texts: Highest ADC input signal frequency for atmega8?

texts:
I am trying to make a simple project which involves acquiring some data from the adc of atmega8 chip and then sending that data to UART. But I cannot figure out what would be the maximum limit of the input signal frequency for it to be a reliable signal acquisition. I am using 10bit adc but don't really mind a 8 bit precision. I should also factor in the time required to transfer my data over the serial port. The data sheet says

  By default, the successive approximation circuitry requires an input
  clock frequency between 50kHz and 200kHz to get maximum resolution. If
  a lower resolution than 10 bits is needed, the input clock frequency
  to the ADC can be higher than 200kHz to get a higher sample rate.

Does that mean the sampling is happening at 200kHz? This is all very confusing to me.


texts: Is this mosfet stable? Trouble with capacitances

texts:
I have the following circuit and I'd like to know about its stability :

From what I've learned from basic electronics courses, the first step is to add the parasitic capacitances.
I know there is one from the gate to the source of the transistor. In this case, Cgs is from the gate to the ground since the source is connected to ground.
Now the capacitance from the gate to the drain Cgd gives me trouble. The gate and the drain are connected so is there any point in adding a capacitance somewhere? And even if I did, where would I place it in the circuit?
I can proceed by finding the poles later but I have to place the capacitances correctly first. If there is indeed no capacitance from gate to drain in this case, then we only have one pole given by  $$\frac{1}{R_d(C_1+C_{gs})}$$


texts: How do I compare waveforms from multiple simulations in QuestaSim/ModelSim

texts:
I want to compare the waveform result from different tets. So basically the test stimulus changes but the unit under test is the same in all cases. What steps do I need to follow to do this?

Essesntially I want to compare the waveforms themself by having them side by side, atleast two of them.


texts:
I apologize for my ignorance, but does a brand new IC need to be programmed or are they already factory programmed ready to be solder?
I have an M-Audio 49 MIDI controller piano with a bad 24LC16B-I/P IC and can't find a donor board to extract that IC, but they do have the chip on Ebay. I was wondering if brand new ICs have to be code programmed before soldering to the MIDI keyboard PCB, or they are factory programmed ready to solder?


texts:
I know that it's easy to make a unity gain buffer with an op-amp (as a voltage follower):

simulate this circuit – Schematic created using CircuitLab

I also know that it's easy to make an inverting buffer with an op-amp (an inverting amplifier with \$R_1 = R_2\$):

simulate this circuit

However, the accuracy of this inverting amplifier depends on the precision of \$R_1\$ and \$R_2\$ -  if they're not closely matched, the output will be a bit different from \$-V_{in}\$.

Is there a way of making an inverting buffer with an op-amp that doesn't depend on the precision of these resistors, like the voltage follower? Is it a better idea to get higher precision resistors?


texts: What is this grounding connector for devices called?

texts: I need to find the grounding connector/socket (male) like in the photo for my device, but cannot find what it is exactly called or if it is rather something custom-made.


texts:
I have read an interesting formula that says that

\$\mbox{Gain of an amplifier} = \dfrac{\mbox{resistance connected at the output}}{\mbox{total resistance between source and gate of the amplifier}}\$

well, this has simplified the gain calculation and helped me avoid the small signal analysis which proves to be cumbersome in quite many cases.

But i was wondering how to manage the sign in the expression i.e lets say for common source amplifier the gain has a negative sign before it but the common gate amplifier has a positive sign before its gain formula.

Any help as to explain me the significance of the sign?

edit: i am here referring tot he common source amplifiers and the common gate amplifiers, basically types of mosfets


texts: Feedback capacitor in comparator circuit with an OP-AMP

texts:
Greetings,

This is a scheme of a comparator with dynamic hysteresis.

Green line is the output
Red line is the input
Blue line is the positive feedback.

I want to ask for the explanation why C1 does not start charging up at 5.3V (like the green line) but has its peak at 4.3V and goes down from there?


texts: Recommendations for an active, directional RFID sensor

texts:
I have been using two Loc8tor devices (an active, highly directional RFID consumer device) on a personal robot to try to locate an RFID tag.

While the Loc8tor has served its purpose of showing an active, directional RFID sensor with high resolution can be used for locating an RFID tag, the Loc8tor itself is not very hacker friendly. I am looking for an alternative reader and tag that can be integrated into my robot.

Ideally, it would meet the following specifications:

Each reader would be less than $100, cheaper is definitely better
The reader should be around the size of a credit card to a dollar bill
The tag will be placed in ranges of 0.5 to 3 meters from the reader
The reader should run on some voltage less than 5v, ideally 3.3v or less
The higher the resolution of the reader, the better. Say 3 cm resolution at a 1 meter distance.
The (RSSI?) value from the sensor is easily accessible. Meaning I could wire that into an Arduino input pin and use the value.
Could buy in small (1 to 2) or large quantities (100+)

These specifications are ideal, but not all are required (though the price is the most important). I should hopefully be able to list better specifications after I see what alternatives are out there.


texts: Understanding cause of arcing in AC filter circuit

texts:
I have an induction hot-plate that one day blew a fuse in my distribution panel  when plugging it in. (With the obligatory smoke from the device of course)

On visual inspection, only the AC filter PCB shows obvious damage:

simulate this circuit – Schematic created using CircuitLab

(Note: R1 might also be 51kOhm (color codes are damaged), L1&L2 are 20.5 turns on a 1 inch yellow core.)

Description of Damage:

The PCB between the right terminal of L1 (point A on the schematic) and somewhere from L2 (points B or C alternatively, hard to say with a torroid) is severely eroded from arcing.
The casing material of resistor R1 is cracked and slightly blackened but the resistor is not "exploded" as one would expect from a overloaded resistor. It seems possible that R1 was simply in the arc path between the two inductances.
That being said, the terminals of R1 are also blackened. (Maybe due to a "wandering" arc?)

Photograph of PCB:

Bottom of PCB is pristine.

Questions:

Am I right to assume that R1 has no function other than to provide a safe discharge path for C1 e.g. when unplugged?
If so, why is R1 not directly parallel to C1? It seems like an odd design choice to run the discharge through L1...
Any idea what caused the arcing (presumably between the two inductor terminals)?

My gut reaction:

My gut reaction is that there is no real issue with the filter PCB itself, but that a problem from down the line only manifests here.

Since induction hot plates work with high-frequency, is it reasonable to think that a fault with the HF part sends HF back up the line? If so, with HF being blocked by L1 and L2 it jumps between points A and C.

I am surprised, however, that a gap of about 10 mm can be bridged which seems to suggest an unexpectedly high voltage.

(Note: down the line a 1200V (visually undamaged) capacitor is used in the HF part of the hot plate which suggests the maximum voltage that should occur is the circuit...)


texts: Self-made Schottky transistor doesn't behave as I'd expect

texts:
For a project of mine I need to generate UART-like signals with higher voltage (up to 18V) and a baudrate of 115200 bps and later possibly 250000 bps. I tried a basic BJT level shifter which worked as shown below:

(here and later: yellow in IN, green is OUT, plots are 2V/div and 5us/div)

I decided the delay due to BJT saturation may become problematic at higher baudrates, so I threw in a Schottky diode which helped:

However, that's not how a traditional Schottky transistor is made, and I have seen advice that it's better to avoid saturation in the first place rather than fighting the consequences. So I implemented the third prototype which didn't work as I expected:

I understand that the higher LOW level is due to the fact that I now avoid saturation, but the shape of the edges is totally unexpected, and can hardly be called an improvement.

Is this how a Schottky transistor is supposed to work, or can anyone offer an explanation as to why it didn't?


texts: I need some advice concerning the building of a signal inverter for an RS-232 connection. I'm using a MAX3323 to convert a serial tx/rx of an Arduino to RS-232 standard. The point is that I'm not able to use dual power supply, and the MAX is inverting, in this way I end up with a signal having only a negative voltage range. A normal computer is able to interpret the string I'm sending, but the machine I have to command does not do that. I think this is because it requires signal having a positive dynamic, hence I need to invert it. Can you give me any suggestion about the circuit to build?


texts: Can I use the W94AD6KBHX5E SDRAM with STM32F779NIH6 MCU?

texts:
I want install on my board project this sdram IC : W94AD6KBHX5E .
Can I use the W94AD6KBHX5E SDRAM with  STM32F779NIH6 MCU ?
The W94AD6KBHX5E  datasheet: Link


texts:
I am trying to get the Nokia 5110 screen up and running on BeagleBone Black rev b. I am using...

Ken Keller's BeagleBone Nokia 5110 LCD Bonescript library
An Adafruit recycled Nokia 5110/3310 monochrome LCD

When I hook all pins up and run the test program below, it doesn't output anything on the screen. I tested all the pins with a voltmeter and got these readings:
- VCC = 3.373V Constant
- RST = 1.63V Constant
- CS = Sits at .001V when program runs, but has a few pulses up to .040V
- D/C = 3.3V Constant
- DIN = fluctuates between 0-.3xx (so assuming it is sending data)
- CLK = fluctuates as well

Code:

var lcd = require('./LCD_5110.js');
var b = require('bonescript');
var timeout = 0;
var inverseIndex;

//
//  Must define the following outputs to use LCD_5110.js
//
lcd.PIN_SDIN = "P9_21";
lcd.PIN_SCLK = "P9_22";
lcd.PIN_SCE = "P9_23";
lcd.PIN_DC = "P9_24";
lcd.PIN_RESET = "P9_25";

lcd.setup();
setTimeout(loop, 5);

function loop() {
// test bitmap write
lcd.clear();
lcd.bitmap(beagle);

inverseIndex = 0;
setTimeout(loop0, 1000*timeout);
}

function loop0() {
// test inverse video
if(inverseIndex % 2) {
    lcd.inverse(lcd.LCD_INVERSE);
} else {
    lcd.inverse(lcd.LCD_NORMAL);
}

inverseIndex++;

if(inverseIndex < 19) {
    setTimeout(loop0, 50*timeout);
} else {
    setTimeout(loop1, 50*timeout);
}
}

function loop1() {
// test normal character write
lcd.clear();
for ( index = 0x41 ; index < 0x7b ; index++)
    lcd.character(String.fromCharCode(index));

setTimeout(loop2, 2000*timeout);
}

function loop2() {
// test bitmap and string write
lcd.clear();
lcd.bitmap(world_map);

setTimeout(loop3, 1000*timeout);
}

etc.


texts: Difference : Lt spice AC analysis and frequency analysis in time domain

texts:
To do a frequency response analysis in ltspice, you can inject signals at various frequencies. And then use the measure and plot statement to view the results.

How is this different from doing a AC analysis around the dc-point of your system.

Basically: I am asking what is the difference between time domain Frequency analysis and “normal” frequency analysis of lt spice?
When can you use which one?

This link gives an example of the “time domain frequency:

https://www.analog.com/en/technical-articles/ltspice-extracting-switch-mode-power-supply-loop-gain-in-simulation-and-why-you-usually-don-t-need.html

I feel that this has something to do with the linearity of the system


texts: Why is the the permeability of a ferromagnetic material given as B/H not it's slope dB/dH?

texts:
I was going through my Electromagentics book by Sadiku where it was mentioned as a point that permeability of ferromagnetic material is given by the ratio of B(magnetic flux density) to H(magnetic field intensity) and not by the slope dB/dH at a point in the magnetisation or B-H curve.

I am not able to understand why the permeability is given as B/H at a point and not the slope(dB/dH) of B-H curve at a particular point?


texts: How to mount four 6-wire 10V load cells on Arduino or Raspberry Pi?

texts:
I want to connect four 6-wire load cells (Tedea Huntleigh Compression & Tension Load Cell 300kg, 15V dc, IP67, product page and datasheet) into an Arduino or Raspberry Pi and get four independent readings. This is my first time dealing with load cells.

I would like to get an accuracy of 2kg and a range of 25-100 kg on each load cell. The load cells have a recommended excitation of 10V.

My understanding is that, to get a working prototype, I can:

not use the two sense wires in the load cell (first suggestion by DaveEvans in this Arduino thread)
use a breadboard, even though it's not meant for a sensitive circuit
use the 5V supply from the Arduino, which halves the output voltage from the load cell but does not require an extra power supply or an booster converter, with some decrease in precision of the reading
use an INA125P amplifier and the wiring in the first link of this thread and connect each load cell to a single analog pin in the Arduino Uno, which only has 5 analog pins
calibrate the reading from each load cell with two known weights and extrapolate linearly

Would this work? Which shortcuts would be the first to consider to improve the precision of the readings?


texts: Circuit to control an RGB LED strip using potentiometer sliders to change colors

texts: The idea is to control an RGB LED strip (or strips, though independent control of the various strips is not necessary) lighting my desk. I'd like to build 3 potentiometer sliders into my desk to allow me to change the color of the strip(s) on the fly. I should state that I am a complete newbie when it comes to electronic circuits, though I do have some rudimentary understanding. Basically, I'm looking for something like this https://www.superbrightleds.com/moreinfo/rgb-dimmer-switches/ldk-rgb3-three-color-rgb-led-dimmer/117/526/ but using sliders. Hopefully, I'd use the 12v DC power supply that came with the LED strip as the input to the device, then feed the 4 outputs to the strip. I would be grateful for any thoughts you may have and/or pointers to more information that may help me create this.


texts: Why IR remote waveform is a saw-tooth or am I measuring it wrong

texts:
The measurement circuit is as follows:

simulate this circuit – Schematic created using CircuitLab

The waveform looks like this in my measurement:

Is this because I'm measuring it wrong and the diode current source with a capacitance somewhere forms an integrator hence the triangle wave, or is it really a triangle wave?

If really a triangle wave what is the reason for using it instead of a simple on-off modulation?

Edit: trying with different remotes now and get triangle waves everywhere so I suppose it's a parasitic capacitance from the cathode of the diode to ground, probably because I'm using a breadboard.


texts:
I'm trying to obtain 5V DC from a 37V DC power supply. The load is a computer fan that at 5V drains 31mA (around 0.15W).
I'm using a LM350 voltage regulator (LM350 Datasheet).
I get a very precise 5V output but the chip becomes really hot. I measured that the the power supply provides 49mA at 37V. I think that the LM370 use 48mA - 31mA = 17mA, so it dissipates 37V * 17mA = 0.63W. (Please correct me if these calculations are wrong)
It bothers me that the voltage regulator requires more energy than the load. It's normal or I'm doing this in a stupid way? There is a better way to supply a computer fan from a 37V DC tension?

Thanks :)

P.s. On the datasheet it says that the maximum input-output voltage differential is 35V. I'm using it with a 32V voltage differential. Is it safe? I need a better voltage regulator?


texts: L7805CV 5V Voltage Regulator to IP camera over POE

texts:
I am having a problem with getting my IP cameras to work over my home-made POE cable.

The parts I made in order to have POE are the following:

L7805CV 5V Voltage Regulator (for input to the IP Cameras 5v/ground pin. 12V -> 5V) link: http://www.ebay.com/itm/L7805CV-5V-V...item2a259974bb
12V 2A DC Power Adapter Supply For CCTV Camera US (for use on the opposite side of the IP camera to inject into the ethernet cable) link: http://www.ebay.com/itm/12V-2A-DC-Po...item4604a8bda9
Night vision Waterproof Outdoor Wifi Wireless WIFI IP Camera IR 24 LED M-JPEG (The IP camera itself) link: http://www.ebay.com/itm/180810824039...039%26_rdc%3D1
Power over Ethernet PoE Adapter Injector + Splitter Kit (to hook up between the switch and the IP Camera) link: http://www.ebay.com/itm/160680383412...84.m1423.l2649
1000Ft Direct Burial Waterproof Cat 5e Outdoor UTP CMX (used from the switch [garage] to the IP Cameras [outside]) link: http://www.ebay.com/itm/1000-Ft-Dire...vip=true&rt=nc

Now the power supply that comes with it says this:

INPUT: 100-240V- 50/60Hz 0.4A max
OUTPUT: 5V 2A

I noticed when I hook up the original power supply to it-it does not power on. I'm just guessing its because I have the 5V Voltage Regulator in there and its feeding it less than 5V?

But once I connected it up using the POE injectors it works just fine (tested with a ethernet cable about 10ft long or so). Now that I placed them outside I have (again guessing) about ~120ft of ethernet cable from one tree IP Camera to my garage. It's using the direct burial ethernet cable for this (the original test was using a standard ethernet cable).

The power is coming from the 12V 2A DC Power Adapter Supply hooked into the POE injector. From there the POE injector is hooked to the switch and the other end to the direct burial ethernet cable that's going outside to the IP Camera. At night I can see the glow of the red IR LEDs so I know it's getting power. And I also see that its blinking (green led) on the switch so I know it's communicating... But when I try to find its IP on my router it does not show up at all?

And again, I tested this out using the 12V 2A DC Power Adapter Supply/ POE injector and a standard 10ft ethernet cable and it worked just fine.

I tested the voltage with a volt meter to make sure it was getting enough from that long run. I had 12V on one side (the garage) going through the injector/ethernet wire and on the other end (outside at the other injector from the ethernet) I had about 12.4V constant so it really did not drop at all from that 150ft ethernet run.

I also tested to make sure my crimping on the ends of the ethernet were correct (had a gizmo that sent out a signal and showed me what order the wires are in). They all came back the same.

So what all should I try testing out first? Second? Third? I already heat shrink all the connections outside so I hope I don't have to pull those apart to disconnect the POE/splitter!


texts: Why am I getting a lesser negative threshold voltage for my astable multivibrator?

texts:
I've calculated my threshold voltages to be +/-5V but when I probe Vout, I'm getting a -6.42V threshold voltage instead of the expected -5. Why is this? I'm guessing it has something to do with R4 and the diode but i'm not sure what their effect in the circuit really is. What I know is that D1 will be ON when Vout = -Vsat because -V_threshold > -V_sat and OFF when Vout=+Vsat because +V_threshold < +V_sat. What exactly happens when D1 is ON that is causing node Vplus to be less than the expected negative threshold?
Also, I was expecting the charging and discharging time of the capacitor C1 to be the same but its not. I'm not really sure why. I've derived the expression for both and they should be the same. But i guess i'm not accounting the effect of the diode D1 and the resistor R4. Could somebody help explain to me their effect in the circuit? See plot below:


texts: How to strobe high power led while maintaining constant current

texts: I am trying to make a high power tv-be-gone. For those who don't know, it uses arduino or attiny to run through every IR power code for most tv brands. I have made regular ones that use several 5mm IR leds, however in all of the designs they are just connected to transistors and don't limit current, since the pulses are so fast. These designs run off of 3v-5v. My question is, how can I use a constant current source with a 10W led with the device? My concern is that a cc source will not be able to adjust fast enough when pulsing the IR codes. Do I even need a cc source when switching this fast? Also, I am curious as to why the small tv-be-gones don't need current limiting such as resistors for the IR leds. They have a forward voltage of 1.2v, and are being powered directly by 3v-5v. In this case, what determines the current through the led when no resistor/cc source is connected? Why do the 5mm leds not burn out?


texts: Frequency bandwidth which transfers 95% of power of the signal

texts: If I know total power of the signal and spectrum of the signal with amplitudes in dbV, how do I compute bandwidth, which transfers 95% of the power?


texts: Low current to HS gate drive in DRV8825 typical application diagram

texts:
simulate this circuit – Schematic created using CircuitLab

The typical application diagram in the DRV8825 stepper driver datasheet includes a 1MOhm resistor from VM(the motor voltage) to VCP(which is internally connected to the HS gate drive. This resistor forms a parallel RC circuit with a 0.1uF capacitor.

My understanding of this section of the circuit would be that once the capacitor is charged, the bulk of the current would be flowing through the 1 MOhm resistor, and therefore would be very low due to the high resistance. My question is basically this-Why is this resistor included, when it means that the HS gate drive has a very low current flowing through it?

Another confusing element is that the Pololu breakout boards for these chips do not include the resistor, they just include the capacitor.


texts:
I've got a heat gun that has stopped working.  Use of a multimeter tells me that there's a single part that is stopping current from flowing through the whole thing.  This part is indicated

PATENTED
MICROTEMP™
4468A1
SUUC240C

Some research suggests that it is a fusible link which opens (has opened, apparently) at 468F (242°C).

How dangerous would it be to cut this part out and join the wires which previously connected to it?  Would using solder to hold them together provide a similar temperature backstop in that the gun would stop working when that area exceeded the melting temperature of solder?  Would it be better to join the devices in a way which did not rely on solder to hold them together?

The part is located between the fan and the heating element, the heating element being at the air exit point of the gun and the fan being at the back/intake.

The wires are thick enough and the design of the gun such that the wires will hold their position and not flap around dangerously inside if the solder is melted.

It's notable that there is no solder used anywhere in the device: clamps and other techniques are used instead.


texts:
I cannot se how the device is a buck charger when charging and a boost on the output.
Am I stupid or is the datasheet wrong?

"5A Single Cell Li-Ion Switching Battery Charger with Direct
Charge, Power Path Management and USB OTG Boost Mode
"
https://www.richtek.com/assets/product_file/RT9468/DS9468-01.pdf


texts:
I have STM32L053 (link to overview) and I have been using STM32CubeL0 as UART examples. Also I connected FT232RL FTDI module.

Everything was fine. SIM800L and FTDI modules were working fine. Next day with same configuration modules didn't respond. I connected STM32 TX (PA9) pin to oscilloscope. So it is sending something.

Ok, I thought maybe FTDI went down so I tested with Arduino. It worked perfectly. Then I tried STM32 TX connect to Arduino RX. There are the results. A few symbols for some reason received wrong. FTDI does not respond to this and also Sim800L because it doesn't recognized as serial communication?

Here are my code: link


texts: Power consumption NeoPixels vs. direct control?

texts:
At Maker Faire Berlin 2018, an electrical engineer looked at my
project which was shown with NeoPixel LEDs (WS2811). He mentioned
that the NeoPixels waste a lot of energy. It would be better to build
my own circuit with RGB LEDs and use the Arduino’s (ATmega328P) PWM
functionality for brightness control.

Is there any truth in this?

According to the WS2811 spec sheet: “Gray level 256 can be
adjusted and scan frequency not less than 400Hz/s. [sic]” So the WS2811
driver chip is using PWM, of course. I don’t see how it wastes
energy.


texts: FPGA - Injecting an overlay into an HDMI stream

texts:
I am looking to use an FPGA in line with a non-encrypted HDMI stream in order to inject an overlay to the display. The minimum resolution and frame rate I would like to support is 1080p at 60Hz.

My idea to make this work would be to load a fully encoded 1080p frame of the overlay in memory with everything 0's except for the pixel data that I want. Assuming my overlay only uses solid colors (ie pure R, G, or B) I can have the compressed frame saved with only 1 bit depth (about 2.5Mb in memory per channel). Then as the TMDS data for each channel is clocked into the FPGA, and assuming I can detect the start of a frame and synchronize the incoming data with the overlay being read from RAM, I should be able to just OR the two data streams bit by bit as they are being clocked into the FPGA and output the result the very next clock cycle...

Hopefully I am not being too naive with this plan as I am not too familiar with HDMI. Can anyone tell me if there are flaws with this?


texts: How do I shine an LED when a PIR detects movement but keep it shining until a reset button is pressed?

texts:
It's easy even for a beginner like myself to create a PCB where an LED lights up if a PIR chip detects movement, then goes off when movement is no longer detected.  And if more movement is detected, the LED goes on again etc.

I'm struggling though with how to cheaply implement a PCB where an LED stays on continuously when the PIR first detects movement (regardless of how much time passes or whether the PIR detects additional movement), and only goes off when a user presses a button.

I've looked at latching relays but the cost per latched-relay is a lot for what I want to achieve given that my design has about 4 latched states I need to retain.

What component should I use instead to retain state?

(The design I need would still work if the ON state was retained continuously until the power was switched off... but I need the ON state to remain ON regardless of time or of any subsequent PIR movement detection.  Not sure if that makes the requirements any easier...)


texts: NDP6020P P-Channel MOSFET + ESP8266-01 Voltage Drop

texts:
I'm trying to power a ESP8266-01 with a NDP6020P.
My main power supply is a buck converter configured at 3.6V.
I connect the NDP6020P source to 3.6v and the Gate to Ground. If I calulcate the Drain voltage I get close to 3.6V (as expected). If I connect my ESP8266-01 to the Drain the Voltage drops to 2V. I tried increasing the buck converter to 4.2V I get the 3.7V when I connect the ESP8266-01.
Connecting the ESP direct on the Buck converter works fine. No voltage drop.
Any suggestions?
Thanks in advance!


texts:
I wasn't able to find a good guide on this and I only recently discover electronics for myself so have a little knowledge.
I was able to find something like what I need
Article

How does the circuit operate? It's simple: the input signal charges the hold capacitor, and the diode prevents the capacitor from discharging. The input op amp, in conjunction with the capacitor, presents that held value as the output via the driver op amp. As the input voltage increases further, the capacitor is charged to the higher voltage; if the input voltage decreases below the previous value, the voltage on the capacitor stays at the previous peak value.
By adding a simple comparator to the output to compares the present input value to the already held value, it can also indicate that a peak has been reached when the present input value is less than the held peak by some desired amount, Figure 2. This transforms the circuit from providing a peak-hold function to implementing the peak-detect function, with comparator hysteresis to establish a valid-peak threshold.

And here is more thorough info about peak detectors

What I want is

And add peak resetting feature.
Question is, how to unite this two circuits from article and youtube into one?
I just think that some resistors were omitted if not in youtube picture then in schematics from article.
And another one, how to make negative peak detector(ND)? In video he says it easy task.. I mean which can detect gaps between peaks, and then positive peak detector(PD) will reset ND and vice versa.

Think I will be able to increase voltage between top and bottom, so for peak detection and resetting negative peak detector let's have (peak-20mv).


texts: How does potentiometer influence incoming current in the circuit?

texts:
As you can see from the picture, shouldn't the 100 Ohms be the only current influencing factor at whatever the voltage it is supplying? How does Potentiometer on the right side cause decrease in current when I am measuring the current even before current crosses potentiometer?

For example, at 4 V, 100 Ohm(fixed) on the left / 1000 Ohm(potentiometer) on the right I measured 3.59mA

Then at 4 V, 100 Ohm(fixed) on the left / 2000 Ohm(potentiometer) on the right I measured 1.88mA

Am I wrong? Clearly experiment say so...


texts: Monitor status of slow-switching (1 second) signal

texts:
I need to make a circuit that can look at a signal and turn an LED on or off if the signal is actively switching.

The input signal turns off and on for a period of about 500ms, but sometimes will be on 1 seconds or longer. What I want to do is make the simplest circuit that will turn an LED on if the input is pulsing and off it the signal is constantly on for more that about 1 second.


texts: Doubt about the volume of the air gap in an electrical device

texts:
So  for the following device:

I'm trying to figure out the torque. To do that, I need the area of the gap. In the solution, it says that the gap volume is: $$2gh(r_1+0.5g)\theta$$

But the part of \$ r_1+0.5g \$ is really confusing me. I'm not sure where that comes from. Isn't it supposed to be \$ 2gh(2r_1)\theta \$ ?


texts: Decipher Surface Mount Aluminum Electrolytic Capacitor Markings

texts:
I am repairing a Definitive Technology BP-7004 Super Tower's power supply / amplifier that makes a buzzing noise when it is cold. After it warms up, the buzzing slowly fades away. I've attached an image (link below) identifying four surface mount capacitors. I'd like some further insight in determining their values from the markings: 10 25G 405

I've looked online and found various resources, but none seem to be definitive as each manufacturer seems to have their own marking schemes. Is there a way to determine who manufactured these capacitors?

The capacitor with the scratch (lower left) is the bad one. I "tested" it by applying a low temp soldering iron to the top to heat it up a little. The buzzing would go away, I was then able to cool the cap with an inverted can of "dusting air", once the cap was cooled, the buzz returned. Testing each cap with a soldering iron is time consuming, so I was able to narrow down the bad spot by first directing a heat gun at different parts of the board.

I've seen several postings by other BP-7004 owners looking for a method to solve this buzz. Hopefully these capacitors are the bad point on all of the boards that buzz. Replacing a dollar worth of components is much better than the $140 for a new board from the manufacturer.

--Edit with new information --
I have a replacement board from the manufacturer and the "new" capacitors are marked a little differently. The new caps read "h1., 10, 25V". I'm hoping that means 10 micro farad and 25 Volts, I have no idea about "h1." though.
Photo of new capacitors


texts: In clock recovery, how is the recovered clock used to recover data?

texts:
I've been refreshing my memory on clock recovery, and I've hit some issues trying to understand how the recovered clock can be practically used to latch data bits from the input data stream.

For simplicity, let's assume a NRZ line code, such as 8b10b. Because of NRZ encoding, the data stream will transition if a logical 0 follows a logical 1 or vice versa. Any transition on a wire carrying NRZ data will be due to the transmitter clock latching a new bit to be sent.

Assume an analog PLL which generates a square wave on the VCO, an edge detector on the data stream input which creates positive pulses on each transition of the data stream (see page 34 of 2), and a positive-edge-triggered Phase-Frequency detector (see page 35 of 2) which generates the phase difference.

In a traditional clock recovery setup using a PLL/edge detector, the recovered clock's positive edge will eventually align to the transitions in the received bit stream, and thus be aligned to the transmitter's clock.

The problem I see with aligning to the transmitter's clock is that when using the recovered clock to latch the input data into a flip-flop, immediately after latching (or possibly even before due to jitter! A PLL can't lock on to the exact frequency), the data stream as seen by the flip-flop's input will transition. Although small, this is a hold (setup) time violation for the flip-flop. Additionally, I recall that sampling as far away from transitions as possible is ideal to accommodate for jitter.

However, none of the sources I've been reading discuss any solution to my perceived issue of "using the recovered clock as-is to shift in input data". The closest I've seen is a diagram implying that the recovered clock should clock a flip-flop fed with the input data stream.

The naive solution I would use would be to "invert the recovered clock before feeding it to the flip flop which latches the input data". Assuming the problem I perceive exists, what solutions are used to work around the issue?


texts: I'm designing a Z80 microcomputer with dynamic memory (DRAM), and I want to control the memory with 3 chips; an ATF16V8 Generic-Array Logic, and 2 74LS157 quad 2:1 multiplexers. The logic diagram of the circuit to be embedded in the GAL is already done, but I have one problem: How do you reset a D-Flip-flop in the ATF16V8?


texts: Do I need resistors before and after bootstraping a MOSFET?

texts:
I have an N-channel MOSFET called BUK9Y07-30B,115 and a bootstrap IC called PMD2001D,115. I'm going to connect the bootstrap IC with the gate of the MOSFET. But I don't know if I need a resistor before and after or only before or after.
I know that the gate of the MOSFET have a capacitance and it takes time for it to charge up. When the gate is fully loaded, then current can pass from drain to source. Current don't flow through gate to source. Instead, when the operator stop using the gate, e.g lower the voltage, then the current at the gate is going back where it comes from. Just as a capacitor.
So my question, if I want a very fast CMOS-shaped PWM at the gate at the MOSFET. Do I really need a resistor before or after or both the MOSFET/Bootstrap IC?
Because, I know if I place e.g 10k resistor before the bootstrap IC, then it will increase time to power up the NPN transistor and discharge the PNP transistor when PWM goes to 0V. The same thing happens to the other side of the bootstrap IC.
But is it required?


texts: Reading of hex file in testbench : Verilog

texts:
I have converted an image file into hex file which has R,G,B and alpha values in multiple columns. For example :

3c 48 36 ff 1d 2b 19 ff 08 18 06 ff 08 17 05 ff 14 1f 0d ff 1b 22 11 ff 1a 1f 0e ff 1a 1b 0b ff 1d 1a 0b ff 20 1a 0b ff 23 1a 0c ff 23 1c 0d ff 24 1d 0e ff 24 1d 0e ff 21 1c 0d ff 23 1c 0d ff 1f 1a 0b ff 1e 19 0a ff 1c 19 0a ff 1e 1a 0b ff 20 1a 0b ff 24 18 0b ff 23 18 0a ff 21 18 0a ff

Now I want a way to read and store this data as a collection of 32 bits( i.e. 4bytes). If I do not know how bytes are present in the file (since file can be of any size), how can I achieve this?


texts: Digitally programmable switch using minimum space (without relays)

texts:
Possible Duplicate:
  How to short two nodes electronically

I want to make a pcb containing about 32 switches (that do a physical connection between wires) each can be programmed digitally from an arduino board pin. I have a space limitation (as the pcb has to be about the size of a typical mobile phone and contains arduino uno board and some other small components as well) and thus can't use relays to do that. Is there any other way to do it?

P.S. Digital MUX don't serve the purpose since they don't establish a PHYSICAL connection

P.P.S. If it is possible to achieve it at a low cost (<10$) it would be great!

Thanks


texts:
I tried to measure some HDMI signals (the TMDS Clock) from my PS4 with a keysight MSOX3104A Oscilloscope. After my "measurement" the PS4 did not send any HDMI signal to the connected TV. Multiple soft resets (safe boot) did not fix the problem. I also tried another monitor to check on the signals, but same problem.
Setup was a cut open HDMI cable with one end open and following connection to the oscilloscope:

GND from Oscilloscope to TMDS_CLOCK-
CH1 from Oscilloscope to TMDS_CLOCK+
Input impedance was 1MOhm.

Is it possible the oscilloscope damaged the HDMI port?
And why does the PS4 not send a valid HDMI signal anymore?

I can't imagine how this happened because I think I did everything right:

The PS4 was isolated from earths ground.
The HDMI port should be short circuit safe according to the specifications.

Any ideas?

(If this is "off-topic", please let me know where I can ask this question..)


texts: Why doesn't Atmel TWI support I2C START BYTE on TWI?

texts:
I would like to know why Atmel TWI doesn't support I2C START BYTE.

I am reading the AT32UC3C2512C datasheet on the TWI part, and I can see it doesn't support the START BYTE from I2C (it's on page 698), and I would like to know the why, and the implications of this being not supported.


texts: How can I limit the voltage of a circuit so that it is always between 8 and 15 volts?

texts: I am currently working on a project in which I am using piezoelectric material to charge a battery. The voltage output of the piezoelectric material is variable depending on how much mechanical energy is applied to it. I don't want there to be too much voltage or it will fry the battery, and if there is too little, the battery won't charge well. I am using a 9V battery. How can I limit the voltage input to not be too high or too low?


texts: Can a capacitor have high series resistance and low Q and why?

texts:
I measured with an LRC meter (Agilent 1731A) a capacitor at frequency \$1kHz\$, finding \$C=109.4 n F\$.

Then I tried to measure the resistance and quality factor of the capacitor: here is what I got.

Series mode @ \$f_0=1kHz\$ : \$R_C=95 \Omega\$ and \$Q=14.8\$.

As expected I have \$Q=\frac{1}{f_0 2 \pi C R_C}\$

The series resistance is very high and the quality factor very low.. What could be the reason for finding such values in a capacitor? Is it "common" to have high series resistances in capacitors?


texts:
Typically mobile devices that have a mains-powered supply will accept voltage that is multiple of some single battery voltage. For example, 4.5 volts is 1.5 volts (AA primary battery) 3 times and 36 volts is 3.6 volts (Li-Ion battery) 10 times.

Now there're laptops that use external power supplies rated at exactly 19 volts. That isn't a multiple of anything suitable. Puzzles me a lot.

Where does this voltage originate from?


texts: I am measuring a 9W LED with a clamp on ammeter. Why does it only draw 7.62W?

texts:
I bought a UNI T UT210E true rms multimeter.

I measured the current of 9 W LED lamp. It shows 0.033A. For the power I get \$0.033 A \cdot 220 V = 7.26 W\$ only.

But bulb was 9W. Why this difference comes? Actually am new to electric.

I measured also a running 5hp water pump 3 phase with 240 VAC it gives

I1 = 7.35 A
I2 = 6.75 A
I3 = 6.15 A


texts: Power LEDs from wall outlet without transformer plug?

texts:
I want to power part of an LED strip like this one:

http://www.amazon.com/Lighting-EVER-Flexible-Waterproof-Ultimate/dp/B005JR1NUU

... from a standard US wall outlet. I don't want to use a bulky 12V power adapter. Is there a component that can do the job of converting the voltage that would be suitable for hiding in a base of a lamp? (low temp, small)

The purpose is to make an LED lamp with the power transformer hidden. The space it fits in is roughly 2" wide, 6" long and 1" tall


texts:
How do I calculate the Luminous Intensity (cd) of multiple LEDs spread across a 1.5m2 internally illuminated sign element?

I have done this by treating it as a point source and adding each led module, but from what I have read it doesn't work that way.
such as mentioned in
How to add lumens


texts: How do electric and magnetic fields affect electronic circuits?

texts:
I have come across those requirements:

"The equipment shall not be susceptible to DC magnetic fields of up to 60
μT."

"The equipment shall not be susceptible to electric fields of up to 140dBuV/m between 400MHz and 10GHz"

My intuitive idea of how electric and magnetic fields impact a circuit is not enough, it seems.

I know that current through a wire generates a magnetic field decreasing in 1/r, but I don't know if it makes sense to say that we can calculate the current induced in a wire from the magnetic field value and the distance from the source.
Are there any other effect of a parasitic magnetic field on a circuit? Such as inaccuracies in hall effect sensors readings etc.
As for electric fields, I assume it changes the values of the capacitors in the circuit, but I don't know how. I didn't find any answer during my research on internet.
Are there any other effect of a parasitic electric field on a circuit?

I would like to understand those types of requirements (not only those particular ones), what they mean. I only have a vague idea of how magnetic and electric fields can impact a circuit, and clarification if possible with examples would be much appreciated.


texts: Combing two DC voltages, one high volt low current the other low voltage high current

texts:
I am a new member and have found lots of useful information on this forum whilst learning about electronics.

I am wondering if I connect a low voltage high current source to a high voltage low current source, if I might get a high voltage source that could use the current from the low voltage high current source.

I have previously joined similar low voltages through two independent bridge rectifiers and then placed them in series across a filtering capacitor which I could manipulate to a higher voltage (x2 volts) out or a higher current out (volts x 1). This worked well. But before I try combining a high voltage such as say 500VDC at 100ma with a low voltage say 1VDC at say 50amps, I would like an expert opinion of the possible outcome, given that each supply will be isolated.


texts: Effect of AC output impedance on a ratiometric measurement

texts:
I was planning to make a measurement with a ratiometric IC, so I will sense both the Vcc and the Vout from the chip as shown below. For cleaning up the noise and stability I also want to add a 5V voltage regulator right before the IC. The IC is basically measuring differential pressure.

I have heard from someone that I might need to verify whether the voltage regulator has a low AC output impedance. What could be reason for such inquiry for this application and why would it matter? What is meant by AC output impedance?


texts: How do I calculate a PCB embedded capacitor? (2 in series)

texts:
LTM2881s datasheet suggests a pair of embedded PCB capacitors to "minimize any high frequency differential voltages and substantially
reducing radiated emissions".

In the eval board and datasheet they suggest it to be done like this:

The the Eval Board .pdf states the following:

  1 - Four layer PCB, allowing for isolated side to logic side
  ‘bridge’ capacitor. The bridge capacitor is formed between
  an inner layer of floating copper which overlaps
  the logic side and isolated side ground planes. This
  structure creates two series capacitors, each with approximately
  0.008" of insulation, supporting the full
  dielectric withstand rating of 2500VRMS. The bridge
  capacitor provides a low impedance return path for
  injected currents due to parasitic capacitances of the
  LTM2881’s signal and power isolating elements.

I have failed to find the dimensions to the planes on the available .pdfs, and I would like to not have to resort rescaling the images with the known IC size to find out the dimensions (its a nice opportunity to learn something).

Its quite easy to find calculators for a single capacitor made of two planes on the PCB, but how do I calculate 2 capacitors in series with parts of one plane not overlapping? (Namely the parts of the Layer 2 - Ground Plane that do not overlap with Layer 1, do I ignore that?)

p.s.: or are the dimensions not that critical and a few pF are enough?


texts: Led panel sending and receiving card working

texts:
I understand how a RGB LED panel is driven from sparkfun's explanation (here).

From manufacturers like Huidu and Novastar I get that in a setup you often need a sending and receiving card. Like you could see (here at page 3)

In which the sending card divides the image you would like to show to the right parts and sends it to the right receiving boards.

But I wonder how the communication happens for an asynchronous LED sending card, if you display a static picture.

Does the sending card once send the needed information to the receiving cards and they buffer the data in their memory and display the image stored in the memory?
Or does sender card continuously send the same static image to the receiving cards?

I would like to know this because I'm thinking about building my own asynchronous LED sender card and send the data to existing receiving cards.


texts:
I am a bit confused about Impedance Matching for maximum gain and for maximum power transfer.

I knew that the conjugate matching between, for instance, an amplifier's output port and a load Zl, is given by the condition Zout = Zl*. Under this assumption, reflection at the interface between them will be zero.

Does this operation correspond to maximum gain condition, or maximum power condition, or both? Is there a difference between these two conditions?


texts:
I'm sure there's an easy explanation, but I'm stumped.

I'm trying to understand Sparkfun's Venus GPS, which can be put into sleep mode by cutting the 3.3v and letting it run from the supercap shown above.
According to my math, the 330 resistor has a voltage drop of almost 3v, leaving no where near 2.9v.
How is this capacitor charged?
Thanks!


texts: How to store the difference of 2 voltages on capacitor?

texts:
Suppose we have two voltages V1 and V2 how can we store the voltage  difference (V1-V2)  on a given capacitor?
I tried charging the top plate of the capacitor to V1 and then charged the bottom plate of the capacitor to V2. but the value of the voltage across the capacitor is not V1-V2, how can we do this?

Basically I want to perform subtraction of 2 voltages, with a simple circuit which does not consume much power and area


texts: How are analog thermocouple meters calibrated?

texts:
In most modern thermocouple measuring equipment, the input is high impedance and approximates a perfect voltmeter. This makes the thermocouple measurement easy because there is no current flowing through the system and you calculate it directly from a lookup table.
However, older analog gauges that used a coil to displace a needle have much lower impedances like 10-15 ohms. In this case, the resistance of the hookup wire and the thermocouple itself start to come into play since they make up a non-trivial percentage of the total voltage drop.
How were were these gauges calibrated? Did it have to be performed on the final installation or with a specific thermocouple/gauge pair?


texts: Determine maximum length of repetitive sequence in synchronous FSM

texts:
I have the following realisation:

The figure shows a synchronous circuit with the clock on Rising Edge. The circuit will generate a sequence of values on the output (abcde) of the five D-flip-flops.
For \$t=0\$ the output abcde = \$"10000"\$.
I am asked to determine the length of the maximum repetitive sequence of the circuit, but I don't know how to.
I have the answer to this question, and it turns out that the longest sequence has a length of 16. But there is no explanation of how you arrive at this answer. Can someone clarify how the procedure is done?


texts: Configuring UART TX and RX pins to accept CAN TX and RX signals

texts: The microprocessor I'm using, the BeagleBone Black, has an option to send CAN messages to/from it through the UART Tx and Rx pins. I'm not sure, though, if this is a 1:1 translation (i.e. the UART TX port corresponds to the CAN TX port) or if it's vice versa (i.e the UART TX port corresponds to the the CAN RX port).


texts: How to use Voltage Measurement in Matlab Simulink?

texts: I am a beginner in MatLab Simulink and would like to measure the voltage across two electical nodes. I use Voltage Measurement to perform this task. However, i can not connect the positive and negative terminals of the Voltage Measurement to the nodes. There is a red circle appearing on the nodes. Anyone has similar problems and solve it? Thank you for your help in advance.


texts: Adding an Activity Led to an IR receiver circuit

texts:
I am building an IR Receiver for use with a raspberry pi. The receiver is a vishay TSOP 4838. Connecting the device to a raspberry pi is straightforward. The following diagram reflects the receiver manufacturers recommended circuit.

I would like to add an "activity" led into the circuit so that when the device receives IR input the activity led flashes. I know it can be done - but how to do so eludes me even after looking at many IR receiver circuits.

How can I add an IR activity led?


texts: Timer for turning LED's on for 4 seconds and then off for about 200 seconds

texts:
I want to build a very small, low power timer that will allow several LED's on for 4 seconds and then off for about 200 seconds, then repeat. 4.5VDC. No programming.

Help please - thanks.


texts: This is an apparently simple opamp circuit that i cannot solve... The question is: is the voltage at blue probe the same as at green probe? (imagine no probes are there, they are just to locate voltage points). I can calculate current trough R2 and R3 but i do not know how to calculate current at opamp exit (between opamp and blue probe) with that value i could solve the problem easily... eventhough is it possible to solve it without that current value?


texts:
I'm more programmer than electrical engineer. I have connected Arduino with an AD5668 DAC. I want to control analog synth such as Korg MS-20M. For the filter, it takes -5 to 5V.
Right now I can generate only 0-5V with digital values 0-65535.
I want to generate -5V to 5V straight out of Arduino with digital values 0-65535.
AD5668 takes a reference voltage. Right now I supply it 5V from Arduino. Could this be a solution? To supply -5V reference voltage? I would like to make some simple DIY solution hopefully without any new parts in the circuit. I was thinking that AD5668 has all the required in itself like OP-AMP, but I guess it does not generate smooth -5 to 5V voltage.


texts: LM35 max temperature I read is 75C while thermocouple says 120

texts:
as the title indicates, the max temperature I can read with a LM35 sensor attached to a heater is 75C, but a thermocouple reading is 120C, and my hand also thinks the heater temp is above 75C by far. The exact number chip is LM35DZ, and the datasheet says the maximum temperature is 150C, so 1200 mV are expected for the heater.

I've seen dozens of examples around this sensor, but almost all of them are room thermomethers (around 25C). I've tried reading directly to the chip, and through an opamp non-inverting amplifier, and the max temp for both are 75C. It seems the chips is stuck at such reading. By the way, the power supply is 5V. Maybe it's a faulty sensor, so I will need to get a newer one ASAP. It's a frustrating issue because it's such an easy chip to use.

What could be the cause of this difference in readings?


texts: In my project, I use a atmega16 to send data to PC via USB to TTL converter at baud rate of 9600 and internal RC of 4Mhz. If I power the atmega16 using my laptop through a usb cable I can receive the data perfectly, but when I power the same using a 9v DC battery and 7805 regulator, I get garbage value on the PC. Please help me out.


texts: Boolean Algebra Question (Logic Circuits)

texts:
I'm stuck on an engineering question about boolean algebra.
I've been trying all day and asked my other students however I am still stuck. Could you please help me to draw a logic diagram and truth table for the Boolean expression "(A + B) . (A + C)". I also need to minimize the expression and do a logic circuit and truth table for it also.

I tried first attempt and got this:

However I am not sure if it was right so I started researching and got this for my second attempt:

I haven't completed the truth table, it's wrong I think.
Could you guys comment on which attempt was the correct one, thank you!

My final attempt:

Please tell me someone, is this finally correct? Both truth tables and logic diagrams?


texts: oscillation in overcurrent shutdown circuit

texts:
I've tried to design an overcurrent shutdown circuit, what turned out to be more complicated than I thought.
The specifications:

PSU from 5V to 40V
Shut down at currents >= 1A
At most a Watt or so of dissipated power after shut down
Very low voltage drop in "on" state (say at most 0.5V)
No use of electro-mechanical relays
No use of surge current thermistors (I dislike them)

So, my proposed      solution was to test the voltage drop in a resistance of 0.01Ohm, and to switch a low on resistance hexfet on or off. I ended up with the following circuit:

When running a simulation with LTspice, with a voltage ramping from 0 to 20V it turned out that the circuit works almost as desired (to shut down when the current exceeds 1A), but in place of shutting down, it sends very sharp peaks from 0 to 1A (see figure below), at a frequency depending on the value of the capacitance of the capacitor (without a capacitor, the frequency is very high, with a 1mF capacitor, the frequency is of 0.1Hz or so). Note that the location of the capacitor is not mandatory: it can be put in many other places, with a similar effect. I've struggled to prevent these oscillations, without success.
It seems that the circuit want to shut down, but the FET struggles to maintain its gate high.

My questions are:

What is the exact cause of these (relaxation?) oscillations ?
How to make this circuit work ?


texts: generic term for inductors/capacitors/transformers for power-handling applications

texts:
Can anyone think of a generic term to cover capacitors and magnetics for power-handling applications? (is there one?)

I want to distinguish from power semiconductors and signal-level capacitors/magnetics.


texts: Why does my AVR reset when I call wdt_disable() to try to turn the watchdog timer off?

texts:
I am having a problem where executing a disable watchdog sequence on an AVR ATtiny84A is actually resetting the chip even though the timer should have plenty of time left on it. This happens inconsistently and when running the same code on many physical parts; some reset every time, some reset sometimes, and some never.

To demonstrate the problem, I have written a simple program which...

Enables the watchdog with a 1 second timeout
Resets the watchdog
Flashes the white LED on for 0.1 seconds
Flashed the white LED off for 0.1 seconds
Disables the watchdog

The total time between the watchdog enable and disable is less than 0.3 seconds, yet sometimes a watchdog reset occurs when the disable sequence is executed.

Here is the code:

#define F_CPU 1000000                   // Name used by delay.h. We are running 1Mhz (default fuses)

#include <avr/io.h>
#include <util/delay.h>
#include <avr/wdt.h>

// White LED connected to pin 8 - PA5

#define WHITE_LED_PORT PORTA
#define WHITE_LED_DDR DDRA
#define WHITE_LED_BIT 5

// Red LED connected to pin 7 - PA6

#define RED_LED_PORT PORTA
#define RED_LED_DDR DDRA
#define RED_LED_BIT 6

int main(void)
{
    // Set LED pins to output mode

    RED_LED_DDR |= _BV(RED_LED_BIT);
    WHITE_LED_DDR |= _BV(WHITE_LED_BIT);

    // Are we coming out of a watchdog reset?
    //        WDRF: Watchdog Reset Flag
    //        This bit is set if a watchdog reset occurs. The bit is reset by a Power-on Reset, or by writing a
    //        logic zero to the flag

    if (MCUSR & _BV(WDRF) ) {

        // We should never get here!

        // Light the RED led to show it happened
        RED_LED_PORT |= _BV(RED_LED_BIT);

        MCUCR = 0;        // Clear the flag for next time
    }

    while(1)
    {
        // Enable a 1 second watchdog
        wdt_enable( WDTO_1S );

        wdt_reset();          // Not necessary since the enable macro does it, but just to be 100% sure

        // Flash white LED for 0.1 second just so we know it is running
        WHITE_LED_PORT |= _BV(WHITE_LED_BIT);
        _delay_ms(100);
        WHITE_LED_PORT &= ~_BV(WHITE_LED_BIT);
        _delay_ms(100);

        // Ok, when we get here, it has only been about 0.2 seconds since we reset the watchdog.

        wdt_disable();        // Turn off the watchdog with plenty of time to spare.

    }
}

At startup, the program checks to see if the previous reset was caused by a watchdog timeout, and if so it it lights the red LED and clears the watchdog reset flag to indicate that a watchdog reset happened. I believe that this code should never be executed and the red LED should never come on, yet it often does.

What is going on here?


texts:
This is a bit of an open question but I am seeking advice on further research and also some search terms so I can find the best solution.
The project requires a 48V source from a battery pack which needs to be boosted to 600V-800VDC (allowing a smaller CSA cable to be used), this will then be stepped down again to a more useable voltage for a load with a 500W power requirement.
I would ideally like to use a dedicated management IC but cannot find anything that meets the voltage/power requirements, so looking for advice on what SMPS or power conversion topologies to investigate further.


texts: LED and Photodiode Data Acquirement System

texts:
So I am to develop a project this semester and wanted to be shed some light on certain topics.
The goal of the project is the following: Detect a pendulum's period using an LED and a photodiode and it has to work in daylight conditions.

The system I thought about using (still untested,) which will be later sent to an ATMega microcontroller:

LED/PD
Transimpedance op amp
High pass filter (for DC cutoff, hopefully filtering some sunlight?)
Buffer
Notch filter (cutting the 100Hz lab light)
Full wave precision rectifier (for all pulses to be positive)
Op amp for more gain.

I also figured I'd use some rubber tubes around LED and PD while directing them at each other, hopefully reducing background light in my signal.

Is there something you guys think won't work or could be improved with this system?

Also, I have no clue which LED to choose (IR, green or red) or if it makes any difference for that matter. Maybe a green one would be easier to detect since its light carries more energy?

And finally, we get bonus points if the system can detect what material the ball on the pendulum is made out of, but honestly I am clueless to how to do this, was hoping for a hint if it isn't too much to ask.


texts:
I am trying to synthesize my Verilog code, which I wrote using Modelsim tool for 8-bit MAC in Cadence Encounter. The file that is generated after synthesis has to be re-checked for functionality in Modelsim. However, this time it is generating many errors of the form:

    ** Error: /ugassignments/ma3ps139/cadence/vedic8_syn/synthesis/fsd0k_a_generic_core_21.lib.src(21703): $width( posedge CK:350 ps, :400 ps, 159 ps );

Also, the synthesized code file shows to have many "UNCONNECTED" wires, which is why it is not generating the results. However, when I try to trace back that part of the synthesized code to the original code, no such dangling wires seem to be there.

I am new to this. Please help.


texts: buzzing sound at times from regulator circuitry

texts:
I am using Lm2596-ADJ for input power regulation in my circuit. Below is the schematic.

It powers an AVR and a sim800H gsm module. When the sim800H is about to power On or when making a call I hear a buzzing sound from the board as at these times the current requirements are higher. LM2596 should handle this easily, the Input current I am providing is 1.2A @12VDC which should be enough as well. I would like to know which component is responsible for this noise and How to eliminate it. Apparently there is no effect of this on the working of the board as neither AVR nor sim800H shows in problem.

Here is the sound recording ... https://soundcloud.com/dost-muhammad-shah-531566807/buzzing-sound


texts: GPS Power consumption MTK3339 vs SirfIII for periodic logging application

texts:
I am currently working on redesigning a SirfIII based battery operated GPS logger. A MTK3339 based GPS module has been selected due to overall (advertised) performance.

The GPS logger uses a microcontroller to enable the GPS receiver in a periodic time interval, waits for a position and then turn off the receiver (leaving backup supply enabled that keeps the ephemeris data in RAM, allowing faster TTFF).

After some testing the results show that the old SirfIII logger is still outperforming the new MTK3339 version. Standby current of the new logger is only 1/4th of the old design.
Closer investigation showed now that the SirfIII GPS chip is featuring a special mode called Sirfaware. This is resulting in 50-75% shorter position acquisition times compared to MTK3339.

Question:

a) Is anyone using MTK based GPS modules and found a way to improve position acquisition or overall power consumption?

b) Is MTK3339 the right choice for a battery operated logging application?


texts:
I'm new to EE in general and I've gotten myself a bit confused. My apologies if this is a stupid question, but my research isn't helping too much.

I am working on a project to control 7 LED strips with an Arduino and MOSFETs. The strips require 12V and say they use 24W. I was hoping to find a power supply to power all 7 strips, instead of one supply per strip (seems silly).

So if, 24W = I * 12V then each strip should need 2 amps. This means, to power all 7 strips, I need a 12V 14amp power supply. I'm noticing most power supplies deal in watts for some reason, so that means I need a 12V 168W supply, maybe 200W for safety.

So, with the backstory in check, 2 questions:

1) Do my 200W power supply calculations seem correct?

2) When I find this power supply, is it safe to put 14amps at 12V through a breadboard's power rails? That seems like a lot? Seems dangerous? I really have no idea...

Thank you in advance!


texts:
I would like to commute a 12V siren with an ESP01. I thought to use NPN or PNP transistors TO-92 that I have since a long time in my drawers.

The ESP01 has 3.3V maximum at the output, and the siren work at 12V and drive a current about 300 mA.

I found for example a NPN transistor S8050 which can draw up to 700 mA. The power dissipation is about 0.625W, whereas the siren consume about 3.6W. I don't know if it is a problem or not...

Is this NPN transistor is ok for my application, or should I use a MOSFET ?

Thanks


texts: Do I need to put a resistor at the collector of this MOSFET driver?

texts:
When I look at this schematic, I think of two scenarios but I don't know which one is correct:

Collector resistor does not exist. So, Both the transistor and the Mosfet provide a short circuit. A very high Current flows from the positive terminal of the battery to the collector and then comes out of the emitter and enters the gate of the Mosfet and exits from the source. Therefore, a resistor MUST connected between the positive terminal of the battery and collector to limit that high current.
Collector current is limited by the forward current of the diode which is limited by the resistor (R1). So, There's no need to use a resistor at the collector.

Which one of these scenarios is correct?

Thank you very much,


texts: Help identifying and finding shematics/datasheets for circuit board

texts:
Does someone know what kind of circuit board this is?

(Click to zoom)

I found it in an old cardboard box in the basement yesterday. "Sung Wei 08V0-A" is written at the top.

Where can I find schematics, datasheets or technical information about this product?


texts:
I have two IR diodes and I want to connect them to my Raspberry Pi. From Pi I have 3.3V voltage. Diodes are TSAL 6200 .

Can I connect them to PNP and my PI without resistor safely with this wiring?


texts: Methods to accurately move an object across a 2-D plane

texts:
This is the opposite/complement of my previous question, which concerned measuring the precise position of an object as it is moved/drawn by someone over a short duration. Assuming I use one of @Rocketmagnet's suggested approaches (probably using linear encoders), next:

Suppose I have tracked/recorded the X-Y position data as an object is moved arbitrarily through some pattern across a 2-D plane by someone:

Goal: Now I would like the object to replicate that same recorded movement pattern, i.e., I would like the object to move through those same X-Y positions -- but automated this time.

In other words, I would like the system to carry/displace the object from the recorded (X1, Y1) to (X2, Y2) to (X3, Y3) and so on. Again, completely constrained to a 2D plane/surface, like so:

Constraints:

I would like fairly controlled/accurate movement of the object, with no greater than 0.5mm error.
The domain of points for the object to move will extends across a 30cm X 30cm square.
Exact duration/path between points is NOT critical -- since I will have a fairly well-populated point set (so it will already be pretty close to continuous movement).

The one potential solution I have considered for this (and I think one that is easy to implement) is to use motors placed on the edges but somehow connected to the object. But I am not sure how to connect them in a way that allows 2 degrees of freedom simultaneously, and moreover, I'm not sure how/if it's possible to attain the desired movement accuracy using motors.

So my question is: What are potential methods I can try for this kind of accurately controlled 2-dimensional movement? There are very few physical limitations on my setup as it currently stands, so I am open to toying with (reasonable) implementations of any level of complexity!

One piece of good news is: Since I will have a precise measurement/tracking system (from the previous question), it would be possible to integrate feedback / calibrate during the movement, which I suppose will be essential if I want to assure the 0.5 mm maximum error.

EDIT: In case the exact application is of interest: The system is my attempt at a simplified electronics-art demo of action-replication, i.e., a person's action is recorded and it is then duplicated either after a period, or on a duplicate system nearby. I initially tried working with shape memory alloys (nitinol specifically), but recording a 3-D movement of a multi-point shape was not easy (FAR from it!), hence my simplification to a "single-point" object across a 2-D plane.


texts: How to model a noisy Zener diode in LTSPICE?

texts:
I'm trying to simulate a white noise generator of the Zener diode style.  I'm going with current amplification, rather than the more traditional voltage amplification just because.  My problem is that I don't know how to simulate the behaviour of the diode, D1.  With the 30 volt supply, I'm hoping that the 24 volt Zener will be running in full avalanche mode, spewing out a whole pile of white noise.

I'm using LTSpice, but that only has models for the reverse breakdown voltage of Zeners.  Consequently the following circuit only produces a steady DC voltage at the “noise” node.  How can I fully model this transistorised circuit shown below?  Is it even possible, or do I have to actually build it and physically measure the noise?  My sense is that as tens of these diodes have probably been sold world wide, there must be data out there that I can't find.  I'm looking for concrete numbers rather than theory (or any sort of integration symbol) that I can plug into LTSpice.

Supplemental:

I've got as far as adding a white 1 mV P-P noise source (@1 MHz???) in front of the Zener, with a 15-0-15 supply as so:

which seems to kinda work producing the following trace at "noise".  This seems to me as perhaps how a noisey breakdown at the diode would appear.  It looks as if LTSpice has set a voltage gain of 100ish.  Of course, this is a somewhat moot without a better estimate of the actual noise levels.


texts: MOSFET Selection based on peak drain current

texts:
While selecting a MOSFET for application how do we calculate the peak currents which can occur in the circuit?
I am designing a DC/DC interleaved synchronous Buck Converter (2 MOSFETS per rail) for 2KW and for selecting the MOSFET I am calculating the Power losses in few MOSFETS to get a comparison between different MOSFETs. So fro my application per interleaved rail will carry 41.67A RMS output current. How do I decide the continuous drain current required for my application according to peak currents which can appear in the circuit? What can cause these peak currents in the circuit? Is it a good enough assumption to have a margin of 100% or more?
The device will be operating in continuous conduction mode and the ripple is very low due to high value of inductance chosen and interleaving of the rails.


texts: Can I make PCB panel with PCBs with defined assembly variants in Altium designer?

texts:
I have two PCBs that make one system, each PCB have two assembly versions. I need to make PCB panel that contain one of each PCB with right selected version.
It is possible to make PCB panel just for fabrication easy, but I don't know how to make assembly that depend on version. I can remove lines of elements that in version is not about to be placed in pick-and-place file, but this could be done in some othe proper way, right?


texts:
I am wondering why USB isn't recognised at all.
I followed Sparkfun Pro Micro specs.
Firmware upload works fine (Adrduino Leonardo)
Any help welcome !..


texts:
TOday, I have built an LED cube. I put it all together, arduino, mess of wires and all, and it doesn't work. Fiddling with it a little bit, I find that if I short certain wires to ground, the LED's work. Therefore, I think that it is the transistors controlling the pathway to ground that are the problem. This is the transistor circuit:

T1
EBC
||+Led Cathode
|Arduino Pin
Ground

T1 is a NPN transistor, EBC are Emitter, Collector, and Base. Base to arduino pin, Emitter to Circuit ground, and Collector to Led Cathode. What I believe should happen is when I send HIGH to the base of the transistor, the LED cathode and the Circuit Ground should be connected. However, this is not working. Is there anything I'm doing wrong?


texts: Altium shows little black blocks on my GND pads and tracks

texts:
After many years of using altium designer this time I faced to new problem.

After updating the schematic to PCB document it shows all of my GND pads and tracks covered by little black blocks as shown in picture:

It's not my software problem because it shows other files correctly, also it's not about my rules because I've not changed them yet.


texts:
I'm building a device which includes oscilloscope, signal generator and multimeter. I have trouble deciding how to properly ground each part, so my questions are:

Can oscilloscope ground be connected to the signal generator ground? What happens if these grounds are then connected to different potentials when in use?

If device is powered by 5V external power supply (like phone charger), does this mean that device ground is "virtual"?


texts:
I know there are multiple tutorials and questions regarding converting an ATX power supply, new or old, to a benchtop power supply for projects. I'm fully aware of how to make the basic conversion to get 12V and 5V connections but I would like to take it a step further.

I have a relatively new 900W power supply which I got for very little money and would ultimately like to turn it into a variable high power supply. I plan on adding all of the extra circuitry to do what I want to do in an external housing and have the cables from the ATX power supply simply plug into my new box. The list of what I intend to do is as follows:

Use an active load balancing circuit to combine all 5 of the 12V rails into one 12V rail that can handle roughly 70A.

From what I understand most supplies use the same power source and multiple voltage regulator circuits to get the different rails.

Use a Boost Converter Circuit on the new combined line above to produce voltages up to say 50-60VDC
Use a Buck Converter on either a single 12V rail or the combined line to get voltages below 12VDC.

My question is, can I do the above as I intend? Are there issues with following an active voltage regulator load balancing circuit with an adjustable boost converter to step the voltage up and down? Same goes for the Buck Converter? Any alternative suggestions that would accomplish the same goal?

I am aware I could buy a decent variable power supply but I don't have the money currently for that and I thought this would be a fun project in power electronics. I intend to use the supply for some motor control development and testing, hence why I want to get much higher amperage than 1 12V rail can provide.


texts: SSD1351 Display showing random bars across the screen

texts:
I recently bought this Display and wanted to use it with an ESP-WROOM-32.
After some problems I got it to work using this schematic and the Adafruit SSD1351 library. (I connected the 13V of the Display directly to a 13V voltage converter I had laying around because the FAN5331 is not working yet.)
I also had to lower the default SPI frequency from 20MHz to 5MHZ in the library because otherwise it would display some random stuff.
After successfully working with the display I slowly tried increasing the SPI frequency again to get the Display working a little bit faster. But as I did this, the Driver on the Display got really hot and it started to show some random bars across it. So I lowered the frequency again and retried it but with the same problem.
Thinking that I had destroyed the Display, I ordered a new one and tried it. But this one shows the bars even though I never used it with a high frequency. The only difference is, that the second Display is not getting hot at all.
So my question is, do you think that I just got a faulty Display or is there anything special that I should check in my schematic the could cause this issue?
Thanks for any help.


texts: Sense coil based leakage current meter (with LCD display)

texts:
This is the circuit diagram of the previous Leviton GFCI receptable without auto-monitoring self test.

Do you (or others) know whether the current coming out of the sense transformer or sense coil is directly the differential current of say 3mA? Or does it come out much lesser than that (for example 3 uA) and the chipset has to amplify it to become 3mA?

Because if the leakage current existing the sense coil is actual.. then one can simply put an ammeter before the chipset and lcd display to output the actual leakage current.

Original message:

I'm looking for a meter that can not only detect but also DISPLAY leakage current (in an LCD display) that is based on the sense coil technology in GFCI. So imagine a plug-in meter where you can plug to existing outlet or extension cord then your appliance plugged to the device and can show (by means of DISPLAY) whether it's leaking 1mA to 50mA leakage current.

Anyone has encountered such device? I want to study how different appliance leaks to study nuisance leaking in GFCI application.


texts:
I found a transformer from an old kit I had, I think it was the 10 in one electronic lab from GeoSafari. I'm really confused, as it only has three leads coming out of it (instead of the minimum of four I usually see), and can't find the model or part info. Guessing that the center terminal is the common ground and the other two are the input and output leads. Has anyone else ever encountered a transformer with a similar configuration (only 3 leads, all on one side)?

(Sorry if I look like I'm an idiot. I've never really worked with transformers.)

Leads are abused pretty badly. The transformer is about 3/4" on each side.

I just did some testing with LEDs. Current will flow between the second and third pins (in both directions), but not between the first and second pins or the first and third pins. I'm starting to think that the first pin is broken or disconnected, or just a dummy pin.


texts: What is the advantage of a "straw hat" (inverted cone) LED?

texts: LEDs with a concave cone-shaped lens are sometimes called "straw hat" LEDs. What is the advantage compared to the more common hemispherical lens?


texts: I want to make a USB cell phone charger. I know USB operates in 5 volts which means i need to drop down voltage if i have battery potential greater than 5 Volts. I have 12 volts sealed lead acid battery (SLA) of capacity 9AH. I need to drop down the voltage for which i am using LM2596 buck regulator ( Switching power supply) and it can deliver 3 amperes of current. But my cell phone charger(came with the product) is rated for 2A. So i was wondering how can i limit the current so that it doesnot blow my Cell phone. Thanks


texts: When does differential signalling become necessary

texts:
Is there an industry rule of thumb or application note etc for when differential signalling becomes necessary for reliable communication?

I'm thinking mainly in terms of distance and signal speed (and voltage levels), assuming a "normal" level of EMI from the environment.

Edit: To clarify, when I say differential, I mean using two wires per signal, with each wire having the opposite signal level to the other (one wire goes high when the other goes low, and vice versa). This is for two or three level signals (i.e. signals that have only high/low or high/zero/low). Examples include USB, LVDS, CAN, DDR clocks, and most other high frequency/high noise immunity signals.

The emi environment is, as mentioned, just the emi environment that you would expect in a normal city environment, not directly next to any rail switching gear or electric motors.


texts: Finding specific components in EDA software

texts:
I'm looking for the best protocol for finding specific parts in EDA software?

I've been mainly using EasyEDA for the past few months and have enjoyed how easy it is to search parts in the libraries available. This usually has about 90% of the parts already with symbol, footprint, and all for most of my designs.

I have been looking to upgrade lately to a software that is more widely accepted and has more features like design rules. So far, I have played with Eagle, Upverter, and DipTrace. In doing this I have become really confused with what actually is the proper why to find and select components for any design within the software. This is because how limited it appears all of these other software's libraries are compared to EasyEDA. For instance, if I go to search for a common component like the IRFZ44N I found:

1) Eagle does not have it in the included libraries (I figured this would have everything based on its reputation).

2) DipTrace takes 15+ seconds to "filter" it out (it also crashes frequently which leads me to believe I am doing it wrong).

3) Upverter has the symbol but only the TO-220 package.

If I look for a less common component such as the SUM70060E none of these software's default libraries even have it. In both cases EasyEDA has both (granted it may not be as cross-validated, but I happened to check this one and it seemed good).

I know this is just a single example but I have come across many more. It seems to me like I am missing some fundamental understanding. Is there some cross-platform "master library" out there I should install or should I not be searching for specific parts and rather just generic symbols and manually update their footprints as I go (even though this seems extremely tedious, especially if you want to do a simulation)?

Any insight would be appreciated.


texts: What is the significance of 75mV in available 100A current shunt resistors?

texts:
I'm considering doing part of How to Install an Ammeter in the Black & Decker CMM1200 Cordless Electric Mower  but first with just a shunt resistor and voltmeter, versus hooking in a dial ammeter (may hook in a dial later).

But, when examining shunt resistors, I found What Is A Shunt which states:  "This shunt is calibrated such that the voltage drop across it is 100mV when the current flowing through it is 100 Amps".

So, in order to acquire such a shunt resistor to directly read current as amps being equivalent to the voltage reading on a voltmeter (in mV), I would need a 100A 100mV current shunt resistor. But, when I search specifically for 100mV 100A current shunt resistors on Ebay all that is returned are 75mV ones (EDIT: A better search link).

What I want to know is why 75mV and not 100mV in those listings? What is significant about them having to be 75mV and not just 100mV?


texts:
Rectifying square wave voltage seems to give us DC directly without the need of a capacitor. so, why do we prefer sine wave over it?
What would change if I powered any adapter (laptop adapter as example) or any power supply with a square wave inverter instead of sine wave?

Edit: I understood from answers and comments that sine wave is better at generating and transmission, let's consider this a special case about "Powering power supplys (with input rectification) with inverters."


texts: How to measure small current in high voltage environment?

texts:
I would like to measure the current in a circuit with very high DC voltage. The maximum current produced by the source is 0.5mA, and the maximum voltage is 25kV.

I know that I can measure current using a hall sensor, but it's too expensive for my experiment.

I can also measure the voltage drop across a known resistance, but I'm unsure over how exactly I should calculate the resistance. Using Ohm's Law the resistance is 50MΩ, but I don't know if that's the correct way of doing it.

Any other cheap and conventional methods for me to measure said current?


texts:
I bought these big yellow capacitors from ebay, just to try them

(only information present there: "10pcs Yellow feedthrough capacitors axial capacitors 100V 15UF").

Obviously, they are simple axial capacitors, that have nothing of a "feedthrough". They are not electrolytic as well, since they are not polarised. I suspect they are "film" capacitors but I'm not sure.

Anyway, I found them particularly effective for killing medium to high frequency noise of PSU: Even for a switching PSU whose noise (near 2.5MHz in my case) is particularly difficult to filter, such a single bypass capacitor at PSU output kills half the noise.

Someone knows what are really these yellow capacitors, and for what they are used?


texts: L293D Problem- can't run both motors together

texts:
I am making rf based metal detecting robo and I had used 8051 for controlling the operation. The rf is fine and programming is also okay I think as I am getting desired outputs at 8051 output pins and L293 output pins.

The problems arise when I connect motors to the L293d's output pins.

1) Even if I get 8V at both sides of L293D, the motors didn't work when I connect them. (The motors are fine.)

2) When I connect one motor to L293D, then the motor works ... and on other side the output is 8V too; but as soon as I connect the second motor too... the first motor also stops.

3) If I keep running one motor with L293D, after 10-15 seconds the robo stops.

I am getting this problem first time in my experience. I have no guide / partner, so I am sharing it with you people. Hope, someone here will help me please.

(And can this be problem that I have used only one 9V battery on the entire circuit of 8051-L293D and H12D (RF IC)?
But also the output is 8V on L293D,
then why the motors are not working?)

Please help as I had to make my robo work asap.

Regards,

Er S


texts: I've been having difficulty finishing the routing on a PCB I've designed. This is the first time this has happened really. I have miles of free space, yet it only gets to 96.4%. Anyways, I can't find what these readings mean that display on the bottom left of my screen while auto router is running. Can someone please explain what the numbers mean?


texts: How does a capacitor work as a filter in rectifier circuits (with equations)?

texts:
I've looked at many places and everyone seems to give a qualitative explanation of the filtering process, which does explain some part but I think fully understanding the stuff needs some equations too.

In the circuit above, it seems to me that the input and output voltages should he same at all times but it is evidently not. Why?


texts: I am trying to make an H-bridge using N-channel MOSFETS (IOR IRLB8721PbF). So far I made what was a working complete H-bridge on a breadboard, using an Arduino's 5v pin and ground pin to power the circuit and an IO pin to switch the MOSFETS on and off ( digital IO so 5v or off only). My problem is that now I have attempted to transfer the circuit to perfboard, and now one MOSFET wont fully turn on (my multimeter reads just 3v across the MOSFET's drain and source pin). Is there an obvious reason for this or is it more likely that I have soldered the circuit together improperly. Thanks


texts: One stepper motor of two getting really hot

texts:
I'm using two 28BYG-48 stepper motors rated for 12V. These are unipolar motors with 5 wires. 1 Common wire and 4 wires to control the 2 phases. The motor that is getting hot has around 76-77ohm the common pin and the other pins, while the motor that is cool has around 78-79 ohms.
Both motor are wired the same way through a ULN2003 driver. For my current tests, I was running the motor very slowly. Almost 1 step per second, I'd expect both motors to be cool as the current rarely switches direction.
Is it possible that one motor is getting more power than the other? That would explain why one is getting hot.
When I switch motor positions, the motor that was cool gets hot and the motor that was hot stays cool. My guess is it's a problem with the ULN2003 chips.
One other thing, the ULN2003 connected to the hot motor is quite cool compared to the ULN2003 connected to the cool motor. When there is no activity (no motor switching direction), one of the two motors gets hot progressively.

How can I fix this?
What could be actually causing one motor to get excessively hot?

Note:
After taking pictures, I realized I mixed up the namings, those are ULN2003 chips. I have L293D chips but they're for other motors.


texts: Is there a technical reason why the Arduino Uno has such a distinctive board shape?

texts: Why does the Arduino Uno have that slanted shape at the right of the board? Is there a particular technical reason for this design choice, or was it just for esthetics?


texts: Confused on Fourier Transform. What is amplitude spectrum and phase?

texts:
I am learning fourier transform by myself and I am confused on the description below.

I can't understand how can I get the second formula by using the Euler formula on the first equation. Why is there no summation symbol in the second equation?


texts: Difference between conventional Eye-diagram voltage plot and "Eye-density" plot in ADS Keysight Simulation

texts:
I know what is eye diagram. It is the sampled voltage plot at the clock frequency (Usually) of my circuit and superimposed. If the logic 0 corresponds 0V and logic 1 corresponds 1V then for the ideal case, the eye diagram Amplitude will also plot the superimposed samples of the signal which corresponds to 0V and 1V. For the lossy channel, the amplitude moves away from the 0V and 1V level for logic 0 and logic 1 respectively. And that movement depends on the attenuation and loss of the channel. Generally I have seen so far to be around 0.8V or 0.9V for logic 1. Like below.

This eye diagram is actually PAM4 level eye diagram. I generated in Cadence Virtuoso using its eye diagram tool using its embedded calculator. I am fine with that.

Now, I have experienced in ADS Keysight simulation that they have Eye density which also produces Eye diagram. but I see it always plot the eye diagram amplitude into half. Like my below eye diagram that I generated in ADS using its generic TX, RX driver and low pass filter like channel. I have driven the TX with V_low = -1V and V_high = 1V PRBS signal. So, the difference is 2V. At the receiver (in simulation), it produces the eye with V_high around 0.4V to 0.6V. This is the case most of the time I experienced in ADS. So I was confused that Eye density is not exactly the conventional Eye diagram plot (Maybe or my conception of Eye density is not clear).

Eye density Summary:

In the help of ADS it is written like below:

  Density: A temperature view of the 3-dimensional eye histogram. The
  eye is automatically centered and displayed over 2UI on the horizontal
  axis. Color indicates the number of crossings of a segment in the
  time-voltage plane. Blue areas are cold, whereas red indicates
  comparatively more crossings.

  In statistical mode, the density histogram is plotted as if 1e6 bits
  are run.

I am confused about what exactly then it produces if it is temperature view...because it is also showing the voltage amplitude of the signal. And the Amplitude (as it is showing in the summary is around 0.698V whereas my input signal difference is 2V. My channel was normal passive low pass filter-like channel.

So, is the Eye density plot in ADS different from conventional Eye diagram? If it is what is then? Because the definition in ADS help is not enough for me to understand density.


texts: How do I write this circuit (returns 1 if the number of 1s in input is odd, otherwise returns 0) using a MUX?

texts:
Here is the truth table:

The exercise is to write the SOP of this truth table using a multiplexer with 2 select lines and 4 inputs. I got the SOP expression:
$$(\lnot a\lnot b c)+(\lnot a b \lnot c) + (a \lnot b \lnot c) + (abc)$$

I assume that each expression in the parenthesis is one of those 4 inputs.

I understand how a multiplexer works I just don't understand exactly how I am supposed to apply it here. My professor wants us to use a 74151 chip. Here is the datasheet

I think I am only supposed to use one of those 2 outputs...

The question is: "Write the SOP expression so as to implement a multiplexer with 4 inputs and 2 selectors. Use the chip 74151 and NOT gates if necessary".

I don't understand the idea behind using a multiplexer here. Can someone explain? Thanks


texts: We have all seen the little symbols on electronic connectors that indicate its polarity. But is there a term for describing it other than something like positive inside, negative outside or negative tip, positive barrel/ring, and such?


texts:
I'm searching for a schematic of a low power DC-AC inverter, to convert the output of USB, which is in DC to AC for electromagnetic induction application. I'm a self learner, I would like to know whether this whole idea is possible.

Also, do i need to step up the 5V of the USB to 12V? I did found some 12V to 110AC inverter circuit, however, they usually requires high power, 100W above.

I hope I'm clear with my question. Thank you in advance.


texts: Differences in voltage measurement at the input of a circuit

texts:
I am trying to understand the difference I am seeing in voltage signals, that I am applying to my circuit's input.

So the basic layout is shown in the diagram, I have a connection, A from my function generator that I split and connects to B the oscilloscope and D my circuit input. I also have a probe from the oscilloscope C, connected to the input for the circuit at D.

What I expected is that the signal measured at both the inputs for the oscilloscope should be the same, as they all connect to the same point in the end D, and are grounded. But what I see is this

The connection from the function generator to the scope displays some oscillation while the probe from C is smoother.

I do not understand why. I am hoping someone could explain what is happening, is there some inductance from the length of the cable between the circuit, function generator and oscilloscope, or possible reflection from the input of the circuit or combination of both that may be causing this?


texts: What name is given to conversion between data of different widths?

texts:
Assuming  e.g that one part of design transmits 8 bit data word at a time but receiver needs a 16 bit word, we would need to concatenate two 8 bit words together to create a 16 bit word. If both blocks work at same frequency, the receiver shall receive input word every other cycle.

In opposite case e.g where transmitter sends 16 bit word every cycle, the 8 bit receiver shall have to work at twice the frequency to be able to keep up with it. Or maybe data does not come every cycle.

Is there a term used to describe this conversion between data widths?

The first case is simpler, just concatenation. The second is more tricky to implement
 There maybe need to use some FIFO between the two as well.


texts: dealing with noise from an external USB device

texts:
I am redesigning a system that has an two exteram usb ports.
One is used to program a sam51 µcontroller. The other one is used to communicate serially with an external tablet.
The schematic was based on reference designs.
For both, the grounds are connected directly to the PCB's main GND, while the shield is connected via a ferrite SMD inductor.

For each usb, gnd is the leftmost pin and is connected directly to the main GND plane. The shields have a mutual local GND plane which is connected via FB4 to the main GND plane
When I connect the external tablet to the PCB (via either one of the USB ports) the noise level on all the traces I sample (on scope) increases dramatically.
I of course assume that the noise is conducted and not radiated. The tablet cannot change.
Are the layout considerations seem correct?
Hoe can I mitigate that noise?
Is there something to improve?


texts: Optimal tradeoff between ADC bit depth and sampling rate

texts:
I have a 24-bit ADC sampling at 31250 samples per second. I am collecting these on a wireless device, and sending them in real-time to a PC for recording (and later analysis). My band of interest is 0-1000 Hz and the ADC produces noise which is more or less Gaussian with a level of around 19 LSB RMS.

My radio link has limited throughput, so I cannot send every sample from the ADC to the PC (would require 750kbps) and must instead send a subset of the data (less than about 190kbps).

The goal is to get the lowest possible noise level on a spectrum plot (e.g. using Welch's method) for a given duration of data (e.g. 10 minutes).

With that goal in mind, is it better to average more 24-bit samples together and send the full bit content (lower sampling rate, higher # of bits) or is it better to average fewer 24-bit samples and discard the lower noisy bits (higher sampling rate, lower # of bits)?

If I can discard noisy bits then how many must I keep for adequate oversampling on the PC side?

Is there an alternate processing method which would provide better results than simple averaging? It seems like Delta-Sigma can only be applied while the analog signal is being digitized, not after the fact (and I cannot change my hardware).

UPDATE:

I have been doing a lot of reading on the subject since I asked this question, and discovered that I had many misconceptions.

The central point that I did not understand is that having a higher sampling rate does not allow one to reduce the white noise in the band of interest. I was confusing the idea of reducing quantization noise by oversampling and decimation with the idea of reducing noise in the power spectrum by averaging over a longer time period.

On the surface, they both seem to indicate that having more data allows one to remove more noise. But in the case of Welch's Method, this is only true if the time window under analysis is lengthened. It doesn't help to increase the sampling rate (and in fact increasing the sampling rate creates a heavier processing burden).

On the flip side, the technique of oversampling and decimation cannot reduce thermal noise (or any other analog noise). It simply reduces quantization noise in-band by spreading the fixed noise power over a wider frequency range. Once the quantiaztion noise in-band has been reduced below the analog noise level, further application of oversampling and decimation becomes markedly less useful.

There is an all digital technique to reduce quantiaztion noise in the band of interest called Noise Shaping. It is an integral part of the operation of a Delta-Sigma converter, but can be applied independently such as when reducing bit depth. As with oversampling and decimation, it can do nothing to thermal noise, as that's already part of the measured signal. Since quantization noise is not a limiting factor (as I control the on-air bit depth) it is of limited usefulness to me.

With this new knowledge, it seems to me that I should reduce the sampling rate as much as possible without distorting or adversely affecting the signal's passband (e.g. being mindful of the Nyquist rate). I can limit the sampling rate to the minimum and thus save power by not using the radio's maximum throughput. As an added bonus this reduces storage requirements and processing complexity.