texts: LAN9512 keeps disconnecting from RPi Compute Module

texts:
Main problem

I'm using a RPi CM and I connected a LAN9512 to it.
However it keeps disconnecting:

usb 1-1.1: USB disconnect, device number 3
smsc95xx 1-1.1:1.0 eth0: unregister 'smsc95xx' usb-20980000.usb-1.1, smsc95xx USB 2.0 Ethernet
smsc95xx 1-1.1:1.0 eth0: hardware isn't capable of remote wakeup

Power rails

18.0V
5.0V (generated from 18.0V)
4.1V (generated from 18.0V)
3.3V (generated from 5.0V)
2.5V (generated from 3.3V)
1.8V (generated from 5.0V)

All powers are generated by MP2359.
This SMPS is able to power consumers up to 1.2A so it should be enough for the RPi CM.

RPi CM needs 3.3V and 1.8V, LAN9512 needs 3.3V.

LAN9512's layout

Note: its ETH and USB lines are routed in differantial mode:

ETH TX: 65.655mm length, 100% matched.
ETH RX: 62.341mm length, 100% matched.
USB: 41.545mm length, 99.7% matched.

This is a 4-layer PCB, and USB lines are wired on the 3rd plane. 2nd plane is GND, so as the 4th one.

What could be the issue?


texts: I have been looking at various different external storage ICs that would work with an arduino. When I looked at the specs of some EEPROM chips and compared it to the specs of other RAM chips, I noticed that they had relatively similar specs in terms of Read/ Write frequency and storage capacity. So if they have such similar characteristics, why would you use a RAM chip over an EEPROM chip? Wouldn't an EEPROM chip be much more useful as it is nonvolatile?


texts: Energy harvesting - drain capacitor when voltage is reached, ultra low power

texts:
I want to connect tiny solar cell to a capacitor, let it charge it and once voltage reaches 2V - flush it through tiny red LED.

Could anyone suggest how to implement that given that charge current is very small (1 uA - 10 nA) and this periodic discharging should obviously have some hysteresis? I suppose I need some CMOS/FET active elements, but beyond that I have no idea.

Ideally it should make these flashes more frequent when more light is present.


texts: Combine two power sources with higher priority for one source

texts:
I have two power sources, one is solar panels (DC), another is from grid (AC). Is it possible to combine these two power sources with solar getting higher priority ? By high priority I mean draw power from grid only if solar is not sufficient or absent. Final output is required to be AC

One way would be to convert grid ac to dc, matched to dc output of solar panels, and then some how combine them (with priority for solar) and then convert back to AC.

Grid-tie setup is not possible. Also Grid is too unstable (not available every 3rd or 4th hour) so I am going to need batteries any way. I want to prioritize use of power sources in this way:

Solar
Grid
Batteries.

So if solar is not sufficient it should tap grid (if available) for deficit power else it should use batteries. I want to minimize cycling of batteries and use only as a last resort.

I have come across a Taiwanese product which supports solar first, then battery and lastly Grid. Manual states that You can set the discharge voltage level of battery at which point it will point back to grid until batteries are fully charged then back to batteries and so on.

Maybe I am being too conservative with cycling of batteries. I would like to know if use of batteries only as a backup is possible given my required priorities.

This question uses only one source at the a time but I want to use both sources at the same time such that if solar is insufficient, don't turn it off, rather augment it with grid. For example if solar can deliver 2 Amps and I need 5 amps in total, I want a way to be able to draw remaining 3 amps from the grid. And if load requires 2 amps, stop taking from grid. Is it possible ?

For simplification lets assume grid also supplies in DC. Also I have some controller d1 connected with Panels which convert output of panels to 24v dc and another device d2 to convert grid to 24v dc as well. I want to combine d1 and d2 to add currents with above mentioned priorities.


texts: Electronic flasher with low load detection

texts:
The circuit above is an existing flasher without low load detection. I am trying to develop electronic 2-wheeler flasher with low load detection. While Googling, I got a circuit with relay in it, one relay used for flashing and another one for load detection, I mean when there is a load changes then the flash rate doubles. Specifications which I am looking for:

21W or 45 W flasher,
operating voltage- 9 to 12V,
Flash rate-85 c/m,
Indication of the bulb failure- flashing frequency doubles at single lamp failure,

Can I replace the flash relay with MOSFET? Load sense relay by sensing resistor and comparator? I actually don't know how I have to implement the low load detection in the circuit, since I am a beginner.


texts:
I would like others to explain how to make an buck or boost circuit using UC3843-IC.

I am constructing a solar power supply, that can be setup as an alternate power source so that it can be fed to main lines.

For an ordinary solar panel the generated voltage output ranges from 6 to 10V; but it's necessary to step-up this voltage to constant 12V in order to charge a 12V battery that we are using.

As it being our college project, we have to implement the boost DC-DC circuit with IC UC3843. Can any one explain me how to design a DC-DC boost converter circuit, that can able to step up 6-10V DC to 12V DC.


texts: How does a multi-meter diode check work and how to test an RF diode with it?

texts:
This is a followup question for Can I debug this simple circuit without VNA and proper RF equipment? which I am still fighting. The diode as a nonlinear element could explain all the weird behavior I am seeing. But how would I verify this?
Question 1: I have a Keysight 34461A Digital Multimeter with diode check functionality. Interestingly it is nowhere explained how this test works: Does it generate a constant fixed current (1mA) and measures the voltage? Does it generate a fixed voltage and measures current? A combination of it? How would such a multimeter ensure that it does not destroy diodes? (e.g., some diodes have tens of volts of breakdown voltage, some just a few volts). Ideally, it would slowly step up current/voltage.
Question 2: For me, it's an HSMS-285C Zero Bias Schottky diode for RF applications. The datasheet only specifies the forward region nicely. BV spice parameter is 3.8V, max. reverse voltage is 2V and max reverse leakage is 175uA. Can I test this diode with the diode measurement function? If not, how else to test it? Also, is it reasonable to believe the diode is working (at RF) if the DC check is successful?
Question 3: I tried the multimeter already and measure 185mV as forward voltage (which I think is correct) and for reverse voltage 400mV. How can this be? Is the diode broken or not? If it's broken, shouldn't it be ~0V? (Note: there are 4 of them in the circuit and all show 400mV)
Question 4: I tried to modify the spice model with BV=0.4 in the hope to reproduce the measurements in Can I debug this simple circuit without VNA and proper RF equipment?. Unfortunately this makes the LTspice simulation even less similar to the measurements. Given a diode model like
.model HSMS285x D(BV=3.8 Cjo=0.18p Eg=0.69 Ibv=3e-4 Is=3e-6 N=1.06 Rs=25 Vj=0.35 Xti=2 M=0.5)

what are possible ways to model a broken version of this diode?


texts: Purpose of a resistor at the input of a linear regulator

texts:
I am working on a circuit that uses a LT3080 linear regulator to create an output Voltage of 15VDC from a 28VDC source supplying a load that draws about 200mA. Based on the datasheet, the output voltage is set by connecting a resistor (R1) to the SET pin according to the formula Vout = R1 * 10uA. The current circuit has a resistor (R2) connected to the input pin of the regulator. Is there a reason for the R2 connected to the input pin?

simulate this circuit – Schematic created using CircuitLab


texts:
I'm pretty much brand new to both stepper motors and PLC's and electrical in general, although I have an idea of the theory of how they work/what they do.

I am trying to achieve is to be able to have a input (a lever, distance sensor, or a control knob), that will result in the stepper motor moving to a certain position.

So when the lever is right down (or the distance sensor is at 6m) I want the stepper motor to be at 0degrees, when the lever is half way (or distance sensor at 4m) the stepper motor needs to be 45degrees, and when the lever is right up (or distance sensor is at 2m), stepper motor needs to move to 90 degrees.

Obviously I only need to use one of these inputs on each setup.

My questions are:

Is this even doable?
If so, how difficult will it be for me being a NOOB? And where should I look to for advice/basics? Or do I need to hire a professional?

I have managed to find info on the net about people doing this with Arduino, however I am told that Arduino isn't really ideal for Industrial application. We are using Crouzet PLC's in another application currently, so ideally I would go for that brand.


texts: Can two usb gaming controllers be wired together to act as one?

texts:
Let's say I have two USB gaming controllers. Those generic ones.

Is it possible to make it so they work as one? So if you press Left in Controller one and B on controller 2, they both get sent and identified as if were sent from the same controller.

I honestly think it wouldn't work because of drivers, and maybe because of the power loss considering it is now shared by two similar devices.


texts: I need to place two of these transformers in a case. How close am I allowed to place them? Can they touch each other (of course, they will be electrically isolated)? Is their orientation with respect to one another important? What kinds of closest placement types do you suggest?


texts: How to record electrical signal through PC sound card as an audio file?

texts:
I am doing some study on the frequency of electrical supply. I need to do the analysis on MATLAB. I want to record the electrical signal as an audio file in my laptop.

As I am a beginner  working   with 220V mains, I have a fear of busting my soundcard .          I need expert advice  on     how I can develop my circuit and what type of protective measure should be taken.

So far my idea is to use a transformer of 220/12 volts then using a voltage divider circuit. But I actually don't know what is the limit of Line-In voltage for PC soundcard. Up to what extent should I attenuate my     signal?


texts: Any Hazards Associated with a High Current Conductor

texts: For a conductor carrying a low voltage (say 12V) and high current (say >500A), are there any hazards that we should beware of?  I assume it is safe to touch the uninsulated conductor even when it is carrying a high current. I know when an inductor is involved, disconnecting the circuit could cause a high self-induced emf. But does that apply to any high current circuit?


texts: Calculating output voltage of a boost converter circuit

texts:
This a problem with a circuit of an up-converter, consisting of a constant voltage supply (E), a switch (SW), a diode (D), a coil (L), a capacitor (C), and terminals as shown in the figure.
i(0) = 0 and v(0) = E.
The switch is shorted from t = 0 to T0, then opened until T1 with i(T0+T1) = 0. This operation is repeated n times.
The goal is to find v(n(T0+T1)).

simulate this circuit – Schematic created using CircuitLab
From here is my own understanding, I might have missed something.
From t=0 to T0, we have E = L di/dt so i(t) = E/L t;
i(T0) = E/L T0
From T0 to T1, we have the equation,
$$E = L \frac{di}{dt} + \frac{1}{C}\int{i dt}$$
By taking LaPlace transform
$$\frac{E}{s} = Ls I(s) + \frac{1}{Cs} I(s) - \frac{1}{C} i(T_0)$$
Yielding after reverse transform,
$$i(t) = \frac{E\sqrt{LC}}{L}sin(\sqrt{LC}t) + \frac{i(T_0)}{LC}cos(\sqrt{LC}t)$$
Then
$$ T_1 = \frac{1}{\sqrt{LC}}(-\alpha + \pi/2)$$ with  $$ \alpha = tan^{-1}(\frac{\frac{E}{L}\sqrt{LC}}{\frac{T_0}{L^2C}})$$
There is an intermediary question, that asks to prove i(n(T0+T1))=0. I am not sure about this but it can be done using mathematical induction on n.
$$for\ n(T_0+T_1)<t<n(T_0+T_1) +T_0:\ \ \ i(n(T_0+T_1)+T_0)=\frac{E}{L}T_0$$
$$for\ n(T_0+T_1)+T_0<t<n(T_0+T_1) +T_0+T_1: \ \ \ i((n+1)(T_0+T_1))=0$$
As for the v(n(T0+T1))
I think for n=1, we can just take the
$$v(T_0+T_1) = \frac{1}{C}\int_{0}^{T_1}i(t)dt =  \frac{1}{C}\int_{0}^{T_1}Acos(\sqrt{LC}t+\alpha)dt $$


texts: What do these numbers mean on a transformer schematic?

texts: What does the .7, .6, 1, .5, .6, 1.2, and .3 mean in this picture? Why isn't there a number between terminal 8 and 6?


texts: Component selection - difference between 4027 and 4027N flip flops

texts:
I am building a simple circuit that will use a J-K flip flop to enable me to use a momentary switch as a toggle.

The circuit diagram states that a 4027N should be used.

My local supplier has a 4027 in stock.

This is a really basic question I'm sure, but is this the same thing? What does that trailing N in the name mean?


texts: How is this capacitor connected between the inverting input and ground being used?

texts:
I found a schematic for a lithium polymer battery charging circuit where an op amp is used as a comparator. The battery voltage (adjusted by a pot on the left) is compared with a 3V reference provided by a zener diode. Can anyone tell why the 1 uF capacitor was included between the inverting input of the op amp and ground? Here's the schematic:

from https://www.homemade-circuits.com/usb-automatic-li-ion-battery-charger/


texts:
I am working on a control and interface board for high voltage supplies, which requires some current measurement to be implemented. The general terms of the question are similar to this one. The device through which I want to sense the current is at up to +5kV DC but the ground is not guaranteed to be isolated so implementing low-side current sensing is non-trivial. In writing this question up, I have also found this answer which is for a very similar application, but I am expecting the current drawn to range from nano-amps to maximum of about half a milliamp in my case.

I wish to measure output current from the high voltage power module across a few decades, ideally from sub-microamps up to milliamps. The ultimate "display" of the data will be handled by a microcontroller, but in order to access the required dynamic range I've been thinking of using a LOG112 to directly sense the current relative to a reference. To get hold of the current from the high voltage circuit in the first place, I've been told that an optocoupler will work down to a few microamps and I've been recommended the Vishay CNY66, which in a simplified sense I intend to implement as below:

simulate this circuit – Schematic created using CircuitLab

In practice I'm using a LOG2112 since this whole system will have two high voltage channels. As a current reference I'm taking the logarithmic amplifier's onboard 2.5V reference and putting it through a sense resistor.

Does this sort of architecture seem sensible? I'm not entirely sure how I should choose the value of R lim (R2) or what sort of sensitivity I should expect.

Any advice will be appreciated.

Merry Christmas.

EDIT: Changed the diagram to fix an error with the high voltage load's connection.


texts: Circuit design - How to fix power supply overheating and reduced performance?

texts:
Goal
I'm trying to make a IOT radiator valve so I can manage the heating of every room in my house automatically with a system I'm building.
Context
I've pulled apart a cheap "smart" radiator valve to salvage its 3.0V (25 Ohm) motorised worm-screw component, that adjusts the flow of water through the actual TRV valve that is on the radiator (to regulate its heat).
I'm using a 3.3V battery power supply (0.5 Amps) to power the ESP-01S control board I'm using along with the wormscrew motor.
I've allocated two GPIO pins on the ESP-01S board (represented as A and B below) for controlling the direction of the motor, since it is not a servo. I've coded the board so that the pins will never be both +ve at the same time (to prevent the following control circuit from short circuiting).

Above is an image of the circuit diagram I've developed to handle the polarity switching that the motor requires, in order for the flow of water through the TRV valve to be increased/decreased on demand. When the wormscrew is fully retracted, the valve is closed, but when it is fully extended, the valve is fully open.
When A is "on" (+ve), B will be "off", resulting in A's NPN transistor (Aₜ) to be on, while B's NPN transistor (Bₜ) stays off. This allows current to flow from A to Ground through the motor making it spin in one direction and vice-versa when the polarity of A and B are swapped.
The transistors are 'S8050'.
The problem
The motor spins fine when connected straight to +ve pin and ground. However in my circuit, it runs much slower and the power supply for the board and motor gets so hot that it almost blows out and it's scalding to touch. Any ideas to why this is happening and how I can stop it would be much appreciated!
I've played around putting some resistors on the base pins of the transistors to reduce the current going through them, but that just makes the motor stop all together. Is the resistance of the circuit too high and so it is pulling too much power, or is the opposite true?
I am a complete noob when it comes to electronics, but I don't want that to stop me making this project for my Dad, so any advice would be greatly received! If I have missed any crucial information, please feel free to ask and I will try my best to supply it.


texts: Is there a convention for the ordering of phases in three-phase power in the US?

texts:
I recently moved my small machine shop to a new location. Both locations had 3-phase power, and I wired up a 3-phase air compressor in both locations.

In both locations, I used the convention of black-red-blue wiring on L1-L2-L3 bus bars in the electrical panel.

But in the new location, the motor is running backward, indicating reversal of two of the wires (or that the previous location was “incorrect”).

I can't find anything online that says L2 should lag L1 by 120°, and L3 should lag L2 by 120°, but is that the convention? Are the mains leading into my panel (new or old) mis-wired? Or did I just make a mistake somewhere?

My specific question: what is the required phase relationship between L1, L2, and L3 (if any)?


texts:
I just bought a few SN74HC595N and they are doing some weird stuff. I was testing them and output just does not come out. I know it's not a problem with my circuit, since I had a couple laying around and have tested them with a simple binary counter. This is it with the ones that work. It's powered from 5V, updated by a custom class running on an ATMega328p, and the resistors are 1kΩ.

If I swap the right register for one of the new ones, something weird happens:

The LEDs driven by the old one are still working, so \$Q_H'\$ is clearly working. But the other outputs \$Q_{A,B,\dots,H}\$ are completely blank. Is this just a clear case of busted output transistors or is there something I'm missing? Because the 10 chips I got are like this, so It's pretty frustrating.
Is there any test I could do to check if this is just dead or if there's some other behavior that has been changed in a recent revision?
The packages are a little different, by the way:

Old one is above, new one is below. Any suggestions would be appreciated.


texts: Multiple simultaneous Interrupts PIC16F88

texts:
I'm new to PIC microcontrollers (I have some experience with Arduino but wanted some "real" experience =P ). I got myself a PIC16F88 and I intend to make a simple robot with two 2 DC motors. Each motor will be independently controlled via PWM.

I want to implement the PWM signals in software (ya I know, quite a good learning experience!).  This microcontroller only has one PWM module, but I would want to do it in software even if it had more.

Without further ado:

What happens when two timer overflow interrupts occur at the same time? Does the controller ignore one? Will they both call the interrupt vector one after another?


texts:
I've been reading up on LED drivers and found some common connection schemes. Yet, I recently came across the following LED driver circuit at this URL:

I tried to find out what exactely was going on here but I do not understand why the LEDs are fed back to the input voltage (usually they are connected to ground). What I understand from the schematic so far:

We have an AC voltage source, this is rectified by diodes D3,D4,D5,D6. CTRL (which sets the current in conjunction to RS2) is set to a fixed level, defined by 1M and 69.8k. SHDN is set to high to enable the device. D2 makes sure that CVIN is constantly charged, thereby keeping VIN enabled (even when there is a zero crossing on the input). OPENLED is pulled up to INTVCC and PWM high enables the device (as well).

Now, the current is driven into L1 (and switched on/off using M1 to achieve a constant current), through D1, through the current sense resistor RS2 (connected to Pins ISP and ISN) and then (and this is the part I really don't get) back to PVIN.

So, actually there's three parts I do not understand:

Why is the string of LEDs not terminated at ground (I have seen this multiple times with other LED drivers and also the application note for this LED driver has a similar connection scheme). What would the voltage before the first LED be (since there is a voltage drop across the 4 LEDs)
What exactely is the purpose of the FB. The datasheet mentions "Voltage Loop Feedback Pin". But I do not understand the use of the transistor and the 392k resistor.
What is the use of RS1 (being 40mR)

It would be really nice if you could shed some light on this specific configuration.

This is the link to the datasheet of the LT3755.


texts: For a project I'm working on, I wanted to use a LED Switch for a 28V load, and the switch itself is rated for 30V, 10A. Even though the switch is within spec, is it good practice to use a switch rated for the voltage you need, and not oversize it (i.e. using a 60V switch for a 28V load)? This is the power supply I am using in case that information is needed. And the load isn't anything specific, it could be anything within the power limit of the supply.


texts: Choice of Wire Gauge for 5v 26A LED Power Line

texts:
I am planning on having a large number of programmable LED strips powered by a 5v 150W supply I got from Digikey.  The LEDs (APA102) will be controlled using an Arduino, which will also be powered by the same supply. The 5v supply will be wired to the LED strips individually.  The total number of strips will be 32 (30-60cm lengths) hanging from the ceiling.  The longest run of the 5v power line will be 10 meters.  The highest current, near the supply, will be 25A.

Do you know what gauge wire I should use for the 5v supply line?

I was thinking of sacrificing a good power cable and having the strips soldered to the cable at various points. Do you think this should work well and safely?

Thanks in advance.


texts: How can an op-amp act as a precision diode?

texts: I read in an article on application of op-amp that it can act as a precision diode. Precision diode is an ideal diode having very much less forward voltage drop. I am not able to understand this concept. Please explain it to me.


texts:
Typically, through-hole LEDs seem to have the cathode (-) side connected to the "anvil" and the annode (+) connected to the "post" (see diagram below).

...But I now have in front of me an LED that does not follow that convention.

MPN: C4SMF-RJF-CT0W0BB1

The light is coming from the annode (+) side.

Note that this LED does not have a "flat spot" as seen in the diagram. The lens is actually ovular instead of round.
The cathode is still the shorter leg, so I assume that convention that is more universal.

As for the anvil/post, why would this one LED be different, and is there any purpose to either convention?


texts: How to determine velocity profile for two stepper motor in robot driving

texts:
A robot has 2 parallel driving wheel. I don't know the friction of the ground surface. However, I can set the acceleration, starting velocity, ending velocity. The velocity profile has to be symmetrical, which has a trapezoidal shape if there's acceleration. If there's no acceleration, the motor starts with the maximum velocity. Though it's possible starting with maximum velocity proved by experiment, I would like to know some theory to make these decision rather than blind testing.

stepper motor specification
motor controller


texts: Why does the current waveform become non-linear in a bridge rectifier?

texts:
This is my bridge rectifier circuit, and I'm trying to understand why the current waveform of the source deforms the way it does when you approach an ideal capacitor. Source V1 is 9VAC.

I simulated the current through V1 for capacitor C1 values from 10uF to 1F, and the current waveform changes from a sinusoidal to a very peaky deformed waveform

Here is a zoomed in trace of the waveforms. The light blue difference between line voltage and voltage at the capacitor:


texts: SEPIC converter : why average secondary inductor is the output current?

texts:
I can't get the reason the why the average secondary inductor current is the output current.
Simulation confirms it's true, as well as documentation.
But I haven't found any clear explanation. Sorry if it seems obvious to you.
Thank you.


texts:
Basic question guys,

I'm looking at replacing a pump motor, and the existing motor is rated for 1.25. My question is simple, is a 1.25 hp rating equivalent to 1/25HP?


texts: Solid State Electronics: Depletion vs Space-Charge region, what's the difference?

texts: I'm studying Solid State Electronics (can't make much of it) but I was wandering what is the difference between space-charge region and depletion region in a diode or in a BJT or in a MOSFET. Are they the same thing? If not, can you give an example of how space-charge region is formed?


texts:
In this Linear Tech App Note 13, page 28, Jim describes:

  A final form of probe is the human finger. Probing the
  circuit with a finger can accentuate desired or undesired
  effects, giving clues that may be useful. The finger can be
  used to introduce stray capacitance to a suspected circuit
  node while observing results on the CRT. Two fingers,
  lightly moistened, can be used to provide an experimental
  resistance path. Some high speed engineers are particularly
  adept at these techniques and can estimate the capacitive
  and resistive effects created with surprising accuracy.

Was he joking? If not, how do the such techniques work in practice to provide accurate estimation? Could anyone describe an actual scenario that those engineers applied such techniques?

The application note, and my question is in regards to low voltage, high speed signals, not mains or high voltage.


texts: Why are the poles of the stator and rotor taken differently in the picture below?

texts: The rotor and stator in the picture below have the same orientation of flux lines yet the are taken as opposite that is flux lines leaving the stator is taken as a South Pole while flux lines leaving the rotor is taken as a North Pole. Why ?


texts:
I want to power a uC project (uC is a STM32, supposed to be powered with 3.3V) over a LiPo battery. Since LiPo's output ranges from 4.2 volts to 3.7 volts, I feel unsure whether to use a step-down or a step-up converter, i.e. step-down or a step-up.

In the data sheet of the TPS63031, I saw in one characteristic (at the first page) an example of 3.3 V out for 3.6 V in, but I couldn't understand if this step-up converter, would also 'step-down' the maximum 4.2 volts to 3.3 volts.

Maybe I just misunderstood how DC-DC converters can be operated, since I thought for up- or down-converters, you always have to be significantly below your target voltage.

Thank you all very much :)


texts: STM32, mass storage device. how to properly erase memory sectors?

texts:
I want to organize a USB stick based on STM32F105RBT + AT45DB041.
Problem: after reconnecting the device to a PC, windows7 asks to format the disk.
Problem identification algorithm:

Connect to PC
Format the USB flash drive (formatting is completed successfully)
Write any file to a USB flash drive
Disconnect the USB flash drive from the PC
Connect device to PC
Result: Windows asks to format the USB flash drive

Everything works fine if:
Size of file (-files) <= 12KB
(After reconnecting the USB flash drive to the PC, the file opens successfully, the data is not damaged)
SPI memory AT45DB041 has a total of 2048 pages of 264 bytes each. Writing / reading is performed at 256 bytes per page. Writing a 512 byte block requires two pages of memory.
I am sure that the problem is in the procedure for erasing memory sectors, in the STORAGE_Write_FS function, but I don’t understand where I went wrong?
    int8_t STORAGE_Write_FS(uint8_t lun, uint8_t *buf, uint32_t blk_addr, uint16_t blk_len)
    {
      /* USER CODE BEGIN 7 */
      AT45dbxx_ErasePage(blk_addr*2);
      AT45dbxx_ErasePage(blk_addr*2+1);
      AT45dbxx_WritePage(buf, 256, (uint16_t)blk_addr*2);
      AT45dbxx_WritePage(buf+256, 256, (uint16_t)blk_addr*2+1);
      return (USBD_OK);

      /* USER CODE END 7 */
    }

void AT45dbxx_ErasePage(uint16_t page)
{
    page = page << AT45dbxx.Shift; // AT45dbxx.Shift = 9 For 264 byte per page
    AT45dbxx_Resume();
    AT45dbxx_WaitBusy();
    HAL_GPIO_WritePin(_45DBXX_CS_GPIO,_45DBXX_CS_PIN,GPIO_PIN_RESET);
    AT45dbxx_Spi(AT45DB_PGERASE); // CMD 0x81
    AT45dbxx_Spi((page >> 16) & 0xff);
    AT45dbxx_Spi((page >> 8) & 0xff);
    AT45dbxx_Spi(page & 0xff);
    HAL_GPIO_WritePin(_45DBXX_CS_GPIO,_45DBXX_CS_PIN,GPIO_PIN_SET);
    AT45dbxx_WaitBusy();
}

void AT45dbxx_WritePage(uint8_t *Data,uint16_t len,uint16_t page)
{
    page = page << AT45dbxx.Shift;  // AT45dbxx.Shift = 9 For 264 byte per page
    AT45dbxx_Resume();
    AT45dbxx_WaitBusy();
    HAL_GPIO_WritePin(_45DBXX_CS_GPIO,_45DBXX_CS_PIN,GPIO_PIN_RESET);
    AT45dbxx_Spi(AT45DB_MNTHRUBF1);  // CMD 0x82
    AT45dbxx_Spi((page >> 16) & 0xff);
    AT45dbxx_Spi((page >> 8) & 0xff);
    AT45dbxx_Spi(page & 0xff);
    HAL_SPI_Transmit(&_45DBXX_SPI,Data,len,100);
    HAL_GPIO_WritePin(_45DBXX_CS_GPIO,_45DBXX_CS_PIN,GPIO_PIN_SET);
    AT45dbxx_WaitBusy();
}

Functions for working with memory work correctly in the entire range of pages. The flash drive is formatted using windows before recording.


texts: LTE 4G simultaneous connected devices for one cell site

texts:
I'm trying to find out how many simultaneous connected devices can handle a typical LTE 4G or 3G public cell site.

I know my question sounds broad, but i'am developping an mobile application which is used during a concert, and can be used by hundred to thousand of people in the same place. The application hold a web socket connection to the server, which allows devices to receive descending messages. Messages are short (less than 1,000 octets) and only sent every 2 minutes (but sent to every devices at the same time).
I've already successfully tested it with 500 devices. But I need to know what is the hypothetical limit.

Is it 1,000 devices, 10,000 devices? And where can I found elements of responses?

I was not able to find any article or website talking about this limit. Is there a limit? Or connection bandwith is always shared between the connected devices without any limit?

Thank you

Edit:
I am aware that in dense area, network operators "simply" reduce cell radius and deploy more base station, but the number of cells in an area is usually chosen for a "normal usage": Something like : "One people take its phone, look something for several seconds, and then close it and put it back in his pocket for 10 min". So that way, even if it's a very large crowd, the usage is not very high.
But my scenario is different : I will ask to a crowd of 3000 people to use their phone at the same time.

Will the cell site will be able to handle it? Or will it be a massive failure because half of user will have no connection?
This is what i am trying to answer.
(Note that the web server will be powerful enough)


texts:
I would like to ask if packet loss in p2p LAN is a normal behavior in LAN.

And now in more details:

I am connecting PC to target board with TI's chip and LAN9221 controller.
I am doing a ping-pong test, with udp protocol:

PC is sending the first packet.
target wait for packet, and on receive, it send the same packet back to PC.
PC wait, and on receiving send a new packet (increment data in the UDP packet), and so on....

Running the ping-pong test, I see that once in a while the target did not receive the packet correctly. It is easy to notice the failure because the ping-pong test stops whenever one of the side did not receive a packet.
When the failure happens, I see that the first bytes the target detected is actually the the 5th byte that the PC send (I see in WIRESHARK).

I also observed that these failures always happens when a another packet is sent about the same time from PC as the packet from the test , as if a collision happened.

If I add firewall rules, which take care that only the ping-pong packets shall be delivered in the LAN, then there is no failure at all.

So, the question is if the collision failures is a normal behavior in LAN ?

EDIT: seems the problem was related to (sw) driver error, not to collision, thank you for the solutions, which emphasized that in p2p there are no collisions.

Thank you!


texts: I always thought that the COM port on a classic PC implements the RS-232C serial interface.  But I just noticed that the COM port is a DB-25, whereas RS-232C only uses 8 or 9 ports, and therefore tends to use DE-9.  Does the DB-25 serial port implement RS-232C, or does it implement some other serial interface, and if so, what standard is this interface?


texts: Measure resistance (make connection) between array of points

texts:
I have array of connectors where I will plug in various types of resistors, I would like to be able to connect to each of the points as addresses and measure resistance between these points. Here is an illustration to make it clearer:

I have used serial encoders to pass I/O data to a array of points, but this is a bit different. The resistance part in this question is irrelevant, question is more about connecting two points together. What IC could be relevant, what should I search for to learn about this topic? I have heard a term 'multiplexing' - would that be relevant to this problem ?


texts: What's the cheapest/fastest way to put a potentiometer on an ac fan?

texts:
I'd like to control a couple ac fans running on mains voltage (US) using a potentiometer. I believe they're in parallel but I'm not certain. Each fan is rated at 15/13 watts @ 115 volts.
What's the best way to do this, preferably by dismantling broken appliances?


texts: DC Power supply voltage swing when load turns on

texts:
Below is flow diagram of my pcb power side, the issue is when relay turn on a 12V 30 watt heater element the voltage drops (or swing) and stay down until load disables. This drop cause issue on my amplifier circuit and I want to know why other regulator dont regulate the voltage back to normal. (I have tried external AC/DC converter with Rigol DL3000 DC load and voltage drops too)
The most interesting is this does happen some time and some time by just turning on and off unit it goes away but mostly is over there.
Note: 5V buck  regulator below is typo

Below graph shows' the input supply when load turns on and off

Below graph is 12V buck boost regulator (Different recording)

External Supply :  RACM230-24SG Output
24V 9.58A 80 ~ 264 VAC, 120 ~ 370 VDC Input
Let me know if I you need more info


texts: I have a 12-bit resolution high speed pipelined ADC on PIC24FJ128GC010 micro-controller. It has an internal input [from an another peripheral internal to the chip]. Now, I would like to add another analog input to the ADC externally [to one of the ANx pins]. Can I achieve this with very little noise? What care must be taken in this case?


texts:
I was just simulating the quantization behavior of ADCs of different bits, on data sampled by a 24-bit ADC. What I noticed that as we go towards ADCs with less bits  a DC bias in the signal becomes more and more evident, with maximum value at 1 bit-ADC. The reason for this is, acc. to what I think, is that there are different number of digital codes representing positive and negative analog voltage values, for example in case of 8-bit ADC, we have 1-127(127 digital codes) for positive, 0 for 0 voltage, and -1 to -128(128 digital codes) for negative values, so negative voltages have one more digital code for them. and this effect becomes very clear with 1 bit ADC, where we have only digital codes of 0 and -1, so the sampled signal will always have negative bias,
Please see the video below where I do the simulation and you can clearly see the signal moving downwards as I decrease the number of bits, The ADC voltage range is +50 to -50 units. So at 1-bit, I only have 0 and -50 samples and a clear negative DC offset.

https://drive.google.com/open?id=1EyNR13oIShwoWfcd1FWQgl8tJhFvIaWN

So my question, how much of an issue is this ? I can simply remove the DC offset by using a high pass filter in Digital domain, are there any other concerns and ways in which my signal is affected ? Is this a very common issue and what else can I do to remove this DC offset ? Are there ADCs which have equal number of digital codes for positive and negative voltages ? What are they called ?


texts: Is there any difference between using a decoder for the alu op code vs using a multiplexer?

texts:
I am a programming student studying electrical engineering fundamentals on the side. I have come across two different methods for getting the result of an operation onto the bus.

A decoder accepts the op code. Each operation has an enabler attached to the output. All operations are performed and the results are stored in the enablers. The enabler that is selected gives the output of the operation.
The output of each operation provides the input for a multiplexer. The op code is the selection input for the multiplexer. The output of the multiplexer is then put onto the bus.

Is there anything functionally different between these two variants? What are the advantages and disadvantages?


texts: Skew planar wheel antenna - is it circularly polarised or not?

texts:
'Skew planar wheel' antennas are popular for uhf. They are often described as circularly polarised, but I don't see how they would be. Are they instead just a mixed polarisation omnidirectional antenna ?

If they are circularly polarised, where would the equivalent 90 degree phase shift come from, as used in a normal circularly polarised antenna.

This account of testing this antenna indicated strong circular polarisation:

  The results showed that this Skew-Planar is strongly right-hand circularly polarized, as expected.  At my end, Clare's signal was S8 with his right-hand helix, and dropped to S1 when he switched to his left-hand helix.

http://www.ve3byt.com/SkewPlanarAntenna/

Practical designs discussed here, also noteworthy is that the polarization is apparently determined by the direction of lean(skew?) of the four elements : http://www.slvrc.org/902band/skewplanar.htm


texts: How to configure USB OTG as power supply

texts:
I have an ARM computer with an USB 2.0 OTG port, and I want to use it as 5V 100mA power supply (to drive a couple of leds). However, when I connect a load (LED+resistor) via an OTG cable, the power is not supplied constantly. The LED blinks shortly 4 or 5 times, and then shuts down until I replug the OTG cable. Additionally, dmesg command reports:

musb-hdrc: configured as A device timeout

I suppose that means the OTG host supplied the power for a short time, but could not detect a USB slave on the bus and powered off the connector.

What does it take to trick the OTG host controller to believe there is a connected slave, so it keeps supplying power? Is this possible to achieve with a simple schematic, or is it absolutely necessary to implement the USB protocol? Is there a chip with low power consumption I could use for this?


texts: Capacitors choice for MHz resonance circuit

texts:
I am implementing a resonance circuit (for wireless charging) in MHz frequency (\$5-10~MHz\$) , and now, I am looking for suitable capacitors. The peak voltages and current through the capacitors are around \$350~V\$, and \$12~A\$. I know that I must go with low loss capacitors (\$NP0\$). In addition to the voltage rating, ESR will set a thermal limit for maximum current.

But I am not sure what are the critical parameters that I should look for.

For example, consider the following two from the same manufacturer with very similar specs:

  VJ1808A101KXHAT4X MLCC, SMD/SMT 1808 NP0 100PF 3KV 10%

  VJ1111D101JXRAJ   MLCC - SMD/SMT 1111 100pF 1500V C0G 5% HI FREQ

My feeling is that the first one may not suitable for the high-power application, but all look similar in the specifications. Just that the former has more information about the ESR and Q-factor in the datasheet, and also specifically mentioned that it is suitable for RF power applications.

But all the MLCC (NP0) manufactures do not have this information.

In general, (Not specifically for the above two. Two examples are just for a comparison) What should I look for when deciding if a capacitor suit for high-power application (even if it is NP0 and sufficient voltage rating). For now, I am paying attention to the size of the cap.

Additional info: as the application is a high-Q resonance circuit, harmonics will be very small.


texts:
I am a student of Electronics and Telecommunication. For personal projects and learning, I would like to learn how to build embedded systems (like the once that we see on those cool projects). So here is the catch, my college will teach the basics of microcontroller in 3rd year, and that too Intel 8086. I want to learn ARM microcontrollers like how do you build boards with sensors integrated into them and how to communicate between multiple processors. I have no idea about any of those technical stuff (like I2C, SPI, UART, Clock, PWM, etc.). It's not like I have never heard about them, but I am sure I don't know enough to start building an embedded system. I have worked with Arduino and RPi (this has to count).
After reading a few blogs on Microcontrollers, I know datasheets are used to figure out the value of the resistor, capacitor, and other things. And this brings me to my question again: how do you integrate other sensors with the main processors.

Side note: I know this not the best way to learn things like jumping directly on to an advance topic without knowing the basic, but I need to learn this right now.

I know many people have asked questions on "how to get started with microcontrollers," and I have read them, but none of them answered what I wanted to know.
I am new here, so please don't throw this question out.


texts: Could audio line-out (from a PC) be used to flash an Atmel or PIC?

texts:
First question is probably how much power can standard PC line-out provide?

Unfortunately I can't seem to find it easily via Google yet, or how to calculate it and from what.

Otherwise, are there any more or less obvious arguments against, that I don't realize being an electronics newbie?

Thanks for any help.


texts: Multiple power supplies in home-made circuit

texts:
I'm planning to build an ebb-and-flow hydroponic system (nope, not for weed) and as my electronics skills are close to zero, I'm trying to put things together before soldering anything. I'm a decent software developer, so coding is not the issue here. I know it's ambitious, but well... I want to learn :)

I'm facing power problems and I'm not sure about my solution.

My set-up includes :
- a barebone arduino (5v, 70mA)
- a submersible pump (12v, 3W, 250mA), controlled by an arduino pin and a mosfet
- a RTC DS1307 (2mA)

I made these working together, using USB for the arduino, and a 12v battery for the pump.
To achieve a definitive set-up, I plan to use a laptop charger (15v, around 4A) and to split its output to 2 home-made lm2576 circuits (12v and 5v, both rated for an overkill 3A).

Next step would be power LEDs... and I'm getting even less confident about it.
These LEDs look like what I need : 3W, warm white (forward voltage : 3.5-4.5v max, 750mA max).

I know LEDs need constant current, and among many others, this circuit seems simple and efficient enough.

If I understand everything, 1 LED would require 4V, 2 LEDs in series : 8V, and so on... Current must stay at 750mA (max). I plan to use only one LED as I don't think my basil will require more, so I'll stick to 4V.

Here are all my search results, but I still don't know if these circuits will work together :

15v laptop charger
    \ lm2576 (12v) --> pump
    \ lm2576 (5v) --> ICs
                              \-> constant-current supply (0.5V dropout) --> 1 LED (4.5V max)

Arduino will turn the LED on and off through (I guess) another mosfet, just as the pump.

So there I am, humbly asking for a educated eye on these questions...

Thanks in advance,
D


texts: Why my single-phase induction motor's velocity decreases after 100Hz?

texts:
I have made a single-phase inverter with control V/F using Freescale S08P and IRAMS. However when the frequency of 100hz  passes the motor decreases the velocity.
Some problem with my system or V/F is really limited?

Data:

PWM - 15Khz

Motor single-phase permanent capacitor (without it) - 1/8 HP or 1/6 HP (unreadable)

Modulation:

$$V_{Main} = \frac{V_{dc}}{2} + Vf * sin(wt)$$

$$V_{Aux} = \frac{V_{dc}}{2} + Vf * cos(wt)$$

$$V_C = \frac{Vdc}{2}$$


texts: TMP36 sensor temperature spiked to 200+ (actual temperature of the component)

texts:
I've been learning Arduino and playing with the TMP36 sensor, trying to read temperature of my room. To do that I've assembled a super-easy scheme just to read the values to Serial monitor, something very similar to the following pic.

The problem is that silly me inserted the sensor facing the wrong way (not how it is depicted in the picture above but the other way around) and the temperature of the sensor went to 200+C. The actual component temperature also spiked since and I actually burnt my fingers when I touched it. I'm struggling to understand why this happened.
Now obviously the problem is caused by the fact that power went through the pin that was supposed to be ground, however why did the temperature spike? Does this have something to do with the internal structure of the TMP36 sensor or is it something fundamental to this process that I don't understand?


texts: Altium: Designing a switch with 3 pads, 2 positions but only single contact

texts:
I want to design a switch which commutes a single contact between 2 pins.
I have drawn a schematic with 2 pins.

IRL, the switch has 3 pads, one is unconnected.

I can't associate the physical design to the logical one because they don't have the same number of pads/pins.

How can I do this?

Thanks.


texts: How can i connect laptop webcam RJ E85792 CK 77 94v-0 wire to usb cable

texts:
Camera wire colours

Unshield
Green
Yellow
Orange
Red
White
Brown
Unshield


texts:
In a project I'm working on, there is a need to supply satellite navigation receiver with signal from very precise external oscillator. Device, part of which receiver is, should be able to convert oscillator's 5 MHz sine wave to 10 MHz sine wave required by receiver.

What are the ways to do this conversion, without significantly reducing signal quality?

Looking for any guidance, as I know nothing about this kind of analog electronics.

Oscillator example: link.


texts: I have a question regarding the base resistor value for a transistor. I am already familiar with finding this value (using the min hfe value and using Ohms law to find the desired resistance) but I was wondering if it was also necessary to multiply the base current by the MAX hfe value to ensure that it does not exceed the transistors maximum collector current rating? Is this necessary to do, or does the transistor have a way of regulating itself when the collector current is above its max? Thanks!


texts: How can 8.4V stacked super-capacitors (EDLC) not require balancing?

texts:
I've recently seen 8.4V stacked super-capacitors which advertise themselves as "not requiring any balancing".  Namely, the 196HVC series from Vishay.

How can this be true?  Even if the cells are extremely well matched, wouldn't wear and tear eventually cause a sufficiently large mismatch to require balancing after all?

EDIT:

I actually bought some of these to try them out, and it turns out the cells slowly discharge from 8.4V (maximum voltage) down to around 7.8V over the course of 12hrs or so. Afterwards, the voltage stays at 7.8V for a very long time (i.e. months). This most certainly points to an internally balancing mechanism, using SAB MOSFETs, clamping diodes, or something else.

The verdict is still out as to how these particular super-capacitors implement the balancing.


texts: How to make the electromagnet of a magnetic-levitator?

texts:
I saw pictures of magnetic-levitators on the internet. That's amusing.

I wanted to make one of those. So I started searching in Google.

And I found out that these devices have a big electromagnet which is controlled by a micro controller such as AVR or by a passive circuit using an op-amp.

My question is about their electromagnet:

How to make the electromagnet that it can give a force of 10N ( be able to hold 1kg )?
for example :

-What kind of wire to use to get the most efficiency?
-how many meters wire to use?
-which material to use for the core to get the most efficiency?
-How many turns ?
-what diameter for the core?


texts: What is the meaning of 16 Bit instruction format in 8 bit microcontroller?

texts: While studying about PIC18 I came across this weird thing. I understand what instruction format means and I also know what '8 bit' means in case of 8 bit Microcontroller. But my doubt is that, "If the Microcontroller is having  8bit architecture then how does it have 16 bit instruction format?"


texts: Doubt about an exercise on leapfrog filter

texts:
I'm asked to find the order, type, number of poles and zeroes and the dc gain of the following filter:

Since the output of each integrator is the input both of the following and the preceding integrators, this filter is a leapfrog filter. In particular, I know from the theory that it is a low-pass filter implementing an all-pole low-pass ladder. As a consequence, there are no zeroes. The number of poles (and thus the order of the filter) is given by the number of integrators: 4.
I then have this equivalent circuit:

Now, I draw the corresponding flowgraph:

Considering the red loop, then by multiplying all the incoming branches by R and dividing all the outcoming branches by R, I can transform the currents into voltages. In particular, the state variables I2 and I4 become V2' and V4', respectively.

Question: is there an error in the exercise? Indeed, if you consider for example the output of the second integrator V2':

according to my flowgraph, V2' should go directly (+1) as input of the following integrator, and should be swapped (-1) at the input of the preceding integrator;
according to the exercise scheme, V2' gets swapped at the input of the following integrator, and goes directly (without swapping) at the input of the preceding integrator.


texts: How do you measure a distance along the Z axis in Altium?

texts:
If you hit CTRL+M, it's easy to take a measurement along the x or y axis. If you want to measure along the Z axis (for instance, the height of a 3D body), how do you do it?

I googled "measure the along the Z axis altium", "measure standoff height altium", and did the same searches here. No luck.

Thank you in advance for anyone who can help this altium beginner.


texts: How to calculate accurate temperature based on a sensor

texts:
I am writting a program which gets temperature from a QMC5883L sensor.
The sensors contains:
TOUT[7:0] and TOUT[15:8]

and it says that The temperature coefficient is about 100 LSB/℃.
My program looks like this:
int magnetometer_get_temperature() {
    uint16_t buff[2];
    magnetometer_read(MAGNETOMETR_TEMPERATURE_LSB_REGISTER, buff, 2);
    return ((int)(buff[1] | buff[0]))/100;
}

It does not return a correct temperature even after some hours in 23℃.
How to receive good temperature?

Edit after recive a hint.
This should be a correct, right?
int magnetometer_get_temperature() {
    uint8_t buff[2];
    magnetometer_read(MAGNETOMETR_TEMPERATURE_LSB_REGISTER, buff, 2);

    int result = (int) ((buff[1] << 8) | buff[0]);

    return (int) (result / 100) + SOME_ABSOLUTE_VALUE;
}


texts: Is this transistor configuration considered "Push-Pull"?

texts:
I have read that the output stages of some operational amplifiers use push-pull transistor configurations. I was looking over the datasheet for the LM741 and was wondering if this was one of those instances?

Q14 and Q20 appear to be connected together in a push-pull manner, but their bases are driven independently, or so it seems.


texts: EFT Simulator Duration Time Setting / IEC 61000-4-4 / KeyTek CE 40

texts:
I've got an antique EFT simulator, it's a KeyTek CE-40.  I'm debugging a device for EFT as per EN 61000-4-4.  The manufacturer doesn't provide support for the device anymore and I don't have a product manual.

As per the standard, the burst duration should be 15 ms.

When I go to the device burst duration setting, I see some weird time symbol that is not in "ms" -- picture is attached.

Does anyone know what the time symbol they are showing there is?  Is it a microsecond?

Anyone from the early 90s have any ideas?


texts: How difficult is it to build a device that can read credit card data from the mag-stripe...from scratch?

texts:
I was wondering about the feasibility and difficulty of building a device that could read the information the magnetic stripe on a credit card. I think I understand the basic principles, but I'm not clear on how the audio signal is transformed My understanding of the basic functionality of something like the card reader manufactured by Square:

https://www.google.com/patents/US8231055

My understanding of it is this:

The magnetic strip of a credit card is passed through a Tape Head, like those used on a tape deck.

This produces and audible signal, depending on the shape/encoded bits on the strip. There is a specific name for this effect, and I had a wikipedia page on it, but I've lost track of it (If anyone knows who discovered this, or what this is called, I would appreciate it. I think there was also a patent on it)

In the case of Square, the part of the peripheral which connects into the Headphone audio jack has a microphone that picks up the sound? Or is it the microphone on the mobile device? Either way, this signal is picked up, and somehow decrypted back into whatever raw data it encodes (Cardholder name, card #, expiration date, etc,etc)

This data goes into some software/API.

I've seen a few scattered resources on youtube/blogs, but nothing really comprehensive about building this from scratch. Is it even possible? I'm a hobbyist without too much knowledge of EE, so please tell me if I'm horribly wrong about anything I've said so far.

My main questions are this:

How do the magnetic grooves within the Mag Strip get converted to an audible signal - is there a name for this effect?
Where would someone source a Tape Head such as the ones used by Square in the first version of their Card-Reader? Anywhere that they can be purchased online, or do I have to pull apart old Tape Decks?
How is the auditory signal transformed from a card swipe to digits? Is there a formula that is applied to parts of the waveform? Is there any software available? (I can't imagine there would be any legitimate third-party non-enterprise entities fofering this functionality...)

Would all of this be easier to do by just buying a generic Credit Card reader from Ebay? Does every card-read manufacturer have their own card-audio-signal transformation software bundled into their device somewhere?


texts: Displacement strategy for (Computer) Cache

texts:
Here, under displacement strategies, the following is written (Unfortunately, only in German available):

Laszlo Belady's method of displacing the memory area that will not be
accessed for the longest time is optimal. However, it is applicable
only when the complete program flow is known in advance (i.e., it is a
so-called offline procedure, in contrast to FIFO and LRU, which are
online procedures). However, the program flow is almost never known in
advance; therefore, the optimal procedure cannot be used in practice.
However, the optimal algorithm can serve as a comparison for other
procedures.

I wonder why the program has to be known in advance to make this routine an optimal method. Sure, I understand, that, sometimes, when a memory not used for a while, will be thrown out but needed immediately afterwards, is not optimal but this behaviour is the most reasonable and hence, "optimal"? It's actually not about the wording, I really wonder this method isn't as good as it seems.


texts: sequential circuits; clocked SR flip-flop

texts:
I'm learning about sequential logic and am wondering about the behavior of a clocked SR flip-flop.

If R=S=0, then the AND gates evaluate to 0. In that case, and if the recurrent inputs to the NOR gates are initially 0, then both evaluate to 1. But then the recurrent inputs will switch the output of the NOR gates to 0, which will then cause the NOR gates to output 1 again, and so on. Given the speed of electricity, wouldn't you end up with many oscillations of the output of this circuit within the space of a half clock tick? If what I'm think makes sense, does that mean that such a case must be avoided by initializing the circuit?


texts:
My code is here:

#include <91x_lib.h>
UART_InitTypeDef UART_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;

void SCU_Configuration(void);
void GPIO_Configuration(void);

u8 i;
u8 name[]="ABCDE";
u8 c;

main()
{
    c=0; i=5;
    SCU_Configuration();
    GPIO_Configuration();
    UART_DeInit(UART0);
    UART_InitStructure.UART_WordLength = UART_WordLength_8D;
    UART_InitStructure.UART_StopBits = UART_StopBits_1;
    UART_InitStructure.UART_Parity = UART_Parity_No ;
    UART_InitStructure.UART_BaudRate = 9600;
    UART_InitStructure.UART_HardwareFlowControl = UART_HardwareFlowControl_None;
    UART_InitStructure.UART_Mode = UART_Mode_Tx;
    UART_InitStructure.UART_FIFO = UART_FIFO_Disable;
    //UART_InitStructure.UART_TxFIFOLevel = UART_FIFOLevel_1_2;
    //UART_InitStructure.UART_RxFIFOLevel = UART_FIFOLevel_1_2;

    UART_Init(UART0, &UART_InitStructure);

    UART_ITConfig(UART0, UART_IT_Receive    , DISABLE);
    UART_ITConfig(UART0, UART_IT_Transmit   , DISABLE);

    UART_Cmd(UART0, ENABLE);

    while(i--)
    {
        UART_SendData(UART0, name[c++]);
        while(UART_GetFlagStatus(UART0, UART_FLAG_TxFIFOFull) != RESET);
    }
}

void SCU_Configuration(void)
{
    SCU_MCLKSourceConfig(SCU_MCLK_OSC);
    SCU_PLLFactorsConfig(192, 25, 2);
    SCU_PLLCmd(ENABLE);
    SCU_RCLKDivisorConfig(SCU_RCLK_Div1); /* RCLK @96Mhz */
    SCU_HCLKDivisorConfig(SCU_HCLK_Div1); /* AHB @96Mhz */
    SCU_FMICLKDivisorConfig(SCU_FMICLK_Div1);/* FMI @96Mhz */
    SCU_PCLKDivisorConfig(SCU_PCLK_Div2); /* APB @48Mhz */
    SCU_MCLKSourceConfig(SCU_MCLK_PLL);  /* MCLK @96Mhz */
    SCU_BRCLKDivisorConfig(SCU_BRCLK_Div2 );

    SCU_APBPeriphClockConfig(__UART0, ENABLE);
    SCU_APBPeriphClockConfig(__GPIO3, ENABLE);
}

void GPIO_Configuration(void)
{
    GPIO_DeInit(GPIO3);

    GPIO_InitStructure.GPIO_Direction = GPIO_PinOutput;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
    GPIO_InitStructure.GPIO_Type = GPIO_Type_OpenCollector ;
    GPIO_InitStructure.GPIO_Alternate = GPIO_OutputAlt3  ;
    GPIO_Init (GPIO3, &GPIO_InitStructure);

    GPIO_InitStructure.GPIO_Direction = GPIO_PinInput;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
    GPIO_InitStructure.GPIO_IPInputConnected = GPIO_IPInputConnected_Enable;
    GPIO_InitStructure.GPIO_Alternate = GPIO_InputAlt1  ;
    GPIO_Init (GPIO3, &GPIO_InitStructure);
}

I thought that I did everthing right but I couldn't see on serial window.
I use MCBSTR9 board.
why?


texts: What does the schematic for a 5 to 1 multiplexer look like

texts: I'm having a hard time grasping the concept of a 5-to-1 mux. How can you have 5 inputs if you use 2-input AND gates?


texts: I read a statement in my textbook-" The short circuit current of the externally-excited 3phase induction generator is limited" which I am unable to understand. Kindly help


texts: Does anyone know this LiFePO4-battery cell? (40138-type?)

texts:
My first question on StackExchange - I was not able to find sufficient information anywhere else, so far.

I got a bunch (~150) of used Li-Ion battery cells (see picture 1). Chemistry is LiFePO4; cell type seems to be 40138 (40mm diameter, 138mm length without connector screws); imprint on cell says "9 A 0 5 - H"; barcode reads "4BF1M331-0720"; the batteries come from electric go-carts and weight is ca. 360g +/- 5g.

Unfortunately, I have no reliable information about these battery cells concerning capacity, nominal/(dis-)charge voltage etc. I was told, the cells are not produced any longer; the follow-up model is blue.

So, my question is: Does anyone out there know exactly this battery cells and can provide reliable specifications - perhaps even a data-sheet?

I started to characterize each single cell using a battery tester and a tailored test procedure, but the first cells show highly deviating results. Since I found also a lot of different specifications online about similar (but not the same) cells, I would like to assure myself with reliable information.

Thanks a lot!


texts: Identifying strange burnt resistor color code

texts:
I'm trying to figure out the resistance of a burnt resistor in the PCB of a Hoover FD22G 011 (a cordless vacuum cleaner, with rotating brush; should be the same as the Deik ZB1516, which is the actual code on the PCB).

The resistor is marked as R27 (so it should indeed a resistor and not a similar-looking component), is between the negative battery terminal (B-) and the negative brush (not vacuum!) motor connector (SB-). It's ~4.5 mm in diameter, so it should be a 1 W resistor.

Despite being burnt (it left some horrible black marks on the PCB, plus the usual burnt resistor smell), some color bands are still visible. I'm quite certain about the black on the left, the red on the right, and I'm decently confident about the gold, second from right.

However, to me this doesn't make much sense, as AFAIK black cannot be neither the first nor the last band in a resistor! Same as the gold one - how can it be second or second to last?

To try to investigate this further, I tried to scratch a bit over the wire to measure the resistance between a terminal and several different windings. Bizarrely, I found very small resistance (under 0.2 Ω per winding, and I don't even know if I should trust my multimeter for such small values), which seems to me quite strange - such a big beast of resistance to introduce a minimum resistance on a DC motor? Doubly bizarre if we think that the crude contacts that bring the current from this PCB down to the brush will introduce more resistance than this...

Any idea?

Update: forgot to say, there's a similar, non burnt resistor in the circuit:

Sorry for the much lower quality photo, I don't have my camera with me now; the colors are a bit altered by the phone camera, but here the rings are definitely black, yellow, violet, silver and (most probably) brown.

The position in the circuit seems similar (it's between the negative battery terminal and the negative fan motor wire), so we can suppose it's a current sensing/limiting resistor as well, but unfortunately it isn't the same resistor - the power rating is lower for sure, as it's a little shorter and thinner (it's ~4 mm of diameter). However, this still sports:

the initial black ring (so, it's not that it's charred in the burnt resistor) - so, maybe it's actually a leading zero?; in that case, this would make it a 0.47 Ω  ± 1%;
the shining ring, that here is clearly silver;
the final ring, which is most probably brown, and it may be compatible with the orange-ish tint of the last ring of the burnt resistor.


texts: Question on 3DS power adapters, minor voltage difference

texts:
I am going to be traveling overseas and bringing my Nintendo 3DS which the adapter outputs DC 4.6V 900mA.

I found an unofficial USB cable to charge it and I was curious if the minor variance in the voltage would cause any issue. Say if I use an iPad 5.2V charger or the iPhone 5V one, being I have them and they support 240V input.

Thank you!


texts: Clamp multimeter RMS current measurement, AC versus DC confusion

texts:
This question doesn't relate to a specific meter, I am using AMPROBE AMP-220 manufactured by Beha-Amprobe. I believe am an experienced engineer but only in the digital world, not really in power and AC field.

I am apparently confused by understanding the current measurement, specifically the difference in the three measurement functions:

AC A
DC A
DC+AC A

The circuit under test is a 1200VA/60Hz transformer with two 37Vrms secondary coils sharing one wire (center tap), also called 37V/0/37V.

simulate this circuit – Schematic created using CircuitLab

My calculations of expected current is I = Urms/R; that is I = 37Vrms/1.6 Ohms = 23.125 Amps

I do see this current... but on 'unexpected' meter setting. I was planning to use the AC setting, but the current is on DC+AC setting.

Clamp meter is properly aligned with the wire. Can someone please in layman terms explain me why I measured these values:

AC setting shows 9.7A
DC setting shows 20.5A
DC+AC setting shows 22.95A (closest to my calculation)

Thank you for clarifying this. While my circuit currently has high power resistor to test the newly purchased clamp meter, the goal is to have lead-acid battery instead and to measure the Irms charging current. Which setting of the clamp meter is correct to measure this charging current?


texts: Non white lines on 1920x180 LVDS controlled TFT

texts:
We are integrating a LVDS 27" 1920x1080 panel with a commercial DVI to LVDS controller board.
We have a PC, that has a DVI output, and we connect it to the Video controller.
The video controller it is 12V powered, and has a 350mm LVDS cable connected to the TFT. This LVDS cable it is a good quality one, has a protective earth screen, and it is connected to the ground on the video controller. All the LVDS pairs are correctly twisted.
The backlight of the TFT has an external DC/DC converter, that provides the current to the backlight (the leds of the backlight of the display had a different connector).
We have the screen on portrait mode (turned 90º).
What it is happening us it is that sometimes, when we switch on the system, we have some white vertical lines on the screen. There are not real vertical lines, it is like a ghosting effect. From my point of view it looks like a scanning error, so the pictures are blurred because some vertical lines are not drawn on their right position.
This effect lasts until we switch off the video controller and the TFT for about 10 seconds. After waitint, we are able to provide again power to the system and it starts working again.
When this happens, we are able to see this effect with the "OSD Video controller info" that appears for some seconds. It allways shows the text 1920x180 60Hz, but this text it is not correctly shown when this problems arises. So, we think that the problem it is not caused by the PC.
We have tried to reproduce the problem switching off and on the complete system using a relay for hundreds of times, or changing the position of the cables, without being  lucky enough to be able to reproduce it.
We have also tried to remove the protective earth on the LVDS cable, or to make this cable longer, without being  lucky enough to be able to reproduce it.
Any suggestion of what it is happening well be very helpful!
As a picture it is a lot better than a thousand works, please have some reference pictures:


texts:
I have downloaded the Spice file for the TLV9062 here. I have now created a custom symbol LTV9062 that lives in my AutoGenerated folder and links to the TLV9062.cir file for the Spice model.

When I make a schematic it runs fine on the original machine but won't work on any other computer because the folder path is different for the symbol and the circuit. Is there some way I can include this symbol and circuit such that it takes it from the same directory as my schematic?

What I want to do is to be able to zip my schematic and all custom circuits that it uses into a single folder. When I email it to someone I want them to be able to run the schematic without having to relink all these parts.

I tried looking at libraries but am still confused.


texts: Principles for premature failure analysis of PCB tracks and vias

texts:
I have just given a task to implement a setup to detect whether or not a track or via on a PCB is going to fail in any time in the future. The PCBs are supposed to be used in harsh environment e.g. somewhere with a lot of thermal cycles (ambient temperature to something near 100 or even higher degrees Celsius.

For the simulation, I have access to a smart oven which I can give thermal profiles to stress these PCBs for weeks or even possibly months.

My question is, what exactly should I focus to measure. My initial guess will be inducing a fixed and accurate current into the tracks and measure the voltage drop. I would guess if the tracks and vias are being aged (I think for vias it is called barrel fatigue?), the most obvious characteristic to change would be their resistance. But I have a feeling that this is not necessary the only thing that I should rely on.

What would be the contribution of other characteristics such as capacitance and inductance? are they going to be as important as the resistance?

I want to perform very accurate LCR measurement on a brand new DUT PCB and in the process of the stressing in the oven, I measure changes and compare them with the original measurements which I made in the first place.

Then what would be the conditions to tell if the PCB is going to fail if it stay for another X units of time in the test environment?

Please let me know if you need more information!


texts: Why do PCI Express riser/adapter cards have electrical components?

texts: I'm looking to make a custom PCI Express right angle adapter because the ones on the market don't work with my space constraints. Now, because it's basically an extension cable, I'd imagine it should be just straight traces running from the female connector to the male board edge. However, the adapter boards and even extension cables appear to have resistors or capacitors AND don't appear to have straight traces. Why is that?


texts:
From this Reference Design I have two questions:

They are doing PSR (Primary Side Regulation) with LM5020. However, according to the datasheet LM5020 is a Current Mode PWM Controller which was not designed for PSR, compared to other controllers like UCC2871x for example, that clearly specify that are optimized for PSR. So, would LM5020 work in PSR at the expense of less accuracy or something?

Is the output Pi filter (C8, L1, C9) needed? Could I remove L1 and leave just a capacitor at the expense of more noise?


texts: Stuck on a simple piecewise linear element problem

texts:
See the schematic of interest on a picture. \$V_S = 5 \,\rm{V}\$, \$R_S = 4700 \,\Omega\$, \$R_P = 5800 \,\Omega\$. The cucumber-shaped element is a nonlinear element. The only thing we know about it is that it behaves like a nonlinear resistor (see voltage versus current relationship on the graph). My goal is to find out the element's \$V_X\$ (Volts) and \$I_X\$ (Amps) in this circuit. Here is why i am stuck:

I derived possible resistances Rx of the element from the graph above and then tried to apply a simple current divisor first with Rx = 1K to see if the Ix is within 1mA range and then with Rx = 2K and again check if the Ix is within 2mA range. This does not work

I don't understand whether or not i am wrong with such a logic.

edit:

We have only two possible values for RX=dV/dI. And the Thevenin of VS, RS, and RP is VTH=VS*RP/(RS+RP) and RTH=RP ∣∣ RS, with RX now in series with RTH. Plug in the two possible values for RX and you will find two boundary currents, both of which are well within one of the segments. You only have one alternative, now. The answer is captured by the boundaries. Then you get two possible ix currents ix = 0.76 when Rx = 1k (which is right) and ix = 0.6 when Rx = 2k. The reason 1k current turned out to be right is because the two boundaries both lie on the same segment. So that segment is the one that applies. It is convenient that this segment also crosses through 0.0


texts: Ringing in MOSFET H bridge when connected load through LC filter

texts:
I'm currently making a pure sine inverter using a MOSFET H bridge with following specs.

Vin=360VDC

Vout=230VAC at 50Hz

Output Power=750W

Switching frequency=16kHz

I use Sine modulated PWM(SPWM) as shown below.

At this stage I'm still operating in 100VDC.Earlier I had problems with voltage spikes appearing in the DC bus line which was solved by moving C11 & C12 closer to the H bridge in the PCB layout.when i connect a resistive load directly to the bridge, the waveform of Q2 are almost perfect as shown below with no spikes when Q2 is off and Q4 is switching as in the previous question.

Vgs:cyan   Vds:Purple    Id:Green

However when I connect the LC filter, a ringing appear in Vds.

What is the reason for this?

How can i minimized or avoid this ringing?

How this affects the MOSFETS?

Thanks in advance...


texts: Using DAC to control supply voltage of bus transciever?

texts:
I am designing simple logic analyzer with SN74LVC16T245DGGR bus transceiver which could be used for 1.2V to 5V logic levels I would like to control supply voltage of input port with DAC, currently TLV5624, but this DAC could deliver only 1mA current and I doubt that it's enough for transceiver so I put LM321 OPAMP but this OPAMP has 1.5V voltage drop so with 5V supply I can get only to 3.5V which doesn't enable me to interface 5V logic.

Is there any single supply OPAMP with lower voltage drop? I would need to get to at least 4.5V. And using some charge pump to get higher supply voltage is not the way for me, because it should be USB powered and I don't want to have high power consumption.

Or would it be better to control feedback of some buck voltage regulator with DAC? It seemed to me as overkill to use voltage regulator for this with all inductors and capacitors and I think that these regulators have high voltage drop as well.


texts: Variation in collector current if we change the collector resistor in a common emitter transistor

texts:
If we increase the collector resistance then how will the collector current change?
I understand the circuit behavior if i neglect early effect but when i try to include it that is allow Ic to vary with Vce i get lost because everything changes and it's as if i lose the grip on all variables.

P.S I'm a self studying person solely dependent on internet and books, so I hope that this question isn't blocked because it may look like a homework problem.
Thanking you in advance.


texts: How can I use an Nvidia GPU with an open-source embedded board?

texts:
Is it possible by any means or method, to use an Nvidia GPU with an (probably open-source) embedded board? If yes, how do I go about achieving that? I have a few ideas but I'm just a beginner, hence not sure about the feasibility:

Replace the on-board GPU with Nvidia GPU (since the board schematics are available, this should be somehow possible right?)
Connect the GPU externally on a board with an exposed PCIe interface. (I'm pretty sure I don't understand this, but if its possible to hook up an Nvidia GPU to a laptop/PC and start gaming, shouldn't this be feasible? )

Why Nvidia GPU?
I need to run a CUDA-based application for my project. For details on my problem: Embedded board (preferably < $150) with external gpu support?


texts: Power of an adapter working with different input voltages

texts: I have a laptop adapter which, according to its label, works with 100-240 V, 1.8 A, 50-60 Hz as its input. Since only one input current has been mentioned, does it mean that its consuming power is higher in countries with 220-230 V mains electricity than in countries with 110-120 V electricity?


texts:
In the context of a competition, I need to set up a wireless link between a base station and a mobile target.

The mobile target:

-> will always be within the same 180 degree cone from the base station's perspective (i.e. the mobile target will always be 'in front of' the base station and never 'behind')

-> will go out pretty far (1 km - 2 km) away from the base station

-> needs to stream low-quality video back to the base station

-> may be NLOS sometimes; the mounds behind which the mobile target will go that make it NLOS aren't very big (1 m - 2 m)

-> is in a desert-like setting (no trees, no structures, no giant rocks) so the signal shouldn't be bouncing (thus no multi-path problem)

One of my thoughts was to use a hardy wireless router that runs 802.11n and thus MIMO and change it's 4 omnidirectional antennas for 4 large directional ones, placed a few meters up on a mast. I would select the antennas to each have about a 60 degree cone and place them so that they cover the 180 degrees.

I know MIMO is better known for solving the signal multi-path problem but I was hoping my idea was sound and that by using 4 directional antennas (with higher gain than 4 omnidirectional ones), I could effectively handle the 180 degrees that need to be covered; the MIMO technology would be used to coalesce the signal received at the antennas.

In other words, I was hoping the MIMO technology would make sure that whichever directional antenna the signal from the mobile target is hitting, the wireless router would reconstruct it as one signal. This would effectively be the same as having 1 giant 180 degree directional antenna.

How wrong am I doing this?


texts: Capacitor on line with high frequency digital signal?

texts:
Capacitors act as a short for high frequency signals. If I place a capacitor on a digital 5V PWM line or perhaps a motor encoder line does the cap still act as a short to ground for the square wave signal? My PWM signal is about 50kHz.

Here is the circuit diagram


texts:
The author explains it as a synchronous demodulator. Here we can see that two multipliers which multiply both the inverted and non inverted signals.

Can I do the same with only one switch for non inverted signal?

Circuit shown here is from a lock in amplifier milliohm meter.
5 V pulses are coming from the reference oscillator.
1.8 V pulses are input signal coming from a preamp that amplifies drop across a milliohm resistance.
Here is the link http://cappels.org/dproj/dlmom/dlmom.html


texts: PIC 16F887 and the mysterious System Clock Select bit (SCS)

texts:
I'm using a PIC 16F887 and I'd like to use the internal oscillator HFINTOSC. To accomplish this, I set the IRCF 2:0 bits to 110 (4Mhz prescaler) and the FOSC 2:0 config bits to INTOSC.

Now I should do something I really can't understand: according to the datasheet (see pag. 61) I should set the bit SCS in order to use the internal clock source (see the final MUX on the diagram on pag. 61).
Because the SCS bit is in the OSCON register I should set it programmatically on my code but the code itself needs a clock source to be executed! How can I execute a code to set a bit to use a clock if the code needs a clock source in the first place?????

I quote the datasheet for the SCS bit:

  4.6.1 SYSTEM CLOCK SELECT (SCS) BIT The System Clock Select (SCS) bit of the OSCCON register selects the system clock source that is used
  for the CPU and peripherals. • WhentheSCSbitoftheOSCCONregister=0, the
  system clock source is determined by configuration of the FOSC<2:0>
  bits in the Configuration Word Register 1 (CONFIG1). •
  WhentheSCSbitoftheOSCCONregister=1, the system clock source is chosen
  by the internal oscillator frequency selected by the IRCF<2:0> bits of
  the OSCCON register. After a Reset, the SCS bit of the OSCCON register
  is always cleared.


texts: Li-Po USB Charger with PIC, voltage is not falling to 0V

texts:
I am designing a single cell Li-Po charger with a PIC. I have this:

I drive the transistors from a 12F PIC microcontroller. As you can see in the square wave on the top of the oscilloscope the signal is not falling to 0V, it falls to 1.85V and the highest voltage it reaches is 5V so I have 5-1.85 = 3.15V on the battery and I need 4.2V to charge it.

Why the voltage is not reaching 0V ? I have tried whit a 2N7000 Mosfet but driving it at 5V provides too much Rds resistance and voltage reaches 5V but falls to about 4V only. Is there any other solution you can think in ?

R1 is suppose to be the battery draining 500 mA as much (USB limit) and R3 is used for current sense.

Thank you !


texts: Can I dynamically change the input clock frequency of the AT91SAM3X8E?

texts:
Background:

I'm attempting to use an AT91SAM3X8E microcontroller (for Arduino Due compatibility) to create a USB to \$I^{2}S\$ interface. Most \$I^{2}S\$ CODECs require a master clock that is \$MCLK=256*BCLK\$ where BCLK is the bit clock, which in turn is \$BCLK=64*F_{s}\$. This would be trivial to generate if I was only dealing with one sample frequency, but I would like to retain compatibility for all common values (44.1kHz, 48kHz, 88.2kHz, 96kHz, 196kHz).

I plan to use the microcontroller's Synchronous Serial Controller (SSC) for this task, which it seems very well suited for.

Problem:

All of the \$I^{2}S\$ clock signals must run off of a multiple of the sampling rate, which varies between two sets - multiples of 44.1kHz and multiples of 48kHz. This means that the clock driving the serial controller must be dynamically switched between two values. At first, I thought that driving the serial controller's transmit clock with the appropriate frequency would be the best option, but that doesn't allow for dynamic clock division for supporting different sampling frequencies. I concluded (perhaps incorrectly) that I need to be able to switch the master clock of the microcontroller in order to address all of these issues.

Question:

Can the AT91SAM3X8E support dynamically changing the clock that it receives on the XIN pin or would that cause run-time errors? If so, would there be a way to get around those (such as temporarily using the RC oscillator)?


texts: Why does a 741 op-amp get driven to the negative rail when the non-inverting terminal is left open?

texts: In the case of a 741 op-amp with R2 = 100k and R1 = 1k the gain should be -100.  The output voltage should then be 101 times whatever the input is.  I understand that given a large input voltage to the non-inverting terminal, the output should be saturated to the positive rail, but in both simulations and in the experimental procedure I have found that leaving the input open causes the output to be around -8V when my saturation is +-10V. I know leaving the terminal open is not a practical implementation of the op-amp, but theoretically, I would like to know what causes this output voltage to be driven the way it is.


texts: Calculate maximum deviation of quartz crystal

texts:
How can I calculate the maximum deviation of a quartz?
This is from datasheet (12MHz):

Frequency Tolerance at +25° C => +- 30ppm

temperature tolerance  -20°~ + 70°C => +-50ppm
aging (first year) => +- 2ppm

I want to calculate the maximum deviation for a specific period.

For example first quartz is at -20°C then the tolerance is 50 ppm or 50 ppm + 30 ppm? So +- 50 ppm or +-80ppm?
The second quartz the same but it works at 70°C.

The following calculation is after one year so I add 2ppm.
So when it is 82 ppm then the first quartz can operate at the worst case with 12MHz - 984 MHz and the second quartz is working with 12MHz+984MHz. Is this correct?

I am not sure because the frequency tolerance is at 25°C.


texts: I'm using classical GM tubes for radiation measurement (gamma plus beta, natural radiation levels) and would like to know if there is a more "electronic" sensor for radiation.


texts:
Im trying to do research for something I can't even name. Basically it goes like this:

It's kind of like a multi-vibrator, but I need it to give a short pulse on the output, while input is a constant voltage. Maybe some of you know some circuits, that would be capable of such task.


texts: How to implement 5V NPN component to a 3.3V MCU input pin

texts:
I just want to make sure about how to implement this

to an MCU's input pin, if the MCU is limited to 8mA sinking/source current. And 3.3V input voltage.


texts:
I need to design a switching voltage regulator, all parts work fine but I am having trouble figuring out the feedback, on the negative terminal of my comparator i have a triangular wave that cycles between 5-10 volts. on the negative terminal have have the output from the error amplifier. the error amplifier takes a reference voltage which is to be controlled by the user, and change it to a scale which can be compared to the output from the triangular wave.

I have tried many things but I cannot seem to get the feedback right, I will appreciate any and all help and suggestions.

below is a simulation of the circuit from OrCad and also from falstad.
i believe my trouble comes from the part circled in red.

enter image description here


texts: DC-DC converter isolation capacitance return path?

texts:
For those isolated DC-DC converter bricks like seen in the photo below:

The data sheet specifies an isolation capacitance in the order of picofarads. And in order to meet EMC requirements they recommend coupling either side of the isolation barrier with a cap to reduce loop area of the current leakage. That part makes sense to me, but I am struggling to see how else the current could return say if the cap weren't there? (assuming the DC-DC converter is the only component "bridging" the two isolated circuits).


texts: Find Vo in an op-amp - transistor circuit

texts:
I have a schematic with this system and can't find out how it works:

simulate this circuit – Schematic created using CircuitLab

How do I find Vo in this network? Please explain it "for dummies".

simulate this circuit


texts: Controlling 64 stepper motors with arduino

texts:
I have seen many post on this site for controlling stepper motor with arduino.
And arduino is pretty good at it if provide with good shield/Driver.
My query is How can is use to arduino control more than 2 stepper motors i.e(64 stepper motor). It seems to be a huge project for me.
Each motor will move at same speed but won't have same steps. More like MIT inForm

For now we are just making a prototype.
I have attached the internal structure of or device
where we will be using  full stepping mode and only 2 pins for controlling Stepper motor as rest of the 2 pins are just complement of first 2 pins

a  b  a' b'
1  0  0  1
1  1  0  0
0  1  1  0
0  0  1  1

our basic theory/logic is arduino will generate 2 pulse of each motor pass it to serial to parallel converter and this will further send the pulse to PIC that will generate rest of the 2 pulse and pass it to stepper motor. Each pin on arduino will generate pulse for 4 stepper motor
i.e. 8 bit per pin.
I will be using 28BYJ-48 stepper and ULN2003 having configuration of stepper motor as 64:1 ratio
the thing is at what rate I need to send 128 bits(8 words) of data from arduino to shift register. so the motor should run at decent speed
So any one can help us to achieve this and guide us with the project.
All reviews are welcome.


texts: Definition of link gain for an optical system

texts: Is the link gain the gain of the whole system or just over the diode? And why does the threshold current of a diode laser have no impact on link gain whereas increases in slope efﬁciency have a major impact?


texts: 4.4V vs 3.7V LiPo -- Is there such a thing?

texts:
I was looking through a very legitimate well known product, noticed the battery pack is stamped with 4.4V.  I think this is actually the nominal voltage it provides.

The reason I think that is that this is a $100MM+ company, and I know from professional experience, LiPo battery markings and regulatory compliance has gotten extremely tight in the last few years when you ship batteries in products.  These guys ostensibly are dotting all the i's and crossing all the t's.

The 4.4V stamped battery, has a much higher mAh stated amount than any corresponding 3.7V LiPo, on a volume basis, then we've ever been quoted.

Is there such a thing as a 4.4V LiPo?

PICTURE AS REQUESTED:


texts: Determining Parallel Resistances in Solution of Circuit by Thevenin's Theorem

texts:
I have the following circuit

In this example http://www.electricaltechnology.org/2014/01/thevenins-theorem.html how are they saying that 8kOhm Resistor is in Parallel with 4KOhm Resistor.Parallel Resistances should be connected end to end like the following.. right?


texts: Is there a way to compare both signed and unsigned binary words?

texts:
By that I mean, is there a circuit that can compare two signed words against one another, but also be able to compare two unsiged words together, not comparing a signed word to an unsigned one.

I am currently working on a 4bit ALU and I intend on making it support operations for both signed and unsigned inputs. But to the extent of my knowledge, the 2's complement representation of signed words means that the only way to make it work is just to have one comparator for unsigned and one for signed inputs.

Is there a single circuit that can perform those comparisons?


texts: ngspice simulation : random signal source

texts:
I'm new at the ngspice simulator and I don't understand this line of a Netlist that I found

Vn 1 n1 dc 0V ac 1mV trrandom(1 5us 0s 125m 0m)

if the random signal is only used in the transient simulation why did they keep the ac signal with an amplitude of 1mV ?


texts: Difference between indoor and outdoor PV panels

texts:
I am building an energy harvesting sensor for building installation, and I have to choose between two panels:

Indoor, 5V, 47uA Isc @ 200 Lx
Outdoor, 6V, 15.9mA Isc @ 50 kLx (note the different light level rating)

Given that they have similar dimensions (negligible difference for the application), one would say that the indoor panel would be more efficient with narrow band light such as the one generated by a lamp.

The problem is that this last detail is not included in the technical data sheet, as it's not included the I-V curve, that can however be traced from measures or taken from models.

Now, the strange thing is that the outdoor panel has shown a better performance (in terms of power given at the MPP) under the same - indoor - light conditions; this test has been done in a working environment, that should be lighted at about 500 Lux; the lamps are probably fluorescent, and probably with a quite good "white" light. Also with shading (a hand above the panel) the outdoor one gives more power.

Now we decided to use the outdoor, but can you find a reason for that? And what would be (apart from price) the advantage in using the indoor panel?


texts: Is it possible to get a floating power supply to power multiple MOSFETs

texts:
Hey guys this is my first post on stack exchange so please go easy on me!

I have a hobby project where I was trying to make a few batteries go in series using a micro controller and a floating power supply (in this case an isolated DC-DC converter), the arduino is powered separately.

I've attached a schematic of the rough problem.

simulate this circuit – Schematic created using CircuitLab

The arduino needs to be isolated from the rest of the higher powered battery stuff which is why I have used an isolated DC-DC converter and an opto-isolated mosfet driver

The output of the opto-isolated driver is hooked to the gate of the mosfet and the COM terminal of the dual output converter is hooked to the sources of both mosfets. This lets the mosfets see a +15V and the -15V drive signal. (please dont pay attention to the irf530 i just used the default on circuit labs and have some mosfets that can handle +/-30V for gate to source voltage)

My issue is that instead of buying more DC-DC converters and opto-isolated drivers to drive each next pair of mosfets, is there a way to power the next set using the same DC-DC converter and isolated driver? I need to add six more pairs of mosfets and batteries and thought that someone might know a cheaper way than buying more converters and drivers. Perhaps someone knows how you could use caps, resistors or diodes etc to do it.

Another issue that I have had is that if I were to connect the output of the isolated driver to the gate of the next pair of mosfets that would be okay but if i go to connect the COM terminal to sources of the next pair aswell it would create a short that bypasses the next battery.

Specifics:

DC-DC converter is the DPU01M-15
Driver is the FOD3150
Switching frequency range from 1Hz - 3kHz

I hope that makes sense

Thanks for any help in advance!

EDIT:
The switches will turn on and off simultaneously


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EDIT
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The first picture is of a BJT in small signal analysis. although it is BJT i just wish to say that i understand how the Rin values and Rout values are found in this case.

1)
Now in the following image is a MOSPET problem i have been trying to solve. Ignoring the values i am just trying to get a conceptual grasp of What Rin would be and what R out would be (Ignore the fact R in is given as 500K Ohms). I have attached the small signal circuit i drew of this MOSFET circuit also. I drew the T model and Pie model.

So if we just look as the T model. To me i see that R in = (R1)||((R2||1/gm)+2Kohm Resistor) || (R4)(through the current source) ?

Would my Rin conceptual analysis be be correct here? This is were i am confused. What is the resistance of the dependant current source and R4. they are most definitely in parallel with the other circuit elements in the t model.

To analysis this would you have to look into the circuit between Rin to ground in a thevenin analysis style. And apply as current source at the input if vgs Was not given in order to solve for R4?

2)
Looking at the Terminal Vo (2nd Image) and then analysisng Rout from location of Vo relevant to the t model. Would Rout=(2Kohm resistor)||((R2||1/gm)+(gm.vgs+R4||R1))?

3) How can the Pi model ignore the gm (conductance) of the mosfet. 1/gm = resistance.

Thanks guys and gals.


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