texts: What are my options for supplying power to an M140 M-Type JAPAN 2+ W laser diode running off of a 5A constant current laser driver?

texts:
Background: I am building a laser that is running off of an M140 M-Type 2+ W 445 nm laser diode and an adjustable constant current driver.

Here are the specifications for both the driver and the diode as stated by the seller.

DRIVER
8 - 12V Operation
Adjustable Constant Current Output up to 5A (preset to 500mA)
Suitable for Laser Diodes up to 7W+
0 - 5V TTL/PWM Input Control
0 - 150kHz Frequency
2x 12V Fan Driver
Delayed Startup - <10 Seconds
Includes 2-pin JST-XH Crimp Connectors
Driver is ON by default when powered.

DIODE
This listing is for ONE Brand New Nichia M140 M-Type Japan 445nm 2+
Watt 5.6mm Laser Diode mounted in 12mm x 30mm Metal Housing Module
w/ G-2 Glass Lens, ~6" 22AWG Silicone Leads. The diodes are
meticulously extracted from a new laser diode array. Recommended
current is 1 to 1.6 Amps. A constant current driver must be used to
power the diode. Do not connect directly to battery or unregulated
power supply!

As of now, I have the diode in module with a lens and leads, the driver, and a heat sink which is currently on its way.

Problem:

What I need to do now is supply power to the driver. Since the driver is operational up to 12V, I am considering running 3 18650 batteries rated at 3.7V in series. This will give me a total voltage of 11.1 volts. My concern, however, is that I am unsure if the current of these batteries running in series matters. I know that the current remains the same, however, does the input current need to match the preset current on the driver (500mA)? Does the input current need to be more? If so, how much more? What is a safe amount of current that can be driven to the driver so that it does not break down. I am having trouble understanding how a constant current driver steps down the incoming current without messing up the driver. I apologize if these questions seem silly, but I am genuinely interested in this project, and I would like to power it properly and safely.

Also, how can I calculate the output power of the laser diode? If Watts is equal to voltage * amps, and the driver is sending 500mA to the diode with 11.1 volts, the output power SHOULD be 5.55 Watts. However, this doesn't sound right since the diode is rated at 2 Watts AND since the seller recommends a current between 1.0 to 1.6A. Is my calculation wrong?

Note: My major is in chemical engineering. I am very unfamiliar with electronics. I have tried my hardest to learn everything there is to know in order to successfully build a high-powered laser. If there is anything wrongly stated, please correct me.


texts: Colpitts oscillator: how to reduce amplitude thermal drift?

texts:
I have built this circuit, supply ±12V:

I am using a LM6172 amplifier.

I have found the transfer function of the filter involved:

\$H(j\omega)=\frac{1}{1 + \frac{R_3}{R_1} - L\omega^2(C_2+C_1\frac{R_3}{R_1})+j(\frac{L\omega}{R_1} - R_3C_1C_2\omega^2(L\omega-\frac{1}{C_e \omega}))}\$

Upon my calculations, the gain provided by the op amp should be of ~1 but it didn't start and I had to increase the gain to 1.8 (R2/R1). Also, without the R4 resistor the op amp is acting strangely, saturates - very high peak to peak amplitude - and oscillates at very high frequency (10 times the one of the oscillator) and heats a lot.

My problem is that the amplitude of the oscillations - at 1MHz - is very unstable as temperature varies slightly.

I just have to blow on the ciruit to change the peak-to-peak amplitude by ~2V

I also tried with thsese values:

\$R_1=1k\Omega,R_2=10k\Omega\$

But I got the same behaviour.

I don't know if the problem comes from the resistors as they change of value with little temperature variations or if it comes from the op amp directly.

Maybe I have badly chosen the values of the components?

Is there a way to reduce this amplitude thermal drift of this circuit?

UPDATE: I just figured I was using carbon film resistors which have a high temperature coefficient. I will try to replace them by metal film resistors.Results: Didn't change anything.


texts:
I'm trying to find pieces (comparators or op amp) to make a window voltage comparator. My window range is 180VDC to 230VDC. Did you ever heard of high voltage input comparators? I don't need a high voltage supply, all I want to do with my window is to drive a LED to know if the voltage is in the window of not.

Thanks a lot

Boris


texts: How to check currently which PWM device is active and in which pwmchip on BeagleBone Black?

texts:
I would like to control a servo motor using PWM. I have loaded the following .dtbo's in the slots in bone_capmgr directory as shown below:

root@beaglebone:/sys/devices/platform/bone_capemgr# cat slots
0: PF----  -1
1: PF----  -1
2: PF----  -1
3: PF----  -1
4: P-O-L-   0 Override Board Name,00A0,Override Manuf,BB-SPIDEV1
5: P-O-L-   1 Override Board Name,00A0,Override Manuf,am33xx_pwm
7: P-O-L-   2 Override Board Name,00A0,Override Manuf,bspwm_P9_22_3

For PWM, I have successfully loaded pin P9_22 configured as output with mode3 as ehrpwm0A.

Now how do I identify which pwm device is active from the four pwmchips as shown below?

root@beaglebone:/sys/class/pwm# ls
pwmchip0  pwmchip2  pwmchip4  pwmchip5  pwmchip6

I am using BeagleBone Black with the following version:

root@beaglebone:~# uname -a
Linux beaglebone 4.1.18-ti-r53 #1 SMP Thu Mar 17 19:41:05 UTC 2016 armv7l    GNU/Linux

I generated the .dts using the dts generator found HERE. Below is the .dts I used:

 /dts-v1/;
 /plugin/;

 / {
     compatible = "ti,beaglebone", "ti,beaglebone-black";

/* identification */
part-number = "BS_PWM_P9_22_0x3";

/* state the resources this cape uses */
exclusive-use =
    /* the pin header uses */
    "P9.22",
    /* the hardware IP uses */
    "ehrpwm0A";

fragment@0 {
    target = <&am33xx_pinmux>;
    __overlay__ {
        bs_pwm_P9_22_0x3: pinmux_bs_pwm_P9_22_0x3 {
            pinctrl-single,pins = <0x150 0x3>;
        };
    };
};

fragment@1 {
    target = <&ocp>;
    __overlay__ {
        bs_pwm_test_P9_22 {
            compatible  = "pwm_test";
            pwms        = <&ehrpwm0 0 500000 0>;
            pwm-names   = "PWM_P9_22";

            pinctrl-names   = "default";
            pinctrl-0   = <&bs_pwm_P9_22_0x3>;

            enabled     = <1>;
            duty        = <0>;
            status      = "okay";
        };
    };
};
};


texts:
Consider following circuit made of n resistors with r resistivity like as a mobious strip

I want to find a recurrence equation for equivalent resistor in terms of r and vs.
In other words, An equation for equivalent resistor between Req(n+1) and Req(n)

And I want to find Thevenin circuit between A and B.

I think I should use source splitting for Vs. While I don't know how!?


texts:
I currently have project trying to recover a 1980s homebuild CP/M computer.

Mostly everything is working, except the keyboard.

I have trouble identifying how it's working as there is neither an internal nor external clock applied.

Of the keyboard's many lines only  +5v, GND, a3 (STROBE) and a22-25,c22-25 (Data) are connected to the terminal.

The individual keys simply pull down two lines each. (X0-11 + Y0-7)

here is the main circuit:

and here the keys

As I read it the !OE of the 2716 must be low for the EEPROM to decode the input into a char code, but that line only traces to an unconnected pin (or inputs of other ICs)

Where does the clock come from?

Dito for the strobe line.

The circuit seems rather dead, wherever I put my probe at, even while typing.

Anyone able to help me debug this?


texts:
Suppose I want to control a portable electric stove in order to bring a big pot of water to, say, 70°C.
The first thing that came to my mind was the simplest: use one of those power plug+termocouple controllers that outputs power when the temperature sensed by the thermocouple is below A°C, and not when the temperature is aboove B>A°C.
However this system seriously overshoots, due to:

the heat capacity of the stove
the heat capacity of water

So, another idea would be to use a more intelligent controller, say, a PID. Do you think such a controller would be able mantain the target temperature without (drastically) overshooting?


texts:
I am a high school student, with a basic understanding of physics.I am trying to learn how a resistive touchscreen works.

I found this link from Texas Instrument to be the best source. But the information there is still to general.

On page 2, it explains how a touscreen detects a touch before determining the coordinates. A positive voltage is applied at Y+. Current will therefore flow from Y+, the point of high voltage, to Y-, the point of low voltage.

I am not sure:

Where the pullup resistor is in the picture.
Why they have to have significantly higher resistance than the total resistance of the touchscreen.
(referring to the previous bullet) What is meant by the "total resistance of the touchscreen". Which part of the circuit shown is the touchscreen.
What do "high" and "low" mean in the picture.
(See paragraph below)What is pin.& What is a "pin-change interrupt".

Here is the exact paragraph that explains this:


texts: electromagnet repelling permanent magnet

texts: I have an electromagnet (turned off) with an iron core in front of a permanent magnet. At this stage they attract each other. Will any current do if I want them to repel each other, or is there a formula for calculating how much current is required to set the polarity of the electromagnet?


texts:
I want to control a DC motor using a P-channel MOSFET.

I tried the motor with a 5VDC power supply. It works perfectly and speeds up in no time. I measured the current flowing through, it's around 0.15 A.

Now, I wanted to include a MOSFET. I used FQP12P20. I connected the source to +5V, the gate to GND, and the drain to the same motor. The motor still works, but it takes seconds to speed up. The current flowing through and the voltage on the motor is the same.
What could be the problem?

Thanks,
lszabi


texts: 10Gb link data transfer between FPGA && PC

texts:
I'm trying to transfer data from 10Gb ETH subsystem of FPGA to 10GB ETH card of PC. SFP, RJ45 and ETH cable comprise of this data transfer pipeline. The RTL code is ready for testing and I'm looking forward to develop a PC side application to initiate the 10G protocol to initiate the link between the FPGA and PC to acheive successful data streaming without data loss.
Can anyone help me with where do I start and what all do I need to learn and understand to solve this problem.


texts: Why is X(jw) real and even if x(t) is real and even

texts:
So I'm going through Oppenheim's (really excellent) textbook "Signals and Systems" (2nd ed.) and the associated MIT course and I'm having an issue with the properties of the Fourier transform. On page 308 (Sec 4.3, Properties of Continuous-time fourier transform), he makes the claim that if x(t) is real and even, X(jw) is real and even. These are the steps he goes through to prove it:

First, the definition of the fourier transform
$$
X(j\omega) = \int_ {-\infty}^{\infty} x(t)e^{-j\omega t} dt
$$
replacing the argument with its negative,
$$
X(-j\omega) = \int_ {-\infty}^{\infty} x(t)e^{j\omega t} dt
$$
then making the substitution $$ \tau = -t $$
he claims that
$$
X(-j\omega) = \int_ {-\infty}^{\infty} x(-\tau)e^{-j\omega \tau} d\tau
$$
and so, since we are assuming x(t) is real and even, we can replace this with

$$
X(-j\omega) = \int_ {-\infty}^{\infty} x(\tau)e^{-j\omega t} d\tau
$$
which shows that
$$
X(-j\omega) = X(j\omega)
$$
and so X(jw) is even. But he seems to have ignored the differential substitution, because when making the variable switch, since
$$
d\tau=-dt
$$
The whole term on the left would become negative, and we would find the opposite of what the author intended to prove, that for a real even x(t) X(jw) is in fact odd. Am I missing something, or is there a more rigorous proof that the author doesn't go over here?


texts: Re-design for common anode instead of common cathode

texts:
I have a very simple circuit, and I want to use a tri-color LED to indicate which 1 of 3 outputs is on. I currently have a design that works for a common cathode 4-pin LED. However, I have easier AND cheaper access to this function of LED with a common anode.

It has to be red, yellow, and green. Each output has to drive a separate 10Ω resistor, exactly as shown in the pics. Only 1 output is on at a time.

The picture on the left is common cathode, and works as intended. How can you change the picture on the right (common anode), in order to acheive the same result?


texts: Microphone closest to mimic human ear (not just few inches away)

texts:
I am currently doing a project that require sensitive microphone as in human ear for voice recognition - but not sure where to start.
From what i understand common microphone could only pickup sound few inches away, while our ear can hear many thing at a distance; quacking bird, boiling water in kitchen, meow cats, etc
Therefore i need to be able to pickup something like 30 feet distance, Omnidirectional, and relatively small in size (just like our ear do)
How can achieve that? I am fairly new in this area so any suggestion approach would be very appreciated!


texts:
I'm trying to learn how to use opamps as a comparator. uA741 was easy, but it's way too slow for an uncoming lab I'm going to do, so I switched it to LM393 instead which is rail-to-rail and very fast.

Problem: LM393 is open-collector, and I have been pulling my hair for two hours now and can't get it to work. I follow datasheet guidelines (3k pull-up), but everything connected to the output (NPN-transistor, etc) does NOT behave as there is a "1" coming on that signal.

So for now I give up open-collector, I will re-try this another day when I got more time.

What I'm trying to achieve is to drive a NPN-transistor from the LM393-output. Using 3k pull-up, I measure around 1V on the output when opamp is "high". It's supposed to be 5V, but isn't.

That's why the next step won't work either: as soon as the opamp has gone high, I'm trying to latch the output high by sending the output to another NPN which pulls in- to GND. in+ can only be 5V or 1V (never GND) so the output will always be high.

But I can't get it to work because of the open collector confusing me. I get it to work out-of-the-box with a non-open-collector (like uA741).

EDIT: See schematic. I added R10 as per the comments suggesting this. Q2 does now open, but the opamp-output is around 2V (why not 5?). If I raise R10 to 10k, opamp-output is ~5V which is expected, but I think 10k is a bit too high for the NPN-base, isn't it?

If I connect the feedback-resistor R7 to the output, the output slams down to GND no matter what the output is supposed to be. The purpose of R7 + Q3 is to latch in- to GND, so the opamp-output is permanently high until powered off.

I am probably making multiple errors here. I'm trying to learn, so please bear with me.

(Side-question: Which common opamp / comparator, without open-collector output, is a good replacement for LM393? "Common", as in "Go into RadioShack to buy")

EDIT 2: New screenshot (with irrelevant circuitry / components removed)

This shows how the circuit works without the latch. The red line is the voltage supposed to be strangled permanently after the first hi-to-low-transition, i.e. the first time opamp goes low. The green line is the opamp output: High at first (correct), then low when triggered (correct), but then it goes high again, and this is incorrect. It's supposed to stay low here on.

I've added a temporary Q3 to the circuit. In theory, this should bring the in- to ground, making in+ higher at all times. But, because the opamp starts high, it means Q3 will bring in- to ground immediately, which I do not want.

I don't know if I can use Q3 like this, but I'm just trying to show a point here, how I'm thinking.

Instead of Q3, I have also tried to add another LM393 (there's two in the IC), trying to make the feedback go through it instead of Q3, but the results are roughly the same.

How can I solve this? That is, latch the opamp in low / "off" state as soon as one first transition has been done.


texts: What type of wire should I use to connect my buttons/sensors from 3 feet away?

texts: So I've got a little prototype using some buttons and pressure sensors plugged right into the breadboard. My next step is that I actually put the buttons and sensors where I want them, but they're going to be about 3 feet away from the breadboard. Should I just use standard 22 AWG hookup wire cut to length?


texts: purpose of diode in this 555 timer application

texts:
I'm a newbie in electronics.
I need to make a 555 timer base circuit(Refer to the schematic below) such that O/P pin of 555 is held LOW by default at power on, and the I/P pin is held initially at HIGH at power on.

The main requirement of my circuit is that  until I/P pin is held LOW for say 200ms, then only the O/P pin must go HIGH and must remain HIGH as long as I/P pin is held LOW.

For all  other cases,  at I/P pin, the O/P  pin must remain held at LOW, even if LOW pulses of less than 200ms arrive at I/P pin of the circuit.

The schematic below shows a circuit that I came around while struggling to design  such a circuit reliably using 555 timer.

Now I have 6  questions regarding this circuit:

Is the purpose of diode D1 is to cause never to finish the timeout, so that O/P pin of 555 never become LOW until trigger is HIGH? or something else?
What will happen if I pull up the control pin to Vcc by say a 1k resistor and remove the capacitor C3? Is the functionality of this circuit affected in some way then? I don't remember where but I definitely saw such a circuit which have this pull-up resistor.
What will happen if I remove R1 and C1 and just simply connect discharge and threshold pins together and to R4 directly, without diode D1?
What if I keep Threshold pin left unconnected and rest all is same in this circuit? - ie anode of diode D1 is now connected only to Discharge pin, R1, C1 and not to Threshold pin! Will now the circuit work to fulfill my purpose?
Is the condition R2xC2 < R1xC1 need to be hold true here?
This is in reference to this question actually. Any suggestions for values of R2, C2, R1, C1, and R4?
On some tutorials it was specifically mention to use electrolytic capacitors for C1 and C2 here in schematic even for 1uF values (though they did not say that you must use electrolytic caps but they had drawn schematic with electrolytic caps.). Is it necessary?
Will it make any difference? Why can't we use ceramic capacitors here for C1 and C2?

Please enlighten me. Thanks.

EDITED on 2012-07-06 :  Added Question# 4,5,6

Update on 2012-07-13:

So far, I've settled on the below ckt, as till so far, it seems to follow my requirements consistently.

Please see the "EDITED on 2012-07-13:" section of my answer for more info.

Now I wanna know that how reliable this circuit is?

I mean to say that what things I need to consider so that this circuit functions reliably and accurately. Absolute accuracy is not required - a tolerance of few tens of ms will work.

For e.g I want say, minimum value of 0.4 x R2 x C2 to be 880 seconds, no less. A 1 second value should be typical.

What things need to be considered?

Whether I should use Aluminium electroyte cap.  or ceramic(eg K7R/K5R) for C2 and C3 in this ckt. ?

Whether I should choose higher capacitance for C2 and lower resistance for R2, or higher resistance for R2 and lower capacitance for C2, for 0.4 x R2 x C2 to be = 1 second typical  and  880ms minimum?

Will it make any difference if i/p is driven from totem-pole o/p stage or open collector stage?

Any other considerations or suggestions?


texts: Detrmining open loop gain of an amplifier in LT-spice using a transient simulation

texts:
Normally I would test an amplifier design in SPICE by using a method such as this:

Source: Analog tips open loop gain
I would run a .ac simulation and plot the result.
The amplifier I want to design is a chopper and so .ac sims do not work because I need to find the open loop gain at DC and my DC signal is being modulated. This restricts me to a .tran simulation.
How can I find a DC Open loop gain with a chopping amplifier in SPICE?
Right now I am using a sweeping b source as my input
V=1*sin(2 * pi * time * (1 + (2 * time))) and a transient simulation, and observing the output, it is not giving me the correct open loop gain close to DC.
This is the circuit of interest for simulation:

Real Question
My real question is how do I find the open loop DC gain for this circuit (on paper and in spice)?


texts: Using external watchdog with NXP MK64 CPU

texts:
I'm using external watchdog timer in my board to reset the MK64 in case no strobe is passed to it (I know there's also internal watchdog in the MK64).
What I don't understand is what should happen while burning the internal flash of the MK64. Since no strobe will pass to the watchdog timer, the watchdog will reset the board all the time (in loop).

Any idea how to avoid such scenario?

(I've placed pull up resistor on the PB_RST (pushbutton reset pin) but that will not help in case of burning the flash).


texts: Current step generator - ideas for completing the implementation?

texts:
I'm working on a circuit that can act as a current sink or source. The goal is to control it using some digital means so it can output the required current. Right now I am not sure about the implementation of the resistor control, perhaps someone has a suggestion? The circuit has to be very accurate and stable.

simulate this circuit – Schematic created using CircuitLab

The output is set by adjusting R2. If R1 = R2 the output will be 1mA (I1), if R1 = 2 x R2 the output will be 2mA (2 x I1). If the current is fed sourcing, this will act as a current source. If the current is fed sinking (reverse current source polarity) this will act as a current sink.

The design requires stable current source / sink.
The design requires very low input bias current op-amp - something that costs $15+ and can be obtained easily
The design calls for very accurate resistors as the relations between them sets the output. I would like to put 2 or 3 resistors with relays instead of R2 and switch between them.

What do you think about a digital potentiometer?


texts: Output Capacitor Voltage Holding time during dropout

texts:
I have a buck converter.

Vin = 12V
Vout = 5V
Iload = 0.5A

I have one dropout requirement. The input voltage will drop from 12V to 4V for 10s. Including ramp up/down time of 10ms. During this time, my 5V output should be stable.

Q: How to calculate the value for my input/output reservoir capacitors value so that I have constant 5V during dropout time. Is there any formula?


texts:
I'm having trouble figuring out the response of this circuit, specifically the voltage across the capacitor in my homework. The input from the source is a unit step function, and there are no initial conditions for the capacitor or inductor.

simulate this circuit – Schematic created using CircuitLab

I first turned it into a norton equivalent, and used node analysis to arrive at the differential equation.

$$\frac{d^2}{dt}e_1+\frac{d}{dt}e_1(\frac{R_2}{L}+\frac{1}{R_1C})+e_1(\frac{1}{LC}+\frac{R_2}{CLR_1})=\frac{d}{dt}\frac{R_2}{C}I_1+\frac{R_2}{LC}I_1$$

I know that the solution to this equation takes the form:

$$ e_1(t) = Ae^{-\alpha t}cos(\omega_dt+\phi)$$

So I think my next step is to find A and phi by the following expressions:

$$e_1(0)= ?$$

$$\frac{d}{dt}e_1(0) = ?$$

However, I am a bit unsure about how exactly to go about this. My reasoning suggests that they are both 0 - at the moment the source switches from 0v to 1v, the capacitor is a short circuit and the inductor is an open circuit. So all the current flows through the capacitor, and there is no voltage drop since the current source is shorted - so \$e_1 = 0\$ and \$e_1'=0\$. However, this means that A and phi are also both zero, so this is confusing for me. Can someone give me some help with finding A and phi?


texts: Arduino GPS shield giving incorrect altitude readings

texts:
I've been playing around with an Arduino and the SparkFun GPS shield.  For about a week, it was working well, but it has now developed an interesting error.

While my latitude, longitude, date, time and course are correct, the GPS is telling me that it is 10 000 000 m above sea level.  Previously, it was giving readings between 90 and 110 m, which would be correct for my local area.

I have tried everything I can think of to fix the problem; reinstalling the libraries and using a couple of different sketches off the internet, but they all have the same problem.

I'm not sure if the GPS module has gone bad because all other outputs are working, but this being my first GPS project I'm not 100% on how it determines altitude figures. I am willing to pay another $80 to get a new module but I'd rather not if it's not the problem.


texts: Strange current reading, LED's in series

texts:
I have a 19.4v/2.37A power adapter. I have 5 LEDs (3.2v-3.4v 20mA) connected in series. When I measure the current, the reading says 0.08A, which is total of 4 LEDs, not 5, but close enough. Strangely, when I add another LED to the chain, the reading says 0.02A instead of 0.10A. All I'm trying to do is measure how much amps all 5/6 LEDs use together.

When I adjust the units, the decimal places do not change, regardless, if I set 10A or 2mA, it always says 0.08 or 0.02, is my multi-meter broken?


texts: Altium: Save all schematic sheets in once

texts:
I have schematic document with 15 sheets, when I anotate all the sheet it will modify all the sheets sometimes. I want to be able to save all the sheets in once without saving all of them one by one.
How to do this ?


texts: Safety of powering 5V circuit of 240V main outlet using adapter

texts:
I have created a circuit using an ATTiny that will need constant power. I was thinking of using one of the 240V to 5V USB adapters that come with many phones to power this circuit.

Will I need to put a voltage regulator into my circuit or is such an adapter sufficiently stable/protected, that I can run the 5V directly into the circuit.

Also does the amp rating make a difference for this, as some output 1A and others 2A?


texts: How should I choose the resistors in a voltage divider?

texts:
I would like to measure tree signals by using a ucontroller.

the signals are between

-5V to 5V
0V to 2V
-20V to 20V

The frequency of the signals are between 1MHz and 5MHz.
The ADC range is between 0 and 3V.

I built the following simulation, where I am dividing and shifting the measured signal:

I have the following questions regarding the circuit:

How should I choose the resistors in the voltage divider and OP-AMP gain?
How can I make 'dynamic' voltage divider? I mean controlled by microcontroller? I checked the analog switches in the TI website but I am not really familiar with those switches.
How can I protect the circuit from over voltages?


texts:
I am working on an embedded systems project using an Arduino Uno, and I wanted to convert my project over to a breadboard using the ATMega328-PU IC with the bootloader.  Initially, this worked flawlessly, and I was satisfied with the results.

However, I wanted to incorporate ADC analysis into my project.  So first I made sure that the project ran smoothly off of the Arduino Uno, which it did.  When I loaded the code to the IC, however, I noticed that all of my read-in ADC values had dropped by ~20%.  I measured the voltage at the pin using an o-scope, and the readings from the scope were accurate to what I expected, so I was not inclined to believe that it was a voltage problem.  Besides, all other features of my project appear to be working perfectly fine - it is ONLY the ADC that is spitting back undesired results.  I am even trying to feed it a DC voltage to avoid any oscillation, and it is still giving me 20% less than the applied value.  From reading online, I know it is a common problem, so to be clear, my IC and the applied source do share a common ground.

I am currently a college student, doing this project for fun, so I asked one of my professors for advice, and he suggested decoupling my breadboard VCC and GND rails using a 0.1uF capacitor.  So, I tried this, but it showed absolutely no improvement.

Later today I can make a block diagram of my project, if that would be helpful.  But in the meantime, I will briefly describe it:

As stated, the project uses the ATMega328-PU, and I have applied a 16MHz oscillator to the clock pins, which are respectively in series with 22pF capacitors that go to ground.  The Rx/Tx pins are used to communicate with an HC-05 bluetooth module (paired to a smartphone, controlled by an app).  A digital pin is assigned to an LED in series with a resistor.  A 9V battery powers the project by first passing through a 5V voltage regulator that feeds the 5V output to the VCC rails and the ground to the GND rails.  The unregulated battery supply is passed through a voltage divider to drop it by 5/9.  This divided voltage is then passed to an analog input pin on the ATMega.  Since the values were not particularly consistent, a smoothing capacitor was also placed between the analog input and ground since there is an occasional (and undesired) fluctuation in the applied analog input.  I have tried to measure with and without this capacitor, but the margin of error is the same.

Since the Arduino handles the code with this circuitry just fine, I am convinced that it is not a software problem.  Also, it is only when the programmed chip is placed on the breadboard that I get these false readings.  Therefore, I believe either I should have used a different decoupling capacitor along my rails (though 0.1uF seems to be the consensus when I look online...) or I am missing some additional external circuitry that the Arduino has but my breadboard does not (though, if it exists, I cannot find any references to any additional circuitry for this...).  I would like to state again, the other features of the project work fine.  It just seems to be the ADC that is struggling to perform correctly.

Any thoughts or suggestions would be much appreciated!


texts: Brushless 3-phase motor (BLDC) in generator mode dropping current

texts:
I am making a winch that will spool out line under tension.  I've had success using an old brushed motor.  I short the windings, so that when I unspool the line, the motor provides braking torque and line tension.  The old motor is not powerful enough, so I upgraded to a stronger, brushless motor with 5000w power rating.

Here's the problem: as I unspool the line from this motor, it builds torque until it reaches a certain value (130lb in my case), and then the current and torque suddenly drop to zero and then build up again, then drop again.

The motor has 3 phases (which are shorted for the generator mode) and a 5-pin hall sensor connector (unused here).  Here's the exact motor: http://www.aliexpress.com/item/Electric-bike-brushless-dc-hub-motor-5000w-for-electric-bicycle-5kw-ebike-hub-motor/32234157960.html

Why is it dropping the current in generator mode?  Do these motors have some kind of a built-in internal protection?  I thought that there was nothing inside but windings and magnets (and halls), as this one uses an external 100Amp controller.

Any thoughts would be appreciated.
PS.  Does this 3-phase brushless generate AC or pulse DC?


texts:
I received an 8-page schematic from someone else, and I'm trying to make sense of it all.  So I see a net coming out of a chip, and want to know where it goes.  I tried the Tools->Search command.  It doesn't seem to have a way to search for a net, but you can search for a pin.

So I tried that, and it always comes back with "1 pins(s) pin_name found!" followed by the sheet number and coordinates of its first occurrence.

But what I want is a global search, so I can find all the sheets where the net is going to in the schematic.  There doesn't seem to be an option for this in the Search dialog, and I couldn't find anything under Help.  A search on Google only pulled up global searches just for libraries.

I am using the latest version, CadSoft Eagle Professional 7.5.


texts: Brushed DC motor control MOSFET selection

texts:
I want to control a brushed DC motor of the below specification:

Motor: Permanent magnet DC brushed motor
Voltage: 180V
Current: 5 Amps
RPM: 1500

The control method is PWM switching through a microcontroller, with speed as a feedback.

This is the basic control block diagram:

How to select the MOSFET for controlling the above motor?

What should be the MOSFET continuous current Id, Drain-Source VDS, RDS, VGS (for the given motor rating)?

Switching Frequency 10 KHz

MOSFET Package: Through hole will be apt

Based on the ratings I have designed the circuit below is the same with component specification:

The control circuit is working fine, except I have encountered once MOSFET failure, that is why I was wondering if I have to increase the MOSFET rating.

Mosfet Details:

IRFP460
VDS = 500V
RDS = 0.27ohm
Id = 20 A (at 25°C)

And I have put considerable heat sink to dissipate heat from the MOSFET.

So I thought if there is a standard way of choosing the MOSFET, then I could compare with the one I have already chosen.


texts:
I have a large number of components that need to be placed at specific positions. The Altium docs, and this post seem to suggest you can do this by going to File->Assembly Outputs->Generate Pick and Place, editing the coordinates in the generated file, and then going to Tools->Component Placement->Place From File and loading the edited file.

The pick and place file generator lets you generate it in two formats - CSV, and text. Text is just the CSV file laid out as an ASCII table.

I generated both files, and edited a few of the coordinates. The Place From File command expects a .pik file. I tried renaming both files to .pik and loading them.

The CSV file doesn't give any errors, but also doesn't move any of the components.

The text file gives an exception when parsing it (and actually deleted one of the components).

Does anyone have any idea how this is supposed to work?


texts:
I am investigating some circuit we have with a USB HUB component: USB2504A-JT (please search google, can't attach link) that using this oscillator- CPPC7LTA7BP-24.0000TS

I measured on the oscillator those voltages:
VDD (pin 4)- 3.34V, OE (pin 1 -NC)- 2.95V, Output (pin 3)- 24Mhz moving from 0.8V to 2.4V compared to GND of the component (pin 2).

This output doesn't fit the datasheet, which mentioned:
max VOL=0.4V
min VHL= 3.3-0.4=2.9V
Please see attached picture of the osccilator connections and the relevant part from the DS.

(C323 PN is NFM21PC105B1A3)

Any idea why it happens? Do you think that the USB hub component has something to do with those voltage levels? (the CLKIN_EN pin is pulled high as it supposed to be)

Maybe I missed something and the OE of the osccilator must be pulled up/down?

Please tell me if you can think on any explanation.


texts: Setting the PCA9685 PWM module prescaler

texts:
I'm trying to make a 60Hz frequency, this is How I do it :

    freq_hz = 60
    pca9685_frequency = 25000000.0 #pca9685 clock : 25Mhz
    pca9685_resolution = 4096.0 #12 bits resolution
    freq_in_step = pca9685_resolution*float(freq_hz)
    prescaleval = pca9685_frequency/freq_in_step
    print "prescaler value = {}".format(prescaleval)
    prescale = int(math.floor(prescaleval + 0.5))
    print "however only round values can be set so we wil use {} as a prescaler value".format(prescale)
    print "which makes a frequency of {}".format(pca9685_frequency/(prescale*pca9685_resolution))
    oldmode = self.pca9685_device.readU8(self.MODE1);
    newmode = (oldmode & 0x7F) | 0x10    # sleep
    self.pca9685_device.write8(self.MODE1, newmode)  # go to sleep
    self.pca9685_device.write8(self.PRESCALE, prescale)
    self.pca9685_device.write8(self.MODE1, oldmode)
    time.sleep(0.005)
    self.pca9685_device.write8(self.MODE1, oldmode | 0x80)

On the screen the result is :

prescaler value = 101.725260417

however only round values can be set so we will use 102 as a prescaler value    which makes a frequency of 59.8383884804

But with my oscilloscope, a Tektronix TDS210 I get a 64.1Hz frequency, not 59.84Hz

Did I make a mistake somewhere?

https://www.nxp.com/docs/en/data-sheet/PCA9685.pdf


texts: How does a low power device make a direct uplink to iridium satellite?

texts:
I was always fascinated by this idea. You are literally able to communicate or open a web browser from anywhere in the world. I am OK with the low power device able to receive data from satellites, but directly transmit the signal.. How is it doing it? It doesn't even have a parabolic antenna.

Take a look:


texts: I'm going to use a microcontroller to switch a vehicle horn on and off intermittently for maybe one second on and one off for a period of 15 seconds; the horn will pull an estimated 3 Amps. I know I can do this with either a relay or transistor, but saving space/money is a concern and I'm really just not sure which way to go.


texts: Why use PI controller for speed, instead of full PID?

texts:
I am building a two-wheels self-balancing robot and using PID controller to control its speed. The measured value is the encoder signals from the Hall sensors on the back of the DC geared motors. But in my notes, it mentions only to use PI controller, meaning that the  Derivative term is set to zero. But i can't understand why? Isn't it better to use a full PID controller to achieve the best results?

I researched online and the best explanation i could find is that for a PI controller which controls the speed, there is a need for faster response so the Derivative term can be omitted. But i am not convinced of this explanation... Maybe someone can offer a better and more complete explanation?

Also, for the angle balancing part, why is the PD controller preferred instead of PI controller and why not use full PID?


texts: Oscilloscope Auto Trigger Mode Unstable Display

texts:
I have a question because I'm learning in my own time about oscilloscopes. I set the trigger mode to automatic instead of normal which would capture a steady signal such as this.

When the trigger mode is at automatic. **`

  Why does the signal on the oscilloscope become less stable when I
  reduce the voltage from the function generator

At 1 volt I get:

At .7 volts I get

Disclosure: I'm observing an op-amp powered by 15 volts + -.... 2000 and 39000 Ohm resistor in series in an non-inverted op-amp


texts: How to drive the output pin on FPGA with small delay?

texts:
I have an FPGA board with two Virtex-2Pro FPGAs on it. I try to send data from FPGA1 to FPGA2 and then send it back from FPGA2 to FPGA1. I use a register (always block in verilog) to drive each of out pins and a GPIO pin for probing.
I observe a 7-8ns delay between the two FPGAs by probing the GPIO pin using oscilloscope and my clock speed is 24MHz.

How do I reduce this delay? Is this long delay mainly due to the wire between FPGAs or is it because of the capacitance added by the GPIO pin and the probe?


texts: Will quickly switching polarity on a peltier damage it?

texts:
I am experimenting with different ways to heat up and cool down a peltier to a specific setpoint. Heating up the peltier to a setpoint using a PID has been relatively simple, and right now I am working on optimizing the speed of cooling it down.

My design right now is to use a DPDT relay to flip the polarity, and reversing the PID. This seems to work well in theory, but I have concerns that the rapid temperature difference might hurt or break the peltier over time (like running cold water over hot glass). Does anyone know if this concern is valid? If it is, does anyone have any advise on how quickly I can cool down the peltier without damaging it?


texts:
I'm a bit confused on the sign of charges in circuits like these.

The bottom (negative) plate of C1 has -Q charge and the top plate (positive) of C2 has +Q charge. However, these two plates are at the same node, so they are the same plate essentially.

How can they have a different charge each???


texts: I want to upload program/debug ATmega644P using STlinkV2(JTAG). Is it possible? Which IDE support make debug ATmega644 using STlinkV2.


texts: LTspice simulation of AD8421 instrumentation amplifier giving incorrect output voltages

texts:
I am trying to run a simple simulation of an instrumentation amplifier (AD8421, model from here) running on a single supply, but the output does not seem to be correct. The screenshot below shows the schematic and simulation output. I am setting both the common mode voltage and in-amp reference voltage to 2.5 V, or half the supply voltage of 5 V. The in-amp gain is set to 100, and the input differential voltage steps from -5 mV to +5 mV. Therefore, I expect my output voltage to go from 2 V to 3 V, and be linear. This is not what I see.

I have checked that this is a good operating configuration for the AD8421 using the tool here. Is there an error with my simulation configuration, or something else wrong?

EDIT: Per the suggestion in the comments, upping the supply voltage to 10 V (and Vcm and Vref to 5 V) gives the correct output.


texts: Ultra-basic question: where is the voltage in this simple circuit diagram?

texts:
I'm trying to understand the role of pull-up resistors, and keep coming across this basic circuit diagram illustrating the "floating" condition.

I'm struggling to understand how the switch at S1 could make any difference whatsoever, since all I'm seeing is a Gnd at one end of the switch, and I have no idea what's happening after node #2. Is it to be assumed that there is some positive voltage at that end? That doesn't make sense given the direction of U1A's "arrow", which seems to indicate that positive voltage would be at #1. So I don't understand how this circuit is even a "thing" (obviously it needs a pull-up or pull-down resistor, but that's not the issue here).

Contrast diagram #1 with diagram #2 showing another undesirable condition where 5V is shorted to Gnd when the switch is closed. This one is more clear - Vcc is going into #1, through #2 and presumably at some point after #2 to Gnd.

So what's the deal with diagram #1?

I would have thought that for the example, a circuit like this would be more accurate - please note, I'm not suggesting my circuit is a "good" circuit - I know it suffers from the same problems solved by the pull-up resistor. I'm specifically talking about how the first diagram doesn't show a positive voltage source, where mine explicitly does. (Please forgive me, that's my first time in circuit lab. I hope I used the right symbols)

simulate this circuit – Schematic created using CircuitLab


texts:
I have some time series data, with values of active power every minute in kW. Now, I am not an electrical engineer, and I would like to average them out per hour.

My questions I guess are:

do I simply work out the mean every 60 min to work out this average value of power in kW? Is it that simple?
Also, if I compute the mean of the power varies in 60 min buckets, won't the final averaged value be in kWh?
Finally, what if I had vales in kWhh (kW per half hour)? If I took the mean of such two kWhh values (1/2hr spread), will I end up having kWh?

I am sure these are most likely daft questions, but I would like to make sure of the above before proceeding to do the analysis on the time series.


texts: What are the physical limitations of a SSD drive for long term cold storage?

texts:
As I understand it, SSD drives do not suffer mechanical failures, but are subject to a finite number of writes before failing.  I have stored mechanical drives for 5+ years and have been able to recall data.

QUESTIONS

If an SSD device is used for long term cold storage (disconnected and put in a safe for many years): What are the dominant factors that would limit how many years a SSD device remain in cold storage and return data?  I am concerned that storing data for 3-10 years risks losing data.

Is there any quantitative measurement that can be performed to determine if my cold storage SSDs are at risk of data loss?


texts: 4g router not working after powering it with a 12V battery

texts:
I needed to power a Huawei router with a 12V power supply as this will be living in my garage where there is no power available.
My current setup is a 12V car battery hooked up to a small fuse box. I'm currently powering an EZVIZ camera with this setup with no issues and I've also got a USB cable hooked to the fuse box via a buck converter - also with no issues. All fuses in the fusebox are rated at 10A.
I tested the router in the house first with the original power supply which is rated at 12V, 1A.
I then tested it with another power supply I had lying around with the same specifications and the router ran fine again. I used this spare power supply to cut the cable off so I can wire it to the mini fusebox I have connected to the car battery. I double checked the polarity of the original power supply and made sure the cable I wired in the fuse box matched before plugging in the router.
The moment I connected up the router, it started up for a second and then powered off. It now doesn't power on at all, even in the house with the original power supply.
The car battery is currently charged at 12.5V.
I opened up the router and everything looks fine, no blown resistors etc. There are 7 controllers on the board though that I cannot tell if they're fine just by appearance.
After the failure, I tested the original power supply and the output was 11.98v. Could the slight overvoltage of 12.5V from the car battery have damaged the router?
EDIT: I found that culprit. 2 micro chips under one of the covers have blown. these were directly above the barrel connector. I can only assume that the slight overvoltage was the blame!
If anyone has any other theories, please share them.
I'll be ordering a new router which will be fed via regulator to keep the voltage constant at 12v. I hope that works!


texts:
I have a ZedBoard FPGA device and I'm trying to implement an I2C interface to communicate with a camera module. I'm using Vivado 2014.2 and I have added an AXI IIC block to my design with the SCL clock frequency set to 90KHz. The physical SCL/SDA pins have a 10k pullup resistor to VCC (tried 4K7 also). For some reason, my scope shows both pins as already having some kind of invalid signal being output on them, when it should be asserted low as I have not setup any actual communication in software yet. Also notice that the speed of these signals is 24MHz! Which happens to be the speed of the onboard processor clock for some reason (no, the pins are NOT mixed up). Here is the scope output with the SCL/SDA pins:

Any idea why this is happening?


texts:
This circuit essentially takes a control input and then doubles it when presenting it to the load. I would like a circuit that controls the current to the load.
How would I modify the circuit to do current control with a sense resistor in series with the load?
So the transfer function would look something like this:
$$ V_{IN} = R_{sense}I_{load}$$

simulate this circuit – Schematic created using CircuitLab


texts: Importance of the constant voltage charging of li-ion

texts:
Hello everyone is it necessary to have the constant voltage (CV) process when charging 18650 li-ion batteries?

What happen if I usually skip the CV? Does the li-ion battery got memory?
I know the CV is needed to charge the battery full but it's really time costing. Thanks


texts: MC34063 boost converter + PWM dimmer unstable output problem

texts:
I use NE555 & MC34063 to build a LED driver with dimmer function. The crcuit of NE555 , MC34063 & LED are bridged by a IRF640N NMOSFET. NE555 is responsible for adjusting the brightness and MC34063 is responsible for light up the LED.

Under 90% duty cycle, everything is fine. However, the LED start to flicker under 10% duty cycle.

Here are plot charts of 10% & 90% duty cycle & the circuit of MC34063.
(The values in both charts are sampled by 10X probe, please multiple them by 10.)

I guess that the root cause might be the MC34063 entered DCM.

There are some triangles in 10% duty cycle snapshot. Are these evidence of DCM or just big ripple? Should I replace the inductor in MC34063 circuit with bigger one? What if I just replace the output capacitor?


texts: Converting battery voltage 12 volts to -5,5 volts at about 3 mA

texts:
My team and I are trying to power a sensor.  We need to get -5.5 volts and were not too familiar with making or acquiring negative voltages.  So it doesn't have to be a 12 volt.  Ultimately we'd like to use one battery and split out different rails from it to power two different devices.

http://www.ti.com/lit/ml/szzn001/szzn001.pdf and
http://www.eetimes.com/document.asp?doc_id=1272382
  seemed to be insightful.  There are solutions out there to acquire negative voltages.
We are looking for cheap and simple and the "Split rail" option looks like a path.

But upon looking at a few online there seems to be poor efficiency at the 3 mA load levels.

Could anyone point me in a good direction of research for a good solution to get a negative 5.5 voltage from a positive voltage at a very low amp level (3mA).

Please and thank you from Chuck a ELE student, having fun researching for senior project.


texts:
I'm designing a PCB in KiCad and I'm new to this so I have two doubts. The circuit is an audio amplifier.

1) I want to be able to put a signal generator at the input for measuring, and an audio jack for listening to real music, too. I came up with this:

The problem is that I don't know how to connect the jack - which pins go to ground and which one goes to the input. How is this done?

2) I have a similar problem but with the speaker. I want to be able to measure on a load resistance, but also I want to connect a speaker to the circuit to be used when the circuit is working.

But here, also, I don't know how to connect the speaker. How can this be done?


texts: Designing a 2S Li-ion charger with 5V 2A input

texts:
I'm interested in designing a few similar charging circuits based on the specs of the title which is getting a charging for 2 cells in series(or more) from a 5V input.

Now my question is:

Assuming I can easily boost the voltage up what should I consider in the actual charging circuit in term of max safety?(Assumming I also have a BMS installed in this pack) and having other useful example circuits for multi cell charging would also be useful.

Thanks for helping!


texts: Using small solar panels together, worth it?

texts:
I am messing around with some solar landscape lights to improve their capabilities.  I have gutted their internal workings and replaced them with small neopixel light boards and connected them all back to a controller that runs them all individually.  The system being run off an Arduino Mega connected to a Raspberry Pi and 6v/20aH SLA battery.

Each of the landscape lights has an embedded solar panel that puts out about 2.4v/45mA in bright sun.  Considering that there are about 35 lights altogether, it seemed like a good amount of power that was being wasted that could be being used in the recharge period.  I was curious if it's worth anything to connect the panels back to some kind of regulator circuit and use it to supplement the battery recharging.

I don't have a lot of design experience with solar panels or the finer points of battery recharging, so I was hoping to get a little guidance on a suggested approach.  Things like: Is it better to wire the panels in series or parallel? Or would I need some sort of regulator circuit.  Or is it even worth bothering with at all?  Anyone have any thoughts?

Jerry


texts:
In the circuit below L1 is a shunt coil rated at 115 VDC with DC resistance of 300 ohms. I need to use the same coil in an application with wide voltage 130-1000VDC from a bridge rectifier. I will apply a 30 ms pulse to the MOSFET. This means the coil won't see the high voltage for a long time. My thought is that if the pulse is that quickly the coil wouldn't get damaged. I'm thinking now how I choose the rating of the FET and what additional protection I would need to add. What do you think of adding a resistor in series with the coil to share the voltage stress and choose a 800V FET with a TVS diode to clamp some overvoltage between drain and source?

I'd appreciate your suggestions. I'll work on the math to calculate FET peak power.

Proposed schematic:

Possible MOSFET: IPN80R2K0P7ATMA1


texts: Voltage doubler - common ground for MOSFET?

texts:
I have a transformer putting out 24VAC, which I then rectify to drive some solenoids using mosfets.  Some of my solenoids need higher voltage though, so I've constructed a voltage doubler:

However, I'm not sure how a common ground will work here..  My mosfets are controlled via 5V, which has a common ground with the 24VDC, so they can be controlled fine.  But technically that same ground is in the middle of C1+C2 of the doubler, I think?  So I'm not sure I can tie the 50VDC ground (- of C2) to the same ground as the 24VDC ground... Or am I overcomplicating things and that will be fine?  I get how the doubler works, in theory, and how rectifying AC gives you a ground, in theory, but not well enough to see how they all connect together...


texts:
I've been seeing a lot of videos online of people using neodymium magnets to make a motor spin to generate electricity.

If we can generate electricity from magnets why isnt this being used more often?

I'm assuming there are limitations.
E.g heat or the amount of energy the magnets can generate?

Can someone explain why this isnt a viable source for power?

Edit:
apparently all the videos are fakes


texts: Need help with the BLDC drive inverter circuit problem

texts:
I am building a BLDC drive circuit for a 24V/60W BLDC motor. I chose SI4564DY(P+N) and FAN3278 to realize it as shown below (I only include A+ and A-, B and C are exactly the same). The FB indicated at SI4564 output was short-circuited on the PCB using solder during the test.

When I tested the circuit using 12V as VCC to drive the motor at low speed, SI4564 became hot very quickly even when the current from DC power supply showed less than 200mA. I checked the gate signals at FAN3278 input (A+ is PWM with 15% duty cycle, A- is full-on) and SI4564 gate input signals AH and AL

I noticed that there are rich ripples at SI4564 AH and AL and the minimum voltage at AH is about 2.5V rather than 0V. So my questions are

Does the circuit has any problem? If yes, would anyone please
suggest how to change it.
What could be the reason the SI4564 became so hot under such small
current?
What could have caused so many rippled on AH and AL? Could it cause
any damage to the chip?
Why are there voltage offset (~2.5V) in AH?

This is my first design and I really appreciate anyone's help. Thanks in advance.

Edited

Since I can only use two links at this moment, I have to combine several pictures into one. So, to reply to Bruce Abbott for the current issue, I added another picture, marked as Fig 2-4. Fig2-4 is the current sampled by a 0.1 ohm resistor at the lower arm of the bridge to sample motor phase current, and the peak value is 0.23V, which means motor phase current is 2.3A.


texts: Finding a small, low-actuation pushbutton

texts:
I'm looking for a small kind of pushbutton that I'm not even sure exists.

I want it to have these properties:

Width: 7mm (Will compromise for 5mm-10mm)
Travel distance of 2mm (Will compromise for 0.5mm-2.5mm)
Actuation force: 40g (Will compromise for 40g-45g)

I've emailed a bunch of suppliers but none of them have a button like that.

Is anyone aware of a button like that?

Is there anywhere where I could post a cash bounty for someone to find a button like that for me?


texts:
Im building a homebrew 8 bit computer and having some problems with video output.

I want to know if its possible to generate high resolution, say 640x480, monochrome video output, PAL or NTSC, using a microcontroller, say atmega328 running at 20MHz, a 8 bit PISO shift register and a DRAM external framebuffer, address bus can be controlled by another SIPO shift register.

Can I generate an 640x480 monochrome output with an atmega? Is there a better way?


texts: neodymium magnet - how it affects a circuit

texts: I am trying to develop a connector which can join both sides by a magnet. I got the idea of using a neodymium magnet , but I was thinking that if this could in one way or another affect circuit operation. This is an example of what I'm trying to do


texts: Unity-gain closed loop Miller OPAMP fails to follow the input after a few microseconds?

texts:
I implemented a Miller OPAMP. After I have checked it reaches the desired gain and swing, I put it into the simplest form of closed loop with UNITY negative feedback. The schematic is as follows:

As you can see, the loop is simply a direct negative feedback. I expect the overall gain to be 1. So I am expecting the output signal is exactly the same one as the input sine. However, after a period of time, it fails. Really strange as it can follow in the few microseconds, but fail later.

The green curve that is covered and thus invisible is my input; the blue one is the output.

Where goes wrong and how may I fix it?


texts: how to calculate sampling rate for DAC from its data sheet

texts:
I need to find the sampling rate of the DAC from its data sheet, could you please suggest me any formulae to find the sampling rate from settling time, no of bits, bandwidth.

As I didn't find sampling rate from the data sheet of DAC's


texts:
A traducer's analog output is generated by its DAC as seen in the below plots. The plots are from the same data with increasing zoom. Plots obtained by using a DAQ. It seems like the DAC outputs 3 voltage values per second(see the last plot). But it is raw and not filtered and thus not smooth. It looks like this transducer doesn't filter/smooth the DAC output. It is in discrete steps not smooth as you see(created by samplehold of DAC).

I have couple of questions:

1-) Is a smoothing filter needed if I am only interested in the mean value of the voltages? Is filter only needed in applications like sound outputs?

2-) I'm sampling this DAC output by a DAQ device(sampling rate 500Hz) and obtain the below plots. What would you say about the noise here? Is that something to do with sampling rates or DAC being not smoothed?


texts: Is current with a frequency less than 1 Hz still considered DC?

texts:
We had a big argument last night with vague conclusions. Is the current with a frequency less than 1 Hz considered DC?

It would still resemble a wave...


texts:
I am desining a colpitts oscillator to oscillate at around 16Khz. I tried to simulate the circuit in LT spice.

The tank circuit looks right to me but I can't get the circuit to oscillate.Also, the circuit satisfies the berkhausen criterion with $$gain*attenuation = 3.1 (approx)$$.I even tried getting it close to 1 by adjusting the attenutaion but still, it doesn't work.
I think it's something to do with the other capacitors like C1 and C5 or maybe L1.
My book doesn't go into much detail about these components and it mainly focuses on the barkhausen criterion and how to calculate it. I have much confusion, for example, i can make the tank circuit oscillate by choosing other values of inductor and capacitors but there should be a way so that i don't choose a very high or low value of these components.

My questions are-

What other things are to be considered apart from the tank circuit to make these kinds of oscillators work properly?
How to decide which capacitor C1 and C5 to use for the circuit to work properly? if possible please help me with a detailed mathematical explanation.


texts: What properties vary with the number of blades on a BLDC fan?

texts:
In general, what properties vary with the number of blades on a axial BLDC fan when physical and electrical dimensions are the same (e.g.: rated at approximately 12V and 0.15A and 60mm Ø)?

So far I've seen fans with 7, 9 and 13 blades and unfortunately not all fans come with a datasheet.

Things that I can think of myself include, but don't know how they would be influenced by blade count:

Fan speed (rpm)
Volume (\${\text{m}^\text{3}}\cdot{\text{min}}^\text{-1}\$)
Application (mounted directly on a heatsink or mounted in equipment housing)
Artistic mood of the designer

13 blades:

9 blades and 7 blades:


texts: Is there a reason that both a fuse and a circuit breaker would operate? From my understanding, the fuse should blow first and kill any current flowing through it leaving the breaker intact. So why would a fuse blow, and then an upstream breaker trip and lock out?


texts:
My schematic as below. I  have connected 8 hall sensor as shown in picture. Problem i am facing here is SO, s1, s2 The Led light are not glowing .Even the forard voltage across is 3.9v. i have tested with multimeter LED working fine. Please let me know why might be reason to not glow when upload below code.

SO,S1,S2 are selective pins for MUX IC. Here i am scaling up to 24 after that. I found The digital Io across are getting properly as per truth table or array mentioned.

#include <avr/wdt.h>
int SO_enable=7;
int S1_enable=6;
int S2_enable=5;
int Enablepin=4;
int Sensor_Value0=0;
int Sensor_Value1=0;
int Sensor_Value2=0;
float  voltage0;
float voltage1;

float Current_Mux1[9];
float Current_Mux2[9];
float Current_Mux3[9];
float ARDUINO_ANALOG_SCALING=0.004799608993157;
int row,column;
int DigitalHigh=8;
int DigitalHigh1=9;
static float  Mux1_array[9]={
  0.0};
static float  Mux2_array[9]={
  0.0};
  static float  Mux3_array[9]={
  0.0};

 float Current_Value1[9]={0.0};
 float Current_Value2[9]={0.0};
int array[9][4]={
  {    0,0,0,0  }
  ,
  {    0,0,0,1  }
  ,
  {    0,0,1,0  }
  ,
  {    0,0,1,1  }
  ,
  {    0,1,0,0  }
  ,
  {    0,1,0,1  }
  ,
  {    0,1,1,0  }
  ,
  {    0,1,1,1  }
  ,
  {    1,0,0,0  }

};

void setup()
{
  wdt_enable(WDTO_8S);
  pinMode(SO_enable, OUTPUT) ;// pin can enable/disable using digital IO 7 of arduino
  pinMode(S1_enable, OUTPUT) ;// pin can enable/disable using digital IO 6 of arduino
  pinMode(S2_enable, OUTPUT) ;// pin can enable/disable using digital IO 5 of arduino
  pinMode(Enablepin, OUTPUT) ;// pin can enable/disable using digital IO 4 of arduino
  pinMode(A0, INPUT) ;
  pinMode(A5, INPUT) ;
  pinMode(DigitalHigh,OUTPUT);
  pinMode(DigitalHigh1,OUTPUT);
  Serial.begin(9600);
  Serial.print("Channel\t");
 Serial.print("MUX1_V \t"); Serial.print("MUX1_C \t");
   Serial.print("MUX2_V \t"); Serial.print("MUX2_C \t");
   Serial.print("MUX3_V \t"); Serial.println("MUX3_C \t");
}

void loop()
{
  wdt_reset();
  digitalWrite(DigitalHigh,HIGH);
  digitalWrite(DigitalHigh1,HIGH);
  for(row=0;row<9;row++)
  {
    int k=(8*array[row][0]+4*array[row][1]+2*array[row][2]+1*array[row][3]);

   // Serial.print("k:");
    Serial.print(k);
    Serial.print("\t");
    digitalWrite(Enablepin,array[row][0]);
    digitalWrite(SO_enable,array[row][1]);
    digitalWrite(S1_enable,array[row][2]);
    digitalWrite(S2_enable,array[row][3]);
   delay(100);
    Sensor_Value0=analogRead(A0);
    Sensor_Value1=analogRead(A5);
    Sensor_Value2=analogRead(A3);

   Mux1_array[row]=(Sensor_Value0 * ARDUINO_ANALOG_SCALING);
   Mux2_array[row]=(Sensor_Value1 * ARDUINO_ANALOG_SCALING);
   Mux3_array[row]=(Sensor_Value2 * ARDUINO_ANALOG_SCALING);
    Current_Mux1[row] = (Mux1_array[row]*35.1428571429)-87.6571428571;
    Current_Mux2[row]=(Mux2_array[row]*35.1428571429)-87.6571428571;
    Current_Mux3[row]=(Mux3_array[row]*35.1428571429)-87.6571428571;

  Serial.print( Mux1_array[row]);Serial.print("\t");Serial.print( Current_Mux1[row]);Serial.print("\t");
Serial.print( Mux2_array[row]);Serial.print("\t");Serial.print( Current_Mux2[row]);Serial.print("\t");
Serial.print( Mux3_array[row]);Serial.print("\t");Serial.println( Current_Mux3[row]);

  }
 Serial.println("...................................................................");
 Serial.print("Channel\t");
 Serial.print("MUX1_V \t"); Serial.print("MUX1_C \t");
   Serial.print("MUX2_V \t"); Serial.print("MUX2_C \t");
   Serial.print("MUX3_V \t"); Serial.println("MUX3_C \t");
 delay(500);
}

simulate this circuit – Schematic created using CircuitLab


texts: Controlling the PWM output of MCU (STM32L152RE)?

texts: Is it, by some means, possible to change the time period of the PWM output of the same microcontroller rather than only its duty cycle? I would like to have a 50 % duty cycle for data logic-0 and a 75 % duty cycle for data logic-1, but the time period for data logic-1 should be twice the data logic-0. The MCU I am planning to use is STM32L152RE, but I am flexible.


texts: Implementing a 4-bit ripple carry adder/subtractor using structural VHDL

texts:
I have to create a 4-bit ripple carry adder/subtractor. The circuit will have two 4-bit data inputs (A and B), a control line (Add/Sub), a 4-bit data outputs (S) and a carry out bit (Cout).

I have no idea where to get started. I know how to create a ripple adder but have no idea how I am supposed to create a 4-bit ripple carry adder/subtractor with the specified inputs, control line and specified outputs.
Here is what I have so far:

fulladd:

LIBRARY ieee ;
USE ieee.std_logic_1164.all ;

ENTITY fulladd IS
PORT ( Cin, x, y : IN STD_LOGIC ;
    s, Cout : OUT STD_LOGIC ) ;
END fulladd ;

ARCHITECTURE LogicFunc OF fulladd IS
BEGIN
s <= x XOR y XOR Cin ;
Cout <= (x AND y) OR (Cin AND x) OR (Cin AND y) ;
END LogicFunc ;

adder4:

LIBRARY ieee ;
USE ieee.std_logic_1164.all ;

ENTITY adder4 IS
PORT (  Cin     : IN    STD_LOGIC ;
    X, Y    : IN    STD_LOGIC_VECTOR(3 DOWNTO 0) ;
    S   : OUT   STD_LOGIC_VECTOR(3 DOWNTO 0) ;
    Cout    : OUT   STD_LOGIC ) ;
END adder4 ;

ARCHITECTURE Structure OF adder4 IS
SIGNAL C : STD_LOGIC_VECTOR(1 TO 3) ;
COMPONENT fulladd
    PORT ( Cin, x, y    : IN STD_LOGIC ;
            s, Cout     : OUT STD_LOGIC ) ;
END COMPONENT;
BEGIN
stage0: fulladd PORT MAP ( (Cin Xor X(0)), Y(0), Cin, S(0), C(1) ) ;
stage1: fulladd PORT MAP ( (Cin Xor X(1)), Y(1), C(1), S(1), C(2) ) ;
stage2: fulladd PORT MAP ( (Cin Xor X(2)), Y(2), C(2), S(2), C(3) ) ;
stage3: fulladd PORT MAP ( (Cin Xor X(3)), Y(3), C(3), S(3), Cout ) ;
END Structure ;


texts: Appropriate power supply needed to power 15x 850nm IR LEDs

texts:
I have 15 IR LEDs that I would like to use as a floodlight for my exterior cameras. The thing is I have no idea how to calculate the total voltage and amperage needed. A single LED is rated for 1.7V-2.2V and 700ma.
What type of power supply do I need? Would it make a difference if I wire them in parallel or in series?


texts: Can you send RS232 messages to yourself in PuTTY?

texts: Say you use PuTTY serial mode and a USB to RS232 cable. Can you send messages to yourself if you wire the TX of the cable back to its RX, not haphazardly, there's probably a bit more set up detail. I'm just wondering if it's possible to self-talk on the putty terminal using serial by routing wires back to yourself.


texts: Generating various reference voltages in a circuit

texts:
How does one go about accurately setting reference voltages at various points in a given circuit (e.g. various threshold voltages). Obviously we can have a potential divider from the main power supply but that generally tends to fluctuate a lot, not to mention noise from other parts of the circuit.

I would assume a sort of single voltage reference from which we can derive the rest of the references. Does one use potential dividers after that? Or are there any smarter methods?


texts: Feeding a Full-Bridge from a Boost Converter?

texts:
I have been researching about designing a 3kW DC-DC Converter (Vin 12V from a battery, Vout 350VDC) and actually wired up a simple isolated Full-Bridge based DC-DC converter a few days back converting 12VDC to 140VDC. However, I noticed that it was difficult to vary the output voltage using the duty cycle of the switches. Reducing the duty cycle from 50% to 25% only changed the output DC voltage by 10V or so.

Instead, what worked far better was if I varied the input voltage to the Full-Bridge. So I came up with the idea: why not feed the Full-Bridge with a Boost Converter? I have seen a Buck-Converter feeding a Full Bridge, such as the circuit below, but never a Boost Converter feeding a Full-Bridge. Searching about the issue on the web didn't turn up any schematics or app. notes either.

Is it feasible to feed a Full-Bridge Converter with a Boost Converter and control the output voltage by modulating/controlling the Boost Converter rather than modulating the Full-Bridge switches? I am not very familiar with control (yet) and would rather not go into a design that's a dead-end. If there were some schematics or app. notes on the web, I'd know that the topology would work.

I could go with the Buck fed topology, but then I'd just be stepping down my 12V source and then boosting it back with my Full-Bridge so the logical solution seems to be to first boost the 12V to 48V or so and then drive the Full-Bridge at 50% fixed duty cycle which in turn drives a 48V to 240V high-frequency transformer (30-40KHz). The stepped up voltage is then rectified and smoothed out via a few caps.

The main reason I want feedback in the circuit is that my source voltage is a battery that will vary from 10V to 14V. Without a feedback loop, this will cause rather variations in the output voltage.


texts:
I'm working through this handout I3.PDF to help me understand feedback in common emitter amplifiers.  (The author does not reveal his/her name in the PDF and so I can't ask them directly.)  They show a common emitter circuit at the top and a small-signal model just below it.  What expression defines the resistance \$R_B\$ in the model?
I'm imagining two possibilities.  First, it might be be some combination of \$R_1||R_2\$.  This doesn't seem correct.  In the upper schematic \$R_1\$ appears between base and ground whereas \$R_2\$ appears between \$V_{CC}\$ and the base.  But in the small-signal equivalent, \$R_B\$ appears only between base and ground. The second possibility is that it is simply \$R_1\$ alone.  With us only considering small-signal (AC) voltages, \$V_{CC}\$ would appear as ground and so we ignore it and the resistor directly connected to it?  Both of my guesses seem flawed.


texts: Replacing two ideal with two linear voltage sources

texts:
I am currently learning how ideal sources may be replaced with linear sources to make the application of other circuit theory possible.
Unfortunately, I don't understand how the following conversion is possible.
This is the original circuit.

simulate this circuit – Schematic created using CircuitLab
And my prof. converts it into the following, unfortunately very quickly and with little commentary:

simulate this circuit
with:
$$ V_1^* = V \frac{R_3}{R_1+R_3} $$
$$ R_1^* = \frac{R_1R_3}{R_1+R_3} $$
$$ V_2^* = V \frac{R_4}{R_2+R_4} $$
$$ R_2^* = \frac{R_2R_4}{R_2+R_$} $$
Ultimately, the question in this exercise is what voltage-drop occurs over \$R_5\$, but my question relates more to the conversion above, and less to the accomplishment of said goal. I only mention it, since it may allow some simplifications which would not be possible, would we seek information about other specific nodes or currents, for example.
Let's only consider \$V_1*\$ and \$R_1*\$ since the conversion for the other voltage-source is equivalent.
The voltage itself of course stems from a voltage-division between \$R_1\$ and \$R_3\$. Yet I don't quite see how this comes about, since, going from the cathode and through \$R_3\$, our remaining voltage should at first glance be smaller, the larger \$R_3\$ is. A second glance gives me even more trouble, since I don't see a way for current to travel from the upper cathode to the upper anode while going through the rest of the circuit (since it would ultimately have to be at node A again before going through \$R_1\$ and into the anode.
When calculating the inner resistance, the resistors \$R_1\$ and \$R_3\$ are clearly considered to be parallel. But, considering one of the voltage-sources, I see no way that current could travel from cathode to anode without going through both resistors.
I assume that in both cases my problem is that I consider only one of the sources at a time, while I should consider them both at once. They supply the same voltage, and are oriented so that no potential-difference occurs between their cathodes, which means that there is no potential-difference between their anodes as well. In this exercise they actually stem from a single source, which got split into these two to make a simplification of the circuit possible.
So, why can we make the above replacements, and why are the relations the way they are? Am I right that I should consider both sources at the same time? Some explanation and/or pointing to relevant theory would be highly welcome.


texts:
I have a light sensor IC.
I have 2 questions:

The I2C Lines is connected between the microcontroller (3.3V domain) and the light sensor IC. The microcontroller is placed on a PCB and the light sensor is placed on a separate PCB. Both PCBs are connected by a cable of length 30cm.

In this case, is it correct to place the pull ups of the I2C near the microcontroller on the microcontroller PCB, or should I place it on the light sensor PCB? As far as I have read, the pull-up resistors should be placed close to the master and hence I am thinking it should be placed close to the microcontroller. Please confirm.

I am not planning to use the INT pin. INT is an open-drain output pin from the datasheet. I don't want to use that pin because it will help in one connector pin less. So, in order to not use the INT pin, what should I do? The datasheet doesn't recommend what to do with unused pins. So, what should I do?
As far as I know, since the INT pin is an open drain pin, can I leave it floating.
Please confirm.


texts: Equilibrium points of a circuit with a diode

texts:
The given circuit is shown in the first picture, whereas the characteristic curve of the diode in the second one. I want to calculate a model in the form of $$\frac{d\textbf{x}}{dt}=f(x,u) \\ \textbf{x}=\begin{bmatrix} i_L & u_c\end{bmatrix}^T$$ for the circuit and then calculate its equilibrium points. I am having problems with this task because I am not sure how to deal with the diode and its function only shown visually. Well, what I did up until now is first, apply Kirchhoff's circuit laws to get two differential equations:
$$
u_R+u_L+u_C=u\\
Ri_L+L\frac{di_L}{dt}+u_C=u\\
I: \frac{di_L}{dt}=\frac{1}{L}(u-u_C-Ri_L)
$$
$$
i_L=i_C+i_d \\
i_L=C\frac{du_C}{dt}+h(u_d) \\
II: \frac{du_C}{dt}=\frac{1}{C}(h(u_d)-i_L)
$$
Next, I tried to calculate the equilibrium points of the system (u=5V, L=1H, C=1F, R=1):
$$
I: 5V-u_C-i_L=0\\
II: h(u_d)-i_L=0 \\
I+II:5V-u_C+h(u_d)=0 \rightarrow 5V+h(u_d)=5V+h(u_C)=u_C
$$
But with this result I cannot find any solution, so I guess I did something wrong in my calculations, but what and where? Can someone help?


texts:
I need to control a 12V 100A DC motor and I was thinking of using this circuit, I saw many post and application notes that talk about parallelizing MOSFETs but I did not see any circuit using MOSFET drivers or in H-Bridge, my question is if this circuit is ok
BTW: The mosfet that I will use are IRF1404, Rds=0.004 ohm
Edited: sorry I avoid the circuit


texts: Problem with ADC configuration - atmega328p

texts:
What's up folks?

I've been developing a project using atmega328p and avr-gcc.
Recently, I've tried to configure the ADC to single sample.
The codes below show my main.c, ADC.c and ADC.h

//main.c

#include <avr/io.h>
#include <stdint.h>
#include <avr/sleep.h>
#include "drivers/ADC.h"

volatile int timer_counter = 0; //value of timer_counter
volatile uint8_t converteu;

int main (void){
        CLKPR = (1<<CLKPCE); // enabling bit writing in clock divider
        CLKPR = 2; //clock divider = 4, from 8 MHz to 2 MHZ
        configure_ADC(); // clock = 62.5 KHz, AREF = AVCC, single sample

        DDRB = 7; // PB0, PB1, PB2 as output

        while(1){
           sei();
           set_sleep_mode(SLEEP_MODE_IDLE);
           sleep_mode();
        }
}

//ADC.c

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

ISR(ADC_vect){
        PORTB ^= 2;
}

void configure_ADC(){

        ADMUX |= (1<<REFS0); //short circuiting AVCC with AREF, ADC0 is the port enable to be read

        ADMUX &= ~((1<<MUX0)+(1<<MUX1)+(1<<MUX2)+(1<<MUX3)); //selecting ADC0
        ADCSRA |= (1<<ADEN); //ADC enable
        ADCSRA |= (1<<ADPS2) + (1<<ADPS0); // AVCC as reference

        ADCSRA |= (1<<ADIE); //enabling interruption
        PRR &= ~PRADC; // no low power on ADC
}

//ADC.h
void configure_ADC();

These code should do nothing, just configure ADC to run in single sample.
However when I run it in my microcontroller, without activating ADSC (bit that starts a conversion), the PORTB 2 is activated. The only place that enables PORTB 2 is in the ADC's ISR.

The ISR is executed without activating the ADSC bit.

What's happening with this code?


texts: How to isolate several voltage sources that feed a single voltage meter

texts:
I need a way to isolate several voltage sources around a large vehicle that feed a single voltage meter some distance away on a panel. Each source is selected by a momentary-spst (at the source).

Here is a block diagram, with 2 discrete options:

All current is DC. Voltage sources run 4.6 VDC to 54.0 VDC. Desired display accuracy is 0.1 Volt. All the power supplies share a common ground.

The (arbitrarily) colored areas display the core differences in the current two options. Option one (green) uses 'ultra-low loss diodes' (ideally an IC array), Option 2 (blue) uses typical signal diodes (1N4148) and a post diode voltage adjustment.

For option 1, the MAX4020 came to mind, but the voltages are out of range. Is their an IC / IC array designed for this?

For option 2, what is the best way to adjust the voltage up 0.7 V?

We're somewhat stuck with the basic layout of using multiple momentary-spst feeding a single voltage meter, so a rotary selector switch is out.

edits:

updated 'mom' body text to 'momentary' for clarity.


texts: What would be an acceptable tolerance for length matching trace, for DDR3 SDRAM?


texts: LTC4418 interfacing VALID1 with a microcontroller

texts:
I want to use LTC4418 fuctionality of detecting which one of power supplies is on at this moment. Here is my approach to it:

PS_VALID1 is connected directly to VALID1 of LTC4418 (without any additional components), same for PS_VALID2. BLE_GPIO is a GPIO of 3.3V powered microcontroller.

What I got confused by is the documentation stating:

Output Currents
VALID1, VALID2, CAS..............................–2mA/+5mA

VALID1 and VALID2 are open-drain outputs, fine, they pull-down to GND or are Hi-Z, but why there is a +5mA output current stated in the docs? Is this circuit correct then?


texts: 3.7V to 5V step up not providing enough current

texts:
I'm trying to power up a circuit that consists of an Arduino Nano, 3x 3W stereo audio amplifiers (PAM8403), an audio player module and 20x RGB LEDs. The power source is a lithium battery 3.7V 500mAh. The circuit works perfectly from any USB power bank or USB 2.0 computer port (500mA) plugged directly into the Arduino USB socket, but it doesn't work properly with the step up circuit I chose.

The system only crashes when the volume is louder, so I can assume it's a current issue. The step up DC/DC converter I'm using is the CE8301A. Below is the circuit:

Then the Vout line passes through the audio amps first to then reach the Arduino 5V pin and all the rest.

Now I'm considering three options:
1) Change the values of some components.
2) Try a higher capacity battery.
3) Try another step up such as the ME2149.

What would be the best solution? And if the component values can be changed to allow more current to flow, which ones should that be?


texts: How can I determine the maximal output voltage of a battery (https://shop.righthere.nu/topfuel-power-x-1800-2s.html)? It has  \$1800\text{ mAh}\$ and \$35 \text{ C} \implies i_{\max}=1.8\cdot 35 \text{ A}=63\text{ A}  .\$


texts:
We have been trying to figure out for weeks why these flyback transformers keep failing. They are these specific transformers http://www.pca.com/Datasheets/EPC3205G-X-LF.pdf

We are running them at 24V input, and are used to charge a capacitor bank to 200+ Volts. We run them at around 900 mA at 355kHz in a DC/DC circuit.

I know that's not a lot to go one but we have somewhat ruled out overheating and over current as the culprit. They don't get hotter than 60 degrees C, and verified with a scope that the current does not exceed 1 A. Nearly out of ideas as to what to do so any advice would be welcome.

SOLVED:

Advice to anyone looking to build something similar:

Don't go with the PCA transformers! We ordered some nearly identical transformers from PULSE PA0367ANLT and they are doing a lot better! No more random failures. Plus they are cheaper.


texts: Probing with oscilloscope causes current drop

texts:
We are testing a fabricated chip with expected output current of around 4mA which is then used to charge a button cell. The input is from a PV cell.
However, when we attach an oscilloscope probe onto one of the pin outs of the chip (i.e. the ring oscillator and the clock), we detect a significant current drop at the output, from 4mA to around 1mA. The current from the PV cell also drops.

what would be the cause of this current drop?

We tried with a different oscilloscope, and still detected a drop in current, albeit of a different value.

Attached is the block diagram of the DUT.

implemented in 65nm CMOS

note: the buffer is connected to the rectifier through offchip capacitors.


texts: Observing frequency of waveform in LTspice

texts: I'm using Ltspice for circuit simulation. I stimulate the circuit using run command in the menu stimulate. But I didn't find how to measure(simply in hertz) frequency from there. So how can I observe the frequency of a waveform from LTspice?


texts:
I am having trouble with a randomly floating digital signal. Transmission is between a microprocessor and a CPLD unit and is used to run a  half bridge. Measurement was taken after the output resistor of the processor and appeared after about 5 to 50min of running time for multiple times. Do you have any idea what could have caused this?
From my point of view a mechanical loose connection didnt cause this, because its first to fast and also the system does not respond to mechanical forces.
Here you can see the problem (green signal), red is the other signal sent towards the CPLD. Blue can be ignored, this was the error output by the CPLD because of the signal received.


texts: Wiring 3 Transformers in Series on 240V?

texts: If I have 3 transformers (120V transformers) in series (on the input side) on a 240V circuit, will the transformers experience a voltage drop? If so, how much and will this affect the secondaries by the transformer equation?


texts: I have a +3.3V supply and ground through usb on a board. I want to get a -3.3v supply from it for giving reference to an adc. Do you know how to do it?


texts: LiPo Battery: series to parallel charging switching circuit

texts:
simulate this circuit – Schematic created using CircuitLab

So, I have two 2000 mAh LiPo batteries that are going to be powering a GSM modem (on an arduino shield) a GPS and a motor.  I considered just boosting to the motor (needs 6V), and using the batteries in parallel, but decided that it would make more sense to hook the batteries up in series and use LDOs to get down to the 5V needed for the shield and 6V needed for the motor.

The problem then arises: how do I charge the LiPo batteries back up, using only my external microcontroller and the charge controller that came with the first battery?  The charge controller can charge at up to 500mA.

My gut instinct was to create a MOSFET controlled circuit to switch the batteries to a parallel configuration, and to then connect the charge controller to the batteries.

4 MOSFETS feels like overkill though.  Does anyone have any better ideas?

Here are the specs for the charge controller


texts: Calculation of active power using two waveforms with harmonics

texts:
I came up with the following example on a textbook I was given.

Let's suppose we have an R-L load. I want to calculate the active power P when the voltage and the current applied on the load are given with the following functions:
$$u(t)=200 \sqrt2\sin(ωt)+ 200 \sqrt2\sin(5ωt+30^{\circ}) $$
$$i(t)=26.19\sin(ωt-68.2^{\circ})+ 6.22\sin(5ωt-85.4^{\circ}) $$

In the answer it is given that we get:
$$ P = \tilde{V_1} \tilde{I_1} cosφ_1 + \tilde{V_5} \tilde{I_5} cosφ_5 \Rightarrow   $$
$$ P = 200\frac{26.19}{\sqrt2}cos(68.2^{\circ}) + 200\frac{6.22}{\sqrt2}cos(85.4^{\circ})
 $$

What I don't get is why the angle φ5 is not calculated as :
$$ φ_5 = 30^{\circ} - (-85.4) = 115.4 ^{\circ} $$ since
$$ φ_n = θ_v - θ_I $$ where θv is the angle of the voltage harmonic and θi is the angle of the current harmonic. Isn't this the right was to calculate it or am I missing something?


texts: TTL-based computer/video frequency limit

texts:
I was quite impressed by Ben Eater's breadboard computer, and I would like to build something similar, especially with a VGA card like the one he built, but with my own 6845-like text mode generator using the full VGA resolution.
However I learned in his videos that there's a hard limit on the frequency that can be handled by such breadboard designs: something around 1 MHz.
What frequency limit can I expect if I move to a stripboard or even to a PCB? The VGA pixel clock for the modes I'm interested in is 31.5 MHz (which I plan to divide to get around 8 or even 16 MHz for the CPU). But even if the board can handle such frequencies, will the TTL chips be fast enough?


texts: CMOS output voltage depending on Vss and Vdd

texts: How does output voltage in CMOS depend on Vdd and Vss? As far as I know, it is limited by Vdd when Vss = 0 (ground) but what when Vss is not 0 (for ex. -2.5 V?)


texts: Multiple channel independent AC dimmer using Arduino

texts:
I want to build a 8 channel, independently controlled AC dimmer using Arduino. I have successfully tested a single channel dimmer but i am stuck in expanding it to 8 channels. The circuit I am referring is as below

The arduino code i am using is as below

/*
AC Voltage dimmer with Zero cross detection
Author: Charith Fernanado http://www.inmojo.com
License: Creative Commons Attribution Share-Alike 3.0 License.

Attach the Zero cross pin of the module to Arduino External Interrupt pin
Select the correct Interrupt # from the below table:
(the Pin numbers are digital pins, NOT physical pins:
digital pin 2 [INT0]=physical pin 4
and digital pin 3 [INT1]= physical pin 5)

 Pin    |  Interrrupt # | Arduino Platform
 ---------------------------------------
 2      |  0            |  All
 3      |  1            |  All
 18     |  5            |  Arduino Mega Only
 19     |  4            |  Arduino Mega Only
 20     |  3            |  Arduino Mega Only
 21     |  2            |  Arduino Mega Only

In the program pin 2 is chosen
 */

int AC_LOAD = 3;    // Output to Opto Triac pin
int dimming = 128;  // Dimming level (0-128)  0 = ON, 128 = OFF
/* Due to timing problems, the use of ‘0’ can sometimes make the circuit
flicker. It is safer to use a value slightly higher than ‘0’
*/
void setup()
{
  pinMode(AC_LOAD, OUTPUT);// Set AC Load pin as output
  attachInterrupt(0, zero_crosss_int, RISING);
// Chooses '0' as interrupt for the zero-crossing
}
// the interrupt function must take no parameters and return nothing
void zero_crosss_int()
// function to be fired at the zero crossing to dim the light
{
  // Firing angle calculation : 1 full 50Hz wave =1/50=20ms
  // Every zerocrossing thus: (50Hz)-> 10ms (1/2 Cycle) For 60Hz => 8.33ms

  // 10ms=10000us
  // (10000us - 10us) / 128 = 75 (Approx) For 60Hz =>65
  int dimtime = (75*dimming);    // For 60Hz =>65
  delayMicroseconds(dimtime);    // Off cycle
  digitalWrite(AC_LOAD, HIGH);   // triac firing
  delayMicroseconds(10);         // triac On propogation delay
                                 //(for 60Hz use 8.33)
  digitalWrite(AC_LOAD, LOW);    // triac Off
}
void loop()  {
 for (int i=5; i <= 128; i++)
{
 dimming=i;
 delay(10);
 }
 }

Any ideas about how can i expand the code and circuit to work with 8 channels that can be INDEPENDENTLY controlled ?


texts:
I would like to model a transformer in LTspice with hysteresis and saturation (or just hysteresis would be nice). I have already tried the Chen model which I don't like and tried to model a regular transformer with the inductor parameters found here but got an error.

Here is an example of my LTspice netlist

.param Is=2A a=3
.param Ind 1000mH
K2 L4 L3 1
L4 0 N008 {2*Ind} Ipk=2 Rser=10
L3 0 N007 flux={Ind*Is}*tanh((x/{Is})**{a})**{1/a} Ipk=2 Rser=110

I get an error that says: mutual inductance statements aren't supported between arbitrary inductors

My question is: is there some way to combine an ideal transformer and a non-linear inductor to make an accurate model and simulate in LTspice?
Are there other ways to effectively model a transformer with hysteresis in spice?


texts: How can I control two motors using only two wires?

texts:
Yesterday I bought an old RC Car from a junk sale. I assume this circuit has a built in motor driver, which is how it gets the forward/reverse of the motor working. This circuit is running of a 9v household battery, not the car battery for the motors.

I want to scale this up so I can use it on an old electric mobility scooter, but here's my problem:

The motor is driven by switching the polarity of the driver output wires.

In order to control the 12v motors (Powered from a car battery), I need to use a relay device (I'm using an opto-coupler) and know I need the below circuit:

However, if I were to complete my circuit using the yellow wires in the above diagram, the other relay device would be activated and both motors would turn. I don't want this to happen, just one motor should turn.

Unfortunately, I don't know how I can achieve my expected result, if it's even possible. Perhaps some kind of logic IC is needed? I'm not sure which one.

Thanks in advance.


texts: what's the purpose of parallel RL circuit on mains recifier?

texts:
simulate this circuit – Schematic created using CircuitLab

Hi, I was reading a datasheet for DC1744A which is a demo board of LT3799 and this is the rectifying circuit of the board in their datasheet.

I am not sure the purpose of RL parallel circuit before the bridge rectifier
and also why they used the choke inductor (L3) after the rectifier not before. (if it is just a choke inductor of course)

The circuit drives a transformer with high frequency FET switch.

Could someone help me please?


texts:
so I am watching this lectures ( since the coranva virus , I am studying again  electronics ).
so at this lecture he is talking about MOSFET current mirros :
https://www.youtube.com/watch?time_continue=12&v=SqnCGvtvDq0&feature=emb_logo

at 19:31 he writes that Vgs_1=Vgs_0 ,and I cant understand really why. I also did simlutaion of this circuit and he is write ,Vgs_1=Vgs_0. But I cant really understand why , could anyone explain me plise ?
here is the circuit I am talking about :


texts: Solid State Relay two switch based on headphone audio output to control dc signal

texts:
Need to turn on an LED if there is any audio present out of the headphone jack of a cell phone (0.6v peak voltage). If there's no audio, need to turn off led. My plan is to hook up audio signal to the input of the relay and have the relay control a dc current of 5V that lights an led if relay is ON.

Any ideas what kind of relay or specs I should look for?


texts: Can someone break down how this receiver works?

texts:
I'm having difficulty understand how this receiver works due to its size. It was taken from this site: http://jap.hu/electronic/rf.html. It is on top labled toy car receiver.

The toy car transmitter is easy enough to understand, and I suspect that the receiver is essentially working the same way, but backwards and with more filtering.

I need someone to break down the circuit into its components and explain in depth how it works.

Here it is:


texts: Ho can I light number of LEDs based on current flowing through circuit

texts:
I am trying to create a water tank level indicator which will have 2 wires going into tank one with resistors attached at increment levels and one simple wire. Is it possible to light up number of LEDs based on current flowing through circuit.
Some of the solutions refer to lm3914 and measure the voltage and light LEDs based on that but can anybody explain how that will work with this design.
Thank you


texts: What does a multiplier on a component value mean?

texts:
I have this circuit schematic that shows a *2 behind the value for Cin and Cout.
Does the designer mean two capacitors of that value in parallel on the input and output? Is that a common way of doing that? It looks very error prone to me.
(full datasheet)


texts: AVR Rapid Fire Mod... I hit a wall and need some help

texts:
Title says it; I'm making a rapid fire mod chip with the 328p family of chips right now (I'm going to scale down to whatever the smallest chip is that will safely hold the final software). I'm a fan of BASIC so I'm using Bascom and a USBASP programmer.

I've hooked up the chip with a 20Mhz clock and 22pF caps, as well as a power\status LED, and an LCD for visual debugging (because it really does make a huge difference). So it's a very basic setup.

Here's the problem: when I'm on the BB with a regular tactile switch, I can get the program to work totally fine. However, when I run wires from the contact points on the controller and hook them up to the corresponding points on the AVR, the program acts as if there's no button present, or rather it almost is looking like it's acting as if I'm just holding the button down, and I'm not. I've tried high side, low side, every possible side, and it isn't working as it should.

Most people use the PIC controllers, and they just run the controller contact points direct (or through 330R) without a problem. I've installed plenty of these for other people, and it's not complicated. So in theory I should be able to do the same, so why is it tripping out?

Here's my Bascom code:

   'Name: Azula Outlaw Mod MCU Firmware
   'Version: a1
   'Designed by: Dominic M, Luciano
   'Development MCU: ATMega328P
   'Oscillator: 20 MHz Crystal
   'Copyright: (c) 2014-2015 Dominic M. Luciano, Luciano Incorporated, and Azula Microtech
   'All Rights Reserved.

   $regfile = "m328pdef.dat"
   $crystal = 2000000

   'PIN\IO INITS
   '---------------------------------------
   'OUT
   'Init LCD Backlight  (For Visual Debugging)
   LCDLIGHT Alias PortB.0
   Config LCDLIGHT = Output

   'Init PWR LED
   PWRLED Alias PORTB.1
   Config PWRLED = Output

   'IN
   'Init Function Switch, Start Pull Up
   F_SW Alias PinD.2
   PortD.2 = 1
   Config F_SW = Input

   'LCD INIT
   '---------------------------------------
   'Config the LCD for visual debugging
   Config lcd = 16 * 2
   Config lcdpin = PIN , DB4 = PORTD.4 , DB5 = PORTD.5 , DB6 = PORTD.6 , DB7 = PORTD.7 , E = PORTD.1 , RS = PORTD.0
   Config lcdmode = PORT

   'VARIABLE AND SUB CALLS
   '---------------------------------------
   Declare Sub FClick()
   Dim FCount as Byte
   Dim FState as Byte                                          'State flag

   'INTERRUPTS AND SLEEP\STANDBY
   '---------------------------------------

   'STARTUP SEQUENCE
   '---------------------------------------
   LCDLIGHT = 1                                                'Start LCD Backlight
   PWRLED = 1

   'MAIN LOOP
   '---------------------------------------
   Main:

   Cls
   LCD "No Activity"

   'Stabilize
   Waitms 250

   Do

   If F_SW = 1 Then

   If FState = 0 then
   Gosub FClick
   ElseIf FState = 1 Then
   Waitms 500
   FState = 0
   End If

   End If

   Loop

   'Subroutine for the function button
   '(The button that tells the AVR to take commands)
   Sub FClick()

   Cls
   LCD "Input Settings"

   '~2 second wait until reset and goto Main

   Dim Flash as Byte

   Do
   PWRLED = 0
   Waitms 500
   PWRLED = 1
   Waitms 500
   Incr Flash
   Loop Until Flash = 2

   'Change State Flag
   Incr FState

   'Set Vars
   Flash = 0
   FCount = 0

   'Exit Sub and Return to Main Loop
   Goto Main

   End Sub

Sorry about any mess in my code. It's still really rough. I was trying to get one subroutine down because the rest of it is all the same subs basically.

Here's a shot of my workspace. Once again, sorry for the mess:

So if you can offer any help, I'd appreciate it. Thank you!


texts: Amps / current doesnt add up to the expected figure - Ohm's law failure on my part!

texts:
Can anyone offer suggestions as to where I am going wrong please?

In my circuit (diagram below) the system voltage is 12.03 V and the lamp resistance is 2.9 ohms (measured with power disconnected through circuit). I was expecting to measure a current of 4.1 Amps (12.03/2.9 = 4.14)

However the DMM ammeter reads 0.450 A DC (positive lead to positive side of circuit). Screenshot below.

This doesn't tally with Ohm's law so I suspect that I am doing something wrong rather than Mr Ohm!

Thanks in advance for any help (first post here)

thanks for you comments. It appears then, that one cannot test for actual operation resistance from cold - I take it then one would need to operate circuit for some time, then disconnect power and then test resistance to gain a true reading. Haven't seen a mention of this real world scenario when reading about ohms law!

Once again thanks - off to re-test!
N

Reply to all again. Re-tested. Voltage has dropped to 11.5
Closed the circuit and left it for 5 mins to heat up, tested current again, now showing as 1.74Amps. Took battery lead off and quickly tested circuit ohms and they momentarily showed a peak of 9-10ohms before quickly falling away (as bulb temp drops). So expectation might be 11.5v/1.74A=6ohms - something much nearer. I was (naively?) imagining this was all rather simpler than the real world appear to show!
Thank you all - i have adjusted my expectations accordingly