texts: Reducing noise in elementary audio circuit

texts:
I wish to hook up the line-out from a digital piano to a surplus 4 ohm 15w speaker unit. I bought a simple Amplifier module and connected it up.

My plan was to roughly assemble the circuit and, if it worked ok, transfer to strip-board with RCA connector for Audio and a DC power socket and some sort of quick connector for speaker cable.

When I play a note on the piano I get a good level of sound from the speaker but the quality is very poor.

I guess I need to use better wiring on the input side of the amp?

Circuit:

Here's a photo:

Battery: 12V SLA 3.3Ah
Speaker: 4 Ohm 15W
Amplifier: Kemo M031N 4.5-12V, 3.5W "Music power", for 4-15 ohm speaker, 40Hz-20kHz,
Source: Line-out 1/4" TR connector (left channel, set to mono).
Pot: 10K Linear

The speaker is a rear satellite speaker unit from an old TV that had 5.1 surround-sound. The speaker enclosure contains two sounders (approx 5" and 1").

The digital piano is powered through a mains adapter (100-240 VAC 0.2A 50-60Hz) connected using a USB cable (5V 1A). It is light so assume switched mode.

Notes sound rather buzzy. There is mains hum in the background.

What steps can I take to improve the quality of the sound?


texts: Converting low volt (2.7), high amperage, (6) to a higher voltage at 90%+ efficiency

texts:
I have a solar panel set up which produces 2.7v at 6 amps and I want to increase that voltage to around 5-10 volts with reduced amperage at around a 90+% efficiency. The problem is that the voltage is too low to power a 555 timer driven boost converter and that a joule thief severely limits the output current.
I'm thinking of using a self-oscillating boost converter that will utilize an LC circuit to produce a sine wave which will then drive the boost converter, but I fear that my electronics skills and lack of an oscilloscope or any way to measure inductance will severely limit that idea.
Does anyone have any suggestions that would be simple and effective? (My current level of electronics knowledge is all theory from physics and some practical.)


texts:
I looked at the dimensions drawing of the SOIC‑14 package from texas instruments.
But I am a bit confused about the way texas instruments marked some lengths.
Why there are two values seperated by a horizontal line for one length?
Which one is the correct?


texts: How to add run-time initialization and power source stabilization delay in software for NXP LPC11E67?

texts:
I am using LPC11E67 microcontroller for the project and using MCUXpresso IDE for software development. I want to clear memory and initialize content of global variables at the startup, I am not sure if that is already covered in the cr_startup file. If not then how to add that? Also how to add delay in startup code so that program starts running after power supply stabilized.
Thanks for help!


texts: Wiring Transformers in Series With a 240V Plug From a Generator?

texts:
How should I wire 2 transformers in series (either primaries or secondaries)(not sure which I should use) using a NEMA L14-30 plug from a generator socket? I'm using 2 Microwave Oven Transformers to make a homemade stick welder. I was thinking about using a shared neutral for both.

Questions:

1)Is this a good configuration? (Generator/Shared Neutral)

2)If it is, should I wire the primaries or secondaries in series, and what advantages (or much more likely disadvantages) will be involved in either choice?

3) Can you show/describe the best (or at least a recommended) approach for doing this off of this type of plug?


texts: Scaling PWM amplitude by switching an analog DC voltage?

texts:
I'm trying to make a quick-and-dirty voltage-controlled volume control circuit, using a minimal number of components.

A microcontroller is outputting two 5V p-p, 625 kHz PWM signals: an audio waveform and a volume control voltage. Instead of building a full VCA circuit, I'm trying to do something simpler:

First, filter the volume PWM output to get a DC signal. Then use the digital (unfiltered) audio PWM signal to switch the volume signal. The result should be the audio PWM waveform, with its amplitude scaled down to the level of the volume signal. Lastly, filter it to get an analog audio output.

My question: what circuit should I use to do the switching? Tried a 74HC4066, and it kinda works, but I don't want to use an entire 4066 for just one switch. I was also thinking about an optocoupler, but I'd need one with very high bandwidth. How about a MOSFET like the 2N7000? I don't know much about MOSFET switching circuits though.

Any other ideas? A software implementation is my last resort, I want to avoid degrading the audio signal as much as possible.


texts:
I am seeing an unexpected side effect, and could use some pointers. I am working on a project which uses five TCS34725 color sensors. These sensors are being interfaced via I2C on a TI F28069M DSP Launchpad. The first problem I faced was that the color sensors all have the same address (and they cannot be rewritten). I was given a DG407 dual 8 channel analog mux to attempt a solution. At first I thought this solution was rather straightforward -- I'd use the mux for SDA and SCL. What I am seeing however is that the first mux address I set, works perfectly fine, I can read the color sensor ID and read/write config registers etc. The next mux address I set, causes the I2C bus to register as busy on the TI DSP.

My theory is that the mux transitions temporarily to high impedance between address changes, and that high impedance state is somehow being seen as a start condition by the DSP, therefore forever busying the bus until a reset.

According to the DSP's technical reference manual, I can set I2CMDR.IRS bit to 1, which effectively disables the peripheral, resets its status bits, and retains its configuration. I tried setting this bit, delaying 10uS, switching the mux, waiting 10uS, then clearing the bit, but I still see the issue.

Any ideas as to how I can chase down this problem?

Circuit diagram below.

simulate this circuit – Schematic created using CircuitLab


texts: Which case count as leading PF in Salient plot generator?

texts:
In the figure above we can see the location of two armature currents. In case 1, \$I_{a1}\$ is leading \$Vt\$ (terminal voltage) but lagging \$E_f\$ (excitation voltage). In case 2, it is obvious that \$I_{a2}\$ is leading both voltages.

I have seen many cases that have stated that case 2 is a leading pf. However, in a few references, I have seen people use case 1 as a leading pf. I would like to ask to make sure about which case is right when the machine is in generator mode with leading PF.

It is obvious the internal PF angle will have a different value in each case.


texts: Why is this Diode and Capacitor present on the VBUS discharge path?

texts:
I'm struggling to understand the function of this Diode, Capacitor and 470ohm Resistor on the discharge path for VBUS. The datasheet only says to ensure discharge current is less than 50mA, hence the 1K resistor. Can someone explain please.

Here is the full schematic

And the datasheet can be found
HERE.


texts: Is it possible to power a monitor with 5 V if the power supply specification is DC 9-36 V?

texts: I'm attempting to turn an NES clone into a handheld device, therefore adding a power supply and a monitor as well as a few other minor things. After some research, I pulled all the parts together I needed and realized that the monitor I got says it takes DC 9-36 V but my power supply is 5 V as that's what the console requires. I've done some research and found a few answers saying that the monitor might be able to run at a lower voltage but nothing concrete. I'd rather not break/connect anything if I'm not sure that it can work. One suggestion I've seen is using a 12 V power supply instead and then using a step down regulator for the rest of the console to get the necessary 5 V. Although that may be my answer I was hoping I could find a way to make this work with what I already have if possible. If it wasn't already obvious, I'm not only new to here, but also electrical work like this. It's a new hobby but I'm trying my best to learn my way through, any advice would be highly appreciated!


texts: How to transition multiple down counters using 74ls193 in a 'one at a time' sequence

texts:
I've been messing with this circuit but i'm struggling to find the solution i'm looking for?

Trying to create a sequence of down counter, so when the first completes the next starts and so on until the last then repeats. I thought it would just be a case of adding a flip-flop between each counter to help with the transition to the next counter. Instead the first counter and the third start and then when second switches over it doesn't stop?

Also tried using a 4017 divider/counter instead of the flip-flops, this would give the correct sequence, however i'm unsure how to connect the CP0 pin, since it would require all the RCO pins connected together??. Tried adding a four input OR gate but that didn't work? Not sure if that's an issue with Multisim?

Any help on this would be really appreciated.
Thanks.


texts: Possibly connect second charger to Lithium Iron Phosphate battery

texts:
I have a sump pump system that includes a 12 volt backup sump pump. It is managed by this Pump Spy system: https://www.amazon.com/PumpSpy-PS2000-Battery-Internet-Monitoring/dp/B07N8FY4L9
I have a 200Ah AGM battery. I'm tired of the AGM batteries losing total capacity so quickly. I'm looking at a 200Ah Lithium Iron Phosphate battery. I understand LiFePO4 needs a different charger that supplies 14+ volts. The Pump Spy brains charges the battery (12 volt) and monitors the health. I'd like to keep the Pump Spy monitoring functions working, but charge the LiFePO4 battery to full capacity. I asked, and there is no supported way to disable the Pump Spy charging function. Is there a good way to connect a proper charger without interfering or conflicting with the built in Pump Spy charger? I'd be fine preventing the PumpSpy charger as long as it is still able to monitor. Thanks.


texts:
I have just learnt how PN junction work, depletion region etc.
And finally I got what actually multimeter's diode test is measuring.

If there is potential difference between P and N material, and multimeter is showing it, will multimeter show 1.5v voltage drop if I put AA battery instead of a diode?

PS: I'd like to experiment, but I cannot loose my multimeter.


texts: Convert 0-5DC to low current high voltage AC signal

texts:
I'm experimenting with electro vibrations. This principle is about simulating textures using low current electricity on an insulated conductive surface (see Wikipedia: http://en.wikipedia.org/wiki/Electrovibration).

I've started to use some EL-wire IC's to create a AC signal from a DC powersupply since i need a high voltage AC signal (max 115 vpp). With the IC's i got some results but i'd like to have more freedom in the output (the ic gives a fixed voltage and frequency).

Actually what i'm looking for is a high voltage, low current signal generator circuit. 80-115 Vpp (AC) and 80-400 HZ. I'd like to control it with arduino. So ideally it would be a way to amplify and convert the 0-5 DC signal to a 80-115Vpp AC signal.

What's the best way to do this?

Cheers,


texts: How to re-generate a previously saved SIRC protocol waveform?

texts:
I am trying to replicate the remote control for my Sony home theater system. I started with anaylzing the demodulated signal of power on button using a TSOP1738 IR demodulator. It looks like this:

You can see the signal (along with the decoded command).
Next I replicated the signal using the Arduino (and as per SIRC protocol, chose 1/4 duty @ 38Khz). Below is the signal of a complete one to show the code sent and a zoomed one to show the 38Khz 25% duty burst within the signal.

Now to drive an IR LED using this signal, I fed this into a 2N2222 NPN BJT transistor's base with its collector connected to +5V and base to IR LED -> Series Resistance -> GND. And to test the signal I fed this "generated" signal through the TSOP1738 again and probed the output.

The signal I get looks like an IR signal except for the 1's (when TSOP1738 goes LOW) instead of being LOW for a duration, as in the first image. I see a lot of toggling going on:

The "generated" signal, of course, does not work. Any idea what's going in here ?


texts: How to conclude region of operation for a series combination of MOSFET

texts: I understand that M1 is on and for M2 to be on the intermediate voltage(drain on M1 and source of M2) should be less than 1.5V. Also if M2 is ON then M2 is in saturation since Vds>(Vgs-Vt) for M2. Now coming down to M1 and applying the same condition I understand that if the intermediate voltage is less than 1V then M1 is in linear region and if the intermediate voltage is between 1V and 1.5 V then M1 is in saturation.However, I'm stuck at this point. How do I conclude the region of operation for both the Mosfets? Is this problem to be solved using intuition assuming regions of operation and then the condition that same current flows,if then please explain.


texts: Why is SLEW RATE in nMOS amplifiers worst when the output is going from LOW to HIGH?

texts: And, of course, why in pMOS amps the SR is worst in the other case (output going from HIGH to LOW).


texts:
I would like to open and close a shutter (acousto-optic modulator) really fast. Really fast in this case means 2 MHz. However, the shutter should not be modulated periodically, e.g. with constant frequency. The shutter shall open, when an analog input signal Uin is above a certain threshold U1 and close again above another threshold U2.

Furthermore, the voltages U1 and U2 are provided digitally as 16 bit numbers. Both are not static, however. They will change in the worst case with a frequency of 1 MHz.

An added bonus would be, if the actual level of Uout does not have to be binary but could also be modulated with 1 MHz.

I tried to sketch a schematic for this:

simulate this circuit – Schematic created using CircuitLab

So obviously I thought to solve this problem using either a window-comparator or a FPGA. The latter one would give me more flexibility on future changes. Looking a bit on the National Instruments website, I did not find a fast enough FPGA (actually the DA/AD outputs/inputs are not fast enough).

The problem itself seems very basic to me. Am I overlooking an obvious implementation?

Thanks


texts:
From my understanding, to use karnaugh maps to simplify an expression, you would have an SOP expression that does not have to be canonical and then group the 1s in the table.

So that got me wondering. Does this mean I can then have a POS expression and then group the 0s instead of the 1s?


texts: efficiency problems connecting multiple solar panels

texts:
I cannot understand why doubling the amount of solar panels gives only a few percent increase in total amount of power.

Here are the test results of a single 10-cell panel:
Single solar panel efficiency tests http://imageshack.us/a/img43/6561/nlgd.png

Here are the test results of two panels connected in series:

And here are the test results of two panels connected in parallel:

My expectations were:

to see the voltage of 9.3V under load in serial connection, yet I've
got 4.3
to see the current of 5.2A under load in parallel connection, yet I've got 2.6
to see the wattage doubled in both serial and parallel connection, yet I've got 10%,20%

Can someone explain the reasons behind such a weirdness?

The tests we repeated with the two different multimeters swapped in places to measure voltage and amperage.

The tests were conducted 1.5 - 1.0 hour before the noon, on a clear sky conditions, so there's a bias of few percent in measurements due to increase solar elevation angle.


texts: Passive audio phase shifter (180°) - can it be done?

texts:
I understand that most analog hardware phase shifting circuits seem to use OpAmps to get their job done.
I am trying to build a tiny, non-powered in-line adapter for Mp3-players and such to quickly sum up multiple signals - which can easily be accomplished without external power using just resistor signal mixing.
However, to make this adapter really nifty and interesting, a phase shifting switch would really make the icing on the cake.
Now, this leads me to the question in the title of this thread:
a passive audio phase shifter/inverter - can this be done?

Any input/idea/feedback/suggestion is greatly appreciated!


texts: Differential amplifier - what is the differences between CMRR and CMR?

texts:
I know that CMRR is Common-Mode Rejection Ratio, but what is CMR?

$$CMRR = \dfrac{A_{dm}}{A_{CM}}$$

I didn't find any mention of it in Sedra & Smith bible.

Does anyone know what CMR is?


texts: Inside a CPU, what happens in a single clock cycle?

texts: In grossly simplified terms, a processor calculates 1 instruction in a single clock cycle.  But what does that even mean?  If a processor is a bunch of transistors, is 1 clock cycle simply 1 state change (or the potential for a state change) for all those millions of transistors?  Is 1 clock cycle how often the state of every transistor get evaluated?  What exactly is happening, electrically, in 1 clock cycle?


texts: ATMEGA resets c program when starting and stopping reading data from a PC

texts:
I'm sending data from an ATMEGA 328 to a PC and I have an incrementing line counter for each block of data I send. (4 integers)
When I start and stop the receiving program on the PC, it resets the count in the ATMEGA. Why?
What I have noticed is that the transmit light continuously flicks when sending data (PC receiving data or not) and once I start my receiving program on the PC, it stops momentary like it is being reset and then carries on sending however my line counter is now reset to 0.
It looks like the PC is sending a request to send or something like that and this is resetting the program. Any suggestions?
Thanks Wallace.


texts:
The controls of my alarm clock seems to not respond and I thought that pushbutton springs may have stopped working. Hence I crack oppened it in order to replace them with some spare pushbuttons I had.
Once I oppened them I found out that the design of the pushbuttons are the following:

So How I can replace them? These are not in the familiar design of the push button:

What I see are a metal plate covered by tape and I understand that there's some sort of spring underneath. Once I pull the tape the metalic cap peels off. Do you have any idea how I can fix this?


texts: Fraction resistance and negative resistance

texts: Is it possible that the resistance will be fraction or negative number and what's happened?


texts: Detecting ball moving between IR pair and handling ambient light changes

texts:
I plan to use the SEN-00241 IR Emitter and Detector pair to detect a ping pong ball moving fast between them.

I understand I could watch for voltage changes to detect this passing object, however how do people generally deal with ambient light changes? From my research it seems that the voltage will change with ambient light, and although I can take steps to create funnel vision between the 2 I'm sure it may still be an issue.

Would you take constant readings and find averages over 10 consecutive readings to allow for changes in ambient light and set a new baseline reading? Then if the voltage changes dramatically and only for a few reads then I know that was the ball and not to change the baseline reading.


texts: What's wrong with an opamp as a voltage regulator?

texts:
I was watching a video about power supply design and it was mentioned that an opamp being used as a regulator like this:

simulate this circuit – Schematic created using CircuitLab

in practice, isn't an inherently stable configuration - "it's very tricky to get it stable over a range of output loads and capacitances"

Why is this? What happens in this circuit to make it unstable?


texts: In Directed-mapped cache, a problem in exercise!

texts:
5.2 Caches are important to providing a high-performance memory hierarchy
  to processors. Below is a list of 32-bit memory address references, given as word
  addresses.

  3, 180, 43, 2, 191, 88, 190, 14, 181, 44, 186, 253

  5.2.1 For each of these references, identify the binary address, the tag,
  and the index given a direct-mapped cache with 16 one-word blocks. Also list if each
  reference is a hit or a miss, assuming the cache is initially empty.

  5.2.2 For each of these references, identify the binary address, the tag,
  and the index given a direct-mapped cache with two-word blocks and a total size of 8
  blocks. Also list if each reference is a hit or a miss, assuming the cache is initially empty.

It is easy to answer this question, just calculate the tag, index, and offset, then we  are done. For examples, we are given in 5.2.1 a directed-mapped cache with 16 one-word blocks, therefore we have index n=4, and tag is 32 - (4+0+2)=26, but in the solution sheet here (see the figure for a solution instead of taken several minutes to see the answer in the link), tag: 32 - 4 = 28! how to deal with this problem? It is really confusing! in the book, it says: tag = 32 - (n + m +2), where n is the index and m is the number of word in one block.

Could someone explains to me whether the solution sheet made a mistake or me!

Here is the solution in figure:

Here is a figure taken from the book in the page the explains how to find the tag:

Thanks in advance!


texts: Darlington pair open circuit output behaviour

texts:
I have a GPIO driving a logic inverter which is then connected to the input of an NPN Darlington pair IC (ULN2803). The MCU and inverter are powered by the same 3v3 rail.

I am seeing behaviour which I did not expect at the output of the Darlington pair, even when the output is not connected to anything. I have observed this behaviour in LTSpice (when I approximately modelled the ULN2803 internals) and on my physical circuit (by probing with a CRO). The simulation is shown below.

When the input to the Darlington pair is logic low, the output is (as expected) basically 0V. However, when the input is logic high, the floating output of the Darlington pair appears to read ~630mV.

I'm struggling to understand this observation - any insights would be appreciated (even if it means pointing out some aspect of my stupidity :-) ) Thanks!

Green Trace = output of V1

Blue Trace = Collector of Q1 & Q2


texts: VHDL - big difference in schematics between integer with and without range

texts:
I just discovered something that I would like some expert to comment on.

CODE EXAMPLE A:

entity PipelinePoc is
    Port ( clk : in STD_LOGIC;
           led : out std_logic_vector(0 downto 0)
           );
end PipelinePoc;

architecture Behavioral of PipelinePoc is

begin
process(clk) is
variable x : integer;
variable y : integer;
begin

    if rising_edge(clk) then
        if(x = 299)
        then
            x := 0;
            if(y >= 500)
            then
                y := 0;
            else
                y := y + 1;
            end if;
        else
            x := x + 1;
        end if;
        if((x+y) / 49 > 200)
        then
            led(0) <= '1';
        else
            led(0) <= '0';
        end if;

    end if;
    end process;
    end Behavioral;

CODE EXAMPLE B (Only difference is limited range on the integers):

    entity PipelinePoc is
        Port ( clk : in STD_LOGIC;
               led : out std_logic_vector(0 downto 0)
               );
    end PipelinePoc;

    architecture Behavioral of PipelinePoc is

    begin
    process(clk) is
    variable x : integer range 0 to 1280 := 0;
    variable y : integer range 0 to 960 := 0;
    begin

    if rising_edge(clk) then
        if(x = 299)
        then
            x := 0;
            if(y >= 500)
            then
                y := 0;
            else
                y := y + 1;
            end if;
        else
            x := x + 1;
        end if;
        if((x+y) / 49 > 200)
        then
            led(0) <= '1';
        else
            led(0) <= '0';
        end if;

    end if;
    end process;
    end Behavioral;

SCHEMATICS FOR EXAMPLE A:

SCHEMATICS FOR EXAMPLE B:

I would expect some difference between the example a with no range, assuming 32 bit may be representing the x and y values while the range 0 to 1280 can be represented with only 11 bit.

But the difference between the corresponding schematics is so huge, that either:
- I may be missing some bug in my example be, allowing for the compiler to greatly simplify the logic
- Or the FPGA has some small units that can do operations of a certain size (I am using a Basys3 board).

Can anyone explain why I end up with these very different schematics with only adding integer ranges?

Thanks


texts: I have been researching the best circuit design for LED VU meters and a popular choice is the LM3914/5/6 series of IC's. You can find may videos of these chips used in videos on YouTube, as an example. Many of these designs from other people show a very fast LED response to audio, however the data sheet provided (pg. 21) says there is the option for "slow"- Fade bar or dot display (doubles resolution). I am having trouble finding how I could 'slow' the response, as mentioned in the data sheet using these IC's. Hopefully someone can clarify.


texts: Variable Frequency Drive with AC motor, 30kW

texts:
I have a VFD that controls an AC motor which compresses air. It is an 30kW motor. I have set the parameters required to drive the motor and it runs the motor but not properly.
During the test the lamps in the room start to vibrate,plus we measure voltage between phase-neutral it drops by 10V(not running motor 238V when running 228V). The VFD outputs 80 amps ,however it is 3-4 times of the current required by the motor. During the motor startup sequence 0hz - 50hz we can observe huge mechanical vibration, the motor was shaking so hard, it is not normal vibration.

The VFD's type:3G3RX

I don't know what to do at this point.


texts: Estimating a sinc period and width of a rectangular pulse

texts:
For a rectangular pulse that has as a fourier transform of a sinc function like so:

How can I estimate its sinc period in the frequency domain and compute the width of the rectangular pulse in the point-spread function?

I would like to do it in Matlab (if necessary), but I have no idea how to start off.


texts:
I have been looking at some datasheets for standard LR20 batteries and found that they seem to have a higher capacity when you decrease the load. Here are two graphs taken from two different datasheets that illustrate what I mean.

In the first graph it clearly states that I get more capacity when the load (Discharge) is decreased. In the second graph I can see that I get more than twice the service hours when the load is halved.

This brings me to my question. Say I have a portable stereo that uses 10 LR20 batteries in series and I can have it play for 12 hours on one set of 10 batteries. And say that I need to have it playing for 36 hours. So to solve this I will need 3 sets of 10 batteries. Will I be able to run the stereo longer if I build a battery pack that is 3x10 batteries (3 packs in parallel of 10 batteries in series)?

My thought is that by putting them in parallel I will decrease the load on each battery and therefore get more capacity out of each battery. Is there something I have missed or am I correct in assuming this will give me more battery capacity?


texts: In this answer stevenvh suggests that Flash memory uses the same floating-gate technology as EEPROM. However! Looking at a random AVR datasheet it says for EEPROM 100 000 erase/write cycles, while for Flash (on the same chip!) this is only 10 000. Whence this difference?


texts: How to modify existing circuit to additionally control it from outside by raspberry?

texts:
I found a great circuit for light home automation: circuitdb.com, but I would like it to be more than a momentary light switch bricked up in the wall.I would like to control it by raspberry or arduino.

How must this circuit be modified to send light status to raspberry and from the raspberry to the enable relay? Connections between raspberry and circuit would be made by a UTP wire. I want to add a 230V relay.


texts: Use multiple transistors in order to control multiple buttons on a remote

texts:
It is my first time using a transistor. I saw tutorials on the internet and thanks to those tutorials I manage it to work. But the tutorials only illustrate this using one button. I got one button working but when I try multiple it does not work.

My goal is that when I send a small voltage to the transistor for it to connect two cables simulating the press of a button.

I already managed to do this with a relay but my goal is to do this without a relay. I already got this working but it only works when I wire each button individually. The moment I wire all the buttons together it does not work. Can someone hemp me figure out what I am doing wrong?

The remote only has 4 buttons of interest that I am trying to remote control:

So this is partially working. For example I am able to simulate a button press like this:

From the picture all the transistors are facing in the same direction having the left leg as the collector, middle leg as the base and right as emitter. I am able to simulate a button press if I do each button individual. The moment I connect the 4 emitters to the same end of the negative battery the remote control does not work! I guess the remote control is having a problem when all the buttons are connected together even though only one side is connected. How can I solve this problem? Having 4 raspberry pi would be a solution but it makes no sense. Before I was using relays it will be very cool if I can use a transistor.


texts: How to debug serial communication with RealTerm?

texts:
I am trying to debug an LCD device with an RS232 UART interface.
I am using RealTerm on a Windows 10 machine.
The UART interface works properly. I have checked the sending device, using an oscilloscope (see below). On power-up, the device sends a hexidecimal sequence "5A A5..." to the UART interface.

However, when using RealTerm, I am not able to get this data on startup, or any other data. I am using a FTDI TTL 5V cable, as recommended.
I have checked if the TX/RX wires are mixed up. This part is OK, I think. (Connected output of LCD to yellow input wire of FTDI cable.)
Voltage between red and black wire is 5V, measured with a multimeter.
The settings in RealTerm are OK, I think. I use baudrate 115200, 8N1, which agrees with the datasheet. I have also checked the settings with the company of the LCD. On startup, I see BREAK and Error becoming red in the status panel.
I am debugging by connecting and disconnecting the power wires between the UART and the FTDI cable.
I don't know in which direction I should look further to debug this.
I haven't installed anything from FTDI (like a dll driver) yet on my computer. Maybe that's the issue?


texts: How does this phantom-power receiver actually work?

texts:
I took the power supply section from Figure 7 of this app note, also copied here, as part of a phantom-powered project, but I can't figure out what the author was thinking for R3 and R14:

simulate this circuit – Schematic created using CircuitLab

I've studied it a while and simulated it in my head, and I think I understand how it works:

R1,R2 provide the base current for Q1,Q2 to operate.  Other than that job, they're supposed to stay out of the way to avoid loading the AC signal.
R3 completes a voltage divider with R1||R2 to set the base voltage around 10.7V or so, which is stabilized by C1.
Q1,Q2 are used as emitter-followers, providing a stable 10V or so, which is stabilized/decoupled/bypassed/[your term here] by C2,C5 and used as the supply for the rest of the circuit.
As seen from the SIGnal lines, Q1,Q2 are high-impedance current sinks and therefore don't affect the differential-mode signal very much while drawing common-mode power from them.

What I can't figure out is the author's comment of:

  R14 (marked **) is described as 'S.O.T', or select on test. This
  resistor needs to be chosen so that the DC is about 10V with a normal
  phantom supply of 48V. A zener may be used instead, which will give a
  little more voltage range - depending on the opamp used.

I thought the better place for a zener would be in place of R3, not R14.  Then R14 could be removed entirely.  Is this also a high-impedance current source into the ~10V point, so as to behave like a classic zener regulator as the author suggested?


texts:
Y5V capacitors are much more temperature dependent, but is that really critical for decoupling capacitors and a product operating over a -40°C to +85°C range maximum (typical -20°C to +55°C)?

The reason I ask this is the cost is much lower, compare 0.8p with 8p per capacitor.


texts: How to generate custom digital signals without microprocessors?

texts:
I'm in IT but I'd like to try some EE without any programming...

I'd like to make a circuit that outputs some custom digital signals. For example, an SOS signal:

0 1 0 1 0 1 0 0 0 1 1 1 0 1 1 1 0 1 1 1 0 0 0 1 0 1 0 1 0
  .   .   .       _____   _____   _____       .   .   .
      S                     O                     S

I'd like to make something that would generate signals like that on repeat, without using microprocessors. (just resistors, capacitors, inductors, transistors, OpAmps, Logic Gates, etc.)

My 1st idea is to take the desired digital signals and turn them into analog.

I'm thinking of using something like a Fourier Transform:

Choose an output function
Calculate the Fourier Transform
Build a circuit to add several sine waves using results of the transform

However, build a (hopefully) small circuit using Fourier (with capacitors and Schmitt triggers to smoothen the signals) would probably be too impractical as I'll mainly be using prototype boards. (I'll make my PCB milling machine later)

My main question: What are some ways I can:

Take some digital function (just a few dozen bits in length at most)
Transform that signal into something that can be made by a simple non-programmable circuit (probably with a bunch of tiny function generators)
Design a non-programmable to generate those digital signals

Edit:

I only want to not program the circuit. Calculations like the sinusoidal waves for a Fourier would all be done by the computer.
The Fourier Transform is just my 1st idea. I'm asking for more ideas and possible routes to take.
I don't mind too much if it's hard and complicated. A challenge will be fun anyway. I just want the final circuit (on either a prototype board or a DIY milled PCB) to be small and compact enough to carry around.
The length of the whole signal (which is to be looped over and over until I switch off the power) is meant to be pretty short (a few dozen bits) but it would be great if I can find some methods that would work for long signals as well.


texts:
I want to generate VGA signal with microcontroller. But I have hard time finding solution online how to generate them in software. For e.g. Usually all online VGA signal generation just explains timing requirement for HSYNC and VSYNC along with back and front porch timing with for some fixed values like 640x480@60Hz or 1024x786@70Hz etc. But what is not given is how to calculate them and pixel clock and other things. So, how to calculate timing for VSYNC and HSYNC along with front and back porch for any random resolution at some random refresh rate for e.g. 480x240@60Hz?

Thanks for answers.
Ashutosh


texts: ISM band rules for spread-spectrum: how much do I need to spread?

texts:
I'm doing a preliminary study for a 5.8 GHz ISM band data downlink for a cube satellite.

I know that spread-spectrum is mandatory for ISM, but the FCC rules seem pretty opaque on how much I need to spread (for DSSS). The only references I could find were these snippets from 15.247 (the rest seems to refer exclusively to FHSS):

  Systems using digital modulation techniques may operate in the 902-928
  MHz, 2400-2483.5 MHz, and 5725-5850 MHz bands. The minimum 6 dB
  bandwidth shall be at least 500 kHz.

And:

  For digitally modulated systems, the power spectral density conducted
  from the intentional radiator to the antenna shall not be greater than
  8 dBm in any 3 kHz band during any time interval of continuous
  transmission. This power spectral density shall be determined in
  accordance with the provisions of paragraph (b) of this section. The
  same method of determining the conducted output power shall be used to
  determine the power spectral density.

So basically, my question is - how much do I have to spread? I'm planning on using QAM with a half-rate Turbo Code. The modulation order will be defined by the bandwidth available to me.


texts: EMI shielding for VFD and DC PSU's for CNC controller

texts:
The plan was to mount a VFD (Spindle) and (x3) 48V Power supplies on MDF and near it I want to mount 4 TB6600's for motion controlling a CNC machine. I would like to make it enclosed with some small fans for cooling.

I will be using cable glands on the AC side but I want to use aviation connectors for the penetrations on the DC Stepper and signal side, the steppers will be wired with shielded 18/4, while the limit switches will be going through a low pass filter on the control board also maybe shielded.

How to shield the DC side from the AC poison in the same controller box?


texts:
Many PIC microcontrollers such as PIC24EP512GU810 have 5V tolerant pins.

My question is how does this work. Do these devices have clamping diodes for ESD protection?

Would clamping the input voltage to [3.3V + diode forward voltage] to interface a 12V signal be a good idea.


texts: How to maintain equal discharging on batteries

texts:
I am currently building a robot that has one 12V battery for each drive motor.  The system was originally setup so that the two motor/motorcontroller/battery systems were completely separate.  After testing, I discovered that one motor is used significantly more resulting in the batteries discharging at different rates.

I would like to leave the batteries on opposite sides of the robot for weight reasons. Would it be possible to connect the batteries so they would recharge each other when one battery was low?


texts:
We are trying to program the potentiometer with I2C using Arduino Due. The SCL-SDA of AD5242 are connected on the SCL-SDA (D20-D21) of the Arduino.
We are using MATLAB to program and operate the Arduino and in-turn the programmable potentiometer.
clearvars; clc
a = arduino('COM3', 'Due', 'Libraries', 'I2C');

tmp102 = device(a,'I2CAddress','0x2E');

%%writing to AD5242 RDAC resgister
write(tmp102, 0x5C, 'uint8'); %%Slave address byte
write(tmp102, 0x00, 'uint8'); %%Instruction byte
write(tmp102, 0x00, 'uint8'); %%Data byte

%%read back RDAC register value
write(tmp102, 0x5D, 'uint8'); %%Slave address byte
out = read(tmp102, 1)

The output always returns 128 (which indicates that the pot is reset during power ON), however, we are unable to program the RDAC register. AD5242 datasheet
What are we missing?


texts: Can a board like Arduino charge a Li-ion 3.7V battery?

texts:
Some people have made Li-ion 3.7V chargers with MCP73831 and LM358n. The first link mentions that charging such a battery is sensitive to voltage and current:

Li-ion
batteries need to be charged following a carefully controlled constant
current/constant voltage (CV-CC) pattern that is unique to this cell
chemistry. Overcharging and careless handling of a Li-ion cell can cause
permanent damage, or instability and potential danger!

Is it possible to charge such a battery with a programmable circuit (Arduino, Adafruit Circuit Playground, Raspberry Pi, etc.) with a voltage divider on the 5V output, and the current charge controlled by software? If so, I would like to try it: can you add pointers for circuits, code repositories, or tutorials?


texts: Raspberry Pi controlled power on/off switching of an Ethernet connection

texts:
I want to power on/off an (Gigabit) Ethernet connection physically by using some circuit. The main idea was to use a transistor with the Raspberry Pi GPIO to switch an Ethernet cable. The schematics are in the link below.

Could this work? Or do you have any alternative ideas on the matter?
Which ground could the cable and the Transistor + RPi use?

Schematics:


texts:
I was trying to overwrite the AVR Fusebytes  for AVR16A

sudo avrdude -p atmega16 -P usb -c usbasp -U lfuse:w:0xFF:m -U hfuse:w:0x99:m

before overwriting it was l:0xe1 h:0x99
after overwriting it gives an error .

avrdude: error: program enable: target doesn't answer.
1 avrdude: initialization failed, rc=-1
Double check connections and try again, or use -F to override
this check.

How do I recover from this mistake?

Edit: When I run with -F option
avrdude: error: program enable: target doesn't answer. 1
avrdude: initialization failed, rc=-1
avrdude: AVR device initialized and ready to accept instructions
avrdude: Device signature = 0x88fbe8
avrdude: Expected signature for ATmega16 is 1E 94 03
avrdude done.  Thank you.


texts: Will linear voltage regulator step up current?

texts: I have a regulated 9 volt 300mA power supply I want to step it down to 5 volt using Linear Voltage Regulator LM7805 , I want to know how much current can I can draw at 5 volts, will it be 300mA or will it be close to 540mA, since power = voltage * current.


texts: Maximum Deliverable Power analysis for 2-bus system with Pi-model transmission line

texts:
In Chapter 2 of Voltage Stability of Electric Power Systems by Van Cutsem and Vournas, the maximum deliverable power for a fixed power factor is analyzed on a 2-bus (bus 1 is slack and bus 2 is PQ) simple system with transmission line impedance \$Z = R + jX\$, and the load modelled as an impedance \$Z_{\ell}\$. I would like to extend this analysis to a \$\Pi\$ model similar to one found in the MATPOWER manual:

The only difference I need to handle seems to be the transformer and the line-charging susceptance \$b_c\$. Any hints on how to proceed? Thanks!


texts: Can I use this switch with pull-up inputs?

texts:
I'm currently using the mbed Application Shield on an Arduino-type board. I want to use the centre button as an input for interrupts but the internal pull-up resistors are causing me problems.

While debugging, however, I couldn't understand why I would read 2.7 V on the input when the switch was not pressed when I expected to read 3.3 V regardless of whether the switch was pressed or not.

Is it possible to make this configuration work or will I have to make a separate circuit for a push-button?


texts:
I am using stm32cubemx to create an I2C project. I am using nucleo64 L476RG to connect with I2C ds2482-100, and another 1-wire DS28EC20 is connected with I2C. I am very new to this project. The first thing I need to figure out is the I2C address for the MX_I2C1_Init() function, in the line hi2c1.Init.OwnAddress1 = ?.

My questions are:

For this 3 parts system (microcontroller, I2C, 1-wire), I just want to read data from 1-wire DS28EC20. Is I2C a master or slave?
Shall I find this I2C address in the ds2482-100 datasheet? I could not find the address!


texts:
I have the output of a wheatstone bridge going into an ADS1115.

I am exciting the bridge with a 24VDC supply and the ADS1115 with 3.3VDC through a Raspberry Pi.

The issue I am having is that when I look at the output from the bridge I see around 6.5mV and as soon as I connect this to the ADS there is no output.

Nothing can been seen through my software even if I turn the gain up to the maximum.

I have tried commoning the grounds of both of my supplies and still no joy.

I was wondering if anyone else had seen this issue and could shed some light on this.


texts: How could i connect a 18650 Lion to be able to supply my embedded device while charging?

texts:
I'm designing an embedded device that should be always connected to a solar panel to regularly plot his V-I curve.I will embedd two(2) 18650 Lion battery for the autonomy. So to control and protect the batteries while charging, i found a BMS circuits, as in the picture. I'm looking for the best configuration that can allow supplying the load whith input power and charging the battery when needed.

Do you think this configuration is correct  ?

Regards.


texts:
I have the following circuit and I am trying to find VB, VE, and VC, and consequently IB & IC. The "hints" I am given are (1) to assume that vs has a DC value of 0V, (2) to use the large-signal BJT model, and (3) I can neglect CE.

From what I understand, the equivalent large-signal model for an npn BJT in the forward active region (that is assuming the setup above is in forward active region) is shown below:

Now given that the DC value of vs is 0, and applying KVL to the base-emitter loop (also assuming that VBE = 0.7V), I'm getting VB = -5V and VE = -5.7V. Now before I go further, I have a gut feeling that this is wrong, but I'm having a hard time understanding why. My thought is that since vs has 0VDC, VB should be 0 as well?
The theory behind BJT operation is a major point of weakness for me so any help is appreciated!

simulate this circuit – Schematic created using CircuitLab
 Here is the circuit I performed the KVL on based on the hints given to me and the assumption I made that the BJT is in forward active region.


texts: How does powerline ethernet work in terms of home wiring?

texts: I know that not all power sockets are in the same circuit, they are separated in the fuse box.How does powerline ethernet work across different circuits then?


texts: Electret microphone weird offset problem

texts:
Hi I am trying to amplify my output from electrec (analog microphone) with below design. When I used 1uF capacitor it has -300mV offset, so that I changed capacitor to lower value with trial-error applications. With 200pF ı was able to remove offset (it was something like -10 mV). But when I connec it to an opamp it had an offset again from the same point!

To be more clear When I don't connect it to opamp I was getting a nice output from the - leg of the capacitor. When I connect -leg of the capacitor I got an offset around -200 mV from the -leg of the capacitor. Which is really weird I think I couldn't come up with a solution. I am Using LM741


texts: Do electromagnetic shielding stickers do anything?

texts:
I recently bought some cellphone accessories, and as a free gift, the merchant gave me a "24K gold plating electromagnetic shielding sticker", whose instructions are all in Chinese, but I guess you're supposed to stick it onto your cellphone, and that's supposed to protect you from nasty E-M radiation.

My initial reaction is that this is total quackery, but let me ask those more knowledgeable in the field: is there any substance to these things?


texts: S-Domain Current Equation for Natural Response of LC Circuit

texts:
Problem Statement: In the following circuit, in the initial condition, K is closed and a steady state is reached. At t=0,
the switch is opened. What is the current through the inductor?

What I Think So Far:

$$I_L(0) = 5A$$

$$I_C(0) = 0V$$

$$KVL: sLI(s) - LI_o - \frac{I(s)}{sC} = 0$$

$$I(s)=\frac{LI_o}{sL-\frac{1}{sC}}$$

My Confusion: I run into problems when I go to do a partial fraction expansion / inverse Laplace transform on s-domain current. Am I setting this up correctly? All the examples I find in the text and online have a resistor included in the circuit, which seems to make the equations a little nicer. Any help would be appreciated.


texts:
I am building new project, which I will power up the water tank heater from my smartphone.
I have few safety though I want to ask here to get your opinion.

I am going to use AVR to run a relay, that will be connected to the main AC line.
my heater takes about 11-12Amp on 240VAC.

I want to use MOSFET n-channel, instead of NPN (2N2222) transistor, to make sure it will be able to handle the 2 relays (I need 2 relays for safety, 1 on each main AC line).
Do you think I am right? Did someone think I should use the BJT? What is the advantage of a BJT (I can see the MOSFET is better in any section, beside price and size)

I am still not sure if I am going to use Mechanical relay (T9A) or SSR.


texts:
Question 1: what is the name for this DC connector?

Question 2: Why are there 3 connections for a DC connector, and what are they for.


texts:
I need your help or advice. I need somehow to make a linear motion with stroke of 50 mm and starting force about 10N, the holding force after pull (stroke of 50mm) should be at least 20N. The holding state should be more then 12 hours continuously.

I was looking for some kind of linear solenoid (AC 230V/50hz), but at these parameters they are either big (overall size and also holding forces are needlessly big) or too expensive.

Do you have any idea or advice, how to solve this?


texts: How to reverse engineer I2C and SPI protocols?

texts:
If I have an unkown device which talk I2C or SPI how can I reverse engineer the protocol. Basically I am looking for something similar as snoop or tcpdump.

For software Mac is preferred but can also run PC under parallels.


texts: Reading data from serial lvds 12bit ADC into Kintex-7 using Xapp524 ref design - corrupted data

texts:
I'm trying to capture ADC data from TI ADS6422 (64xx) using KC705 Board from Xilinx,
I connected the board using FMC-ADC Adapter that connects the ADS6422 EVM board to KC705:

I did a little research and found out that Xapp524 ref design from Xilinx is the best ref design for serial LVDS ADC deserialization: https://www.xilinx.com/support/documentation/application_notes/xapp524-serial-lvds-adc-interface.pdf
I need the ADC to operate in:
12-bit resolution
40 MHz sample rate
2-wire interface
DDR
the Xapp524 documentation states that this is a valid combination.
I connected my pins to the constraints of the design, configured the attributes to my specific ADC needs, and run the ILA debugger.
this is how the data look:
Sampling Frequency: 40 MHz
ILA sample clock: MemClock which is 200MHz from MMCM
Sampled Data: Output data from memory used as a buffer.
Data signal: 5MHz @ -5dBm
run 1:

run 2:

run 3:

Data signal: 8MHz @ -5dBm
run 1:

run 2:

run 3:

As can be seen, the data I get is corrupted, If I'll keep running the samples, I can get even nice looking sine wave, but a sample or two after it, the data is corrupted again.
I tried to look for solutions for this problem, and I found out that because this is an old reference there is a need to do small adaptations like in the ISERDES attributes,
for example, there is 2 ISERDER for each data lane, one for a positive edge and another for a negative edge, so for my understanding, the negative edge ISERDER samples the positive edge - which is wrong, so need to change the attributes:
    DYN_CLKDIV_INV_EN   => "FALSE",             -- string
    DYN_CLK_INV_EN      => "FALSE",             -- string

to
DYN_CLKDIV_INV_EN   => "TRUE",          -- string
DYN_CLK_INV_EN      => "TRUE",          -- string

and it may work, but I tried to change it in the negative edge ISERDES of AdcData and FrameData and still the same alignment problem.
The TopLevel schematic:

Can I have an investigation leads? I'm really stuck here.
Any additional information and code provided for who ask for it,
Thanks!


texts: Log potentiometers were the mainstay for volume controls in radios .I have seen values of 5 to 10K in early solid state radios .Valve radios would use 250K to 1 meg .Crystal cartridge record players would use 1 to 3 meg.Sure these ballpark values reflect the impedance levels .Given that impedance levels can now be easily dealt with by active means there is a choice of resistance values .What   log pot    resistance values give the best reliability? 10K? 100k ? 1K ?


texts: what is the function of the trigger coupling in an oscilloscope?

texts:
Could someone please explain to me what's the functionality of the trigger coupling in an oscilloscope (the difference between ac trigger coupling and the dc trigger coupling) ?

Thank you .


texts: Measuring Rotary Encoder Signal with Multimeter

texts:
I'd like to measure the A and B signal of an encoder (https://www.amazon.co.uk/gp/product/B079H3C98M/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1) using my multimeter.

I've tried testing the A channel (CLK) by connecting one lead to the CLK output, and the other to GND. As I turn the encoder, the signal always remains at 5V. Can anyone explain why this is?

Note:

I've connected the encoder to an mbed, and although the results are not perfect, the mbed does seem to detect a change in pulse, which makes the matter even more confusing.


texts: Software needed for ATMEL ATMEGA8A-PU microcontroller in Ubuntu 18.04?

texts:
A few days ago I discovered a ATMEL ATMEGA8A-PU microcontroller and I wanted to write code on it . But I don't know what software to use in Ubuntu 18.04 for the microcontroller.

Can I use the Arduino IDE for writing code for it ?? How do I burn the code into the microcontroller ?? Do I need additional drivers for it ?? & If yes then what are those drivers ??

Please help me , I am a beginner for AVR microcontrollers.

Note :- I use Ubuntu 18.04 as OS & I am looking for the software suite for writing and burning code into my microcontroller.


texts:
I want to wirelessly communicate over low frequencies (<1kHz), and I noticed during some tests that 60Hz noise is showing up a bit at 180Hz (3rd harmonic), and also slightly at 300Hz (5th harmonic):  (Ignore the stronger signal I was transmitting)

Why are only the odd harmonics of 60Hz noise visible?

Why are the harmonics of the signal I am transmitting not visible (e.g. 3rd harmonic of 125Hz signal is 375Hz)?

More generally, what frequencies should I assume to be occupied when transmitting in this low frequency range?  I originally assumed 50/60Hz and all their harmonics (i.e. 100/120Hz, 150/180Hz, 200/240Hz, etc) should be avoided.  Do I not have to worry about even harmonics?  Are there other low frequencies commonly occupied in an in-home environment?

Edit  Thanks for the answers.  I just wanted to add that looking through a few papers on harmonic noise from appliances, it seems a foregone conclusion that only odd harmonics are significant.  Here is a diagram showing some slight even harmonics (source):


texts: Accuracy when measuring THD with LT Spice for AB Audio Amp

texts:
I've designed and built my own AB class audio amplifier circuit. I designed it to have as low THD as possible, using LT Spice to run my simulations with the .four command, so I created a bunch of circuits and picked the one with the lowest THD.
I want to know how accurate is the THD value provided by LT Spice compared to reality? (I don't have any instrument I could use to measure THD) Has anyone compared the LT Spice reading with a real measurement of distortion using proper instruments?
This is my LT Spice set up:

EDIT: This is the output stage, I'm using real MOSFET and BJTs devices (with the .lib files provided by the manufacturers), behind that there is a tone control - not relevant for this matter.
It's rated 80W over an 8 ohms speaker.

And this is what I get:
Total Harmonic Distortion: 0.000533%(0.004577%)
This is quite low, what makes me think that could be wrong.
PS: Why is LT Spice providing two values as output, is the second one between parenthesis THD+N?


texts:
I am using an LM358 as a voltage follower.
I was reading the electrical characteristics of the IC.  I don't understand why this IC has two electrical characteristics table with different input common mode voltage range and input  and how I should decide like which value I should follow.

DATASHEET:https://www.ti.com/lit/ds/symlink/lm158-n.pdf


texts: Using Three-state logic to speed up floating point multiplication

texts:
This question is idle pondering but...

Given "double-precision" is 53 bits, so takes 53^2 (or 2809) largely ordered sequential operations to perform multiplication.  Whereas the equivalent ternary is 33 "trits" and takes only 33^1.58 (or 255) Ternary multiplication operations (cf. Karatsuba algorithm)... and considering...

Binary can (in part) be sped up with a nibble "look up table".
But all Ternary ops can all be done in parallel silicon.

I find (even ignoring balance ternary parallelism potential) that ternary multiplication is 11 times faster then double precision binary multiplication.

So given that most chips actually use "Three-state logic" leads me to this question...

Question: Does any CPU/chip out there do a ternary (or sneaky binary conversion to ternary) to harvest this 10 times improvement in speed?

(BTW: I'm guessing that ternary addition is only 30% faster, if the numbers are of the same sign, and 50% faster if of different signs)


texts: quazi-isotropic broadband bowtie antenna design?

texts: I am not an expert in radio-electronics, as you will see shortly (a biochemist by training), and I am reading on ways to focus electromagnetic waves (light, actually), across a spectrum of lambdas (400-800 nm -- i.e. visible light) that would be quasi-isotropic (say, be sensitive to 1/2 or 1/4 of the solid angle and enhance the EM field 100-1000-fold, I understand an antenna cannot be truly isotropic). E.g. if on takes the classical bowtie antenna (say, 2 pairs of 2 rods) sensitive to decimetre waves, and revolves is around its axis, crating an array of rods, would this contraption be sensitive to a wider angle than a regular 'flat' bowtie? Are there tools I could use to model this?


texts:
The circuit diagram below shows two possible options for a circuit:

simulate this circuit – Schematic created using CircuitLab

The difference between both circuits is the use of the optocoupler, the first one has a common ground between the controller circuit and the mains supply. The second one however has both supplies isolated, they don't share the same ground. Instead they are indirectly connected via an optocoupler. So the question is whether or not is it really necessary to use an optocoupler?

I'm aware that option B is a lot more safer should there be a fault, but that doesn't mean that option A doesn't function correctly, right?
The reason I'm asking this is due to the amount of circuits that I've seen that isolate high voltages (such as mains) from controller circuits. I've come to the conclusion that it is just a safety precaution in the event of an accident, such as a live wire touching the controller, albeit not something that is required assuming that everything goes according to plan.

Thanks


texts: Read and Write Protection to pic18f4520?

texts: I am working on pic18f4520 using MPLAB C18 compiler. I have just completed a project (Asked questions about it earlier,see my other posts) and now I want to lock the data of the micro-controller so that no one can read or write it any more. Can anyone plz upload sample of a code on how to protect data in pic18f4520.


texts: Does changing the Voltage and the Current passing through an LED affect the result in the same way?

texts:
More directly : passing electricity that is 0.5 times the amperage of the one required will make the LED half bright, right?
Is it the same with halving its voltage requirement? Or will it not turn on at all if it doesn't half 100% of its required voltage?

And similarly : What kills an LED? Powering it at 25mA where it demands 20mA ?
Is it the same with voltage : Does powering it at 3V when it requiers 2V kill it?


texts:
An Ethernet connector seems to use a surprising choice of signal placement in its RJ45 connector. Does anyone know the reasoning behind:

The decision to make pair 2 straddle pair 1?
Why Ethernet uses Pairs 2&3 as in the left hand image?
Why Ethernet does not use E.G. Pairs 1&4 as in the right hand image?

The choice seems odd at the point it comes to lay out the PCB. If we are to make nice differential pair traces, the choice of signal placement is surprising.


texts: LC Circuit LTSpice Simulation With Time Switch

texts:
I'm sorry if this topic isn't adequate for the forum.

Does anyone know how can I make this LC circuit simulation for \$v_{c}(t)\$?

The original circuit is the one shown in the figure.

\$v_{C}(t)=\left(-\dfrac{RC\omega A}{1+(RC\omega)^{2}}\right)e^{-\frac{t}{RC}}+\dfrac{A}{\sqrt{1+(RC\omega)^{2}}}\sin({\omega t+\arctan{(RC\omega)}}) \quad , t\leq 0.24\, s\$
\$v_{C}(t)=v_{C}(t=0.24^{-})\cdot\cos{^{2}(0.24\cdot\omega_{0})}+v_{C}(t=0.24^{-})\sin{(\omega_{0}t)}\quad ,t> 0.24\, s\$

I'm trying to do the LTSpice analysis for \$t\geq 0.24\, s\$.

I found  \$v_{c}(t=0.24)=-0.143118\, V\$ with the values that were given (R = 120Ω, C = 0,1mF, L = 1mH and ω = 120π) which I used as the initial condition along with \$i_{L}(t=0.24)=0\, A\$ as it is shown here:

But I'm not getting the sinusoidal curve and I can't understand why.

Thanks in advance!


texts: How to perform correct MCU interface analysis based on VIH,VIL,IIH,IIL?

texts:
So I had interfaced a microcontroller (TI CC3200) with a keypad, using a 5V power supply with maximum current rated at 225mA.

Everything worked fine, until I replaced the 5V power supply with a new one that has a bigger maximum current rating of 2A (Same 5V). This immediately burned my chip.

To investigate why this happened, I looked at the datasheet and realized I've made a very simple mistake that I've pulled the input pins to 5V (PORTX[4]-PORTX[7]) on a 3.3v rated microcontroller. VIH and VIL are rated at 0.65 × VDD and VDD + 0.5 V, so no wonder they would burn out.

However, what I don't understand is why the chip didn't burn out on my first power supply, where it was also 5V. Is it because the power supply had a lower maximum current rating? If this is the case, on top of worrying about the VIH and VOH level, do I also need to calculate exactly how much current I need to pull the input pins with based on the value of IIH and IIL? But then if you look at the datasheet, it only shows the nominal values for IIH and IIL, not min/max.

What is the proper way of doing an interface analysis on voltage/current level?


texts: Suggestions for incorporating wireless capability to a simple sensor based project

texts:
So I have a simple application that involves reading the input over terminal via UART, and then responding accordingly, be it toggling an LED or outputting a sensor reading over I2C.  As a step up, I have been thinking about incorporating some wireless capability so the data could be sent/read over the air i.e WiFi or Bluetooth.

I personally think for this simple application, Bluetooth would be more than enough considering even the max standard the baud rate (0.256Mbps) is lesser than what bit rate you could achieve with Bluetooth (~2Mbps) but from a learning standpoint, what would be the suggested approach?

A simple use case that I thought of with BLE was to connect to a mobile app, and send/receive data over the air and UART from the module to the MCU.

For WiFi, I haven't done much research but I'd have to set up a local server first, connect the module to wifi internet, set up get/post requests and some backend processing I guess.

I have an STM32F4 MCU.


texts:
Would it be possible to multiplex video signals transmitted from multiple cameras to a MCU? For example, can 4 OV9655 cameras modules communicate with a STM32f4 MCU?

OV9655 is a CMOS image sensor and generates 10-bits parallel video data. Other than the parallel data signals the sensor transmits 3 digital signals to the MCU, pixel clock, HSYNC, VSYNC. So if 16-bits 4:1 multiplexing is possible, then this problem would be solved.

But without using a FPGA, could one achieve this?


texts:
If I place my decoupling capacitor (more or less) like shown in the figure:

I wonder: can the vias be inside the pads?  (one via inside each).

Two advantages I can see are: (1) we avoid the inductance of the trace from the capacitor pad to the via, since we eliminate that trace.  And (2) we save space on the board.

One inconvenience I can see is that it will disrupt the estimates of the amount of solder paste one has to place.  For "manual" reflow solder projects, one can certainly compensate for it.  Is this a real problem for automated soldering/assembly setups?

Are there any other reasons to avoid this?  (seems like an interesting trick with certain advantages --- the fact that I can't find a single reference to it when searching online tells me that there's probably some fundamental reason why this should not be done)


texts: What will reverse polarity in an Energizer AAA, unpowered, dead battery, circuit?

texts:
Circuit is a three-LED reading lamp. Batteries were left in for "a long time, but it worked last time I used it" according to Mom. Unknown if switch was 0 or 1. All three batteries were inserted correctly. Spring,-|+,post; in device. Tested one battery with a Sperry BT500. Black to Neg, Red to Pos. Needle jumped in the WRONG direction. Reversed leads. Needle swung to middle of "REPLACE" range on analog scale, and slowly started dropping further from the "GOOD" range of the scale.

I had searched on Startpage for "Energizer "AAA" reversed polarity", and the first link in the list was "Possible causes for AAA battery to explode".

Mine didn't explode, there were three in the circuit (correctly), no IR, no charging capability.


texts: Is it possible to physically measure the input and output impedance of a component?

texts:
Input and output impedance is an important property of complex electronic components. Is it possible to physically measure them like we measure resistance?

Is it possible to measure it for BJT based transistor amplifiers and FET based transistor amplifiers? Also, can the same be done for complex ICs like FPGAs and microprocessors and PHY chips?

Related to this is the source of impedance in complex circuits, i.e what makes up the internal and external impedance. For high speed design we like to have matched impedance to prevent high speed effects in circuit operation. Usually this means making the signal track on PCB a 50 ohm trace and possibly use termination resistors also. A signal going into the input of the IC however has to travel on the PCB track, then  through the pin on the package of the IC, through the bonding wire and then into pad and into the input buffer on the die inside the IC package. Do all these different components connected together have 50 ohm impedance each?


texts: Eagle PCB design: wire names for multiple power/gnd pins

texts:
I am working on a schematic using Eagle (free version, v7.5) for a part that has multiple VCC/VBAT pins with each pin requiring a decoupling capacitor. Currently, my schematic looks like the one below, with 3.3V tag connected to all power pins and decoupling caps attached directly to the part instance (U1).

simulate this circuit – Schematic created using CircuitLab

For better documentation and cleaner schematic, I would like to attach tags to the power pins in the part instance, and then separately connect each tag to 3.3V and corresponding decoupling cap. Something like this:

simulate this circuit

Can I insert multiple tags on a wire in Eagle? Or is there any other way I could achieve the same objective of cleaner schematic / better documentation?


texts: Can I run an Arduino Nano with 12V for this VU meter project?

texts:
Here is my project diagram:

Here they use a 5 volt LED but I have a 12V LED. That's why I want to use a 12V power supply. Can I use it?


texts: Flip a Schmitt-Trigger when current flows through a Zener diode

texts:
I am trying to design a circuit using an intermitent power source (a bicycle hub generator), which is rectified and filtered, and regulated at 6,8V.

Now I want to "detect" when the power source is ON or OFF. I made an experimental circuit (below) to validate the idea that if I put a pull-down at NODE1, when VCC rises above 6.8V, current flows through the zener, the mosfet is activated, and the LED shines.

simulate this circuit – Schematic created using CircuitLab

This seemed to work as expected, but there was some ripple, and the on/off transition was not as sharp as I need. So I thought about using a Schmitt trigger, since I have some ICs around (namely a CD4093BCN). I tried replacing the MOSFET with a double-inverter configuration using two of the IC gates, and the triggering works when I probe the trigger input with a direct wire from Vcc or Ground, but not when I connect the input to NODE1.

simulate this circuit

While measuring V at NODE1, I found out it does not rise enough to trigger (does not go above 2/3 of VCC).

My questions are:

What am I doing wrong?
How could I properly activate the Schmitt trigger when the Zener is "on"?
Would I be better served with an OpAmp Schmitt trigger instead of a Logic-Gate one?


texts: Why does bringing TL072/TL074 non-inverting input low cause output to go high?

texts:
I was building a circuit using a Texas Instruments TL074 as a comparator, when I noticed some strange behavior. I isolated the chip and tested it with a couple of potentiometers. Basically, when I put two DC voltages on the inputs of one of the op-amps, everything works as expected except for the case where the non-inverting input is taken below about 0.8 V above Vee. Then the output swings high (when I would expect it to be low). Is this behavior common for op-amps, and is it described somewhere on the data sheet?

I don't have a TL071 to test, but I tried the experiment on a TL072 and found the same behavior. I have Vcc at +5V and Vee at -5V.

I know that I'm not supposed to use op-amps as comparators, but that's what I have on hand today.


texts: Does this vacuum motor use DC or AC power?

texts:
If this is not the right SE for this, which would be a better one?

This is a listing on Aliexpress. I gave the motor DC power at 12, 24, and 32vdc and did not limit the amps. The motor gave one shake each time but otherwise did not run. The listing does not say if this is an AC or DC motor, but then I noticed there are 3 wires on this.

Current listing is here.

Thank you.

EDIT: I just realized I don't know how to tell which driver board will work with this motor though I did learn about why these need drivers.


texts: Optional feature in PCB layout of MMCX board edge connector. What's it for?

texts:
I'm designing a circuit requiring MMCX board edge connectors, specifically using the Molex 73415-0961 jack. When looking through the datasheet for suggested PCB layout, I see mention of an additional optional feature. But there's no mention of purpose for this option and I'm curious what it's designed for.

Here's a screenshot of the layout with the optional feature highlighted:


texts: As far as I know , a simple AM reciever can consist of a LC filter(connected at antenna) which amplifies the selected frequency, a demodulator( a diode for example) which rectifies the signal,an amp and a/more speakers.Now how would a simple FM reciever work?Could I just have to tune the LC circuit at a corresponding frequency to recieve FM?Or perhaps there is another way to do it?I looked on the web,but the only thing I could find were schematics that I don't understand.


texts:
I am using the IRF9321 P channel MOSFET for controlling my BLDC motor.
The MOSFET is driven via a transistor which in turn is run by a freescale controller(3.3V pin). Now, when turning it on, it works fine. But, when turning it off its a disaster with the  MOSFET taking almost 5ms to come to '0' Volts.

My circuit is shown below.

I have been through the datasheet and it says turn off delay time is 180nSecs (approx .1uSecs).

Am I missing something?


texts: Difficulty getting HF filter to work: maybe PCB layout?

texts:
I am trying to build a set of HF filters using the values from the Alex filters from HPSDR. I'm having difficulty getting the input impedance to be 50Ω as it should. Based on wide variations in measuring capacitance before and after installation, I'm wondering if my PCB layout may be to blame.

The layout is a simple one-sided affair, which I'm making a prototype in the basement:

And here's the schematic (I've added pads for up to 4 capacitors in parallel, and 1x4 headers at the ends.)

I don't have any fancy test equipment, but I do have a RixExpert antenna analyzer, and testing it against some parts in the parts bins, it's accurate as long as I pick a frequency where the impedance magnitude is around 50Ω. For this 1200pF capacitor I'm testing, I used 2.7MHz. Here's the test setup:

I pulled the inductors out of the board so I can measure across each of the capacitors. Most of them are pretty close, but for 2 of them, not so. Testing the capacitor in the pictures above (the one near "L10") soldered directly to the testing jig, I read 1205pF, just 5pF off the expected value. Soldering the same capacitor to the board as in the picture, I read 1556pF.

I've checked the board for shorts multiple times and found none. Any ideas on what explains my observations?


texts: Detect continuity in AC line during load shedding and take action via DC circuit?

texts:
I'm a noob. I have asked another question in this forum, but in component level. As the answer of that question says to use 12v and 5v relay. I reached out to local electroni6c market. But for covid-19 everything is shutdown in Bangladesh, local online electronic suppliers also stopped their services. So I need another solution. Any help would be great.

I have a 4g modem with WiFi hotspot. As my main home router doesn't support sim card, so I have to use this in some situations, but not all the time. But now I also need this to work during the load shedding. So I tried to modify it. But for not having the skills required to do all this, I couldn't.

Here is my existing setup:

Numbers in blue are the parts number:

A 12V 1A power supply.(I'll replace this with a 12V 3A power supply in few days)
A IR RGB LED controller with maximum output of 3A. But I have connected only 0.2 meter LED strip instead of 1 meter.
A 12V to 5V 2A buck converter. This circuit bord is actually from my car phone charger.
A desktop fan to keep everything cool, specially the router. Cuz it gets so hot that after working for 30 to 40 minutes without fan, it stops working.
The router.

So to make it work during the load shedding, I added a 5V 1A power powerbank circuit. Which doesn't support pass through charging. So I had to add that like this:

But it creates more problem then it solves. Because, I found out that, connecting the both input and output line in parallel of the powerbank circuit will fry the chip in the powerbank circuit. Also I was about to add the 12V fan line to the powerbank. But, I couldn't. So during the load shedding even if I separately run the router from the powerbank, it's gets hot due to no cooling fan. (I can add another fan parallel to the router, but it will spin all the time instead of only when the power bank is powering)

Even if I connect desktop fan parallel to the router, this will blow the chip in powerbank, 12V buck converter and the router as this will bypass the 12V to 5V buck converter.
As the purple colour 1 marked red line shows this in the below photo:

This is only my DC circuit problem. I also want to add a feature exactly like intelligent LED lights. Where if I cut the AC line via switch, everything should turn off, like the router, fan, LED driver. But if the switch is on but no AC power due to load shedding. The fan and router should be on and consume power from the powerbank.

Finally the question is over as I thik I have explained everything. But if you have any questions please let me know. Also any suggestion regarding improvement of the question would be appreciated.

Note: I could have just used the intelligent LED light circuit I had bought, but It is a very low quality circuit with a 4V lead acid battery. It didn't had any battery protection ic. So I searched for better LED light with li-on battery and minimum protection circuit. But in my area all electronics shops only keep this as they are cheap.


texts:
I am working with this circuit:

I am using a snubberless triac (BTA216X) and hence I am getting rid of snubber circuit (39 ohm res and 0.01 uF cap circled in red). Am I right in doing so?

Besides this, can I get rid of 330 ohm resistor circled in blue? As per my understanding, it works like a pull down resistor but I have seen some comparable circuits not using this resistor.

How critical is this component and what problems might occur if I don't use it?


texts: Solar lipo charger: circuit design and validation

texts:
I was looking for some simple and cost effective solar lipo charger for my DIY projects...I've seen the GreatScott video about solar lipo charger and i've realized one of it using the same schematic reported in the original video and easyeda project page: here
For my own needs, I've added a MCP1700T 3.3V regulator at the same point of connection of BAT+, as you can see in the attached image, the rest of circuit is the same as reported on EasyEda.

The (when i attach the external Solar Panel) circuit charges without any issue the Lipo battery,  the MPTT works fine (with 21V panel) and the 5V boost converter and the 3.3V step down regulator (MCP) works flawlessly!
...but there is a strange issue that I want to solve about...basically, when I attach only the battery (without the external Solar Panel), the 3.3V and 5V step up converter does not work unless I connect manually the GND of the circuit and the BAT- pin.
Every time i need to "start-up the board" i have to do this kind of magic trick...is this an issue? Why is the circuit acting like that?
I need to wire the Gnd of the circuit to the BAT- pin?
If I do this, the battery protection will still be operative?
I'm a little bit confused...it's my first approach to solar and lipo charging world, so, please..
Be patient!


texts: How do you show the Phase Angle on Pspice?

texts:
Here's what my circuit looks like:

I'm trying to get Pspice to show me the phase angle between Vsource and Vcapacitor. How do I achieve this?


texts: How do I choose a ferite bead for power supply filtering?

texts:
I want to put a ferite bead on positive SMPS supply rail that goes to analog part of the mixed digital/analog circuit.

Now on parametric search at Digikey I can see several parameters: Current rating, DC resistance, Impedance @ frequency. I understand current rating and dc resistance, I understand impedance, but how do I make my choice - should I look for the greatest impedance @ 100MHz with acceptable DC resistance and current ratings for my application?


texts:
Is there any way to interface a battery with voltage range 0-5V to a fpga with ADC range at 3.3V while maintaining full input voltage range i.e 0-5V mapping on 0-3.3V. I have gone through the following methods

Using Resistor divider
cannot use this as there will be always a path for the battery to discharge through them
Using a transistor as a switch or a diode clamp circuit
with these methods the range of input gets reduced
active opamp circuit
the only other thing that remains is using an active opamp circuit :- this will require the use of external components . Are there any other methods to achieve the same ?

EDIT-- Can a transistor operating in linear region be used to achieve this  ?


texts: Is there anything inherently wrong whith this fpga project?

texts:
I am a software engineer in 3d graphics by day so please bear with any obvious mistakes. I am looking for a project that I can use my software knowledge with in hardware and am thinking of creating a frame buffer and lcd to display it. I have looked around and think I can accomplish it with this fpga:

https://xess.com/prods/prod048.php

And this LCD:

http://www.sparkfun.com/products/8335

I think they have:

480 x 272 = 130560 pixels on the screen

130560 x 24-bit = 3133440 bits for the frame buffer

67108864 bits of sdram to store the frame buffer

So I think I'm ok there. And I think can run the fpga at 9 MHz (that the lcd needs) because it has "digital clock managers" to change from 12 MHz. Which I believe I will need 3133440 Hz to write the entire buffer. I think I can also get input from the usb for writing the pixel colours to the buffer.

The fpga can output either 5, 3.3 or 1.2 v for logic, but the lcd requires 2.5v however in the manual it says "0 ~ +4.5"... So could I use the fpga logic voltage directly?

I am learning as I am doing this so I am going to make a lot of mistakes, but is there anything obvious I am missing or am I good to get our my breadboard and have some fun?

Thank-you


texts: Explanation for: A monopole antenna must contain a resistor (or equivalent) and therefore must have 2 terminals?

texts:
Could someone explain why this sentence makes sense:

  A monopole antenna transfers energy from electrical domain to the electromagnetic domain, hence must contain (equivalently) a resistor, hence must have 2 or more terminals.

Why must it contain a resistor and how can you conclude that you need 2 terminals because of the resistor?

Also,

  A monopole is half of a dipole with groundplane in its symmetry plane and the drive is between antenna-feedpoint and ground(plane)

What is the symmetry plane? What does drive mean here? The transmitter?


texts: Transfer function and bode plot of an op-amp circuit

texts:
Given is a op-amp circuit which has to be solved using the nullor model to find the transfer function as shown below:

Using the nullor model of an ideal op-amp I tried to find the transfer function and plot frequency and phase response graphs. I change variables and indexes to a more common used once.

The resistor R1 has no effect as there is no current and no voltage drop.
As I don't know if this can be even built I have know idea if this is correct or if this is more a theoretical approach in order to use the nullor model. The original circuit using an op-amp with this forth input at the bottom of the op-amp symbol which only shows that the nullor model has to be used. I couldn't find any thing similar to that symbol and it seem like that only my professor uses it which doesn't really help.


texts: I'm using LPC1347 board which has two group interrupts. I'd like to write simple program which uses only one pin group interrupt (for testing only). Edge interrupts works well but when I change interrupt type to low level sensitive (or / and - it doesn't matter) I can't clear interrupt status so the program is stucked in the ISR... Writing one to CTRL register has not effect. Is a different way of clearing level group interrupts?


texts:
I want to simulate a parallel plate capacitor, I am using ANSYS HFSS for this purpose.
I made 2 PEC sheets 50mm x 50mm. The distance between the plates is 1mm (vaccum). I need to draw a rectangle to add a lumpedPort, but I don't get where to draw this. The way I have drawn does not give me a correct answer. Also what frequency do I simulate this at? I want to get the impedance vs frequency plot so that I can see the spikes towards the higher frequency values.


texts: what is exactly 'gain and loss' is and how is it used?

texts: I'm kinda confused by its definition. I know that gain is a measurement and gain and loss is the calculation (??). I'm still in 12th grade. Please guide me.


texts: For any motor text say that, the rotor field follows the stator field with a certain torque angle. And in case of generator, the stator field follows the rotor field with a negative load angle. The underlying principle is that one field is attracted to another, say in motor the lagging rotor field is attracted to stator field. But why cant the motor action be driven by field repulsion rather than field attraction. For example in motor action, why cant rotor field be leading stator field and be repelled by it to cause motion? This in theory would still cause rotation.


texts: High impedance divider measurement with instrumentation amp

texts:
I'm having trouble with getting an accurate measurement with this circuit and I was hoping for some more help.

See the circuit, which I have breadboarded and am testing. I step down a voltage through a 1 to 100 voltage divider. The intent is that I can connect to different parts of the divider, and get a different step down ratio.

If I leave the divider and the unity gain buffer out of the circuit, I get excellent performance from the AD620 in-amp. I can input a voltage between -1 and 1V, and get effectively exactly the same voltage out, which is what I want. My input point would be right before the two 1k resistors.

When I introduce the divider, the voltage I get at the output is no longer accurate. I thought it was because the impedance of the divider was too high for the 1nA input bias current of the AD620, so I added the buffer that you see on the positive input. But this didn't help things! I still don't have an accurate voltage at the output. The buffer is an OPA376AID.

Is there something wrong with my approach to stepping down the input voltage with the divider? I know this worked on another design with a single ended input. Is it because the positive and negative side of the instrumentation amp are being loaded differently?

Thanks


texts: Will a loop antenna work with only two turns?

texts:
I am considering the design of a manually-wound AM loop antenna roughly following this guide. It must be tunable in three ranges - 3.33MHz, 7.85 MHz and 14.67 MHz. The highest range would simply have a varicap in parallel with the antenna, and the lower two ranges will switch in a fixed capacitor to lower the resonant frequency.

The varicap with the widest range I have found so far is the BB640, tunable between 3.05-69pF, giving a geometric mean of C=14.507 pF.

The challenge is that given that kind of capacitance and 14.67 MHz, the antenna inductance needed is quite low. Following the widespread UMR EMC Lab formula adapted for a square antenna,

$$
n = 2 \text{ turns} \\
w = 100 \text{ cm} \\
r = 4 \text{ cm} \\
L = 8\times10^{-9} \cdot n^2 w
\left(
   \sqrt 2 - 2 +
   \ln \frac
   {4 w}
   {r (\sqrt 2 + 1)}
\right) \\
L \approx 10 \text{ uH} \\
C = \frac 1 {(2\pi \cdot 14.67\text{ MHz})^2 L} \\
C \approx 11.8\text{ pF}
$$

\$r\$ is the inter-turn spacing. \$w\$, the width (and height) of the winding frame, is large because the signal is expected to be weak. \$n\$ must be small because higher turn counts impractically increase the turn spacing. The needed \$C\$ seems close enough to the geometric mean of the varicap.

For the purposes of this exercise I'm disregarding the effect of impedance matching, but eventually the single varicap would be replaced with an impedance-matching network with an apparent capacitance that would resonate with the antenna.

Questions:

Will high \$r\$ decrease performance by decreasing \$Q\$, or have other unwanted effects? Conversely, will it improve performance by decreasing inter-winding capacitance?
With tuning capacitance values so low, will it be difficult to tune this circuit once parasitics rear their ugly head?
Would it be practical or desired to decrease the effective tuning capacitance by adding a series capacitor so that \$L\$ can increase, allowing for more or closer loop turns?


texts: How to estimate battery voltage in STM without extra component

texts:
I want to make a portable data logger. So it should be a battery-powered device. One of tasks that I should do is estimating battery voltage and displaying it but because of the power problem I don't want to use voltage divider and ADC. I'm exploring circuit of a similar device in market. I'm sure that there is no voltage divider with resistors and there is no additional IC in circuit because I explore completely the circuit and I know role of each component in circuit. Microcontroller is stm32f103cBt6.

I can't understand how the device estimate battery voltage without any additional circuitry. How they do that in your opinion?

Thanks


texts:
I made a terrible mistake connecting -15VDC to the pin 18 of AD7849 instead of pin 17 and powered it up for a minute until i understood the problem.It was without the protection diode for power supply sequencing i realized later unfortunately.
I still have a bit of hope that i command it in a wrong way but not burn the chip.
I try to send data to it via Arduino Nano via SPI.
My connections are,

Vdd is actually +15V It is written wrong in the schematic!
Pin 4 of AD7849 is connected to Arduino D9 which is wrong in the schematic!
and test code is,
#include <stdint.h>
#include <Arduino.h>
#include <SPI.h>

#define AD  9

 void setVoltage16(int dacpin, uint16_t mV)
{

   SPI.beginTransaction(SPISettings(8000000, MSBFIRST, SPI_MODE0));
   digitalWrite(dacpin,LOW);
   SPI.transfer(mV);
   digitalWrite(dacpin,HIGH);
   SPI.endTransaction();

 }
 void setup() {

   pinMode(AD, OUTPUT);
   SPI.begin();

 }
 void loop() {

  setVoltage16(AD,0xFFFF);
  delay(500);
  setVoltage16(AD,0x0000);

 }

the output i get from Vout of DAC is around 0v and some high very high freq noise.
Am i on the right way or should i put this chip to trash in despair? :)


texts: I am trying read the output of ov7670 camera. To read the output image you must read the value of 8 pins in quick succession, the result of which is byte. This is pretty difficult unless microcontroller reading is fast enough. So, i was curious if there is a logic circuit designed for thus. Reads 8 pins(bits) outputs(serial/spi) a byte. Seems like this would be something needed occasionally with circuits.


texts: Problems when sharing a battery between motors and radio in an RC car

texts:
Background

I am building an RC Car that I am trying to modify to control from an Android phone.

When I  connect the remote control module as well as the car circuitry (servo & motor) to separate batteries, everything works as expected.

When I connect the two parts to the same battery, its behavior is strange.

If any of the switch in the remote is "ON" the car circuit malfunctions.

For example, if Back is pressed it will move forward, left, right, back (seems all ON)

The  car circuit malfunctions even if switch in the remote is pressed manually (removing Android Controllable Circuits , but both (Remote and Car Circuits ) connected to single battery )

The Asks

What is the reason behind this?


texts: What is the maximum current for Quick Charge 2.0, 3.0, and 4.0?

texts:
On the Qualcomm website, it says that for QC 3.0 and 4.0, the max current is "2.6A, 4.6A." Why are there 2 different values? My guess is that the lower current is for USB 2.0 and the higher is USB 3.0, or maybe USB-A vs USB-C connectors. But I don't know if either of these theories are true.
Also, for QC 2.0, the max current is listed as 3A. Does this require USB 3.0 ports or does USB 2.0 support currents that high?


texts: digital bandpass filter with parallel inputs

texts:
I have a high speed ADC connected to an FPGA. The ADC is designed such that you get 16 samples every FPGA clock cycle (that's samples, not bits). The 16 samples are from a single ADC input channel, they are just collected over time and sent as 1 big chunk (samp[0] is the earliest sample in time, samp[15] is the latest sample in time).

I need to design a band pass filter for the parallel-stream, but the digital implementations I found online always assume I have single sample per clock cycle (one sample gets pushed into the filter structure, one sample comes out of the filter structure). I cannot simply create an internal clock that is 16x faster, as this high-frequency would be too fast for the FPGA. I need to be able to filter it, but every clock cycle I send in 16-samples and output 16 filtered samples.

Can someone help me get started? What would this kind of filter be called? Is there some math-trick where I can just build 16 parallel digital filters, and then do some math-magic on the output (decimation in time filter?)


texts: What is the point of the transistor to drive the relay coil

texts: In the circuit the relay is controlled from a manual switch on a 12v bus. I can't understand why you would want to add the extra components of the transistor and diodes to the circuit? ie why are D4, R1, T1, D1 needed? Thinking about cost and component count here.


texts: Smith chart plot from simulation is opposite from experiment?

texts:
I did a simulation of an antenna and replicated the antenna in an experiment however the simulation is coming out to be roughly the opposite. From the experiment I was expecting this plot to spiral from 1420 to 650 clockwise, however it's counterclockwise.

I don't have a background in electrical engineering and I was wondering, what could flip the pattern like this? Could it be that my dielectric for the simulation isn't chosen correctly or could it be that the dimensions of the simulation are incorrect? Any help would be greatly appreciated!

EDIT: the measurement was done with a vector network analyzer connected to the antenna with a SMA connector cable on one port. It's a two port system but the other port has a 50 ohm terminator.


texts: Why would a datasheet's typical application diagram vary so much from the layout guideline on the same datasheet?

texts:
In reference to this datasheet, if you see pg2 has the typical application and pg12 has the layout guide. Why would the BST/SS/TON pins be shown unconnected compared to the typical application? They show the other pins/components wired up, but not BST/SS/TON.

Also, can I leave those three pins unconnected?

Here are the images from the mentioned screenshot for reference:


texts:
Possible Duplicate:
  How to interface a digital scale strain gauge weight sensor with a microcontroller

How to interface a digital scale strain gauge weight sensor with a microcontroller?
It is a Load Sensor SEN-1638 (similar to the SEN-10245 from Sparkfun.

It can be used to Measure up to 110 Pounds. How can I interface the above sensor with a Microcontroller Component? Can I use the Load sensor directly to measure the load by means of using a power supply and Digital Multimeter?


texts: How do I simulate this unconventional Joule Thief?

texts:
Here is a transistor-based simulation of the manually-commutated switched-capacitor SMPS circuit discussed at the bottom of this question, that helps me to think and verify the performance of this circuit.  Nonetheless, the linked simulation above does not inspire confidence in me because different transistor combinations result in wildly-ranging efficiencies (from 60% to 87%).  That is what this question is about -- What is the correct way to simulate this manually commutated switching mode power supply?

The fall time is critical for the efficiency, and a spark gap (I believe) should have a much shorter fall-time than the best bipolar transistor.  That's one aspect of what I think should be better.

Why am I trying to optimize this circuit? I like having deep understanding of things, partly because I am a teacher, and partly because I am an innovator, and both of those benefit from deep knowledge.

EDIT: Above is a better introduction to this question, and below is most of the original content of the question.  The question did not ask the question the right way, so it did not get a good response, hence the edit.

Here is the schematic for a teaching transistorless and transformerless Joule Thief that I built, but it had a short-circuiting design flaw -- holding the manual switch closed unnecessarily drained V1:  (this schematic is not runnable, but was manually executed)

Figure 1 -- First manual transistorless, transformerless Joule Thief, but short-circuiting

Here is the improved design that improves efficiency and prevents the indefinite short-circuiting of the power source, and is a switched-capacitor design.  This design has an efficiency of about 80 % so far in simulation (see the link to a bipolar circuit used for simulation).

Here is the improved manually-commutated switched-capacitor circuit represented in LTSpice (this schematic is not runnable, but was manually executed):

Figure 2 -- Transistorless and transformerless manual switching capacitor Joule Thief design

How do I improve simulation of this unconventional Joule Thief?


texts:
I am designing a driver circuit to drive 4 mosfets connected in parallel as shown in figure below (4 mosfets instead of 3).

Mosfet data sheet : http://www.infineon.com/dgdl/Infineon-IPT020N10N3-DS-v02_00-en.pdf?fileId=db3a30433e9d5d11013e9e58035b0158

I have look around the internet and there are a few criteria to look into for selecting a suitable gate driver.

Maximum average output current of the driver must be higher than calculated from the mosfet. (How do I calculate this?)
Peak gate current must be higher than calculated.
I peak=(Vdr-V_plateau)/(Rg+Rg_internal)?
Switching frequency. (assume to be 20 kHz)

QUESTION!

How do I calculate the average current?
Is the peak gate current formula above correct? If not, how should I calculate it?
Is there anything else I should look into?

Got stuck with this for quite some time, searching around google and my question is still unsolved. Please guide me through this. Thanks in advance!
Regards,
Brandon Lok Toong Yin


texts: I have been thinking of putting a 18650 Li-ion battery salvaged from an old laptop power battery to use so, I bought a few of those cheap TP4056 battery protection and charge circuit modules and I am a bit confused. I accidentally bridged the two B+ and OUT+ solder pads and now I am having a tough time removing the solder from them so I was wondering if I could directly connect the battery to the B+ and B- charging pads while the OUT+ is still connected to the B+. Will it be ok if I do so and will it affect the charging circuitry?


texts: Closed loop vs. open loop system analysis and design

texts:
I have found questions similar to mine in the forum but none were quite answered to my full satisfaction. I have two questions:

1) Why is controller design is traditionally done with the open-loop system? Is it simply that if the system responds in a stable and desirable manner in an open loop setting (e.g., step response), it will similarly do so with a changing input once the loop is closed?  What if the system's feedback is not unity, but contains some transfer function?

2) Why is it that open-loop characteristics are always analyzed for a system? I understand that stability margins/crossover frequency are properties exclusive to the open loop, but I'm talking about more descriptive concepts. For example, a closed loop bode plot describes how the system will actually respond to a given forcing function, so why not report on the closed loop phase lag and system gain?

Thank you in advance.


texts: Are ground fault currents shown as RMS or Peak in GFCIs?

texts: When a GFCI (Ground Fault Circuit Interrupter) states that it trips for example at 30 mA, is this value RMS or Peak?