texts: TrueStudio flashing board gives "Unknown MCU found on target error"

texts:
I am attempting to flash a custom PCB using Atollic TrueStudio and a Nucleo board. I have the PCB connected to the SWD header on the Nucleo. In TrueStudio I have set the target device and am using ST-LINK as the debug probe with the GDB Connection Settings set to "Autostart local GDB server", and the Interface set to JTAG. When I click debug, it builds the project, but then gives me an error:

Target unknown MCU target

Error in initializing ST-Link device.
Reason: Unknown MCU found on target.

What does this error mean?

I have also tried debugging using the SWD interface, but when I use that I get the error:

Target no device found

Error in initializing ST-Link device.
Reason: No device found on target.

I have searched for explanations of these errors, but have not been able to find anything helpful. I have also looked through tutorials on using TrueStudio, but I have not been able to figure out why this fails to flash my board or what is going wrong.

Also, I am new to TrueStudio, so please explain. Thanks!


texts:
I often notice usage pull resistor for base of bipolar transistor, e.g. \$R2\$ here:

Why it's used? I understand pull resistors for FETs, because of gate's high impedance an EMI can easy switch it. But BJT need base's current to open and, I think, EMI has too high internal impedance to give enough current.

Is it safe to leave floating base in BJT switch?


texts: I accidentally bought an HDMI (male) to VGA (male) cable that isn't an adapter or converter of any sort. Does this product have any value?

texts:
I have a laptop with an HDMI port. I have a monitor with a VGA port. I wanted to connect the two. The website I bought this cable from labeled it as an 'adapter' so I assumed it would do the conversion job. Now the store tells me it's not a converter and that it is merely an 'adapter'.
I would really like to believe this isn't a scam and that I simply made a rookie mistake not checking this has an actual DIGITAL to ANALOG converter.
But I feel like this is a scam since I don't understand how this cable (or 'adapter') is a product.
To my understanding, if VGA could carry an HDMI signal or vice versa, then indeed this product would have value and it is an actual adapter and indeed this would be my mistake. But I understand that this is not possible.
So... In what scenario does this cable actually serve a purpose?


texts: can leds take varying voltage > listed voltage, with constant current?

texts:
My confusion stems from a an led that shows: Input(DC): 600mA-700mA / 3V-3.4V.
the product suggests a constant current led driver (same brand as LED) that shows:  Output: Current 600mA (Constant) ; Voltage 18-34V

In researching I have read that excessive current will burn out the LED and over time as the battery drains the amps drawn gets smaller resulting in the need for a constant current led driver.

I am having trouble finding information for my question: Can LEDs receive a voltage above their recommended value if the current is constant?

Also, side question, if the current is constant at 600mA and the led's current takes 600mA, then I don't need a resistor?

update:

Thank you for all of your input. @mkeith was correct when saying "I think the point of confusion is that you don't understand the relationship between the power source and the load."

I was under the impression that only the value of the Amps through an led mattered. I thought that since the company suggested the driver with a minimum output voltage of 18V, when the LED that it was referenced from, had a voltage of 3-3.3V, that that meant the constant current is what mattered. I was asking if the higher voltage (18V from the driver vs. 3.3V of the LED) with the correct Amps would be okay.

I have com to realize why this driver was suggested. wiring the 3V LED in series to get about 18V maybe have been the intended use.
additionally, I better understand the difference between constant current and constant voltage and how the LED will control the amps (when constant voltage is applied) and the Volts (when constant current is applied)


texts: Which resistor do I need to replace to power a Gumstix Pre-Go board with 3.3 V?

texts:
I purchased a Gumstix Pre-Go PPP with SMA connector. On the product page, it states:

  Logic levels are at 3.3V, and the board is powered by the 5V supply; however, by removing and replacing a jumper resistor, the board can be powered by a 3.3V source.

Which specific resistor is it that needs to be removed, and what are the specifications of the resistor that it needs to be replaced with, in order to power this GPS module with a 3.3 V source?


texts:
I'd appreciate a clear explanation on:

If RFID readers of one frequency (like 13mhz MFRC500) can read other/lower frequency RFID cards (like cheap 125 khz cards)
If it's possible to build a 125 khz RFID reader without application specific ICs like MFRC500


texts: Should I use a differential mode amplifier for mixing up to four stereo signals together?

texts:
I'm designing (probably over-designing, but I want the experience) a four-input, four-output, stereo mixing setup for my PC setup, but I'm concerned that just tying all the ground lines from that many inputs is going to cause ground loops and similar issues.

The inputs are going to come from my PC, an FM radio board, and other headphone-jack style input sources, while the outputs are going to go to my PC speakers, a pair of headphones, the line-in jack on the PC, and a spare auxiliary output.

Would capacitors between the inputs and the amplifiers be enough to decouple things, should I use op-amps in differential mode (like this example shows, though adapted for stereo), or is there another option?

Granted, in a couple of cases, like the PC's input, I'll have to tie the ground to actual ground, as I'm also passing the microphone signal through from the headphones, so I can't cause similar problems the other way around.
(I should also be able to get away with using the same ground as the radio module, given that I'm actually providing it with a ground reference, and the fact that it's using the same ground for the headphone jack as the one it's given)

I should note that I'm still in the process of designing the whole project, which means that I don't have a power supply chosen, haven't selected volume controls, and don't know what values to use for any of the resistors yet.
(yes, I'm asking this question very early in the design process)


texts:
I am testing my circuit but my result seems to be false, I know something is wrong but I can not find the mistake, any help will be appreciated.

with best regards.


texts: Relationship Between Resistance and Magnet Strength for Electromagnets

texts:
I am working on a project using an electromagnet to vibrate the strings of a guitar at their resonant frequency. I have this working pretty well with an electromagnet I have on hand, I'm currently looking at other commercially available electromagnets to see which ones have the best characteristics for what I'm doing. By looking up the supplier of my original electromagnet I found the following product page, which shows that this model is available at a variety of resistance specs:

What I'd like to determine is what affect resistance has on the strength of the magnetism generated by a given voltage. Will a higher resistance lead to less magnetic strength? Is this relationship linear or are there other factors at play?
Ideally I'd like to source a magnet that gives me the strongest magnetism for the lowest current. I have a lot of experience with low voltage audio electronics but fairly new to working with electromagnets so all input is much appreciated, thanks!


texts: I need to take one sample of a fast changing signal at exact time with high precision. Slow sample rate ADC's have better accuracy, but I wonder about actual aquisition time - the time at which ADC is doing sample and hold. I guess it effectively averages the signal between some points in time. Can a slow (say 10 ksps) ADC take a fast snapshot, say less than 1us? Or is it always related to samples per second? 1 msps ADC obviously does sample and hold in less than 1us, but how about 100ksps, 10ksps ADC? After looking at some datasheets, I'm still confused.


texts: How to get Power into a Power over Ethernet cable?

texts:
I need to feed 12 volts into an Ethernet cable. The vendors datasheet states:

  Power Method: Passive Power over Ethernet (pairs 4, 5+; 7, 8 return)

Does that mean I connect both the 4 and the 5 to the same 12 volts positive cable and 7 + 8 to the negative? Is this standard procedure? It seems weird to me to split up the volts and send them through 2 cables.

Please note that I'am a beginner in this field and thus I have only a very basic understanding of how electronics work.


texts:
Possible Duplicate:
  What's the cheapest way to link a few microcontrollers wirelessly at low speeds over short distances

What's a cheap, low-power radio system for doing some point-to-point radio connections?  I'm thinking of something like wireless doorbells or light switches, which can operate for long periods of time on a single battery.

Full-duplex operation would be nice, but not required; perhaps these could be two different solutions.


texts: PIC16f877: MPLAB X error 1250 (Could not find space for variable)

texts:
I am using Pic16f877 microcontroller for my project. I am trying to declare a char Array as

char dataPkt[256] = {0};

While compiling, i received an error

error: (1250) could not find space (256 bytes) for variable dataPkt

Can anyone guide me how to resolve this error ??


texts: How can I turn a clock signal into a logic high that also goes low when the clock drops out?

texts:
I have a differential clock signal coming from an IC. If the signal is present, I need a TTL "high" to enable a high-side FET driver. When certain conditions are violated, the IC will send the differential signal to ground which will disable the driver and the FET will turn off.

The issue is turning the clock signal into a logic high and also getting a logic low when the signal is sent to ground. I had the thought of comparing the output signal with the clock through a differential amplifier, but I feel that might be too susceptible to noise - especially considering the application is for an electric vehicle. Is there an easier way to do this?

Tl;dr: I need a logic high if the clock is present and a logic low if it is not.


texts:
In this circuit, the HV+ point ranges from 100 to 1200 VDC. The two MOSFETs are rated at 800V, which makes 1.6kV breakdown. D7/D8 are 300V each, so they have a clamping voltage of 600V. My question is:

If R7 is "large" there is no low impedance path to turn on or off Q1 so that turn off would happen very slowly which might be an issue for Q2, as I could get larger voltages on it.

If R7 is small (near zero), when Q2 turns off it would turn off Q1 quickly but the voltage at the Q1/Q2 connection is somewhat unpredictable. I want to get C5/C6 from almost zero volts when the FETs are on back up to half of HV+.  The only path to charge C5/C6 is through R4/R5/R6.  That will take a long time so Q1 might see most of the voltage for a while.

So is there actually a moment when a FET could see a voltage bigger than it can handle? At the end, the purpose of the cascode is to increase breakdown voltage of the main switch.


texts: Calculating inductance values from transformer datasheet

texts:
I want to simulate this transformer using LTSpice:

This is a microphone transformer. To do a simulation in LTSpice I need to know the inductance values for the windings. The datasheet gives impedance values and a frequency range of 30-25kHz, which is strange from my understanding, since impedance can only be specified at a specific frequency. Is there some convention in the industry that would explain how to calculate the inductance values? Is it possible to calculate the inductance from these values?


texts: Meaning of two ADC channels in an LTR-559ALS-01 optical sensor

texts:
I am using an LTR-559ALS-01 optical sensor to read the level of ambient light. Everything works, but from the datasheet I can't make out why there are two analog channels for said reading.
Both channels can be read and display a similar behavior when exposed to light (channel 2 has a slightly higher reading with low light levels but higher when brighter.) A lone table at the beginning seem to suggest that they have a different scale, but I'm not sure.

It mentions a ratio between the two channels, but it's not explained further. Moreover, both channels are subject to the same gain configuration, so I don't think a different scale is the final purpose.
I would like to understand why there are two channels and if I should combine them in some way to get the real value. I might be missing something obvious here, but it's my first time working with this kind of sensor so I'm not sure what to look for.


texts: Question about power drawn from a current limited supply when it is short circuited

texts:
Consider the schematic below:

When the switch is open, the 10 ohm resistor will draw 0.5 amps of current and dissipate 2.5 watts of power. No issue there.

When the switch closes:

We know the power supply output current is limited to 1 amp. So when the switch closes, the resistor is bypassed and the entire 1 amp of current from the power supply will flow through the short to ground. What is the power being drawn from the power supply?

The short circuit current is 1 amp. Power is \$P = {I_{short}}^2 \cdot R_{short}\$.

\$I_{short}\$ will be limited to 1 amp, and \$R_{short}\$ (the resistance of the short) is essentially 0 ohms. So is the power drawn from the supply \$P = 1^2 \cdot 0 = 0\$?


texts:
Very Stale EE here (30 years maybe?), so be gentle ;)  Now I own a horse farm and do lots of equipment maintenance (and other things).  Replacing an engine in a mower with a kit from another manufacturer.

Problem is that kit does not provide a way to drive alternator charge light.  I think the only way I can sense charge is to compare battery output (12v nominally, but of course +/- 1.5v depending state of charge) to rectifier output (battery voltage plus junction voltage of diode).

Lamp should work as follows:

1) Key off, lamp off off

2) Key on, engine not running lamp on

3) Key on, engine running, normal rectifier function - lamp off

4) Key on, engine running, rectifier malfunction (i.e. not charging) - lamp on

Net is anytime battery voltage is higher than rectifier output, lamp should be on.

Lamp is incandescent, 2 - 3 watts I think, max 5w (about 420mA)

Explored transistor switching circuits, but I think the small junction voltage will not be enough to turn the transistor on.

An opamp comparitor is not really a good option - a bit complicated, and I would still need a drive transistor for the lamp, along with several resistors - creates a large parts count.

This design and physical package needs to be small, simple and low parts count - it is in a commercial grass mower.  Planning on soldering parts into a ball and dipping them in plastic to protect.

Thanks in advance!


texts:
How are antenna arrays synchronized for direction finding/localisation?

For example, if the processing unit is located closer to one antenna then another, it will see the signal from the closer antenna first even if it hits them at the same time(voltage propagation speed within the line is at most the speed of light if not significantly less). How is this dealt with? Do you take into account the antenna transmission line lengths and attempt to fix it in software?

Alternatively, suppose you have two receivers each collecting data at their specific antenna locations - how can you synchronize the timing between them? Even if they are locally synchronized then moved, oscillator drift will cause timing mismatches. How is this problem solved?


texts: How to Synchronize two RTC module one internal and other external?

texts: I am developing a data logger based on PIC controller. The PIC has internal RTC but does not have pins for connecting battery so I am using pic's internal RTC to generate interrupt every second and external battery backed RTC to keep exact timing. but the problem is that they both do not get in sync. So after every 5 second when I read time from external RTC it gives value 6 (or) 7. So how should I sync both RTC to get proper value from external RTC? We dont have pin from external RTC connected to MCU so cant get interrupt from external RTC.


texts: How does a diode "rectify" an alternating electrical signal from an antenna in a diode type crystal radio?

texts: In alternating current such as a signal in an antenna the electrical signal in the wire is switching it's polarity back and forth. How does the rectifier keep the other half out? Once you cut the second half out would there not be a "gap" in the electrical signal from the time period that it took to get to the other polarity?  And although not enough room to ask in the original question , one is compelled to ask would not cutting the bottom half also cut into the "voice" part of the signal or is the voice part of the signal a duplicate up an down. By voice part I mean the signal that is somehow "mixed" in with a signal that has a much higher frequency that is called a carrier wave.


texts: Voltage divider for battery monitor ADC - loading effect?

texts: I'm building a voltage divider to use for feeding into an ADC to determine the battery voltage of a device I'm designing. Is it important to consider the input impedance in the ADC and to account for the voltage drop caused by that extra load or should I not even worry about it?


texts: Design a simple circuit to generate -21V..-24V from +5V

texts:
I have got an old-STN-LCD which needs a very negative voltage, -21V..-24V are required in order to do the proper contrast, a current of less than 200nA is required, the LCD controller also requires a little ripple in the negative voltage supply.

How do you suggest me to design such a circuit?

Regards =)


texts: When use As+B in partial fraction expansion

texts:
I'm trying to solidify my knowledge around using partial fraction expansion. In this specific case, when to use
$$ f(s) = \frac{As+B}{s^2+cs+d}$$
instead of using
$$ f(s) = \frac{A}{s+e}+\frac{B}{s+f}$$
Per "Control Engineering", 2nd ed. by W. Bolton, when we have quadratic factors in the denominator, and the quadratic does not factorize without imaginary terms we should use As+B for partial fraction expansion.
So, i made up and worked this problem below where i am applying 12V dc to a circuit (closing switch at t = 0) with the capacitor initially charged, and then solving for i(t):

R = 1Ω, L = 26.5mH (initial current = 0), C = 1000μF (initial voltage VC(0) = 5V), and V = 12 volts.
Solving for i(s) i get,
$$ i(s) = \frac{\frac{V-V_C(0)}{L}}{s^2+s\frac{R}{L}+\frac{1}{LC}}$$
Since the roots of the denominator are,
$$s=\frac{-b±\sqrt{b^2-4ac}}{2a}$$
We can see that we will get complex roots since,
$$\sqrt{b^2-4ac} = ±j\sqrt{\frac{R^2}{4L^2}-\frac{1}{LC}} = ±j194.23  $$
And the roots are thus,
$$s = -18.87±j194.23$$
In my case, i did the p.f.e. as follows,
$$\frac{\frac{V-V_C(0)}{L}}{s^2+s\frac{R}{L}+\frac{1}{LC}}=\frac{A}{s+18.87+j193.24}+\frac{B}{s+18.87-j193.24}    $$
Where,
$$A = \frac{12-5}{-\sqrt{R^2-4\frac{L}{C}}} = j0.683$$
$$B = \frac{12-5}{\sqrt{R^2-4\frac{L}{C}}} = -j0.683$$
$$i(s)=\frac{j0.683}{s+18.87+j193.24}+\frac{-j0.683}{s+18.87-j193.24}    $$
My solution ended up being,
$$ i(t)=1.366e^{-18.87t} sin(193.24t)$$
Which when plotted with a numerical simulation of this circuit was perfectly coincidental with the simulation result for i(t),

So, my solution factorized with imaginary terms, but i did not p.f.e. with As+B, and i still arrived at correct solution.
My specific question is thus, when must we use p.f.e. with As+B?


texts: I have two SDRs and I want to do a simple test: I want to send data values using QPSK modulation with coordinates: (1,1), (-1, 1), (1, -1), (-1, -1), but on Rx site I got all possible values on the circle created by rotation of the square. Why phases of received signal are changed?


texts: Control duty time and frequency with different potentiometers using one 555 timer

texts: How can I regulate duty time and frequency of 555 timer output with 2 potentiometers?


texts:
I'm trying to control a DC motor with the L298N motor driver and it worked for a brief moment. I've used the setup mentioned in this video tutorial, but someone in the comments said that with this wiring, you might damage the L298N - which I think has happend now.

How can I protect the L298N against damage?

EDIT:
This is the schematic:

It is wired after the above tutorial, where he lists the wiring like this (sorry for low quality):


texts:
I have been reading lately about electricity markets and I have stumbled upon the term "volume risk".

  Volume risk is often used to denote the phenomenon whereby electricity market participants have uncertain volumes or quantities of consumption or production. For example, a retailer is unable to accurately predict consumer demand for any particular hour more than a few days into the future and a producer is unable to predict the precise time that they will have plant outage or shortages of fuel.

Basically, a fault in the prediction of both the buyer and seller may occur and either the electricity that has been purchased, may not end up being delivered or vice versa, the buyer may have ended up purchasing more electricity than needed.

However, I haven't found a clear explanation, what is done in these two cases. Who would cover the electricity difference if the generator does not end up producing the quantity stated in the trade or where would the overproduced electricity go, if the consumer has estimated his consumption poorly?


texts: how is this transformer working with DC?

texts:
As I was going through the SMPS circuits online I came across this circuit:

I searched and learned that the transformer steps down or step up only AC power supplies and then converted to DC using rectifiers and to boost or to decrease them we use buck booster circuits.

I also found that :

As in DC(voltage being always constant), the change in flux is zero so no mutual induction,thus transformers can't work with a DC supply. Moreover, if DC or a similar rating of AC(Voltage & Current) is fed into the terminals of a Transformer there is a high possibility that it would burn the primary coil.

When a dc supply is provided to the transformer primary no self-induced emf will be generated (no back emf). Therefore heavy current will flow in the transformer primary winding which may result in burning down the transformer primary winding.

I also found the above things on Quora:

https://www.quora.com/Will-a-transformer-work-with-DC

https://www.quora.com/What-will-happen-if-a-DC-voltage-is-given-to-the-transformer-primary

https://www.quora.com/How-does-a-DC-transformer-work

The transformer used in this circuit is an SMPS transformer that works on high frequencies. So how this works. I am not able understand it.


texts: How repeatable is the output from an opamp

texts:
I'm having difficulties finding information on how repeatable the output of an opamp in this simple comparator configuration is. Give the following schematic:

simulate this circuit – Schematic created using CircuitLab

I do know that a real opamp has a non zero input offset voltage, so the actual differential voltage required to make the output 0V might be a couple of mV for a jellybean opamp. So in the example above, the actual voltage might be 2.503V and might also drift with temperature, but assumed the temperature stays constant, how repeatable is it? Repeatable meaning at two points in time, how different can the input voltages be so the output is the same?

Unfortunately, not being an EE, I cannot figure out how to read an opamp datasheet properly. How do I find out how repeatable the output an opamp really is?

Bonus question: Is the output from an opamp more repeatable than the output from a comparator or a schmitt-trigger? How can I find this out from looking at the datasheet?

PS: I've run some tests with an LM393 and a 74hc14 and with the voltage references and multimeters that I have access to, I pretty much don't see a difference. Changing the input by 10µV reliably changes the Output between 5V and 0V (at a different absolute voltage of course).

To elaborate on the purpose: The input is an analog signal with a relatively high resolution. I'm not interested in the actual value of the analog signal, but I need to know exactly when it crosses a certain threshold. The absolute value of the threshold doesn't matter as long as it stays as constant as possible.


texts: MCU programming - C++ O2 optimization breaks while loop

texts:
I know people says code optimization should only bring out the hidden bug in the program, but hear me out. I am staying on a screen, until some input via an interrupt is met.

Here is what I see in the debugger. Notice the line inspected and the expression value intercepted.

Code in image:

//...
ui::Context::addEventListener(ui::EventType::JOYSTICK_DOWN, &constant_dynamic_handler);

while (true) {
    if (choice != 0) //debugger pause
        break;
}

ui::Context::removeEventListener(ui::EventType::JOYSTICK_DOWN, &constant_dynamic_handler);

if (choice == 1) goto constant;
else if (choice == 2) goto dynamic;
else if (choice == 3) goto reset;
else if (choice == 4) goto exit;
//...

//debugger view:
//expression: choice
//value: 1

The constant_dynamic_handler is a lambda function declared earlier, that just changes choice to some integer other than 0. The fact that I can pause in the loop means that the loop is not exited, but the value is in fact changed. I cannot step over one step in the debugger as it will fail to read the memory on the CPU and requires a restart to debug again.

choice is declared simply in the same scope as the if-statement block, as int choice = 0;. It is altered only within an interrupt listener triggered with a hardware input.

The program works with O0 flag instead of O1 or O2.

I'm using NXP K60 and c++11, if that is required. Is it my problem? Could there be any thing that I'm not aware of? I am a beginner at MCU programming, and this code works on desktop(Just tried, doesn't work).


texts:
How are OLED screens such as the ones on my cell phone, driven?

From my understanding, an OLED screen is basically a matrix of tri-coloured LEDs. LEDs can be dimmed by using PWM. So does that mean that each color of each pixel on the screen has it's own separate PWM circuit or are they multiplexed in some way or is it all together much more complicated than that?


texts: Design options for tracking relative orientation of two elements

texts:
Background:

I need a system of two discrete elements where one of the elements can continually track the distance and direction to the other, and their respective orientations. The specific requirements are to be able to track distance to within 1mm (preferably closer), and within 1 degree orientation in each degree of freedom. Ideally, one of the two components would be passive (requiring no battery), and both have to be no bigger than an inch cube. The separation of the two parts would typically be a few centimeters at most, and orientation is more important that distance. The data needs to be sampled several hundred times per second, and will be transmitted elsewhere (phone).

Question:

What sensing approach can I use here? My initial thought was to use a permanent magnet in the passive element, and 3 linear hall effect sensors. The problem there is that it'll give me a vector giving the distance and direction to the magnet, it won't give me a relative orientation.

I don't think ultrasonic will work here, and I can't think of another approach.

Ideas?


texts: Connector identification (multipin connector for automotive touchscreen)

texts:
This connector is from a device connected to the touch screen in the car. This device is chinese, so I'm having trouble locating information about any part number or name.

The connector has 4 wires cut and the matching pins in the connector are missing, so the connector needs to be replaced.

I'll appreciate any information you can provide.

Here are the photos:

cable connector:

port in the pcb of the touchscreen:

Thank you in advance!


texts: Do I need to decouple an LM386 if it is run from a battery?

texts: What I would like to do is to put an LM386 in my bass guitar so that I can plug my headphones directly into it for practice. The LM386 was my first choice because it can run off of a 9V battery and requires no external parts. I understand that the output impedance of a 9V battery is fairly low (about an ohm or so). The LM386 has  PSRR of 50dB. Do I need to decouple the power supply going to the LM386?


texts:
So, I have the above circuit and I have to somehow integrate this into a mobile phone cover. So to power it, I was thinking of using a 3.7v 600mAH Li-Po battery. I want to integrate the battery into the cover in such a way that the cover becomes a rechargeable cover. As the Beetle needs 5V, I will need some sort of booster as well. The other alternative is to use 2 coin cell batteries that supply 3.3 V each.

Some more information on the project:

I am creating an interactive game and I basically want this circuit
to act as an input to the game that will be played on a mobile
phone.
The circuit has to fit into a mobile phone cover and the push
buttons that you see on the circuit are to be placed on either side
of the cover. Both buttons have to be pressed simultaneously to
create the required action(s) in the game. I already have this part
working.
In terms of how long I would like the battery to last between
charges: a similar amount of time that a phone battery lasts (if
that's any measure to put things into perspective)

I am not sure what the best solution for this will be; by best I mean the easiest and least complex to implement.

Any assistance will be appreciated.


texts: Can I use Arduino's FTDI chip for another device?

texts:
I have an Arduino UNO (R3) with its main chip and main crystal oscillator accidentally destroyed, but everything else is working I presume.

I started learning PIC (16/18f) and was wondering if I could use the on-board FTDI Atmega 16u2 to program or speak serially to my PIC, as a separate FTDI chip would? (i.e. TX/RX pin headers -> appropriate pins for serial on PIC) Are there any caveats to using it, if so, compared to an FTDI? Would the USB interface work as-is with a computer and be recognised just as it was with the Arduino?


texts: What is the pressure/force sensor used in the Beddit?

texts:
The Beddit sleep-tracking device (Beddit and @indiegogo) has a pressure sensor that looks like a thin (~0.3mm?), flexible tape about 2ft long.  The tape seems to be constructed of several layers internally.  If bent and pressed flat it seems to form permanent wrinkles, but still functions about the same.  It has a two-pin electrical connector at the end.  The sensor is usually placed under a person lying on a bed (0.2-0.5 psi pressure) but can detect tiny, fast variations in pressure/force (best guess from device performance: << 0.001 psi with > 20Hz bandwidth).

Can anyone identify what type of sensor that is?  How can I try to test it?  Where can I get one like it?


texts: Control PWM with potentiometer using atmega328p

texts:
I'm using an atmega328p and I want to control the PWM duty cycle with  a potentiometer.

The frequency is 20ms and the duty cycle is between 0 ms and 2 ms.
Problem : when I simulate this in Proteus the PWM did not work, this is my code:

#ifndef F_CPU
#define F_CPU 16000000UL // 16 MHz clock speed
#endif

#include <avr/io.h>
#include <avr/interrupt.h>

int main(void)
{
    DDRB |= 1<< PINB1 ;

    TCCR1A |= 1<< COM1A0 | 1<< COM1A1 | 1<<WGM11 ;
    TCCR1B |= 1<< WGM12 | 1<<WGM13 | 1<<CS10 | 1<<CS11 ;
    ICR1 = 4999 ; // 50 Hz

    ADCSRA |= 1<<ADEN | 1<< ADIE | 1<<ADPS2 | 1<<ADPS1 ;  // 64 prescaler
    ADMUX |= REFS0 ;
    sei();
    ADCSRA |= 1<<ADSC ;
    while (1)
    {
    }
}

ISR(ADC_vect)
{
 uint8_t low = ADCL ;
 uint16_t tenvar = ADCH << 8 | low ;  // value from potentiometer 10 bit

 OCR1A = 4999 - ((499/1024)*tenvar ); // OCR1A is between 4999 and 4500 (4500 represent 2ms )

 ADCSRA |= 1<< ADSC ;
 }


texts: Understanding the summing-point constraint

texts:
I can't find any source online which explains this in a different way from the others. I'd like to think I'm not just being slow, but it seems that I might be just that, regarding the op-amplifier.

So the summing-point constraint claims that \$x\rightarrow 0\$, if we assume the op-amplifier to be ideal. To me, this makes no sense when you consider the characteristics of an ideal op-amplifier.

Suppose that, due to \$V_{in}\$, a positive voltage \$V_{DIFF}\$ appears at the inverting input. Then a large negative output voltage result at the output.

\$V_{OUT}\rightarrow-\infty\$

(Here's where I don't agree with explanations anymore)

A fraction of this is sent back through \$R_F\$, meaning that \$V_{DIFF}\rightarrow 0\$ with time.

I just don't get this, if I were to use numbers to explain why I'm confused, suppose that \$V_{DIFF} = 0.1\,v\$ initially, and then \$V_{OUT}=-10\,000\,v\$. If a fraction of this is sent back, say \$0.1\%\$. Then the voltage \$V_{DIFF}=0.1+0.001\cdot V_{OUT}=-9.9\,V\$

And it continues to spiral out of control. How does it really work? Why does \$V_{DIFF}\rightarrow 0\$?


texts: X-rated capacitors required for DC input voltage circuits

texts:
In my project I am using 12V DC from external power supply and EUT will load max 2A; in which I am using EMI EMC filter.
I have considered Input MOV’s for common mode and differential modes, differential noise filter, common mode choke. Can I need to use X capacitor too my circuit to comply the EMI EMC testing??
If yes how I can calculate capacitor value?


texts: Inverting interrupt edge (STM32 wake up pin)

texts: A sleeping STM32 can be woken up by a rising edge on its wake up pin. But if the IC on the other end of the line only interrupts as falling edge, is it possible to invert it somehow ?


texts:
What I have: 5VDC and / or 12VDC, a PIC micro

What I want: Floating 9VAC 50Hz, able to output 1A.

Googling details for this kind of inverter seemed to be a tricky case. There are a few DIY-pages that describe the innards of an inverter doing 5VDC -> 220VAC using a PIC, SPWM, and an H-bridge using four MOSFET with drivers. The common denominator for many of these is that they hook a low-pass filter to the MOSFET-outputs, and then to the load. But, applying the same theory, but for 9V, would mean not getting a floating 9VAC (18Vp-p) but an output with a 18Vp-p with a 9VDC offset. I do not understand how that would work.

Another solution for the output stage, instead of an LC-filter, is to add a transformer and let the MOSFET output feed the primary. However, I do not find any transformer that can work with sine pulsating 12V input and give 9VAC output. Digikey parameter search gave nothing but a 24-9-transformer at best.
For proper 50Hz sinus replication, I would need a reference clock for the drivers. This can either be generated with an analog oscillator (using a couple of LM358), or using software controlled PWM (using variable duty cycles) with a PIC micro. Either way is fine for me, as this controls the output frequency.

What I'm still puzzled about is that I fail to understand how the output amplitude is controlled. If I use a transformer, then bombing it with pulsating 5V to let it transform it up (to whatever voltage) isn't the challenge, but if I don't use a transformer; what part / block in my circuit will be the one deciding the amplitude? Higher PWM-frequency, higher output amplitude?

In the case of not using a transformer, but an LP-filter instead, is there any way to get the output to "float" without DC-offsets? I know capacitors block DC, but I cannot see how that would work given that there are no negative reference voltages.

As you can see, I have quite a vague starting point for this experiment. I know what output I want, but I'm having a hard time finding what parts / topics I need to learn to reach my goal.

Question: Where do I start? What should I dive into first?


texts:
What does this circuit do?  It looks a little bit like a flip-flop to me, but it doesn't exactly match the circuit for an SR flip-flop on Wikipedia.

Is this just a different way to implement an SR flip-flop, or is it something else entirely?

Thanks!

Edit: To clarify, DTR and RTS in this circuit are both 3.3V level signals, not RS-232 level signals.  This circuit comes from this schematic.  (So, DTR and RTS are coming from the CP2104 USB-to-serial converter chip.)


texts: How to find connections on board? - DIY Keyboard from Old Laptop

texts:
I have a project that I have hit a wall on. I need your guidance!

I need to find the spots on the board for the 4 USB connections.
The attached photo is of the board.
There are 4 connections I need to find are: 5v+, data -, data +, ground
It came out of an Apple MacBook Pro early 2008 A126C w/ bad mother board.

I've found instructions online for the models newer and older than mine on how to solder a USB cable to the controller board to use the keyboard and trackpad. I can't find anyone who has figured out the connections on mine. Can anyone help? I don't even know where to start... Is this even possible to do?  I have searched the other topics but none had suggestions on how to find the connections.

Any thoughts or insight is welcome at this point!

Thanks!!!


texts: I found this schematic (in Spanish) and annotated it with my interpretation. Anyone care to correct me or add?


texts: Is a high open circuit voltage still beneficial when you have a high voltage/frequency pulse arc starter?

texts: In welding, I know a high open circuit voltage is a major factor in the strength/quality of your arc when you scratch start, but how much of a factor is it when you have a pulse starting mechanism? Is it still necessary to have a high OCV to maintain a strong arc or is does the starter reduce its importance? If I have two identical welders that put out 200 amps at 50 OCV DC and I connect their secondaries in series, does that give me a 200 amp 100 OCV welder? Is that the only way to increase OCV, by increasing the total power? By extension, how is the OCV related to the voltage during welding? Is it a linear correlation?


texts: Sandisk SDHC Card Responding with Illegal Command to CMD8 by SPI?

texts:
I was trying to initialize a Sandisk Micro SD card, High Capacity, using SPI. CMD0 returns 0x01, which is good. But then CMD8 returns 0x05 as the first 8 bits received, indicating an illegal command, which doesn't make sense because this is SDHC.

I did the following (The clock is at 200kHz. Data is sent MSB first, Data is read MSB first).

For 100 clock cycles: MOSI = 1; CS = 1
Next 48 clock cycles: CMD0 is sent through MOSI with CS = 0: 0x400000000095
Next 8 clock cycles: Read MISO line: 0x01
Next 48 clock cycles: CMD8 is sent through MOSI: 0x48000001AA0F
Next 8 clock cycles: Read MISO line: 0x05

I've tried substituting CMD58 in for CMD8 in those steps, and that returned a legal command, so I don't think it is a timing issue. But I can't think of a reason why it would return an illegal command error for CMD8 when this card is SDHC. Can anyone help me with this issue?


texts: Cheap Low Power Signal Transmission To Smartphone

texts:
For my university project I'm making a certain sensor which has to (one-way) communicate with a smartphone. The sensor needs to be as cheap/simple as possible (aiming at +- €0,50 in total) and only has a 1.5V, 1.5mA max power source.

Now I want to send out a wireless signal from this sensor to a smartphone. Preferably without an extra receiver device. It has to have range of more than 1 meter. It only has to send out a few signals, no real data has to be transmitted, only a signal which the phone has to pick up.

I've looked into solutions like Bluetooth Low Energy (BLE) but this is already too expensive and consumes too much power.

Do you have any experience with building a simple, cheap wireless signal transmission to a smartphone?


texts: Is 3.5mm audio jack suitable for rotating connection?

texts:
I am designing a product where a removable accessory part should be connected while allowing rotation - boom microphone connected to a headset - you can plug and unplug and it should be possible to move with boom mic up and down as needed by the user.
The question is if a standard 3.5mm audio jack is a suitable connector for this purpose. I am afraid that it might lose contact after some time of use.
Would you accept using jack or recommend anything else?
Thanks


texts: what protection is required between op amp and 5v adc?

texts:
I've created this small circuit to translate voltage drop over a shunt resistor into a usable range for arduino (5v atmega32u4) adc.

This is to measure current out of and into (charging) a 12v battery on a boat.
The shunt is low side (connected to Bat-). My circuit has Bat- as Ground, Vin at high side of shunt. The shunt is 75mV at 100A.

The circuit seems to work nicely (though center was ~0.8v below the expected 2.5?)

Question(s):
It should probably be some form of protection in there. If I float Vin, output goes >9v and uC-pins would be unhappy. Is a zener diode enough?

Anything else that's missing? 0.1u caps on input and output?

simulate this circuit – Schematic created using CircuitLab


texts: Using a diode or resistor, to supply minimal voltage to LED Driver (Help!)

texts:
I'm using a dual 60W LED multi-chip pendant lighting (a.k.a. "high bay" pendant light with two 60W LED chips). This light is using an RGB driver (one per multi-chip) that has a remote control to adjust the LED. It can do several things to mix the color output, as well as strobe, flash, dimming, etc of the chip. Very nice to have, however those "features" of the driver/remote control are causing me a problem.

How it's wired currently:
I'm using an electronic timer that shuts the driver off during certain hours of the day. The timer is pretty simple as it connects to 110V and has 2 circuits of output. Meaning it will turn on/off 2 different output circuits. Here's a sample of how the timer is wired to the LED light (L being "live" and N being "neutral". 3-4 and 5-6 are timer circuits on/off).

The problem:
With the light powered on I set the light to a specific setting (using the remote control). When the driver loses power and shuts off via the timer I also lose my memory settings on the LED driver. This means when the timer again turns on the light (provides power back to the driver), the light will turn on with a default setting. This setting just happens to be a "flash" pattern and not the setting I set with the remote before it turned off. It tells me there is no "non-volatile memory" on the LED driver.

I need the driver to retain memory when it is turned off via the timer.

I've asked the manufacturer to tell me how much power is it going to take to retain memory only as I just want that little bit and not enough to turn the driver back on or light the 60W multi-chip LED until the electronic timer says "on" with full 110V power.

My thought is to use some kind of resistor or diode (not sure what term I should be using here), between the two leads as shown in this figure. (Testing with something that gives me 25, 50, or 75% power output to see what it takes for the driver to retain memory):

Anyone have any ideas on what I should be asking the manufacturer or what I should be using to make this work? Am I on the right path?

Of course I'm working on obtaining a driver that does what I need (asking the manufacturer if they can re-design the driver with flash or non-volatile memory and/or to have the driver default to a setting I need specifically). In the meantime I'm looking to see what I can do to rectify the problem. It could be months before they get me a working product.

Anything you can assist with to HELP me... would be greatly appreciated!!


texts: What is the difference between operational, differential, and instrumentation amplifiers?

texts: RS Components lists three categories of similar amplifiers: Operational Amplifiers, Differential Amplifiers, and Instrumentation Amplifiers. I think that there should be a single section called Operational Amplifiers. Why do these three separate sections exist? What is the significance of this difference?


texts:
I have an application where 12 input bits need to generate 6 output bits in a user configurable manner.  Of course this requires using a RAM based look up table.

I've noticed that the fastest static RAM available has an access time of about 10ns which limits the look up table access speed to 100 Mhz

How do microprocessors manage to access their internal caches in 1 clock cycle - typically 30 times faster than this?  Is the RAM chip speed being limited by it's external communication bus or is it something else?


texts:
As a beginner, I am confused with setting the adequate toolchain (the whole concept in new for me). My goal is to program the ARM Cortex-A9 on the board Zynq 7000 using the Xilinx SDK.

In order to write C project, the SDK wizard automatically selects Cross GNU ARM Toolchain and asks me to select the toolchain name and configure its path.

My questions are:

Cross + GNU + ARM toolchain, can anyone explain me the relation between those 3 or what do they mean together ?

When looking for Cross GNU ARM Toolchain I found in the ARM website they cite :

  GNU Arm Embedded Toolchain Pre-built GNU toolchain for Arm Cortex-M
  and Cortex-R processors

Does that mean that there is no Cross GNU ARM Toolchain for Cortex-A ? if that the case, so how can we program the processor of the zynq board ?

I may be confusing some concepts, so any hint and clarification would be helpful.


texts: Best practice on providing AVdd and DVdd from single source

texts:
I generally work in a purely digital world, however I'm working on a design at the moment that requires a separate power supply for analogue and digital components. What's the best practice from providing separate analogue and digital VDD from a single power source, such as a battery?

I assume that I'd just take the raw battery, have separate conditioning/power management for the analogue and digital supplies and then adequately decouple?

I'm asking this question as I've perused the internet but can't seem to find any good resources on this subject. I know that resources must exist but my Google skills obviously aren't strong enough to find them - any pointers to some relevant literature will be greatly appreciated.

EDIT: I should add that the analogue end of this circuit is for the precise measurement of a very low power signal.


texts: Can I expect a solderpaste circle to reliably reflow onto a smaller circlular pad?

texts:
For various reasons, I need to pad a bit more solder paste onto a fixed-size pad, and I cannot change the stencil thickness without messing up other footprints.
The pad is a 1.2mm diameter circle, and I've drawn the paste to be 1.36mm diameter, so about 0.16mm of the paste extends paste the pad.  On my 120um stencil, this 0.16mm "extension" increases the solder on the pad by my target amount of about 28%.
But this is only true if this extension of solder sucks into the pad during reflow.  Is it reasonable to expect this to be the case?
In green is the copper, and in teal, is the solder paste.


texts:
I'm working on the design of the "Sensor head" for a metal detector. Schematically it is:

It is a set of Tx and Rx coils arranged inside a shield. Some photos of the prototypes that I have built:

Summary of the constructive parameters and electrical characteristics obtained:

The results obtained are not bad, but I want to find the design with which this "stage" is optimized.

That's why the questions:

How much increase the number of Rx turns?
How much increase the number of Tx turns?
How to choose inductance value Tx and Rx?
Any extra information will be welcome!


texts: I am using a computer PSU to power a 92 watt(12V 6A) peltier device.The PSU has a rating of 450W,it has got 2 rails of 12V ,one delivering 15A and another delivering 16A.However when I connected my peltier device the current drawn from these rails are not more than 1.6A ,is there a problem with the psu or am I wrong somewhere?


texts:
(Schematic taken from here)
I can't make heads or tails of the push-pull stage similar to the one below - I'd rather try to understand it before this goes to a prototype board.
Q1 will start to conduct as soon as its \$V_{BE}\$ is roughly 0.7V, but how will that happen when its emitter terminal is floating?
May I assume Q3 and it's gate capacitance is discharged at the beginning which provides 0V to the node connecting the emitters of Q1 and Q2?
I guess my question is in large part about the circuit's initial conditions and my assumptions about them, but feel free to set me straight.


texts: Would it be possible to use a standard 12V DC LED dimmer together with a thermoelectric element to control the temperature? I'm talking about a very simple application with no need of fine tuning. Assuming that the output current provided by the dimmer is enough to drive the TE, I'm interested in knowing if the use of a PWM LED dimmer could possibly affect the life of the TE. A number of studies have shown that the PWM frequency has little or no significance on the life of the TE.


texts: Understanding ARM instruction for numerical literal

texts:
I have done an instruction trace while trying to find a bug on a Cortex M3. There is one part of the command I cannot understand.

STRB R1, [R3], #+0x01

According to ARM documentation, this stores a byte in R1.

I would think that R3 gets stored into R1, but I cannot figure out what the #+0x01 does.

I have seem this notation elsewhere in my trace, and while I understand #0x01, I cannot figure out what the "+" does to a literal. What does "#+0x01" mean ?

Below is a screenshot of my instruction trace taken from Seggar's Ozone.


texts: Sending Multiple Messages using Sim300 gsm/gprs module

texts:
I have interfaced SIM300 Gsm module with lpc2468 through UART. My main motive is to send SMS when some special sequence run. Now my requirement is that I should send the same messages to two numbers.

Is it possible to send message to multiple numbers giving AT+CMGS command only once?

Right now I do:

AT+CMGF=1 //TEXT MODE
AT+CSCS ="GSM" //SET GSM MODE
AT+CMGS="+9198........." //FOR FIRST NUMBER
> HELLO
CTRL+Z

AT+CMGS="+91981........" //FOR SECOND NUMBER
> HELLO
CTRL+Z

Is something like this possible

AT+CMGS="+9198........","+91981........."
>HELLO
CTRL+Z


texts: How to make my automatic night light circuit dimming?

texts:
I am working on a project named as automatic night light.The idea is simple; LEDs are on when there is dark then LEDs turn off when the circuit detects light.

However I have constructed the circuit I have mentioned above, I want to add dimmer to the circuit to make it sensitive to the amount of light seen by LDR. I mean I don't want it just to go on and off.

Here is my circuit diagram:

It is normally on and when the light seen, it goes off but it makes instantaneously. What should I add or do to add dimmer here?


texts: RC Oscillator for high frequency not working

texts:
Im now using Boylestad's book as a reference for making an RC Oscillator. it says in the book that for an RC Oscillator to Oscillate it needs

1) AV >= 29

2) that the phase shift of the RC network to amount 180 total.

the books says the formula F = 1/2pi(C)(R)(√N) will produce a 180 degree phase shift where N is the number of RC in the circuit

my target frequency is 4Mhz, and the available Capacitor is 100pF then
4Mhz = 1/2pi(100pF)(R)(√6)
R = 162

Av for inverting amp is AV = Rf/R1

29V = Rf/162
Rf = 4698 Ohms

but the output im getting is like a noise and is random, and its super small in the femto volts region. at low frequency(60Hz ) this method works, but when i simply changed the values after doing the calculations provided by the book i can no longer make it work pls help

heres the output from my 4Mhz RC oscillator


texts: How do I figure out the voltages at these 3 nodes of a circuit?

texts:
To start, imagine the branch containing the current source as a node, a point currents flow in and out of. This gives us: $$i_3+i_4-i_1-i_2=12mA$$.

We also know by summing all  currents flowing in and out of Node1 that: $$-i_1-i_2=12mA$$.

From these 2 equations, we know $$i_3=-i_4$$.

We know $$i_3=\frac{V_2}{6000}$$ and $$i_4=\frac{V_3}{3000}$$. So we can conclude that $$V_2=-2V_3$$. (V2 is the voltage at node 2)

We need another equation invovling V2 and V3 to solve them. If we look at the battery, we see that: $$V_3-V_2=6$$. We solve these 2 equations to get V2=-4V and V3=2V. Now we need to find voltage at node1, V1.

To do that, we look back to the equation summing all currents coming in and out of node1: $$12mA-i_1-i_2=0$$. We plugged in the expressions for i1 and i2 in terms of V. We have:$$0.012-\frac{V_1-V_3}{4000}-\frac{V_1-V_2}{2000}=0$$
Solving it and plugging in the values we got for V2 and V3, we have $$V_1=14V$$.

NOW there is a problem with these values for V. I tried testing them by plugging into the equation for summing currents at node2. $$i_2+i_5-i_3=0$$.

$$i_2=\frac{V_1-V_2}{2000}=9mA$$
$$i_5=\frac{V_3-V_2}{1000}=6mA$$
$$i_6=\frac{V_2}{6000}=-0.667mA$$


texts: What connector is appropriate for a 500V electrostatic speaker?

texts:
A research group just bought an electrostatic speaker that came with a long cable that is meant to be soldered to the speaker wires.  However it would be more convenient to have a connector(s) there.  There are 3 wires (+ shielding): audio negative, audio positive (500V peak to peak) and bias voltage (450V).  Given the high voltage (but low currents 0.25A), I'm not sure what connector would be appropriate.  I doubt typical audio connectors would be rated for 500V.  I'd also prefer something that locks and cannot be touched.  I was thinking XLR because of phantom power, but I couldn't really find specific voltage ratings...  Any suggestions, references, comments?

Edit: Manufacturer said anything rated for 115 W is more than enough.  (I added the max current for the speaker above.)  I learned about Paschen's Law (for spark risk in air) and calculated that I'm ok with pins spaced by 0.1 mm or more.  Whatever insulation is used in the connector, I assume it's at least as good as air...  But I'd still rather use something rated for 450V if someone has a suggestion.


texts: How to measure the impedance of a given coil?

texts:
What's the best way to measure the resistance and inductance of a coil at a given frequency? I need these parameters for my LTSpice-Simulation which assumes an RL series circuit.

The coil has 8 windings and is printed on a PCB. The eDesignSuite from STMicroelectronics estimates an inductance of 1.72µH. DC-resistance is approx. 1.27Ohm (measured).

Will the resistance at 13.56MHz be equal to the DC-resistance? (How can I verify this?)
How can I verify the inductance of the coil at approx. 13.56MHz?

Thanks!


texts: Replacing a Lithium-Ion battery with an array of lead-acid batteries

texts:
I have an electrical bicycle that I rarely use, and I'm thinking about turning it into a project.

The electrical bicycle has a 36V Lithium-Ion battery. When it's fully charged, it produces around 42V (36V is measured when it's fully discharged). It's completely okay, but I want to test out something different.

I figured out that for the price of a new 15Ah 36V Lithium-Ion battery I can get 3 12V 41Ah (99RC) lead-acid batteries. If put in series, it'll produce 36V for 41Ah. That's more than twice the energy for the same price!

Except for the lead acid batteries having a slightly lower voltage (36V < 42V) than the Lithium-Ion counterparts, shorted lifetime and disregarding weight and size, what major disadvantages will the lead-acid batteries have?


texts:
Why do we need 3 phase?
For the reason that voltage will never be zero in 3 phase? OR we need high voltage?


texts:
Can someone suggest a source and part number for insulated, stranded small-gauge wire (around 22AWG) that is flexible and doesn't hold its shape?  Something along the lines of the wire found on multimeter probes.  I want something to connect to my bench power supply that will lay flat on the workbench; standard stranded hookup wire is too stiff and retains the shape of the spool.  When searching Mouser, there are multiple choices for stranding, jacket material, and wire type, but I don't know how to correlate those to my needs.

Thanks!
Brian


texts: Royer oscillator - frequency shifting in WPT

texts:
I am having a problem with my WPT resonant application. In my circuit modified Royer oscillator feeds LC tank. Receiver coil nearby is connected to rectifier and variable resistor. I know about frequency splitting phenomena caused by strongly coupled resonant systems but it depends mainly on coils distance. I did two measurements with the same LC circuits on both sides for two different coupling factors. Royer oscillator as shown below
I do not know why my Royer oscillator shifts the frequency dependently on load resistance. With k=0.1 frequency is changing slowly but in case of strongly coupled coils the curve is sharp and Mosfets are crying and seems that Royer does not know which frequency to choose. Measured values shown below
In the sharp area I see destroyed sine wave on oscilloscope but highest efficiency occurs.
Do you have any explanation of frequency shifting problem in dependence on load resistance?
Thank you for you answers


texts:
I've already asked about this antenna system.
However, I still have some questions and somethings I do not understand.

I heard that the antenna only receives POWER, not voltage. From this fact, I thought that the current will be 1 / (antenna resistance + load resistance). That is, the input power is constant.

Let us define the transmit signal with power 50 Watt is
$$s(t) = 10\cos(2\pi f_c t).$$
And we assume that the receiver receives the signal that is reduced a half of the transmit signal, i.e., the power of the received signal is 25 Watt.

Then, is the voltage source defined as
$$
v(t)=A \cos(2\pi f_c t)
$$
such that $$\frac{\frac1T\int_T |v(t)|^2 dt}{R_{antenna}+R_{load}}=25$$
?


texts: Small solar panel dc to 5vdc for charging

texts:
I have a small solar panel which i want to use as cellphone, batties charger or any other gadget that requires 5vdc. I tried using 7805 but it reduces volts to 3.something. 7805 works fine on 9-12v battries. How can i do that. I need simple circuits because many ics used in those circuits may not be available here.My solar panel has

Maximum power (Pmax) = 5w
Voltage at Pmax (Vmp) = 17.2V
Current at Pmax (Imp) = 0.30A
Open circuit Volatage (Voc) = 21.6V
Short circuit Current (Isc) = 0.31A

I think it has enough power to charge powerbank or cellphone.Is there anything usefull that i can pull from other circuits. I have plenty of them.


texts: Capacitor across motor vs capacitor across motor and transistor

texts:
I am currently building my own control board for a high power brushed DC motor (24V 16A). I am using an Arduino to provide a PWM signal to an IRLB8743 MOSFET. The reason I am trying to build my own is because I have blown up so many cheap unbranded controllers, and I want to implement a safe-boot routine and slow-start functionality, along with a few other custom functions.
From disassembling wasted boards, I have noticed that large electrolytic capacitors (63V 470uF) are placed in parallel across the power supply. From my knowledge, small 6V motors have ceramic capacitors across the terminals for smoothing.

simulate this circuit – Schematic created using CircuitLab
Here is the schematic of the board I plan to create, but it is unfinished; I have salvaged two of these capacitors from other bards, but I can't decide where to put them. Should I copy the control boards, and place both caps at C1, or should I move one cap to C2 for some smoothing benefit? I don't really understand the purpose of either C1 or C2.
Another final mention is that I hope to swap out the motor in the future for an even bigger one, and maybe power it from 48V.


texts: Can somebody please explain the antenna and mixer stage of this AM superheterodyne receiver?

texts:
This is from an Elenco AM/FM superheterodyne radio receiver kit.

The shown area is the AM antenna and mixer stage. The wire leading from the top right corner is Vcc.

Q7 simultaneously oscillates at the IF and mixes this with the received signal.

It appears that the right side of L4 is for the IF oscillator tuning and the left side picks up the signal from the air.

I do not understand what capacitors C28 and C30 are for. The instructions are slightly vague at this point.

Could someone please explain what they may be for?

Why is Vcc leading into the RF tank circuit?


texts:
I want to build this circuit but I do not have a 7555 low power timer so wondered if I can use a NE555? Also can I use a 2N2222 trasistor instead of a BC108? I don't want to try and build it without making sure I won't damage some components.

Here is the link to the project Light-sensitive Alarm Project and here is the schematic in question, note that while the schematic shows a 555 the parts list mentions a 7555 :


texts: Snubber circuit for 3 phase inverter designed for BLDC motor

texts:
I'm designing a motor controller for 3-phase BLDC motor. I'm using following components,

Gate driver - IR2184
MOSFET - IRF540N

The complete circuitry and output waveforms are available here.

I have developed circuitry on the PCB as you can see in figure 1 in the link given.

With resistive load I have perfect BLDC commutation waveforms that I can observe and it is clear from figure 3 in the link.

But when I use same circuitry for the BLDC hub motor with following specs,

Power 250 W
Rated voltage 36 V
Max current limit 10 A
Motor load - No load, motor is running free on a mounting

As from figure 4 it is clear that circuit is not behaving as expected with an inductive load as motor coils do not have any other path to release magnetic energy but by body diode of MOSFETs. Snubber seems a solution to this problem. I have googled for 3-phase inverter snubber design but I could not find material specifically targeting 3-phase inverter snubber design.

Could I get some direction in the design of snubber for 3-phase inverter?


texts: This LM311 powered LED is not activating properly

texts:
I am taking the tractive voltage and dividing it by a factor of about 20 and comparing it with the reference of 3V. If the tractive voltage is 80V, that should be divided to 4V and that is greater than the non-inverting input of 3V. This should turn the LED on. And it does. But when the tractive voltage is 20V (so 1V) LED should not turn on. But mine does below.
I have been picking my hair out for hours trying to figure out what's wrong with this LM311 set-up. I may be making a rookie mistake though.

edit: someone asked to show some voltmeters, so i attached one for both inputs and at the output for across the LED
so it turns out that the circuit behaves correctly when I put a voltmeter across the LED. this is really weird to me. why does the presence of a voltmeter cause it to function properly?


texts: Is there any relation between the input and output of bridge rectifier that can explain this sentence?

texts:
Energy can be extracted independently of the excitation type and frequency, as long as \$V_p\$ exceeds the output buffer voltage \$V_{buf}\$,I am not understand what does this sentence mean,it seems that there is a relation,i don't know, between the input and output of bridge rectifier.Can anyone explain this to me?

By the way,i just saw the author said the \$C_p\$ limit the energy extraction when using an FBR(Full Bridge Rectifier),why?

As we know ,the remain voltage after passing the diode is the blue part,and V has relation with I,but i can't correspond it voltage to current,i mean,the second picture must have relation with the third picture,but i can't understand it.

PEH=Piezoelectric Energy Harvesters


texts:
I have built an AC/AC cuk converter for an assignment I am doing. It works as such, I provide 50V AC in and I get an adjustable voltage out from 0V to 50V AC, depending on the duty cycle of the PWM that I gate to the MOSFETs. It is designed to supply a max of 1A rms to the load. I have included a schematic below, drive circuit as not been shown.

It works extacly as I have explained. However, I would like to incorporate some sort of rudementry simple short circuit protection.
Any ideas would help, thanks.


texts: How to transmit the signal of N switches with a CAN network

texts:
I currently use N inputs from my microcontroller to read the N signal switches. But when the number of switches is too large, this becomes unfeasible. With this I started to study a CAN network to transmit using only two wires. But I do not know how to do this in the case of switches, whether to use a CAN module for all or not.

How do I transmit the signal of N switches with a CAN network?

simulate this circuit – Schematic created using CircuitLab


texts: Specific current mirror explanation-source

texts:
I am trying to understand the following current mirror, though I haven't found any book that describes it. Is there any source in which I can see how it works and its pros and cons? The drawing is from https://patentimages.storage.googleapis.com/93/7e/df/722ee75b28e661/US4550284.pdf in which they do some sort explanation but I think it need more of description,

Thank you,


texts: How do I get a clean PWM (Modulation) signal to my RF supply/control for my laser?

texts:
I connected a PWM signal to the MOD input for the RF power supply.  On the scope, it changed from a relatively clean signal to a very noisy signal.  The laser head did turn on and fire, however, the PWM generator controller started to show garbage on the LCD after about 30 seconds, and the RF supply started smoking.

I tried a second device that makes a PWM signal (0-10V).  After connecting to the RF supply/control, the high signal dropped to 1V.  There was no output from the laser and the RF supply was quiet.


texts: The control voltage output for a phase locked loop

texts:
I am designing a low power phase locked loop in cadence with a phase detector, charge pump and VCO.The control voltage output for my circuit at the output of charge pump is as shown below

But when I zoomed into the waveform I saw some oscillations like this

Does this mean that my PLL is not locking properly because I thought, the control voltage must be constant when locked. But, here it is varying for 0.1Vpp. So how should I interpret my result? Is it right or wrong? Please, any help is appreciated.


texts: How to achive mutual inductance and CM choke simulation in CircuitLab?

texts:
This site is using CircuitLab. In some SPICE programs it is possible to simulate CM choke. For example:

  Mutual Inductance is designated in a SPICE netlist by beginning the
  first word (label) of a new line with the letter "K".  It is unique
  among the basic circuit elements in LTspice in that a schematic symbol
  is not used to represented it.

Is there a way to achieve this by using CircuitLab?


texts:
Ok so i've got a BTHQ128128 fstn display that i'm tryinf to drive via an ATMEGA128 AVR chip using gnu-c (avrlibc). Found some code on the interweb, but still not able to get the display to show anything.

The screen driver is a UC1698 (colour although the screen in black&white)

Has anyone ever attempted this and succeeded?

Also is there an other type of driver that is similar to the uc1698 that a library could be ported from.


texts:
newbie here.

As I read through webpages, i got to know that Oscillators are capable of changing DC to AC. I made a phase shift circuit in Multisim, but I got no idea what should I do next.

I was thinking using DC source as input and it will produce AC output, like some sinusoidal graphs. But if use AC Sweep, DC definitely will be open.

Any idea?
Thanks!


texts: How important is it to track from centre of pad in PCB routing?

texts:
When reading through the review comments of a PCB, there was one which raised some questions for me:
"Aim to route tracks out of pad centres and in line with the pad, not exiting at an angle."

I usually try to route from the centre of pads, as most PCB tools snap the track in, so it can be usefully tied in when moving things around. But I'm not sure how important that is for EMC, PCB creation, manufacturing or reliability. Does the trace out of the pad cause a thermal path to make the solder pull away enough during soldering to potentially cause issues?

The second part of the comment, the not existing at an angle is also strange. Why would an angle matter? I can't see how that would matter, and many connections are round (BGAs, and through hole pins for instance). Is there something I don't know, or is this historic?


texts: What type of sensor has diamond pinout like shown? Resistive bridge? Wheatstone?

texts:
I have worked with basic resistive sensors before, but I have never seen a pinout like this one and I'm not sure how the voltages work for these pins. I was told it may be a resistive bridge, but it seems to me there are some differences between this one and the examples I've seen in articles. I also don't see much of an explanation in the datasheet for this sensor (a pressure sensor):

http://www.mouser.com/ds/2/589/-219572.pdf

I am not sure what other terms I can search for to understand how to use this sensor in my project. Is it a resistive bridge? If so, how does this one differ from a basic example (i.e. why does it seem to be separated down the middle instead of connected?). What is the theory of operation? What are the meanings of +V exc, -V exc, +Sig, -Sig and so on? Any information would be helpful!


texts: Read and Write multi variable (Struct) from/to external FRAM memory over SPI by ATMEGA Using Code Vision

texts:
I am working on a project to read some data from ADC and store them in external FRAM over SPI.
I have 8 different float values which need to save when the power is off or other specific situation and after power get on read each value and continue from saved variables.
So my question is if I save them in array ot structure how can I write and read them from FRAM.
Thanks in advance.


texts: How to create a negative voltage supply?

texts:
I am trying to incorporate a LEM LAH 100-P current sensor  into a project. It requires a dual polarity voltage supply between +/- 12 and 15 volts. What is the best way to implement it?

Digi-key has an article which references many other application notes. But I don't have knowledge of power electronics which makes adapting them difficult. This application note seems promising but components used are for an output of -3.3 to -5.5 volts (part at digikey and datasheet).

Figure from the application note:

What components could be used to create a negative supply of 12 to 15 volts? Any suggestions welcomed.


texts: voltage differential vs max input of regulator?

texts:
so im trying to assemble a circuit to take my 120VAC wall line and ultimately power a small smart hub, small transformer i found somewhere that was actually labeled with which pins were input/output, 110VAC yields 11.7VAC, but because its a cheap transformer its putting out 21v unloaded, which is way higher than an 1117 can take, so i went looking at what else i had. find an old 1084 regulator i looked at the datasheet and instead of listing a maximum input voltage, it lists "Maximum Input to Output Voltage Differential" as 27V. so if the max differential is 27v, and the output is (to simplify math) 3v, my max input is 30v, correct?

for the sake of my understanding, would the component be able to take input floating between 30 and 40 VDC, and with the proper voltage divider on the adjustment pin, regulate to 24v?

lastly, is this unique to this device or is this just how voltage regulators worked and i never understood?


texts:
In this picture, when v1 and v2 are 0, M1,M2 are on and M3,M4 are off. V_T(threshold) = 1.7V, V_DD = 5V.

Why is it that M1 and M2 are ON under these conditions? I thought when there is no power through the gate the MOSFET will be off. Is it because M1, M2 are p-channel and M3, M4 are n-channel.

PS: This is an introductory EE course. So I'd really appreciate it if you please kindly keep your answer on n00b level.


texts: I am just trying to figure out the max current which i could expose my new micro JST cables to. It says here that they are rated for 1A and 50V. Converted to power that would be 50W. that sounds very high for such thin wire. Am I understanding the ratings correctly? Could the current be increased if the voltage was reduced? Many thanks.


texts: Transformer Outputs Voltage High Above Expected Voltage

texts:
I have recently put together this circuit, which works basically as expected.

Due to my lack of certain parts, however, I had to replace the 68 Ohm resistor with a 52 Ohm resistor, and the MOSFET I'm using is an IRF3205.

I am powering the circuit with a 7.4V LiPo battery.

Despite the changes I've made, the circuit drives the transformer fairly well, and the MOSFET doesn't get too hot, especially with a decent heatsink.

However, after attaching the secondary of  my transformer to a high voltage bridge rectifier, the output measured by my multimeter was above 600V! With 10 turns on the primary, and 275 turns on the secondary, I expected about 200V.

Output Voltage = Input Voltage * (Secondary Turns / Primary Turns)

Output Voltage = 7.4 * (275 / 10)

Output Voltage = 7.4 * 27.5

Output Voltage = 203.5

I figured a smoothing capacitor might help with the reading on my multimeter, so I added a 150uF 450V capacitor in parallel to the multimeter.

Still, the voltage quickly rose to the cap's maximum rated voltage (according to my multimeter), so I deactivated the circuit.

Is my multimeter wrong?

Or is my math wrong?

What is the cause behind this?


texts: Length to make magnetic loop antenna/probe for 1.6GHz?

texts:
I'm making a near-field probe to to search for GNSS (GLONASS) blocking signals on my PCB.

According to http://www.eryptick.net/unisold/loop.html the wire length for a loop should be 1/3 the wavelength to be resonant and avoid a tuning capacitance to resonate out the wire's inductance, so my loop is this length.

It's single ended so the end of the loop is grounded (I've also tried open ended).

I'm using an aluminium wire for the loop which is soldering into the barrel of a BNC male-to-male adapter then feeding this to a spectrum analyser.

However it doesn't seem to work at all — it's been a while since I made one of these and I have a feeling I'm doing something silly

Does any of the above seem incorrect?


texts:
I've been trying to restore an old HP400D Vacuum Tube Voltage Meter. Section 5-20(f) in the manual says:

  Measure the direct current in the lead from V7 (pin 1) which must be less than 60mA... Excessive current indicates a short or partial short in the circuits of the voltmeter amplifier section. A clip-on type milliammeter should be used for this measurement.

Presumably, the manual is saying to use something like the HP Model 428B. Unfortunately, I don't have one. Therefore, I am wondering if there is another way to measure the DC current without having to cut the wire. Since I'm only testing for a short (or near-short), and the expected current is very small, I don't think need an extremely accurate measurement. Any ideas?


texts: Connecting a 12V LED strip to a 7.4 2s Li-po battery in addition to two motors

texts:
I know this is going to be a completely stupid question, but since I'm working with a Li-Po I want to make sure I get this right.

What I am building is a modified Nerf blaster that has two motors connected in parallel drawing 20A each (40A in total) at peak, far less most of the time. Now, if I'm not mistaken, if I need to add an LED strip I would need to connect it in parallel to the motors, right? Is it a big problem if the voltage is far lower? Will the lights simply be dimmer (which is totally fine for my needs) or will they simply not work at all? Will I need any sort of short circuit protection when dealing with LED strips? Also, some people mentioned having to connect a capacitor as well but I'm not sure why.

Sorry for the dumb questions but I haven't done all that much work with anything other than very basic circuitry.

Thanks.


texts: External pull-ups with Atmel microcontrollers: what assumptions can be safely made about the impedance in tri-state mode?

texts:
Using an ATmega (the 48/88/168/328 family, if relevant) with a very weak supply, the internal pull-up resistors have proven to draw too much current.

The microcontroller is driven at very low clock speeds, with a supply between 2 and 3 V, with everything non-essential turned off, so that it uses less than 100 µA. This is all fine, but the device needs a few buttons. If I just connect the buttons to the ground, and use the integrated pull-up resistors, a single button, when pressed, can draw more current than the rest of the microcontroller. This would lead to the collapse of the power supply. Therefore I intend to set the pins to "tri-state", and use a much higher external pull-up than the integrated 20-50 k.

However, I have trouble specifying the value of the external pull-up. Obviously, I would like to have it as large as possible, while still being able to reliably detect a high logic level.

My problem is, that I couldn't find in documentation how high the high-Z really is. Searching through several forums the only indication was that it's measured in megaohms. But how high is it really? And what is the lowest value it can take? How can I find it out, besides trying to contact the manufacturer directly?

I wouldn't trust in an empirical method, as the internal pull-ups are specified in the datasheet as 20-50 k, a very generous range, so I guess the impedance in tri-state could also vary significantly.

I tried it with 330 k, and it worked, with a tolerable current draw in the 10 µA range. One method would be to increase the resistor until it no longer works, and then take a value significantly lower than that. However, as I don't know how much the impedance of the pin in tri-state mode can vary between devices, I doubt this would be the best approach.

Does anyone have more information or experience about it?


texts: Using a microcontroller to program another microcontroller (on a wireless board)

texts:
I am working on a project in which I want to include the functionality of reprogramming the main microcontroller via wireless transmission.

First, I have figured there needs to be a dedicated microcontroller programmed to facilitate this function, but how exactly would it need to be implemented?

Assuming the code is already compiled before transmission, would the code need to be stored in any specific way prior to being read and used to program the main controller?

Also, what exactly is the process required to facilitate the actual programming of the controller?


texts:
The Ring doorbell is a pretty simple and useful product. I was wondering: how does the Ring doorbell get power without activating the chime? As far as I know, a doorbell works by shorting two wires when the button is pressed and causing the chime to chime. But, with the Ring doorbell, the two wires are always connected because it needs to be always on. So why doesn't it ring the chime if the two wires are always shorted? I know there is "Ring Power Kit" you connect at the chime. You can see pictures of it here.

I am a rookie and I just started out playing with Arduino and ESP chips. I hope someone can explain this to me.

I am asking this question because I want to make a smart video doorbell with an ESP32 connected to a camera. I want to know how would I power the ESP32 without shorting out the two wires.


texts: Altium PCB design: Vias stitching problem

texts:
I need to create a VIA stitching on my design but the option doesn't work:

I select the width of my VIA, the area where I want to place all of them, and the net to be connected.

At the end it displayed:

  Unable to add any stitching vias to net GND_3

(GND_3 is the name of my ground plane)

I have 10 layers on my board. No tracks are passing under my area, and no components are placed.

note: It was working when no tracks were routed. So maybe the option has no place for the vias...

Thanks for reading and maybe helping.

EDIT 04.04.18:
The placment of the vias stitching is placed on the design but there are no via on it (always the same message "unable to add stitching via"). I have like 20 vias stitching area but with no via.

Altium version: 1,0,11 (build 97) Altium NEXUS


texts:
As I understand the datasheets boot0 pin and boot1 bit (in a register) control how the CPU boots up, which are Main Flash memory, System memory and Embedded SRAM. I honestly don't know the differences in functionality of these memory sections, nor do I want to care right now (feel free to tell me why I should).

My use-case requires programming it through SWD as needed (so not a one-time deal) and boot from it.

I'm not interested in various flash configurations or having bootloaders to program the chip over other protocols. I'm not going to mass-produce this.

Would pulling boot0 pin low through a resistor and simply connecting the SWD connector allow me to do this?


texts: Correctly powering amplifier and speakers

texts:
I have a few speakers that I salvaged from broken electronics and I plan on buying an amplifier board to drive the speakers. I'm currently looking at an amplifier such as this one and have sketched a diagram on how I believe it should be wired and powered as to not blow the speakers.
I'm not sure if this is correct or if my calculations are entirely off. I appreciate any help and corrections you could provide.

Also, is there an ideal way to supply the 12V and 11V? I have an old pc psu and some adapters but I'm not sure if those are the best approach.

Thanks


texts: Decoupling cap: Closer to chip but with via or farther without via?

texts:
This may "yet another" question about decoupling but the question is pretty precise and I can not find an answer.

I have a 40 pin QFN where I need to fan out signals and then place tens of decoupling caps. To make things worse, the IC sits on a socket that occupies 8x the area of the QFN (5mmx5mm). (The socket occupies much area but does not add significant parasitics; it is rated up to 75 GHz). On the same layer I cannot place components within a radius of ~7mm. The backside is restricted as well due to the mounting holes of the socket but at least I can use partial real estate on the back side. But I would need to via down for that. However, I could place 50% of the capacitors onto the thermal ground paddle that I also created underneath the chip on the backside.

Now I have read multiple times there should not be a via between the coupling cap and the pin. But what is worse? Via or longer wire?

In terms of inductance, a 7mm trace would be around 5-7nH (http://chemandy.com/calculators/flat-wire-inductor-calculator.htm). A 22mil diameter/10mil hole is far below 1nH (http://referencedesigner.com/rfcal/cal_13.php).


texts: How do I deal with multiple, separate shields?

texts:
With HDMI or USB3.0/3.1, a cable assembly, in addition to the main braided shield, has multiple separate shields for each differential pair, here an example of a USB3.0 cable:

Image source

The inner shields are connected to the GND_Drain pin on the plug:

With HDMI, it's even more complicated. There, every single one of the four differential signal pairs has its own ground connection on the plug:

How am I supposed to connect these additional ground connections together on a device? Coming from this question, the outer shield could be connected to power ground directly - a few more options are outlined here - and should be connected to the case of my device if that's made from metal. That's easy enough, but what about these additional connections? Would connecting them directly to the outer shield reduce their effectiveness?


texts: Why does this microswitch datasheet specify a minimum load current?

texts: The Omron VX series datasheet mentions on page 6 that "Using a model for ordinary loads to open or close the contact of a micro load circuit may result in faulty contact.", and shows that their micro load models even still require a minimum of 1mA @ 5V. Their D3V datasheet goes further and explicitly marks the low end as being an "inoperable range". But neither datasheet explains why a microswitch would have a problem with a low load condition. Why is this, and what would happen if a microswitch was operated at loads lower than the minimum operating range?


texts: Voltage regulation vs relative voltage tresholds?

texts:
There is a part of my circuit that uses resistance to output a voltage, in which is compared to a voltage threshold to output a digital signal.

However +Vcc can vary and any voltages too far from 5V will cause this comparator to function wrongly and toggle at the wrong resistances, since the output voltage is a percentage of +Vcc while the voltage threshold is determined by a zener diode, which won't change even if +Vcc is changed. Which makes calibrating the comparator useless since any change in +Vcc throws the entire module off.

I'm not sure which of the two solutions are the best to implement, or to do both?

Use a linear regulator to maintain a 5V +Vcc signal, so that the output voltage will always be calibrated since +Vcc won't change at all.
Make it such that instead of using an absolute-value threshold like a zener diode, use a voltage divider so, like the output voltage, is relative to +Vcc, therefore it will remain calibrated (the comparator will still toggle at the same resistance).

I'm kind of in for #2 because it feels like "good practice" to work relative to +Vcc, but it also introduces some problems like it is difficult to compare two voltages directly. #1 also seems nice because it allows us to work with numbers directly.

If I do both one of them may feel unnecessary. #2 may make it such that a wide range of voltages may be used (up to a certain power limit), but may be harder.

#1 may make it such that everything will be more accurate, especially when there are some unavoidable constants that won't vary with +Vcc such as the diode forward voltage.

So, #1 or #2, or both? Or something else entirely? :/


texts: Increasing supply rails for low size MOSFETs

texts:
With decreasing sizes of MOSFETs, the supply voltage has also scaled down so as that the electric fields in the device are not large enough for them to breakdown. However if this depends only on relative voltages, can we not increase the bulk voltage so that the supply voltage can also increase?
Specifically what I'm asking is that if I can stack one NMOS above another, the bottom one has its bulk grounded and its drain voltage does not exceed the nominal supply voltage given in the datasheet of 1.2V. The top NMOS however can have its bulk connected to say 0.6V and its drain can be connected to 1.8V. So the electric field across no device will exceed the breakdown voltage
Edit: In case it wasn't clear, my question is that if I increase all voltages (bulk, drain, source and gate) then can the absolute drain voltage exceed 1.2V. The relative potential differences between any two junctions would the same as in a normal design
This could potentially be a problem because the substrate is grounded and I might end up breaking down some junction with it


texts:
I have a basic doubt in understanding the concept of equivalent inductance. When two inductor coils are in series the equivalent inductance is calculated as

\$ L_{eq} = L1+L2 \pm 2M \$ (depending on the dot convention)

where L1 and L2 are independent coil self inductance and M is the mutual inductance dependent on coupling between the coils k (coupling coefficient). M is calculated as

\$M = k \sqrt{L1. L2} \$

k can take values from 0 to 1, 0 for no coupling and 1 for perfect coupling between the coils.

So if two coils are placed adjacent to each other very far where there is no coupling between the coils then k = 0 and \$ L_{eq} = L1+L2 \$ because M = 0.
If the coils are so far that L2 has no impact on L1 should we still consider L2 for calculating \$L_{eq} \$ ?


texts:
I've got an USBASP v2 programmer with 10-pin ICSP output. Could anyone tell me which pins to connect to program my ATTINY2313 with AVRDUDE (under Ubuntu). For some reason, I keep getting:

avrdude: warning: cannot set sck period. please check for usbasp firmware update.
avrdude: error: programm enable: target doesn't answer. 1
avrdude: initialization failed, rc=-1
         Double check connections and try again, or use -F to override
         this check.


texts: Does MMU starts functioning from the device boot or the kernel starting point.?

texts:
When an ARM device is booted and before the kernel starts, does the device have the knowledge of the address of the devices that needs to be initialized to a bare minimum?
When does the MMU functionality starts? from the booting or the kernel?
if from kernel, who manages MMU functionality before kernel.?


texts:
A lab-sized microgrid (island) has been set up to test some equipment. An inverter+battery is being used as the source, with the inverter operating at very low power compared to its rating. This makes the system PF low and capacitive.

What's confusing me is looking at our power and energy measurements from the inverter's output. With positive indicating energy/power import, and negative indicating export, here is a graph of power (top) and energy (bottom):

Here, power is consistently negative, as one would expect from an inverter's output. But energy oscillates between negative and positive at a regular interval. The magnitude of the negative is twice that of the positive, so overall it's reading energy exports, but why would it ever be importing?

My one guess has to do with how the meter in question measures energy, which is as an accumulated field (ie it just has 2 counters going up, one for imports, one for exports). If there was a teeny amount of energy imported at certain points of the inverter's switching cycles, even too low to be measured by the instantaneous power readings, it would eventually accumulate to an amount that would be read by the energy field.

That's just a hypothesis though, would appreciate someone who could explain what's going on here in more detail.

EDIT: Worth noting is that the positive spikes are correct, in that if they're disregarded as erroneous, energy and power do not match up at all (energy accumulates about twice as fast as it should), however if those positive spikes are added to the negatives, energy accumulates at the rate expected from a 60 something watt load.


texts:
Just a simple question,

In https://en.wikipedia.org/wiki/Random-access_memory says that each bit of data in RAM/DRAM stored in a single pair of transistor and capacitor in memory cell.

So let's says the RAM has 4GB memory that mean it can store about 4billionx8bit = 32billion bit of data.

So that i want to ask is, is that true that there are at least 32 billion capacitor in a single 4GB DRAM ? and is that possible to put 32 billion capacitor that can fit on a single board of RAM size? or am I just wrong?


texts: Antenna matching using L-sections does not always yield a "matched" solution

texts:
I created a program to compute the component values of a T network to match a reactive load (R+jX) to a 50 ohm source, based on the procedure outlined by M. Walter Maxwell in  his book "Reflections".  I then verify the match using LTSpice, expecting to see half the input amplitude, and the current being in phase with the voltage if the match is perfect.  This only seems to work sometimes, and I am still trying to understand what it is about the impedance of the load or the target Q value I design the network for that determines whether a "good" match is indeed obtained.
Below is the approach and program used:

Rs1 is the load resistance, while the load reactance is absorbed into Xs1.   The procedure uses the following equations to compute the reactances of the L-sections:

Rv is a virtual version of the the matched parallel Rp used as the load for "section 2" -- it is not ultimately in the matching network.  It should be greater than both Rs1 and the source impedance, so Q must be selected to ensure this.
I start with the antenna load, and select a Q for that section.  I enter the source impedance, and the resonant frequency, and the program calculates all the reactances and determines the corresponding L-C values.  The reactances can be inductive or capacitive, but the sections must be L-C or C-L, never L-L or C-C.
Taking for example a match to a load with impedance 9.84 +j120 (at 40.68MHz), and Q=100, the program yields: L1 = 3.4uH, Ls2=8.7u, Cp =5.7pf.
When I verify these on LTSpice,
I expect the voltage at Vmatch to be half the input voltage (since Rs =Rl = 50), and  the current to be in phase.  However, this is what I get:

Vmatch is greater than expected, and the current is not in phase with Vmatch.
However, I believe the code to be correct because I do get working matches for other loads and Q.  If I match a 12+j20 load, with a Q=5 at 3.5Mhz to 50ohms, I get:
Ls1 = 1.8u
Ls2=5.2u
Cp=1.06nf
When I simulate these values, I get the expected results:

What could be the reason the matching calculations work in some cases but not others?
Here's the code I wrote for reference:
# Matching Network
# 10/13/2020

import numpy as np
import re

# Series-Parallel equivalent circuit equations
# Q = Xs/Rs = Rp/Xp
# RP=Rs(Q^2+1)
# Rp/Rs=Q^2 +1
# Q = sqrt(Rp/Rs-1)
# Xs = Q*Rs
# Rs = Rp/(Q^2+1)
# Xp = Rp/Q

#T-Network
ttype=int(input('Enter 1 for L-C-L or 2 for C-L-C T-Network: '))
q1 =float(input('Enter Q1:\n'))
rload = float(input('Enter Load Resistance: '))
xload = float(input('Enter Load Reactance (negative for capacitive, pos for inductive: '))
rsrc  = float(input('Enter Source Resistance: '))
f0 = float(input('Enter Resonant frequency:  '))

#f0 = 40.68e6
#q1 = 100
#rload = 9.838
#xload = 2*np.pi*f0*469.91e-9
#rsrc = 50

rs2=rsrc
rpv = rload*(q1**2+1)
q2 = np.sqrt(rpv/rs2 - 1)
print('Q2 = ', q2)
print('rpv = ',rpv)

if(ttype ==1):
    print("I'm here")
    xs1 = q1*rload - xload
    xp1 = -rpv/q1
    xs2 = q2*rs2
    xp2 = -rpv/q2
else:
    xs1 = -q1*rload - xload
    xp1 = rpv/q1
    xs2 = -q2*rs2
    xp2 = rpv/q2

print('xs1 = ',xs1)
print('xp1 = ',xp1)
print('xs2 = ',xs2)
print('xp2 = ',xp2)

xpcomb= xp1*xp2/(xp1+xp2)
print('xpcomb = ', xpcomb)

if(ttype==1):
    Ls1 = xs1/(2*np.pi*f0)
    Ls2 = xs2/(2*np.pi*f0)
    print('f0 = ',f0)
    print('xpcomb =  ',xpcomb)
    Cp = 1/(2*np.pi*f0*xpcomb)

    print('\nLs1 = ', Ls1)
    print('Ls2 = ', Ls2)
    print('Cp = ', Cp)

else:
    Cs1 = 1/(2*np.pi*f0*xs1)
    Cs2 = 1/(xs2*2*np.pi*f0)
    Lp = xpcomb/(2*np.pi*f0)

    print('\nCs1 = ', Cs1)
    print('Cs2 = ', Cs2)
    print('Lp  = ', Lp)


texts: Voltage Divider to protect P-FET gate on a Polarity Inversion Circuit

texts:
I'm trying to implement a polarity protection using the P-MOSFET technique on a 30v DC circuit

How can I protect the gate of a IRF9540N (Vgs 20v)?

I saw that I can use a voltage divider using 2 resistors or 1 resistor and 1 zenner?

Which one is the best?

How can I calculate the resistor values properly?

I saw this circuit on a Indestructables

simulate this circuit – Schematic created using CircuitLab

Thank you very much.


texts:
I need a circuit that generates rectangular waves. It shouldn't be lo-hi-lo-hi, but a random sequence of lo-hi-hi-hi-lo-lo is needed. It also has to oscillate like that, at at least 20MHz. I don't mind getting a special IC... Anything to make the job easier is fine by me.

Alright, I'm looking for really dead-easy ones and so thanks Nick for the solution. I'm also considering something possibly even smaller.

Please bare with me.

Maybe I can use an ordinary digital oscillator and then dynamically change its oscillating frequency (change in frequency also in terms of MHz), so that the level signals get dilated and compressed, giving the effect that we have randomly generated bitstreams. Though we have to set the targeted frequency (in this case, 20MHz), as the lower limit of changing the frequencies.

Something like this, an LTC6905 - http://cds.linear.com/docs/en/datasheet/6905fd.pdf (ok, not exactly cheap), and then vary the setting resistor in small increments/decrements randomly.

Of course there is a problem of randomly changing the resistance that is itself at least pseudo random. So it's back to square one. Any comments on this??


texts: Less expensive galvanometers (or alternatives)

texts:
I am working on prototyping a product and the ideal solution, from similar designs, seems to be using galvanometers, specifically mirror galvanometers.  In doing my research the majority of Galvanometers that I found were extremely expensive. I understand that more precision in any device will generally increase the price.

The theory behind galvanometers seems really simple.  So what makes them so expensive?  Is it something in the manufacturing that is inherently costly?

Are there less costly alternatives to the mirror galvanometer besides a stepper motor?  A stepper motor might need quite a bit of design time to get accuracy to where I want it.  If it is even possible.