texts: The 3rd and 4th column in the image below (from wikipedia) says "enhancement, no bulk". What does "no bulk" mean?


texts:
I am designing an LC Colpits common base Oscillator for the FM broadcast band. The project is going to be extremely low radiated power as I will only be using it in my car.

I am currently using this circuit

The gain is controlled by the C1/C2 ratio which I plan to keep fixed, the transistor transconductance, and R3. I can achieve fairly pure oscillation with the highest harmonic content -40dB down from the fundamental. The gain compression to limit the RHP poles causing the isolation currently is from the non linearity of ib vs vbe and ic vs vbe. This leads to some fairly nasty distortion of greater than -20dB on the 3rd harmonic when R3 isn't carefully chosen.

I have found that I can vary R3 and get over -50dB down at the 3rd harmonic but it involves tuning R3 very carefully to get the loop gain as close to 1 as I can get it.

Obviously this won't work once implemented on a PCB as there are distributed inductances and capacitances, temperature swings, and other non ideal characteristics to account for. I could set a potentiometer at the required gain but I am afraid that the loop gain fluctuations caused by temperature changes, slight bumps, and environmental capacitances will require me to constantly be tuning it.

I had considered using a JFET combined with a peak detector feedback network to act as R3 but I think for an RF circuit that would just cause problems.

My question is, are there any more obvious gain compression methods to consider? I have read that circuits exist where large amplitudes change the bias point, thus reducing small gm but I have not found any.

I do not want to just filter the output down as I plan to have this tunable over a large portion of the FM band if I can manage it.

I realize this question may be too vague for the guidelines so if that is the case please let me know.

Thank you


texts: synchronous buck - nmos current flow direction

texts:
As far as I know in nmos the current flow from the drain to the source, and the drain and source are determined by the pin with the higher voltage on it (such that the source is the pin with the lower voltage).
The bulk is always connected to the source so that the Vth won't change, however it appears that the source is the pin which is connected to the ground.
Therefore my question is -
(1) how come does the current flow when Q2 is on, from the ground to Vsw?
(2) Is it flowing from the source to the drain? how come?
(3) And why not use a pmos instead, so that the current will flow from the source (the ground) to the drain (Vsw)?


texts: Eagle - How to attach a pin not shown on schematic symbol?

texts:
In Eagle, I would like to include SN74HC595 shift registers in my project. I found a library online a few months ago (can't find source anymore) that has this part.

The symbol looks like this:

However, I noticed the symbol does not have power and ground pins, which is contrary to all of the other devices I've seen and created before. I had no idea how I would actually connect it to the same power supply I'm using for all other components in my schematic.

So I opened up the device in the library, and it looks like this:

It seems there's a second symbol (on the left) that goes only to VCC and GND, and those are assigned to the relevant power and GND pads on the package.

My issue is that my power rails on my schematic are labeled '5V' and 'GND'. I've read that I can 'simply' rename the 'VCC' pin to '5V' and that it will automatically connect to any '5V' net in whatever schematic I put it in. This, however, didn't work.

I've also consulted Eagle's awful product support pages to no avail.

How do I hook this component up to my '5V' line?

[ note: GND hooks up automatically to the 'GND' net in my schematic ]


texts: CAN Stub node termination in a network - 9.28k resistor

texts:
In a CAN network, the ends of the network has to be terminated with 120 ohm - I understand this. The middle node in the below diagram is the stub node and it does not have to be terminated, my stub CAN node design has high ohmic 9280 ohm resistor. Any idea why 9280 ohm(Two 4.64k in series) is chosen, what is the idea behind this.

I came across another app note about stub node termination where they have used two 1.3k ohm resistors, but in my stub CAN node, two 4.64k resistors are used. Any idea why 4.64k resistors are used. I referred many application notes but did not find anything regarding two 4.64k resistor termination network.


texts: How to solve for voltage using node voltage method?

texts:
How would you solve for \$V_x\$ using node voltage method. I can solve this using \$Q_{initial}=Q_{final}\$, but I can't solve it using node voltage.

Using node voltage I get \$v(t)-v(0)=\frac{k}{170\mbox{ aF}}\$. I'm not sure how to solve for the k constant or if this is even correct.


texts: Equivalent Thevenin voltage of a circuit with three capacitors in parallel

texts: In the circuit above, I think the Thevenin voltage across terminals a-b should be equal to 22.5 V since the voltage divides equally across the 5F capacitor and the 2F and 3F capacitors which have a combined capacitance of 5 F. The bottom node is the ground node, so the potential difference across terminals a-b appears to be 22.5 V, but the correct answer is 15 V. Can someone explain why this is incorrect?


texts: Relationship between power supply unit Rated Voltage and Li-ion rechargeable battery Maximum Charging Voltage

texts:
The datasheet for a power/battery management module that I am interested in mentions that:

The rated voltage of the PSU(Power Supply Unit) must be at least 1V above the maximum charging voltage requested by the battery.

My AC/DC power supply outputs 12V, and the maximum charging voltage requested by my 10.8V 3S2P Lithium-Ion rechargeable battery is 12.6V. Based on the quoted block, my power supply and rechargeable battery would not work with the power management module.
Is there any reason behind the quoted statement? Trying to make a purchasing decision regarding the PM module...
Any input is greatly appreciated @.@


texts: Why most measurements equipment uses 10 MHz as reference?

texts:
This is just a question about this value of frequency. I mean, this is a industry standard, to use 10 MHz as a reference, but, where this value comes from?

Is this something historical? That a company start using this value, and others follow, or there is a technical reason for it? (more than a round value to get other frequencies with up and down conversions)


texts: I am designing a board with high speed HD-SDI signals. The data is single ended HD-SDI. There are circuits which convert it into differential HD-SDI followed by another circuit that converts it into single ended HD-SDI. Now, before going into layout I would like to simulate it for any signal integrity issues. Is Microwave Office a good tool for such an analysis? This is just a preliminary doubt. Any other open source tools that can do the same?


texts:
I don't understand what the square braces mean in the following Verilog code. Can someone please explain their purpose?

wire signed [I_width : -F_width] p_to_pipe[order : 0], x_to_pipe[order : 0];

Where I_width= 5, F_width=5 and order=2


texts: How practical would it be to make an equivalent of a 14500 Li-Ion battery that outputs 1.5 volts as a regular AA battery?

texts:
A 14500 Li-Ion battery has AA battery size and terminal layout and so it fits mechanically where an AA battery fits. AA battery has 1.5 volts nominal voltage and 14500 battery has 3.7 volts nominal voltage so most devices that use AA batteries will not work on 14500 batteries and will likely get damaged.

Some flashlights can use either regular AA alkaline batteries or Li-Ion 14500 rechargeable batteries - they identify the battery type electrically and just work. That's cool but it requires support in the device.

Surely it'd be much better to have a rechargeable battery with Li-Ion performance (very durable, low self-discharge, fast charging, high output currents) that fits into AA battery compartment. That would require adding a circuit into a 14500 battery casing that steps the voltage down such that it has 1.5 volts on terminals. Surely that circuitry would require some space so the "chemicals" part of the battery must be reduced. Other than that it looks like this is doable and may be implemented as a commercial product.

How practical would such adjustment be?


texts: EEPROM: Same driver for similar chips, different behaviours

texts:
I have two very similar eeproms (M24C01-x and M24C64-x), both driven by the same standard library provided for my STM32F2.

For the M24C64-x, all is fine. However, the M24C01-x is interpreting the address byte of a write transaction as a data byte, and can only write on the first page. (Reads work fine.)

A quick look through the datasheets reveals that the main difference between the chips is that one has a 16 byte page size, and the other a 32 byte page size, which I have accounted for.

What difference between these two eeproms could cause the standard library driver to break down and behave in this manner?


texts: Connecting a parallel port to an Arduino

texts:
This is my first Arduino project and while I remember a (tiny) bit of electronics from school I'm struggling to get this working - in fact I've just fried a parallel port PCI card!

I'm looking to communicate via a PC's parallel port to an Arduino, so when printing to LPT1 (as plain text + ESC/P) this can be captured on the Arduino. I've read up on the parallel port and pinouts and I think I have everything wired up correctly, but I'm a bit unsure on the resistors to use. Some of my references so far have been:

http://retired.beyondlogic.org/spp/parallel.pdf
http://nemesis.lonestar.org/reference/computers/interfaces/centronics.html
http://computer.howstuffworks.com/parallel-port1.htm
http://arduino.cc/en/Hacking/ParallelProgrammer

The ParallelProgrammer example uses 220 ohm and 470 ohm resistors, but without explaining why and this I believe is also interfacing with the Arduino serial port not the digital pins. This isn't helped by the fact that there appears to be significant variation in the specs for parallel port sink and source currents (explained in the retired.beyondlogic link).

Firstly, am I right in thinking that I will be sourcing current from all computer -> arduino pins and sinking current to all arduino -> computer pins?

If this is the case, is the use of a 470 ohm resistor on source pins to limit the current to 12mA @ 5V? Why the use of the 220 ohm resistor? I've seen other specs here (http://www.ahmetozkurt.net/comporg/ekonomi/hw2006/selen2/howtoconnect.htm) which also suggest that parallel ports source 2.6mA @ 2.4V but can sink 24mA @ 4.2V.

Assuming I can get to the bottom of the source / sink current and voltage, do I need a resistor for each pin except ground?


texts: Xilinx PCIe Integrated Endpoint - Using the other transceiver on the tile

texts:
This question is specifically about the Spartan 6-75LXT (FG676) but can be applied to any Spartan 6 (and possibly other Xilinx parts as well).

When using the GTP wizard by itself, there are 2 pairs per tile.  In this specific case, they are MGTTXx0_101/MGTRXx0_101 and MGTTXx1_101/MGTRXx1_101.  This is on tile GTPA1_DUAL_X0Y1.  When using the PCIe integrated endpoint, MGTTXx0_101/MGTRXx0_101 is the hard-coded transceiver.

I made a mistake in my board design, and assigned a transceiver pair (with a different purpose than PCIe) to MGTTXx1_101/MGTRXx1_101.  I am wondering, does anyone know if there is a way to still use this channel AND the integrated endpoint.  The only other 2 options I can see are both unattractive.  Re-design the board or design my own soft-core PCIe interface using the GTP wizard.

I am hoping for an easier option.

Thanks in advance.


texts:
An old circuit board I have (that is very old) has these inductors on it.  I can't find any mention online of a 2-band color code.  What value would these inductors be?

I thought maybe one of the colours had faded but even on close inspection I can't see any indication there used to be another band anywhere.

]1


texts: 3 Phase AC Motor controled by an atmega328pb

texts:
I will ensure you from the start that I have more than 6 months of googling and tweaking this problem in order to find a fix, but in the end, I have to ask for help.

The system:

I have designed a PCB from scratch to control 3Phase AC pumps for the irrigation systems.
Do not think of something complicated with 3phase speed control and things like that no...is very basic but has created me so many problems.

How it works:

Atmega328 activates a relay which closes the circuit of 24V AC for a CONTACTOR, and this contactor closes the 3phase circuit and starts the motor at full speed... and this how must be.
In total are 8 relays and 8 contactors (1 is the 3phase ac, the rest of them are high-pressure solenoids)

the circuit: [Simplified]

The problem:

At first, the chip gets reset itself by any turn-on of any contactor from the circuit, and I had added snubber circuits everywhere and also on the contactors and seams this problem is solved like 90 % (some times get reset...but not every time...and I had code if it got to start again. so not big of a deal.

The clip is working on Internal 8mhz crystal (because I was afraid of higher frequencies that might get noticed more easily but I don't know at this point)

The new problem:

The system starts the timer is on the screen (LCD 2004 i2c) and some times randomly ....it FREEZE...the chip freeze with all his ports "Active" means...that my pump it will run all the night until morning where I had to manually reset the board....in order to "revive the chip"...

I have refactored the code in a way to have only a timer and that's it (no menu, nothing...the chip still gets randomly) ....the noise from this motor I think is the cause...but I have a bord made by someone with an Arduino pro mini......a relay and screen and NEVER got this problem (and I have 2 years since I am using that bord....) and it didn't have all my "high noise filters" and still works ...
Maybe is from atmega328PB...
maybe code...

I really don't know...

Thank you for your time,
George.


texts: Dimming multiple LED panels without PWM to LEDs; modified DMX control or something else?

texts:
In driving a single LED from a 9V battery, for example, you put an appropriate resistor in series with the LED, and the current is reduced.   Vary the resistor, and the light intensity from the LED changes.  The other way is to vary the apparent intensity is to use pulse width modulation (PWM) with the same sort of circuit, but turning the LED on and off rapidly. This all makes sense to me, and I've done this many times, for single LEDs.

I need to drive a bunch of LED panels, that are usually built up from 100+ LEDs in series/parallel.  The way you can drive these is with LED drivers, like the Meanwell LPF-60D or ELG-240 series.  They accept 1-10V, PWM, or variable resistor inputs to control their intensity.  The good thing about these drivers is that they provide true variable current, rather than PWM chopping of the signal.  I need true variable current to vary the intensity, for this particular application.

However, I've got to drive a lot (30+) panels (24 VDC, current could be up as high as 10 Amps, hence the different Meanwell drivers) at specific intensity levels via computer, and am wondering what might be a cost-effective way to do this.

These panels don't need to be varying quickly; I just need to be able to set the intensity at variable levels for various tests for a few seconds.  No flashing or blinking required.

DMX controlled LED controllers are relatively ubiquitous, and they use PWM outputs (i.e., from Amazon - 32 Channel 96A RGBW DMX 512 LED Decoder Controller DMX Dimmer DC5-24V).   One way is to use the DMX decoder is to drive the Meanwell units with PWM.  This seems like it will work.

This may be a stretch, but I'm wondering if it is possible to modify DMX output, so the output looks like a variable current.  In order to drive higher currents (limit is 3 A on the one above), I'd use a different DMX box, or multiple DMX boxes.

Is this possible, or is the DMX to Meanwell architecture the way to go?  One way to drive the Meanwell units directly is with 1-10 V from some D/A board, but generating 1-10V from an analog output system seems wrong (you'd be going from digital to analog to digital).

The other advantage of the DMX system is that you don't need AC power, just DC.  I didn't know if DC-DC LED controllers existed in that voltage/current range that do the same thing (without PWMing the outputs to the LEDs); the Meanwell site only shows lower current ones (only up to an amp or so).

Each individual panel will be calibrated by a solar cell/photocell so that an intensity levels can be known for each driver/LED panel pair.


texts:
Hello I'll be brief because my English isn't good thank you for your patience
I'm working on a system that drives this memory:
module Buffer_m #(
parameter Word=8,
parameter bits_Buffer_address)
(
    input  logic Clk,
    input  logic [bits_Buffer_address-1:0] Address_R,
    input  logic [bits_Buffer_address-1:0] Address_W,
    input  logic R,
    input  logic W,
    input  logic [Word-1:0] Data_buffer_in,
    output logic [Word-1:0] Data_buffer_out
);

localparam  Buffer_deep = 1 << bits_Buffer_address;
logic [Word-1:0] Buffer [Buffer_deep-1:0];

always_ff @(posedge Clk)
begin
    if (R) begin
        Data_buffer_out<=Buffer[Address_R];
    end
    else Data_buffer_out<= '0;
    if (W) begin
        Buffer[Address_W]<=Data_buffer_in;
    end
end

endmodule // Buffer

and give these results
Image 1: correct working
I think this is a normal behaviour but when I drive it with my module
a couple of FSMs ,(not showing all, It's 277 lines )
I don't think this is a problem with the logic but with syntaxis or other thing.
assign Address_R = Reg_address_R_Buffer;
assign Address_W = Reg_address_W_Buffer;

...
assign R           = R_Data           || R_Bus;
assign W           = W_Data           || W_Bus;
...

...
always_ff @ (posedge Clk) begin
    if ( Reset || Address_W_0 ) begin
        Reg_address_W_Buffer<='b0;
    end else begin
        Reg_address_W_Buffer <= Reg_address_W_Buffer + Address_W_1;
    end
end

//FSM
always_ff @(posedge Clk) begin
    if (Reset) State_data_in <= 2'd0;
    else State_data_in <= Next_data_in;
end

...

always_comb begin

    ...
    W_Data           = 1'b0;

    case (State_data_in)

        2'd0:
        begin
            ...
        end
        2'd1:
        begin
            ...
            W_Data           = 1'b1;
            ...
        end

and the same way for R,
I hope this is enough code......
and that give me the same waveforms for the inputs but the outputs are wrong

Image 2: incorrect working
As you see it doesn't save the first byte, I think it's a race condition but
I'm not so sure.
------------------------------------------------------EDIT---------------------------------------------------------
I ran it in Synopsys VCS and gave me different results than image 2

Image 3:incorrect working in VCS
I don't know why but modelsim delayed W one clock cycle,
so I'll continue with VCS
As @Oldfart pointed  there is a race condition when (R && W && Address_R==Address_W) but the problem persists even with R=0

Image 4:Still not working with R=0
I think it could be that buffer reads W before my module update it at the posedge
but I am not sure.
Thank you for your time.


texts: Used Fluke 87V multimeter working correctly?

texts:
I'm just a hobbyist but I like to purchase quality tools so I purchased an "only used once" Fluke 87V on eBay.  The calibration sticker says the calibration expired last year.

Anyways, when I turn on the multimeter the milliamp reading shows a few mA even when I'm not touching anything.  It usually settles down to 0 mA after about 10 seconds though.

Is this normal?

Also, when I'm checking capacitance it always shows an nF value and never gets to 0 nF.


texts: How to improve my digital filter to extract DC from noises?

texts:
Digital filter description:

The filter's input are sensor data and output will be provided to a PID controller.
Sampling rate: 64kHz
Noises spectrum: from DC to 10kHz
Filter target: to get DC component only and reduce noises as much as possible.
Characteristic of DC: it varies very slowly, say at 0.000001Hz.

More about the system

The system input (ref or reference is zero). And actually the goal of the controller is to maintain the output of the system at zero.
In this system, there are also disturbance and noises. The disturbance has the shape of roughly a ramp, however by nature more like random events at very low frequency
The controller is a simple PI controller. It strives to compensate the influence from disturbance while get rid of noises.
The noises are from sensors and the filter between controller and sensor is what I am looking for help about here.

My current way of filter design:

The data will go into a decimator for decimation firstly. The decimator is an 320 tap average filter, which average every 320 data and exports one averaged result. The results will be at 200Hz.
The averaged data will then further go into a 20 tap averaging decimator. The results will be at 10Hz.
At last, the data at 10Hz will go into an IIR or again, a moving average filter. The final result shall ranges from 1Hz to 0.2Hz.

My concerns: Insufficient desgin

The averaging decimator may not be sharp enough, since they are basically FIR with same coefficients of 1/320. Since the filters are not sharp enough, decimation(downsampling) may introduce high frequency noises mapping into the filtered results.

The following diagram is the response for 1/320 averaging filter

May not be bad

Since the several stages of decimation is basically averaging the signals. The results shall be DC component, since that is how DC is defined.

Advice needed

How to improve my current design?


texts: Why use an optocoupler with opto-driver instead of isolated amplifier using optocoupler for feedback

texts: Why do so many feedback circuits rely on a optocoupler driver instead of using an isolated amplifier to directly transmit the feedback voltage to the switch controller?


texts:
From the XBee/XBeePro product manual page 24 (link to pdf):

Sleep Modes enable the RF module to enter states of low-power consumption when not in use. In order to enter Sleep Mode, one of the following conditions must be met (in addition to the module having a non-zero SM parameter value):

Sleep_RQ (pin 9) is asserted and the module is in a pin sleep mode (SM = 1, 2, or 5)
The module is idle (no data transmission or reception) for the amount of time defined by the
ST (Time before Sleep) parameter. [NOTE: ST is only active when SM = 4-5.]

What is meant by "asserting a pin"?


texts:
I tried two solutions for a lowpass filter:

Fig.1 - Normal RC lowpass with cutoff range of about 30-300hz according to the frequency cutoff formula.
Fig.2 - Acoustically, this is closer to what I was looking for but I don't know what happens exactly.
Two questions:

The filter in fig.1 doesn't give the cutoff range I was looking for because of the mixing resistor. Is it possible to isolate the mixing resistors from the RC filter using minimal space (no IC or only one IC with just a few components)?

As for the solution in fig.2: with R1 = 0 it works normally as an RC filter; in the initial range of the potentiometer (about 0-500R), more than affecting the cutoff, it sounds like a gain control for the high frequencies; in the rest of the range it seems like a gain control for the whole audio signal, without affecting the cutoff. Is it correct to consider the potentiometer R1 in fig.2 like a gain for the high frequencies?


texts: Will moving transformer to separate case reduce noise in opamp-based circuit?

texts: I'm building a simple phono preamp for my friend. I've designed a transformer based power supply to be on the same board as an opamp, then I hesitated - will I get less mains interference if I move the transformer and linear regulators to separate box that will be far away from the preamp?


texts: Confused about frequency and bandwidth in BP filter?

texts:
I am trying to design a simple bandpass filter and I am confused what should be my central frequency and bandwidth should be.

I have a 1MHz square wave with 20% duty cycle, so the signal is on for 200nsec and off for 800nsec. I have a rise time and fall time of 10nsec.

The desired filter is passing this signal and eliminating all the noise. If my bandpass filter centered around 1MHz, how wide it should be so that I can maintain a decent rise time. According to the relationship between rise time and bandwidth (0.34=tr*BW) my signal bandwidth to observe 10nsec rise time is 34MHz. If my filter is 1MHz +/-5KHz, I would loose the rise time granularity (At least this is what I think since the FFT of that sharp edge will be in higher frequencies and will be cut off)

Bonus question: How can I design a BP filter that still allows for sharp rise and fall time and narrow around 1MHz?


texts: Analyzing RC circuit that has two "switch"

texts:
I need to find Vc(t) between 0<=t<=0.01 secs , but teacher draws the second switch as opened. We want to find Vc(t) when t is "less or equal" to 0.01, then why we dont take the switch as closed? Because it is closed at t=0.01 sec.
Is it because of its limit from the left? Because vc(t-) is not equal vc(t+).

And another thing that makes me confused, when v goes infinite, teacher takes this circuit to find v infinite.(I am talking about the first part of the question. 1-Find vc(t) when 0<=t<=0.01 secs)

But after long time (after 0.01 secs), the second switch must be closed. Because infinity is greater then 0.01 sec. Then why we take that switch as opened?

Thanks!


texts: Reusing Quartus block schematic symbol file in another project

texts:
I am working on a Quartus project, requiring the usage of some designs previously created as block schematic design files in some other Quartus projects. I generated symbol files from the top design schematic using File -> Create / Update -> Create Symbol Files for Current File... and then copied the generated file into the new project, then added the component to the schematic design of the new project. Upon "Analysis and Synthesis", I encounter the following error:

Error (12006): Node instance "inst" instantiates undefined entity "[name of the old project]"

And as a result, I can't find any way to reuse the component symbols generated in an old project, in a new one. Generated symbols from the current project work as expected, however.
How is it possible that I could reuse the old project's designs in the newer one?
Note: Both projects and design files are created with the exact same version of Quartus.


texts: How to calculate a simple mixed parallel/series resistor circuit

texts:
I'm trying to understand how to calculate resistance in simple mixed parallel and series resister circuit.  Below is a question from a worksheet I've been playing with to better understand the topic (Question 5 ->Figure 6).

I can see the 220Ω and 100Ω resistors are in parallel, but I do not understand how to break out and calculate the 470Ω and 330Ω resistors.

The answer given is 80.54 Ω, but I cannot seem to reach this on my own.

How do I calculate the resistance between points A and B?

Source:
AllAboutCircuits.com - Series-Parallel DC Circuits Worksheet


texts: Reducing transformer lamination thickness

texts: What will happen if you reduced the core thickness of a 200 kVA transformer  lamination. I am trying to reduce the lamination of a 200 kVA transformer, so that my coil can go in freely but I am wondering if it will have any effect on the transformer.


texts: Can I replace multiple series diodes with one zener diode?

texts:
In the datasheet for the MAX15500, it says I need to use several diodes in series:

  ... to ensure a voltage difference of 2V to 3.5V from AVDD to AVDDO and
  from AVSS to AVSSO.

It seems to be that a 2V- 3.5V Zener diode should be able to replace all 5 of these diodes. If so, why are Maxim suggesting such an overly complicated circuit? Am I missing something?


texts: Obtaining rated current from 5 volt rail of pc PSU

texts:
I need to supply a minimum of 0.5 amps to each port of a number of 10 port USB 2.0 hubs.  I have succeeded using 8 amp wall warts so I'm reasonable sure the hubs are capable.  I'm powering 8 hubs  so that's more wall warts than I want to deal with.  I modified a PC PSU, adding a load resistor (10 ohn 10 watt), power led and on/off switch following the many on-line guides.

I have 6 cables off the 5 volt bar, everything is solder and shrink wrap, psu starts as it should.  It does supply power to the USB hubs but only a limited amount.  I estimate it's about 2.5-3 amps, as all ten of the devices do not work correctly.  The measured voltage at each line is 5.01 volts.

I have modified 2 PSU's, one rated at 400 watts with 28 amps for the 3.3 and 5 volt rail combined.  The second PSU is rated at 40 amps for the 3.3/5volt rail combined.

I think the problem is because these are "regulated" power supplies, but I'm a noob and I'm totally lost at understanding why I'm not getting even close to the rated current of the PSU's.  I would appreciate any advise or constructive criticism.


texts: Is this network of resistors in series and parallel, the way I intended?

texts:
https://www.circuitlab.com/circuit/gu5zh6pdvj8q/parallel-and-series-question-circuit/

simulate this circuit – Schematic created using CircuitLab

Do these circuit schematics accurately represent these other 2 circuit schematics, which I made using Tinkercad?

If so, is the resistor network for C2 built to match the equation

1/(1/(330 + 330 + 330 + 220) + 1/(330 + 330 + 330 + 100))

Which represents one serial circuit with a combined value of 1110 ohms, and another of a combined value of 1090 ohms, both in parallel, which should give a combined ohm value at the output of the circuit of 570 ohms?

If yes, how come my multimeter reads 500 ohms at the beginning and the end of these resistor networks?

EDIT:

Solved, the 400/500 ohms is because of the tolerance.


texts: If mobile chargers give output of 5V DC supply to phone Li-ion battery which has maximum charge voltage of 4.2V at full charge and phone has internal circuitry to protect the battery from overcharge , if this protection circuit fails, battery gets overcharge(due to 5V supply) and possible to explode. How will this be taken care of by manufacturers ?


texts: Airport radar is interfering with my circuitry

texts:
I am using an arduino, but this is not an arduino question. And unfortunately, I cannot share my schematic. I can tell you though that I have a stack of three arduino-sized boards which create two ground loops, each about the size of an arduino. I also have an RFID reader board connected, which has about a 2 inch coil in it. But it seems like that coil should be isolated from the arduino by the RFID board's ICs. Altogether I'm pulling a max of around 250 mA out of 6 AA batteries, though the actual current draw varies on short timescales as I transmit wireless data via Xbee.

Somewhere, I'm picking up noise, and it's only happening when I take my devices closer to the radar station about a half mile away. It's actually crashing and rebooting my arduino program. I'm positive an external source is the culprit. since tinfoil shielding prevents the problem, but I cannot add shielding to my design until a later date.

My coworkers and I believe the noise must be affecting the power to my processor, since it seems like processor voltage drops/spikes would most certainly be the only things to cause such behavior in the microcontroller. If that's the case, then I should be able to add line filters. Does that seem reasonable?

I could apply filters to the main power into the arduino, and also add something to the 5V and 3.3V output buses to the peripherals. My initial instinct is to add a 1000uF low-ESR electrolytic across the main power, and some smaller 470uF caps across the 5V and 3.3V buses. But I know it should depend on the frequency of the noise I'm trying to filter. Airport radar operates in the 2.7G range, so I guess I should try filtering 2.7G, right?

Is this the right way to go about the problem?


texts: how to get the angle from a 3 phases synchro signal

texts:
I'm trying to understand how to get the value of the shaft position from a synchro. I've looking in mutiple documentation  but none explains how to calcuate the angle value from :

I'm looking to get Theta

I'll be thankful for any hint


texts: Union member and size of char array in c

texts:
Years ago I had a good working experience in C. Now it is rusty.
Can not find the correct way to create a union with 2 elements

typedef struct {
// multiple elements
}SETTINGS;

 typedef union{
       SETTINGS PROC;
       unsigned char BYTES[sizeof PROC];
 }PROCESS_SETTINGS;

I want to use sizeof here but can not find how anymore?
sizeof PROC reports an error.


texts: Modding a Fender princeston chorus, having issues reading this part of the schematic

texts:
I am trying to add some wires for the left or right channel of this fender amp, and having trouble understanding the schematic here:

There are 2 1/4" phono jacks on the front that are input no 1 and input no 2. I have a red/white RCA connectors I would like to hardwire into one of the inputs. But there are NINE pins for each input channel. The actual connector's model isn't showing up on initial google searches

Any ideas how I should hook this up internally?


texts:
I am looking to take a 3.5mm microphone line, insert a press button switch (a foot pedal in my use case) between the headset and the computer. I would like the switch to mute the mic connection when not pressed, and allow the mic sound when pressed. I am no electrical engineer, so something super simple would be great!

Anyone have ideas on how to accomplish this? What switches to use?


texts:
I jump started a car with an AGM battery and later discovered that the 30A fuse connected to its positive terminal had blown. I suspect that this occurred while performing the jump start.

How many amps would have gone through the fuse to cause it to blow?

If I attempt to jump start a car again in the future using this battery, should I use a fuse with a larger amp rating, should I remove the fuse completely from the positive terminal or are AGM batteries simply not suitable for jump starting cars?

EDIT:

Note that the 30A fuse was attached to the AGM battery that was used to jump start the car battery. There was no fuse attached to the car battery.

Also the 30A fuse attached to the positive terminal of the AGM battery is not indicative of the specifications of this particular battery. I purchased this battery to chain to a Goal Zero Yeti solar generator / battery to increase its capacity. The manufacturer of this product recommends attaching a 30A fuse to any battery to which it is chained.


texts: Very low power pulse generation switch-based circuit for MCU wake-up

texts:
We have a circuit like the one I attached to this post.

The idea behind it is to generate a pulse every time the switch is closed.

We have two constraints for this circuit:

a. The pulse should be at least 50 micro-second

b. The max current of this circuit when the switch is on  should be less than 250 nA while the switch is closed (only the analog, without the MCU part)

However, This circuit suffers from unwanted pulses in the MCU IO pin because the pull-down resistor is too big.

How can we solve it?

Or design another circuit with these constraints (and also the pulses problem...)

Any ideas?


texts:
Can someone help me identify these connectors, I haven't seen them before, tried searching on digikey but there are a lot of connectors, and some of them don't have pictures so it's proving difficult to identify it.

I need both types female and male of the connectors.

And tools that I would need to attach them to wires.


texts: 2 NMOS in series, connected source to source

texts:
I am working with DC2418A evaluation board (Link to datasheet is HERE)

Schematic is on page 5
I am using version A, so we ignore Q1

My question is about Q2 and Q3: Why are they connected source to source? Q2 seems oriented properly, but Q3 seems like it should be flipped so current goes drain to source. I thought it might be because of a protection feature but I am not sure.

Any help is appreciated. Here is the portion of the circuit I am talking about (schematic taken from datasheet)


texts: Relationship between cutoff frequency with GBW and slew rate

texts: How should I answer d) and e)? From my understanding, the 3dB cutoff frequency is not affected by GBW and slew rate.


texts: Solder Paste and Solder Land in Altium Designer / CircuitStudio

texts:
I am designing a footprint for the SOT765-1 using Altium CircuitStudio, and I am a bit confused regarding the solder paste and solder land definitions found on Page 3/5 of this datasheet. For the bottom-left pad, should I make the pad 0.3mm × 0.65mm and set the "Solder Mask Expansions" to 0.1mm? And can I consider solder land to be a synonym of copper pad?
From datasheet:


texts: Discharging static electricity touching chassis macbook pro?

texts:
I was following some instructions from Apple here about changing RAM memories in a macbook pro laptop when I had a question. In these instructions, step 3 tells specifically "Touch a metal surface inside the computer to discharge any static electricity from your body." while showing the next image:

However, we cannot see in that picture (neither in the instructions) that the laptop is connected to ground through a power cable. Is it possible to discharge static electricity like this?


texts: Do I need a current limiting resistor when powering an LED below its forward voltage?

texts:
I've reviewed the questions:

Why can you use an LED below voltage?
Is a current-limiting resistor required for LEDs if the forward voltage and supply voltage are equal?

But combining them begs another question:

If an LED (example: a 3.2 \$V_F\$ white LED) lights satisfactorily when powered using two alkaline cells (3V), is there a need for a current limiting resistor? Assuming the battery source never varies above the \$V_F\$ of the diode, can too much current ever be applied?

If it is recommended to always have a current limiting resistor, as in Martin's answer to the second question, does that mean the best option is to use three cells (4.5V) and add the resistor?


texts:
A mathematical operator is generaly a mapping between a domain set of functions and a range set of functions.One example is the derivative operator L ( L[f] = f'  ) for example.

Can i say every representation of a electronic/electrical system ( input-output representation, statespace representation, block diagram representation) can be generalized to be formed by mathematical operators. Can i generalize to say that every electronic/electrical system  ( filter,ac/dc converter, amplifier,etc ) is simply an operator ?


texts: LED modeling with Shockley diode equation

texts: I'm working on a project where I need to model the voltage/current relationship of various LEDs.  I'm wondering what values I would need to use for the saturation current in the Shockley diode equation for various colors - I know the proper thing to do would be to take the LEDs in question and measure the forward voltage at various currents and fit a curve, but at the moment for my rough calculations I don't need that level of accuracy.  Anyone have any "ballpark figures"?


texts: Multichannel design in a Multisheet hierarchy project (Altium)

texts:
I'm working on another design that has multiple channels for a few circuits with in a multisheet design in Altium Designer.

I have a top sheet that contains all my sub systems as sheet symbols. One of the sheet symbols is for motor control signals and sensors. This sheet contains two sheet symbols setup as multichannel sheets. When I compile the project I get the multiple top level document error. I have been working for about two hours trying to resolve this issue reading through the Altium wiki but I can't seem to figure out how to fix it. I am unsure whether or not I am allowed to have sub sheets with their own sub sheets, the example in the Altium wiki leads me to believe I can but so far I am unable to get the project to compile this way. Is there a way to formally set which schematic sheet is the top sheet for the project? I think that might be what I need to do but I can't seem to find the option within Altium or from googling around. Anyone here have any idea?


texts: How long till Capacitors Discharge Naturally?

texts:
I am a super noob at this and never done anything before like this but want to try. Here is the problem I have Samsung SyncMaster 226BW that is known for bad capacitors and I think I am a victim of this and want to try to repair the monitor before shelling out at least $133 bucks for a new monitor.

There are some tutorials on how to open up my monitor and check but I still am gathering information on how to all do this as I never done it before.

Someone suggested that I should discharge the capacitors what makes sense. My plan was to unplug the monitor and then wait a few hours. Open it up what probably be an hour or 2 and then check what capacitors I need and then get them.

So this probably would be 2 to 4 hours when all said and done.

I don't really want to start buying every tool under the sun for this one job but I of course want to do it safely.

I am wondering how many hours should I leave it unplugged till I start working on it?

According to some repair kits you can buy on ebay to fix my monitor problem these are the most common ones that go

820uF-25V 105ºC Capacitor
680uF-25V 105ºC Capacitor
330uF-25V 105ºC Capacitor
47uF-50V 105ºC Capacitor

How long should I wait?

Not sure if this makes a difference but the computer monitor will have been on for 8 hours before unplugging.


texts: Possible calculation error using current divider rule on a non ideal current source circuit

texts:
I am going through my notes in preparation to an exam, the following was taken straight from the board as my lecturer wrote it.

As far as im aware the current divider rule should be $$I1 = It * (Rt/R1)$$

However it is written here as $$I1 = It * (R2/Rt) $$

there must be something I am missing bit I cant figure it out.

Any help would be very much appreciated.

EDIT:

This was the formula that I thought was valid across the board : -

However Spehro Pefhany has shown this is not valid for all cases.


texts: Overshoot percentage of a critically damped system

texts:
My textbook explains how we recognize an underdamped , overdamped or a critically damped system and all their characteristics.

Later on, in another chapter, without going into much detail I'm given the following two transfer functions and the systems' responses. $$G_1(s)=\frac{1}{(s+1)^2}\\ G_2(s)=\frac{s+0,5}{(s+1)^2}$$

It is known and written that these are two critically damped systems.
It is then just stated that the overshoot happens because of the s=-0,5 zero of the second system. Should that be a good enough explanation for me ? Because I don't get why it happens.

Also , if I'm asked to adjust the systems so that I have a certain overshoot percentage how would I achieve that ? I'm only aware of a formula for underdamped systems which doesn't stand here.


texts: What is the thought process for specifying an EMI bypass cap on line transformer secondary?

texts:
Update

It turns out I had mistakenly interpreted the role of the capacitor in question here as an EMI filter for line noise. It looks like a capacitor in that position actually serves as a snubber for high-frequency rectifier switching spikes/noise. Although perhaps unlikely to be conducted to later stages of the circuit (being contained by the reverse-biased rectifier diode), without snubbing that high-frequency noise might be radiated.

I'm specifying an EMI bypass cap for placement on the secondary winding of a line transformer. It feeds a simple linear supply that acts as the bias supply for a DC Lab Power Supply I'm designing as a learning project, (C5 in the schematic below):

I'm pretty sure the right answer is a roughly 0.1uF 100V (maybe 250V) film capacitor because that's what I've seen used in other circuits. But I want to understand how to go through the design process myself, even if I end up with the same answer in this case.

Here's what I have so far:

The capacitor shouldn't be bigger than necessary, because it will shunt a significant level of the wanted 60Hz AC current. For example, a 1uF capacitor would shunt about 25mA RMS.
The frequency response of the cap needs to be good so it gets rid of high-frequency noise well into the MHz range.
If the capacitor is too small, it might not bypass lower frequency noise very well as its impedance at a given frequency is inversely related to its capacitance (C).

Here's what I don't know:

The practical range of EMI frequencies we'd be looking to bypass in this sort of situation. I'm not sure what's typically around, and perhaps not all of that gets through the transformer because of its natural inductance or something.
Whether the working voltage of the cap needs to be bumped up to accommodate possible high-ish voltage transients that might get through.
Why a plain-old ceramic cap wouldn't get it done just fine.

Can someone help me understand the design space for this component?


texts: How to convert Inductor to series transmission line?

texts:
My objective is to understand the travelling wave amplifiers, but I am stuck on how to realize inductors in transmission lines.

But, I am basically stuck on how to convert a series inductor to a series tranmission line.

I used this - http://www.rfcafe.com/references/electrical/lumped-distributed-components.htm

I tried this in ADS. I could replace the series inductor with a short-circuited transmission line, but it does not work with series connected line.

This actually works (S11 and S22) are same, but the problem is the TLIN is short circuited. I want something in series (for travelling wave amplifier topology). I tried the following as well, but I got S22 as 50 ohms.

If you could give any suggestions on how to realize inductors using series transmission line, it would help.

The substrate definitions are below:


texts:
I have a few transistor (example 2n3906, 2n2222, etc) models and have used them with ngspice & gnucap with no issues.

I would like to use another transistor (example 2n4401) but I am not able to find the model for that transistor that is ngspice compatible.

What parameters I should change from my 2n3906 or 2n2222 model + datasheet to create a model for 2n4401?

Is there a translator available that would translate pspice models to ngspice?


texts: correctly choosing a relay in term of breaking current

texts:
I would like tu interrupt a resistive load on AC of about 1 kw at 220 Vac.
I'm looking at this relay, that claim to have a 10A current ( that sounds enought to me )
but the breaking current is just 0.12A at 220 V. What does it exactly mean? Would this relays just guarantee to break without damage a current of 0.12 A ? Which breaking current should I design for a load as described ?


texts: What is the recommended maximum length of time to leave a soldering iron hot, to prevent damaging the tip?

texts:
Let's say I'm soldering a PCB, and re-holster my iron, still hot at 320 °C, to fiddle with some components or documentation. How long will it be before tip damage occurs?
In other words, what is the recommended maximum length of time a soldering iron can be kept hot? At what time should it be turned off to prevent tip damage?


texts: What are the initial conditions used to find the coefficients in the current equations?

texts:
Suppose a RLC series circuit. R, L and C are in series with a battery and a switch. The switch is open. L and C are discharged.

At t=0, the switch is closed and the battery (V1) feeds the circuit.

I apply KVL to the circuit and find three equations:

CRITICALLY DAMPED

\$ V_C(t) = (At + B) \thinspace e^{-\alpha t} \$

OVERDAMPED

\$ V_C(t) = Ae^{m_1t} + Be^{m_2t}  \$

UNDERDAMPED

\$ V_C(t) = e^{- \alpha t}[K_1 \thinspace Cos(\omega_d t) + K_2 \thinspace
Sin(\omega_d t) ] \$

To find the coefficients of those equations I apply the two initial conditions:

I solve the equations for t=0 and for the initial voltage across the capacitor.
I take the derivative of the equation and solve for t=0.

Now lets talk about the current equations.

I never understood why but apparently the current equations are the same, or

CRITICALLY DAMPED

\$ i(t) = (At + B) \thinspace e^{-\alpha t} \$

OVERDAMPED

\$ i(t) = Ae^{m_1t} + Be^{m_2t}  \$

UNDERDAMPED

\$ i(t) = e^{- \alpha t}[K_1 \thinspace Cos(\omega_d t) + K_2 \thinspace
Sin(\omega_d t) ] \$

What are the two conditions I must use for the current equations to find the coefficients?

In the voltage equations I used the initial voltage across the capacitor and the derivative of voltage (current).

Now I have the current equations.

One condition must be to solve the equations for t=0, but what about the second condition? How do I find the coefficients of the current equations?


texts: Is this transfer function impossible with a low-pass Sallen-key filter?

texts:
I was given this transfer function and instructed to use a Sallen-key cascaded with a 1st order filter to achieve it.

$$H(s)=\frac{628^3}{(s+628)(s^2+628s+628^2)}$$

The first order transfer function is

$$H(s)=\frac{628}{s+628}$$

So if I choose \$c=10\mu F\$, then \$R=159\Omega\$.

That leave the Sallen-key transfer function to be

$$H(s)=\frac{628^2}{(s^2+628s+628^2)}=\frac{\frac{A}{R^2C^2}}{s^2+\frac{2}{RC}s+\frac{1}{R^2C^2}}$$

So \$A\$ must be equal to \$1\$ and \$\frac{1}{R^2C^2}=628^2\$. The same values for R and C as the first order filter work here.

The problem is that middle term, \$628s=\frac{2}{RC}\$. This contradicts the other values. It works fine if this was a typo and that term was meant to be \$\frac{1}{2}\$ that value. Did I make a mistake here? I've wasted hours deriving and rederiving the transfer function for the filter to no avail.


texts: How to mix to video sources into a split screen (two inputs, one output)

texts:
I want to build a circuit for my car (It has two cameras, front and rear) that shows me the front and rear camera in the same screen (splitted), top half the video from the front camera and bottom half, the video from the rear camera.

The cameras are the "regular" cameras used in cars as "backup cameras".

Is this possible with a DIY circuit?, any ideas about how to build the circuit?


texts: Wiring up a 1602L/1602S LCD and switches

texts:
I need to replace a 1602L LCD (winstar i think) with an ACM1602S LCD.

The original lcd had this resistance RA

also the end of the white wire from the switch was connected to the part that is marked J16, but not I can remember which of the three points.
I think the other connections are equivalent. Full gallery here.

If anyone can help me, I would be grateful

Datasheet for the original lcd is here


texts: Build failed with XC8 compiler: error the PIC18 extended instruction set was enabled

texts:
As per the Microchip's guidelines, I downloaded MPLAB X IDE 3.8v and also installed the XC8 compiler version 1.38. I wrote the following example code for blinking LEDs:

Configure registers like this:

#include<xc.h>

// CONFIG1L
#pragma config WDTEN = OFF      // Watchdog Timer Enable bit (WDT disabled (control is placed on SWDTEN bit))
#pragma config STVREN = ON      // Stack Overflow/Underflow Reset Enable bit (Reset on stack overflow/underflow enabled)
#pragma config XINST = ON       // Extended Instruction Set Enable bit (Instruction set extension and Indexed Addressing mode enabled)

// CONFIG1H
#pragma config CP0 = OFF        // Code Protection bit (Program memory is not code-protected)

// CONFIG2L
#pragma config FOSC = ECPLL     // Oscillator Selection bits (EC Oscillator, PLL enabled, CLKO on RA6)
#pragma config FCMEN = ON       // Fail-Safe Clock Monitor Enable bit (Fail-Safe Clock Monitor enabled)
#pragma config IESO = ON        // Two-Speed Start-up (Internal/External Oscillator Switchover) Control bit (Two-Speed Start-up enabled)

// CONFIG2H
#pragma config WDTPS = 32768    // Watchdog Timer Postscaler Select bits (1:32768)

// CONFIG3L

// CONFIG3H
#pragma config CCP2MX = DEFAULT // ECCP2 MUX bit (ECCP2/P2A is multiplexed with RC1)
#pragma config MSSPMSK = MSK7   // MSSP Address Masking Mode Select bit (7-Bit Address Masking mode enable)

// #pragma config statements should precede project file includes.
// Use project enums instead of #define for ON and OFF.

And my code is:

#include<xc.h>

#include"config.h"

#define _XTAL_FREQ 8000000

void main()

{

  TRISB=0X00;

  PORTB=0X00;

  while(1)

  {

    PORTB=0XFF;

    __delay_ms(1000);

    PORTB=0X00;

    __delay_ms(1000);

  }

}

The issue is:

  config.h:13: error: (1504) the PIC18 extended instruction set was
  enabled

but is not supported by this compiler

  (908) exit status = 1

  nbproject/Makefile-default.mk:100: recipe for target
  'build/default/production/main.p1' failed

  make[2]: Leaving directory

  '/Users/saiteja/MPLABXProjects/TEST.X/example.X'

  nbproject/Makefile-default.mk:84: recipe for target '.build-conf'
  failed

  make[1]: Leaving directory

  '/Users/saiteja/MPLABXProjects/TEST.X/example.X'

  nbproject/Makefile-impl.mk:39: recipe for target '.build-impl' failed

  make[2]: *** [build/default/production/main.p1] Error 1

  make[1]: *** [.build-conf] Error 2

  make: *** [.build-impl] Error 2

  BUILD FAILED (exit value 2, total time: 468ms)


texts: Convert from signed magnitude to twos complement

texts: If I have the number x=1111001 in signed magnitude what would x be in two's complement? Is it 0000111? What about -x in twos complement?


texts:
I'm using a PIC 18F4550 to blink an LED in a breadboard through a resistor. I think the circuit is correct because a simulation with Proteus works fine.

The physical circuit doesn't work unless I hold the LED with my hand.  When I release my hand it stops.

I used a typical 0.1uF ceramic decoupling capacitor between Vcc and Vdd.

now I connected the two pairs of (vcc ,ground)

What could be the cause of my problem?


texts: Setting Over voltage and Under voltage limits for LTC4364

texts:
I am trying to set under voltage, over voltage and over voltage clamping limits in a circuit for Overvoltage Output Regulator with Reverse Current Protection using LTC4364 device. The LTC4364 uses an external resistor voltage divider to set the over, under voltage and overvoltage clamping(FB pin) limit set points.

In the datasheet they have some example circuits with OV, UV and Overvoltage clamping limits with Resistor voltage divider but i am not able to understand how they calculated resistor values for certain OV and UV limits.

with Vin=12V and to set UV to 6V they have used 383K(R1) and 100K(R2) as well
to set OV to 60V they have used 475K(R1) and 10K(R2). I am not able to get these values with basic voltage divider fromula.

My question is I want to set UV to 18v and OV to 32 V and overvoltage clamping to 35V at FB pin with Vin as 24V.Can anyone help me how to calculate resistors values for desired set limits.

The LTC4364 data sheet is here LTC4364


texts:
A cache with a line size of L 32-bit words, S number of sets, W ways, and
  addresses are made up of A bits. Assume that the cache is word addressed, i.e., the low two bits of the address are always 0.

  If this is a direct-mapped cache of size 16 words, line size 4 words, what is the cache size in bytes? This number should include just the data portion of the cache
  What is the total number of bytes required to store the tags?

This problem is very abstract for me, so helpful hints on calculating the cache size and tags would be apreciated.

If the words are 32 bits, and there are a total of 16 words, does that mean the cache size is 16 * 32 = 512 bits = 64 bytes (Question 1)? This would also be important to answer 2) the number of bytes required to store the tags.


texts:
I've made a code in Verilog for a variable duty-cycle digitally controlled PWM generator. I will be using it in a system I am designing for controlling a buck-boost converter that will regulate the voltage of big solar panel.

My code works fine in simulations and here it's:

`timescale 1ns / 1ps
module PWM_gen(
    input clk,
    input [7:0] duty,
    output sig
    );

    reg [7:0] count = 8'b00000000;
    reg signal;
    wire [7:0] threshold;
    assign threshold = duty;

    always@(posedge clk)
    begin
    count <= count + 8'b00000001;
    assign signal = (threshold >= count);
    end
    assign sig = signal;
endmodule

The frequency of the PWM signal is

$$f = f_{clk}/2^N$$

where N is the size of the count register in bits. The duty cycle can be set by the duty input bus, if 50% duty cycle is required, duty must be set to 7F and so on.

The problem is, although it's working is it the correct implementation? I found a paper specifying different methods and designs of digital PWM generation circuits, the problem is should I follow those methods? what is usually used in the industry and what are the drawbacks of this implementation, I feel that it's very simple.


texts: How to get the dynamic power waves of a FPGA when a program is running in VERTEX-5. Where to connect the DSO to FPGA


texts: How does USB superspeed electrical signaling work?

texts:
I've been reading a bunch, including the USB 3.0 spec, and I still don't get it.  The transmit data lines are both capacitively coupled, so at the connector, SSTX are 0 V average?

Yet the voltage level diagram shows single-ended signals with a 0.3 VDC bias, is this before or after the coupling caps?:

Wouldn't this produce negative voltages on the receiver?  Aren't the receiver ICs single supply?  Is there a DC bias on either input or output?  I read the part about how "8b/10b coding is DC-free", but I don't think that matters; it's like sending a 50% duty cycle square wave?

This is the closest I can find to an equivalent circuit (for a TI redriver):


texts: What should my resistor wattage be to run a LED on 240VAC?

texts:
I'm looking for a sanity check on my figures here because I'm concerned my resistor wattage is unrealistic.
I would like to run a red LED on a 240 VAC line.  I have found that the forward voltage for a red LED is 2V and a max current of 20mA.
To calculate the resistance I used ohm's law and set a target of 18mA:
R = V / I
R = (240VAC - 2V) / 0.018A
R = 13222 ohms or about 13.2k ohms
What about the wattage?  This is a high voltage after all...
W = V * V / R
W = (240VAC - 2V)^2 / 13222 ohms
W = 4.28
Does this seem right?  Do I really need close to a 5W resistor to handle this?

Thanks everyone for the help.  I think the big message here is that there is a much better way of doing this than dumping the extra power as heat from resistors and that the reverse voltage needs to be considered when dealing with the LED.
EM Fields thank you for posting such a detailed explanation of the options along with a diagram.  Thanks to uint128_t who had a good comment about 240VAC being the RMS value and provided the equation to calculate the 340V peak.
Using a capacitive reactance method (shown in diagram c of EM Fields answer), which I had never heard of, is a better way to approach this type of circuit.  I know that several of you have mentioned it which was very helpful.  Thank you Dwayne Reid, Evan, and anyone else I missed.
For anyone else who is new to this like me then I found these additional resources to be helpful:

Blog post and video source

Introduction to reactance and impedance


texts:
I am reverse engineering a old circuit board, probably from the late seventies (specifically an Enteron sk-1600-a industrial controller), And I am having trouble finding data sheets.

Firstly I am guessing that Motorola has sold off the divisions making many of the chips on this board and that they are now sold under some other name (ie Motorola moc3021 is obviously from how it is used on the board an opto-isolated triac driver and Fairchild moc3021 fits and has the same pinout, similarly their uln2003a could now be made by texas instruments although using a darlington bridge with flyback diode seems like overkill for driving the moc3021, and the mc14020b could fit the counter by on semiconductor as it is near the clock crystal).

Secondly I am guessing that some have gone the way of the dodo like the ami 8616 (looks like an eight bit processor) and the ami 8424 (probably a parallel io chip).

If anyone can partially endorse the modern data sheets (these parts are mostly compatible with their predecessors) or even better has the right data sheets, It would certainly be appreciated.


texts: Can you split track width among layers to equal one big trace?

texts:
Assume you want a trace to be able to carry 20 amps of current on 1oz copper with a temperature rise of 20. Using an online calculator this yields 12.60mm trace width.

My question is, can you split that width among bottom and top layers (6.30mm each) and stitch together those layers using vias? If so, is there any special considerations with this method?


texts: When driving power MOSFET from a microcontroller pin, is there a need for protection?

texts:
I'm making a simple design where a power N-channel MOSFET is driven from a microcontroller pin. In all sources I can find they say it can be done using a single resistor. However, my friend says that due to large gate-to drain capacity of the MOSFET (I' using IRF3205, which has 3.2 nF gate capacity) the microcontroller pin circuit can be destroyed by a higher drain voltage (24V). He says that he experienced it and recommends placing a Zener diode from gate to 0.

I never read about this possibility before, so the question is: can this happen? Can a 24 volt drain voltage destroy a 6 volt CMOS transistor pair via 3nF capacitor or it is just an imagination?


texts:
I have two sets of LED ladders (12 in each ladder, so 24 LED's) that I want to control from my microcontroller. I don't have enough inputs for 24 LED's (and want to make it scalable), and the microcontroller has other tasks to attend to, as well as control the LED ladders.

I don't have a set amount of PIN's I can dedicate for a ladder, but the lesser the better  (if a number is required, maximum of 8 pins per ladder)
The LED's will be updated very infrequently (every few hours), so I don't want to eat up processing power by multiplexing continously.
My microcontroller doesn't have a DAC

Currently, I am thinking of using shift registers (8 bit and 4 bit cascaded). However, since shift registers are "one way" devices I'll have to clear the registers to set a lower value.

I don't think this is a big problem (for me, as they get updated infrequently), but are there better methods to control an LED ladder?

Edit: By an LED ladder, I mean a single line of leds (like a bar of an equalizer) that shows a level of something. The LED's don't need to be controlled individually.


texts: Low voltage - high current AC motor speed control

texts:
What we are trying to accomplish is digitally controlling the speed of a 18VAC motor, which can easily pull 1A (specifically old H0 Märklin locomotives, which can reportedly pull 5A at peaks). The supply power in our case is fixed at 18VAC.

Ideas we considered:

Voltage divider with digital potentiometer which is probably not feasible due to the high current requirement.
Using a DIAC+TRIAC dimmer circuit (with a digital potentiometer), but the existence of low-breakover-voltage DIAC's seems to be a myth. I found one 15V SIDAC but that still seems to high for our 18VAC motors.

Dimmer circuits for AC with voltages below 30V don't seem to be popular so I hope one of you can come up with/knows a circuit able to do this. Or perhaps you know an alternative for the DIAC? Not sure if this helps but a microcontroller with PWM capabilities is available.


texts: Capacitor Discharge through Constant Current Source

texts:
I was just thnking of how to model the voltage decay from a fully charged capacitor through a constant current source (CCS). A good approximation to this would be to model the constant current source as a resistor sized by the initial voltage divided by the current of the CCS, giving the formula:

$$  V(t) = V(0) * e ^{\frac{-t}{RC}} $$

... but is there a closed form analytical formula for the CCS case?

   +------------+ V(0)
   |            |
   | C          |
 --+--          /\
 --+--          CCS (I)
   |            \/
   |            |
   +------------+
   |
  -+-
  GND

  Some ASCII circuit art for good measure...

Obviously I'm only interested in the model up to the point where the current that the capacitor is able to supply is still above the demand of the current source, and that the voltage is greater than GND (i.e. the realizable time).


texts: Unable to intercept the code of my remote control at 433 MHz with RaspberryPi

texts:
I'm trying to reproduce the code generated by my universal 4-channel radio control with RaspberryPI.

I cloned my remote with a universal remote like this:
I used the libraries included in 433Utils to test my transmitter and receiver components and `work properly.

I'm using:

Transmitter: MX-FS-03V (3.5 - 12V DC)
Receiver: MX-05V (5V DC)
Transmission power: 10mW / Frequency: 433MHz

But when I try to read the code registered in my remote control using the RFSniffer library, I don't receive any data.
Instead I tried using rpi-rf, if I send a code using the 443Utils send tool, I can read it (with noise).

If I use it with my remote control I can't find any code that makes sense for me:

    //the result of a long-pressed key

    2019-12-19 23:17:34 - [INFO] receive: Listening for codes on GPIO 27
    2019-12-19 23:17:39 - [INFO] receive: 992 [pulselength 454, protocol 3]
    2019-12-19 23:17:44 - [INFO] receive: 512 [pulselength 375, protocol 1]
    2019-12-19 23:17:44 - [INFO] receive: 64 [pulselength 384, protocol 1]
    2019-12-19 23:17:44 - [INFO] receive: 256 [pulselength 379, protocol 1]
    2019-12-19 23:17:44 - [INFO] receive: 128 [pulselength 376, protocol 1]
    2019-12-19 23:17:44 - [INFO] receive: 64 [pulselength 379, protocol 1]
    2019-12-19 23:17:44 - [INFO] receive: 512 [pulselength 1180, protocol 2]
    2019-12-19 23:17:44 - [INFO] receive: 514 [pulselength 382, protocol 1]
    2019-12-19 23:17:44 - [INFO] receive: 128 [pulselength 380, protocol 1]
    2019-12-19 23:17:45 - [INFO] receive: 1540 [pulselength 380, protocol 1]
    2019-12-19 23:17:45 - [INFO] receive: 1990 [pulselength 380, protocol 1]
    2019-12-19 23:17:45 - [INFO] receive: 2082 [pulselength 381, protocol 1]
    2019-12-19 23:17:45 - [INFO] receive: 4 [pulselength 530, protocol 1]
    2019-12-19 23:17:45 - [INFO] receive: 1152 [pulselength 381, protocol 1]
    2019-12-19 23:17:45 - [INFO] receive: 130 [pulselength 380, protocol 1]
    2019-12-19 23:17:45 - [INFO] receive: 2 [pulselength 378, protocol 1]
    .....

My only idea is that the RFSniffer library is NOT able to identify the communication protocol of my remote control.

How can I find the code?

**************************[EDIT: STEP 2]****************************

I used Audacity to view the wave that is being produced by my signal receiver when I press the button on the remote control. To do reverse engineering of the communication protocol.

How do I decode the signal (without knowing the protocol and the clock)?


texts: How can I add redundancy to the flyback diode protection across an inductive load?

texts:
Dear StackExchange users,

I want to add redundancy to a flyback diode system that is protecting an N channel MOSFET from flyback of an inductive load but I don't know how to accomplish this!

I am using a Zener Diode + normal diode. I think when the Zener is going bad, then it will conduct the current without any resistance, So adding a parallel diodes is not going to work.

What shall I do?

Thank  you


texts: Calculate number of LEDs, and resistor values, when some is turned on/off from time to time?

texts:
The LEDs that I have available is 3.2V ~ 3.4V and 20mA (exLED 5mm LED). (i'm planning to use the clear ones).
The resistors is 1/4W metal film resistors (1/4W Resistance Metal Film Resistors).
And this powersupply - that says 14.8V 700mA.

I want to use this power supply in particular because of the plug in the other end. That way I don't have to "destroy" any other wall warts, and this one, to connect it...

What I basically want to know is how many white LEDs I could have connected, and turned on all the time as a light, in addition to 5 green ones that is turned on and off from time to time?

I'm planning to only use the clear ones. Those light up in different colors.

So I put the data (14.8V, 3.2V, 20mA, 10) into this online calculator, and it returned a couple of variations to choose from. I put in ten LEDs because of 5 green LEDs (it has to be exactly 5), and 5 white ones (can be whatever, but minimum 4).

I've learned that there's a bit different in voltage from various colors?
I'm not sure exactly what voltage each of the LEDs are since I don't have any datasheet to look into...

The real life scenario goes like this:
The white LEDs should turn on, and stay on, all the time when the power supply is connected. Just like a light (it's a lightbridge for a slot car race track).
In addition to this light. There's a start light with 5 additional green LEDs (clear, but light up in green) that is turned on from time to time (when a race starts, and is on until its over/paused) by a mechanical relay (Keyes 5V Relay).

I was hoping to be able to use the same power supply for both actions... The green starting part is controlled by a microcontroller - if that matters...

My concern is when the green LEDs is not ON, there's going to be more voltage in the circuit. By using higher resistors on the white LEDs would prevent them from being overloaded, but would make them very dim when the green LED's is on - which is when they are needed the most...

Any suggestion would be highly appreciated...
I'm a beginner to electronics, and don't know a lot of terms, and solutions, and available components, and such yet...


texts:
I'm looking into using this display for a small project I'm working on, but I'm not positive what kind of connector it has:

http://www.alibaba.com/product-detail/2-4inch-transparent-oled-screen-240_1935783651.html?spm=a2700.7724838.2017115.372.40fbe7700UN3sx

What I can't tell is if it's a standard ribbon cable that'll connect with MIPI/DSI interfaces or if it's something totally different. All it says about the display is that it uses an 8bit Parallel Data with MPU (8080-series MPU).


texts: Can I use Li-ion in series to power a 12V motor?

texts:
I'm investigating options to power a small trolling motor, which is designed to be used with a 12V lead-acid battery.

My main constraint is weight, and from the research I have done so far it looks like Li-ion batteries have the highest energy/mass ratio, so this would potentially be the best option for getting the most power in the smallest package.

So I am comparing to a commercial LiFePO4 battery with the following specs:

Voltage: 12.8V
Continuous Discharge: 40A
Capacity: 40Ah
Weight: 5.9kg

So for instance, if I look at a Panasonic NCR18650B, with the unit specs:

Voltage: 3.6V
Continuous Discharge: 4.9A
Capacity: 3.4Ah
Weight: 47.5g

Then I have calculated that I should be able to configure these with 4 in series, and 12 in parallel to achieve:

Voltage: 14.4V
Continuous Discharge: 58.8A
Capacity: 40.8Ah
Weight: 2.28g

So it looks as if this battery would achieve more power than the commercial version, with the same capacity at less than half the weight.

So my questions would be:

What will happen if I connect a 12V motor to a 14.4V power source?
Is there some way to regulate the voltage coming out of the battery?  I.e. can I have the battery output at 12V somehow?
If it is possible to convert the voltage, then is there a drawback to this approach?  I.e. am I going to lose efficiency?  Or what effects does this have on the system?

edit: The motor takes max 17A (204W) at top speed.


texts:
I am trying example about SDIO with board Open407V-D. I get problem with reset SD card (CMD0). When checking status for sending CMD0, bit 11 (CMDACT) of status register is always set 1. Therefore, time out occurs. How to fix this problems???

 /* CMD0: GO_IDLE_STATE -------------------------------------------------------*/
 /* No CMD response required */
 SDIO_CmdInitStructure.SDIO_Argument = 0x0;
 SDIO_CmdInitStructure.SDIO_CmdIndex = SDIO_GO_IDLE_STATE;
 SDIO_CmdInitStructure.SDIO_Response = SDIO_Response_No;
 SDIO_CmdInitStructure.SDIO_Wait = SDIO_Wait_No;
 SDIO_CmdInitStructure.SDIO_CPSM = SDIO_CPSM_Enable;
 SDIO_SendCommand(&SDIO_CmdInitStructure);

 errorstatus = CmdError();

 if (errorstatus != SD_OK)
 {
    /* CMD Response TimeOut (wait for CMDSENT flag) */
    return(errorstatus);
 }

 //-------------------checke timeout--------------------//
 static SD_Error CmdError(void)
 {
   SD_Error errorstatus = SD_OK;
   uint32_t timeout;

   timeout = SDIO_CMD0TIMEOUT; /* 10000 */

   while ((timeout > 0) && (SDIO_GetFlagStatus(SDIO_FLAG_CMDSENT) == RESET))
 {
   timeout--;
 }

 if (timeout == 0)
 {
    errorstatus = SD_CMD_RSP_TIMEOUT;
    return(errorstatus);
 }

 /* Clear all the static flags */
 SDIO_ClearFlag(SDIO_STATIC_FLAGS);

 return(errorstatus);
 }


texts: EM waves inside a transmission line clarifications

texts:
I just wanted to ask several clarifying questions to make sure I have an accurate picture of what happens in a transmission line.

A transmission line is usually made up of conducting material. If you connect a voltage source to a transmission line, is the "voltage wave" that gets sent down the transmission line just a change in electric field inside the line with respect to time and position?

If it is indeed a change in electric field inside the line, how is that possible if electric field inside a conductor is supposed to be 0? Is it that perturbations caused by the voltage source make a transient change in the charge distribution in the conductor, resulting in the change in electric field? My understanding is that people say that electric field inside a conductor is 0 in a steady-state context: after a long time under the same conditions, electric field inside a conductor is 0.

If the EM wave is inside the conductor, is there also a wave inside the medium that is between the two wires? If there isn't a wave inside the medium as the EM wave propagates, why does the characteristic impedance of the medium matter? I ask this because the EM wave is trapped inside the conductor.

Suppose you have a transmission line with a short on one end and an open on the other end, and you power the line with a quick pulse, say by connecting and quickly disconnecting a voltage source. Is the EM wave that reflects inside the transmission line inside the medium, or inside the line?


texts: Why is the mechanical power of a DC brushed motor at a maximum at around 50% of the stall torque?

texts:
I don't currently fully understand how a DC brushed motor reaches maximum mechanical power at around 50% of their stall torque. I know that a decrease in the speed of the rotor will decrease back-EMF and in turn, increase current, thus the increase in power.
However, I don't exactly understand why the maximum power stops at around 50% of the stall torque. What determines the stop at 50%?


texts: Maximum protusion length for through-hole component pins

texts:
I'm working on a PCB that has through-hole components on both sides of the board. The "top" side of the board is mounted flush to a Delrin plastic block (the only top-side component is a gas sensor that is fed air samples through hose fittings in the plastic block).

The flush mounting means that I have to add grooves to the plastic block to accommodate the soldered pins of the bottom-side components. Assuming a standard 0.062" thickness FR4 board, how deep do I need to make the grooves in the plastic block? The only thing I could find is this NASA workmanship standard that states 0.5mm to 2.29mm, but I'm not sure if that will always hold true.


texts: Can I use this 950° soldering iron on electronics?

texts: I purchased this soldering iron yesterday and after doing some research I'm not convinced it is safe to use on electronics. It doesn't state the wattage anywhere and I can't find it online. It only says that it heats to 950°F, which I'm pretty sure would destroy a PCB. Should I return this and buy a 25 watt soldering iron?


texts: What is GMAC/EMAC and does it define a physical connection to an ethernet chip?

texts:
Background

I'm trying to understand if there is a dedicated protocol that dictates the way CPU on an embedded board is connected to an Ethernet chip. For example if it's some dedicated equivalent to ONFi for interfacing a NAND ic or is it a more generic protocol like SPI

This study got led me to find references to GMAC/EMAC but have so far failed to understand what does it define.

Would a cpu and an Ethernet chip have dedicated GMAC/EMAC pins or does it represent a protocol interface (which goes over say UART)?
What benefits does it bring over providing Ethernet through a USB dongle (if price isn't the issue). Would it put less load to the CPU?


texts: External interrupts in STM32CubeMx on both Rising/Falling?

texts:
I'm using STM32Cube to generate the configuration. It creates the following code by default for MX_GPIO_Init in main.c:

...
GPIO_InitStruct.Mode = GPIO_MODE_IT_RISING;
...

However, I also want it to be triggered on falling, so I have to manually change it to:

GPIO_InitStruct.Mode = GPIO_MODE_IT_RISING_FALLING;

Since I need regularly to change the setup (because I am both a starter, and want to gradually add pins), is there a way in STM32CubeMX to set this, so it is generated?


texts: Need alternative way to deal with LDOs minimum current requirement

texts:
I am designing a circuit that uses an LDO to produce 3.3v from a 10 to 18v input.
I sometimes will need 1.2 amps from this regulator and at other times I only need microamps. When I need even less I can shut down the regulator but there will be times when I need regulation and my circuit will only draw possibly .5 or 1 milliamp. My circuit contains a microcontroller.

My datasheet says my LDO requires 5ma minimum load. It's a Micrel/Microchip MIC29150.

So my question is, other than putting a resistor on one of the GPIO pins of my micrcontroller and burning off electricity at around 5ma when I want to, are there any other techniques I can use that are better?

One of my thoughts were to put a zener in series with a resistor so that if the voltage goes over 3.5 or so that it burned off some milliamps but that seems dangerous to me.


texts:
I am working on a Arduino based quadcopter. The Arduino being used is a Blend Micro. Not shown in the following diagram are 4 infrared sensors, 1 ultrasonic sensor and a 9 axis accelerometer.

The issue is that when the propellers are spinning the GPS "freaks out." The fix light flashes randomly as opposed to 1Hz as it does when the motors are not spinning.

If I had to make a guess it would be that the current passing through the snubber diodes does not completely re-enter the respective motors, causing fluctuations in the voltage attached to Vin of the GPS. I do not know if this correct and if it is, I am not entirely sure how to fix it. Perhaps a voltage regulator?

Edit: The GPS module is the "Adafruit Ultimate Gps"


texts: voltage divider with 2 power sources, Vout?

texts:
simulate this circuit – Schematic created using CircuitLab

If V2 is NOT present(VB=GND) i can solve it easily using voltage divider formula:
I know the steps:

I = V1/(R1+R2)
Vout = I * R2 =>(i have 'I' from step 1,R2 is known)=> Vout = (V1*R2)/(R1+R2)

Questions:

A) I would like to request some help on how to solve it when v2 = 3.3 volts is
present. Please do not skip steps if you answer it.

B) Vout is calculated with reference to GND. Right? If yes, that means
     the voltage drop at R2 equals to Vout = Vout - GND = Vout - 0 = Vout
assuming GND as reference point?

C) Is it correct to say the voltage drop at R2 = Vout - VB? (So in
this case i do not take GND as a reference point).

D) So there are 2 different ways to describe voltage drop? Like case B) and
case C).Am i correct?


texts: Charging 12V batteries in series-parallel using a 24V charger

texts:
Would it be okay to charge four identical 12V batteries in series-parallel, using a 24V charger, as shown?

I am trying to create a 24V battery bank, so naturally I need to connect two 12V batteries in series. I also need a larger capacity than these batteries can supply, so I intend to wire up two more 12V batteries in parallel for a total of four. I have a 24V charger for this battery bank, but will it be able to safely and effectively charge all four of the batteries wired in this configuration?


texts: Using HI7190 ADC, value does not match Vref?

texts:
I built the following circuit featuring the HI7190, 24-bit ADC, straight off the datasheet:

Since there is no available negative supply I built one using ICL7660, as AN9601 recommends. For VRef, as a test, I used a TL431. The actual measured VRef is 2.495V.

If I short Vin pins, the ADC gives a reading of around -10 to +10, which is to be expected because of the low quality reference and circuit construction. (This is still an impressive 6uVpp noise floor).
If I put a slightly discharged AAA battery, about 1.4V, between the input pins, I get a reading of about 3 500 000.
If i turn the battery around, the reading is about -3 500 000.

In both cases, Vinhi and Vinlo are floating. The battery terminals are connected to Vinhi and Vinlo and nothing else.

The problem I have is that the ADC reading does not match the actual values between Vinhi and Vinlo. The ADC has a voltage reference of (nominal) 2.5V. The readings of 3,500,000 would mean: (3500000 * 2 * 2.5)/(2^24) = 1.0431V. This is far from the 1.4V that are at the inputs. It's about 1.345x lower.

I have noticed this error is constant across all the range. I tried several voltages at the input and they are all off by the same factor.

I have measured the reference voltage, supply voltages, ground. It's all OK.
I have even replaced the IC and the problem persists.
The ADC has calibration registers. They are a all "auto calibrated" at power up. I have also overriden them by overwriting them like the datasheet suggests, but nothing seems to change.

Is there something I'm missing?


texts: What prevents this op-amp reference buffer from oscillating?

texts:
I was just perusing the open-source schematic for an ECG amplifier, found here.
The schematic contains what I take to be a reference-voltage buffer, with heavy use of capacitive filtering:

From what I understand, using an op amp in unity-gain configuration to drive a large capacitive load (C24) will tend to reduce phase margin and make unwanted oscillation likely. So is there some element here that prevents this? In particular I was wondering if C22 played a role.


texts:
I am attempting to read two hall-effect flow meters through the audio-in (mic) port of an Android device. I want to be able to read both flow meters independently. The audio-in port is a standard headset port so it only has one channel for the mic.

The first problem is the +5v provided from the audio-in port provides only 2mA which is not enough to power both flow meters. I figured I could splice into the USB cable that would be powering/charging the android device and use its +5v and ground to power the flow meters.

The second problem is knowing which pulse came from which flow meter. I was suggested using an R-2R to mix the pulses into one signal but with voltages (and thus amplitudes) at 25% and 50%. That way, when I read a pulse I know if the pulse has an amplitude of 25% it was from flow meter A, 50% is from flow meter B, 75% is from both. Is this a good approach?

Now the problem is how to feed the output voltage from the R-2R to the audio-in port's ground. It seems I need to use the output voltage from the R-2R to control the voltage of the audio-in port's +5v. After doing some research I found you can use an op-amp to create a "voltage follower" that will match the voltage of one circuit with the voltage of another. Sounds like exactly what I need, but is it?

I put together a schematic as best I could - I am still pretty new to EE. Can I get some confirmation on its correctness? Any changes or improvements?:
http://www.digikey.com/schemeit/#1fwi

These are the flow meters I am using now:
http://www.adafruit.com/products/828

These are the flow meters I want to use eventually:
FT-330 from Gems Sensors (sorry, can only post 2 links - can Google "FT-330" and it's the first and second result).

So far I have been testing with my desktop PC. I wrote a Java app that can detect pulses (interrupts?) from the audio-in (mic) port. I am able to hook up a single flow meter by connecting the +5v from the audio-in port to the +5v of the flow meter and the ground from the audio-in port to the pulse line of the flow meter. I don't know if this is the proper way, but it works in that I get a signal from the flow meter and I can see the pulses like so:

Well, I got all my parts in and my circuit does not work.

I discovered my flow meters change between an "on" and "off" state depending on the location of the wheel and do not send out a single pulse like I thought. When they are "on" +5v can be read from the pulse pin to the ground. When they are "off" it is 0v.

The R-2R seems to work. When neither of the flow meters are "on" I read +0.02v from the output of the R-2R (combined pulses) to ground. When only flow meter 1 is "on" I read +0.95v. When only flow meter 2 is "on" I read +1.95v. When both are "on" I read +3.24v. While this will work, I expected to get +1.25v (25%), 2.5v (50%), and 3.75 (75%) respectively. Why don't I?

The op-amp does not do what I want at all. When the op-amp's VCC is +3.24v (both flow meters are on) reading between the op-amp's OUT and the mic's ground gives me -1.2v. Why this negative voltage? I thought that the op-amp would change the voltage from IN+ (mic's +5v) to OUT (mic's ground) to match the voltage from VCC to GND. What am I missing here?


texts: Circuit for Atmel (now Microchip) Single Wire Interface (SWI) using actual TTL UART?

texts:
Atmel defines a Single Wire Interface (not to be confused with 1-Wire) for their ATSHA204 chip.
AVR274 describes how to use a UART for SWI. But how to wire a generic TTL UART for this?(for example from a Raspberry Pi) Is it really as simple as connecting TXD and RXD together?


texts: How to Test if wire is connected with Arduino

texts:
I have an Arduino to control an actuator, which moves up and down reversing the current using a couple relays controlled with the arduino.

I would like to be able to detect when the actuator is up and when the actuator is down. When the actuator is up one of the wires in the relay becomes disconnected and when is fully down it is the other wire that becomes disconnected (I.e. Not connected to either VCC or Ground). Is there a way to test is the a wire is connected? I thought I could measure the voltage but I get 0 volts, which is the same voltage I get when connected to ground.


texts: So, today I started to wounder how pixels are stored, then push though the graphical bus. I have not really done much with LCD or touch screens. I do know from my programming background they are buffered, maybe in an array like binary structure. But I'm not sure. Does anyone have a good resource for how pixels are sent to the screen? Or can tell me?


texts: SX1276 LoRa - Implicit mode - Not knowing PayloadLength at reception

texts:
I'm trying to use SX1276 in Implicit Header Mode, and extracting the PayloadLength after ValidHeader interrupts. The first byte is the payload length. The reception works OK 80% of the time. For the rest of the time, it just reads random data.
Config:

BW: 125khz or 500Khz - no influence
AFC BW: 250khz
CR: 4/8 or 4/5 - no influence
I have taken into account the Errata recommendations for SF6.
For Explicit Header mode, SF7, its 100% reliable

Valid Header IRQ:
void RF_IRQ1_handler() {
    if (RF_module.config.modulation == Lora) {
        RF_write_reg(Lora_RegFifoRxBaseAddr, 0x00);
        RF_write_reg(Lora_RegPayloadLength, 0xFF); //Not to trigger TxDone based on last transmission
        uint8_t rx = RF_read_reg(Lora_RegFifoRxByteAddr);
        while (rx == RF_read_reg(Lora_RegFifoRxByteAddr)) { //It waits for 4ms for data to be written to FIFO
        }
        RF_write_reg(Lora_RegPayloadLength, RF_read_reg(Lora_RegFifo));
    }
}

How can I improve my transfer rate?


texts: How to stabilize adc output display on 7 segment

texts:
I am designing a simple voltmeter. I am using 8 bit ADC of PIC16F72 and Mikro C compiler with a multiplexed 7 segment display. I am getting ADC value on 7 segment display but its continuously fluctuating (for example 1670mV fluctuates in between 1660 & 1680mV). I have tried everything in hardware, adding a cap on ADC and ground etc.

Here is my code:

void StabilizeVoltage()
{
     unsigned int ADS;
     if (flgAC)
      {
      ADS = ADC_Get_Sample(0);
      Voltage_FLOAT =(float)ADS *19.6078431372549;
      a= Voltage_FLOAT;
      Voltage_INT=a;
      //if(63<Voltage_INT && Voltage_INT<78 )
       if(Voltage_INT <=1050 )
      {
      Relay1=0;
      Relay2=0;
      Relay3=0;
      Relay4=0;
      }
      else if (1050<Voltage_INT && Voltage_INT<=1150)
      {
      Relay1=1;
      Relay2=0;
      Relay3=0;
      Relay4=0;
      }
      else if (1150<Voltage_INT && Voltage_INT<=1350)
      {
      Relay1=1;
      Relay3=1;
      Relay2=0;
      Relay4=0;
      }
      else if (1350<Voltage_INT && Voltage_INT<=1450)
      {
      Relay1=1;
      Relay3=1;
      Relay2=1;
      Relay4=0;
      }
      else if (1450<Voltage_INT )
      {
      Relay1=1;
      Relay3=1;
      Relay2=1;
      Relay4=1;
      }
      }
      flgAC = 1;
}
void main()
{
      InitIO();
      ADC_Init();
      InitTimer2();
      InitDisplay();
     while(1)
     {
         UpdateDisplay();
         StabilizeVoltage();
     }
}

Do I need any software filter ??


texts: Overcurrent protection, limit for nominal current or stall?

texts:
Background: I'm currently working on a robotics design that will drill through soil.
I have selected a 48V motor who's nominal current is 3.17A and has a stall current of 42A. I will be driving the motor with a microcontroller and motor driver.
However I am having some trouble with my design.
The motor driver includes over current protection circuitry, and I need to select a resistor to set the max allowable current.
Would it be more optimal to use a resistor that caps the current at exactly 3.17A? Or would it be better to provide some margin, and make it 4A?
The over current circuitry has a feature where it resets itself after every PWM cycle and checks if the current is too large again. I believe this is "current chopping" so the motor should start up. (Startup time is not necessarily important for this.)
Extra information:
Here's a link to the datasheet (overcurrent info starts at the bottom of page 12) https://www.ti.com/lit/ds/symlink/drv8412.pdf?ts=1608116336564&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FDRV8412%253Futm_source%253Dgoogle%2526utm_medium%253Dcpc%2526utm_campaign%253Dasc-null-null-GPN_EN-cpc-pf-google-wwe%2526utm_content%253DDRV8412%2526ds_k%253DDRV8412%2526DCM%253Dyes%2526gclid%253DCjwKCAiA_eb-BRB2EiwAGBnXXjIwXdpz1L1nXdPJPRXSLugDHtAnJE25B3C8Q-H9L3S2S25mG7D48hoC3S0QAvD_BwE%2526gclsrc%253Daw.ds
Here's a link to the datasheet for the motor in question, the 148877 https://www.maxongroup.com/medias/sys_master/root/8841119236126/EN-141.pdf
Any input would be appreciated. Thank you for reading


texts: I am allowing the current through a DC motor to flow through a small resistor and measuring the voltage across it. I need to give this analog Voltage to an ADC of micro-controller to do some signal processing on it. My problem is that the Micro-controller runs on an Isolated supply and the voltage to be sensed is on the non Isolated side. I feel that using an analog isolator is not a good solution. One solution to it is using an External ADC on the nonisolated side and digitally isolating the ADC output, but this ADC cannot take negative voltages when motor runs in other direction. Please help.


texts:
I'm confused about the role of the

Let's assume that I want to use it along with a  and I want to flash it with  .

The adapter should be used with both CP2102 and the relay or just with the relay?


texts: Is it the frequency that determines the current in a LC Tank Parallel Circuit?

texts:
Jump a head to the question if you aren't interested in the background of my project

Background of my project

I want to create objects of metal. So I need to be able to cast a metal. Aluminium seems great as its strong, light weight, easy to obtain, but most importantly: its not toxic. So I want to be able to melt aluminium (933 Kelvin is the melting point).

I was thinking about induction. Its effective and easier than using liters of gas.

I tried to make my own induction heating circuit, but I keep blowing MOSFETs (royer oscillator design) when I ramp up the voltage to increase the power (my 12Vac versions work, but prepared for 48Vac they break down, let alone 230Vac. Now I spend enough money on fancy MOSFETs, so I bought myself a 2 Kilowatts induction cook-top that should get me melting some aluminium.

The cook-top has a 0.33uF (MKPH marked) capacitor in parallel with the original flat spiral coil, running at a varying frequency of 20-24Khz, depending on the distance of the steel pot on top of the cook-top. the specs of the original flat spiral coil: 24 windings of Lytz wire, 58mm inner diameter, 153mm outer diameter.

Now I replaced the flat spiral coil that I found inside the cook-top with a self wound solenoid of isolated wire (1.75mm diameter) with the following specifications:
143 mm height, 50mm radius, 32 windings => yielding an approximate induction of 53.75uH according to my calculations.

This works! I heated up a piece of heavy iron with aluminium inside until the aluminium melted. Though it was fun, my setup is far from practical. I used a water bath to cool the coil and glass jar inside the coil to keep the water away from the work piece and put the work-piece inside the glass jar. Finally the glass cracked, and the water bath in combination with a coil @ 230Vac isn't typically safe. The self wounded solenoid must be cooled because if the isolation would burn or melt, the chance of a short in the solenoid is high, probably breaking down the circuit of the cook-top.

So I need a solenoid that needs no isolation as the windings are distant from each other. Now I have a nice wounded solenoid of copper pipe with the following specs: 110mm height, 28mm radius, 11.5 windings. It should have an inductance of 3.03uH according to the same calculations I applied for the self wounded solenoid.

53.75uH / 3.03uH = Factor 17.73 less inductance. So can I apply this solenoid with less inductance if I replace the capacitance with 17.73 greater value? Which would be 0.33uF * 17.73 = 5.85uF.

The question:

If I replace a solenoid in a LC parallel circuit with a solenoid with X times less inductance, and increase the capacitance with the same factor X, keeping the resonance frequency the same, does the current stay the same as well?

EDIT: I tried calculating impedance of the overall circuit. But with 12Vac royer oscilator test circuits I build, the measured current differs from my calculations. I used the "Example No1" calculation from this website: http://www.electronics-tutorials.ws/accircuits/parallel-circuit.html


texts:
I'm trying to define dimensions of the connector.
And don't understand what is "No of spaces".

What does it mean "No of spaces" (highlighted)?


texts: How do you know what parts to use in a circuit?

texts:
This is a beginner question but it has been frustrating me since ever and I do not seem to find a proper answer. I have been watching electronics videos and tech building tutorials etc., playing with Arduino and electronics in general. And I do not understand how do they know what parts and how the circuit should look like.

For example, how do I know that in a FM transmitter I need to use x number of 1 M ohm resistors or x number of y F capacitors etc. I have been struggling with this for months and I cant figure it out. Is there a theory behind all this that I do not know of? Or is it just math and proper arrangement of electronics?

Please, if you know anything inform me. Thank you for your time!


texts: Choosing a MOSFET for solenoid control via Arduino

texts:
I'm trying to drive a solenoid I took off an old pinball machine with an Arduino.
The pinball machine ran on 25 V AC and I've found that the solenoid was 2 Ω online (so 12.5 A). The Arduino puts out 5 V @ 40 mA. After some googling, it seems I want to use a MOSFET with a logic level gate to do this. However my electronics knowledge isn't nearly enough to understand most of what's going on. I'm looking at different MOSFETs on Digikey and it gives me choices for a lot of stuff. Some of them I think I've figured out and others I still have no idea about:

FET Type: I'm not sure what the difference is between N and P channel
Drain to Source Voltage (Vdss): I'm assuming this is the max voltage
it can handle going through it, so I should be finding a MOSFET that
will support 25 V+?
Current - Continuous Drain (Id): Assuming this is the max amperage
going through it, so looking for one with 12.5 A+
Vgs(th) (Max): I think this has something to do with the activation
voltage applied to the gate that will make it activate, so I need one
with less than 5 V?
Power - Max: Assuming this is the max power it can handle. I've
calculated the power the solenoid would need as
P = V*I = 25 V * 12.5 A = 312.5 W, so I need a MOSFET that can handle more than
312.5 W?
I don't know what Rds On (Max), Gate Charge (Qg), or Input
Capacitance (Ciss) mean. Are they important for my uses?

Based on searching with these numbers, the cheapest MOSFET returned was this one. Would this work?

On AC coils: I tested the coil with a 25V DC current, and it still operated fine.  Unless there is some detrimental aspect to this that I'm not thinking of, I don't think there should be anything wrong with just using a 5V DC source for the Arduino and a 25V DC source for the coil?