texts: Auto-ranging voltmeter circuit with PIC uC ADC

texts:
I want to design an autoranging voltmeter with a PIC microcontroller and its ADC.

Requirements:

Measure voltages from +0.2v to +50v
Protect against reverse inputs or slightly higher voltages
Input impedance can be quite low, drawing up to a few mA.
Accuracy of around 1% or better (although not necessary for smaller voltages)
Sample time of around 0.5ms or better

I have a circuit in mind, and would appreciate feedback. Perhaps there are simpler circuits I could use. The PIC will be on a 5v supply. I would probably use a basic, cheap op-amp running from 0v and a +12v rail. The tristate uC outputs would either set the input voltage dividers or alter the gain of the op-amp circuit to higher than unity.

simulate this circuit – Schematic created using CircuitLab

Does this look reasonable?


texts:
I am building some project that requires me to measure the saturation corrent of some homemade inductors winded on scavaged ferrite cores, so I decided to try and create a circuit that will aid me in measuring.

From what I know and read the current thru the inductor at a constant voltage rises linearly with time and when core enters saturation the current start to rise exponentially. So I've came up with something like this:

simulate this circuit – Schematic created using CircuitLab

The idea behind this is I would measure the voltage across a sense resistor R take its derivative and pass it thru a differential amplifier which will compare the current value with a previously obtained fixed value stored in S/H circuit. And if the difference is bigger than some preset value the comparator would output a high value.

Why I think this might work: The derivative of the linear function is a constant and the derivative of the exponential function is exponential function. So when the circuit would sense the that the output voltage from OA1 is not a constant it would trigger and shut off the MOSFET. I would then read on the oscilloscope the time the output was high and calculate the saturation current.

But for it to work I would need to update the S/H circuit frequently, I am planning to do this every second iteration. However I dont have this quite worked out yet, because I am stuck at the first part, the differentiator:

simulate this circuit

I've searched thru the web and found out how and why it works but never found the equations that would describe its behaviour. I would need a unity-gain differentiator with cut-off frequecies at around 100-1k Hz and 100k-1M Hz. So I decied I would go and write the equations myself. This is the furthest I've come:

Transfer function:
$$H(s)=\frac{sC_1R_2}{s^2C_1C_2R_1R_2+s(C_1R_1+C_2R_2)+1}$$

Its magnitude (in hope to find cut-off frequencies):
$$|H(s)|=\frac{\omega C_1R_2}{\sqrt{\omega^4 C_1^2C_2^2R_1^2R_2^2+\omega^2C_1^2R_1^2+2\omega^2C_1C_2R_1R_2+\omega^2 C_2^2R_2^2+1}}$$

I see whoule bunch of squares in the square root, but have no idea how could I simplify it.

Excuse me if this is to long of a post, but I want to make sure that this is the right approach/path that I've taken.


texts: Measuring Discharge Rate of LiPo battery

texts:
I am attempting to change the temperature that a 3.7v rechargeable LiPo Battery is discharged in and am seeing how this affects the capacity and discharge rate of the battery. My setup currently uses an Ammeter and Voltmeter to log the data over time. However, from my research, I have found that I must use a constant Power load or a constant current load for this setup. Since I do not have access to these, is there no way that I can find a discharge rate with what I have?
If not, what can I find out/compare at different temperatures with the data provided?


texts: How exactly is an LCD damaged by DC current?

texts: LCD displays are driven by AC waveforms. I've seen many references referring to permanently damaging them with DC current. When exposed to DC, LCD's fail and conduct excessive current. My question is: what exactly changes physically? Does a contact become "plated" with liquid crystal molecules preventing current flow? Do electrons permanently migrate? Are molecules broken down?


texts: Help with basic transimpedance amplifier circuit

texts:
I'm a physics student and doing a project where I need to detect moderate intensity of light with a response as linear as possible (measuring angles using Malus law (linear polarization)). Anyways, I was using photodiodes in photoconductive mode without amplification (just a resistor in series) and it was working reasonably well, but some days ago I've got VERY noisy readings (i'm using an Arduino as ADC). I do not know the source of the noisy readings, but I suppose I should invest time into making the whole circuit more resistant to noise. Apart from low-pass-filters, I was thinking that amplifying the signal on the sensor side would help (there is a cable of about 1m length between sensor and arduino).
So I was looking into basic amplifying circuits using op-amps and transimpedance amplifier circuits seemed quite straightforward to me, yet I was wrong. I'm trying to reproduce simple op-amp circuits like the one I show in a circuit below, but it just doesn't work. I'm using an LM324N op-amp.

I'm thinking about using the photodiode in photoconductive mode later (more linear as far as I know?), but first I want to get running the more simple photovoltaic-mode-circuit.

Can someone look at my connections and point out if there are some obvious flaws in it? The op-amp seemed adequate for the job. It's driving me crazy.

The circuit doesn't react to light, and instead gives me a constant output of about 779 (about 3.8V).I tried using different resistors (100 Ohms, 5kOhms, 1Mohm), and I obviously tried flipping the diode ;).

any help would be appreciated!

Edit: As has been pointed out, the circuit was wired wrongly. I did make changes to the wiring, and now I'm getting constant zero values, and very low values when illuminated with a bright, white led (20-40 on arduino scale depending on the cathode orientation, so in the order of 100mV)


texts: True GPS Location - At the Antenna or Receiver Chip?

texts:
Suppose I have a GPS unit attached to an antenna through a 50 meter coax cable.

How would the location as calculated by the GPS unit be affected by the cable length?  As a bonus question, how would the time accuracy of the GPS be affected by the cable?


texts: Operation without power: Passing analog video

texts:
Okay, the title sounds odd, I'll admit. I need my project to work without power. That is, a complete power failure may happen, and no additional power (such as a battery or supercap) is available mainly due to size and cost restrictions. The ground will always be connected during a power failure. The power failure may also include, for example, a short circuit placing the 3.3V buck regulator into a protection mode, causing a loss of power.

Here is the scenario. I'm developing a video processor which has multiple video inputs (two in most cases.) It uses an analog switch (ADG733 or TS3A24157, depending on version) to select the desired video feed, all software controlled. With power, it selects either one. However, when no power is present, I don't get a good video signal, because the mux goes into some kind of null state, with both inputs kind of conducting but very weakly.

The result is without power, a video picture which looks like this:

The output amplitude is large enough to allow a TV card to sync onto it, but not large enough to provide a clear picture.

So, I need some kind of circuit which activates when there is no power and passes through either video input (one or the other, but not both) as a sort of fail safe for when power is lost or a bad hardware problem occurs.

I was thinking of a PMOS, as a negative gate potential will turn that device on, but wasn't sure how to make that work properly.

As this is video, we are talking about low on resistance; preferably less than 10 ohms. The analog mux probably has quite a high resistance when powered down, so as long as the circuit which provides the backup has considerably lower resistance, it should be possible to override it.

Also, it should be small, and low cost to implement. The current board is just 50mm x 39mm.


texts: Convert from a specifc range to another one

texts:
Can anyone explain how one would convert one voltage range to another? I'm going to need to convert a range of -10 to +10 volts into a range of 0 to +5 volts. How would this be accomplished? Thanks!

Let me say  something more. Inside of a torpedo there are gyroscopes. This gyroscope give -10 volts when the torpedo have 180 degrees of deviation to the west and 10 volts when the deviation is to the east. This signal is DC, so i need to change this range a range: 0 to 5 v DC . Thanks


texts: Correct way to do "power injection" from multiple DC supplies?

texts:
I'm using a PixLite controller to run a bunch of pixel LED strips.  Since I'm sticking to 5V I need to use multiple power supplies (PSUs) to "inject" extra power for the number of LEDs I'm running.  However, as described here, if not wired correctly:

Small variances in PSU output voltage can cause large currents to flow between PSUs.
Common grounds can allow "ground noise" to feed back and affect the data signals from the Controller to the LED strips.

What is the correct way to wire this?  (Or "best" way to avoid these two – and any other – problems.)  Following is my guess:

simulate this circuit – Schematic created using CircuitLab


texts: TVS unidirectional vs bidirectional in Hbridge

texts:
I have used this circuit (I found online last year) to drive big dc motors without much thinking but with great success.
http://obrazki.elektroda.pl/4961105700_1437649469.jpg : -

But yesterday I noticed something; there are 3 TVS (two from each motor terminal to GND and one from VCC to GND) BUT THEY ARE BIDIRECTIONAL

Now i am thinking, isn't it better to use unidirectional instead in such circuit?

Another aspect, should I add 2 more TVSs across the high side MOSFETs also?

Please give your opinion, maybe these diodes are not needed at all?

NOTE : i am using locked anti-phase or sign magnitude drive methods WITH synchronous rectification.


texts: How does this IF alignment procedure work?

texts:
Simple question (I hope!)  I've been looking at AM radio alignment techniques recently and IF alignment in particular.  The "generic" approach in a valve(tube) radio is to feed the IF frequency into the control grid of the mixer/frequency changer valve and monitor for peak output at the speaker whilst tuning the IF transformers.  I would imagine the same technique is generally applicable in transistor radios also.

The control grid of the frequency changer is the RF input with the LO signal arriving on a separate grid.  What I don't understand is how the LO signal doesn't interfere with the generated test IF signal fed into the control grid?

The general consensus says that you can perform an IF alignment leaving the LO signal in-place and changing the LO shouldn't affect the IFT output.  But doesn't the mixer valve hetrodyne the two signals to produce the IF products (subsequently tuned by the IFTs).  So, if you leave the LO signal as an input won't you get variable products and won't it affect the output?


texts: BCD Switch Resistor Network for Proportional Voltage Output

texts:
My goal is to wire a BCD switch in a 5 volt system and get a voltage proportional to the 0-9 on the switch.  My first thought was BCD -> R/2R network.  That does not work because the R/2R network expects its inputs to be Vdd or Ground.  The BCD switches produce short-to-common or open-circuit.  Some solutions have occurred to me:

Use a digital buffer with pull-ups between the BCD switch and the R/2R network. The 74ALC746 can do this but it seems unlikely that I will find one in stock.
Use a BCD switch with both complement and non-complemented outputs.  Those are expensive switches!
Use an R/2R/4R/8R network and a constant current source.  Are there R/2R/4R/8R resistor networks?  This seems to be less energy efficient than #1.
Use a microcontroller.   That will work but a simple, purely hardware approach is preferred.

Do you have any suggestions?

Thank you


texts:
I am trying to setup USB communication with an STM32F446RE
It is a custom board where:

The clock source is an external 8Mhz quartz
There is a micro USB port with USB+ connected to PA12 and USB- connected to PA11

The external quartz is working (I can load a firmware that just blinks a led) but I fail to enumerate the USB device with below message in the computer syslog.
I am using mbed with the NUCLEO F446RE configuration, I just enabled USB in the target configuration (USE_USB_OTG_FS type)
Also, I noted that if I plug the board even without a firmware that is supposed to use USB, my computer tries to enumerate the device, however it shows a different message (like it's trying to enumerate a low-speed device instead of high-speed)
Do you have any idea/clue what could be going wrong?
Oct 23 19:13:51 destiny kernel: [4213209.733361] usb 1-10: new full-speed USB device number 17 using xhci_hcd
Oct 23 19:13:51 destiny kernel: [4213209.861500] usb 1-10: device descriptor read/64, error -71
Oct 23 19:13:51 destiny kernel: [4213210.097415] usb 1-10: device descriptor read/64, error -71
Oct 23 19:13:51 destiny kernel: [4213210.333311] usb 1-10: new full-speed USB device number 18 using xhci_hcd
Oct 23 19:13:51 destiny kernel: [4213210.461545] usb 1-10: device descriptor read/64, error -71
Oct 23 19:13:52 destiny kernel: [4213210.697528] usb 1-10: device descriptor read/64, error -71
Oct 23 19:13:52 destiny kernel: [4213210.805438] usb usb1-port10: attempt power cycle
Oct 23 19:13:52 destiny kernel: [4213211.461355] usb 1-10: new full-speed USB device number 19 using xhci_hcd
Oct 23 19:13:52 destiny kernel: [4213211.461721] usb 1-10: Device not responding to setup address.
Oct 23 19:13:53 destiny kernel: [4213211.669583] usb 1-10: Device not responding to setup address.
Oct 23 19:13:53 destiny kernel: [4213211.877357] usb 1-10: device not accepting address 19, error -71
Oct 23 19:13:53 destiny kernel: [4213212.005324] usb 1-10: new full-speed USB device number 20 using xhci_hcd
Oct 23 19:13:53 destiny kernel: [4213212.005568] usb 1-10: Device not responding to setup address.
Oct 23 19:13:53 destiny kernel: [4213212.213745] usb 1-10: Device not responding to setup address.
Oct 23 19:13:53 destiny kernel: [4213212.421346] usb 1-10: device not accepting address 20, error -71
Oct 23 19:13:53 destiny kernel: [4213212.421442] usb usb1-port10: unable to enumerate USB device

```


texts: Why does duty cycle seem relevant when calculating inductor current in boost converter circuit?

texts:
I've been working hard to understand boost converters and the role of inductors in the boost converter circuit.  I found a pretty good list of basic calculations from Texas Instruments and I started doing some back of the napkin calculations for the TPS61232.

My logic so far has been to say, roughly:

  If I need 5V at 1.2A, that's 6W of output.  If I get 80% efficiency
  I'll need 7.5W of input at 2.8V worst case . . . so I'll be pulling
  2.7A from the source.

As I read through that TI document, I noticed that D and (1 - D) show up pretty often in these calculations.

So, I computed D for my circuit:

$$ D = 1 - \frac{V_{in(min)} * η }{V_{out}} = 1 - \frac{2.8V * .8}{5V} = .552 $$

Then, I read about computing the ripple current:
$$ ΔI_{L} = \frac{V_{in(min)} * D}{f_{s} * L} = \frac{2.8V * .552}{2.0MHz * 1uH} = .7728A $$

The datasheet says the input voltage ripple is ±200 mV and the TI document says you can usually estimate inductor ripple to be 20% - 40% of the output current.  My calculation at 1.2A is .7728A which is about 60%; that seems kind of high, but I can't tell that I'm doing something wrong.  Maybe it's by design?  Maybe it's because they're more optimistic about their 90% efficiency?  Or, maybe it's based on their output current rating of 2.1A?

In any case, I wanted to know how much DC current the inductor needed to be rated for at various output currents, so I tried to come up with a formula.  I saw that the I(max out) formula uses ΔI(L)/2.  I assumed that's because the ripple is half above and half below V(in)?

So, I decided that something along these lines is probably pretty close:

$$ I_{L} = \frac{ΔI_{L}}{2} + \frac{V_{out} * I_{out}}{V_{in(min)} * η} $$

As I was factoring I(out) out, I realized that my formula could be expressed as to:

$$ I_{L} = \frac{ΔI_{L}}{2} + \frac{I_{out}}{1 - D} $$

So, I thought, "hey, there's that duty cycle again.  Why does it keep showing up?"  What is a duty cycle and why does it seem so important to switch mode power supply circuits?

Based on this formula, I looked at the effects of output current on the inductor current and came up with these:

$$ I_{L} = .3875A + \frac{1.2A}{.448} \approx 3.1A $$
$$ I_{L} = .3875A + \frac{0.75A}{.448} \approx 2.1A $$

Am I even in the ballpark here?  If I am, how much should I derate inductors?  I mean, if I'm looking for 3.1A in the inductor, should I look for a thermal and saturation DC rating greater than, say, 130% of 3.1A?  200%?


texts:
Is it possible for an out-of-control (e.g. due to stack corruption) user application to inadvertently invoke the bootloader sector code in an AVR (e.g. ATmega1284p)? Said differently, is it possible for self programming instructions in the bootloader sector to execute at any other time but on a reset?

What I'm worried about is runaway code inspiring the bootloader to corrupt the application image. If that's plausible, what if anything can be done to prevent it or at least minimize the impact of it happening.


texts:
We are designing a RF link (2GFSK) using the CC1125, to replace and older system.

The older system uses NRZI data encoding with bit stuffing.

Bit stuffing is used to remove the present of stop flag (0x7E) data and to avoid having too many 1's in a sequence.

An older RF engineer told me that bit stuffing where important, not only for synchronization, but also because the receiver adjust to the center of the two frequencies, to acheive optimum reception. It is therefor sensitive to a long sequence of equal bits, as it would track away from center and towards the frequency f0 or f1, depending on the sequence.

But, in the case of CC1125, or any orher RF chip, how do I calculate the effect on receiver sensitivity (BER) due to a long sequence of equal bits.

Example: If we send 24-bit preamble, with 32 bytes payload, how do I calculate the maximum number of allowed equal bits, that would cause some precent error. ?


texts: Can't uploading on Atmega328P-MU after a while

texts:
I am having a problem to upload sketches via Arduino IDE on the Atmega328P-MU chip on a custom board.
Shortly after I have mounted the chip on the board everything works fine. I can upload a bootloader and then sketches. After a certain time, suddenly everything seems to freeze(LED-blinking, etc.). I found out that if I heat up the chip again, everything works fine for another little while again (2-5min). This procedure is relatively reproducible for me.
I have tried it with many chips from two different suppliers.
Note that I can just "reset" the chip to a working state, if I heat it up and upload a new bootloader.
My guess is that I might not even heat up the chip only, but instead another component and therefore changing its values to work properly. Is that a possibility? What values of the other components might cause that behaviour? Though, when trying to heat up just other parts nothing will work.
Schematics for chip can be found right here.


texts:
I have an old settop box, model - humax nd 1000c. I no longer use it for my TV since the city I've moved to doesnt have the relevant service provider (afaik).

I want to try and hack into the box to just fiddle around with its OS (I believe it to be some flavor of embedded linux) and use it in my robotics projects if possible. I've done a large amount of surfing on the web but haven't really found anything I can use to get ahead. Plus, the fact that the box doesnt have a serial/parallel/usb out compounds my problem. It just has a i/p for a co-ax cable (I assume) and RCA o/p's. Is there any way I can interface with this guy?

Let me know if a picture or other details will help.


texts: Do they make variable isolation transformers?

texts:
As I start to set up my work bench, I've been looking at various isolation transformers, and I wondered if they have ones that use a variac as a secondary?
I know variacs are autotransformers so it's just one winding, but couldnt that mechanism be implemented as a secondary winding in a regular transformer? In other words it would be a 1:1 transformer with an adjustable variable center-tap? Thanks!


texts:
I made this circuit to power up an ac appliance using a weak mecahnical switch:

R1 = 1K

U1 = Diac

Q1 = BTB16-800 BW

The appliance connects between OUT and NEUTRAL (not shown).

While testing, I Disconnected LIVE from MT2 of the triac and connected it directly to left end of R1 and to my surprise, the load got powered up. Resistor was heating up as well as expected.

Is this an expected behavior? How can I safeguard my circuit from such accidental connections? Will increasing the value of R1 be enough?


texts: What is the easiest way to identify what leg of a 220V panel a 110v outlet is on?

texts: I need to connect two devices on the same leg so they can communicate. Basically I am trying to send my internet to my remote garage over the power line. I need to have them both on the same leg in order for it to work. I have a 220v 100A line from my house to the garage. I need to plug one device in my computer room outlet and one in my garage in an outlet wired to the same leg as the one in the house. How can I easily identify which is which?


texts: approximation of a digital signal using the harmonic

texts:
I'm new to EE, still struggling in understanding some basic concepts. I'm reading a book which says about approximation:

To make the shape of the analog signal look more like that of a digital signal, we need to add more harmonics of the frequencies. We need to increase the bandwidth. We can
increase the bandwidth to 3N/2, 5N/2, 7N/2, and so on. The picture belows shows the effect of this increase for one of the worst cases, the pattern 010.  We use the first, third, and fifth harmonics. The required bandwidth is now 5N/2, the difference between the lowest frequency 0 and
the highest frequency 5N/2.

I'm confused, below is my questions:

Q1-why we have to third, and fifth harmonics? Can't we use second, fourth harmonics? does it have to be odd harmonics?

Q2-I'm from CS background, can I put the approximation in this way:

To simulate the pattern 010 in a channel whose bandwidth is 3N/2(to get more precise result than N/2), does it mean we need to send two analog signals simultaneously, the first analog signal's frequency to be N/2, the second signal's frequency to be 3N/2, and let they interfere with each other, and the result would be an better approximation of a digital signal 010?

Is my understanding correct


texts: AC, Negative instantaneous power x Wh consumption measurement

texts: If a load is connected to an AC power source, and the current wave on it is shifted from the voltage wave of the power source, for some periods of time the instantaneous real power (Vinst x Iinst) will give a negative instantaneous power value, due the voltage value be positive and the current value be negative at the same instant, or vice versa. How this "negative power" affect the Wh real power consumption measurement? How it accounts in cumulative energy measurement?


texts:
I have a 40W soldering iron and using 60/40 rosin core. I'm soldering wires onto a LED light strip (WS2812B) but the heat isn't strong enough and I might be doing things the wrong way.
When I touch the iron tip to the LED pad, it doesn't heat up enough for the solder to melt on the pad. I have to either melt the solder onto the iron tip and let it 'flow' down onto the pad, or I have to use the flat side of the iron tip to heat it up.
I could let the iron heat up for 15 minutes, touch the tip to the pad, and by the time it heat up enough to melt the solder, the LED pixel nearest to it will usually be destroyed.
The tip is not all that sharp, it's got a visibly round nose.
I'm sure there's a technique failure here, but I'm not sure what, and are there other tips I could use for this application that could make soldering work easier?


texts: AVRDUDE does not recognize USBasp device

texts:
I'm am having issues with my USBasp programmer (Windows 10). I installed the WinUSB driver using zadig 2.4.

When I run AVR dude with the following parameters

avrdude -c USBasp -p m32u4 -u -U flash:w:justahex.ino.hex:i

It immediately returns with this error:

avrdude: error: could not find USB device with vid=0x16c0 pid=0x5dc vendor='www.fischl.de' product='USBasp'

It looks for a USB device with vendor ID "0x16c0" and product ID "0x5dc". This is the correct set of IDs according to Zadig:

Also the device manager seems to find the device without issues:

When I google the topic I see a lot of forums where people have issues getting their USBasp device working under windows 10. But they mostly are having issues with the libusb /WinUSB drivers (Which seems to be fine in my case thanks to the Zadig tool).

So I find myself stuck in getting further. Are there any other things I can check? Or is the device broken somehow (which would surprise me as it does get installed properly in windows)


texts:
I have a KXO-V97T 8MHz crystal. It looks like it's an unusual crystal.
The datasheet contains the following pinout:

1 - h or open
2 - GND
3 - OUTPUT
4 - VCC

A crystal with VCC? I am surprised. The resistance between 2 and 4 is about 80МОhm.
I want to connect the crystal with a STM32 3v3, STM32L152.

Can you show the connection diagram of a similar crystal and STM32?
Can this crystal work with an STM32L152?
Can VCC be 3 volts?
How can I connect this crystal to an STM2? Crystals have one output, but the chip has two pins for the crystal.
How to calculate a capacitor value?


texts: Can you identify this substance on PCB pads?

texts: Can anyone identify what's going on on the PCB pads in the following photo? This is from an automobile ECU that had to be reprogrammed and so was opened and resealed a few days ago. Thermal (silver) paste was applied on the other edge of the PCB (not pictured), RTV silicon (ultra black) was used to reseal the unit. Unit worked fine for two days then started to exhibit issues (very bad misfiring on one cylinder). Reopening the unit revealed that the pictured substance had developed on several pins on one edge of the PCB. Substance seems to be conductive as scraping it off eliminated the ECU misfire malfunction. Substance flakes off easily with light pressure. The ECU was exposed to humidity (car wash) and sulfur (exhaust leak). As you can imagine, it wasn't sealed as well as it should have been.


texts: Equality 4 bit with 4 bit by IC 74181 (ALU)

texts:
Pin 14 in IC 74181 when 2 numbers (4bit) equal this pin must be high.

This pin is open collector. I connect this pin to Vcc & Res but not high or red.

I've created this circuit in Protheus.

What should I do high on this pin?


texts:
I've connected an Arduino with a LCD1602. I've followed this exact tutorial:
Link to the tutorial
Whenever I see my LCD at a right angle (upfront) I can't see anything. But whenever I see my screen sideways from the top I can see the characters.
What's wrong?


texts: Analogue Hall sensored brushless outrunner motor position control

texts:
I would like to produce a low cost high power:weight servo drive using a brushless outrunner motor, like those use in radio control planes:

Some of these motors leak enough magnetic flux out the sides that Hall sensors can detect it. Since, this is supposed to be a low-cost design, I'd like those same Hall sensors to act as accurate position sensors, so that I can do sinusoidal current control and high resolution position control.

Question: If I set up the three current controllers to drive current proportional to the (correctly scaled and offset) outputs from the analogue Hall sensors, will this produce a smooth motion? Would I need to phase shift the Hall signals depending on the speed of the motor?

Has anyone done this before? I can't seem to find anyone publishing such a project online, which makes me wonder...


texts: Is Transmission Line Reflection Frequency Dependent?

texts:
I'm currently sending high speed serial over a coax cable. I've got an oscilloscope hooked up (on the load end) trying to watch the clock pulse signal. I've got a 10 ft coax cable with a 12.5 Mhz clock signal. I'm unsure of the coax impedance and the load impedance.

The clock signal appears to be deformed. I'm curious if this deformation is due to the cable acting like a transmission line and specifically due to transmission line reflection.. However, I'm unsure on some of the properties of the reflection.

Is the reflection of a signal frequency dependent? Thus the superposition of all of the frequencies in the square wave would be phase adjusted and report a bad clock signal?


texts: Converting 32 bit 2's complement to decimal number

texts:
I have data coming from a V9261F energy measuring chip (link to datasheet), that sends it data through a UART to my Arduino microcontroller. When I read register 0x0119, I read the active power measured by the chip. But the problem is that this feedback is in 32 bits 2's complement and I can not decode it.

Starting from the 4th byte in the stream are the data bytes in which the measured variables are stored (see data sheet pg 56 - 57). For reading register 0x0119, this should be in databyte 10 - 11 - 12 and 13 (D1) respectively 0x55, 0xE7, 0x0E and for databyte 13 0x00.

So the feedback for the active power all the bytes combined I have is 0x000EE755 -> subtract 1 (for 1 complement) = 0x000EE754 -> invert it to become decimal number = 0xFFF118AB (4293990571 dec).
But this insane big number should only represent an active power of 6.2 Watts.

What do I do wrong with converting from the 2's complement to decimal? How should this represent 6.2 watt?


texts: Weird behavior on a pull-down resistor in my design

texts:
I am using a 74LS173 D Flip Flop that has some control lines that may be floating at times before they are asserted. To avoid the control line from doing something I don’t want it to do doing this floating state, I am using pull up / down resistors as necessary to not “assert” the line. For example, on the 74LS173 there is an MR signal that will clear the flip flops if it is HIGH, so that line is pulled down with a 10K resistor.

The strange behavior I am seeing is that my breadboarded version of the attached schematic works as I would expect. If I disconnect the MR line, the 10K pull down keeps the line perfectly low. However when using an SOIC version of the same chip on my PCB, the line jumps to 1V when I disconnect the MR line.

Note I have removed the 74LS245 just to isolate to the 74LS173 and the behavior does not change.

I’ve attached my schematic and the analog capture of the MR line using my DLA.

Also, note the external signal driving the MR signal on the 74LS173 is named CLR on the schematic.


texts:
I am all out of MCU pins and would like to add a voltage sense function. This will only be necessary when the device first starts up. I have a somewhat sensitive signal already connected to my ADC, but I would like to add my voltage sense signal to this original signal as follows:

simulate this circuit – Schematic created using CircuitLab

When the device first starts up, there will be negligible potential on the signal line. This means I should measure 3 volts, scaling it up in software by 50/3 to get my supply voltage reading. When the signal circuitry powers up, will the effect of the supply sense divider be 100 times smaller than that of the signal because of the resistance ratios? Is such an approach unlikely to succeed  for other reasons I have overlooked?

Edit: Forgot to mention that the signal is high-impedance before I fire up that part of the circuit.


texts:
USB2.0 supports 0.5A for a downstream port. This means that the controller or hub can support a 0.5Amp USB load.I am not referring to the speed now. Suppose I have a load that runs on USB 2.0 speed but requires higher current, say 0.8Amps.

Can I not use a regulator on my hub( this will be a custom hub) that will provide the necessary power ? Is there any impact on the wire gauge in case of USB 2.0 ? USB cables usually carry 28AWG wires. They are sufficient for almost 1.4Amps. So would that not be sufficient ?

In that case why is there a cap/standard of 0.5Amps on the power for any USB slot ? Should it not technically just limit itself to speed and not power ?


texts: Firmware only runs when I press the reset button

texts:
I've created a board using the STM32F405R6T6.

I am experiencing some problems: after I program the firmware onto the microcontroller, withdraw the power and reinsert, the firmware only starts to run when I press the reset button.

In the debug configuration it works: I program the chip and the code starts running. But when I program the release-configuration code I need to press the reset button.

I think it might be something related to the bootloader circuit, or even the proximity of reset capacitor. I've attached the circuits below, if someone has already gone through it or has a hint how could solve the problem, I'll be extremely grateful.

Sometimes during programming it also gives the following error "error erasing flash with vflasherase packet". Sometimes the error disappeared when activating boot, but not always.

SOLUTION:I found the problem. I currently have a switched source (L7981A) that converts the input voltage. The time for the voltage to go from 0V to 3.3V was 35ms (I looked at the oscilloscope). Removing this switched source and externally feeding system works perfectly. I'll have to rethink the source with the L7981 and see why it takes so long to get to the output voltage.


texts: Via on pad for bga decoupling. Is this ok when hand soldering?

texts:
I have understood that via on pad is bad for automatic assembly processes, but can be fine for hand soldering, since it is easy to compensate for the solder that wicks into the via.
I am doing a small hobby project with a BGA FPGA on the component side. Dog bone pattern, no buried/blind vias. I can get the BGA pre-assembled, but not decoupling caps on the bottom side. Filled vias is not an option.
In order to avoid 0201 caps, I would need to put the bottom bypass caps over the dog bone vias. Is there any risk that hand soldering the bottom pads may cause solder to pop up under the BGA and cause a short? Or is there any other reason not to do this in these circumstances?


texts: A question on temperature regulation of a nichrome wire

texts:
A heating-nichrome-wire will be heated by conducting unipolar PWM currents switched by a MOSFET with an adjustable duty cycle. I will first calculate the heat required from this calculator and find the current required. This will be the target current in the rest of my setup. In that formula the current is continuous DC. In my case should I calculate the Irms of the current?

I will sense the current as in the illustration below:

Above the green section is basically two op amps which will low-pass-filter/integrate and amplify the voltage across the shunt resistor to be read by ADC of the uC. So I can calculate the current knowing the op amps' gain and the Rshunt values. For better accuracy I will subtract the offset(coming from the input offset voltages) at the beginning when the MOSFET is off.

So since the current is pulsed and I will send the integral of it to the ADC. What I actually send is the data about the average voltage or current values for the Rshunt.

In the illustration above I tried to simplify the scenario. First the temperature will be set as in Figure1 and I want the temperature to be regulated when the wire gets shortened or longer. I want the nichrome-heating-wire to be at the same temperature when it is shortened or extended.

So logically if the wire length changes, the duty cycle also should be adjusted by the uC. Otherwise it will pass excessive current or not enough current. The data read by the ADC somehow should be used to adjust the duty cycle. This is the programming side.

My question is:

Is the hotwire's temperature proportional to the Iavg or Irms.
If it is proportional to I_avg. I just need to adjust the duty cycle such that it produces the same Iavg or Vout which was set at the beginning. But if the temperature is directly proportional to Irms than I should adjust the duty cycle such that it produces the same Irms which was set at the beginning.

In my case, regulating the PWM current's average or rms value to a pre-set value should be used?

And is that all? Is temperature only related to current in this case? Length has no significant effect? (Electrical power changes by the length of the wire if the current is kept the same; but in this case I want to keep the temperature same in any length)

Edit

An absolute temperature measuring IC or sensor would be more reliable if one is not sure every detail is not ignored. Is there an IC which can measure the temperature of the wire or any IR sensor ect any other direct temperature measuring method?


texts:
I have designed a common-emitter RF amplifier, with input and output impedance matched for my load and source impedance. I have used Smith Chart for the matching.

The matching is good for the designed frequency, but when using other frequencies the matching is poor (I get large reflections in my spice simulation).

I know that wideband matching (one that works for all frequencies) is not possible.

But if I want to make a fair matching in a frequency band, say 200 MHz to 600 MHz, is there any good technique for this?
(Except just trial and error with the Smith Chart).


texts: find a point on root locus for specific damping ratio?

texts:
Although I have seen many types of root locus plots which have some curved behavior. I cannot find the poles for which my system has a given damping ration of \$ \zeta = 0.59 \$. I need to somehow find the intersection point between the root locus path and the damping ration line by hand, without using MATLAB.
for the following 3rd order system:
$$ G(s)= \frac{K}{s(s+3)(s+7)}. $$


texts: How to wire up the XP Power 8-pin isolated DC-DC converter?

texts:
I want to use the XP Power IEU0312S12 12V DC-DC converter but can't see how I should wire this.

What do they mean with "Single" and "Dual" ?
Can I put 12V on Pin 1 and 4 and then get the output on Pin 5 and 7 without connecting any external component or doing something else, is that it ?
What do they mean with "Common" ?

The datasheet can be found here


texts: Voltage spikes when driving DC motor with N-channel MOSFET

texts:
I'm trying to drive a DC motor (12V, 100W) with MOSFET IRFP054N. PWM frequency is 25 kHz. Here's the schematic:

I know DSEI120-12A is not the best diode for this but I don't have any better right now. 3A Schottky diodes, which I also tried, get hot very fast.

Here are scope waveforms (A = MOSFET drain (blue), B = gate drive (red)):

Smaller duty cycle:

I'm getting a voltage spike at MOSFET turn-off which lasts about 150 ns and has an amplitude of max. 60 V. The amplitude stays whether I increase duty cycle, voltage, or load on the motor. The width of the spike depends on the load on motor (probably depends on current).

I've tried:

Increasing gate resistor to 57Ω for slower MOSFET turn-off.
Adding Schkottky diodes (SR3100, 3A) across motor and MOSFET.
Putting various capacitors across DC link and motor. This sometimes helps when operating with low duty cycle and low voltage, but when power is increased spike is present again.

None of this things helps to completely eliminate the spike. Interesting thing: the spike doesn't destroy the MOSFET (since it's rated for 55 V), but I would like to do this driver correctly.

I'm looking for suggestions of what else to try, and why this spike is limited to 60 V.

Update:
I think 1 mF electrolytic cap couldn't absorb the energy spike from the motor. Now I've added a 2.2 uF film capacitor on 12V line, 200 nF ceramic cap on the motor, and 100 nF ceramic cap across MOSFET.

This helped to lower the spike although now I get ringing at turn off - probably need to improve snubber on MOSFET. But the voltage amplitude is much lower (30 - 40 V at load).


texts:
I've been researching how to design a circuit for a two-wire switching sensor.

It can be operated as a PNP or NPN switch. I need to design a circuit to detect whether the sensor is switched or not.

Sensor specs

The sensor has 1mA current when it's off, and minimum 5mA when on. I'm using 24V.

I think I can design the sensor like this:

I'm going to put a load of 4K ohm:

off state: V=IR = 1mA * 4K = 4 volt across resistor
on state : V=IR = 5mA * 4K = 20 volt across resisor

simulate this circuit – Schematic created using CircuitLab

Is that right? But then what is the significance of:
internal voltage drop 5V or less?
In the off state the resistor would have a voltage drop of 4V which means the sensor will have 20V > internal drop voltage. Will this fry it?


texts: Do they make anti-parallel diodes in 2-lead packages?

texts:
Sometimes diodes in an anti-parallel configuration are used on the inputs to high-gain instrumentation amplifiers in order to protect against large differential voltages.
Does anyone know if the industry produces 2-pin packages in this kind of configuration? If so, what is the name of this configuration?

simulate this circuit – Schematic created using CircuitLab


texts: I have recently purchased a 10W polycrystalline solar panel with 30A battery clips, a 20A solar charge controller (intelligent regulator with 12V/24V USB display) and a 12V 7Amp lead acid rechargeable battery. Setup seems simple enough but the charge controller did not come with instructions. My concern is that if I hook up the 3 in a circuit that battery will overcharge and gas. I want to charge it in my room (medium size, not large and not small) but I am not sure how to prevent overcharging. What can I do and is there cause for concern? Can I incorporate an LED to burn off excess charge or something like that? Will the charge controller prevent overcharging? What happens when the battery is full and the panel is still delivering energy? Thoughts? Thank you!


texts:
I am planning to setup multiple esp8266 in my home to control electric appliances offline using browser.

I want to connect to single esp8266 as a controller(Master) using browser/mobile and all other esp8266 as Slave with Master so that I should communicate to Master and then it will further communicate to the interested Slave. So the communication must be Browser/Mobile -> Master -> Interested Slave.

Approaches I am aware and/or found on Google are

MQTT - https://github.com/martin-ger/uMQTTBroker
Mesh - https://github.com/Coopdis/easyMesh
Client-Server - default example provided in Arduino IDE for client and server

I already tried to all of the above methodology that I am aware of but for some reason none of these found to be useful for my application or I must have doing something wrong hence expected help from community because the scenario(one to many or vice versa) I am trying to implement is obvious and most of you must have done this.

Challenges I am facing implementing this idea with mentioned approaches are:

MQTT : (I don't want to use RaspberryPI) I am using library uMQTT broker on master and subscriber on all other slaves and obvious client app(MQTT lens) on windows desktop app so that each slave will listen to specific topic and work as expected. Challenge: uMQTT broker on esp8266 is only able to connect to one subscriber at a time, pretty strange

Mesh : I used MESH library so that I could be connect to master and then master could be connected to all other slave Challenge: In Mesh, I am not able to identify specific slave may/may not be with chip id so that to be control from master. Apart from this I am only able to connect single slave and no other slaves are even searchable

Client-Server: In this approach what I understood is, unless and until client request to server, server don't respond it means I cannot have single server and multiple client because I want to serve to clients so the instruction will be in one direction only(may be response will be in another direction i.e. request = browser->master->slave and response = browser<-master<-slave) hence this approach will not serve my purpose. There are so many examples available collecting data from sensor being slave and then sending that data to specific server esp8266 which is not applicable for my case.

So I was planning for creating multiple server(Slave) and connect then with single client(Master). Here client(Master) will act like server and client both. Now here I will instruct client and it will instruct interested server. But this approach is not yet practically tried and I don't know whether it is doable or a good approach to go for.

Apart from this one more approach is TCP IP communication but I don't know whether this will solve my purpose or not.

Please help me understanding the best case scenario to go for as per my application. I am using default examples for testing purpose with slight modifications.


texts: Understanding battery capacity with solenoid application

texts:
I am working on early stage of product design and was hoping I could get some guidance/ help.

My product will use between 12 and 15 individual, small (less than 1" diameter) rotational, self-returning solenoids.

I do not yet know the force requirements, but anticipate they will be relatively modest.

When power is applied to the solenoids, they will rotate (45-90 degrees).  When power is cut, they will need to return to their starting position.

There will be a single power on/off switch and we want all the solenoids to always engage and dis-engage together.

I am hoping that its possible to run all of the solenoids from one battery or set of batteries.

The solenoids would be engaged for approximately 5 seconds at a time.  I am trying to understand power requirements and and also to figure out how many times could the set of solenoids be engaged before batteries are drained

The Solenoid I am looking at requires requires .93w

If I use a single D battery with 13,000 mAh capacity to power all 15 solenoids in the device, does that mean I should be able to power the 15 solenoids in the device approximately 931 times (13,000/15/.93)

I do not understand how to take into consideration that the solenoids will be powered up for only approx. 5 seconds at a time and how the hourly value in the mAh should be considered.

Thank you very much,

Jonathan


texts: Combining resistors in series with a voltage source in between

texts: Am I allowed to combine the resistor R and coil Xl as if they were right next to each other? I want to make this into a current generator, without many transformations.


texts: What are the things to watch out for when switching from AVRs to Cortex M3?

texts:
I've just recently gotten my Cortex M3 (LPC1343) up and running, following Microbuilder's instructions to get a GNU C compiler working for it. I've run some example code and in general, the code seems to be a lot more complex than what I've been used to with AVR's.

What are the major differences in programming AVR's (8-bit ATMEGAs) and Cortex M3's? Anything I should watch out for?


texts: How to observe transfer characteristics of MOSFET?

texts:
I have built a simple Mosfet circuit now I want to check the Vds vs Id characteristics.

But the problem is when the Vcc(Supply) and Vgs(Gate to Source) (according to the following characteristics) is fixed how can I increase Vds to observe the (Vds vs Id) characteristics?


texts: Z80 Simple Computer Troubleshooting: IORQ pin not going low

texts:
I'm following the instructions at http://www.reocities.com/SiliconValley/2072/z80proj1.htm to build a "proof of concept" Z80-based computer. I have wired everything on my breadboard, and programmed the EEPROM with the following program (first instruction is at address 0):

LD A,#FF
OUT (#02),A
OUT (#03),A
LD A,#01
OUT (#00),A
JP #000A

This program should just turn on an LED wired to the I/O chip (a 6522 VIA) by setting a port output pin high; however, nothing is happening. I verified that the program in the EEPROM is the one posted here, and that I used the correct opcode values. I have a 1 Hz clock signal, and can "see" activity on the Z80 address and data pins with my logic tester. I also double-checked the wiring, but still nothing.

Working backwards, I noticed the I/O output pin connected to the LED never changes to high. I also noticed that the phase-2 clock on the I/O chip is always low (i.e. it doesn't oscillate); this explains the LED not lighting, since the I/O chip only reads on the rising edge. Per the instructions, I have connected this clock to the IORQ pin of the Z80 through an inverter; however, in my project, the IORQ pin is always high. From the Z80 datasheet, this pin should go low when a port is addressed, but this isn't happening. So I'm stuck, and not sure how to proceed from here.

Am I correct in thinking the IORQ pin should go low during OUT instruction? If so, what steps should I take to figure out why this isn't happening? Other theories on what may be wrong are also welcome.

Thanks in advance!


texts: Is it possible to run a 3ph 220/440V motor on a standard 120/240V home circuit?

texts:
I have only basic knowledge in electronics and am looking for advice.
I have the opportunity to get a really good deal on a Band Saw, a Jet J8203K. A manual for this saw can be found here http://pdfstream.manualsonline.com/9/964a3ee1-de46-4476-9a6b-a82d8d2d1b9b.pdf
The problem is that this is an industrial quality saw with a 3ph motor supplied with 220/440V. Currently my workshop is powered with a long extension cord running from the kitchen with a 120/240V connection. As it is my table saw has tripped the 20A breaker when other things are running in the kitchen.
Is there a safe way to operate this saw given my circumstances? Are there converters that will step up 240V to 440V? I'm not in a position to afford major electrical updates.
In fact, since I'm asking, is it unsafe to be operating my 14A table saw on a 20A circuit with a 100ft extension cord?
Thanks for any/ all advice!


texts: Signal to the audio jack of a smart phone

texts:
I have a 3.3 V square wave that consists of groups of 5 pulses at either 12.5 khz and 15.625 khz. Each group of 5 pulses represents either a 1 or a 0. I would like this signal to be passed to a smartphone through the microphone input.

From what I have read (please correct me if I am wrong) the voltage will need to come down to a few mV, the signal will need to be AC coupled. Will the phone be able to consistently differentiate between the frequencies or will some sort of frequency change be required?

What circuitry would be recommended for accomplishing this task?


texts: Building a simple mcu-driven array of LEDs

texts:
I'm planning to put together a simple shift-register driven array of LEDs as a first project, something akin to this:

But using a 74HC595 shift register (two, eventually) and a transistor to drive each individual LED alone.

It's been twenty years since my (limited) formal electronics education, and I have a few questions:

I believe understand why the resistors in line with the LEDs are necessary, because an LED essentially behaves like a short circuit, and will draw a lot of current from the register, right up until either it dies or the register dies. Is this correct?
Why the "1K or 2.2K" resistor on the base of the transistor? Will I need one on each of the bases? Is this to limit the current between the base and emitter of the transistors? How do I know what value to use?
Should I use 2N2222 transistors or should I use something like a 2N3904? What is the difference, other than the 2N2222 seems to have a much higher collector-emitter capacity? Does that affect the choice of resistor I need?


texts: What is the meaning of "Demodulation in quadrature sense"?

texts:
With regard to stepped frequency radar, what does it mean when we say that the transmitted signal is "demodulated in a quadrature sense"?

The property of interest in this kind of radar is the phase difference. We basically obtain a phase delayed version of the Tx signal on receiving.

How does "demodulating in I/Q sense" help convert the phase difference into distance information?

I understand basic digital I/Q modulation.

Any help is highly appreciated!

Thanks,


texts: Electrical Characteristic of a piezo buzzer

texts:
I stumbled upon this piezo buzzer and I don't know how to interpret its specifications. What's the difference between

Rated Voltage (Vp-p Square Wave): 5Vp-p

and

Operating Voltage: 1 to 20 Vp-p

?


texts: Why there is RC filter between optocoupler and schmitt trigger?

texts:
I want to use schmitt trigger after optocoupler to have clean signal and connect it to MCU.why there is RC filter between optocoupler and schmitt trigger in many designs?

How should i connect optocoupler to schmitt trigger ic (74hc14)?


texts: Why the power line interference harmonics appear gaussian?

texts:
I have a recorded signal from a data acquisition system.
I am getting this noise in my signal:

The picture shows the FFT of the signal. I checked the frequencies of the noise and they are 50 Hz apart which are the harmonics of 50Hz. The signal is not filtered, it is a raw signal without processing.
I do not understand why or what could cause the harmonics to appear as shown below, I would've expected the harmonics, at least, the odd ones to decrease as the frequency increases but they are not.
Is this noise normal? What could cause it to appear as so? Could it be pure hardware problem in the DAQ?


texts: Do active PZT audio buzzers (with built-in driver) create dangerous spikes on power supply?

texts:
I am planning to add a active piezo element audio buzzer with built-in driver (BESTAR BPT-14X or LOUDITY LD-BZEL-PB04-1408 ) to my recent quite complex MCU project.

These buzzers come with built in generators, so can be driven directly by DC voltage. I have a square pulse output from PNP transistor that I also monitor with MCU. I would like to add acoustic signaller here - so connect buzzer in parallel.

I heard from many sources (sadly mostly guesses) that these active PZT come with internal coil, so they can cause large voltage spikes on their positive pin (in my case connected also to MCU input - so any spike could easily kill MCU).
Is that a fact? In datasheets there are no mentions about this. I would test this, but my scope in not in working condition right now... If this is correct, what kind of protection would you recommend? Schottky diode is probably wrong since I am drivnig with 3,3V. Maybe TVS or zenr diode?


texts:
I'm a college student and I was supposed to draw the Bode-plot of the following resonant circuit.

I obtained this.

My questions are: shouldn't I have obtained a bell-shaped curve? How can I find the resonance frequency using the plot itself?

Thanks for your attention.


texts: Free circuit simulator for educational purposes

texts:
I am looking for a free circuit simulator for educational purposes. My requirements are:

Visual ("draw a circuit diagram, click simulate")
It should contain light bulbs as circuit components such that

2.1. They become (visually) brighter if you apply more power

2.2. You can change the manufacturer specs for example "3.5V,0,2A"
It should contain swiches, npn-transistors, diodes and LEDs as well (the LEDs should react to interactive changes in the simulation)

Any recommodations for this? It would be nice if the simulator runs under Linux, but that's not a strict requirement.


texts: calculating the average power using the oscilloscope

texts:
I am trying to measure the real power of an inductor, and in the manual it is said that I have to connect a resistor with low resistance to the inductor and then see the voltage difference between the current and voltage.

Question: Why do I need a resistor? Why don't we just connect the oscilloscope across the inductor and see the phase shift?


texts:
I am trying to implement a quality check for our PCBs. We have a pick and place machine and a vapour solder machine. But, unfortunately, even after optical inspection and such, we end up with a lot of tombstones.
The worst are the 0201 package passives. They are so small that even after manual inspection, many are assumed to be ok as they are a tiny speck.
Is there any documentation that can guide me for a thorough quality check of inhouse PCBs please.
I am sure that PCB houses have their own quality checks and protocols. Can anyone share a document that details out the process please.
What are the testing and quality control standards implemented by PCB assembly houses ?


texts:
Currently I'm building the electric part in my converted RV. I got all components that I need and want to start to wire them now. But my biggest lack of understanding is the grounding part.

The power inverter needs to be grounded, that's for sure, and is mentioned in the manual. Grounding the AC breaker box is for sure, just because it's 120V and needs to be grounded. But I'm unsure about grounding the battery bank. I asked an electrician and he told me that I don't need to ground my battery bank. But after a lot of research I found many diagrams online where the battery bank is grounded.

So my questions:

Do I need to ground my battery bank? (2x 12V GEL Batteries connected in parallel)
When doing this, will I have problems with the lights, heater etc. of my RV? Everything is just connected with a plus wire and grounded to the metal frame. My starter batteries are grounded to the frame as well.
When doing this, which cable size should I choose? Mostly all other components are wired with short 4 AWG cables. But the grounding wire will have a length of 7 feet.
Can I ground the AC breaker box on the same metal frame as the other components? For my understanding I've the 12V minus and 120V grounding connected on the same place. Is this possible?!
The manual of my solar charger mentioned that the charger is positive grounded and when I have a negative grounding system I shouldn't ground it. So I don't need to ground it? I attached a screenshot of the manual.

I'll appreciate your help.


texts:
I have the following parameters. Now I want to calculate the VAh for he online UPS.
Input:
Input Voltage Range (Load < 50%):   118 ~ 295 V (± 5 V)
Input Voltage range ((Load > 50%)): 160 ~ 295 V (± 5 V)
Frequency:  40 ~ 70 Hz
Power Factor    ≥ 0.99 @ full load
Battery
DC Voltage  72 V (6* 7.0 Ah battery inside)
Charge current  1.5 amps
UPS Overload / UPS Short-Circuit    110% / 300%
Output
Voltage Range   208 / 220 / 230 / 240 V AC
Frequency Range (Synchronized Range)    47 ~ 53 Hz or 57 ~ 63 Hz


texts: Is noise in a TL494 based push-pull converter causing low duty cycle?

texts:
I have assembled a push-pull converter based on a TL494. Here is the circuit

simulate this circuit – Schematic created using CircuitLab

V1 is a 12 volt battery, V2 is the reference regulator in the TL494.

Not shown are two 1000 ohm resistors connecting Pin 1 (1IN+) and Pin 2(1IN-) to V_ref and ground. This disables one of the error amplifiers.

I have temporarily disabled R11 by shorting it.

I have temporarily disabled the other error amplifier by shorting R6.

The diode D1 and the capacitor C1 are a protection network for the MOSFET. The same exists on M2 but is not depicted for brevity.

Varying R9 allows the operating frequency to be changed.

XFRM1 is a small coil I made with 20 turns total on the primary and 10 turns on the secondary. The voltage should be approximately unity. R10 is the load in this case, I also have a LED and a resistor to visually indicate the presence of current.

Powering up this circuit heats R10, so it works. I've also looked at both gates on the MOSFETs and they are actually relatively clean. The problem is I cannot get the dead time to an acceptable value. The duty cycle never goes above 75%. I was concerned I was getting noise from a switching power supply, so that is why V1 is a battery. I thought perhaps that voltage induced into the circuit from XFMR1 was causing issues, so I disconnected the supply from V1. The duty cycle does not change.

I scoped V1 and V2 and found noise. There is also noise on the ramp oscillator, one leg of C2. To try and eliminate this I added a 10 pF cap directly between VCC and GND on the chip. I also added a 20nF cap to V1 down on the board. I've also tried temporarily adding other capacitors  of various values with no change. All the way from 10 pF up to 47 nF.

In the scope traces below I am triggering the scope on CH1, the gate of one of the MOSFETs.

Here is the scope shot of V1 with AC coupling

Here is the scope shot of V2 (the reference regulator) with AC coupling

Here is the scope shot of the ramp oscillator

Here is the scope shot of the dead time control (DTC) pin

Here is the scope shot of the ground pin on the chip

As you can see, the MOSFET gate voltage does not change until the ramp oscillator is about 25% of the along its oscillation. Is the noise in the circuit the cause of this, or should I be checking elsewhere? What are the possible sources of the noise in this circuit? Keep in mind I have XFMR disconnected from V1 in all the above scope shots. So this circuit is only charging and discharging the gates.

Here is a physical shot of the setup

Update

I disconnected the gates of the MOSFETs, this reduces the current in the circuit to almost zero. This should eliminate the opportunity for any noise induced the from high currents in the gate circuits. I measured the emitters of the TL494 directly with my scope. I see the same behavior, so something other than noise from the gate current is preventing the correct operation of the TL494.


texts:
Could someone explain what "bias" is.

And why do some devices need an external bias resistor?


texts: How do I calculate the terminal-to-terminal resistance and capacitance from an impedance matrix?

texts:
If I have a circuit with \$N\$ ports (and therefore \$2N\$ terminals), how can I calculate the terminal-to-terminal resistance and capacitance from a given impedance matrix \$Z\$? We can assume a shared ground for all ports.
Edit: I specifically mean the terminals of two different ports.


texts: 2 / 4 quadrant switches - how can current have opposite direction to voltage?

texts:
I am learning about 1, 2 and 4 quadrant switches, used in inverters etc. I am however struggling to understand how, in the 2nd and 4th quadrant, the voltage can have an opposite direction to current. Using this picture for example

I dont understand here how you can have a positive voltage but current in the opposite direction. For e.g.

On the left, current would flow clockwise, and on the right, current will not flow, but if it did (i.e. if diode was replaced with a resistor) it would be anticlockwise. However, the 2nd and 4th quadrants indicate current in opposite direction to voltage - but I can't imagine how this could happen since (conventionally) current goes from positive to negative - the electromotive force is acting in one direction; how could current ever flow the opposite way?

Any help understanding this would be greatly appreciated; thank you.


texts:
I'm looking for an adapter for my Keyboard piano. I am not sure about the specifications of the original adapter, but I've looked up some online and I've found two adapters that supposedly should fit my keyboard. The problem is that one of them says for the output: 12V 1A while the other is 12V 600mA.

My broken adapter is not original but it says Output: 12V 600mA on it.

Is it very bad if I would use the 1 Ampere adapter?


texts:
Is there any tool to strip ribbon cables (all wires at once)?

It's too time consuming and error prone to do it one by one.


texts: Differential to Single-ended conversion clipping issue

texts:
I am attempting to convert the differential output of a DAC to a single-ended signal using the following circuit from a TI datasheet:

The signals going into this amplifier look like this:

And the output signal looks like this:

The Op-amp I am using is the LMC6484 (rail-to-rail) with V- to GND and V+ to +5V. My understanding is that the subtraction of signals results in a negative value for half of the waveform resulting in the clipping behaviour. What I am looking for is a way to bias the signal to avoid this clipping? I am trying to avoid having to add a negative voltage rail.

I am having a hard time figuring out how this is possible. Any suggestions?


texts: Question regarding collector leakage current with open emitter

texts:
In a transistor, we know that current amplification factor \$ \alpha \$  (DC) for CB Configuration is given by:

$$
\alpha = I_{C} / I_{E}
$$

Where, \$I_{C}\$  = collector current; \$I_{E}\$ = Emitter current

This implies that:

$$
I_{C} = \alpha * I_{E} \space \space (1)
$$

Also, the total current is given by:

$$
I_{C} = \alpha * I_{E} + I_{CBo} \space \space (2)
$$

Where, \$I_{CBo}\$ = collector base current with open Emitter (leakage current)

From 1 and 2,

$$
I_{C} = I_{C} + I_{CBo}
$$
$$
I_{CBo} = 0
$$

This means for any numerical values of alpha, \$I_{C}\$ and \$I_{E}\$, the leakage current is always going to be \$0\$. But practically, this is not the case. A small current of the order of micro/nano amps flows as Leakage current. This contradicts the above equation. Does this mean to say that the above equation is faulty?
Please explain.


texts: How to amplify 3.3 volts PWM to 5 volts PWM

texts: im working on a project to drive a motor using a motor driver that accepts 5 volts PWM (for 100% duty cycle) but im using raspberry pi 3 that has a PWM of 3.3 volts (for 100% duty cycle) as a result, i cant really reach the maximum speed that i want. how should i resolve this? is there a way to amplify PWM signal without messing up with the frequency? thanks!


texts: How much max current does this soldering-iron-station drive from the mains network?

texts:
This might sound a simple question, but I'm kind of confused. Here i the device and data sheets:

http://www.velleman.eu/products/view/?id=385738

http://www.velleman.eu/support/downloads/?code=VTSS4N

On its label it is written: 48 Watt 230V ac/50Hz.

Can we say the max current it will drive from the mains hot wire is:

Correction (48 W / 230 V = 0.21 A)

Is 230V ac directly applied to the soldering device's resistance?


texts: Connect DAC IC to current sinking controller

texts:
I want to supply a 0-5V signal to this process controller using the DAC8555. The DAC8555 datasheet states:

  Each output buffer amplifier is capable of [...] driving a load of 2kΩ in parallel with 1000pF to GND. The source and sink capabilities of the output amplifier can be seen in the Typical Characteristics.

There's a graph showing the source current capability:

Q1. Is the 2kΩ a minimum and the 1000pF a maximum? So it can drive >2kΩ and a capacitance of <1000pF?

The controller manual (p9) states about the 0-5V input:

  NOTE: This is a current sinking device. The receiving circuit is essentially a 250 ohm resistor to ground.

Q2. Can the DAC supply this input or will it draw too much current? If so, is there a way to connect it while still getting the full 0-5V range from the DAC?

Many thanks for your help


texts:
Here is the example with its solution:

The problem is that when I apply KVL to the circuit (the second circuit) from the 10V source to the ground at the bottom, I get wrong values. Here is what I did:

$$-10 + 4700 \times I_C + V_{CE} + 3300 \times I_E = 0$$

$$I_C = \alpha I_E = \frac{\beta}{\beta+1}I_E = (100/101)I_E$$

$$\rightarrow -10 + 4700 \times \frac{100}{101}I_E + V_{CE} + 3300 \times I_E = 0$$

This gives that \$I_E = 1.23\$ mA which is different from \$1.6\$ mA.

What is wrong ?


texts: Why (almost) all HDMI connectors in devices are female?

texts:
I have just bought an HDMI 10m cable and of course it comes with male plugs on both ends, and that's because almost all HDMI devices have a female socket.

But why is that? I can understand that when a sender-receiver difference is not clear that can work, e.g. the always wrong type RS232 connector, but for HDMI there clearly is a device that produces video, and a device that consumes it, end of story. Of course there's some sort of symmetric communication going on but the data flow is pretty clear.

This came to my mind since you can't make longer chords just by plugging two extenders one in another, as you would do with mains extenders. You can yell at me that's out of spec, but female to female adapters exist and who the hell cares about the standard anyway?

Some of the reasons that came to mind:

you only need to design female pcb/panel mound connectors, and male cable connectors
you can use tha same physical connector both as an input and an output (maybe capture video on a VGA?)
?

I'm hoping not to get opinion based close votes since I (want to) believe that there's a perfectly legitimate reason behind this choice.


texts: Heating a 10W, 22-ohm ceramic resistor on a standard perfboard

texts:
I have a small project that consists of controlling the temperature of a 10 W, 22-ohm ceramic resistor. The circuit is assembled on a regular perfboard; I could just make use of both legs and keep the resistor at some height. But I would like to assemble the resistor so that it is fixed in the perfboard.
The temperature will vary between room temperature (no heating) and 75ºC.
My question is: in order to keep both perfboard and resistor in a good condition, can I solder the resistor completely flat on the perfboard?
I think 75ºC might damage the touching surfaces of the perfboard and the resistor, or the lack of airflow under the resistor might overheat it and make the control process a bit harder, so the resistor might need to be fixed at some height with the help of other components. In that case, can anyone suggest a reliable method that will both protect the perfboard from melting/burn marks and ensure a fixed position for the resistor?
Thanks in advance.
EDIT: As the question is a bit unclear, let me try to rephrase it: is there any material/component I can place between the ceramic resistor and the perfboard that will both hold the resistor in place and protect the perfboard from melting or charring? I thought of an IC socket (which actually prevents the resistor from moving to the sides) with a layer of some insulator on top... is it a good solution?


texts: Changing the value of a PL SelectIO pin with the PS

texts:
Using the Zynq architecture,
Is there a way to tie a PL SelectIO pin directly to memory address shared by the PS and the PL ?
Let's say address 0x000FFFF holds a std:vector  0101
I want PL selectIO pins to reflect the address 0x000FFFF so it can be controlled by the PS
AE9 ->  1st bit in address 0x000FFFF = 1
AE10 -> 2nd bit in address 0x000FFFF = 0
AE11 -> 3rd bit in address 0x000FFFF = 1
AE12 -> 4th bit in address 0x000FFFF = 0


texts: How much can I push the limits of a device's VDD?

texts:
On a PCB I'm designing, I'm using two chips with very similar voltage requirements. Among other voltages, one requires 1.2v, and the other requires 1.1v. in fact, looking at the datasheet, the allowable voltage ranges slightly overlap.
The USB7206 has a range of 1.09v to 1.21v (nominally 1.1v).
The CX3 has a range of 1.15v to 1.25v (nominally 1.2v).
Would it be crazy to pick a single voltage to run both of them? Could that be 1.2v, or would 1.175v be more sensible?


texts: Whether Demultiplexer and Decoder are same terms or different one?

texts:
I'm really confused between above these terms.  First I want to clarify what I understood till now.

In Demultiplexer, there is one input and many outputs. Whereas in Decoder, there are many inputs and many outputs.

In Demultiplexer, there are control/ select lines present whereas in Decoder there are no such control/ select lines present.

But on some websites and books also these two terms are used interchangeably . Here is an example IC 74138 datasheet .
So can anyone tell me whether Decoder and Demultiplexer are same terms or different one? If different, how?
Also, where Demultiplexer is uses and where Decoder are used perticularly?


texts:
I have some problem with Arduino and Ethernet shield.

I have a small project with Arduino. Sensors send data to webserver. Everything works fine when arduino getting power from PC usb but when i give power from power supply Ethernet shield not connect to web server after pushing restart button on arduino shield it works...I cant push restart button every time when i turn on Arduino. pls help me

PS Arduino gets power from convertor out 24 V in 7 V and i checked on arduino 5V pin gets 4.5 V and 3.3V pin gets 3.28 V
please help


texts:
What kind of behaviour change should I expect to see, if I feed a 12V 50kHz frequency, with 50% duty cycle,
or a 100Hz 50% duty cycle, across a DC Motor?


texts: Wound Rotor Induction Motor Generator Conversion

texts: I have a 3 phase wound rotor induction motor which I would like to convert into a generator. I was wondering if it is possible to excite the rotor windings using a DC current. I attempted to do this, but I don't think the rotor windings were wired for that. The rotor windings are three phases with a common neutral inside the motor. I'm not sure if the approach I'm suggesting is possible. But I would think that applying a DC current through the rotor windings would produce a magnetic field. But it only worked as a "generator" when I applied an AC current


texts: Why is hardware multithreading not more common in embedded systems?

texts:
Hardware multithreading is common in personal computers (most Intel x86 systems support two threads per core), servers (POWER7, 4 threads per core; SPARC T5, 8 threads per core; SPARC64 VII+, 2 threads per core; Itanium 9500, 2 threads per core; and Intel's x86), network processors (commonly with 4 threads per core), and even the earlier version of Intel's Atom (2 threads per core), but multithreading seems to be noticeably less common in embedded systems outside of networking.

While MIPS developed a Multithreading Application Specific Extension specifically for embedded systems where equivalent multicore implementations would require licensing more core designs, use more chip area, and be less flexible in certain respects, it is not obvious that such has been broadly used. (The white paper "Optimizing Performance, Power, and Area in SoC Designs Using MIPS® Multithreaded Processors" offers an overview of some arguments in its favor, but one must consider the source.)

(Of course, most embedded systems do not advertise such details, but it seems from my very limited exposure that multithreading is not broadly used.)

One might consider various shadow (or banked) register mechanisms as very limited forms of switch-on-event-multithreading (SoEMT). The more common presence of such mechanisms makes it even more strange that even SoEMT is not adopted.

Obviously, multithreading would not be attractive for all uses. The trade-offs associated with shared versus dedicated resources would apply. (A shared resource can be more flexibly allocated to different users, but sharing may sacrifice optimization by specialization opportunities and tends to require better handling of contention. For energy use, the trade-offs for multithreading versus multicore, especially heterogenous multicore, can be complex and workload-dependent.)

Since many embedded systems have well-defined resource requirements and many have real-time performance requirements (both of which can reduce advantages from more flexible resource allocation), multithreading might not be especially attractive for such systems. Even the mindset of embedded system designers might slightly unjustly bias choices away from flexibility.

(Note that a multithreaded core does not require that tasks be multithreaded, though an OS would be required to guard against race conditions in its own data. On the positive side, with the sharing of local memory/L1 cache, locks would have lower overhead than with multiple cores. Alternatively, one could have one OS per hardware thread. Also, the general multithreading concept can support a variety of scheduling alternatives from fixed slot allocation through as-ready execution to dynamically weighted scheduling with multiple weight factors.)

I also suspect that lack of familiarity with the hardware implementation (and validation) of multithreading and with the use of such hardware may also be holding back adoption. Even with a mature software development infrastructure, multithreading might inherently add more complexity (with development and reliability costs) than benefits in other areas.

For microcontrollers, simple pipelines and predictable memory access delay would reduce the benefit of interleaved multithreading. In addition, the fraction of chip area used for the core is so small (and the licensing costs might be tiny and per licensed design not per instantiation) that adding multithreading might not be attractive relative to adding more identical cores; adding multithreading is much less costly in area than adding cores. (Coding closer to the metal, as is more common there, would also discourage diversity in core types much less dynamic diversity in performance.)

Are the above the only reasons that multithreading is not more common in embedded systems? What changes could make multithreading more common in embedded systems?


texts:
I am looking for an ADC IC and while I could just take the plunge and pick one, I was wondering if anyone had any experience with any particular devices? I need it to:

Connect to an AVR via I2C/SPI (I2C preferred)
Have at least 8 bit resolution (10+ would be nice)
Have at least 3 inputs

Currently I am looking at the ADS7830. Any recommendations would be fantastic.


texts:
I'm having some trouble simulating a closed loop buck converter I designed.I am using PSIM for verifying the correctness of my circuit, but I can't figure out why the output is all wrong.

It is supposed to be a 12 V to 5 V buck chopper at switching frequency = 200 kHz.Output power = 50 W.When a friend simulated a similar circuit on ORCAD, he used an isolation component for the gate drive part of MOSFET, but there seems to be no such block on PSIM.
How can I correct this?
EDIT 1:
Yes I did connect my n-channel MOSFET wrong, but correcting it (or using p-channel MOSFET) didn't give me the right output voltage of 5 V)


texts: ESD protection of capacitive touch doorknob circuit?

texts:
This is a follow-up to my question: How can I use a generic doorknob as a capacitive touch sensor?

I am now ready to move beyond the proof-of-concept stage, but I have not yet learned of a satisfactory answer for how to protect the microcontroller U1 in this circuit from ESD. I have tried adding a small-valued capacitor (C1 connected between the input pin and ground) on the theory that it might be enough to absorb a zap, and while it reduces the sensitivity of the circuit drastically I believe I can compensate in the software. But will it actually protect the microcontroller pin? And if so what's a reasonable capacitance value to use?


texts: How exactly would I go from 7 output lines to 127 outputs. Since you can encoder a value of 127 with 7 lines I would imagine this should be possible.


texts: What electrical component serves or can serve this function?

texts: I was thinking about what diodes can do to AC current, how they can be used to rectify alternating current by only letting it pass in one direction, so only the positive part of the wave or the negative part will pass.  What I'm curious is if there's a component or a type of circuit which will only let current through or let more current through if the voltage is increasing or decreasing.  So it would pass the portion of the wave from the peak to the trough, but not from the trough to the peak (the decreasing voltage but not the increasing voltage).


texts:
I have a schematic that I'm making that uses the same "block" multiple times.  I would like to design that block only once, and then use it in a bunch of different places, so I can edit the block if I like and have that edit show up everywhere.

Hierarchical sheets seem to be the way to do this, however you can't import a single sheet multiple times.

Is there a simple way to do this?


texts: Need help finding the drain current of a jfet

texts:
I have this simple dc jfet circuit (homework):

First of all I had to find the values of the drain and source resistors given the data above, this was pretty simple and I got:
$$R_D=4k\Omega $$
$$R_S=11k\Omega $$
Next, \$I_{DSS}\$ get's doubled to \$8mA\$, now I'm asked to find \$I_D\$.
Using: $$I_D = I_{DSS}\left [ 1-\frac{V_{GS}}{V_P} \right ]^{2} $$
I've found out that:
$$I_{D1} =1.16mA$$
$$I_{D2} =1.0258mA$$
During the calculations I've assumed the transistor is saturated thus:
$$V_{DG} > V_P $$
It seems like both \$I_D\$'s fulfill the above requirement.
How can I tell which one is correct ?


texts:
The input voltage should be roughly 5 volts for the TP4056 charger module with protection.
How much is the maximum input current for this module?


texts: I own a Mini Maglite Pro AA and the chip has a habit of getting really hot. I lubricate and seal every threaded part with Vaseline.


texts: Unexpected results when measuring MPU6050 sample rate with RaspberryPi

texts:
MPU6050 datasheet says that maximum accelerometer data output is 1Khz, so in theory when measuring time it takes to receive 1000 data samples through I2C, so I should receive all data in no less than 1 second, but somehow i always get sub 0.3 seconds.

Does CPU clock halts when waiting for data incoming from I2C slave?
How to have constant MPU6050 1khz output data rate, and measure it?

#include <wiringPi.h>
#include <wiringPiI2C.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define Device_Address 0x68 /* i2c-MPU6050*/

#define PWR_MGMT_1   0x6B
#define SMPLRT_DIV   0x19
#define CONFIG       0x1A
#define GYRO_CONFIG  0x1B
#define INT_ENABLE   0x38
#define ACCEL_XOUT_H 0x3B
#define ACCEL_YOUT_H 0x3D
#define ACCEL_ZOUT_H 0x3F
#define GYRO_XOUT_H  0x43
#define GYRO_YOUT_H  0x45
#define GYRO_ZOUT_H  0x47

int fd;

void MPU6050_Init(){

    wiringPiI2CWriteReg8 (fd, PWR_MGMT_1, 0x00);    /* Disable sleep mode*/
    wiringPiI2CWriteReg8 (fd, SMPLRT_DIV, 0x07);    /* 8khz/(1+7)=1khz */
    wiringPiI2CWriteReg8 (fd, CONFIG, 0x00);        /* FSYNC and DLPG_CFG disabled for maximum bandwith*/
    wiringPiI2CWriteReg8 (fd, GYRO_CONFIG, 0x00);   /* +- 200°/s, and acc by default +-2g's*/

    }
short read_raw_data(int addr){
    short high_byte,low_byte,value;
    high_byte = wiringPiI2CReadReg8(fd, addr);
    low_byte = wiringPiI2CReadReg8(fd, addr+1);
    value = (high_byte << 8) | low_byte;
    return value;
}
void passtime(int uSeconds)
{

    // Storing start time
    clock_t start_time = clock();  //time in microseconds.

    // looping till required time is not achieved
    while (clock() < start_time +uSeconds);

}

int main(){
    double time_spent = 0.0;

    float Acc_x,Acc_y,Acc_z;
    float Gyro_x,Gyro_y,Gyro_z;
    float Ax=0, Ay=0, Az=0;
    float Gx=0, Gy=0, Gz=0;
    fd = wiringPiI2CSetup(Device_Address);   /*Initializes I2C with device Address*/
    MPU6050_Init();                          /* Initializes MPU6050 */
    int count =0;
    passtime(10000);

    clock_t begin = clock();

    while(count<1000)
    {

        //Maximum output rate of MPU6050 is Accelerometer+Gyroscope = 1khz => 1 data read per milisecond
        /*Read raw value of Accelerometer and gyroscope from MPU6050*/

        Acc_x = read_raw_data(ACCEL_XOUT_H);
        Acc_y = read_raw_data(ACCEL_YOUT_H);
        Acc_z = read_raw_data(ACCEL_ZOUT_H);

        Gyro_x = read_raw_data(GYRO_XOUT_H);
        Gyro_y = read_raw_data(GYRO_YOUT_H);
        Gyro_z = read_raw_data(GYRO_ZOUT_H);

        /* Divide raw value by sensitivity scale factor for +-2g's, and +-250/s */

        Ax = Acc_x/16384.0;
        Ay = Acc_y/16384.0;
        Az = Acc_z/16384.0;

        Gx = Gyro_x/131;
        Gy = Gyro_y/131;
        Gz = Gyro_z/131;

        //printf("\n Gx=%.3f \tGy=%.3f \tGz=%.3f \tAx=%.3f g\tAy=%.3f g\tAz=%.3f g\n",Gx,Gy,Gz,Ax,Ay,Az);

        count++;

    }

        clock_t end = clock();

        time_spent += (double)(end-begin)/CLOCKS_PER_SEC;

        printf("Time spent %lf after %d data reads\n",time_spent,count);

    getchar();
    return 0;
}
/* OUTPUT:
 * Time spent 0.2312s after 1000data reads*/


texts:
I have used a digital caliper to measure inside and outside of this 6v 500ma DC connector

5.5mm outer 2.1mm inner - 12.5mm long

Question is, I can't find a connector with these 2 little notches cut out - what are these and are they required?


texts:
This is the problem:

And this my solution:

Is it correct ?


texts: Why is there a low pass filter in a DSBSC demodulator?

texts:
In analog communication, DSBSC (double side band suppressed carrier) is way of modulating signal.
In this the carrier is simply multiplied with the message signal.
At the demodulator, the carrier is multiplied back which gives the message signal back.

The first signal is my message signal
The second is the modulated signal
The third is the demodulated signal i.e I can get the msg by simply tracking the peak voltages

Now the demodulation process seems to be complete but the part that I am missing is a low pass filtee at demodulator.  Why is it required?  I have my signal back. Why should I pass it through a low pass filter? All the books have the filter.
Please explain why the low pass filter is required after the demodulator.
Matlab code

t=0:1e-4:30;
f=5;
y=sind(2*pi*f*t);
subplot(3,1,1)
plot(t,y)
hold on
yline(0)
xline(0.2)
ylim([-2 2])
hold off
subplot(3,1,2)
y1=sind(2*pi*100*t);

y3=y1.*y;

plot(t,y3)
hold on

yline(0)
hold off
subplot(3,1,3)

y4=y3.*sind(2*pi*100*t);

plot(t,y4)
hold on
ylim([-2 2])
plot(t,y);
hold off


texts: Verilog - Iterating Over All Cases In Testbench

texts:
In coursework, we are creating multiple circuits and explicitly testing every single case in Verilog.  The way that we have been writing test benches so far is the following:

initial begin
    $monitor("%d %d %d %d | %d  %d", A, B, C, D, F1, F2);
    A=0;B=0;C=0;D=0;#10;
    A=0;B=0;C=0;D=1;#10;
    A=0;B=0;C=1;D=0;#10;
    A=0;B=0;C=1;D=1;#10;
    A=0;B=1;C=0;D=0;#10;
    A=0;B=1;C=0;D=1;#10;
    A=0;B=1;C=1;D=0;#10;
    A=0;B=1;C=1;D=1;#10;
    A=1;B=0;C=0;D=0;#10;
    A=1;B=0;C=0;D=1;#10;
    A=1;B=0;C=1;D=0;#10;
    A=1;B=0;C=1;D=1;#10;
    A=1;B=1;C=0;D=0;#10;
    A=1;B=1;C=0;D=1;#10;
    A=1;B=1;C=1;D=0;#10;
    A=1;B=1;C=1;D=1;#10;
end

I feel like there has to be a better way to iterate over every state of the input and view the output.  Does anyone know of a way to have a test bench do this?


texts: Why do we suppress the input when calculating the Norton/Thevenin resistance?

texts:
When we calculate the thevenin/norton resistance of a 1-port circuit, we suppress the independent inputs, be it voltage or current. But, my textbooks do not explain as to why we do this.

So my question is, why do we suppress the inputs?


texts: What if I don't connect all the GND pins on the USB Type-C

texts:
Do I need to connect all the GND pins (A12, B1, B12, A1) to their respective pads or will it work just fine with only pins B12 and A1 (which are on the opposite side)?

I'm asking this because I don't have the space for pads A12 and B1... and yes I'm already using a small receptacle (USB 2.0 Type-C with 16 pins). Thank you.


texts: Having a series instead of parallel LC circuit in a crystal radio

texts:
I've been drawing the circuit diagram for a crystal radio I am going to build. (This is my first real electronic project). By using the theoretical knowledge I have, I figure I should have to have an LC series circuit (for the discrimination of the waves) like so: (please note that the numbers attributed to the figures do not mean anything, this is purely qualitative)

simulate this circuit – Schematic created using CircuitLab

However, upon researching other designs, I see the LC element of the circuit in parallel like so:

simulate this circuit

I don't understand how the parallel one would work, by what I understand, if the reactance of the inductor=the reactance of the capacitor in parallel, there should be no current passing at all whereas this is the perfect setup in my series diagram where in this case (capacitor reactance = inductor reactance), the receiver should favor a specific frequency.

Could anyone clear me up on where I'm going wrong and whether my design (first diagram) would work? Thanks for any responses


texts: Sparkfun's Quadstepmotor driver and different velocity: concurrency problem?

texts:
I'm using quadstepper motor board from Sparkfun:

with Arduino Uno / Leonardo. I can currently driver motors at the same time, but I can't change the velocity separately.

I use this code for driving motors:

void oneStep(int STEP_PIN, int delay_velocity) {
    digitalWrite(STEP_PIN, HIGH);
    delayMicroseconds(delay_velocity);

    digitalWrite(STEP_PIN, LOW);
    delayMicroseconds(delay_velocity);
}

But if in my main loop I have something like:

void loop() {
    oneStep(6, 100);
    oneStep(8, 600);
}

the motors run with the same velocity.

I think this could make sense because delayMicroseconds are blocking function so IMHO the way for make them running with different velocity should be thinking on some concurrent function, but I'm not a guru with microcontrollers so I don't know very well how to manage this. Some help?


texts: Raspberry Pi: How to connect global_en with gnd on a 5v signal?

texts:
On a Raspberry Pi 4, you can perform a hard reset by pulling the global_en pin to low.
I want to control this reset by using an external 5v signal. When the signal is high, the reset is performed.
I know this could be easily done by using a 5v relay. However, I am not happy with this solution because the switching noise of a relay is too loud for my application.
My question is if there is any other simple solution without using a relay.


texts: What is name of process used to change sample bit depth?

texts:
Changing sampling rate is called up sampling or down sampling depending on which way or is done. If the factor is an even number then the process becomes very simple.

However, what term is used to change bit depth e.g 16 bit samples to 8 bit samples? Certainly this requires "re-quantization" rather than just throwing away least significant 8 bits.


texts: variation in source votlage is allowed in a constant current circuit?

texts:
Reference question: understanding constant current source circuit

With respect to the linked question, I am seeing a variation in the load current as I change the voltage \$V_2\$ to and fro from \$10 V\$ to \$20 V\$. Is it expected or am I operating the device in it's undefined region?


texts: Pulse skip modulation vs Phase cutting for AC inductive loads?

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What is preferred and safe mode for controlling power to an Inductive AC load when driven by a Triac?

I am using a microcontroller with zero crossing optocoupler to drive the control signal and the load is Cieling fan.

If only one is suitable for it then what is the other method used for  ? Resistive loads?


texts: Chip behaves differently in debug vs flash

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I'm currently working on a program for an 8-bit freescale chip (MC9S08QG8) in CodeWarrior v10.3 which uses the timer/ period capture to turn a frequency to an analog voltage.

I've gotten the thing to work pretty well in debug mode, but I noticed when I just flash the .abs file to the target to test the release build, it behaves as if the timer register is skewed.
 In other words, a 20ms period will normally turn on a DAC in debug mode (as intended). However, when the file is flashed directly, the DAC turns on at about 17.4ms. Ditto for other other cases; an event that's supposed to happen at 6.64ms happens at 5.75ms.

The code is interrupt-based - does anyone know what's different in debug vs direct flash that could cause this? Anything I can disable in debug mode to make it behave like a release build?


texts: Op-Amp Astable Multivibrator - Effect of bypass Switch

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For your consideration, I have this Astable-multivibrator via a classic Op-Amp Schmitt Trigger delivering a square signal (here 1.82Hz).

I am fine with the circuit with SW1 open as C2 is basically in Series with C1 making CT = 5uF.
However, I am not sure about the effect of SW1 being closed.

Can someone enlighten me?

Figure 1. Switch Open

Figure 2. Switch Closed


texts: Making aysnchronous sequential circuits hazard free

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The problem I am stuck at requires me design a hazard free asynchronous sequential circuit for a given problem description. I have followed the routine steps as follows:

I have obtained the primitive flow table from the problem description
I have reduced the flow table using state minimisation routines of incompletely specified FSM
I have assigned the output symbol preventing glitches
I have done the state assignments of the reduced flow table

Let us assume that I require three secondary variables \$ y_1,y_2 ,y_2 \$ for the state encoding.

Now I have the resulting flow table. I am stuck at how I should proceed for hazard checking. I know the general procedure of checking and removing static and dynamic hazards, given a function and some transitions.

In this problem,

For static hazards, I guess, I should check the KMap for each  \$y_1 ,y_2,y_3\$ and thereby check for adjacent \$1's \$. Am I right?
For dynamic hazards , I really have no clue how to proceed.Descriptive answers would be very helpful

Thank you in advance for all your answers.


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My laptop broke a while back, so I opened it up. I took the speakers out today, and hooked them up to one of those cheap 3 watt PAM amplifier modules. To my surprise, it didn't work that well. Above 70% or so volume on my phone, the speakers would stop working intermittently, and the current draw would spike. It would crackle as well.

When I had a look at the power draw of the module, it had peaks of about 500mA. I instead connected a much bigger 10w speaker to the module, at full volume, it worked perfectly. It was much louder that the two laptop speakers combined. The current draw had maximum peaks of just over 100mA.

So what's going on? How is it that those tiny laptop speakers are drawing so much more current than the big 10w speaker? Has it got something to do with the resistance?


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This might be a silly question but I can't find any information about this or maybe I am not asking right.

I have a AM1117 5V voltage regulator that is usually powered by a 12V to 16V battery.

Now I have certain situations where I want to just put 5V power on the board (like USB). I am pretty sure that if I put 5V into the AM1117 I won't get 5V out of it :-)

However how could I solve this issue on a simple level. Trying to avoid putting more components on the board.

Thanks,

Andy


texts: 3V6 Zener Diodes With Very Poor Accuracy

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I have a question about the regulation accuracy (or lack of) of a 3V6 Zener diode. I wanted to confirm that I wasn't doing anything stupid.

I set up the standard test circuit shown below.

No load except for the DMM.  The two Zeners in question are: BZX55C3V6 (3V6 - 500mW) and 1N4729A (3V6 - 1W).  Both Zeners came from separate suppliers.  \$V_{CC} = 5\$V and is relatively stable (total variance no more than 40mV).
I know that Zeners need a minimum current to regulate properly and I worked out the optimum current through the combination of \$I_{zt}\$ from the datasheet and the following "rule of thumb" calculation: $$I = \frac{(P/V) \times .7}{4}$$

Taking the 1N4729A as an example, the \$I_{zt}\$ is roughly 70mA.
Working out the current limiting resistor we have: $$\frac{5 - 3.6}{70\text{mA}} = 20\Omega$$

When I tested the zener with a \$20\Omega\$ resistor I get a \$V_z\$ of just over 4V!  In fact, as I increase and decrease the resistor value, the Zener voltage increases and decreases along with it.  It's like the Zener resistance isn't decreasing as the current increases, which is not what I'd expect.  What's odd is that the BZX55C is showing more-or-less the same behaviour although with different resistors.  Is this normal?


texts: Calculation of common emitter output impedance with output resistance

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I don't understand why \$g_{m}\$ survives. Since \$v_{\pi}\$ is equivalent to \$\Delta V\$ , which is perturbation of signal, which is then set as AC ground. Doesn't that mean \$v_{\pi}= \Delta V = 0\$? Thus make \$g_{m}\$ open for calculation? How can I calculate the output impedance like so? With inspection method assuming \$g_{m}\$ is open, I'm getting \$R_{out} = ( r_{\pi} || R_{E} ) + r_{0} \$ also could you show how to calculate the input impedance as well?


texts: Is it reasonable to qualify a component by testing only?

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Just got assigned (sole) responsibility of a major product group in my company.  I have discovered that we regularly use components outside of their specifications, and justify that by testing the snot out of them.

Specific example --- We have a switch rated at 10A 240V.  But we're switching maybe nominal 20A @ 12V load which is a motor and thus can ALSO suffer massive surge (startup/stall) currents far larger than 20A and of course also experience inductive arcing.

Been doing it for years apparently.    They just test a bunch of samples of the the switch to failure and get the vendors to promise if they change the switch in any way, they'll contact us.

So am I nuts to think that's nuts?   That we shouldn't just seek out switches that are actually rated for the loads we're putting on them???