texts: Solving transient circuit with serial RLC using Laplace Transform

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I'm trying to solve this using Laplace transform:

(U - voltage, I - current). I am to get Uc. My attempt was to calculate I and then get Uc using ohm's law, but I wasn't able to find the I yet.

Here it's for t < 0, to get initial conditions

And then I try to solve it for t > 0:

(I with hat is current in laplace domain)

There I got kinda stuck, I don't know how to proceed. Also, it's possible I've made some mistake.

How do I get current in the time domain? It should be some kind of damped wave, looking at the poles, but I'm not sure how to do the inverse transform of this.

Thanks for help!

(ps sorry if I use incorrect terminology, I'm translating it from Czech and am not sure about some things.. I hope you can understand it like this.)


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I've made a design for reading 13 FSR with only 1 channel ADC. I want to apply the DAC voltage to only one of the FSRs using MUX. But when I choose one, I see voltage in others. For example, when I apply 1.5volt, I see 1.5V in the selected sensor, but in others, there are different values like 0.4.0.5.0.7. this makes my value with ADC wrong. Other sensors need to be 0 volts.
For example, when I select the sensor at point A, the result is not only A dependent also B, C and others dependent.

Is there something I've overlooked with the internal structure of MUX?(Leakage etc.)
Do you recommend a circuit structure where 13 sensors can be read with a single ADC and a single MUX?

Notes:
FSR:Force sensing resistor
MUX:74HC4067

I'll try this one


texts: Customized torch/flash light using a perfboard with an attiny

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I am currently working on customizing the flashing frequency of a torch light (customized intervals between on&off).
To program the individual frequency I have made use of an attiny 85 microcontroller that I have programmed with the help of an arduino. On a breadboard my experiment worked well.
I have attached the pins of the attiny 85 as follows:

Pin8:  Long lead LED & + side of the battery;
Pin5: Small lead LED;
Pin 4: -  side of the battery;
To realize this experiment for a torch light I have disassembled a torch light and replaced the board (see figure)

with a self-made one making use of a perfboard (see figure)
.

Well if I attached the red wire (of an external battery box) to pin  8 and the black wire (of an external battery box) to pin 4 of the attiny85 the torch works well. However I wanted to replace the board and it should work the way it worked before with the programmed mode making use of the battery of the torch light as power source.

The battery within the torch light is placed on the back side.
There only the plus side of the battery touches the spring and this gets again in touch with the self made perfboard. Here I am aware that the energy wlil flow through the spring to the soldered microcontrller. Hence alle soldered and connected pins of the attiny 85 will have the voltage of the battery. However I cannot determine certain pins to be charged and some not to be...( here I think I am missing a point)
The problem I experience is that only the plus side of the battery, placed in the torch light, gets in touch with the perfboard.   The torch light does not work using my perfboard.
I know for sure that the torch will work if both the plus and the minus side of the battery are attached to the microcontroller(pin 4/8).
However the initial torch light was also attached only to the plus side of the battery, and it did work. I don't know how.
This is the cicuit   I applied on the perfboard. The batteries are not feasible to be connected that way. Therefore the experiement on the bread board worked unlike with the perfboard applying on its torch light. I dont get the minus and plus side of the battery to touch only the respective pins of the attiny.

1.I know I am doing something wrong or thinking little naively, can you give some hints in order to get the torch / flash light to work making use of my customized perfboard?

Do I have to ensure that  pin8 and pin4 of the attiny 85 are attached with the respective side of the battery to get my torch/flash light work or is there another way to get the flash light to work?


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In my circuit diagram I measured +/- 0.7V across the motor. This barely moves the motor as it needs about 5-6V. The resistors in the circuit diagram are 1K.

I've tested the circuit with a low powered motor. What would be your suggestions on increasing the voltage/current across for a higher powered motor? Ideally 5-6V and 4-5A. I think it would also be useful to know that I'm using a 505 std servo from china.

Thank you!

EDIT: New cct diagram


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In BJT biasing the voltages Vbe and Vce are always present in calculations.
Is the voltage Vbc absent from any equation because one of the collector, base and emitter is grounded or any other reason concerning the theory of semiconductors?


texts: How do you plot pulse positions for a simple sine wave in MATLAB?

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If you goto 14 minutes and 53 seconds of this video: https://youtu.be/xfxQ-zBp2OQ
you will see a plot of Pulse Width Modulation (PWM) and Pulse Position Modulation (PPM) for a simple sine wave signal.

The picture should look something like this:

How do I implement a PPM for a sine wave in MATLAB? Here is what I am thinking:

t = 0:1/1e3:60;
d = [0:2:60;sin(2*pi*0.05*(0:2:60))]';
x = @rectpuls;
y = pulstran(t,d,x);
plot(t,y)
hold off
xlabel('Time (s)')
ylabel('Waveform')

But this gives me a plot of rectangular samples of the sine wave:

not the PPM as shown in the first graphic above.

So even though I understand what the YouTuber is doing graphically, I'm not sure how this can be implemented in MATLAB from an algorithmic standpoint.

I would appreciate any feedback from the EE community.


texts: How does a transmission line/Guanella transformer maintain Balun action at high frequencies?

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A 1:1 Current or Guanella Balun is formed by winding a transmission line around a core and is used at RF frequencies as a broadband Balun.

Here is an example of a terrifically broadband balun rated to work from 4 MHz to 3 GHz: MABA-007159

Descriptions on the web are scarce and I find most hand wavy at best, but here is what I have gathered so far:

The low frequency operation is easily understood by viewing this as a simple transformer/Common mode choke. Flux coupling between the two coils ensures equal but opposite current. Now if we connect a balanced load at the output, and drive the input with an unbalanced source, we get a balun.

At higher frequencies, the core non idealties means we can no longer explain the workings using standard transformer theory. Also, the winding "parasitics" start behaving like transmission lines so transmission line theory must be employed. This is where I am unsure of its operation.

As I grasp it, at high frequencies we are simply left with a transmission line from source to load. How are we still achieving broadband balun action? If for example the workings are the same a standard microstrip transmission line balun (such as a Marchand Balun) it should be narrow band i.e. quarter wavelengths?


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Can someone help me to understand what we expected in the output(Voutn,Voutp) of the circuit of figure 1?I have searched for months a lot of books but I can't understand the operation of the rail to rail stage.Why someone to use it? The rail to rail stage will amplify furthermore the signal vin1(which is the amplified signal of amp)?

The figure 1  presents an amplifier with a gain approximately 50, and the output of amplifier connects to the first input of rail to rail circuit.The second input of the rail to rail circuit is a triangular waveform with a frequency that we set it up.

Also, I have found that we use rail to rail stage because we don't know the DC level of vin1 signal so if we had used only for example nmos transistor and the DC level of vin1 was 0.2V (with VDD 1.8V) maybe the nmos transistor was off so the signal couldn't analyzed further.Is this true?

The link for rail to rail stage:

  http://ocean.kisti.re.kr/downfile/volume/ieek/E1STIF/2015/v4n4/E1STIF_2015_v4n4_291.pdf

I would like to notice that the circuit in figure 1 it isn't in the same logic of paper but only uses the rail to rail stage and the other stages from the paper.To make it clear the difference is that the figure 1 has different inputs for rail to rail stage compared the inputs of the paper link.

Figure 1


texts: How can I model a variable current sink in spice?

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For a project I am working on (related question here) I need to model a nonideal variable current sink in spice.

Simply reversing the orientation of a current source or inverting its value is not sufficient because it is still sourcing current, just in another direction.

I am fairly certain there is a 'trick' using some built in components to simulate a variable resistance since as far as I understand, that may be the most accurate model for this component.


texts: The schematic of the LM113 precision reference shows a 75pF capacitor integrated in the IC. Looks huge to me. What's the limit when integrating capacitor on-die?


texts: How to assign physical pins of FPGA to Xilinx ISE Verilog modules?

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Recently I started learning FPGA programming. I have the " Verilog QuickStart book" and downloaded Xilinx ISE Webpack v14 and watched a number of YouTube videos. At this moment I can build my circuits and test them by the inbuilt simulator but I don't know how to assign the physical pins of the FPGA ( the I/O buffers).

For example let's assume we have a very very simple design: just an AND gate ( Module ports include IN1, IN2 and OUT). It is easy to make the circuit on the software but assume I want to assign the IC I/O pin number 7 as IN1, pin 9 as N2 and pin11 as OUT ( all I/O ports without VREF) . Nowhere in the software (as well as the book) I saw how to do this assignment.Can anyone help me on that please?

Any help appreciated in advance.


texts: ATMEL STUDIO: avrdude.exe: ser_open(): can't open device

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I just followed all the instructions to set up Atmel Studio on a new computer for the ATmega2560. Bare in mind that I have already had Atmel Studio installed on another computer where it worked fine, so I am not a total newbie.
I did the following in "External Tools":

I also installed the drivers and generally did the recommended instructions.

However, when I compile a GCC C++ Executable Project, I get the following error every time in any project: avrdude.exe: ser_open(): can't open device "\\.\": The filename, directory name, or volume label syntax is incorrect..
Keep in mind that I have unplugged all other cables from my laptop, as well as from my Arduino.

And YES the COM ports are matching.


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I'm interested in putting together both a fixed rack, and a modular rack system using gigabit ethernet for the backplane.
I was thinking of this where the fixed backplane would use something like a 14-port switch chip to allow for 12 in rack modules, plus a possible 'upstream' and 'downstream' connection to extend the rack.
For the modular rack, where the rack is built by clipping additional modules in, it would use something like a 3-port switch in each module.  With 'upstream', 'downstream' and 'module' connections.
It appears that 803.2ap or 1000basekx are the 'standards' for backplane ethernet, however I've been unable to find any switch ICs that would match what I would expect for this.
Does anyone know of vendors / chips which support this?
I've seen some chips from Microchip VSC7511 (4-port switch with SimpliPHY), although the pin count for these chips seems a lot higher than I would have expected.  e.g. the VS7511 (4 port) has a pin count of 172 (QFN) vs something like the KSZ9896 (6 port) with a pin count of 128 (QFP).
I really would like to avoid having to use magnetics twice on every link however.
I'm open to any other ideas for a nice (modern) multi-master backplane bus system also.


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Here Altium PCB on the picture. I rotate component on 45 degree and place it on the PCB.

What is gray area under the component?
Should it be rotated also?
Can it be a problem if it s not rotated?
How can I rotate it if necessary?


texts: Draw 10A from a 18650 Li-Ion battery safely

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I understand that the title may sound ridiculous but for my project I need to connect two 18650 Li-Ion batteries in parallel (In parallel so I can easily and safely charge them using 2 charging ICs). Since I need to draw up to 10A from each battery I cannot use the protection board I was intending to use (it limits the draw to 4A). To protect the circuit from shorts I will put 4 6.5A fuses (connected in parallel) into the circuit.

However now I still have the problem of getting an undervoltage on the batteries. Is there a way to protect them without limiting the current?

I have already done quite some research on these Li-Ion batteries and it seems that a lot of things can go wrong, so I am putting a lot of focus on safety.


texts: Do electronics distributors require NDA or manufacturer consent to buy certain items such as imaging sensors?

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I am looking to buy imaging sensors but the manufacturers are reluctant to engage because of low volume production. I don't have an NDA nor any official datasheets. However, there are leaked datasheets online. Also distributors (Avnet, Arrow, Digi-key etc.) have the particular sensors in stock and theoretically I could put in an order.

Now, would the order go through? And is there a danger of being found out by manufacturers for going against their wishes?


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I am using arduino Uno for developing my project. There are totally 24 analog hall sensor out put,1 temprature ananlog output, 1 Rshunt voltgae measurement.
There are totally 26 Analog sensor.I am distributing 24 analog channel in 8:1 analog multiplxer usingAnalog Multiplexer; Where it used totally 3 analog ,1 temprature,1 voltage sesnor.

Now @ digital side i need

3 For selecting 8:1 Multiplexer
1 for error status
1 for Blink led
1 for SPD status
1 for disconnector status
2 for MODBUS communication
2 for serial communication
8 Pins for selecting Device ID using DIP Switch totally i need 19~20Pins.
SO i  need Method of reducing it. Please look my schematic attached If any alternation i can do here let me Know.And my question here is this method correct , Switch i represented here is dip Switch followed by 1k resistor.

I wanted to How can i configure device ID 255 No,

simulate this circuit – Schematic created using CircuitLab


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I recently bought some IC's with 8 and 16 pins.
I was used to work with bigger ones, so now I cant test them in the breadboard without soldering an individual wire to each pin (which would probably destroy the IC).
I thought about sockets, but it doesn't make the distance between pins bigger.

Is there any device I can use to connect the small IC's to the breadboard?

Thank you for your help.


texts:
In the attributes of a MOSFET, Digi-Key lists several different voltages.  I think I understand what most of them are, but there's one I don't understand: "drive voltage."

Let's take this P-channel MOSFET as an example:

So, there's "Drain to Source Voltage", which is 100V, which is the maximum voltage the MOSFET can switch.

There's "Vgs(th)", which is 4V, which is how much the gate voltage has to change in order to get the MOSFET to switch.

There's "Vgs(Max)", which is ±20V, which I'm guessing is the maximum voltage that can be applied to the gate.

Then there's "Drive Voltage", which is 10V.  This is the one I don't understand.  What does it mean?


texts: Can I put vias on routing I2C lines traces on FR4 PCB?

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I am using a MSP430FR2633 micro controller and ADS122C04IPWR DAC over I2C at 100kHz.

Can I route the I2C lines through vias in a 2 Layer PCB?


texts: Laplace Transform without given continuity variables

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simulate this circuit – Schematic created using CircuitLab

So I was trying to solve problems in preparation for an exam regarding Laplace Transforms. I was able to solve some problems and then I came up with this circuit. I cannot go anywhere since I find it hard and not sure how to simplify the circuit at t = 0- and at t > 0.

Just wanna get an idea how to first simplify and solve the circuit at t = 0- and hopefully I'll be able to take it from there.


texts: How to stabilize voltage when controlling 12V motor

texts: I have 12V bus which is connected to motor via polarity changing MOSFET configuration (see image), also I have connected to 12V NE555P and CD4041UB. Problem is when I am switching motor, on my 12V bus occurs up to 23V (see image). It is short oscillation but I have no experience if NE555P with 18V absolute max. ratings and CD4041UB with 20V absolute max. ratings can handle it. Best practice would be certainly limit these oscillations, but they are very short and I am not sure how. Zener diode or op amp would not be fast enough I guess. Should i use coil? If yes with what value?


texts: How does FPGA knows the configuraton file is present in Flash memory during bootup?

texts: Which areas in flash memory are scanned during bootup to make sure that there is configuration file present in the external flash memory?


texts: Reviewing Basic amplifier stage properties, I found unanimously that a Current Amplifier has a Very Low (ideally zero) Input Impedance and a Very High (ideally infinite) Output Impedance. The Emitter Follower's Input/Output impedances however show totally contrasting properties (High Input and Low Output impedance), and from small signal models its quite easy to see that the Emitter Follower does provide a significant current gain (β+1). Quite naturally I am not being able to comprehend these conflicting facts, from an intuitive viewpoint. Does it have to do with the fact that it is a voltage buffer? Please help.


texts: Want to reverse AC Motor direction - need help

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I have this old Westinghouse motor it turns clockwise and I need counter clockwise. It has 3 leads at a junction on the rear, 2 line and 1 middle lead labeled 0.

Anyone know how to help?
It is a 110v 3/4 hp single phase motor model 89z123a.


texts:
I am designing a circuit that will give me an adjustable 220DC voltage. The load is approximately 2kohms, so the maximum current that will flow is 100mA.And I have design restrictions, it needs to be small in size. I will probably use this schematics:

simulate this circuit – Schematic created using CircuitLab

I calculated the capacitor value from|
$$V_{ripple} = \frac{I}{2fC}$$

I = load current (100mA)
f = AC frequency (50Hz)
Vrip=1V

The question is; would this circuit work? And if it is working, how can I make it more safer? I will put fuse in the 220AC input and make an insulator box for it. But I am open to recommendations. Thanks, for reading and further help.

Update:

So as suggested I asked variacs to local stores and it turns out it is very expensive and big. But one of the store managers come with the idea to use dimmer switches(similar to this) with 220-to-220 transformer(and cheap!). So new schematics looks like this;

simulate this circuit


texts: Single wire two-way serial communication - hardware configuration

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I have several servos that can give feedback data that I want to read. The servos use special protocol so I need to use Rx/Tx pin on my Arduino Mega to communicate with them. The problem is that a servo has only one serial communication pin so I cannot use the usual Rx/Tx wiring.

I have heard that there are some hardware configurations to properly convert UART signals to half duplex type. One is to use 2 resistors connected to Rx and Tx of Arduino and the pin of the servo. Another is to use a transistor. However, I could not find exact circuit drawings and rules to choose the values for the resistors or the transistor. Can somebody provide more information on that and explain in terms of hardware exactly how these configurations prevent the Tx writing to the Rx and the servo feedback writing to the Tx.

EDIT: The servo is Dynamixel XL-320 (http://support.robotis.com/en/product/dynamixel/xl-320/xl-320.htm). The communication is half-duplex serial: I can write to the servo, but I can also read values, e.g. load (therefore I need to use both Rx and Tx pins on my arduino). NOTE: the servo manual proposes using a multiplexer and a digital pin on the arduino as a select bit in order to covert uart to half-duplex. However, I am specifically asking for other, more passive alternatives.


texts:
The LCD's original power supply has the same conectors as a regular PC power supply.
My main concern is if the PC power supply has the correct specs to be used by the LCD.
The original power supply has this specs:

200Watt power supply W/PFC

AC Input 115-230V ~ /4-2A / 60-50Hz
DC     +3.3V | +5V | +12V | -5V | -12V | +5Vsb
Output 17 A  | 12A | 10A  | 0.3A| 0.5A | 1.5A
           +3.3V & +5V Total output 65W

An this are the specs from the PC power supply

450Watt power supply

AC Input 115/230V ~8/4.5A 60/50Hz
DC Output     +3.3V | +5V | +12V | -5V | -12V | +5Vsb
Direct current  28A | 35A | 18A  |0.8A | 0.5A | 2A
Constant Power   230 W    | 216W | 10W | 2.5W | 10W
                     340W        |       23W
-----------------------------------------------------
Power peak           425W        |       33W

Can I use this PC power supply to replace the LCD's original power supply?


texts: Is this normal that pin 1 & 2 are shorted with HT1628 led display driver?

texts:
I just received from China, components to build my own induction cooker (yeah, I know it's strange but I want to add my own features on it ;-) ) and I'm a little disappointed with the build quality of the controller board. However, what surprised me the most, is that on the display driver for the control panel, pins 1 and 2 of the ht1628 led display driver are shorted. Can someone tell me if this can be “by design” (is there a valid reason to do this with this chip) or if it's included in the low build quality (i.e. Is this a bug or a feature ? ;-) )
EDIT : Since I needed to have a proof it doesn't work, I faced my fears of breaking it beyond repair and tested it, as is... And it appears it works. I don't understand how...


texts:
I am reading the book Electronic Principles by Malvino and I found the circuit shown below.
It asks to find the A(gain) when the switch is in position 1 and in position 2.

I am not sure about this but in position 1 I found that A = 10k/10k + 1 = 2.

What about position 2?


texts:
For a project that I am working on, I need a circuit that can take a momentary pulse of voltage and then output a constant voltage until the other input is triggered. Kind of like a flip flop but with two inputs:

So when a voltage is applied to A, P will output a voltage until B has a voltage applied to it.

Does such a circuit exist and if so, what is it called?

Thank You!


texts:
I have an N-channel MOSFET circuit like this, except there is a more detailed (still resistive) load circuit in place of the LED and R1.

I attach my oscilloscope probe to gate (no other connections to gate at that point), and ground to ground. I can see drain-side circuit voltage fluctuations (measured separately) on the scope (low current, low voltage).

I thought the gate was pretty well insulated from the drain side; I don't know but based on my currently limited knowledge of MOSFETs I am wondering if the MOSFET is fried.


texts: How is the sinc function used to reconstruct an analog signal from a digital signal?

texts:
My lecture notes say it's done by interpolation.

I do see that they have interpolated several sinc function peaks
What I don't get is how the sinc function comes into the equation?
why is sinc used?


texts: What is the value of the current (i) and what is the right way to do it?

texts:
What exactly went wrong with the below method?

Here, in the same circuit I am getting a different value for the current in the mid wire only by rearranging the circuit.

I was trying to solve this unbalanced Wheatstone bridge and found that the current (\$i\$) in the mid wire (in image 1) is 3 A. This result was achieved by using the node voltage method.

Then I rearranged the same circuit to the form shown in the second image.

And at this point I flipped the right half of the circuit so as to obtain the equal resistors on the same side.

Now I again rearranged the circuit as shown.

Here, the final circuit is a balanced Wheatstone bridge and thus the current (\$i\$) must be 0 A.

So clearly something went wrong in there.

I posted a question before this one just to make sure that there is no mistake in rearranging the circuit in the way I have done.

The mid wire is a complete connected wire. The gap in the mid wire near the arrow was inevitable.


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I get that if you put a resistor in series with a capacitor and add DC voltage, the cap will take longer to charge up.

How can I calculate, how long it takes for the capacitor to charge up/discharge with the given capacitance and resistance and how can I calculate the voltage at a given time?


texts: Material with fairly high resistivity, but allows flow of charge

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Is there a material with fairly high resistivity (at least semi-conductor level), but also allows the flow of charge through it (and subsequently to the ground)? The flow of charge does not need to be fast, it can be very slow if necessary. The higher resistivity, the better.

So ideally, if that material is left alone on the ground, its steady-state should have very little charge, and thus have negligible or zero electric field (even if you initially applied some charge to it). Basically, the material is able to be discharged in finite-time, regardless of its fairly high resistivity.

The speed of discharge is the property I'm particularly interested in, but based on what I've seen, this property might be independent of resistivity.

I am not sure if such properties are documented, so if you know what the property is called, please tell.

Thanks

Edit: My wording is apparently confusing, so let me try to put it in other words. Here is a phenomena I have observed. There is a piece of rubber and a piece of glass on the ground, both equal in size and resistivity. I apply a static charge to both, and the rubber ends up discharging (to ground presumably) much faster than glass. What is that material property called?


texts: How does the current flow through the collector-base junction of an NPN transistor operating in saturation?

texts: From what I understand, in the saturation mode of NPN transistor, both EB and CB junctions are forward biased. Now, if the voltage across CB causes it to be forward-biased, how does the current flow in the opposite direction of voltage applied? - i.e from collector to emitter. How can a PN junction be forward biased while allowing a current of opposite direction to flow through it?


texts: What is shunt regulator in comparison with voltage reference

texts:
I know what is voltage reference but I am really confused about the difference between voltage reference and shunt regulator

for example TL431 can I use it as voltage reference ?

what is the applications for the shunt regulator anyway?


texts:
I am designing a system which has a mcu (with usb peripheral). The whole system is powered by a 18650 Li ion battery. Now, imagine I am charging the battery by plugging the usb to a computer usb socket or even a wall adapter. The max current via the usb 2.0 is 500mamps. But this is a 3400mAH battery and so would take hours.

I then saw som articles on DCP (dedicated charging port). So basically I will have to short the d+ and d-  via a very small resistor. By doing so it goes into a high charging current mode.

Now imaging I am using a Li ion charger like the rt9511. It can charge the battery using only a max of 500mAmps. How can it take more than that leave alone 1.5Amps. Or do we have different Li ion charger ic that can manage charging up to 1.5Amps ?


texts:
A few years ago I was making layout changes to a PCB and wanted to be 100% sure that one particular interface did not change at all. My layout contractor generated an ODB++ compare file (I would also call it a diff file) that contained all the layers of the Rev 1 PCB, followed by all the layers of the Rev 2 PCB, followed by a corresponding set of diff layers that highlighted the differences between Rev 1 and Rev 2 on each layer.

Is this a standard trick/ tool for comparing ODB files? If so, is there an existing tool that will compare/ diff ODB files? Either Open Source or licensed. Or is this likely something done with a proprietary in-house script/ tool by the layout contractor?

I'm just curious how they did this.


texts: What use are the transistors in this (LM317 based) power supply circuit?

texts:
I am looking to do a small bench power supply project and am studying various designs based around a LM317. Basic I know but I still seem to manage to have  have some questions.

Fig 22 on page 8 of the datasheet shows a design I am trying to understand. I've tried to redraw the schematic too, shown below.

I understand that the adjustment pins are tied to -10 v to allow the output voltage to go down to 0 v. As I understand this is because of the voltage drop across the LM317. However I do not understand the function of the transistor. If I am reading the schematic correctly they are N channel depletion type MOSFETs. This would mean there should be a path from drain to sink (-10 v) unless a voltage difference exists between source and gate. Given the gate does not appear in the schematic so I guess is not tied to anything so is floating, does this hold some significance? It would appear to me that current is free to flow from drain to source in the current state, so what is the the use of the transistors?


texts: FM Transmitter Power and approx Transmission Distance Calculation

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I am a beginner of electronics and mostly fascinated by hobby circuits right now. I do not have any Electronics Degree. Internet and hobby Electronics books are the only places where I learned lill-bit of Electronics. One of the most popular circuits being shared by Experts on internet and in those books is an FM Transmitter.

I've made a so-called 'powerful FM transmitter' and measured the peak current across the Amplifying transistor's collector-emmitter. It reads approx 300mA. The overall circuit consumes approx 400mA. I am operating the circuit at 16V.

Sorry for the 3 questions, all at once. But I guess they are related.

Is this one really a 4.8 Watt FM Transmitter? If not, how do you
calculate the Wattage of FM Transmission of a typical FM Transmitter?
How the wattage of the transmitter is related to dB
rating of a transmitter?
Is there a formula/rule to calculate how much distance an FM signal can propagate in open and obstructed (populated) areas?


texts: ATXMega ADC - What is bandgap reference and temperature?

texts:
On my ATXMega128A1U, I am using ADCA to measure an input voltage (roughly ~1.70V) and I plan to use a VREF of 2.5V. I was reading the XMEGA manual, specifically for the REFCTRL register where I would set REFSEL to 010 for AREFA as seen below:

However I am a bit confused by what the bandgap and temperature bits are for as in I am not sure whether I need to enable them or not. I have seen some other projects set these bits but I was wondering what exactly does it do? What happens if I don't set these bits at all and use the ADC?
Edit: Link to XMEGA manual http://ww1.microchip.com/downloads/en/DeviceDoc/doc8077.pdf


texts: Best way to simulate a load in Circuit Simulator

texts:
I'm a bit new to simulating circuits and I'm looking for advice on the best way to simulate a load. I'm trying to build a current limiting circuit, using a current sense resistor and a set of transistors. The end application that I have will probably exceed the current limit of the transistors, so I'm trying to replace them with MOSFETs.
The issue I have is trying to find a good way to simulate varying loads drawing too much power, so I can trigger the current sense transistor to shut off the circuit.
I tried using different value resistors where the load is, but I don't think that's an accurate simulation.
Any advice? Thank you!


texts: What are the connection between bandwidth, Nyquist criteria and quantization?

texts:
I am trying to solve the below problem and I was not able to find the relation between bandwidth, Nyquist criteria and quantization. Can you please provide some hint?

Imagine that the possible transmissible symbols are 64. Whenever the transmitter needs to transmit a value=n, it sends n-1 bits to the channel, each one T/(n-1) seconds apart starting from the beginning of the same slot. What is the maximum bandwidth of an analog signal that can be transmitted without losing any information through this system if 4 bits are used for its quantization?


texts:
I'm trying to build a circuit to control a 5V DC motor with Arduino. My issue is that I can't understand the resistance value within this scheme:

Which resistor should I use in order to make work properly the TIP132 transistor (datasheet)?


texts: For a seasoned programmer Arduino or something else?

texts:
My Background:

I have done software fro quite a while, and I am more or less proficient in C, C++, Java, Ruby, Erlang, Haskell, Lua and Python. I also took a class in lab electronics, but apart form one brief lab with a pump, it was all about getting a signal into and A/D and from there into a x86 with LabView (not my choice of programming environments) I would like to get back into tinkering with hardware with an eye towards home automation. (I think I can do better then this for less then $500)

Question:

I was going to cut my teeth on an Arduino, but the more I read the more it feels like the main advantage of that system is that it is simple to program. Is this a good place for a software (who still needs to buy a soldering iron) guy to start or is there something that would suit me better?

(P.S.  I have more time then money)


texts:
I'm trying to feed a 3.3V ADC from a gas sensor that operates at 5V. I know I can use a voltage divider, but am a bit confused how it would apply here.

Datasheet: https://cdn.sparkfun.com/datasheets/Sensors/Biometric/MQ-6%20Ver1.3%20-%20Manual.pdf

It appears that this circuit operates as a voltage divider already, with the sensor acting as a variable resistor (B1 and B2 are internally connected, as is A1 and A2). If that's the case, can I still add another voltage divider after this, as follows:

With GAS_V then going to the ADC, or am I missing how this would work?


texts: Using a LiPo battery or different battery for outside project

texts:
First I am sorry if this is the wrong section to post this, I have been searching for a clear answer and haven't found one yet.

I have a project that I want to keep outside. I have a solar panel, charging circuit and a Lipo battery. It works great, though I have read a lot about how LiPo batteries can fail and catch fire.

I am wondering if Lipo is the way to go for something that will stay outside for years. It could get cold and hot from the sun :/

Should I redesign to use a lead acid? Would it be safer???

I know that was a lot, If this is the wrong place for this please let me know and I can remove this post,

If this is the right place, thank you so much for the assistance.s


texts:
I have an arduino that is powered by a 9v block battery and enabled by a switch. I want to change the curcuit, so that when the switch is turned off the arduino remains powered until certain actions are finished, and then turn off.

However I dont just want the arduino to sleep, the power should be disconnected. This is important, because I have additional components draining power from the 5v pin (around 300mA) and I want those to shut down too.

My first idea was to use a relay in parallel to the switch. When the switch is turned on, the arduino turns the relay on too. When the switch is turned off, the arduino is still powered via the relay. The arduino detects when the switch is turned off (the switch is double pole, so i can detect its state with a digital input pin) and powers off the relay when the remaining actions are finished.

Is there a better way than using a relay? Can I use a mosfet or something  else instead of the relay?

And maybe, in the future, I will need the 9V for additional components, which should turn off too when the arduino decides to shut down. But when the relay/mosfet/..? is placed between battery and arduino VIN I can just connect those between relay/mosfet/..? and the arduino. So this should be simple.

Edit:
Based on Passerbys answer I came up with this:

The motor is just a placeholder for my additional components that drain power from the battery and should be shut down too.


texts: How can a CPU dynamically change its clock frequency?

texts: My Intel CPU changes clock speed depending on the usage, but how does it decide what clock speed to run at? Is the clock speed determined by the OS software using an algorithm, or is it hardware based? Is it dependent on the # of interrupts? The cache turnover? Does the CPU itself set its own clock? Or does a separate controller set it? Or software?


texts: Talking to external device over serial with Arduino

texts:
I have a small device that has a 3.5 mm jack for the serial connection. The protocol is uses is known so I don't have to worry about figuring that out. What I am having trouble with is figuring out how to physically hook it up.

Is it as simple as:

Device TX ---> Arduino RX
Device RX ---> Arduino TX

The device runs on a small coin cell battery so am almost sure the voltage levels will be the same.


texts: Which passive filter corresponds to this transfer function?

texts:
We've have been asked to find a passive circuit for the following function:
$$H(t) = A\exp(-bt) + C\exp(dt)$$
With these coefficient values:
$$A = 77.25$$
$$b = -0.00175$$
$$C = 22.75$$
$$d = -6.557 \times 10^{-6}$$
Then, we've converted it to Laplace domain, so we have:
$$H(s) = \frac{(A+C)s + (dA+bC)}{s^2 + s(d+b)s + bd}$$
Next, we should look for a filter which had a configuration like that transfer function but we don't have much knowledge about filters yet, so... what kind of passive filter could fit these requirements?


texts: What is the expression for an oversampled signal?

texts:
Problem: A simplified schematic of an oversampling circuit is shown below. A data sequence, \$x[n]\$, is transmitted by REG1 which is in clock domain \$C_{tx}\$. \$x[n]\$ is oversampled by REG2 in the clock domain \$C_{rx}\$, resulting in the sample sequence \$y[m]\$. The clock \$C_{tx}\$ has frequency \$f_{tx}\$ and the clock \$C_{rx}\$ has frequency \$f_{rx}\$ and the oversampling rate is defined as \$ \beta \in \mathbb{R} \$.

simulate this circuit – Schematic created using CircuitLab

Definitions:

\$n = 0,1,2,\ldots \$
\$m = 0,1,2,\ldots \$
\$ \beta = f_{rx}/f_{tx} \$

Question:

What is \$y[m]\$, expressed in terms of \$x, n, m\$ and/or \$ \beta \$? Assume \$ \beta \geq 1\$. Also, REG1 and REG2 may be treated as zero-delay models: \$T_{propagation} = T_{setup} = T_{hold} = 0\$. For simplicity, you may assume \$\phi_{tx}(0) = \phi_{rx}(0) = 0\$, where \$\phi_{tx}(t)\$ is the phase of \$C_{tx}\$ at time \$t\$, and \$\phi_{rx}(t)\$ is the phase of \$C_{rx}\$ at time \$t\$.

All answers are welcome, but the accepted answer must provide analytical proof of the proposed expression. Intuitive explanations or a few evaluated cases are not analytical proof.


texts: Prevent desktop from switching off when power inverter switches from mains to backup

texts:
I'm using a desktop computer over a power inverter that's connected to a 12V lead acid battery. When the main power supply fails, the inverter switches to battery backup and can power my desktop for 4-6 hours. However, during the transition, my desktop shuts down (the transition time from mains to backup is too large for the desktop).

Is there a circuit / device that'll power the desktop for a few 100 milliseconds till the inverter backup takes over (something like a big capacitor).

Additional info:

An alternative is to connect the desktop to a UPS but that'll cost another $70-$100. I'm wondering if there's a cheaper option at a fraction of that.

Some inverters have a "UPS mode" that has a faster switchover time. The downside of this mode is that the operating input voltage range is narrowed i.e. the inverter switches to backup if voltage is outside a narrow range. This isn't a great solution when power quality is low.


texts:
we are developing constant current circuit with "High" current rate, about 3A.

We are testing the second prototype, the circuit is this:

Behaviour its ok, but we have observed, when we set high current (We apply PWM with RC filter into non-inverting input of the OPAMP), we have to many noise in VIN source, and if we change VIN voltage, the current doesnt mantain constant. It change a lot. (With this condition, we also have lot noise almost all PINS and NODES, it is seems that OPAMP is oscillating)

We have take some measures with osciloscope and at currents about >1A we have this issue. Searching the problem, we thought about the stability of the OPAMP with this network, and we placed CAP + RESISTOR into the circuit, like this:

This solved all of our problems, but we want to know why, i am trying to simulate the stability of the circuit, but i dont remember how, is it a good way, to apply AC source into Non-Inverting input, and plot DB(VOUT/V(NON-INVERTING) and P(VOUT/V(NON-INVERTING) to view that? , i am not sure, it also posible to need study this circuit into OPEN-LOOP mode....

Thanks for all

Carlos

EDIT:

Thank for the info Andy, i have been thinking about your explanation, in the Datasheet we have Phase Margin and BDW of the OPAMP, and InputCapacitance (Its the same in this case as Gate Cap because we have "same" potential over Source and Drain), and we supose that unity gain its about 0.7 ( Source Follower equation say that if you apply very low resistor, your gain begins to fall)

The network without "compensation" is a LowPass filter, all right, i have simulated this filter, and as you told me it produces shift in the phase about 45Deg. So the OPAMP  can´t achieve 1.4Mhz for unity Gain and phase margin falls until oscillation point

But i dont understand, how this network (With C1 and R4) affect to OPAMP, i have simulated this network (Without the OPAMP) and i obtain similar BODE PLOT like only RC filter. Maybe i will need to simulate also with the OPAMP...

EDIT2:

I have simulated both circuits, and i think that i could see the effect of this Cap and Res, in the first case, without:

We can see, that Pm, its abour 40Deg, it could not be enought for the stability

But if we set Cap and Res (As Andy said, turn OPAMP into integer) we obtain Pm more than 100Deg. But the system turn slower.

I think that we can achieve Cap and Resistors values to get balanced system.


texts: Troubleshooting failure (low output) in LED tube bulb

texts:
I’m looking to troubleshoot and repair which component has failed in a LED tube bulb driver. The bulb is a GE led14et8/g/4/835, and requires a ballast. These bulbs are commonly used to retrofit T8 fluorescent fixtures with LEDs.
Ideally, I’d like to either:

Discover what SMD component has failed, and re-solder them myself.
Bypass the embedded driver and supply 12V myself directly.

Troubleshooting:
When I plug in the bulb to a fluorescent light fixture with ballast, it emits a low hum and the LEDs output a very small amount of light. Thus, they were thrown out for a reason.
Testing individual leds inside the bulbs at 12V causes them to be overloaded.  Applying 3.7V causes nice bright output.
There seems to be two drivers- one at each end, with each powering 36 LEDs. I observed no obvious shorts or burn marks.
Image of what I think is the driver / power regulator, at the end of the tube:

I’ve googled the model number and different variations on the issue. I’ve also googled identifiers printed on the PCB to no avail.
Conclusion:
The LEDs work. I could scratch off the coating that connects the series of LEDs, solder to that and supply my own power.
Or, I could test each component, find the faulty one and replace it. However, several of the SMD components have no label on the top, and don’t seem to have colored labeling similar to resistors.
marketing pdf sheet


texts: Common base configuration, input V-I characteristics

texts: In input characteristics of a common base transistor input current Ie increases with increase in output voltage Vcb. I know the answer is something to do with early effect, "the answer says that because of early effect the number of recombination at the base decreases and thus the input current increases."I want to know why decrease in number of recombinations at base increases the input current.


texts: Is it easy to predict or get notified about obsolescence for DIP ICs?

texts:
The question here might seem a bit tangent for this Stack Exchange but here it goes.

In the product development phase, one of the important factors under consideration is the availability of selected components. If the plan is to sell a particular product for the next 10 years, the components used need to be available throughout this time.

So the questions are:

Is it true that DIP chips and ICs are going to be obsolete in the near future?
Is it wise to consider the SMD packages for development starting 2020?
For example, will DIP versions of MCP3004/8 or ULN chips go extinct shortly (in the coming 5 years) and decision should be taken to move to SMD versions of the same?
Moreover, irrespective of the chips, is there a way to predict or get notified as to when the chips will be made obsolete?


texts:
I'm trying to get an I2C bus working but there's a ton of noise and I don't really know what's causing it.  The circuit is pretty simple, an ITG-3200 and an Arduino DUE.

Here is the problem:

As you can see, there's a significant amount of undershoot on both lines.

Hard to see in this picture but theres a lot of weird stuff going on with the SDA line.  Also note faint the undershoot peaks on both signals


texts: Permanent magnets inside electric motor create stress

texts:
I am trying to do a simple project, a brushed DC motor, in my free time to check what I learn in lessons in real life and I've encountered something I didn't think of before while studying the EMF concept.  That is the magnetic force on the metal rotor.
Since the only thing I can use for my rotor is some steel screws on which I am winding my coils in a 4 pole configuration, the magnets in my motor create lots of inertia on the steel screws and motor cannot overcome it so it's not spinning but there is stress on the motor which I can feel from the vibrations. I don't have a large DC power supply and best I can do is 12V. Next, I will try to use thicker wire because I am currently using 0.4mm copper wire and will upgrade it to 0.8mm which in theory will increase my current up to 4 times hopefully and therefore emf will increase 4 times as much but still I am concerned if there is another way to overcome this magnetic pull on the rotor.


texts: Circuit version of a simple if else program

texts:
I have written a simple program that controls two motors (outputs) each with two states ( positive, negative) with an Arduino. The motors states based on the status of four buttons (inputs) (Up, Down, Right, Left). Only one button can be active at a time.

if( up ) {
    motor1 = positive ; // +
    motor2 = negative ; // -
} else if ( down ) {
    motor1 = negative ; // -
    motor2 = positive ; // +
} else if ( left ) {
    motor1 = negative ; // -
    motor2 = negative ; // -
} else if ( right ) {
    motor1 = positive ; // +
    motor2 = positive ; // +
}

The logic table

      | Motor1 | Motor2 |
-------------------------
Right |   +    |   +    |
Left  |   -    |   -    |
Up    |   +    |   -    |
Down  |   -    |   +    |

The program seems simple enough that I think I should be able make a circuit instead of using a micro controller. Using a micro controller seems like a wast for just a simple application.

I have designed the right and left circuit and the up and down circuit separability trying to simplify it. Now I have to merge these two circuits together.

I assume that I will have to use few relays and a "OR transistor" to make the merged circuit. But I am not sure where to start.

Suggestions, comments or diagrams would be greatly appreciated.

Note: These motors are going to be used in a CoreXY table. I created these diagrams with CircuitLab


texts: Apologies if this is a simple question, I'm very new to hardware. I'm wondering if using PN532 NFC/RFID controller (http://www.adafruit.com/products/364) I can determine which of two RFID tags is closer. Basically I want to identify which of two people is closer to the controller (they'd each have an rfid card with them).


texts: VSD (Inverter) current measurement on 3 motor phases

texts:
I'm working on a project to build a rig for testing various sized Variable Frequency Drives (VSD's / inverters), the kind that you'd use to run a squirrel cage induction motor. The range would be from 10 to 140A (75kW max), 0 - 65Hz @ 415VAC. There will also be a variable mechanical load on the motor shaft.

The test I need to perform is to measure the current in each of the motor output phases, U, V & W through the VSD's speed range of 0 to 60Hz. At first this sounds easy, just measure the RMS current of each phase with a CT or hall effect current sensor. But the devil's in the detail.

The output of a VSD is not a pure 3 phase sinusoidal waveform but is a PWM square-wave that is smoothed out into a rough sinewave by the inductance of the motor windings. This means there's a lot of harmonics that spoil the readings of most RMS digital current meters. There are some meters that will now compensate for this using a built in low-pass filter. Link

Also the VSD output is variable voltage (Hence current) and variable frequency. AC current transformers become useless as the frequency approaches zero. A hall effect based sensor would probably be better here.

So, I'm looking for some kind of current sensor, probably something that has a built in low-pass filter for reasonably accurate (5%) readings and gives out a proportional signal, e.g. 0-10V / 0-20ma / 4-20ma. The lowest frequency I would expect it to work at - from my experience - would be about 10Hz.

Ideally, something like an industrial sensor version of the Fluke 87V DMM referenced in the link above.

If all else fails, then just a current shunt and analogue meter would suffice but ultimately I'm looking to capture the data into a PC for graphing.

Any advice would be appreciated... ;-)

Edit: Although this sounds like a shopping question - it probably is - it may end up as an electronics design question because I think there's nothing on the market that exists to solve this problem.


texts: I'm currently studying the concept of slew rate and everything I read or watch I don't fully understand. I was hoping that someone could explain it like you were teaching a child. Another question I had is for op amp design: Do we generally want a high or low slew rate? and why? (I know this is a basic concept but for some reason I cannot wrap my head around it).


texts: AC Current Sensing Switch Using Current Transformer

texts:
I'm struggling to design a circuit that will interpret signals from a SCT013 current transformer and trigger a constant 5v signal (which will go to a microcontroller) when a certain current threshold is met.

I thought I may be able to achieve this by taking the burdened AC signal from the CT and rectifying it with a bridge rectifier and smoothing capacitor. Then hook this up to the base of a transistor that will emit a 5v low current signal.

simulate this circuit – Schematic created using CircuitLab

I thought that by adjusting the value of R2 I would be able to have the transistor 'trigger' at different current levels. The choice of transistor was arbitrary, I just wanted to see if I could get the rectified signal to 'trigger' the transistor. The CT produces a current between 0 and 50ma, its ratio is 1:2000. I would like the circuit to send a signal if the AC current is above 1 or 2 amps.

When I test this circuit there seems to be some problem with tying the bridge rectifier to ground.

I'm very new to circuit design and especially to using transistors, so I apologize in advance if this design is totally ridiculous. If it is, what would a more direct way be to achieve the same thing? I realize that I could hook the CT output up to a ADC on the microcontroller and just see if current is flowing that way. But I was interested in the challenge and I'd like to learn more about circuits and transistors.

Thank you!


texts: Continuous Filter design for measure signals from Boost Converter out

texts:
So, I found a simulation that uses PID to control the voltage of a DC bus, for voltage measure the author use a "func transfer" in simulink. I wish to know what kind of filter he design and how can I design a filter like this.

There is any way to find the behavior of this filter and indicate how design something like this ? I search a litte bit but not found any transf fcn with "1e" elements in the denominator


texts: Convert an analog voltage into digital and relay it in serial over a single wire

texts:
I have Engineering background but not Electrical. I am working on a project where I have to integrate a sensor which has an analog voltage output to a LoPy module for IoT applications. Another person is taking care of the LoPy module stuff but I do need to provide him the output in 8-bit digital serial form over a single connection so that it can act as an input to the module (I have been told that that's how the input is provided to the module). Is there a way to achieve this without using microcontrollers?

EDIT 1: I meant 2 wires. I understand that a ground wire would also be needed.


texts:
I'm working on designing some hopefully simple RF (912 MHz) attenuators. I need a few different levels of attenuation but each different attenuator can be fixed.
I have prototyped one using just off the shelf resistors in a T-pad configuration that gives me a decent level of attenuation (pretty flat 19dB) when I perform an S21 measurement using my network analyzer.
However, the smith chart is all over the place when I measure S11.
Now I should mention that my prototype is very shotty. Basically I took apart a coaxial cable and hand soldered in some close-to-calculated carbon 5% resistors in between the two SMA connector ends.
My questions are as follows: What is a Smith chart and how do I use it to improve my attenuator+cable design? Is this a feasible method for creating basic fixed RF attenuators given that they don't need to be super accurate and only need to function over a very specific range of frequencies (905-920 ish MHz)?
As always, thanks for your help.
EDIT:
This is the SC of my taken apart coaxial cable WITHOUT the attenuator

This is the SC of my cable WITH the attenuator in the middle of it
Here are the log plots of attenuation over the frequency range I am interested in:
First no attenuator:
Second with attenuator:
Also, another question struck me. If I'm just trying to reduce signal power at the output, does it matter where/how the loss happens? So I know poor impedance matching as indicated by my charts means a higher VSWR... but doesn't that just help attenuation? Thanks again.


texts: How to achieve 100ohm impedance for HDMI differential pair on FR4?

texts:
I have a 6 layer FR4 PCB, and want to achieve 100ohm impedance on HDMI differential pairs. I am only using top and bottom layer for differential pairs, and following are my parameters:
Trace width= 3.75mils
Trace gap: 12mil
Trace thickness: 1.4mil
Dielectric Constant Er: 3.8-4.2 (taken from PCB manufacturer)
I am not sure what the Dielectric thickness would be. My PCB has a thickness of 62mil, but I am not sure if that is considered dielectric thickness or not.

I have tried different online calculators and none of them are close to 100ohm differential impedance.

I would really appreciate your suggestions!
Thank you


texts: Why are capacitors usually marked on the negative terminal, not positive?

texts:
Does anyone know the reason (historical, practical, etc) that polarized capacitors usually have the negative lead marked instead of the positive lead?

I would expect markings to indicate a positive potential. Since we commonly ground the negative lead and refer to "ground" as "zero" volts in reference to the rest of a circuit, the positive side would be the "hot" or "dangerous" side, so you would think that would be the marked side, especially on high voltage caps... We color positive wires red, we indicate the "hot" side of AC circuits, etc.  Emphasizing the negative lead seems backward to me.


texts: Can a 16-bit microcontroller contain 32-bit microprocessor?

texts: I am new to the field of embedded systems. I am wondering if 16-bit microcontroller can contain a 32-bit microprocessor. How will the data transfer take place as data busses in the microcontroller will be 16-bit wide and the microprocessor's data bus will be 32-bit wide. Please give the answer in simple words


texts: Is there a way to measure three discrete resistances simultaneously?

texts:
I'm working on a test box for fencing body cords. These cords are always 3 wires, and will plug into a box that I'm still designing. The test box I currently use connects to a multimeter and has a switch to change from line to line to test each individually. I'd like to build a circuit that can test all three simultaneously using an Arduino. So far, I've been able to use a set of voltage dividers in parallel to measure the resistances, however in the case that one of the plugs has been mis-wired (A wired to B pin, etc) this circuit will not know the difference. Is there any way to isolate each of the circuits, so that I both know that pin A is wired to pin A (B to B, C to C) and can also measure the resistance across the wire?

For reference, here's the current bread board layout that I'm playing with (as well as some code that I've borrowed for making an Arduino ohmmeter) http://123d.circuits.io/circuits/755318-basic-fencing-wire-test-box/embed#breadboard The three resistors near the top are the 3 I'm interested in testing.


texts: Can I Test Bug Zapper's Voltage With Multimeter?

texts:
I have The Executioner bug zapper:

Although it uses 2 AA 1.5v batteries, it also has voltage multiplier like Cockcroft–Walton generator i guess and would like to know if it is safe and would make sense to use multimeter for measuring zapper's voltage output and preferrably resistance as well.

UPDATE: Can i also test voltage output with voltage tester like this? Will it be better than multimeter in this case?


texts:
I have an issue regarding the typical application for FAN5333B LED driver.

According to the spec, SW output can achieve 30V to GND.
Can this influence the input voltage which is typically about 5V ? Both point are directly connected for DC.


texts:
Category 5 cable on Wikipedia:

  The bandwidth of category 5 and 5e is the same (100 MHz) and the physical cable construction is the same, and the reality is that most Cat 5 cables meet Cat 5e specifications, though it is not tested or certified as such.

So what does cable bandwidth mean? is it correct to say that cat 5 cable frequency response is almost flat in a region with 100Mhz width and 3-dB attenuation? Something like this with B=100Mhz:

If correct, what is  f0  frequency for cat 5 cable?

And how the cat5 max speed, i.e. 100Mbps, is related to 100MHz bandwidth?

If we want to send digital signal with some simple line code such as NRZ, what will be the duration of a bit (bit time) in milliseconds?


texts:
I'm two weeks away from completing my first college digital logic design course, and apparently there isn't going to be a final project--just a tedious final exam.

So as any curious student would do, I looked into what FPGAs actually are and what I was being spoon-fed in class. And I've decided to complete a simple FPGA project. I'm using a Basys2 Spartan-3E FPGA, and I'm familiar with digital logic and using ISE to push logic gates around, but I don't know VHDL/Verilog (I'm sure I could pick it up easily).

Does anyone have any project ideas for a beginner? I've done a lot of lab demonstrations, but nothing too fancy.


texts:
I have an AC motor that came from a microwave turntable on the back it says 120v 2w 6rpm.  I would like to use it as means to generate some electricity.  I have a full wave bridge rectifier to convert it to DC.

What is the simplest means to convert it to an usable voltage? A small wall transformer?

Any efficient leds to match the output once i step it down?


texts: What is the PIC equivalent to AVR's ICP?

texts:
On many AVR devices (afaik every one that includes at least one 16bit timer), there is an ICP (Input Capture Pin) that fires an edge-triggered interrupt. What's the equivalent on a PIC micro? Does anybody know a site like http://www.avrfreaks.net/?module=Freaks%20Devices&func=devCompare where you can select PICs depending on number of pins or certain features.

I simply need the smallest, cheapest PIC that's available from my distributor that has something like an ICP.

Any pointers are greatly appreciated.


texts: Can I convert my 3.7 volt lithium ion batteries into a usb charging power bank?

texts:
I have several high capacity 3.7 volt Li-ion batteries. How might I convert them into a USB charger for my phone? I'm not interested in the most elegant solution, or if this would be less financially viable than simply buying one on eBay, I'm just curious what the easiest way to do it would be.

Thanks.


texts: I have hit 3 while tracing, I have hit shift w to open my favorites and it shows me favorites, but for some reason the program will not change the width of traces. It is stuck at 10mil. Anyone know how to fix this issue? Altium 19.1.9 and Altium 20. Tried in both same issue, tried making a new project, same issue. Don't understand what is going on. I just want to change the width of a trace in the interactive router.


texts:
What exactly do authors mean when they say 'memristance' increases by changing certain parameters of an input waveform to a Memristor. Case in point in Strukov's paper it is mentioned that Memristance increases with decreasing frequency:

EDIT: A Google search will show the following result of Memristance:

Memristance is a property of an electronic component. If charge flows in one direction through a circuit, the resistance of that component of the circuit will increase, and if charge flows in the opposite direction in the circuit, the resistance will decrease.

There are 2 problems with this definition:

The i-v characteristic is a loop. So at a given Voltage there can be 2 Memristance values.
The authors seem to indicate lower slope means lower Memristance, that makes Memristance same as Resistance i.e R = V/I


texts: Can digital sequences be generated without a micro controller?

texts:
Lets say I want to send the data 10110101 through a wire with standard timing using only discrete gates like and, or, not and transistors, resistors, crystals etc.

I would want the data to be sent with the press of a button or something.

How complicated would it get to create a digital stream of data with only discrete gates and components and how would it be done?


texts: Is the 100 ohm resistor needed in this mains power supply?

texts: Do I need the 100 ohm resistor in the below circuit? Is there any problem if I don't use it?


texts: If I Don't Wire USBASP to ATmega 328-PU Will I Burn Out My Chip

texts: This is a simple, noob question. I'm trying to connect a USBASP with an ATmega 328-PU. If I incorrectly connect them, such as put ground into vcc or miso into mosi, will I kill my chip?


texts:
I am trying to impose an AC ripple of 0.9V peak to peak (1kHz) on 36 volts DC supply for one of the test using following circuit.

Without any load connected, I get the proper AC imposed DC voltage but as soon as I connect a resistive or capcitive load to the output, the AC ripple of 0.9V just vanishes. Only 36 volts is left behind. The AC current source is capable of sourcing 400mA which is much higher than my actual current requirement of 280mA DC input current of load.

What could be the reason of vanishing of AC ripple when the load is connected ?

Do I need to use higher  current sourcing AC source?
Does the value of the coupling capacitor need to be increased to reduce the output the impedance?

Any other means to achieve the functionality are also welcome!!


texts: Can I use custom data types to exchange data between modules in VHDL?

texts:
I'm new to VHDL and currently try to get more complex data types working, so that code becomes more readable... However, it seems that I cannot define a type in VHDL before the entity statement, which is using the type inside it's port statement.

Hence, it seems I need to somehow write my own library for that. I assume this must work, as types as std_logic_vector must be defined somehow too. Or did they hardcode these types into the VDHL compiler... and if so, why do we still need to include the libraries for it?

I want to do something like in the following code example. However, the compiler doesn't let my define the type in Test.vhdl as mentioned above. Anyhow, it seems to be valid to define the component in TOP.vhdl.
I also would like to avoid to redefine the component and the data type in TOP.vhdl anyway. Is there a way to do this?

Test.vhdl

   library ieee;
   use ieee.std_logic_1164.all;
   use ieee.std_logic_unsigned.all;
   use ieee.numeric_std.all;

   type MyRecordType is record -- Compiler complains about this!
     x : std_logic_vector(2 downto 0); -- expects 'entity' or 'architecture'
     y : std_logic_vector(2 downto 0);
   end record;

   entity Test is
     port(
       clk : in std_logic;
       input : in MyRecordType;
           output : out std_logic
     );
   end entity;

   architecture RTL of Test is

   begin
     process (clk) is
     begin
       if rising_edge(clk) then
             if (input.x = input.y) then
                   output <= '1';
                 else
                   output <= '0';
                 end if;
           end if;
     end process;
   end;

TOP.vhdl

   library ieee;
   use ieee.std_logic_1164.all;
   use ieee.std_logic_unsigned.all;
   use ieee.numeric_std.all;

   entity TOP is
   end entity;

   architecture SIM of TOP is

          type MyRecordType is record
                 x : std_logic_vector(2 downto 0);
                 y : std_logic_vector(2 downto 0);
          end record;

          component Test is
                 port(
                        clk    : in  std_logic;
                        input  : in  MyRecordType;
                        output : out std_logic
                 );
          end component;

          constant period : time := 20 ns;
          signal clk      : std_logic;
          signal result   : std_logic;
          signal myRecord : MyRecordType;

   begin
          dut : Test port map(clk => clk, input => myRecord, output => result);

          clk <= not clk after period / 2;

          process is
          begin
                 myRecord.x <= "000";
                 myRecord.y <= "000";

                 wait for 20 ns;

                 if result = 0 then
                        report "TEST 1 - FAILED.";
                 else
                        report "TEST 1 - PASSED.";
                 end if;

                 myRecord.x <= "000";
                 myRecord.y <= "010";

                 wait for 20 ns;

                 if result = 1 then
                        report "TEST 2 - FAILED.";
                 else
                        report "TEST 2 - PASSED.";
                 end if;

                 wait;

          end process;

   end architecture;


texts: How to count EEPROM wear cycles when flipping an address back and forth?

texts:
I'm trying to determine the life of some EEPROM. I will be erasing a byte (setting to 0x00, clearing a parity bit) as frequently as I will be writing to it. So if setting it to 0x00 counts as a wear cycle, I will effectively be having the number of cycles I can use that address.

Does writing a 0 count as a wear cycle or not?

EDIT: it is the act of flipping a bit back and forth that I am trying to estimate wear on, not writing a 0, since EEPROM is 0xFF when erased. So, if I start with erased memory (0xff) set an address to 0x00, then back to 0xff, then back to 0x00, does this count as two wear cycles or three?


texts: Mixing structural and behavioral in VHDL, does it make sense?

texts:
I've designed a VHDL unit, quite complicated, using a structural fashion, i.e. I designed the subcomponents and the interconnected them in the top unit.

Each of this component, including the top one, are implemented using combinatorial logic, i.e. there's no state machine in it.

Now I need to use this unit for a larger design, and basically for this design I would probably need a state machine (because I need some events to be timed). The only solution I then see is to used a mixed description (because state machines cannot be described without processes).

My question is, does this think of mixing designs descriptions make sense? I know I could do it, but I don't know it does make sense or not in general (i.e. if it is a common practice in the engineering community xD).

Just to give an idea of what I'm up to, it's something like the things below:
There are two new blocks, that I have to design as well. As you can see there's a feedback from the block I currently have implemented. That feedback I assume could need at least a register.


texts: Factors to consider when swapping a battery with a power supply

texts:
I'd like to swap an 18V lithium-ion battery with an 18V DC power supply for use in battery-powered hand tools (cordless drill, reciprocating/circular saw, weed whacker, etc.).

Logistical issues aside, are there any electrical considerations where a fully-charged battery may behave differently than a power supply of the same voltage?

For example, these tools are likely highly inductive loads, and the datasheet for this power supply states outputs are protected to short circuit conditions (~5.5A draw). Even so, I am not sure how this compares to the characteristics of a li-ion battery.


texts:
I wanted to automatically Identify some structures in HDL code (Verilog/VHDL), let say an adder. I need to automatically detect how many adders in the design. I am not sure from where to start, should I like convert my code into AST (abstract syntax tree) look for pattern and then convert it back to Verilog/HDL ? can anyone mention an example  or a small tutorial on how to do such tasks ?
Thanks


texts:
10GBASE-R using 64b/66b encoding scheme (3% overhead)
10GBASE-X using 8b/10b encoding scheme (20% overhead)

10GBASE-R is achieved with single xcvr lane
10GBASE-X is achieved with 4 XAUI xcvr lanes & 2 RXAUI lanes.

Looking at the advantages 10GBASE-R having today, is 10GBASE-X is still being used in today Ethernet world? Or it is just a legacy protocol?


texts:
I'm looking for a small fairly rugged normally open switch that closes when a "pin" is removed. It needs to take about 12V It needs to be passive and not require power. Is there such a component?

Basically, I want to be able to pull out a pin or a small plug to turn a device on.

I can think of a mechanical solution, a plastic pin that blocks the current flow, once removed the contacts would press together. But, for my application (a drone) I don't think I can build something rugged enough.

So is there a type of store-bought component that will do this?


texts: Are SV5-5 spade connectors proprietary / trademarked?

texts:
I wish to advertise a product as using SV5-5 forked terminals. I am worried that I would be infringing someones trademark if I use the words "SV5-5 10AWG forked connectors"
Is it a generic standard? Cheers!


texts: How to pick a switching transistor to drive LEDs? Or, how to read a transistor data sheet?

texts:
I'm going to be driving a bank of 20-25 LEDs from a single output of a PIC micro. Obviously, I need a transistor, because that's going to be somewhere in the vicinity of 400 mA (the LEDs are speced at 20 mA with 3.2V of drop, which I'll get close to by using a 100 ohm resistor and a 5V power supply).

I get into trouble when I try to figure out what sort of transistor I should use for this, because I don't understand how transistors are rated. In discussions of general transistors, the 2N3904G & 2N3906G come up as good, all-around NPN & PNP transistors. How do I look at the transistor data sheet and understand that these transistors will work? What parameters do I need to pay attention to? I want to be sure the transistor can handle the load, and I want to be sure that my PIC's output can force the transistor all the way on.

I've got some familiarity with digital electronics, but when we get into the analog world I just don't have enough of a frame of reference yet.


texts: Can copper-zinc be substituted for silver-zinc?

texts:
Silver-zinc batteries are in the news (the pop science news) these days because they are being researched to compete with lithium ion batteries. But the price is high because silver is expensive. So it got me thinking about copper.

Just quoting the values as given by wikipedia:

Copper has an electronegativity of 1.9 and resistivity of 16.78 nΩm.

Silver has an electronegativity of 1.93 and resistivity of 15.87 nΩm.

They seem really similar. Can't the copper-zinc chemistry substitute for the silver-zinc chemistry? Wouldn't this have similar performance in a battery (either primary or rechargeable)?

I'll finally note that copper-zinc is one of the oldest battery chemistries ever built, all the way back in 1800 by Alessandro Volta. So I'm suspicious that there's something not so great about it (or otherwise silver-zinc wouldn't be needed). I just don't know what it might be.


texts:
yet another noob here. answer is probably obvious for most but not for me really. Just wondering how to interpret markings on these capacitors (red circles)

ps. first lesson learnt :)


texts: "USB is also a serial communication method" is this true?

texts: I'll repeat the title. Is it true that USB is also a serial communication method ? (a bit confused, someone told me @ facebook :D)


texts: Using an optocoupler to tap into digital PLC signals

texts:
How can i design a circuit for tapping digital DC signals from PLCs?

I desire to create a circuit with a MCU which can be attached to a PLC signal in the range 0-24V and log the signals on the MCU. I only need to log on/off state of the PLC. "Off" is defined as 0-5V and "on" as 13-24V. It is of high importance that the PLC and MCU are isolated from each other. I have thought of using either Darlington or linear optocouplers.

My design thoughts are to use a single resistor or a voltage divider to scale the PLC voltage down in the range of the optocoupler in order to not burn the diode. However I doubt that if I do this it is possible that the circuit mesh with the PLC signal? Eg. pull it lower than 24V. I have never worked with PLCs before so I have no clue what the general or standard output current is.

Any thoughts/experience or good advice?
Thanks!


texts: How to measure ripple factor automatically for a pulsating dc output(0-300 v)?


texts:
I think I understand the buck converter operation (continuous conduction mode) except I'm a bit confused about the ripple current. Here is what I know so far

I understand everything up until the last statement in red. I can't seem to understand it. I'd appreciate some clarifications on ripple current. (continuous conduction mode for the inductor is assumed)


texts:
I have connected a 3906 PNP transistor base to a GPIO pin of ESP32 board. Emitter is connected to 5v and collector is connected to a buzzer. When I program the buzzer (send a HIGH from ESP32), it is permanently on. When I check it against a multimeter, the transistor turns on even when base current is 3.4v (when I though it turns on only if voltage is less than 0.7v).

To cross check the transistor and buzzer, I directly connect base to 5v and the transistor is turned off. Connecting to ground turns on. So, it works correctly when connected directly.

For those who would like to suggest a NPN transistor, I have tried using 3904 NPN transistor and everything works as expected. However the issue is that when programming, all the pins of ESP32 are high by default and the buzzer is ON until programming done.

Can someone tell me how to solve this issue? I need to use PNP transistor only. Thanks in advance.


texts: If I'm using an RTC and ATMega328p (arduino UNO chip), do I need two crystals?

texts:
If I'm using an RTC that requires an external crystal, do I need a second external crystal for my ATMega328p? Or can the two share? What is standard practice for this kind of thing? I'm making a simple wristwatch, and so timing on the ATMega is not so important since the RTC is responsible for keeping track of time.

Hope this was specific enough...thanks!


texts: Increasing the number of parallel cells for batteries

texts:
I am using Texas Inst IC for a lithium ion battery which is in the 4Serial-3Parallel cell configuration. In addition, I don't use LED or LCD in this lithium-ion battery. My cells have 3500mAh capacity.

I am planning to increase the number of parallel cells but I am not sure about maximum number of parallel cells(for example 4Serial - 8 Parallel Configuration).

Especially, my concern is about cell balancing. Becasue internal balancing current is 5mA.

What are your recommendations? Can I use this PCB with 4Serial-8Parallel configuration?

EDIT:

As I said before, I have PCB(with bq20z655-r1) and it is working very well for 4Serial-3Parallel configuration.
Now I am planning to use 2 parallel PCB. I mean 4S-3P + 4S-3P with 2 PCB.
Please check the image:

Maybe It can be solve something for balancing. What is your idea for that?

Please check this document for cell balancing: http://www.ti.com/lit/an/slua340c/slua340c.pdf


texts: Is it possible to control 3 DC motors (12V, 5A) with a single driver (BTS7960-43A) if the motors should rotate 1 at a time?

texts:
I have to use 3 DC motors in a project, each of them are 12V-5A, controlled by Arduino. At any given point, only one motor will be operating. So I want to avoid 3 separate drivers for 3 motors. Instead, is it possible to use single driver for 3 motors (using BTS7960 - 43A driver)? If yes, how can I keep other 2 motors off when one of them is running?

Similar setup like in pic


texts: How over-discharge protection function works on this circuit?

texts:
How this circuit to protect so call "over discharge"? since there's no output + and - terminals on the board and this case the load should connect directly to B+ and B- without any protection for discharging.
CUUSINHVIEN


texts: Below I have the loop gain and the Bode plot for it, however I do not understand the phase plot. Why does it start at -90 degrees instead of 90 degrees since we have a zero? Please explain.


texts: Desoldering CPU from PCB or holding it in reset

texts:
I am currently working with a NAND flash that I want to dump. The goal is to take a look at the data that is stored in the filesystem.
To do so I soldered 8 wires to the NAND flash to access it while it was still placed on the PCB. To read out the memory I used a Bus Pirate.
I managed to dump the entire flash like that but when I started to retrieve the data I ran into a bunch of problems.

After some research I found out that it can be problematic to access the NAND flash while it is still located on the board because it is possible that the CPU gets powered up during the process and corrupts the dump.
The best way to handle this would be probably desoldering the NAND flash from the board and dumping it again.
However I know that the CPU has a reset pin on the board that becomes active when it is pulled to ground. What I am asking myself is would it be also a viable to establish a connection between the reset pin and a ground pin (e.g. connecting them with a wire) to hold the CPU in reset and to dump the content of the flash afterwards or do I really have to desolder the flash from the board?


texts:
I am building a small LED lamp from a jar(about 100ml), so all components should fit in it. I decided to use a LED drive/Joule Thief, that I found at online Chinese store.
Datasheets (all I can find is in Chinese language):
https://pdf1.alldatasheet.com/datasheet-pdf/view/1133536/SHININGIC/YX8122.html
https://datasheetspdf.com/pdf/785935/ETC/YX8122/1
I also found similar question:
LEDs driver circuit
The circuit is very simple, but I still failing to make it work. I have a white 5mm LED(3.3V, 20mA), 3v button battery and 47uH inductor, but the LED won't light up. I don't know what I'm doing wrong, if I increase inductor to 1mH the LED is glowing, but not at the full power. I tried to connect red LED (1.8v, 20mA), but it glows even weaker. I don't want to change battery type as it perfectly fits in the jar and I can't use two batteries, for the same reason, they won't fit.
In summary, the goal is to make white led glow as long as possible using 3v button battery. Is it possible to make it by using yx8122 led drive? If no, then what the purpose of this IC?


texts: 2 Possible Currents and Vdrops from same Resistor: Which Will it Be? [Beginner]

texts:
simulate this circuit – Schematic created using CircuitLab

Let's say I have a power supply that supplies 5v and 3A.

If I add a 2 ohm resistor, it could do 2 different things.

Realizing that resistance = volts/amps...

either it will drop the voltage by 1 volt and give 0.5A, as 1/0.5 = 2 ohms

OR it will drop the voltage by 4 volts and give 2A, as 4/2 = 2 ohms.

Let's just assume the power rating on the resistor is high enough that we don't have to worry about it for this example.

Question

So which one of these two scenarios will become the reality if I have just the power source and a single 2 ohm resistor? And why? Otherwise, if you suspect there is some concept I fail to misunderstand, please explain that as well. I'm basically saying, according to ohm's law it seems both these scenarios are possible when deciding a voltage drop and current to find a resistor value. I'm trying to ask a basic question to understand resistors, not asking because of a real life application.


texts:
I am googling too much stuff regarding it and the noise on there has got me completely confused and there is no a single fixed range I should be checking my system with. ( I am software engineer and the board I am working on has PA as well as Power controlled by software). We are looking to get a long range something around.

We have a class 1.5 BLE v5.0 and I have been asked to get as much as range possible and no solid numbers. I am currently getting a range between 9-12 meters only.

I am not looking really for a solution with this question. I just want to know on what the BLE range depends on other than the following :

BLE Power
Rx Sensitivity
BLE Class
Power Amplifier used.

Does having a lot of other BLE / Bluetooth / WiFi around affect my range?

Here are the links that gets me confused totally.

Nordic's Long Range BLE

it states 600/1300 meters as per PHY used.

while Wikipedia states 100+ Meter.

Edit 1 :
Article about Wireless Range and how it's calculation is done may help someone who stumbles upon this question in future.


texts:
What are DIO and STB pins in below IC?

If DIO means digital input or output, then how to set it to Input or Output mode? Is it using STB?


texts: I have two phone cameras, rear and front, but I don't know which type of connectors are these?


texts: What causes the Inverting input of this op amp to conduct current?

texts:
When I analyse this circuit to understand it's working,  I got stuck at one point. Have a look on this circuit. When the feedback resistor value is 2.2k as shown in fig, I got the expected output with the DC offset at the output pin. There is some nA of current flow at the inverting input pin of this Op-Amp. There is only 3mVrms voltage at the inverting input.
When I increase the feedback resistor to 100k, the gain also get increased. I understood. Due to that, output signal also get clipped since the voltage swing is limited to 5V at the positive and negative side.
The intriguing part is the inverting input of the op amp. After increased the gain to 100k, significant amount of current up to some micro Amps of current starts to flow. This causes around 3.3 Vrms drop at the inverting input side.
The question is, why current flow increases at the inverting input pin after increases the gain of the op amp via feedback resistor. What happens there?
Also, I could not bring the voltage drop of 3Vrms at the inverting input via calculation.
Kindly help me to understand!!!


texts: How does the lead polarity work on a D'Arsonval galvanometer?

texts:
Following an illustration of D'Arsonval movement such as the following...

I notice that the N polarized part of the coil is connected to the positive lead and the S polarized part of the coil is connected to the negative lead. Why is the galvanometer configured this way? Does the meter always have to be configured this way?


texts:
I'm considering to use the Omron G5V-1 Relay in order manage a 5 VDC 1.5 A charge.
Reading the datasheet I did not completly understood what is the Relay maximum supported current, considering that I'm working at 5 VDC.
What's the difference between Rated Carry Current and Max Switching Current? Which of these two should I consider as the current limit?

In the last page of the datasheet I found this paragraph:

Long-term Continuously ON Contacts
Using the Relay in a circuit where the Relay will be ON continuously
for long periods (without switching) can lead to unstable
contacts, because the heat generated by the coil itself will affect
the insulation, causing a film to develop on the contact surfaces.
Be sure to use a fail-safe circuit design that provides protection
against contact failure or coil burnout.

What Long-term means? Are we talking about hours, days or what?


texts: Optional pump capacitor connection on RS232 line driver/receiver Chip

texts:
Why is it on RS232 line drivers/receivers such as ICL3222, MAX3222, ADM3222, etc.. the C3 capacitor can be connected either to GND or Vcc?.

There's nothing on the datasheet regarding the differences except for this portion:

"When replacing a device in an existing 5V application, it is acceptable to terminate C3 to VCC as shown on the Typical Operating Circuit. Nevertheless, terminate C3 to GND if possible, as slightly better performance results from this configuration."

Ok, so it says "something" about it with no explanation as to WHY. I'd like to know WHY it's possible, and why not just specify to connect always to GND.

Even the internal circuit diagram could help to understand this.


texts: Can a USB WiFi adapter transmit 501 milliwatts of power?

texts:
I purchased a "hfield Wi-Fire" adapter recently because it claimed extended range. I found it new in the box at a discount store. It's a 2.4 ghz only adapter. It comes with a small clamp to allow you to attach it to the top of your laptop. Otherwise it is pretty standard, connecting to your laptop via USB.

When I plug it in, I can do the following on my Ubuntu desktop to get the transmit power information.

ericu@ericu-desktop:~/Downloads$ iwlist wlan0 txpower
wlan0     unknown transmit-power information.

          Current Tx-Power=27 dBm   (501 mW)

I was intrigued by this, because 501 milliwatts is a huge transmit power compared to most devices. I am pretty sure this number is just reported by the driver in the linux kernel, so it could be programmed to say anything. I opened up the unit, which was quite easy.

The design of the internals appears to be a typical WiFi USB stick feeding a yagi antenna. The drive element appears to be a partially folded dipole. I'm really unsure what functions as a ground plane in this design, unless it is the coax cable itself.

There is also a patent number listed which is 6307524. More information on that patent here. The patent appears to cover the PCB design for the antenna only. The description is a little curious, since it describes an antenna with the transmission line impedance matching the driven element. This is a desirable quality in most antennas. I guess they are really just saying this antenna design does not require a matching transformer.

Is it possible that this WiFi adapter actually transmits 501 milliwatts of power? Or does that figure include the effective gain of the Yagi antenna printed on the circuit board?


texts: Is there an easy way to test if my PS/2 -> USB adapter is passive?

texts:
I own a couple of PS/2 to USB adaptor/converter connectors that look like the following:

Is there anyway to test if these adapters are passive without disassembling them (or risking damage by disassembly)?  In all likelihood, they are passive as the active converters usually have a chip of some kind embedded in a cable to actively convert the protocol.


texts:
While trying to make a TV tuner radio like I saw here I got myself a I2C PLL Tuner from an old TV and powered it up without connecting I2C bus lines to the circuit. Not even to the pull-up resistors.

After 2-3 minutes smoke came out of the tuner. When I opened it the PLL IC was burned.

My question is if I power up a device with I2C without connecting or before connecting the bus to pull-ups, are there any chances I will destroy that device? Or it just happened with that tuner?

Here are the schematics of my power supply and tuner.

Tuner needed 5V for the digital part, 12V for the analog part and 33V for the varicaps.


texts: Mechanical Switch in parallel to the Micro Controller working in Sync

texts:
Here is the image for my requirement,want to operate Load Lamp of 230V AC with Mechanical Switch in parallel to Controller where one can 'ON' the Load Lamp from the Mechanical Switch and 'OFF' from the controller and vice versa.

Here only issue is that Mechanical Switch can't work as A FAIL SAFE option as XOR logic gate is involved.

A FAIL SAFE option is my requirement where Mechanical Switch can turn 'ON' the Load Lamp even if the controller or XOR GATE gets fried up or fail's to operate.

In this circuit have shown XOR gate but have doubt whether any XOR gate is available which can operate at 230V AC?

Or is there any way to use XOR logic through other Electronic Components?

Or I don't mind using other logic?

Please help I'm badly stuck because of this FAIL SAFE option

[Edit by @transistor. OP to update table below.]

| MECH | OPTO | LAMP | Notes
| Off  | Off  | off  |
| On   | Off  | on  |
| Off  | On   | on  |

| On   | On   | off  |

The last status I have highlighted because if an XOR gate so available for 230V AC than in code, I can program in way such that if the device is 'ON' from Mechanical Switch and one needs to 'OFF' the Load Lamp than I just need to turn 'ON' the SCR hence as per logic of XOR gate the Load Lamp will be 'OFF'.

Or if any other Electronics component or circuit is available which helps in choosing or manipulating then only last status of logic table change.

Operating voltage, so mentioned in the circuit, for the load lamp is 230V AC and for the controller and opto coupler ia around 5V DC.

Also I need to control the Controller over the Internet.

Also can't use the 2-Pole normal Mechanical Switch as I can't change all existing switches and its a retrofitting job with limited resources.

can't use relay logic due to space constraint.


texts: P-Channel Mosfet switch and Capacitor Discharge on Drain

texts:
I'm using the following circuit with a P-channel mosfet to switch the positive line to a transceiver.  I want to keep the transceiver grounded and switch it off to stop current draw from the battery.

The circuit gives the desired results and switches the transceiver off, and I get near 0 current draw when the digital pin is high.

My question is in relation with the capacitors on the transceiver.  After power is cut from the transceiver if I place a voltmeter across the load (Drain and ground), I get a voltage of ~0.5V which decreases.  I'm assuming this is the capacitors discharging when the voltmeter is applied.  There is no current drain if I connect an ammeter to the batteries negative side, as you would expect.  I'm not sure of the specs for the capacitors but I'm assuming they are typical for filtering noise etc.

Do I need to be at all concerned with this discharge voltage from the capacitors, and can it negatively impact the mosfet?


texts: Understanding STEVAL-ILM001V1 DALI transceiver schematic + adding protections

texts:
I'm working on implementing a DALI bus interface circuit.

DALI has a few specifics that make this tricky: The device should draw at most 2mA when receiving, it transmits by shorting the bus (250mA is limited by the supply). The normal voltage is 16-22V, BUT the bus must survive polarity reversal and also a short to 230VAC (this is for the case when a technicial installing it wires it wrong).

Here's the STEVAL-ILM001V1 schematic that I determined to be the closest to what I want - there are several simpler circuits online, usually with no 230V protection whatsoever.

I understand most of it, but there's a few details I need to understand before implementing it:

Why is the resistor R2-4 split to three 68k resistors. Is this just to achieve the right value more precisely, or does it have soemthing to do with power dissipation?
What is the function of those resistors anyway? I understand that the two transistors form a current limiter. What role do those resistors play here? The current is set by U(CE_Q1)/R5, if I understand it right
What is the function of C1? (maybe related to C2 - next point)
Ditto for C2 - is this to allow keeping the bus shorted for the required time to send a pulse? My understanding is that the current supply won't supply anything when the bus is shorted, and the Q2 gate would sink to GND via R6? So I guess it might oscillate or go into some non-standard state where e.g Q2 is in the resistive region and dissipates heat?
edit Also, what's the purpose of R1? A "fuse"?

Next, I plan to improve the 230VAC protection by adding a small-signal NMOS (e.g. BSS123) like this: - can this work? I want R11 to get some voltage on it when D4 conducts, taking the Q4 gate above the gate threshold and switching it on - so when my MCU tries to transmit, nothing happens.

thanks for all answers!

simulate this circuit – Schematic created using CircuitLab


texts: USB-UART Converter Design based on CH340G not responsive

texts:
I have designed boards that were using the CH340G USB-UART converter based on the below schematic. And they worked just fine, and back in the day I also paid zero attention to things like differential pairing/impedance matching etc. I even used the auto router to route everything back then.

Now I am about to lose my mind, I have the below layout. And the thing is that when I connect this to the  computer, it does nothing or gets recognized but the computer tells me that the device doesn't work properly. In any case it doesn't work.

I have tested the same chip on another board to see if it is busted. But it works perfectly fine on a board I designed previously. The only thing that are different are the smaller smd Crystal and I have accidentally routed the differential pair on 0,2mm width. It should have been 0,4mm.
The upper copper pour is ground, below is 3,3V.
To see what is worng I have tried:
1)I replaced the crystal and soldered a larger THT crystal on the smd pads. Did not work.
2)I cut out the D+ and D- traces, and replaced them with twisted wires. That also did not work.
I am failing to see my own error. I would appreciate any input.


texts: Understanding sink currents for IO expanders

texts:
I'm looking at using a GPIO expander to control some LEDs.  I plan to sink the LED current through the GPIO expander (so configure port to output and set to 0 to switch LED on).  I'm looking at using this part: http://www.nxp.com/documents/data_sheet/PCA9555.pdf and trying to work out how much current I can sink per pin

Table 13 says absolute max output current is +-50mA which I take to mean 50 mA is absolute max sink current per pin.

Note 2 on page 19 says we can't go over 25 mA per pin, 100 mA per pin bank and 200 mA device total.

Table 14 lists low level output current (I_OL) this is somewhat more confusing.  It talks about a low level output voltage (V_OL) but surely if set an output to 0 the pin will go to 0V?  (Unless I do something like connect the pin to the middle of a potential divider to try and hold the voltage above that).  It then gives currents at two different V_OL values (0.5v and 0.7v) with somewhat non-specific typical currents (8 to 20 and 10 to 24 mA respectively).

Can anyone explain the datasheet to determine possible sink currents?


texts: How to remove error in below verilog statement while running for ise simulator?

texts:
I wrote few lines of code and it is giving error. The code is below:

module tb();
wire [7:0] m1,m2,m3;
reg [7:0] a,b,c;
reg en;
reg clka=0;
s_three call(m1,m2,m3,a,b,c,en,clka);
always begin
 #10 clka<=~clka;
end

initial begin
en<=1'b1;
a<=8'h00;
b<=8'haf;
c<=8'ha2;
end
endmodule

module s_three(m1,m2,m3,a,b,c,en,clka);
input [7:0] a,b,c;
input en,clka;
output [7:0] m1,m2,m3;
wire [7:0] m11,m12;
s1 s0(m11,m12,a,b,en,clka);
endmodule

The error given below:

  ERROR:HDLCompiler:329 - "tb.v" Line 29. Concurrent assignment to a
  non-net a is not permitted

  ERROR:Simulator:778 - Static elaboration of top level Verilog design
  unit(s) in library work failed

How can I resolve it ?
Thank you


texts: Does the rotation speed of a synchronous machine affect the voltages induced?

texts:
We know that synchronous generator are the go to for power generation. They essentially need an excitation current for the rotor and an external force to rotate it. This would induce a voltage in the 3 stator windings that has a frequency proportional to its rotation speed.
The thing that I don't really understand is how do these machines produce a voltage amplitude that is independent of its rotation speed while Faraday's law clearly states that the EMF produced is dependant on the rate of variation of the flux. (So let say, I increase the rotation speed consequently the frequency will increase but will that affect my voltage?)
Additionally, how do these generator provide sine waves, wouldn't that require a variation of the number of wire turns in each slot of the stator?

Thank you :)