitor voltage also reduces, but it cannot discharge since there is no path. So how does it reduce its voltage ?


texts: Transformer Open-Circuit & Short-Circuit Tests

texts:
I need to find the losses of a transformer through simulation.
I am measuring voltage, current & power.
I know the method to find the losses but I am unsure if I should use the rms or peak values for the measured voltage & current in the calculations of the losses.
Can someone please advise?


texts:
This is my first post on Electrical engineering, so bear with me.

I'm making a project for school that is supposed to mimic a wind turbine. So, it will use a case fan for a computer as the "turbine". When looking at diagrams on Google, I see that there are usually only 4 wires:

yellow (tachometer)
black (ground)
black (ground)
red (12V or 5V).

Some diagrams literally say 12V or 5V.

My question is: how do I tell what the red wires voltage is? I would prefer 5V.

Thanks in advance! I can provide more info if needed.

Edit: like this: https://youtu.be/jiAhiu6UqXQ


texts:
I'm working with ESP8266 Wemos D1 Mini and HC SR-501 (PIR sensor) in one particular project (please, see the circuit image in annex). The question is the HC SR-501 stay always LOW. I tried change the PIR Sensor by ultrasonic sensor (HC SR-04) and the circuit works fine (obviously, little things was changed)!
Why this circuit not work with PIR sensor? Could be the PIR sensor with some problem?
PS: i used two PIR sensor and both not work.

Thank your for help.


texts: Why asymmetrical current limiting on ESD Diodes?

texts:
I was reading this:

https://www.analog.com/en/analog-dialogue/articles/esd-diodes-as-voltage-clamps.html

And came by this:

Why would anyone choose the configuration in Figure 1, which limits current for negative spikes but not positive ones, over Figure 2?


texts: Interfacing a flow control sensor with a microcontroller

texts:
How can I interface this sensor with a microcontroller?
It has a normally open output and it will work @ 24V.
If I feed the BK contact from the sensor to a pin of the microcontroller through a voltage divider, would that be a good design?


texts: Open Collector Output connection to a relay

texts:
Hey sorry if this question is too simple, as i am not an expert in this.
I have a device ( industrial router, works at 0- 30vdc) which has a Galvanically isolated Open collector ( External 0-30 VDC, 0.25A ) and the GND. I also have OC output ( External VCC 0-30 VDC ). These OC outputs can be remotely switched on and off using http . I need to attach a relay to this connections so that I can power up big flood lights ( 300 W ) on and off . Can the this flood lights be powered up by any chance ?


texts: Reducing a line signal in the home HiFi system

texts:
In my HiFi system the CD player is playing way too loud compared to the other sources (radio, streaming gadgets, tv. etc)

I figure a simple voltage divider say 33kohm and 27kohm would reduce with about 6dB. Simply hack the circuit into the cd player, where there is plenty physical room around the connector inside.

Something like this

*---,
    |
   33K
    |
    +-----*
    |
   27K
    |
*---+-----*

But, will this hack be bad for the fidelity?

Should I aim for 50kohm as imput impedance or is best practice different when we are dealing with stereos from '90?

Also, a friend of mine told me to add a 220nF cap in series with the output to block DC components, but I failed to understand where they should come from.

*---,
    |
   33K
    |    220nF
    +-----||----+----*
    |           |
   27K         56K
    |           |
*---+-----------+----*

The CD is a NAD 5240 and the preamp is a NAD 1155 in case any of you think it might matter.


texts: Digital PLL behaviour when signals start off at the same frequency but out of phase

texts: I am studying Digital PLL's.  I'm puzzled by what happens when the two input signals (input + feedback) start at the same frequency but at different phases.  As far as I can see the error signal from the phase detector will cause the VCO to change to a different frequency ( either larger or smaller than the input frequency, depending on which of the two input signals is leading). Assuming that the initial phase difference is quite large, does the feedback frequency immediately change to a substantially different frequency and then slowly converge back to the input frequency as the difference in phase of the two signals gets smaller ?


texts:
How can I use my computer as a Profinet IO device,

I need to have some read-write parameters for this purpose.

I found this python code: https://github.com/devkid/profinet/tree/master/templates

But when send connection request and receive answer this code does not catch reply so how can I solve this or how can I find the software ?


texts: I am currently designing a circuit in Autodesk Eagle which requires a 555 timer IC. The timer may be any 555 chip, such as an ne555, tlc555, or lm555, or even one of their 556 variants, but the lm555 would be best. I am able to add the device to the circuit just fine, but, as it does not automatically have a model, I am unable to simulate it. After hours of scouring the internet, including but not limited to EE Stack Exchange, I have been unable to find a SPICE, NGSPICE, or LTSPICE model for any of these chips. If anyone could help me to find such a model compatible with Eagle, it would be much appreciated. Also, as this is my first time working with SPICE simulation in Eagle, installation instructions would be further appreciated, but are less important than the model itself.


texts:
I'm trying to learn how to use transistors to amplify current and I can't wrap my head around how to use them with diodes, specifically LEDs which display nonlinear properties.
I know that they have IV curves, meaning that doubling voltage won't mean only a double in current. It will be much more.
How do transistors deal with diodes?

simulate this circuit – Schematic created using CircuitLab
I learned that (generally) the collector current is Beta * Base current. In this example let's make it easy and make beta = 100
Also, once the current in the base reaches a saturation value, Vce is 0 due to the current gain causing a complete drop in the voltage before the transistor.
I've always had trouble when it comes to LEDs, but does the Ic = Beta * Ib apply even with an LED?
If the base is receiving 0.2mA, then Ic = 20 mA, and from the LED datasheet that means the LED drops (for example) 2.5V. I can find the R1 value which would allow this to work with Ohm's Law (325 Ohms).
But what happens in this circuit when I apply, lets say, 0.1mA to the base? Now 10 mA runs to Ic, meaning the LED drops (lets say from a fake datasheet) 1.2V, and the 325 Ohm resistor has to drop 7.8V. This means that 24mA is running through it.
How does the math work in this situation? I am completely lost. Thank you!


texts: Coil trembling/shaking with IRF520-520N MOSFET

texts:
I'm trying to control a (cd rom - head) coil for experimenting with power MOSFETs and transistors. I control it with a potentiometer connected as a voltage divider. It works right I suppose but I get a tiny tremble. Is it normal? Can it be eliminated? (currently I don't use any heat-sink for the MOSFET). The power supply is a wall wart with 1 Amp rating.

simulate this circuit – Schematic created using CircuitLab


texts: Minimal Hall effect sensor circuit to keep something off after certain RPM achieved

texts:
I have a somewhat limited understanding of electronics and circuits. I'm trying to build a circuit that will keep a transistor in an off state after a given threshold of RPM is achieved using a A3144E Hall effect sensor.

For example, anything let's say that is below 500 RPM, I would like the transistor to be in an on state, and anything above 500 RPM, the transistor should be in an off state.

How could this be achieved using minimal and common parts without the use of a microcontroller, etc.?


texts: Are pull-down resistors included in the mbed USB ports?

texts: For the mbed LPC 1768, I am trying to establish a USB connection with an external device (pins 31, 32, and 39 for D+, D-, and Vbus, respectively). According to USB in a NutShell: Connectors, a 15kΩ resistor must be connected to D+ and D-. Are these resistors included within the mbed, or will they have to be connected externally?


texts: Verilog/System Verilog restrictions on generate block and continous assignment

texts:
I took the carry look-ahead code from  link and modified it to be wrong. The part I modified are  assign w_G[jj]   = (i_add1 & w_P[jj]); assign w_P[jj]   = i_add1[jj] | w_G[jj];, now simulating the cirucit using icarus causes the simulator to hang. I want to figure what is causing the simulator to behave in such a way. However, commenting the above lines one after the other poses no problem to the simulator.
Fulladder.sv
module fulladder(input logic i_bit1,i_bit2, i_carry, output logic o_sum, o_carry);
    assign {o_carry, o_sum} = i_bit1 + i_bit2 + i_carry;
endmodule : fulladder

Carry look-ahead module (wrong though)
`include "fulladder.sv"

module carry_lookahead_adder
  #(parameter WIDTH=3)
  (
   input [WIDTH-1:0] i_add1,
   input [WIDTH-1:0] i_add2,
   output [WIDTH:0]  o_result
   );

  logic [WIDTH:0]     w_C;
  logic [WIDTH-1:0]   w_G, w_P, w_SUM;

  // Create the Full Adders
  genvar             ii;
  generate
    for (ii=0; ii<WIDTH; ii=ii+1)
      begin
        fulladder full_adder_inst
            (
              .i_bit1(i_add1[ii]),
              .i_bit2(i_add2[ii]),
              .i_carry(w_C[ii]),
              .o_sum(w_SUM[ii]),
              .o_carry()
              );
      end
  endgenerate

  // Create the Generate (G) Terms:  Gi=Ai*Bi
  // Create the Propagate Terms: Pi=Ai+Bi
  // Create the Carry Terms:
  genvar             jj;
  generate
    for (jj=0; jj<WIDTH; jj=jj+1)
      begin
        assign w_G[jj]   = (i_add1 & w_P[jj]);
        assign w_P[jj]   = i_add1[jj] | w_G[jj];
        assign w_C[jj+1] = w_G[jj] | (w_P[jj] & w_C[jj]);
      end
  endgenerate

  assign w_C[0] = 1'b0; // no carry input on first adder

  assign o_result = {w_C[WIDTH], w_SUM};   // Verilog Concatenation

endmodule // carry_lookahead_adder

Testbench
`include "cla.sv"

module carry_lookahead_adder_tb ();

  parameter WIDTH = 3;

  logic [WIDTH-1:0] r_ADD_1 = 0;
  logic [WIDTH-1:0] r_ADD_2 = 0;
  logic [WIDTH:0]  w_RESULT;

  carry_lookahead_adder #(.WIDTH(WIDTH)) carry_lookahead_inst
    (
     .i_add1(r_ADD_1),
     .i_add2(r_ADD_2),
     .o_result(w_RESULT)
     );

  initial
    begin
      #10;
      r_ADD_1 = 3'b000;
      r_ADD_2 = 3'b001;
      #10;
      r_ADD_1 = 3'b010;
      r_ADD_2 = 3'b010;
      #10;
      r_ADD_1 = 3'b101;
      r_ADD_2 = 3'b110;
      #10;
      r_ADD_1 = 3'b111;
      r_ADD_2 = 3'b111;
      #10;
    end

endmodule // carry_lookahead_adder_tb
```


texts: How to convert SIMetrix schematic into netlist

texts: Is there a feature where the schematic created can be automatically converted to its netlist equivalent?


texts:
I want to crimp these guys.

Is it better to just not use a ferrule at all if I cannot find the right crimping tool, and just fold the wire on two, or is there a good manual way to do it? I have googled suggestions, and some people suggested pilers, others were against, and so on. So I don't know what is a legit manual way to do it (if it exists).

Also I see there are a lot of tools with different types of mechanisms, which one do you prefer and why? And will a cheap one (that I think I got, but I can't find it), do the work?


texts: How do I solve this circuit using nodal analysis?

texts:
Hey guys I cannot wrap my head around this damn circuit and how I'm supposed to solve it using nodal analysis. I chose the bottom node as my reference node and I got to these equations:

Node A is the left one, node B is the middle one, node C is the right one and the reference node is the bottom one.

Node A :        (Va/100)  -4  + (Va-Vb)/50 + (Va-Vc)/20 = 0

Node B :        -(Va - Vb)/50 + 4 - 10 -2 + (Vb-Vc)/40 = 0

Node C:         2 + (Vc/25) -(Vb-Vc)/40 -(Va-Vc)/20 = 0

I am supposed to find Vx.

Are my equations right? How do I find Vx?


texts:
I want to calculate \$U+,U-,U_A,P_Q\$ of the following Circuit:

I have redrawn the Circuit to:

For an ideal Opamp, there is no current into it so:

\$i_{R=10k} = \frac{4V}{10k} = 400\mu A\$

\$P_Q = 1.6mA\$

As the Potential at Virtual Ground is the same as at \$U_-\$ i can say:

\$ U_+ = U_- = U_Q = U_A \cdot \frac{30k}{20k+10k}\$

so: \$ U_A = 4V \cdot \frac{20k+10k}{30k}=6.6V\$

but Falstad-Circuit-Simulator dont show me my calculated Values..
what I am doing wrong?

Here is the Falstad-Circuit Link: Circuit


texts: Can galvanic isolation be performed at the user interface (UI)?

texts:
With capacitive touch sensing and transparent materials, it seems like it would be possible to run small digital devices from A/C mains without a transformer isolated supply.

Is there a flaw in this thinking?

Would it make a capacitive dropper power supply from mains power safe, if the packaging is sealed up water-tight?

Is this how modern stoves etc are designed?

Picture from a different question.   Putting UI into the switch plate form factor.


texts: 2.2K ohm resistor in series with 1A power linear supply circuit, is that right?

texts:
Here's right after the bridge there's 2.2k resistor in series with the regulator.
This circuit is supposed to provide 1A current to the load! is that correct?


texts: Why are the SF amps and FL amps different even though SF = 1.0?

texts:
This motor has a service factor (SF) of 1.0 and yet the SF amps > full load amps (FLA).
As I understand it, service factor is the allowed total load in an overload situation (not sure for how long, but I assume something like high starting torque situations which are brief).
So this motor seems to be saying, in effect, that no overload is allowed. Therefore I would have expected that the FLA = SFA, but it does not.
Comparing the actual SFA and FLA values, SFA is about ~1.14 of FLA. So you'd think that would be roughly the SF as well.
This was used on a machine (air compressor) labelled as "6 HP" and the motor nameplate also reads 6 HP in the crease of the label (to the right of the model #).
Why are the SFA and FLA different for this motor?


texts:
I'm at my wit's end trying to figure out methods to separate Dupont wires.
I ordered an 8 pin SOIC clip from eBay.  Due to low funds I had to opt for the cheapest alternative. It arrived along with a 40 bundle of Dupont wires.
Initially, after attempting to connect the Dupont wires to the clip, I noticed that the Dupont connector is too large for the clip (4 connectors to a side) to fit all 4 sides of the clip. After stripping the clip's plastic fitting out of it to a barebones wire with the metallic adapter it fits.

Link to original large image on Imgur
Will the Dupont wire connector as a barebones metallic adapter short out my chip if I use it to connect it to a Raspberry Pi?
I'm trying to get it to a state where I can reprogram the chip with my Raspberry Pi without shorting it.
Would using paper in between be sufficient to stop it from frying? Nothing else will fit to separate it unless there is an alternative I could do with household items. There really isn't any alternatives for me as I can't afford a "Pomona" clip due to their expensive pricing.


texts: What is the use of these capacitors in this circuit?

texts: I'm pretty new to electronics, and while exploring the web I came across this circuit for a 180v Nixie tube power supply. http://www.electronics-lab.com/project/hv-nixie-dc-dc-switching-power-supply/ (Schematic is here http://www.electronics-lab.com/wp-content/uploads/2015/03/schematic38.png). Most of the components are just capacitor of various type between Ground and Power (12v and 180v). What is their purpose? Would the circuit still work if I remove some or all of them?


texts:
Anyone have any idea how I could remove this component?

I've tried blowing hot air, used solder wick, tried to poke the holes with two soldering irons, cut the pins to near the PCB, but it won't budge.

It would be ideal if I had a rectangular piece of metal that could get up to around 380 degrees celsius and that I can just place on the pins all the while pulling to remove the component.


texts: Please Identify this adjustable inductor (ferrite-core bobbin)

texts:
Can anyone identify this component and suggest where to get more of them---or provide a manufacturer/model number? I need more for an HF radio project but haven't found them.
These are for hand-winding variable inductors with ~0.1mm wire and then it is tunable by twisting the ferrite-core.  The 2x3 pin arrangement allows for winding your own center-tapped RF transformers:


texts: Do home UPS (mostly advertised as inverters) have a rectifier built in?

texts:
This is regarding home UPS/inverters which are typically known to convert the DC from the battery to AC,  so the AC can be used for household purposes.
What I don't understand is how the batteries are charged.
From my understanding the 12V or 24V batteries be it lead-acid or Li-ion are charged using DC current. The batteries don't understand AC current either for input or output. They take DC and output DC. But the typical household gets AC current.
Which device is converting the AC to DC for the batteries to get charged?
Is it done by the UPS/inverter device?
For example take this device (branded and sold as UPS not an inverter) - Home UPS 900VA Zelio+ 1100 and these devices (branded as inverters and sold as UPS.) - Exide UPS/Inverters


texts:
I'm building an analog drum machine and want to have a 3 tone control circuit to individually adjust the bass, midtones, and treble frequencies on each of my instrument channels.

I thought it would be fairly simple to find a circuit that I could modify to my liking, but it's proving to be more difficult than I thought. I found this Three-Band Active Tone Control circuit using the OPAx22x Low Noise Operational Amplifier from Texas Instruments (Page 26 of Datasheet)

This is exactly what I'm looking for, except no design equations are given and no description of how the circuit works is provided. I really want to understand how this circuit works intuitively/mathematically and would greatly appreciate any explanations and equations.


texts:
I have the following problem.

Consider the circuit below, where the bottom of the arrow is the +-pole of the voltage drop:

What resistor value for \$R_2\$ gives a damping factor of \$d=0.9\$ for the filter transfer function \$\frac{V_{out}}{V_{in}}\$.

Okay so first thought is to find the transfer function. We can write a node equation for \$V_{out}\$.
\$ \frac{V_{out}}{R_2}+\frac{V_{out}}{600 \Omega}+\frac{V_{out}}{330 \text{nF}}+\frac{V_{out}-V_{in} }{5.1 \text{uH}} =0\$
Rearranging this equation with Maple gives me following transfer function.
\$ \frac{V_{out}}{V_{in}}=\frac{196080 \cdot R_2}{1+3.22638\cdot 10^6 \cdot R_2}\$
But from here I'm kind of stuck, since I don't know where to go. However, I have these equations from my notes that might help me.
\$ d=\frac{1}{Q_{factor}} \$
\$ B_{bandwidth}=\frac{f_c}{Q_{factor}} \$
Where \$ f_c\$ is the resonance frequency.
I hope someone can help me with this.


texts:
I'm trying to estimate the power consumption of an in-wheel electric motor. I used the formula

$$P = T\cdot\omega + K_m\cdot T^2$$

where T is the torque, ω is the motor angular velocity and \$K_m\$ is a constant who takes into account power electronics and motor copper losses. I plotted the power over time.

Is this the right way to calculate the power consumption? How can I treat this topic in a not too detailed but exhaustive way?

All the best.


texts:
I'm trying to learn more about automatic current range switch and stumbled across Nordic's nRF6707 power profiler kit that has very interesting topology to choose between three different current ranges.

Now I "understand how" this circuit works but what I'm having hard time with is figuring out how to start analyzing thresholds, different initial conditions and in general doing analysis of this circuit in order to modify it.

Here is the screenshot of the schematic portion for automatic switch:

What I'm having trouble with and could really use help with, is suggestions on how to start analyzing automatic switch portion. I'm not sure how to find steady-state values and also initial conditions (although I assume both SW1 and SW2 should be off on power-up with no load) and also how to analyze transitions when measured current crosses Vref On/Off thresholds (in up or down direction).

Any help or suggestions would be much appreciated!


texts: Measuring generated power (kW) in a power plant and storing/logging values

texts: Given an electric power plant (hydro energy) that currently has just an analog indicator for how much power (kilowatts) is generated, which components would be needed to measure the generated power digitally in real time and take that measurement into something like an Arduino and/or Raspberry Pi so that I can log the values over time in custom software?


texts: What happens when DC is applied to a piezo crystal?

texts: I've heard that when an alternating current is passed through a piezo crystal it vibrates. But what happens if a direct current is passed through the crystal? I'm assuming depending on the direction of the DC applied the crystal either compresses or expands. Am I right? I'm interested in compressing a cuboidal shaped piezo crystal. How do I do it with DC. I haven't bought a crystal yet so I would like to know theoretically what direction of DC will cause the crystal to compress or expand?


texts: Trying to Get the Most Cooling Power out of TEC Peltier Element: Smaller or Larger Peltier?

texts:
I am trying to achieve the strongest cooling effect using a TEC Peltier element.

Currently, my set up is two small, 20mm x 20mm peltier TES1-4902 run with a 5V 2.4A USB Battery Pack per peltier.

I need a way to reduce my costs while keeping the same cooling power.

Right now, it is expensive for me to run this set up due to the fact I need two batteries, and I am also looking to improve my efficiency while cutting out an entire battery and/or Peltier.
The reason I have two separate battery packs is that I can not find a cheap, small, and thin battery pack that will output 4.8 Amps: however, putting two battery packs in a series may help eliminate one peltier.

So, I have a few branching question that center around a theme:

1) Would a larger Peltier allow for a stronger cooling effect as a result of a larger surface area, say like a 50MM x 50MM peltier, despite the fact (presumably) that it may be more difficult to cool one single peltier than 2 smaller, seperate ones?

2) Is there a Peltier size that would allow me to reduce my power consumption while maintaining a similar cooling effect?

3) Is there a way that I can output 5V 4.8A that is not in two separate USB battery packs that is small and relatively cheap, as battery price:output ability for small scale consumer is quite high and USB battery packs have been the cheapest source of sustainable power for me.

My problem stems from the fact that I am trying to pump as much power and achieve as much cooling power as possible without having to have, say, two battery packs and make the project too expensive. I need a way to reduce my costs while keeping the same cooling power.


texts: Circuit analysis with node voltage method

texts: The problem requires I determine the value of I0, I think my solution is correct but I don't know how to check because I got the problem from a text with no answers. Looking for more experienced eyes to check for me.


texts: In all the configurations common collector, common base and common emitter, is the base always the input?


texts:
I have to place this Teensy 3.1 on a PCB, I am planning to make the PCB such that it has headers on which the whole Teensy will fit. Essentially, it is similar to making a shield like we make for normal big Arduino boards.

I am wondering how would I connect the SMD Digital IO pins to the PCB? For other IO pin with holes I could just place 0.1" male headers, but what to do for SMD pins which are on the back of Teensy (pin number 28-33)?

Front Image:

Back Image:


texts: How does this electrostatic generator operate?

texts:
I'm trying to understand how this piezoelectric static generator works.

I've found this video and I would love for someone to explain to me the operation of this device, and maybe assist me with a working schematic using a AC Source

https://www.youtube.com/watch?v=d0qttk70vrQ

Maybe start off with the electron.

simulate this circuit – Schematic created using CircuitLab

simulate this circuit


texts: How to maximize the voltage range using an operational amplifier (differential amplifier)?

texts:
I'm trying to maximize the voltage range using voltage dividers and operational (differential) amplifiers, but am not able to do it. I do not have an electrical engineering background, but my project involves using it, therefore, I have to understand how to do this.
I understand how voltage dividers work, but the bigger problem is with op amp. The voltage divider's formula that I found was: V_out = V_in/(R_1+R_2)*(R_2).

The diagram that we used during the introduction for a differential op amp is: https://goo.gl/yaRlx9 and the formula that we used was (and just to mention, we did not derive this formula): V_out = (R_2/R_1) * (V_2-V_1)

I have a sensor which acts as a variable resistor with resistance varying between 60~180 [ohms]. The output voltage has a range of 0 and 5 volts (and I have to maximize this range).

Using a voltage divider and even after optimization, the maximum voltage (output) range that I was able to achieve was ~0.25 of the above range.

Now, the help that I need is a diagram for a circuit (with values for the resistors and the voltages) that uses differential op amp and voltage divider and is able to maximize the voltage range (of the final output).

I think I have a pretty good understanding of voltage dividers, but not of op amps, therefore if you could also help me understand how you use two inputs in the differential op amps (example, do I use two voltage dividers?), it would be very helpful.

Any help will be appreciated, plus if there is any need for correction in the question, feel free to post it.

Thank you!

*When I say 'maximize the voltage range', what I mean is that it should be able to cover all the values (0 to 5 volts) and this should be for the final voltage that the op amp gives out (v_out in the diagram and the final output will vary because of the variable resistor, which is the sensor, according to me).

**I haven't included a diagram of my schematics because I really don't know how the final circuit will look like. There should be a voltage divider, but because I don't know how it will look like (example, will there be multiple voltage dividers or single), I haven't included it.


texts: Getting around two dimensional array prohibition

texts: The textbook I just bought, Verilog HDL: A Guide to Digital Design and Synthesis by Samir Palnitkar, says it's impossible to have a two-dimensional array directly, but someone who's used Verilog says there's a way to work around that. Furthermore, if my quasi-two-dimensional array is value "outer" and i does not equal j, then the array associated with "outer[i]" is not necessarily of the same length as the array associated with "outer[j]". Can anyone tell me how to code this in Verilog?


texts: How to interpret this CAN bus data and find an equation?

texts:
I am trying to reverse engineer the data sent from an old CAN bus data logger. It sends a single ID which is selectable from a dip switch.

The only bit of data I am struggling with is the RPM

I plan to feed this data into a STM32F Discovery, in the past most of this type of data is linear and easy to work with, for example RPM=CANbus data x 0.32 but looking at my data below it is not linear and I cannot find a simple way of interpreting it:

RPM      CAN Bus Decimal Data

1000 = 0312

1250 = 0389

1500 = 0464

1750 = 0541

2000 = 0613

2250 = 0688

2500 = 0762

2750 = 0828

3000 = 0903

3250 = 0979

3500 = 1058

3750 = 1140

4000 = 1226

4250 = 1313

4500 = 1401

4750 = 1485

5000 = 1568

5250 = 1653

5500 = 1736

5750 = 1821

6000 = 1900

6250 = 1984

6500 = 2063

6750 = 2144

7000 = 2224

7250 = 2301

7500 = 2377

So I need to come up with an equation so I can put it in my code to calculate the RPM.

RPM = Data x 0.3 + 12 is very close but not close enough

I have plotted the above on a graph and the line of best fit is:
y=0.00000357058x^2+0.29145x+11.9358 but this seems very complicated to try to replicate in code and I also cant see why the designer would have made the data so complicated.

So my question is how can I take the above data and come up with an equation or code so my device can interpret the RPM from the CAN bus data?


texts: How should microphone impedance relate to input impedance?

texts:
I have:

a Boya BY-MM1 microphone which has a nominal impedance of 300 ohms
a Steinberg UR-12 with a balanced microphone input that has a nominal impedance of 4 kOhm

I connect the microphone to the audio interface (via a 3.5mm cable and a 3.5mm->XLR adapter, if that's important) and I hear no sound. Another microphone, which is instrumental and for which I don't know the exact impedance or model, works perfectly (it is connected via an XLR cable, if that's important.)
I am suspecting that the impedance ratio is too off. Am I right or have I missed something else? If I'm right, what should the ratio be? I've read it should be about 10, but it doesn't seem like the case here.


texts: Efficient strategy to acquire multiple spi interfaced sensors data in parallellover several spi buses?

texts:
I want to continuously acquire temperature from many ( ~20) thermocouple MAX 31856 all on one PCB ultimately. This chip interface with spi. The project language is python
Because of the sensor latency, One multislave spi bus will be too slow.
So I would like to break down the sensors  in several (4 or 5) independent spi buses that I could address in parallel with multithreading from a small computer ( raspi or other) on One addressable bus.
I have found  mcu with 2 spi master but none with more than that.
I am considering using small mcu like the raspi pico for example and address them separately over an usb bus but i have not found any project doing that. Is there a problem with that approach?
What will be other  alternatives?


texts:
I've built a watchdog circuit for my Raspberry Pi using a NE555. In the astable configuration I'm counting ~5 minutes and then I kill the switch unless there is a signal from GPIO that discharges the C of the 555. I have a mosfet RFP70N06 with the gate directly connected to the OUT of the 555, and when C is 2/3 full out goes to GND, the mosfet is open and the power of the RPi is gone.

simulate this circuit – Schematic created using CircuitLab

My question is about the ground. The RPi does not initially share the supply ground as the rest of the circuit, since the GND of the supply of the RPi is on the Drain of the MOSFET. But then I'm using a GPIO pin, and I also used one of the GND pins on the header.

Since the RFP70N06 has an Rds=0.014 ohm I have my RPi with a 0.014 resistor on its ground, but from the GPIO header I have GND directly to the GND of the supply.

Does this makes sense? Should I be using an opto-coupler for the GPIO? I don't want a track on the PCB of the RPi being used as fuse.


texts: Is sum of currents equal to capacitor current for NMOS Inverter with Capacitor as Load?

texts:
I found this in my lecture notes and could not understand how drain current is equal to sum of load and (IL) capacitor currents (ICL) given in the figure for a NMOS Inverter with capacitor load. By looking at the direction of currents, I would assume load current would be equal to sum of drain and capacitor load currents.
I would appreciate if there is anyone who can make it clear for me.


texts: Your thoughts on connecting multiple leds in parallel and series

texts:
I would like to connect 32 3W LEDs together. All the LEDs are the same.

Each LED (32 of them):
750mA
2.2V
3W

Power Source:
Constant Current
3A
100W

I thought making 4 chains, 8 LEDs connected in serial in each chain and connect the 4 chains in parallel so 750mA falls on each chain. I may have to put a resistor on each chain according to the Voltage range of the power supply. I know I can connect all the LEDs in parallel but that is quite allot of soldering and more resistors in the project :)

I know that this may be risky if one of the LEDs fail. I thought of placing a 0.8A-0.9A fuse on each chain or even a current limiting resistor. I have no problem that all the LEDs won't work if one LED is burnt.

Will this work?

Gilad.


texts: I need to program a test with a ramp rate of 2.7V/sec to 12V. Im having troubles finding a PS that can do this. Can an Arbitrary Wave Form Generator achieve this for me?


texts:
I have built a Mach Zehnder interferometer in which a laser beam is first split. After each splitted beam is passed through a AOM driven at a fixed RF in my case 40 MHz and 40.04 MHz they  are recombined. The envelop of laser rep rate is modulated at the difference frequency, 40 kHz in my case.  Its a pulsed laser with 80 MHz rep rate. The attached image 1 shows the laser rep rate profile on a scope and after changing the horizontal scale (keeping everything same) you can see the modulated envelop(image 2). How can we calculate the modulation index from this?

The second query is related to the same modulation scheme in which I monitor the waveform after modulation on the FFT display of my lock-in (SR 865a). Image 3 shows when the signal to lock in is provided by splitting the photodiode signal with a BNC t and supplying signal to scope and lock in simultaneously. The fourth image shows when the photodiode output is dedicately fed to the lock in. They are many side bands each equally spaced at 40kHz. Also, if we see the dB value of the signal they in the range of 30-40. Is it satisfactory as my lock in is not able to "lock-in" when i feed the photodiode signal as a reference. However if I use a photodiode amplifier it locks in readily. How can I remove the sidebands ?


texts:
I have a simple MOSFET amplifier design and want to set Q1 drain to be one-half of VDD0 for mid-point biasing.

It may be achieved by tuning during simulation with a variable resistor in divider R2-R3, but I need to calculate the divider with equations. I know that for midpoint biasing I need R1 voltage drop to be one-half of VDD0. It will determine the Id current. For that Id current I need to correctly setup Vgs. For that I need Id,on, K-value and Vth of that MOSFET transistor. Using it from the datasheet will be very approximately. How can I build the additional schematic to measure Idon, K and Vth? Or do another solutions exits?

The schematic for measure Id vs Vgs

Multisim MOSFET model:

Modified amplifier:

MathCad calculations:


texts:
I've been trying to use my arduino as a thermal anemometer based on the excellent and tiny IST FS5 "thermal mass flow sensor" - there is more information and a datasheet here - http://uk.farnell.com/ist/fs5-0-1l-195/sensor-flow-gas/dp/1778049. I've set up the circuit as recommended in the data sheet, albeit using a different op-amp and transistor (and excluding the calibration resistor) and it seems to work nicely. The only problem is the output is between 5 and 10V, and obviously the arduino likes something in the 0 - 5V range. I've used a simple voltage divider to scale the voltage between 2.5 and 5V, but it would be nice to use the full range... unfortunately my electronics knowledge is far too limited for this!

I've read some similar forum posts and tried to use a 5V voltage regulator and another opamp to produce something useful but failed miserably! I'd really appreciate it if anyone could give me some hints on how to use an op-amp to achieve this. I feel like it also must be possible to change the wheatstone bridge arrangment so as to produce this voltage range in the first place, but have no idea how!

Thanks all!

schematic here - http://dl.dropbox.com/u/7549930/aaSchematic1.png

snap here - http://dl.dropbox.com/u/7549930/arduino_anemometer.JPG


texts: Choosing a stepper for antenna tracking system

texts:
I am building a prototype for an antenna tracking system. The following animation will make it slightly easier to understand what I have in mind:

https://youtu.be/DZ0LRf6_Zew

The two antennas are: https://www.wimo.com/xquad-antennas_e.html

2.3kg each (5lbs)
1.46m long (less than 5 ft)
They will have to be placed 2.8m apart (just above 9ft).

I intend to mount them on the horizontal mast so they are balanced.

I have what I believe is a good guidance algorithm that uses an IMU (a small sensor with magnetometer, accelerometer, gyroscope) that does not require feedback from the motors (azimuth and elevation).

The installation of this antenna will be temporary for a few hours at a time and I'd rather NOT use a designated antenna rotator like the Yaesu G5500 for this prototype.

I would like a mechanical resolution of roughly 1degree. I do not have strict values for speed, ideally it should take less than 10-15 seconds for the first move to track the satellite. After tracking has started, a full rotation typically takes several minutes, however I'd like to avoid mechanical oscillations. This will be used outdoors in controlled conditions, but there might be some wind. I am not too worried about rain at this point.

My question is: where do I start to size the motor and possibly a gearbox for this? Being a hobby prototype I am not ready to invest a huge sum of money for top notch motors, and I see that the internet has relatively cheap NEMAxx motors available, with options for a planetary or wormgear reduction, from 1:3 to 1:100. At this point, I don't know how to size the mechanical components, and before I commit hundreds of dollars in motors, gearboxes, drivers, I'd like to hear from somebody that has more experience.


texts: Can GPIO pins interfere with each other?

texts:
I have a simple circuit where I bitbang I2C (SCL/SDA is GP5/GP4) on a pic 12F629. It works perfectly, all the timings are correct, no errors etc. The exact schematic is irrelevant because I deconstructed the whole circuit to basic blocks and tested each part separately to make sure the slave is not at fault.

Note that I tested with different chips and different models and the problem persists.

Now I want to drive a random pin, say GP2 low. The moment I do this, the I2C waveform goes crazy.
Here's the waveform after pulling GP2 low (SDA blue, SCL yellow):

After some experimenting, here are my conclusions:

In I2C the devices are only allowed to either pull down or release SDA/SCL (in which case they are pulled up by the pull ups). So in order to designate HIGH we set SDA or SCL pin to input and thus it gets released and pulled up to +5V, and to designate LOW we set it to output and it is driven LOW.
Of course for it to drive SDA/SCL low when setting them to output, during the program's initialization both these pins are first set to output and given the value LOW, so now everytime they're switched from inputs to outputs during the i2c comms they automatically drive LOW.

And that last part is where I think it all breaks.

If after some point, after an i2c communication, I drive a GPIO pin eg. GP2 LOW or HIGH, this somehow affects the GPIO value of the OTHER gpio pins (namely SCL/SDA) which messes up everything. ie. SDA/SCL GPIO pins are set to 1, so when they are switched from input to output during the i2c comms, they get the value 1 instead of 0 and thus instead of driving the i2c bus LOW they drive it HIGH which isn't allowed. And now the only way to make it work again is:
 1. Set SDA/SCL direction in TRISIO to OUTPUT
 2. Set SDA/SCL value in GPIO to 0
 3. Set SDA/SCL direction back to input to release the bus and let it get pulled up by the pullups.

And now we're ready to resume communcations. Until I pull another GPIO high or low of course where everything is screwed again.

Now my question is this:
How could one go about fixing this? Could this be a read-modify-write problem?
I thought this would be a common problem, I was sure there would be a lot of people using i2c and a gpio pin at once and have them interefere with each other, but my searches returned no results.

Keep in mind there is nothing connected to the uC but the oscilloscope. I removed everything one by one to find the problem and the problem still persists.


texts: How to chose an IF, or how bad is zero-IF really?

texts:
In a superheterodyne receiver, what must one consider in order to chose an intermediate frequency?

Specifically, I'm working on a radio telescope project. It is basically a superheterodyne receiver where the IF signal is 1-bit sampled and then stored.

The bandwidth of the signal is 20 MHz. Now, to minimize aliasing, I'll be using a sample rate somewhat above the Nyquist rate. That means the minimum sample rate is ca 50 MHz. The highest I could sample, on the other hand, is about 120 MHz.

This would however mean an IF range from 0 Hz to 20 MHz. If we drop the lowest 1 MHz, this equals to 4.3 octaves.

The observing frequency is 1421 MHz, if that matters.

I'm mostly worried about the high fractional bandwidth of the signal.
So, my questions are:

Would it be problematic to amplify the 1-20 MHz (or even 0-20 MHz) signal using a high-speed OP-Amp (considering that many electronic components' behaviour is (inversely) proportionally dependent on the frequency)?
Is the high fractional bandwidth a problem? i.e. Would the SNR improve significantly if I used a 40-60 MHz range?
Low IF receivers are used to evade brown noise (noise power constant per octave) zero IF systems inherently suffer from. How much does it practically matter for an application like this?


texts: Best way to reduce battery consumption for LED device?

texts:
I'm building a device that needs to "light up" to indicate status to the user. I of course want to use LEDs to light the device up, but I'm worried about battery consumption since I would like it to last for a year on batteries if possible. The device will be using its LED(s) for around one hour each day.

What are the best ways to get power consumption down for the LEDs? Using PWM? Is it better to use a high-intensity LED or several lower-intensity LEDs? Blinking the LEDs is ok, in fact that is the most obvious power-savings trick I've found.


texts: What is the voltage range on an Arduino pin when doing analogRead()?

texts:
I know what an Arduino's ADC generates a number with 10 bits of resolution (0 to 1023).
How is this number generated? Is there a minimum and maximum voltage it will assign 0 and 1023 to, respectively?

I'm taking input from an amplified electret microphone.
Also, when I give the Arduino input, the value is not 0 when I'm not making noise in the mic. Sometimes is around 500, sometimes around 300, it changes. What could be the reason for this?


texts: unsure how to calculate power spectral density after passing through low pass filter

texts:
Unsure how to answer this question any help would be greatly appreciated
i have uploaded my attempt at an answer however i feel that i have done the conversion from dBm to Watts incorrectly
Im also unsure how to determine the power output of the filter


texts: How to assign clock/reset to sram in Quartus?

texts:
I'm building a system in Quartus according to this question

How to upgrade a Quartus II project from SOPC to QSys?

Now a part of the problem is how to assign clock/reset pins to my sram. In Quartus I don't have the options.

Can you help me?

Update

The suggested changes did not work for me as Quartus displays error messages that I can't interpret:

Update 18:07 130828

Now I only have 1 error left in the component editor:

Error: reset_sink: Synchronous edges DEASSERT requires associated clock

What does it mean?


texts: I am working on layout. I have two power supplies. For this when I took a via from Metal1 to n well I got no issues. But when i consider another via from Metal1 to n well, I am getting the following issues: a. welnotr_StampErrorMult, b. welnotr_StampErrorConnect. Please any one can suggest why these errors are coming and how to modify the layout?


texts:
I have a low level DC signal from a thermopile sensor of 0-9.1mV with 7uV increment. I feed this to an INA114 instrumentation amplifier with gain of 550 to get 0-5V output.

I tried introducing RF noise by means of GMS (phone call or SMS) with the output moving up from 0 - 1V (0 - 1.82mV input). I have a voltmeter on the input and output to monitor it at the same time. With the noise present, the input is perfectly fine while the output ruined.

I then set the gain to 1 so that input is equal to output. Still, the input is perfectly fine while the output is ruined. It seems that the interference is hitting the INA114.

Why is this happening and how would I overcome it?


texts: Getting a consistent and precise voltage for sampling

texts:
I have a 9V battery connected to an LM317T voltage regulator and it's regulating the voltage almost perfectly but I intend to use it for sampling and it fluctuates over a few mV. Generally between 1.628 and 1.63V.

I'm wondering if there is anyway to correct this effect or if it won't be a problem once my amplified signal is also applied?


texts: Faint power supply seen even when electrical switchboard sub switch is in the off position

texts:
A switchboard sub switch "P33" controls the electricity supply to the guest room.
When the sub switch "P33" is in the on position, the guest room wall sockets would have the full power supply. The tester plug shows the indicator lights brightly lit up in the correct configuration.
When the sub switch "P33" is in the off position, there is still a faint power supply on the wall sockets.
The sub switch "P33" is under the main switch "DB2", which is different from the main switch "DB1".
When the main switch "DB1" is off :
the guest room wall sockets would have no power.
When the main switch "DB1" is on, and the sub switches are all off :
the guest room wall sockets would also have no power.
When the main switch "DB1" is on, and some of the sub switches are on :
the guest room wall sockets would have a faint power supply.
It doesn’t matter which sub switches are on. The greater the number of sub switches turned on, the stronger the faint power supply. It just takes 4 sub switches turned on and we can see a faint power supply on the tester plug.
When there was a flash of lightning outside, I could see the tester plug briefly increase the indicator light intensity, then fall back to the faint light again.
By right, if the switchboard sub switch "P33" is off, there should not be any power at all on the guest room wall sockets.
I wonder what is causing this phenomenon.


texts: Describe this type of rotor from a three phase induction motor?

texts:
After CNC machining the rotor, to expose the outer surface of the silicon iron, this proves to be exactly the same as the inner surface was (the one facing the core).Just plain electric iron rings without skews/copper/aluminium bars. There are just six iron rivets holding them all together.
There was a thin sheet of aluminium (about 0.25mm thick) covering the rotor's electric steel from the inside too. What type of rotor is this? Where can i look it up?


texts:
The transconductance of an NMOS is

$$ g_m = \frac{\partial i_d}{\partial V_{gs}} $$

Is the transconductance of a PMOS the same?


texts: Is there any example, preferably by photos, how does assembly layer on PCB differ from the silkscreen? I understand, that silkscreen reference designators should be left visible after the parts are mounted on the board, and assy layer information can be obstructed after the assembly process. Is that the only difference? I cannot find any exact information on this over the internet, everything I have found is a unclear to me. Thank you.


texts: Driving solenoid valve using LM358 as comparator and ULN2003

texts:
I'm trying to drive a 12V DC solenoid Valve with following diagram.
In 1st block the PC input is compared with 2.2V and its output goes to block2 and ULN2003 for driving the valve.
The 2nd block is a pulse generator which is used to drive a Buzzer.
As said the 3rd block is used to drive Valve and buzzer.

1- When I try to connect the PC input (Using 2 separate wires for GND and +5V), connecting each wire(just 5V or GND is connected) causes that the valve to be on/off many times, It also happens when I touch the PC input wires, what should I do to prevent this?

2- Each output of ULN2003 is 0.5A but The the valve uses 0.8 A, is it reasonable to connect several inputs and outputs for driving the valve or should I use another IC to drive the valve? it's working but afraid if it brokes the ULN2003 in long time.

Update 1:
When a function generator is connected to input with no wave, Output of comparator is expected to be zero but it is a 50Hz Clock pulse as below.
What I've done wrong?

The comparator circuit.

Output when there is no signal and connected to PC or function generator.


texts:
I need to measure the noise performance of an DAC + Amplifier combination. The system has a bandwidth of ~100MHz and the expected noise level is approx. 1-2 mV rms.
What is the preferred instrument to do this?
I know there is the R&S URE3, which is only 30MHz and discontinued.
Is a spectrum analyzer the best choice? If yes which parameters are critical for this application?
Money is not an issue :)


texts:
From my GSM provider I have bought a stationary Internet access point from LTE.
Additionaly I have bought an antenna for it. Unfortunately when I was plugging it together I have damaged the plug. (Mainly because I want the to avoid this strong electrical field close to my workplace for health reason.)

Question 1:
Can someone help me to identify this plug. It looks like:

The outer diameter of the metal cylinder which is inserted is around 3.8 mm.

Based on my googleing, I suspect it is an male MMCX connector or an SMB connector. Can anybody confim this? In electronic catalogs also an impedance is given (e.g. 50 Ohms). What impedance is best for LTE antennas?

Question 2:
I'm thinking to extend the cable from currently 1 m to 5m by making an extension cord with male & female connector. Do you expect that the signal quality is strongly affected by this? Any points on which I should take special care here?
For mounting I i intent to follow this video: https://www.youtube.com/watch?v=nKLvaCi_TiA


texts:
Whats the difference between using:

ENTITY MyDemo is
    PORT(X: IN STD_LOGIC; F: OUT STD_LOGIC );
END MyDemo;

and

ENTITY MyDemo is
    PORT(X: IN BIT; F: OUT BIT );
END MyDemo;

What are the limitations of using BIT over STD_LOGIC and vice-versa? Are they completely interchange able? I understand that if I've define STD_LOGIC I can't use it with a BIT_Vector to access the elements in the array. But I can't seem to see the difference.


texts: transistor characteristics - Ube0 number meaning

texts: i'm trying to guess meaning of value marked as Ube0 in datasheets. (datasheet adress: http://www.datasheetarchive.com/dlmain/Datasheets-36/DSA-700258.pdf, the transistor I want to use is Tesla KF-508). I want to regulate secondary circuit by voltage divider on base. Does this value means that max allowed voltage on base is 7 volts and I must design voltage divider to not allow more than 7 volts and current no more than 2.2 mA ?? (computed from measured parameter h21e = 233, max current that I want trought collector = 0.5 A)


texts:
I need to capture the posedge of a signal (ONSWA) and output another signal (PSHOLD) high until I see another posedge of ONSWA. My solution is to use a DFF with an inverted output with ONSWA as the clock and D <= !Q. Now my question is how to properly ensure this circuit is reset when powered up. My solution is to use a RC circuit on both D and CLK but I want to know if there is a better/simpler way. My main concern the power usage--the circuit should not use too much power while in the "off" state (since it's battery powered). I also would like to avoid having PSHOLD high for a small period during reset if possible. If there's a better solution than a DFF or a better part, I would like to know that as well.

EDIT: Okay I've updated the design to use a DFF with (re)set.


texts: Is a very large capacitor the same as a short circuit?

texts:
This is a theoretical question. Let's say that we have two black boxes, each with two terminals. One contain an infinity (or arbitrarily) large capacitor in series with a 1 ohm resistor and the other contains just a 1 ohm resistor.

Is there a way to tell which is which using finite finite resources (e.g. upper bound on experiment time, upper bound on voltage sources, upper bound on equipment accuracy, etc)?

My thinking is that since the capacitor is arbitrarily large, it will not get charge to a noticeable voltage in a given finite time and thus will be identical to a short (zero voltage regardless of finite current).


texts: Step down switching regulator heating up with light loads

texts:
I built a step down switching regulator based on a Diodes AP5100 using the datasheet example circuit with this layout.  The voltage is being stepped down from 15V to 12V and the AP5100 is heating up to 60°C+ under light or no load at all(0-40ma).  At about 80ma load the temperature is more reasonable at about 40°C and runs relatively cool(low 30s) above 150ma.  The circuit that is being powered by this operates at low current(<20ma) 85% of the time and the other 15% at about 250-500ma, so it would be nice to have it run cooler under the light load.  Should I try increasing the inductor size to improve the light load efficiency?

EDIT:

The circuit that I am using is shown above and it's for 3.3v. The only change that I have made is to use 3.6k with 49.9k to get 12V. And also, I have substituted the B230A with a STPS2L60A. The caps are all ceramics at the proper voltages including the 10uF(35V) and 22uF(25V). The inductor is 3.3uH with these specs.


texts: Cannot find efficient current/voltage regulator to power LEDs

texts:
I have a 12V 4-pin common-anode RGB PWM'd signal being used to power some LED strips, and I would like to use it to power the VL-H01RGB00302 Vollong 3W RGB High Power LED - which is basically a set of 3 LEDs:

forward current and voltage:
  Red:          400mA, 2.5V
  Green, Blue:  350mA, 3.4V

Unfortunately heat dissipation would be a major issue if I merely used resistors: perhaps 10W wasted as heat ((12V-2.5V)400mA + 2(12V-3.4V)*350mA), which I am loathe to do even with a heatsink. I tried it on some high-power resistors and it gets really hot (mirage illusion hot).

I consequently have been looking for a few months for a very small driver/regulator circuit (perhaps at most a cubic inch) that is very efficient and therefore produces almost no heat, and can be powered from the 12V without requiring its own power supply. I imagined that I might be able to use a switching (or other highly efficient, e.g. 90-95%+ efficiency, non-linear) voltage or current regulator, and just pretend the PWM signal is the power supply. (I would assume it would work if it had a fast power-on/off-time and no built-in anti-ripple capacitors or other mechanisms.)

I would prefer a component with long pins I can just carefully bend and screw-mount onto a binding post, and something with minimal wiring. Though the holy grail of this would be a current regulator, I've also considered a 4.5V voltage regulator... but that still forces one to dissipate something like 2W across the resistors.

The issue is that I have not been able to find such a device anywhere. Almost all regulators specsheets I see hide their efficiency (or do not provide the information necessary to determine it for various operating ranges). The efficient ones I've found specsheets of I cannot find where to order from (goggling for the part name reveals nowhere I can buy them). I've also looked for efficient DC-DC converters and haven't been able to find any (except one, which I bought which unfortunately would not work with PWM).

So my question would be:
What is the easiest way to do this? Are these the components I am looking for? Where does one get such components?

(I could make a complicated circuit perhaps that uses the PWM as input to modulate a brand new 3.4V signal, but have minimal experience with complicated designs, and due to wiring issues (have to hang this), I'd rather just keep the 12V 4-pin common-anode RGB PWM as the only electrical input to the system. I would consider all simple solutions though.)


texts: Is it possible to use a Microchip PIC32 as a USB host and device at the same time?

texts:
I'm designing a system and maybe (if I don't find better alternatives) I will need to use a PIC32 as a handler in between two USB devices and a host. My plan is to use the PIC32 to hide the devices, so the PIC has certain protocols downstream and another protocol upstream. I've been reading a lot about the USB specification and about the support of USB on Microchip PIC32 micro controller series. But still, I have one fundamental doubt: is it possible to connect two devices downstream of the PIC and to connect the PIC upstream to a host at the same time? In other words, is it possible for the PIC32 to act as a host and device at the same time?

I would really appreciate any hint or suggestion about this

Thanks in advance.


texts: How Long Will This Battery Keep My Fridge Powered For?

texts:
I have an interesting mathematical/electrical dilemma and I'm not sure where to start.

I am considering buying this fridge (specs on page).

I will be hopefully buying a battery pack with it to support a long-road trip (a few months) wherein I'll keep medication in the fridge (powered by the battery pack when parked and by the car when driving). The medication needs to be keep between 2 and 8 degrees C at all times.

Here's the battery pack I'm thinking of getting:

Can someone please help me understand what I need to do in order to calculate whether or not this fridge + battery combo will work, and if so, how much time will I be able to power the fridge for.

Ideally, I need a combination of fridge and battery which will allow me to have the fridge constantly powered, assuming I sleep in the car for approx. 8 hours a night and drive for the rest of the day (although, there will be times which I'm away from the car during the day for several hours + times where I hope to have access to a wall outlet).

Specs:

Fridge:

Input voltage (AC 220-240 V
Input frequency 50/60 Hz
Rated input power (AC) 64 W
Rated input power (DC) 46W DC12V/50W DC24V W
Input voltage (DC) 12/24 V

Battery:

Capacity: 453Wh
Battery Type: Lithium-ion
Input Voltage: AC 110-220 V, 50/60 Hz; Solar Power: 18 V; Car Input: 12 V
Output Voltage: AC 110V 60 Hz; DC Output: 4 * 12V 4 A (Max.10 A); USB Output: 4 ports: 2* 5V 2.1 A and 2* 5V 1 A
Power Output: Rate 500 W Peak/Surge 1000 W


texts: Nodal Analysis - solving 2 variables with 3 equations

texts:
There are three conditions:

before the switch is closed (opened)
while the switch is closed (closed)
after the switch is closed (opened)

I think I need to solve them sequentially, because the system has memory.

Here are the system equations (before the switch is closed):

\$\Large\frac{9+9}{R_6+R_9}+\frac{9-V_d}{R_4}+\frac{9-V_c}{R_1}=0\$
\$\Large\frac{V_d-9}{R_4}+\frac{V_d-V_c}{R_8}+\frac{V_d}{R_5}+\frac{V_d-V_d⋅{(1-e^{-\frac t{R_7⋅C_2}})}}{R_7}=0\$
\$\Large\frac{V_c-9}{R_1}+\frac{V_c-V_d}{R_8}+\frac{V_c}{R_2}+\frac{V_c-V_c⋅{(1-e^{-\frac t{R_3⋅C_1}})}}{R_3}=0\$

Also, the current flow of \$V2\$ before the switch is closed is meaningless; if I try to cut the wire between \$V2\$ and node \$a\$ to see the graph before and after, it won't alter \$V_c\$ and \$V_d\$. So it is meaningless. That's why I'm not including this current flow in the equation number 1 above.
Edit: Sorry, it did alter, but for a tiny amount

Some strange things happened after plugging in the \$R\$ values. When I use Microsoft Mathematics to solve equations \$2\$ and \$3\$, I get the correct graph, but if I try to solve the equation \$2\$ with \$1\$, or \$3\$ with \$1\$, I get the wrong graph. What's wrong?


texts: LM567 (NE567) tone decoder lower input AC voltage bound and DC level

texts:
I've been trying to figure out the lower input bound for the LM567/NE567 tone decoder. Supposing the pin 7 is connected to ground, is the minimum input voltage 0V or can it go negative?
In the datasheet (poorly written BTW) the input pin is always AC-coupled using a capacitor, so I guess this suggests the voltage can indeed go negative. The datasheet says the upper bound is Vcc+0.5V, I was wondering if the lower bound is GND+0.5V.
The input signal I'll use on it has a DC offset level. So if there's no coupling capacitor, could the IC get damaged by the DC offset (when no AC component)?


texts: Thevenin Equivalent Resistance of complex circuit

texts: I'm trying to find the Thevenin equivalent of a circuit of which I have already found the Thevenin voltage. Unfortunately I can't figure out how these series parallel combinations work to find the Thevenin resistance. Any help is appreciated. A numerical solution is not required so the values of the resistors are not given.


texts:
i am working with a half duplex RS-485 Transceiver ic SP3485EN with 10Mbps Data Rate
datasheet :https://www.maxlinear.com/ds/sp3485.pdf
i actually want the maximum working voltage (Viom) of design purpose, but only  esd rating and supply voltage is mentioned in the data sheet is there a that i can find the maximum working voltage


texts: Do I need diodes or resistor for PWM controlle RGB LED?

texts:
I am planning to build a custom keyboard, using a pro micro and QMK firmware, and on my plan there would be an excess of 3 PWM pin. So I thought I can maybe put RGB leds on it on parallel. But the problem is how, it is just possible that I will just wired them on parallel, then it will work or I need to put some resistor or diodes on it? Also IF I want to control its brightness what should i need?

I will appreciate any advice will come, thanks.

BTW I don't have the parts for now so I cant test it. I am on the process of sourcing the part on where to buy for it.

I hope this is the right place to ask about this, please forgive I am very new in electronic, I just need some guidance.

Edit:

Pro Micro Link to Aliexpress.

I am planning to put 7 individual LEDs or if possible I will put 15 or 25 LEDs so all the keys has LEDs


texts:
Let's say there's some 50 ohm resistor connect across the input of some 2 port network that has an input impedance of 50 ohm, so like this:

simulate this circuit – Schematic created using CircuitLab

Does the input resistor (in the two port box) get counted in the thermal noise calculations?  If it does, then it would seem as though the voltage across it would then be
$$
V_\mathrm{Two\ port\ resistor} = \sqrt{4kTBR}
$$
and so the power would be
$$
P_\mathrm{Two\ port\ resistor} = \frac{\sqrt{4kTBR}^2}{R} = 4kTB
$$
however, wherever I've read seems to say that the noise power delivered to a matched impedance is \$kTB\$.  What I don't understand is, this only seems to take into account one of the two impedances.


texts: I am making a project for some practical application. I require to use a relay which can control up to 1kW AC power. Though there are cheap 5V relays available with about 220VAC and 10A rating which satisfy the requirement but I highly doubt their truthfulness and lifetime. At the same time I want to make the project cheap so I want to avoid costlier ones. Can someone please suggest a good compromise between the choices. And how far can I probably go with the ratings of cheap ones(rough idea).


texts:
I'm using CircuitStudio for pcb design and I've run into a fairly significant limitation: no gerber import.  Now I have a set of gerbers I'd really like to get into a new editable CircuitStudio design, so I wonder if there is some (even if very manual) way to do that.  I'd like to basically import an image of each gerber layer, and scale them until they are about the right size, then route the board over that manually using it as a reference image only.  Even that isn't quite working - the only image import requires black and white image or a dxf (and has other limitations: 1 pixel = 0.2mm fixed size).
What is the best way to do what I'm trying to do?  Are there any decent workarounds here?


texts: Silicon Labs CP2102 usb recognition error

texts:
Good Morning everyone,
I have recently designed a circuitry design for the named chip "CP2102N-A02-GQFN24". Problems appear after connecting the chip to the computer. It doesn't get recognised properly. It shows that the connected device is not functional.
My guess is actually that there is problem with my circuitry. As the documentation wasn't  too easy to read. And even after many hours of research, I am not too sure if VREGIN needs to be connected to VBUS or just to VDD/VIO. Do I need to connect pin 25 to Ground?

Everything looks fine? -> probably a soldering/component issue right?

If more information is needed please remind me kindly.
Thank you for any help in advance.
EDIT: Note that this circuit is just for a bus-powered Application.


texts: How switch a 3v load high side, from a uC powered from same 3v?

texts:
I have a uC (Arduino Mini) powered from 2xAA battery pack.
The Mini display some data on a circuit with a MAX7219 + 2x7segments 4 digits led (a total of 8 numbers).

Because it is powered from battery (and for learning) I want to switch off the load totally when Arduino sleeps, and power on only when needed.

So, this is the very basic schematic (U1 the uC and U3 the load)

simulate this circuit – Schematic created using CircuitLab

I know that for the high side switch I need a PNP, and with a PNP I need mantain GPIO HIGH (right?). But if Arduino sleeps, how it can mantain high?

But, other this question, I'm tryng to study transistors and FET/Mosfet from some months, but I find they very difficult to learn.

Please, can you help me with:

1) Know if circuit is right (R1 for limit base)

2) How can I select a transistor? What I need to check in datasheet?

3) I have some part available, are there some part available for my goal? (Mix of NPN, PNP, FET and Mosfet:

PNP:

2N3906

NPN:

P2N2222A
2N3904

N CHANNEL MOSFET

FQP30N06L
2N7000

P CHANNEL MOSFET

NDP6020P

NPN POWER

BD239C
TIP120

N CHANNEL JFET

PN4391

DARLINGTON

ULN2003A

Thank you


texts: Using a HT12D pulse to drive a latching relay

texts:
I am receiving a signal via RF and using a HT12D to decode it and send a 5V DC pulse.  I want to use this pulse to drive a latching relay.  On the first pulse it will make the relay latch in NO position and the next time there is a pulse I want the relay to return to the NC position.  I want the relay to retain its position even if the power is interrupted and if possible have a push button to change between states also.  The relay needs to handle either 24V AC at 500mA or 12V DC at 500mA.

I have read about a 74hc73 to clock the signals but I became somewhat confused where to attach the signal input and it seemed to have more than one relay.
Can someone help me out with a previous post and online link or some personal experience?

I am including a schematic that supposedly will allow a high signal to latch and unlatch a relay.  I'm not sure what type of relay to use and where to input the 5v pulse for my HT12D at.

Could someone look at the schematic and tell me:
1. Will it work to latch and unlatch relay with input of 5v pulse from HT12D?
2. If so where should I connect the HT12D?
3. What type of relay should I use?
4. Will this reset if power is lost? I don't want that so how can I keep it from doing so.


texts: Internal resistance of non ideal current and voltage sources

texts: Why is real current source represented with resistor parallel with the source, while in the real voltage source resistor is in series with the generator? Can you give me an example for this situations?


texts: How do I go about intentionally aliasing a signal, and upsampling work with audio file in MATLAB

texts:
My objective is to show the results of:

  How do I go about intentionally aliasing a signal?
  undersampling
  Nyquist rate sampling and oversampling

I'm first going to get the MATLAB code working well, then I'll rewrite it for the MSP430.

First I need to downsample the .wav file to get an incomplete or impartial data stream that I can then reconstuct. Here the flow chart:
analog -> sampling analog filter -> ADC -> resample down -> resample up -> DAC -> reconstruction analog filter

This is my first signal processing project using MATLAB (v2010), so be nice. Original code below; updated code here.

    %Play decimated file ( soundsc(y,fs) )
%Play Original file ( soundsc(play,fs ) )
%Play reconstucted File ( soundsc(final,fs) )

[piano,fs]=wavread('piano.wav'); % loads piano
play=piano(:,1); % Renames the file as "play"

t = linspace(0,time,length(play));          % Time vector
x = play;
y = decimate(x,25);

stem(x(1:30)), axis([0 30 -2 2])   % Original signal
title('Original Signal')
figure
stem(y(1:30))                        % Decimated signal
title('Decimated Signal')

%changes the sampling rate

fs1 = fs/2;
fs2 = fs/3;
fs3 = fs/4;
fs4 = fs*2;
fs5 = fs*3;
fs6 = fs*4;

wavwrite(y,fs/25,'PianoDecimation');

%------------------------------------------------------------------

%Downsampled version of piano is now upsampled to the original
[PianoDecimation,fs]=wavread('PianoDecimation.wav'); % loads piano
play2=PianoDecimation(:,1); % Renames the file as "play

%upsampling
UpSampleRatio = 2;  % 2*fs = nyquist rate sampling
play2Up=zeros(length(PianoDecimation)*UpSampleRatio, 1);
play2Up(1:UpSampleRatio:end) = play2; % fill in every N'th sample

%low pass filter

ResampFilt = firpm(44, [0 0.39625 0.60938 1], [1 1 0 0]);

fsUp = (fs*UpSampleRatio)*1;
wavwrite(play2Up,fsUp,'PianoUpsampled');

%Plot2
%data vs time plot
time=(1/44100)*length(play2);
t=linspace(0,time,length(play2));
stem(t,play2)
title('Upsampled graph of piano')
xlabel('time(sec)');
ylabel('relative signal strength')

[PianoUpsampled,fs]=wavread('PianoUpsampled.wav'); % loads piano
final=PianoUpsampled(:,1); % Renames the file as "play"

%-------------------------------------------------------------
%resampleing
[piano,fs]=wavread('piano.wav'); % loads piano
x=piano(:,1); % Renames the file as "play"
m = resample(x,3,2);

**%this is were i would need to sample it at the different frequecys (both above and below and at) nyquist frequency.*I think.***

soundsc(left,fs) % shows the resaultant audio file , which is the same as original ( only at or above nyquist frequency however)

How can I improve this? How do I sample at different frequencies?

Note that I've crossposted this on SO, here.


texts: Eagle: How do I make a component from a board?

texts:
I recently discovered the fantastic Arduino shield components in LadyAda's latest Eagle library. Now of course I'd like to make my own, using the mechanical layer from an existing Eagle board file. But the Google has been unhelpful on this topic. And my fumbling around has not unearthed any obvious affordances for copying a drawing from a board editing window to a component editing window. (I have made some simple components starting from the pads of an existing component, following one of the many tutorials that explain THAT process.)

How do I make a component footprint from an existing board drawing?


texts: Vout = 12V, Iout= 15A, 180 W Switching regulator

texts:
I have experience of designing DC-DC converter upto 5A.

But now for one of my application, I need to design circuit with following specs:

Vin  = 24 - 25 V,
Vout = 12V,
Iout = 15A,
Pout = 180W

So, Is there any switching regulator capable of such high power rating?

( Any application note will extend my knowledge for High Power Design )

Thank you in advance.


texts:
my goal is to achieve a HIGH  SPEED RESPONSE AC COUPLING, as I want to totally get rid of the DC component even though its changing rapidly

I have a signal coming from a sensor ( a proximity probe), the output of the proximity probe has 2 components:

DC out-put that determines the position or the GAP
AC component on the top of that DC voltage to determine the vibration

the thing is, this DC value is going to change rapidly, when the DC changes let's say from 1v to 2v, and if the AC coupling circuit has a high response then the ac part of the signal will be just oscillating around 0 volt as the coupling circuit will take care of the DC part. but this is not the case, when the DC offset increases (for example), the output will go up for a while before it gets back to oscillate around zero volt. I don't want this GOING UP or DOWN thing.

here is the Ac coupling circuit I used, its so simple its just a filter that filters out the low frequencies

I built this circuit in the real life and its working fine as it removes the dc part

here is the original signal with a DC offset

and here is the output when the DC is removed :

(the solid line is almost zero volt, its a little bit off because of some calibration issues)

so to sum it up, the problem is when I change the DC value(or it changes by itself as its a sensor signal), the AC moves up or down( depends on weather I am increasing or decreasing the offset ) I want my circuit to highly response so the AC will always be oscillating around zero volt regardless of what is going on on the DC

the frequency of my signal is going to be 50 Hz, if this is needed somehow

Edit: as suggested in the answers:
increasing the cutoff frequency and using sallen key filter will improve the performance
cascading 2 passive filters also improved the performance even more than using sallen key filter

here are the circuits


texts: How to calculate the voltage of these capacitors?

texts:
simulate this circuit – Schematic created using CircuitLab

My task is to represent the voltage values of nodes a, b and c by using known parameters such as V0, R1, C1, etc.

The question is, before the voltage source V0 is powered on and is able to provide some electric potential, the voltage values across all capacitors are 0, which means we have to consider the process of capacitors' charging rather than simply the steady state of this circuit. And the expressions I need should include the charging process.

I presumed that there is a difficult differential equation waiting to be solved. Am I right? Any advice on how should I analyze a circuit like this? And more importantly, how can I solve this one?
(multiple horrible capacitors are in this circuit, because it is actually a part of RC thermal model, where actually the fewer resistors and more capacitors are what we usually deal with.)


texts: I am making a circuit to acquire EOG signals and read it via the analog pin of Arduino. The arduino reads only positive signals, which is why I am unable to see the negative spikes in voltages caused due to eye movement. I think a voltage level shifter should solve my problem. I plan on using a summing amplifier as a voltage level shifter. Is any better way to tackle this problem? Or a better design for a voltage level shifter?


texts: When can FPGA's be used and Microcontrollers/DSPs not?

texts:
I have to choose between a course on advanced microcontrollers and a course on advanced FPGA's.

I have had introductory courses in both subjects, and what troubles me now is that I am already pretty good at firmware development for microcontrollers, and I fail to see what products/projects I can make with an FPGA and cannot with an microcontroller/DSP.

Can you come up with some applications/products/projects where a microcontroller or DSP wouldn't be sufficient, and why?

Cameras? High-speed cameras? High-speed image processing?


texts: Communication Theory - Basic Transmission Errors

texts:
I have a question regarding some basic transmission error:

My confusion is with the solution to combat errors (transmit each frame 3 times). I would have though that the probability of receiving a bad frame now would be the probability of each frame being in error and since they are all independant it would be N^3pB^3 but that's incorrect apparently. I don't know why.


texts: Calculation of the resistors values in a voltage divider

texts:
I'm working on a circuit where a 3.3v flash memory, which comunicate with SPI protocol, has to be interfaced to an 8-bit PIC microcontroller working at 5v. For the MISO signal there should not be any problem, but for MOSI, SCK and CS there are. So the solution i came across is a voltage divider. I've done this calculations but don't know if they are ok.
_ First of all, i've calculated r1 in this way:
(5-3.3)/0.001=1700 ohm
_ Then i've resolved the equation
Vout = Vin * (r2 / (r1+r2))
3.3 = 5 * (r2/(1700+r2))
...resolving the equation in order to find r2...
r2=3300 ohm.
Is that correct? i have not any tester and i have just one flash memory. i don't want to fry it...
Is the method i've used proper (first determinate r1 with the current and then find r2)?
Thank you very very much.
Greetings from Italy.


texts:
I ve got a signal that consists of 2 square waves at 2 different frequencies at the kHz range, about 10 Hz apart.I need to determine the relative amplitudes of 2 different known frequencies and I was thinking to build a module based around the AD630 modulator. The ultimate objective would then be to get the signal through 2 AD630s and harvest the 2 distinct DCs, but before doing that I would like to test it with a single AD630 and two frequencies. The circuit is the one from the data sheet (with a different low pass filter, in my case a simple RC, with R=10kΩ and C=3.3μF, and no opamp/noise/attenuator at the input) and +-12V power supply.

As a proof of concept, I am trying to test it using square waves from two arduinos. I pass the arduino pin output through an capacitor to remove the DC component, since my understanding is that AD630 prefers AC coupled signals for both reference and the actual input.
My problem is that I am not 100% sure as to what to expect at the output of the low pass filter for the different scenarios, so I would really appreciate if someone told me if the following behaviour is expected.

No input & No ref & Out= 9V DC (weirdly it's -9V after an input is introduced)
input=0V (actually 10mV) & No ref & Out=10mV DC
No input & ref=0V (again 10mV) & Out=200mV DC
input=0V (again 10mV) & ref=0V (again 10mV) & Out=400mV DC
input=4.4V (+-2.2V),f=100Hz & ref=4.4V (+-2.2V),f=100Hz & Out=-4V DC (same arduino)
input=4.4V (+-2.2V),f=100Hz & ref=4.4V (+-2.2V),f=95.2Hz & Out=250mV DC
input=4.4V (+-2.2V),f=100Hz & ref=4.4V (+-2.2V),f=100Hz & Out=+-4 AC (~20sec beat) (different arduinos)

Is this behaviour the expected? Especially at cases 3 and 4, the dc output seems to be quite high. Finally, since I am interested only in the relative amplitudes, does my reference need to be a sin wave?


texts: How to avoid ±voltage on capacitors in astable multivibrator

texts:
I've been experimenting with oscillators, and am particularly fond of a very low-current MOSFET design that uses ceramic capacitors and oscillates at about 1 to 10 Hz.  However, I am having trouble adjusting its frequency and duty cycle.

The resistors involved are the largest I've got, so to slow it down a little I decided to use larger capacitors, like a 1μF electrolytic instead of 0.01μF ceramic.  Instead of slowing it down by a factor of 100, it just had some weird smoothing effect on the square wave, depending on which side was connected to the load.  In fact, 100μF and 1000μF had the same frequency, just more smoothing.

I figured I just had the capacitor in backwards, and flipped it around, but this often made no difference, and it never made the frequency "correct".  Also, even with 100μF on one side and 0.01μF on the other, the duty cycle was as close to 50% as I could measure.

I used a multi-meter to check which way the capacitor should really go, and was shocked to find it was always backwards.  Eventually I discovered that the voltage was swinging from -130mV to +130mV, and if the capacitors weren't balanced or the phase of the moon was wrong, it would sort of get stuck on one side, and the other capacitor would handle all the oscillating.

Through many hours of simulating oscillators in spice and the falstad.com simulator, I have found that some of my oscillators maintain 0 to +V across the capacitors over the entire wave, but some configurations are more like -0.5V to 3V across the capacitors.  I have no idea what controls this.

  How does one design an astable multi-vibrator to have a specified voltage range across the capacitors? (Ideally, given a fixed frequency and duty cycle, and maintaining low current.)

If it matters, I substituted ON 2N7000's for the depletion mosfets, and this works with ceramic capacitors, just not polarized capacitors.


texts: Why does my new 220V AC to 12V DC transformer only allow one Halogen light to work?

texts:
I'm trying to revive an old Ikea "Trettio" lighting set. The set is made up of a 220V to 12V transformer and 5 Halogen lamps connected to it in parallel.

Remembering that the original transformer was defunct, I've replaced it with a new one. Now when I connect one Halogen lamp to the transformer and turn it on, the lamp lights up. As soon as I connect another one both lamps turn off.

I've tried rotating lamps and rotating across the 5 plugs where the lamps connect to the transformer, to no avail.

Is it possible my new transformer is too weak or otherwise incompatible with the Halogen lamps?

The new transformer specs are:

Electronic Led* Converter
Prim.: 220-240VAC, 50/60Hz
Sec.: 12VDC, Max 1.25A, 15W

Each Halogen lamp's specs are:

12V 5x Max 10W

For reference, the old transformer specs are:

Electronic Transformer
Prim.: 220V-240V ~50Hz 0.26A COS 0.98
Sec.: 11.5V, Max 60W

* I know :)


texts: How much power is dissipated as heat in a 12V MR16 Led Bulb

texts:
I just installed a dimmer for a set of (non-dimmable) MR16 bulbs wired in parallel. The dimmer sits between a 12V power supply and the bulbs.

My observation when trying to dim the non-dimmable bulbs is that the brightness stays the same until the input voltage to the bulbs drops to below roughly 1V. Then the brightness drops rapidly.

I suspected that the bulbs were drawing more current in order to compensate for the drop in input voltage in order to keep the amount of power drawn the same. So I measured it, they weren't.

So therefore I know that as input voltage drops from 12V to 6V the power drawn by each bulb drops, but I also know the apparent brightness of the bulbs does not. I can only conclude that the extra power drawn from a bulb run at 12V must be dissipated as heat.

My question is: is my conclusion correct? Is there a reason to run my bulbs at 12V or is 3V good enough? Will running the bulbs at a lower voltage lengthen their life? Is there a simple (UK A-Level / US High-School-Diploma) circuit diagram that can explain the behaviour and be used to calculate how much power is converted into heat?


texts:
How critical are parameters like trace length matching, differential impedance, vias, etc. when designing a 10BASE-T only application? I know that due to the reduced frequency, there is a larger margin for error than for higher data rates, but there must be good-practice maximums and minimums.

For example, in a two-layer PCB that I am designing, I have the following parameters:

TX+ length: 25.946mm
TX- length: 26.764mm
RX+ length: 26.420mm
RX- length: 27.769mm
Differential impedance: 123ohm
Odd impedance: 61.7ohm

The 8P8C connector has integrated magnetics and the MAC/PHY is the ENC28J60. Sorry about the messy labels.


texts:
If I select internal clock source to run my TIM3 in TM32F103 (TIMxCLK from RCC) as shown in the attached picture:

CK_INT

Then how to find out what is the freq of this clock?

I am using External Crystal 8MHz to get 72MHz as my SYSCLK.


texts: How is this oscillator circuit supposed to work?

texts:
This answer shows a circuit including a LM311N voltage comparator. Its stated purpose is to be a oscillator, allowing identification of an unknown inductor L1. It has similarities to the Free-Running Multivibrator shown in the datasheet. I expected that the resonance frequency of the tank circuit L1 and C7 would introduce a square wave due to the comparator, thus allowing to calculate L1 due to a known C7.

Trying to understand it, I simulated it in SPICE with a LM311 model from a forum. Furthermore I replaced the LM311 with the LT1011, which claims pin compatibility to the LM111 (~LM311 with extendet ratings). The tank circuit oscillates with a starting peak of 12..20mV until it dies out within less than 200 µs in both simulations. I also tried to change resistor values and introduced series resistances for L and C to start the oscillation, but to no avail.

Building the physiscal circuit on a stripboard provided no useable results when I measured the available potentials with a scope.

How can the circuit be used? What behaviour should it show?

I had problems understanding the circuit, as it connects the collector output straight to Vcc, while the emitter is connected to ground over its internal 4 \$\Omega\$ Resistor.


texts: VPC0820 Li-Ion Capacitor how to understand the 97% Self Discharge (V) parameter

texts: Does anyone know what does the self-discharge parameter mean? I know what self-discharge is, but what does over 97% mean?


texts: How to change pad size in design rule in Eagle?

texts:
I’m very new to Eagle. When learned to create a library I followed these instructions from Eagle’s documentation tutorial:

“Default value for pad diameter is auto. It should not be changed. The final diameter in the layout results from the values given in the Design Rules.”

See the highlighted part in the picture!

After creating the library I’ve done a schematic and then its board, and I tried to change the pad size in board editor but nothing happend, and as far as I know there is no settings for pad size in design rule.

How do I change the pad size in board editor as Eagle says in its tutorial document ?

Please Help!


texts:
SRD-05VDC-SL-C relay does not turn to OFF sometimes.
Loads - is light bulbs 220V E27.
Ilyich light bulbs (tungsten filament) - work correctly.
Problem in LED bulbs and fluorescent bulbs.
20% LED bulbs in 30% of the time does not turn OFF.
50% fluorescent bulbs in 50% of the time does not turn OFF.
Relays is sticks/adhere/latching due to inductive loads.
LED indicator (example L1A15) turns off, but bulb does not.
What need to do?


texts: Relay sequencing: Inhibit state change of one relay if the other is on

texts:
I'm trying to find a way to have one relay lock its state if the other is on.

Example, 2 relays total:

If relay 1 is on then relay 2 can't change state, either turn on or off. Meaning if relay 2 is on when you turn relay 1 on then you CAN NOT turn relay 2 back off. And, if relay 2 is off and you turn relay 1 on then you CAN NOT turn it on. Both relays need to be able to work independently i.e. no flipflop action or toggle action.

Practical application = Relay one is a 32v supply. Relay 2 is a series of relays that can flip a transformer around (swap primary and secondary) to flip step-up step-down function. You can turn on the 32v with relay 1 without consequence regardless of relay 2's state. However, if you already have relay 1 on and flip transformer around (relay 2) then you will damage the circuit from the voltage spikes. So, if relay 1 is on and you want to change the state of relay 2 you must first turn off relay 1.

It seems like something in the SR latch world may help but I'm having a tough time actually figuring the circuit out. The switches to activate the relays can be momentary or latching, as I can make either work.


texts:
I have an idea for a DIY electronics project which involves a camera where I want the camera to be small.

I thought may be to get a camera component similar to the ones used in smart phones. But my Internet searches proved unfruitful. All I see is big cameras, or off-the-shelf final product filming and photographing machines. :(

I don't know what words to search for (and it is a rare phenomenon; normally I get the thing I want on the first Google results page).

Or is the component I am searching not available for general consumption?

And what about the communications interface of the device? Are there standards for phone cams to operate equally among different vendors or not? I had read a little about MIPI CSI and CSI, but I got confused!

UPDATE:

After @Transistor comment, which made some good observations, I will make a bunch of things clear:

Purpose of the project is to transmit capture from camera to a phone. I've thought Bluetooth would be the best way, but I am receptive to alternatives, if they seem better to someone of you all
I want live video
Ideal resolution would be Full HD, but HD is also acceptable. Anything  over Full HD is a waste of resources and battery life. Frequency: 30Hz minimum, 60Hz ideally.
No processing. Just live transmission.


texts: Understanding how to add storage for custom SoM made with Xilinx FPGA SoC with ARM A9 as Hard Core

texts:
I am a university student developing SoM for computer vision purposes I am directed to use Xilinx zynq 7000 series which is an FPGA SoC with ARM A9 hard core. I was able to find out we can use eMMC storage or 1GB nanad storage which will act like ROM and SD card. Since I require storage more than 8GB I cant use that option we faced some issues with SD card previously and hence require a robust storage solution and hence leaves only eMMC as an option. I am not sure how non-volatile storage, I had some doubts if someone help me with some of them I would be thanksful

Which communication protocol eMMC storage use, My initial search directed me to 8bit data channel still not clear what protocol to use

How we can store image and extract the same from eMMC storage, I am aware of sector design and use of FAT file system but still not clear about how will it work like our system has to go from multiple power cycle and hence how FATfs will know the data location after the restart.

Is there support or data transfer from RAM to storage using DMA or the A9 has to do that manually, similarly taking data from storage to RAM also if this stuff need to be done manually (like addressing DMA to do the transaction ) or some C library will do it for me.

For debugging I require the data to be displayed in the host computer is this possible ( as different file systems are in use) although when in use it need not to do that.

If someone can address some of the doubts I shall be thankful. Any additional data required please ask me in comments


texts:
I want to apologize in advance for any ignorance throughout this post, I'm not anywhere near an electrical engineer.

Basically I have a consumer which requires 220v and is not operating all the time. Whenever not in operation I would like to cut the current from the outlet automatically. For the purpose I figured I'd use a relay, so I got a 5VDC/220VAC relay which is going to be powered by 5V going out of the consumer which is basically going to keep itself alive and once it stops operating the relay will also switch off since no current will be going to its 5V end.

The problem is, how do I power it on initially, since the relay is turned on by the consumer to which it is supposed to allow current to flow to. So I figured I'd use a small battery + button circuit to manually switch the relay on and from then on the consumer will continue to supply power to keep it on.

Warning: very amateur schematic incoming

It doesn't seem to me that it's okay to mix these 2 5VDC power supplies like that. I assume that for the brief moment when the contact is engaged and the consumer is supplying 5v as well the circuit will not like it. I know that if the 5v power supplies are chained in series then the voltages add up and that would burn the relay, but I'm not sure what's the case when they are connected the way they are on the schematic. Also what if I add 2 diodes on the inner circuit that will only allow current to flow out? I basically have no idea how ignorant the stuff I'm saying actually is so I'll just cut it out here and let you guys tell me how far I am from reality.

EDIT: after looking at what I just posted I thought to myself am I fing stupid, isn't something like this going to work?


texts:
I'm trying to make a led screen. I have 1088AS led matrix (8x8).

http://www.ebay.ch/itm/MAX7219-Microcontroller-4-In-1-Display-with-5P-Line-Dot-Matrix-Module-Arduino-/282073774611?

With an arduino I can control each led for the 4 led screens. Can I add an infinity number of others matrix? Have I a maximum?

I want to build a screen 1m / 2 meter.

If not possible, have you another solution to build that?

Thnaks
Best regards


texts:
In the book "Grounds for Grounding", p. 573, it give a figure:

And it states：

  In a perfectly balanced circuit (i.e., \$Z_{H} = Z_{L}\$ and \$Z_{HG}
> = Z_{LG}\$), where \$Z_{HG}\$, and \$Z_{LG}\$ are also much larger than \$Z_{H}\$ and \$Z_{L}\$, high common-mode rejection is achieved
  and no measurement errors are observed, that is, no differential
  voltage offset exists across the input impedance, \$Z_{M}\$. In
  practice, however, \$Z_{HG} \gg Z_{LG}\$, thus \$Z_{HG}\$ actually
  amounts to an open circuit and the circuit in Figure 7.87 transforms
  to that shown in Figure 7.88.

Similar statements also appear in HP's "AN123 Floating Measurements And Guarding".

My question is why \$Z_{HG} \gg Z_{LG} \$ in practice? Apparently we can use an instrument amplifier as the front end of a measurement apparatus. And make the difference between ZLG and ZHG as small as possible.


texts: Voltage drops keeping the current same as source/supply curent

texts: My question is "How to reduce the DC-voltages without changing current ". In my case I've 3.7 V Li-ion cell of 2 Amp i want to convert into 2 V and 2 A.


texts:
I am split an audio signal coming from an op amp to both a line driver buffer and a VU meter buffer, as shown in the schematic. My trouble is in determining the correct placement and value of resistors R1 and R2 in order to split the audio signal without affecting the level. Are resistors placed correctly? What are they used for? I have taken them from a similar schematic and don't really understand why the signal has to be shunted to ground.

(I'm aware of the rectification needed after the VU buffer and before the actual meter.)

simulate this circuit – Schematic created using CircuitLab

Is this a generic way of splitting an audio signal to two sources without affecting the signal level?

How do the input resistors of the two op-amps OA1 and OA2 come into play? Will they function as a voltage divider between themselves and the other resistors?


texts: How does temperature affect wireless transmission?

texts:
I'm working with Xbee Pro with wire antenna to transmit data from inside a refrigerator. The receptor outside is the Xbee with RPSMA antenna. I use an extern MCU to control the data transmission, transmitting every second.

When temperature is about 4 °C or higher, the reception is ok, every second I get the data. But when the temperature drops from that point, reception starts to be poor, starting to receive each 5 seconds or less.

The transmitter is reporting the Not Ack Received notification. The input voltages seem to be fine (3.3 V) and both the Xbee and MCU are working.

Does temperature affect the transmission or the antenna in any way? Should I change the antenna of the receiver or transmitter?


texts: What are the main power draws within a mobile phone radio?

texts:
It is often quoted that "3g uses more power than 2g on voice calls" or other similar things, but it seems from a theory perspective that transmitting low bandwidth voice data with a high bandwidth protocol like UMTS, HSDPA etc. with more spectrally efficient modulation should use less energy than transmitting the same data over an older standard network like GSM which has less spectrally efficient coding, lower data rates, and longer timeslices.

Rumour is that the majority of the power in new protocols is not used in the actual emitted radio waves, but instead in the electronics that process, amplify and modulate the signal.  Is this the case?  Are there any public studies/numbers to back this up?

Thanks in advance,
Oliver


texts:
I am trying to program a PIC 16F876A using mikroC. I need the program to run when I push a button to a certain point, stop and wait till the button is pushed again before finishing.

void interrupt() // ISR
{
 INTCON.INTF=0; // Clear the interrupt 0 flag
 PORTC=~PORTC; // Invert (Toggle) the value at PortD
 Delay_ms(1000); // Delay for 1 sec
}

I have read that using a hardware interrupt is the way to do this but can not get mine to work.