texts: Large exponentials and 8-bit PIC processors

texts:
Does anyone know if 8-bit (PIC) processors could typically handle large exponentials, e.g., 5^15 mod 23, with a reasonable speed? Does doing so result in more cycles than on 16-bit processors?

I'm hoping to implement Diffie-Hellman Key Exchange on one, but the thought of computing large exponentials seems daunting.

Are large exponentials commonly done on 8-bit processors? Is DH key exchange commonly implemented on such low-end devices?


texts: QAM modulation - how data in different frequencies are laid out?

texts:
I know that QAM modulation uses a change in phase and amplitude to send data. But We use a series of frequency spaces as bandwidth to send data.

However, we know that different frequencies oscillate differently. So, if we modulate data using several frequency spaces together, how are data laid out?

Is it that size of data in each frequency is different? Or is it something different?

Thanks.


texts: Can the Signal from a Coaxial Cable be Transmitted via Bluetooth?

texts:
If so, can the coaxial signal be maintained without degradation (think inserting a transmitter in the middle of a coaxial connection to relay that signal wirelessly without actually interrupting the original coaxial path)?

Can it send this information to multiple (up to 7) devices (Android and IOS) without its signal being degraded from sharing between them?

Any ideas as to what module would I look for to do this? (maybe on DX.com?)

At the core I would like to know if this idea is even possible. It would be gravy to figure out how I'd go about doing this and what parts I'd need.

Thanks to anyone who can help!


texts:
What is the formula to calculate how many ohms your speakers will put on a power amp?

For example two 8 ohm speakers daisey chained together


texts:
I have designed a circuit with some resources from this website and I attached it here. I have given circuit connection in a breadboard and successfully run and control the speed of the motor. After a while, I moved on to the pad-per-hole PC prototyping PC board. I have given the same connection on that board. But there is no output from pad-per-hole PC prototyping PC board.

I checked connection thrice but there seem no flaws in connection. I have measured voltage in a circuit. It is as follows.

Input voltage for optocoupler - 1.2 V in breadbaord and 1.17V in pad-per-hole PC board.
Output voltage(between c and E in phototransistor) - 0.005 V (in pad-per-hole board)
Could not find what is the problem in pad-per-hole PC prototyping PC board connection. What might be the problem?


texts:
It is known that the return current starts following the conductors as the frequency increases:

So as long as one keeps the distance between the conductors large enough there shouldn't be the need for local ground planes.

Why then some people suggest the use of localized ground plane, like the answer to this question: https://electronics.stackexchange.com/a/15143/4512 It is suggested that the ground plane will work as a patch antenna.

But the current on the ground plane will closely follow the conductor, resulting in a small loop area. And the generated magnetic field is given by Faraday's law:
$$\oint_{\partial A} \mathbf{E} \cdot d\mathbf{r} = - \frac{\partial}{\partial t} \iint_A \mathbf{B} \cdot d\mathbf{s}$$

By using a smaller localized ground plane the generated EM radiation will be the same, because the loop will be the same. Additionally, the localized plane can introduce plane resonance, and one needs to avoid crossing it with high frequency signals.

So, what are the benefits of using a localized ground plane?


texts:
I'm setting up an attiny2313 to drive an array of LEDs and blink them in different patterns.  Rather than putting a series resistor in line with each LED (they'll be controlled separately, so I can't do tricks like putting them in series with each other), I was wondering about just using a couple diodes to get the voltage down to the right range.

The system is running at 3.3V (with a regulator to keep it pretty constant), and two 1N4001 diodes will drop that down to 1.9V - right in line with the lower end of the 1.8 - 2.2V these LEDs are specced for.  Since the diodes will always want to maintain the same voltage drop across themselves, I don't have to worry about that voltage changing as I turn the LEDs on or off.  Overall I save 6 components.

Has anyone else tried something like this?  Any gotchas I've overlooked?  I realize the diodes will have to dissipate the full current from all the LEDs, but for this small amount of current that doesn't seem like it will be an issue.

(edit:  I'm putting these diodes between the common cathode of the LEDs and ground)


texts: Why not connect battery negative to chassis?

texts:
I am making a mobile robot with a metallic chassis. Usually, a non-moving appliance will have the ground pin of the wall socket connected to the chassis, but in a moving device, there is only the virtual ground, AKA the minus side of the battery. Thus I conclude that that should be connected to the chassis. In what instance would that be inadvisable?

(Side note: my system doesn't have separate logic ground and power ground, so that shouldn't be a concern. Also, if that is in any way relevant, I am also using the chassis as a heat sink.)


texts:
When creating components in VHDL and instantiating them in a source file, does it matter if component have outputs that have the same name.
For example component A has an output called Out_1 and component B has an output also called Out_1. They are nested in source files in a way that when I instantiate components A and B, I am assigning output values Out_1 => Out_1.
Now when I simulate in a test bench, the signals are orange and uninitialized. Is this something that should be avoided?


texts:
I need to switch 15V, 1.5A AC into a resistive load with a 5V control signal. Will this SSR work?
http://cpc.farnell.com/crydom/aso242/ssr-2a/dp/SW03811

To be specific, I do not understand the term 'minimum operating voltage: 24Vrms'.


texts: Circuit to measure Voltage and Current (will it work?)

texts:
Hello,

I have a question, If my circuit will work:

Function:
Gate is on GND
Supplying a voltage betwenn 0V and 10V
10V Input is ~3.3V output
If the voltage goes above 10V the diodes D2 and D3 clamp it to ~3,3V
(This works as I understand)
Function
Vgate = 3.3v
Supplying a current between 0mA to 20mA
the voltage drop at R3 should "Supply" the voltage divider
again max output is 3.3V

Will the 2nd function work?


texts: I was wondering what would happen if you took a 2.7v super-cap and began to charge it with 2.5V then while continuing to charge it the input voltage drops to 1V. Also what would happen the other way around if you began charging with 1V and then raised the voltage to 2.5V.


texts: How to measure resistance of resistor in PCB?

texts:
I have a resistor 1MOhm soldered in a PCB that looks like that
And the schematic is looking like that:

When I measure the resistance by touching the a multimeter on the two ends of the resistor the measured value is around 500KOhm. When the resistor is not soldered the value is the correct one 1MOhm measured by the same multimeter in the same way. Why is that and what is the resistance value seen from the resistor "input"?

If we make the equivalent circuit of the measurement it looks like that, doens't it?:

simulate this circuit – Schematic created using CircuitLab


texts:
I have a CPLD XC9536XL-10VQG44C. On this CPLD I have one input "INPUT_4", one clock at 4MHz "clock" and 2 outputs "OUTPUT4_1" and "OUTPUT4_2", I also have 1 LED to drive that takes the same value than the input.

What I want to do is:

When INPUT_4 goes high, turn OUTPUT4_1 high and OUTPUT4_2 low for 50ms then put them both back to low.
When INPUT_4 goes low, turn OUTPUT4_1 as low and OUTPUT4_2 high for 50ms then put them both back to low.

So what I wanted to do was look for the input, and as soon as there is a change on it, do the corresponding change on the output and starting counting the 100ms. When the 50ms is finished, put them back low.

I appreciate that it is probably easier to do with a microcontroller but I cannot change the hardware.

For that I wrote that vhdl:

entity test_vhdl is
Port ( Input_4 : in  STD_LOGIC;
       Output4_1 : out  STD_LOGIC;
       Output4_2 : out  STD_LOGIC;
       LED_4 : out  STD_LOGIC;
       Clock : in  STD_LOGIC); --4MHz
end test_vhdl;
architecture Behavioral of test_vhdl is
constant overflow : natural := 200000; --50ms pulse with a 4MHz frequency
signal COUNTER_4   : natural range 0 to overflow;
begin
    LED_4<=Input_4;
output4: process(Input_4, Clock) is
    begin
        if rising_edge(Input_4)then
            Output4_1 <= '1';
            Output4_2 <= '0';
            COUNTER_4 <= 1;
        elsif falling_edge(Input_4) then
            Output4_1 <= '0';
            Output4_2 <= '1';
            COUNTER_4 <= 1;
        end if;
        else
        if rising_edge(Clock) then
            if COUNTER_4 /= 0 then
                COUNTER_4 <= COUNTER_4 + 1;
                if COUNTER_4 = overflow-1 then
                    Output4_1 <= '0';
                    Output4_2 <= '0';
                    COUNTER_4 <= 0;
                end if;
            end if;
        end if;
        end if;
    end process output4;

end Behavioral;

I simulated it and it works fine. But when I try to synthesize it I get the error:

  Signal Output4_1 cannot be synthesized, bad synchronous description. The description style you are using to describe a synchronous element (register, memory, etc.) is not supported in the current software release.

Maybe it comes from the fact that I check the rising edge of two different signals in the same process. I am still in the learning curve of VHDL, how can I resolve this problem or is there a better way of doing what I need to?


texts: How do ceramic disk insulators support the weight of transmission lines?

texts:
I know that the transmission lines are held a certain distance away from tranmission towers using those ceramic disk insulation arms and the number of disks is proportional to the voltage of the lines, but I've always wondered what provides the strength of those 'disk arms' to hold up the cable.
I envision the disks have a center hole and are threaded onto a steel rod to provide tensile strength, but that of course would defeat the purpose.


texts: How to know the memory occupied by the various memory segments in a microcontroller

texts:
I'm using STM32 based microcontroller, IAR embedded workbench and STlink v2 debugger. I just want to know how to check the memory utilized/used by the program/system in various memory segments like:

Data segment(initialized and uninitialized)
heap segment
stack segment

any suggestions regarding this would be appreciated.


texts: How does a high amperage (100 Amps or more) MOSFET handle the current flow without overheating?

texts:
High amperage MOSFETs like the 511-STP200N3LL say they can handle 120 Amps of current.  Is this possible?  If yes, then what prevents the small wires coming out of the device from melting or getting too hot?  The package for the specific device I'm referring to is TO-220-3.

Here is a datasheet link:
https://www.mouser.com/datasheet/2/389/stp200n3ll-1063226.pdf


texts: Choosing decoupling cap for M74HC595B1R shift register

texts:
I want to use a bunch of cascaded M74HC595B1R shift registers in my project. VCC will be 5V, clock frequency 8-10 MHz. Outputs of these registers will be driving gates of 2N7000 N-MOSFETS if that matters.
My questions are

Should I install decoupling caps for my shift registers and what value if yes?
VCC and GND pins are rather far apart on the opposite corners of package. Does it matter if I physically place the cap as shown with red lines (unequal distances to VCC and GND pins)  or as shown with blue lines (equal distances from pins on the opposite side of the board)


texts: MOSFET - Derivation of I/V Characteristics - Small Vds

texts:
I'm following Razavi's CMOS Analogue IC design book and I'm having some trouble how he did an approximation.

He did the following

My question is - how did he come up with that condition of V_DS being less than 2 times (Vgs - Vth). I saw a brief explanation in one of his videos but it didn't make much sense to me. I know this equation is applicable when Vds is small and he just quantified how?


texts: Select internal/external DVDD source for OV5640

texts: How to select between internal or external source for the DVDD digital core in OV5640. Do I simply provide voltage to the DVDD pins and if it is more than 1.5V it will automatically use internal LDO to get 1.5V, or when they are unconnected/grounded it starts generating its own 1.5V, or there is a proper way to do it?


texts:
I have seen a friend place an RJ45 connector at the output of RS232Mux on a board he developed and then make another PCB with RJ45 connector and 3 RJ11 connectors so that muxed connection can be connected to respective devices.

I wonder what is the criteria for selection of a particular connector for a particular purpose?

Rephrasing the Question to meet the standards of StackExchange:

I have a PCB which has RS232 Mux. I have another PCB with RJ11 connectors for devices where the muxed outputs will go. Which connector/cable arrangements should I choose to connect the first PCB to the Second PCB.

what are the criteria should I consider for the selection?


texts: Two-phase boost converter output capacitor selection

texts:
I am designing a boost converter for my board. Here I am planning to have a smaller capacitance at the output. So I am using the IC from linear technologies ie. LTC3787. This can be configured as two-phase or multi-phase mode boost converter. I tried getting the waveforms for the output capacitor current and derive the capacitor value. But somehow i feel i am in the wrong direction. Could somebody help me on this ?

Here is the equivalent model of for the 2-phase boost converter.

and the waveforms i figured out at various points:

Please check and correct me if i am wrong anywhere.


texts: Specific transistor for voltage regulating?

texts:
In 2SD1047 NPN transistor datasheet described the application for power supplies and the description is:

  The device is a NPN transistor manufactured using new BiT-LA (Bipolar
  transistor for linear amplifier) technology. The resulting transistor
  shows good gain linearity behavior.

How do we know which transistors used the "BiT-LA technology"? is it described somewhere in the datasheet?
Does it really make a difference between this transistor and for example a general purpose transistor like 2N3055 (I know the packages are different but what about the performance)?
Which specifications makes a transistor ideal for using it as main voltage regulating transistor in power supplies?


texts:
0
I'm writing a user interface program for USB device in C++ using Visual Studio 2019. I'm using libusb library. I want to do bulk transfer to the device, and I'm trying to understand the exact function of libusb_bulk_transfer, more specifically - does it add CRC? The definition from the documentation:
 int libusb_bulk_transfer(struct libusb_device_handle *devh, unsigned char
 endpoint, unsigned char *data, int length, int *transferred, unsigned int
 timeout)

 Perform an USB bulk transfer.  A timeout value of zero means no
 timeout.
 The timeout value is given in milliseconds.
 Returns 0 on success,

 LIBUSB_ERROR_TIMEOUT if the transfer timed out,
 LIBUSB_ERROR_PIPE if the control request was not supported,
 LIBUSB_ERROR_OVERFLOW if the device offered more data,
 LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and a
 LIBUSB_ERROR code on other failure.

From what I've understood, the function libusb_bulk_transfer creates the packet and transfers it to the desired endpoint for me, and I only need to supply it the data itself. when this function builds the packet, does it add a CRC?
If it doesn't, is there a different method to do the bulk transfer so I can control whether the CRC is added or not?


texts: Can the input of the op amp be 1kV? and can Oscilloscope read such high voltage?

texts:
I work on this circuit but I am little confusing about the capability of the op amp to do its work because the input voltage is 1kV to the buffer and a little less for integrator.

and can oscilloscope read such HV? Knowing, the sample here meant ceramic capacitor.


texts: Loading one line from Three Phase Power Delta Configuration

texts:
I have been trying to determine whether or not I can run one line from 3-phase power into a power conditioner that requires single-phase input.

The current draw on this line would be around 10 A. Would this cause issues with current unbalance?


texts: Can't reach desired voltage on opamp output

texts:
I have tried to make signal amplifier just to gain some op-amps knowledge, but unfortunately it doesn't work. It simply doesn't reach desired voltage (set by resistors). I have used my old cellphone headphone audio output as  an input for op-amp. The OPA454 was powered by +/-15 VDC from two 5V to 15V step-up conventers. The wiring looks like:

And SSs from scope with different gain. Please see peak-to-peak voltage below graphs:

For some reason it can not exceed 10V peak-to-peak even through it should (based on my poor knowledge). Why it does so? One more thing is that I use adaptor so that it is possible for me to plug OPA454 to breadboard, but I am pretty sure it is designed / soldered correctly. I have tried swapping opamp to another one but it does't change anything. What could be potential issue?


texts:
I am making a regulated power supply for guitar pedals similar to the following schematic:

Instead of having several outlets I have only one, that switches between 9v and 18v.

I was told that by basic rule, when designing a power supply, to accomplish 18v DC and 300mA, I need a transformer rated at 18.2v AC and 600mA.

I want to know what is the max electric current I can supply at each voltage? (9v and 18v). Is it 300mA in both cases, or they are different?


texts: good afternoon i bulid a circuit to convert 220v ac to 12v dc so i can power a 12v dc relay. once i attach the output to the relay the voltage drop to 2v once i disconnect it and attach the positive 12v to the relay it work but then i have the disconnect it again if i want to powr it again.


texts:
My laboratory developed an IC, where it will be necessary to have an external 10nA current source to supply it, with an accuracy of <5% and output resistance in the order of 5M ohms or higher. It was specified that the solution must supply a current mirror, which will enter on our circuit. We have a power source where we can make a 10nA reference from it, and use it in our current mirror.
I know how to implement a current mirror using transistors, but since precision is an extremely critical element in my system, I was looking for integrated circuits that have such characteristics.
I did not find an IC on the internet for this. In fact I even had difficulties to find current mirror ICs.
What I found was the "REF200", which features an integrated current mirror. However I was in doubt if it can be used for currents in the order of 10nA where precision is required. In the datasheet, this is not specified, as can be seen below:
https://www.ti.com/lit/ds/symlink/ref200.pdf?HQS=dis-dk-null-digikeymode-dsf-pf-null-wwe&ts=1610688356316
I would like to know what solutions for creating a precise 10nA CM with my specifications are viable? Is the REF200 feasible to generate 10nA currents?


texts: Reasons for having MCU pin-states default to pull-up/down out of reset

texts:
On many MCUs, pin-states default to tri-stated (a.k.a. analog inputs) when the MCU resets so as to not affect the circuits they are connected to until software configures the pins.  The tri-stated pins also allow the HW designer to choose the pull state of each pin on a case-by-case basis in function of the underlying circuitry.

However, there are some MCUs (and SoCs) that default their pins to instead activate an internal pull-up/down.  For example, the LPC845 defaults all pins to pull-ups coming out of reset.

Is there a reason defaulting pins to pull-up/down is preferable to tri-stated (other than the possible incremental power savings when coming out of a reset, or the marginal BOM cost savings)?

If anything, I rarely find that pins should be pulled-up coming out of reset (I typically need to pull them down, if at all).


texts: Calculate Power Dissipation of 0ohm resistor

texts:
I have a 0 Ohm resistor here.
Can someone tell me how the power dissipation will be calculated for this type of 0 ohm resistor.
The part says it has a power rating of 0.1W.
But, if we use either V squared over R formula or the I squared R formula, in both of the case, we would either get 0 or infinity for the power dissipation of the resistor.
So, how to calculate? If we cannot calculate, then why does the manufacturer provide a power rating value?


texts: 12v DC motor not running on 12v battery?

texts: I don't know anything about electronics really, it's not my field but I do know that my 12v DC motor should be turning on 12V and it is not. I'm not sure what the problem is really I need help. Is trying to power a 12v 1000rpm dc motor with a 12v a23 battery a mistake on my part? Or is my motor bust?


texts: Will this temperature compensation work?

texts:
I have a circuit and as a part of it I need to measure the battery voltage under a load. Naturally I would need this load to be constant each time I measured it to accurately know the battery levels which is important for me. However, if temperature changed the voltage drop over the transistor would increase or decrease and that would in turn change the load that would be on the battery.

Here is the circuit I have devised, assume that the diode is matched to the transistor drop:

simulate this circuit – Schematic created using CircuitLab

So the idea is that voltage drop increases in Q1 will be compensated by matched drops over D1 as that will push up the voltage at the base. In my head that is how it works but I am trying to actually step through it on paper to see how it would work and I now am doubting it...

Does anyone know if this will work and if not how I can improve it / what should I be doing instead?


texts:
What to replace a relay with?

I read the above article and its links, and the main article is from 2002.  I wonder if they haven't solved all/most of those issues with SSR's by now.  Also I watched plenty of youtube videos on them working perfectly.

Point 5 raised in the article about liking the relays clicking sound, well I hated it.

It is part of a 120v ac outlet strip with a max of 15A on any one device.  Obviously, I would want rated higher than 15A for safety and etc.

The problem is the relay wears out after only a couple years because the default is OFF and so the relays are ON 100% of the time till they die.  There are 8 of these so they waste even more power.  Also the manufacturer has a short warranty so we can't get them fixed.

Anyway I would like to know what SSR (solid state) relay I should use to replace this traditional relay?
Does a relay exist with 10x the lifespan?

Additional errata:

The max is 15A shared, but any outlet can draw whatever it wants to a total of the max.  All of the outlets will be on 24/7, and the only time any of them will be turned off is during a power outage. Certain devices will be turned off remotely to give more run time (on the UPS) to important devices.
The way the circuit is currently designed on the PCB is that the relay/ssr needs power to turn the outlets on, and so the replacement must be reliable when active 24/7 for years, and only occasionally off.


texts: Reactance / Inductance / Impedance of a 1:1 Transformer

texts:
I've searched around and poored through what references I have available, and haven't been able to find an answer to this question.

Regarding 1:1 transformers, I found a website where an audio amplifier electronics guy mentioned that it doesn't seem too much to matter how many winds you put on a 1:1 transformer so long as the reactance/impedance is at least about 4x the circuit impedance.  He said "about" as if there was no magic way he calculated it -- it was simply based on his experience building and fixing amplifiers and transformers.  I was wondering if someone shed some light on this issue.

I'm most interested in a full-load transformer.  Here's a circuit showing an inductor and resistor in series with the transformer.

What is a practical Z for the primary coil of the transformer to make sure it works properly?  And what kinds of problems will arise if my Z is way too low?

So for the sake of total extremes.  Assume I only had 100 Volts and 0.9amps in the primary circuit, limited mainly by the resistance and impedance of R1 and L1  Let's assume the resistance of the transformer is minor for simplicity.  What is going to happen in the secondary circuit if my impedance on the transformer primary is near zero?  Will I just get no power at all in the secondary?  Will I get some current with very small voltage?

And what will happen if the reactance of the transformer primary is 100Ohm making it very similar to the L1?

Thanks in advance.

EDIT: I should clarify that by "full-load" transformer, I'm meaning the condition that the transformer secondary is dead-shorted.  The diagram is showing an amp-meter (A) between the leads.


texts: Behavioral inductor (current dependent) in LTspice

texts: I am trying to make current dependent inductor in LTspice according my mesurements. LTspice includes feature flux where "x" is referred to inductor's current but when I used it in combination with my measured results flux=(2E-11*x*x - 3E-09*x + 1E-06)*x it does not work and gives me wrong value. Measured current reffers to value L=1uH but it should be L=1.19uH. Can anyone help me with this problem or give me any advice how to make current dependant inductor which will be represanting my measurements? If you need any further info please ask. Thank you very much in advance for your help.


texts: General Guidelines for Bipolar ADC Power Supply

texts:
I’m building an AC Power Meter using the ADS131E08 from Texas Instruments and am trying to find the best way to generate a 400mA +/-2.5V supply from a +5V source. The 5V source is the isolated DC-DC converter from Murata (NXJ1S0505MC).
My only requirements here are I’d like to source ~400mA max for the ADC, additional op-amp, and serially controlled 8-channel analog switch. I’m also looking for something as space-conscience as possible (going on a small PCB) and don’t care about the price. My gut reaction was two separate switching voltage regulators (+2.5V and -2.5V), but am curious if anyone here has any other recommendations from bipolar power supply design experience (I have none).
To sum up my two questions are: 1) is two separate supplies the way to go, and 2) is a switching supply the best topology/if so what do I have to watch out for using two different chips at possibly different switching frequencies?
Other options I’ve thrown around are: using the isolated 5V supply as my +/-2.5V, but then I’d still need to generate a GND or ‘0V’ level. Or, using a +/-5V isolated supply and bucking it down to +/-2.5V (still wouldn’t resolve the missing GND level dilemma)
Thanks!


texts:
I need add Bluetooth to my hardware. I never worked with Bluetooth before, so I was wondering which approach I should use. I some did quick research on internet and found some solutions using a Bluetooth IC like CC2540 and CC2541 from TI. I also found solutions using a module such as the RN41 and RN42 from Microchip as well as solutions using a dongle.

I need to add bluetooth functionality to my hardware, however, I want it inside the system with the hardware, and not using USB if possible. That leaves the question between the module or chip.

With  the CC2541, I will need to make the antenna on my PCB, but the RN41 comes with an integrated antenna. The price of a RN41 is 4.5 times the CC2541 price. Probably I will need some hundreds of units, so... I'm wondering, besides the antenna, how much more work would I have using the CC541 instead of the RN41?

I read this article on Digikey, and here is a quote that stood out to me:

  If your team has sufficient RF expertise and the software skills to
  integrate the controller’s application code with the code required to
  support the protocol stack, investing 12 to 18 months of development
  time will be handsomely repaid by a more efficient design and lower
  production costs.

I would like to know what is necessary to develop a Bluetooth solution and integrate it to an embedded design? What do I need to add Bluetooth to my hardware, starting with an IC and not using a module?


texts:
I'm looking for FOSS (for commercial use) VCL components for Delphi or libraries for Visual Basic/C/C++/C# ... basically, just something to abstract the h/w for development, although a h/w simulator might be useful for testing.

Does anyone know what is available?


texts:
I am working on ATSAM4E8C on custom board. The uart0 and its interrupt is working fine but while on uart1 I faced an strange issue. The uart1 is sending the data but interrupt handler is not calling while data reception. I have also confirmed the data reception using polling. Then I copy pasted the same code in ASF where it is working fine (the interrupt handler is invoking). Below is the code. The same code is working in ASF (Echo the received character). Any help is appreciated.

void clk_init()

{

PMC->CKGR_MOR |= (CKGR_MOR_KEY_PASSWD | CKGR_MOR_MOSCRCEN); //Enable Fast RC oscillator but DO NOT switch to RC now

/* Wait the Fast RC to stabilize */
while (!(PMC->PMC_SR & PMC_SR_MOSCRCS));

/* Change Fast RC oscillator frequency */
PMC->CKGR_MOR = (PMC->CKGR_MOR & ~CKGR_MOR_MOSCRCF_Msk) |
CKGR_MOR_KEY_PASSWD | CKGR_MOR_MOSCRCF_12_MHz;

/* Wait the Fast RC to stabilize */
while (!(PMC->PMC_SR & PMC_SR_MOSCRCS));

/* Switch to Fast RC */
PMC->CKGR_MOR = (PMC->CKGR_MOR & ~CKGR_MOR_MOSCSEL) |
CKGR_MOR_KEY_PASSWD;

}

void UART1Init()
{

PIOA->PIO_PDR|=PIO_PDR_P5;  //Disable PIO
PIOA->PIO_PDR|=PIO_PDR_P6;

//Enable peripheral
PIOA->PIO_ABCDSR[0]&=~PIO_ABCDSR_P5;
PIOA->PIO_ABCDSR[1]|=PIO_ABCDSR_P5;

PIOA->PIO_ABCDSR[0]&=~PIO_ABCDSR_P6;
PIOA->PIO_ABCDSR[1]|=PIO_ABCDSR_P6;

//Enable uart clock
PMC->PMC_PCER1|=(1<<13);
//Set Baud rate
UART1->UART_BRGR= 78; // baud rate is 9600

UART1->UART_MR|=UART_MR_PAR_NO;
UART1->UART_CR|=UART_CR_TXEN|UART_CR_RXEN;
UART1->UART_IER|=UART_IER_RXRDY;
irq_register_handler(UART1_IRQn, 0);

}

void U1WriteData(char data)
{

while(!(UART1->UART_SR&UART_SR_TXEMPTY));    //Wait For Transmitter to become ready
//Now write
UART1->UART_THR=data;

}

int main (void)
{

clk_init();
UART1Init();

while(1)
{
}

}

void UART1_Handler()
{

uint8_t data=UART1->UART_RHR;

U1WriteData(data);

}


texts:
Can someone help me with voltage scaling? I've seen some Logic Level Converters from SparkFun but time is matter so I cant wait to get those shipped. I found a topic here:
Scaling DC Voltage [0V-6.5V] to [0V to 10V]
and this scheme is fine for my project, but since i'm pretty fresh in components, i would like to ask what components would be ideal for this voltage scale. Thanks

EDIT: So my question is, which op-amp should i use to not exceed max output voltage of 5V, and which resistors in combination with that op-amp?
My idea is to pick up signal from various sensor in car engine (MAP, MAF, cam positon, fuel system) and scale them down from 5v-0v to 3.3v-0v, process them in Raspberry Pi software i made, and send them processed back to ECU scaled from 3.3v-0v to 5v0v. In global, piggyback ecu with realtime tuning for pre 2000's diesel cars.


texts: Single phase appliance on 3-phase circuit

texts:
Is it possible to have a single phase socket on a 3-phase circuit?

It is a 3-phase radial circuit on a 16 A breaker. The last 3-phase socket on the circuit basically wants converting into a single phase socket to be able to plug the fridge in, it is a 2 kW fridge.


texts:
I'm doing a full-adder using logic gates and I want to express the carry bit with a gate.

So I found the minterms of the carry bit

x'yz + xy'z + xyz' + xyz

Is there a 3-input gate that does that expression just like the 3 way XOR?

for example:

x XOR y XOR z = x'y'z + x'yz' + xy'z' + xyz


texts: In order to have a quad volume control, I thought of having a single log pot between a DC negative source and 4 gates of 4 matched JFET's as shown above. We're talking audio here, I haven't calculate the level of the input signal yet, but I assumed it's gonna be arround 500mvpk-pk. Will it work? I know I could just buy a 4 gang log pot, but they are hella expensive.


texts:
When there is no load connected to the secondary, E is equal to U, and no current flows in an ideal transformer. Now if we connect a load on the secondary of a transformer, the primary will draw a current because E<U (temporarily), why when E gets equal to U the transformer will still be drawing a current "I1" from the mains, doesn't that violate the reason current started flowing in the first place?
I know that the secondary field must be counterbalanced at all times by the primary field, but I have a confusion about the fact that even though there is no potential difference because E=U there is still a current flowing.
Can anyone explain that? And please correct me if I am making any thinking errors.

Image from: DC Machines and Transformers by K Murugesh Kumar


texts: How to define a transfer function for a given system?

texts:
I just finished reading this paper, on how to "draw" Bode plot for a given transfer function. After done reading I realized that it would be pointless to learn this stuff, if I wouldn't know how to make a transfer function of some system (filter, amplifier, etc.) by myself. So, how to make one? What kind of skills are needed for this task to be performed? Can it be done easily or does it require some higher math understanding?

On the other hand, I am wondering, whether is it even worth of struggle, when it comes to understanding of transfer functions of some system? Nowadays computer programs are able to do all that hard work in a matter of seconds, while a person might be struggling with some system for hours and not finding right solution. For example, LTSpice draws a Bode plot (magnitude/phase) for a given circuit for free. So, is there any good in studying and understanding such topics?


texts: How can we say charger's output is 5V and 2.1A without giving resistance?

texts:
Label on my phone charger says it's output is DC 5V and 2.1mA. I find this confusing, because at school I was thought that you can only talk about current when you know exact voltage AND RESISTANCE. So, using Ohms law, I thinks manufacturer assumes that resistance of my battery is exactly 5/2.1=2.38 Ohms.

But how can they assume that if people might use this charger for different types of batteries? Why don't they simply say it's 5V?


texts: I want to drive an AC 220 V load(heater) controlled PWM from Microcontroller. I want to use power FETs to load drive upto 2000 Watts. I m not guessing any valuable circuit design. If anyone have any idea to do this, please help me out... thanx for all...


texts: matrix transformation for state space matrices

texts:
Can we use matrix transformation for the A,B,C,D matrices involved in the state space analysis?
e.g.

In the above figure the state variables are not numbered, like which one is X1 and which one is X2 and the same goes with U. It implies that every time i change the notation of the state variables, i am going to get another set of state equations.
The picture shows two such cases:

My doubt is:"can i apply matrix transformation to A,B,C,D matrices individually which should in a way imply that the naming doesn't affect the matrices as they are transformable from one form to another(as long as the state variables are not changed)."


texts:
I'm currently working on some simple circuits to learn about circuitry, and being a Physics major I have a pretty good grasp of the mathematics and concepts, but I'm a little confused about capacitors. I understand how they work, but am curious about their placement in a circuit.

As a simple example lets say I wanted to charge a capacitor in a circuit quickly and then discharge it slowly. Obviously I would slow the discharge rate by connecting the capacitor across a resistor, but the charging process is where I have a question. Would I still need a resistor? I feel like it depends on what the input to the capacitor would be, and resistors could be used as needed to control the rate of charging. Even still I feel like having a resistor would be a safer approach. Not really sure.


texts: Smart mosfets, logic level input(mosfet replacement)

texts: Basically diesel heater ecu my car uses has an shorted "smart" mosfet BTS141, which drives the glow plug. I don't know much about it since i cant determine the manufacturer. Basically it accepts logic level input and then switches current to the glow plug(glow plug resistance around 0.3-0.6ohms cold and increases very fast) for less than a minute i would guess(glow plug itself is the current limiter etc). What should i keep in mind when i'm temporarily trying to replace it with different mosfet? I will try to find another BTS141 but right now i need something to test and use it for a few weeks. I would have guessed i could just replace it with any mosfet but seeing as its an "smart" one i would rather ask first.


texts: Designing a high voltage AC signal generator

texts:
I'm trying to design a high voltage AC signal generator for some lab experiments.
This schematic is as far as I've got and I wanted to sanity check the basic approach before I continue as I'm used to working on low voltage DC stuff.
EDITED because I completly mischaracterised the nature of the wave forms:
I need to generate various bipolar pulses with a peak no load voltage of around 120V, but at very low power - around 3 watts maximum. The pulses are of a fixed length, but are sent at a variable frequency (So there are gaps between pulses for anything below max frequency.
For Example: A sawtooth wave where the wave length is 2.5 milliseconds, and one complete wave may be sent anywhere from once every second to 400 times a second.
I've based it around a 3 watt fully differential audio amplifier driven by two 12 bit DACs (an MCU will control the two DACs.) The amplifier output drives the secondary coil of a transformer - currently 6V secondary and 240V primary 50/60Hz. The primary coils go through a relay so they can be disconnected from the equipment's output terminal.
The equipment needs to be portable so it will run from a battery.
Is this approach going to work, or am I heading in completly the wrong direction?

As a bare minumum I need to reproduce the following waveform. It is 5ms long and would, at the maximum rate, equal 200Hz. Anything beyond this is a bonus.

I did some bench tests with a DAC, an audio amp (NOT the one in the schematic) and a 6V 2.5VA to 240V 50/60Hz transformer. Unfortunatly the output from the audio amp is a bit distorted.


texts: Is this the correct way of measuring Zi in LTSpice?

texts:
I need to simulate the parameters of this common collector npn amplifier, I've calculated Zi to be 20kOhm with BF=420 (minimum value in datasheet for the model). However the AC analysis gives me Zi of 16kOhm at most.

The transistor should be a BC547C (fairchild), but since there was only the spice model for BC547B in their website, I changed BF to the average value BF=610. For BC547B model BF=1340 (even though the datasheet has ~325), isn't the datasheet value I should use in the model?

I can't test the real circuit, so I feel blind trying to adjust values to what I can calculate...


texts:
I have a few questions regarding CAN bus load

Is there any derived equation/formula to calculate the bus load?

I need transmit below frames(Assume Standard frame format) at baud rate 500 kbps on the bus
5ms  ----- 50 frames.
10ms ----- 10 frames.
100ms ---- 30 frmaes.
Event messages ---- 10 frames.

How to calculate bus load, does anyone knows kindly illustrate the same?

What is the maximum bus load on CAN bus?


texts: How to simulate analogue output sensor with MCP3008 ADC. Can I use a 10K potentiometer with Raspberry Pi 3.3v?

texts:
I am working through a series of lessons with the Raspberry Pi 3 Model B and the next lesson is Raspberry Pi Starter Kit Lesson 10: Raspberry Pi SPI Ports which involves hooking up a MCP3008 ADC output to several pins on the Raspberry Pi and then connecting two of the ADC analogue input pins to the 3.3v rail and the GND rail with a reference voltage of 3.3v from the 3.3v rail.

What I would like to do is to be able to vary the input to the MCP3008 ADC to simulate a sensor such as an analogue temperature sensor.

I was wondering if I could do this by adding a 10K ohm potentiometer in connection between the 3.3v rail and CH0 of the MCP3008 ADC?

Addendum: adding PWM driven LED with varying levels

After adding in the potentiometer, connecting the wiper output to CH2, and looking at the numbers change as I changed the knob setting, I then modified the circuit by adding an LED to GPIO #18, the hardware PWM pin.

So the modified application used a loop to query the relative voltage level, 0 to 1023, from the MCP3008 on the channel to which the potentiometer was connected, CH2. The value was then used to set the Duty Cycle of the GPIO #18 pin which was provisioned as Pulse Width Modulation (PWM) with the default range of 1024. Changing the Duty Cycle in turn changed the illumination level of the LED. So as the knob on the potentiometer was twisted to a new setting, the LED brightness level changed.

Addendum: Use photo-resistor with MCP3008 as alternative

An alternative to using a potentiometer is to use a photo-resistor connected to ground with a 10K ohm pullup resistor connected to the 3.3v rail. A connection is then made between a channel pin of the MCP3008 and a connection point between the 10K ohm resistor and the photo-resistor.

The result of this circuit is to provide voltage levels that vary depending on the amount of light the photo-resistor sees. Light levels can be made to vary by using a shading device such as a physical paper tube over the photo-resistor or by using a flashlight to illuminate the photo-resistor.

Addendum: SPI protocol with MCP3008

Here is a nice tutorial and explanation of the MCP3008 and how to interface to it with SPI. Interfacing an SPI ADC (MCP3008) chip to the Raspberry Pi using C++ (spidev).


texts: Scope voltage drop across a 7R5 resistor

texts:
I am currently measuring the current draw of a PCB and have managed to get down into the uA range. I am able to read 8uA when I use my TENMA 72-7780 as a current sensor.

However when I use a 7R5 current sense resistor and two scope probes either side of the resistor, both referenced to the ground connection of the N93CX power supply I get a ~600uA calculated current draw from V = IR, 0V005 = I 7R5 .

I had a look at the input resistance of my probes ( P6060 ) and they are 10MR, which should only give ~0.3uA draw. The power supply has a ~0.5m cable from it to the 7R5 resistor. The scope probes are ground referenced by their clips to the end of the ground cable.

Does anyone have any idea where this 600uA calculation error is coming in?

simulate this circuit – Schematic created using CircuitLab


texts: How to protect input against both ESD and reverse polarity?

texts:
I need to protect an external input on a device against both reverse polarity and ESD (IEC61000-4-2 +-8kV).  The normal input is +5V dc at 100-200mA; the reversed input could be -5V and that should be blocked (maybe with a few uA leakage).
I tried to design this using a TVS device (TI TPD3 or TPD4 series) and a low Vf Schottky diode (PMEG2005 or similar).  The problem is that whichever device is put first would be damaged by the condition that the other one protects against.
Option A:  TVS first

Reverse polarity would damage the TVS - it is definitely not rated to have an input go below ground-0.3V, especially not one with decently high current.

Option B: Schottky first

simulate this circuit – Schematic created using CircuitLab
Here ESD would probably damage the reverse-voltage blocking diode D2.  I actually don't know what happens if an ESD strike hits the diode.  At moderate voltages above its rating the diode would go into avalanche, and that can damage it if the total energy is high enough to cause localized heating.  A single ESD strike doesn't necessarily have enough energy to cause bulk heating, but the available power levels are very high, and the current may channel to small areas.
I know there are TVS devices which handle symmetrical voltages around ground (essentially back to back zeners).  Unfortunately, in addition to this 5V 100mA input, I have some data inputs that are 0-5V.  I'd like to protect both with a single TVS device. I pick a symmetrical TVS, I can put the TVS first and that basically works, but in the case of a negative-polarity strike on the data lines it would only limit the current to the negative clamp value, not to ground.  So it is likely to do damage to anything connected to the data lines behind the TVS.
What is the best way to protect a device against both ESD and reverse polarity?


texts: Estimate data transmission rate on a given frequency using FM

texts:
How can I estimate how much data can I transmit on a given radio frequency range using FM?

My goal is to consider using radio to transmit data packages, and I want to evaluate bandwidth.

Plus points for the question: how much of a problem will distance be? We are looking for something like 100km on an open field.


texts: Help understanding this equivalent mechanical circuit of a piano string?

texts:
I'm studying this article to help with an audio synthesizer design for guitar/piano strings.

Musical strings can be conceptualized as having both vertical (perpendicular to the soundboard/body) and horizontal vibrations. Slight differences in the horizontal and vertical vibrations contribute to the sound. In particular the vertical vibrations tend to decay a bit faster due to greater coupling with the soundboard/body. The horizontal and vertical vibrations influence one another by coupling at the bridge pin where they are attached.

This can be modeled as a mechanical equivalent circuit like so:

I don't have much experience in circuit design. I am trying to understand the way the signal flows in Figure 3. I have a few questions:

What do the hollow circles at the top and bottom portion of the circuit represent?
Which way does the circuit flow throughout the entire diagram? Can you add some arrows to illustrate?
eg. The arrows for force (f) and velocity (u) indicate that a horizontal string excitation (f3,u2) will pass through the bridge pin transformer and create an excitation (f2,u1) that can then pass through the soundboard and this should lead to ground as per Fig 2. Is the whole bottom of the circuit in Fig 3 ground?
eg. How would a horizontal string excitation make its way into exciting a reactive vertical string excitation in this model? Or vice versa? They should be able to excite one another directly in either direction through the bridge pin. Where does the signal flow both ways in Fig 3 to allow this?

Thanks for any help. I think if I understand the signal flow I should have a better chance of understanding this behavior.


texts: TEC 12706 not drawing more than 1.6A when powered by a 12V PC SMPS

texts:
I have recently bought TEC 12706 device from Sunrom.com; The specification says that the device can draw more than 6A current at 15.4V and internal resistance is ~2 ohms.  But when I measured the internal resistance, the device shown ~6.5ohms and when I powered it using 12V PC SMPS, the device did not draw anything beyond 1.6A. I had tried connecting the device to my fully charged inverter battery (12v 120Ah) measuring a float voltage of ~13.5V.  To my surprise, the device drew just over 2A max.

I was using a slightly larger heatsink with a cooling fan on the hot side and was keeping the cold side open.

The SMPS can easily supply 10A.
Heatsink was typically 3 times the area of the peltier device

What could be wrong in my configuration?

Datasheet: http://hackerstore.nl/PDFs/TEC1-12706.pdf


texts: parallelism and puncturing in Turbo Codes

texts:
I understand that puncturing is the deletion of certain bits in the encoder output according to a matrix, but I am having trouble understanding the benefit of this. Does this just provide better way of overlaying the data to decode it? And if bits are deleted how exactly is it recovered?

Similarly, I am having trouble understanding parallelism. My current understanding is that it is kind of like diversity combining and multiplexing. How exactly is it different?

I have asked both questions under the same post because they are both concepts involved with Turbo codes.


texts: What is the relationship between bandwidth and noise bandwidth

texts: What is the mathematical formulae for noise bandwidth for a 1st order low pass system (and a second order LP systems analysis if possible). What is the importance of this concept, how and when is it applied? A nice graph showing the noise BW and the BW and mathematical derivations would be excellent (for both 1st and 2nd order systems).  Extensions to bandpass filters would be helpful too.


texts: I2C Bus is Not Responsive When Engine Is Running. How to Diagnose and Fix?

texts:
I've got a solder-less bread-boarded prototype microcontroller with a few I2C devices that take some measurements on a motorcycle. For now, The MCU is powered by a LM7805 with decoupling caps near the device from a 12v source. The devices are working fine when the power is on, but when the engine is started the I2C devices become unresponsive, but SPI still works just fine.

There are only two wires which are connected between the MCU and the motorcycle. 12v power and ground. The rest of my devices are isolated.

How do I diagnose the issue? I've got a very basic scope, logic analyzer, and a nice multimeter. Where should I begin? What other information can I provide?

Is there any kind of filtering that I can try? Maybe Some type of Low-Pass Filter on the 12V feed?

Update: Per the comments and answers, it seems that the engine running engine is introducing some type of noise which is causing the issue.(I suspect the charging system/alternator, but I can't say). Also, with my lack of a pro-grade oscilloscope, I am unable to actually see the noise. Some possible solutions are:

ditch the breadboard for a PCB
better power supply/filtering
I2C Bus isolation
All of the above?

Update: I was thinking about some comments and EMI and remembered that the device worked when I had it on the bench but still connected to the motorcycle with the engine running. I had the breadboard fixed to the top of the gas tank and the I2C bus was not working. So, I just lifted the breadboard off of the gas tank about 3 inches above and the I2C bus became responsive after a power cycle of the system. When I moved the breadboard slowly back down toward the tank, the I2C would get corrupted! Note: The ignition coils are just beneath the tank as well.

So, is this an EMF/EMI issue? How Do I mitigate this?

Are there any low cost, easy to implement, low noise regulators that I could try instead of the the LM7805? What simple things could I try to fix this?

I've designed a PCB, but hesitant to order/make one unless I know this it's going to work in my case. Is there any type of PCB peer review where I could get an "OK" on my design?


texts:
I am designing a USB JTAG adapter using FT2232D.

Most JTAG reference designs use a level translator to drive JTAG pins with VREF. I understand VREF is used because different voltage levels at target boards can be programmed this way.

But I am using fixed 3.3V with an LDO from 5V USB power supply, so I don't want to use level translators.(I will only use JTAG adapter to access 3.3v target boards)

Only design, which I found, that doesn't use level translator is in this document(page 23) http://www.risec.aist.go.jp/project/sasebo/download/SASEBO-GII_Spec_Ver1.01_English.pdf

In this design VREF is connected to JTAG adapter's 3.3V supply. Is this necessary? I don't understand why VREF is connected to JTAG adapter. Isn't only GND connection enough to drive JTAG port since target board and JTAG adapter has same voltage level which is 3.3V?


texts: Adding Blinking LED to Low Battery Circuit

texts:
I'm thinking of designing a PCB based on this low battery indicator circuit:

It hooks up to your battery of choice and has a green and red LED, and uses a trimmer pot to adjust at what voltage want the red LED to turn on and the green off. I want to add a function where the red LED will start blinking when the battery life is extra low, or right about to die. If I can't make the existing red LED blink, i'm open to adding a third LED (a blinking one), and possibly having to add another pot to specify its voltage. If I were using a 7.4v battery pack, this would make the new setup: Green - 6.5v-8.4v; Red - 6.3v-6.4v; Blinking Red - 6.2v. The first two settings can be set with the existing potentiometer, I just need to add the third setting.
Thanks!


texts: What are some disadvantages of having exposed pins on a connector?

texts: For example, the Apple Lightning connector has exposed pins. What are some disadvantages of exposed pins besides corrosion (and shorting out the power supply when not in use, which shouldn't be a problem if the power is only turned on when plugged in)?


texts: Identifying a 3-Terminal Component (probably some sort of magnetic device?)

texts:
I am trying to identify this component from a circa 70s AM/FM radio.  It was attached to a flip clock, which makes me think that it is a magnetic device responsible for the "flipping" action of the clock.

The three terminals are labeled N.O., COM, and N.C., in that order.  Google search isn't being my friend right now, and is giving results which seem completely unrelated.


texts: Can someone explain the different relay schematics contact types?

texts:
I'm looking at relays and there are multiple types of contacts forms, such as: A, B, C, X, Y, Z and much more. Searching around found different schematics for same form.
Can someone explain them or show me a picture of the different contact forms?


texts: Confusion with KCL in Telegrapher's equation's derivation

texts:
In a text about the derivation of Telegrapher's equation the following is given:

But what is the last term I pointed with a red arrow in KCL? There is only one current entering and two leaving through C and G. To me the currents in the KCL should be the following marked in red:

What is i(z+Δz, t) in their KCL? It is very counterintuitive. Isn't already i(z+Δz, t) is equal to the sum of the current through C and G?


texts: What is or what "fast-ramping batteries" means at this context?

texts:
I'm trying to do a economics report of Battery Storage, but I'm from Brazil, so I have to find especific words used in portuguese to describe certain things in electrical setor. I find this term "fast-ramping" and have no idea what this means. I think if someone explain the means and a context for this expression so I can find an equivalent word in my language.

Context:

"Balancing grid supply and demand.  Batteries can help balance electricity supply and demand on multiple time scales (by the second, minute, or hour).  Fast-ramping batteries are particularly well suited to provide ancillary grid services such as frequency regulation, which helps maintain the grid’s electric frequency on a second-to-second basis."


texts:
I'm developing a data logger powered by Li-SoCl2 (http://www.100y.com.tw/pdf_file/02-SAFT-LS33600.pdf) battery and I have no idea on how to overcome the problem of estimating the residual charge of the cells.
The discharge voltage curve is so flat and also changes with temperature (on board I have a very precise temperature reading).

Does anyone have a suggestion?


texts: Establish connection between analog and GSM modem

texts: I want to know if I can call a GSM modem (a SIEMENS MC55) from a normal analog (PSTN) modem. If so, how do I have to configure the GSM and the analog device? I've read about the +FCLASS and +CSNS commands but the connection doesn't work - I'm getting a BUSY or NO CARRIER. Are there other requirements?


texts: What is the impedance of this Common Emitter transistor

texts:
I see this question on EE but the other question is slightly different of what I am asking.

Suppose this circuit:

Suppose I will add a capacitor to the input but I need to calculate the input impedance of the circuit on the picture.

Suppose the impedance was fixed for all frequencies. If I understand correctly, if the impedance could be measured by a multimeter it would be the "resistance" measured from the point IN to ground, right?

If this is true, it would be R2 in parallel with the sum of rEE and Re, or in other words

Rin = rEE + Re

where rEE is the base/emitter resistance (25mV/Ie), right?

Then, if that transistor is biased at 1mA,

rEE = 25mV/1mA = 25Ω.

So, if R1 = 20kΩ, R2 = 2.7kΩ, Rc = 3.9KΩ and Re = 470Ω

So Rin = 2700 // (25 + 470), that would be 418.3Ω...

but I have found one author saying Rin is in fact equal to βrEE and does not even include Re.

... and now I have found a post on EE showing a very complex formula that takes into consideration R1, R2, Re and other components.

What is really the impedance of such circuit?


texts: Debug Netduino without .NET Micro Framework

texts: I have a Netduino, but I am programming it using the GNU ARM toolchain in Eclipse and VisualGDB so the .NET Micro Framework (NETMF) firmware has been removed. Is there a way I can set it up for debugging from Eclipse or VisualGDB?


texts: What is typical power consumption of FPGA devices

texts: I am new to this site and had one question. I know typical CPUs have power consumption (TDP) in range of 100-200W, for example Intel Core2. I wanted to know what is typical power consumption of FPGAs. I saw this paper, where it says power consumption of Xilinx xc5vlx330 is 30W, but it gives no reference. I wanted some authoritative reference of any FPGA board (preferably high-performance FPGA) and any company. I searched online where they provide datasheets, but they do not clearly tell the power value, but only direct to power estimation tool.


texts: Relation between forward bias and current in a diode

texts:
I have seen the VI graph to depict the relationship between forward bias and current. (left graph) and I think I get it. I have also seen another graph (right graph) to depict the relation between forward bias and current.
Are both these graphs depicting the same relationship?
If so, why they look different for the forward bias part?


texts: Soldering capacitors onto a board that is spinning

texts:
So i need to solder a 4.7 uF capacitor in parallel to a 0.1uF capacitor to a very small pin of an MCU.

This is doable and I have done using tantulum capacitors, but the problem is that for the time being these capacitors are being attached to a prebuilt board thats application has it spinning quite quickly.

This often results in the wires breaking and needing to be resoldered, but each time it becomes more difficult and more likely i will bridge the pins. I have another board to use, how would I attach these capacitors so that they arent tugging on the pin and thus less likely to unattach?


texts:
I am using LTSpice with the following NMOS model from the library included in the famous book 'Sedra & Smith, Microelectronic circuits' :

*       Level-1 Model for the 0.5-um NMOS Transistor (Part NMOS0P5)
*       (created by Anas Hamoui & Olivier Trescases)
.model  NMOS0P5 NMOS(Level=1 VTO=0.7 GAMMA=0.5 PHI=0.8
+       LD=0.08E-06 WD=0 UO=460 LAMBDA=0.1 TOX=9.5E-9 PB=0.9 CJ=0.57E-3
+       CJSW=120E-12 MJ=0.5 MJSW=0.4 CGDO=0.4E-9 JS=10E-9 CGBO=0.38E-9
+       CGSO=0.4E-9)

Well, to analyze my simulations, I try to make my pencil and paper analysis to notice possible differences.
However, I need to know several things about my MOS, and I can't find the factor ' K = mu_n * C_ox '.
Where should I find it ? Under which name ? I see that often other MOS models for SPICE include this factor in the model definition, which I can't find in the one I am using.

For information, this model, under SPICE, works perfectly well.

Thanks a lot for your help,
Ryl


texts: DIY SMD - options for covering exposed vias?

texts:
I printed a PCB + got a kapton stencil made for a project I'm working on. One of the components is a BGA chip, and has vias close to the bga pads. The vias on the board don't have solder mask on them, and I'm concerned that this may lead to a short I won't be able to see. Is there something I can apply manually to minimize the chances of this, or should I not worry about it and hope that the stencil won't allow enough solder in there for a bridge?

I assume whatever it is, needs to have a high-enough melting/burning point that it won't catch fire during reflow, and also have a low - enough surface tension to not create a bump that will mess with the chip clearance?


texts: Demostration of relation between Synchronous speed and Line frequency

texts:
In several books the stator magnetic field frequency is related to the line frequency of the stator current using the number of poles (which is the double of the pole pairs) do you have a demonstration of this?
Even a detailed pdf is usefull.
Thank you


texts:
I've been struggling with a problem given to us during a exercise-session of waveguides.
First part of the exercise was calculating the electric field inside of a waveguide in the form of 2 parallel plates, with it being a TE1 mode. This was simple enough and I won't bother you with the numerical values:
$$E_y = C.sin(\beta_x x)e^{-\beta.j.z}$$
With \$j=\sqrt{-1}\$ and \$C,\beta,\beta_x\$ constants.
Now the part with which I have difficulties is the following task:
Find the expression of the electronic field in the frequency domain of the uniform plane wave that causes this TE mode.
The solution given to us afterwards is this:
$$E_y = \frac{C}{2}e^{-j\beta z+x\beta_x}$$
The constants still have the same values and there is little to no explanation given with these solution. I've tried to convert the sine in the first equation to its exponential form, which takes care of the factor 0.5 and turns it into a similar expression as the second expression. But now I'm just lost, I don't know how I can convert this into a uniform planar wave.

Some extra information: the whole situation is considered to be lossless and the 2 plates are conductors so there is only reflection (though I don't think this is relevant)


texts:
I have one solar related question, but please bare in mind that I am a complete newbie in this field so if my questions are stupid, I apologize.

I want to use a solar panel with this USB controller/charger for smartphone/tablet charging:

(source: https://www.aliexpress.com/item/OOTDTY-5V-2A-Power-Bank-Solar-Panel-Voltage-Controller-Charge-USB-Regulator-5V-20V-Input-5Vdc/32825541743.html )

I found a lot of different solar panels that match my needs (primarily, by their dimensions) but when it comes to watts, I dont know what to select (or better yet, I dont know what is enough). So, if it is possible, can you tell me how many watts is enough to charge today's smartphones or tablets?


texts:
I'm designing a self sustaining guitar that has 6 amplifiers onboard and runs on a li-ion pack.
Power draw is a about 2.5A when on "full power" and I decided to make my own step up converter to get the 3.7v from the battery pack to 6v.
I went with a MAX1771 controlling an IRF630 mosfet and just followed the reference example circuit from the datasheet, the bootstrapped version as apparently it's better for a low Vin.
Without load the circuit works fine but when plugging it to the amp board the output goes back to Vin through the diode, the controller's duty cycle is 90% ON at 50Khz -max power I assume- and can't see any voltage spikes on the inductor from the switching.
Now the mystery:
Why if I connect a resistive load to the output I can easily draw 500mA from the output and with the controller being quite relaxed on a low duty cycle, while if I connect the amps board the Vout goes back to battery level even if they're not using any power and the current draw is just 50mA?
one note: I noticed that when trying to power the amp board, SW out of the controller to the mosfet is 3.5v that seems a bit low to make the mosfet fully conductive. Though this signal can't be more than Vd and if Vd=Vout=Vin how is it supposed to start the system?
Any ideas?
Thank you in advance!
Cheers


texts:
I'm trying to do FM modulation on a signal and pass it to the PC and demodulate it using matlab. Matlab requies the frequency deviation in addition to the carrier frequency to do the demodulation. I considered using timer 555, Xr2206 and Icl8038 to do the FM modulation but their data sheets don't show anything about the default frequency deviation or how to set it. How can I find it? and if there is another option to do FM modulation with a known frequency deviation please share it with me. I know that frequency deviation can be calculated by the modulation index, but even that I couldn't find it on the data sheets. Here are the links for the data sheets of the 3 chips.

https://www.google.ae/url?sa=t&source=web&rct=j&url=https://www.sparkfun.com/datasheets/Kits/XR2206_104_020808.pdf&ved=0ahUKEwja3YCX87_RAhVJVhQKHZtyACwQFggYMAA&usg=AFQjCNFXtU-KvN2EznTFZbg1HQhIdJzUyQ&sig2=cCA2-zfyAj9R3PUqVtso1Q

https://www.google.ae/url?sa=t&source=web&rct=j&url=https://www.intersil.com/content/dam/Intersil/documents/icl8/icl8038.pdf&ved=0ahUKEwjfpcXu9L_RAhXFaRQKHRUEBiwQFggYMAA&usg=AFQjCNGATe_GMj8vKnVTuETXAEj4-n_JRw&sig2=QCGBQEXSTJuNZZ6fKQWVww

https://www.google.ae/url?sa=t&source=web&rct=j&url=http://www.ti.com/lit/ds/symlink/lm555.pdf&ved=0ahUKEwihlIXj9L_RAhVJ7RQKHR4jDioQFghLMAs&usg=AFQjCNHIrM2lP_uK2NRBO9CQr5erPxOu0Q&sig2=ana5qX18si_Oz5Yxe1-7ug

Thank you


texts:
I am studying Transistors from the book - "Arts of Electronics" by Paul Horowitz and Winfield Hill (second edition).

In the text, there is the following circuit (under title - Transistor Switch) on page 63:

simulate this circuit – Schematic created using CircuitLab

I understand that the transistor would work in the saturation state, because otherwise the collector voltage would be -84V, i.e. less than the emitter voltage (which in this case in zero).

However the text mentions,

  Overdriving the base (we used 9.4mA when 1.0mA would have barely sufficed) makes the circuit conservative.

  Incidentally, in a real circuit you would probably put a resistor from base to ground (perhaps 10k in this case) to make sure the base is at ground with the switch open.

My questions:
1) What does the first line (from the text) mean? What is the meaning of a circuit becoming conservative?

2) Why would we have to place a resistor from base to ground? How do we decide the base voltage in absence of current i.e. switch is open? Because in that case collector voltage would be 10V and emitter voltage would be 0V, how do we determine base voltage?


texts:
I am confused about when to use KVL/KCL or ohm's law to solve the circuit question?

I need to compute voltage in point B and point C, every current pass through R1 R2 R3 R4

R1= 100 ohm, R2=300 ohm, R3=250 ohm, R4=500 ohm

V1= 5V, Is=20mA

I tried to use ohm's law to find all current first, but I don't know how to use
Is to help me. Or find out the total resistance then finding total current?

And how to use Is when applying KCL, is it a current source?

Or I can separate circuit into two independent circuits to solve the question.

I hope someone can help me to clear my electricity concept.

the resistance of r1 and r2 =1/(1/100+1/250)= 500/7 ohm ≈ 71.4 ohm

total resistance of a circuit = 500/7 + 300 + 500 = 6100/7 ohm ≈ 871 ohm

current supply from 5V : I = V/R = 5/(6100/7) = 7/1220 A ≈ 5.74mA

I1=5.73 mA

I1=I2+I3

5.73= (VB-VGround)/250 + (VB-VC)/300 = VB/250 + (VB-VC)/300

5.73=VB/250 + (VB-VC)/300  -(1)

I4+Is = (VC-VGround)/500

I4+ 20mA = VC/500 -(2)

apply KVL:   VB-(VB-VC)+VC = 0 -(3)

Is it correct, should I continue?


texts: Circuit Analysis with constant current and voltage sources

texts:
This is a homework question of sorts. I am supposed to find the voltage across AB.

I know that the answer is 24 volts by traversing from B to D to C to A adding up voltages of resistors, but should I not be considering the contribution of other elements in the circuit, for example, the 10 V source? Pretty sure there's a gap in my knowledge.


texts: audio-taper potentiometer in 50-100 ohm range

texts: Anyone know where to source an audio or logarithmic taper potentiometer in the 50 or 100'ish ohm range ?   Mouser and Digikey don't show anything, even non-stocked.  I'd like to build an adjustable current source with an LM317, and the current is proportional to the reciprocal of the adjustment resistor - so a linear taper is far from ideal.  Thanks !


texts: Clarification about the effect of feedback resistor on the input impedance of an inverting amplififer

texts:
Below is a typical inverting op amp topology:

I was about to answer to this question, but I wasn't sure about the conclusion and couldn't find a supporting document so far.

Normally in tutorials they explain the input impedance of this topology simply as:

Rin = R1.

This is because the voltage at the inverting input is "approximately" zero, so one can say: I = (Vi  - 0)/Rin .
This looks like an approximation neglecting the effect of Rf.

I'm trying to derive the input impedance in terms of feedback equation to see the effect of Rf.

Calling "a" as the open loop gain.

Ir=If=I

Vo = -a*Vd

Vd = (Vi-I*R1-0)

Vo = Vi-I*(Rf+R1)

-a*(Vi-IR1) = Vi-I(Rf+R1)

Vi(1+a) = aIR1 + I*(Rf+R1)

Vi(1+a) = I(a*R1+R1+Rf)

Vi/I = (R1*(1+a) + Rf) / 1+a

Rin = Vi/I = R1 + (Rf / 1+a)

So is the equation Rin = R1 + (Rf / 1+a) correct?


texts: 3d printer MOSFET can't use on car bulb, but can use on other load (ie. LED, dc motor, relay)

texts:
I want to use a MOSFET that can handle high current use for switching, so I decided to use the external MOSFET for 3d printer. I tested it out on other loads such as motor, LED, relay it is able to conduct when I connect the control to a 12v voltage. But when it comes to a car bulb it doesn't seem to light up.

The car bulb is able to light up when connected directly to the 12V car battery, but cant light up when connected through the MOSFET.

The MOSFET power source is from a 12v battery, the load part is connected to the light bulb and the control pin is connected to a 12v dc source, and has also tried to connect it directly to the 12v battery. In which both cases are able to switch on other loads but not the car bulb.

The VGS of the MOSFET is 10V, in which when 10V is applied across the gate the source and drain of the MOSFET is suppose to conduct current.


texts: Need circuit to close switch on detecting current (12V)

texts:
I have a project where I need to detect whether a 12V circuit is live or not.  If it is I want to close a switch (actually close a digital IO input on an Adicon SECU16 Digital IO controller).

I am not an EE and would prefer to find a component off the shelf that I can tie into the 12V circuit and provide the relay.

I could choose to not use digital (Supervised) input and instead do analog, but I really don't care how much voltage I'm seeing just whether it's on or off.

I'm capable of soldering a few components on a prototype board, but my lack of EE knowledge means I need some serious help selcting the right components.  The simpler the better.

Thanks in advance.


texts:
So I have this simple OP-AMP circuit that is supposed to be a low-pass filter for which I made the calculations so it passes all frequencies below 1591 Hz (approx). The values of the components are in the image.

However, the frequency response in my simulation program (LTSpice) is way higher (two orders of magnitude!) above my theoretical ones.

To make it even funnier, empirically I got the correct frequency response (in a bread board with an LT1013 Amp) so what's wrong in my simulation?

[![LTSpice Simulation.

For Circuitlab I got the expected output as well. Same circuit. Is LTSpice that bad?

simulate this circuit – Schematic created using CircuitLab


texts: This may be more suited for another exchange site, but I thought it'd try here anyway. I'm trying to figure out how to get pitch and roll relative to the ground. Say my vehicle is going up a hill, but my vehicle is level with that hill as it goes up to a degree. How would I go about getting that pitch? I've been playing with the MPU6050 and this still boggles my mind.


texts: Why do French power sockets have a protruding ground?

texts:
French power sockets have a protruding ground. Why did they make this decision?

I can't see any major benefits from it, it saves some pennies on each power cord, but it exposes the ground connection to people nearby, which can be dangerous as in real life grounds are not perfect, they can have a live voltage and are a risk of electric shock if there's lightning nearby.

Once someone told me they are safer because the ground connects first, but this is also nonsense as the order of connection depends on the size of the plugs alone and not where they are.

In case you don't know what I am talking about:


texts: There are multiple things to be discussed regarding LEDs and KVL

texts:
simulate this circuit – Schematic created using CircuitLab

I have 3 Red LEDs and a 3 volt cr2032 coin cell. All the LEDs are in series with the cell. Obviously, none works as the combined forward voltage is more than supply voltage. But voltage across each LED is 0.12 volt, but it should be around 1 volt. The main problem is with sum of the voltages; the supply voltage is showing 2.88 volts on multimeter whereas adding the voltage across each led gives me only 0.36 volts. Where is the rest of the voltage? since Total voltage = V1 + V2 +V3. Is there any theory behind it? The same problem occurs with LEDs of different forward voltages with the same cell. For example, white in series with red.

I think that when these LEDs are in series there is a small current flowing through the circuit. And according to its V-I curve, for that small current, LED gets a particular voltage across it. Because when only 2 LEDs of same forward voltage (same colour) are in series they satisfy V=V1 +V2. Please help with this one and thanks already.


texts: TXE bit not reset in USART communication

texts:
I am programming an STM32F2 Cortex M3 chip (reference manual here). Specifically, I want to transmit bits through the USART. Reading pages 620 and following, I understand that the TXE bit of the USART status register should be reset by hardware after writing data to the data register.

I have not been able to get the TXE to reset. It is set at bootup, and even after writing to the data register, it stays set.

The reason I'm reading the TXE bit is because I want to make sure that I'm not overwhelming the USART with transmit requests. How can I get the TXE bit to reset? Should the TXE bit be read in normal communication?


texts: MC34063 help - step-up with an external switch

texts:
I'm attempting to design a ~200V, relatively low-current (10mA expected, I'm allowing a bit more though) power supply for some Nixie tubes, and I've decided on using an MC34063 step-up converter. It is my understanding that to reach >40V some kind of external switch is necessary. By looking at specs and at several other designs like this, I have chosen the following components:

Switch: IRF720
Rectifier: BYV26B

I should add that I am relatively inexperienced in this area, and I'm trying to use this as a learning opportunity.

Looking at the formulae on the MC34063 datasheet, the very first calculation for ton / toff (related to duty cycle) is:

V    + V  - V
 OUT    F    IN (min)
---------------------
   V         - V
    IN (min)    sat

Assuming these calculations are even valid for an external-switch configuration, I'm stuck with how to determine Vsat.

If the saturation voltage from the datasheet (1V typical, 1.3V max) adds with the gate-source threshold voltage of the IRF720 (2V min, 4V max), the worst case scenario well exceeds my minimum input voltage (4.75V, I'm allowing 5V ± 5%). This immediately smells like it's not going to work.

Upon further examination, all the designs I've been referencing have either a higher input voltage (~12V) or use another external transistor to drive the MOSFET.

Does anyone have any advice on how to choose a more suitable external switch, or how to calculate these parameters correctly for an external switch configuration?


texts: battery management IC - duracell alkaline

texts:
I'm trying to monitor the health of my duracell consumer battery.

Is there an IC that can do this? I've come across the MAX6775, but it appears that you have to use a voltage divider. Isn't this drawing excessive current? This is for a ultra low power application.

Ideally, I'd like to switch on and off the monitor IC every 10 minutes, take a reading and turn it off again so as to minimise power.

Can someone please suggest how to do this/suggest a suitable low-power IC?

Many thanks in advance,


texts: How to find a capacitor for LDO that meets ESR requirements

texts:
I am searching an suitable input and output capacitor (for example MLCC) for following Low Dropout Regulator (LDO): Analog ADP151.

The datasheet says that the ESR of the caps should be between 0.001 and 0.2 Ω.

I know the ESR vs. Frequency graphs on the capacitor manufacturer pages, but at which frequency do I have to look to find a suitable capacitor?


texts: Sorry for amateur and maybe "cheap ass" question, but i was thinking if desoldered solder can still be useful. Can it?


texts: How to setup the oscilloscope for measuring power supply response

texts:
I need to measure the overshoot and to modify some capacitor values in the feedback loop of the operational amplifiers in order to find the best response of the power supply (it's a linear power supply).

I am using a GDS1052U oscilloscope from GWInstek.

I am using a switch load made by LM555 and a power mosfet and the signal coming from 555 can be seen on the 10ms/div while the overshoot can be seen only on the 250-500ns/div.
I did not found any information for measuring this by using my type of scope. If I use auto settings there nothing appears on the screen.

Please let me know, how to measure this with my scope and what setting should I use?

This is the screenshot on 250ns/div
]1

This is the signal generated by the LM555:

Why the overshoot can be seen on 250ns/div, while the comutation signal of the load can be seen at 10ms/div?


texts: Delta Modulation Frequency in the Integrator

texts:
Ok guys, I can't understand a thing, I have made this circuit, that is a delta modulator:

As you can see with an input of 5Vpp, in the output of the integrator I found a square wave signal, that has a frequency of 10Khz
But if I put an alimentation of 1mVpp as you can see [With the same Frequency of the input Signal] I have in the output of the integrator a signal that has a frequency of 200KHz:
Why this happen?How can I calculate this frequency?


texts:
Most op amp chips have frequency compensation added to them. It is
  introduced to ensure they remain stable and do not produce unwanted
  high frequency spurious oscillations. - source

Does this mean the opamp is not good at high frequencies  ?

Some manufacturers, promote their opamps as 11MHz, such as TI's OPA140.

So what did I miss here ?

What is the effect of frequency and bandwith of opamp on amplification ?

The more lower the more good operation or reverse ?


texts:
it is known that in an ideal waveguide (with a perfect electric conductor and with non-dispersive and non-conductive dielectric) there is a cut-off frequency, for each mode, such that for higher frequencies the electromagnetic wave propagates without attenuation (the wave vector is purely imaginary), for minor frequencies it propagates with attenuation (the wave vector is purely real).

Briefly, the wave guide is a high pass filter, for each mode.

Now my question is: let's consider the situation in which the frequency is lower than the cut-off frequency. There is total attenuation of the EM wave. Which is the reason for that? Where does the EM energy go, since the dielectric is non - conductive?


texts: 1-Wire Serial communication to standard RX/TX Serial ports in microcontrollers

texts:
I just want to start by saying that I'm relatively new to electrical engineering in general, so if I sound absolutely retarded please bear with me.

As part of a learning project I'm working with a few color sensors, specifically Parallax's ColorPAL 28380s, and I have both an Arduino Uno and Arduino Mega 2560 lying around to grab data off them. I've been fiddling around with the specifics for this project over at the Arduino SE but I suppose this question could be for any microcontroller in general. These sensors use a communication method known as 1-Wire/MicroLAN wherein they use only one pin for transmission and reception depending on the state of the pin they're attached to, among a few other specifics. Now, I have three of these, and my final objective is to be able to grab data off  all of them in the same point in time repeatedly so that I can send the data over to some other program I'm writing to run an algorithm. The problem is that the example used is based on an emulated serial port on the Arduino that doesn't like working with multiple instances.

Now, the Mega 2560 has three sets for Serial communications embedded into it which would be perfect... only if I could separate the RX and TX from the 1-Wire. A user over at Arduino SE suggested I use a transistor to separate it. Call me silly, but I don't have any spare around so I'll be out to test it soon once I can go out to a nearby electronics store. Yet, searching around the internet I've read that 1-Wires should never be connected to native serial ports because of how they work with states.

In summary, can 1-Wire sensors communicate with native serial ports in microcontrollers if I make a circuit to split the signals? And, if this is possible, what are the specifics behind such a circuit?


texts: LED producing heat and best power supply

texts:
I was wanting to get a bulk lot of small LED lights similar to Basic LED - 5mm Yellow. I want to put them in balloons so that the balloons appear to glow in
a dark environment, so I have a few questions:

Would the heat produced by these lights be likely to burst the
balloons? I understand that most LEDs produce little to no heat.
Is there a decent and inexpensive alternative that have a power
supply "built in" or attached? (so we dont have wires running from the
balloons). Failing this is there an alternative that just need a small
battery to be connected?


texts:
I got given a piece of electronics to take apart that has a magnetic swipe card reader built into it.

Upon taking it apart the card reader itself (which appears very much like a tape deck head) seems to have 5 pins, only three of which have wires attached in the current circuit (I'll call these 1 through 3 and will ignore the disconnected pins).

Pin 2 is obviously the ground, as it's connected to the outer case (this was also obvious from the circuit board it was attached to).

Resistance from pin 1 to pin 3 is about 65 ohms. 1-2 and 2-3 are OL.

I tried putting +5V (limited by a 1k ohm resistor) across 1 with 3 hooked up to my oscilloscope, but the voltage was a steady +5V with no change when I swiped a card.

Same results for +5V through 3 with 1 hooked up to the scope.

Oscilloscope does not show any voltage through ground (pin 2) when voltage is applied to 1 or 3.

So I'm sort of stuck.

I tried googling around, but so far I haven't really found much information on how the mag stripe readers actually work that gives me a better idea of how I might provoke a reaction from this thing.

Do any of you guys have any thoughts or suggestions?


texts: Cannot understand how does Arduino memory work for program code

texts:
I am using Arduino Lilypad and Uno. At first, I've developed my code and ran it on the UNO because its easier to use, but after that I've uploaded it to the Lilypad and it worked too. The intersting point is that the code is about 19-20  KB and the Lilypad's Flash memory is only 14-16 KB!
How is this possible?

The arduino IDE also allowes for maximum of about 30 KB for Lilypad and about 32KB for UNO. Where did those numbers come from? the UNO has this capacity in its Flash, the Lilypad doesn't!


texts: Arduino: faster alternatives to digitalread() and digitalwrite()?

texts: What are the fastest alternatives to calling the Arduino functions digitalread() and digitalwrite()?  AVR-specific or chip-specific solutions are acceptable.


texts: bias-disable vs bias-high-impedance GPIO in Devicetree

texts: What is the difference between bias-high-impedance  and bias-disable? I would like to completely deactivate some GPIOs that are causing conflicts on my board. I have two pins acting as default as I2C. Is there a way to put them on floating mode without recompiling the device tree?


texts: Karnaugh map subcube with no unchanging variables

texts:
I am tasked with using a 5-variable k-map to minimize a SOP expression. The minterms are 3,7,12,14,15,19,23,27,28,29,31, and the don't cares are 4,5,6,13,30. (Where, in the class I am taking, you start counting from zero)

There is one subcube that can be drawn that includes positions 3,4,5,6 and 27,28,29,30. This subcube has no unchanging variables for it... so what would its expression be?

This same problem can also appear in a 4 variable kmap if positions 5,6, and 9,10 are part of a subcube. What would you write for this?

Please note: this is a homework problem, so please do not solve the entire system for me. I am only asking because we did not learn in class what to do in this case, and I cannot find anything helpful online.


texts: Microcontroller and LDO and +5V pull up sneak path

texts:
I am using this 3.3V LDO whose input Vin=5V (regulated input.)
Output is 3.3V with load current of 200mA

This 3.3V is given to this Microcontroller for GPIOs.

I have taken 2 outputs (these are sctive Low signals during normal operation and must be active high during sleep) from this 3.3V GPIO domain and connected to another IC with a +5V pullup. (Connected the +3.3V port to a +5V pull-up to meet the Vih/Vil levels of the connected IC and due to lack of +5V GPIO ports)

These two outputs are configured as open drain outputs (with no internal pull-up enabled inside the micro,) as we have pullups outside the micro, snd these are fed to the IC.

Micro is driving these two outputs as active high during sleep time.

During microcontroller sleep state, I am observing +4.2V at the 3.3V LDO output cap.

What might be the reason?
Why am I getting +4.2V instead of +3.3V at the LDO output?

During normal operation, it works fine. I am getting only +3.3V at the LDO output.
Main concern is only during the sleep state.

Does the internal clamping diode inside the micro do something (create a sneak path?)
Can I infer something from the internal LDO Architecture?

I have attached a simple crude image of my problem. Please check.

What could be the reason and what could be a possible solution to overcome this?

Thanks


texts:
Trying to make a circuit for a door sensor. The objective is send a RF signal when door opens, another one when door closes (in the simulation, all RF part is simulated as a 1k resistor and door open/close is simulated as a switch: door open = switch off, door close=switch on).

In order to save energy, RF module will be powered only immediately after door is open and until a few seconds after door closed (to allow RF module to send the pending messages).

The first try is following circuit:

(simulation is here)

Problems:

1) There are a delay between open door and RF power on (mosfet open). This is not acceptable, because it means a fast door open-close could be not registered by the system.

2) Mosfet is in cut when door is closed, this is ok, and in linear mode when door is open, it could be better in saturation.

Could someone suggest some changes to reach these objectives?

Thanks.


texts: Proof;Only Reciprocal Circuit are passive circuit

texts:
Consider a two-port reciprocal network : $$  \
   Y=
  \left[ {\begin{array}{cc}
   0 & -1/2 \\
   -1/2 & 0 \\
  \end{array} } \right]
\ $$
then how can we proof that it is a passive network or circuit?

I have no idea how to prove it ....any hints or suggestions please...?


texts: Measuring current usage in a wheelchair power assist device

texts: I am working on wheelchair configuration methods to reduce upper extremity overuse syndrome in daily users.  I want to compare two tire types over a course that consists of obstacles that place strain on the upper extremities.  A power assist device called SmartDrive pushes the chair along by a single wheel and a lithium ion powered motor trailing behind the wheelchair.  Is it valid, or even feasible to use a recording ammeter plugged into the charger port on the SmartDrive to measure amp hours used over a specific course and compare between wheelchair A and wheelchair B?  If so, is there a simple and inexpensive way of measuring amp-hours consumed over a course?


texts: About 18650 batteries possible accidents with reversed polarity

texts:
We all know that lithium batteries are dangerous and can blow up if we use them the wrong way. My doubt is, if I accidentally place them in the following sequence in series (Pay attention to the polarity):

simulate this circuit – Schematic created using CircuitLab

Can I end up blowing up one of them?


texts:
Consider the above example earlier I used to form a differential equation and then do its solution using Laplace,but for this example the differential equation comes out to be non-ordinary.

Please help to find I(t) consider initial rest.

My approach


texts: Combinational System Theoretical Question

texts:
I'm currently taking an MIT-OCW course, where it says that a system built from smaller combinational systems following the following compositional rules is combinational:

Each component of the system must itself be a combinational device.
Each input of each component must be connected a system input, or to exactly one output of another device, or to a constant voltage representing the value 0 or the value 1.
The interconnected components cannot contain any directed cycles, i.e., paths through the system from its inputs to its outputs will only visit a particular component at most once.

However, it then states:

is combinational.

However, it looks like C is connected to two outputs of other devices - to A and B. How is this then still combinational? In general, I don't understand the point of why it would only need to be connected to exactly one output of another device.

Apologies if this is the wrong StackExchange, wasn't sure where to ask this.


texts: I have a .75 Watt/8 ohm speaker. Do I need to use an amplifier, what specs should I look for?

texts:
I salvaged a pair of speaker drivers from USB-powered computer speakers that is .75 Watts/8 ohm per channel (2 channels total, L/R). I want to be able to drive audio through it and have volume control. I know that a basic audio system requires:

Signal source  (For simplicity, I want my device to take the signal via AUX port)
Power amplifier
Speaker driver

With such a low RMS power rating, I'm tempted to connect the L/R channels from a source directly to the speakers but I'm not sure of the energy of the source signal.

Link to speakers I have:
https://www.bestbuybusiness.com/bbfb/en/US/adirect/bestbuy?cmd=catProductDetail&showAddButton=true&productID=BB12339197


texts: Do LTE modules depend on specific carrier?

texts:
I am looking to buy LTE modules. So I searched in digikey. I found two similar parts:

MOD HL VZW LTE 1.8V W/ ATT 3G

MOD HL ATT LTE 1.8V W/ VZW 3G

They are both the same except the description.

So if I buy MOD HL VZW LTE 1.8V W/ ATT 3G would it work on other carriers besides AT&T?


texts:
Can this system in package be used raw without any other components(resistors,capacitors,inductors,crystal etc)?

If I create a test board with holes for every pin to test it with arduino ide would it work?


texts: Why RXD text are uncomplete in atmega328 intrupt driven USART?

texts:
I have an Atmega328p MCU which is connected to USB port by ch340 chip and I've connected it to GSM module by hardware RX/TX/GND pins. I don't send any command to USB port all commands are send by micro controller.
So I've found this tutorial which has a pretty simple functions to receive USART_RXD interrupt from RX pin. I've break it down into these two functions, one for copying received data from RX to a variable:
void copy_command ()
{
    // The USART might interrupt this - don't let that happen!
    ATOMIC_BLOCK(ATOMIC_FORCEON) {
        // Copy the contents of data_in into command_in
        memcpy(command_in, data_in, 8);

        // Now clear data_in, the USART can reuse it now
        memset(data_in[0], 0, 8);
    }
}

and a function for interrupt handling:
ISR (USART_RX_vect)
{
    // Get data from the USART in register
    data_in[data_count] = UDR0;

    // End of line!
    if (data_in[data_count] == '\n') {
        command_ready = TRUE;
        // Reset to 0, ready to go again
        data_count = 0;
    } else {
        data_count++;
    }
}

The problem is, even I've changed data_in and command_in variable size to 32 character and changed this line memcpy(command_in, data_in, 32); and removed memset(data_in[0], 0, 8);, the output is some how unacceptable.
for example when the module should send RING in terminal it return NG or when I do sizeof command_in it always return 8 even there is nothing with size of 8 in my code. I assume 8 is the size of one character in byte, but isn't command_in suppose to get a string including all RX characters?
How can I fix this to receive full RX response to process?


texts: Is it bad to run traces directly over each other on separate layers?

texts:
A bit new to PCB design, I have to run two traces between two pins, and the best way I can think of is to have one trace go to the bottom layer through a via and then run directly under the top layer trace.

Are there any issues that can come about doing this? They're pretty low power signal traces, but can the traces affect each other through induced fields, or are the top and bottom layers generally isolated?

edit: The traces are running over each other for about 700mils. They're SPI data lines.


texts:
I need to connect a relay to my old truck to turn on the "soon to add" electric fans.

The ECM has an engine coolant temperature sensor that uses the output resistance to determine coolant temperature.

From the service manual, I have this data:

If you can not see the pic above:

__Condition________________|_Engine coolant temperature decided
Just as ignition switch is |
turned ON or Start_________|_20°C (68°F)_______________________
More than 6 minutes after  |
ignition ON or Start_______|_80°C (176°F)______________________
                           | 20 - 80°C (68 - 176°F)
Except as shown above______| (Depends on the time)_____________

So, is there a way to get some sort of Relay that would turn a switch ON when Resistance translates to a certain value (like 185°F or so)?

EDIT More Pics!


texts: Choosing the right transistor for a switching circuit

texts:
I want to control a siren speaker (has a built-in driver) with an Arduino.

The siren needs 12V and consumes about 480mA.
The Arduino output pin is 5V and can source 40mA maximum.

I would like to use a transistor to switch the siren on and off. Is this an OK application for a transistor? I'd rather not have to use a relay or a SSR because I don't have any on hand.

Based off of those numbers I calculated my load (siren) resistance to be 25 ohms using Ohms law, R=E/I. (I'm using Amps, Volts, and Ohms as units)

$$\frac{12V}{0.48A} = 25 \Omega$$

I have found various calculations to determine what kind of transistor I need and I'm not quite sure which is the best one. One of them is like this:

$$h_{FE(minimum)} = 5 \times \frac{Load\;Current}{Arduino\;Pin\;Max\;Current}$$

Which gives me a minimum \$h_{FE}\$ of 60.

$$5 \times \frac{0.48}{0.04} = 60$$

This is where I get a little confused. I have a few transistors and their datasheets but I'm not quite sure how to read them. I have read many resources and I am just as confused now as before.

I know I should probably use a NPN transistor but would it matter if I use a PNP instead? Do the same calculations apply? I understand that the circuit changes, active high instead of active low, but are there any drawbacks to PNP over NPN?

The NPN's I have are PN2222A, BC337, BC547B and a BC517 darlington.

The PNP's I have are PN2907, BC327 and a BC516 darlington.

How would I go about choosing the right transistor for the job? I don't want to overload the transistor.


texts: What is this strange component from 1950 radio reciever

texts: A while ago I took apart my grandpa's really old radio receiver with vacuum tubes. I recognize everything except for this one strange component. It seems to have some sort of heat sink on the outside and it has a cylinder-like shape on the inside. On one of the sides, it says 6846446 and + and Zenith and 212-23. The + seems to tell me that it is some sort of polarized component but I have no idea what it could be. Here is a picture:


texts: Why SD card is less durable than internal storage in smart phones?

texts: For instance, Raspberry PI managed to destroy SD card in few weeks. (It seems to be a common problem.) However, internal storage in a smartphone works well for several years (5-years-old Nexus One is still working well). Is the internal storage made by different technology?


texts: Is this asking for a POS equation or SOP?

texts:
So here's the question:

We want to design a circuit that determines if a four-bit number is less than 10 and is also even.

a. (10 points) Write an expression of M such that M=1 if the four-bit number X (x3 x2 x1 x0) is less than 10
and is also even.

Is this asking for the answer in POS form since it is using "M" instead of "m"?