Trying to determine the output of a RC-filter with load


I have a low pass filter like this:

schematic

simulate this circuit – Schematic created using CircuitLab

$V_{out}$ is measured right after $R_1$, which I suppose means that it is measured over the parallel part.

$R_2$ is the load of the filter. When this circuit is measured with an oscilloscope it seems like it is not dependent on the frequency at all. I would like to investigate why.

I tried to calculate the transfer function for the filter, but I am not sure that it is right.

$$ H(omega) = frac{1}{R_1(jomega C+frac{1}{R_2})+1}$$

I’m using $R_1 = 33text{k}Omega$, $R_2 = 1text{k}Omega$, and $C = 220$pF.

If I plot the frequency responce in Matlab with this, I just get a straight line going from the origin through (1,.5), (2,1) where (Hz, H(w)) and so on.

Is this correct?

Question regarding Orientation of P-Mosfet in Arduino/Microcrontrollers


I was wondering why in the Arduino schematic, and other microcontroller schematics, the P-Mosfet is connected such that the Drain is to the USB while the Source is to the input of the LDO, and not the other way around?

From my basic understanding of how a P-Mosfet works is that current flows from the source to drain.

enter image description here

You can see the full schematic here

Thanks for the help in advance!

How hard/possible it is for an engineer to make this happen?


I need to get one of these power supplies to use it in something I’m developing. The problem is that where I live there are no shops that sell this.

What I need is this:

enter image description here

If I’m not mistaken, this is a power supply with a special form factor. This is exactly the form factor I need for my project.

However, like I said, no one sells it here, so I need to fabricate it from scratch.

Do you think this is a viable project for an Electronics Engineer?

I wonder maybe these power supplies are manufactured by machines and it is impossible/tricky for a someone to do it.

Edited: a PS of 12v and 2A will do.

Can Altera GPIO pins read the input voltage?


I have ALtera DE2-115, and I have a light sensor module, the output of the light sensor is a voltage, how can I use the Altera GPIO pins to read the coming voltage? Thanks

Analog and Digital Output protection?


I know it’s important to protect analog and digital inputs. My question is should you also protect outputs, both analog and digital?

For the inputs, right now I’m using clamping diodes, an MOV, a series resistor, and a series ferrite bead for high frequency noise rejection.

If outputs should be protected, how should this protection differ from inputs?

voltage sources in parallel without any resistors [duplicate]


This question already has an answer here:

Electric current of inductor


I have a homework problem that was solved by our instructor:

“Calculate the electric current of the inductor at $t=0^+$.”

enter image description here

He calculated $1/30$ but the answer sheet was says $-1/30$.

Which of them is correct?

Our instructor’s work:

enter image description here

enter image description here

enter image description here

Pointer to an Memory Address of Flash Memory


I think that the following question is simple, but it is important for me to know.

I am working on microcontrollers. I have seen some code to access the data from the flash memory.

For example in order to read the contents of the 0xA010 address of the flash there is the following code:

           #define ADDRESS_TO_READ      0xA010

           uint8 *Read_Ptr = NULL;
           Read_Ptr = (uint8 *) ADDRESS_TO_READ;
           value = *Read_Ptr; 

This is working fine. My question here is, since Read_Ptr is uint8, how is it storing the value 0xA010, which is a short value (16-bit Address)? How the read and write functions will occur in this memory, when the pointer is uint8?

Hold-up time calculation with high capacity MLCCs


I am designing a linear voltage regulator for 5V (from 30V) at 10mA for a low cost application. Everything works out so far, but I need around 10ms hold-up time in case of an input voltage failure. All the hold-up energy has to be provided by the 5V output capacitor as I cannot use a decoupled input capacitor.

With the help of an LTSpice simulation model I found out that I need around 44μF to provide around 2.7V (which is sufficient) at the end of the 10ms interval. Of course, these results assume ideal capacitors and in this application electrolytic caps would be close enough to ideal.

However, I would prefer to use MLCCs to save a few cents but unfortunately these are not ideal. Their capacitance changes by a large amount if a voltage close to the rated voltage is applied. The measurements regarding this I have seen so far refer to the small signal capacitance under DC bias and I suspect that I cannot use this figures in this application. In fact, in this application there is some kind of DC bias that decreases in an interval of 10ms.

Does the capacitance “recover” during this decrease, even if there is no energy supplied externally?
Are there any guidelines how to calculate the discharge to obtain a hold-up time figure?

How to configure task in Single Task activity of visual studio 2013 workflow for share-point 2013 list?


I am creating Sharepoint 2013 Workflow using visual studio 2013. I have followed steps as shown in figure. But while assigning task i am facing roblem. Task is not getting generated. I am using Host web URL list and when item is created in list task should get generated for Approver.

In my case only workflow is starting when item is created but task is not generating as well as it is getting automatically cancel after some time!
Can anybody help me in this case?enter image description here

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